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Up Topic Welding Industry / General Welding Discussion / Stainless kept cracking?
- - By phaux (***) Date 03-13-2011 18:57
I was tig welding on a pressure vessel yesterday that was made of stainless. The customer was not going to be using it under pressure. It had some pinholes in it he wanted me to weld up. Every time I welded on it as soon as it cooled it would crack all around the weld! I'd weld the crack and a new one would form! Welded some other stainless for him but this was the only thing that did this. What was I doing wrong? Was running a tig setup off my SA250 and ER308L filler, 2% thoriated tungsten.
Parent - By texasrigwelder (**) Date 03-13-2011 19:51
Depends wat grade stainless it is. Always been told if don't know use inconell
Parent - - By Joseph P. Kane (****) Date 03-14-2011 00:47
Phaux

Please be carefull!!!!!  Your repairs could kill people if that repair fails under pressure!!!!!!

Look at the ASME Data plate on the PV, and find out what it is made of.    If you are in a "Code State", you may not be able to legally make any welds on a PV unless you have a National Board "R" stamp, or you have the appropriate ASME B&PV Manufacturers Stamp.

CYA pal.
Parent - By phaux (***) Date 03-14-2011 02:43
Reread the original post, the customer is not using it as a pressure vessel. It originally was but they are now using it to hold water. I don't weld high pressur cylinders or things that have/or have had fuel in them.
- - By Hoo (*) Date 03-13-2011 22:44
Thickness?  Pre/Post Heat?  Did you grind out the crack to being with or just wash over it?
Parent - - By phaux (***) Date 03-14-2011 02:44
Couldn't tell thickness, guessing 1/16"-1/8". No pre or post heat. Washed over.
Parent - - By Tommyjoking (****) Date 03-14-2011 10:31
I would try a gentle preheat around the area your trying to patch up.  The inconel might be a good idea...
Parent - - By phaux (***) Date 03-15-2011 13:37
So what exactly about Inconel makes it so great on ss?
Parent - - By js55 (*****) Date 03-15-2011 15:16
Not all inconels are created equal.
Many experience their own crackng issues.
But the first thing is to determine why the thing is cracking.
If its a contaminate hot cracking, as I suspect, inconel is probably not going to help much.
Inconel, some inconels, work real well with shrinkage cracking with non ductile materials.
Its coefficient of expansion is close to ferritics and so stresses are minimized. This may help you. With SS it can absorb some of the shrinkage stresses.
There is also the fact that inconel solidifies austenitically and stays that way and does not transform so 'junk' is not as likely to concentrate as severely in segragated areas as with prior grain boundaries and SS's. The very reason ferrite is so important in SS weld metals.
You need to take the cracks completely out before rewelding.
Parent - - By scrappywelds (***) Date 03-15-2011 23:02
Drill the ends of the cracks,then grind out the cracks, back purge the vessel, use slight pre-heat and weld toward the center from both sides.
Parent - - By Tommyjoking (****) Date 03-16-2011 02:34
js55     I was thinking inco 82 but that is a shot from the hip....actually this is the first time I have heard of using it on stressed out ss, notice I said "might".   Thought people who know would weigh in on it.   I have used inco 82 to repair cracks on heavily heat worked aircraft parts...so I figured it was a more 'flexable' alloy for that reason.

I am assuming the phaux did the normal things as far as removing the cracks + purging or providing gas on the backside I should have mentioned it.  carry on I am in the way here.
Parent - By OBEWAN (***) Date 03-16-2011 08:30
It really depends on what kind of crack he is fighting.  If it is a hot crack, any Inconel could just hurt since in the hot crack chemical equation high nickel content is one of the bad actors.  IF it IS a hot crack then 312 might be the desired filler metal.  But we really need to know the cause of the crack to implement the best cure.
Parent - - By phaux (***) Date 03-16-2011 12:39
Not to sound like a fool... but, is purging the backside necessary or helpful when dealing with cracks or pinholes on ss?
Parent - By fschweighardt (***) Date 03-17-2011 01:36
Might be getting a low FN
Parent - By scrappywelds (***) Date 03-17-2011 03:48
If the root is exposed to the atmosphere it is. To get rid of the oxygen in the HAZ to keep it from sugaring up.
Parent - By js55 (*****) Date 03-17-2011 11:33
82 can be a good choice. Inconel is used as a generic term for many alloys and it is sometimes applied to alloys that aren't inconel. Inconel is brand name essentially though it has become synonymous with nickel based alloys as a whole, or more specifically 600 series alloys.
Keep in mind however 82 is stabilized with Cb and some have concerns about Cb fillers used on N containing base metals, the same reason NiCrMo-3 is not the filler of choice for AL6XN anymore.
And obewan makes a good point. 312 might be a better choice, but you have to determine why its cracking.
Parent - - By north_fl_cwi (*) Date 03-18-2011 01:36
Depends.  You still haven't said what grade stainless steel you are working on.  All recommendations are just guesses until you know what you are working on.

If it's a stamped vessel and you changed or altered it and do not have the proper credentials, you need to remove the ASME nameplate.  You never know where that vessel will be sold or used down the road.  If you made a non-code repair and they sell the vessel later or someone decides to use it for a pressure vessel again..... asking for trouble.  Just my opinion.
Parent - - By phaux (***) Date 03-19-2011 12:53
There' was no plate, stamps, letters, or marking of any kind any where on the object. Thus, I do not know what type of stainless steel it was.
Parent - - By north_fl_cwi (*) Date 03-20-2011 23:30
If you have no idea what grade stainless it is, how do you know what to weld it with?
Parent - By jpill (**) Date 03-21-2011 14:31
"When in doubt, 309 it out", thats what the old hands always said.
Parent - By PipeIt (**) Date 03-28-2011 16:11
This sounds like carpenter or CB20 this stuff's a ***** its' been many years I am not sure it was called that but something close.
Parent - - By Lawrence (*****) Date 03-21-2011 16:01 Edited 03-21-2011 16:06
Tough situation.

