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Up Topic Welding Industry / Inspection & Qualification / Arc Marks
- - By MBlaha (***) Date 03-04-2006 14:42
I am having trouble conveying to our welder's and a couple of the foremen that we cannot allow arc marks and that they have to be ground flush. I have showed them in D1.1 where it states they shall be ground smooth. I know that if left, eventually they can lead to cracks, basicaly playing connect the dot. What I would greatly appreciate is any information on this subject, even better, if someone could put me onto some pictures of where arc marks left have led to failure of a part so I could show them would be great.

Thank you in advance and have a great day :)

Mike
Parent - By Lawrence (*****) Date 03-04-2006 15:19


http://www.dnv.com/publications/classification_news/No_4_2001/Failureofintermediateshaft.asp


This one discusses untempered martensite developed at "Arc-Strike" points in High strength steel
http://www.boulder.nist.gov/div853/Publication%20files/NIST_IIW_report_Siewert_2001.pdf

Hobart Institute has a Weld Quality Control training course that also has an inspection emphasis on arc-strike in Section 4. It comes with a nice little student study/reference guide on defects and discontinuities for only about 12 bucks... Good for in-house training.
Parent - - By chall (***) Date 03-04-2006 16:06
We took a steel plate and dragged an electrode over it fast (leaving a line of arc strikes). After that we flapped the plate to remove the obvious signs of the arc strikes. Than we bent it in a bend jig like we would a bend test. The arc strikes open up in a very dramatic, convincing way.

Charles
Parent - By JTMcC (***) Date 03-04-2006 17:31
The method they use in pipeline construction seems to work very well. Sometimes they will let you get away with it once (sometimes not even that), but the second time the welder is run off.
Of course arc strikes usually result in a cut out, which is an expensive repair.

JTMcC.
Parent - - By jwright650 (*****) Date 03-04-2006 23:07
Charles,
That is interesting, I'm going to have to give that a try. My guys look at me funny when I circle up the strikes that are outside of the joint and asked that they are ground smooth. I would love to show them the bend test that fails where the strikes were.
John Wright
Parent - - By vonash (**) Date 03-05-2006 02:16
Hello Neighbor,
Arc strikes are a no-no as mentioned above. I recommend copying this post and answers to provide some teeth for your plea.
Very best regards,
VONASH
Parent - - By MBlaha (***) Date 03-05-2006 17:00
I would like to thank all that responded. This should be quite helpful. I would still like any leads to more photos should anyone have any.

This was greatly appreciated, thanks

Mike
Parent - By jwright650 (*****) Date 03-06-2006 17:37
Mike,
see my pics posted below...
John Wright
Parent - - By 803056 (*****) Date 03-05-2006 16:38
Good articles Lawrence.

Thanks for the great posts.

My lists of great welding articles grows everyday thanks to the forum folks.

Best regards - Al
Parent - - By swnorris (****) Date 03-06-2006 12:19
If not properly removed, an arc strike has the potential of propagating fatigue cracks. Arc strikes located in tension areas need to be removed by grinding. They can result in unacceptable hard spots or small cracks. After the arc strikes are removed, every location where they occur where the steel is in tension should be checked. Mag-particle testing on all arc strike locations could be performed to assure that no cracks are present. Hardness tests could also be ran on all locations to assure that no unacceptable hard areas are present. Hardness values should not exceed the higher of Rockwell C30 or the hardness value measured in the steel outside the location of the arc strike. If the above testing reveals unacceptable results, the flaw can be removed by grinding and the steel be retested to assure that the flaw has been completely removed.
Parent - - By Lawrence (*****) Date 03-06-2006 15:35


I conducted the demo Charles mentioned (dragging an electrode quickly over plain A36) in class today.

It was as convincing as advertised.

A nice demo to add to every course.

Thank you Charles!
Parent - By jwright650 (*****) Date 03-06-2006 15:37
L,
I'm about to do the same....in a few minutes.
John Wright
Parent - - By jwright650 (*****) Date 03-06-2006 16:56 Edited 01-16-2008 18:24
Here are my results..... ASTM A36 3/8" bar x 2" x 8"





John Wright

edit: material on far left was plain material w/o arc strikes.
All 5 of these pieces came from the same stick of A36 material.
Parent - - By vonash (**) Date 03-06-2006 21:46
I'm impressed. Nice pics.
Parent - - By jwright650 (*****) Date 03-06-2006 21:52
I wish our camera here at work was a quality piece where I could get a better macro shot of the fractures up close. But it blew some minds here at work when I showed them what happened. Several guys saw me working on this and none of them thought anything like this would happen from that little ole arc strike. I lined the 4 pieces up side by side and drug the rod quickly across and only produced a spray of small droplets on the surface. Then I ground them smooth and polished it with a flap disc to where they were not visible any longer, then bent them in my coupon bender with a radius for up to 50ksi material.
John Wright
Parent - - By tito (**) Date 03-07-2006 00:27
Well that sux. I can't view the pics. There is a firewall denying me access. Curious though, on the samples, you ground them, polished them, and they still "failed"?
Parent - - By jwright650 (*****) Date 03-07-2006 00:32
Sorry tito,
It must be on your end, I can view them from my home computer and I posted them from work today. Yes, I ground them smooth and used a sandpaper disk to smooth them further and they still failed across where the arc strike was.
John Wright
Parent - By MBlaha (***) Date 03-07-2006 02:17
Thank You everyone. I also did that today and bent them. Was too late to show them to the people I needed to have see them but will show them tomorrow.

