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The Technology of Controlling the Microstructure of the Flash Welded Joint of the 350ht Rail with the 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 control, 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: 2022-08-05
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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  • The Technology of Controlling the Microstructure of the Flash Welded Joint of the 350ht Rail with the Lower Limit of Mn Content

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] The flash welding process with the heat input of 4.0MJ and the upsetting amount of 11.0mm was adopted, and the European standard R350HT heat-treated rails with a mass fraction of Mn of 0.75% and a mass fraction of Cr of 0.11% (the C content is in the middle and lower limit, Si≤0.30 wt%, Cr0.11~0.12wt%, Rm≥1175MPa, A≥9%, tread hardness≥350HB) for flash welding. After the flash welding is completed, the joints are placed in the air to cool to room temperature naturally.

[0030] According to the EN14587.2 standard, the joints obtained by the above welding process and post-weld treatment method are inspected and analyzed. The microstructure of the rail head and the rail foot at the specified position of the joint center surface is pearlite, and no harmful structures such as martensite are found; The hardness of the joint outside the softening zone is in the range of the average hardness of the base metal -30HV ~ +60HV; the three-point bending static bending test is 2000kN ...

Embodiment 2

[0032] The flash welding process with heat input of 4.9MJ and upsetting amount of 11.8mm was adopted, and the mass fraction of Mn was 0.80% and the mass fraction of Cr was 0.11%. wt%, Cr0.11~0.12wt%, Rm≥1175MPa, A≥9%, tread hardness≥350HB) for flash welding. After the flash welding is completed, the joints are placed in the air to cool to room temperature naturally.

[0033] According to the EN 14587.2 standard, the joints obtained by the above welding process and post-weld treatment method are inspected and analyzed. The microstructure of the rail head and the rail foot on the center surface of the joint is pearlite, and no harmful structures such as martensite are found; except for softening The hardness of the joints outside the area is in the range of the average hardness of the base metal -30HV ~ +60HV; the three-point bending static bending test is 2000kN continuously, the maximum deflection is 25.6mm; the three-point support physical fatigue test is not broken for 5 mil...

Embodiment 3

[0035] A flash welding process with a heat input of 5.3MJ and an upsetting amount of 12.0mm was used for the European standard R350HT heat-treated rail with a mass fraction of Mn of 0.88% and a mass fraction of Cr of 0.12% (the C content is in the middle and lower limit, Si≤0.30 wt%, Cr 0.11-0.12wt%, Rm≥1175MPa, A≥9%, tread hardness≥350HB) for flash welding. After the flash welding is completed, the joints are placed in the air to cool to room temperature naturally.

[0036] According to the EN14587.2 standard, the joints obtained by the above welding process and post-weld treatment method are inspected and analyzed. The microstructure of the rail head and the rail foot at the specified position of the joint center surface is pearlite, and no harmful structures such as martensite are found; The hardness of the joint outside the softening zone is in the range of the average hardness of the base metal -30HV~+60HV; the three-point bending static bending test is 2000kN continuousl...

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Abstract

The invention discloses a process for controlling the microstructure of a R350HT rail flash welding joint with a 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 the flash welding joint of R350HT rail is easy to cause martensite structure, the invention provides a process for controlling the microstructure of the flash welding joint of R350HT rail with a lower limit of Mn content, including welding process and post-welding treatment; welding; In the process, the welding heat input is controlled to be 4.0-5.5MJ for pulsation or preheating flash welding, and the welding upsetting amount is 11.0-12.5mm; in the post-weld treatment, the joint is placed in the air to cool 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 R350HT rail flash welded joint with a lower limit Mn content. Background technique [0002] With the rapid development of seamless track technology in passenger, freight and high-speed, 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 breakage, falling blo...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B23K11/04B23K11/16B23K11/34
CPCB23K11/04B23K11/34B23K11/16
Inventor 陆鑫李大东王若愚邓健
Owner PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP