阅读说明：本技术 75kg/m过共析钢轨与共析钢轨气压焊接方法及焊接件 (Air pressure welding method and weldment for 75kg/m hypereutectoid steel rail and eutectoid steel rail ) 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75kg/m过共析钢轨与共析钢轨气压焊接方法,包含以下步骤：步骤一,第一阶段加热,其中,氧气流量为95～105SLM,乙炔流量为105～115SLM,加热时间为250～300s；步骤二,第二阶段加热,其中,氧气流量为85～90SLM,乙炔流量为90～95SLM,加热时间为80～100s,待钢轨的待焊部位的表面温度为1250～1320℃时关闭燃气以停止加热；步骤三,执行顶锻焊接；步骤四,执行推瘤并保压；步骤五,喷风冷却；以及步骤六,热处理。该方法解决解决现有重载铁路上共析钢轨与新上道过共析钢轨的焊接困难问题。本发明同时公开了一种使用该方法焊接的焊接件。(The invention discloses a gas pressure welding method for a 75kg/m hypereutectoid steel rail and eutectoid steel rails, which comprises the following steps of: step one, heating in a first stage, wherein the flow of oxygen is 95-105 SLM, the flow of acetylene is 105-115 SLM, and the heating time is 250-300 s; step two, heating in a second stage, wherein the oxygen flow is 85-90 SLM, the acetylene flow is 90-95 SLM, the heating time is 80-100 s, and when the surface temperature of the to-be-welded part of the steel rail is 1250-1320 ℃, the fuel gas is closed to stop heating; thirdly, performing upset forging welding; step four, performing tumor pushing and maintaining pressure; fifthly, air spraying and cooling; and step six, heat treatment. The method solves the problem that the eutectoid steel rail on the existing heavy haul railway and the hypereutectoid steel rail on the new upper track are difficult to weld. The invention also discloses a welding part welded by using the method.)

1. A75 kg/m hypereutectoid steel rail and eutectoid steel rail gas pressure welding method is characterized by comprising the following steps:

firstly, heating a part to be welded of the steel rail by using oxygen-acetylene flame in a first stage, wherein the flow of oxygen for heating in the first stage is 95-105 SLM, the flow of acetylene is 105-115 SLM, and the heating time is 250-300 s;

secondly, heating the part to be welded of the steel rail in a second stage by using oxygen-acetylene flame, wherein the oxygen flow rate of the second stage heating is 85-90 SLM, the acetylene flow rate is 90-95 SLM, the heating time is 80-100 s, and when the surface temperature of the part to be welded of the steel rail is 1250-1320 ℃, gas is turned off to stop heating;

thirdly, performing upset forging welding;

step four, performing tumor pushing and maintaining pressure;

fifthly, carrying out air blasting cooling on the welded joint of the steel rail; and

and sixthly, performing heat treatment on the welded joint of the steel rail.

2. The gas pressure welding method for the 75kg/m hypereutectoid steel rail and the eutectoid steel rail according to claim 1, wherein the first step further comprises applying an initial pressure of 8-9T to the to-be-welded portion of the steel rail during heating.

3. The method for gas-pressure welding of a 75kg/m hypereutectoid steel rail to a eutectoid steel rail according to claim 1, wherein a heater of the gas-pressure welding apparatus is oscillated in an amplitude of 5 to 10 mm.

4. The gas pressure welding method for a 75kg/m hypereutectoid steel rail and a eutectoid steel rail according to claim 1, wherein the upset forging time of the upset forging welding is 1 to 3 seconds, and the upset forging amount is 30 to 33 mm.

5. The gas pressure welding method for a 75kg/m hypereutectoid steel rail and a eutectoid steel rail according to claim 1, wherein the pressure maintaining comprises applying a pressure to the welded joint of the steel rail for 20 to 30 seconds for 30 to 35T.

6. The gas pressure welding method of 75kg/m hypereutectoid steel rail and eutectoid steel rail according to claim 1, wherein the final cooling temperature of the welded joint after the cooling by the blast is less than 450 ℃.

7. The pneumatic welding method for a 75kg/m hypereutectoid steel rail and a eutectoid steel rail according to claim 6, wherein the air-cooling air-jet pressure is 0.3 MPa.

8. The gas pressure welding method of a 75kg/m hypereutectoid steel rail and eutectoid steel rail according to claim 1, wherein said sixth step comprises reheating and normalizing the welded joint of said steel rail.

