980 MPa-grade cold-rolled Q&P steel suitable for conventional continuous annealing production line and manufacturing method thereof

Abstract

The invention provides 980 MPa-grade cold-rolled Q&P steel suitable for a conventional continuous annealing production line and a manufacturing method thereof. The 980 MPa-grade cold-rolled Q&P steelcomprises the following components including 0.16%-0.20% of C, 0.6%-1.0% of Si, 1.8%-2.0% of Mn, 0.05%-0.07% of Nb, 0.02%-0.03% of Ti, 0.40%-0.60% of Al, less than or equal to 0.02% of P, less than orequal to 0.01% of S and the balance Fe. Two-phase zone annealing is adopted, heating is performed to 810-850 DEG C, two-phase zone annealing is performed, slow cooling is performed to 720-760 DEG C,then cooling is performed to 260-300 DEG C at the cooling rate larger than or equal to 25 DEG C/s, quenching is performed, then heating is performed to 340-380 DEG C, partitioning is performed, finally cooling is performed to the room temperature, the annealing temperature is low, and the 980 MPa-grade cold-rolled Q&P steel can be implemented on the existing conventional continuous annealing production line. The steel meets the requirements for high strength and plasticity, good cold forming performance, resource saving, cost reduction and the like of automobile steel.

Description

technical field [0001] The invention belongs to the technical field of material heat treatment, and in particular relates to a 980MPa grade cold-rolled Q&P steel suitable for a conventional continuous annealing production line and a manufacturing method thereof. Background technique [0002] The reduction of vehicle weight, energy saving and emission reduction, and the improvement of safety requirements have promoted the application of high-strength steel, especially advanced high-strength steel, in automobile manufacturing. The first generation of advanced high-strength steel represented by DP (Dual-Phase) steel has low alloy content and excellent formability and welding performance. It has been widely used at present, but its low strength-plasticity product (generally within 15GPa%) cannot meet the requirements. The stamping forming requirements of complex parts, and the parts have less collision energy absorption, do not meet the growing needs of automobile safety; althou...

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Problems solved by technology

However, due to the one-step distribution process, the quenching end temperature is high, and the martensite content is insufficient, so it is necessary to add higher C and Mn elements in the composition design to improve the strength, which is not good for the welding performance of the material. Al content of 0.5-1.0% is prone to metallurgical defects such as inclusions, which is detrimental to surface quality

[0009] The patent literature with the application number CN201510504662.7 introduces a niobium alloyed TAM steel and its manufacturing process. The new process adopts a complete austenitization and quenching process (heating at 10°C / s) before conventional continuous annealing. to the austenitizing temperature of 900-920°C for 600s, and then cooling down to room temperature at 50°C / s), the added process requires high equipment and cannot be realized in large-scale production at present

[0010] The patent document with the application number CN201610297645.5 introduces a Q&P steel plate and its two-partition preparation method. The tensile strength of the steel plate produced according to the method introduced in the patent is ≥1200MPa, the elongation is ≥20%, and the strength-plastic product is ≥25GP·%. , but its two-partition method is complicated and cannot be realized in large-scale production at present

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