JMitchell SS 316 L tube and Carbon steel tube sheet seal welding to tube to tube sheet. I would suggest that you think of S.S 310L- Mo or SS 309L- Mo -i.e, Low carbon grades of S.S. 309 or 310with Mo / cb stabilized grade filler wires - if available. S.S 308 does not have Mo and should nto be considered for this dissimilar between S.S. 361L and C.S joints. You have to take into consideration of dilution while seal welding between the S.S 316 L tube to C.S tube sheet. S.S 310 L - with Mo is available in the market. So is S.S 309 L - with Mo. Try TIG for seal welding usng Reverse polarity and 1.5 mm filler wire dia. You will have successful welding. I suggest that you inform the vendor to use S.S 310 L-Mo or S.S 309 L-Mo filler wire. You are right in not agreeing for S.S 308 filler wire for this dissimilar welding. Keep purging after seal welding is done. Inspect the joints by DPT. Avoid if possible welding too many adjoinign tube to tube sheet joints. A staggered apporach will give you higher quality welding. I wonder why you have thought of seal welding. Consdiering the temperature the joint will be subjected, you could think of stength welding. You can discuss with the vendor on joint design with strength welding instead of seal welding. if it is a double - groove design as per TEMA Class C or R at the tube sheets. strength welding would give you more trouble free operation - in my opinion. C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai India April 1 E-mail:nishi@vsnl.com >We have requested that 316L heat exchanger tubes be seal >welded to carbon steel 516-70 tubesheet with 309 wire >filler. The vendor is claiming that 308 is a better >selection for this joining. The process fluid is 50,000 TDS >aquifer heated to 600F. > >We are confident in our selection of 309 for joining carbon >steel to 316 or 309, but have no direct experience with >joining 316L to carbon steel. > >Seeking insights or direct experience. Thanks.

JMitchell: We also agree that 309 filler metal or electrode is a better choice for joining carbon steel to 316SS. 308 filler metal does not have enough chromium to prevent forming a hardenable (%7E9-12 chromium) alloy when diluted with carbon steel base metal. If you believe that you need extra pitting resistance, you could weld with 309-Mo. Hope this helps! David Hendrix The Hendrix Group Inc.