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Process for controlling microstructure of flash welded joints of r350ht rail with lower limit of mn content

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: 2021-07-13
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 for controlling microstructure of flash welded joints of r350ht rail with lower limit of mn content

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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 2000...

Embodiment 3

[0035] The flash welding process with heat input of 4.5MJ and upsetting amount of 11.3mm is adopted, and the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 0.80% 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.

[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 2000...

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Abstract

The invention discloses a technique for controlling the joint structure of flash welding joints of R350HT rail with lower limit 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 martensitic structure in the flash welded joint of R350HT rail, the present invention provides a process for controlling the microstructure of the flash welded joint of R350HT rail with a lower limit of Mn content, including welding process and post-weld treatment; In the welding process, the welding heat input is controlled to be 3.5-4.5MJ pulsation or preheating flash welding, and the welding upsetting amount is 10.0-11.5mm; in the post-welding treatment, the joint is naturally cooled to room temperature in the air. 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 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 Patents(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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