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Process of controlling the microstructure of flash welded joints of r350ht rail with the upper limit of mn content

A technology for R350HT and welded joints, which is applied in the field of controlling the upper limit Mn content of R350HT rail flash welded joints, 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: 2022-08-09
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 the microstructure of flash welded joints of r350ht rail with the upper limit of mn content

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0033] Using flash welding process with heat input of 8.9MJ and upsetting amount of 15.3mm, the European standard R350HT heat-treated rail with Mn mass fraction of 1.15% (C content is in the middle and lower limit, Si≤0.30wt%, Rm≥1175MPa, A ≥9%, tread hardness ≥350HB) for flash welding. After the flash welding is completed, the infrared thermometer is used to measure the temperature of the center of the welding seam on the running surface of the naturally cooled rail joint. When the temperature drops to 585°C, the aluminosilicate fiber cotton insulation device with a thickness of ≥30mm is immediately used. , keep the area of ​​200mm on both sides of the joint fusion line; continue to monitor the joint temperature during this process, remove the device when the temperature of the center of the welding seam on the driving surface is lower than 250 ℃, and finally put the joint in the air to cool to room temperature naturally .

[0034] According to EN 14587.2, the joints obtaine...

Embodiment 2

[0036] The flash welding process with heat input of 9.5MJ and upsetting amount of 16.0mm was adopted, and the mass fraction of Mn was 1.21% for the European standard R350HT heat-treated rail (C content was in the middle and lower limit, Si≤0.30wt%, Rm≥1175MPa, A ≥9%, tread hardness ≥350HB) for flash welding. After the flash welding, the infrared thermometer is used to measure the temperature of the center of the welding seam on the running surface of the naturally cooled rail joint. When the temperature drops to 575°C, the aluminosilicate fiber cotton insulation device with a thickness of ≥30mm is immediately used. , keep the area of ​​200mm on both sides of the joint fusion line; continue to monitor the joint temperature during this process, remove the device when the temperature of the center of the welding seam on the driving surface is lower than 250 ℃, and finally put the joint in the air to cool to room temperature naturally .

[0037] According to EN 14587.2, the joint...

Embodiment 3

[0039] The flash welding process with heat input of 8.5MJ and upsetting amount of 15.5mm was adopted, and the mass fraction of Mn was 1.18% for the European standard R350HT heat-treated rail (C content was in the middle and lower limit, Si≤0.30wt%, Rm≥1175MPa, A ≥9%, tread hardness ≥350HB) for flash welding. After the flash welding is completed, the infrared thermometer is used to measure the temperature of the center of the welding seam of the running surface of the naturally cooled rail joint. When the temperature drops to 580℃, the aluminosilicate fiber cotton insulation device with a thickness of ≥30mm is immediately used. , keep the area of ​​200mm on both sides of the joint fusion line; continue to monitor the joint temperature during this process, remove the device when the temperature of the center of the welding seam on the driving surface is lower than 250 ℃, and finally put the joint in the air to cool to room temperature naturally .

[0040] According to EN 14587....

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Abstract

The invention discloses a process for controlling the microstructure of a rail flash welding joint of R350HT rail with an extremely upper limit Mn content, belonging to the technical field of rail flash welding. In order to solve the technical problem in the prior art that the flash-welded joint of the R350HT rail is easily caused to appear martensite, the invention provides a process for controlling the microstructure of the flash-welded joint of the R350HT rail with the upper limit Mn content, including the welding process and the post-weld treatment; In the welding process, the welding heat input is controlled to be 8.5-9.5MJ for pulsation or preheating flash welding, and the welding upsetting amount is 15.5-16.0mm; in the post-weld treatment, the joint is naturally cooled to 575-585 ℃, and then cooled to ≤250℃, and finally cooled 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 rail flash welded joint of R350HT rail with an extremely upper limit Mn content. Background technique [0002] With the rapid development of seamless track technology in passenger, freight, high-speed and 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 br...

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 陆鑫李大东白威徐飞翔
Owner PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP
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