Great bunch of guys and gals in this forum.

Mike
Parent - By 803056 (*****) Date 03-07-2006 03:36
Nice photographs. Great looking demonstration.

Best regards - Al
Parent - By billvanderhoof (****) Date 03-07-2006 07:10
And that's plain old, easy to work with a-36. Very impressive.
Bill
Parent - - By Sean (**) Date 03-09-2006 20:26
John,

Great pictures and very timely. I was having some issues with folks not taking arc strikes seriously that is until they saw your pictures.... I hope you don't mind I'm showing them to some of our welding supervisors (with your name attached) during tool box talks. We are also going to try your experiment.

Sean
Parent - By jwright650 (*****) Date 03-09-2006 20:50
Sean,
I don't mind at all, I posted them for that very reason. I was very convinced to say the least. I had always had our people grind them when I saw them, yet really I didn't realize or understand the severity of the problem until I bent those pieces and showed our people here what happened. Needless to say it opened a few eyes around here.
John Wright
Parent - - By chall (***) Date 03-07-2006 16:27
You're welcome.

One of the transmission line companies we worked for had us use a solution of water & ammonium persulphate to verify complete removal of arc strikes.

It's a pain in the arse. You have to grind and polish the strike smoothly to blend in with the adjacent base metal; swipe the solution over the effected area and look for darkening. If it darkens up, you haven't removed all the traces of the "heat zone" so you have to repeat the steps.

Once all traces are gone, you have to check wall thickness using a UT tool. If too much material was ground out, the section has to be cut out and replaced.

It is obviously better to avoid arc strikes.

Charles
Parent - By gyadon (**) Date 03-07-2006 22:34
I worked a job for EXXONMOBIL where we used the same process and it was a pain but after a few repairs the problem got better. I also did the arc strick and bend. Yes they did open up.

Gary
Parent - - By 803056 (*****) Date 03-07-2006 21:38
It sounds like your client's engineer has a background in welding for the Navy. They have similar requirements when the carbon exceeds a certain threshold.

Al
Parent - - By thcqci (***) Date 07-07-2006 13:22
OK guys.  I, too, am looked at funny for circling arc strikes on our structural steel to have them ground out.  I remembered this thread and have planned to perform this little experiment in front of our welders to demonstrate to them what I have been preaching.  Well, yesterday we had some arc strikes on our steel and we were very temporarily slow (like for for the next 37 minutes) so I decided to gather up a few welders and perform this demonstration in front of them.  I used A36, 3/8" 2" bar stock, dragged a FCAW electrode all the way across 6 of them lined up side by side.  Had an arc strike line from one side to the other.  Flap wheel sanded 3 of them until most, if not all evidence of strikes was gone.  Stuck them in our bender and guess what I saw?  Looked just like a regular bend test with a weld on it; no cracks, nothing but what looked like a small, thin weld bead.  Now, when I showed that to my welders, they say UH-HUH.  Arc strikes really aren't as big a problem as you always make it out to be.  I looked like a fool!  My camera is out being used on a job site else I would post some pictures.  What did you guys do differently?
Parent - - By jwright650 (*****) Date 07-07-2006 13:45
Hi Doug,
I'm curious why you have welders leaving arc strikes outside of the joint, if they are using FCAW? I used SMAW in my demonstration because that is the process where I see the problem with arc strikes occurring with these hard to re-start E7028 tacking rods that we use during fit-up.

edit: PS. Best to experiment first before gathering the whole shop around for a demo. ;)
Parent - - By new tito (***) Date 07-07-2006 14:00
LOL!!  Yeah, that would be my luck.  I almost always do my experiments in secrecy before going public, because of that reason.

T
Parent - - By thcqci (***) Date 07-07-2006 16:20
FCAW arc strikes usually are occurring during fitup operations.  Careless handling of the gun is the main cause.  Sometimes it is a poor ground while fitting up sub-assemblies while having them sitting on main members.  The other time is while welding pipe columns.  I hit them with is when our bench tops are not ground well and they roll the column across it while welding cap or base plates.  We usually attach the ground directly to the column.  Have tried grinding bench tops and rolling on angles also, but with no consistent results.  Directly hooking the ground works best. 

We have most of our welders SMAW certified also but SMAW is used perhaps 1% of the time here.  Almost exclusively FCAW.
Parent - - By thcqci (***) Date 07-07-2006 19:08
The reason I did not do it for myself in advance was because so many others here had already done it and I was sure what would happen.  Heck, John even posted great pictures so I knew what was gonna happen.  Live and learn.
Parent - By jwright650 (*****) Date 07-07-2006 19:29
I dunno Doug.....You must not have drug the electrode quick enough and you actually deposited some weld metal. The stick was alot easier to do and you saw the results. Do ya have pics of your attempt?
Parent - By jwright650 (*****) Date 07-18-2006 15:02
Doug,
Have you tried this any more?
just curious,
Parent - By jwright650 (*****) Date 07-07-2006 19:36
I'm really kinda surprised to hear about arc strikes outside of the joint using FCAW, just because of the mechanics of how it works. Our guys usually mess up and miss the joint using the stick to tack with while holding their shield in their hand all the while trying to get the E7028 tacking rod to re-start.
Up Topic Welding Industry / Inspection & Qualification / Arc Marks

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