Cryogenically super-hardened high-chromium white cast iron and method thereof
AssigneeTownley Foundry & Machine Co., Inc.
InventorRoman Radon
Life of this patent
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Abstract
A highly abrasion-resistant, high-chromium white cast iron alloy containing the following elemental analysis in percent by weight: 2.4-3.8% carbon, 0.4 to 2.0% manganese, 0.2 to 1.9% silicon, 0.0 to 3.0% copper, 1.5 to 4.5% nickel, 12.0 to 29.0% chromium, and the remainder iron; and super-hardened by placement in a cooling medium at a temperature of at least -55.degree. C. for a time sufficient to cause the iron alloy to have a hardness of at least about 700 HB.
Claims22
A process for making a high-chromium white cast iron alloy, said process comprising the steps of:
- (1) preparing a molten metal composition having an elemental analysis in percent by weight of the total consisting essentially of 2.4 to 3.8% carbon, 0.4 to 2.0% manganese, 0.2 to 1.9% silicon, 0.0 to 3.0% copper, 1.5 to 4.5% nickel, 12.0 to 29.0% chromium, and the remainder being iron;
- (2) pouring the molten metal composition into a mold to form a casting and cooling the casting to room temperature without precipitation of substantial amounts of secondary carbides in the matrix of the casting;
- and,
- (3) placing the room temperature casting in a cooling medium at a cryogenic temperature of about -55.degree. C. or less for a time sufficient to cause the casting to have a hardness of at least about 700 HB, said cryogenic cooling being carried out without prior heating of the room temperature casting sufficient to cause precipitation of substantial amounts of secondary carbides in the matrix of the casting, and said hardened casting having a martensitic matrix which is substantially free of precipitated secondary carbides.
A product comprising a high-chromium white cast iron alloy having a hardness of at least about 700 HB and a martensitic matrix which is substantially free of secondary carbides, said alloy having been made by a process comprising the steps of:
- (1) preparing a molten metal composition having an elemental analysis in percent by weight of the total consisting essentially of 2.4 to 3.8% carbon, 0.4 to 2.0% manganese, 0.2 to 1.9% silicon, 0.0 to 3.0% copper, 1.5 to 4.5% nickel, 12.0 to 29.0% chromium, and the remainder being iron;
- (2) pouring the molten metal composition into a mold to form a casting and cooling the casting to room temperature without precipitation of substantial amounts of secondary carbides in the matrix of the casting;
- and,
- (3) placing the room temperature casting in a cooling medium at a cryogenic temperature of about -55.degree. C. or less for a time sufficient to cause the casting to have a hardness of at least about 700 HB, said cryogenic cooling being carried out without prior heating of the room temperature casting sufficient to cause precipitation of substantial amounts of secondary carbides in the matrix of the casting, and said hardened casting having a martensitic matrix which is substantially free of precipitated secondary carbides.
Dependencies are inferred from the claim text.