CN115780979B - A flash welding and joint heat treatment process for pearlite rails containing Cr, Nb and RE - Google Patents
A flash welding and joint heat treatment process for pearlite rails containing Cr, Nb and RE Download PDFInfo
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Abstract
The invention discloses a flash welding and joint heat treatment process of a pearlitic steel rail containing Cr, nb and RE, which comprises a flash welding process and a joint heat treatment process. After the flash welding head process and the joint heat treatment process are used, the normal pearlite structure of the pearlite steel rail joint containing Cr, nb and RE can be ensured, abnormal structures such as bainite, martensite and the like do not exist, the problems of low hardness, poor drop hammer performance and low joint collapse of the high-strength and high-hardness steel rail joint are solved, the performance matching of the steel rail joint and a base metal can be effectively improved, the comprehensive mechanical performance and the contact fatigue performance of the joint are improved, and the service performance of the joint is effectively improved.
Description
Technical Field
The invention relates to the technical field of steel rail welding, in particular to a flash welding and joint heat treatment process for a pearlitic steel rail containing Cr, nb and RE.
Background
Flash welding is widely applied to the production of long rails of 500 meters as one of important connection modes of steel rails. The welding performance of the steel is mainly affected by the chemical components of the steel, the research and development of the pearlitic steel rail in China all belong to the category of high carbon, low silicon and medium manganese, and alloy strengthening elements such as chromium, alum and the like are added according to different strength and hardness requirements. As the high-strength and high-hardness pearlite steel rail for heavy haul railways has high carbon content, the welding performance is poor, and the weld performance is mainly characterized in that ① welding overheat areas have more defects, and the overheat areas of flash welding have carbon-manganese component segregation along austenite grain boundaries, so that abnormal microstructures such as bainite or martensite appear on joints in a supercooled state, and the brittleness of the joints is increased. ② The grain size of the welding heat affected zone is obviously increased due to the cyclic heating of the welding heat affected zone, and the toughness of the flash welding joint is reduced due to the unbalanced process of rapid heating and cooling of the joint, so that the joint impact is only about 50% of that of a base metal, and the risk of rail breakage at the joint is easy to occur when a rail line is in service. ③ Because of the burning loss of carbon and alloy in the welding process, the mechanical property of the joint is obviously reduced, particularly the hardness of the joint is obviously reduced, the joint is poorer in performance matching with a base metal, the characteristics of high strength and high hardness of the steel rail for a heavy-duty line cannot be reflected, saddle-shaped abrasion and joint stripping and blocking phenomena can occur in the line service process, and the smoothness of a seamless line is seriously influenced.
The steel rail flash welding process and the joint heat treatment process directly influence the joint organization performance and the service state. The defects of over-burning, unwelded joint, excessive gray spots, liquefied cracks and the like of the joint can be caused by improper flash welding process, the metallographic grain size of the joint is coarser and only about 1-2 grades in the welding state, and the joint performance is poor. The weld joint is subjected to normalizing heat treatment, the microstructure of the weld joint is obviously refined, the grain size is increased from level 1 to more than level 8, the toughness of the flash welding joint is well improved, but the weld joint heat treatment process is improper, such as the characteristics of high and low heating temperature, high and low heating speed, nonuniform high-temperature residence time, nonuniform temperature distribution, continuous cooling under air cooling conditions and the like, the joint, especially a heat affected zone, is easy to have coarse structure, even easy to form martensite and other harmful structures, the joint is easy to have hardening, embrittlement and other phenomena, and the joint is extremely easy to break under the action of wheel rail stress in the line service process, thus becoming a weak link of line operation.
Aiming at the high-strength and high-hardness pearlitic steel rail flash welding containing Cr, nb and RE for heavy haul railways and the joint heat treatment process, the invention can ensure that the joints are all normal pearlitic structures and have no abnormal structures such as bainite, martensite and the like. The problems of low hardness, poor drop hammer performance and low joint collapse of the high-strength high-hardness pearlitic steel rail joint containing Cr, nb and RE are solved, and the excellent joint matched with the base material performance is obtained, so that the joint performance meets the requirements for the mechanical performance and drop hammer inspection of the joint in the section 2 of welding of TB/T1632.2-2014 steel rail, namely flash welding.
