LEAF SPRING AND MANUFACTURING METHOD THEREFOR

PROBLEM TO BE SOLVED: To provide a manufacturing method capable of manufacturing a leaf spring lower in a carbon amount than conventional spring steel, enabling omission of a tempering treatment, and having high toughness in a wide hardness range including high hardness and high settling resistance necessary for the leaf spring, and to provide the leaf spring obtained by the manufacturing method.SOLUTION: A steel material having a chemical composition containing, by mass%, C:0.15 to 0.35%, Si:0.50% or less, Mn:0.40 to 1.50%, S:0.025% or less, Cu:0.50% or less, Ni:0.50% or less, Cr:1.60% or less, Al:0.100% or less, N:0.0200% or less and the balance Fe with inevitable impurities is prepared, the steel material is worked to a leaf spring, and then a hardening treatment is applied to the leaf spring, and then a setting treatment is conducted on the leaf spring so that permanent set of a surface layer is 0.15% or more without applying a tempering treatment to the leaf spring.SELECTED DRAWING: Figure 2 【課題】従来のばね鋼よりも炭素量が低く、焼戻し処理の省略が可能であり、高硬度を含む広い硬さ範囲で高靱性を有し、かつ、板ばねに必要な高い耐へたり性を備える板ばねを製造可能な製造方法及びこの製造方法によって得られる板ばねを提供すること。【解決手段】質量％で、Ｃ：０．１５〜０．３５％、Ｓｉ：０．５０％以下、Ｍｎ：０．４０〜１．５０％、Ｓ：０．０２５％以下、Ｃｕ：０．５０％以下、Ｎｉ：０．５０％以下、Ｃｒ：１．６０％以下、Ａｌ：０．１００％以下、Ｎ：０．０２００％以下を含有し、残部がＦｅ及び不可避的不純物よりなる化学成分を有する鋼材を準備し、鋼材を板ばねに加工した後、板ばねに焼入れ処理を施し、その後、焼戻し処理を施すことなく、表層の永久歪みが０．１５％以上となるように板ばねにセッチング処理を行う。【選択図】図２