Process for Controlling Microstructure of Flash Welded Joints in R350ht Rails with Medium and Upper Mn Contents

Abstract

The invention discloses a technology for controlling the flash welding joint structure of R350HT rail with upper and lower Mn content, and belongs to the technical field of rail flash welding. In order to solve the technical problem in the prior art that easily leads to the martensite structure of the R350HT rail flash welding joint, the present invention provides a process for controlling the upper limit Mn content of the R350HT rail flash welding joint structure, including the welding process and post-weld treatment; In the welding process, the welding heat input is controlled to be 7.0-8.5MJ pulsation or preheating flash welding, and the welding upsetting amount is 14.5-15.5mm; in the post-welding treatment, the joint is naturally cooled to 525-560°C, and then heat-preserved and cooled to ≤250°C, and finally cool down to room temperature naturally. Through the comprehensive control of the chemical composition of the rail, hot rolling process, welding process, and post-weld cooling, it is ensured that there is no abnormal structure such as martensite in the rail flash welded joint, and at the same time, the mechanical properties of the joint are 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 R350HT rail flash welding joints with the upper and lower Mn content. Background technique

[0002] With the rapid development of seamless track technology in passenger transport, freight transport, high-speed and heavy-duty railway construction worldwide, the quality of rail joints has attracted more and more attention from relevant departments. As the direct carrier of train operation, the quality and reliability of railway lines is the key to the safe operation of trains. Rail flash welding joints are the weak link of the whole line, and their quality can directly affect the safety of the railway. In the matrix of rail flash welded joints, the martensite structure belongs to the hard and brittle phase, which has high hardness and extremely low toughness. Cause rails to break on the line, drop blocks or ev...

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