The patent with publication number CN201810708275.9 discloses a heat treatment method of a steel rail flash welding head, which is characterized in that the welding joint of an hypereutectoid steel rail and a different steel rail of the eutectoid steel rail is directly subjected to three-stage controlled cooling after welding, the temperature of the joint in a high-temperature welding state is reduced from 1000-1400 ℃ to 650-720 ℃, the temperature of the first cooling stage is reduced to 350-410 ℃, and the temperature of the third cooling stage is reduced to 10-30 ℃. The invention is aimed at welding of a steel rail movable flash welding machine, the cooling medium can be water mist mixed gas, the drop hammer requirement of a movable flash welding head is 15 continuous according to the requirement of a TB/T1632.2 standard, compressed air can only be used for joint cooling treatment, the requirement of a standard pair joint heat treatment process is not met, and the invention also does not meet the continuous 25 continuous requirement of a fixed flash welding head.
The patent with publication number CN202010886023.2 discloses a 1300MPa grade low alloy heat treatment steel rail post-welding heat treatment method, which carries out three-stage cooling on a steel rail welding joint with residual temperature of 900-1100 ℃ formed by a welding joint, wherein the first stage is naturally cooled to 650-720 ℃, the second stage is controlled to be cooled to 480-550 ℃, and the second stage is controlled to be cooled to 10-30 ℃. The invention is aimed at welding of a steel rail movable flash welding machine, the cooling medium can be water mist mixed gas, the hardness of the joint is detected by Vickers hardness, and the requirements of a TB/T1632.2 standard on the heat treatment process and performance inspection of a fixed flash welding head are not met. The joint has a punctiform martensite abnormal structure with a certain proportion, and the running safety of the joint line is seriously affected while the standard requirement is not met.
The patent with publication number CN201510319185.7 discloses a post-welding heat treatment method for a welding joint of an hypereutectoid steel rail, which comprises the steps of adopting medium-frequency or oxyacetylene flame to rapidly heat a welding joint area to 900-920 ℃ by a flash welding joint or an air pressure welding joint of the hypereutectoid steel rail, cooling the joint to 430-450 ℃ at a cooling speed of 2.2-2.8 ℃ per second, and cooling the joint to room temperature in air. The full-section weld joint impact energy Aku of the patent is more than or equal to 9J, meets the requirement of standard more than or equal to 6.5J, but has lower impact performance index relative to base metal, and has the hardness reaching 105% of base metal after heat treatment, and the hypereutectoid steel rail welded joint has the excessively high hardness, so that the joint has abnormal structure, high hardness and low toughness, and the service performance of the joint and the running safety of a line are seriously affected.
Disclosure of Invention
The invention aims to provide a flash welding and joint heat treatment process for a pearlitic steel rail containing Cr, nb and RE, which can ensure that the pearlitic steel rail joint containing Cr, nb and RE is of a normal pearlitic structure and has no abnormal structures such as bainite and martensite after the flash welding head process and the joint heat treatment process are used.
In order to solve the technical problems, the invention adopts the following technical scheme:
The invention relates to a welding process for flash welding and joint heat treatment of a pearlitic steel rail containing Cr, nb and RE, which comprises the following steps:
Flash welding process:
The GAAS80/580 fixed flash welder is adopted to weld the steel rail, the oil temperature of the welder is controlled to be about 40 ℃, the water temperature is controlled to be about 20 ℃, and the voltage of a power grid is 416-425V;
The joint quantity of the steel rail welding seams is controlled to be 10-12 mm, the arch starting quantity is controlled to be 0.35-0.55 mm, the flash welding preheating times are controlled to be 11-13 times, the secondary preheating current is controlled to be 58-63 KA, the flash welding upsetting quantity is controlled to be 14-16.5 mm, the upsetting force is controlled to be 515-670 KN, the welding time is controlled to be 110-120 s, and the melting end speed is controlled to be 2.60-2.80 mm/s;
Air-cooling the high-temperature welded joint to below 200 ℃, ensuring that each position of the joint is completely phase-changed, and properly accelerating cooling when the joint is less than or equal to 280 ℃;
the joint heat treatment process comprises the following steps:
The method comprises the steps of using a joint double-frequency normalizing machine to perform induction heating, namely performing low-frequency induction heating on the joint, namely heating the joint from 0-200 ℃ to 810-840 ℃ by using 57-65 kW of low-frequency power for 70-90 seconds, and ensuring that the core part of the rail head of the steel rail can be heated to a required temperature by using low-frequency heating;
After the joint reaches the target temperature, the joint is immediately subjected to high-frequency induction heating, wherein the temperature of the joint under the tread of the rail head of the steel rail can be heated to the target temperature by adjusting the temperature of the joint to 68-77 kW, heating the joint to 890-910 ℃ from 810-840 ℃ by using a normalizing machine with high-frequency power for 65-80 s, and the total heating time of the joint is controlled to be 135-170 s;
After the joint reaches the target temperature of 890-910 ℃, stopping heating, immediately performing air-spraying accelerated cooling treatment on the joint and the rail web, wherein an air-spraying opening of air-spraying cooling is 20-30mm away from the rail web and 50-60 mm away from the rail web, the air-spraying pressure is 0.34-0.40 MPa, the air-spraying time is 110-130 s, the air-spraying final cooling temperature of the joint is controlled to be 350-430 ℃, then air-spraying cooling is stopped, and the joint is naturally cooled to room temperature.
