CN116770048A - Fixed flash welding and joint heat treatment method for rare earth high-strength heat-treated steel rail - Google Patents
Fixed flash welding and joint heat treatment method for rare earth high-strength heat-treated steel rail Download PDFInfo
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- 238000010438 heat treatment Methods 0.000 title claims abstract description 86
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- 239000010959 steel Substances 0.000 title claims abstract description 78
- 238000000034 method Methods 0.000 title claims abstract description 58
- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 30
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 30
- 230000008569 process Effects 0.000 claims abstract description 40
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- 230000006698 induction Effects 0.000 claims description 9
- 238000005507 spraying Methods 0.000 claims description 9
- 229910001562 pearlite Inorganic materials 0.000 claims description 8
- 229910000734 martensite Inorganic materials 0.000 claims description 7
- 229910001563 bainite Inorganic materials 0.000 claims description 5
- 229910001567 cementite Inorganic materials 0.000 claims description 5
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical group C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 claims description 5
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Abstract
The invention discloses a method for fixing, flash welding and joint heat treatment of a rare earth high-strength heat-treated steel rail, which comprises the following steps ofThe rare earth high-strength heat-treated steel rail takes C, S i, mn, cr as main elements, is added with V, RE micro-alloying elements, and is subjected to production processes such as controlled rolling, online heat treatment and the like, so that the steel rail has the characteristics of high strength and high hardness, can meet the application of heavy haul railways with the axle weight of more than 25t, and after being treated by the joint heat treatment process, the tensile strength Rm of the joint is more than or equal to 1119MPa, the joint extension A is more than or equal to 10.5 percent, and the joint impact KU is more than or equal to 2 Not less than 13.5J, average hardness H of joint J Average value H of hardness of base material P The ratio of (2) is as follows: h J /H P Not less than 0.93, average hardness H of joint soft point J1 Average value H of hardness of base material P Ratio of (3): h J1 /H P And the softening area W is more than or equal to 0.82 and less than or equal to 15mm.
Description
Technical Field
The invention relates to the technical field of steel rail welding, in particular to a method for fixing, flashing and welding a rare earth high-strength heat-treated steel rail and heat-treating a joint.
Background
The rare earth high-strength heat treatment steel rail takes C, S i, mn and Cr as main elements, and is added with V, RE micro-alloying elements, and the steel rail has the characteristics of high strength and high hardness through the production processes of controlled rolling, on-line heat treatment and the like, and can meet the application of heavy haul railways with axle weights of more than 25 t. The rare earth high-strength heat treatment steel rail has poorer welding performance due to higher carbon content and carbon equivalent, and is mainly characterized in that: 1) Defects of a overheat area and abnormal microstructure of the joint in a supercooled state are easy to form in the flash welding process; 2) The burning loss of carbon and alloy in the welding process obviously reduces the hardness of the joint, the performance matching of the joint and a base metal is poor, saddle-shaped abrasion and joint stripping block phenomena can occur in the line service process, and the smoothness of a seamless line is seriously influenced.
The high-strength heat treatment flash welding process and the joint heat treatment process of the rare earth directly influence the joint organization performance and the service state. The defects of over-burning, unwelded joint, excessive gray spots, liquefied cracks and the like of the joint can be caused by improper flash welding process, the metallographic grain size of the joint is coarser and only about 1-2 grades in the welding state, and the joint performance is poor. The weld joint is subjected to normalizing heat treatment, the microstructure of the weld joint is obviously refined, the grain size is increased from level 1 to more than level 8, the toughness of the flash welding joint is well improved, but the weld joint heat treatment process is improper, such as the characteristics of high and low heating temperature, high and low heating speed, nonuniform high-temperature residence time, nonuniform temperature distribution, continuous cooling under air cooling conditions and the like, the joint, especially a heat affected zone, is easy to have coarse structure, even easy to form martensite and other harmful structures, the joint is easy to have hardening, embrittlement and other phenomena, and the joint is extremely easy to break under the action of wheel rail stress in the line service process, thus becoming a weak link of line operation.
The rare earth high-strength heat treatment steel rail fixing flash welding and joint heat treatment method provided by the invention can ensure that the rare earth high-strength heat treatment steel rail flash welding joints are all normal pearlite structures, no abnormal structures such as bainite, martensite, secondary cementite and the like exist, and simultaneously solve the problems that the hardness of the rare earth high-strength heat treatment steel rail joints is low, the drop hammer performance of the joints is not matched with the joint collapse, and the excellent joint matched with the base metal performance is obtained, so that the joint performance meets the following requirements of TB/T1632.2-2014 steel rail welding part 2: and the requirements for the mechanical property of the joint and the detection of drop hammer are met in flash welding.
