CN117161528A - Method for improving internal hardness of rail head of steel rail flash welding head and steel rail - Google Patents
Method for improving internal hardness of rail head of steel rail flash welding head and steel rail Download PDFInfo
- Publication number
- CN117161528A CN117161528A CN202311153000.0A CN202311153000A CN117161528A CN 117161528 A CN117161528 A CN 117161528A CN 202311153000 A CN202311153000 A CN 202311153000A CN 117161528 A CN117161528 A CN 117161528A
- Authority
- CN
- China
- Prior art keywords
- rail
- head
- steel rail
- welding
- hardness
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000003466 welding Methods 0.000 title claims abstract description 141
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 139
- 239000010959 steel Substances 0.000 title claims abstract description 139
- 238000000034 method Methods 0.000 title claims abstract description 95
- 238000001816 cooling Methods 0.000 claims abstract description 78
- 238000010438 heat treatment Methods 0.000 claims abstract description 67
- 230000008569 process Effects 0.000 claims description 42
- 206010028980 Neoplasm Diseases 0.000 claims description 30
- 239000000463 material Substances 0.000 claims description 12
- 239000000126 substance Substances 0.000 claims description 11
- 229910001562 pearlite Inorganic materials 0.000 claims description 5
- 239000011324 bead Substances 0.000 claims description 4
- 238000003825 pressing Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 3
- 238000005422 blasting Methods 0.000 description 17
- 239000010953 base metal Substances 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- 210000001503 joint Anatomy 0.000 description 9
- 229910001338 liquidmetal Inorganic materials 0.000 description 9
- 230000007246 mechanism Effects 0.000 description 9
- 229910001566 austenite Inorganic materials 0.000 description 7
- 229910000734 martensite Inorganic materials 0.000 description 6
- 229910001563 bainite Inorganic materials 0.000 description 4
- 230000002159 abnormal effect Effects 0.000 description 2
- 230000014509 gene expression Effects 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000004781 supercooling Methods 0.000 description 1
Landscapes
- Heat Treatment Of Articles (AREA)
Abstract
The invention discloses a method for improving the internal hardness of a rail head of a steel rail flash welding head and a steel rail, wherein the method comprises the following steps: flash welding the rail, comprising: sequentially carrying out an electrifying and heating stage and a pressurizing and upsetting stage; wherein the voltage of the electrified heating stage is 340-410V, the average current is 50-300A, and the duration time is 150-300 s; heat treating a flash welded rail comprising: and (3) performing accelerated cooling on the top surface, the side surface and the jaw of the rail head near the weld joint area of the rail joint, wherein the initial temperature of the accelerated cooling is more than 700 ℃, the end temperature is 430-500 ℃, and the average cooling speed is 5-35 ℃/s. The invention can improve the hardness of the rail head inside of the steel rail flash welding head, thereby improving the wear resistance and the service life of the steel rail welding head.
Description
Technical Field
The invention relates to the technical field of steel rail welding, in particular to a method for improving the internal hardness of a rail head of a steel rail flash welding head and a steel rail.
Background
The steel rail is used as the most main organization part of the railway line, and the service environment with large axle weight and high frequency has higher requirements on the service performance. Mainly shows wear resistance and fatigue performance. Studies have shown that the higher the hardness, the better the wear resistance, without taking into account other factors such as wheel-rail matching, wear media, etc., and therefore the hardness value is generally taken as one of the main indicators for measuring the wear resistance of materials. The method for representing the hardness of the base metal of the steel rail is mainly tread hardness and section hardness, and the method for representing the steel rail joint is mainly tread hardness and longitudinal section hardness.
Currently, the main welding method of steel rails is flash welding. The flash welding of steel rail is a resistance welding method which uses the resistance of current passing through small contact points on the contact surface of the end of steel rail and the heat generated by electric arc to heat the end to be welded of steel rail, and applies pressure to the joint after proper time to make the whole area of the butt joint surface of steel rail be firmly combined together. The method has high automation degree and stable welding quality, and is a main method for the field construction welding of the domestic and foreign seamless lines. The production method is mainly divided into two types of fixed flash welding and movable flash welding. Fixed flash welding generally secures the welding equipment within the plant and is also commonly referred to as factory welding or base welding. Fixed flash welding is typically performed by directly shorting the rails and heating the rails by resistive heating without (or with little) concomitant flashing. At present, the most widely used mobile flash welding machines at home and abroad mainly comprise K950 and YGH-1200TH mobile flash welding machines, and the K950 mobile flash welding machine can ensure the high quality and the long service life of the welding machine head.
How to improve the hardness of the steel rail flash welding head so as to improve the wear resistance and fatigue performance of the steel rail is a technical problem to be solved in the field.
