No answers here, but a few points to ponder:
Even tho You are working with DC it is not totally smooth DC like You would get from a battery. There is still some fluctuations from the 60hz primary current.
Materials that don't stick to a magnet are still acted upon by a magnetic field, that is how an old fasioned car spedometer works. there is a magnet turning inside an aluminum cup, the cup tries to rotate too, but is working against a spring. The needle is atached to the cup.
With regards to arc strikes and untempered martinsite, this is the cause of the rivet yoke failures I have mentioned on several ocasions. I don't know where to direct anyone to find proper documentation of it, but plain & short, the arc heats a small portion of the material above critical, and the heated material is quenched by the surrounding mass of cold material. If the material is hardenable, there will me a hardened but not tempered area with a stress riser [the arc crater] just waiting to start a fracture.

LOL!!  Third finger?  I don't know if thats the official name or not, but it works for me.

With regards to  Lawrence and  Geralds posts ....I misspoke when I said carbon steels...cause come to think of it, its always high alloys that seem to do it regularly.  4130 does it a lot, Inconels, ss etc.  That one idea of the types of metal that display it has the answer and the mystery.  I am enjoying reading the theories here immensely!   

The whole arc strike floating thing....hmmm  hard to see that as being it.  When I fail to to place a block or third finger (lol) on a very light part especially a polished one....a rash of arc strikes may be the result table side but no "boogie" to go with it.   And I agree with others comments that an inadvertent bump or touch can often set the "boogie" off.     A particular machined part I do on a regular basis will do it every single time on a certain weld joint if it is not somehow restrained.

Best regards
Tommy

I would go with semi-automatic

Machine/Mechanized suggests greater control by the machine/program than what you describe

Semi auto can be anything from pulling the trigger on a mig to... Synchronized pulsed GTAW with adaptive feedback, and multiple arc strikes on multiple surfaces within a programmed weld schedule.. The operators still makes adjustments on the fly, within the schedule.

Manual is well..... manual  :)

D17 is minimalist... this sort of question will be answered in A3.0  

Having said that... Bringing terminology in conformance with A3.0 is kind of an ongoing struggle for the folks who publish the codes.  It ain't perfect

Lawrence

"arc strikes will occur on the bottom of the work which can be a cause of untempered martensite in some alloys." I've heard this one before, and seen it, but cannot seem to find documentation on it. Do you happen to know a reliable book or source for this information?

Ok, I'm smellin what you guys are cooking here.  What about this though on carbon steel if you had a bad connection while tig welding a t-joint all it would do is put little arc strikes on the bottom of the piece and you wouldn't get any hopping.  I've never had a carbon piece get to ah hoppin on me.  Maybe because the arc strikes weld it to the table a bit easier then stainless and therefor creating a better connection.  Also what if the arc strikes that you find on your stainless if you find any at all are from the hopping.  For instance while it's hopping it's constantly losing connection by just a little bit.

hmmmm  I have experienced this phenomena on parts well over two pounds (always some sort of steel) but yea they do that boogie.   I have always thought this was due to heat input and some kind of kinetic distortion phenomena happening.  A quick lock down in the vice cures this.

I have noticed with tig in particular that laying upon the table does not nesseceraly mean a good ground. The Third Finger which I believe is what Lawrence is describing is an invauable tool to the tig welder.  A long piece of roundstock bent at 90 at one end and sharpened...the remander a long length with a crosspiece/bar welded to it so the 90 end will always point downwards with max weight and pressure.  These devices prevent the boogie and also help prevent inadvertent arc strikes from the part trying to get a solid grounding. Strange how this always in my experience applies only to steel (carbon, ss, what have you).   Yep you bet i am phising for some of those gurus to provide scientific explanation for this one.  this is a good post comon you guys

Ray,

Thats a good quesiton.  And boy have I had that experience.

I know it has to do with the L'ectricity flowing from the work to the table and a less than adequate connection. But I would also like to hear a more technical explaination.

I also know that if the connection is very bad that little arc strikes will occur on the bottom of the work which can be a cause of untempered martensite in some alloys.

For fine tig work on small pieces we do one of two things.... 

A small pinch clamp or a good sized aligator clamp with a lightweight braided cable that is attached to the table is a good thing to clip to your work if the work clamp is too heafty to attach directly to the work itself.

Secondly, a nice piece of heavy scrap (2x3x1") with a little piece of 3/8 round stock 10" with a 90 degree bend at the last 3 inches... The end of the roundstock can be laid atop the work will hold it down and control the boogie.

Tom  I could not tell you exactly what freq the arc start will be on DCEN but definitely on the majority of older machines it will be the same as the constant high freq but will last only say .5-1sec.    The problem here in lies with the amount of current flowing thru a given conductor with this high frequency superimposed over it.....more current equals more wattage therefore more transmission power available thru the open air to be captured by other conductors like circut boards in CNC equipment.   Most CNC equipment built after 1980 or so (please dont make me pull out NEC code) is rated for a certain amount of shielding capability on the controls.  Modern stuff is well shielded against interference.  The problem specifically occurs when there is a reasonable wattage (think power) radio freq transmitter is nearby.  The power (wattage) is high enough to induce emf (electro motive force) in anything conductive nearby.  This in turn can induct  current in said conductors and cause failures.  Most electronic circuts built on the principals of the transistor only require .7 volts or less to function.  A high wattage radio transmitter can easily induce more voltage than .5 volts in a nearby conductor.  Therefore high freq ....it can shut it off or do any function inadvertently that can occur by the push of button on its controls any other device which functions on a solid state circuitry built on the premiss's of less then a volt unless its properly shielded by modern technology.  

