Debasis S.R and solution annealing of materials as per code rules may differ. ASME code specifies for S.R - a thumb rule - soaking at PWHT holding temp at 1 hr per inch. The same more or less applies to Solution annealing temp holding. For thin tubes- such as your TP 304 L - you have to be careful that this can warp the tubes if you hold for too long. Theoretically, even holding at SR temp will do from MEA - to prevent on-set of SCC. Mill anneal of SS 304 itself will be mostly suffice. Since Solution anneal is at higher temp - 1050 deg cent- the thin tube will be held at mill anneal as well as at solution anneal temp sufficient to reduce effects of all unwanted stresses and un-wanted precipitates in solid solution. I think the supplier might have taken into account the key effect to prevent warping of this thin tube at 1050 deg cent. Hence suggested to hold as short a time as possible at 1050 deg cent. Effective removal of all stresses will be there with this approach. For MEA service even this short time holding at 1050 deg cent may be helpful with no damage done to warp the tubes while forming or inserting in tube bundle. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India July 28,2008 E-mail nishi@vsnl.com >SA 213 TP 304L ( SS 304L ) Tubes (19.5 OD x 1.65 thk) to >be used in MEA service in reboiler. After cold bending the >vendor has subjected the U tubes to solution annealing at >1045C - 1068C. >But they have given only 20-30 seconds soaking time . > >Q1. Is there any code support to justify/ validate this 20 - >30 seconds soaking time ? >Q2. Does this very short soaking time sufficient for the >purpose of solution annealing ? >regards

Debasis It depends. If the tube is heated by induction process with and in a guided fixture to avoid warping, chances that the entire tube will be heated to 1050 deg cent even for short time holding like 30 sec - 45 sec. Your entire tube thickness will get more or less uniform temp of 1050 deg cent (solution annealing temp) followed by immediate fast air or water quench even with small time holding like this. Please check with supplier about this. If it is furnace heating to get 1050 deg cent - chances that uniform temp attainment may not be good for the entire tube length. The entire tube may not have the conducted heat of 1050 deg cent in this approach. Holding time may have to be something 5-10 minutes at soaking temp - 1050 deg cent. Then holding time has to be increased but chances of warping will have to be countered with out fixtures in the process of heating and cooling. Tubes have to have fixtures to hold through out the length to avoid warping. If you have still doubts, perform a mock test and see the tube microscopically and then assess if all carbides had gone in solid solution. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India July 30 E-mail: nishi@vsnl.com >Dear Sir, >This 20-30 second soaking time w.r.t. thin tube >warpage/distortion is OK but so far as the purpose of >solution annealing to dissolve all the harmful carbides back >into solid solution - does this 20-30 second is sufficient ? >regards >