Shane, I will concede to your experience. I do have to ask; did you see a prevalence of tungsten inclusions that were pointed or rounded?

I can't recollect seeing one that didn't have rounded ends, i.e., they may have been oblong rather than spherical. Then again, my experience with RT is not extensive.

Al

Al,
With all due respect my friend I have to strongly disagree.
I spent 4 yrs as a radiographer and after viewing a multitude of tungsten inclusions I can honestly say none of them were ever "rounded".
The tungsten is ground to a sharp point and when it is broken off due to poor welding technique it will show up on the graph as a very sharp pointed indication (less sharp if it has been in use for a while but no where near rounded).
I think the API committee may have failed to include TI's because the use of GTAW on a pipeline would not be considered "normal practice".
Cheers,
Shane

Since your referenced API 1104, they don't specifically address tungsten inclusions. However, one could approach the problem by treating the tungsten inclusion as you would porosity. The justification being that tungsten inclusions are typically rounded, unlike slag inclusions that often have sharp end conditions. Basing the acceptance on porosity, the criteria for a single pore hole is as follows:

9.3.9.2 Individual or scattered porosity (P) shall be considered
a defect should any of the following conditions exist:
    a. The size of an individual pore exceeds 1/8 in. (3 mm).
    b. The size of an individual pore exceeds 25% of the thinner
        of the nominal wall thicknesses joined.
    c. The distribution of scattered porosity

I was going to say, "check the pipe wall with a flashlight, if the light doesn't shine through, you're good to go." 

Hope that helps - Al

Checkout - https://app.aws.org/forum/forum_search.pl?words=tungsten+inclusion&user=&board=0&field=body&min=&max=&order=desc

IN ASME B 31.3 Table No. 341.3.2 criteria are  given

Slag inclusion, tungsten inclusion, or elongated indication
Individual length ≤ T w /3
Individual width ≤ 2.5 mm (3⁄32 in.) and ≤ T w /3
Cumulative length ≤ T w in any 12T w weld length

Slag inclusion, tungsten inclusion, or elongated indication
  Individual length ≤ 2T w
  Individual width ≤ 3 mm (1⁄8 in.) and ≤ T w /2
  Cumulative length ≤ 4T w in any 150 mm (6 in.) weld length

when we qualify 2 welders (gtaw+smaw) there is a tungsten inclusion in RT Film , if the smaw welder qualify or not, kindly mention it in ASME IX standard

Dear sir,

Can you advice the acceptance of Tungsten Inclusion(TI) for as per  API1104.?
I found 4mm length of Single TI . Is it acceptable or rejectable ?

please Advise.

Many Thanks
Regards
Abhi Thakkar

When discussing porosity or undercut under Section IX, Authorized Inspection and National Board auditors often have a response along the lines of  "...Section IX is a testing code, unlike Section VIII which is a production code".

Slightly off subject here but I believe the glossary in Section IX does list a definition for undercut, even though the code does not address it.  And Section VIII, Div 1 does not explicitly address weld undercut. However, look at UW-35, it mentions a reduction in thickness due to welding and I recall that can not exceed 1/32" or 10% of the wall thickness, whichever is less, so this would imply internal or external undercut. Section VIII Div. 1 really gets some yardage with the term "rounded indications", as they can be slag, tungsten inclusions or porosity.

Hello Allan,
We  completed the weld last week with some difficulties. The suggested Ceriated tungsten was the better choice especially for the open root pass. It directed the arc better than the balled pure tungsten. Bridging the gap was much easier with the sharper Ceriated tungsten.  RT showed some porosity and some tungsten inclusion. The Hi-Freq arc start wasn't working henceforth the tungsten inclusion. At least that's my story and I'm sticking to it haha. And AL is very susceptible to porosity on RT's.

Fortunately, the 2" root ID was accessible from the inside of the vessel for visual inspection and minor grinding so that was a big plus.

At the end of the day, it passed RT and can be placed back in service.
One note, there was a third of the pipe that just did not weld like the rest of the pipe. That is the unknown variable when welding on materials that have been in service for decades. You just don't know until you fire up on it...

Thank you for all of your help. It was greatly appreciated.

Tim

Allan, thank you for the helpful info. That is an interesting technique that you mentioned. One welder did a square butt and got full penetration but had lots of porosity in the RT. It also had a visible lack of fusion line on the root ID. It was easily removed with light grinding. Not sure if we'll be able to access the ID on site or not. I do wish that we'd have time to run a few with your mentioned technique but time won't allow it this late in the game.  We had lots of tungsten inclusion with the pure tungsten on a standard open butt weld and I'm not sure if it was technique, the pure tungsten or perhaps the machine as we were experiencing inconsistencies with it. I've always used pure tungsten on Al but not opposed to trying 2% thoriated or other.

Allan,
They hire locals because the hands don't get per diem or travel. Apparently this is how they can financially justify this world class RT failure rate.
"Just all depends on how you view life."
Well, if you set your standards low enough, you can be content with anything.

I DO manage to stumble onto some doozies though.
Back in 2008, I was on a refinery where we had a 316SS peroxide line with a Zero tungsten inclusion clause in the specs. That first run of RTs had an 87% fail rate after about 60 shots. And I thought then "Surely this will be my all time record"!
Little did I know...
The bad news is; I'll never have another gig with a worse number.
Just prior to my arrival, there was one joint in particular (can't really call it a weld BECAUSE!) they went to R2, FAILED! Then the weld was cut out and went to R2 again before acceptance.
Not every weld here was an RT failure, but a few of the examples such as mentioned actually drove the numbers to an even 100%!
This kinda stuff keeps me well entertained.

Well I ducked out for a few hours, and this thread had gotten big on me.

Back to my original premise, If we can visually detect anything that is not complete fusion (slag, flux, tungsten, or oatmeal) it would seem to me that this violates the requirement in table 6.1. It would be helpful if an inclusion was specifically listed as a form of incomplete fusion, but it does not appear to be that way. 

Departing from the code a bit, for me, complete fusion is just exactly that, 100% fusion.  if there is anything other than weld metal in there, and it is solid (to qualify as an inclusion rather than porosity), is represents less than 100% fusion, which means less than complete fusion, which (to me) means rejectable per 6.1

AWS 3.0:2010
Inclusion:
"Entrapped foreign solid material, such as slag, flux, tungsten, or oxide"

Slag Inclusion:
"A discontinuity consisting of slag entrapped in weld metal or at the weld interface"

Weld Metal:
"Metal in a fusion weld consisting of that portion of the base metal and filler metal melted during welding.  See also mixed zone and unmixed zone."

Weld Interface (partial)
"The boundary between weld metal and base metal in a fusion weld,"...

Base Metal:
"The metal or alloy being welded, brazed, or cut.  See also base material and substrate."

Incomplete Fusion:
"A weld discontinuity in which fusion did not occur between the weld metal and the fusion faces, or the adjoining weld beads.  See Figure B.29.  See also complete fusion."

Per AWS D1.1:2010 Table 6.1 (2)
"Complete fusion shall exist between adjacent layers of weld metal and between weld metal and base metal"

If a "slag inclusion" (or any other type of "inclusion") or any "incomplete fusion" is present and dectectable visually, either in the "weld metal", or the "weld interface" that would not be considered COMPLETE fusion. 

Ergo, rejectable based on VT

Welcome Weldinstructor!

As a retired Boilermaker/Tube Welder/Mechanic one of the first things I had to learn to do with GTA welding otherwise also known as TIG welding, was to practice how to strike an arc without using any Hi-frequency and without a foot pedal because just about every job I have been on, the machines and torches are set-up that way and only once in a while would a contractor have torches with start and amperage/current control either built in or adapted to work with these accessories...

So I would start out by teaching your students how to scratch start an TIG arc by first explaining how it works and then to demonstrate how to go about doing do with out contaminating the joint with W/Tungsten inclusions (See below for a factoid on W/Tungsten)... How you do this is really simple and it would be best to show you than to try and describe this technique to you in written form... Since they have some experience already in TIG welding from what you have taught them so far which means that you're training them how to start a weld differently from what they're already used to and you're not re-inventing the wheel so to speak... They shouldn't have a problem adapting to this method of starting a GT Arc to Weld...

I'll try to give you a simple enough description but a picture or video is worth a thousand or more words so, I'll begin with explaining that with the foot pedal method of starting a GT Arc to Weld, the power output from the power source/welding machine to the torch is off when the student doesn't have the foot pedal depressed... However, when using the scratch start method of starting an Arc to TIG weld or GTAW (Gas Tungsten Arc Welding) the power output from the power source is always live if the power source/welding machine is turned on so, one must be much more careful of how to handle the torch around ant metal that's connected to where your work cable is attached to or or any metal the tungsten electrode makes contact with that's also making contact with any metal the power source's work (Not ground!) clamp is attached to and this is really important to drill this into their heads to be aware of...

In fact, many torches in the field are now fitted with an on/off switch so that it's a lot safer to use a live torch in confined spaces however for the most part, pipe GTAW is done out in the field with "live" torches... Once they're extremely aware of this - you can then continue to begin to show them the very simple technique of scratch starting a TIG weld root on pipe...

To do this, place the filler wire that is usually 3/32" or 1/8" diameter into the pipe joint in between the members that has a 1/8 root opening and make sure the wire is making contact with both members of the joint, and then scratch the end of the wire towards the other end to a distance of about 1/16"  or less and with a height between the tungsten and the filler rod of about at lease 1/4 - 3/8" then once the arc is started and without hesitation move the torch towards the one of the 2 bevels inside the joint as closest to the land as possible and back to the beginning of the filler wire to start building up the molten metal and begin to fuse the beginning of the puddle on to the bottom of the bevel as close as possible by feeding the rod and then manipulating the torch in a circular motion and forming the puddle for the root of the the weld... Now remember that all of what I just described must be done within 2 to 3 seconds the most! So you want to make sure that you have set the power source output current to easily melt the filler and penetrate through the root opening in order to have adequate root of the weld reinforcement...

It's a whole lot easier to show somebody how to do this as opposed to attempting to describe it with words or just audio without any visual aid so pay attention to the video's especially where the welder is shown starting the arc and forming the puddle and you can do that by placing your cursor right where the bar below the video shows you how much time in the video has already been shown and repeatedly going back and forth with your mouse to see in slow motion so you can see how the arc, puddle and the weld is started in the root opening of the pipe joint... Never scratch start the arc on the base metal because you then contaminate the weld with tungsten inclusion(s) which will show up on an X ray shot!