Disclosure of Invention
The invention mainly aims to provide a method for improving the hardness of the inside of a rail head of a steel rail flash welding head and a steel rail, so as to solve the technical problem of how to improve the hardness of the steel rail flash welding head.
According to one aspect of the invention, a method for improving the hardness of the interior of a rail head of a steel rail flash welding head is provided, which comprises the following steps:
flash welding the rail, comprising: sequentially carrying out an electrifying and heating stage and a pressurizing and upsetting stage; wherein the voltage of the electrified heating stage is 340-410V, the average current is 50-300A, and the duration time is 150-300 s;
heat treating a flash welded rail comprising: and (3) performing accelerated cooling on the top surface, the side surface and the jaw of the rail head near the weld joint area of the rail joint, wherein the initial temperature of the accelerated cooling is more than 700 ℃, the end temperature is 430-500 ℃, and the average cooling speed is 5-35 ℃/s.
According to one embodiment of the invention, during the electric heating phase, the opposing pressure applied to the two ends of the steel rail to be welded is 80-160 kN, and the consumption of the steel rail is 10-35 mm.
According to one embodiment of the invention, the flash welding of the rail further comprises: the pressing upsetting stage is followed by a tumor pushing stage, and the time from the end of the pressing upsetting stage to the complete end of the tumor pushing stage is 5 to 10s.
According to one embodiment of the invention, the temperature of the two side rails in the area which is 0-25 mm away from the end face to be welded is 900-1650 ℃ and the duration is 180-350 s in the whole flash welding process.
According to one embodiment of the invention, the voltage of the energizing heating stage is 400V, the average current is 200A, and the duration is 150s; the initial temperature of the accelerated cooling is 710 ℃, the final temperature is 480 ℃, and the average cooling speed is 25 ℃/s.
According to one embodiment of the invention, the voltage of the energizing heating stage is 400V, the average current is 210A, and the duration is 200s; the initial temperature of the accelerated cooling is 770 ℃, the final temperature is 490 ℃, and the average cooling speed is 30 ℃/s.
According to one embodiment of the invention, the voltage of the energizing heating stage is 340V, the average current is 50A, and the duration is 150s; the termination temperature of the accelerated cooling is 430 ℃, and the average cooling speed is 5 ℃/s.
According to one embodiment of the invention, the voltage of the energizing heating stage is 410V, the average current is 300A, and the duration is 300s; the termination temperature of the accelerated cooling is 500 ℃, and the average cooling speed is 35 ℃/s.
According to one embodiment of the invention, the steel rail to be welded is a high-strength railhead hardened pearlitic steel rail, the mass fraction of C element in the main chemical composition of the steel rail is 0.74-0.86%, the mass fraction of Si element is 0.10-0.60%, the mass fraction of Mn element is 0.75-1.25%, the mass fraction of P element and S element is not more than 0.020%, the mass fraction of Cr element is not more than 0.30%, and the mass fraction of V element is not more than 0.01%; the tensile strength of the steel rail at the gauge angle is at least 1172MPa, and the hardness of the steel rail at the depth of 25mm from the surface of the outline of the rail head is more than or equal to 370HB.
According to another aspect of the present invention, there is provided a steel rail produced by the method as described above, wherein the hardness of the head inner region of the steel rail near-bead region is 95% to 110% of the hardness of the head inner region of the steel rail base material, and the pearlite area ratio in the microstructure of the head inner region of the steel rail near-bead region is 97% or more, wherein the head inner region is a region having a depth of 0 to 25mm from the head surface.
In the method for improving the internal hardness of the rail head of the steel rail flash welding head according to the embodiment of the invention, the internal hardness of the rail head of the steel rail flash welding head can be improved by improving the related parameters of the flash welding process (particularly the parameters of voltage, current, time and the like in the electrified heating stage) and the related parameters of the post-welding heat treatment process, so that the wear resistance and the service life of the steel rail welding head are improved.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 illustrates a schematic view of a railhead interior region of a near weld in accordance with an embodiment of the present invention;
FIG. 2 illustrates another schematic view of the interior region of the rail head of the near-weld zone in accordance with an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
It should be noted that, in the embodiments of the present invention, all the expressions "first" and "second" are used to distinguish two entities with the same name but different entities or different parameters, and it is noted that the "first" and "second" are only used for convenience of expression, and should not be construed as limiting the embodiments of the present invention, and the following embodiments are not described one by one.
The invention provides a method for improving the internal hardness of a rail head of a steel rail flash welding head, which comprises the following steps:
flash welding the rail, comprising: sequentially carrying out an electrifying and heating stage and a pressurizing and upsetting stage; wherein the voltage of the electrified heating stage is 340-410V, the average current is 50-300A, and the duration time is 150-300 s;
heat treating a flash welded rail comprising: and (3) performing accelerated cooling on the top surface of the rail head, the side surface of the rail head and the jaw of the rail head near the welding seam area of the rail joint by adopting special equipment, wherein the initial temperature of the accelerated cooling is more than 700 ℃, the end temperature is 430-500 ℃, and the average cooling speed is 5-35 ℃/s.
