CN117139802A - Method for prolonging service life of rail head of steel rail flash welding head and steel rail - Google Patents

Method for prolonging service life of rail head of steel rail flash welding head and steel rail Download PDF

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Publication number
CN117139802A
CN117139802A CN202311148487.3A CN202311148487A CN117139802A CN 117139802 A CN117139802 A CN 117139802A CN 202311148487 A CN202311148487 A CN 202311148487A CN 117139802 A CN117139802 A CN 117139802A
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China
Prior art keywords
rail
stage
head
steel rail
cooling
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CN202311148487.3A
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Chinese (zh)
Inventor
陆鑫
王若愚
邓健
黄洁
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Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
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Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
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Priority to CN202311148487.3A priority Critical patent/CN117139802A/en
Publication of CN117139802A publication Critical patent/CN117139802A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/04—Flash butt welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/36—Auxiliary equipment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01B—PERMANENT WAY; PERMANENT-WAY TOOLS; MACHINES FOR MAKING RAILWAYS OF ALL KINDS
    • E01B11/00—Rail joints
    • E01B11/44—Non-dismountable rail joints; Welded joints
    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01B—PERMANENT WAY; PERMANENT-WAY TOOLS; MACHINES FOR MAKING RAILWAYS OF ALL KINDS
    • E01B5/00—Rails; Guard rails; Distance-keeping means for them
    • E01B5/02—Rails
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

The invention discloses a method for prolonging the service life 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: the method comprises the steps of sequentially performing a first cooling stage, a heating stage, a heat preservation stage and a second cooling stage, wherein the end temperature of the first cooling stage is 25-100 ℃, the end temperature of the heating stage is 800-1100 ℃, the temperature interval maintained by the heat preservation stage is 800-950 ℃, and the start temperature of the second cooling stage is greater than or equal to 800 ℃ and the end temperature is 420-480 ℃. 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

Method for prolonging service life of rail head of steel rail flash welding head and steel rail
Technical Field
The invention relates to the technical field of steel rail welding, in particular to a method for prolonging the service life 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 prolonging the service life 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 extending the useful life of a rail head of a rail flash head is provided, 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: the method comprises the steps of sequentially performing a first cooling stage, a heating stage, a heat preservation stage and a second cooling stage, wherein the end temperature of the first cooling stage is 25-100 ℃, the end temperature of the heating stage is 800-1100 ℃, the temperature interval maintained by the heat preservation stage is 800-950 ℃, and the start temperature of the second cooling stage is greater than or equal to 800 ℃ and the end temperature is 420-480 ℃.
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 average cooling rate of the first cooling stage is 5-10 ℃/s.
According to one embodiment of the invention, in the heating stage, the top surface of the rail head, the side surface of the rail head and the jaw of the rail head near the weld joint area of the rail joint are heated, and the average temperature rise speed is 2-30 ℃/s.
According to one embodiment of the invention, in the heat preservation stage, the top surface of the rail head and the jaw of the rail head near the welding line area of the rail joint are subjected to heat preservation, and the heat preservation time is 50-200 s.
According to one embodiment of the invention, in said second cooling phase, the head top and head side surfaces are accelerated cooled, the head top surface having an average cooling rate of 30-40 ℃/s and the head side surface having an average cooling rate of 15-25 ℃/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 prolonging the service life 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 (particularly the parameters such as voltage, current, time and the like in the electrified heating stage) of the flash welding process and by carrying out fine phased control and reasonable design parameters in 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 expressions of "first" and "second" are used to distinguish two entities with the same name but different entities or different parameters, so that "first" is visible "
The "second" is merely for convenience of description and should not be construed as limiting the embodiments of the present invention, which are not described in detail in the subsequent embodiments.
