METHOD FOR MANUFACTURING CAST Ni-Cr-Mo STEEL HAVING HIGH STRENGTHIMPACT RESISTANCE AT LOW TEMPERATUR

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The present invention relates to a method for manufacturing a high-strength Ni-Cr-Mo steel cast material and a steel cast manufactured thereby. According to the present invention, the method comprises : (a) a step of casting a molten metal including 0.4-0.5 wt% of C; 0.4-0.5 wt% of Si; 0.5-0.8 wt% of Mn; 2.0-2.5 wt% of Ni; 2.0-2.5 wt% of Cr; 0.3-0.5 wt% of Mo; 0.1-0.2 wt% of V; above 0 to 0.5 wt% of Ti; above 0 to 0.05 wt% of Al; above 0 to 0.005 wt% of B; remaining Fe; and other inevitable impurities; (b) a step of fully annealing at 850-900 ° C; (c) a step of quenching at 805-870 ° C; and (d) a step of tempering at 500-550 ° C. According to the present invention, the method is capable of successively conducting a full annealing, quenching, and tempering under an optimized thermal treatment condition for an Ni-Cr-Mo alloy steel cast by adding a minimized volume of expensive rare metal for improving mechanical characteristics such as strength, manufacturing a steel cast of 1300 MPa with a remarkably enhanced strength over that of a commercial Ni-Cr-Mo alloy steel cast, and providing a steel cast which can be usefully used as material for a steel cast product requiring a high strength such as an impeller blade for a sand pump.COPYRIGHT KIPO 2019