High-strength hot-rolled strip steel having favorable stretch-flangeability and production method thereof

Abstract

The invention relates to high-strength hot-rolled strip steel having favorable stretch-flangeability, which comprises the following components in percentage by weight: 0.03%-0.05% of C, 0.01%-0.50% of Si, 0.40%-1.00% of Mn, no more than 0.015% of P, no more than 0.005% of S, no more than 0.006% of N, 0.030-0.10% of Als, 0.10-0.25% of Ti and 0.0010-0.0035% B. The production method comprises the following CSP production steps: smelting and continuously casting to obtain slabs; heating the continuous casting slabs; rolling; performing laminar cooling; coiling; naturally cooling to room temperature; and finishing. According to the invention, the tensile strength is no less than 780 MPa, the metallurgical structure is 95-100% ferrite, the elongation percentage is no less than 15%, and the hole expansion rate is no less than 80%; a proper amount of cheap Ti microalloy is used to reduce use of expensive alloys of Mo, Ni, Cu and the like, thus lowering the manufacturing cost of steel; and thin slabs are used instead of thick slabs, and hot rolling is adopted instead of cold rolling, thus further lowering the manufacturing cost of steel for automobiles. The production of molding-complicated automobile components and parts can be satisfied, the existing equipment can be utilized without adopting ultra-fast cooling equipment or the like, the production efficiency is high, and less investment is needed.

Description

technical field [0001] The invention relates to a steel for automobiles and a production method, in particular to a high-strength hot-rolled steel strip with good elongation and flangeability and a production method, and is especially suitable for producing hot-rolled steel strips with a thickness of 1.2-4.0mm. Background technique [0002] In recent years, with the advancement of automobile energy-saving and emission-reduction technologies, automobile lightweight has become a development trend, and the demand for thin-gauge high-strength automobile steel is becoming more and more urgent. When used in the manufacture of more complex parts such as wheel spokes, in addition to the need for higher strength, the requirements for the extension flangeability of steel are getting higher and higher, but the extension flangeability of steel generally decreases with the increase of steel strength. Therefore, the development of high-strength steel plates with high strength and excellen...

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Problems solved by technology

[0004] The above-mentioned two patent documents have a common deficiency: due to the large hardness difference between ferrite and bainite in the steel, the stretch-flangeability of the steel is not high, especially for high-strength stretch-flange dual-phase steels above 590MPa. In addition, the C content in the two steels is too high, which will adversely affect the stretch flangeability and the welding performance of the steel; the high Mn content in the steel will also easily lead to the formation of Mn segregation in the center of the steel plate, which will have a negative impact on the steel. Detrimental effect on the stretch flangeability of the

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