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Aluminothermic welding post-weld heat treatment process for bainite steel rail

A technology of post-weld heat treatment and post-heat treatment, which is applied in the field of rail welding and can solve problems such as easy damage

Active Publication Date: 2021-04-16
METALS & CHEM RES INST CHINA ACAD OF RAILWAY SCI +3
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] However, the joints welded by the existing treatment process are still prone to damage during service. Therefore, it is still necessary to improve the existing process and provide an improved post-weld heat treatment process to further ensure the service life of the thermite welded structure. safety

Method used

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  • Aluminothermic welding post-weld heat treatment process for bainite steel rail
  • Aluminothermic welding post-weld heat treatment process for bainite steel rail
  • Aluminothermic welding post-weld heat treatment process for bainite steel rail

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0054] Gleeble-1500D thermal simulation testing machine is used to determine the transformation temperature of the steel by using the expansion or contraction of the volume of the steel during the phase transition. The round bar sample is taken from the welded joint, and the sample is heated by the thermal simulator to a constant temperature. Rapid cooling, measure the temperature-expansion curve of the sample, use the tangent method to determine the characteristic phase transition temperature point, and use the computer to draw the "temperature-time (logarithmic)" curve to obtain the CCT curve. Among them, the joint obtained by thermite welding is cooled to room temperature, and then the joint sample is heated by the built-in equipment of the thermal simulator. The heating temperature is 980 ° C, the heating time is 5 minutes, and the heat preservation is 10 minutes; The transformation curve obtained after cooling is as image 3 shown.

[0055] The microstructure of the join...

Embodiment 2

[0057] At room temperature, the microstructure of the samples obtained in Example 1 at different cooling rates was observed with a DM15000M metallographic microscope. Samples were taken from samples obtained at different cooling rates, and the microstructure of each sample was observed after pre-grinding, polishing and erosion treatment. The FM-7 automatic microhardness tester was used to test each sample. After observing the microstructure, the microhardness was tested by indentation method with a load of 0.2kg, and the indentation size was measured to determine the microhardness. The results are shown in Table 2.

[0058] Table 2 Microstructure analysis results and hardness test results of joint samples obtained at different cooling rates

[0059]

[0060]

[0061] It can be seen from Table 2 that under the conditions of 8°C / s and 4°C / s, the structure of the welded joint is martensite, and the microhardness is above 500HV; under the condition of 2 to 1°C / s, the struct...

Embodiment 3

[0063] 1. Cool the joint obtained by thermite welding to room temperature, then heat the joint to 900-1000°C, and keep it warm for 10 minutes; then use a cooling rate of 0.2-0.8°C / s to slowly cool the joint obtained through heat preservation treatment , until the temperature of the joint reaches below 100°C, and then the tread hardness test is carried out.

[0064] With reference to TB / T 1632.3-2019, the tread hardness test is carried out on the welded joint at room temperature, sawing the welded joint longitudinally along the rail, grinding and polishing the top surface of the rail, and testing the weld hardness at the transverse position of the weld center on the top surface of the rail, testing 3 Point Brinell hardness, the calculated average hardness value is recorded as the tread hardness of the weld, and the test method of Brinell hardness is carried out in accordance with the provisions of GB / T 231.1-2009.

[0065] The results are shown in Table 3, where "no heat treatm...

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Abstract

The invention provides an aluminothermic welding post-weld heat treatment process for a bainite steel rail. The post-weld heat treatment process comprises the following steps of: step (1). cooling a joint obtained by aluminothermic welding to a room temperature, heating the joint for 5-10 minutes, and carrying out heat preservation for 5-10 minutes; then carrying out slow cooling treatment on the joint obtained through heat preservation treatment at a cooling speed of 0.2-0.8 DEG C / s until the temperature of the joint reaches 100 DEG C or below; and step (2). heating the joint treated in the step (1), then carrying out heat preservation, and naturally cooling to a room temperature.

Description

technical field [0001] The invention relates to the technical field of rail welding, in particular to a post-weld heat treatment process for bainite rail aluminothermic welding. Background technique [0002] Seamless track is an important achievement of track structure progress, and it is also the best choice for today's high-speed railway and heavy-duty railway track structure. Since our country began to lay seamless lines on Jingmen Branch Line (Beijing) and Zhenxi Branch Line (Shanghai) in 1957, after several years of unremitting efforts, the mileage of seamless lines has been greatly increased. The comprehensive technical and economic effect of the seamless line is outstanding, which has been confirmed by the railway practice of various countries in the world. Seamless lines can extend the service life of rails, reduce maintenance and repair labor and materials, reduce energy consumption for train operation, and reduce additional laying costs. [0003] Rail welding is ...

Claims

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Application Information

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IPC IPC(8): C21D9/04C21D9/50
Inventor 冯子凌崔成林宋宏图高松福任金雷林云蕾
Owner METALS & CHEM RES INST CHINA ACAD OF RAILWAY SCI
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