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Process for controlling medium and lower limit Mn content R350HT steel rail flash welding joint structure

A technology for R350HT and welded joints, which is applied in the field of controlling the microstructure of the R350HT rail flash welded joint with the lower limit Mn content, can solve the problems of increasing the martensite content in the joint, and achieve the effect of simple control process and good prospect of popularization and application.

Active Publication Date: 2019-11-22
CHENGDU ADVANCED METAL MATERIALS IND TECH RES INST CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In foreign countries, the rail flash welded joints are only strengthened for heat treatment on the rail head. During the natural cooling process of the joints after welding, compressed air is used to forcibly cool the weld area to increase the hardness of the joints, and this method can inhibit martensite and Elimination is not helpful, if not properly controlled, it will increase the content of martensite in the joint; and for some heat-treated rails and all types of heat-treated rails, no post-weld treatment measures are adopted, that is, only natural cooling after welding

Method used

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  • Process for controlling medium and lower limit Mn content R350HT steel rail flash welding joint structure

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] The heat input is 5.6MJ, the flash welding process is 12.8mm, and the mass fraction of Mn is 0.85%, and the mass fraction of Cr is 0.10%. wt%, Cr 0.10~0.11wt%, Rm≥1175MPa, A≥9%, tread hardness ≥350HB) for flash welding. After the flash welding is completed, directly place the joint in the air to cool down to room temperature naturally.

[0030] According to the EN 14587.2 standard, the joints obtained by the above welding process and post-welding treatment method were inspected and analyzed. The microstructure of the rail head and the rail foot on the center plane of the joint was pearlite, and no harmful structures such as martensite were found; except for softening The hardness of the joints outside the area is all within the range of the average hardness of the base metal -30HV~+60HV; the three-point bending static bending test is 2000kN continuously, and the maximum deflection is 26.3mm; the three-point support physical fatigue test is 5 million times unbroken, and ...

Embodiment 2

[0032] The flash welding process with heat input of 5.0MJ and upsetting amount of 12.0mm is adopted, and the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 0.95% and a mass fraction of Cr of 0.10% (C content is in the middle and lower limits, Si≤0.30 wt%, Cr 0.10~0.11wt%, Rm≥1175MPa, A≥9%, tread hardness ≥350HB) for flash welding. After the flash welding is completed, directly place the joint in the air to cool down to room temperature naturally.

[0033] According to the EN 14587.2 standard, the joints obtained by the above welding process and post-welding treatment method were inspected and analyzed. The microstructure of the rail head and the rail foot on the center plane of the joint was pearlite, and no harmful structures such as martensite were found; except for softening The hardness of the joints outside the area is all within the range of the average hardness of the base metal -30HV~+60HV; the three-point bending static bending test is ...

Embodiment 3

[0035] The heat input is 7.0MJ, the flash welding process is 14.5mm, and the mass fraction of Mn is 0.91%, and the mass fraction of Cr is 0.11%. wt%, Cr 0.10~0.11wt%, Rm≥1175MPa, A≥9%, tread hardness ≥350HB) for flash welding. After the flash welding is completed, directly place the joint in the air to cool down to room temperature naturally.

[0036] According to the EN 14587.2 standard, the joints obtained by the above welding process and post-welding treatment method were inspected and analyzed. The microstructure of the rail head and the rail foot on the center plane of the joint was pearlite, and no harmful structures such as martensite were found; except for softening The hardness of the joints outside the area is within the average hardness of the base metal -30HV~+60HV; the three-point bending static bending test is 2000kN continuously, and the maximum deflection is 26.5mm; the three-point support physical fatigue test is 5 million times unbroken, and all indicators ar...

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Abstract

The invention discloses a process for controlling a medium and lower limit Mn content R350HT steel rail flash welding joint structure, and belongs to the technical field of steel rail flash welding. According to the process for controlling the medium and lower limit Mn content R350HT steel rail flash welding joint structure, the technical problem of a martensitic structure easily caused by a R350HT steel rail flash welding joint in the prior art is solved. The process comprises a welding process and post-welding treatment; in the welding process, the welding heat input is controlled to be 5.0-7.0 MJ pulsation or preheating flash welding, and the welding upsetting amount is 12.0-14.5 mm; and in the post-welding treatment, the joint is naturally cooled to the room temperature in air. By comprehensively controlling the chemical components, a hot rolling process, the welding process and the post-welding cooling of a steel rail, abnormal structures, such as the martensitic structure, cannotexist in the steel rail flash welding joint, and the mechanical property of the joint is ensured at the same time.

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 a middle and lower limit of 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 bloc...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B23K11/04B23K11/16B23K11/34
CPCB23K11/04B23K11/16B23K11/34
Inventor 陆鑫李大东王若愚邓健
Owner CHENGDU ADVANCED METAL MATERIALS IND TECH RES INST CO LTD
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