オイルテンパー線の疲れ強さに及ぼす残留オーステナイトの影響
1998 年 1998 巻 43 号 p. 1-12
詳細
1998 年 1998 巻 43 号 p. 1-12
High tensile strength of oil-tempered wire is intensely required for higher fatigue strength of coil spring. For this subject, wire has been developed in terms of increasing carbon level and/or applying high alloy of chemical composition. This study investigates the effect of retained austenite on the toughness of high tensile strength of oil tempered wire and on fatigue strength of coil spring.
The experimental results are as follows;
(1) Oil-tempered wire developed to increase retained austenite should be tempered inevitably with low value of tempering parameter in order to produce the required strength. As the results, the toughness of the oil-tempered wire is reduced.
(2) Nevertheless it is possible that the retained austenite in the oil- tempered wire is transformed into strain induce martensite by coiling spring and/or shot peening, and the surface hardness of the coil spring is induced to increase.
And also the toughness of the coil spring is induced to restore by stress relief annealing after coiling.
As the results, the fatigue strength of coiled spring with the oil-tempered wire, which contains a lot of retained austenite is higher that of coiled spring with the oil-tempered wire which contains a little of retained austenite.
