Fixed flash welding process for R350HT high-strength heat-treated steel rail containing trace alloy elements

Abstract

The invention discloses a fixed flash welding process for an R350HT high-strength heat-treated steel rail containing trace alloying elements, which comprises the following steps: preparing a steel material of the steel rail, the chemical components of the steel material meeting the European standard EN13674 requirements, and the chemical components of the steel material in industrial production comprise the following components in percentage by mass: 0.76-0.80% of C; 0.50 to 0.58% of Si; 1.0 to 1.20 parts of Mn; p < = 0.020; s is less than or equal to 0.025; the steel rail comprises the following components in percentage by mass: 0.10-0.15% of Cr, 0.01-0.03% of V and the balance of Fe, a proper amount of the steel rail is added according to the limitation of residual elements of the components, and the components are subjected to smelting, continuous casting, steel billet slow cooling, rolling, heat treatment and the like to produce the steel rail. The size of a steel rail continuous casting billet is 280 mm * 380 mm, and the rolling section is 60E1.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical materials, and in particular relates to a flash welding process for fixing a R350HT high-strength heat-treated rail containing trace alloy elements. Background Art

[0002] According to the current welding situation of the railway bureau's rail welding base, during the flash welding process of rail fixing, the joint is the weak link of the entire line, and its quality can directly affect the safety of the railway.

[0003] In order to reduce the wear of rails, various means are used in the prior art to improve the strength and hardness of rails to improve wear resistance, such as increasing the C content in steel to a hypereutectoid component, increasing the density of cementite to increase its wear resistance, and then refining the pearlite structure and improving the hardness through full-section accelerated cooling (i.e., online heat treatment), while inhibiting the precipitation of free cementite to ensure sufficient toughness and plasticity of the so-called hypereutectoid heat-treated rails. However, the above rails are characterized in that their C content exceeds 0.70% and their organizational structure is pearlite. For pearlite rails, the strength of 1300MPa is basically close to the limit by combining alloying and heat treatment. If the strength is further increased, it is difficult to avoid the high-carbon brittle (lamellar or twin) martensitic structure that is not allowed to exist under such high carbon content. Since the martensitic structure in the matrix of the rail flash weld joint belongs to the hard-brittle phase, it has very high hardness and very low toughness. It is a special-shaped structure that has a more serious impact on the parent material and the joint during the rail welding production process. It is very easy to cause the rail to break, fall off or even peel off on the line, seriously affecting the safe operation of the train.

[0004] In view of the above factors, a fixed flash welding process for R350HT high-strength heat-treated rails containing trace alloy elements is provided, and the welding process is studied around R350HT high-strength heat-treated rails containing trace alloy elements. By designing reasonable welding process parameters based on the chemical composition and mechanical properties of the material, the R350HT welding process is formed, which has very important production and economic significance for increasing the service life of the rails. Summary of the invention

[0005] The object of the present invention is to provide a flash welding process for fixing a R350HT high-strength heat-treated rail containing trace alloy elements, so as to solve the problems raised in the above-mentioned background technology.

[0006] The object of the present invention is achieved through the following technical scheme: a flash welding process for fixing a R350HT high-strength heat-treated rail containing trace alloy elements, comprising a steel material for preparing the rail, the chemical composition of which must meet the requirements of industrial production, and the specific chemical composition by mass percentage is: C 0.76-0.80; Si 0.50-0.58; Mn 1.0-1.20; P≤0.020; S≤0.025; Cr0.10-0.15, V0.01-0.03, and the rest is Fe, with a total mass fraction of 100%;

[0007] The rails are produced by smelting, continuous casting, slow cooling of steel billets, rolling and heat treatment of the above components. The size of the rail continuous casting billet is 280mm×380mm, and the rolling section is 60E1;

[0008] The specific steps include:

[0009] A. Rail fixed flash welding

[0010] The rust on the rail ends of the 60E1 high-hardness rail produced by rolling is removed, and the rust on the end face of the rail to be welded and the surface of both sides of the rail waist within 300mm from the end face is removed to expose the metallic luster;

[0011] For the rust-removed rails, a ground roller is used every 5m to support them, so as to ensure that the rails to be welded are in a straight line longitudinally and are basically level. Before welding the main line, the screw is adjusted by the rotary welding machine to adjust the pre-arch amount of the rails. During the construction process, the pre-arch amount of the welding head is measured at any time and can be adjusted at any time according to needs;

[0012] GAAS80 / 580 fixed flash welder is used for rail welding. The oil temperature of the welder is controlled at about 40℃, the water temperature is controlled at about 20℃, and the grid voltage is between 416 and 425V.

