If the base metal is also 316L SS, there's nothing to worry about. The welded metal will have the same corrosion resistance as the base metal. But if the base metal is 316 SS (with no L), then you'll have corrosion problems due to dilution first (the 316L will pick up some of the carbon of the 316) and then to chromium carbide precipitation on the grain boundaries ( a problem known as "sensitization"). However, I'd guess that the base metal IS 316L (otherwise you wouldn't be using a 316L rod), so don't be concerned.
Giovanni S. Crisi
Sao Paulo - Brazil
By -
Date 05-11-2000 16:34
Thanks so much for your kind, prompt reply.
BTW, we are not using any rod. The material is thin (.05") The weld would only involve the pieces of 316L SS being joined.
Do you know if there could be a problem of "crossing" at the overlap weld at the end of a circumferential seam weld?
Thanks again.....
Lynne
Please, I do not wish to insult any persons intelligence but, do the people involved here know what the L in 316-16L indicates?
The suffix L indicates "Low carbon content". Most stainless steels pertaining to the 300 series (316 among them) have a carbon content of 0.08 percent when there's no L in the designation and 0.015 percent when the letter L shows up.
Giovanni S. Crisi
Sao Paulo - Brazil
Dear Lynne:
Both process, GTAW and resistance, imply fusion of the base metal for the join; then you will always obtain a heat affected zone (HAZ) around the weld metal and zones with temperatures range betwen 450C and 900C wich is the "sensitization range" for austenitic stainless steels. In this range the carbon reacts with the chromiun and forms "chromiun carbides" (Cr23C7 most of them) at grain boundaries; the trouble is the chromiun depleted zone around the carbides wich has a lesser corrosion resistance that the base metal. One way to avoid this situation is use a low carbon SS like yours (316L), because you have no enough carbon for the reaction with the chromiun. Then, like my friend Mr. Crissi said, you don't have to be concern with this weld, but I want to add something: if you have to do crossing welds, then you need to use filler metals with low carbon content (like the base metal) for avoid the presence of HAZ in weld metal (when you do a weld over other weld) with enough carbon for impair the corrosion resistance. If you need more help, please contact me.
Jorge Giraldo
MedellĂn, Colombia