In the embodiment of the invention, the hardness of the rail head of the steel rail flash welding head can be improved by improving the related parameters of the flash welding process (particularly the parameters of voltage, current, time and the like in the electrified heating stage) and the related parameters of the post-welding heat treatment process, so that the wear resistance and the service life of the steel rail welding head are improved.
The main function of the heat treatment is to eliminate the internal stress of the welded joint, refine austenite grains, homogenize the structure and improve the strength and hardness of the joint. After the steel rail welding is finished, the structure of the joint at the high temperature stage is an austenite structure. As the rail joint cools, the austenite structure undergoes austenite to pearlite, austenite to martensite or bainite transformation at different temperature stages and cooling rates. Martensite and bainite belong to harmful structures in the pearlite steel rail, can obviously reduce the service performance of the joint, and influence the running safety of a train. The austenite is cooled to a speed higher than the critical cooling speed of the steel rail material, and when the temperature is lower than the initial transformation temperature of bainite and martensite, the inside of the joint has harmful structures such as martensite or bainite. Therefore, it is necessary to control the termination temperature to 430 to 500℃and the average cooling rate to 5 to 35℃per second. Meanwhile, in order to ensure that the hardness of the joint at the center of the rail head is improved, austenite needs to have enough supercooling degree at a high enough temperature, so that the initial temperature of accelerated cooling is more than 700 ℃, and the top surface, the side surface and the jaw of the rail head near the welding joint area of the rail joint are accelerated cooled.
The temperature of the rail joint and the cooling/temperature rising speed directly influence the phase change process of the metal material. All of the time, current, voltage, pressure, and heating temperature, cooling/temperature rise rate, and cooling termination temperature of the welding process defined by the present invention act synergistically to achieve the desired properties of the rail weld joint.
In some embodiments, the steel rail to be welded is a high-strength railhead hardening pearlitic steel rail, wherein the mass fraction of C element in the main chemical composition of the steel rail is 0.74-0.86%, the mass fraction of Si element is 0.10-0.60%, the mass fraction of Mn element is 0.75-1.25%, the mass fraction of P element and S element is not more than 0.020%, the mass fraction of Cr element is not more than 0.30%, and the mass fraction of V element is not more than 0.01%; the tensile strength at the gauge angle of 12.7mm away from the tread and the side surface of the rail head of the steel rail is at least 1172MPa, and the hardness at the depth of 25mm away from the surface of the outline of the rail head is more than or equal to 370HB. The high Jiang Guitou hardened pearlitic steel rail flash welding head in the prior art has lower wear resistance and short service life, and the invention provides a method for improving the internal hardness of the steel rail flash welding head to solve the problem.
In the embodiment of the invention, the voltage, the current and the time value are set so that the steel rail to be welded is mainly in short-circuit contact in the electrified state in the electrified heating stage, and the steel rail is heated by utilizing heat generated by continuous lintel blasting formed between liquid metals on the end surfaces of the steel rail to be welded.
In some embodiments, during the electrically heated stage, the opposing pressure applied to the ends of the rail to be welded is 80-160 kN and the rail consumption is 10-35 mm. Thereby maintaining continuous stability of the lintel blast.
In some embodiments, the flash welding the rail further comprises: the pressurized upsetting phase is followed by a pushing phase. By pushing the nubs, the surface of the welding seam can be molded and attractive, and the welding quality is improved. The integral profiling steel rail tumor pushing mechanism can be adopted for tumor pushing. In some embodiments, the time from the end of the pressurization upsetting stage to the complete end of the pushing stage is 5-10 s, thereby ensuring joint quality and the effect of the subsequent post-weld heat treatment.
In some embodiments, the flash welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing and upsetting, and rapid pushing, wherein the temperature of the region, which is 0-25 mm away from the end face to be welded, of the steel rails on two sides is 900-1650 ℃ and the duration time is 180-350 s in the whole flash welding process.
The invention also provides a steel rail prepared by the method, the hardness of the inner area of the rail head of the steel rail near-welding area is 95-110% of the hardness of the inner area of the rail head of the steel rail parent metal, and the pearlite area ratio in the microstructure of the inner area of the rail head of the steel rail near-welding area is more than or equal to 97%. Referring to fig. 1 and 2, the weld-near zone (also referred to as a weld-near zone) may be a heat affected zone 1-10 mm each from both sides of the weld line; the interior region of the head may be a region of 0 to 25mm depth from the head surface (which may include a region of 0 to 25mm depth from the head profile surface at the head top surface, the rail pitch angle, both head sides and the head chin).