[0013] During welding, place the rail between two pairs of electrodes of the welding machine and apply the cylinder clamping force F1 to clamp it. When the power is turned on, the welding frame clamps the rail forward under the action of the feeding force F2. The end faces of the rails are in contact and flash burning occurs continuously under the action of the current. When the temperature of the end of the rail reaches the predetermined process requirement, the clamping device of the welding machine drives the rail to close quickly and squeeze out the molten metal and impurities under the action of the upsetting pressure F2.

[0014] Air cool the high-temperature welded joint to below 200°C to ensure that every position of the joint undergoes a complete phase change. When the joint temperature is less than 300°C, the cooling can be accelerated appropriately.

[0015] B. Heat treatment after flash welding

[0016] Flash welding post-heat treatment uses split-type heating coils for heating. The coils are divided into two symmetrical left and right parts. The two coils are closed by the cylinder and then induction heating is performed.

[0017] After the induction heating is completed, the two coils are separated by the pull of the cylinder, and the cylinder positions the rail to ensure that the rail and the heating coil are kept at the same distance around them.

[0018] C. Flash welding post heat treatment mark

[0019] Each rail weld joint is marked after flash welding and heat treatment.

[0020] Furthermore, in the rail fixing flash welding, the rail weld seam amount is controlled between 8-10 mm, the arch amount is controlled between 0.35 and 0.55 mm, the flash welding preheating times are between 10 and 12 times, each preheating time is 1.5-2 s, and the interval time is 3-4 s.

[0021] Furthermore, in the rail fixing flash welding, the upsetting amount of flash welding is controlled between 10 and 13 mm, the upsetting force is controlled between 580 and 690 KN, the welding time is controlled between 130 and 140 s, and the final melting speed is controlled between 2.40 and 2.60 mm / s.

[0022] Furthermore, the control of the induction heating temperature measurement deviation in the fixed flash post-heat treatment of the rail adopts the Curie point temperature plus time control method;

[0023] The details include as follows:

[0024] After welding, the rail joint with residual temperature in the rail weld is heated. During the induction heating process, the rail passes through the Curie point temperature, which causes the induction heating speed to decrease and the electrical parameters to change. The position where the rail passes through the Curie point temperature is found, and based on the process from this position to the final heating temperature, the time limit and the upper and lower allowable deviations are set to ensure the quality of post-weld heat treatment.

[0025] Furthermore, the rail temperature before the rail fixing flash welding should not be lower than 10°C; the convex margin of the rail head and rail bottom and the slope of the top surface of the rail bottom of the welding joint should not be greater than 1mm, and the convex margin of other positions should not be greater than 2mm;

[0026] After embossing and without grinding, a ruler and feeler gauge should be used to check the misalignment of the joint. The misalignment of the joint should be measured and calculated at a position 15m on both sides of the center line of the weld.

[0027] Furthermore, the joint misalignment position rule is as follows:

[0028] When the position of the joint misalignment is in the vertical direction of the longitudinal center of the rail top surface, the maximum allowable value of the joint misalignment shall not exceed 0.5mm;

[0029] When the joint misalignment is in the horizontal direction 12mm-16mm below the top surface of the working side rail, the maximum allowable value of the joint misalignment shall not exceed 0.5mm;

[0030] When the joint misalignment is in the horizontal direction of the rail foot edge, the maximum allowable value of the joint misalignment shall not exceed 1.5mm.

[0031] Furthermore, the average hardness H of the rail fixed flash weld joint is J The average hardness of the base material H P The ratio satisfies: H J / H P ≥0.90, average hardness of joint soft spot H J1 The average hardness of the base material H P Ratio: HJ1 / HP≥0.81, softening area W≤20mm.

[0032] Furthermore, the flash welding post-heat treatment mark is located on the same side rail waist, 1m-3m away from the weld, and the mark should be identifiable within at least one maintenance cycle. The mark ensures that each finished rail welding joint can be traced according to various production records or information.

[0033] A fixed flash welding process for R350HT high-strength heat-treated rails containing trace alloy elements is applied to smelting R350HT rails with good strength and toughness ratio and excellent wear resistance, and is used to increase the service life of the rails during welding of R350HT rails.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention utilizes the characteristics of Baosteel's own ore and unique equipment for producing rails to smelt R350HT rails with good strength and toughness ratio and excellent wear resistance. Aiming at the fixed flash welding process, reasonable welding process parameters are designed through the chemical composition and mechanical properties of the materials to form the R350HT welding process, which has very important production and economic significance for increasing the service life of the rails.

