Beware of 317LMN Castings!
(New York state)
Dear Elia- We are a manufacturer of chemical processing equipment, and as such, we frequently weld base materials that must be strong and highly resistant to corrosion. On a daily basis we weld Duplex, Super Duplex,High-nickel alloys and titanium. We recently experienced a problem while welding a high molybdenum version of 317L stainless steel. The material is UNS S31726 containing 4-5% Mo. We were welding flanges or couplings to matching grade 1/2" wall pipe. Our coupling joint sees rugged service and must be able to withstand torque and bending loads. We prepare the joint by machining a double "J" groove into the coupling and sliding the coupling onto the pipe. We call the side of the coupling that is flush with the face of the pipe the "Face" side and the inboard groove is the "radius" side. We normally weld the face side complete and then start the radius side. In this case we were welding with an ENiCrMo-3 electrode, SMAW process, maintaining 300F interpass. We found that our radius side BASE metal was indicating micro-cracks alongside the weld edge. I guess it would be safe to say the cracks were in the HAZ. The cracks were oriented parallel to the axis of the weld, and only in the base metal. We were surprised to encounter the problem. Welding information for 317LMN is very basic. The only rule is to use a high moly filler metal. We started to investigate and noticed something odd on our Material Test certificates-the mechanical properties appeared questionable. Our paperwork showed an Elongation value of 26%. We expected to see a minimum of 40%. We also noticed the document made no reference to forging. We visited the vendor's website and found that the flanges were produced by a spinning casting process. We are in the process of double-checking the chemical analysis of the material at an independent laboratory. I suspect we are going to find elements such as sulfur, phosphorus and possibly lead are out of specification. I would suggest to your readers that they specify forged 317LMN if they plan on welding product forms other than plate or pipe.