In summary, the invention mainly aims at the technical problems of low wear resistance and short service life of the high-strength rail head hardening pearlitic steel rail flash welding head, and provides a method for improving the internal hardness of the steel rail flash welding head.
The following is a description of specific examples and comparative examples.
Example 1
In the main chemical components of the steel rail material used in the embodiment, the mass fraction of the C element is 0.78%, the mass fraction of the Si element is 0.50%, and the mass fraction of the Mn element is 0.89%. The tensile strength at the gage angle of 12.7mm away from the tread and the side surface of the rail head of the steel rail is 1175 MPa-1210 MPa, and the hardness at the depth of 25mm away from the surface of the outline of the rail head is 370 HB-385 HB. Including two main processes of welding and post-weld heat treatment. The welding method is rail flash welding, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing upsetting, rapid pushing of the steel rail, and the like. Throughout the welding process, the duration was 180s. The method comprises the steps of carrying out short-circuit contact on a steel rail to be welded in a welding heating process mainly in an electrified state, heating the steel rail by utilizing heat generated by continuous lintel blasting formed between liquid metals on the end surfaces of the steel rail to be welded, wherein the voltage during continuous lintel blasting is 400V, the average current is 200A, the duration time is 150s, the opposite pressure applied to the two ends of the steel rail to be welded in the heating process is 100kN, and the consumption of the steel rail is 15mm; the rapid tumor pushing stage of the welding process adopts an integral profiling steel rail tumor pushing mechanism, and the time from the end of upsetting to the complete end of tumor pushing is 5s. After the welding is finished, special equipment is adopted to accelerate cooling of the top surface of the rail head, the side surface of the rail head and the jaw of the rail head near the welding line area of the rail joint. The initial cooling temperatures at the head top, head side and head jaw were about 710 c, the average cooling rate at accelerated cooling was 25 c/s, and the end temperature at accelerated cooling was 480 c. The longitudinal section hardness test was performed on the joints 5mm and 25mm below the tread with reference to AS1085.20 standard, and the joint was examined for microstructure with reference to BS EN 14587. The result shows that the ratio of the hardness of the rail head near the weld line area to the hardness of the rail base metal at the same position of the high Jiang Guitou hardened pearlitic rail flash welding head formed by the method is 98-90%, and the area ratio of the microstructure pearlitic is more than or equal to 98%.
Example 2
In the main chemical components of the steel rail material used in the embodiment, the mass fraction of the C element is 0.81%, the mass fraction of the Si element is 0.58%, and the mass fraction of the Mn element is 0.88%. The tensile strength at the gage angle of 12.7mm away from the tread and the side surface of the rail head of the steel rail is 1259MPa to 1380MPa, and the hardness at the depth of 25mm away from the surface of the outline of the rail head is 390HB to 420HB. Including two main processes of welding and post-weld heat treatment. The welding method is rail flash welding, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing upsetting, rapid pushing of the steel rail, and the like. The duration of the whole welding process was 280s. The method comprises the steps of carrying out short-circuit contact on a steel rail to be welded in a welding heating process mainly in an electrified state, heating the steel rail by utilizing heat generated by continuous lintel blasting formed between liquid metals on the end surfaces of the steel rail to be welded, wherein the voltage during continuous lintel blasting is 400V, the average current is 210A, the duration is 200s, the opposite pressure applied to the two ends of the steel rail to be welded in the heating process is 120kN, and the consumption of the steel rail is 23mm; the rapid tumor pushing stage of the welding process adopts an integral profiling steel rail tumor pushing mechanism, and the time from the end of upsetting to the complete end of tumor pushing is 8s. After the welding is finished, special equipment is adopted to accelerate cooling of the top surface of the rail head, the side surface of the rail head and the jaw of the rail head near the welding line area of the rail joint. The initial cooling temperatures at the head top, head side and head jaw were about 770 c, the average cooling rate at accelerated cooling was 30 c/s, and the end temperature at accelerated cooling was 490 c. The longitudinal section hardness test was performed on the joints 5mm and 25mm below the tread with reference to AS1085.20 standard, and the joint was examined for microstructure with reference to BS EN 14587. The result shows that the ratio of the hardness of the inner part of the rail head near the weld line area to the hardness of the rail base metal at the same position of the high Jiang Guitou hardened pearlitic rail flash welding head formed by the method is 98% -100%, and the area ratio of the microstructure pearlitic is about 99%.
Example 3
In the main chemical components of the steel rail material used in the embodiment, the mass fraction of the C element is 0.81%, the mass fraction of the Si element is 0.58%, and the mass fraction of the Mn element is 0.88%. The tensile strength at the gage angle of 12.7mm away from the tread and the side surface of the rail head of the steel rail is 1259MPa to 1380MPa, and the hardness at the depth of 25mm away from the surface of the outline of the rail head is 390HB to 420HB. Including two main processes of welding and post-weld heat treatment. The welding method is rail flash welding, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing upsetting, rapid pushing of the steel rail, and the like. Throughout the welding process, the duration was 180s. The method comprises the steps of carrying out short-circuit contact on a steel rail to be welded in a welding heating process mainly in an electrified state, heating the steel rail by utilizing heat generated by continuous lintel blasting formed between liquid metals on the end surfaces of the steel rail to be welded, wherein the voltage during continuous lintel blasting is 340V, the average current is 50A, the duration time is 150s, the opposite pressure applied to the two ends of the steel rail to be welded in the heating process is 80kN, and the consumption of the steel rail is 10mm; the rapid tumor pushing stage of the welding process adopts an integral profiling steel rail tumor pushing mechanism, and the time from the end of upsetting to the complete end of tumor pushing is 5s. After the welding is finished, special equipment is adopted to accelerate cooling of the top surface of the rail head, the side surface of the rail head and the jaw of the rail head near the welding line area of the rail joint. The initial cooling temperature of the rail head top surface, the rail head side surface and the rail head jaw is more than 700 ℃, the average cooling speed during accelerated cooling is 5 ℃/s, and the final cooling temperature during accelerated cooling is 430 ℃. The longitudinal section hardness test was performed on the joints 5mm and 25mm below the tread with reference to AS1085.20 standard, and the joint was examined for microstructure with reference to BS EN 14587. The result shows that the ratio of the hardness of the inner part of the rail head near the weld line area to the hardness of the rail base metal at the same position of the high Jiang Guitou hardened pearlitic rail flash welding head formed by the method is 95-96%, and the area ratio of the microstructure pearlitic is about 99%.
Example 4
In the main chemical components of the steel rail material used in the embodiment, the mass fraction of the C element is 0.78%, the mass fraction of the Si element is 0.50%, and the mass fraction of the Mn element is 0.89%. The tensile strength at the gage angle of 12.7mm away from the tread and the side surface of the rail head of the steel rail is 1175 MPa-1210 MPa, and the hardness at the depth of 25mm away from the surface of the outline of the rail head is 370 HB-385 HB. Including two main processes of welding and post-weld heat treatment. The welding method is rail flash welding, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing upsetting, rapid pushing of the steel rail, and the like. The duration of the whole welding process was 350s. The method comprises the steps of carrying out short-circuit contact on a steel rail to be welded in a welding heating process mainly in an electrified state, heating the steel rail by utilizing heat generated by continuous lintel blasting formed between liquid metals on the end surfaces of the steel rail to be welded, wherein the voltage during continuous lintel blasting is 410V, the average current is 300A, the duration time is 300s, the opposite pressure applied to the two ends of the steel rail to be welded in the heating process is 160kN, and the consumption of the steel rail is 35mm; the rapid tumor pushing stage of the welding process adopts an integral profiling steel rail tumor pushing mechanism, and the time from the end of upsetting to the complete end of tumor pushing is 10s. After the welding is finished, special equipment is adopted to accelerate cooling of the top surface of the rail head, the side surface of the rail head and the jaw of the rail head near the welding line area of the rail joint. The initial cooling temperature of the rail head top surface, the rail head side surface and the rail head jaw is more than 700 ℃, the average cooling speed during accelerated cooling is 35 ℃/s, and the final cooling temperature during accelerated cooling is 500 ℃. The longitudinal section hardness test was performed on the joints 5mm and 25mm below the tread with reference to AS1085.20 standard, and the joint was examined for microstructure with reference to BS EN 14587. The result shows that the ratio of the hardness of the inner part of the rail head near the weld line area to the hardness of the rail base metal at the same position of the high Jiang Guitou hardened pearlitic rail flash welding head formed by the method is 100-110%, and the area ratio of the microstructure pearlitic is about 99%.
