440 MPa-grade continuous-annealed and cold-rolled structural steel plate and production process thereof

Abstract

The invention discloses a 440 MPa-grade continuous-annealed and cold-rolled structural steel plate and a production process thereof. The steel plate comprises the following components in percentage by mass: 0.06-0.12% of C, 0-0.10% of Si, 1.25-1.50% of Mn, 0.002-0.006% of N, 0-0.025% of P, 0-0.010% of S, 0.015-0.050% of Als, and the balance of Fe and unavoidable impurities, as well as ferrite with a volume ratio of 90-95% and pearlite with a volume rate of 5-10%; and the production method of the steel plate comprises the steps of continuous casting, hot rolling, cooling, coiling, cold rolling, continuous annealing and the like. According to the steel plate and the production process thereof disclosed by the invention, a 'low C-low Si-Mn' micro-alloying process thought is adopted in combination with techniques such as external refining, a controlled rolling and controlled cooling process, a process for controlling a relatively low cold rolling reduction ratio, a process of continuous annealing in a two-phase region, and the like, a fine-grained ferrite and pearlite structure containing cold-rolled structural steel plate is obtained.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and more specifically relates to a 440MPa continuous annealing cold-rolled structural steel plate most suitable for automobiles and its production process Background technique [0002] my country's automobile industry has entered a period of rapid development of passenger cars. In order to meet the needs of "weight reduction, energy saving, safety, and environmental protection" in the automobile manufacturing industry, more and more high-strength thin steel plates are used for auto parts. Passenger car bodies The material used for the body and car body is mainly cold-rolled thin steel plate with a thickness of less than 2.5mm, which accounts for more than 50% of the total vehicle weight. The use of high-strength steel plate can make up for the adverse effects on vehicle safety due to thickness reduction. According to the data, every 1% reduction in the weight of the car body can save fuel by 0....

AI Technical Summary

Problems solved by technology

However, although the existing high-Si and high-Mn process idea can improve the relative strength of the solid depth strengthening of the steel plate, the disadvantage is that the cost is high and there is fayalite FeO Fe on the surface of the steel plate that is difficult to be removed by pickling. 2 SiO 4 phase, resulting in poor surface quality