They'll need to practice the root pass a few times in order to sharpen their technique in how to deposit root passes that will have the necessary build up inside of the joint @ the root of the weld and once they get that down, you can go through the positions especially 5G, 2G, and 6G joints which will end up being the majority of configurations they'll be welding on in the field with 5G being the most likely out of those 3 positions and 6G to be used for testing and some 2G joints also... If they're in a shop, they will more than likely be welding a lot of the joints in the 1G position usually and a welding turntable/positioner but, Boilermaker/ Welders don't find themselves doing that kind of gravy work out in the field so don't spend too much time with that position and instead focus more on training the students to become proficient in welding in the 5 & 6G positions instead with 2G rounding out the course if they're able to become proficient enough with the first two positions...

You could teach them how to weld the root pass free-hand otherwise known as lay wire & the other key-holing/walk the cup method, and then once they become proficient with the root pass, and some Boilermakers are taught to use the filler and feed in through the pipe whereby they look into the pipe joint and monitor the root of the weld as it's forming inside the joint while walking the cup in order to maintain consistent weave pattern on the outside of the joint in between the bevels... Now this is a little tricky at first but, once they get the hang of it, their confidence in their welding skills will improve and sometimes dramatically...  

You could teach them how to use the "walking the cup" technique for the hot and all of the other passes also because once they go out into the field, they will have to know how to do both and some contractors will not even give you a test if you don't know how to walk the cup... What you will be teaching them will be just enough for your students to be proficient enough to take a weld performance test however, there's sooooo much more to being a Boilermaker/ tube welder apprentice which is what they will more than likely start out as for their first few years... And during that time, they will be going through sooooo much more training in various subject related to being a Boilermaker/Tube Welder/Mechanic/Journeyman... 

As a fully experienced Boilermaker/tube welder/ mechanic/journeyman, one must know how to perform all sorts of other tasks besides welding such as fitting, tube preparation, be proficient in interpreting engineering drawings, rigging, Quality control, NDT methods, inspection etc... And they must also put in the years (For me it was 5 years) in order ot gain the necessary experience to be relied upon with confidence that they can do the work to best quality required and with minimal supervision... So let them know right off the bat that you're only preparing to get them prepared to take a tube test and that they will have to go through much more training after they get into the union and the same will be true even if they do shipyard work or non-union work also...

So if I got you confused, I apologize and maybe these video's will make it up to you so have fun watching them okay? Good luck and all the best!

https://www.youtube.com/watch?v=0h5yw-qrl9c

https://www.youtube.com/watch?v=QYYkPELEBRU
   
https://www.youtube.com/watch?v=UKaPIpxIneE

https://www.youtube.com/watch?v=PPKstOZSZug

https://www.youtube.com/watch?v=rzrfrSMEOo4

https://www.youtube.com/watch?v=dRoxXTlRa_I

Well, that's about it for now... I hope this post and the video's can help you out training your students to learn how eo GTAW C/Stl. pipe in both 2" nominal and 6" OD.

Respectfully,
Henry

P.S., Here's the factoid below regarding Tungsten or Wolfram and the history of those 2 names:

What's in a name? From the Swedish words tung sten, which mean "heavy stone." Tungsten's chemical symbol comes from its eariler, Germanic name, Wolfram. The name Wolfram comes from the mineral wolframite, in which it was discovered. Wolframite means "the devourer of tin" since the mineral interferes with the smelting of tin.
Say what? Tungsten is pronounced as TUNG-sten... History and Uses:Tungsten was discovered by Juan José and Fausto Elhuyar, Spanish chemists and brothers, in 1783 in samples of the mineral wolframite ((Fe, Mn)WO4)... Today, tungsten is primarily obtained from wolframite and scheelite (CaWO4) using the same basic method developed by José and Elhuyar... Tungsten ores are crushed, cleaned and treated with alkalis to form tungsten trioxide (WO3)... Tungsten trioxide is then heated with carbon or hydrogen gas (H2), forming tungsten metal and carbon dioxide (CO2) or tungsten metal and water vapor (H2O)... Pure tungsten is a light gray or whitish metal that is soft enough to be cut with a hacksaw and ductile enough to be drawn into wire or extruded into various shapes... If contaminated with other materials, tungsten becomes brittle and difficult to work with. Tungsten has the highest melting point of all metallic elements and is used to make filaments for incandescent light bulbs, fluorescent light bulbs and television tubes... Tungsten expands at nearly the same rate as borosilicate glass and is used to make metal to glass seals... Tungsten is also used as a target for X-ray production, as heating elements in electric furnaces and for parts of spacecraft and missiles which must withstand high temperatures... Tungsten is alloyed with steel to form tough metals that are stable at high temperatures. Tungsten-steel alloys are used to make such things as high speed cutting tools and rocket engine nozzles... Tungsten carbide (WC) is an extremely hard tungsten compound. It is used in the tips of drill bits, high speed cutting tools and in mining machinery... Tungsten disulfide (WS2) is a dry lubricant that can be used to temperatures as high as 500°C... Tungsten forms compounds with calcium and magnesium that have phosphorescent properties and are used in fluorescent light bulbs.

Not speaking to compliance here... Just to my own personal opinion.

I see very little value to RT on austinetic stainless sheet or tube under .90 in thickness.

If something has gone wrong that isn't clearly found on the visual inspection, on thin material RT is pretty useless in my opinion...

For example:  A tungsten inclusion that is large enough to be rejectable is prolly gonna be poking out of a piece of .035 coupon.

Destructive bend testing has more value here if you are trying to build quality into your systems....

Things like carbide precipitation or embrittlement will not be sniffed out by RT.

RT may be quick and easy, but again, I don't see it really boosting your quality system much.

Edit
Sometimes we get in "compliance mode"  and look for the best/easiest ways to satisfy the code and can forget that the time we spend on testing should have *production value*.    I'm NOT pointing fingers here... Just a thing I have dealt with and thought to share.

Sir,

With all due respect – a commendable, enjoyable, respectful and profound read.

I do agree. This is one of the lessons that I was allowed to learn here quite early. It is the American Welding Society Forum and good that is. I do not really know any other forum dealing with our trade in such a remarkable, yes I'm almost tempted to say, honourable way.

That, in my opinion, may also be one of the reasons for that it is attracting persons obsessed with welding, even from way beyond the pond.

I do agree. As such, being the AWS forum, specific AWS terminology/nomenclature complying with AWS codes and standards should be recommended being used. Simply for achieving common understanding – entirely independent of ones personal "agreement" or "disagreement" as when it comes to the particular welding/joining topic dealt with.

Nonetheless, couldn't I read somewhere recently, "No one works in a vacuum"?

Hence, I stick to this. The AWS in my eyes wouldn't be the AWS if it would "exist in a vacuum". On the contrary I suppose moreover it is the open discussion with all these different "organisations" and those fellows from around the world, that considerably contributes to its excellent reputation.

This, amongst others, was the reason for me granting "46.00" some humble though but honestly meant comment.

Anyway, coming back to these "few relevant definitions extracted from AWS A3.0-2010 Standard Welding Terms and Definitions" for:

•  "Slag: A nonmetallic product resulting from the mutual dissolution of flux and nonmetallic Impurities in some welding and brazing processes."

I should like to stick to the term "nonmetallic impurities" asking moreover, as the Welding Institute's had not particularly covered that in depth; if nonmetallic impurities may cause "slag" to occur and the TWI parent metals (autogeneously welded without employing "fluxes"), wouldn't it be possible then that the sort of "contamination" found along with this study may have been caused through "nonmetallic" parent metal impurities (whatever these were)?

Provided that is so. May we then use the AWS A3.0-2010 Standard term "slag" for what's been found adhering to the weld bead surface?

We could negate this question immediately, when, (and this is just mentioned in order to provide a rather more complete picture) instead of using AWS A3.0-2010, we would comply with the British Standard BS 499-1:2009' definition of "slag" which is stated as:

•  "Non-metallic substance that results from fusion of an electrode covering, a flux core or a powdered flux and which, after solidification, partly or totally covers the weld metal".

Further to AWS A3.0-2010.

•  "Slag Inclusion: A discontinuity consisting of slag entrapped in weld metal or at the weld interface."

From the aforementioned I dare to suggest then that, provided were allowed using the AWS "slag" term, this definition just implies that TWI has found (in this particular case employing these particular boundary conditions) "slag" irregularly deposited across the bead surface.

Returning to BS 499-1:2009 that defines "inclusion" as:

•  "Slag, flux, oxide, copper, tungsten or other foreign matter entrapped during welding; the defect is usually more irregular in shape than a gas pore; inclusions can be linear, isolated or clustered in their formation."

And, something that may eventually fit approximately in to the "non-standard" term "slag track", i.e. "linear inclusion" ("slag line") as:

•  "Inclusion of linear form situated parallel to the axis of a weld."

Of course I have to admit. This is confusing at the very least, since TWI = Most Honourable British Institution should have referred to British Standards - I suppose.

As a logical consequence the appreciated fellow that had written the final report should not have made use of the term "slag" for describing his contamination findings.

However, considering the study conducted in 1988 or so I’m certainly unable to say how "slag" was defined at that time in compliance with British Standards. 

Finally I do respectfully agree with another part of your statement: "... that's what I call an interesting conversation."

That it is.

Thank you.

EDIT: According to the statement of 'MMyers', saying: "...this thread is kinda useless without a reference link back to the original discussion, paper being discussed..." which I fully agree to, I should like to attach the corresponding link that, in my understanding and amongst others, may have caused this thread:
http://www.twi.co.uk/news-events/bulletin/archive/pre-1998-articles/1988-articles/how-tig-welding-procedure-affects-penetration-and-slag-island-formation-part-1/.

I didn't intend to hijack the other thread and get into a long drawn out discussion about the term "slag tracks." With that in mind I decided it would be best to address the subject as a new thread where the subject can be discussed in more detail.