The invention provides a method for prolonging the service life of a rail head of a steel rail flash welding head, which is characterized by comprising 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: the method comprises the steps of sequentially performing a first cooling stage, a heating stage, a heat preservation stage and a second cooling stage, wherein the end temperature of the first cooling stage is 25-100 ℃, the end temperature of the heating stage is 800-1100 ℃, the temperature interval maintained by the heat preservation stage is 800-950 ℃, and the start temperature of the second cooling stage is greater than or equal to 800 ℃ and the end temperature is 420-480 ℃.
In 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 (particularly the parameters such as voltage, current, time and the like in the electrified heating stage) of the flash welding process and by carrying out fine phased control and reasonable design parameters in the post-welding heat treatment process, so that the wear resistance and the service life of the steel rail welding head are improved.
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 prolonging the service life 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.
In the embodiment of the invention, the postweld heat treatment process mainly comprises 4 stages of a first cooling stage, a heating stage, a heat preservation stage, a second cooling stage and the like, and the next stage is started after the former stage is ended. The foregoing defines the starting temperature, the ending temperature and/or the soak temperature for each stage.
In some embodiments, the first cooling stage has an average cooling rate of 5 to 10 ℃/s.
In some embodiments, during the heating stage, special equipment may be used to heat the top surface of the head, the side surface of the head and the jaw of the head near the weld zone of the rail joint, with an average temperature rise rate of 2-30 ℃/s.
In some embodiments, in the heat preservation stage, special equipment can be used for preserving heat of the top surface of the rail head and the jaw of the rail head near the welding line area of the rail joint, and the heat preservation time is 50-200 s.
In some embodiments, during the second cooling stage, special equipment may be used to accelerate cooling of the head top surface and the head side surface, with an average cooling rate of 30-40 ℃/s for the head top surface and 15-25 ℃/s for the head side surface.
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. The initial temperature of the first cooling stage of the heat treatment process is the temperature at the end of the welding process. Because the thicknesses of all areas of the full section of the steel rail are different, the rates of all areas are different under the natural cooling condition, and in order to ensure that the joint does not generate martensite, bainite and other structural phase changes in the cooling process of the first cooling stage, the cooling rate of the first cooling stage needs to be controlled to be 5-10 ℃/s; the end temperature of the cooling in the first cooling stage is controlled to be 25-100 ℃ so as to ensure that the surface and the core of the rail joint are all converted into pearlite. The main function of the heating stage is to make the joint area cooled to 25-100 ℃ and completely subjected to pearlite transformation re-transform into austenite, and in order to ensure that the temperatures of the interior and the exterior of the joint and the areas of the whole section are uniform, the temperature rise speed of the heating stage needs to be controlled to be 2-30 ℃/s. After the steel rail is heated to the expected temperature, the heat preservation treatment is carried out on the joint to further ensure that the temperature of the whole section of the steel rail is uniform, the heat preservation temperature is too high, the time is too long, and the width of a heat affected zone of the joint can be widened; the heat preservation temperature is too low and the soaking effect can not be achieved in a time span, so that the time for carrying out heat preservation 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 line area of the rail joint is 50-200 s, and the temperature interval is 800-950 ℃. The cooling process of the second cooling stage has the effects of rapidly cooling the tread area of the rail head, increasing the supercooling degree of the cooling process, enhancing the transformation driving force of austenite to low-temperature tissue transformation, enabling the supercooled austenite tissue to be completely transformed into pearlite tissue, and achieving the purpose of refining the interlayer spacing of austenite grains and pearlite, so that the initial temperature of the second cooling stage is more than or equal to 800 ℃ and the end temperature is 420-480 ℃. In order to refine the core structure of the joint rail head far from the tread and improve the hardness, the cooling strength of the rail head side face and the rail head jaw is required to be enhanced. The air cooling strength of the rail head top surface can be properly reduced to avoid the occurrence of the harmful phase transformation processes of martensite, bainite and the like by supplementing the cooling of the rail head side surface and the rail head jaw. Therefore, the rail head top surface and the rail head side surface are subjected to accelerated cooling, the average cooling speed of the rail head top surface is 30-40 ℃/s, and the average cooling speed of the rail head side surface is 15-25 ℃/s.
