Process for flash welding medium control limit Mn content R350 HT steel rail with joint structure

A technology for R350HT and welded joints, which is applied in the field of flash welded joints of R350HT rails with limited 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 for flash welding medium control limit Mn content R350 HT steel rail with joint structure

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0033] Using the flash welding process with heat input of 6.5MJ and upsetting amount of 14.0mm, the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 0.90% (C content is in the middle and lower limits, Si≤0.30wt%, Rm≥1175MPa, A ≥9%, tread hardness ≥350HB) for flash welding. After the flash welding is completed, first use an infrared thermometer to measure the temperature at the center of the weld seam on the road surface of the naturally cooled rail joint, and when the temperature drops to 515°C, immediately use an aluminosilicate fiber cotton insulation device with a thickness of ≥30mm Insulate the 200mm area on both sides of the joint fusion line; continue to monitor the joint temperature during this process, and remove the device when the temperature at the center of the welding seam on the driving surface is lower than 250°C, and finally place the joint in the air to cool naturally to room temperature .

[0034] According to EN 14587.2, the jo...

Embodiment 2

[0036] Using the flash welding process with heat input of 6.8MJ and upsetting amount of 14.7mm, the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 0.98% (C content is in the middle and lower limits, Si≤0.30wt%, Rm≥1175MPa, A ≥9%, tread hardness ≥350HB) for flash welding. After the flash welding is completed, first use an infrared thermometer to measure the temperature at the center of the weld seam on the road surface of the naturally cooled rail joint. When the temperature drops to 545°C, immediately use an aluminosilicate fiber cotton insulation device with a thickness ≥ 30mm Insulate the 200mm area on both sides of the joint fusion line; continue to monitor the joint temperature during this process, and remove the device when the temperature at the center of the welding seam on the driving surface is lower than 250°C, and finally place the joint in the air to cool naturally to room temperature .

[0037] According to EN 14587.2, the joints o...

Embodiment 3

[0039] Using the flash welding process with heat input of 8.0MJ and upsetting amount of 15.0mm, the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 1.10% (C content is in the middle and lower limits, Si≤0.30wt%, Rm≥1175MPa, A ≥9%, tread hardness ≥350HB) for flash welding. After the flash welding is completed, first use an infrared thermometer to measure the temperature at the center of the weld seam on the road surface of the naturally cooled rail joint. When the temperature drops to 530°C, immediately use an aluminosilicate fiber cotton heat insulation device with a thickness ≥ 30mm Insulate the 200mm area on both sides of the joint fusion line; continue to monitor the joint temperature during this process, and remove the device when the temperature at the center of the welding seam on the driving surface is lower than 250°C, and finally place the joint in the air to cool naturally to room temperature .

[0040] According to EN 14587.2, the joi...

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Abstract

The invention discloses a process for flash welding a medium control limit Mn content R350 HT steel rail with a joint structure, and belongs to the technical field of steel rail flash welding. By means of the process, the technical problem that a process in the prior art easily results in a martensite structure on an R350HT steel rail flash welding joint is solved. The process comprises a weldingprocess and post-welding treatment; in the welding process, the welding heat input is controlled to be 6.5-8.0 MJ pulsation or preheating flash welding, and the welding upset forging amount is 14.0-15.0 mm; and in the process of post-welding treatment, the joint is naturally cooled to 515-545 DEG C, is subjected to heat preservation, then cooled to less than or equal to 250 DEG C, and finally naturally cooled to room temperature. By comprehensively controlling the chemical components, the hot rolling process, the welding process and the post-welding cooling of the steel rail, no abnormal structures such as the martensite structures in the steel rail flash welding joint are guaranteed, 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 medium-limit 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 un...

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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