| 摘要 |
PROBLEM TO BE SOLVED: To develop cast steel which has excellent properties to impact fracture. SOLUTION: The high-tensile and high toughness cast steel has a composition containing, by weight, 0.3 to 0.7% C, 1.0 to 2.0% Si, 0.8 to 2.0% Mn, 0.3 to 1.5% Mo, 0.3 to 1.5% Cu,≤0.1% P,≤0.07% S,≤1.0% Ni,≤1.0% Cr and≤1.0% V, and the balance Fe with impurity elements. The cast steel has a bainitic structure containing 2 to 30 vol.% retained austenite by austempering treatment. The cast steel has a tensile strength of 1,100 to 1,900 MPa and a dynamic fracture toughness of 80 to 110 MPa m<SP>1/2</SP>. Molten steel is cast to form into a casting stock, and the casting stock is subjected to austenitizing treatment at 850 to 1,000°C for 30 min to 3 hr and is subjected to isothermal transformation treatment at 250 to 450°C for 10 min to 2 hr. COPYRIGHT: (C)2004,JPO
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