Hot rolled bainite steel rail and production process

Abstract

The invention discloses a hot rolled bainitic steel rail and a production process. The hot rolled bainitic steel rail comprises the following chemical compositions in percentage by weight: 0.10 to 0.35 percent of C, 0.80 to 2.00 percent of Si, 0.80 to 3.30 percent of Mn, less than 2.00 percent of Cr, 0.0010 to 0.0100 percent of N, 0.01 to 0.10 percent of Nb, 0.02 to 0.2 percent of V, 0.005 to 0.06 percent of Ti, 0.10 to 0.40 percent of Mo, less than 0.00005 percent of H and the balance of Fe and inevitable impurities. The process is characterized in that: a hole pattern method is adopted for the rough rolling of the steel rail, a universal method is adopted for the precision rolling of the steel rail, the rolling interval of adjacent passes in the rough rolling is controlled to more than 5 seconds and not more than 35 seconds, and the steel rail after the rolling is naturally cooled in the air to room temperature. The production process limits the size of residual austnesite in M-A islands and between lath bainitic ferrite; the proportion of the lath bainitic ferrite is over 75 percent; comprehensive indexes of performance such as specific elongation and the like are improved; andthe production process can be also applied to turnout bainitic steel rails and bainitic AT rails.

Description

technical field [0001] The invention belongs to the production technical field of railway steel rails, and in particular relates to a steel rail containing bainite structure and a production process. Background technique [0002] The cost of bainitic rail alloy is relatively high. In addition, because the production technology of rail tempering is not suitable for the existing production line and affects the production efficiency, the large-scale adoption and development of bainitic rail is limited. [0003] For example, the introduction of the literature (The Development of Bainitic Steel for Special Railway System Requirements, 39TH MWSP CONF PROC, ISS, VOL XXXV, 1998-1015) shows that the content of Mo in the bainitic rails it studies is as high as 0.8%, and it needs to be heated at 550°C Temper. [0004] Other documents such as "High-speed quasi-high-speed railway road fork high-performance wear-resistant steel and its manufacturing method" (patent number: 98112095.4), "...

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Problems solved by technology

[0004] Other documents such as "High-speed quasi-high-speed railway road fork high-performance wear-resistant steel and its manufacturing method" (patent number: 98112095.4), "medium and low carbon manganese series bainite steel" (application number 03150092.7), "improved carbide-free bainitic steel" The steel rails introduced in "Benite Steel and Its Production Method" (Patent No. 96192013.0) not only need to be tempered but also do not describe the microstructure. In fact, within the chemical composition range designed in the above documents, the bainite microstructure Different microstructures will make bainite rails have different levels of strength and toughness. If unfavorable microstructures are produced: large M-A islands (about 10 μm), the proportion of lath bainitic ferrite is low, and in About 30%, resulting in very little lath-shaped retained austenite, most of the retained austenite exists in the M-A island, and it is easy to induce martensitic transformation. Due to the instability of the retained austenite, the rail is resistant to hydrogen and non Metal inclusions are more sensitive, which will make the performance of the rail unstable, the elongation rate is low, and even lead to a decrease in the safety of the rail

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