CN114054916A

CN114054916A - Gas conveying device and steel rail flash welding method

Info

Publication number: CN114054916A
Application number: CN202111434566.1A
Authority: CN
Inventors: 陆鑫; 李大东; 邓健; 徐飞翔
Original assignee: Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd
Current assignee: Pangang Group Panzhihua Steel and Vanadium Co Ltd; Pangang Group Panzhihua Iron and Steel Research Institute Co Ltd; Pangang Group Xichang Steel and Vanadium Co Ltd
Priority date: 2021-11-29
Filing date: 2021-11-29
Publication date: 2022-02-18
Anticipated expiration: 2041-11-29
Also published as: CN114054916B

Abstract

The invention discloses a gas conveying device and a steel rail flash welding method, wherein the gas conveying device is used for providing shielding gas when a workpiece is welded, the device comprises a first pipeline and a second pipeline, two openings of the first pipeline are respectively butted with two openings of the second pipeline, so that the first pipeline and the second pipeline form a closed pipeline, the inner wall of the closed pipeline is provided with a gas outlet, and the outer wall of the closed pipeline is provided with a gas inlet. The invention can provide protective gas during welding to improve welding quality.

Description

Gas conveying device and steel rail flash welding method

Technical Field

The invention relates to the technical field of welding, in particular to a gas conveying device and a steel rail flash welding method.

Background

The flash butt welding of steel rails is a welding method in which steel rails on two sides are clamped by clamping devices such as conductive electrodes, the steel rails are in end contact after being electrified, resistance heat is generated at the contact point by conducting current, the contact point is rapidly melted to form flash and accompanied with strong splashing, and a certain upsetting force is applied after a certain flash allowance, so that the steel rails are recrystallized and formed at a high temperature.

The flash welding joint for steel rail belongs to the weak link of the whole line, the quality of the flash welding joint can directly influence the safety of the railway, and the welding defect in the flash welding joint for steel rail directly influences the welding quality of the joint. The current research shows that the defects of the steel rail flash welding head caused by the welding process mainly comprise gray spots, non-welding, overburning, overheating and the like. A large number of test statistics and research results show that the gray specks are the main inherent defects in the flash butt welding of the steel rail and are the most main factors of the failure of the steel rail drop weight and static bending tests.

In all domestic and foreign documents, "gray spot" ("dark spot", "flat spot", "mat spot" or "marco flat") defects are described as "having a surface without metallic luster, dark gray compared to the surrounding metallic matrix, and containing non-metallic inclusion oxides inside". From the mainstream view at home and abroad, the flash welding is characterized in that a fire hole is formed by large lintel blasting at the burning flash stage, elements such as silicon, manganese and aluminum in the fire hole are combined with [ O ] or ferric oxide in the air to form a non-metal inclusion oxide of aluminosilicate under the condition that metal steam does not sufficiently protect a joint, and the aluminosilicate has high melting point, is solid after being generated, has poor fluidity and is easy to be solidified on a melting surface. If the fire hole is deep, the aluminosilicate is not easily extruded during upsetting and remains in the pit, thereby forming silicate inclusion type soot spot.

At present, the formation of the gray spot defect is mainly controlled at home and abroad by adjusting the burning speed, the burning amount and the upsetting force at the final stage of a burning flash stage in steel rail flash welding process parameters. However, the gray spot defect is still the most main welding process factor influencing the service performance of the steel rail flash welding head so far, and if the gray spot defect in the flash welding head can be eliminated, the drop weight, the static bending and the service performance of the flash welding head can be improved powerfully.

Disclosure of Invention

The invention mainly aims to provide a gas conveying device and a steel rail flash welding method, which can effectively reduce the size and the number of gray spot defects in a joint and improve the steel rail flash welding quality.

According to one aspect of the invention, a gas delivery device is provided for providing shielding gas during welding of workpieces, the device comprising a first pipe and a second pipe, wherein two openings of the first pipe are respectively butted with two openings of the second pipe, so that the first pipe and the second pipe form a closed pipe, an inner wall of the closed pipe is provided with a gas outlet hole, and an outer wall of the closed pipe is provided with a gas inlet hole.

According to one embodiment of the invention, the workpiece is a steel rail, the shape of the inner wall of the closed conduit is matched with the cross-sectional shape of the steel rail, and the cavity enclosed by the inner wall of the closed conduit comprises a first enlarged part corresponding to the head part of the steel rail, a second enlarged part corresponding to the bottom part of the steel rail and a contracted part corresponding to the waist part of the steel rail.

According to an embodiment of the present invention, the air outlet hole is provided on an inner wall at the constricted portion, and the air inlet hole is provided on an outer wall at the second enlarged portion.

According to one embodiment of the invention, the inner diameter of the first pipeline and the second pipeline is 25-30 mm; and/or when the closed pipeline and the steel rail are concentrically arranged, the gap between the closed pipeline and the steel rail is 20-25 mm; and/or the aperture of the air outlet is 4-8 mm; and/or the aperture of the air inlet hole is 18-20 mm.

According to another aspect of the present invention, there is provided a rail flash welding method, comprising: the method comprises the following steps of an early stage flash flattening stage, a short circuit preheating stage, a burning flash stage, an upsetting stage and a pressure maintaining post-heating stage; the method further comprises the following steps: and the gas conveying device is adopted to provide protective gas to protect the welding area.

According to an embodiment of the invention, the early flashing stage adopts 1-2 stages for segment control, and for each stage: the displacement limit is 5.0 mm-6.0 mm, the phase control parameter of the voltage is 800-850%, the flash current is 10.0-11.0 kA, and the maximum flash speed is 3.0-6.0 mm/s; and/or

In the short circuit preheating stage, the preheating cycle time is 7-12 times, the time of each heating is 4.5-5.1 s, the pressure applied each time is 100.0-240.0 kN, the phase control parameter of the voltage is 450-510 per mill, and the time of each separation for heat conduction is 1.2-1.6 s; and/or

The burning flash stage adopts 3 ~ 5 stages to carry out segmentation control, and for each stage: the displacement limit is 8.0 mm-19.0 mm, the phase control parameter of the voltage is 750 per thousand-900 per thousand, the flash current is 9.0 kA-244.1 kA, and the maximum flash speed is 0.5 mm/s-2.7 mm/s; and/or

The upsetting stage comprises a first upsetting stage and a second upsetting stage which are sequentially carried out, wherein

In the first upsetting stage: the limit of upsetting time is 0.2 s-0.5 s, the limit of upsetting displacement is 20.0 mm-25.0 mm, and the phase control parameter of voltage is 260-275 per thousand;

in the second upsetting stage: the limit of the upsetting speed is 2.6-3.0 mm/s, the limit of the upsetting time is 0.1-0.6 s, the limit of the upsetting displacement is 30.0-38.0 mm, the upsetting pressure is 480.0-520.0 kN, and the upsetting current is 30.0-32.0 kA; and/or

And performing segmented control on the heat stage after pressure maintaining by adopting 1-2 stages, wherein for each stage: the heating time is 0.3 s-1.0 s, the applied pressure is 420 kN-520 kN, the phase control parameter of the voltage is 0-275 per thousand, and the displacement limit is 30.0-38.0 mm.

According to one embodiment of the invention, in the short-circuit preheating stage, the preheating cycle number is 11-12 times, the time of each heating is 4.7-5.1 s, the pressure applied each time is 108.0-140.0 kN, the phase control parameter of the voltage is 470-510 per mill, and the time of each separation for heat conduction is 1.3-1.6 s; or

In the short circuit preheating stage, the preheating cycle time is 7-9 times, the time of each heating is 4.7-5.0 s, the pressure applied each time is 140.0-240.0 kN, the phase control parameter of the voltage is 450-510 per thousand, and the time of each separation for heat conduction is 1.3-1.6 s; or

In the short circuit preheating stage, the preheating cycle time is 10-12 times, the time of each heating is 4.5-5.0 s, the pressure applied each time is 100.0-120.0 kN, the phase control parameter of the voltage is 450-510 per mill, and the time of each separation for heat conduction is 1.2-1.5 s.

According to one embodiment of the invention, during the short-circuit preheating phase: the deformation limit is 0.8mm to 1.2mm each time, and/or the separation distance is 2.4mm to 3.5mm each time; and/or

After the early flash stage, a pair of rails to be welded are separated by 1.0 s-1.2 s, and then the first contact of the short-circuit preheating stage is carried out.

According to one embodiment of the invention, after the heat stage after pressure holding is finished, the welded joint is directly placed in the air and naturally cooled to the room temperature; and/or stopping the supply of the shielding gas after the upsetting stage is finished.

According to one embodiment of the invention, after the welding process is finished, the average current of the early flashing stage is 23.0 kA-41.0 kA, the current of the short circuit preheating stage is 46.0 kA-68.0 kA, and the average current of the burning flashing stage is 10.0 kA-17.0 kA; and/or the time of the whole welding process is 98 s-155 s, and the actual upsetting amount is 9.0 mm-20.0 mm.

In the gas conveying device according to the embodiment of the invention, the welding area is protected by adopting the protective gas to prevent the introduction of impurities, so that the generation of gray spot defects is reduced, and the flash welding quality of the steel rail is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 shows a schematic view of a gas delivery device according to an exemplary embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention are described in further detail with reference to the accompanying drawings.

It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are used for distinguishing two entities with the same name but different names or different parameters, and it should be noted that "first" and "second" are merely for convenience of description and should not be construed as limitations of the embodiments of the present invention, and they are not described in any more detail in the following embodiments.

Fig. 1 shows a schematic view of a gas delivery device 1 according to an exemplary embodiment of the present invention, as shown in fig. 1, the gas delivery device 1 is used for providing shielding gas when welding a workpiece, the gas delivery device 1 comprises a first pipe 10 and a second pipe 20, wherein two openings of the first pipe 10 are respectively butted against two openings of the second pipe 20, so that the first pipe 10 and the second pipe 20 constitute a closed pipe 30, an inner wall 32 of the closed pipe 30 is provided with a gas outlet hole 42, and an outer wall 34 of the closed pipe 30 is provided with a gas inlet hole 44.

In the embodiment of the present invention, the above inner and outer are relative to the center of the gas delivery device 1, and relatively speaking, the inner is closer to the center and the outer is farther from the center. The closed duct 30 serves as a passage through which gas flows, and the inner wall of the closed duct 30 encloses a receiving space in which a workpiece is placed, and the gas outlet hole 42 is provided toward the receiving space, thereby supplying gas to the workpiece in the receiving space. In an orthographic view of the closed conduit 30, the closed conduit 30 is a double-layer structure having an inner layer and an outer layer, the air outlet holes 42 being disposed adjacent to the inner layer and the air inlet holes 44 being disposed adjacent to the outer layer.

In one embodiment, the workpiece is a rail 2, the inner wall of the closed conduit 30 is shaped to fit the cross-sectional shape of the rail 2, and is substantially "I" shaped, and the cavity defined by the inner wall of the closed conduit 30 includes a first enlarged portion 34 corresponding to the head of the rail, a second enlarged portion 36 corresponding to the foot of the rail, and a constricted portion 37 corresponding to the waist of the rail. The inner layer and the outer layer are both in the I shape. By arranging the inner wall of the closed pipeline 30 to be shaped like a steel rail, the closed pipeline 30 can better enclose the steel rail to provide gas, and the gas protection effect is improved.

The main body structure of the gas conveying device 1 is a split structure which is bilaterally symmetrical, the main bodies on the left side and the right side of the gas conveying device 1 are steel rail profiling pipelines, and the gas conveying device 1 is mainly used for conveying gas protection media to a steel rail welding area. The protective gas is inert gas. The shielding gas enters the closed conduit 30 through the gas inlet holes 44 and enters the receiving space enclosed by the closed conduit 30 through the gas outlet holes 42, and the welding area of the rail 2 is disposed in the receiving space, so that the gas shielding can be provided for the welding area. In the embodiment of the invention, after the preparation work before welding of the rail to be welded is completed, the gas delivery device 1 is installed in the welding area of, for example, a flash welder and is overlapped with the rail gap of the rail to be welded.

With continued reference to FIG. 1, gas outlets 42 are provided in the inner wall 32 at the pinch 37 at a location corresponding to the mid-region of the rail to facilitate uniform supply of shielding gas; the air intake holes 44 are provided in the outer wall 34 at the second enlarged portion 36 at a position which is low to facilitate mounting of the air intake component. The number of the outlet holes 42 and the inlet holes 44 may be one or more, and the inlet holes 44 may be symmetrically distributed on the first pipe 11 and the second pipe 12.

In the embodiment of the present invention, the inner diameters a of the first pipe 10 and the second pipe 20 are phi 25mm to phi 30 mm; when the closed pipeline 30 and the steel rail 2 are concentrically arranged, the gap b between the closed pipeline 30 and the steel rail 2 is 20-25 mm; the aperture c of the air outlet 42 is phi 4 mm-phi 8 mm; the aperture d of the air inlet hole 44 is phi 18 mm-phi 20 mm. It should be noted that, although fig. 1 shows the distance b between the side of the closed duct 30 adjacent to the center of the bottom of the steel rail and the steel rail to be welded, since the closed duct 30 is similar to the shape of the steel rail 2, when the closed duct 30 and the steel rail are concentrically arranged, the gap between the closed duct 30 and the steel rail 2 is the same at each position, that is, the distance b in the figure represents the gap between the closed duct 30 and the steel rail 2 as a whole, and the gap may refer to the distance between the tangent line at each point of the closed duct 30 and the tangent line at the corresponding point of the steel rail 2 at the side of the closed duct 30 close to the steel rail 2. The gap is in particular a gap between the inner wall of the closed conduit 30 and the rail 2.

According to another aspect of the present invention, a method of flash welding a steel rail includes: the method comprises the following steps of an early stage flash flattening stage, a short circuit preheating stage, a burning flash stage, an upsetting stage and a pressure maintaining post-heating stage; the method further comprises the following steps: the gas delivery device 1 described above is used to provide a shielding gas to protect the welding area to prevent the introduction of impurities during welding that can cause defects in the joint.

It is known that flash welding is mainly classified into fixed flash welding and moving flash welding. The movable flash welding is usually used for construction welding on a track laying site due to the characteristics of small equipment, convenient movement and the like; while fixed flash welding of rails typically fixes the welding equipment within the plant, it is also commonly referred to as factory welding or base welding. The greatest difference between the two is the way in which the rail is heated, apart from the application scenario. The movable flash welding heats the steel rail by intermittent pulse flash blasting or continuous flash blasting, so the movable flash welding can be divided into pulse flash and continuous flash. Stationary flash welding is generally known as short circuit preheat flash welding, in which the rail is heated by means of resistance heat by directly short circuiting the rail, with no (or little) flash being associated with the heating process. The flash welding method can be realized by adopting a steel rail fixed flash welding machine and a gas conveying device.

The various stages of the flash welding process of the present invention are described in detail below.

The early flashing stage comprises: a voltage is applied to a pair of rails to be welded, the end faces of the rails are brought close to each other gradually to make local contact, a short-circuit current is passed at least locally, and these contacts are heated by resistance heating. The main function of the early stage flashing stage is to enable the to-be-welded section of the steel rail to be flat and clean through flash blasting, and provide favorable conditions for subsequent flashing and heating to be relatively uniform and flat. In order to achieve the above object, in the present invention, the early flashing stage adopts 1-2 stages for segment control, and for each stage: the displacement limit is 5.0 mm-6.0 mm, the phase control parameter of the voltage is 800 per mill-850 per mill, the flash current is 10.0 kA-11.0 kA, and the maximum flash speed is 3.0 mm/s-6.0 mm/s. In the early stage of flash-leveling, the two rails are continuously moved relatively to each other to perform heating and flash blasting.

The short-circuit preheating stage mainly has the effects that short-circuit current is continuously applied to two ends of the steel rail for multiple times, the steel rail is heated by resistance heat, a certain temperature gradient is formed in the longitudinal direction (namely the length direction) of the steel rail, the end face of the steel rail is heated to an enough temperature, and conditions are established for accelerating the homogenization process of flash. The short circuit preheating phase comprises the following steps: a voltage is applied to a pair of rails to be welded, and the end faces of the pair of rails are cyclically brought into contact and separated a predetermined number of times, and a short-circuit current is applied to the pair of rails to heat the pair of rails and apply a predetermined pressure. In the short circuit preheating stage, the preheating cycle time is 7-12 times, the time of each heating is 4.5-5.1 s, the pressure applied each time is 100.0-240.0 kN, the phase control parameter of the voltage is 450-510 per mill, and the time of each separation for heat conduction is 1.2-1.6 s. The phase control parameter of the voltage is an analog signal which represents the proportion of the applied voltage relative to the power grid voltage, and the voltage is represented by a thousandth ratio, wherein the power grid voltage is generally a power electric voltage and is between 380V and 400V. These parameters are the main parameters of the short-circuit preheating phase, wherein the preset times of cyclic contact and separation, the contact time, the separation time, the condition of applied voltage and the like all play an important role in the heating condition, and the applied pressure defines the force application condition and is a part of the key parameters of the invention. The above parameters will be different when welding different rails, and will be described in more detail below by way of example.

A first steel rail: the rail head hardened high-strength heat-treated pearlite carbon steel rail has a profile OF 136RE in American ENGINEERING standards, wherein the American ENGINEERING standards refer to American society for railway ENGINEERING (AREMA), American society for railway ENGINEERING (AMERICAN RARIWAY ENGINING AND MAINTENNCE-OF-WAY ASSOCIATION), the mass fraction OF carbon in the steel rail is 0.74-0.86%, the mass fraction OF silicon is 0.10-0.60%, the mass fraction OF manganese is 0.75-1.25%, the mass fractions OF phosphorus AND sulfur are not more than 0.020%, the mass fraction OF chromium is not more than 0.3%, the mass fraction OF vanadium is not more than 0.01%, the minimum tensile strength OF the steel rail is 1179MPa, AND the minimum hardness OF the head OF the steel rail is 370 HB.

The second steel rail: the steel rail comprises a standard strength carbon steel rail, the outline of the steel rail is a 115RE outline in American engineering standard, the mass fraction of carbon in the steel rail is 0.74-0.86%, the mass fraction of silicon is 0.10-0.60%, the mass fraction of manganese is 0.75-1.25%, the mass fractions of phosphorus and sulfur are not more than 0.020%, the mass fraction of chromium is not more than 0.3%, the mass fraction of vanadium is not more than 0.01%, the minimum tensile strength of the steel rail is 970MPa, and the minimum hardness of the head of the steel rail is 310 HB.

A third steel rail: the high-strength pearlite steel rail for the heavy-duty railway has the profile of 136RE in American engineering standard, the mass fraction of carbon in the steel rail is 0.72-0.82%, the mass fraction of silicon is 0.50-0.80%, the mass fraction of manganese is 0.70-1.05%, the mass fractions of phosphorus and sulfur are not more than 0.025%, the mass fraction of chromium is 0.30-0.50%, the mass fraction of vanadium is 0.04-0.12%, the minimum tensile strength of the steel rail is 1280MPa, and the minimum hardness of the head of the steel rail is 370 HB.

The rail head hardened high-strength steel rail and the high-strength steel rail for the heavy haul railway generally refer to pearlitic steel rails after the rail head of the steel rail is subjected to online heat treatment, and the strength of the pearlitic steel rails is generally more than 1000 MPa. The standard strength carbon steel rail is generally referred to as a pearlite steel rail, and the strength thereof is generally 970MPa or more. At present, the pearlite rail is the most widely applied globally except for part of turnouts. The pearlite steel rail is hot-rolled and heat-treated pearlite steel rail with carbon mass fraction of 0.60-0.90%. A pearlitic rail is a rail whose microstructure is entirely pearlitic in the supplied state.

The profile of the rail determines the cross-sectional area of the rail, and the tensile strength of the rail determines the environment in which it is used. Generally, the larger the cross-sectional area of the rail, the greater the total amount of heat input required during the flash welding process. Meanwhile, the temperature distribution on the cross section of the steel rail with different profiles is also different. The chemical composition of the rail generally determines the electrical resistivity, thermal conductivity, and resistance to deformation at high and low temperatures. The total heat input amount, the longitudinal temperature gradient of the steel rail, the total welding time, the required upsetting force and the like required by the steel rails with different chemical compositions are different. I.e., rails of the same chemical composition and different profiles, and rails of the same profile but different chemical compositions, will all use different welding processes. Slight changes in the welding process affect the mechanical properties of the flash welding joint of the steel rail, thereby affecting the service performance of the steel rail.

For the first steel rail, in the short-circuit preheating stage, the preheating cycle time is 11-12 times, the time of each heating is 4.7-5.1 s, the pressure applied each time is 108.0-140.0 kN, the phase control parameter of the voltage is 470-510 per mill, and the time of each separation for heat conduction is 1.3-1.6 s; or

For the second steel rail, in the short-circuit preheating stage, the preheating cycle time is 7-9 times, the time of each heating is 4.7-5.0 s, the pressure applied each time is 140.0-240.0 kN, the phase control parameter of the voltage is 450-510 per thousand, and the time of each separation for heat conduction is 1.3-1.6 s; or

For the third steel rail, in the short circuit preheating stage, the preheating cycle time is 10-12 times, the heating time is 4.5-5.0 s each time, the applied pressure is 100.0-120.0 kN each time, the phase control parameter of the voltage is 450-510 per thousand, and the heat conduction time for each time of separation is 1.2-1.5 s.

In addition, the following parameters can be further set in the short circuit preheating stage: the limit of deformation is 0.8mm to 1.2mm each time, and the distance of separation is 2.4mm to 3.5mm each time. After the early stage flash stage, the pair of rails are separated for 1.0 to 1.2 seconds, and then the first contact in the short circuit preheating stage is performed, that is, the first separation time in the burning flash stage is 1.0 to 1.2 seconds, and then the contact and separation are performed cyclically.

The stage of burning flash is similar to the stage of early flash to a certain extent, except that the strength of relevant parameters is different from the degree of progress, voltage is applied to the pair of steel rails, the pair of steel rails are moved relatively, short-circuit current flows in the contact process, and the end faces of the steel rails are heated by resistance heat. The main function of the burning flash stage is to form a protective atmosphere for preventing the end surface from being oxidized in the whole welding area, and finally form proper temperature field distribution to provide conditions for upset forging. In order to achieve the purpose, the burning flash stage of the invention adopts 3-5 stages to carry out fine sectional control, and for each stage: the displacement limit is 8.0 mm-19.0 mm, the phase control parameter of the voltage is 750 per thousand-900 per thousand, the flash current is 9.0 kA-244.1 kA, and the maximum flash speed is 0.5 mm/s-2.7 mm/s.

For the first steel rail, the displacement limit of each stage of the burning flash stage is 10.0 mm-19.0 mm; for the second steel rail, the displacement limit of each stage in the burning flash stage is 10.0 mm-19.0 mm; for the third rail, the displacement limit of each stage of the burning flash stage is 8.0 mm-17.0 mm.

The upsetting stage comprises: an upsetting force is applied to press the end faces of the pair of rails against each other. In an embodiment of the present invention, the upsetting stage includes a first upsetting stage and a second upsetting stage, which are performed sequentially, where in the first upsetting stage: the limit of upsetting time is 0.2 s-0.5 s, the limit of upsetting displacement is 20.0 mm-25.0 mm, and the phase control parameter of voltage is 260-275 per thousand; in the second upsetting stage: the limit of the upsetting speed is 2.6-3.0 mm/s, the limit of the upsetting time is 0.1-0.6 s, the limit of the upsetting displacement is 30.0-38.0 mm, the upsetting pressure is 480.0-520.0 kN, and the upsetting current is 30.0-32.0 kA. The first upsetting stage may be a preliminary upsetting performed rapidly and the second upsetting stage may be a more main upsetting stage.

For a first rail, in a first upsetting stage: the displacement limit is 22.0 mm-25.0 mm, and the phase control parameter of the voltage is 270-275 per mill; in the first upsetting stage: the limit of the upsetting time is 0.2 s-0.6 s, and the upsetting pressure is 510.0 kN-520.0 kN.

For the second type of rail, in the first upsetting stage: the displacement limit is 22.0 mm-25.0 mm, and the phase control parameter of the voltage is 270-275 per mill; in the first upsetting stage: the limit of the upsetting time is 0.2 s-0.6 s, and the upsetting pressure is 510.0 kN-520.0 kN;

for the third rail, in the first upsetting stage: the displacement limit is 20.0 mm-23.0 mm, and the phase control parameter of the voltage is 260 per thousand-275 per thousand; in the first upsetting stage: the limit of the upsetting time is 0.1 s-0.5 s, and the upsetting pressure is 480.0 kN-510.0 kN.

The heat stage after pressure maintaining comprises: the rail joint is continuously loaded and heated. The main effect of the hot stage after pressure maintaining is to continuously apply load to the steel rail joint in the process of metal crystallization of the joint after the steel rail is upset, so that the joint bonding strength is enhanced. In order to achieve the purpose, the hot stage after pressure maintaining of the invention adopts 1-2 stages to carry out sectional control, and for each stage: the heating time is 0.3 s-1.0 s, the applied pressure is 420 kN-520 kN, the phase control parameter of the voltage is 0-275 per thousand, and the displacement limit is 30.0-38.0 mm. It can be known that, in the hot stage after the holding pressure, the rails are welded together, and at this time, the relative displacement basically does not occur any more, and the displacement limit setting plays a main role in guarantee.

In an embodiment of the invention, the supply of protective gas is stopped after the end of the upsetting phase.

In the embodiment of the invention, after the heat stage after pressure maintaining is finished, the welded joint is directly placed in the air and naturally cooled to the room temperature, and air quenching treatment on the welded joint is not needed. The air quench treatment may be used to improve properties such as the hardness of the joint. The hardness of the longitudinal section of the steel rail flash welding joint is that after the steel rail is cut along the longitudinal rolling direction of the steel rail, the hardness value of the steel rail flash welding joint within the range of 3-5 mm below the traveling surface of the joint and the range of the two sides of the fusion line of the joint exceeding the width of a heat affected zone by 20mm is detected, some standards adopt Rockwell hardness, some adopt Vickers hardness, or both the Rockwell hardness and the Vickers hardness. The hardness of a steel rail welding joint is an important factor influencing the smoothness of a high-speed railway track, and the joint can be ensured to have consistent wear resistance with a line steel rail in a service period only if the hardness level of the joint is equivalent to that of a base metal. The problem that prior art exists is that the joint no matter is the welding state or the heat treatment state all has the softening zone, can appear saddle-shaped wearing and tearing during the in service, leads to the circuit smoothness to deteriorate. The correct post-welding treatment process can improve the joint structure, reduce the softening degree and meet the requirement of the wear resistance of the joint as much as possible. In the embodiment of the invention, the flash welding method can realize good welding quality, and ensure that the performances of the joint such as hardness and the like meet the standard, so that air quenching treatment is not required.

According to the flash welding method, after the welding process is finished, the average current of the early stage flash flattening stage is 23.0 kA-41.0 kA, the current of the short circuit preheating stage is 46.0 kA-68.0 kA, and the average current of the burning flash stage is 10.0 kA-17.0 kA. The time of the whole welding process is 98 s-155 s, and the actual upsetting amount is 9.0 mm-20.0 mm.

For the first steel rail, after the welding process is finished, the average current in the early stage flash leveling stage is 23.0 kA-27.0 kA, the current in the short circuit preheating stage is 56.0 kA-68.0 kA, and the average current in the burning flash stage is 10.0 kA-16.0 kA. The time of the whole welding process is 140 s-155 s, and the actual upsetting amount is 11.0 mm-20.0 mm.

For the second steel rail, after the welding process is finished, the average current in the early flash leveling stage is 37.0 kA-41.0 kA, the current in the short-circuit preheating stage is 46.0 kA-64.0 kA, and the average current in the burning flash stage is 15.0 kA-17.0 kA. The time of the whole welding process is 98-108 s, and the actual upsetting amount is 11.0-17.0 mm.

For the third steel rail, after the welding process is finished, the average current in the early stage flash leveling stage is 23.0 kA-27.0 kA, the current in the short circuit preheating stage is 51.0 kA-66.0 kA, and the average current in the burning flash stage is 10.0 kA-16.0 kA. The time of the whole welding process is 136 s-145 s, and the actual upsetting amount is 9.0 mm-15.0 mm.

The invention mainly provides a gas shielded flash welding method. The method can effectively reduce the size and the number of the gray spot defects in the joint, and effectively ensure that the microstructure, the macroscopic power, the longitudinal section hardness and the static bending performance of the steel rail flash welding joint can comprehensively meet the technical requirements of the multinational steel rail welding standard.

It should be noted that the rail flash welding joint static bending test is the most widely applied rail joint overall performance evaluation method at home and abroad at present, and all rail joint inspection standards are specified. The method mainly comprises two indexes, namely load and deflection. The static bending test is to apply load to the steel rail joint at a certain loading rate by adopting a three-point or four-point supporting method until the load reaches a standard specified value and is continuous, and the maximum deflection is greater than the standard specified value, so that the static bending performance of the joint is judged to be qualified, and different rail types correspond to different load and deflection values. In the standards of various countries, the Russian STO RZD 1.08.002:2009 standard has the highest quality requirement, the lowest load and deflection of a joint are required to be not less than 2100kN and 30mm (65kg/m steel rail and head of the rail are compressed), and the lowest load when the head of the 60kg/m steel rail is compressed is 1907kN and 30 mm. European standard BS EN14587-2:2009 requires that the minimum load and deflection of the joint is not less than 1600KN and 20mm respectively (60kg/m rail, head compressed). European standard BS EN14587-2:2009 requires that the minimum stress of the joint rail bottom is 900MPa, and the minimum load and deflection after conversion are not less than 1670KN and 20mm respectively (60kg/m rail, head of rail is pressed). The standard requirements of China on static bending are that the breaking load is not less than 1450kN (60kg/m, the railhead is pressed), and no requirement is made on the deflection. The static bending load mainly reflects the indexes of the joint such as the bonding strength, the joint appearance and the internal defects, and the deflection mainly reflects the index of the joint strength and toughness. If the welding process of the joint is poor, the joint is likely to break before the joint does not reach the load value specified by the standard due to defects of dust spots, incomplete fusion or overburning, or the joint is hard or soft due to improper matching of heat input and upsetting amount of the joint and improper treatment method after welding, so that the deflection of the joint does not reach the standard requirement.

In addition, macroscopic low-power indexes of the rail flash welding joint generally include the width, the angle and the like of a macroscopic heat affected zone. The weld line specified in the american standard amama should be perpendicular to the rail rolling direction. The width of a visible heat affected zone is regulated to be within the range of 20-45 mm in European standard BS EN14587, and the visible heat affected zone is symmetrical about a fusion line; it can be seen that the difference between the maximum and minimum values of the width of the heat affected zone should not exceed 20 mm. Australian standard AS1085.20 specifies a heat affected zone in the range of 30 to 50mm and the joint heat affected zone is at an angle of less than 5 ° to the rail base.

The following description will be made based on specific examples and comparative examples.

Example 1

The test material of this example was a head hardened high strength heat treated pearlitic carbon rail of 136RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.82%, 0.55% and 1.18%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The early stage flashing stage adopts 1 stage to perform segmented control: the displacement limit is 5.0mm, the phase control parameter is 850 per mill, the flash current is set to be 11.0kA, and the maximum flash speed is 3.0 mm/s.

The first separation time of the short-circuit preheating stage is 1.0s, the heating time is 5.0s, the preheating pressure set value is 108.0kN, the phase control parameter is 470 per mill, the heat conduction time is 1.3s, the separation distance is 2.4mm, the deformation limit is 1.0mm, and the preheating cycle number is 12.

The burning flash stage adopts 5 stages for segment control: the displacement limit 1 is 10.0mm, the phase control parameter 1 is 900 per mill, the flash current is set to be 1 to be 10.0kA, and the maximum flash speed is 1.6 mm/s; the displacement limit 2 is 12.0mm, the phase control parameter 2 is 850 per mill, the flash current is set to be 2 to be 244.1kA, and the maximum flash speed is set to be 2 to be 1.3 mm/s; the displacement limit 3 is 15.0mm, the phase control parameter 3 is 800 per mill, the flash current is set to be 3 to be 244.1kA, and the maximum flash speed is 3 to be 1.6 mm/s; the displacement limit 4 is 16.0mm, the phase control parameter 4 is 750 per mill, the flash current is set to be 4 to be 244.1kA, and the maximum flash speed is set to be 4 to be 1.7 mm/s; the displacement limit 5 is 18.2mm, the phase control parameter 5 is 800 ‰, the flash current is set to 5 to 244.1kA, and the maximum flash speed 5 is 2.7 mm/s.

