WO2023284187A1

WO2023284187A1 - Method for laser strengthening and toughening treatment of steel rail welding joint

Info

Publication number: WO2023284187A1
Application number: PCT/CN2021/128972
Authority: WO
Inventors: 曾晓雁; 刘旭; 胡乾午; 孟丽; 王邓志
Original assignee: 武汉瀚海智能激光工程有限公司; 武汉新瑞达激光工程有限责任公司; 华中科技大学
Priority date: 2021-07-12
Filing date: 2021-11-05
Publication date: 2023-01-19
Also published as: CN113604650A; CN113604650B

Abstract

Provided in the present invention is a method for laser strengthening and toughening treatment of a steel rail welding joint, relating to the field of railway steel rail maintenance. The method is: using an area with a lower hardness than the average hardness of the base metal and the difference thereof exceeding a first preset value as a softening area, and performing laser quenching treatment or laser shock hardening treatment on same to improve the surface hardness and wear resistance thereof; if there is an area with a higher hardness than the average hardness of the base material and the difference thereof exceeding a second preset value, then using same as a hardening area, and performing laser annealing treatment or laser tempering treatment on same to reduce the surface hardness and wear resistance thereof, thereby ensuring that the wear resistance of the steel rail welding joint and the base material is the same or substantially the same. The present invention can implement synchronous wear between each area of the steel rail welding joint and the base material, prolonging the service life of the steel rail, and eliminating the risk of blocks peeling off due to the poor bonding of the coating metal and the base material in conventional welding repair processes, so that there is no need for cumbersome grinding and rust removal processes, having greater adaptability and being capable of effectively increasing machining efficiency.

Description

Laser strengthening and toughening treatment method for rail welded joints

【Technical field】

The invention belongs to the field of railway rail maintenance, and more specifically relates to a laser strengthening and toughening treatment method for welded joints of rails.

【Background technique】

The use of seamless steel rail not only significantly slows down the impact of wheel and rail, prolongs the service life of wheel and rail, but also improves the stability, comfort and reliability of the track. The main technologies to realize the seamless connection of rails include flash welding, gas pressure welding, aluminothermic welding and other rail welding technologies. While these technologies realize high-efficiency rail connection, they also bring some problems. Taking flash welding as an example, a large amount of heat input during welding makes the microstructure of the weld zone and heat-affected zone of the welded joint significantly different from the base metal, resulting in obvious differences in hardness and wear resistance of the corresponding area and the base metal. Among them, the hardness and wear resistance of the heat-affected zone of the welded joint are the lowest, and the hardness and wear resistance of the weld zone are the highest. With the continuation of service time, the tread of welded joints will suffer from subsidence in the heat-affected zone due to inconsistent wear resistance, that is, the formation of so-called "low joints". If these "low joints" are not treated in time, not only will there be severe wheel-rail impact, aggravated rail damage, and even lead to broken rails in serious cases, bringing serious safety hazards to railway transportation.

At present, there are two methods in the industry to deal with low joint defects: one is manual arc welding welding repair, which is not only time-consuming and laborious, but also has the risk of falling blocks after welding repaired joints have been in service for a long time, bringing new hidden dangers; Another method is to use a large grinding machine for overall maintenance grinding. This method not only eliminates joint collapse, but also accelerates the consumption of base metal, resulting in a significant reduction in the overall service life of the railway line and huge economic losses. Therefore, if technical means can be used to strengthen and toughen the welded joints of the rails so that their hardness and wear resistance are comparable to those of the rail matrix, it will not only eliminate or even eradicate the phenomenon of low joints in the welded joints of the rails, but also prevent problems before they happen To avoid all kinds of broken rail accidents, and can greatly reduce the number of grinding, so as to greatly reduce the maintenance cost of the railway engineering department, ensure the safety of the railway transportation line, and generate huge economic and social benefits.

At the same time, in the prior art, only the problem of "low joints" easily formed due to the decrease of hardness in the heat-affected zone was considered, and the problem of "high joints" easily formed due to the increase of hardness in the weld zone was ignored. For seamless rails, whether it is a "low joint" or a "high joint", as long as there is an uneven track surface, it will seriously affect the safe operation of the railway. pose a serious safety hazard.

In view of the defects of the prior art, the object of the present invention is to provide a laser toughening treatment method for welded rail joints, aiming at solving the problems of high processing cost of welded rail joints and affecting the service life of rails.