Comparative example 1
The mass fraction of the C element, the mass fraction of the Si element and the mass fraction of the Mn element in the main chemical components of the rail materials used in this comparative example were 0.78%, 0.50% and 0.89%. The tensile strength at the gage angle of 12.7mm away from the tread and the side surface of the rail head of the steel rail is 1175 MPa-1210 MPa, and the hardness at the depth of 25mm away from the surface of the outline of the rail head is 370 HB-385 HB. Including two main processes of welding and post-weld heat treatment. The welding method is rail flash welding, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing upsetting, rapid pushing of the steel rail, and the like. The duration of the whole welding process was 100s. The method comprises the steps of carrying out short-circuit contact on a steel rail to be welded in a welding heating process mainly in an electrified state, heating the steel rail by utilizing heat generated by continuous lintel blasting formed between liquid metals on the end surfaces of the steel rail to be welded, wherein the voltage during continuous lintel blasting is 320V, the average current is 40A, the duration is 80s, the opposite pressure applied to the two ends of the steel rail to be welded in the heating process is 50kN, and the consumption of the steel rail is 9mm; the rapid tumor pushing stage of the welding process adopts an integral profiling steel rail tumor pushing mechanism, and the time from the end of upsetting to the complete end of tumor pushing is 10s. After the welding is finished, special equipment is adopted to accelerate cooling of the top surface of the rail head, the side surface of the rail head and the jaw of the rail head near the welding line area of the rail joint. The initial cooling temperatures at the head top, head side and head jaw were about 500 c, the average cooling rate at accelerated cooling was 40 c/s, and the end temperature at accelerated cooling was 410 c. The longitudinal section hardness test was performed on the joints 5mm and 25mm below the tread with reference to AS1085.20 standard, and the joint was examined for microstructure with reference to BS EN 14587. The result shows that the ratio of the hardness of the rail head near the weld line area to the hardness of the rail base metal at the same position of the high Jiang Guitou hardened pearlitic rail flash welding head formed by the method is 90%, the area ratio of the microstructure pearlitic is more than or equal to 90%, and a large amount of martensite abnormal structures are detected, so that the use requirement is not met.
Comparative example 2
The mass fraction of the C element, the mass fraction of the Si element and the mass fraction of the Mn element in the main chemical components of the rail materials used in this comparative example were 0.81%, 0.58% and 0.88%. The tensile strength at the gage angle of 12.7mm away from the tread and the side surface of the rail head of the steel rail is 1259MPa to 1380MPa, and the hardness at the depth of 25mm away from the surface of the outline of the rail head is 390HB to 420HB. Including two main processes of welding and post-weld heat treatment. The welding method is rail flash welding, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing upsetting, rapid pushing of the steel rail, and the like. The duration of the whole welding process was 400s. The method comprises the steps of carrying out short-circuit contact on a steel rail to be welded in a welding heating process mainly in an electrified state, heating the steel rail by utilizing heat generated by continuous lintel blasting formed between liquid metals on the end surfaces of the steel rail to be welded, wherein the voltage during continuous lintel blasting is 420V, the average current is 310A, the duration time is 350s, the opposite pressure applied to the two ends of the steel rail to be welded in the heating process is 180kN, and the consumption of the steel rail is 45mm; the rapid tumor pushing stage of the welding process adopts an integral profiling steel rail tumor pushing mechanism, and the time from the end of upsetting to the complete end of tumor pushing is 11s. After the welding is finished, special equipment is adopted to accelerate cooling of the top surface of the rail head, the side surface of the rail head and the jaw of the rail head near the welding line area of the rail joint. The initial cooling temperature at the head top face, head side face and head jaw was 700 ℃, the average cooling rate at the time of accelerated cooling was 50 ℃/s, and the end temperature of accelerated cooling was 400 ℃. The longitudinal section hardness test was performed on the joints 5mm and 25mm below the tread with reference to AS1085.20 standard, and the joint was examined for microstructure with reference to BS EN 14587. The result shows that the ratio of the hardness of the rail head in the near-weld line area to the hardness of the rail base metal in the same position of the high Jiang Guitou hardened pearlitic rail flash welding head formed by the method is 105% -115%, the area ratio of the microstructure pearlitic is more than or equal to 87%, a large amount of martensite abnormal structures are detected, and the use requirement is not met.
Comparative example 3
The mass fraction of the C element, the mass fraction of the Si element and the mass fraction of the Mn element in the main chemical components of the rail materials used in this comparative example were 0.81%, 0.58% and 0.88%. The tensile strength at the gage angle of 12.7mm away from the tread and the side surface of the rail head of the steel rail is 1259MPa to 1380MPa, and the hardness at the depth of 25mm away from the surface of the outline of the rail head is 390HB to 420HB. Including two main processes of welding and post-weld heat treatment. The welding method is rail flash welding, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing upsetting, rapid pushing of the steel rail, and the like. Throughout the welding process, the duration was 180s. The method comprises the steps of carrying out short-circuit contact on a steel rail to be welded in a welding heating process mainly in an electrified state, heating the steel rail by utilizing heat generated by continuous lintel blasting formed between liquid metals on the end surfaces of the steel rail to be welded, wherein the voltage during continuous lintel blasting is 340V, the average current is 50A, the duration time is 150s, the opposite pressure applied to the two ends of the steel rail to be welded in the heating process is 80kN, and the consumption of the steel rail is 10mm; the rapid tumor pushing stage of the welding process adopts an integral profiling steel rail tumor pushing mechanism, and the time from the end of upsetting to the complete end of tumor pushing is 5s. After the welding is finished, special equipment is adopted to accelerate cooling of the top surface of the rail head, the side surface of the rail head and the jaw of the rail head near the welding line area of the rail joint. The initial cooling temperature of the rail head top surface, the rail head side surface and the rail head jaw is more than 700 ℃, the average cooling speed during accelerated cooling is 4 ℃/s, and the final cooling temperature during accelerated cooling is 580 ℃. The longitudinal section hardness test was performed on the joints 5mm and 25mm below the tread with reference to AS1085.20 standard, and the joint was examined for microstructure with reference to BS EN 14587. The result shows that the ratio of the hardness of the rail head in the near-weld line area to the hardness of the rail base metal in the same position of the high Jiang Guitou hardened pearlitic rail flash welding head formed by the method is 78-85%, the serious collapse occurs, the area ratio of the microstructure pearlitic is more than or equal to 99%, and the use requirement is not met.
