High strength bainitic steel rail and heat treatment process thereof

Abstract

The invention provides a high strength bainitic steel rail and a heat treatment process thereof. The steel rail comprises the following chemical compositions by weight percentage: 0.10%-0.32% of C, 0.80%-2.00% of Si, 0.80%-2.80% of Mn, Cr less than 1.50%, 0.10%-0.40% of Mo, 0-0.5% of Ni, wherein Mn, Cr and Ni satisfy the relation of: Mn+Cr+0.5Ni<=2.8%, and the balance of Fe and unavoidable impurities. The process is as below: conducting hot rolling on the steel rail or air cooling on the steel rail to room temperature, then reheating to 850-1000 DEG C for austenization; cooling the steel rail head to 620-570 DEG C with a cooling rate of 0.3-15 DEG C / s; when the temperature is lower than 620-570 DEG C, cooling to 350-200 DEG C with a cooling rate of 0.5-5 DEG C / s; and then conducting air cooling to room temperature. The invention avoids generation of excessive unstable thick M-A islands in granular bainite during air cooling to room temperature in hot rolling, reduces the risk of straightening fracture (or delayed fracture)of hot-rolled steel rail, and improves the adaptability of steel production process. The steel rail has tensile strength higher than 1400MPa, and realizes optimum matching of strength, toughness and ductility, and excellent rolling contact fatigue resistance and wear resistance.

Description

technical field [0001] The invention relates to a railway steel rail and its manufacture, in particular to a high-strength bainitic steel rail and its heat treatment process. Background technique [0002] With the advancement of railway heavy-duty transportation technology, my country's railway heavy-duty transportation capacity is constantly improving. It is common for existing passenger and freight mixed transportation lines to pass a total train weight of more than 100 million tons per year, and the axle load of trucks is gradually increasing. In 2008 The transportation volume of the Daqin line reached 340 million tons. In this context, the development of railway rails suitable for heavy haul transportation has been promoted. [0003] Heavy-duty transportation puts forward higher requirements on the rail's resistance to peeling off blocks, that is, its resistance to rolling contact fatigue. Bainite rails just meet this requirement with their excellent resistance to rollin...

AI Technical Summary

Problems solved by technology

[0006] The prior art "Bainitic steel and bainite rails for curved and heavy-duty rails and its production method" (CN101921971A) mainly considers the production of hot-rolled rails, and does not consider the operability of accelerated cooling process conditions. For example, when raising steel When all hardenable elements reach the upper limit of composition, on the one hand, the range of heating temperature and cooling rate in the quenching process specification must be very narrow; on the other hand, it is very easy to find martensite under the optical microscope, which seriously reduces the impact toughness and fracture toughness organization

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