The owner "says" it won't be used for pressure...  Are you willing to bet lives that this is true?

Joe K's admonition is the most important text in this entire thread.

If the thing is cut in half and your watering cattle with it, that's another matter.

The whole "weld it with inconel" thing is BS... Inconel is an entire family of alloys.. (more than 20)... Some are good for dissimilar metals joining.. IF THE DISSIMILAR METALS ARE KNOWN and an engineering level decision has been made.  Besides,,, Most folks who thought they were welding dissimilar metals with Inconel were probably actually joining them with Hastelloy W (AMS 5786).

If the cracks were centerline I think we could get someplace here, by talking about surface prep, stip drills and backup/purging... But you described cracks "around" the welds... This is disturbing... And any filler metal suggestions are just shots in the dark.

Edit:
"Washing" over cracks in stainless or super alloys is always a bad idea.  Cracks should be routed fully out and the back side cleaned.. The stop drills that Scrappy mentioned can also be helpful.  If it is 300 series stainless than backpurge is required for a quality full pen weld.
Parent - - By phaux (***) Date 03-21-2011 16:38
So what do yall do when you show up to a job and the person says they have no idea what ss grade it is, tell them too bad? Just curious

Ya, the cracks were around the welds, like an outline of the weldment.
Parent - - By north_fl_cwi (*) Date 03-21-2011 17:46
Yes, that is absolutely correct.  We have done it more than once.  Remember, when you are sitting in front of a judge and jury, and the lawyer is drilling you about how you made your filler metal selection.... what will your answer be?

Maybe it's because I have seen it happen, but I always do my work as if it were going to a lawsuit.  It seems so many end up that way these days.  It's one thing for the "owner" to engineer and direct you what to do in writing, it's another for you to show up and the owner/engineer lay the responsibility on you.  You better have your paperwork spot on in case something happens.  Because the owner will claim they hired you for your expertise, and a jury is not going to buy "when it doubt, 309 it out". LOL.  And most likely, if you are not performing to the industry standard, your insurance company might not back you either.

Some times it's better in the long run to turn a job down.  You might have to skip a meal, but save your company in the long run.
Parent - - By jpill (**) Date 03-21-2011 18:27
I never said it was right. Just said thats what the old hands USED to say. Truth be told though there is a massive amount of maintenance welding done in plenty of industrial plants every day that the material being welded is unknown, or dissimilar and it is all welded with the latest and greatest stoody, eutectic, mg messer, etc. flavor of the week "maintenance rod or filler" that is nothing more than dolled up 309. Seen it done, and done it myself several times when I was running the roads as a millwright. Although none of it was ever on a pressure tank so you got me there.
Parent - - By DaveBoyer (*****) Date 03-23-2011 01:35
Your post brings back memories of Certanium 747. Best maintainance rod for every job & material, but they won't say what is in it.
Parent - - By Shane Feder (****) Date 03-23-2011 03:19
Hi Dave,
Certanium bought out by Cronatron in 2001
All positional low hydrogen electrode
Flux Composition - Iron Oxide, Manganese, Silicon Carbide, Titanium Dioxide, Calcium Fluoride (Cellulose) and Calcium Carbonate
Tensile - 90,500 psi
Yield - 81,000 psi
Hardness - 17 - 21 HRC

Hope that helps,
Cheers,
Shane
Parent - - By DaveBoyer (*****) Date 03-23-2011 04:01
Thanks, Shane, I have a few small packs of the 747 and probably some 707 as well. They are over 20 years ol, and I never used them.

A welder at the plant gave them to Me.
Parent - By Smooth Operator (***) Date 03-23-2011 20:02
Super certainium 747 !!!!!!! Made by Co-ordinated Industries from Glennwillard, PA. Long gone, biggest customer............... J&L later to be LTV Steel (the good ol' days):sad:
Parent - By MBSims (****) Date 03-29-2011 01:14
With those properties, I would suspect nothing more than E312-16, which what most "magic rods" are.  With a little coloring in the flux of course.
Parent - - By aevald (*****) Date 03-23-2011 22:52
Hello Dave, just noticed the comments about the Certanium rod, believe we have a number of sealed 10lb. containers of the stuff. Originally came from the Hanford Nuclear Reservation probably 25 to 30 years ago. Can't say that I have run any of it though, maybe I'll have to break some out and give it a test drive. Also seem to remember that the cannisters used an opening system similar to some of the canned fish packs, utilized a key and required inserting a tab from the cannister into a slot and rolling it around the key to open it. Best regards, Allan
Parent - - By James Kelly Date 04-17-2011 22:39
Phaux - "some kind of stainless" Wasn't magnetic, was it? 

A little bit of metallic zinc paint will do a nice job of making austenitic stainless, or nickel alloy, crack.
Parent - By kidblue (*) Date 04-28-2011 19:23
First,

If the vessel were previously used for pressure it should have an U1 form, also you may need to contact an Authorized Inspector (HSB or an insurance company) to make a repair and your company shall have the R stamp. If you are not sure what s/s are you working on try an PMI (positive material inspection). Also the owner should tell you what kind of chemical were passing thru the equipment. Start with that then you will be sorrounded with enough people to make right job.
Up Topic Welding Industry / General Welding Discussion / Stainless kept cracking?

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