CN113618194B - 60kg/m hypereutectoid steel rail air pressure welding method and device - Google Patents
60kg/m hypereutectoid steel rail air pressure welding method and device Download PDFInfo
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- CN113618194B CN113618194B CN202110945238.1A CN202110945238A CN113618194B CN 113618194 B CN113618194 B CN 113618194B CN 202110945238 A CN202110945238 A CN 202110945238A CN 113618194 B CN113618194 B CN 113618194B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K5/00—Gas flame welding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K5/00—Gas flame welding
- B23K5/22—Auxiliary equipment, e.g. backings, guides
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- Engineering & Computer Science (AREA)
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- Pressure Welding/Diffusion-Bonding (AREA)
Abstract
The invention discloses a 60kg/m hypereutectoid steel rail air pressure welding method, which comprises the following steps of: heating a part to be welded 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 fuel gas to stop heating; step two, performing upset forging welding, and performing one-time pressure maintaining after the upset forging 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.
Description
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 tracks represents a major breakthrough and milestone in railway construction and railway construction. The hypereutectoid steel rail usually has the carbon content 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 hypereutectoid steel rail of 60 kg/m. At present, the welding modes of the steel rail of the seamless rail mainly comprise three types of flash welding (also called contact welding, including base flash welding and mobile flash welding), thermite welding, pneumatic 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 part to be welded of a steel rail by using oxygen-acetylene flame, wherein a heater of an air pressure 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 a steel 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 surface 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 which are opened towards the rail waist of the steel rail and have the diameter of 0.7 mm;
a plurality of rail bottom triangular area fire holes which are opened towards the rail bottom triangular area 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 angles of the steel rails 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 rail bottom plate middle 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, one pressure maintaining comprises applying the pressure to the welding joint of the steel rail for 3-5 s and for 55-60T.
According to one embodiment of the invention, the secondary pressure maintaining comprises applying 25-30T of pressure to the welding joint of the steel rail for 15-25 s.
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 end milling and grinding, rail pulling and rail aligning before welding.
According to the present invention, a gas pressure welding device 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 distribution of fire holes 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 do not 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 gas pressure welding and large 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 upset forging time usually depends on 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 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 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 to 1.10 percent of C,0.20 to 0.80 percent of Si,0.40 to 1.20 percent of Mn,0.2 to 0.70 percent of Cr,0.1 to 0.12 percent of V,0.01 to 0.004 percent 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 need 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 position is away from the vicinity of the weld to avoid contamination of the weld. After supplying air for 3-4 s, the heater is ignited by an igniter. It will detonate upon ignition, but 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, 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 at the time of 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 vibration energy of atoms is increased by the heat absorbed by the steel rail along with the rise of the temperature, the amplitude is increased, the diffusion is rapidly accelerated, the temperature can be monitored by a portable infrared thermometer and matched software in the heating process, and the gas is closed to stop heating when the surface temperature of the part to be welded of the steel rail is 1250-1350 ℃.
And step two, performing upset forging welding. In the example of the present invention, the upset force of the upset welding is preferably 55 to 60T, the upset speed is preferably 12 to 16mm/s, and the upset amount is preferably 29 to 33mm. And (3) performing one-time pressure maintaining after the upsetting welding is finished, namely continuously applying pressure 55-60T to the welding joint (namely the welding joint) of the steel rail for 3-5 s to ensure that metal atoms on the end surface 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 finish the steel rail welding process.
And step three, performing convex pushing and secondary pressure maintaining. The secondary pressure maintaining comprises the step of continuously applying pressure to the welding joint of the steel rail for 15-25 s for 25-30T, 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 welding 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 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 and the heating temperature is high during gas pressure welding, 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 at each part along with the change of the shape and 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 steel rail is heated quickly and uniformly. 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 railways top face fire holes that are 0.7mm towards the top surface opening of rail and the diameter are a plurality of railways top side fire holes that are 0.8mm towards the top side opening of rail and the diameter, a plurality of railways waist fire holes that are 0.7mm towards the web opening of rail and the diameter, a plurality of railways bottom triangle district fire holes that are 0.8mm towards the railways bottom triangle district opening and the diameter of rail, a plurality of railways bottom corner fire holes that are 0.5mm towards the railways bottom corner opening and the diameter of rail are 0.6mm and 0.7mm towards the railways bottom corner of rail and the transition position fire hole that is 0.6mm and diameter of rail bottom plate middle thickness transition position opening and diameter to and the rail bottom plate middle fire hole that is 0.8mm towards the rail bottom plate middle opening of rail. 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 the embodiment, in order to ensure the gas pressure welding quality, a special end milling machine is adopted to mill the steel rail before welding, and 30mm of rust and oxides near a welded junction are polished completely 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 pipelines and equipment needs to be checked again, and operators pay attention to not stepping on various adhesive tape pipelines when walking so as to prevent a 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 are adopted in each step:
and (3) after the pressure maintaining is finished twice, after the gas pressure welding joint is cooled to be 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 crystal 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 are 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 carrying out the steps of heating, upset forging welding, extruding and pressure maintaining 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 be 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 crystal 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 are 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 ℃. The rail is 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 weld beading is excessive with 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.
Heating the part to be welded of the steel rail by using oxygen-acetylene flame, and sequentially carrying out the steps of heating, upset forging welding, extruding and pressure maintaining according to the following parameters. The following welding parameters are adopted 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 are 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-of-weld 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-of-weld 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 oscillation amplitude, compared to examples 1 to 5, whereas the method of comparative example 2 is lower in the heating temperature of the portion to be welded. 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 in drop weight, and comparative example 1 failed in drop weight by second hammer-breaking and drop weight failure because the heater did not swing during heating, the heating range was narrow, the upset amount was insufficient, and the joint had unwelded defects. Comparative example 2 second hammer-off, drop hammer was not acceptable due to insufficient heating temperature, insufficient upset amount, 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 air pressure welding process, so that a welding seam has no decarburized layer, which is a place superior to flash welding in air pressure 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.
Claims (9)
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 forging welding, and performing one-time pressure maintaining after the upset forging welding is finished;
step three, performing secondary pressure maintaining after the convex pushing; and
and fourthly, carrying out heat treatment on the welding joint of the steel rail.
2. The gas pressure welding method for 60kg/m hypereutectoid steel rails according to claim 1, wherein the first step further comprises applying an initial pressure of 7 to 8T to the to-be-welded portion 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 which are opened towards the rail waist of the steel rail and have the diameter of 0.7 mm;
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.
5. The gas pressure welding method for 60kg/m hypereutectoid steel rails 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 pressure to the welded joint of the steel rail for 25 to 30T for 15 to 25 s.
8. A 60kg/m hypereutectoid steel rail gas pressure welding method 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.
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