Gui Gonsolez S.S 410 is a general purpose martensitic S.S. This requires slow heating to reach 980 deg cent and hold sufficient time before oil quenching. To attain hardness in the range 40-45 HRc, slowly heat to 980 deg cent and oil quench. In hardened condition, tempering is necessary for this at 200 deg to 450 deg cent - depending on the hardenss desired, Hold at tempering temperature for duration long enough to get uniform temperature in section thickness. A two hour tempering temperature holding is desirable. If you are particular to get a higher hardness in the range of HRc 43-45 then you may have to hold at tempering temperature of 200-250 deg cent for two hours after oil quenching from 982 deg cent. Trust this will help you C.V.Srinivasan Nishi Engineers Pvt Ltd India Dec 20,2006 E-mail: nishi@vsnl.com >We have a castings Impellers in 410, your thickness is 19 mm >and the hardness is 45/50 HRC. >We made the heat treatment at 980 C and cooling in oil at >60 C and the harness was 30 HRC >Retreatment at 980 C and cooling in strong air at 60 C - >strees relifing at 320 C and the hardness was the same. >What is the apropriate heat treatment for this pieces? and >if has a answer to a very low hardness for this pieces? >Regards