奥氏体韧性铁ASTM A439 奥氏体韧性铁ASTM A439 奥氏体韧性铁:A439型D-2,A439型D-2B,A439型D-2C,A439型D-3,A439型D-3A,A439型D-4,A439型D-5,A439型D-5B,A439型D-5S 韧性结节石墨铁