阅读说明：本技术 60kg/m过共析钢轨气压焊接方法及装置 (60kg/m hypereutectoid steel rail air pressure welding method and device ) 是由 王若愚 李大东 陆鑫 白威 于 2021-08-17 设计创作，主要内容包括：本发明公开了一种60kg/m过共析钢轨气压焊接方法,包含以下步骤：步骤一,使用氧-乙炔火焰加热钢轨的待焊部位,其中,气压焊接装置的加热器以3～5mm的幅度摆动,加热时间300～350s,氧气流量75～90L/min,乙炔流量85～95L/min；待钢轨的待焊部位的表面温度为1250～1350℃时关闭燃气以停止加热；步骤二,执行顶锻焊接,并在顶锻焊接完成后执行一次保压；步骤三,执行推凸和二次保压；以及步骤四,对钢轨的焊接接缝进行热处理。该方法有效提高了60kg/m过共析钢轨焊接接头的质量。本发明同时公开了一种用于执行该方法的装置。(The invention discloses a 60kg/m hypereutectoid steel rail air pressure welding method, which comprises the following steps: heating a to-be-welded part of a steel rail by using oxygen-acetylene flame, wherein a heater of a pneumatic welding device swings in a range of 3-5 mm, the heating time is 300-350 s, the oxygen flow is 75-90L/min, and the acetylene flow is 85-95L/min; when the surface temperature of the part to be welded of the steel rail is 1250-1350 ℃, closing the gas to stop heating; step two, performing upset welding, and performing primary pressure maintaining after the upset welding is finished; step three, performing convex pushing and secondary pressure maintaining; and step four, carrying out heat treatment on the welded joint of the steel rail. The method effectively improves the quality of the welded joint of the hypereutectoid steel rail of 60 kg/m. The invention also discloses a device for executing the method.)

1. A60 kg/m hypereutectoid steel rail gas pressure welding method is characterized by comprising the following steps:

heating a to-be-welded part of the steel rail by using oxygen-acetylene flame, wherein a heater of a pneumatic welding device swings in a range of 3-5 mm, the heating time is 300-350 s, the oxygen flow is 75-90L/min, the acetylene flow is 85-95L/min, and when the surface temperature of the to-be-welded part of the steel rail is 1250-1350 ℃, gas is turned off to stop heating;

step two, performing upset welding, and performing primary pressure maintaining after the upset welding is finished;

step three, performing convex pushing and secondary pressure maintaining; and

and fourthly, carrying out heat treatment on the welded joint of the steel rail.

2. The air pressure welding method for the 60kg/m hypereutectoid steel rail according to claim 1, wherein the step one further comprises applying an initial pressure of 7-8T to the to-be-welded part of the steel rail during heating.

3. The gas pressure welding method of 60kg/m hypereutectoid steel rail according to claim 1, wherein the heater is a jet-suction type split heater comprising a plurality of fire holes which are arranged to jet flames toward the portion to be welded of the steel rail and have a diameter of 0.5mm to 0.8 mm.

4. The gas pressure welding method of 60kg/m hypereutectoid steel rails according to claim 3, wherein the plurality of fire holes comprise:

a plurality of rail top fire holes with the diameter of 0.7mm and opening towards the top surface of the steel rail;

a plurality of rail top side fire holes which are opened towards the top side of the steel rail and have the diameter of 0.8 mm;

a plurality of rail waist fire holes with the diameter of 0.7mm and opening towards the rail waist of the steel rail;

a plurality of rail bottom triangular region fire holes which are opened towards the rail bottom triangular region of the steel rail and have the diameter of 0.8 mm;

a plurality of rail base angle fire holes which are opened towards the rail base angle of the steel rail and have the diameter of 0.5 mm;

transition part fire holes which are opened towards the transition part between the rail bottom angle of the steel rail and the rail bottom plate and have the diameters of 0.6mm and 0.7 mm; and

a plurality of rail bottom plate middle fire holes with the diameter of 0.8mm and opening towards the middle of the rail bottom plate of the steel rail.

5. The gas pressure welding method for a 60kg/m hypereutectoid steel rail according to claim 1, wherein the upset force of the upset welding is 55-60T, the upset speed is 12-16 mm/s, and the upset amount is 29-33 mm.

