阅读说明：本技术 一种提高钢轨滚动接触疲劳强度的激光在线复合调控方法 (Laser online composite regulation and control method for improving rolling contact fatigue strength of steel rail ) 是由 杨胶溪 崔哲 柯华 刘哲 周正 徐宏超 肖俊恒 于 2020-12-10 设计创作，主要内容包括：本发明涉及一种在线提高钢轨滚动接触疲劳性能的激光复合调控处理方法,针对磨损严重的钢轨。首先利用激光作为热源,对裂纹延伸区进行激光重结晶处理,消除因磨损产生的表面拉应力,或者将拉应力转化为压应力,一定程度减小微裂纹尺寸。然后再通过脉冲激光进行激光冲击强化处理,激光作用结束后,由于冲击区域周围金属材料的反作用,其力学效应表现为较高的残余应力,促使裂纹的闭合,延长疲劳裂纹的萌生及扩展寿命。最后在磨损区域制备出0.2-0.5mm冶金质量良好的新型合金化涂层,前期的预热处理过程减小了淬硬倾向和冷裂纹的产生,制备的合金化涂层与基体冶金结合良好,且具有较为优异的综合力学性能。本发明预防微裂纹的产生或消除接触面已存微裂纹。(The invention relates to a laser composite regulation and control processing method for improving the rolling contact fatigue performance of a steel rail on line, which aims at the steel rail with serious abrasion. Firstly, laser is used as a heat source, laser recrystallization treatment is carried out on a crack extension area, surface tensile stress generated by abrasion is eliminated, or the tensile stress is converted into compressive stress, and the size of a microcrack is reduced to a certain degree. Then, the laser shock strengthening treatment is carried out through the pulse laser, and after the laser effect is finished, the mechanical effect is represented as higher residual stress due to the reaction of the metal material around the shock area, so that the closing of cracks is promoted, and the initiation and the service life of fatigue cracks are prolonged. Finally, a novel alloying coating with good metallurgical quality of 0.2-0.5mm is prepared in the wear area, the hardening tendency and the generation of cold cracks are reduced in the early preheating treatment process, and the prepared alloying coating is well combined with the matrix metallurgy and has excellent comprehensive mechanical properties. The invention prevents the generation of microcracks or eliminates the microcracks existing on the contact surface.)

1. A laser composite regulation and control processing method for improving the rolling contact fatigue performance of a steel rail on line is characterized by comprising the following steps: the alloy powder used comprises the following elements in percentage by mass: cr: 8-12 wt%; ni: 3-6 wt%; si: 0.3-1.0 wt%; c: 0.02-0.05 wt%; b: 1.0-1.50 wt%; mn: 5.0-7.5 wt%; nb: 0.03-0.08 wt%; v: 0.8-1.2 wt%; the balance being Fe;

when in online laser composite regulation and control treatment, a continuous laser and a pulse laser are adopted to carry out laser remelting alloying-impact strengthening composite treatment on the fatigue microcrack area of the steel rail, and the laser remelting alloying process parameters are as follows: polishing the steel rail by using a polisher, wiping and drying the steel rail by using alcohol, placing the steel rail below an induction coil for preheating, and keeping the vertical distance between the upper surface of the steel rail and the coil for 5cm in the preheating process until the upper surface of the steel rail shows 500 ℃ below an infrared thermometer; moving a laser head to a position 15mm above a to-be-processed position of the preheated steel rail through a demonstrator, wherein the laser power is 6000W-10000W, the scanning speed is 2-5m/min, the rectangular light spot size is (10-30) mmx (1-3) mm, the lap joint rate is 2-5%, the powder feeding rate is 60-150g/min, and the included angle between a laser beam and the normal direction of the surface of the steel rail is 5-30 degrees; meanwhile, a pulse laser is adopted to carry out impact strengthening treatment on the laser remelting alloying area, and the process parameters are as follows: the laser wavelength is 1.06 μm, the light spot is (10-30) mmX (1-3) mm, the laser pulse energy is 10-50J, the pulse width is 10-30ns, the frequency is 5-10Hz, and the included angle between the laser beam and the normal direction of the surface of the steel rail is 5-15 degrees.

