Bauschinger effect in spring steels

The objectives of the present work were twofold: first, to characterize the sag behaviour of SAE grades 5160 and 9259 spring steels with the Bauschinger behaviour approach using different experimental methods; and second, to determine an effective method which displays the most distinct difference in the Bauschinger effect measure as caused by different microstructures. The materials studied were 5160 and 9259 spring steels in the hot rolled and quench-temper conditions. The experimental methods used were tension-unloading-tension-compression testing, compression-unloading-tension testing, and tension-unloading-compression testing. Results indicate that the Bauschinger effect was larger for material in the hot rolled than the quench-temper condition. Also, the 9259 showed a larger Bauschinger effect and, consequently, should have a higher sag resistance that the 5160 steel in the same heat treatment condition. All Bauschinger effect parameters measure deviation from ideal plastic behviour: however, the permanent softening method has shown itself to be the best way to detect the difference in Bauschinger behaviour.