6. The gas pressure welding method for 60kg/m hypereutectoid steel rails according to claim 1, wherein the primary pressure maintaining comprises applying a pressure of 55-60T to the welded joint of the steel rail for 3-5 s.

7. The gas pressure welding method for 60kg/m hypereutectoid steel rails according to claim 1, wherein the secondary pressure maintaining comprises applying a pressure to the welded joint of the steel rail for 15-25 s for 25-30T.

8. The gas pressure welding method for 60kg/m hypereutectoid steel rails according to claim 1, wherein said heat treatment comprises reheating and normalizing after said welded joint of said steel rail is cooled to 450 ℃ or lower.

9. The gas pressure welding method for 60kg/m hypereutectoid steel rails according to claim 1, further comprising the steps of performing end milling and grinding, rail pulling and rail aligning before welding.

10. A gas pressure welding apparatus, characterized in that it performs the method of any one of claims 1-9.

Technical Field

The invention belongs to the technical field of welding, and particularly relates to a 60kg/m hypereutectoid steel rail gas pressure welding method and a device for executing the method.

Background

The rise and development of seamless lines represents a major breakthrough and milestone in railway construction and railway construction. The hypereutectoid steel rail usually has the carbon content within the range of 0.90-1.10 wt%, the tensile strength of more than or equal to 1300MPa and the tread hardness of more than or equal to 390HB, and is suitable for manufacturing high-strength and ultra-large steel rails, such as a typical 60kg/m hypereutectoid steel rail. At present, the welding modes of the steel rail of the seamless track mainly include three types of flash welding (also called contact welding, including base flash welding and mobile flash welding), thermite welding, gas pressure welding and the like. The base flash welding is mainly used for in-plant welding; and thermite welding is adopted for on-site replacement, laying, locking and rail breakage repair. Thermite welding of rails places high demands on the flux and on-site welding process. Because the welding flux composition and the preheating temperature are difficult to control, the welding seam is a casting structure, the joint quality is not high, the hardness of the thermite welding seam is far lower than that of the base metal, and the joint on a heavy-load circuit is seriously abraded.

Therefore, the heavy-load seamless line welded joint is a weak link, and has important significance for researching how to carry out strengthening and toughening welding on high-strength and oversized steel rails and obtaining the expected target of the joint which is comparable to that of a base metal.

Disclosure of Invention

The invention discloses a pneumatic welding method for a 60kg/m hypereutectoid steel rail, which solves the problems that the quality of the 60kg/m hypereutectoid steel rail is unstable due to the adoption of mobile flash welding, the internal component segregation of the steel rail affects the welding quality, and the continuous 15 joints are difficult to pass through a drop hammer. The invention also discloses a device for executing the method.

According to the invention, the invention provides a 60kg/m hypereutectoid steel rail gas pressure welding method, which comprises the following steps:

heating a to-be-welded part of a steel rail by using oxygen-acetylene flame, wherein a heater of a pneumatic welding device swings in a range of 3-5 mm, the heating time is 300-350 s, the oxygen flow is 75-90L/min, and the acetylene flow is 85-95L/min; when the surface temperature of the part to be welded of the steel rail is 1250-1350 ℃, closing the gas to stop heating;

step two, performing upset welding, and performing primary pressure maintaining after the upset welding is finished;

step three, performing convex pushing and secondary pressure maintaining; and

and step four, carrying out heat treatment on the welded joint of the steel rail.

According to an embodiment of the invention, the first step further comprises applying an initial pressure of 7-8T to the part to be welded of the steel rail during heating.

According to one embodiment of the present invention, the heater is a jet-suction type split heater including a plurality of fire holes arranged to spray a flame toward a portion to be welded of the rail and having a diameter of 0.5mm to 0.8 mm.

According to one embodiment of the present invention, the plurality of fire holes comprises:

a plurality of rail top fire holes with the diameter of 0.7mm and opening towards the top surface of the steel rail;

a plurality of rail top side fire holes which are opened towards the top side of the steel rail and have the diameter of 0.8 mm;

a plurality of rail waist fire holes with the diameter of 0.7mm and opening towards the rail waist of the steel rail;

a plurality of rail bottom triangular region fire holes which are opened towards the rail bottom triangular region of the steel rail and have the diameter of 0.8 mm;

a plurality of rail base angle fire holes which are opened towards the rail base angle of the steel rail and have the diameter of 0.5 mm;

transition part fire holes which are opened towards the transition part of the rail bottom angle of the steel rail and the middle thickness of the rail bottom plate and have the diameters of 0.6mm and 0.7 mm; and

a plurality of rail bottom plate middle fire holes with the diameter of 0.8mm and opening towards the middle of the rail bottom plate of the steel rail.

According to an embodiment of the present invention, the upset force of the upset welding is 55-60T, the upset speed is 12-16 mm/s, and the upset amount is 29-33 mm.

According to one embodiment of the invention, the primary pressure maintaining comprises applying the pressure to the welding joint of the steel rail for 3-5 s for 55-60T.

According to one embodiment of the invention, the secondary pressure maintaining comprises applying pressure to the welding joint of the steel rail for 15-25 s for 25-30T.

According to one embodiment of the invention, the heat treatment comprises reheating and normalizing the welded joint of the rail after it has cooled to below 450 ℃.

According to one embodiment of the invention, the method further comprises the steps of performing end milling and grinding, rail pulling, rail aligning prior to welding.

According to the present invention, a gas pressure welding apparatus is provided, which performs the above method.

Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages:

1. by adopting the technical scheme of the invention, the connection of the hypereutectoid steel rails of 60kg/m can be successfully completed by using air pressure welding, the internal defects of the steel rail joints are few, the welding quality is stable, and 15 continuous joints pass drop hammer type detection;

2. the heater swings in a specific amplitude range in the welding process, so that the parts to be welded are uniformly heated, and the welding quality is further improved;

3. and maintaining the pressure after the upsetting and the pushing to ensure that metal atoms on the end surface of the steel rail to be welded mutually permeate and diffuse under the action of pressure to form connection among the metal atoms, and crystallization is finished under the action of pressure, so that a joint forms a forging structure, and the quality of the joint is greatly improved.

Drawings

FIG. 1 is a schematic diagram of a GPW-1200 full-automatic numerical control large-scale gas pressure rail welding machine;

FIG. 2 is a flow chart of a 60kg/m hypereutectoid steel rail gas pressure welding method according to the present invention;

FIG. 3 is a cross-sectional view of a jetting and sucking type split heater according to the present invention;

FIG. 4 is a schematic view of a fire hole distribution according to the present invention.

In the figure, the position of the upper end of the main shaft,

the device comprises a movable end 1, a push convex device 2, a heater 3, a body 31, a cavity 32, a gas inlet 33, a water inlet 34, a water outlet 35, a fire hole 36, a static end 4, an upsetting oil cylinder 5, a water-gas valve block 6, a clamp 7 and an operation box 8.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The principle of gas pressure welding is a solid welding method by heating and pressurizing the surface to be welded of steel rail. The gas pressure welding equipment comprises small-sized gas pressure welding and large-sized movable gas pressure welding. The traditional small numerical control gas pressure welding plays a certain role in the construction of seamless railways, but due to the limitation of equipment, a plurality of workers are required to be skillfully matched to complete the welding task, the quality is not easy to control, the production rate is not high, the labor intensity of the workers is high, the welding quality is easily influenced by human factors, for example, the upsetting time is often determined by the personal experience of the workers to judge the temperature of the steel rail, so that the application range of the steel rail is limited. As the small-sized gas pressure welding is no longer suitable for the requirement of the rapid construction of the current railway, on the basis of the small-sized gas pressure welding, the YHGQ-1200 gas pressure welding rail car independently researched and developed in China is configured with a GPW-1200 type welding machine, the structure of the welding rail car is shown in figure 1, a machine head adopts a four-guide-shaft clamp type design, and the machine head generally comprises a movable end 1, a push-convex device 2, a heater 3, a static end 4, an upsetting oil cylinder 5, a water-gas valve block 6, a clamp 7 and an operation box 8. The welding machine is hydraulically driven, and a series of functions of automatic alignment, automatic clamping, pressure maintaining and the like of the working edge of the rail to be welded can be realized through a control system. Before welding, inputting all welding parameters (swing amplitude of a heater, heating time, gas flow and the like), and realizing automatic control in the whole process through PLC programming without intervention of operators in the welding process, and automatically recording a welding process curve. The present invention preferably employs a GPW-1200 type welder as described above, it being understood that one skilled in the art may also use other similar types of pressure welders to perform the method of the present invention depending on the actual operating conditions.

