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AssigneesKabushiki Kaisha Toshiba, Toshiba Ceramics Co., Ltd.
InventorsToshio Shikata, Hirokazu Tokoro, Takanobu Nishimura, Masaharu Kinoshita, Norio Masuda
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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.
A lapping tool comprised of spherical graphite cast iron, said spherical graphite cast iron having a graphite particle diameter of less than 100 .mu.m, a density of graphite particles greater than about 70/mm.sup.2, and a Vickers hardness of greater than about 200.
A lapping tool that is the product of a process comprising the steps of
Dependencies are inferred from the claim text.