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 heating temperature, cooling/temperature rise rate, cooling termination temperature in the above-described process defined by the present invention act synergistically to achieve the heat treatment effect as described above.
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 area ratio of pearlite 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 prolonging the service life of the steel rail flash welding head.
The following is a description of specific examples and comparative examples.
Example 1
The mass fraction of C element in the main chemical components of the test steel rail used in the embodiment is 0.74%, the mass fraction of Si element is 0.60%, the mass fraction of Mn element is 0.75%, the mass fraction of P element and S element are 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 minimum tensile strength at the track gauge angle of 12.7mm from the tread and the side face of the rail head of the steel rail is 1200MPa, and the minimum hardness at the depth of 25mm from the surface of the profile of the rail head is 375HB, comprising two main processes of welding and post-welding heat treatment. The welding method is flash welding of the steel rail, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing and upsetting, rapid pushing of the steel rail and the like. In the whole welding process, the temperature of the steel rails at the two sides, which are 0-25 mm away from the end face of the steel rail to be welded, is 900-1650 ℃ and the duration time is 200s. And in the heating stage in the welding process, the steel rail to be welded is mainly in short-circuit contact under the electrified state, 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. The voltage during continuous lintel blasting is 380V, the average current is 80A, and the duration is 150s; when the continuous lintel in the heating stage is exploded, the opposite pressure applied by the two ends of the steel rail to be welded is 100kN, and the consumption of the steel rail is 25mm. The rapid pushing stage in the welding process adopts an integral profiling steel rail pushing mechanism. In order to ensure the quality of the joint and the effect of the subsequent post-welding heat treatment, the time from the end of upsetting to the complete end of pushing the tumor is 7s. And performing postweld heat treatment after welding, wherein the postweld heat treatment process mainly comprises 4 stages of cooling in a first stage, heating, heat preservation, cooling in a second stage and the like, and entering the next stage after the former stage is finished. The average cooling speed of the first cooling stage of the postweld heat treatment process is 8 ℃/s, and the cooling termination temperature is 80 ℃; a heating stage of the post-welding heat treatment process, wherein special equipment is adopted to heat the top surface, the side surface and the jaw of the rail head near the weld joint area of the rail joint, the average temperature rise speed of the heating process is 10 ℃/s, and the termination temperature of the heating stage is 1000 ℃; in the heat preservation stage of the postweld heat treatment process, special equipment is adopted to preserve heat of the top surface of the rail head and the jaw of the rail head near the weld zone of the rail joint, the maintained temperature is 900 ℃, and the heat preservation time is 100s; in the second cooling stage of the post-welding heat treatment process, special equipment is adopted to accelerate cooling of the top surface of the rail head, the initial temperature of the accelerated cooling is 900 ℃, the average cooling speed of the top surface of the rail head during accelerated cooling is 35 ℃/s, the average cooling speed of the side surface of the rail head during accelerated cooling is 15 ℃/s, and the final temperature of the accelerated cooling is 460 ℃. 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%, and the area ratio of the microstructure pearlitic is more than or equal to 97%.
