A kind of 900mpa grade thick gauge high toughness hot-rolled steel strip and its preparation method

Abstract

A 900MPa thick and high-toughness hot-rolled steel strip and a preparation method thereof, belonging to the field of structural steel. The chemical composition of the steel strip and the mass percentage of each component are: C is 0.06~0.08%, Si is 0.15-0.18%, Mn is 1.4~1.6%, P≤0.012%, S≤0.008%, Cr is 0.8~ 1.2%, B is 0.005~0.012%, Ti is 0.01~0.03%, and the balance is Fe and inevitable impurities. The product is obtained through the processes of smelting and casting, rough hot rolling, finishing hot rolling, and cooling and coiling. Through reasonable composition design and controlled rolling and cooling process, the steel strip has a yield strength of 900MPa, which can replace steel plates of the same grade obtained through TMCP + tempering process or heat treatment process.

Description

technical field [0001] The invention belongs to the field of structural steel, and in particular relates to a 900MPa-level thick and high-toughness hot-rolled steel strip and a preparation method thereof. Background technique [0002] With the continuous improvement of the mechanization level of the coal mining machinery industry, the demand for high-end hydraulic supports continues to increase. In order to meet the requirements of high strength and high reliability of the support, and at the same time reduce the weight of the support as much as possible to facilitate underground transportation and installation, the requirements for the strength and toughness of the steel used for the support are getting higher and higher. At present, the strength level of the steel used for the support has been raised from the yield strength of 600MPa and 700MPa to the yield strength of more than 900MPa. At the same time, higher requirements are put forward for the toughness of the steel, e...

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Problems solved by technology

[0004] Compared with the controlled rolling and controlled cooling process, the heat treatment process not only leads to an increase in production costs, but also the low-temperature impact toughness of the physical steel plate is generally low, which makes it difficult to meet the high-standard product quality requirements of downstream users. Low-cost high-toughness high-strength steel products

[0005] Chinese patent CN102699031A discloses a 900MPa-grade high-toughness low-alloy steel and its manufacturing method. In order to meet the performance requirements of a yield strength of 900MPa, alloy elements such as Ni, Cu, Nb, Mo, and V are added to the design of the alloy composition, resulting in The cost of steel plate alloys has increased significantly

At the same time, the process it adopts is TMCP+off-line tempering, which must be tempered after the controlled rolling and controlled cooling process, which increases the process flow and manufacturing cost, and the composition design and process route of the product cannot meet the requirements of low cost and high performance

[0006] Chinese patent CN103526111A discloses a hot-rolled steel strip with a yield strength of 900 MPa and its preparation method. Although the quenching and tempering heat treatment process is canceled for the steel strip designed in this patent, Ti, Nb, Mo, and Ni are still added to the alloy composition design. and other alloying elements, and the Ti content reaches 0.15-0.19%, which increases the cost of the alloy and has a certain gap with the low-cost process route. At the same time, due to the addition of a large number of micro-alloying elements, the corresponding precipitation strengthening is its main strengthening mechanism One, as a result, the low-temperature toughness value of the final product is low, and the maximum impact energy of the physical steel plate at -40°C is only 126J, which is difficult to meet the requirements of high-toughness steel

However, from the performance index of the final product, its yield strength can only reach 800MPa, and because the increase in precipitation strengthening will significantly reduce the low-temperature toughness of the steel plate, its impact energy at -40°C is less than 100J, so this patent can only be used Manufacture high-strength steel with a yield strength of 800MPa and a low-temperature toughness value lower than 100J, which cannot reach a yield strength of more than 900MPa

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