i can't seem to find a reference to tungsten inclusion for rejection of a weld. xray shows it very clearly but i can't find it in the Code manual.

been a long night!

thanks in advance

So you want to be a mirror welder ah, I have done this many times, on the bottom rows of convection boxes ,wall and roof tubes in the radiant sections in heaters and furnaces and weld after weld on boiler repair jobs. My suggestion is to first be a master of welding in the open right handed and left handed before atttempting to mirror weld (for rt quality production welds). I also recommend using gtaw for your process,better control and no speckling of the mirror. The practice method is the key, using a 2" or 3" coupon get use to runnig your root looking through the gap right hand and left hand from one focal point without the mirror.This is how your going to have to run your root in the field and is much easier once you learn how. When you master that it`s time to fill and cap. Start off not yet using the mirror but getting used to welding with the filler rod bent to the OD of the pipe laying in the groove and just walking over it. To further explain:( this is the trick of the trade that not too many welders know about) , bend your rod in a half circle making sure it is tight to the OD of the groove,this gives you one less thing to worry about(feeding rod), it also gets your rod feeding hand out of the way from your sight in the mirror. Practice this until you master it taking note on the heat your running and most important the timing of you movements from side to side and your travel speed. Then set up your coupons in a resritcted jig of some sort reletive to welding expected in the field. Non fusion and tungsten inclusion is your worst enemy. Check each pass before applying the next one and grind if you need to , just like you were in the field. My last suggestion is to not run your machine too cold, this will hirt you more than help you ( NON FUSION) run your normal heat. Gerald has already given you some excellent advice so I nead not go in to any more details. Let us know on your progress and if you need any help , just ask and someone will be glad to help you. Good luck and Have a good one!

Hello Daon!

I hope the info I posted in a previous post helped...

Does this inverter have a built in HF start/HF continuous feature?
I only ask this because, I believe it's important to compare what amount of watts are being drawn from the generator into the inverter when the HF start is on - when you start to weld, and how much is being drawn from your generator with the HF completely off - when you start to weld...
When you compare these amounts to what the manufacturer shows in either their manual or what their tech support people tell you, then you'll be able to find out whether or not it's either a Generator output issue or a problem with the inner electronics of the inverter... A couple of questions should also be asked so, I hope you do'nt mind...

Have you checked the connections to see if there is an opening or area covered by electrical tape somewhere on the cables? Is the voltage output from the generator consistent? Are the input voltage "jumper links" set to the appropriate voltage inside the inverter?

One other possibility is that either your inverter is'nt properly grounded when drawing power from the generator or that the work lead from the inverter is'nt properly grounded to the work or is too far from the actual welding location or the length of the cables connected to the torch are too long which might, and I say might be affecting the HF transfer to the joint...
You also may have HF "leaking" at the junction where the welding lead or output is connected to the torch...

You really do'nt need HF start in order to start your welds like mostly everyone suggested in earlier replies to this issue... I think flatjwl made an important point about where you should start your weld with regards to the joint geometry, in order to achieve high quality welds and not worry so much about tungsten inclusions showing up in the RT's... I only want to add that alot of times in my experience, I would make sure that everything is connected properly, and that all of the torch parts, including the tungsten itself, be relatively clean, and new... To make sure that the tungsten tip is grounded properly because, if the grounded lines on the tungsten are'nt in the direction parallel to the length of the tungsten, then this also can cause arc and HF starting problems... I would also if possible, first make contact with the tungsten to the work with the power off first then, either turn the power on by the means of a footpedal or the use of a torch mounted switch or a torch mounted - fine amperage control, without making contact with the pipe... These type of torches are readily available from a variety of manufacturers... I would also make sure that I have the correct size tungsten also...
Hope this helps out... Shalom!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

JTMcC, I`ve welded pipline myself ,before I got in to inspection and I have done inspection work on pipeline jobs. When you open your API 1104 Standard you will will see the first paragraph on page 1 states the differtent processes allowed, smaw,saw,gtaw,gmaw and oaw. As you may know with the exception of smaw these processes are very capable of internal reinforcement greater than .125. So API could in fact address this issue, instead of leaving it up to the owner of the equipment to detail a spec not allowing internal rienforcement greater than,say, .125. A large % of the pipeline work is still performed using the old E6010+,E7010,E8010 etc. These rods are fast freezing and will burn through and wash out the landing and the wall before exessive penetration is a factor. Maybe that`s why API has not added this to the accept/reject criteria. As far as the tungsten inclusion issue is conserned ,tungsten allthough it is metal, it is the "wrong metal" and is considered a foriegn object such as sand and many other materials that are not spelled out in API 1104 as a cause for rejection. Tungsten inclusion is often considered a volumetric imperfection and is accepted or rejected accordingly.

If there are no limits for tungsten inclusion and excessive penetration according to API 1104, every amateur welder can pass welder qualification and do anything with joints!!!
How is it possible API not to consider these two defects?

