900MPa-grade hot-rolled and pickled complex-phase phase steel with low yield ratio and high hole expansion rate and production method of 900MPa-grade hot-rolled pickling complex phase steel

Abstract

The invention relates to hot-rolled and pickled complex-phase steel, in particular to 900 MPa-grade hot-rolled and pickled complex-phase steel with a low yield ratio and a high hole expansion rate and a production method of the 900 MPa-grade hot-rolled and pickled complex-phase steel. The steel comprises the following chemical components of, in percentage by weight, 0.085%-0.162% of C, 0.08%-0.85% of Si, 1.15%-2.50% of Mn, 0.10%-0.30% of Al, 0.10%-0.75% of Cr, 0.08%-0.65% of Mo, 0.025%-0.070% of Nb, 0.030%-0.155% of Ti, 0.0020%-0.0050% of B, 0.010%-0.060% of rare earth elements La + Ce, P less than or equal to 0.020%, S less than or equal to 0.007% and the balance Fe and inevitable impurities. The method comprises the following steps that (1), a continuous casting slab with the thickness of 80-300mm is put into a heating furnace to be heated to be 1130-1270 DEG C; (2), the initial rolling temperature of rough rolling is not higher than 1080 DEG C, the thickness of an intermediate billet is 25-50 mm, the finish rolling temperature is 840-900 DEG C, the thickness of a finished product is 1.8-5.3 mm, and the total reduction rate is larger than or equal to 85%; (3), after finish rolling, front-section rapid continuous laminar cooling and curling are adopted; (4), after being curled, the steel plate immediately enters a slow cooling cover to be slowly cooled, and a steel coil is taken out and air-cooled to the room temperature; and (5), pickling is carried out . The steel has ultrahigh strength and good formability, and is suitable for manufacturing automobile structural parts, reinforcing parts and safety parts; and the steel has excellent anti-fatigue performance, welding performance and cold forming performance.

Description

technical field [0001] The invention relates to a hot-rolled pickled multiphase steel, in particular to a 900MPa hot-rolled pickled multiphase steel with low yield ratio and high hole expansion rate 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., with a strength range of 500-1600MPa, which has both high strength and better In automotive manufacturing applicat...

AI Technical Summary

Problems solved by technology

[0008] The existing hot-rolled pickling multi-phase steel has low yield strength, low tensile strength, low elongation, high yield ratio, low plasticity, and high anisotropy, which do not meet the requirements of high-strength formed automotive structural parts; and fatigue resistance Performance, welding performance, cold forming performance are not ideal

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