| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide Pb-free steel having excellent internal cracking suppressing property in continuous casting and also having superior breaking and splitting property and machinability. <P>SOLUTION: The Pb-free steel has a composition which contains 0.2 to 0.6% C, ≥0.1% V, 0.5 to 2% Mn, 0.03 to 0.1% S, ≥0.0003% Ca, ≥0.0003% Mg, and 0.01 to 0.3% Bi and in which the mass ratio between the above Mn and S, Mn/S, is made to ≥17.5. It is desirable that this steel contains ≤0.6% (not including 0%) Si, ≤0.1% (not including 0%) P, ≤0.05% (not including 0%) Al, and ≤0.02% (not including 0%) N, and further contains 0.01 to 1% Cr. Moreover, it is desirable that the carbon equivalent Ceq defined by equation Ceq=[C]+0.28×[Mn]-1.03×[S]+0.323×[Cr]+1.69×[V] is made to ≥0.8. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