Please keep in mind that we are in the AWS Forum, not the TWI Forum or some other organization's forum. As such I believe is fitting to use AWS terminology considering the fact that one goal is communicate more effectively as well as to expand our horizons. I do appreciate that we have participants from around the globe. I believe that is one facet that makes this forum all the more valuable to all of us. I for one truly enjoy the conversations and discussions that can be found here. I find it interesting to read other people's prospective and I also enjoy reading the local vernacular used by different industries, regions of our country, and other countries. I admit that it can cause confusion and in some instances the source of some very interesting discussions.

Back on track; I poked a little jab at a member of our forum for his use of the term "slag track" in another post. I pointed out that there is no slag present in a welding process that does not use flux as a part of the welding process. That statement is based on standard AWS terminology. Again, I make it a point that this is the AWS Forum. Here are a few relevant definitions extracted from AWS A3.0-2010 Standard Welding Terms and Definitions for:

Slag: A nonmetallic product resulting from the mutual dissolution of flux and nonmetallic Impurities in some welding and brazing processes.

Slag Inclusion: A discontinuity consisting of slag entrapped in weld metal or at the weld interface.

Inclusion: Entrapped foreign solid material, such as slag, flux, tungsten, or oxide.

The term “slag tracks” is not found in AWS A3.0. While the term may be used in literature and while it may be an "official" term used in another country or even a different American welding standard, it is not considered to be proper in regards to AWS literature when flux is not used. Since the other thread mentioned gas tungsten arc welding, I believe I am not too far off track in assuming bare filler metal is used. Since GTAW typically does not use a flux as part of the process it would be impossible to have a slag inclusion. Granted, if the user did use a product, whether it was "painted" on to the weld joint or if it was applied to the filler rod, the term "slag inclusion" could be appropriate. However, a slag inclusion or slag tracks is not possible with a welding process that uses bare filler metal without supplementary flux.

The aforementioned is consistent with AWS' publication A B1.10-2009 Guide for the Nondestructive Examination of Welds. Table 2 found in B1.10 lists the discontinuities typically associated with the common welding processes. That table is the reference used in the CWI training and the basis of several CWI examination questions. Per that table, slag is not associated with either GTAW or GMAW.

What is the proper terminology for the deposits found on the surface of the weld bead deposited with either GMAW or GTAW? I suggest they are simply silicates and silicon oxides or as some people call them, silicon islands.

Many of our discussions are related to terminology. Whether the term is proper, standard, or nonstandard is dependent on the welding standard in use. What may be considered standard terminology by one welding standard may not exist in a different standard. One example of that would be the word “undercut.” The term is widely used by those involved with welding and most of us have no difficulty in knowing exactly what the word means. However the word “undercut” is nonexistent in ASME Section VIII. As an inspector, I cannot reject a vessel constructed in accordance with Section VIII because the discontinuity called “undercut” is excessive. I am limited to accepting or rejecting the vessel based on the criteria provided by Section VIII or based on the customer supplied criteria.

It is customary in the US for a welding standard to contain a glossary of terminology. Welding terminology that is unique to hat standard will be included, for other terminology related to welding; the standard usually defaults to AWS A3.0. The goal is to promote better communication in the welding industries. The goal cannot be met if there is no agreement on the proper terminology to be used. The use of colloquialisms only causes confusion and further complicates matters.

Perhaps it would help reduce confusion and misunderstandings if a writer were to identify terms that are not standard AWS terms. While many of us may assume everyone understands the meaning of a slang term, it is often not the case. This is especially the case when dealing with an international audience. How many discussions have been initiated by readers that misunderstood what a poster has said because the jargon used was or is not universally understood? Add to the mix that each of us has a different sense of what is funny and what isn’t; you have the ingredients for some serious bruised egos. I still have some bruises left from our discussions, but that's what I call an interesting conversation.

One of my good friends often says, "I might not be right, but I'm never wrong." Sound familiar? No, I‘m not referring to myself! It cannot be me, according to my wife I’m wrong more often than I’m right.

Slag tracks? Could he have been referring to incomplete fusion? I don't know.

Best regards - Al

<<<<<<<<<<<<<<<<<<<<<<<<<

>>>>>>>>>>>>>>>>>>>>>>>>>

*MODERATOR EDIT* Adding the link to the prior discussion for clarity:
http://www.aws.org/cgi-bin/mwf/topic_show.pl?tid=32366

We change out-side venders that RT our parts and the new vender doesn't mark where the porosity or tungsten inclusion are we have to figure that out ourselves. My question is there a book that tells you how.

              M.G.

Henry,
Yes Sir I did see the fillet welds and they were well positioned for maximum deposition speed. Still, under field conditions (wind!) with what was most likely an air cooled rig that overheats easily, and ceramic cups that shatter after a few hot and cold cycles, 45 minutes for a 24" (6' 3-3/8" total linear length) pipe is far beyond the capabilities for the common welder.
Since this does not appear to be an API 1104 job, the arc strike was not a concern. Tungsten inclusions are far easier dealt with outside the joint, and usually not an issue on a project like this.
I'd loved to have just hung out, handed him rod and brushed his stops and starts for him. Looked like a fun and hopefully profitable gig.
Good job Tommy!

Thank you for your kind words electrode...

Btw, I do have volume 1, "Welding Science and Technology" by A.C. Davies...
The volume you have in the link 46.00 posted is "The Science and Practice of Welding" which is different in format and content although interesting as is the volume I have.

I'm going to quote from "The Science and Practice of Welding" starting from page 160.

Quote; "Square wave power output units (AC/DC). Power units are now available in which the voltage and current waves are not sinusoidal, but have been modified by solid state technology and using printed circuit boards (P.C.B's) to give a very rapid rise in the AC wave from zero value to maximum value to give a square wave output.

When GTA welding of aluminum using a sinusoidal wave form current, the arc tends to become unstable and the electrode is easily overloaded.
This gives tungsten inclusions in the weld (spitting) and leads to faults in the weld bead and more rapid consumption of the tungsten electrode.

Square wave current overcomes these drawbacks and the arc is greatly stabilized and the risk of inclusions greatly reduced.
In addition, MMA (SMAW) welding characteristics are greatly improved and the arc is smooth with reduced spatter.

The units are designed for AC precision welding of Aluminum etc. and for DC TIG (GTAW) and Manual Metal Arc welding or MMA (SMAW).
they have a transformer and silicon bridge rectifier, SCR (Silicon Controlled Rectifier) or thyristor with a square wave output. A memory core stores energy proportional to the previous half cycle and then injects it into the circuit just as the wave passes through zero at the beginning of the next half cycle.

The rapid rise of the wave from zero to maximum, of about 80 microseconds from peak to peak means that the high frequency and high voltage at the beginning of the cycle needed in order to initiate the arc and often to keep it ionized without touchdown, need only be applied when the arc is first initiated. After this first initiation the HF is switched off automatically."

Well this doesn't give me a complete answer to your student's query Larry so I decided to look in a publication more suitable for folks on this side of the pond and I came across with this: AWS Welding Handbook ninth edition, Volume 2, Welding Processes part 1, Chapter 2 Shielded Metal Arc Welding, age 94, Arc Stability.

A stable arc is required if high quality welds are to be produced. Discontinuities , such as incomplete fusion, entrapped slag and porosity (blowholes), can be the result of an unstable arc. The following are important factors influencing arc stability:

1. The open circuit of the power source.
2. Transient voltage response characteristics of the power source.
3.Size of the molten drops of filler metal and slag in the arc.
4. Ionization of the arc path from the electrode to the workpiece.
5. Manipulation of the electrode.

The first two factors are related to the design and operating characteristics of the power source. The next two are dependent on the type of welding electrode. The last one represents the skill of the welder.

The arc of a covered electrode is a transient element in the circuit even when the welder maintains a fairly constant arc length. The welding machine must be able to respond rapidly when the arc tends to extinguish because of the resistance of the arc momentarily increases or when a large droplet partially or totally short circuits in the gap. In these instances, a surge of current is needed to restore the arc. With AC, it is imperative that the voltage cycle leads the current cycle to sustain the arc. If the voltage and current were in phase, the arc would be very unstable. This phase shift must be designed into the welding machine/power source.

Some ingredients of the electrode covering tend to stabilize the arc. These are necessary ingredients for an electrode to operate well on AC. A few of these ingredients are titanium dioxide, feldspar,  and various potassium compounds (including the binder, potassium silicate). The inclusion of one or more of these arc stabilizing compounds in the covering provides arc plasma that readily ionizes and achieves a quiet arc. Thus, the electrode, the power source, and the welder all contribute to arc stability."

This was simple enough to go over yet I wasn't satisfied either Lawrence, so I kept digging for more... I'll post it tomorrow because I need some rest... I'm worn out from all the drugs and the crap of being ill...

Respectfully,
Henry

The copper flash is volatized by the heat of the welding arc. OSHA raised the flag back in the later part of the 70's / early 80's and made the manufacturers eliminate the copper flash because the copper was considered a heavy metal. The filler metal would rust so quickly it became clear that the steel wire needed some form of protective coating and OSHA caved.

Copper melts at about 1981 degrees F while steel metals at higher temperatures (2500 - 2800) depending on the carbon content. No carbon/low carbon steel melts at temperatures around 2800 and as the carbon is increased, it melting at temperatures closer to 2500 degrees F. Copper, being a low melting constituent stays liquid in the molten weld pool until the temperature drops below 1981 degrees. It has very low solubility, thus only a small fraction goes into solution with the iron. The copper usually solidifies along the grain boundaries and usually toward the centerline of the weld bead since that is the last region to solidify. That isn't to say it will not segregate toward any grain boundary when the solidification is rapid as is the case with stringer beads.

I use copper to induce cracks for test samples used for NDT training. A very small whisker of copper wire from a welding lead is one of the easiest ways to cause a weld in steel to crack.

As for an inclusion, I don't know. As noted, the copper usually is found along the grain boundaries rather than in a "clump" as is the case of tungsten which has a melting point well above that of steel, i.e., 6100 degrees for tungsten versus 2500 to 2800 for steel. Tungsten usually appears as a rounded indication that appears to be very white compared to the surrounding area.

As for the radiographer calling a less dense indication a copper inclusion, I don't know. I've had that happen when there was spatter on the face of the weld and I've read RT reader sheets reporting slag inclusions when the weld was made with GTAW. Go figure!

Best regards - Al

Regarding what it would look like, cu's characteristic K radiation is =1.5418Å As I recall copper tends to have a high diffraction ratio..
It's density is considerably off that of iron (Steel ~7.85 gm/cm^3 copper ~8.94 gm/cm^3). http://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html
I would suspect an inclusion if one were possible would contain a diffraction halo around it similar to what thin (.05" or less) titanium welds sometimes have. There would be only a slight difference in density given that by comparison, tungsten is ~19.6 gm/cm^3 which shows up strong on a graph. It would be a shadow at best on the film unless there were a large volume of it.

Thats my WAG on it.

I've seen that to. It was the comparison to tungsten inclusions that I am questioning.

The acceptance criteria will be provided by the code (which you haven't provided us). An inclusion is an inclusion for sure.  Size of defects/discontinuity allowed will be provided in the code.

I understand where the source of tungsten inclusions might be... What is your source for copper?

How about the acceptance criteria for copper and/or tungsten inclusions? Is it similar acceptance  as to slag inclusions

Does copper inclusion can exist on a weld, is it the same density as tungsten when viewing the RT film? May I also know the acceptance criteria for inclusion particularly copper and tungsten.

Hey guys, very interesting thread. I am definately learning a lot from it.  We just ran some SEM tests on the "bearding" and I wanted to share a few pictures which you guys will probably find interesting.  The first shots were taken of the bearding while still on the taper of the electrode.  We then scraped off the bearding and reshot the flakes.  In both instances the composition of the bearding showed high levels of tungsten with some locations also showing thorium, Fe, Ti, & Ca.  I am still trying to wrap my head around the whole tungsten eutectic mechanism and how it could be occuring in our application.  I am going to have one of the electrodes cross sectioned and etched at the recommendation of Niekie to see what I see.  I am no metallurgist by any means, so I was wondering how I might be able to identify eutectics within the cross sectioned sample if they are present? Will it be obvious? Also do I need to use a special type of etchant? 

We are performing an informational x-ray immediately after weld that we have proven is sensitive enough to verify tungsten inclusions .015 or greater (which is around the size we were previously seeing when getting all of the rejects).  We have passed the last 9 production parts through this operation which is a little encouraging.  I have noticed the bearding was pretty much non existant on the electrodes used to weld these parts which is interesting.  We haven't really changed a whole lot from how we were welding them when we were seeing the inclusions previously.  We did change our bm cleaning procedure around a little and have been really paying attention to it, but other than that the only other thing we did was try to drop the wire as far away from the electrode as we could without it dragging.  Even this was relatively inconsistant between parts however, as mulitple adjustmants to the wire height are made throughout the length of the weld. 

As I am fairly confident after looking at these SEM results, that this "bearding" is where the inclusions we have been seeing is coming from, I would like to run some tests to attempt to reproduce the bearding.  My first thought was to drop the arc gap closer to the bm, but because I still do not fully understand the mechanism that is causing the bearding I thought you guys might have some better ideas or recommendations. 

Since its finally letting me attach things I went ahead and also attached some pictures of some of the oxides we have been seeing in the weld as well as bearding on the electrode during weld.  I also attached a short video where the arc hits an oxide from the previous toes and you can see material from the oxide/weld jump up and actually land on the side of the electrode (you have to look really close).  The last video shows the arc running over an oxide from the previous toe which causes the arc to flutter back and forth.  I thought maybe this is when the bearding could be falling into the puddle but thats only a theory.  The bm oxides are consistant throughout the weld no matter how much we clean the part.  We are getting ready to run a series of tests with the bm and fm to try to pinpoint what is actually causing the oxides. 

Keep the good posts coming.  Thanks

Brett

[img][/img]

"There are some good posts on here about making homemade trailers out of sintered copper and such."....taken out of context the way search engines like to do, this sentence is going to give a big ol mindf*ck to some hobby welder searching for tips on building a trailer..the kind with axles that is

Back on topic...  To fschweighardt, its a bandsaw cut [no coolant/lube] then an acetone wipe, then vixen filing down to bright metal.  This procedure worked fine for the outside corner joints done on the same assembly with the same metal.
  To Tommyjoking, big cups are on order tomorrow.  Just last week I did some 3/16"flat to 3/16" tube repairs on a fishing frame.  It presented many of the challenges present in AL GTAW.  Dirty base metal, hydrated oxide, rewelding same plates back on so I needed to clean out the old weld metal.  Ended up doing two passes, with a slight weave on the second pass, and no problems with shielding or dirty puddle.  Ultimately I think it was a combination of a weird joint and fatigue/shaky hands.  I got the first one done this afternoon, and I'm headed out tonight to finish the other.
To 803056, playing the part of the dummy...HA!..I've read your posts sir...yes using AC on a Lincoln Invertec V205-T.  The ceriated has always worked in the past, and even at different joints on the same assembly no problems.  But I've never been fully satisfied with their performance.  I'm running a 1/8" tungsten at 80Hz, 53% EN, 190 amps.  If I weld on a freshly ground tungsten, even with a relatively blunt point, the tip of the tungsten melts in weird ways and forms little bumps.  If the Elephant Man was a tungsten, that's what it looks like.  So I grind a 140 degreeish point, crank the balance down to 35%, and blast it with the footpedal until it melts into a ball, then turn the balance back up and start welding.  At 190 amps, even dropping the balance down to 50% will cause the ball to sag and the arc gets a bluish tinge. Tungsten inclusions??  Are Zirconiated tungstens suitable for this machine?  Clean gloves with nitrile exam gloves underneath, so no contamination there.  I know the alcohol after the file and brush is recommended, but I'm lazy.  Maybe it's starting to bite me in the ass.

I can only provide some simplistic response here.  I know people who know more about this and pointed you in their direction in earlier posts.

Oxides may be reduced with improved gas shielding... Custom argon gas trailing shields can provide this.   In my opinion simple may be best.

Next; (if improved gas coverage does not reduce oxides that you suspect affect "bearding")  8 hours is a very long arc-on time for any electrode.    Do you have data confirming when exactly your inclusions are happening during the weld cladding cycle?    If the bearding is comming near the end of the 8 hour cycle..  Why not consider changing your procedure to include a stop, tungsten change and restart at the point in time when you *haven't* yet observed contamination.

Your inspection criteria is so strict (you have mentioned it in earlier posts) that it seems to me that the time expended in a process schedule change to freshen your tungsten mid-stream might be worth while vs the expence of rework/rejection and the hastle your going through to solve this problem without adjusting your 8 hour weld cycle.

I still think it's a process control issue.  Some small detail that when set right will solve your issue.

Edit:

I have been involved in projects with automated GTAW with weld cycles in excess of 8 hours, and have found that alloy and vendor of tungsten electrodes both can have an effect on tip life....  We were running at lower current levels than you I suspect, and our criteria was not as tight...  Nonetheless I feel your pain. 

Our in house testing and experience demonstrated that Lanthanum 1.5 was superior to both thorium and cerium... But again our trials were on pulsed currents well below 100 amps, and that can make a difference.    The best as far as brand was "Bavarian Alloys"  the sad news is that they no longer produce electrodes under that name...  If anybody knows if they are still producing under a different name (Euro Friends?) that would be a good place to start.  When we ran out of those (a sad day) we selected Sylvania.

I attached results of some SEM tests we performed on one of our 2% thoriated electrodes used to clad fm 82H onto carbon steel using the GTAW process.  Intial testing shows the bearding contains W.  To be certain we are having the bearding scraped off and evaluated further.  The weld itself is an 8 hour spiral clad. We have been getting tungsten inclusions showing up at X-ray which we now believe may be due to an unstable arc from welding over large oxides which are located on the toes of the previous bead.  We collect video during the weld and have seen heavy deflection of the arc after running over these large oxides.  I attached a picture of the weld before and after hitting one of these oxides. The inclusions are consistantly showing up at this areas in the parts.  The other thing we've noticed is the bearding on the electrodes as shown in the attachement. The bearding is not consistant on every electrode and on some its much more severe than others.  We are cleaning the base material surface exceptionally well and our wire is triple melted to vaporize and minimize tramp elements.  We have yet to go into a lot of testing towards the base material, but this is likely where the oxide issue lies.  The problem is we have so much of this particular base metal heat and will likely have to continue using it.  I wanted to throw these results up to possibly spark some discussion on the following topics:

- theories as to what actually causes bearding on electrodes and/or other formations on the tip? (there appears to be 2 types of formations possibly, flake type and globular type)
- any suggestions on minimizing bearding
- what are the likely causes of the large oxides seen in the weld (base metal chemistries, which elements are worse, etc)
- if base metal and/or filler metal cannot be changed, what changes to make to help break up oxides into smaller pieces. (We have been testing electrode taper angle with some success on helping to break oxides into smaller pieces)
- thoughts of lanthanted vs thoriated electrodes with regards to electrode life and tungsten inclusions
[img][/img]

Hey Niekie,
We already x-rayed 6 pieces of bm and 6 spools of wire and did not find any tungsten.  we also cut out one of the inclusions out of the cladding, took the cross section and ground back to the inclusion and evaluated it using SEM.  Heres a link to the findings:

http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=220850;hl=

see first post.

We are currently trying to eliminate the large oxides we have been seeing in the puddle.  We think it may be due to our base metal cleaning procedure.  Will let you guys know how it turns out.

