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Process for Controlling Microstructure of Flash Welded Joints in R350ht Rails with Medium and Upper Mn Contents

A technology for R350HT and welded joints, which is applied in the field of controlling the upper and lower Mn content of R350HT rail flash welded joints. It 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 in R350ht Rails with Medium and Upper Mn Contents

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0033] Using the flash welding process with heat input of 7.0MJ and upsetting amount of 14.5mm, the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 1.05% (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 550°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 7.9MJ and upsetting amount of 14.8mm, the European standard R350HT heat-treated steel rail with a mass fraction of Mn of 1.13% (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 560°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 1.15% (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 525°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 joints obtained by ...

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Abstract

The invention discloses a technology for controlling the flash welding joint structure of R350HT rail with upper and lower 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 the martensite structure of the R350HT rail flash welding joint, the present invention provides a process for controlling the upper limit Mn content of the R350HT rail flash welding joint structure, including the welding process and post-weld treatment; In the welding process, the welding heat input is controlled to be 7.0-8.5MJ pulsation or preheating flash welding, and the welding upsetting amount is 14.5-15.5mm; in the post-welding treatment, the joint is naturally cooled to 525-560°C, and then heat-preserved and cooled to ≤250°C, and finally cool down to room temperature naturally. 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 the upper and lower 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 ev...

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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