345MPa-grade low-yield-ratio weather-resistant steel and preparation method thereof

Abstract

The invention discloses 345MPa-grade low-yield-ratio weather-resistant steel. The 345MPa-grade low-yield-ratio weather-resistant steel comprises the following components in percentage by mass: 0.04 to0.12 percent of C, 0.50 to 0.75 percent of Si, 0.43 to 0.50 percent of Mn, 0.06 to 0.09 percent of P, 0.010 to 0.020 percent of Ti, less than or equal to 0.004 percent of S, 0.25 to 0.40 percent of Cu, 0.15 to 0.35 percent of Ni, 0.30 to 0.60 percent of Cr, 0.02 to 0.04 percent of Al and the balance of Fe and unavoidable impurities. The preparation method of the weather-resistant steel comprisesthe following steps: (1) smelting: performing smelting, refining, alloying and calcium treatment on raw materials to obtain molten steel; (2) performing continuous casting: performing continuous casting on a molten steel upper plate blank; (3) soaking: performing soaking treatment on the casting blank; (4) performing steel rolling: performing steel rolling after removing phosphorus; (5) performingrelaxation: performing relaxation on a thin steel plate after finishing rolling; and (6) cooling. The preparation method of the weather-resistant steel has low yield ratio, high-temperature and low-temperature toughness, extensibility and high properties.

Description

technical field [0001] The invention relates to a production method of weathering steel, in particular to a 345MPa grade low yield ratio weathering steel and a preparation method thereof. Background technique [0002] In recent years, the demand for high-toughness and low-yield-ratio weathering steel for railway vehicles with thin gauge, large and wide medium-thick plates has been increasing. The traditional metallurgical structure design can meet the quality requirements of high-strength weathering steel. However, The weathering steel produced with ferrite + bainite or martensite main structure still has the disadvantages of high yield ratio, low low temperature toughness and poor elongation, and it is difficult to produce and unstable in performance. [0003] The chemical composition directly determines the application performance and production cost of the final steel product. Therefore, a reasonable ratio of alloying elements plays an important role in improving the stre...

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Problems solved by technology

In the prior art, in order to achieve the above effect, the 345MPa grade weathering steel generally adopts the design principle of low carbon and high manganese, and at the same time adds appropriate amount of alloying elements with strong affinity with carbon and nitrogen, such as Mo and V. The formation of carbonitrides is characterized by the precipitation of fine carbonitride particles to inhibit grain growth and precipitation strengthening, but the addition of alloying elements such as Mo and V will increase the carbon equivalent and welding crack sensitivity coefficient of the steel. Adversely affect soldering performance

In addition, in the prior art, wide-width weather-resistant steels for railway vehicles are all produced by hot continuous rolling production lines. The hot continuous rolling production line has the characteristics of continuous rolling and self-tempering after rolling, but the steel products produced stronger than higher

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