Technical Field

The invention relates to a laser online composite regulation and control method for improving the rolling contact fatigue strength of a steel rail, which mainly comprises preheating treatment, a laser recrystallization technology, a laser shock strengthening technology and novel alloying powder, wherein the novel alloying powder is used for regulating and controlling the contact fatigue crack of the steel rail on line so as to improve the rolling contact fatigue strength of the steel rail.

Background

Compared with a traditional gas or solid laser, the semiconductor laser related to the patent has the characteristics of high electro-optic conversion efficiency, long service life and the like, and is widely applied to the fields of surface treatment, welding, additive manufacturing and the like of materials. The laser recrystallization technique is a novel manufacturing technique which takes laser as a heat source to melt and recrystallize a metal powder material so as to improve the surface strength of the material.

The laser shock strengthening technology is a surface modification technology for strengthening a metal material by using plasma shock waves formed by laser induction. The method has the advantages of good strengthening effect, strong controllability, good applicability and the like, is applied and researched more and more widely in recent years, and mainly plays an important role in improving the fatigue performance of parts and prolonging the service life of materials. The technology relates to a plurality of process parameters, and the matching among different parameters has great influence on the strengthening effect and mainly comprises laser process parameters, impact angles, pulse widths, impact times and the like.

The preheating treatment is to heat the structural member wholly or locally before processing the material, and aims to slow down the temperature gradient and the cooling speed of the structural member after hot processing, properly prolong the cooling time of a processing area, facilitate the escape of hydrogen in a coating, reduce the generation of a hardened structure and prevent the generation of cold cracks.

The common preheating methods mainly include flame heating, infrared heating and induction heating. The preheating method related to the patent is induction heating, and an alternating magnetic field is generated on the upper surface of the steel rail by using alternating current with the industrial frequency of 50Hz to form eddy current, so that heat is generated to heat the steel rail. Due to the skin effect, heat tends to concentrate on the upper surface layer of the steel rail, and then the infrared thermometer is used for measuring the temperature of the surface of the steel rail in real time to prevent overheating and oxidation.

Railway transportation is one of the most important modes of China, the current Chinese railway operation mileage is up to 13.1 kilometers according to the top of the world, and the progress of national economy is greatly promoted by virtue of the advantages of large transportation volume, high safety, convenience, rapidness and the like. However, with the rapid development of high-speed railways and the expansion of routes, the requirement on the abrasion performance of the steel rail is increasingly improved, and once the strength of the steel rail cannot keep up with the running speed and the axle load capacity of a train, serious rail breakage danger can occur, which is a terrible traffic accident.

At present, the damage condition of domestic steel rails is very serious, only 2000 years exist, the damage quantity of domestic main track steel rails reaches 23.98 thousands, more 35 thousands are reached in 2005, the gross weight of annual transportation is 4.4 hundred million tons according to statistics data of Daqin track in 2011, the shortest service time of turnout junction is only 72 hours, then the turnout junction is required to be replaced, the average service life is only 3-4 months under normal conditions, and the position with serious abrasion needs to be replaced immediately after about 20 days. However, the high-speed railway turnout is high in manufacturing cost and severe in service condition, and needs to face huge friction force and side impact all the time, so that the invention of the regulation and control method for improving the rolling contact strength of the steel rail is urgent.

The damage of the steel rail mainly comprises side surface abrasion, surface plastic deformation, surface fatigue crack and the like, and the defects cause the risk of failure or derailment of a wheel rail system in the high-speed running process of the railway. At present, a surface treatment method for healing the rolling contact fatigue crack of the steel rail on line is urgently needed.

