stainless welds, 309L, more or less likely to crack?

I am currently doing a gig as a repair/consultant with the manufacturer of some high end kitchen gear that is subject to high heat (400+f). the welds they are currently laying down are very tidy "sanitary" welds, perhaps autogenous (no filler added), but not sure.

very small welds, deeply concave, with very little ripple, actual weld root thickness often something like .015-.030" (on 304 14 ga)

not surprisingly, they break.

I have recommended tripling the weld cross sectional area, repeatedly, with pictures, with limited success .

the question at hand is; is there any risk of greater cracking if one used 309 filler (instead of 308)? I know that some welds are better "under matched", such as many chrome/moly (4130-4140) tube structures, where the greater ductility of an ER70S-2, (or -7 as some have recommended) greatly reduces the chance of weld cracking.

the austenitic nature and greater tolerance for carbon of the 309 should reduce the chance of cracking even though the UTS of the filler is slightly greater, and it is an "overmatch", I think? what do you say, any experience with this?

thanks in advance

I think the problem is surely the small cross-section. Are these corners, flat butts, what? People love to say, "Don't over-weld, only use as much weld as needed to carry the load" IME if your weld section is not equal to the parent metal, cracking is not "if'" but "when"..

agreed, it's lack of weld cross section. problem is, as a consultant I can only recommend improvements (it seems perfectly obvious to me and many others), but for some reason, there is resistance.

'cmon, step on the pedal guys! use a little filler metal, don't be shy!

but.. just... not.. happening..

this is occurring on a bunch of different joint configs ( lap, flair bevel grove, tee), but the question is, if I recommend 309, and they are still not using enough filler, will the higher UTS, and greater carbon tolerance improve the chances it will survive, despite overmatch? I think so.

Test it

do some sample parts - maybe you have to bring in a welder that works for you and SHOW what works.

same filler, more weld

different filler


Is the mass of the part chilling the parts suddenly and cracking then, or is it cracking in service ?

Maybe some post heat in that case.

What kind of weight or load is on it in service, does it vibrate or wiggle




You're showing us nothing and we are guessing at everything

cracking in service, can't show much here, propriety non disclosure etc.. loading is mostly static, except for the thermal cycling. roughly measured in hours not seconds.

the problem is perfectly known here, no mystery. the only question is the chance of cracking increasing or decreasing going to 309, in general.

I am not getting paid enough for the full test program, or for the "show 'em how", and it seems like they won't listen anyway..

just trying to get a little feedback before I make another recommendation that will probably be ignored...

Just a guess that adding filler and more heat adds to distortion on any stainless so that may be the reason they are reluctant to try that ?

Pretty much all the non 304/308 SS fillers are going to be an over match. If the material is 308 then E308 & E309 are recommended. If the material is 308L then the recommended fillers are E308L or E347.

Prolly not the filler though, my neighbors’ shop does a tidy biz fixing local restaurant junk. Some spot welded junk, some filler welded junk, brazed junk & junk that just cracked or broke...

Good luck,
Matt

thanks Matt, yup, we know its not the type of filler..just not enough of whatever. going to recommend the 309L and hope the added strength and resistance to ferrite formation helps a tiny bit.

yes Jim, sure that's a reason, easier to get it out the door looking good with less weld distortion, but then it just starts falling apart. doesn't look so good then!

From my experience giving advice, it is better to tell them what they NEED to hear, even if they do not want to, than to give advice that is palatable but not right. In the long run the latter encourages not listening and degrades your credibility. Can you go up the command chain?

yes agreed, believe me, I probably never told them anything they WANTED to hear!
that could be part of the problem.. but I'm trying to say it the right way..

I report directly to the owner of the "brand", but the fab shop is its own turf.

I fix this kind of stuff for the same type of outfit. They make the nice 1" round corners but they over polish the welds and they begun to crack and things like 3 bay sinks and stuff.

The problem is mist people aren't getting enough penetration on the welds and the gaps are splitting.

I deal with this with my own employees learning how to weld up Sanitary things. Some welds are fine with 10% penetration, some welds needs 50% some need 80% etc. Well most of them just weld at 10% because they like having 1 setting and not deal with proper welding procedures all day long. For example, one guy thought it was OK to do a 10% weld on a 10% weld, then go a 10% weld on a motor mount. "because they were on the same machine" he didn't think it mattered.



Edit, dealing with stainless warping is such a horrible business to be in sometimes. I've welding things up and warped them, and it's just because the stainless felt like warping. Such a pita
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