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Process of controlling lower-limit Mn content of R350HT steel rail flash welded joint structure

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

Active Publication Date: 2019-11-22
PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP
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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 of controlling lower-limit Mn content of R350HT steel rail flash welded joint structure

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] The heat input is 3.5MJ, the flash welding process is 10.0mm, and the mass fraction of Mn is 0.66%, and the mass fraction of Cr is 0.13%. wt%, Cr 0.12~0.13wt%, 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 within the range of the average hardness of the base metal -30HV~+60HV; the three-point bending static bending test is continuous at 2000kN, and the maximum deflection is 25.5mm; the three-point support physical fatigue test has not broken 5 million times, and ...

Embodiment 2

[0032] The flash welding process with heat input of 4.5MJ and upsetting amount of 11.5mm is adopted, and the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 0.65% and a mass fraction of Cr of 0.13% (C content is in the middle and lower limits, Si≤0.30 wt%, Cr 0.12~0.13wt%, 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 within the range of the average hardness of the base metal -30HV~+60HV; the three-point bending static bending test is cont...

Embodiment 3

[0035] The flash welding process with heat input of 4.5MJ and upsetting amount of 11.3mm is adopted, and the mass fraction of Mn is 0.80%, and the mass fraction of Cr is 0.13%. wt%, Cr 0.12~0.13wt%, 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 range of the average hardness of the base metal -30HV~+60HV; the three-point bending static bending test is continuous at 2000kN, and the maximum deflection is 24.6mm; the three-point support physical fatigue test has ...

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Abstract

The invention belongs to the technical field of steel rail flash welding and discloses a process of controlling the lower-limit Mn content of an R350HT steel rail flash welded joint structure in orderto solve the technical problem that an R350HT steel rail flash welded joint is likely to have the martensitic structure in the prior art. The process of controlling the lower-limit Mn content of theR350HT steel rail flash welded joint structure, provided by the invention, comprises the steps of welding and postweld treatment, wherein in the welding process, pulsation or preheating flash weldingis conducted by controlling the welding heat input to be 3.5-4.5 MJ, and the welding upset forging amount is 10.0-11.5 mm; and in the postweld treatment process, the joint is naturally cooled to the indoor temperature in the air. According to the process, no abnormal structures such as the martensitic structure existing in the steel rail flash welding joint are ensured through comprehensive control over chemical components of a steel rail, the hot rolling process, the welding process and postweld cooling, and meanwhile, the mechanical performance of the joint is ensured.

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 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 blocks or even ...

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 PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP
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