The patent with publication number CN201810708275.9 discloses a heat treatment method of a steel rail flash welding joint, which is characterized in that the welding joint of hypereutectoid steel rails and heterogeneous steel rails of eutectoid steel rails is directly subjected to three-stage control cooling of the joint in a high-temperature welding state after welding, the temperature of the first cooling stage is reduced from 1000-1400 ℃ to 650-720 ℃, the temperature of the second cooling stage is reduced to 350-410 ℃, and the temperature of the third cooling stage is reduced to 10-30 ℃. The invention is aimed at welding of a steel rail movable flash welding machine, the cooling medium can be water mist mixed gas, the drop hammer requirement of a movable flash welding head is 15 continuous according to the requirement of a TB/T1632.2 standard, compressed air can only be used for joint cooling treatment, the requirement of a standard pair joint heat treatment process is not met, and the invention also does not meet the continuous 25 continuous requirement of a fixed flash welding head.
The patent with publication number CN202010886023.2 discloses a 1300MPa grade low alloy heat treatment post-welding heat treatment method for steel rail, which comprises three-stage cooling of a steel rail welding joint with residual temperature of 900-1100 ℃ formed by a welding joint, wherein the first stage is naturally cooled to 650-720 ℃, the second stage is controlled to be cooled to 480-550 ℃, and the second stage is controlled to be cooled to 10-30 ℃. The invention is aimed at welding of a steel rail movable flash welding machine, the cooling medium can be water mist mixed gas, the hardness of the joint is detected by Vickers hardness, and the requirements of a TB/T1632.2 standard on the heat treatment process and performance inspection of a fixed flash welding head are not met. The joint has a punctiform martensite abnormal structure with a certain proportion, and the running safety of the joint line is seriously affected while the standard requirement is not met.
In the literature 'welding performance of rare earth heavy rail steel', for the welding performance of BNBRE rare earth heavy rail steel produced by die casting, a Gleeble-1500 thermal simulation experiment machine is utilized to carry out thermal simulation experiments of flash welding and thermite welding heat affected zones, the hardness and impact value of a welding joint obtained according to a thermal simulation sample in the literature are greatly different from actual detection results, the mechanical performance index of the actual welding joint of a steel rail cannot be reflected, and experimental data are only used for reference in the research process.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a method for fixing and flash welding a rare earth high-strength heat-treated steel rail and a joint heat treatment method, aiming at the rare earth high-strength heat-treated steel rail, after the flash welding head process and the joint heat treatment process are used, the fixed flash welding head of the rare earth high-strength heat-treated steel rail can be ensured to be of a normal pearlite structure, and abnormal structures such as bainite, martensite, secondary cementite and the like are not existed; the invention solves the problems of low hardness, inadequacy of drop hammer performance and low collapse of the joint of the rare earth high-strength heat-treated steel rail joint, can effectively improve the performance matching of the steel rail joint and the base metal, and improves the comprehensive mechanical property and contact fatigue property of the joint, thereby effectively improving the service performance of the joint.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention relates to a rare earth high-strength heat treatment steel rail fixing flash welding and joint heat treatment method, which comprises the following chemical components in percentage by weight: 0.71-0.81%, si:0.50 to 0.80 percent, mn:0.80 to 1.20 percent, cr:0.25 to 0.40 percent, V:0.04 to 0.08 percent, RE:0.0005 to 0.0020 percent, P is less than or equal to 0.025 percent, S is less than or equal to 0.025 percent, al: less than or equal to 0.010 percent, and the balance of Fe, and the steel rail is produced by smelting, continuous casting, slow cooling of steel billets, rolling, heat treatment and the like;
1) Derusting and polishing the end surfaces of two rare earth high-strength heat-treated steel rails with the same cross section and 60kg/m and the same material and electrode clamping ends, and preparing for flash welding;
2) Adopting a GAAS80/580 fixed flash welder to weld the steel rail; the oil temperature of the welder is controlled to be about 40 ℃, the water temperature is controlled to be about 20 ℃, and the voltage of a power grid is 418-424V;
3) The joint fixing flash welding process comprises the following steps: the joint quantity of the steel rail welding seam is controlled between 10 and 12mm, the arching quantity is controlled between 0.45 and 0.60mm, the preheating times are about 12 times, the secondary preheating current is controlled between 61 and 64KA, the upsetting quantity is controlled between 16 and 18mm, the upsetting force is controlled between 480 and 520KN, the welding time is controlled between 125 and 130s, and the melting end speed is controlled between 2.35 and 2.38 mm/s;