A great example of this is the cheap cd boombox attached to my toolbox...it works fine most of the time but when I am playing a cd sometimes when welding aluminum (only aluminum) it will shut completely off an arc start....it laks quality shielding   Well imagine having two or more hours into a program on a cnc and the welder strikes an arc and its GONE....That is a reality Tom Cooper....on newer machines I do not see it happening.......but anything pre 1985  you betcha.....and even on modern machines if the shop electrical supply is improperly setup...a good backfeed could cause the same result.  Look in the CNC cabinets do you see coaxial wire and aluminum strips on the cabinets.

Now as far as making shielding to prevent such I say look at the common coax cable built from space technology......a conductor inside a shield which is also part of the signal.    The reason that shield works is the woven strands...geometry....opposite directions but still connected....ok you see the idea...it has to do with magnetic poles and how radiation can can conduct itself.    If the shielding is aligned 90 degrees against (each other' itself":molecularly" then it will cancel itself out in propagation (wattage) from the source.  It works the same essentially with an induced signal ......the cross conductors eat away the influence of the signal power wise.  So in other words a ferrous conductor woven in the traditional basket weave method makes a powerful shield against any high freq or other radio signal now matter what the wattage for all intents and purposes.

So in summery I can say without question the fears of your machinists are grounded in hard scientific fact.....check to make sure their controls are safe before venturing into their space.

Here is how I see it,  No physics, just rubber meets the road.

GMAW Axial Spray:
The higher the relative voltage the longer the open arc.  The longer the open arc the more metal is volitized and the greater the opportunity for the atmosphere (Oxygen/Nitrogen) to mix with the volitized metals.  The byproduct of (relative) high voltage GMAW is greater smoke.

This is why I prefer a consistant light crackle when I run spray transfer GMAW. (Edit: others prefer a quiet arc, including the Hobart institute who I hold as the best presenters of entry level welding media)  The crackle along with the ability to see a pinch at the end of the electrode wire tells me that I have spray transfer with the shortest arc length possible. Too low voltage will cause globular transfer or at high wire feed rates may cause short circuits that cause spatter. 

Other benefits of minimal (relative) arc voltage for GMAW spray is a reduction in undercut.  The longer the spray transfer arc, the more bell shaped the plasma column becomes, until it the arc width exceeds the toes of the puddle and begins to eat away at base metal.

Minimum relative arc voltage... Just means the minimum voltage required to get spray transfer versus higher voltages that produce longer open arcs but still produce spray transfer (or high and low voltages within WPS parameters)...  Gas has it's effect too.. Optimum arc voltage with 98/2 will be slightly different than optimum arc voltage for 90/10 or 85/15.

In short... Reduction of voltage within operating parameters will reduce smoke.

As far as push VS drag...  Well I just don't see any positive reason at all to run a drag travel angle for Spray transfer GMAW with carbon steel (but I do see lots of negatives)  so I won't consern myself with that part.

Globular??  Why would anybody run globular transfer in production on purpose...?    I demonstrate it in order to show welders how to avoid it.  But I suppose the arc is more Chaoitc, often globular transfer is due to over high voltage with CO2 which will cause a repelling force which is why most globular arc plasma is so chaotic in the first place.  When spray transfer gasses are used and voltage is too low, globular transfer also occurs, in this case the tip of the electrode wire balls up and sometimes that large droplet will not detach before it strikes the weld pool, causing spatter and great disturbance in the arc colum which might contribute to smoke.

Tom, we've done tons of "similar" seats in my shop and I admit, we've had only limited success.  Just a couple of comments to consider, which are likely extraneous to your condition; we do PT's on this stuff to avoid arc strikes altogether.  How is your preheat being applied?  Previously, we used an industrial oven and brought our parts to in excess of 500F for thicknesses in the range of 2 - 3" this has proven burdensome and we've recently acquired some wonderful induction heating equipment from Miller but have yet to try it out.  In my own experience, you need to slow cool this stuff also.  In our case, we post bake at around 450F for an hour per inch (commonly referred to as a hydrogen bake out) but again, this may not be applicable in your case although it may help reduce residual stresses before reaching room temperatures.  Avoid mechanical finishing after overlaying if possible or, if you must, use a watercooled bench grinder instead of a lathe or manual tools.  The list goes on and one but as I mentioned, this may all be extraneous to the issues you're experiencing.  Good luck!

Tom

I recently watched a commercial testing lab perform  "Arc Strike MT" on several valves and fittings.   These pieces were to be heat treated in subsequent operations.  I was shocked and asked the Lab why they would do this.  They actually played dumb, and continued to arc strike during the whole week I was there.  (They were not doing this on my job, so I couldn't say much more.)

One of my customers makes Nuclear Power Reactor Valves.  They have Prod type MT performed on their "Cast-to-near-net-shape" & "then forged",  valve bodies and require the supplying company to do MT and certify that it has been done.  Then, upon receipt of the valve body, they perform an inch by inch visual insppection for arc strikes.  Then they perform their own specail type of heat treatment.  If there are any copper depositing arc strikes from the MT operation, the copper can melt, combine with the steel and cause shallow cracks.  These valves seats are actually then welded while the valve body is at a very high temperature, so that when the valve body is cooled, the welded seat is in compression.  I was told that even a little copper contamination can cause cracks.  These cracks are usually shallow.

I have always known that copper melting on steel can cause cracks. A contact tip melted into a molten weld will cause micro cracks that can coalesce into larger cracks.

The copper deposits cannot always be easily detected, thus the vigorous visual inspection.  If there are any cracks on these valves,  when they are finished with the welding and machining, they are permamnetly rejected.  No repair is permitted.

I recommended a prod made by a Swiss company that does not arc strike but the Customer would not allow any changes.

CWI555 - recently on a different job, we were playing around with a central conductor type MT inspection. Our setup was very clumsy and in a very awkward position - we got arc strikes!!  Wasn't aware of the lead pad idea. Thanks for that.

Now an arc strike from an MT power supply is not very intense, so I can see where a trace of copper could be slightly burned in from a low spark, but how could this "contamination" result in cracks that propagate to a 1/4" deep?
Thanks.

The bridge tack to the best of my memory (16years ago) consisted of 1/4"thk x 3/4" wide strips. I think about 3 on smaller pipes 8" and below. I'm sure more on larger pipes although I was only in their fab shop a couple times and it caught my eye on their methods. They tacked the temporary attachments to one pipe, placed a gap spacer, then brought the next pipe in made the fit and tacked it off.
They would weld up to the bridge, stop and remove the bridge steel then resume until the next or the top. I am not suggesting all Brits did this as I only worked the one job there but I do think that was their way especially the small wire on the root pass. As far as the arc strikes Allan, I do not remember how particular they were about that for their work. If we ever used temporary attachments or inadvertant ark strikes in the nuclear plants there or here we had prior approval for the temps and had visual and usually NDE upon the removal. We did not weld outside the groove without approval.

Out RT's went well but they killed us with UT. Babcox and Wilcox NDE I think they used 7 different transducers. I didn't pay much attention to the details on the UT back then Just think they were still mad about the revolution and all. I was told B & W bid on the work that we did and maybe didn't like the yanks taking their work. Or maybe we had I. F. Never seen UT that sensitive. We never saw the indications with our eye. Doesn't mean it wasn't there. I prefer the RT. At least I can see the film. I am not UT qualified.

Hello swsweld, I do have a question about the method that the Brits used. Was there any concern for having situations arise from tacking these bridges to support the root gap? We have all had exposure to arc strike conversations and I am curious if this type of bridging method could introduce any of the issues that arise from arc strikes as far as leaving residual stresses or introducing any possibilities of fractures. I'm just curious and wonder if you have had any conversation in this regard? Sorry to take this post off track but the question came to me after this post. Regards, aevald

makeithot

Nothing to add really to the good posts above...

Reason to change the setting:  If you arc wanders, flutters, flashs and (all connections are good especially ground, tungsten in proper shape, gas, elec supply etc. parameters are proper) then increasing intensity can bring back a more desirable stable arc and increase its ability to start easily (machine without arc start boost).  Why not just keep it at max all the time??  Well you are more prone to get inadvertantly bit (shocked) and increase chances for arc strikes on the ground side (think part laying on table).  I always run it as low as it will run well....put a lead twice as long on the machine or a heavier lead and you might have to crank it up a bit to get the same results. 

Hope that helps
Tommy

Hello Stephan and batanony;

I bet there is an English translation for Curie's work somewhere. Now all I have to do is an internet search to find it.

You have to remember, we Americans don't have the linguistic capabilities many Europeans do. I tried Spanish in High School. My instructor told me that I was the only person in her twenty-seven year career of teaching Spanish that she had to ask to take a different subject. "Alberto, you my friend will never be able to speak Spanish." She would die laughing to find out I now teach a welding engineering course in Venezuela. Luckily, I have an excellent translator (when she's not laughing at me).

My daughter is a chip off the "old block"; she took several years of Spanish. She had a Spanish roommate when she attended college. Jill tried to impress her when she first met her and tried to converse with her in Spanish. The young lady looked at her in surprise and said, "Jill, I think you're trying to talk to me in Spanish, but trust me, you aren't!" I'll never forget that look!

batanony;
You might want to use a non-conductive ceramic backing in place of the copper guide. It is a common problem; trying to stay in the groove when welding underwater. However, the copper will cause the carbon steel weld to crack if the welder in advertantly strikes the arc on the copper and some of the copper enters the weld puddle. The ceramic backing can be obtained as round or recangular bars. Some have adhesive on on side or aluminum tape to "stick" it to the underside of the weld. Another trick is to "tack weld" a welding rod (with the flux intact) beside the weld groove to act as a guide istead of using the ceramic backing. I used to use the "welding rod trick" on welding tests and it never failed to "amaze" the inspectors because the cover pass beads were perfectly straight and uniform.  

I use copper, introduced into the weld puddle, to make cracked weld samples for NDT training.  

Best regards - Al

Hey Sourdough, did you mean to say "arc strike", just curious? There are a couple of threads that have gone to fairly great lengths to discuss the pros and cons or possible damages that can result from arc strikes. Just wondering. Regards, aevald

The original question was "Has anyone else experienced faulty UT indications due to the different material types?  If so, what was done to remedy the situation?" Actually we need more information. He didn't state where the transducer was located when he saw the indications. Where are the veins located and what is their orientation? From what side of the weld are you seeing the indications? Is it the clad or unclad side. Your description says only one side is clad. Have you tried polotting these indicaitons to see where thay are located?
If you are seeing it from one side and not the other side you can pretty much rule out planar flaws (almost). If you are seeing it from the unclad side it is most likely the interface of the cladding. It is difficult to tell without actually having your hand on the transducer. I am having a hard time understanding why one side is clad and the other is not.

Of course when sound passes from one medium to another you will have reflection, refraction and mode conversion. The angle change is directly proportional to the velocities of the two materials and the mode of propogation and the angle of reflection is equal to the angle of incidence.  If the velocities are the same there will be no change. If the velocity increases so will the angle and so forth. But when I say there is reflection and refraction, I mean the sound will reflect out and not back to the search unit unless it strikes something that will make it reflect back to the search unit like a flaw.

Then again, if nothing shows up with PT after excavation, it's possible that you are removing the defect when you excavate.

Weld progression is stated on the WPS that you are testing to. Normally uphill. Pipeliners downhill.
Yes you should start at 6 and end at 12.  Usually four tacks. Feather all tacks, especially your starts. Makes it easier to tie into. Don't set gap too tight or you will not get the penetration you need to pass xray. Most testing supervisors will not allow grinding on the I D. Get a good fit. A little hi-lo on the fit-up can cause internal undercut. Make sure you get some penetration on the ID(1/16 is ideal) Grind the root pass thoroughly to remove most slag, undercut, irregularities, etc. Do not grind so much that you will burn through on the hot pass. Fine line there. I put my hot pass in with 3/32 7018s some people use 6010 on the hot pass. If you use 7018 grind your start at 6 before you start up the other side. After the hot pass I run fairly hot but not too hot. Remove slag completely every pass, remove porosity if you get any, avoid undercut, fill out completely (you can bust out for underfill on the cap) arc strikes only in the groove, if you cap with stringers overlap them more than 50%, do not leave valleys between beads. Plan your bead placement, don't leave a sharp corners at the toe of the welds it will trap slag, try to fill coupon just below flush before you cap it.

I do not grind all starts and stops throughout the test, shouldn't have too. Just chip the slag at the stop before you restart the next rod. If you grind too much the tester might question your ability. I've taken test with only a file no grinder after he accepts fit-up.
Remember xray sees almost everything. If you can see it, remove it. Check with the test shop supervisor to see what he allows and does not allow, (grinding,hot pass rod, ? much penetration)Try to stay calm, keep it clean and good luck. Let us know how it turns out.

Bert,

Welcome to the forum,

Forget the points, they have nothing to do with tungsten spatter.  If the arc strikes when you hit the foot pedal and you are not observing rectification (very rough AC arc) than the points are dandy.

Sounds to me like the electrode is overheating

A water cooled torch will help.

A full length 3/32 or 1/8  Zirconium or Cerium electrode will help as they can carry much more current than a pure tungsten.

If you have balence control set it to 7 or 8 to keep more heat off of the tungsten.

Isopropol Alcohol or Acetone are preferable to thinner (less residue).

Try that and let us know what happens.

Good Morning,

I suggest to get some practical visual examples of what might go wrong from the defects you mark up, A while ago, I think John or someone had an excellent post about cracking caused by arc strikes. Furthermore anything that is subjected to vibration should be virtually 100% defect free, this is just fracture mechanics, Just do some reading on cyclic stresses and you will see the dangers of stress raisers in service where it is subjected to vibration. Vibration is the breaker of all structure, sooner or later, so you have to be prepared for the worse. We weld subsea pipelines and yes we also want the most lenient criteria for a job, but all our welds are subjected to very severe testing before these criteria is established. Stick to your guns and mark it up, and read about the cause and effect of failures, and if someone then asks you: " do you know?" Then you can give a clear indication of what might happen in similar service conditions.

http://www.key-to-steel.com/default.aspx?ID=Articles

here is a link with some general Steel Properties and Fracture mechanics etc etc

here is the link to the sicission on arc strikes and subsequent cracking
http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=58419;hl=arc%20strike%20crack#pid58419

Goodluck

HF

arc strikes are not permitted in any aircraft work.......simply I presume for the possibility of stress cracks forming in the parent material....sure sucks ass when im doing aluminum

One consideration that hasn't been mentioned (at least I didn't see it) is the condition of loading, i.e., is the load static as in the structural frame of a building, or cyclic as in a bridge or piping system that undergoes thermal cycles or variations in pressure?

An arc strike adjacent to a weld that is subjected to static loads is not going to be a major concern. If the load is static and the arc strike is in an area subjected to compressive loads, it is even less concern.

The same can not be said for an arc strike on the exterior of a pipe. The vast majority of piping systems are pressurized, thus the OD of the pipe is subject to tensile hoop stresses. Most piping systems in a power plant or chemical plant are going to undergo fluctuations in pressure or temperature or both. A bridge structure or supporting structural framing for a crane is going to be subjected to cyclic loads. The piping system, bridge structure, or the crane system are the "worst" case for arc strikes located in areas subjected to cyclic tensile stresses. Anything resembling a notch type discontinuity is going to affect the service life of the structure. The notch could be undercut, overlap, changes in geometry, and yes, metallurgical notches associated with arc strikes and the HAZ of the welds.

This sounds like a good project for someone with access to a fatigue testing machine. Even if there are papers that already have looked at the problem, it would still be a good exercise.

I do a demonstration for my courses with E70S-X filler metal for GTAW. I cut 1/8 inch diameter wire in to 18 inch lengths. One third of the group is left round. The second third of the group is filed with a flat in the center of the length on one side about 1/32 (or less) inch in depth (no sharp corners mind you, blend the flat). The last few rods are nicked in the center of their length with the corner of a rectangular mill file so the notch is the same depth as the rods that were filed with a flat. 1/3 of the class get rods that are round, 1/3 of the class get rods that have a flat, and the lucky few get the rods with the notch. Each group grasps their pieces of filler metal at the ends and bends them back and forth until they break. The round rods provide a real workout. Make sure everyone tracks how many times their piece is bent back and forth. The results are surprising even to those that already recognize the notched rods will fail first. It drives the point home of how much influence a notch or change in geometry has when subjected to cyclic loads.

Best regards - Al

David,
I would, honestly, have to leave that possibility open. Since, my sources for what the research actually says is not my own reading, unfortunately, (because I have as yet not found the D#&$ thing in my library, although I know I have it somewhere), but quotes from other knowledgeable individuals. Though until proven otherwise I doubt it, considering the title of the document is "Visual Weld Acceptance Criteria", with no mention of Section 11. And in small print at the top of the title page it states as topics "Nuclear Power Plant, Construction, and Inspection." Nothing about Inservice Inspection. AND, in my opinion seems to be very consistent with D1.1's approach where grinding and visual inspection is acceptable. And since the idea was origianlly expressed to me by a gentlemen who sits on D1.1 it is clear that at least some of the committee members have read and assimilated the document and accept its conclusions. Perhaps more than a few.
But if so, what an interesting tangent. Though I know this wasn't your intent. For, if a flaw is considered irrelevent in accessing the ID in a pressure boundary application such a piping, is that flaw relevent at all? Doesn't every compromise of a pressure boundary have to access the ID at some point? Even if it is a sudden catastrophic failure. Would EPRI, under a study for ID emphasized Section 11, as you state, conclude that arc strikes are irrelevent to inservice inspection if catastrophic failure were possible?

Many of the arguments in this thread seem a bit messy to me. There seems to be a consensus for a real concern for arc strikes and the catastrophic damage they can cause. Yet, at the same time an implicit assumtion that the AWS requirements are acceptable. Can visual examination really reveal the extent of cracking?
I would have to argue that an acceptance of AWS's requirements for arc strike evaluation is not consistent with a maximum concern for catastrophic failure due to arc strikes. I would say that the quoted pipeline or military specs ARE consistent with this concern. And I would conclude that I think the truth lies in the middle somewhere and that concern is engineeringly justified based upon material and application. In other words, sound engineering judgment. In other words, consistent with AWS (do we really want D1.1 to break out each possible application and material seperately?) and EPRI (should EPRI be concerned with military applications?). Do we want arc strike requirements on non bearing columns or beams, mini storages, or plant air and water lines to be consistent with main steams, submarines, and natural gas lines?

Nothing drives a lesson home like a demonstration or an example of the topic being discussed.

I would love to see the pipe.

I have performed PT and MT on some arc strikes. On occation I've seen some small surface cracks, but none that had any appreciable depth. Seeing is believing and anytime you can show a real world example, it takes the wind out of the nay sayer's sails.

Best regards - Al

darren says:

i just wish there was a way to impress people in the industry to be more careful and not let the arc strikes happen in the first place, because repairing one is not so bad but repairing hundreds from careless tacking drives a guy nuts.

I says:

There is and it's been effectivly employed for decades in cross country pipeline construction. Arc strikes are a cut out, repeat offenders are fired. It's a simple system.

JTMcC.

some of the third party inspectors that go over our final product will let some obvious flaws go through the door but stop the advancement on the TINIEST of arc strikes because for whatever reason the purchaser of the product has it in their mind that the entire thing will fail if there is an arc strike. and in the end it doesn't have to make sense we just have to get paid, and its the customer who is always right.
after reading the thread there are obvious places an arc strike would matter but i am sure it is a lot less then standards would dictate. have a friend in russia right now and they butt all their pipe together weld with 7018 and if it leaks weld over the leak. he says its crude but seems to be working. so somewhere between the too much control sometimes exercised in the first world countries and the total lack of control in second and third world countries would probably be the best.
but i am just a simple welder and have to rely on the experience of the industry as a whole to keep me safe and keep the products that i work on effective and safe for the end consumer. so no arc srikes is no arc strikes.
i just wish there was a way to impress people in the industry to be more careful and not let the arc strikes happen in the first place, because repairing one is not so bad but repairing hundreds from careless tacking drives a guy nuts. (a lit rod is not a flashlight to be used to find the next tacking spot while your helmet is down)
darren

I concurr Bozak!

The USN is especially serious when it comes to arc strikes anywhere in or outside of the "Boat" or as everyone else call them - ships!!! I wish I had a nickel for every arc strike I repaired on submarine hulls or inside either within the pressure hull or in the aft or foward main ballast tanks... Then there's the arc strikes that hold pipe hangers or any other weldments that the Navy inspectors wo'nt sign off on so in go the mirror welders like myself that make these type of repairs in some of the darndest places... Cost overruns anyone?

Unfortunately, some of the folks that worked @ EB were classic cases of the wrong person for the job and some of them were basically NUTS!!! I mean, if they got suspended for missing time or insubordination, these poor excuses for human beings would literally commit sabotage within the confines of these submarines!!! The end result was costly repairs to total rip outs of parts, components, piping to complete trim ballast bottles that were situated in between certain hull frames in various compartments within the subs!!!

If they caught these scum or found evidence that they were implicated in doing these childish acts of intentional destruction of government property then, they were handled appropriately and prosecuted to the fullest extent of the law!!! This type of sabatoge was one of the main reasons why the Los Angeles and Trident/Ohio class - attack & FBM's took so long and cost so much to make asides from the fact that the technology incorporated into these boats at the time of their construction were at that time -state of the art and the prototypes just took longer to complete -PERIOD!!!

Now do'nt get me wrong folks!!! Most of the personnel that worked in hte yards @ EB were very patriotic and focused in their work there... However, all it takes is few isolated incidents where intentional acts of revenge or outright stupidity to delay and increase the costs of such a sophisticated compilation/integration of very complex systems and subsystems that make up the components and parts of a nuclear powered submarine!!!

