| 摘要 |
PURPOSE: To continuously produce a spring having superior shape by regulating the existence area of a negative segregation zone, existing in a specific range from the surface layer, to a specific value. CONSTITUTION: The steel has a composition containing 0.6-1.00% C, 0.1-1.0% Si, 0.1-0.5% Cr, and <=0.003% Al. This steel is refined and cast into a 300×500mm billet by continuous casting. This cast billet is formed into a 122mm square billet by blooming and then formed into a 5.5-mm wire rod by wire rod rolling. The existence area of segregation zone, existing in the area between the surface layer of this wire rod and the position at a depth of <=1/7 of a diameter, is regulated to a value not higher than 5% of the cross-sectional area of the wire rod. This 5.5mm wire rod is wiredrawn to 2.9mm, patented, and formed into a steel wire of 0.9mm final wire diameter. A spring is formed by using this steel wire as material. By this method, spring forming can be stabilized.
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