590MPa-grade cold-rolled dual-phase steel with excellent hole-expanding performance and production method thereof

Abstract

The invention discloses 590MPa-grade cold-rolled dual-phase steel with excellent hole-expanding performance and a production method thereof, and belongs to the technical field of rolled steel. The 590MPa-grade cold-rolled dual-phase steel is prepared from the following chemical components in percentage by mass: 0.06-0.09% of C, 1.4-2.1% of Si+Mn, 0.01-0.02% of Nb, 0.03-0.06% of Al, less than or equal to 0.06% of P, less than or equal 0.010% of S, less than or equal to 0.006% of N, and the balance of Fe and inevitable impurities. According to the dual-phase steel disclosed by the invention, volume fraction of ferrite in a micro structure is 70-80%, volume fraction of martensite is 10-25% and volume fraction of bainite is 5-10%. Low-Al content is adopted, and smelting casting is improved; crystalline grains are refined by a low-temperature rolling process of 540-600 DEG C and Nb micro-alloying, and diffused distribution of a hard phase (martensite and bainite) is promoted; and a sectional cooling process of slow cooling, quick cooling I and quick cooling II is adopted, so that a proper amount of bainite is obtained, and therefore, hole-expanding performance is improved.

Description

technical field [0001] The invention belongs to the technical field of steel rolling, and more specifically relates to a 590MPa grade cold-rolled dual-phase steel with excellent hole expansion performance and a production method thereof. Background technique [0002] With economic development and social progress, energy saving, environmental protection and safety have become the development trend of the automobile industry. As the key material with the largest proportion of application in automobile manufacturing, steel has become an inevitable trend to develop towards high strength. Due to its good strong-plastic matching, dual-phase steel overcomes the problem of poor formability of traditional low-alloy high-strength steel products characterized by ferrite and pearlite. increasingly widely applied. [0003] With the increasing application of dual-phase steel, the structure of parts is becoming more and more complex, and the forming methods are becoming more and more div...

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Problems solved by technology

[0008] Aiming at the problem that the hole expansion performance of the 590MPa grade cold-rolled dual-phase steel in the prior art is not high, the present invention provides a 590MPa grade cold-rolled dual-phase steel with excellent hole expansion performance and its production method. On the basis of Nb micro-alloying and low-temperature coiling process to refine grains, adopt segmental cooling during continuous annealing to obtain an appropriate amount of bainite, thereby producing 590MPa grade cold-rolled dual-phase steel with a hole expansion rate ≥ 75%. steel

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