Heat treatment method for U71MnH steel rail welding joint

A heat treatment method and technology of welded joints, which are applied in the field of rail welding, can solve the problems of low hardness of welded joints, achieve the effects of improved performance status, normal microstructure, and good promotion and application prospects

Active Publication Date: 2018-12-18
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

[0005] The invention aims to solve the problem that the hardness of the welded joint is low due to the generation of harmful tissues such as martensite due to the local cooling rate higher than the critical transformation temperature during the cooling process of the welded joint of the rail

Method used

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  • Heat treatment method for U71MnH steel rail welding joint
  • Heat treatment method for U71MnH steel rail welding joint
  • Heat treatment method for U71MnH steel rail welding joint

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0031] Intermediate frequency heating is used to heat the weld area of ​​the 60kg / m U71MnH rail welding joint to 935℃ and then stop heating, and the heating time is 141s. After the heating is stopped, when the temperature of the rail joint tread drops to 785°C, perform air jet cooling. The air nozzle is 30mm away from the rail joint surface, and the air pressure of the air jet is 0.1±0.05MPa. When the temperature of the joint tread decreases to the final cooling temperature At 431°C, the spray cooling is stopped, and then the rail joints are naturally cooled to room temperature. According to the requirements of the TB / T 1632.2-2014 standard, the HR-150A Rockwell hardness tester is used to test the 5mm Rockwell hardness under the tread of the rail head on the longitudinal section. In this embodiment, the ratio of the average hardness HJ of the 60kg / m U71MnH rail post-weld heat treatment joint to the average hardness of the parent material HP is 0.95, and the ratio of the average...

Embodiment 2

[0033] Intermediate frequency heating is used to heat the weld area of ​​the 60kg / m U71MnH rail welding joint to 915°C and then stop heating, and the heating time is 135s. After the heating is stopped, when the temperature of the rail joint tread drops to 810℃, perform air jet cooling. The air nozzle is 30mm away from the rail joint surface, and the air pressure of the air jet is 0.1±0.05MPa. When the temperature of the joint tread decreases to the final cooling temperature At 405°C, the spray cooling is stopped, and then the rail joints are naturally cooled to room temperature. According to the requirements of the TB / T 1632.2-2014 standard, the HR-150A Rockwell hardness tester is used to test the 5mm Rockwell hardness under the tread of the rail head on the longitudinal section. In this example, the ratio of the average hardness HJ of the 60kg / m U71MnH rail post-weld heat treatment joint to the average hardness of the parent material HP is 0.93, and the ratio of the average ha...

Embodiment 3

[0035] Intermediate frequency heating is used to heat the weld area of ​​the 60kg / m U71MnH rail welding joint to 921℃ and then stop heating, and the heating time is 136s. After the heating is stopped, when the temperature of the rail joint tread drops to 800℃, the air jet cooling is performed. The air nozzle is 30mm away from the rail joint surface, and the air pressure of the spray air is 0.1±0.05MPa. When the temperature of the joint tread decreases to the final cooling temperature At 432°C, the spray cooling is stopped, and then the rail joints are naturally cooled to room temperature. According to the requirements of the TB / T 1632.2-2014 standard, the HR-150A Rockwell hardness tester is used to test the 5mm Rockwell hardness under the tread of the rail head on the longitudinal section. In this embodiment, the ratio of the average hardness HJ of the 60kg / m U71MnH steel rail post-weld heat treatment joint to the average hardness of the parent material HP is 0.91, and the rati...

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Abstract

The invention relates to a heat treatment method for a U71MnH steel rail welding joint, and belongs to the technical field of steel rail welding. The problem that harmful structures such as martensites are generated to influence the joint hardness due to the fact that the local cooling speed is higher than the critical transition temperature when an existing steel rail welding joint is cooled in the heat treatment process is solved. The heat treatment method for the U71MnH steel rail welding joint comprises the steps that a U71MnH steel rail welding joint welding seam area which is cooled to 300 DEG C or below after being welded is heated to 915-935 DEG C, then heating is stopped, air spraying cooling is adopted and stopped after the steel rail joint tread temperature is lowered to 405-432DEG C, and natural cooling is conducted till the room temperature is achieved. By adopting the method, it is guaranteed that the joint structure is normal while the hardness of the U71MnH steel railflash welding joint is effectively controlled.

Description

Technical field [0001] The invention belongs to the technical field of steel rail welding, and specifically relates to a heat treatment method for a U71MnH steel rail welding joint. Background technique [0002] Rail welding has the characteristics of high heating temperature, fast heating speed, short residence time at high temperature, uneven temperature distribution and continuous cooling under air cooling conditions. The joints, especially the heat-affected zone, are prone to coarse structure, and even martensite and shellfish Harmful structures such as tensite cause hardening and embrittlement of the joints; at the same time, internal stresses are generated in the joints after welding. Under the action of complex external stresses, fractures are extremely easy to occur, which becomes a weak link in line operation. In order to relieve stress, refine grains, change the structure of the joint, and improve the reduced performance state, post-weld heat treatment is required for t...

Claims

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Application Information

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IPC IPC(8): C21D9/50C21D1/42C21D1/52
CPCC21D1/42C21D1/52C21D9/50Y02P10/25
Inventor 陆鑫李大东王若愚邓健
Owner PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP
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