[0036] The present invention is based on the R350HT high-strength heat-treated rail fixed flash welding process containing trace alloy elements to ensure that the ratio of the hardness average value HJ of the joint to the hardness average value HP of the base material satisfies: HJ / HP≥0.90, the ratio of the hardness average value HJ1 of the joint soft spot to the hardness average value HP of the base material satisfies: HJ1 / HP≥0.81, the softening area W≤20mm, the weld and the heat-affected zone are typical pearlite structures, there is no martensite, bainite or secondary cementite harmful structure, and all performances meet the standard requirements.

[0037] The present invention utilizes the R350HT high-strength heat-treated rail fixing flash welding process containing trace alloy elements to meet the requirements of heavy-duty railways for the smoothness of rail joints, improves the risk of "saddle-type" wear or fracture caused by abnormal microscopic structure of the joints due to excessive difference in hardness of the parent material in the welding area and the joint during the service of the line, and ensures that the high-hardness rails and joints meet the service requirements of heavy-duty railways and the safety of line operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the misalignment of the joint of the present invention;

[0039] Figure 2 It is a schematic diagram of fixed flash welding of the present invention;

[0040] Figure 3 It is a schematic diagram of sampling the longitudinal section of the joint of the present invention. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0042] like Figure 1-3 As shown, a flash welding process for fixing R350HT high-strength heat-treated rails containing trace alloy elements includes a steel material for preparing the rails, the chemical composition of which must meet the requirements of industrial production, and the specific chemical composition by mass percentage is: C 0.76-0.80; Si 0.50-0.58; Mn 1.0-1.20; P ≤ 0.020; S ≤ 0.025; Cr 0.10-0.15, V 0.01-0.03, and the rest is Fe, with a total mass fraction of 100%;

[0043] The rails are produced by smelting, continuous casting, slow cooling of steel billets, rolling and heat treatment of the above components. The size of the rail continuous casting billet is 280mm×380mm, and the rolling section is 60E1;

[0044] The specific steps include:

[0045] A. Rail fixed flash welding

[0046] The rust on the rail ends of the 60E1 high-hardness rail produced by rolling is removed, and the rust on the end face of the rail to be welded and the surface of both sides of the rail waist within 300mm from the end face is removed to expose the metallic luster;

[0047] For the rust-removed rails, a ground roller is used every 5m to support them, so as to ensure that the rails to be welded are in a straight line longitudinally and are basically level. Before welding the main line, the screw is adjusted by the rotary welding machine to adjust the pre-arch amount of the rails. During the construction process, the pre-arch amount of the welding head is measured at any time and can be adjusted at any time according to needs;

[0048] GAAS80 / 580 fixed flash welder is used for rail welding. The oil temperature of the welder is controlled at about 40℃, the water temperature is controlled at about 20℃, and the grid voltage is between 416 and 425V.

[0049] During welding, place the rail between two pairs of electrodes of the welding machine and apply the cylinder clamping force F1 to clamp it. When the power is turned on, the welding frame clamps the rail forward under the action of the feeding force F2. The end faces of the rails are in contact and flash burning occurs continuously under the action of the current. When the temperature of the end of the rail reaches the predetermined process requirement, the clamping device of the welding machine drives the rail to close quickly and squeeze out the molten metal and impurities under the action of the upsetting pressure F2.

[0050] Air cool the high-temperature welded joint to below 200°C to ensure that every position of the joint undergoes a complete phase change. When the joint temperature is less than 300°C, the cooling can be accelerated appropriately.

[0051] B. Heat treatment after flash welding

[0052] Flash welding post-heat treatment uses split-type heating coils for heating. The coils are divided into two symmetrical left and right parts. The two coils are closed by the cylinder and then induction heating is performed.

[0053] After the induction heating is completed, the two coils are separated by the pull of the cylinder, and the cylinder positions the rail to ensure that the rail and the heating coil are kept at the same distance around them.

[0054] C. Flash welding post heat treatment mark

[0055] Each rail weld joint is marked after flash welding and heat treatment. The mark is located on the same side of the rail waist, 1m-3m away from the weld. The mark should be identifiable within at least one maintenance cycle. The mark ensures that each rail weld joint can be traced back according to various production records or information. Specific embodiment one:

[0057] The C content of R350HT rail is relatively high. The fusion line and overheating zone in the fixed flash welding process are prone to segregation of elements such as C and Mn, microstructural defects and secondary cementite. Therefore, the welding process and joint heat treatment process parameters of high hardness rails are invented. The flash welding process and joint heat treatment process of 760E1 high hardness rails are determined by adjusting the preheating current, preheating times, top end amount, and tail burning rate for multiple times, combined with comparative analysis of joint mechanical properties and drop hammer results.

