1500MPa-grade high-formability alloying hot galvanizing dual-phase steel and preparation method thereof

Abstract

The invention discloses 1500MPa-grade high-formability alloyed hot-dip galvanized dual-phase steel and a preparation method thereof, and belongs to the technical field of hot-dip galvanized high-strength automobile steel. The steel comprises the following components in percentage by mass: 0.21 percent to 0.24 percent of C, 0.71 percent to 0.80 percent of Si, 2.66 percent to 2.85 percent of Mn, 0.91 percent to 1.10 percent of Alt, 0.71 percent to 1.10 percent of Cr, 0.21 percent to 0.35 percent of Mo, 0.041 percent to 0.085 percent of Nb, 0.051 percent to 0.095 percent of Ti, 0.003 percent to 0.005 percent of B, 0.035 percent to 0.070 percent of P, less than or equal to 0.004 percent of S, less than or equal to 0.0025 percent of N, 1.62 percent to 1.90 percent of Si and Al, 0.92 percent to 1.45 percent of Cr and Mo and the balance of Fe and inevitable impurities. Crystalline grains can be obviously refined by adding Cr, Mo, Nb, Ti, B, P and other elements and controlling technological parameters, the strength of the dual-phase steel is improved through refined grain strengthening, solid solution strengthening and precipitation strengthening, the formability is improved by adding C, Mn, Si and Al elements and introducing retained austenite, ferrite and martensite grains are ultra-refined and uniformly distributed, and the strength of the dual-phase steel is improved. And a large number of fine and dispersively-distributed nanoscale second-phase particles are formed, and the hydrogen embrittlement sensitivity of the dual-phase steel is improved. The tensile strength of the high-formability alloyed hot-galvanized dual-phase steel is larger than or equal to 1510 MPa, the yield strength is larger than or equal to 805 MPa, and the percentage elongation after fracture is larger than or equal to 8.0%.

Description

technical field [0001] The invention belongs to the technical field of hot-dip galvanized high-strength automotive steel, and in particular relates to a 1500 MPa grade high formability alloyed hot-dip galvanized dual-phase steel and a preparation method thereof. Background technique [0002] With the development of the automobile industry, the requirements for ultra-high-strength automotive steel are getting higher and higher. Dual-phase steel has the advantages of low yield ratio, high work hardening rate and good welding performance, and is widely used in automobile anti-collision, structural or strengthening parts. [0003] The microstructure of the dual-phase steel is mainly composed of martensite distributed on the ferrite matrix. As the strength of the dual-phase steel increases, the proportion of ferrite decreases and the proportion of martensite increases, resulting in a significant decrease in plasticity. With the continuous development of the trend of weight redu...

AI Technical Summary

Problems solved by technology

As the strength of dual-phase steel increases, the proportion of ferrite decreases and the proportion of martensite increases, resulting in a significant decrease in plasticity

With the continuous development of the trend of weight reduction and energy saving, the strength level of dual-phase steel is getting higher and higher, which usually leads to the decline of formability, and it becomes difficult when stamping some auto parts with complex shapes, and the problem of forming cracking often occurs, which greatly limits The application of ultra-high-strength dual-phase steel with a strength level above 1200MPa

[0004] When the strength increases to 1500MPa, the proportion of martensitic structure in ultra-high-strength dual-phase steel increases significantly, and the formability and ductility of the material decrease significantly , it is difficult to meet the factory's requirements for high formability and high plasticity of ultra-high-strength steel

Therefore, the problems of poor formability and insufficient ductility of ultra-high-strength grade automotive steel need to be solved urgently.

The hot-dip galvanizing process is limited by the process layout and equipment capacity, and the cooling rate is not high, which will affect the microstructure of the dual-phase steel, and then affect its mechanical properties

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