FIG. 2 shows the flow of the 60kg/m hypereutectoid steel rail gas pressure welding method according to the present invention. The method can be suitable for hypereutectoid steel rails with the tensile strength of more than or equal to 1300MPa and the tread hardness of more than or equal to 390 HB. The welding parent metal comprises the following chemical components in percentage by weight: 0.90-1.10% of C, 0.20-0.80% of Si, 0.40-1.20% of Mn, 0.2-0.70% of Cr, 0.1-0.12% of V, 0.01-0.004% of Al, and the balance of Fe and inevitable impurity elements. Wherein, the impurity elements comprise but not limited to the following components in percentage by weight: p is less than or equal to 0.020 percent, and S is less than or equal to 0.025 percent.

In order to ensure the quality of the gas pressure welding, the steps of polishing, derusting and end milling are required to be carried out before the gas pressure welding of the steel rail. In the example of the invention, a special end milling machine can be used for milling the steel rail before welding, and 30-40 mm of rust and oxides near the weld crater are polished clean until the metallic luster is exposed. The inclination deviation of the end face of the steel rail after treatment is less than or equal to 0.2mm, the clearance after seaming is less than or equal to 0.3mm, burrs at the edge of the end part of the steel rail are treated by a file after end milling is finished, and the treated welding end face is immediately welded. Avoid receiving secondary pollution such as greasy dirt after handling, carry out hoist and mount centre gripping with the rail, wash the rail tip section with carbon tetrachloride before the welding. The treated steel rail is centered, the air pressure welding of the steel rail adopts a constant displacement control process, the smoothness and the welding quality of the welded steel rail are ensured, the initial pressure maintaining pressure is applied to the steel rail in advance in the heating process, meanwhile, the longitudinal displacement of the steel rail before upsetting in the welding process is ensured to be unchanged through a welding machine control system, and the thermal stress change of the welded joint of the steel rail before upsetting freely changes along with the change of temperature.

After the end face is qualified, before ignition and welding, the state performance of the pipeline and the equipment needs to be checked again, and when an operator walks, the operator does not need to step on various adhesive tape pipelines to prevent the heater from blasting and tempering. And the detonation ignition is adopted, namely smokeless ignition is adopted. The ignition location is spaced from the vicinity of the weld to avoid contaminating the weld. And after supplying air for 3-4 s, igniting the heater by using an igniter. The ignition will detonate without soot. After the preparation is completed, the following steps can be executed:

firstly, heating a to-be-welded part of a steel rail by using oxygen-acetylene flame, wherein a heater of a pneumatic welding device swings in a range of 3-5 mm, the heating time is 300-350 s, the oxygen flow is 75-90L/min, and the acetylene flow is 85-95L/min. Preferably, the initial pressure during heating may be set to 7 to 8T (tons). In the gas pressure welding process, heating is closely related to upset forging. When heating, the steel rail absorbs heat along with the rise of temperature, the vibration energy of atoms is increased, the amplitude is increased, the diffusion is rapidly accelerated, a portable infrared thermometer and matched software can be used for temperature monitoring in the heating process, and when the surface temperature of the to-be-welded part of the steel rail is 1250-1350 ℃, gas is turned off to stop heating.

And step two, performing upset forging welding. In the present invention, the upset force of the upset welding is preferably 55-60T, the upset speed is preferably 12-16 mm/s, and the upset amount is preferably 29-33 mm. And (3) performing one-time pressure maintaining after the upsetting welding is finished, namely continuously applying pressure of 55-60T to the welding joint (namely the welding joint) of the steel rail for 3-5 s, so that metal atoms on the end face of the steel rail to be welded mutually permeate and diffuse under the action of the pressure to form connection among the metal atoms, and finishing the welding process of the steel rail.

And step three, performing convex pushing and secondary pressure maintaining. The secondary pressure maintaining comprises the step of continuously applying pressure for 25-30T to the welding joint of the steel rail for 15-25 s, and the forging structure of the welding head is further perfected on the basis of the same principle as the primary pressure maintaining.

