Welding Tips and Tricks

Ok guys I’m new here, I’ve just been a lurker. So please be gentle if I have wrong forum etiquette.

So a little about what I work on. We build small structural (I’m using that term loosely) items that have water pumped through them. 2-35 PSI or so. It’s all 304ss and most of it is made from sch10 pipe from 2" to 6". Every once and a while we'll use Sch 40.

So I have one welder that likes to cool off their welds with a wet rag. Then I have another welder that is causing me all kinds of grief about it, by not only giving me crap about it, but also has gone to my boss, my bosses boss and also our QC dept. I'm wondering what y’alls take is on quench or cooling off a weld and around a weld on 304ss. I've always that that lower stainless like 304 is fine to quench. He keeps saying that it is weakening and making the weld brittle. Can someone give me the science behind it, one way or the other? Or even something in writing somewhere. TIA.

TFPWelder wrote:Ok guys I’m new here, I’ve just been a lurker. So please be gentle if I have wrong forum etiquette.

So a little about what I work on. We build small structural (I’m using that term loosely) items that have water pumped through them. 2-35 PSI or so. It’s all 304ss and most of it is made from sch10 pipe from 2" to 6". Every once and a while we'll use Sch 40.

So I have one welder that likes to cool off their welds with a wet rag. Then I have another welder that is causing me all kinds of grief about it, by not only giving me crap about it, but also has gone to my boss, my bosses boss and also our QC dept. I'm wondering what y’alls take is on quench or cooling off a weld and around a weld on 304ss. I've always that that lower stainless like 304 is fine to quench. He keeps saying that it is weakening and making the weld brittle. Can someone give me the science behind it, one way or the other? Or even something in writing somewhere. TIA.

304 is fine to quench, with two caveats.
304 is low in carbon and ferrite, so does not harden the way carbon steels do.

If it is welded with 308, this is a ferrite-bearing rod and can induce cracking. Don't quench until the color has subsided.

Also, 304 is far more prone to shrinkage in the heat affected zone than carbon steels, so applying quenching at the wrong time or place can pull your weld out of square.


Steve

If it is welded with 308, this is a ferrite-bearing rod and can induce cracking. Don't quench until the color has subsided.

How about if its welded with 316 filler?

TFPWelder wrote:

If it is welded with 308, this is a ferrite-bearing rod and can induce cracking. Don't quench until the color has subsided.

How about if its welded with 316 filler?

316 is also ferritic.

312 is lower in ferrite, and 347 is fully Austinitic. These present their own problems, though. Cold-cracking, specifically. Cooling of the weld has to be tightly controlled.

In my opinion, I'd chose 308, and rather then quenching, I'd air-cool with an extended blast from an air nozzle on your compressor. Interpass temperature for 308 on 304 is around 350*F, so you don't have to cool it to ambient to keep going.


Steve