Economic high-strength cold-rolled TRIP steel with product of strength and elongation greater than 20 GPa*% and manufacturing method of TRIP steel

Abstract

The invention relates to a production method of economic high-strength cold-rolled TRIP steel with the tensile strength no less than 800 MPa and the product of strength and elongation greater than 20 GPa*%. The steel is made from main chemical components, by weight percentage, 0.15-0.25% of C, 1.3-1.7% of Si, 1.5-2.5% of Mn, no more than 0.030% of P, no more than 0.020% of S, and 0.02-0.06% of Al, with the balance being Fe and inevitable impurities. The manufacturing method comprises the following steps: (1) melting and solidification; (2) hot continuous rolling of a casting blank or ingot casting; (3) pickling and cold rolling; and (4) continuous annealing. The product of strength and elongation of the TRIP steel is greater than 20 GPa*%, and can reach as high as 26.3 GPa*%. At the same time, the sheet shape, the surface quality, the stamping property and the welding property of the TRIP steel are ensured.

Description

technical field [0001] The invention relates to the field of cold-rolled automobile steel manufacturing, in particular to a production method of economical high-strength cold-rolled TRIP steel with a tensile strength of more than 800 MPa and a strength-plastic product greater than 20 GPa·%. Background technique [0002] Higher requirements for weight reduction, emission reduction, and high safety of automobiles have prompted the steel used in automobiles to gradually become lightweight and highly strengthened. As the strength increases, the toughness of the material will inevitably decrease. Therefore, when developing high-strength steel, the formability of the material must also be taken into account. At present, the strength-plastic product of traditional high-strength steel is generally below 15GPa·%, and TRIP steel, which has an excellent combination of high strength and high plasticity among the first generation of advanced high-strength steels, generally does not excee...

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Problems solved by technology

[0004] The patent document with the application number CN 103088255 introduces a production process of high-strength plastic product low-alloy high-strength steel cold-rolled sheet for automobiles. Its advantage is that it can produce high-strength plastic product The low-alloy high-strength steel cold-rolled plate has a maximum strength-plasticity of 15GPa·%; the disadvantage is that due to its low-alloy high-strength composition design, its tensile strength is only 500MPa. Due to the limitation of strength, the lightweight effect after application is not obvious

[0005] The patent document with the application number CN 104264039 discloses a TRIP steel plate containing rare earth La and a tensile strength of not less than 780 MPa and a preparation method, but because it adds rare metals (rare earth La), the production cost is increased, and its strong The plastic products are all below 20GPa·% (the elongation is converted to A 80 : A 80 =A 50 ×1.15)

[0006] The patent document with the application number CN 103555902 discloses a heat treatment process for 980MPa-grade high-strength plasticity automotive steel, which is characterized in that the treated TRIP780 cold-rolled steel plate is quenched and then heated to a certain temperature for distribution to obtain a high-strength plasticity of 26.3 ~26.8GPa·%, 980MPa grade high-strength plastic product automotive steel with an elongation rate of 23.8~24.2%. The process has high requirements on the cooling rate and heating rate after annealing. The current annealing line cannot meet the process conditions, and it is difficult to realize large-scale industrial application.

[0007] The patent document with the application number CN 101353761 discloses a production method of high-strength Al-containing hot-dip galvanized TRIP steel. 22GPa; the disadvantage is that the Al content is too high, which leads to difficulties in continuous casting production, and it is difficult to achieve mass industrial production. At the same time, it will cause surface defects such as inclusions; manufacturing cost

[0008] The patent document with the application number CN 104694816 introduces a preparation method of high-Al medium-manganese steel with a strength-plasticity product greater than 30GPa·%. , the disadvantage is that the content of Mn and Al is too high, which leads to high production cost, difficulty in continuous casting and rolling, and difficulty in large-scale industrial application

[0009] The patent literature with the application number CN 102912219 introduces a high-strength plastic product medium Mn-TRIP steel, which is characterized in that the Mn content is between 3 and 8%. The advantage is that this steel has good strength and elongation, and the strong plastic product Reaching above 30GPa·%, the disadvantages are high Mn content, high production cost, difficulty in continuous casting and cold rolling, and difficult to achieve stable batch application

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