I'm trying to substitute a heat treated 17-4PH material for a design that currently uses 4340 heat treated (tempered at 1100°F) steel. It looks like a 17-4 H1075 or H1100 will work for my application, but I need information on the impact strength of these two heat treated conditions in a subzero state (10°F to -100°F).

Cranston 17-4 PH is a martensitic grade S.S - PH grae material with higher strength (mechanical properties). In heat treated at 1150 deg F it will have good impact strength at room temp conditions with hardness in the range of 277 BHN. For sub -zero conditions given in your enquiry, 17-4 PH - any one from H 1075 or H 1100 or H 1150 grades may behave erratically from impact strength values. Impact properties may vary from 10-40 joules compared to 1075 to 1150 deg F - solution annealed and heat treated for 4-5 hrs at 1075 to 1150 deg F conditions ( i.e., aged at 1075 to 1150 deg F conditions) where you can get reasonably good Charpy impact values of 40-108 Joules.). Charpy values for 1150 F treated 17-4 PH will be the best and consistent at Room Temperature conditions. Due to likely low and erractic behaviour in impact values at sub-zero conditions for martensitic grade PH materials - especially 17-4 PH it is not advisable to try. Reason for this could be the residual retained austenite can change to martensites at sub -zero conditions and this can lead to dramatic variation in impact strength for this material. It is not advisable to use this material for low temperature at sub zero conditions and for high temperature use above 350 deg centigrade. Trust this is of some use for you C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai 20 India Dec 7, 2004 E-mail: nishi@vsnl.com >I'm trying to substitute a heat treated 17-4PH material >for a design that currently uses 4340 heat treated >(tempered at 1100°F) steel. > >It looks like a 17-4 H1075 or H1100 will work for my >application, but I need information on the impact strength >of these two heat treated conditions in a subzero state >(10°F to -100°F).