Method for sulfurizing cast iron
AssigneeKabushiki Kaisha Toyota Chuo Kenkyusho
InventorsMikio Obayashi, Naoyoshi Watanabe
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Abstract
Cast iron is pretreated in an aqueous solution of nitric acid and then immersed in molten sulfur until a sulfurized layer is formed on its surface. The sulfurized layer is very thick and stable and has excellent molten aluminum resistance. Its uniformity is further improved by a subsequent diffusion treatment at elevated temperatures.
Claims7
A method for sulfurizing cast iron, which comprises the steps of pre-treating cast iron material by immersing the material in an aqueous nitric acid solution consisting essentially of nitric acid and water for a period of from 20 minutes to 3 hours, the concentration of nitric acid in said solution being from 1 to 10 percent by volume, and thereafter sulfiding the material in molten sulfur, thereby forming a sulfurized layer on the surface of the material.
Dependencies are inferred from the claim text.