Manufacture of white cast iron

Claim 1

A method producing a martensitic and/or lower bainitic low chromium white cast iron having a chromium content in the range of 0.5 percent to 3 percent and a maximum section thickness of about 2- 1/2 inches comprising the steps of, a. preparing a melt of a molten cast iron having a hardenability increasing alloy content consisting of from 0.5 percent to 3 percent chromium and from trace to 3 percent of a material selected from the group consisting of nickel, molybdenum, copper, manganese and vanadium, b. casting the molten cast iron into a mold having a maximum cavity section thickness of about 2.5 inches, c. retaining the casting in the mold until it cools to a shake-out temperature in the range of 1,700*F. to 1,950*F., d. cooling the casting after shake-out in still air to a temperature in the range of 1,325*F. to 1,650*F. and thereafter quenching the casting when at a temperature in the range of 1, 325*F. to 1,650*F. by immersing it in a bath liquid quenching medium selected from the group consisting of aqueous solutions of organic polymers, polyvinyl alcohol, salt bath and conventional quenching oils at a temperature above 80*F. so as to cool the casting at a rate of cooling sufficient to prevent the formation of pearlite without cracking or distorting the casting.

Claim 2

A method producing a martensitic and/or lower bainitic high chromium white cast iron having a chromium content in the range of 8 percent to 15 percent and a maxium section thickness of about 2- 1/2 inches comprising the steps of, a. preparing a melt of a molten cast iron having a hardenability increasing alloy content consisting of from 8 percent to 15 percent chromium and from trace to 3 percent of a material selected from the group consisting of nickel, molybdenum, copper, manganese and vanadium, b. casting the molten cast iron into a mold having a maximum cavity section thickness of about 2.5 inches, c. retaining the casting in the mold until it cools to a shake-out temperature in the range of 1,700*F. to 1,950*F., d. cooling the casting after shake-out in still air to a temperature in the range of 1,325*F. to 1,650*F. and thereafter quenching the casting when at a temperature in the range of 1, 325*F. to 1,650*F. by immersing it in a bath liquid quenching medium selected from the group consisting of aqueous solutions of organic polymers, polyvinyl alcohol, molten salt and conventional quenching oils at a temperature above 80*F. so as to cool the casting at a rate of cooling sufficient to prevent the formation of pearlite without cracking or distorting the casting.