Preparation method for ultrahigh-strength thermoforming steel for car

Abstract

The invention discloses a preparation method for ultrahigh-strength thermoforming steel for a car, and belongs to the technical field of high-strength steel. The preparation method comprises the following steps of: combining stamping forming with low-temperature bainite isothermal treatment; comprehensively utilizing refining technologies such as micro-alloy refining, controlled-rolling controlled-cooling refining, pre-deforming and low-temperature bainite isothermal treatment, thereby obtaining an ultra-fine structure which consists of carbide-free bainite, a little blocky type retained austenite and martensite with volume fraction smaller than 10%, and the ultra-fine structure has tensile strength of 1500-2200 MPa, and ductility of 10-20%. A preparation process for ultrahigh-strength steel comprises the following technological process: smelting, continuous casting, hot rolling, cutting, thermal stamping forming and low-temperature bainite isothermal treatment. During thermal stamping forming, a cut hot-rolled plate is re-heated to Ac3+50 DEG C for austenization, and heat is preserved for 0.5-1 hour, and then, the plate is immediately moved onto thermal stamping equipment to perform stamping forming; the quick cooling and quenching effect of a thermal stamping mould is utilized for cooling super-cooled austenite to a temperature lower than Ms point, is subjected to isothermal treatment for 0.5-1 minute, is quickly put into a salt-bath furnace or a resistance furnace of 200-300 DEG C to perform isothermal treatment for 4-6 hours, is subjected to isothermal bainite transformation, and is taken out for being air-cooled to the room temperature.

Description

technical field [0001] The invention belongs to the technical field of high-strength steel, and relates to an ultra-high-strength hot-formed steel for automobiles and a preparation method thereof. Background technique [0002] With the improvement of relevant laws and regulations in our country and the improvement of people's awareness of safety and environmental protection, more and more attention has been paid to the energy saving, emission reduction and safety performance of automobiles. The development and application of high-strength steel and ultra-high-strength steel can improve automobile safety and reduce automobile weight. , Realizing the lightweight of automobiles and reducing fuel consumption are the development trends of modern automobiles. Ultra-high-strength steel hot stamping forming technology, as a new shape technology to realize the lightweight of automobiles, satisfies the market demand well with its characteristics of light weight, high strength, good fo...

AI Technical Summary

Problems solved by technology

[0011] The invention aims at the problem that the ultra-fine bainite steel has ultra-high strength and cannot be adopted by ordinary forming methods. At the same time, the strength level and plasticity of the steel for hot stamping forming need to be improved urgently. The hot stamping forming is combined with bainite isothermal transformation. Improve the hot stamping forming process to produce ultra-high-strength auto parts, develop ultra-high-strength hot-formed steel for automobiles with a tensile strength of 1500-2200 MPa and an elongation of 10-20%

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