Ford Motor Company Limited

Roman M Nowicki

Bela V Kovacs

Charles A Stickels

Gerald S Cole

Chia-Ming Yen

A method is disclosed for forming a surface hardenable cast iron article by development of metastable retained austenite in the cell boundary of a ductile or semiductile cast iron. The method comprises (a) controlling the solidification of a cast iron melt to extend the eutectic arrest time to 4-12 minutes, the melt having by weight percent a carbon equivalent (carbon plus one-third silicon) equal to 4.3-5.0, manganese 0.55-1.2, nickel 0.5-3.0, and the remainder essentially iron, the melt having been treated to form cell boundaries in the solidified iron with a high proportion of the manganese being segregated in the cell boundaries; (b) subjecting the solidified cast iron to an austempering heat treatment to permit the segregated manganese in the cell boundaries to form metastable retained austenite; and (c) terminating the heat treatment prior to the conversion of the metastable austenite to a stable microstructure. To obtain the benefits of wear resistance, the method further comprises using the heat treated cast iron by stressing a surface region thereof and transforming the microstructure of such surface region to martensite.

Hardenable cast iron and the method of making cast iron

A method is disclosed for controlling the metallurgical structure of cast metals containing nonmetallic second phase structures. The method comprises (1) prior to making casting of the metal, determining a mathematical value associated with the rate of temperature change at liquidus recalescence and a value associated with the rate of temperature change at the eutectic arrest of a measured cooling curve for a sample of the metal melt; (2) comparing the determined values obtained with previously gathered values of the same type that have been correlated to known metallurgical structures; and (3) if the determined values are different than previously gathered values for a desired structure, add modifying and/or refining agents to promote a metallurgical structure change in the melt.

Method of controlling metallurgical structure of cast aluminum

A method is disclosed for making compacted graphite cast iron of improved strength and hardness while retaining excellent thermal conductivity, low shrinkage, and excellent damping characteristics. A ferrous alloy is melted consisting essentially of, by weight, 3-4% C, 2-3% Si, 0.2-0.7% Mn, 0.25-0.4 Mo, 0.5-3.0% Ni, up to 0.002% sulfur, up to 0.02% phosphorus, and impurities or contaminants up to 1.0%, with the remainder being essentially iron. The melt is subjected to a graphite modifying agent to form compacted graphite upon solidification. The solidified casting is heat treated by austempering and quenching to produce an iron having a matrix of bainite and austenite.

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Bloomfield Hills, MI, United States of America

Roman M Nowicki