| 摘要 |
PROBLEM TO BE SOLVED: To produce non-refining steel for hot forging excellent in the smoothness of a broken face, in which the smooth broken face can be obtained in forced breaking separation at <=25 deg.C without depending on the hardness of steel. SOLUTION: This non-refining steel for hot forging excellent in the smoothness of the broken face contains, by weight, 0.10 to 0.90% C, 0.05 to 0.50% Si, 0.20 to 2.50% Mn, 0.005 to 0.050% P, 0.01 to 2.00% Cr, 0.0020 to 0.0100% B, <=0.035% Al, <=0.005% Ti and 0.0050 to 0.0200% N, and the balance Fe with inevitable impurity elements. Alternatively, the steel moreover contains, as elements for improving strength, one or two kinds or more among 0.01 to 0.50% Mo, 0.01 to 0.10% V and 0.01 to 0.50% Ni or furthermore contains one or >= two kinds among 0.005 to 0.100% S, 0.01 to 0.09% Pb, 0.04 to 0.20% Bi, 0.002 to 0.050% Te, 0.01 to 0.20% Zr and 0.0001 to 0.0100% Ca.
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