抄録
It has been found out in low-carbon 9 to 10 Ni high-toughness ultra-high strength steels that high-temperature solution treatment above 1200°C improves their toughness (vE shelf) significantly. This corresponds to the solution of coarse M6C carbides greater than 0.3μ, which are retained in the steels at the state as rolled or as ordinarily heat-treated. These carbides again precipitate between 900 to 1100°C during cooling after high-temperature solution treatment at the cooling rate slower than 0.5°C/s. The steels high-temperature solution-treated exhibit excellent vEshelf without deterioration of proof strength and ductile-to-brittle transition temperature, compared to conventional heat treatment, when they were again austenitized at lower temperature before aging.
