TRIP/TWIP high strength plastic automotive steel with excellent processability and preparation method thereof

Abstract

The invention discloses a TRIP / TWIP high strength plastic automotive steel with excellent processability and a preparation method thereof. The TRIP / TWIP high-strength plastic automotive steel comprises the following chemical components in percentage by weight: 0.10%-0.45% of C, 0.6% of Si or less, 10%-20% of Mn, 0.30% of Al or less, 0.20% of P or less, 0.005% of S or less, 0.05%-0.30% of Re, 0.004%-0.05% of N, 0.1% of Nb or less, and the balance of Fe and inevitable impurities. The method comprises the following steps of: carrying out vacuum smelting and casting at the casting temperature of 1,450-1,550 DEG C to obtain a billet; heating the cast billet at the temperature of 1150-1,250 DEG C, and keeping the temperature for 30-60 minutes; rolling the cast billet at the starting rolling temperature of 700-1,150 DEG C and the final rolling temperature of 600-850 DEG C, and carrying out water quenching on a rolled steel plate at the cooling rate of not less than 30 DEG C / s; carrying out cold rolling on a hot rolled plate at the reduction ratio of 40%-80% to obtain a steel plate with the thickness of 0.8mm to 2.0mm; carrying out thermal treatment on a cold rolled belt in a static furnace at the temperature of 600-1,000 DEG C, keeping the temperature for 3-10 minutes, and fast cooling at cooling rate of not less than 20 DEG C or carrying out water quenching to room temperature. The invention can obtain an organizational structure with certain component proportion by hot rolling control and thermal treating processes with preferable components, sufficiently utilizes the high strength of TRIP effect and the high plasticity of TWIP effect and organically combines the two effects to obtain the steel plate which has TRIP and TWIP effects and excellent comprehensive performances.

Description

technical field [0001] The invention belongs to the technical field of special steel heat treatment processing, and relates to a high-strength, high-plastic thin steel plate for automobiles with good processability and two effects of TRIP and TWIP and a preparation method thereof. Background technique [0002] The important development direction of modern automobile structure, performance and technology is to reduce weight, save energy, reduce emission and improve safety. With the development of the metallurgical industry, DP and TRIP steels have been developed successively, which have played a powerful role in promoting the development of the automobile industry. The research and development of TWIP steel is a major breakthrough in the comprehensive performance of steel in terms of strength and ductility. It not only has high strength and formability, but also has a good ability to absorb impact energy. With obvious advantages, it has become the development direction of a ...

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Problems solved by technology

[0003] However, the traditional TWIP steel is evolved on the basis of Hadfield steel, and its processing performance is very poor. The main reasons are: (1) The ultra-high content of Mn element (≥20%) reduces the thermal conductivity of the steel rate, and the free line shrinkage value (2.4% to 3.0%) is 2 to 3 times that of ordinary carbon steel, resulting in a coarse as-cast structure of the steel, and hot cracks are prone to occur on the surface of the original billet / ingot, and the cracks intensify after hot rolling

(2) Since the steel contains a large amount of Mn elements, it may cause the composition segregation in the steel and the segregation of S and P elements at the grain boundaries during casting, weakening the grain boundaries, and a large number of brittle carbides (M 23 C 6 , M 5 C 2 ) precipitation makes TWIP steel very prone to intergranular cracks during hot rolling

(3) The inherent high work hardening rate of high Mn steel leads to high rolling deformation resistance, which increases the load of the rolling mill and makes it difficult for cold forming

There is no report on the patented technology of automotive steel with the comprehensive effect of TRIP / TWIP

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