Furthermore, the end faces of two steel rails with the same section and made of the same material are polished and derusted before welding, and the clamping ends of the electrodes are polished and derusted.
Further, the weight percentage of the chemical composition of the steel rail welded by flash is C：0.73～0.83％,Si：0.50～0.80％,Mn：0.80～1.10％,Cr：0.30～0.60％,Nb：0.01～0.03％,RE：0.0005～0.0020％,P≤0.010％,S≤0.005％,A l：≤0.004％, and the balance is Fe.
Further, the rolling compression ratio of the steel rail is not less than 9:1, and the final rolling temperature is not higher than 950 ℃, so that the grain size of the original austenite of the steel rail is ensured.
Further, the tensile strength Rm of the joint is more than or equal to 1139MPa, the joint extension A is more than or equal to 12.0%, the joint impact KU 2 is more than or equal to 15.7J, the fatigue load cycle of the joint is 2 multiplied by 10 6 times, the ratio of the average hardness value H J of the joint to the average hardness value H P of the base metal is more than or equal to H J/HP and is more than or equal to 0.91, the ratio of the average hardness value H J1 of the soft point of the joint to the average hardness value H P of the base metal is more than or equal to H J1/HP and is less than or equal to 0.82, the softening area W is less than or equal to 20mm, the joint drop weight is 25, the weld joint and the heat affected zone are of typical pearlite structures, no martensite or bainite harmful structures exist, and all performances meet standard requirements.
Compared with the prior art, the invention has the beneficial technical effects that:
Based on the method, the tensile strength Rm of the joint is more than or equal to 1139MPa, the joint extension A is more than or equal to 12.0%, the joint impact KU 2 is more than or equal to 15.7J, the fatigue load cycle of the joint is 2 multiplied by 10 6 times, the ratio of the average hardness value H J of the joint to the average hardness value H P of the base metal is more than or equal to 0.91, the ratio of the average hardness value H J1 of the soft point of the joint to the average hardness value H P of the base metal is more than or equal to H J1/HP and is more than or equal to 0.82, the softening area W is less than or equal to 20mm, 25 joints are not broken, the weld joint and the heat affected zone are typical pearlite structures, no martensite or bainite harmful structures exist, and all performances meet the standard requirements.
The invention can effectively improve the mechanical properties of the Cr, nb and RE containing pearlitic steel rail flash welding head, and improve the joint strength, hardness and toughness, so that the joint strength, hardness and toughness are matched with the properties of base materials. The welded joint can meet the requirement of 25 drop hammers of the joint, improve the risk of ' saddle ' -shaped ' abrasion or fracture caused by microscopic abnormal structure of the joint due to overlarge hardness difference of a welding area in the service process of a steel rail, fully exert the characteristics of high strength, high hardness and high toughness of a pearlitic steel rail containing Cr, nb and RE and the joint, and ensure that the steel rail and the joint meet the service requirement of a heavy-duty railway and the running safety of the line.
Drawings
The invention is further described with reference to the following description of the drawings.
FIG. 1 is a graph of CCT of a pearlite rail containing Cr, nb, RE;
FIG. 2 shows the results of the test of the joint of example 1 in longitudinal section (test line 1);
FIG. 3 shows the results of the test of the joint of example 2 in longitudinal section (test line 1);
FIG. 4 shows the results of the test of the joint of example 3 in a vertical section (test line 1).