Comparative example 4
The mass fraction of the C element, the mass fraction of the Si element and the mass fraction of the Mn element in the main chemical components of the rail materials used in this comparative example were 0.78%, 0.50% and 0.89%. The tensile strength at the gage angle of 12.7mm away from the tread and the side surface of the rail head of the steel rail is 1175 MPa-1210 MPa, and the hardness at the depth of 25mm away from the surface of the outline of the rail head is 370 HB-385 HB. Including two main processes of welding and post-weld heat treatment. The welding method is rail flash welding, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing upsetting, rapid pushing of the steel rail, and the like. The duration of the whole welding process was 100s. The method comprises the steps of carrying out short-circuit contact on a steel rail to be welded in a welding heating process mainly in an electrified state, heating the steel rail by utilizing heat generated by continuous lintel blasting formed between liquid metals on the end surfaces of the steel rail to be welded, wherein the voltage during continuous lintel blasting is 320V, the average current is 40A, the duration is 80s, the opposite pressure applied to the two ends of the steel rail to be welded in the heating process is 50kN, and the consumption of the steel rail is 9mm; the rapid tumor pushing stage of the welding process adopts an integral profiling steel rail tumor pushing mechanism, and the time from the end of upsetting to the complete end of tumor pushing is 10s. After the welding is finished, special equipment is adopted to accelerate cooling of the top surface of the rail head, the side surface of the rail head and the jaw of the rail head near the welding line area of the rail joint. The initial cooling temperatures at the head top, head side and head jaw were about 550 c, the average cooling rate at accelerated cooling was 55 c/s, and the end temperature at accelerated cooling was 400 c. The longitudinal section hardness test was performed on the joints 5mm and 25mm below the tread with reference to AS1085.20 standard, and the joint was examined for microstructure with reference to BS EN 14587. The result shows that the ratio of the hardness of the rail head in the near-weld line area to the hardness of the rail base metal in the same position of the high Jiang Guitou hardened pearlitic rail flash welding head formed by the method is 80-90%, the serious collapse occurs, the area ratio of the microstructure pearlitic is more than or equal to 97%, and the use requirement is not met.
Those of ordinary skill in the art will appreciate that: the above discussion of any embodiment is merely exemplary and is not intended to imply that the scope of the disclosure of embodiments of the invention, including the claims, is limited to such examples; combinations of features of the above embodiments or in different embodiments are also possible within the idea of an embodiment of the invention, and there are many other variations of the different aspects of the embodiments of the invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, and the like, which are made within the spirit and principles of the embodiments of the invention, are included within the scope of the embodiments of the invention.
Claims (10)
1. A method of increasing the hardness of the interior of a rail head of a flash joint of a rail, comprising:
flash welding the rail, comprising: sequentially carrying out an electrifying and heating stage and a pressurizing and upsetting stage; wherein the voltage of the electrified heating stage is 340-410V, the average current is 50-300A, and the duration time is 150-300 s;
heat treating a flash welded rail comprising: and (3) performing accelerated cooling on the top surface, the side surface and the jaw of the rail head near the weld joint area of the rail joint, wherein the initial temperature of the accelerated cooling is more than 700 ℃, the end temperature is 430-500 ℃, and the average cooling speed is 5-35 ℃/s.
2. A method according to claim 1, characterized in that during the electrically heated phase, the opposing pressure applied to the ends of the rail to be welded is 80-160 kN and the rail consumption is 10-35 mm.
3. The method of claim 1, wherein flash welding the rail further comprises: the pressing upsetting stage is followed by a tumor pushing stage, and the time from the end of the pressing upsetting stage to the complete end of the tumor pushing stage is 5 to 10s.
4. The method according to claim 1, wherein the temperature of the two side rails in the region of 0-25 mm from the end face to be welded is 900-1650 ℃ and the duration is 180-350 s during the whole flash welding process.
5. The method according to claim 1, characterized in that the voltage of the energized heating phase is 400V, the average current is 200A, and the duration is 150s; the initial temperature of the accelerated cooling is 710 ℃, the final temperature is 480 ℃, and the average cooling speed is 25 ℃/s.
