| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel for a torsion bar which shows superior low- temperature ductility even at a temperatures below the freezing point, and is used for a seat belt winding-up device. SOLUTION: The steel has a composition comprising, by mass%, C in a range of 0.002-0.05%, solid solution N reduced by an addition of Al and Nb, in order to secure strength and ductility, and P and B added to develop adequate ductility even at a temperature below the freezing point, in such a proper amount as to satisfy (1) 0.007% or less P and 0.003% or less (including 0%) B, or (2) more than 0.007 to 0.02% P and (0.1×P content (%)-0.0007) to 0.003% B. COPYRIGHT: (C)2004,JPO
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