1. No limits defined for limit on penetration. The only ref is to burnthrough as defined in clause 9.3.7. But I did have a client whi imposed the limits for excess weld metal or "reinfoircement"as described in clauses 7.8.2/7.9.2
2. Tungsten inclusion is not defined as a defect as per API 1104

May somebody answer these questions?
1.According to API 1104, how much is maximum allowable root penetration?
2.Does this standard consider tungsten inclusion as a defect?
Please refer your answers to the parts of standard.

May somebody answer these questions?
1.According to API 1104, how much is maximum allowable root penetration?
2.Does this standard consider tungsten inclusion as a defect?
Please refer your answers to the parts of standard.

If you are experiencing gas inclusion in Hastelloy X welds made by GTAW, here are some guidelines :

(1) cleaning of joint preparation before welding with M.E.K. (*)
M.E.K. = Methy Ethyl Ketone (safest, cheapest and best cleaner for nickel alloys ; acetone will leave a thin film/layer on the metal that will vaporise into the weld pool)
(2) use a new pair of welding gloves , remove dirt / oil / ...
(3) don't use weld markers etc. on the weld
(4) lower the welding current , at high current the pool gets overheated and will include gaz
(5) if you're using a watercooled torch : take a look if ther's a little leak from where water can vaporize into the shielding gas

Don't blame the tungsten ...
Watch out with grinding dust from other metals (rust, carbon, dirt, grease, oil, ...) it may cause porosity and cracks

Excellent coverage of this topic. I'll repeat the info that we learned the hard way.

Porosity: Our experience with what you describe was cured by eliminating the use of abrasive cleaning (as stated above). If you have to do last minute cleaning only use a machining process (router bit) or stainless. We have gone to the use of 80/20 (Ar/He) gas in some cases. Truthfully though, I think we were not cleaning properly. We changed the gas and fixed our cleaning technique at the same time. I think the best step was making sure the cleaning was done properly.

Tungsten inclusion: Tungsten too small, technique unforgiving.

One last thing, experience in welding steel (no matter how good you are) does not gaurentee you will be able to do aluminum well. Charles Hall

To elaborate on the above post and to add the your cleaning process that is already in place: Clean the inside of the pipe atleast one inch back from the weld. Use stainless steel wire brushes immediately preceding any welding, everytime you stop, before welding again use the stainless brush. Running too cool (low amperage) will also cause porosity by allowing premature solidification of the weld metal. The tungsten inclusions can be caused by using too small of a tungsten. Aluminum sch. 80 pipe needs at least 1/8" or 5/32". If the tungsten is dipped, welding must stop immediately and the weld and the tungsten must be ground. Use a gas post flow if possible, check your flow meter (35-40 cfh). Check your cup size too. Porosity is caused by gas trying to escape the molten puddle, eliminate the source of the gas, keep the puddle molten long enough to let any remaining gas escape and you should eliminate your problem. One last note, check your equipment too, a leak or bad connection somewhere in the gas or water lines will give you fits.

Mike Sherman

In Al, porosity is generally caused by hydrogen. You need to eliminate all sources of moisture or hydrocarbons.

Have a look at your oxide removal again. It must be clean because the oxide attracts water out of the atmosphere. In addition, you must be carefull with the acetone. Some acetones have oils in that can leave a residue when you use it to clean with.

The Tungsten inclusions are basically a problem with welder technique. They must not scratch-start or in any other way touch the base metal with the tungsten.

Hope this helps.

Regards
Niekie Jooste

Again, without specific info, it's guess work at this point.

At 80 amps you will be near the upper limit for a 1/16" EWP electrode which may result in tungsten splitting and the possibility of contamination in the form of inclusions in the weld. The wave balance may also reduce the maximum current carrying capacity of the electrode depending on the polarity ratio (percentage of electrode + vs electrode -). As previously stated, the gas or gas mixture will make a substantial difference as well including flow rate, current, etc. If a helium rich mix is used then the flow rate will increase due to the lighter gas (He is approx. 10 times lighter in weight than Ar).

15 cfh is the flow rate of the gas (a good starting point by the way) depending on the gas or gas mixture and depending on the nozzle size.

20 psi is the pressure for XX flow rate, these are two different values.

MORE INFO if this weld is important to you.

Example:
A PJP corner joint with a 1/16" root opening welded in the overhead position will require much less current than a CJP butt joint with 0 root opening in the flat position.

In 1991 I was sudying for my CWI and working at an aerospace company that welded almost nothing but ducting for various aircraft/aerospace applications (Boeing). We welded a lot of Inco 718 as well, but most of the welding related problems were IJP or tungsten inclusions. Porosity was never a major problem to my knowledge.

