Process of controlling the microstructure of flash welded joints of r350ht rail with the upper limit of mn content

Abstract

The invention discloses a process for controlling the microstructure of a rail flash welding joint of R350HT rail with an extremely upper limit Mn content, belonging to the technical field of rail flash welding. In order to solve the technical problem in the prior art that the flash-welded joint of the R350HT rail is easily caused to appear martensite, the invention provides a process for controlling the microstructure of the flash-welded joint of the R350HT rail with the upper limit Mn content, including the welding process and the post-weld treatment; In the welding process, the welding heat input is controlled to be 8.5-9.5MJ for pulsation or preheating flash welding, and the welding upsetting amount is 15.5-16.0mm; in the post-weld treatment, the joint is naturally cooled to 575-585 ℃, and then cooled to ≤250℃, and finally cooled to room temperature naturally. Through the comprehensive control of the chemical composition of the rail, the hot rolling process, the welding process, and the cooling after welding, it is ensured that there is no abnormal structure such as martensite in the rail flash welded joint, and the mechanical properties of the joint are also guaranteed.

Description

technical field

[0001] The invention belongs to the technical field of rail flash welding, and in particular relates to a process for controlling the microstructure of a rail flash welded joint of R350HT rail with an extremely upper limit Mn content. Background technique

[0002] With the rapid development of seamless track technology in passenger, freight, high-speed and heavy-duty railway construction around the world, the quality of rail joints has attracted more and more attention from relevant departments. The railway line is the direct carrier of train operation, and the reliability of its quality is the key to the safe operation of the train. The rail flash welding joint is the weak link of the whole line, and its quality can directly affect the safety of the railway. In the matrix of the rail flash welded joint, the martensite structure belongs to the hard and brittle phase, with high hardness and extremely low toughness. The occurrence of such phenomena as rail br...

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