6. The method according to claim 1, characterized in that the voltage of the energized heating phase is 400V, the average current is 210A, and the duration is 200s; the initial temperature of the accelerated cooling is 770 ℃, the final temperature is 490 ℃, and the average cooling speed is 30 ℃/s.
7. The method according to claim 1, characterized in that the voltage of the energized heating phase is 340V, the average current is 50A, the duration is 150s; the termination temperature of the accelerated cooling is 430 ℃, and the average cooling speed is 5 ℃/s.
8. The method according to claim 1, characterized in that the voltage of the energized heating phase is 410V, the average current is 300A, and the duration is 300s; the termination temperature of the accelerated cooling is 500 ℃, and the average cooling speed is 35 ℃/s.
9. The method of claim 1, wherein the steel rail to be welded is a high-strength railhead hardened pearlitic steel rail, the mass fraction of the C element in the main chemical composition of the steel rail is 0.74-0.86%, the mass fraction of the Si element is 0.10-0.60%, the mass fraction of the Mn element is 0.75-1.25%, the mass fractions of the P element and the S element are all not more than 0.020%, the mass fraction of the Cr element is not more than 0.30%, and the mass fraction of the V element is not more than 0.01%; the tensile strength of the steel rail at the gauge angle is at least 1172MPa, and the hardness of the steel rail at the depth of 25mm from the surface of the outline of the rail head is more than or equal to 370HB.
10. A steel rail produced by the method of any one of claims 1 to 9, wherein the hardness of the head inner region of the near-bead region of the steel rail is 95% to 110% of the hardness of the head inner region of the base material of the steel rail, and wherein the pearlite area ratio in the microstructure of the head inner region of the near-bead region of the steel rail is 97% or more, wherein the head inner region is a region having a depth of 0 to 25mm from the head surface.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311153000.0A CN117161528A (en) | 2023-09-07 | 2023-09-07 | Method for improving internal hardness of rail head of steel rail flash welding head and steel rail |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311153000.0A CN117161528A (en) | 2023-09-07 | 2023-09-07 | Method for improving internal hardness of rail head of steel rail flash welding head and steel rail |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN117161528A true CN117161528A (en) | 2023-12-05 |
Family
ID=88931495
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311153000.0A Pending CN117161528A (en) | 2023-09-07 | 2023-09-07 | Method for improving internal hardness of rail head of steel rail flash welding head and steel rail |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN117161528A (en) |
-
2023
- 2023-09-07 CN CN202311153000.0A patent/CN117161528A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN114054915B (en) | Flash welding method for preheating short circuit | |
| Weingrill et al. | Temperature field evolution during flash butt welding of railway rails | |
| JP5531845B2 (en) | Post-heat treatment method near the flash butt weld | |
| EP2412472B1 (en) | Device and method for cooling welded rail section | |
| CN104520052A (en) | Lap welded member, automobile component, method for welding lapped part, and method for manufacturing lap welded member | |
| US20130153092A1 (en) | Method of production of welded joint | |
| WO2020238724A1 (en) | Construction method and cooling apparatus for post weld joint heat treatment of bainite steel rail | |
| CN109022750A (en) | The post weld heat treatment method of rail | |
| CN114054916B (en) | Gas conveying device and steel rail flash welding method | |
| WO2024093184A1 (en) | Method for improving bonding strength of rail flash-butt welded joint | |
| Kuchuk-Yatsenko et al. | The Paton Welding Journal 2020 № 07 | |
| CN117161528A (en) | Method for improving internal hardness of rail head of steel rail flash welding head and steel rail | |
| KR20110074136A (en) | Post weld heat treatment of high carbon steeel | |
| CN117161529A (en) | Method for increasing hardening thickness of rail head of steel rail flash welding head and steel rail | |
| WO2012100577A1 (en) | On-line process for enhancing performance of welding heat affected zone | |
| CN110438327A (en) | Hypo eutectoid steel rail weld joint heat treatment method | |
| CN117139802A (en) | Method for prolonging service life of rail head of steel rail flash welding head and steel rail | |
| CN117161527A (en) | Method for welding and heat treatment of deep hardened layer steel rail and steel rail | |
| CN117139803A (en) | Method for improving wear resistance of rail head of steel rail welding joint and steel rail | |
| CA2700100C (en) | Intermediate piece for connecting molded articles of manganese steel with carbon steel as well as method for connecting austenitic manganese steel casting pieces with standard rails | |
| CN110438328A (en) | A kind of hypo eutectoid steel rail weld joint heat treatment method | |
| AU2018303285B2 (en) | Frog for switches and crossings | |
| RU2797491C1 (en) | Method for welding the crosspiece made of manganese steel with a rail made of carbon steel | |
| US20240150971A1 (en) | Frog for switches and crossings | |
| RU2774792C1 (en) | Method for welding a manganese steel cross with a carbon steel rail |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |