HIGH TEMPERATURE BRAZE HEAT TREATMENT FOR PRECIPITATION HARDENING MARTENSITIC STAINLESS STEELS

摘要

1293116 Brazing UNITED STATES ATOMIC ENERGY COMMISSION 19 April 1971 [16 April 1970] 26845/71 Heading B3R [Also in Division C7] The mechanical and corrosion resistance properties of a semi-austenitic stainless steel braze assembly are improved after joining by rapidly heating the assembly to 2045-2150‹ F. for up to 5 mins. by (a) cooling to 1900-1925‹ F. in less than 30 mins. and holding thereat for 50-70 mins., (b) cooling to 1700-1725‹ F. in less than 30 mins. and holding thereat for 50-70 mins.; (c) quenching to below 1100‹F. in up to 20 mins. and to room temperature in up to 60 mins.; (d) sub-zero cooling, within 48 hours of completion of previous step, to -100‹ to -125‹F. for 170-190 mins. and warming to room temperature; and finally tempering at 985-1015‹ F. for 170-190 mins. with subsequent cooling to room temperature (e.g. in less than 1 hour). A suitable steel is as set forth in U.S. Specification 2,799,602, viz. C up to 0À15%, Cr 12-18%, Ni 3À5-7%, Mo 2-3%, Si up to 0À5%, Mn 0À25-20% and N 0À05- 0À15%, balance Fe plus impurities. A suitable brazing alloy is that sold under the trade name AMD 72-1 100 which contains 18À5-19À5% Cr, 9À8-10À3% Si, and up to 1% each of Fe and Mn, the balance being Ni. The brazing and subsequent steps may be effected in hydrogen with a dew point not greater than -90‹F, The tempering may be effected under a vacuum of less than 1 x 10SP-4/SP mm. Hg.