In summary, after the loss of the "Thresher" and the "Scorpion" submarines of the USN, Rear Admiral Hyman Rickover instituted the USN's SUBSAFE program of quality control that is very strict as Jon mentioned... In fact many civilian code governing bodies have adapted many of the programs strict controls...
That is why most of the ASME nuclear code standards originate from similar standards used by the USN's SUBSAFE standards... Walk into any commercial Nuke plant in the US and most of the folks working there are ex-navy nukes!!! Did anyone ever wonder the reasons why??? Figure it out!!!

Respectfully,
Henry

Gerald,

Since you refined your question I had to think myself. 

Even though I have no worries about thorium and radioactivity. None.  I still purchase Cerium and Lanthanum for my DC- usage...

...bottom line, I purchase no thorium.

Stephen,

During my career in the Aerospace field I was part of a team that worked with Sciaky Accuweld automated GTAW equipment.  Many of our projects required adaptive feedback monotoring of Arc Voltage integrated into controls for the Z-axis (realtime adjustment of electrode distance from work)  Our requiements were very strict because 1/10 volt fluctuation could cause the electrode to dive into the work or lift away so far that problems occur. Even a few degrees difference on the included angle of the tip prep would cause significant differences in arc voltage in relationship to axces control.

We did trials on tungstens during R&D projects, some programs could run as many as 300 arc strikes from a 0.040 tungsten electrode with each arc strike required to be perfect in order to heat a very small weld area. Other trials were single arc strikes that would run as long as a 6 or 7 hour duration with synchronized pulsation on buildups of large diameter (0ver 50 inches)  thin (some lands as thin as 0.025) knife edges composed of inconel 718, Hastelloy X, Inco 901 and titanium air seals. We found that nothing worked even close to lanthanum. All other mixes tended to gather a sort of *oxide dust* at the tip that would eventually distort the arc and cause voltage fluctuations.

The worst lanthanum electrodes (due to differing powder metallurgy practices in production) were overly ductile (something you don't want in a tungsten) and tended to have very small longitudinal fractures that were difficult to see without magnification but would become apparent once the automated program sequence began (a big headache to restart)

As an operator rather than an engineer in these trials my focus was on what made nice welds and required the least amount of attention from me as the programs went through their sequences.

I'm sure Thorium is the most common on the U.S.

Europe is another matter.. ISO/EU/En's don't like thorium.

Thorium, Cerium, Lanthanum........ Are pretty much indistinguishable when manual GTA welding DC- on Ferrous. Stainless, Exotics.

For Automated GTA welding you will get more arc strikes and more consistant arc voltage for adaptive feedback systems with Lanthanum 1.5 (But the quality of lanthanum electrodes varies among vendors)

For our shop I choose Cerium... With lots of beginners who tend to want so sharpen both ends of the electrode (removing the color code) it is hard to identify what you have when you enter a work station. Cerium will perform well on AC or DC- with inverters or transformer rectifiers.

If it were not "our shop" and it was only "my shop"  I would use Lanthanum 1.5 for DC- and Zirconium for AC with all varieties of power supply.

This is a good thread...... a good idea to keep talking about this.

I think where the rubber meets the road is cost.

Requiring a safeguard mechanisim such as a surface temper etch after every arc strike removal will be costly... and the higher the carbon content the greater risk that grinding itself will also provide positive surface temper etch indications.

Grinding arc strikes sufficiently to remove the hard spot may also reduce material or cross sectional thickness to such an extent that the item is outside of engineering limits. (As evidenced by the severe restrictions of our cross country pipeliners)

A reality that must be recognized is that code committees are indeed composed of experts from industry... those experts often factor the bottom line of their employers into the decision making process when it comes to tollerances....... Not a bad thing, the bottom line is important too.. Just something to be recognized.

After examining the *code welds* in modern buildings, bridges and parking structures destroyed by the Loma Preata, LA and Kobe earthquakes, FEMA and others did indeed dictate more robust low hydrogen electrode regulations.  Those welded structures may not have had cracks, but they did not perform to design either... It would be hard to sift through rubble to discover if Arc Strikes were a factor too but we sure do know they change the quality of the surfaces they are struck on.

Mwccwi,
Not sure of the meaning of 'convincing enough for most'. My point has never been that changes in microstructure, as the article mentioned, do not take place, my point has never been that something doesn't need to be done, even if only from a workmanship standpoint, as I made clear in earlier posts, and my point has never been that the possibilty of cracks does not exist. So I myself am convinced of, something. And perhaps we agree more than what some posts seem to imply.
But I would ask the question in the context of the article posted: since the cracks in the article were discovered at 60X magnification (and at 600X mag the deepest crack seems to have a rounded tip which may indicate that the ductile BM has arrested the crack), why is it AWS itself does not require greater examination of arc strikes than, and I quote "ground to a smooth contour and checked to ensure soundness". No definition of what checked to soundness might be. And in the commentary to 5.29 says, and I quote, "MAY result in hardening or LOCALIZED cracking, and MAY serve as POTENTIAL sites for initiating fracture.(capitals mine)". Can "checked to ensure soundness" really verify that cracks do not exist? Or is AWS implicitly concuring with EPRI to a certain extent?
Look close enough you will find something. There has never been a weld made in a manufacturing environment that didn't have flaws or discontinuities in it. In fact, the very concept of weld denotes discontinuity.
The question is, are those flaws or discontinuities responsible for failures. EPRI found that in many instances the answer is no. I think to a certain extent AWS implicitly concurs. Otherwise with every arc strike they would perhaps work to find a way of examining arc strikes with much more thoroughness than "checked to ensure soundness".
If indeed my point is invalid then perhaps AWS D1.1 needs to add considerable robustness to their arc strike requirements. Because the language appears to be grossly inadequate.
My point is, perhaps not. I think maybe they got it right. Minimalist wisdom. Workmanship as a minimum standard approach which engineering facts can justify.

I did a quick scan of the article. I will read it in more detail later becasue it certianly seems important.
I would comment however upon what I read of arc strikes, for this context.
It seems their conclusion was solidly and justifiably logical, but still speculative, as is most of the workmanship standards associated with D1.1 inspection criteria, in that they anticipate a stonger inclination to cracking, and greater risk of stress corrosion. But still no hard evidence of the risk in which they are concerned.
Also, the HAZ of the tested weld bead was hitting HV's of over 300 at the start and over 400 near the stop. Not out of line with the arc strike.
The other thing is, they mention greater risk of stress corrosion. But that would depend upon the thickness of the material. The corrosive medium is going to be on the ID. Whereas the HAZ of the arc strike is going to be on the OD (unless of course you are perfomring a backweld), and it will probably not penetrate through the thickness very far. So what is it in the atmosphere that is going to contribute to corrosion?
This is very similar to other alloys and applications where we have conerns for OD issues that really aren't related to service viability since it will never come into contact with the corrosive medium, unless, for example, we're talking about SS at a desalination plant on the coast where there are real OD corrosion issues.
And this is really the point. Instead of a knee jerk response to arc strikes, I don't believe it hurts to take a real engineering viewpoint.
Having referenced the EPRI report, it should be kept in mind that their results would certainly not speak for phemomena beyond the alloys they tested.
But this is essentially the same argument I make. Making too general a statement form things that from an engineering standpoint should be specific.

I just came off of a job like that. just imagine how hard it is to avoid arc strikes when you have three bead hands, two hot passers, two hot fillers, and two cappers all taking turns on the same joint. there were a few cut outs but the inspectors let us use sanding discs on the minor ones as long as they were near the bevel.

If you think grinding and inspecting arc-strikes is hogwash, you would have a hard time with some of the pipeline customers I have encountered.  One such customer prohibited all arc strikes.  If an arc strike outside the joint was found, the whole joint area including the arc strike was to be cut out and re-welded.  If a grinding mark was made outside the joint, it was assumed that someone was trying to cover up an arc-stike and the whole joint and grind are was cut out.  I don't mind so much when customers only want arc strikes ground and inspected.

js55, you found my week spot, lol... I tend to be rather spontaneous at times but will always say whats on my mind even when it bites me in the behind... yeah, this fitness for duty thing has been around a good long while... I remember way back when Naval Joining Center (among a few others) were creating artificial undercut (which actually can be beneficial when done properly) and then the studies on how porosity can actually "strengthen" welds... I apologize if I sound less than forward thinking on some of these issues... lol!  I still say hogwash to the arcstrikes and porosity issues even with the greatest respect for EPRI...

Tell us what you really think Jon. LMAO!!!
My post was not meant to disparage a workmanship criteria. If it was, I wouldn't have created a QC Manual here at my plant with standards beyond that required by AWS or
AISC utilizing the exact same idea.
This post was meant to create a discussion and awareness of what can often be the extreme difference between workmanship criteria as opposed to engineering criteria, and metallurgical theory as opposed to engineering and service reality.
We all inherit patterns of thinking that must constantly be reevaluated in the face of new facts.
I will continue to reject arc strikes, but will no longer have so much heartburn with the possibility of missing a few.
I am annoyed at myself since I know I have this document and the significance of parts of it was apparently lost upon me the first time I read it.

Related article.  Although it mentions EPRI: "Arc strikes and associated blemishes are acceptable provided no cracking is visually detected", we will continue to follow D1.1.  I agree with jon20013 that arc strikes cannot be ignored.

http://www.steelstructures.com/StlInspNews/NEWS%20arc%20strikes.htm

js55, with all due respect to EPRI, I say hogwash.  Failures in service due to arcstrikes?  Hard to say, although I'm sure we've all seen John Wright's photos of bend testing arc strike plates, very little to debate there.  Certainly the process causing the arc strike would have some affect also, i.e., copper inclusions.  Speaking strickly from a mechanical perspective, I cannot find it in my mind to simply ignore arc strikes.  Whether or not they contribute to failures over the lifetime of an assembly is, as you mention, open ot a hotbed of discussion.  There's my $0.02. ;-)

Just spent the last two days at a conference. And came upon a revelation I thought I would share for comment. This is an old subject in here but it always justifies further discussion. Especially with such a startling concept to present. Startling at least to me.
Arc strikes
AWS D1.1 in its establishment of Table 6.1 addresses arc strikes, and essentially all other visual acceptance criteria, from a strictly workmanship standpoint and NOT an engineering standpoint (although those who determiend Table 6.1 certainly represent decades of engineering experience). Therefore D1.1 has language pertaining to arc strikes to effect of: visual evaluation, grinding, removing, verifying with NDE, and rewelding if necessary.
However, there is no research that verifies the contribution of arc stikes to service failures.
And the only document available that has perfomed an 'Engineering' evaluation of the effects of arc strikes is an EPRI document "Visual Weld Acceptance Criteria", that indicates that not only is it not necessary to grind arc strikes, but it is not even necessary to consider them. Now keep in mind that EPRI are some rather serious folks here. And that this document was generated with the Nuclear industry in mind. So the conclusions are not to be taken lightly.
I have this document stashed somewhere in my library and intend on digging it up to verify, but I suspect that the presenter has no motivation to misrepresent the conclusions of this prestigeous and comprehensive document.
Now, what this means from a practical standpoint is nothing. The code still must be complied with. But perhaps the debate on this issue deserves reconsideration.