Some situations actually required the electrode to extend well beyond the nozzle's end. There was no other way to obtain acces to the joint. All of the purge's, dams and trailing cups were home made. But the parts we welded were tested by radiography daily, so we had to be on our toes. I am also curious about porosity just being at the surface, have any of these parts been X-rayed (if the part geometry will lend itself to this method) to confirm if the discontinuities are only present on the surface? The cleaning materials may have something to do with your problem...

I did the same welds for another company in the 80's using simple welding power sources (no pulsing, squarewave, etc.) and porosity was not a problem here either, only the discontinuities mentioned above. If you have more info it might help to solve your problem. There are also some very experienced TIG welders that use this forum as well, maybe they can help.

Dale,

Thank you for more fully explaining the technical aspects of my advice about *cleaning* tungsten electrodes. I know myself to be longwinded in my responses at times, but when a topic is not fully detailed we get criticism in the form of posts such as the one above. Generally I ignore critics but this is a safety Issue, your swift and accurate words are a benefit to everybody who reads them.

The quality point that Guy did manage to make is this. One really ought to check out advice and be sure that the topical authority applies to the job at hand.

Now in giving this particular advice I used data gathered from first hand training and experience in the aerospace industry. Beltsanders are employed for cleaning aluminum deposits from tungsten electrodes all through the trades. Boeing, Lockheed, The United States Navy and Airforce all supply belt sanders to craftsmen in order to clean aluminum from tungsten electrodes. This is a black and white Issue and not up for debate. Putting aluminum onto a rotating grinding wheel is wrong and an unsafe practice. If you have been doing so please ask your shop supervisor redress the wheel or replace it.

Two nice links to grinder safety online for those who appreciate sourced material

http://www.tarleton.edu/~policy/safe0401.htm
http://www.ganoksin.com/borisat/nenam/grinding.htm


As for diamond wheels, the aluminum will just clog them up and quickly render them useless. Your boss will not be happy to pay for ruined diamond wheels at $100 bucks a pop. I have written several posts on the blessing a diamond wheel can be, but aluminum-welding operations are not top of the list for this type of equipment.

Furthermore, Tapping a pointed tungsten electrode on a steel surface will only fracture the point and make more likely the possibility for tungsten inclusion/contamination of the work at arc initiation. Tungsten is harder than steel-(any steel) and will be splintered and chipped rather than blunted by the tapping, the resultant fractured pieces, not being cleanly removed, are then ready to fall off into the weld puddle. Just try it once and look at the thing under magnification.... When an Electrode is cleaned and prepped with the desired angle, If you wish, you may remove the sharp point on the wheel or belt in order to achieve the desired tip geometry. Lanthanum electrodes are particularly susceptible to fractures so if you're using them this advice is extra important.


Lawrence Bower
Welding Instructor
United Airlines

http://www.aws.org/cgi-bin/mwf/topic_show.pl?id=1460 <---Here is a link to some discussion within this message board
focused on electrodes.

The specific reason that Thorium alloyed electrodes are problematic for use with Aluminum and Magnesium is that Alternating current (AC) is generally employed and the thoriated electrodes tend to decay if overheated during the reverse polarity side of the half cycle. This degradation of the electrode will manifest itself in two different ways. First the tip shape of the electrode will change mid weld and arc performance will suffer. Second and more important is the problem of tungsten itself transferring across the arc and into the weld pool and its byproduct of leaving unwanted inclusions. If your welding aluminum using DC straight polarity and helium than thorium alloyed electrodes may be an option. Other alloying elements, namely Zirconium and Cerium are blessed with performance properties which are more well suited for AC welding of aluminum and magnesium.

If you require *Sourced* Material, any of the following beginners GTAW manuals and standards have the necessary data

Modern Welding Technology by Howard B. Carey

Gas Tungsten Arc Welding by Lincoln Electric

Gas Tungsten Arc Welding by Miller Electric.

Guide for the Training and qualification of welding personnel, Level II Advanced welder.. By AWS.

Specification AWS A5.12

These two materials can be welded the same way. The inconel may need slightly more amperage. Shielding and backing gas will be argon. The shielding gas should be set to 15-20 cfh, the backing gas will be 3-5 cfh. You can use 2% thoriated tungsten, 1/16 or 3/32 in diameter. I would be more comfortable with the 1/16 diameter for the thin materials. Grind it with a long taper,if you are worried about tungsten inclusions then blunt the end. Just enough to remove the sharp point. You can expect to use an amperage range of 30-35 amps to weld this thickness, that is for a square groove weld. Your polarity will be DCEN. You will not need the voltage unless you are planning to weld this on an automated system. If that were the case than I would use a pulsing amperage of 40 over 20 with equall time on the high and low sides with 3pps. The voltage would be 8.0-8.5 with a wire feed rate of 6 ipm and a travel speed of 6 ipm. That would be a good starting point, you will than need to fine tune the program.
Fixturing will help, try to use copper hold downs and backing. If you e-mail me what you are doing I can give you a hand with some fixturing.
Good Luck