High-strength, high-toughness, low-yield-ratio low-temperature steel for -70°C and manufacturing method thereof

Abstract

The invention discloses a low-temperature steel having high strength, high toughness and low yield ratio used at 70 DEG C and a manufacture method thereof. The low-temperature steel comprises the following chemical components by weight percentage: 0.05-0.20% of C, less than or equal to 0.30% of Si, 0.85-1.50% of Mn, less than or equal to 0.005% of P, less than or equal to 0.003% of S, 0.015-0.050% of Alt, 0.35-0.70% of Ni, and less than or equal to 0.004% of N, and also contains any one or more of less than or equal to 0.10% of Mo, less than or equal to 0.05% of Nb, less than or equal to 0.025% of Ti, and less than or equal to 0.005% of Ca, and the balance of Fe and the unavoidable impurity. The low-temperature steel is manufactured by a steel-making technology, a steel rolling technology and a heat treatment technology, The content of the C and Mn elements can be controlled on component design, so that the yield ratio of a steel plate is reduced, a certain amount of the Ni element is added for guaranteeing the low-temperature impact toughness, the microalloy elements such as Ti, Mo, and Nb are added for improving the welding performance, the contents of P, S and N are strictly controlled, the Ca-Si processing is carried out, and the steel has excellent low-temperature toughness and has low yield ratio.

Description

technical field [0001] The invention relates to the field of alloy steel manufacturing, in particular to a low-temperature steel with high toughness and low yield ratio for use at -70°C and a manufacturing method thereof. Background technique [0002] The yield ratio is the ratio of the yield strength to the tensile strength of the material. A steel with a lower yield ratio can improve the deformation resistance of the steel under severe load deformation, that is, the lower the yield ratio, the material from plastic deformation to The greater the deformation energy required for fracture, the greater its ability to resist large deformations and effectively ensure safety. However, in the application of LPG ship and LPG storage tank materials, since the service temperature reaches -70°C, not only the yield strength ratio of the material is strictly regulated, but also the low temperature toughness of the steel is extremely high. Therefore, reasonable Ensure the matching of yie...

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Problems solved by technology

[0004] The object of the present invention is to provide a low-temperature steel with high toughness and low yield strength ratio for use at -70°C and a manufacturing method thereof. The problem of poor matching, using a feasible production process, suitable for large-scale production operations, and obtaining steel for pressure vessels with good low-temperature toughness and tensile properties

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