In order to achieve the above object, the present invention provides a laser toughening treatment method for welded rail joints, the method is specifically: the method is specifically: the hardness is lower than the average hardness of the base metal, and the absolute value of the difference exceeds the first preset Value area is used as the softening area, laser quenching treatment or laser shock strengthening treatment is performed on it to improve its surface hardness and wear resistance; if there is an area higher than the average hardness of the base material and the absolute value of the difference exceeds the second preset value , it is used as a hardening zone, and laser annealing or laser tempering is performed on it to reduce its surface hardness and wear resistance, thereby ensuring that the rail welded joint has the same or basically the same wear resistance as the base metal.

As a further preference, the softened area is subjected to selective laser treatment by means of lattice strengthening.

As a further preference, when performing laser quenching treatment, the transverse spacing of the quenching spot, the diameter of the quenching spot, the longitudinal spacing of the quenching spot, and the quenching time of each spot are selected according to the power of the laser, so that the wear resistance of the softening zone is the same as that of the base material or basically the same; as a further preference, during laser quenching treatment, the transverse spacing of the quenching spots is 0-10 mm, the diameter of the quenching spots is 3-10 mm, the longitudinal spacing of the quenching spots is 0-10 mm, and the quenching time of each spot is 0.1 s～1s, the laser power is 1800w～20000w.

As a further preference, the first preset value is 0 to 3HRC, the second preset value is 0 to 3HRC, the first preset value and the second preset value are equal or unequal; as a further preference, The first preset value is 2 to 3HRC, and the second preset value is 2 to 3HRC; or the first preset value and the second preset value are both equal to 0, thereby ensuring that the steel rail after the toughening treatment is welded The joint has the same wear resistance as the base metal.

As a further preference, when laser tempering is performed, the surface temperature of the hardened zone is controlled at 500°C to 650°C.

As a further preference, during the laser tempering treatment, temperature monitoring is performed on the corners and the center of the hardened zone at the same time.

As a further preference, when the longitudinal scan length of the hardened zone is less than the transverse scan length, the annealing or tempering treatment is performed in the manner of longitudinal repeated scan; when the longitudinal scan length of the hardened zone is greater than the transverse scan length, the transverse scan Annealing or tempering is performed by repeated scanning.

As a further preference, a single beam or multiple beams are used to treat the softened zone and the hardened zone.

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

1. The present invention proposes to adopt different processes to treat the softening zone and hardening zone of the rail welded joint, thereby ensuring that the rail welded joint and the base metal have the same or basically the same wear resistance, so as to achieve synchronous or basic The purpose of simultaneous wear and prolonging the service life of rails. Compared with arc welding, laser cladding and other rail repair technologies, this method does not need to add foreign materials, and eliminates the risk of peeling off blocks due to weak bonding between the coated metal and the base metal. ; and this method can directly process the rail joints online or offline, without the need for cumbersome grinding and derusting pre-processes. Compared with the welding repair process that requires higher surface finish to be repaired, it has stronger adaptability and can effectively improve the processing efficiency. efficiency;

2. At the same time, the present invention adopts the method of lattice strengthening to carry out selective laser treatment on the softening area, which can form an allotropic surface composite material in which the martensitic hardening area is embedded in the pearlite matrix, thereby effectively avoiding the formation of martensite The problem of fatigue fracture of the rail caused by the organization; and considering that the specific parameters in the laser quenching process directly affect the wear resistance of the rail joint, by optimizing the quenching spot spacing, diameter, quenching power, time and other parameters, the service life of the rail can be effectively improved time;

3. The softening zone and hardening zone can be selected according to the requirements of the working conditions. It can not only use the rail welded joint and the base metal to have equal wear resistance, but also make the wear resistance difference between the rail welded joint and the base metal within an acceptable range ( Usually it can be 0~3HRC), so as to reduce the processing area, improve the processing efficiency and reduce the processing cost;

4. In addition, the present invention also optimizes the surface temperature of the hardened zone, which can ensure that the hardness of the weld zone is reduced to that of the rail base material, avoiding the occurrence of the "high joint" problem, thereby ensuring that the weld joint and the rail base material have and other wear resistance.

The laser strengthening and toughening treatment method provided by the invention is especially suitable for rail maintenance.