Disclosure of Invention

The invention aims to provide a laser composite online regulation and control method for improving the rolling contact fatigue strength of a steel rail, aiming at the problem of insufficient rolling contact fatigue strength caused by complex service conditions of the steel rail, so that the movable processing of a laser technology in the field of high-speed railways is realized, and the service life of the steel rail is greatly prolonged.

The invention relates to novel alloy powder which comprises the following components in percentage by mass: cr: 8-12 wt%; ni: 3-6 wt%; si: 0.3-1.0 wt%; c: 0.02-0.05 wt%; b: 1.0-1.50 wt%; mn: 5.0-7.5 wt%; nb: 0.03-0.08 wt%; v: 0.8-1.2 wt%; the balance being Fe. And (3) polishing the surface of the steel rail to be treated by using a polishing machine, removing rust spots on the surface, wiping by using alcohol, and drying.

Carrying out laser remelting alloying treatment on the fatigue microcrack region, wherein the laser remelting alloying process parameters are as follows: polishing the steel rail by using a polisher, wiping and drying the steel rail by using alcohol, placing the steel rail below an induction coil for preheating, and keeping the vertical distance between the upper surface of the steel rail and the coil for 5cm in the preheating process until the upper surface of the steel rail shows 500 ℃ below an infrared thermometer; moving a laser head to a position 15mm above a to-be-processed position of the preheated steel rail through a demonstrator, wherein the laser power is 6000W-10000W, the scanning speed is 2-5m/min, the rectangular light spot size is (10-30) mmx (1-3) mm, the lap joint rate is 2-5%, the powder feeding rate is 60-150g/min, and the included angle between a laser beam and the normal direction of the surface of the steel rail is 0-30 degrees. Meanwhile, a pulse laser is adopted to carry out impact strengthening treatment on the laser remelting alloying area, and the process parameters are as follows: the laser wavelength is 1.06 μm, the light spot is (10-30) mmX (1-3) mm, the laser pulse energy is 10-50J, the pulse width is 10-30ns, the frequency is 5-10Hz, and the included angle between the laser beam and the normal direction of the surface of the steel rail is 5-15 degrees.

Drawings

FIG. 1 is a schematic diagram of a laser online composite control method

FIG. 2 shows a sample after rolling friction abrasion test (example 1)

FIG. 3 is a graph of test force versus time during a rolling friction wear test (example 1)

FIG. 4 is a microhardness comparison graph of steel rail samples before and after laser composite regulation

FIG. 5 is a comparison graph of the bending angles of steel rail samples before and after laser composite regulation

FIG. 6 is a comparison graph of the wear quality of steel rail samples before and after laser composite regulation

Detailed Description

Example 1

The method comprises the following steps:

(1) the novel alloy powder comprises the following components in percentage by mass: cr: 8.5 wt%; ni: 3.0 wt%; si: 0.4 wt%; c: 0.025 wt%; b: 1.1 wt%; mn: 5.5 wt%; nb: 0.04 wt%; v: 0.9 wt%; the balance being Fe. Weighing the single element powder in the proportion according to the mass percentage of the components, mixing the powder in a ball mill for 3 hours to obtain uniform powder;

(2) drying the powder in a drying oven for 2 hours at the drying temperature of 100 ℃ for later use;

(3) polishing a U75V steel rail by using a polisher, wiping the steel rail by using alcohol, drying the steel rail, placing the steel rail below an induction coil for preheating, and keeping the vertical distance between the upper surface of the steel rail and the coil to be 5cm in the preheating process until the upper surface of the steel rail is displayed as 300 ℃ under an infrared thermometer;

(4) controlling a robot hand to move a laser head to a position to be processed through a demonstrator, adjusting the distance between a cladding head and the surface of the steel rail to 15mm, and preparing remelting alloying treatment;

