Abstract: A cast iron having an austenitic matrix and consisting essentially of from 1% up to 3.5% carbon, up to 1.5% silicon, from 32% to 39.5% nickel, from 1% to less than 4% cobalt, up to 41% of the combined total of nickel plus cobalt and the balance substantially all iron provides a low expansion coefficient, good castability, good cutting properties and good damping capacity.

Abstract: This invention is directed to a cast iron having a graphite structure in an austenitic iron matrix and consisting essentially of, in weight %, at least about 1.0% and not more than about 3.5% of carbon, not more than about 1.0% of silicon, at least about 29% and not more than about 34% of nickel, at least about 4% and not more than about 8% of cobalt and the balance substantially all iron.

Abstract: Spherical graphite cast iron utilized to prepare a lapping tool is manufactured by casting a molten composition into a mold cavity, and by chilling one side of the resulting casting thereby causing unidirectional solidification, the one side being used as the operating surface of the lapping tool. The molten composition consists of 3.0-3.8 wt. % of carbon, 2.0-2.9 wt. % of silicon, 0.3-0.9 wt. % of manganese, less than 0.05 wt. % of phosphorus, less than 0.03 wt. % of sulfur, 0.2-1.0 wt. % of nickel, 0-0.8 wt. % of copper, 0.05-0.5 wt. % of molybdenum, 0.03-0.09 wt. % of magnesium and the balance of iron. The lapping tool made of this casting has a percentage of sphericity of higher than 80%, graphite particle diameter of less than 100 microns, a density of graphite particles of larger than 70/mm.sup.2, and a Vickers hardness of larger than 200.

Abstract: A lapping tool with a flatness in the range below 20 .mu.m which is made of at least cast iron having an austenitic matrix and consisting essentially of from 1% up to 3.5% carbon, up to 1.5% silicon, from 32% to 39.5% nickel, from 1% to less than 4% cobalt, up to 41% of the combined total of nickel plus cobalt and the balance substantially all iron providing a low expansion coefficient, good castability, good cutting properties and good damping capacity. (By % is meant % by weight).

Abstract: Spherical graphite cast iron utilized to prepare a lapping tool is manufactured by casting a molten composition into a mold cavity, and by chilling one side of the resulting casting thereby causing unidirectional solidification, the one side being used as the operating surface of the lapping tool. The molten composition consists essentially of 3.0-3.8 wt. % of carbon, 2.0-2.9 wt. % of silicon, 0.3-0.9 wt. % of manganese, less than 0.05 wt. % of phosphorus, less than 0.03 wt. % of sulfur, 0.2-1.0 wt. % of nickel, 0-0.8 wt. % of copper, 0.05-0.5 wt. % of molybdenum, 0.03-0.09 wt. % of magnesium and the balance of iron. The lapping tool made of this casting has a percentage of sphericity of higher than 80%, graphite particle diameter of less than 100 microns, a density of graphite particles of larger than 70/mm.sup.2, and a Vickers hardness of larger than 200.