【Description of drawings】

Fig. 1 is the processing schematic diagram of the laser toughening treatment of the rail welded joint provided by the preferred embodiment of the present invention;

Fig. 2 is the schematic diagram of division of the hardened zone and the softened zone in the rail welded joint proposed by the present invention;

Fig. 3 is a schematic diagram of the tempering path of the hardened zone provided by the preferred embodiment of the present invention;

Fig. 4 is the longitudinal section hardness curve of U75V rail flash welding joint in the preferred embodiment of the present invention;

Fig. 5 is a schematic diagram of laser toughening treatment of U75V rail flash welded joints in a preferred embodiment of the present invention;

Fig. 6 is the longitudinal section hardness curve of U75V rail aluminothermic welded joint in the preferred embodiment of the present invention;

Fig. 7 is a schematic diagram of the laser toughening treatment of the aluminothermic welded joint of the U75V rail in the preferred embodiment of the present invention.

Throughout the drawings, the same reference numerals are used to designate the same elements or structures, wherein:

1-rail; 1.1-base metal; 1.2-softening zone; 1.3-hardening zone; 1-4-welding bar; 2-quenching spot; 3-laser; 4-galvanometer.

【detailed description】

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

As shown in Fig. 1, the present invention provides a kind of laser strengthening and toughening processing method of rail welding joint, and this method specifically is: take the cross-section where welding bar 1.4 central line is located as longitudinal symmetry plane, will be lower than parent metal 1.1 (rail Substrate) average hardness, and the area where the absolute value of the difference exceeds the first preset value is used as the softening zone 1.2 (generally the heat-affected zone, that is, the L2, L2' area in Figure 2), which is subjected to laser quenching treatment or laser Impact strengthening treatment to improve its surface hardness and wear resistance; the area that is higher than the average hardness of the base metal and the absolute value of the difference exceeds the second preset value is taken as the hardened zone 1.3 (generally the weld zone, that is, in Figure 2 L1 area), laser annealing treatment or laser tempering treatment is performed on it to reduce its surface hardness and wear resistance. The width of the transverse quenching and hardening area is the width of the rail head of the type of joint that belongs to the rail, so as to ensure that the rail welded joint includes The softening zone and hardening zone have equal or substantially equal wear resistance to the base metal, avoiding the appearance of "low joints" and "high joints".

Concrete operation steps of the present invention are:

S1 measures the width of the welding rod and determines the position of the centerline of the welding rod;

S2 According to the type of welding process, the type of rail joint welding and the position of the center line of welding rod 1.4, delineate the area range of softening zone 1.2 and hardening zone 1.3;

S3 Compile the processing technology according to the area range of softening zone 1.2 and hardening zone 1.3, determine the laser quenching spot size, quenching distance, quenching time, quenching power and other parameters; determine the spot type, processing temperature, processing time, etc. of laser annealing or laser tempering Processing path and other parameters;

S4 adopts the laser selective quenching process based on the galvanometer 4 to process the softening area on both sides of the center line of the rail welding bar, and uses the circular spot or square spot scanning process to process the hardened area of the rail.

Furthermore, since the surface of the rail experiences very complex alternating stresses during the operation of the train, if the laser comprehensive quenching process is adopted, the martensitic structure will be generated in the softened zone of the weld and thus achieve comprehensive strengthening, which is prone to failure due to contact fatigue. The martensitic structure produces fatigue cracks, which continue to expand, leading to rail fracture. Therefore, it is preferable to use the lattice strengthening method to carry out selective laser treatment on the rail to form an allotropic surface composite material in which the martensite hardened area is embedded in the pearlite matrix, which can effectively avoid the fatigue fracture of the rail due to the formation of martensite structure hazards. This technology is used to treat the softened area of the welded joint tread. Considering the correlation between the distribution density of the laser selective quenching strengthening area and the hardness of the softened area, the distribution of quenching spots is relatively dense in the area with relatively low hardness, while in the area with relatively high hardness. The distribution of quenching spots in the zone is relatively sparse, which can ensure that the softened zone has the same or basically the same wear resistance as the rail base material.

Further, the first preset value and the second preset value are preferably 0-3HRC, and the first preset value and the second preset value are equal or different. In engineering applications, as long as the wear resistance of the welded rail joints after strengthening treatment meets its safety requirements and reaches the expected service life, in order to improve processing efficiency and reduce processing costs, it is not required that the welded rail joints after strengthening treatment The wear resistance must be equal to that of the rail base material, just close to it. In specific implementation, it is possible to only compare the strengthening treatment for areas that are significantly lower than the average hardness of the base metal (that is, the absolute value of the difference exceeds the preset value), and it is also possible to only strengthen the area that is significantly higher than the average hardness of the base metal (that is, the absolute value of the difference exceeds the preset value). The region of the preset value) is subjected to laser annealing treatment or laser tempering treatment, so the first preset value and the second preset value are preferably 2-3HRC. In addition, in order to ensure that the welded rail joint after toughening treatment has the same wear resistance as the base metal, both the first preset value and the second preset value may also be equal to 0.