(5) connecting a powder feeder filled with novel alloy powder with a powder path channel, and starting laser remelting alloying, wherein the process parameters are as follows: the laser power is 7000W, the scanning speed is 2.5m/min, the rectangular spot size is 10mm multiplied by 1mm, the lap joint rate is 2 percent, the powder feeding rate is 80g/min, and the included angle between the laser beam and the normal direction of the surface of the steel rail is 10 degrees. Simultaneously, pulse laser shock strengthening treatment is carried out on the laser remelting alloying area, and the process parameters are as follows: the laser wavelength is 1.06 mu m, the light spot is 10mm multiplied by 1mm, the laser pulse energy is 20J, the pulse width is 10ns, the frequency is 6Hz, and the included angle between the laser beam and the normal direction of the surface of the steel rail is 5 degrees.

Various performance tests were performed on the sample subjected to laser composite control in this example.

1. Frictional wear test

Preparing a sample into a dynamic load test sample piece, and testing the wear resistance and the rolling fatigue contact performance, wherein the process parameters are as follows: the loading force value is 2000N (the pressure is about 0.92Gpa), the rolling speed is 100r/min, the loading time is 7200s, the indentation depth and the appearance of the sample are subjected to multi-point test by using a three-dimensional appearance instrument after rolling, the weightlessness before and after rolling is measured by using an electronic balance, the average wear mass of the pure matrix U75V is 75mg after weighing, the average wear mass of the sample after laser composite regulation and control treatment is 25mg, and the wear resistance is improved by 3 times approximately.

2. Microhardness

Performing hardness test by using an HV-1000 type microhardness tester, wherein the load is 50g, the loading time is 10s, performing multipoint test on the gradient composite coating and the surface of the substrate, and calculating the average value, wherein the average microhardness of the substrate is 302HV 0.2; the average microhardness of the sample after the laser composite regulation and control treatment is 450HV 0.2;

3. bending resistance test

And testing the bending resistance of the steel rail by using an MTS electro-hydraulic servo universal testing machine, wherein the model of the testing machine is YAW-6000F, and measuring the bending angle and the size of the crack after the penetrant flaw detection treatment after the loading is finished. The results prove that when the steel rail after the laser composite regulation and control treatment meets the bending requirement, obvious cracks and fractures do not occur. Compared with the matrix, the bending strength of the steel rail after laser composite regulation and control treatment is obviously improved.

Example 2

The method comprises the following steps:

(1) the novel alloy powder comprises the following components in percentage by mass: cr: 9.5 wt%; ni: 4.5 wt%; si: 0.6 wt%; c: 0.035 wt%; b: 1.25 wt%; mn: 6.0 wt%; nb: 0.045 wt%; v: 0.95 wt%; the balance being Fe. Weighing the single element powder in the proportion according to the mass percentage of the components, mixing the powder in a ball mill for 3 hours to obtain uniform powder;

(2) drying the powder in a drying oven for 2 hours at the drying temperature of 100 ℃ for later use;

(3) polishing a U71Mn steel rail by using a polisher, wiping the steel rail by using alcohol, drying the steel rail, placing the steel rail below an induction coil for preheating, and keeping the vertical distance between the upper surface of the steel rail and the coil to be 5cm in the preheating process until the upper surface of the steel rail is displayed as 400 ℃ under an infrared thermometer;

(4) controlling a robot hand to move a laser head to a position to be processed through a demonstrator, adjusting the distance between a cladding head and the surface of the steel rail to 15mm, and preparing remelting alloying treatment;

(5) connecting a powder feeder filled with novel alloy powder with a powder path channel, and starting laser remelting alloying, wherein the process parameters are as follows: the laser power is 8000W, the scanning speed is 3.5m/min, the rectangular spot size is 20mm multiplied by 2mm, the lap joint rate is 2.5 percent, the powder feeding rate is 85g/min, and the included angle between the laser beam and the normal direction of the surface of the steel rail is 15 degrees. Simultaneously, pulse laser shock strengthening treatment is carried out on the laser remelting alloying area, and the process parameters are as follows: the laser wavelength is 1.06 mu m, the light spot is 2mm multiplied by 2mm, the laser pulse energy is 35J, the pulse width is 20ns, the frequency is 8Hz, and the included angle between the laser beam and the normal direction of the surface of the steel rail is 10 degrees.

