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.