Hello bjbercaw, it's interesting that you mentioned that you saw "bearding" on the opposite side of the electrode from the wire addition side, wonder if that would indicate a base metal issue with regard to your electrode bearding, could this be associated with whether wire is fed on the front or the trailing end of the weld pool? Meaning that the base metal is possibly shedding or emmitting material during the arc application and this is precipitating onto the tungsten.
     Noticed that you also mentioned the use of thoriated tungsten... diameter? and would a change to another type of tungsten possibly be a more stable choice and possibly curtail the "spitting" that sometimes occurs with thoriated tungsten if it is used at an elevated current level for a given diameter? I have heard of hi-speed videography being able to capture quite a few different things relative to an arc. Any possibility that this could be introduced to your particular challenge to help you out with nailing it down?
     I do have another remote thought to put into the mix, any possibility of "arc blow"? Since this is somewhat sporadic, is there any consideration for this? When arc blow comes into play with most processes there is generally a destabilization of the arc column, which to my way of thinking could contribute to tungsten transfer with higher current levels. Thinking out loud again and throwing things out for consideration or to spark comments from others that are likely much more knowledgable than I.
From the type of inclusion that you have discussed I would not think that shielding gas is associated with your problem. Look forward to more discussion from yourself and others. Good luck and best regards, Allan

Hey Mike,
Good stuff. We are running high frequency start.  We have had issues lately with excessive oxides in the weld (ill attach a few pictures).  At first we thought it was from the base metal, but we are currently welding on an old heat of bm that ran really clean in a previous lot (100% yield), and we are still seeing the oxides.  So now we are leaning more towards wire because we also switched wire heats from the previous successful lot.  The large oxides sometimes stick at the toes of the weld, and when welded over top of, it creates lack of fusion which gets rejected at C-scan.  Im not sure if these oxides could contribute to causing inclusions, but the arc can act pretty wild and flutter pretty bad when it hits these big clumps. Adjusting the voltage from 12 to 11.5 helps to agitate the puddle differently and spin the oxides off the toes better and move them to the crown of the weld where they can get machined off. This is the only way we have been able to pass C-scan.  The main problem still seems to be the tungsten inclusions being rejected at X-ray.  We have done quite a bit of testing of our electrodes the past 2 months including metollgraphic (for oxide dispersement), chemistry (for thorium content), and weld tests, but no matter what we can’t eliminate the inclusions 100%.
I may have forgotten to mention that this is an 8 hour continuous spiral ID bore cladding where if it stops at any point its scrap (cannot restart). We currently are trying a 20 degree taper with a .050" blunt tip on the electrode (previosly 40 degree, .050 blunt tip), in attempt to change the location of where the arc is located with respect to the tip. If you look at the pics on my first post of this thread, you will see a spiral looking line on the taper of the electrode.  We noticed when this line intersects the tip of the electrode where the arc column is emitting, we get heavy erosion on the side opposite the wire.  By changing the taper we have been able to move this line further up the taper away from the tip and hopefully help to minimize the erosion.

The linear locations of the inclusions are pretty sporadic across the 20” pipe.  Some have been towards the start, mid, and end of the weld. We are also purging the entire ID of the pipe and running around 45 cfh at the torch w/ an oversized cup (1.25").  The gas itself is very clean, we have less than 1ppm oxygen at the torch and purge. We run all TIG welded stainless hardlines from a bulk argon tank.  It feels like a contamination issue but when you are rejecting an 8 hr weld for a single .005" tungsten inclusion, it could be a fly farting on the way by for all we know.  Its strange though we will weld 2 or 3 good ones in a row and then the next three will have inclusions.  In 2010 we went 25/25 good ones in a row, granted that was with different bm and fm.  At the time we were using VIM/VAR (triple melt) filler material, which ran very well. After we ran out of that heat, we had it duplicated the best we could and that's what we are currently using. Ever since we started using it though we have seen these inclusions and some porosity. We think we have the best wire money can buy, but maybe there is something in it that is just not wanting to cooperate.  We have also tested various heats of thoriated electrodes and all seem to be giving us similar issues.  Lanthanated electrodes is another option, but we have yet to investigate it much.

Since you brought up the shielding issue, I want to run another issue by you to see what you think.  We have three AMI stations and one AMET station that we use to weld a specific seal attachment weld.  We have recently discovered that we are getting porosity in this seal attachment weld when we use AMI 2,3 or the AMET station, but not when we use AMI 1.  The porosity is 100% all the way around the part. The porosity doesn’t start until the 5th layer each time as well which is important to note. Our gas system is a continuous closed loop system made of stainless hard lines. We bring flexible stainless from the main loop off of each station. The AMI 2, 3, and AMET station are all along the same wall.  AMI 1, however is across the room on another wall.  We have done quite a bit of testing trying to figure it out.  Praxair even came in with their ultrasonic leak checker.  We have also tried using argon bottles to take our gas system out of the equation.  Oxygen and water content is less than 1 ppm on all stations.  Likely unrelated but you never know.  We know its not a material issue because we have used the same bm and fm on AMI 1 and there was no porosity whatsoever.  We are testing flow rates right now. We haven’t had much luck pinpointing the issue, but whats interesting is the issue arose around the same time as the cladding.  I thought you might have some input.  Here are some other links to previous threads on this topic if you are interested. Thanks again. 

http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=220850;hl=\
http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=215476;hl=

Brett

Hey aevald,
Our standoff runs around .130 during welding from the original bm.  We use high purity argon 99.9995%.  As far as turbulence goes, its definiately possible. Do you know why bearding occurs?  Its interesting that we don't see it on every electrode, its sporadic.  From what I have been able to dig up on it, it seems like its due to mostly elements from dirty bm or fm precipating up onto the electrode.  I attached a picture of the bearding builing up on the electrode during welding.  We have seen this formation drop into the weld puddle yet passed with flying colors through x-ray.  Heres a little more background on the process:

- carbon steel pipe id bore cladding of 82h fm using GTAW
- 250A, 11.5V
- Xray requirement = .005 max tungsten inclusion
- cold wire
- 2% thoriated electrodes

We have recently switched taper angles on the electrode.  We have been seeing heavier erosion on the side of the taper opposite the wire. the tungsten inclusions we have been getting range from .01 to .03.  Its crazy though, when looking at some of the electrodes post weld that failed due to inclusions, its hard to believe a piece that large is missing.

[vid=youtube][/vid]

Hey guys, we are still working on trying to eliminate a tungsten inclusion issue in FM82H cladding.  We thought we had it nailed down to a specific heat of electrode, but have recently started seeing similar inclusions using a new heat so we are starting to think it may be due to something else.  We just had one of the electrodes that was used on one of the rejected parts analyzed using SEM and discovered a small piece hanging off the tip was tungsten. We have seen buildup or bearding on the taper in the past, but this really doesn’t appear to be the same sort of thing.  We have had the bearding analyzed before and it showed to contain no tungsten, only elements that have precipitated from the bm or fm.  See the attachment for pictures and SEM results of the recent test.  I was just wondering if you guys have ever seen this sort of thing on any of your electrodes and if you had any guesses as to what may be causing it.  The notable changes we have made since our last run with 0 inclusions was:

-new heat of fm
-new heat of bm
-new heat of electrode
-decreased tilt angle from 5 degrees to 3 degrees
-decreased voltage from 12 to 11.5V

Thanks
Brett

[img][/img]

I just wanted to post two pics of tungsten inclusions in inconel cladding (pic 1) and end buttering (pic 2).  we are using 2% thoriated tungsten electrodes (at least we should be).  you can see in the thorium in pic 2 (dark spots), but nothing in pic 1.  I have had both analyzed using SEM and results came back that pic 1 was pure tungsten, while pic 2 was tungsten w/ approx 2% thorium.  I am still investigating the actual electrode used on the clad to verify it wasn't a pure tungsten (it is highly unlikely this is the case).  I was wondering anyones thoughts on how we could be getting pure tungsten inclusion.  There is also a slim chance one sample was etched and the other wasn't, I am in the process of verifying this as well.  I am not sure if this would have any affect on the thorium showing up or not.  The cladding operation is an approximately 8 hr weld.  we are held to .005 max inclusions.  My thoughts were possibly the thoriated tungsten was breaking down over time exposing pure tungsten.  This is an AGTAW process and dipping is highly unlikely.  I thought someone may have some experience with tungsten inclusions on this scale.  It is also interesting how the inclusion in pic 1 almost looks like it melted. pretty interesting.  Thanks

Brett

[img][/img]

Hanre,

I got your PM today and so far, this is what I've been able to come up with... Now keep in mind that I'm not aware off the top of my head whether one or more of the welding codes or standards require a specific percentage of N in the shielding gas mix and below are mostly recommendations from various DSS producers... There may be someone else who may chime in with some reference to a code or standard where there is some specific amount of N to be used in the shielding & backing gases when welding 2205 DSS...

Cleaning the base metal prior to welding should be done properly and carefully... Scotch bite pads, or abrasive wheels are not recommended, or anything else which may leave a thin layer of any type of unknown residue for that matter... Any discs that were used on Carbon steel must not be used as the iron/iron oxide residue will contaminate & degrade the corrosion resistance... So use only dedicated grinding & surface cleaning discs/medium for Stainless steels and keep them clean!

Gas purity & Dew point are also important factors to consider in both the shielding & backing gases as well as gas flow from the torch (Gas diffuser should be used), and flow rates of both also... Thin stringers should be deposited as opposed to weaving the bead layer deposit...
Cleaning each layer should be done carefully no matter the thickness of the base/parent metal.

Here's a more specific paper regarding recommended welding practices for use on 2205 duplex from ""Sandvik" which will help you some...
It's titles: "Welding practice for Sandvik Duplex Stainless steels SAF 2304, SAF 2205 and SAF 2507." Here's the link:

http://www.sandvik.com/sandvik/0140/internet/se01280.nsf/0/ecd132de31b33bd085256bd5006d666b/$FILE/Welding%20Practice%20for%20Sandvik%20Duplex.pdf

Refer to page 6 for the recommended percentages of N in the shielding gas.

Now Avesta recommends either straight Argon, or Ar+2%N+10-30% He which is different than what Sandvik recommends to use for GTAW shielding their on 2205 Duplex...

Here's the link I'm referring to this .pdf on page 26 of 47:

http://www.engineersaustralia.org.au/shadomx/apps/fms/fmsdownload.cfm?file_uuid=EF9B0598-E8BE-B607-D9A0-96CF65BCB7D6&siteName=ieaust

And this one from Outokumpu on page 8 in this .pdf as well as the one below it also:

http://www.outokumpu.com/35058.epibrw

This one explains why increasing the amount of N may increase the amount of pores... So, up to 2% N is the maximum amount recommended... Meaning, less than 2% N is also something to consider in order to reduce the amount of pores... More than 2% N will not only increase the amount of pores (porosity) in the weld, but also increase the Wulfram (tungsten) electrode degradation at a faster rate than normal thus increasing the possibility of Wulfram inclusions in the weld...

The addition of up to 30% He is suggested in order to increase arc energy, and to increase welding speed considerably (20-30%) also...
Although, I would recommend a trailing shield if He is added to the shielding gas, and is used in a mechanized/automated application to limit the exposure of the still cooling weld surface area from being contaminated with gases that could become entrapped from the no longer shielded atmosphere...