9. The gas pressure welding method of 75kg/m hypereutectoid steel rails and eutectoid 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 welded article of a 75kg/m hypereutectoid steel rail and a eutectoid steel rail, wherein the 75kg/m hypereutectoid steel rail and the eutectoid steel rail are welded by the welding method according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of welding, and particularly relates to a gas pressure welding method for a 75kg/m hypereutectoid steel rail and eutectoid steel rails, and a welding piece for the 75kg/m hypereutectoid steel rail and the eutectoid steel rails welded by using the method.

Background

In response to the development trend of heavy haul railway large axle load and high density transportation mode, the steel rail with tread hardness of more than 420HB has wide market prospect in heavy haul railway. The existing full pearlite steel rail only adopts special production processes of alloying, controlled rolling, controlled cooling and the like, and the highest tread hardness can only reach about 430 HB. Therefore, heavy-duty lines at home and abroad are focused on hypereutectoid steel rails. The hypereutectoid steel rail has the advantages that the carbon content is increased, the metallographic structure is pearlite and a small amount of secondary cementite, and the wear resistance of the steel rail is improved. 75m or 100m fixed length steel rails produced by steel mills are connected to form a seamless line by a welding technology for domestic and foreign heavy haul railways, so that the smoothness of the line is improved, the impact of wheel rails is reduced, and the service life of the wheel rails is prolonged. For hypereutectoid steel rails and eutectoid steel rails with different strength grades and materials, the welding is greatly difficult due to the difference of the properties and chemical components of the base metal.

Therefore, a need exists in the field of railway engineering for a method for welding hypereutectoid steel rails and eutectoid steel rails, which can efficiently and excellently weld the hypereutectoid steel rails and the eutectoid steel rails at a low cost.

Disclosure of Invention

The invention discloses a gas pressure welding method for a 75kg/m hypereutectoid steel rail and a eutectoid steel rail, which solves the problem of difficult welding of the eutectoid steel rail and a new upper-track hypereutectoid steel rail on the existing heavy haul railway. The invention also discloses a welding piece of the hypereutectoid steel rail and the eutectoid steel rail welded by using the method at 75 kg/m.

According to the invention, the invention provides a 75kg/m hypereutectoid steel rail and eutectoid steel rail gas pressure welding method, which comprises the following steps:

firstly, heating a part to be welded of a steel rail by using oxygen-acetylene flame in a first stage, wherein the flow of oxygen for heating in the first stage is 95-105 SLM, the flow of acetylene is 105-115 SLM, and the heating time is 250-300 s;

secondly, heating the part to be welded of the steel rail in a second stage by using oxygen-acetylene flame, wherein the oxygen flow rate of the second stage heating is 85-90 SLM, the acetylene flow rate is 90-95 SLM, the heating time is 80-100 s, and when the surface temperature of the part to be welded of the steel rail is 1250-1320 ℃, gas is turned off to stop heating;

thirdly, performing upset forging welding;

step four, performing tumor pushing and maintaining pressure;

fifthly, air-jet cooling is performed; and step six, 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 8-9T to the part to be welded of the steel rail during heating.

According to one embodiment of the present invention, the heater of the gas pressure welding apparatus oscillates at an amplitude of 5 to 10 mm.

According to an embodiment of the present invention, the upset forging time of the upset forging welding is 1-3 s, and the upset forging amount is 30-33 mm.

According to one embodiment of the invention, the pressure maintaining comprises applying the pressure to the welded joint of the steel rail for 20-30 s for 30-35T.

According to one embodiment of the invention, the final cooling temperature of the weld joint after cooling by the blast is less than 450 ℃.

According to one embodiment of the invention, the pressure of the air jet for cooling the air jet is 0.3 MPa.

According to one embodiment of the invention, step six comprises reheating and normalizing the welded joint of the rail.

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 invention, the hypereutectoid steel rail of 75kg/m and the eutectoid steel rail welding piece are welded by the welding 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 rail of 75kg/m and the eutectoid steel rail can be successfully completed by using air pressure welding, the internal defects of the steel rail joint are few, the welding quality is stable, and the static bending, fatigue and drop hammer inspection can be smoothly passed;

2. the welding is heated in two stages, so that the welding productivity can be improved, the surface temperature and the internal temperature of the part to be welded of the steel rail can be more uniformly distributed, and the welding quality can be improved;

3. the heater adopts larger swing during heating, so that the temperature fields at the left and the right of the welding line are uniformly distributed, the tissue is uniformly changed, and the welding quality is favorably improved.

Drawings

FIG. 1 is a flow chart of a gas pressure welding method of a 75kg/m hypereutectoid steel rail and eutectoid steel rails according to the present invention;

FIG. 2 is a schematic diagram of a GPW-1200 full-automatic numerical control large-scale gas pressure rail welding machine;

fig. 3 is a cross-sectional view of a jetting and sucking type split heater 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.