[0058] The main adjustment parameters of the welding process during the implementation of this embodiment and the corresponding joint hardness and drop hammer test results are shown in Table 1.

[0059] Table 1 Different welding processes and performance during implementation

[0060]

[0061] In the flash welding process of rails in Example 1, no fracture occurred during the drop hammer, and the joint hardness also met the requirements. Increasing the number of preheating times and increasing the amount of upsetting can squeeze out the oxidation products produced during the welding of the weld and minimize or eliminate gray spots. However, too many preheating times will increase the heat input during the flash welding process, causing serious carbon and alloy burnout in the fusion zone of the joint, further reducing the strength and hardness of the joint in the welded state.

[0062] Example 1 Joint longitudinal section (test line 1) test results

[0063]

[0064] The rails are produced by smelting, continuous casting, slow cooling of steel billets, rolling and heat treatment of C 0.76-0.80, Si 0.50-0.58, Mn 1.0-1.20, P≤0.020, S≤0.025, Cr0.10-0.15, V0.01-0.03, and the rest is Fe, with a mass fraction of more than 100%. The size of the continuous casting steel billet is 280mm×380mm, and the rolling section is 60E1. The rust is removed from the end of the 60E1 section high-hardness steel rail produced by rolling, and the rust is removed from the end face of the steel rail to be welded and the surface of both sides of the rail waist within 300mm from the end face to expose the metallic luster.

[0065] For the rust-removed rails, a ground roller is used every 5m to support them, so as to ensure that the rails to be welded are in a straight line longitudinally and are basically level. Before welding the main line, the screw is adjusted by the rotary welding machine to adjust the pre-arch amount of the rails. During the construction process, the pre-arch amount of the welding head is measured at any time and can be adjusted at any time according to needs;

[0066] GAAS80 / 580 fixed flash welder is used for rail welding. The oil temperature of the welder is controlled at about 40℃, the water temperature is controlled at about 20℃, and the grid voltage is between 416 and 425V.

[0067] During welding, place the rail between two pairs of electrodes of the welding machine and apply the cylinder clamping force F1 to clamp it. When the power is turned on, the welding frame clamps the rail forward under the action of the feeding force F2. The end faces of the rails are in contact and flash burning occurs continuously under the action of the current. When the temperature of the end of the rail reaches the predetermined process requirement, the clamping device of the welding machine drives the rail to close quickly and squeeze out the molten metal and impurities under the action of the upsetting pressure F2.

[0068] Air cool the high-temperature welded joint to below 200°C to ensure that every position of the joint undergoes a complete phase change. When the joint temperature is less than 300°C, the cooling can be accelerated appropriately.

[0069] Flash welding post-heat treatment uses split-type heating coils for heating. The coils are divided into two symmetrical left and right parts. The two coils are closed by the cylinder and then induction heating is performed.

[0070] After the induction heating is completed, the two coils are separated by the pull of the cylinder, and the cylinder positions the rail to ensure that the rail and the heating coil are kept at the same distance around them.

[0071] C. Flash welding post heat treatment mark

[0072] Each rail weld joint is marked after flash welding and heat treatment. The mark is located on the same side of the rail waist, 1m-3m away from the weld. The mark should be identifiable within at least one maintenance cycle. The mark ensures that each rail weld joint can be traced back according to various production records or information.

[0073] In the rail fixing flash welding, the rail weld seam amount is controlled between 8-10 mm, the arching amount is controlled between 0.35-0.55 mm, the flash welding preheating times are between 10-12 times, each preheating time is 1.5-2s, and the interval time is 3-4s.

[0074] In the rail fixing flash welding, the flash welding upsetting amount is controlled between 10 and 13 mm, the upsetting force is controlled between 580 and 690 KN, the welding time is controlled between 130 and 140 s, and the final melting speed is controlled between 2.40 and 2.60 mm / s.