Finally, the purity level of the Argon being used should be 99.995% or better especially when combining with the other elements to make up the shielding gas...
The backing gas can be either straight Ar or better yet, a mixture of 90% N and 10% H for certain applications, or straight N instead if one is concerned about Hydrogen absorption, and no amount whatsoever of H should be used in the shielding gas mix...
The amount of oxygen content in the shielding & backing gas should be below 0.25% or 2500 ppm (Parts Per Million)...
I don't agree with this amount... I would go even further to reduce the residual Oxygen on the root side to 0.0030% or 30ppm's.
The data is found on page 8 of 20 in this .pdf:

http://www.avestawelding.com/3756.epibrw

Look for shielding gas recommendations on page 3 of 4 in this .pdf from Techalloy:

http://www.techalloy.com/_assets/brochure_duplex.pdf

Now, I don't know for sure if this will be helpful for you or not because you haven't given us enough background info on your project but, you may also want to consider reviewing this .pdf as well covering "Qualification of welding procedures for duplex stainless steels." Here's the link:

http://www.complianceonline.com/images/supportpages/500768/sample_0402-29.pdf

Here is one of my favorite .pdf's regarding the best practices used in welding Duplex stainless steel and is from Stainless Steel World, and is written by
3 engineers from Fluor Canada... Refer to pages 58 & 59 in the .pdf:

http://www.kcicms.com/pdf/factfiles/duplex/SSW_DEC07_fluor_LR.pdf?resourceId=15

This one is from Stainless Steel World also... Refer to "4.4 Gases" on page 6 of 10 in the .pdf:

http://www.kcicms.com/pdf/factfiles/duplex/DA2_032.pdf?resourceId=14

Keep in mind also that when welding DSS such as 2205, the heat input must be controlled as well as the interpass temperature...
So for GTAW of SAF 2205: 0.5 to 2.5 KJ/mm is the recommended heat input, and the interpass temps should not exceed 200 degrees C.

Here's a very good Power point presentation by Sandvik from WPSAmerica.com and, refer to slides 21 of 44 to 26 of 44 as well as all of the other slides also:

http://www.wpsamerica.com/library/Welding%20Duplex%20Stainless%20Steel.ppt

This from Avesta Polarit/Outokumpu, titled "STAINLESS STEELS Their properties and their suitability for welding."
Look for pages 4 (6 of 11) and, page 6 (8 of 11) for both shielding & backing gas advice and Weld Defects/Practical Advice for GTAW of DSS SAF 2205:

http://www.outokumpu.com/applications/upload/pubs_113155252.pdf

This one is from Rolled Alloys... Refer to page 8 (10 of 16) for GTAW  parameters:

http://www.rolledalloys.com/trcdocs/corrosion/RA2205Bul1071.pdf

This Power point presentation in .pdf form has a very funny ending:

http://www.steeltank.com/Portals/0/docs/Grocki%20Duplex.pdf

This one is from Arc Machines International (AMI)... Scroll down to 1/4 inch diameter 2205 duplex, and read the shielding gas combinations used
and the conclusions of each mix... You need to also read the paragraph titled "Penetration Enhancing Flux":

http://www.arcmachines.com/applications/butt-welding-filler-material/duplex-stainless-steel-tubing

This one is from BOC Australia, and I would refer you to page 9 of 12 in the .pdf:

https://boc.com.au/boc_sp/downloads/gas_brochures/BOC_216521_Gas_shielded_ArcWelding_of_Duplex_Steels_BrochureAUS.pdf

This one is from the IMOA (International Molybdenum Association). Refer to page 48 of 56 in the .pdf:

http://www.steeltank.com/LinkClick.aspx?fileticket=8bPs5I0gTfw%3D&tabid=95

Finally, here's the Avesta Welding Manual... Refer to pages 78 & 92:

http://www.kskct.cz/images/materialy/en/avesta.pdf

Well, that's about it for me... So I hope this will give you enough ammo to convince whoever it is that needs convincing regarding welding practices of Duplex Stainless steels.

Respectfully,
Henry

A few answers

We have done quite a bit of work evaluating tungsten inclusions on SEM's, I'll say it's not outside of the realm of possibility to see missing alloy content. In tungsten it's possible for metal vapors to condensate on the electrode and "drip" into the puddle. Some alloys will form low melt point eutectics  on the electrode and seem to preferentially attack the tungsten. Thus the "drip" will not necessarily be 98-2 W-TH  I've seen one or two odd SEM results in which the tungsten inclusion had a very high concentration of a base metal alloying agent or no thorium.  Mind you this was with automated welding where dipping was never a likely possibility.  I would put it in the round of possibility however.  Sounds like the spec is very tight, I no nothing of the service conditions, but usually we go a step further and characterize flaw major/minor dimensions, I.E a drip in a fill pass is okay because it won't have sharp corners. An electrode tip is rejectable as it creates a big notch. Different code though.

Voltage  does not correspond 1:1 with electrode surface temperature. Current density has an upper limit, after a certain point the plasma column will simply rise up the electrode and cover a greater area.  I believe this is a function of electrode potential and temperature, as the temperature of the electrode increases the resistance goes up at a certain break even point it's easier for the electrons to flow from an area further up the electrode as opposed to trying to come off the very hot tip.  If it wasn't for this theory than electrode size would not have much to do with current carrying capacity, the thermal sink is relatively small between different sized electrodes but the surface area increases exponentially.

I think the voltage issue is unrelated and the difference seen in temperature at the point of your electrode with the changes in voltages you could produce would be negligible.

Isn't your GTAW arc voltage also used for controlling your Z axis/AVC ?   Changes in arc voltage are going to have a bigger effect in standoff distance (between the electrode and work.) 

Those are some crazy strict tollerances..   

What on earth can a 0.005 tungsten inclusion do to the mechanicals anyhow?

Hey guys,
We have just started receiving X-ray results from a group of parts we clad rougly a year ago and are seeing tungsten inclusions.  Our requirements are strict, .005 max inclusions, .015" max pores over a 8-11 hour ID bore cladding operation of FM82H to Carbon Steel.  We had one of the rejected parts cut up and evaluated 3 inclusions using SEM analysis.  The initial evaluation actually showed 100% tungsten w/ no sign of Thorium and we are using 2% thoriated tungsten. I have a feeling something is off with the results though because when we shot a group of tungsten with the XRF gun (including ones used on parts rejected for inclusions) we consistently showed 98% W and around 2% Bi, which probably is being mistaken for Thorium.  There’s a chance SEM may not have been able to pick up Thorium, but we are running more tests to figure that out. I guess the other alternative is the inclusions didn’t come from the electrode, and really is 100% W but I highly doubt it.   Looking at the electrode condition (looks good) it makes me second guess myself though.  Myself and another engineer were discussing how varying voltage changes the temperature of the tip of the electrode.  Increasing the voltage increases heat input into the part, but would that also increase the temperature of the electrode or would it decrease? I was hoping to get anyones initial thoughts/ideas. I will try to attach some pics.

Thanks,
Brett

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Just a few thoughts...

You mentioned you're using AGTAW; what is the active agent you are using, and could the porosity be originating here?

Have you considered going to a cryogenically treated tungsten? I have seen them used in cases where inclusions had been problematic with good success.

I would also think of looking at a trailing gas shield, and possibly reducing the gas flow on the primary shield to 40CFH.  Is there a specific area in the pipe where these defects seem to occur more often, or is it random?

Hey Lawrence,
Thanks a lot for your reply. I agree with you that heat of material should not have a direct relationship to tungsten inclusions.  I was thinking more porosity.  Here is a little more food for thought. The process is AGTAW with AVC. We are using an oversize cup so 50 cfh shouldn’t be too high. The tungsten is ground to a 40 degree taper with approx .050” blunt tip. I will try to attach a pic of the tungsten used on a part that showed a .020” tungsten inclusion at RT.  In my opinion, the tungsten looks great.  There is erosion at the side of the tungsten, but nothing that appears out of the ordinary. The tip looks fine measuring approx .050” as it did initially. The inclusions have us baffled for sure, so any further suggestions would definitely help because currently we are at a loss.  Has anyone had any issues with RT mixing up tungsten inclusions for anything else such as carbide by chance?
We dug up a bunch of info from the previous successful lot we ran (100%) and found we machined the parts ourselves out of solid stock, where all other lots have come in as pipe.  We don’t really know if there’s any significance to that yet but there is a night and day difference between that run and our current run. Those parts were also a totally different heat of base metal.  Other differences between that lot and our current lot include:
-  The wire used on both the previous successful lot and the current unsuccessful lot were both put through the VIM-VAR process. They were different heats however.
-  good lot ran at 12V, bad lot ran at 11.5V (made adjustment to help even out toes)
-  decreased torch tilt angle by 1 degree (made adjustment to help even out toes)

We went over our gas lines, which are all stainless. They all look good. Has anyone ran into any interesting gas issues? I am going to look into the last time our tank was filled but I know we buy the highest purity argon available and we haven’t had any other porosity issues. We have had the analyzer hooked up and everything looks good. We are purging the entire tube as well.  If you guys think of anything else, we would definitely appreciate it.  Thanks again for your suggestions.
Brett

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Hey Brett,

I don't see how tungsten inclusions and Heats/Lots/Melts of filler wire (GTAW I assume) have any relationship to tungsten inclusions... Tungsten inclusions come when the tungsten touches the work, or when it is overheated and "spits" into the work.

Now if your tungsten standoff (distance from electrode tip to work) is governed by arc voltage adaptive feedback systems (Z Axis)  ; A change in filler, a change in tungsten electrode alloy, brand or a change in included angle of tip prep, this could cause a change in arc voltage which would in turn change the stand off distance of the electrode, possibly causing contact with the work, If your voltage settings that control z-axis distance are pre programmed.

50 CFH is not uncommon in oversized gas lenses... If that's what your using.

Porosity (and it sound like your indications are very small) might be related to oxides, which may be delivered via your filler.  This may be why the triple melt was superior.  Those oxides may be on the toes or the parts of your clad weld that are overlapping. What is being called poroisity may be a little lack of fusion in areas where those oxides diddn't melt?????? (just a possibility)

Improving filler quality or (maybe cheaper) an improved argon coverage system, like a custom trailing shield, might improve those "porosity" issues.

