Low-yield ratio, high-plasticity, ultrafine-grain and high-strength steel and manufacturing method thereof

Abstract

The invention discloses low-yield ratio, high-plasticity, ultrafine-grain and high-strength steel and a manufacturing method thereof. The steel comprises the following chemical components in percentage by weight: 0.03 to 0.10 percent of C, 0.10 to 0.30 percent of Si, 1.20 to 1.80 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.040 to 0.060 percent of Nb, 0.006 to 0.020 percent of Ti, 0.010 to 0.050 percent of Al, 0.10 to 0.40 percent of Cr, 0.10 to 0.30 percent of Ni and the balance of Fe and inevitable impurities. The manufacturing method of the steel is to adopt a controlled rolling and offline heat treatment process to obtain ferrite ultrafine-grain structure with bimodal distribution, namely a structure in which ultrafine-grain substrates with a diameter below 1 mu m contain a certain percent of relatively large grains with a size between 2 and 3 mu m. The yield strength of the steel is 450 to 550MPa, the tensile strength is 670 to 720MPa, the elongation is more than or equal to 25 percent, and the yield ratio (Rt0.2 / Rm) is less than or equal to 0.7. In the invention, the production process is stable, the operability is high, the cost is low, and the comprehensive performance of the manufactured material is high.

Description

technical field [0001] The invention relates to the production field of high-strength steel, in particular to a method for manufacturing high-strength steel with low yield ratio and high plasticity and ultrafine grain. Background technique [0002] In the 21st century, steel is still the dominant structural material, and no material can completely replace steel. With the development of society and economy, the iron and steel industry is facing three major pressures: saving resources, saving energy, and protecting the environment. Therefore, improving steel quality, reducing costs, developing human-friendly steel materials, and greatly improving their comprehensive mechanical properties have become the main directions of steel material research. Among them, the low-cost production of fine-grained high-strength steel using thermomechanical controlled rolling technology (TMCP) and deformation-induced ferrite transformation technology (DIFT) is the development direction of the ...

AI Technical Summary

Problems solved by technology

However, the problem of yield ratio has not been solved by the above-mentioned process method

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