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The method of Cast iron steel

The method of producing a wear and abrasion resistant Cast iron steel which comprises, melting an iron alloy consisting essentially of 2.5 to 3.10% carbon, 1.40 to 2.00% silicon, manganese, sulfur in an amount equal to about 0.02 to 0.4% in excess of that required to combine with all the manganese in the alloy and the balance iron, the carbon and silicon contents being selected to produce a carbon equivalent of 3.00 to 3.60%, the carbon equivalent being between 3.00 and 3.30 when the sulfur in excess of that required to combine with all the manganese is below 0.05%; casting said alloy in a sand mold to produce a white iron casting having a microstructure characterized by substantially all of the carbon being in the combined form and appearing as discrete particles of an iron sulfide-iron carbide complex in a pearlitic matrix; annealing the casting for a period of 2 to 20 hours at a temperatutre of between 1650¡ã to 1850¡ã F. to graphitize the iron and at least partially break down the iron sulfide-iron carbide particles;

causing the iron sulfide particles so formed to grow in size by furnace cooling the casting down to a temperature of about 1500¡ã to 1600¡ã F. and subsequently cooling the casting to room temperature at a more rapid rate to produce a microstructure having a pearlitic or martensitic matrix containing graphite in the form of temper carbon and discrete particles of iron sulfide of generally rounded shape visible at a magnification of 100 diameters.

 2. The method called for in claim 1 wherein the carbon equivalent of the alloy is above 3.30% only when the free sulfur content exceeds 0.05% and approaches 3.60% only as the free sulfur content approaches 0.40%.

 3. The method called for in claim 1 wherein the time and temperature of annealing is selected to retain in the microstructure of the finished casting particles of said iron sulfide-iron carbide complex in the matrix in addition to said discrete particles of iron sulfide.

 4. The method called for in claim 1 wherein said step of more rapid cooling comprises cooling the casting in air to produce a pearlitic matrix.

5. The method called for in claim 1 wherein said step of more rapid cooling comprises quenching the casting in oil to produce a martensitic matrix.

6. The method called for in claim 1 wherein the casting comprises a camshaft and said step of more rapid cooling to room temperature is controlled to produce a pearlitic matrix and thereafter the cam surface portions of the camshaft are subjected to a surface heat treatment at a temperature below the annealing temperature to produce a martensitic structure on said cam surface portions of the casting.