Annealing method of ultrahigh-strength hot-forming steel

Abstract

The invention discloses an annealing method of ultrahigh-strength hot-forming steel, belonging to the technical field of heat treatment on high-strength automobile steel. After hot rolling and cold rolling, the ultrahigh-strength hot-forming steel is subjected to annealing treatment to obtain a steel plate substrate before hot forming. The hot rolling process comprises the steps of heating a hot-rolled plate blank to 1,100-1,250 DEG C, and preserving heat for 0.5-1 hour, wherein the final rolling temperature is 800-900 DEG C, the coiling temperature is 600-700 DEG C, and the cold rolling reduction rate is 70-80%. The annealing process comprises the steps of slowly heating the cold-rolled steel plate to a two-phase region (alpha+gamma), namely a temperature above A1; preserving heat for 0.1-5 hours; cooling to a temperature below A1 at a cooling speed of 0.1-10 DEG C per second; preserving heat for 0.1-5 hours; finally, cooling to room temperature at a cooling speed of 0.1-10 DEG C per second. According to the ultrahigh-strength hot-forming steel prepared by the method disclosed by the invention, granular carbides are dispersed on a ferrite matrix of the microscopic structure of the steel plate before hot forming, the carbides are uniformly distributed, the reversion and re-crystallization of the ferrite are sufficient, and the sufficiency and uniformity of austenitizing in a hot forming heating stage are facilitated; compared with a traditional cover annealing process, the annealing time is short, and the production efficiency is high.

Description

technical field [0001] The invention belongs to the technical field of heat treatment of high-strength automobile steel, and in particular relates to an annealing method of ultra-high-strength hot-formed steel. Background technique [0002] With the development of the automobile industry, energy saving and emission reduction has become the focus of common attention in the world today. Automobile lightweight is the main measure to achieve this goal, and more advanced high-strength steel and ultra-high-strength steel are widely used in automobile bodies. [0003] Usually, ultra-high-strength automotive steel with a tensile strength greater than 1000MPa has a narrow range of plastic deformation due to its high strength, poor formability, and requires a large stamping force. When stamping and deforming at room temperature, it is easy to crack, and the springback of the parts after forming is serious, resulting in poor dimensional and shape stability of the parts, and it is more...

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Problems solved by technology

However, the current recrystallization bell annealing process has a long production cycle, resulting in high energy consumption

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