4) Air cooling the high-temperature welded joint to below 300 ℃ to ensure that each position of the joint is completely phase-changed;
5) Joint heat treatment process 1: normalizing the joint by using a dual-frequency normalizing induction heating device, and firstly, performing low-frequency induction heating on the joint: the low-frequency is 1000-1400 Hz, the low-frequency power is 50-60 kW, the heating time is 80-90 s, and the welding state joint is heated to 830+/-10 ℃ from about 200 ℃; the low-frequency heating can ensure that the surface and the interior of the welding seam can be heated to the required temperature;
6) Joint heat treatment process 2: after the low-frequency heating of the joint reaches 830+/-10 ℃, the joint is immediately subjected to high-frequency induction heating: the high-frequency is 2000-2300 Hz, the high-frequency power is 70-80 kW, the heating time is 70-80 s, and the welding state joint is heated to 900+/-10 ℃ from about 830+/-10 ℃; the high-frequency heating can further improve the temperature and uniformity of the joint; the total heating time of the joint normalizing heat treatment is controlled between 150 and 170 seconds;
7) Joint heat treatment process 3: after the normalizing temperature of the joint reaches the target temperature of 900+/-10 ℃, stopping heating, and immediately performing air-jet accelerated cooling treatment on the rail head and the rail web of the joint, wherein an air-jet opening for air-jet cooling is 25mm away from the rail top surface, 35mm away from the side surface of the rail head and 50mm away from the rail web; the air pressure of the air is 0.34-0.45 MPa, the air spraying time is controlled between 115-130 s, the air spraying final cooling temperature of the top surface of the joint rail is controlled between 400-450 ℃, then the air spraying cooling is stopped, the temperature of the joint is controlled between 480-500 ℃, and then the joint is naturally cooled to the room temperature.
Further, the rolling compression ratio of the steel rail is greater than or equal to 13: and 1, the final rolling temperature of the steel rail is not higher than 960 ℃, and the online heat treatment final cooling temperature of the steel rail is not higher than 520 ℃, so that the grain size of the steel rail and the distance between pearlite structure pieces are ensured.
Further, the tensile strength Rm of the joint is more than or equal to 1119MPa, the extension A of the joint is more than or equal to 10.5%, and the impact KU of the joint 2 Not less than 13.5J, average hardness H of joint J Average value H of hardness of base material P The ratio of (2) is as follows: h J /H P Not less than 0.93, average hardness H of joint soft point J1 Average value H of hardness of base material P Ratio of (3): h J1 /H P The W of the softening area is not less than 15mm and not more than 0.82, 25 joints are not broken, the weld joint and the heat affected zone are typical pearlite structures, martensite, bainite or secondary cementite harmful structures are not present, and all performances meet standard requirements.
Compared with the prior art, the invention has the beneficial technical effects that:
based on the above invention, the tensile strength Rm of the joint is more than or equal to 1119MPa, the extension A of the joint is more than or equal to 10.5%, and the impact KU of the joint 2 Not less than 13.5J, average hardness H of joint J Average value H of hardness of base material P The ratio of (2) is as follows: h J /H P Not less than 0.93, average hardness H of joint soft point J1 Average value H of hardness of base material P Ratio of (3): h J1 /H P The W of the softening area is not less than 15mm and not more than 0.82, 25 joints are not broken, the weld joint and the heat affected zone are typical pearlite structures, martensite, bainite or secondary cementite harmful structures are not present, and all performances meet standard requirements.
The strength, hardness and toughness of the obtained rare earth high-strength heat-treated steel rail fixing flash welding joint are matched with the performance of the steel rail base metal, and the requirements of heavy haul railways on joint smoothness can be met. The method improves the risk of fracture caused by saddle-shaped abrasion or abnormal joint structure due to overlarge hardness difference of the base metal and the joint in the line service process, fully exerts the characteristics of high strength and high toughness of the rare earth high-strength heat treatment steel rail, and can meet the application of heavy-duty railways with the axle weight of more than 25 t.
Drawings
The invention is further described with reference to the following description of the drawings.
FIG. 1 shows the results of the test of the joint of example 1 in longitudinal section (test line 1);
FIG. 2 shows the results of the test of the joint of example 2 in longitudinal section (test line 1);
FIG. 3 shows the results of the test of the joint of example 3 in a vertical section (test line 1).