[0075] The control of the induction heating temperature measurement deviation in the fixed flash post-heat treatment of the rail adopts the Curie point temperature plus time control method;

[0076] The details include as follows:

[0077] After welding, the rail joint with residual temperature in the rail weld is heated. During the induction heating process, the rail passes through the Curie point temperature, which causes the induction heating speed to decrease and the electrical parameters to change. The position where the rail passes through the Curie point temperature is found, and based on the process from this position to the final heating temperature, the time limit and the upper and lower allowable deviations are set to ensure the quality of post-weld heat treatment.

[0078] The rail temperature before the rail fixing flash welding should not be lower than 10°C; the convex margin of the rail head and rail bottom and the slope of the top surface of the rail bottom of the welding joint should not be greater than 1mm, and the convex margin of other positions should not be greater than 2mm;

[0079] After embossing and without grinding, a ruler and feeler gauge should be used to check the misalignment of the joint, and the misalignment of the joint should be measured and calculated at a position 15m on both sides of the center line of the weld.

[0080] The joint misalignment position rules are as follows:

[0081] When the position of the joint misalignment is in the vertical direction of the longitudinal center of the rail top surface, the maximum allowable value of the joint misalignment shall not exceed 0.5mm;

[0082] When the joint misalignment is in the horizontal direction 12mm-16mm below the top surface of the working side rail, the maximum allowable value of the joint misalignment shall not exceed 0.5mm;

[0083] When the joint misalignment is in the horizontal direction of the rail foot edge, the maximum allowable value of the joint misalignment shall not exceed 1.5mm.

[0084] The average hardness of the rail fixed flash weld joint is H J The average hardness of the base material H P The ratio satisfies: H J / H P ≥0.90, average hardness of joint soft spot H J1 The average hardness of the base material H P Ratio: HJ1 / HP≥0.81, softening area W≤20mm.

[0085] It can be seen from the process in the implementation that the average hardness H of the joint in Example 1 is J The average hardness of the base material H P The ratio satisfies: H J / H P ≥0.90, average hardness of joint soft spot H J1 The average hardness of the base material H PThe ratio is: HJ1 / HP≥0.81, the softening area W≤20mm, and all properties meet the standard requirements. The strength, hardness and toughness of the fixed flash welded joint of a chromium and vanadium microalloyed R350HT heat-treated rail obtained in Example 1 match the performance of the rail parent material, can meet the requirements of heavy-duty railways for the smoothness of rail joints, improve the risk of "saddle-shaped" wear or abnormal microstructure of the joint caused by the large difference in hardness of the parent material in the welding area and the joint during the service of the high-hardness rails on the line, and ensure that the high-hardness rails and joints meet the service requirements of heavy-duty railways and the safety of line operation. Specific embodiment 2:

[0087] A fixed flash welding process for R350HT high-strength heat-treated rails containing trace alloy elements is applied to smelting R350HT rails with good strength and toughness ratio and excellent wear resistance, and is used to increase the service life of the rails during welding of R350HT rails.

[0088] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0089] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A flash welding process for fixing R350HT high-strength heat-treated rails containing trace alloy elements, characterized in that: The chemical composition of the steel material used to prepare the rails must meet the requirements of industrial production. Specifically, the chemical composition by mass percentage is: C 0.76-0.80; Si 0.50-0.58; Mn 1.0-1.20; P ≤ 0.020; S ≤ 0.025; Cr 0.10-0.15, V 0.01-0.03, and the rest is Fe, with a total mass fraction of 100%; The rails are produced by smelting, continuous casting, slow cooling of steel billets, rolling and heat treatment of the above components. The size of the rail continuous casting billet is 280mm×380mm, and the rolling section is 60E1; The specific steps include: A. Rail fixed flash welding The rust on the rail ends of the 60E1 high-hardness rail produced by rolling is removed, and the rust on the end face of the rail to be welded and the surface of both sides of the rail waist within 300mm from the end face is removed to expose the metallic luster; For the rust-removed rails, a ground roller is used every 5m to support them, so as to ensure that the rails to be welded are in a straight line longitudinally and are basically level. Before welding the main line, the screw is adjusted by the rotary welding machine to adjust the pre-arch amount of the rails. During the construction process, the pre-arch amount of the welding head is measured at any time and can be adjusted at any time according to needs; GAAS80 / 580 fixed flash welder is used for rail welding. The oil temperature of the welder is controlled at about 40℃, the water temperature is controlled at about 20℃, and the grid voltage is between 416 and 425V. During welding, place the rail between two pairs of electrodes of the welding machine and apply the cylinder clamping force F1 to clamp it. When the power is turned on, the welding frame clamps the rail forward under the action of the feeding force F2. The end faces of the rails are in contact and flash burning occurs continuously under the action of the current. When the temperature of the end of the rail reaches the predetermined process requirement, the clamping device of the welding machine drives the rail to close quickly and squeeze out the molten metal and impurities under the action of the upsetting pressure F2. Air cool the high-temperature welded joint to below 200°C to ensure that every position of the joint undergoes a complete phase change. When the joint temperature is less than 300°C, the cooling can be accelerated appropriately. B. Heat treatment after flash welding Flash welding post-heat treatment uses split-type heating coils for heating. The coils are divided into two symmetrical left and right parts. The two coils are closed by the cylinder and then induction heating is performed. After the induction heating is completed, the two coils are separated by the pull of the cylinder, and the cylinder positions the rail to ensure that the rail and the heating coil are kept at the same distance around them. C. Flash welding post heat treatment mark Each rail weld joint is marked after flash welding and heat treatment.

