Chou P4 is air hardening grade. When you weld disssimilar grade of P 11 (P4) material with Alloy 800 H ( P45) the axiom is to take care of buttress welding wich will more or less match the final weld composition - i.e., Alloy 800 H composition. When you weld air hardening grade with P 45, simplest way is to do buttress weld with ENiCr-Mo-3 and immedaitely do a post weld wrap with ceramic wool blanket and hold at an intermeditate temperature as long as possible and then allow slow cool with wrapping continued. That is do not allow air to get in from the time of wrap after buttress welding. This will help a lot for less thick materials (say < 12 mm thickness) An intermediate temp hold with post weld wrap will do a lot of help in avoiding micro-cracks in still air cool for the P11 material. Evaluate the buttress weld by D.P. before doing the P45-P5 welding for the Alloy 800 H. For greater thickness - 1 " (25 mm or greater), do a PWHT at 720 deg centirgrade of the buttress weld and P11 before further welding is done with Alloy 800 H . This will remove all internal stresses in P 11 and the buttress weld before final welding of Alloy 800 H with Alloy 800 H grade filler or electrode. For the final weld betweeen matching Alloy 800 H with Alloy 800 H weld with equivalent welding electrode you need not do any PWHT . Final weld with P45 to P 45 (Alloy 800 H with buttress weld can be with any ENiCrFe-Mo electrode. If the service duty is not severe, you can also do a PWHT for the entire joint - which will not drastically affect the performance of Alloy 800 H for a holding time of 30 minutes to 60 minutes at 720 deg centigrade (Which is the PWHT temperature for P11 material). Trust this will help you. C.V.Srinivasan Nishi Engineers Pvt Ltd India Nov 30,2005 E-mail:nishi@vsnl.com >Simple question. > >If you are welding Alloy 800H (P45) to SA335 P11 (P4) and >per code the SA335 P11 material requires PWHT (over 1/2" per >ASME B31.3) do or don't you PWHT? > >My concern would be the PWHT temperature for the P4 material >is in the low range for age hardening the P45 material. >However, time at temperature isn't sufficient to cause age >hardening. > >Scenarios: > >Could you apply a E309L butter layer to the P4 material, >PWHT and then weld the P45 to P8 using ENiCrMo-3 electrode? > >Or > >Do weld out the joint as normal, apply the PWHT because time >at temperature isn't sufficient enough to cause age >hardening effect on the nickle alloy? > >Or > >Do you apply a butter layer with ENiCrMo-3, PWHT P4 material >then weld out the joint using ENiCrMo-3? > >Looking forward to all responses!!!!!!!! > >Thanks > >Chow