Low-alloy high-strength steel with yield strength of 460 MPa and production method thereof

Abstract

The invention discloses low-alloy high-strength steel with the yield strength of 460 MPa and a production method thereof, and belongs to the technical field of steel rolling. The invention provides the low-alloy high-strength steel with the yield strength of 460 MPa in order to solve the problems that the existing low-alloy high-strength steel with the medium-high-grade strength is large in strength fluctuation and unstable in performance. The low-alloy high-strength steel comprises the following chemical components of, in percentage by weight, 0.07%-0.09% of C, less than or equal to 0.05% ofSi, 1.20%-1.50% of Mn, 0.03%-0.05% of P, 0.025%-0.060% of Als, 0.045%-0.055% of Nb, 0.005%-0.015% of Ti, 0.001%-0.003% of Ca, less than or equal to 0.006% of S, less than or equal to 0.0025% of N, less than or equal to 0.0025% of O, and the balance Fe and inevitable impurities. According to the low-alloy high-strength steel with the yield strength of 460 MPa and the production method thereof, through low-O, low-N and low-Ti control, the quantity density of the carbonitride with micron size does not exceed 3 / mm <2>; thickness distinguishing of large reduction rate, low-temperature coiling, slowcooling of a hot rolling heat preservation cover and the annealing process is adopted for a starting machine frame and an ending machine frame through finish rolling, and stable control over the product strength is achieved. The strength range between the produced low-alloy high-strength steel coils with the yield strength of 460 MPa is smaller than or equal to 70 MPa, the strength difference ofthe middle portions of the coil inner heads is smaller than or equal to 30 MPa, the yield ratio is smaller than or equal to 0.85%, and the low-alloy high-strength steel has the advantages of being lowin cost, excellent in forming performance and small in strength fluctuation.

Description

technical field [0001] The invention belongs to the technical field of steel rolling, and more specifically relates to a low-alloy high-strength steel with a yield strength of 460 MPa and a production method. Background technique [0002] Low-alloy high-strength steel is achieved by adding micro-alloying elements such as Nb, Ti, and V to low-carbon steel to achieve the purpose of precipitation strengthening and fine-grain strengthening, thereby achieving an increase in strength. Low-alloy high-strength steel has the characteristics of excellent formability, good weldability, and low cost, and is widely used in automotive structural parts and reinforcements. The common ones on the market are low-alloy high-strength steels with a yield strength of 260-420 MPa. With the continuous development of automobile lightweight, low-alloy high-strength steel with a yield strength of 460MPa and above will gradually emerge. Today's cold-rolled low-alloy high-strength steel sheets for aut...

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Problems solved by technology

[0006] Aiming at the problems of large fluctuations in strength and unstable properties of high-grade low-alloy high-strength steel in the prior art, the present invention provides a low-alloy high-strength steel with a yield strength of 460 MPa and its production method

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