Post-weld heat treatment method for u71mnh rail welded joints

A technology of post-weld heat treatment and welded joints, which is applied in the field of rail welding, can solve the problems of low hardness of welded joints, achieve improved performance status, good promotion and application prospects, and normal organizational shape

Active Publication Date: 2020-06-02
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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  • Post-weld heat treatment method for u71mnh rail welded joints
  • Post-weld heat treatment method for u71mnh rail welded joints
  • Post-weld heat treatment method for u71mnh rail welded joints

Examples

Experimental program
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Effect test

Embodiment 1

[0032] The welding seam area of ​​the 60kg / m U71MnH rail welded joint was heated to 865°C by means of intermediate frequency heating, and the heating was stopped for 120s. After the heating is stopped, when the temperature of the rail joint tread drops to 735°C, carry out air spray cooling. The air spray port is 30mm away from the rail joint surface, and the spray air pressure is 0.2±0.05MPa. When the joint tread temperature drops to the final cooling temperature of At 458°C, the blast cooling was stopped, and then the rail joints were naturally cooled to room temperature. Referring to the requirements of the TB / T 1632.2-2014 standard, the HR-150A Rockwell hardness tester is used to test the Rockwell hardness of 5 mm below the tread of the rail head on the longitudinal section. In this embodiment, the ratio of the average hardness HJ of the post-weld heat treatment joint of 60kg / m U71MnH rail to the average hardness HP of the base metal is 0.92, and the ratio of the average ha...

Embodiment 2

[0034] The welding seam area of ​​the 60kg / m U71MnH rail welded joint was heated to 925°C by intermediate frequency heating method, and the heating time was 135s. After the heating is stopped, when the temperature of the rail joint tread drops to 730°C, spray air to cool it. The air spray port is 30mm away from the rail joint surface, and the spray air pressure is 0.2±0.05MPa. When the joint tread temperature drops to the final cooling temperature of At 458°C, the blast cooling was stopped, and then the rail joints were naturally cooled to room temperature. Referring to the requirements of the TB / T 1632.2-2014 standard, the HR-150A Rockwell hardness tester is used to test the Rockwell hardness of 5 mm below the tread of the rail head on the longitudinal section. In this embodiment, the ratio of the average hardness HJ of the post-weld heat treatment joint of 60kg / m U71MnH rail to the average hardness HP of the base metal is 0.93, and the ratio of the average hardness HJ1 of th...

Embodiment 3

[0036] Use the oxyacetylene flame heating method to heat the weld seam area of ​​the 60kg / m U71MnH rail welding joint to 882°C and stop heating. The oxygen pressure is 0.6MPa and the flow rate is 4.8m 3 / h, the pressure of acetylene is 0.2MPa, the flow rate is 4.0m 3 / h, the heating time is 210s. After the heating is stopped, when the temperature of the rail joint tread drops to 730°C, spray air to cool it. The air spray port is 30mm away from the rail joint surface, and the spray air pressure is 0.2±0.05MPa. When the joint tread temperature drops to the final cooling temperature of At 462°C, the blast cooling was stopped, and then the rail joints were naturally cooled to room temperature. Referring to the requirements of the TB / T 1632.2-2014 standard, the HR-150A Rockwell hardness tester is used to test the Rockwell hardness of 5 mm below the tread of the rail head on the longitudinal section. In this embodiment, the ratio of the average hardness HJ of the post-weld heat tr...

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Abstract

The invention relates to a post-welding heat treatment method of U71MnH rail welded joints, and belongs to the technical field of rail welding. The post-welding heat treatment method of the U71MnH rail welded joints aims at solving the problem that the hardness of the joints is affected by harmful tissues such as martensite generated due to the local cooling speed being higher than the critical transition temperature when existing rail welded joints are cooled in the heat treatment process. The post-welding heat treatment method of the U71MnH rail welded joints comprises the following steps ofheating welding seam areas of the U71MnH rail welded joints cooled to below 300 DEG C after being welded to 865-925 DEG C, stopping heating, adopting air spraying for cooling, stopping air spraying for cooling after the temperature of the tread surfaces of the rail joints drops to 458-475 DEG C, and naturally cooling to room temperature. According to the post-welding heat treatment method of theU71MnH rail welded joints, the hardness of the U71MnH rail welded joints is effectively controlled, and meanwhile, normal tissues of the joints is ensured.

Description

technical field [0001] The invention belongs to the technical field of rail welding, and in particular relates to a post-weld heat treatment method for U71MnH rail welding joints. 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. In the joints, especially in the heat-affected zone, it is easy to have a coarse structure, and even easy to form martensite, shellfish, etc. At the same time, the joints after welding generate internal stress, and under the action of complex external stress, they are prone to fracture and become a weak link in line operation. In order to release the stress, refine the grain, change the microstructure of the joint, and improve the degraded performance state, it is necessary to perform post-weld heat treatment on the rail joint. [0003] Patent document CN1081...

Claims

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Application Information

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Patent Type & Authority Patents(China)
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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