Various performance tests were performed on the sample subjected to laser composite control in this example.

1. Frictional wear test

The test method is the same as that of example 1, the average abrasion mass of the pure matrix U71Mn is 80mg after weighing, and the average abrasion mass of the sample after laser composite regulation and control treatment is 35mg, so that the abrasion resistance is improved by more than 2 times.

2. Microhardness

The test method is the same as that of example 1, and the average microhardness of the matrix is 305HV 0.2; the average microhardness of the sample after the laser composite regulation and control treatment is 454.1HV 0.2;

3. bending resistance test

The test method is the same as that of the example 1, and the result proves that obvious cracks and fractures do not appear on the steel rail after the laser composite regulation and control treatment when the steel rail meets the bending requirement. Compared with the matrix, the bending strength of the steel rail after laser composite regulation and control treatment is obviously improved.

Example 3

The method comprises the following steps:

(1) the novel alloy powder comprises the following components in percentage by mass: cr: 10 wt%; ni: 6 wt%; si: 0.6 wt%; c: 0.02 wt%; b: 1.45 wt%; mn: 7.0 wt%; nb: 0.03 wt%; v: 0.8 wt%; the balance being Fe. Weighing the single element powder in the proportion according to the mass percentage of the components, mixing the powder in a ball mill for 3 hours to obtain uniform powder;

(2) drying the powder in a drying oven for 2 hours at the drying temperature of 100 ℃ for later use;

(3) polishing a U20Mn steel rail by using a polisher, wiping the steel rail by using alcohol, drying the steel rail, placing the steel rail below an induction coil for preheating, and keeping the vertical distance between the upper surface of the steel rail and the coil to be 5cm in the preheating process until the upper surface of the steel rail is displayed as 500 ℃ under an infrared thermometer;

(4) controlling a robot hand to move a laser head to a position to be processed through a demonstrator, adjusting the distance between a cladding head and the surface of the steel rail to 15mm, and preparing remelting alloying treatment;

(5) connecting a powder feeder filled with novel alloy powder with a powder path channel, and starting laser remelting alloying, wherein the process parameters are as follows: the laser power is 8000W, the scanning speed is 4.5m/min, the rectangular spot size is 30mm multiplied by 3mm, the lap joint rate is 3 percent, the powder feeding rate is 100g/min, and the included angle between the laser beam and the normal direction of the surface of the steel rail is 20 degrees. Simultaneously, pulse laser shock strengthening treatment is carried out on the laser remelting alloying area, and the process parameters are as follows: the laser wavelength is 1.06 mu m, the light spot is 30mm multiplied by 3mm, the laser pulse energy is 45J, the pulse width is 25ns, the frequency is 8Hz, and the included angle between the laser beam and the normal direction of the surface of the steel rail is 15 degrees.

Various performance tests were performed on the sample subjected to laser composite control in this example.

1. Frictional wear test

The test method is the same as that of example 1, the average abrasion mass of the pure matrix U20Mn is 70mg after weighing, and the average abrasion mass of the sample after laser composite regulation and control treatment is 28mg, so that the abrasion resistance is improved by more than 2 times.

2. Microhardness

The test method is the same as that of example 1, and the average microhardness of the matrix is 308HV 0.2; the average microhardness of the sample after the laser composite regulation and control treatment is 452.7HV 0.2;

3. bending resistance test

The test method is the same as that of the example 1, and the result proves that obvious cracks and fractures do not appear on the steel rail after the laser composite regulation and control treatment when the steel rail meets the bending requirement. Compared with the matrix, the bending strength of the steel rail after laser composite regulation and control treatment is obviously improved.