Parag, The intended service is not made clear - presumably in highly corrosive media - as it looks from your question - to give over lay welding of SS for the entire tube sheet thickness. SMAW welding of 1040 mm x 65 mm thick tube sheet - A 516 Gr 60 with 15-16 mm thickness deposit and then machine to required over lay thickness will take considerable time. To my mind this may have to be done in two stages to avoid warping and distortion of tube sheet - due to excess welding of 15-16 mm thickness machined later to 10 mm sound SS over lay. SS 310 Moly electrodes ( with extra low carbon grade) would be better than simple SS 309 Mo (i.e., without low carbon grade SS 309) as dilution of 25- 30% can be expected in the first run definitely and possibly extend upto first two runs. Further runs beyond first two runs can possibly be done with SS 309 Mo - low carbon grades to make up the 15-16 mm thickness. Extra low carbon grade SS 310 Mo with some stabilizing grade alloying elements like Cb/Nb and also SS 309 Mo low carbon grade with stabilizing element like Nb/CB or Ti would most probably be ideal to use than simple SS 309 Mo grade being considered by you (currently). Welding may have to be done in staggered ways to avoid distortion due to excess heat. PWHT - i.e., S.R to suit the 65 mm thick C.S tube sheet after welding or after machining is a "must". If the intended service is likely to promote problems of SCC in SS material, then you may have to do in two stages the S.R for the carbon steel tube sheet. If the intended service is to be used in service that is likely to promote IGSCC (intergranular stress corrosion cracking) , perform a test coupon after qualifying welders (PQR) and welding procedure (WP) as per ASME code needs and perform a corrosion evaluation test before actual over lay is made in staggered stages of heating and cooling. If welding is broken due to large surface area to be covered, an intermediate anneal may become necessary. Also wrapping the tube sheet whenver welding sequence is broken to avoid direct natural air to come in contact. This is necessary - each time a "stop and re-start of welding operation is done". First two layers have to be thoroughly D.P. tested for any surface fissures or cracks due to dissimlar welding and dilution during welding. Final machining by 4-6 mm may work harden the SS over lay. Possibly a final PWHT - to suit carbon steel thickness is definitely needed to relieve all stresses from weld over lay on carbon steel tube sheet and also on the SS over lay weld. Final machined weld over lay - 10 mm - has to be DP tested and also UT flaw check. UT Flaw check can also be done after first run or second run so that you are sure that 100% bonding has been established between two dissimilar grade steels (one C.S - 65 mm thick and SS - to be made as 10 mm over lay weld). Hope this helps you C.V.Srinivasan Nishi Engineers Pvt. Ltd India March 09, 2008 E-mail: nishi@vsnl.com >In a picular case application, client requires to overlay >carbon steel tubesheet with SS 316 materail. > >Tubesheet diameter is 1040mmX 65mm THK, materail of >construction being SA516GR60. Overaly needs to be done in a >diametre of 970mm and total cladding thickness required >after machining is 10mm. > >The procedure we intend to follow is deposition of material >by SMAW process using 309 Moly electrods for first 2 runs >and followed by SS 316 electrods to complete overaly of 14 >to 15mm height in 970mm diameter. > >I would like to know if this procedure will be adequate to >follow and what precautions do I need to take during the >procedure. Also, if any heat treatment is required during or >after the overaly. What are the test required to be carried >out to achieve sound metal deposition and proper cladding. > >I will be using a test coupon to carry ut the cladding of >the materail and establising the procedure prior to carry >out overlay on the job. > >Regards, >Parag