Steel for superhigh-strength hot rolling automobile structure and preparation method thereof

Abstract

The invention relates to steel for a superhigh-strength hot rolling automobile structure and a preparation method thereof, belonging to the field of alloy steel production processes. The steel comprises the following components: 0.08 percent to 0.12 percent of carbon, 0.10 percent to 0.50 percent of silicon, 1.5 percent to 2.50 percent of manganese, less than 0.02 percent of phosphorus, less than 0.01 percent of sulfur, 0.02 percent to 0.05 percent of aluminum, 0.08 to 0.25 percent of vanadium, 0.03 percent to 0.06 percent of nitrogen and the balance of Fe and other inevitable impurities. The production process comprises the following steps of: converter smelting; external refining; continuous casting; hot rolling and reeling. The main process parameters are as follows: the heating temperature of continuous casting slabs is between 1,150 and 1,220 DEG C, the reeling temperature is between 500 and 650 DEG C, and the hot rolling total reduction ratio is more than 85 percent. According to the steel, vanadium-nitride micro alloying is adopted, vanadium precipitation is promoted by enhancing nitrogen, grains are refined, and precipitation strengthening and fine-grain strengthening are used as main strengthening measures, so that the yield strength is more than 700 MPa, the tensile strength is more than 800 MPa, the total elongation rate after fracture is more than percent, and the steel is used for high-strength automobile structures with high plasticity and good cold bending properties.

Description

technical field [0001] The invention belongs to the field of alloy steel production technology, is suitable for the production of alloy steel with vanadium as the main strengthening element, and is especially suitable for the production of ultra-high-strength automotive structural steel with a tensile strength greater than 800 MPa and good toughness and formability . Background technique [0002] At present, the high-strength automotive structural steels produced in China are generally micro-alloyed by adding alloy elements such as Nb, Ti, and Mo. The basic idea is to use Nb to hinder austenite recrystallization and refine grains, and use Ti and V etc. for precipitation strengthening, using Mo to delay pearlite transformation to obtain strengthened structures such as bainite or ferrite. Such a production method adds a large amount of microalloys, and at the same time has high requirements for controlled rolling and controlled cooling technology, and the product performance ...

AI Technical Summary

Problems solved by technology

However, its technological process is a thin slab continuous casting and rolling production line, and the application and promotion of the production process has certain limitations.

At the same time, compared with the traditional process, since there is no precipitation-dissolution-precipitation process of microalloying elements, it is easier to take advantage of the high solid solution of microalloying elements. And the cooling rate in the condenser is much higher than that of the slab under the traditional process, which reduces the coarse dendrites, so the distance between the secondary and tertiary dendrites is shorter, so that the original as-cast structure with a relatively regular shape and small and uniform size is obtained. Coupled with the controlled rolling of large reduction rate and optimized controlled cooling process, the strength of steel plates produced by the thin slab continuous casting and rolling process is generally high

Images