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Process for controlling extreme upper-limit Mn content R350HT steel rail flash welding joint structure

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

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 controlling extreme upper-limit Mn content R350HT steel rail flash welding joint structure

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0033] Using the flash welding process with heat input of 8.9MJ and upsetting amount of 15.3mm, the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 1.15% (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 of the naturally cooled rail joint, and when the temperature drops to 585°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 .

[0034] According to EN 14587.2, the joints obtained by ...

Embodiment 2

[0036] Using the flash welding process with heat input of 9.5MJ and upsetting amount of 16.0mm, the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 1.21% (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 of the naturally cooled rail joint, and when the temperature drops to 575°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 .

[0037] According to EN 14587.2, the joints obtained by ...

Embodiment 3

[0039] Using the flash welding process with heat input of 8.5MJ and upsetting amount of 15.5mm, the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 1.18% (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 of the naturally cooled rail joint, and when the temperature drops to 580°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 .

[0040] According to EN 14587.2, the joints obtained by the...

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Abstract

The invention discloses a process for controlling an extreme upper-limit Mn content R350HT steel rail flash welding joint structure, and belongs to the technical field of steel rail flash welding. According to the process for controlling the extreme upper-limit Mn content R350HT steel rail flash welding joint structure, the technical problem that a martensitic structure is prone to being caused inan R350HT steel rail flash welding joint in the prior art is solved. The process comprises a welding process and post-welding treatment; in the welding process, the welding heat input is controlled to be 8.5-9.5 MJ pulsation or preheating flash welding, wherein the welding upsetting amount is 15.5-16.0 mm; and in the post-welding treatment, the joint is naturally cooled to 575-585 DEG C, then heat preservation is carried out and the joint is cooled to be less than or equal to 250 DEG C, and finally, the joint is naturally cooled to the room temperature. By comprehensively controlling the chemical components, a hot rolling process, the welding process and the post-welding cooling of a steel rail, abnormal structures, such as the martensitic structure, cannot exist in the steel rail flash welding joint, 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 upper limit Mn content of R350HT rail flash welding joints. 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 uncover the phenomenon, w...

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