Low-yield-ratio ocean engineering steel and preparation method thereof

Abstract

The invention relates to low-yield-ratio ocean engineering steel and a preparation method thereof, and belongs to the technical field of ocean engineering steel. The steel and the method solve the problems of high yield ratio, low low-temperature toughness and low service safety of existing ocean engineering steel. The ocean engineering steel comprises the following components of, in percentage bymass, 0.045%-0.05% of C, 3.0%-3.2% of Ni, 1.4%-1.5% of Cu, 0.20%-0.50% of Mo, 0.62%-1.50% of Cr, 0.82%-0.90% of Mn, 0.05%-0.15% of Si, 0.010%-0.030% of Nb, 0.008%-0.018% of Ti, 0.02%-0.04% of Al, lower than or equal to 0.007% of P, lower than or equal to 0.002% of S, and the balance Fe and inevitable impurities. The preparation method of the ocean engineering steel adopts a heat treatment processof two-time quenching and three-time tempering. The method can reduce the yield ratio of the ocean engineering steel and improve the low-temperature toughness of the steel.

Description

technical field [0001] The invention relates to the technical field of steel for marine engineering, in particular to a low yield ratio steel for marine engineering and a preparation method thereof. Background technique [0002] The service conditions of ships and marine engineering equipment are very harsh, and the influence of various harsh sea conditions such as storms, waves, currents, and glaciers must be fully considered. In recent years, with the large-scale development of marine engineering equipment, higher and higher requirements have been put forward for the safety of marine engineering structures and the performance of steel plates used. Among them, high strength is an important trend of steel for large-scale marine engineering equipment. However, For traditional low-alloy steel, as the strength increases, its yield ratio is often higher, even exceeding 0.95, due to the uniformity of the structure; The high yield strength ratio means that the steel plate has a g...

AI Technical Summary

Problems solved by technology

Increasing the soft phase structure in steel (such as retained austenite, reverse transformed austenite, etc.) is not only beneficial to reduce the yield ratio of steel, but also can significantly improve the low temperature toughness of steel, in which the retained austenite is usually formed during the quenching process The content is directly related to the alloy composition of the steel; reverse transformed austenite is usually formed during high-temperature tempering or aging, and has a greater relationship with the heat treatment process. Traditionally, critical zone quenching + tempering is used to improve Tempering temperature and other methods to promote the formation of reverse transformed austenite in steel, but it will bring about a large loss of strength, resulting in a narrow process window for optimal performance. Therefore, in the case of ensuring a small loss of strength, it is necessary to design a The method of significantly increasing the content of reversed austenite is of great significance

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