2. The flash welding process for fixing the R350HT high-strength heat-treated rail containing trace alloy elements according to claim 1 is characterized in that: In the rail fixing flash welding, the rail weld seam amount is controlled between 8-10 mm, the arching amount is controlled between 0.35-0.55 mm, the flash welding preheating times are between 10-12 times, each preheating time is 1.5-2s, and the interval time is 3-4s.

3. The flash welding process for fixing the R350HT high-strength heat-treated rail containing trace alloy elements according to claim 2 is characterized in that: In the rail fixing flash welding, the flash welding upsetting amount is controlled between 10 and 13 mm, the upsetting force is controlled between 580 and 690 KN, the welding time is controlled between 130 and 140 s, and the final melting speed is controlled between 2.40 and 2.60 mm / s.

4. The flash welding process for fixing the R350HT high-strength heat-treated rail containing trace alloy elements according to claim 3 is characterized in that: The control of the induction heating temperature measurement deviation in the fixed flash post-heat treatment of the rail adopts the Curie point temperature plus time control method; The details include as follows: After welding, the rail joint with residual temperature in the rail weld is heated. During the induction heating process, the rail passes through the Curie point temperature, which causes the induction heating speed to decrease and the electrical parameters to change. The position where the rail passes through the Curie point temperature is found, and based on the process from this position to the final heating temperature, the time limit and the upper and lower allowable deviations are set to ensure the quality of post-weld heat treatment.

5. The flash welding process for fixing the R350HT high-strength heat-treated rail containing trace alloy elements according to claim 4 is characterized in that: The rail temperature before the rail fixing flash welding should not be lower than 10°C; the convex margin of the rail head and rail bottom and the slope of the top surface of the rail bottom of the welding joint should not be greater than 1mm, and the convex margin of other positions should not be greater than 2mm; After embossing and without grinding, a ruler and feeler gauge should be used to check the misalignment of the joint. The misalignment of the joint should be measured and calculated at a position 15m on both sides of the center line of the weld.

6. The flash welding process for fixing the R350HT high-strength heat-treated rail containing trace alloy elements according to claim 5 is characterized in that: The joint misalignment position rules are as follows: When the position of the joint misalignment is in the vertical direction of the longitudinal center of the rail top surface, the maximum allowable value of the joint misalignment shall not exceed 0.5mm; When the joint misalignment is in the horizontal direction 12mm-16mm below the top surface of the working side rail, the maximum allowable value of the joint misalignment shall not exceed 0.5mm; When the joint misalignment is in the horizontal direction of the rail foot edge, the maximum allowable joint misalignment shall not exceed 1.5mm.

7. The flash welding process for fixing R350HT high-strength heat-treated rails containing trace alloy elements according to claim 6 is characterized in that: The average hardness of the rail fixed flash weld joint is H J Average hardness of base material H P The ratio satisfies: H J / H P ≥0.90, average hardness of joint soft spot H J1 Average hardness of base material H P Ratio: HJ1 / HP≥0.81, softening area W≤20mm.

8. The flash welding process for fixing R350HT high-strength heat-treated rails containing trace alloy elements according to claim 7 is characterized in that: The flash welding post-heat treatment mark is located on the same side rail waist, 1m-3m away from the weld. The mark should be identifiable within at least one maintenance cycle. The mark ensures that each finished rail welding joint can be traced according to various production records or information.

9. A fixed flash welding process for R350HT high-strength heat-treated rails containing trace alloy elements according to any one of claims 1 to 8 is used in smelting R350HT rails with good strength and toughness ratio and excellent wear resistance, and in increasing the service life of the rails during welding of R350HT rails.

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