High strength large steel forging

摘要

A high strength large steel forging of the present invention has highly balanced strength and toughness, and has high fatigue strength. The high strength large steel forging includes compositions that specify contents of C, Si, Mn, Ni, Cr, Mo, V, and Al, and S as an unavoidable impurity; in which the high strength large steel forging consists of a martensitic structure or a mixed structure of martensite and bainite; a grain size of prior austenite is 19 µm or more and 70µm or less; and a maximum block size of martensite is 15 µm or less and a minimum block size of martensite is 0.5 µm or more.