Not logged inAmerican Welding Society Forum
Lawrence, I agree with the arc strikes causing failures, have seen the pictures evidencing such. I too am waiting for the eggheads, but have been assured by several that A36 is not "hardenable" by quenching and have thus far proven that to myself.
By RonG 
Date 02-28-2007 17:19
Edited 02-28-2007 17:24
No egg head here but I have quenched a heck of a lot of A36 plate with no appreciable hardening. A good deal of it in extreme load applications.
I believe Blaster must have had something with a tad more Carbon in it to shatter like glass.
A36: There is a really wide possibility of alloy elements that could be in A36, as it is a yield strength minimum rather than an alloy requirement. As most steel today is remelted from scrap the ammount of alloys remaining is higher than in yesteryear. Quenching from temperatures above critical [slightly higher than where the steel looses its atraction to a magnet] or a good red heat will harden the A36 if it has enough carbon and other alloys. Quenching from lower temps won't harden it, but the rapid contraction from cooling may cause other problems.
Here is my understanding...
A36 contains only about .25% to .29% carbon, but the carbon is not uniformly distributed. On a microscopic level there are grains of ferrite and grains of pearlite. The ferrite contains .02% carbon but the pearlite is about .80% carbon. With arc strikes the heating is so rapid that there is not enough time for the carbon to diffuse and become uniformly distributed in the austenite. The result is grains of high carbon austenite, and since the cooling is as rapid as the heating, the austenite transforms to untempered martensite.
Will this cause problems? D1.1 says to grind out stray arc strikes, so there must be some basis for concern...
Regards,
Bill
Bill, That sounds like a lot of carbon, I wouldn't have expected as much. No wonder it can get reasonably hard if quenched from above critical. I posted near the bottom of the page with a little more on this subject.
DaveBoyer, I agree, that sounds like more carbon than the "typical" A36 we use at my shop. Bill, are you sure of those carbon numbers for A36? Not being at work as I write I dont have access to my ASTM... I was thinking much lower than what you mention...
ASTM A 36/ A 36M -01 specifies max carbon content ranging from .25-.29% depending on thickness. Max carbon content increases with material thickness. Since these are max values you are probably right that the values you've seen on your material certs are lower than this range. But even if it is actually .20% there will still be pearlite grains of approximately .80% carbon, just less of them.
Abso freekin lutely!!
Well, when you go to the mechanic and say you need your alternater replaced and he quotes you 1000 bucks and you scoff, just remember: If you can't do it yourself, It's gonna cost ya! Most people don't have a single clue what is involved with glueing metal back together. They look at you with your 1000 buck invoice and don't understand it. You can tell they don't agree with it sometimes, but they still fork over a check.
I dont know how many tickets I've had signed by the man that said, " no guarantee ", in my hand writing all because some pusher was in a hurry and didn't want to wait for the product to cool for an hour......I feel your pain brother!!
Jon,
With the utmost due respect I have to disagree with you. ( First time ever)
I teach any young trainees that welding and water do not mix.Can you guarantee that the welder that is told that it is OK to quench A36 carbon steel will know the difference when they happen to be working with chromolly or high tensile steel where it is much more critical. They all look the same.
The only safe way is to stipulate water and welding do not mix - full stop.
Regards,
Shane
Shane, we agree that welding and water do not mix. We also agree that chromolly or high tensile steel all look the same. I use the example of quenching A36 to my guys simply as a very very basic metallurgy lesson. It might be a bad example to be illustrating I admit. I don't think we disagree in actuality; my point was simply that A36 is not a hardenable steel when water quenched (in my personal experience). No disagreement at all on the philosophical issues.
You can relate to this. Flowing refined products line in central Missouri during the middle of the summer. Relative humidity is 80%. Line is flowing at 280 psi and the pipe temp is 74 degrees. Water is running off the pipe from condensation. The next window for reduced pressure is three days away and the weather conditions are not expected to change. Welding 12" X42 Sleeve material over Gr B pipe circa. 1940. Whatcha gonna do? You keep the pear burners running ahead of the weld. You want to MP the weld the next day, but you still have the same conditions. You tell the engineer what is happening, he approves it you blast, coat and move to the next dig. I enter all the information in my journal and move on. That was 12 years ago, the line is still in operation and has passed hydro-test and 2 smart pigs. Field welders face this every day. You do the best you can, but the job has to get done.
dbigkahunna,
Just because something is still in service after 12 years doesn't mean jack.
I hate to think about how many times I have heard "Well we have been doing this for thirty years and never had a problem".