Detailed Description
The invention will be further illustrated with reference to specific examples.
A rare earth high-strength heat treatment steel rail fixing flash welding and joint heat treatment method comprises the following steps:
1) The flash welded rare earth high-strength heat treatment steel rail takes C, S i, mn and Cr as main elements, and is added with V, RE micro alloying elements, wherein the weight percentage of the chemical components of the steel rail is C: 0.71-0.81%, S i:0.50 to 0.80 percent, mn:0.80 to 1.20 percent, cr:0.25 to 0.40 percent, V:0.04 to 0.08 percent, RE:0.0005 to 0.0020 percent, P is less than or equal to 0.025 percent, S is less than or equal to 0.025 percent, al: less than or equal to 0.010 percent, and the balance of Fe.
2) The steel rail is produced by smelting, continuous casting, slow cooling of steel billets, rolling, heat treatment and the like. The size of the steel rail continuous casting blank is 280mm multiplied by 380mm, the rolling section is 60kg/m, and the rolling compression ratio of the steel rail is more than or equal to 13: and 1, the final rolling temperature of the steel rail is not higher than 960 ℃, and the online heat treatment final cooling temperature of the steel rail is not higher than 520 ℃, so that the grain size of the steel rail and the distance between pearlite structure pieces are ensured.
3) And adopting a GAAS80/580 fixed flash welder to weld the steel rails. The oil temperature of the welder is controlled to be about 40 ℃, the water temperature is controlled to be about 20 ℃, and the voltage of a power grid is 418-424V.
4) And derusting and polishing the end faces of two rare earth high-strength heat treated steel rails with the same cross section and 60kg/m and the same material and electrode clamping ends, thereby preparing for flash welding. The joint quantity of the steel rail welding seams is controlled between 10 and 12mm, and the arching quantity is controlled between 0.45 and 0.60 mm.
5) The preheating times of flash welding are controlled to be about 12 times, the secondary preheating current is controlled to be between 61 and 64KA, the upsetting amount of flash welding is controlled to be between 16 and 18mm, the upsetting force is controlled to be between 480 and 520KN, the welding time is controlled to be between 125 and 130s, and the melting end speed is controlled to be between 2.35 and 2.38 mm/s. The time from the completion of flash welding upsetting to the push-out should be controlled within 15 s.
6) And air-cooling the high-temperature welded joint to below 300 ℃ to ensure that each position of the joint is completely phase-changed. And (3) polishing the joint welding rib to be flat, namely, polishing the convex pushing allowance of the rail head and the rail bottom.
7) Normalizing the joint in a welded state by using a double-frequency normalizing machine, and firstly, carrying out low-frequency induction heating on the joint: the low-frequency is 1000-1400 Hz, the low-frequency power is 50-60 kW, the heating time is 80-90 s, and the welding state joint is heated to 830+/-10 ℃ from about 200 ℃.
8) After the joint low-frequency induction heating reaches the target temperature, the low-frequency heating is turned off, and the joint is immediately subjected to high-frequency induction heating: the high-frequency is 2000-2300 Hz, the high-frequency power is 70-80 kW, the heating time is 70-80 s, and the welding state joint is heated to 900+/-10 ℃ from about 830+/-10 ℃. The total heating time of the joint normalizing heat treatment is controlled between 150 and 170 seconds.
9) And after the joint subjected to normalizing heat treatment reaches the target temperature of 900+/-10 ℃, stopping heating, and immediately performing air-jet accelerated cooling treatment on the rail head and the rail web of the joint, wherein an air-jet opening for air-jet cooling is 25mm away from the rail top surface, 35mm away from the side surface of the rail head and 50mm away from the rail web. The air pressure of the air is 0.34-0.45 MPa, the air spraying time is controlled between 115-130 s, the air spraying final cooling temperature of the top surface of the joint rail is controlled between 400-450 ℃, then the air spraying cooling is stopped, the temperature of the joint is controlled between 480-500 ℃, and then the joint is naturally cooled to the room temperature.
The process is compared in the implementation process:
in the implementation process, the comparison analysis of the mechanical properties, drop weight results and the like of the corresponding joint is mainly combined with different welding processes and joint heat treatment processes, so that the steel rail flash welding process is determined, and main adjustment parameters and drop weight test results of the welding process in the implementation process are shown in table 1.