Example 2
The mass fraction of C element in the main chemical components of the test steel rail used in the embodiment is 0.86%, the mass fraction of Si element is 0.10%, the mass fraction of Mn element is 1.25%, the mass fraction of P element and S element are 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 minimum tensile strength at the track gauge angle of 12.7mm from the tread and the side face of the rail head of the steel rail is 1300MPa, and the minimum hardness at the depth of 25mm from the surface of the outline of the rail head is 385HB, which comprises two main processes of welding and post-welding heat treatment. The welding method is flash welding of the steel rail, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing and upsetting, rapid pushing of the steel rail and the like. In the whole welding process, the temperature of the steel rails at the two sides, which are 0-25 mm away from the end face of the steel rail to be welded, is 900-1650 ℃ and the duration is 180s. And in the heating stage in the welding process, the steel rail to be welded is mainly in short-circuit contact under the electrified state, 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. The voltage during continuous lintel blasting is 340V, the average current is 50A, and the duration is 150s; when the continuous lintel in the heating stage is exploded, the opposite pressure applied by the two ends of the steel rail to be welded is 160kN, and the consumption of the steel rail is 10mm. The rapid pushing stage in the welding process adopts an integral profiling steel rail pushing mechanism. In order to ensure the quality of the joint and the effect of the subsequent post-welding heat treatment, the time from the end of upsetting to the complete end of pushing the tumor is 5-10 s. And performing postweld heat treatment after welding, wherein the postweld heat treatment process mainly comprises 4 stages of cooling in a first stage, heating, heat preservation, cooling in a second stage and the like, and entering the next stage after the former stage is finished. The average cooling speed of the first cooling stage of the postweld heat treatment process is 5 ℃/s, and the cooling termination temperature is 25 ℃; a heating stage of the post-welding heat treatment process, wherein special equipment is adopted to heat the top surface, the side surface and the jaw of the rail head near the weld joint area of the rail joint, the average temperature rise speed of the heating process is 2 ℃/s, and the termination temperature of the heating stage is 800 ℃; in the heat preservation stage of the postweld heat treatment process, special equipment is adopted to preserve heat of the top surface of the rail head and the jaw of the rail head near the weld zone of the rail joint, the maintained temperature is 800 ℃, and the heat preservation time is 50s; in the second cooling stage of the post-welding heat treatment process, special equipment is adopted to accelerate cooling of the top surface of the rail head, the initial temperature of the accelerated cooling is 800 ℃, the average cooling speed of the top surface of the rail head during accelerated cooling is 30 ℃/s, the average cooling speed of the side surface of the rail head during accelerated cooling is 15 ℃/s, and the end temperature of the accelerated cooling is 480 ℃. 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%, and the area ratio of the microstructure pearlitic is more than or equal to 98%.
Example 3
The mass fraction of C element in the main chemical components of the test steel rail used in the embodiment is 0.76%, the mass fraction of Si element is 0.55%, the mass fraction of Mn element is 1.05%, the mass fraction of P element and S element are 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 minimum tensile strength at the track gauge angle of 12.7mm from the tread and the side face of the rail head of the steel rail is 1250MPa, and the minimum hardness at the depth of 25mm from the surface of the outline of the rail head is 390HB, comprising two main processes of welding and post-welding heat treatment. The welding method is flash welding of the steel rail, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing and upsetting, rapid pushing of the steel rail and the like. In the whole welding process, the temperature of the steel rail at the two sides which are 0-25 mm away from the end face of the steel rail to be welded is 900-1650 ℃ and the duration time is 250s. And in the heating stage in the welding process, the steel rail to be welded is mainly in short-circuit contact under the electrified state, 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. The voltage during continuous lintel blasting is 380V, the average current is 200A, and the duration is 210s; when the continuous lintel in the heating stage is exploded, the opposite pressure applied by the two ends of the steel rail to be welded is 100kN, and the consumption of the steel rail is 25mm. The rapid pushing stage in the welding process adopts an integral profiling steel rail pushing mechanism. In order to ensure the quality of the joint and the effect of the subsequent post-welding heat treatment, the time from the end of upsetting to the complete end of pushing the tumor is 10s. And performing postweld heat treatment after welding, wherein the postweld heat treatment process mainly comprises 4 stages of cooling in a first stage, heating, heat preservation, cooling in a second stage and the like, and entering the next stage after the former stage is finished. The average cooling speed of the first cooling stage of the postweld heat treatment process is 10 ℃/s, and the cooling termination temperature is 80 ℃; a heating stage of the post-welding heat treatment process, wherein special equipment is adopted to heat the top surface, the side surface and the jaw of the rail head near the weld joint area of the rail joint, the average temperature rise speed of the heating process is 25 ℃/s, and the termination temperature of the heating stage is 950 ℃; in the heat preservation stage of the postweld heat treatment process, special equipment is adopted to preserve heat of the top surface of the rail head and the jaw of the rail head near the weld zone of the rail joint, the maintained temperature is 950 ℃, and the heat preservation time is 120s; in the second cooling stage of the post-welding heat treatment process, special equipment is adopted to accelerate cooling of the top surface of the rail head, the initial temperature of the accelerated cooling is 950 ℃, the average cooling speed of the top surface of the rail head during accelerated cooling is 35 ℃/s, the average cooling speed of the side surface of the rail head during accelerated cooling is 20 ℃/s, and the final temperature of the accelerated cooling is 460 ℃. 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 99%, and the area ratio of the microstructure pearlitic is more than or equal to 98%.
