Effect of Combined Shot Treatment and Nitriding on Galling Property of Die Used for High Strength Steels

The methodologies of controlling the surface texture of die by hybrid (double)-shot treatment and nitiding at a low temperature were examined for the development of long life cycle die applied to the high strength steel sheets. Hybrid-shot improved the galling property because of its lubricating effect, while nitriding at low temperature which is useful for decreasing distortion by heat-treatment had sufficient hardness of 1500 HV for anti-abrasion. Surface texture of die material, evaluated by using Fast Fourier Transformation (FFT) analysis revealed that the ratio of the spectrum amplitude between high and low frequencies was corresponding to the galling generation load.