Table 1 different welding processes and drop hammer results during implementation
As can be seen from table 1, the 5.2 meter drop height performance test was performed for the joints under different welding processes: in the steel rail flash welding process of the embodiment 1, the number of drop hammer breaks is 8, a plurality of broken holes are found to be obvious gray spots and liquefaction cracks, the number of gray spots is more, and the areas of the broken holes are more than the standard requirements; in the example 2 steel rail flash welding process, the number of drop hammer breaks is 2, obvious gray spots are also found at the drop hammer breaks, and the single gray spot area and the total gray spot area are not found to exceed the standard; in example 3, the steel rail flash welding process did not break down the hammer. The preheating times and the upsetting amount are increased, oxidation products generated during welding of the welding line can be extruded away, the number and the area of gray spots at the welding line can be reduced or eliminated, and the drop hammer qualification rate is further improved.
The structural grain size of the rare earth high-strength heat treatment steel rail fixed flash welding joint in the welding state is relatively coarse, only about 2 grades are required, each mechanical property of the joint is very poor, the normalizing heat treatment is carried out on the welding state joint, the microstructure of the welding seam can be thinned, and the comprehensive mechanical property of the flash welding joint can be effectively improved. The comparative schemes of the different joint heat treatment processes in the implementation process are shown in Table 2.
Table 2 comparison of different heat treatment processes during the implementation
The flash welding head after normalizing treatment of example 1-example 3 was welded according to section 2 of TB/T1632.2-2014 rail: flash welding, and performing comparative analysis on Rockwell hardness of longitudinal section of rail head, wherein the comparative analysis results are shown in tables 3-5 and figures 1-3.
TABLE 3 example 1 results of Joint vertical section (test line 1)
As can be seen from table 3 and fig. 1, example 1: average value H of hardness of joint J Average value H of hardness of base material P Ratio of (3): h J /H P =0.87, joint soft spot hardness average H J1 Average value H of hardness of base material P Ratio of (3): h J1 /H P =0.79, the softening zone widths W1, W2 are respectively: 23mm and 28mm do not meet the standard requirements of heat treated steel rails.
TABLE 4 example 2 results of Joint vertical section (test line 1)
As can be seen from table 4 and fig. 2, example 2: average value H of hardness of joint J Average value H of hardness of base material P Ratio of (3): h J /H P =0.88, joint soft spot hardness average H J1 Average value H of hardness of base material P Ratio of (3): h J1 /H P =0.81, the softening zone widths W1, W2 are respectively: 20mm, 23mm. There is some improvement in joint hardness over example 1, but the soft spot hardness and the width of the softened region still do not meet the standard requirements for heat treated steel rails.
TABLE 5 example 3 results of Joint vertical section (test line 1)
As can be seen from table 5 and fig. 3, example 2: average value H of hardness of joint J Average value H of hardness of base material P Ratio of (3): h J /H P =0.93, joint soft spot hardness average H J1 Average value H of hardness of base material P Ratio of (3): h J1 /H P =0.82, the softening zone widths W1, W2 are respectively: 15mm, 13mm. Compared with the embodiment 1 and the embodiment 2, the hardness of the joint is obviously improved, the hardness of the joint and the width of the softening zone of the embodiment 3 meet the standard requirements of heat treatment steel rails, and the hardness of the joint of the embodiment 3 is well matched with the base metal.
According to section 1 of TB/T1632.2-2014 rail welding: general technical conditions sampling method joint stretching and joint impact performance test were performed on the flash welding joint of example 3, and specific results are shown in tables 6 and 7.
TABLE 6 example 3 flash bond head tensile Properties
TABLE 7 example 3 impact Property of flash bond head
As can be seen from tables 5 and 6, the flash welding head of example 3 satisfies the standard requirements for both tensile properties and impact properties, and the joint has a large performance margin.
