800MPa-grade hot-rolled complex-phase steel and production method thereof

Abstract

The invention relates to steel for manufacturing automobile structures, in particular to 800MPa-grade hot-rolled complex-phase steel and a production method thereof. The steel comprises the following chemical components in percentage by weight: 0.055%-0.112% of C, 0.08%-0.40% of Si, 1.15%-2.02% of Mn, 0.10%-0.30% of Al, 0.10%-0.62% of Cr, 0.0020%-0.0050% of B, 0.015%-0.056% of V and / or 0.030%-0.145% of Ti, less than or equal to 0.020% of P, less than or equal to 0.007% of S and the balance of Fe and inevitable impurities. The method comprises the following steps that (1) a continuous casting sheet billet with the thickness of 80-300 mm is placed in a heating furnace, and the temperature is kept for 5-6 hours; (2) a controlled rolling means is adopted, the rough rolling temperature is not higher than 1080 DEG C, the thickness of an intermediate billet is 25-50 mm, the finish rolling temperature is controlled, the thickness of a finished product is 2.0-5.0 mm, and the total reduction rate is larger than or equal to 80%; (3) after finish rolling, front-section rapid continuous stream cooling is adopted, and coiling is conducted; and (4) after being coiled, a steel plate immediately enters a slow cooling cover to be slowly cooled to 120 DEG C or below, the slow cooling speed is not larger than 15 DEG C / h, and a steel coil is taken out and air-cooled to the room temperature. The steel has high strength and good formability, and is suitable for manufacturing automobile structural parts, reinforcements and safety parts.

Description

technical field [0001] The invention relates to steel for manufacturing automobile structures, in particular to an 800MPa hot-rolled multi-phase steel and a production method thereof. Background technique [0002] The development trend of the new generation of automobiles is energy saving, consumption reduction, environmental protection and safety. Advanced high-strength steels are widely used in automobile manufacturing to achieve their lightweight goals. The R&D and application of advanced high-strength and ultra-high-strength steels will be the leading direction of future material technology development. Advanced high-strength steel is mainly composed of five categories, low-alloy high-strength steel, dual-phase steel, complex-phase steel, phase transformation-induced plasticity steel, martensitic steel, etc., and its strength range is 500-1600MPa, which has both high strength and better In automotive manufacturing applications, they all have the advantages of high weig...

AI Technical Summary

Problems solved by technology

By adding Nb, Ti, and Mo elements in the C-Si-Mn composition system, and adopting a five-stage controlled cooling process to produce multi-phase steel, the highest tensile strength is 861MPa and the yield ratio is greater than 0.8, which is high. Does not meet the requirements of high-strength formed automotive structural parts

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