| 摘要 |
PURPOSE:To improve the roughness of the etched surface of a quenched and tempered carbon steel material and the fatigue resistance by reducing the S content of the carbon steel to a specified value or below. CONSTITUTION:When a quenched and tempered carbon steel hoop is subjected to forming such as die sinking, cutting or piercing by etching, the S content of the carbon steel is reduced to >=0.004wt% so as to reduce the amount of sulfide-base nonmetallic inclusions on the etched surface. Local excessive etching caused by the roughening of the etched surface due to the inclusions is prevented, and the fatigue resistance of a hoop member worked by etching such as a spring material is improved.
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