Preparation method of bainite/martensite/austenite composite high-strength steel

Abstract

The invention discloses a preparation method of bainite / martensite / austenite composite high-strength steel, belonging to the field of low-alloy high-strength steel. According to the composite high-strength steel, C, Mn, Si and Cr are used as main alloy elements, Al, Ni, Mo, Cu, Nb, Ti, V and the like are added, and the balance is Fe. The preparation method comprises the following steps: smelting, casting, forging or rolling to prepare rails, thick-wall pipes, large-section bars or thick pipes and the like by adopting a conventional steel-smelting process; carrying out austenitizing; controlling cooling by adopting different cooling media to obtain a part of bainite tissue in the cooling process; instantly carrying out distribution treatment and low-temperature tempering treatment so as to finally obtain a bainite / martensite / austenite composite tissue which is good in strong plasticity and toughness coordination, wherein the distribution time is 30-360 minutes. For a component which is large in size and easy to crack in quenching, the bainite / martensite / austenite composite high-strength steel has wide application prospect.

Description

technical field [0001] The invention relates to the field of low-alloy high-strength steel, in particular to a preparation method of bainite / martensite / austenite composite phase high-strength steel. Background technique [0002] In order to reduce the weight of mechanical components to save energy and resources, low-alloy high-strength steels have been widely used in machinery, automobiles, ships, aviation and other fields. For traditional high-strength steels, as the strength increases, the plasticity will gradually deteriorate. Thereby limiting the application of high-strength steel. The traditional high-strength steel heat treatment process is generally based on the quenching-tempering process. In order to improve the plasticity of high-strength steel, Xu Zuyao (Heat Treatment, 2007, 22 (1)) proposed a quenching-partitioning-tempering process (hereinafter referred to as Q-P-T), This process refers to that after the workpiece is austenitized, it is quenched to a certain t...

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Problems solved by technology

However, there are two unavoidable shortcomings in the traditional Q-P-T process: First, in order to obtain the martensitic structure, a faster quenching and cooling rate is required, but for large-sized components, if the quenching and cooling rate is too fast, it is difficult to achieve Consistent with the structure of the core (generally the surface layer is martensite, the core is still mainly pearlite), and the components are also easy to crack; second, for the traditional Q-P-T process, the distribution time is relatively short (the distribution time is generally 10 to 600 seconds , Xu Zuyao, Heat Treatment, 2009 (6)), if the distribution time is too short, it is difficult to achieve industrial production, and it is impossible to achieve temperature uniformity for large-scale components, resulting in inconsistent performance of the surface and core of large-scale components

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