| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve machinability and to provide high strength and toughness by subjecting a steel, in which chemical composition is specified and also Ni/Cu in the composition and graphitization index are respectively specified, to hot working and to cooling and precipitating graphite and forming a pearlitic structure. SOLUTION: This steel has a composition which consists of, by weight, 0.80-1.70% C, 0.70-2.50% Si, 0.01-2.0% Cu, 0.01-2.0% Ni, 0.0005-0.0100% Ca, 0.001-0.10% Al,⊥.050% P, <0.050% S, <=0.0050% O, <=0.015% N, and the balance Fe and in which Ni/Cu>=0.2 is satisfied and also the graphitization index CE computed by CE=C+Si/3+Cu/9+Ni/9+Al/6 is regulated to >=1.30. This steel is hot worked and cooled to a room temperature. A product is produced by using this steel as a stock, and graphite of >=0.5μm average grain size is precipitated by >=100 pieces/mm<2> and the metallic structure is composed essentially of pearlite.</p> |
