460MPa-grade low-compression-ratio and high-toughness steel plate for ocean engineering, and its production method

Abstract

The invention relates to the field of steels material, and concretely relates to a 460MPa-grade low-compression-ratio and high-toughness ocean steel plate and its production method. The steel plate comprises 0.04-0.07wt% of C, 0.2-0.4wt% of Si, 1.0-1.5wt% of Mn, 0.010wt% or less of P, 0.003wt% or less S, 0.2-0.5wt% of Ni, 0.2-0.5wt% of Cu, 0.2-0.4wt% of Cr, 0.1-0.3wt% of Mo, 0.02-0.05wt% of Nb, 0.01-0.025wt% of Ti, and the balance Fe and unavoidable impurities. The C content, the P content and the S content are controlled in a range of 0.04-0.07%, in a range of not greater than 0.010% and in a range of not greater than 0.003% respectively. Even though compression ratio is low, the heating temperature and the rolling temperature are reduced to realize the recrystallization refinement of austenite grains and ensure the low-temperature impact performance, and tempering after rolling further improves the toughness and the microstructure uniformity. The steel plate produced by the above scheme has a tensile strength of 620- 685MPa, a yield strength of 500-570MPa and a fracture elongation of 20-25%, has (horizontal) Charpy impact energy at -60DEG C reaching 240J, has a -80DEG C low temperature impact of not lower than 150J, has a Pcm value of not greater than 0.22 and a Ceq value of not greater than 0.47, and has the characteristics of easy welding, stable production process, strong operability and the like.

Description

technical field [0001] The invention relates to the field of iron and steel materials, in particular to a 460MPa grade low compression ratio high toughness steel plate for marine engineering and a production method thereof. Background technique [0002] Marine rights and interests are one of the core interests of our country. In recent years, the implementation of the national marine strategy has made marine engineering the focus of construction and development, and has gradually developed from the offshore to the deep sea. The rapid development of the ocean engineering equipment industry will create a huge demand for steel for ocean engineering, especially with the large-scale, high-parameterization, and lightweight of ships, ocean engineering, port machinery, and submarine oil pipelines, the performance of steel is raised. higher and higher requirements. In recent years, Japan’s Nippon Steel and JFE, Germany’s Dillingen, etc. are at the forefront of the world’s steel comp...

AI Technical Summary

Problems solved by technology

Among them, since the method of normalizing usually obtains ferrite plus pearlite structure, the strength is not easy to increase, and it is mainly used to produce marine steel products below 420MPa; while the method of controlled rolling and controlled cooling can obtain high strength, but due to the The thickness is relatively large, and it is difficult to achieve a large reduction in the rolling stage, especially the structure refinement of the core in the rough rolling stage and the austenite deformation in the finishing rolling stage are difficult to guarantee. To ensure toughness under this condition, it is necessary to Larger compression ratio; and the production method of quenching and tempering can improve the strength while ensuring toughness, but compared with the production method of controlled rolling and controlled cooling, when producing steel with the same strength level, the quenching and tempering process needs to be added More alloying elements to ensure strength, which not only leads to cost increase, but also is not conducive to welding, and the cost of quenching and tempering heat treatment process is relatively high

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