Study of the influence of heat treatment modes on the formation of an α-phase layer with a modified structure on the surface of a sheet made of low-carbon Cr–Ni–Mo steel

Abstract

The work investigates the effect of heat treatment on the formation of an α-phase layer with a modified structure, representing polyhedral grains of different sizes, on the surface of rolled sheet products made of high-strength low-carbon chromium-nickel-molybdenum bainitic-martensitic shipbuilding steel. After varying the hardening and tempering modes, metallographic studies and hardness measurements from the surface to the middle of the rolled product with a thickness of 10 mm were carried out. The deformation capacity of the rolled sheet products was estimated based on the results of bending tests at an angle of 180°. It was shown that the duration of high tempering has a decisive effect on the formation of such a layer. Based on the research results, a mode of heat treatment of rolled sheet products with a thickness of less than 16 mm was proposed, ensuring the formation of an α-phase layer with a modified structure of the smallest depth without significant changes in hardness.