| 摘要 |
PURPOSE:To form a sliding surface having hardness and lubricity in combination on the surface of a cast iron product by controlling the graphite shape in the cast iron structure in the position of the cast iron product where the lubricity is to be provided and subjecting said part to surface hardening without melting the above-mentioned graphite. CONSTITUTION:The crystallization of the graphite in the cast iron structure in the sliding surface 4 position of the cast iron product 2 in controlled to crystallize the fine graphite 18 having a small shape by disposing, for example, a chiller 14 in the prescribed position and cooling said part in the stage of casting the product 2. A chill part 4 is formed in the part cooled by the chiller 14. The sliding surface 4 of the product 2 is then subjected to the hardening operation such as laser hardening in the range where the graphite does not melt, for example, at about 950-1,300 deg.C while the small graphite 18 exists in the part of said surface. The carbon component remaining in the base or grain boundary is thus transformed to martensite and (martensite + cementite) structure 20 is formed to the part of the sliding surface 4.
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