Detailed Description
A welding process for flash welding and joint heat treatment of a pearlitic steel rail containing Cr, nb and RE comprises the following steps:
The welded Cr, nb and RE containing pearlitic steel rail takes C, si, mn, cr, nb, RE as a main alloy element, the weight percentage of the chemical components of the steel rail is C：0.73～0.83％,Si：0.50～0.80％,Mn：0.80～1.10％,Cr：0.30～0.60％,Nb：0.01～0.03％,RE：0.0005～0.0020％,P≤0.010％,S≤0.005％,A l：≤0.004％. or more, and the steel rail is produced by smelting, continuous casting, slow cooling of steel billets, rolling, heat treatment and the like, wherein the rolling compression ratio of the steel rail is more than or equal to 11, the final rolling temperature is less than or equal to 950 ℃, and the final cooling temperature is less than or equal to 510 ℃, so that the grain size, the spacing between pearlitic plates, the tensile strength and the hardness of the steel rail are ensured.
The specific flash welding and joint heat treatment process comprises the following steps:
and adopting a GAAS80/580 fixed flash welder to weld the steel rails. The oil temperature of the welding machine is controlled to be about 40 ℃, the water temperature is controlled to be about 20 ℃, and the power grid voltage is 416-425V.
Two ribband steel rails (60 kg/m or 75 kg/m) with the same quality and the same section are selected, and the end faces are polished and derusted, and the electrode clamping ends are polished and derusted. The joint quantity of the steel rail welding seams is controlled to be 10-12 mm, and the arch starting quantity is controlled to be 0.35-0.55 mm.
The flash welding preheating frequency is 11-13 times, the secondary preheating current is controlled to be 58-63 KA, the flash welding upsetting amount is controlled to be 14-16.5 mm, the upsetting force is controlled to be 515-670 KN, the welding time is controlled to be 110-120 s, and the melting end speed is controlled to be 2.60-2.80 mm/s.
The time from the completion of flash welding upsetting to the push-out should be controlled within 15 s. The maximum allowable push-out allowance of the rail head is 2.0mm, the maximum allowable push-out allowance of the rail head jaw and the rail web is 2.0mm, and the maximum allowable push-out allowance of the rail bottom is 1.5mm.
The high-temperature welded joint is air-cooled to below 200 ℃, so that each position of the joint is ensured to be completely phase-changed, and the joint can be properly accelerated to be cooled when the temperature is less than or equal to 280 ℃. And after the joint is cooled, the joint welding rib is polished to be flat, namely, the convex pushing allowance of the rail head and the rail bottom is polished to be flat.
And (3) normalizing the joint in the welded state by using a double-frequency normalizing machine, wherein low-frequency induction heating is adopted firstly, namely 57-65 kW low-frequency power heating is adopted for 70-90 s, and the joint is heated to 810-840 ℃ from 0-200 ℃.
After the low-frequency induction heating of the joint reaches the target temperature, the low-frequency heating is turned off, the high-frequency induction heating is immediately carried out on the joint, the normalizing machine is adjusted to 68-77 kW high-frequency power for heating for 65-80 s, and the joint is heated to 890-910 ℃ from 810-840 ℃. The total time of the joint normalizing heat treatment is controlled to be 135-170 s.
And after the joint subjected to normalizing heat treatment reaches the target temperature of 890-910 ℃, stopping heating, and immediately performing air-jet accelerated cooling treatment on the joint and the rail web, wherein an air-jet cooled air-jet opening is 20-30 mm away from the rail head and 50-60 mm away from the rail web. The wind pressure of the spraying wind is 0.34-0.40 MPa, the air spraying time is 110-130 s. And the air-spraying final cooling temperature of the joint is controlled to be 350-430 ℃, then the air-spraying cooling is stopped, and the joint is naturally cooled to the room temperature.
The process is compared in the implementation process:
The Cr, nb and RE containing pearlitic steel rail has higher carbon content and alloy content, and element segregation such as C, mn and microstructure defects are easy to generate in a superheating area in the flash welding process, therefore, in a welding process parameter adjustment link, key parameters such as preheating times, top end quantity, tail burning rate and the like are adjusted, and the comparative analysis of joint mechanical properties, drop weight results and the like are combined, so that the steel rail flash welding process is determined, and main adjustment parameters of the welding process, corresponding joint hardness and drop weight test results in the implementation process are shown in table 1.
Table 1 results of comparison of different welding processes and properties during the implementation
As shown in Table 1, the performance test of the drop height of the joints of 5.2 m or 6.4 m under different welding processes is carried out, wherein the number of drop hammer breaks is 4 in the steel rail flash welding process of the embodiment 1, the number of obvious gray spots are found at most of the breaks, the number of the broken gray spots is more, the area of part of the broken gray spots exceeds the standard requirement, the number of drop hammer breaks is 2 in the steel rail flash welding process of the embodiment 2, the obvious gray spots are found at the broken hammer breaks, the single gray spot area and the total gray spot area are not found to exceed the standard, the steel rail flash welding process of the embodiment 3 does not break, and the hardness of the joint also meets the requirement. The preheating times and the upsetting amount are increased, so that oxidation products generated during welding of the welding seam can be extruded away, and ash spots can be reduced or eliminated as much as possible.
The metallurgical grain size of the welded pearlitic steel rail joint containing Cr, nb and RE is coarser and only about 1-2 levels, the mechanical properties of the joint are poor, and the weld joint is subjected to normalizing heat treatment, so that the microstructure of the weld joint can be thinned, and the comprehensive mechanical properties of the flash welding joint can be effectively improved. The steel rail CCT curve is an important basis for making a steel heat treatment process, and the steel rail CCT curve shows that the austenitizing can be achieved by the heating temperature of the steel rail joint reaching 679 ℃, as shown in fig. 1. The comparative schemes of the different joint heat treatment processes in the implementation process are shown in Table 2.
Table 2 comparison of different heat treatment processes during the implementation
The flash welding heads after normalizing treatment in example 1-example 3 were subjected to comparative analysis of Rockwell hardness properties of longitudinal section of the rail head according to the "TB/T1632.2-2014 Rail welding section 2: flash welding", and the comparative analysis results are shown in tables 3-5, and FIGS. 2-4.
TABLE 3 example 1 results of Joint vertical section (test line 1)
TABLE 4 example 2 results of Joint vertical section (test line 1)
TABLE 5 example 3 results of Joint vertical section (test line 1)
As can be seen from tables 3-5 and figures 2-4, the average ratio H J/HP of the hardness of the welded joint and the hardness of the base metal in the embodiment 1 and the embodiment 2 is smaller than 0.90, the width W of the softened region is larger than 20mm, the standard requirements on the heat treatment joint in the section 2 of welding the TB/T1632.2-2014 steel rail, namely flash welding, are not met, the joint hardness is too low, the width of the softened region is too wide, the conditions of low collapse, poor wear resistance, a horseshoe saddle-shaped joint and the like can occur in the process of line service of the weld joint, the smooth joint and the running safety of a train are influenced, the hardness of the joint and the width of the softened region in the embodiment 3 meet the standard requirements, and the joint and the base metal achieve excellent hardness matching.
The flash welding head of example 3 was subjected to joint stretching and joint impact performance test according to the sampling method of TB/T1632.2-2014 Rail welding part 1: general technical conditions, and the specific results are shown in Table 5 and Table 6.
TABLE 5 example 3 flash bond head tensile Properties
TABLE 6 example 3 impact Property of flash bond head
As can be seen from tables 5 and 6, the flash welding head of example 3 satisfies the standard requirements for both tensile properties and impact properties, and the joint has a large performance margin.
As can be seen from the comparison of the process in the implementation process, the tensile strength Rm of the joint of the embodiment 3 is more than or equal to 1139MPa, the joint extension A is more than or equal to 12.0%, the joint impact KU 2 is more than or equal to 15.7J, the ratio of the average hardness H J of the joint to the average hardness H P of the base material is more than or equal to 0.91, the ratio of the average hardness H J1 of the soft point of the joint to the average hardness H P of the base material is more than or equal to 0.82, the softening area W is less than or equal to 20mm, the joint drop weight 25 is not broken, and all the performances meet the standard requirements. The joint strength, hardness and toughness obtained in the embodiment 3 are matched with the properties of the base metal, so that the requirements of heavy haul railways on the smoothness of the rail joints can be met, the risk of fracture caused by saddle-shaped abrasion or joint microstructure caused by overlarge hardness difference of welding areas in the rail service process is improved, the characteristics of high strength, high hardness and high toughness of Cr, nb and RE containing pearlitic rails and joints are fully exerted, and the rail and the joint can meet the service requirements of heavy haul railways and the safety of line operation.
The above embodiments are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope defined by the claims of the present invention without departing from the design spirit of the present invention.
Claims (4)
1. A process for flash welding and joint heat treatment of a pearlitic steel rail containing Cr, nb and RE is characterized by comprising the following steps:
Flash welding process:
The GAAS80/580 fixed flash welder is adopted to weld the steel rail, the oil temperature of the welder is controlled to be about 40 ℃, the water temperature is controlled to be about 20 ℃, and the voltage of a power grid is 416-425V;
The joint quantity of the steel rail welding seams is controlled to be 10-12 mm, the arch starting quantity is controlled to be 0.35-0.55 mm, the flash welding preheating times are controlled to be 11-13 times, the secondary preheating current is controlled to be 58-63 KA, the flash welding upsetting quantity is controlled to be 14-16.5 mm, the upsetting force is controlled to be 515-670 KN, the welding time is controlled to be 110-120 s, and the melting end speed is controlled to be 2.60-2.80 mm/s;
Air-cooling the high-temperature welded joint to below 200 ℃, ensuring that each position of the joint is completely phase-changed, and properly accelerating cooling when the joint is less than or equal to 280 ℃;
the joint heat treatment process comprises the following steps:
The method comprises the steps of using a joint double-frequency normalizing machine to perform induction heating, namely performing low-frequency induction heating on the joint, namely heating the joint from 0-200 ℃ to 810-840 ℃ by using 57-65 kW of low-frequency power for 70-90 seconds, and ensuring that the core part of the rail head of the steel rail can be heated to a required temperature by using low-frequency heating;
After the joint reaches the target temperature, the joint is immediately subjected to high-frequency induction heating, wherein the temperature of the joint under the tread of the rail head of the steel rail can be heated to the target temperature by adjusting the temperature of the joint to 68-77 kW, heating the joint to 890-910 ℃ from 810-840 ℃ by using a normalizing machine with high-frequency power for 65-80 s, and the total heating time of the joint is controlled to be 135-170 s;
After the joint reaches the target temperature of 890-910 ℃, stopping heating, immediately performing air-spraying accelerated cooling treatment on the joint and the rail web, wherein an air-spraying opening of air-spraying cooling is 20-30mm away from the rail head and 50-60 mm away from the rail web, the air-spraying pressure is 0.34-0.40 MPa, the air-spraying time is 110-130 s, the air-spraying final cooling temperature of the joint is controlled to be 350-430 ℃, then the air-spraying cooling is stopped, and the joint is naturally cooled to room temperature;
the weight percentage of the chemical components of the steel rail welded by flash is C：0.73～0.83%,Si：0.50～0.80%,Mn：0.80～1.10%,Cr：0.30～0.60%,Nb：0.01～0.03%,RE：0.0005～0.0020%,P≤0.010%,S≤0.005%,Al：≤0.004%,, and the balance is Fe.
2. The process for flash welding and joint heat treatment of Cr, nb and RE containing pearlitic steel rails is characterized in that the end faces of two steel rails with the same cross section and made of the same material are polished and derusted before welding, and the clamping ends of the electrodes are polished and derusted.
3. The process for flash welding and joint heat treatment of a pearlitic steel rail containing Cr, nb and RE according to claim 1, wherein the rolling compression ratio of the steel rail is not less than 9:1, and the finishing rolling temperature is not higher than 950 ℃, thereby ensuring the grain size of the prior austenite of the steel rail.
4. The welding and joint heat treatment process for the pearlitic steel rail containing Cr, nb and RE according to claim 1, wherein the tensile strength Rm of the joint is not less than 1139MPa, the elongation A of the joint is not less than 12.0%, the impact KU 2 of the joint is not less than 15.7J, the fatigue load cycle of the joint is not less than 2X 10 6 times, the ratio of the average hardness H J of the joint to the average hardness H P of the base metal meets the standard requirements, the ratio of the average hardness H J1 of the soft point of the joint to the average hardness H P of the base metal is not less than H J/HP and not more than 0.91, the softening area W is not more than 20mm, the drop weight of the joint is not broken, the weld joint and the heat affected zone are typical pearlitic structures, no martensite or bainite harmful structures exist, and all performances meet the standard requirements.
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| CN116329724A (en) * | 2023-04-13 | 2023-06-27 | 包头钢铁（集团）有限责任公司 | High-speed rail fixing flash welding and joint heat treatment method for plateau area |
| CN116532772A (en) * | 2023-04-18 | 2023-08-04 | 包头钢铁（集团）有限责任公司 | A moving flash welding and heat treatment process for pearlitic rails containing Nb and RE |
| CN116833539A (en) * | 2023-06-19 | 2023-10-03 | 包头钢铁（集团）有限责任公司 | A moving air pressure welding and joint heat treatment process for Nb and RE pearlite rail rails |
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