Just some thoughts

We have had a particular welding application that has given us fits over the years. It involves automatic ID bore cladding FM 82H to a carbon steel pipe that's approx 20" long (flat position).  The weld is a continuous spiral clad (.056" stepover) and arc time is approximately 8 hrs.  The problem is the requirements we are held to is .015" max porosity and .005" max tungsten inclusions. We have had success in the past with different lots (with different heat of bm and fm), but our current lot we are running is not going too well. About a year ago we did a project where we discovered a heat of wire that was triple melted and ran much cleaner than the wire we were using at the time (not triple melted), and we achieved close to 100% acceptance. We tried our best to duplicate the chemistry and processing of the triple melted wire, and are currently using the wire that we developed from this project to clad the current lot. We have found that while this wire runs very clean compared to the wire we used to use that was not triple melted; we are now getting porosity and tungsten inclusions.  The indications are hit or miss with no real pattern in the part.  We are currently at about 50% acceptance for the lot. The part receives a UT Cscan immediately after cladding. When using the old wire (not triple melted), parts were mostly being rejected after c-scan for lack of fusion at the bondline. The ones that made it through were rejected for porosity and inclusions. The recent lot of parts we ran all made it through cscan but are failing xray due to the porosity and tungsten inclusions. We did have two make two changes to the welding parameters to get the new heat of wire we are currently using to run better and eliminate the lack of fusion that we were initially seeing.  We decreased the torch angle by 1 degree and lowered the voltage by a half a volt. We are using 50CFH 99.99% purity Argon.  The flow rate seems high but we have welded well with it before. I thought I would throw this on here to see if anyone may have some experience with this sort of situation and be able to offer any advice. Thanks. 

Brett

ASME is easy. A little harder than API 1104, but not much.

Visual Criteria:
Undercut - no problem - no limit per Section IX
Underfill - no problem - no limit per Section IX
Porosity - no problem - no limit per Section IX
Weld reinforcement - no problem - no limit per Section IX
Root reinforcement -no problem - no limit per Section IX (pipe does not even have to pass gas after welding)
Concave root surface - no problem - no limit per Section IX
Slag inclusion - no problem - no limit per Section IX
Tungsten inclusion - no problem - no limit per Section IX
Complete fusion - must have
Complete penetration - must have

My point is that ASME Section IX has little in the way of visual acceptance criteria. That being the case, any criteria imposed by the inspector has little to do with ASME Section IX and more to do with the inspector's personal opinion.

I do not perform my visual examination based on Section IX. I ask the client what construction code he is working with, i.e., B31.1, B31.3, Section VIII, etc. and apply the appropriate visual criteria as imposed by the construction code. My justification: I do not want a welder in the field or on the production floor that cannot meet the job requirements, especially if my name is on the paperwork. Most of my clients agree with my philosophy. It is too expensive to have to grind every completed weld to improve the weld profile or to go back and make cosmetic repairs.
I believe the welder has a right to know what the visual acceptance criteria is and what results are required to pass the destructive tests. The welder also has a right to know what he can and cannot do on the performance test. He needs to know if there are any limitations on what tools can be used (Bridge Code, no power tools), whether the tack welds have to be feathered (faired in some circles) per the applicable code (B31.3 High Pressure – Yes), etc. The welder is also required to follow a written WPS defining the range for the welding parameters, joint details, etc. There should be no surprises while the welder is taking the test nor should there be any once the test is completed. I provide the welder with copies of the visual acceptance criteria and everything I have mentioned. We review the requirements together before the test and then he is on his own. 

Good luck on your test.

Best regards - Al

However, ASME Section IX was not written by Prof. Silva Telles. ;) Ummmm, I truly believe that we can now continue the discussion in here!!! :) :) :)

With respect to 3.2, I believe he's referring to ISO's definition of what is a low alloy steel...

Various attempts have been made to distinguish ‘low’ and ‘high’ alloy steels, but the definitions vary between countries and between standard-setting organizations. As a general indication, low alloy steel can be regarded as alloy steels (by the ISO definition) containing between 1% and less than 5% of elements deliberately added for the purpose of modifying properties... Now ISO isn't the ASME, so Jeff is correct in his observation also.

Now here's an explanation that refers to AISI (The American Iron and Steel Institute) standards from the: "Key to Metals" website and clearly distinguishes the differences between plain carbon, low carbon, and many other carbon steels as well as the differences in various grades of low alloy steels also... Here's the link:

http://www.webcitation.org/5o9SDyEAb

Just in case the link doesn't function, here's the article from "WebCite":

Abstract:
The American Iron and Steel Institute (AISI) defines carbon steel as follows:Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium [niobium], molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 per cent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60.

Steels can be classified by a variety of different systems depending on:

* The composition, such as carbon, low-alloy or stainless steel.
* The manufacturing methods, such as open hearth, basic oxygen process, or electric furnace methods.
* The finishing method, such as hot rolling or cold rolling
* The product form, such as bar plate, sheet, strip, tubing or structural shape
* The deoxidation practice, such as killed, semi-killed, capped or rimmed steel
* The microstructure, such as ferritic, pearlitic and martensitic
* The required strength level, as specified in ASTM standards
* The heat treatment, such as annealing, quenching and tempering, and thermomechanical processing
* Quality descriptors, such as forging quality and commercial quality.

Carbon Steels
The American Iron and Steel Institute (AISI) defines carbon steel as follows:

Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium [niobium], molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 per cent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60.

Carbon steel can be classified, according to various deoxidation practices, as rimmed, capped, semi-killed, or killed steel. Deoxidation practice and the steelmaking process will have an effect on the properties of the steel. However, variations in carbon have the greatest effect on mechanical properties, with increasing carbon content leading to increased hardness and strength. As such, carbon steels are generally categorized according to their carbon content. Generally speaking, carbon steels contain up to 2% total alloying elements and can be subdivided into low-carbon steels, medium-carbon steels, high-carbon steels, and ultrahigh-carbon steels; each of these designations is discussed below.

As a group, carbon steels are by far the most frequently used steels. More than 85% of the steel produced and shipped in the United States is carbon steel.

Low-carbon steels contain up to 0.30% C. The largest category of this class of steel is flat-rolled products (sheet or strip), usually in the cold-rolled and annealed condition. The carbon content for these high-formability steels is very low, less than 0.10% C, with up to 0.4% Mn. Typical uses are in automobile body panels, tin plate, and wire products.

For rolled steel structural plates and sections, the carbon content may be increased to approximately 0.30%, with higher manganese content up to 1.5%. These materials may be used for stampings, forgings, seamless tubes, and boiler plate.

Medium-carbon steels are similar to low-carbon steels except that the carbon ranges from 0.30 to 0.60% and the manganese from 0.60 to 1.65%. Increasing the carbon content to approximately 0.5% with an accompanying increase in manganese allows medium carbon steels to be used in the quenched and tempered condition. The uses of medium carbon-manganese steels include shafts, axles, gears, crankshafts, couplings and forgings. Steels in the 0.40 to 0.60% C range are also used for rails, railway wheels and rail axles.

High-carbon steels contain from 0.60 to 1.00% C with manganese contents ranging from 0.30 to 0.90%. High-carbon steels are used for spring materials and high-strength wires.

Ultrahigh-carbon steels are experimental alloys containing 1.25 to 2.0% C. These steels are thermomechanically processed to produce microstructures that consist of ultrafine, equiaxed grains of spherical, discontinuous proeutectoid carbide particles.

High-Strength Low-Alloy Steels
High-strength low-alloy (HSLA) steels, or microalloyed steels, are designed to provide better mechanical properties and/or greater resistance to atmospheric corrosion than conventional carbon steels in the normal sense because they are designed to meet specific mechanical properties rather than a chemical composition.

The HSLA steels have low carbon contents (0.05-0.25% C) in order to produce adequate formability and weldability, and they have manganese contents up to 2.0%. Small quantities of chromium, nickel, molybdenum, copper, nitrogen, vanadium, niobium, titanium and zirconium are used in various combinations.

HSLA Classification:

* Weathering steels, designated to exhibit superior atmospheric corrosion resistance
* Control-rolled steels, hot rolled according to a predetermined rolling schedule, designed to develop a highly deformed austenite structure that will transform to a very fine    equiaxed ferrite structure on cooling
* Pearlite-reduced steels, strengthened by very fine-grain ferrite and precipitation hardening but with low carbon content and therefore little or no pearlite in the microstructure
* Microalloyed steels, with very small additions of such elements as niobium, vanadium, and/or titanium for refinement of grain size and/or precipitation hardening
* Acicular ferrite steel, very low carbon steels with sufficient hardenability to transform on cooling to a very fine high-strength acicular ferrite structure rather than the usual polygonal ferrite structure
* Dual-phase steels, processed to a micro-structure of ferrite containing small uniformly distributed regions of high-carbon martensite, resulting in a product with low yield strength and a high rate of work hardening, thus providing a high-strength steel of superior formability.

The various types of HSLA steels may also have small additions of calcium, rare earth elements, or zirconium for sulfide inclusion shape control.

Low-alloy Steels:
Low-alloy steels constitute a category of ferrous materials that exhibit mechanical properties superior to plain carbon steels as the result of additions of alloying elements such as nickel, chromium, and molybdenum. Total alloy content can range from 2.07% up to levels just below that of stainless steels, which contain a minimum of 10% Cr.

For many low-alloy steels, the primary function of the alloying elements is to increase hardenability in order to optimize mechanical properties and toughness after heat treatment. In some cases, however, alloy additions are used to reduce environmental degradation under certain specified service conditions.

As with steels in general, low-alloy steels can be classified according to:

* Chemical composition, such as nickel steels, nickel-chromium steels, molybdenum steels, chromium-molybdenum steels
* Heat treatment, such as quenched and tempered, normalized and tempered, annealed.

Because of the wide variety of chemical compositions possible and the fact that some steels are used in more than one heat-treated, condition, some overlap exists among the alloy steel classifications. In this article, four major groups of alloy steels are addressed: (1) low-carbon quenched and tempered (QT) steels, (2) medium-carbon ultrahigh-strength steels, (3) bearing steels, and (4) heat-resistant chromium-molybdenum steels.

