We are producing a stainless steel pressure vessel. The material is 316l and the size is DN2400x29750x30mm.The welding method is TIG+SAW(X-type groove,1 pass TIG from the 2 sides at the same time as root pass).The Hear Input is kept low and the interpass temperature is no higher than 150.After welding, we know the main chemical element of the welding metal is C(0.030%jCr(18.02%)Ni(11.07%)Mo(2.20%)S(0.035%jP(0.003%) by using PMI testing method. But the welding specimen are both cracking when using the testing method of ASTM A262 Practice E.That's why? Any response will be appreciated. Many thanks.
What is the calculated heat input? You need to be below 35000 Joules/inch of weld (1378 Joules/mm). Heat input should be calculated by (arc volts x amps x 60) / travel speed. Travel speed should be measured in inches per minute or mm per minute.
Also, I don't have A262 here at home. But I'm thinking Practice E is not applicable to 316 or 316L. Check A262 to see if this is correct.
I checked ASTM A262 and found that Practice E does apply to 316 or 316L. I guess I was thinking about the equivalent CF3M and CF8M castings which use Practice F.
I think also that you have to know what your Joule input is..Tig and saw can both put more heat than you need very easily..sounds like you have a haz problem. People are going to Pulse process to get away from saw.. that process works well in controlling your heat input..testing results are also pretty good..
After reading your post again, I see the sulfur content is a bit high for weld metal (0.035%). This may be part of your problem if the cracks are in the weld metal. You should also check ferrite content of the weld to make sure it is not too low to prevent hot cracking. Here's some good info on ferrite number calculation:
http://www.lincolnelectric.hu/pdfek/A_6_ferit.pdf
If the cracks are in the base metal next to the weld, then I suspect the heat input is too high causing sensitization of the base metal. Did the samples fail the Practice A screening test?
Forum