And step four, carrying out heat treatment on the welded joint of the steel rail. And (3) after the secondary pressure maintaining is finished, after the gas pressure welding joint is cooled to below 450 ℃, the welding joint is completely converted into pearlite and a small amount of secondary cementite, and then the steel rail is reheated for normalizing so as to avoid coarse joint grains after normalizing. The purpose of the post-welding normalizing treatment of the steel rail is to control the grain size of the structures of a welding seam area and a heat affected zone of a welding joint and re-austenitize the steel rail with the transformed surface structure of the welding seam area. In the example of the invention, compressed air cooling forced cooling treatment can be adopted, and the clamping of the two ends of the steel rail welding joint is released after the surface of the steel rail is forced to be cooled to a certain temperature.

The rail can be polished after normalizing, the polished surfaces are the rail head tread and the rail side surface, the polished contour should keep the original rail head contour as much as possible, the weld beading at the part below the rail web must be completely polished, and the other part of the weld beading is excessive to the arc of the base metal.

The invention simultaneously controls the flame sprayed towards different parts of the steel rail in the process of gas pressure welding, and the control is realized by adjusting the diameters of fire holes at different positions in the heater. In particular, the present invention employs a jet-suction type split heater 3 as shown in fig. 3. The injector-type folio heater 3 generally comprises a body 31, a cavity 32 defined by the body 31 and intended to receive the rail 9, a gas inlet 33 connected to the two sides of the upper end of the body 31, and a water inlet 34, a water outlet 35 also connected to the two sides of the upper end of the body 31, respectively. When heating, the heater uses gas to spray flames through a plurality of fire holes 36 distributed on the inner wall of the body 31 towards the steel rail 9 located in the cavity 32. Because the shape of the steel rail is complex, the heating temperature is high during the gas pressure welding, therefore, the heater needs to have good performance of keeping the mixture of oxygen and combustible gas to ensure stable combustion, and also needs to change the distribution, size and number of fire holes of each part along with the change of the shape and the section size of the steel rail, and the diameter of the fire holes is proper and the number is sufficient, so that the welding flame is distributed reasonably, the steel rail is heated uniformly, and the rapid and uniform heating of each part of the steel rail is ensured. In an example of the present invention, a heater for a 60kg/m hypereutectoid steel rail gas pressure welding contains a fire hole distribution pattern as shown in fig. 4. Specifically, the inner wall of the heater can be distributed with: a plurality of railhead face fire holes towards the top face opening of rail and the diameter is 0.7mm are a plurality of railhead side fire holes towards the top side face opening of rail and the diameter is 0.8mm, a plurality of railhead face fire holes towards the web opening of rail and the diameter is 0.7mm, a plurality of railhead triangular space fire holes towards the railhead triangular space opening of rail and the diameter is 0.8mm, a plurality of railhead corner fire holes towards the railhead corner opening of rail and the diameter is 0.5mm, transition position fire holes towards the railhead corner of rail and the middle thickness transition position opening of rail bottom plate and the diameter is 0.6mm and 0.7mm, and a plurality of rail bottom plate middle fire holes towards the middle opening of rail bottom plate and the diameter is 0.8 mm. The fire hole distribution modes with different diameters can ensure the uniformity of the temperature field of the steel rail joint, and further effectively improve the joint quality.

The following is a specific example of a 60kg/m hypereutectoid steel rail gas pressure welding method according to the present invention.

Example 1

In this embodiment, in order to ensure the quality of the gas pressure welding, a special end milling machine is used to mill the steel rail before welding, and 30mm of rust and oxides near the welded junction are polished clean until the metallic luster is exposed. The inclination deviation of the end face of the steel rail is 0.1mm after the treatment, the gap is 0.2mm after the joint closing, burrs at the edge of the end part of the steel rail are treated by a file after the end milling is finished, and the treated welding end face is immediately welded. Avoid receiving secondary pollution such as greasy dirt after handling, carry out hoist and mount centre gripping with the rail, wash the rail tip section with carbon tetrachloride before the welding. After the end face is qualified, before ignition and welding, the state performance of the pipeline and the equipment needs to be checked again, and when an operator walks, the operator does not need to step on various adhesive tape pipelines to prevent the heater from blasting and tempering. And the detonating ignition is adopted, and the ignition position is 40mm away from the welding line so as to avoid polluting the welding line. After supplying the gas for 3 seconds, the heater of the pressure welding apparatus was ignited by an igniter.