Fig. 1 shows a gas pressure welding method of a 75kg/m hypereutectoid steel rail and a eutectoid steel rail according to the present invention, which employs the gas pressure welding method. 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 2, a machine head adopts a four-guide-shaft clamp type design, and the machine head generally comprises a movable end 1, a push-bump 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.

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 appearance of the heater, the size of the fire holes and the distribution of the fire holes of the gas pressure welding can obviously influence the distribution condition of the temperature field of the steel rail joint, and further influence the quality of the joint. The invention adopts an injection-suction type split heater 3, as shown in figure 3. The injector-type folio heater 3 generally comprises a body 31, a cavity 323 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.

The gas pressure welding method of the hypereutectoid steel rail of 75kg/m and the eutectoid steel rail can be suitable for welding the eutectoid steel rail and the new hypereutectoid steel rail used at present. Specifically, the eutectoid steel has a metallographic structure of pearlite, and comprises the following chemical components in percentage by weight: 0.72-0.82% of C, 0.5-0.80% of Si, 0.7-1.05% of Mn, 0.001-0.70% of Cr, 0.08-0.12% of V, 0.001-0.004% of Al, and the balance of Fe and inevitable impurity elements, wherein the impurity elements comprise, but are not limited to: p is less than or equal to 0.025 percent, and S is less than or equal to 0.025 percent; the hypereutectoid steel rail has a metallographic structure comprising pearlite and a small amount of secondary cementite, and comprises the following chemical components in percentage by weight: 0.90-1.20% of C, 0.10-0.80% of Si, 0.40-1.30% of Mn, 0.001-0.70% of Cr, 0.001-0.12% of V, 0.001-0.004% of Al, and the balance of Fe and inevitable impurity elements, wherein the impurity elements comprise, but are not limited to: 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 0.1mm, the clearance after seaming is less than or equal to 0.2mm, 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 part to be welded of a steel rail by using oxygen-acetylene flame in a first stage, wherein the oxygen flow rate of the first-stage heating is 95-105 SLM, the acetylene flow rate is 105-115 SLM, and the heating time is 250-300 s. Preferably, the initial pressure during heating may be set to 8 to 9T (tons).

The heating of the steel rail gas pressure welding releases heat through the combustion of fuel gas, and the welded end face of the steel rail is heated in a certain range. The welding heating is divided into two stages, the first stage flame energy rate is slightly larger, the welding productivity can be improved, the second stage flame energy rate is slightly smaller, the heat preservation and soaking effects are achieved, the temperature distribution of the end faces to be welded of the steel rails is more uniform, and the rail waist is prevented from generating the overburning defect. Further preferably, the heater of the gas pressure welding apparatus oscillates in a range of 5 to 10 mm. The adoption of larger swing leads the temperature field distribution on the left and the right of the welding line to be uniform, achieves the uniform transformation of the structure and is beneficial to improving the welding quality.

And secondly, heating the part to be welded of the steel rail in a second stage by using oxygen-acetylene flame, wherein the oxygen flow rate of the second stage heating is 85-90 SLM, the acetylene flow rate is 90-95 SLM, the heating time is 80-100 s, and the fuel gas is closed to stop heating when the surface temperature of the part to be welded of the steel rail is 1250-1320 ℃.

And step three, performing upset forging welding. Wherein the upsetting amount is preferably 30mm to 33mm, and the upsetting time is preferably 1 to 3 seconds.

And step four, performing tumor pushing and maintaining pressure. Wherein, the pressure maintaining process comprises continuously applying pressure to the welded joint of the steel rail for 20-30 s for 30-35T.

And fifthly, carrying out air blasting cooling on the welded joint of the steel rail. After the push button is finished, in order to improve the productivity, the joint is immediately cooled by air spraying, and the air spraying pressure is 0.3 MPa. After the air blast cooling, the final cooling temperature of the welding joint is lower than 450 DEG C

And step six, performing heat treatment, namely cooling the welding joint by blowing air to below 450 ℃, and reheating the steel rail for normalizing treatment after the welding joint of the steel rail is completely transformed into a pearlite structure so as to avoid coarse joint grains after normalizing. The purpose of the normalizing treatment after the steel rail is welded is to control the grain size of the structures of a welding seam area and a heat affected zone of a welding joint, re-austenitizing the steel rail with the transformed surface structure of the welding seam area, performing forced cooling treatment by adopting compressed air cooling, and loosening the clamping of two ends of the welding joint of the steel rail after the surface of the steel rail is forcibly 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 following is a specific example of a gas pressure welding method of a 75kg/m hypereutectoid steel rail and eutectoid steel rail 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 40mm 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 0.15mm 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, 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.

Heating the part to be welded of the steel rail by using oxygen-acetylene flame, and sequentially performing the steps of first-stage heating, second-stage heating, upset forging welding, tumor pushing and pressure maintaining according to the following parameters. The following welding parameters were used in each step:

and after the air spraying cooling is finished, cooling the air pressure welding head to 430 ℃, stopping air spraying, and reheating for normalizing. And (3) polishing the steel rail after normalizing, wherein the polishing surface is 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.

Heating the part to be welded of the steel rail by using oxygen-acetylene flame, and sequentially performing the steps of first-stage heating, second-stage heating, upset forging welding, tumor pushing and pressure maintaining according to the following parameters. The following welding parameters were used in each step:

and after the air spraying cooling is finished, cooling the air pressure welding head to 440 ℃, stopping air spraying, and reheating for normalizing. And (3) polishing the steel rail after normalizing, wherein the polishing surface is 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.

Heating the part to be welded of the steel rail by using oxygen-acetylene flame, and sequentially performing the steps of first-stage heating, second-stage heating, upset forging welding, tumor pushing and pressure maintaining according to the following parameters. The following welding parameters were used in each step:

and after the air spraying cooling is finished, cooling the air pressure welding head to 445 ℃, stopping air spraying, and reheating for normalizing. And (3) polishing the steel rail after normalizing, wherein the polishing surface is 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 3 seconds, the heater of the gas pressure welding apparatus was ignited by an igniter.

Heating the part to be welded of the steel rail by using oxygen-acetylene flame, and sequentially performing the steps of first-stage heating, second-stage heating, upset forging welding, tumor pushing, pressure maintaining and air blast cooling according to the following parameters. The following welding parameters were used in each step:

and after the air injection cooling is finished, cooling the air pressure welding head to 449 ℃, stopping air injection, and reheating for normalizing. And (3) polishing the steel rail after normalizing, wherein the polishing surface is 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.

The steel rails obtained in examples 1 to 4 were stable in welding quality, and could pass static bending, fatigue and drop test smoothly, and no obvious defect was found in the fracture by visual inspection. The results of the static bending and fatigue tests of the pneumatic welding joints of examples 1 to 3 are shown in tables 1 and 2. Examples 1-4 the results of the drop weight test for the pneumatic welding head are shown in table 3.

TABLE 1 static bending result of gas pressure welding joint for hypereutectoid steel rail and eutectoid steel rail

Note: the static bending test refers to TB/T1632.4-2014 standard, the rail is 75kg/m, the pressure test force of the rail head is not less than 1850kN continuously, and the rail is qualified. In the test, the test force is increased by 30 percent and reaches 2405kN continuously.

TABLE 2 fatigue test results of pneumatic welded joints of hypereutectoid steel rails and eutectoid steel rails

Comparative example 1

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

Heating the part to be welded of the steel rail by using oxygen-acetylene flame, and sequentially performing the steps of first-stage heating, second-stage heating, upset forging welding, tumor pushing and pressure maintaining according to the following parameters. The following welding parameters were used in each step:

after the air injection cooling is finished, reheating and normalizing. And (3) polishing the steel rail after normalizing, wherein the polishing surface is 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 2

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

Heating the part to be welded of the steel rail by using oxygen-acetylene flame, and sequentially performing the steps of first-stage heating, second-stage heating, upset forging welding, tumor pushing and pressure maintaining according to the following parameters. The following welding parameters were used in each step:

after the air injection cooling is finished, reheating and normalizing. And (3) polishing the steel rail after normalizing, wherein the polishing surface is 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 has a smaller flame energy rate throughout the heating process than examples 1-4; comparative example 2 although the welding time was proper, the heat input was still insufficient due to the small flame energy rate. The following tests were performed on the rails welded using the methods of examples 1-4 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 pneumatic welding joint of the hypereutectoid steel rail and the eutectoid steel rail of 75kg/m are shown in the following table:

TABLE 3 drop test results and fracture inspection of pneumatic welded joints of hypereutectoid steel rails and eutectoid steel rails

The results show that comparative examples 1 and 2 failed to drop weight, comparative example 1 failed to drop weight for the second hammer break, and failed to drop weight, because the total welding time was 330 seconds, and the welding heat input was small, the heating temperature was insufficient, and the joint had unwelded defects. Comparative example 2 the second hammer-off, drop weight, was not acceptable because the joint had an unwelded defect due to insufficient heat input due to the lower flame energy rate, although the welding time was adequate. It can be seen that performing gas pressure welding on 75kg/m hypereutectoid steel rails using the welding parameters defined herein can result in a weld joint with good performance.

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.