Hello JW

You aren't missing out on anything by not having to lug around prods. Just think of trying to hold a heavy welding lead motionless while holding them over your head. You are not missing out on anything, and no arc strikes to worry about (assuming your yoke doesn't have a short).

Best regards - Al

Hello again bellaru, if you have an opportunity, you may want to get ahold of some books on metallurgy or do some searches on the internet. It is likely that some of this reading may do a better job of explaining what is happening relative to some of the questions that you have. As far as charts go, I don't believe you will find any one chart to give you the kind of explanation that you are looking for. The subject has too many variables and those change with the different materials, alloys of materials, etc. Different types of welding processes can also have a great effect on results of a like material.
     For example, you mentioned arc strikes and the fact that they only take a moment and yet cause all kinds of problems. In the case of the arc strike, the weld metal is at temperature just long enough to melt the electrode and a small amount of the surface metal, it cools this weld metal so quickly that it can cause it to harden considerbly and also cause a shrinkage stress to be present. Then if a bending stress is induced on the surface of the parent material the material from the arc strike won't stretch at the same rate as the parent material and this causes the tearing that willl show up. This is a very simplified version of what is happening. Regards, aevald

i know , thats what got me thinking...are there alot of additional elements lost for example in "OFW"........?   then how about the other end of the scale in terms of "time at temperature",,,,,,"arc strikes" are but a second , yet they cause all kinds of problems......i just cant see taking a peice of lets say , 60 grade ,,,,,taking it to molted and back and if its done right ,  it still holds up as if it was never touched..........is there some sort of a chart that explains the different time frames.....?...............thank you.....

TO: jwright650

I teach welding tech at the high school level.  I have heard of this experiment several times but never tried it.  I saw your pictures and decided to try it with my advanced class that is getting ready to do state certifications.  I took 4 pieces of 1/2" x 2" flat bar 6" long and we bent one as a control (which bent perfectly).  I had a student drag a E6010, E7018, and MIG across the other samples, we then ground them down and buffed them to a good appearance and bent them in our guided bend tester.  The results were exactly like yours.  It was an excellent demonstration of the effects of arc strikes.  Thanks!!!

I have seen the effects of arc strikes in RT and UT in industry but this is an excellent, simple demonstration that gets the points across. 

makeithot,
I think in answer to your question, there is mention of 'repairing' arc strikes in virtually all construction codes in soime manner or another. Some more stringent than others. Most codes will write it as a minimum standard in recognition of the fact that the concern for arc strikes is very alloy and service dependent.

I have seen that example once before when I started out as an apprentice. Nicely done. I feel that it reinforces my belief that an arc strike would be cause for concern testing or other wise. Brings me back to my original question " Is there an actaul written code for repiar of arc strikes " If so where? Or is this normally left to the clients discreation as to what is considerd aceptable.

From all that I read in books, regular carbon steels are not supposed to be bothered by accidental arc strikes.  But I have seen that little hard spot many many many times.  I have also seen the little dot caused by an underbead microvoid coalessence (presumably caused by the arc strike), after the arc strike had been ground down considerably! 

On one pipeline that I saw, the Brooklyn Union Gas company had a requirement in the late forties and early fifties, that all welders had to weld their mark next to each joint that they welded. One Guy had a big flourished signature, welded near everyone of his joints . "E.VanDaly" had a signature that would give John Hancock a complex. 

In the middle 90's, the gas company decided to get rid of all the old spiral wound pipe, because they didn't trust it for MAOP that they wanted to get, so they dug it all up and replaced it with straight seam pipe.  There were Arc Strikes all over this pipeline and it never blew up due to arc strikes and John Hancocks!

As an inspector on a pipeline project, I allowed the fitter to leave small pin punch marks (low stress), (used for alignment, during fit up,) on the pipe.  The NYS Public Service Commission told me I was not allowed to permit those pin punch marks to remain.  I had to treat them like Arc Strikes and have the contractor remove them.  The rules also said that the fittings (Els) had to be marked with Low Stress Markers.  The manufacturers also had High Stress markers on the opposite side of the same piece, but the PSC didn't care about that!

I do not know about failure of the weld as a whole.  (If you meant "Whole")  If youmeant "Hole", I do have a series of film slides showing a burn hole completely through on the weld metal on a pipe joint caused by poor contact of the "Antler" grounding device on a 16 inch Cross Country pipeline. 

As Mr. Hall points out, mostly, I have seen the Amonium Persulfate requirement in Pipline work.  The State Public Service Commission Rules and Federal Pipelins safety rules required this type of handling. 

However in NYS Bridge work, the New York State Steel Construction Manual requires hardness tests for all arc strike removals.

CON-ED also required it for proof of Arc Strike removal on the inside water wall of their power generation boilers.  If you left an arc strike on the water wall tubes they would burn through in less than a week in some areas of the near impingement zone.

I was up on the Alaskan Pipeline in 1974, and the welders were only allowed to have two arc strikes in their lifetime, before being sent down to the lower forty eight.  They had to go back through the Oklahoma Pipe Welders school before they were allowed back on the job. (I was not there as a welder, so I did not understand the significance of this at the time.)

I think the danger of arc strikes, as I suggested in the previous post varies with alloy. For carbon steels I don't know that there is much justification in documented failures for consideration beyond cracking.
However, using hardnesses to demonstrate to welders the effect of arc strikes, even on carbon steels is a excellent idea.