CAST STEEL ALLOY AND METHOD, PROVIDING HIGH ELONGATION AND SAVING MANUFACTURING COSTS, FOR MANUFACTURING AUSTEMPERED HIGH CARBON STEEL HAVING HIGH STRENGTH AND HIGH TOUGHNESS USING THE SAME

PURPOSE: To provide a cast steel alloy which has superior tensile strength compared with austempered ductile cast iron, has high elongation, obtains manufacturing cost reduction effect, uniformly forms ausferrite structure without graphite and shows required mechanical property level or more of steel products, and a method for manufacturing austempered high carbon steel having high strength and high toughness using the same. CONSTITUTION: The cast steel alloy comprises 0.6 to 1.2 wt.% of C, 1.0 to 3.0 wt.% of Si, 0.1 to 0.4 wt.% of Mn, and a balance of Fe and inevitable impurities. The cast steel alloy comprises 0.6 to 1.2 wt.% of C, 1.0 to 3.0 wt.% of Si, 0.1 to 0.4 wt.% of Mn, 0.1 to 1.0 wt.% of Cr, 0.2 to 0.4 wt.% of Mo, 0.6 to 1.2 wt.% of Cu, 1.2 to 2.0 wt.% of Ni, and a balance of Fe and inevitable impurities. The method for manufacturing austempered high carbon steel having high strength and high toughness using a cast steel alloy comprises a process of heating a core part of the cast steel alloy to temperature range of 850 to 1000 deg.C in an anoxic atmospheric furnace, and maintaining the cast steel alloy for 1 to 5 hours from a time when the cast steel alloy reaches the temperature range; and a process of cooling the quenched cast steel alloy in the air after quenching the cast steel alloy in a salt bath for low temperature heat treatment having temperature range of 250 to 400 deg.C for 10 to 120 minutes.