For the specific parameters in the laser quenching process, they are usually selected according to the power of the laser, such as the transverse spacing of the quenching spot, the diameter of the quenching spot, the longitudinal spacing of the quenching spot, and the quenching time of each spot, mainly through the longitudinal spacing of the quenching spot and the diameter of the quenching spot are used to adjust and realize the equal wear resistance of the rail, so that the softening zone after quenching is the same or basically the same as the wear resistance of the base metal.

The following preferred parameter ranges can be obtained through experiments: the longitudinal spacing of the quenching spot (that is, the distance between the edges of two adjacent quenching spots in the longitudinal direction) is controlled at 0-10mm, and the diameter of the quenching spot is controlled at 3mm-10mm, which can avoid quenching efficiency. Too low and the spot energy distribution is uneven. The single spot quenching time and laser power are used to adjust the depth of the quenching layer, which is beneficial to prolong the service life of the rail. Therefore, the single spot quenching time is 0.1s~1s, and the laser power is 1800w~20000w, so as to achieve the purpose of quenching and strengthening while avoiding the melting of the rail surface . At the same time, too large lateral spacing of quenching spots is not conducive to achieving equal wear resistance of the entire rail head tread, so the lateral spacing of quenching spots (that is, the distance between the edges of two adjacent quenching spots in the transverse direction) is controlled at 0-10mm .

Furthermore, if the tempering temperature is too high, it will lead to quenching in the weld zone, which not only does not reduce the hardness of the weld zone, but increases its hardness, which in turn leads to the occurrence of the "high joint" phenomenon. Therefore, when the laser is used to temper the hardened zone 1.3 of the welded joint of the rail, the real-time temperature of the hardened zone is monitored by a thermometer and fed back to the laser. The laser adopts a constant temperature mode to dynamically adjust the power to ensure the surface tempering temperature of the hardened zone Control at 500°C ~ 650°C. At the same time, because the corners of the hardened area dissipate heat quickly and the center dissipates slowly, in order to prevent the central area of the hardened area from being quenched due to excessive temperature, it is necessary to monitor the temperature of the corners and the center of the hardened area at the same time. As shown in (a) in Figure 3, when the longitudinal scan length of the hardened zone is less than the transverse scan length, the annealing or tempering treatment is performed by repeated longitudinal scanning; as shown in (b) in Figure 3, when the hardened zone When the longitudinal scanning length is greater than the horizontal scanning length, the annealing or tempering treatment is performed by repeated horizontal scanning to accelerate heat accumulation and shorten the tempering time.

Further, when performing laser treatment on the softened zone 1.2 and the hardened zone 1.3 of the rail welded joint, a single beam can be used for processing in different sections and periods, or multiple beams can be used for simultaneous processing. Among them, when single-beam processing is used, the softening zone and hardening zone are processed in different periods. The vibrating mirror strengthens the softening zone in the laser selective quenching mode, and toughens the hardening zone in a continuous scanning mode. When multi-beam processing is used, the softened area and hardened area can be processed by multi-galvanometer and multi-laser beams in different periods, and the hardened area can also be processed in a scanning mode by using a circular spot or a square spot while processing the softened area. Tempering treatment.

The laser strengthening and toughening treatment method for rail welded joints proposed by the present invention has no restrictions on the type of rail in use, and can be applied to various types of rail welded joints such as 50kg/m, 60kg/m, and 75kg/m; at the same time, the processing method There are no restrictions on the grades of steel used for rails, and joints welded with the same material or different materials such as U71Mn, U75V, and U78CrV can be strengthened.

The technical solutions provided by the present invention will be further described below according to specific embodiments.

Example 1

Figure 4 is the longitudinal hardness curve of the U75V rail flash welded joint. The average hardness of the base metal 1.1 is about 320HV. The cross section where the centerline of the welding rod 1.4 is located is the symmetrical center and the zero point of the longitudinal coordinates, marking the range of softening zone and hardening zone: L1 Hardening zone ±15mm range, L2 softening zone -75mm to -15mm, L2' softening zone +15mm to +75mm, affected by the rail joint welding process, L1, L2, L2' ranges allow 5mm deviation.

As shown in Figure 5, according to the length division of the hardening zone and softening zone of the U75V rail flash welding joint, it can be concluded that the length of the hardening zone L1 is 30mm, the lengths of L2 and L2' are both 60mm, and the measured rail is 60kg/m According to the industry standard "43kg/m～75kg/m Rail Ordering Specifications", the width of the rail head is 70.8mm. According to the horizontal and vertical dimensions of the softening zone, the diameter of the spot is determined to be 5.5mm, and the number of spots in each row of the softening zone is 6. The lower the longitudinal hardness of the welded joint, the smaller the distance between the quenching spots. According to this, the distance between the quenching spots along the longitudinal direction away from the welding bar is 0mm, 2mm, 7mm, 8mm, and 10mm. The pitch of the laser beam is 3.7mm, the quenching time of a single spot is 0.35s, and the laser power is 4300w. The temperature in the hardening area is controlled at 500°C, a circular spot is used, and the vibrating mirror is tempered in a longitudinal reciprocating scanning manner.

Example 2

Figure 6 is the longitudinal hardness curve of the U75V rail aluminothermic welded joint. The average hardness of the base metal 1.1 is 320HV. The cross-section where the centerline of the weld bar 1.4 is located is the symmetric center and the zero point of the longitudinal coordinates to mark the softening zone and the hardening zone. : L1 hardening zone ±50mm range, L2 softening zone -80mm to -50mm, L2' softening zone +50mm to +80mm, affected by the rail joint welding process, L1, L2, L2' range allows 5mm deviation.

As shown in Figure 7, according to the length division of the hardened zone and softened zone of the U75V rail aluminothermic welded joint, it can be concluded that the length of the hardened zone L1 is about 100mm, the lengths of L2 and L2' are both 30mm, and the measured rail is 60kg/ M model, refer to the industry standard "43kg/m～75kg/m rail order technical conditions", it can be known that the width of the rail head is 70.8mm, according to the horizontal and vertical dimensions of the softening zone, the diameter of the spot is determined to be 6mm, and the number of spots in each row of the softening zone is 3 , the lower the longitudinal hardness of the welded joint, the smaller the quenching spot spacing. According to this, the quenching spot spacing along the longitudinal direction away from the welding bar is 3mm and 9mm, and the horizontal spacing is uniform. From this, the spacing of each row of light spots is calculated as 0mm. The quenching time of a single spot is 1s, and the laser power is 1800w. The temperature in the hardening area is controlled at 650°C, and a circular spot is used to temper through the vibrating mirror in a horizontal reciprocating scanning manner.

Example 3

For U71Mn rail aluminothermic welded joints, the cross-section where the center line of welding rod 1.4 is located is the symmetric center and the zero point of the longitudinal coordinates, so as to mark the range of softening zone and hardening zone: L1 hardening zone ±48mm range, L2 softening zone -80mm to - 48mm, L2' softening zone +48mm to +80mm, affected by the rail joint welding process, the range of L1, L2, L2' allows 5mm deviation.

According to the length division of the hardening zone and softening zone of U71Mn rail aluminothermic welded joints above, it can be concluded that the length of hardening zone L1 is about 96mm, the lengths of L2 and L2' are both 32mm, and the measured rail is 60kg/m, refer to the industry standard "43kg/m～75kg/m Rail Ordering Technical Conditions" shows that the width of the rail head is 70.8mm, according to the horizontal and vertical dimensions of the softening zone, the diameter of the spot is determined to be 3mm, and the number of spots in each row of the softening zone is 6. Low, the smaller the quenching spot spacing, according to this, the spacing of the quenching spots along the longitudinal direction away from the welding bar is 1mm, 2mm, 3mm, 4mm, 4mm, and the horizontal spacing is uniform, and the spacing of each row of spots is 10mm. The time is 0.1s, and the laser power is 4500w. The temperature in the hardening area is controlled at 650°C, and a circular spot is used to temper through the vibrating mirror in a horizontal reciprocating scanning manner.

Example 4

For U71Mn rail flash welded joints, take the cross-section where the center line of welding bar 1.4 is located as the symmetric center and the zero point of the longitudinal coordinates to mark the range of softening zone and hardening zone: L1 hardening zone ±18mm range, L2 softening zone -72mm to -18mm , L2' softening zone +18mm to +72mm, affected by the rail joint welding process, the range of L1, L2, L2' allows 5mm deviation.

According to the length division of the hardening zone and softening zone of U71Mn rail flash welded joints above, it can be concluded that the length of hardening zone L1 is about 36mm, the lengths of L2 and L2' are both 54mm, and the measured rail is 60kg/m model, refer to the industry standard " 43kg/m～75kg/m Rail Ordering Technical Conditions" shows that the width of the rail head is 70.8mm. According to the horizontal and vertical dimensions of the softening zone, the diameter of the spot is determined to be 10mm. The number of spots in each row of the softening zone is 4. The lower the longitudinal hardness of the welded joint , the smaller the quenching spot spacing, according to this, the spacing of the quenching spots along the longitudinal direction away from the welding bar is 3mm, 5mm, 6mm, and the horizontal spacing is uniform, the spacing of each row of spots is 10mm, and the quenching time of a single spot is 0.25s. Power 20000w. The temperature in the hardening area is controlled at 550°C, and a circular spot is used to temper through the vibrating mirror in a horizontal reciprocating scanning manner.

Example 5

For the longitudinal section of the rail head of the welded joint of the rail, the hardness curve in the range of ±110mm from the weld center, the average hardness of the base metal is 320HV, here it is assumed that the first preset value and the second preset value are both 3HRC, after converting to Vickers hardness , then the first preset value line hardness value is 290HV, the second preset value line hardness value is 350HV, the difference between the hardness value of the softening zone and the average hardness value of the base metal does not exceed the first preset value, similarly, the hardness value of the hardening zone The difference from the average hardness value of the base metal does not exceed the second preset value, that is, the hardness difference between the softening zone and the hardening zone is within the allowable range of the preset value. Therefore, the softening zone and the hardening zone do not need laser treatment, and are regarded as equal wear resistance sex.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be Included within the protection scope of the present invention.

Claims

A laser strengthening and toughening treatment method for rail welded joints is characterized in that the method specifically comprises: taking the area which is lower than the average hardness of the base metal and the absolute value of the difference exceeds a first preset value as the softening area, and performing Laser quenching treatment or laser shock strengthening treatment to improve its surface hardness and wear resistance; if there is an area higher than the average hardness of the base metal and the absolute value of the difference exceeds the second preset value, it will be regarded as a hardened area, and its Laser annealing treatment or laser tempering treatment is carried out to reduce its surface hardness and wear resistance, so as to ensure that the wear resistance of the welded rail joint is the same or basically the same as that of the base metal.
The laser strengthening and toughening treatment method for welded rail joints according to claim 1, characterized in that the softening zone is subjected to selective laser treatment in a way of lattice strengthening.
The laser strengthening and toughening treatment method of rail welded joints as claimed in claim 1, wherein, when performing laser quenching treatment, the transverse spacing of quenching spots, the diameter of quenching spots, and the longitudinal spacing of quenching spots are selected according to the power of the laser, The quenching time of each spot makes the wear resistance of the softened zone the same or basically the same as that of the base metal.
The laser toughening treatment method for welded rail joints according to claim 1, wherein the first preset value is 0-3HRC, the second preset value is 0-3HRC, and the first preset value is 0-3HRC. value, the second preset value is equal or not.
The laser toughening treatment method for welded rail joints according to claim 1, characterized in that, during the laser tempering treatment, temperature monitoring is performed on the corners and the center of the hardened zone at the same time.
The laser toughening treatment method for welded rail joints according to claim 5, characterized in that the surface temperature is controlled at 500°C to 650°C.
The laser strengthening and toughening treatment method for welded rail joints according to claim 1, characterized in that, when the longitudinal scanning length of the hardened zone is shorter than the transverse scanning length, the annealing or tempering treatment is performed by repeated longitudinal scanning; When the longitudinal scan length of the hardening zone is greater than the transverse scan length, the annealing or tempering treatment is performed in the manner of repeated transverse scan.
The laser toughening treatment method for welded rail joints according to any one of claims 1 to 7, characterized in that the first preset value and the second preset value are both equal to 0, thereby ensuring the toughening treatment The wear resistance of the rail welded joint is the same as that of the base metal; or the first preset value is 2-3HRC, and the second preset value is 2-3HRC.
The laser toughening treatment method for welded rail joints according to any one of claims 1 to 7, characterized in that the softening zone and the hardening zone are treated with a single beam or multiple beams.
The laser strengthening and toughening treatment method for rail welded joints as claimed in claim 3, characterized in that, during laser quenching treatment, the transverse spacing of the quenching spots is 0-10 mm, the diameter of the quenching spots is 3-10 mm, and the longitudinal distance of the quenching spots is 0-10 mm. The spacing is 0-10mm, the quenching time of each spot is 0.1s-1s, and the laser power is 1800w-20000w.