Yogi Norsok - M 650-6 Mo, UNS S 31254 has a near equivalent to commonly known Type 254 SMO grade aus S.S with 6-7% Mo and N - 0.18 -0.22% addition grade aus S.S material sold in market. Type 254 SMO is highly resistant to chloride resistant environment like sub-sea piping components. Solution Annealing temperature Type 254 SMO - Min: should be to meet ASTM requirement is 2100 deg F or close to 1150 deg cent, hold for sufficient time, followed by water quenching. Norsok M 650 (M 630 standard) probably specified that if a supplier gives with higher Mo content Type 254 SMO grade around 7% Mo and higher N2 around 0.20-0.25% stabilized grades then reaching a higher temperature of 1225 deg cent would be bette from solution annealing temperature to dissolve all precipitates and take on solid solution. Type 254 Mo equivalent grade material tend to form strong intermetallic precipitates while cooling after welding or after solution annealing (if not water quenched immediately) Generally, 1150 deg cent + or minus 10-15 deg cent temp is to be maintained for solution annealing of this material. Attaining 1225 deg cent and holding at 1225 deg cent is more difficult than holding at 1150+ 10 deg cent (even though temp increase is only 50 deg cent higher). Holding at 1150 + or minus 10 deg cent for sufficient time to soak even for higher Mo /N bearing Norsok - 6 Mo grade may be sufficient for all practical purposes. Trust this will help you C.V.Srinivasan Nishi Engineers Pvt Ltd India July 05, 2007 E-mail: nishi@vsnl.com >Hi, >Currently we are working on the one of the subsea >project.For this project we are refering NORSOK std.As per >M-630 for 6 MO material (casting) the solution annealing >temperature shall be >=1225 deg C. but while as per ASTM >std. it shall be 1150 deg C. >During the vendor document review some vendors have offered >the material as per ASTM and some as per NORSOK. >Can anybody tell me why there is difference between the >solution annealing temperature as per these two standards?