| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel for machine structural use excellent in cold forgeability and having high toughness both with just cold rolling and after softening such as spheroidizing, and being inexpensive because of containing no Mo.SOLUTION: A steel for machine structural use contains, by mass%, C:0.30 to 0.55%, Si:0.03 to 0.30%, Mn:0.50 to l.50%, P:0.018% or less, S:0.02% or less, Al:0.010 to 0.060%, Cr:1.2 to 2.0% and Nb:0.005 to 0.06% in a range satisfying the formula (1) and the balance Fe with inevitable impurities. [%C]-[%Si]/2+[%Mn]/5+2[%Cr]≥3.2 (1) |
