17-4 PH Welding Issue

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We have a pump housing that is made of 17-4 PH and the shop doing a repair on the jacket is having issues welding the jacket to the housing, both are of the same material and the welds crack.Filler metal being used is E-630.Does anyone out there have a written procedure for welding 17-4 PH that I could use for a comp to the repair shops?
Reply:I can't give you a copy of the procedure, but for 17-4 our procedure says to use GTAW with ER630 "Only", stringer beads, 50 deg F min preheat and 350 deg F max interpass. That's not to say that you can't weld it with SMAW, just that my employer hasn't qualified an SMAW prrocedure. I don't have much experience with 17-4, so I can't offer any personal advice.
Reply:welds4d,This is the filler metal that is currently being used, however the repair shop is experiencing cracking of the welds.I myself have welded alot of 17-4 and never had any issues, it is one of the easiest materials to weld and for the life of me do not understand why they are experiencing the cracking problem.Perhaps some one else will chime in on this?Thanks
Reply:17-4PH is a heat treatable stainless steel alloy.  It will air harden.  But the cause of the problem may not be the alloy itself.  We need some more information to narrow down the root cause of the problem.Is the weld hot cracking, as it's being welded?  Or is the cracking delayed, only appearing after the weld has cooled?  Is it cracking next to the weld, on the fusion line with the base metal, or along the centerline of the weld?Something else that may be relevant...I'm guessing this a repair to an existing pump.  What does that pump move?  Water, or something else?  Does the area around the crack come in direct contact with the substance being pumped?Hot cracking would point towards a highly restrained joint where the stresses involved are pulling the weld apart as the material in and around the weld softens under heating.  Or it could be contamination with sulfur or another trace element; which could create low melting temp intermetallic compounds in the weld pool.Delayed cold cracking would point towards hydrogen cracking(unlikely) or perhaps thermal stresses and/or formation of very hard, brittle martensite in the weld or HAZ.  Untempered 17-4PH is extremely brittle due to the presence of martensite in the material.  Welding with low heat input and the resulting rapid cooling could promote the formation of martensite.Fill in the missing blanks and we can try to narrow down the list of problems.  From there we can suggest some welding procedure elements that might help.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector