A kind of cold-rolled steel plate with a yield strength of 420mpa and its preparation method

Abstract

A cold-rolled steel plate with a yield strength of 420MPa and a preparation method thereof, belonging to the field of metallurgical technology; the steel plate composition and its mass percentage are: C 0.06~0.09%, Si 0~0.2%, Mn 0.8~1.0%, Ti 0~0.02 %, Nb 0.01~0.025%, the rest is Fe and unavoidable impurity elements; preparation method: 1) According to the chemical composition ratio of the cold-rolled steel plate, melt it into a steel ingot and forge it into a slab; 2) Insulate the slab and heat it After rolling to obtain the hot-rolled plate, it is coiled when cooled to an appropriate temperature at a certain cooling rate; 3) The coiled hot-rolled plate is pickled and then cold-rolled to obtain a cold-rolled plate; 4) The cold-rolled plate is obtained The plate adopts continuous annealing treatment of low-temperature soaking and segmented cooling. The yield strength 420MPa grade cold-rolled steel plate of the present invention has a microstructure that mainly includes ferrite, pearlite and cementite. The yield strength is 435-450MPa, the tensile strength is 518-548MPa, and the elongation A80 is 25.0-26.3%.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, and in particular relates to a cold-rolled steel plate with a yield strength of 420 MPa and a preparation method thereof. Background technique [0002] Lightweight automobile body can reduce energy consumption and CO 2 emissions purposes. Lightweight has been proved to be the key technical route of automobile "energy saving and emission reduction". Every 10% reduction in vehicle weight can reduce fuel consumption by 6%-8% and reduce carbon dioxide emissions by 13%. China is the world's largest producer and consumer of automobiles, and lightweight has become an important issue for the sustainable development of the automobile industry. The high strength of automobile steel is an effective way to realize the lightweight of automobiles, and the high strength of automobile steel has become an inevitable trend. By strengthening the body structure by increasing the use of high-strength steel plat...

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Problems solved by technology

However, the Nb content in this method is 0.04% to 0.05%, and the cost is relatively high

[0008] All adopted high-temperature soaking in the above-mentioned method, this will bring the following problems: (1) under high temperature, hearth roll nodulation very easily takes place, thus easily causes scratch to strip steel in operation process, affects strip surface quality (2) Under high temperature soaking conditions, the precipitated particles are prone to coarsening, and at the same time, the ferrite grains are easy to grow, resulting in a decrease in strength; (3) Under high temperature, the diffusion ability of Si and Mn elements is improved, and the selective oxidation is intensified , it is more difficult to control the surface quality of strip steel; (4) The energy consumption increases at high temperature, and the heating cost is higher

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