The whole reason we have codes, standards, specifications, rules, regulations etc is to try and avoid the 1 in 1000 or 1 in 1000,000 chance of an accident that could potentially kill a lot of people.
Regards,
Shane
Man, I wish this thread would end, but have to say I agree with you Shane. Unfortunately, as has been pointed out here many times, in the USA one typically follows what his/her employer tells them to do even when it is technically wrong. Inspectors "might" help.
I agree Jon. It appears this has blossomed in to something it should not have.
I remind everyone the original question concerned safety and nothing else.
Shane every thing you say is 100% correct in principle but not the always applicable in the real world.
My understanding of Sourdoughs work is mostly wear areas on earth moving equipment and I can tell you for a fact the equipment owners only get paid for the hours a machine is operating and the repair personnel are an expense that comes off the top.
They do not know the 1st thing about welding or Metallurgy and they don't care to know any thing about it. They will be the first to tell "If you can not get the job done there is a man just out side the gate who can".
It's time we moved on.
Shane,
I do not know where you work or who you work for. I do know I have been instructed over the years to do things I do not agree with. However I have mouths(s) to feed. If I refuse, I get fired. Oh I can file complaints with OSHA, DOTOPS, and others, however, as a third party representative I only do what the OWNER request and demands. I have passed several audits from DOTOPS and my journal entries have saved my backside several times. And the fact the repaired products pipeline has passed three required Department of Transportation Office of Pipeline Safety test in the last twelve years does mean JACK!. The fact my original paperwork has withstood two audits in the same period does mean JACK. The fact when the pipeline sold three years ago and the buyer was doing the due diligence and went through all the repair documents to be sure everything was done right does mean JACK. I did not try to hide anything. There was just no other way to do the job. You have a way to weld on a sweating pipeline, let me know. The pear burner ahead of the weld is the only way I have ever done it. Same for the other inspectors I have worked with. You do not shut the pipeline down and drain it for repairs. Today Clockspring does a lot of what was formerly welded.
The most important job a inspector does is keep notes in a bound journal. That is the inspectors defensible document. Dont know what that means, get in a deposition. I told my story to illustrate the fact sometimes in field work you do not get to pick your conditions. I documented the conditions and the welders work. i visually inspected the welds. There was nothing else could be done. Shear Wave was not available. I informed the owner of the conditions and my observation. The engineer asked if I believed the welding was OK. I did and documented my findings. I would like for you to explain to me how I or any field inspector can influence the decisions of the owner. I have to eat. Those who have been there know where I come from.
Sorry if I wasn't clear, the A36 bars did not "shatter" like glass, it snapped very cleanly in half, in a brittle fashion without deformation, like glass. I am not sure if I can post pictures on this website, but I still have the samples and will try an post pics over the weekend if it is possible.
I have no means to positively identify the metal I used as A36, but it was ordered as A36, and I get mill certs with my metal devilerys used for welder certification testing. Obviously there is no way to prove positive that the bar and mill cert in fact go together as the small bar stock has never been individually stamped or stenciled.
If any of you have the equipment, I would encourage you to duplicate the experiment and post your results.
I am pretty sure there is marked difference between a water quench of coupons at 300F - 500F or so, and a water quench of red hot metal.
I have also tried tensile pull testing backing bars after the same treatment I described in my prior post. The water quenched areas did not appreciably neck down like the rest of the bar, prior to the bars breaking. Then bars ended up looking like a bow-tie after pulling apart.
By DaveBoyer 
Date 03-01-2007 04:45
Edited 03-03-2007 04:11
Lawrence & Blaster: I put a post with regard to this, but it is near the top of the page, I should have put it down here. There are homebrew quenchants that incorporate detergent and a few other things to get a more severe quench, blacksmiths use it on cold rolled and A36 to make it somewhat hard. Granted it does not harden like tool steel, but it does get harder than it was. With respect to Lawrence's arc strikes there are possibly 2 mechanisms at work. With regard to martensite formation it is possible that the actual arc impingement was quenched by the cool parent metal and formed untempered martensite. I know this to be a problem in tool steels, We lost many rivet yokes at the plant due to a faulty grounding strap on a welding / riveting fixture - the work was arcing to the yoke. The other problem is that the arc crater causes a stress riser. This is less of a problem on ductile materials, but if there WERE enough alloys in the A36 to form the martensite that small area would loose ductility. The above mentioned rivet yokes were only 33 RC and would not have been particularly notch sensitive had the localised hardening from the arcing not taken place. The yokes were made from AISI S5, an oil hardening high strength shock resistant tool steel.
Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill
