| 摘要 |
PROBLEM TO BE SOLVED: To provide a seamless steel tube for machine structured use excellent in machinability, also having excellent hot workability in a Mannesman's is rolling method and further excellent in toughness. SOLUTION: This seamless steel tube for machine structural use excellent in machinability, hot workability and toughness has a composition containing, by mass, 0.02 to 0.60% C, <=0.5% Si, 0.3 to 2.0% Mn, <=0.04% P, 0.01 to 0.04% S, <=0.006% Al, 0.005 to 0.015% N and 0.0005 to 0.015% Mg and further containing, if required, one or more kinds selected from 0.01 to 2.0% Cr, 0.01 to 5.0% Ni, 0.01 to 2.0% Mo, 0.01 to 2.0% Cu and 0.5 to 3.0% W, and the balance Fe with inevitable impurities.
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