As can be seen from comparison of the processes in the implementation process, the tensile strength Rm of the joint of the embodiment 3 is more than or equal to 1119MPa, the joint extension A is more than or equal to 10.5 percent, and the joint impact KU 2 Not less than 13.5J, average hardness H of joint J Average value H of hardness of base material P The ratio of (2) is as follows: h J /H P Not less than 0.93, average hardness H of joint soft point J1 Is flat with the hardness of the parent metalMean value H P Ratio of (3): h J1 /H P And the softening area W is not more than 15mm and is not more than 0.82, 25 joints are not broken, and the 60kg/m rare earth high-strength heat treatment steel rail welded by adopting the process of the embodiment 3 smoothly passes the fixed flash welding inspection.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (3)
1. A rare earth high-strength heat treatment steel rail fixing flash welding and joint heat treatment method is characterized in that: the steel rail comprises the following chemical components in percentage by weight: 0.71-0.81%, si:0.50 to 0.80 percent, mn:0.80 to 1.20 percent, cr:0.25 to 0.40 percent, V:0.04 to 0.08 percent, RE:0.0005 to 0.0020 percent, P is less than or equal to 0.025 percent, S is less than or equal to 0.025 percent, al: less than or equal to 0.010 percent, and the balance of Fe, and the steel rail is produced by smelting, continuous casting, slow cooling of steel billets, rolling, heat treatment and the like;
1) Derusting and polishing the end surfaces of two rare earth high-strength heat-treated steel rails with the same cross section and 60kg/m and the same material and electrode clamping ends, and preparing for flash welding;
2) Adopting a GAAS80/580 fixed flash welder to weld the steel rail; the oil temperature of the welder is controlled to be about 40 ℃, the water temperature is controlled to be about 20 ℃, and the voltage of a power grid is 418-424V;
3) The joint fixing flash welding process comprises the following steps: the joint quantity of the steel rail welding seam is controlled between 10 and 12mm, the arching quantity is controlled between 0.45 and 0.60mm, the preheating times are about 12 times, the secondary preheating current is controlled between 61 and 64KA, the upsetting quantity is controlled between 16 and 18mm, the upsetting force is controlled between 480 and 520KN, the welding time is controlled between 125 and 130s, and the melting end speed is controlled between 2.35 and 2.38 mm/s;
4) Air cooling the high-temperature welded joint to below 300 ℃ to ensure that each position of the joint is completely phase-changed;
5) Joint heat treatment process 1: normalizing the joint by using a dual-frequency normalizing induction heating device, and firstly, performing low-frequency induction heating on the joint: the low-frequency is 1000-1400 Hz, the low-frequency power is 50-60 kW, the heating time is 80-90 s, and the welding state joint is heated to 830+/-10 ℃ from about 200 ℃; the low-frequency heating can ensure that the surface and the interior of the welding seam can be heated to the required temperature;
6) Joint heat treatment process 2: after the low-frequency heating of the joint reaches 830+/-10 ℃, the joint is immediately subjected to high-frequency induction heating: the high-frequency is 2000-2300 Hz, the high-frequency power is 70-80 kW, the heating time is 70-80 s, and the welding state joint is heated to 900+/-10 ℃ from about 830+/-10 ℃; the high-frequency heating can further improve the temperature and uniformity of the joint; the total heating time of the joint normalizing heat treatment is controlled between 150 and 170 seconds;
7) Joint heat treatment process 3: after the normalizing temperature of the joint reaches the target temperature of 900+/-10 ℃, stopping heating, and immediately performing air-jet accelerated cooling treatment on the rail head and the rail web of the joint, wherein an air-jet opening for air-jet cooling is 25mm away from the rail top surface, 35mm away from the side surface of the rail head and 50mm away from the rail web; the air pressure of the air is 0.34-0.45 MPa, the air spraying time is controlled between 115-130 s, the air spraying final cooling temperature of the top surface of the joint rail is controlled between 400-450 ℃, then the air spraying cooling is stopped, the temperature of the joint is controlled between 480-500 ℃, and then the joint is naturally cooled to the room temperature.
2. The method for fixing, flash welding and joint heat treatment of rare earth high-strength heat-treated steel rail according to claim 1, wherein the method comprises the following steps: the rolling compression ratio of the steel rail is greater than or equal to 13: and 1, the final rolling temperature of the steel rail is not higher than 960 ℃, and the online heat treatment final cooling temperature of the steel rail is not higher than 520 ℃, so that the grain size of the steel rail and the distance between pearlite structure pieces are ensured.
3. The method for fixing, flash welding and joint heat treatment of rare earth high-strength heat-treated steel rail according to claim 1, wherein the method comprises the following steps: the tensile strength Rm of the joint is more than or equal to 1119MPa, the extension A of the joint is more than or equal to 10.5%, and the impact KU of the joint 2 Not less than 13.5J, average hardness H of joint J Average value H of hardness of base material P Is full of the ratio ofFoot: h J /H P Not less than 0.93, average hardness H of joint soft point J1 Average value H of hardness of base material P Ratio of (3): h J1 /H P The W of the softening area is not less than 15mm and not more than 0.82, 25 joints are not broken, the weld joint and the heat affected zone are typical pearlite structures, martensite, bainite or secondary cementite harmful structures are not present, and all performances meet standard requirements.
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