Comparative example 1
The mass fraction of C element in the main chemical composition of the test steel rail used in the comparative example is 0.74%, the mass fraction of Si element is 0.60%, the mass fraction of Mn element is 0.75%, the mass fraction of P element and S element are 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 minimum tensile strength at the track gauge angle of 12.7mm from the tread and the side face of the rail head of the steel rail is 1200MPa, and the minimum hardness at the depth of 25mm from the surface of the profile of the rail head is 375HB, comprising two main processes of welding and post-welding heat treatment. The welding method is flash welding of the steel rail, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing and upsetting, rapid pushing of the steel rail and the like. In the whole welding process, the temperature of the steel rail at the two sides which are 0-25 mm away from the end face of the steel rail to be welded is 900-1650 ℃ and the duration time is 400s. And in the heating stage in the welding process, the steel rail to be welded is mainly in short-circuit contact under the electrified state, 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. The voltage during continuous lintel blasting is 410V, the average current is 350A, and the duration is 350s; when the continuous lintel in the heating stage is exploded, the opposite pressure applied by the two ends of the steel rail to be welded is 180kN, and the consumption of the steel rail is 38mm. The rapid pushing stage in the welding process adopts an integral profiling steel rail pushing mechanism. In order to ensure the quality of the joint and the effect of the subsequent post-welding heat treatment, the time from the end of upsetting to the complete end of pushing the tumor is 8s. And performing postweld heat treatment after welding, wherein the postweld heat treatment process mainly comprises 4 stages of cooling in a first stage, heating, heat preservation, cooling in a second stage and the like, and entering the next stage after the former stage is finished. The average cooling speed of the first cooling stage of the postweld heat treatment process is 10 ℃/s, and the cooling termination temperature is 100 ℃; a heating stage of a post-welding heat treatment process, wherein special equipment is adopted to heat the top surface, the side surface and the jaw of the rail head near the weld joint area of the rail joint, the average temperature rise speed of the heating process is 1 ℃/s, and the termination temperature of the heating stage is 1200 ℃; in the heat preservation stage of the postweld heat treatment process, special equipment is adopted to preserve heat of the top surface of the rail head and the jaw of the rail head near the weld zone of the rail joint, the maintained temperature interval is 900 ℃, and the heat preservation time is 300s; in the second cooling stage of the post-welding heat treatment process, special equipment is adopted to accelerate cooling of the top surface of the rail head, the initial temperature of the accelerated cooling is 900 ℃, the average cooling speed of the top surface of the rail head during accelerated cooling is 20 ℃/s, the average cooling speed of the side surface of the rail head during accelerated cooling is 10 ℃/s, and the final temperature of the 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 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%, the area ratio of the microstructure pearlitic area is more than or equal to 97%, and the joint is severely collapsed and does not meet the requirements.