The part to be welded of the rail is heated using an oxygen-acetylene flame and the steps of heating, upset welding, bulging and pressure maintaining are performed in sequence according to the following parameters. The following welding parameters were used in each step:

and (3) after the pressure maintaining is finished twice, after the gas pressure welding joint is cooled to below 450 ℃, the welding joint is completely converted into pearlite and a small amount of secondary cementite, and then the steel rail is reheated for normalizing so as to avoid coarse joint grains after normalizing. And (3) polishing the steel rail after normalizing, wherein the polishing surfaces are a steel rail head tread and a steel rail side surface, the polishing profile should keep the profile of the original steel rail head as much as possible, the weld beading at the part below the rail web must be completely polished, and the other part of the weld beading is excessive to the arc of the base metal.

Example 2

In this embodiment, the same tip end milling and polishing rust removal steps as those in embodiment 1 were performed.

And the detonating ignition is adopted, and the ignition position is 40mm away from the welding line so as to avoid polluting the welding line. After supplying the gas for 4 seconds, the heater of the pressure welding apparatus was ignited by an igniter.

The part to be welded of the rail is heated using an oxygen-acetylene flame and the steps of heating, upset welding, bulging and pressure maintaining are performed in sequence according to the following parameters. The following welding parameters were used in each step:

and (3) after the pressure maintaining is finished twice, after the gas pressure welding joint is cooled to below 450 ℃, the welding joint is completely converted into pearlite and a small amount of secondary cementite, and then the steel rail is reheated for normalizing so as to avoid coarse joint grains after normalizing. And (3) polishing the steel rail after normalizing, wherein the polishing surfaces are a steel rail head tread and a steel rail side surface, the polishing profile should keep the profile of the original steel rail head as much as possible, the weld beading at the part below the rail web must be completely polished, and the other part of the weld beading is excessive to the arc of the base metal.

Example 3

In this embodiment, the same tip end milling and polishing rust removal steps as those in embodiment 1 were performed.

And the detonating ignition is adopted, and the ignition position is 40mm away from the welding line so as to avoid polluting the welding line. After supplying the gas for 3 seconds, the heater of the pressure welding apparatus was ignited by an igniter.

The part to be welded of the rail is heated using an oxygen-acetylene flame and the steps of heating, upset welding, bulging and pressure maintaining are performed in sequence according to the following parameters. The following welding parameters were used in each step:

and (4) after the pressure maintaining is finished for two times, reheating the steel rail for normalizing when the gas pressure welding joint is cooled to be below 450 ℃. And (3) polishing the steel rail after normalizing, wherein the polishing surfaces are a steel rail head tread and a steel rail side surface, the polishing profile should keep the profile of the original steel rail head as much as possible, the weld beading at the part below the rail web must be completely polished, and the other part of the weld beading is excessive to the arc of the base metal.

Example 4

In this embodiment, the same tip end milling and polishing rust removal steps as those in embodiment 1 were performed.

And the detonating ignition is adopted, and the ignition position is 40mm away from the welding line so as to avoid polluting the welding line. After supplying the gas for 4 seconds, the heater of the pressure welding apparatus was ignited by an igniter.

The part to be welded of the rail is heated using an oxygen-acetylene flame and the steps of heating, upset welding, bulging and pressure maintaining are performed in sequence according to the following parameters. The following welding parameters were used in each step:

and (4) after the pressure maintaining is finished for two times, reheating the steel rail for normalizing when the gas pressure welding joint is cooled to be below 450 ℃. And (3) polishing the steel rail after normalizing, wherein the polishing surfaces are a steel rail head tread and a steel rail side surface, the polishing profile should keep the profile of the original steel rail head as much as possible, the weld beading at the part below the rail web must be completely polished, and the other part of the weld beading is excessive to the arc of the base metal.

Example 5

In this embodiment, the same tip end milling and polishing rust removal steps as those in embodiment 1 were performed.

And the detonating ignition is adopted, and the ignition position is 40mm away from the welding line so as to avoid polluting the welding line. After supplying the gas for 4 seconds, the heater of the pressure welding apparatus was ignited by an igniter.

