GRADIENT ULTRA-FINE GRAINED LOW-CARBON MICRO-ALLOY STEEL AND PREPARATION METHOD THEREFOR

摘要

A gradient ultra-fine grained low-carbon micro-alloy steel and a preparation method therefor, belonging to the technical field of metal material processing and preparation. The gradient ultra-fine grained low-carbon micro-alloy steel comprises the following components by mass percentage: 0.08 to 0.15% of C, 0.5 to 1.5% of Mn, 0 to 1.0% of Si, 0 to 0.05% of Nb, 0 to 0.1% of Ti, the balance being Fe and inevitable impurities. The preparation method therefor comprises smelting, forging, conventional hot rolling and asynchronous hot rolling. In asynchronous hot rolling, a sheet is heated to 950°C to1200°C, held at the temperature for 10 to 30min, and quenched in water to room temperature to obtain a product. Said method combines an asynchronous rolling-compression shearing composite mechanism and a strain-induced ferrite phase change mechanism to introduce a strain gradient and a dynamic phase change gradient, so that a structure morphology having a gradient grain size distribution in the thickness direction is obtained while obtaining ultra-fine grains, thereby the strength and hardness of a metal material are effectively improved while maintaining the plasticity and toughness of the metal material, and the overall performance of the material is improved.