Comparative example 2
The mass fraction of C element, the mass fraction of Si element, the mass fraction of Mn element, the mass fraction of P element and S element in the main chemical components of the test steel rail used in the comparative example are respectively 0.86%, 0.10%, 1.25%, 0.020%, 0.30% and 0.01%. The minimum tensile strength at the track gauge angle of 12.7mm from the tread and the side face of the rail head of the steel rail is 1300MPa, and the minimum hardness at the depth of 25mm from the surface of the outline of the rail head is 385HB, comprising two main processes of welding and post-welding heat treatment. The welding method is flash welding of the steel rail, and the welding process mainly comprises 4 stages of electrode clamping, electrifying and heating, pressurizing and upsetting, rapid pushing of the steel rail and the like. In the whole welding process, the temperature of the steel rail at the two sides which are 0-25 mm away from the end face of the steel rail to be welded is 900-1650 ℃ and the duration time is 150s. And in the heating stage in the welding process, the steel rail to be welded is mainly in short-circuit contact under the electrified state, 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. The voltage during continuous lintel blasting is 380V, the average current is 200A, and the duration is 100s; when the continuous lintel in the heating stage is exploded, the opposite pressure applied by the two ends of the steel rail to be welded is 70kN, and the consumption of the steel rail is 9mm. The rapid pushing stage in the welding process adopts an integral profiling steel rail pushing mechanism. In order to ensure the quality of the joint and the effect of the subsequent post-welding heat treatment, the time from the end of upsetting to the complete end of pushing the tumor is 8s. And performing postweld heat treatment after welding, wherein the postweld heat treatment process mainly comprises 4 stages of cooling in a first stage, heating, heat preservation, cooling in a second stage and the like, and entering the next stage after the former stage is finished. The average cooling speed of the first cooling stage of the postweld heat treatment process is 12 ℃/s, and the cooling termination temperature is 20 ℃; a heating stage of the post-welding heat treatment process, wherein special equipment is adopted to heat the top surface, the side surface and the jaw of the rail head near the weld joint area of the rail joint, the average temperature rise speed of the heating process is 10 ℃/s, and the termination temperature of the heating stage is 900 ℃; in the heat preservation stage of the postweld heat treatment process, special equipment is adopted to preserve heat of the top surface of the rail head and the jaw of the rail head near the weld zone of the rail joint, the maintained temperature interval is 900 ℃, and the heat preservation time is 40s; in the second cooling stage of the post-welding heat treatment process, special equipment is adopted to accelerate cooling of the top surface of the rail head, the initial temperature of the accelerated cooling is 900 ℃, the average cooling speed of the top surface of the rail head during accelerated cooling is 45 ℃/s, the average cooling speed of the side surface of the rail head during accelerated cooling is 30 ℃/s, and the final temperature of the accelerated cooling is 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 1,20%, the area ratio of the microstructure pearlitic area is more than or equal to 87%, and the joint has a large amount of martensitic structure, so that the 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 extending the life of a rail head of a flash bond head for 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: the method comprises the steps of sequentially performing a first cooling stage, a heating stage, a heat preservation stage and a second cooling stage, wherein the end temperature of the first cooling stage is 25-100 ℃, the end temperature of the heating stage is 800-1100 ℃, the temperature interval maintained by the heat preservation stage is 800-950 ℃, and the start temperature of the second cooling stage is greater than or equal to 800 ℃ and the end temperature is 420-480 ℃.
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 average cooling rate of the first cooling stage is 5-10 ℃/s.
6. The method of claim 1, wherein during the heating phase, the rail joint is heated near the head top surface, the head side surface, and the head jaw of the weld zone at an average temperature rise rate of 2 to 30 ℃/s.
7. The method of claim 1, wherein the heat is maintained at the top surface of the head and the jaw of the head near the weld of the rail joint for a period of 50 to 200 seconds during the heat maintaining period.
8. The method of claim 1, wherein in the second cooling stage, the head top surface and the head side surfaces are accelerated cooled, the head top surface having an average cooling rate of 30 to 40 ℃/s and the head side surfaces having an average cooling rate of 15 to 25 ℃/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.
CN202311148487.3A 2023-09-07 2023-09-07 Method for prolonging service life of rail head of steel rail flash welding head and steel rail Pending CN117139802A (en)

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