The part to be welded of the rail is heated using an oxygen-acetylene flame and the steps of heating, upset welding, bulging and pressure maintaining are performed in sequence according to the following parameters. The following welding parameters were used in each step:

and (4) after the pressure maintaining is finished for two times, reheating the steel rail for normalizing when the gas pressure welding joint is cooled to be below 450 ℃. And (3) polishing the steel rail after normalizing, wherein the polishing surfaces are a steel rail head tread and a steel rail side surface, the polishing profile should keep the profile of the original steel rail head as much as possible, the weld beading at the part below the rail web must be completely polished, and the other part of the weld beading is excessive to the arc of the base metal.

Comparative example 1

In this comparative example, the same tip end milling and polishing rust removal steps as in example 1 were performed.

And the detonating ignition is adopted, and the ignition position is 40mm away from the welding line so as to avoid polluting the welding line. After supplying the gas for 3 seconds, the heater of the pressure welding apparatus was ignited by an igniter.

The part to be welded of the rail is heated using an oxygen-acetylene flame and the steps of heating, upset welding, bulging and pressure maintaining are performed in sequence according to the following parameters. The following welding parameters were used in each step:

and (5) maintaining the pressure, cooling the air pressure welding head to below 450 ℃, and reheating the steel rail for normalizing. And (3) polishing the steel rail after normalizing, wherein the polishing surfaces are the tread of the rail head of the steel rail and the side surface of the steel rail, and the polishing profile should keep the profile of the rail head of the original steel rail as much as possible.

Comparative example 2

In this comparative example, the same tip end milling and polishing rust removal steps as in example 1 were performed.

And the detonating ignition is adopted, and the ignition position is 40mm away from the welding line so as to avoid polluting the welding line. After supplying the gas for 4 seconds, the heater of the pressure welding apparatus was ignited by an igniter.

The part to be welded of the rail is heated using an oxygen-acetylene flame and the steps of heating, upset welding, bulging and pressure maintaining are performed in sequence according to the following parameters. The following welding parameters were used in each step:

and (5) maintaining the pressure, cooling the air pressure welding head to below 450 ℃, and reheating the steel rail for normalizing. And (3) polishing the steel rail after normalizing, wherein the polishing surfaces are the tread of the rail head of the steel rail and the side surface of the steel rail, and the polishing profile should keep the profile of the rail head of the original steel rail as much as possible.

The method of comparative example 1 does not set the heater swing amplitude, compared to examples 1 to 5, whereas the method of comparative example 2 heats the portion to be welded at a lower temperature. The following tests were performed on the rails welded using the methods of examples 1-5 and comparative examples 1-2, respectively: the temperature of the steel rail joint is less than or equal to 40 ℃, flaw detection is carried out on the joint, and drop hammer and fracture detection are carried out on the joint after the flaw detection is qualified. The weight of the drop hammer test is 1000kg, the height of the drop hammer is 3.8 m, 2 hammers are continuously qualified, the test piece after the drop hammer test is utilized, the opening at the bottom of the rail is supplemented with hammering and breaking, and whether the fracture has defects is visually checked. The drop test results and fracture inspection conditions of the 60kg/m hypereutectoid steel rail pneumatic welding head are shown in the following table:

the results showed that comparative examples 1 and 2 failed to drop weight, and comparative example 1 failed to drop weight due to the lack of heater swing during heating, narrow heating range, insufficient upset amount, and unwelded joint. Comparative example 2 second hammer-break, drop weight was not acceptable due to insufficient heating temperature, insufficient upset amount, and unwelded joint defects. It can be seen that performing gas pressure welding on a 60kg/m hypereutectoid steel rail using the welding parameters defined herein can result in a weld joint with good performance.

The steel rail is not melted in the process of gas pressure welding, so that a welding seam has no decarburized layer, which is a place where gas pressure welding is superior to flash welding; the gas pressure weld joint is a forged structure, which is where gas pressure welding is preferred over thermite welding. Theoretically, the strength of the pneumatic welding head is not lower than that of flash welding and better than that of thermite welding. The hypereutectoid steel rail adopts gas pressure welding, the segregation of the internal components of the steel rail has no obvious influence on the welding quality, the process parameter range can be widely adjusted, the applicability is strong, and the hypereutectoid steel rail can replace thermite welding to perform on-line locking welding.

The above examples only express embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.