Low-carbon quenched and tempered steels combine high yield strength (from 350 to 1035 MPa) and high tensile strength with good notch toughness, ductility, corrosion resistance, or weldability. The various steels have different combinations of these characteristics based on their intended applications. However, a few steels, such as HY-80 and HY-100, are covered by military specifications. The steels listed are used primarily as plate. Some of these steels, as well as other, similar steels, are produced as forgings or castings.

Medium-carbon ultrahigh-strength steels are structural steels with yield strengths that can exceed 1380 MPa. Many of these steels are covered by SAE/AISI designations or are proprietary compositions. Product forms include billet, bar, rod, forgings, sheet, tubing, and welding wire.

Bearing steels used for ball and roller bearing applications are comprised of low carbon (0.10 to 0.20% C) case-hardened steels and high carbon (-1.0% C) through-hardened steels. Many of these steels are covered by SAE/AISI designations.

Chromium-molybdenum heat-resistant steels contain 0.5 to 9% Cr and 0.5 to 1.0% Mo. The carbon content is usually below 0.2%. The chromium provides improved oxidation and corrosion resistance, and the molybdenum increases strength at elevated temperatures. They are generally supplied in the normalized and tempered, quenched and tempered or annealed condition. Chromium-molybdenum steels are widely used in the oil and gas industries and in fossil fuel and nuclear power plants.

So just using these two standards alone, one can see clearly the differences in defining various grades of steel...

This is from "Efunda's" website:

Steel is the common name for a large family of iron alloys which are easily malleable after the molten stage. Steels are commonly made from iron ore, coal, and limestone. When these raw materials are put into the blast furnace, the result is a "pig iron" which has a composition of iron, carbon, manganese, sulfur, phosphorus, and silicon.

As pig iron is hard and brittle, steelmakers must refine the material by purifying it and then adding other elements to strengthen the material. The steel is next deoxidized by a carbon and oxygen reaction. A strongly deoxidized steel is called "killed", and a lesser degrees of deoxodized steels are called "semikilled", "capped", and "rimmed".

Steels can either be cast directly to shape, or into ingots which are reheated and hot worked into a wrought shape by forging, extrusion, rolling, or other processes. Wrought steels are the most common engineering material used, and come in a variety of forms with different finishes and properties.

Standard Steels
According to the chemical compositions, standard steels can be classified into three major groups: carbon steels, alloy steels, and stainless steels:

Steels Compositions:

Carbon Steels: Alloying elements do not exceed these limits: 1% carbon, 0.6% copper, 1.65% manganese, 0.4% phosphorus, 0.6% silicon, and 0.05% sulfur.
Alloy Steels: Steels that exceed the element limits for carbon steels. Also includes steels that contain elements not found in carbon steels such as nickel, chromium (up to 3.99%), cobalt, etc.

Stainless Steels: Contains at least 10% chromium, with or without other elements. Based on the structures, stainless steels can be grouped into three grades:

Austenitic: Typically contains 18% chromium and 8% nickel and is widely known as 18-8. Nonmagnetic in annealed condition, this grade can only be hardened by cold working.

Ferritic: Contains very little nickel and either 17% chromium or 12% chromium with other elements such as aluminum or titanium. Always magnetic, this grade can be hardened only by cold working.

Martensitic: Typically contains 12% chromium and no nickel. This grade is magnetic and can be hardened by heat treatment.

Tool Steels:
Tool steels typically have excess carbides (carbon alloys) which make them hard and wear-resistant. Most tool steels are used in a heat-treated state, generally hardened and tempered.

There are a number of categories assigned by AISI (American Iron and Steel Institute), each with an identifying letter:

W:   Water-Hardening
S:   Shock-Resisting
O:   Cold-Work (Oil-Hardening)
A:   Cold-Work (Medium-Alloy, Air-Hardening)
D:   Cold-Work (High-Carbon, High-Chromium)
L:   Low-Alloy
F:   Carbon-Tungsten
P:   P1-P19:   Low-Carbon Mold Steels
    P20-P39:   Other Mold Steels
H:   H1-H19:   Chromium-Base Hot Work
    H20-H29:   Tungsten-Base Hot Work
    H40-H59:   Molybdenum-Base Hot Work
T:   High-Speed (Tungsten-Base)
M:   High-Speed (Molybdenum-Base)

http://www.efunda.com/materials/alloys/alloy_home/steels.cfm

Finally, this is from the Former Soviet Union:

Warning! The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.
Alloy Steel

steel that contains—in addition to iron, carbon, and unavoidable impurities—alloying elements, which are added to it to improve its machining or performance properties. Alloying elements are added to steel in various amounts and combinations (two, three, or more elements). Steel with up to 2.5 percent total alloying elements is called low-alloy steel; with 2.5–10.0 percent, medium-alloy steel; with more than 10 percent, high-alloy steel.

Alloy steels are classified according to structure or use. The following structural classes of alloy steel are distinguished:

(1) Steels of the pearlite class, which have the structure of pearlite or its variants (such as sorbite or troostite) or of pearlite with ferrite or hypereutectoid carbides.

(2) Steels of the martensite class, which are characterized by a reduced critical hardening rate and have a martensitic structure after normalizing.

(3) Steels of the austenite class, which have a sharply reduced austenite decomposition temperature, with austenite retained in the structure even at room temperature.

(4) Steels of the ferrite class, which contain elements that narrow the region of existence of austenite; such steels can retain the ferrite structure (sometimes together with carbides) at any temperature up to the melting point and after chilling at any rate.

(5) Steels of the carbide class contain an increased amount of carbon and carbide-forming elements; the structure of such steels is characterized by the presence of carbides (in the cast state, the ledeburite eutectic).

According to use, alloy steels are usually divided into structural steels, tool steels, and special-purpose steels (such as transformer, stainless, and high-temperature steels).

In the USSR, alloy steels are usually designated according to their chemical composition (for example, 18Kh2N4VA). The first number gives the average carbon content. For structural steel, the carbon content is given in hundredths of a percent; for tool steel, in tenths of a percent. The presence of alloying elements is given by the letter N for nickel, Kh for chromium, G for manganese, S for silicon, V for tungsten, F for vanadium, M for molybdenum, D for copper, K for cobalt, B for niobium, T for titanium, Iu for aluminum, R for boron, and A for nitrogen. The numbers after the letters indicate the approximate content of the corresponding element in percent. No number is given if the content of the element is about one percent or less. The letter A at the end of the designation indicates that the steel has a low sulfur and phosphorus content (that is, it is of high quality). The intended use of some steels is indicated by a letter. For example, R18 is high-speed steel with 18 percent tungsten, E3A is transformer steel with 3 percent silicon, and ShKh-15 is ball-bearing steel with 1.5 percent chromium. Some steels are designated by the letters EI or EP with a corresponding number (for example, EI69 or EP220); in most cases these are new steels undergoing testing and adoption in industry.

REFERENCES
Viaznikov, N. F. Legirovannaia stal’. Moscow, 1963.
Mes’kin, V. S. Osnovy legirovaniia stali, 2nd ed. Moscow, 1964.
Houdremont, E. Spetsial’nye stali, 2nd ed., vols. 1–2. Moscow, 1966. (Translated from German.)
Povolotskii, E. Ia., and A. K. Petrov. Proizvodstvo legirovannykh stalei. Moscow, 1967.

A. IA. STOMAKHIN

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

http://encyclopedia2.thefreedictionary.com/Alloy+Steel

In summary, it really depends on which standard one is referring to as well as what "neck of the woods" (Part of the world Giavonni. ;) ) one is from also as I only used three examples of many other examples out there in use or were used at one time. ;)

Respectfully,
Henry

Part A Fundamentals is closed book. It requires you to respond to the question base on the knowledge you have of welding, codes, NDT, welding symbols, etc.

That information is referred to as the "body of knowledge" that you draw upon based on your experience, reading, and training in the industry.

If you study radiography or if you have some working knowledge of radiography or experience looking at exposed RT film you will recollect that a tungsten inclusion represents something that is more dense than the carbon steel, aluminum, etc. and would allow less radiation to pass through. The less radiation that passes through the test piece, the lighter the image. In contrast, a crack that is parallel to the beam of radiation would represent less thickness (or less density) thereby allowing more radiation to pass through and produce a darker image on the film.

Best regards - Al

Looks like a tungsten inclusion to me.

Al

Hi all,
Agree totally with js55 regarding the density.
I still have a graph I have kept for years that has a perfectly symetrical 6 mm (1/4") long tungsten inclusion. Have no idea how the welder broke it off because the point of the tungsten looks as if it has just been sharpened.
On the crescent / half moon indications - the only time I have ever heard of those shapes on radiographs is fingernail marks on the film which show up as very dense.
Regards,
Shane

Hi Mike wiebe 3!

First off, "WELDCOME TO THE WORLD"S GREATEST WELDING FORUM!!! :) :) :)"

Man! That weld pool must be really hot enough to melt the W so much that it actually "swirls" in the molten pool!!! :) :) ;) Remember that W (tungsten) will melt @ approximately 6000 degrees F, or slightly less! ;)

Is the temperature of the molten pool that hot that the W inclusion will almost instantaneously melt and "swirl" around within the shape of the molten pool??? Hmmm... ;) Theoretically this could occur if the conditions were just right, and from what I read in previous posts regarding the welding being performed in completely inert enclosures, the possibility of the arc plasma itself causing the W to partially melt is plausible and it could indeed become a droplet that could quite possibly be stirred within the molten pool if the molten pool is agitated enough and the droplet doesn't have enough time within the temperature of the pool to solidify enough to prevent it from "swirling" around within the pool and resulting in "tungsten smear."

However, the conditions must be just right for this to actually occur IMHO. ;)

Respectfully,
Henry

Okay, I see what you are talking about.

So, tungsten inclusion would be indicated by a light spot on the RT, but, when Mike compared it to LOP, which would be a darker indication, you were 'confused' (my word/description) as to rather he had tungsten inclusion or some other kind of indication.

And, now I am as well.  If it truly shows as a LOP then it is darker which tungsten inclusion would not be. 

Some clarification should be in order in order to truly start coming to proper answers to the problem.

Thank you for responding.  I didn't put that part of it together till now.

Have a Great Day,  Brent