GB746776A - Improvements in or relating to method of heat treating a high carbon alloy cast steel and the resulting product - Google Patents

Abstract

A method of spheroidising high carbon cast steel containing not less than 1,3 per cent or more than 1,65 per cent C, 0,4 to 1,00 per cent Mn, 0 to 0,6 per cent Cr, not more than 0,12 per cent S, 0,15 to 0,50 per cent Si, 0,02 to 0,1 per cent Al, the balance being iron and unavoidable impurities, eliminating grain boundary carbide network, and providing not more than 0,12 per cent graphitic carbon, comprises heating the cast metal to 1600-1900 DEG F., maintaining that temperature for at least one hour, cooling to below the austenite transformation temperature, reheating to 1350-1500 DEG F., maintaining this temperature for at least two hours, and cooling at a rate depending on the hardness required, the relationship between metallic-carbide forming agents (Cr, S) and graphitising-deoxidising agents (Al, Si) to result in the presence of not more than 0,12 per cent graphitic carbon being given by the formula: %C + 0,2(%Si + %Al) + (%Mn-0,70) - 1,5 times %Cr - 5(%S-0,04) - 1,14 = not more than 0,12 %. The final cooling may be in air or by quenching in a liquid, in the latter case a martensiticbainitic structure may be produced, and in the former a pearlitic structure. The final cast steel is stated to have good wear-resisting properties, high tensile strength, appreciable ductility, and high resistance to thermal and impact shocks.