Answer
17-7PH (Nau'in 631) wani yanki ne na hazo-austenitic-hardening bakin karfe da ake amfani da shi don maɓuɓɓugan ruwan raƙuman ruwa da ke buƙatar ƙarfin ƙarfi da juriya na lalata. A cikin yanayin 'CH900', kayan yana sanyi-raguwa zuwa Yanayin C sannan kuma ya taurare a $900^\circ F$ ($482^\circ C$). Wannan tsari yana haifar da kyawawan mahaɗan tsaka-tsaki na aluminum ($ Ni_3Al$) a cikin matrix na martensitic, yana ƙara ƙarfin yawan amfanin ƙasa zuwa kusan $190,000$ zuwa $240,000$ psi. Wannan babban rabo-to-tensile rabo yana ba da damar bazara don jujjuyawa mai mahimmanci ba tare da saiti na dindindin ba. A cikin aikace-aikacen sararin samaniya, an fi son wannan ƙarfe fiye da daidaitaccen bakin karfe 302 saboda yana kiyaye kaddarorin injinsa a yanayin zafi har zuwa $650 ^\circ F$ ($ 343 ^ circ C $), yana ba da kyakkyawan juriya na shakatawa idan aka kwatanta da carbon karfe.