In the upsetting stage, the time limit of quick upsetting is 0.2s, the displacement limit of quick upsetting is 22.0mm, the phase control parameter of quick upsetting is 275 per thousand, the preset quick top end control threshold is 3.0mm/s, the time limit of upsetting is 0.2s, the displacement limit of upsetting is 38.0mm, the set value of upsetting pressure is 510.0kN, and the set value of upsetting current is 32.0 kA.

The heat stage after pressure maintaining adopts 2 stages to carry out sectional control: the heating time 1 is 8.0s, the pressure setting value 1 is 420kN, the phase control parameter 1 is 0 thousandth, the heating time 2 is 3.0s, the pressure setting value 2 is 235kN, the phase control parameter 2 is 0 thousandth, and the displacement limit is 38 mm.

After the welding process is finished, the average current in the flash leveling stage is 24.1kA, the current in the short-circuit preheating stage is 57.1 kA-65.6 kA, and the average current in the burning flash stage is 14.5 kA. The time of the whole welding process was 143s, and the actual upset amount was 11.4 mm.

In the embodiment, the maximum deflection of the flash welding joint of the steel rail is 23.3mm when the three-point static bending load is 2397kN, no fracture occurs, and the standard requirement is met. And breaking the statically bent steel rail joint by adopting a physical steel rail drop hammer testing machine, and observing the appearance of the fracture, wherein no gray spot defect is found.

Example 2

The test material of this example was a head hardened high strength heat treated pearlitic carbon rail of 136RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.83%, 0.54% and 1.19%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The early stage flashing stage adopts 1 stage to perform segmented control: the displacement limit is 6.0mm, the phase control parameter is 850 per mill, the flash current is set to be 11.0kA, and the maximum flash speed is 6.0 mm/s.

The first separation time of the short-circuit preheating stage is 1.0s, the heating time is 4.8s, the preheating pressure set value is 140.0kN, the phase control parameter is 490 per thousand, the heat conduction time is 1.6s, the separation distance is 3.5mm, the deformation limit is 1.0mm, and the preheating cycle number is 12.

The burning flash stage adopts 3 stages to carry out sectional control: the displacement limit 1 is 11.0mm, the phase control parameter 1 is 900 per mill, the flash current is set to be 1 to be 9.0kA, and the maximum flash speed is 1 to be 2.0 mm/s; the displacement limit 2 is 14.0mm, the phase control parameter 2 is 900 per mill, the flash current is set to be 2 to be 244.1kA, and the maximum flash speed is set to be 2 to be 0.5 mm/s; the displacement limit 3 is 19.0mm, the phase control parameter 3 is 990 ‰, the flash current is set to 3 to 244.1kA, and the maximum flash speed 3 is 2.35 mm/s.

In the upsetting stage, the time limit of quick upsetting is 0.5s, the displacement limit of quick upsetting is 24.0mm, the phase control parameter of quick upsetting is 275 per thousand, the preset quick top end control threshold is 2.6mm/s, the time limit of upsetting is 0.5s, the displacement limit of upsetting is 38.0mm, the set value of upsetting pressure is 516.0kN, and the set value of upsetting current is 32.0 kA.

The heat stage after pressure maintaining adopts 2 stages to carry out sectional control: the heating time 1 is 0.3s, the pressure setting value 1 is 516kN, the phase control parameter 1 is 275 thousandths, the heating time 2 is 5.7s, the pressure setting value 2 is 516kN, the phase control parameter 2 is 0 thousandths, and the displacement limit is 38 mm.

After the welding process is finished, the average current in the flash flat stage is 26.8kA, the current in the short circuit preheating stage is 57.7 kA-67.5 kA, and the average current in the burning flash stage is 11.8 kA. The time of the whole welding process was 152s, and the actual upset amount was 18.5 mm.

In the embodiment, the maximum deflection of the three-point static bending load of the steel rail flash welding head is 19.9mm when 2350kN is achieved, no fracture occurs, and the standard requirement is met. And breaking the statically bent steel rail joint by adopting a physical steel rail drop hammer testing machine, and observing the appearance of the fracture, wherein no gray spot defect is found.

Example 3

The test material of this example was a head hardened high strength heat treated pearlitic carbon rail of 136RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.81%, 0.54% and 1.18%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The early stage flash stage adopts 2 stages to perform segmented control: the displacement limit 1 is 5.0mm, the phase control parameter 1 is 800 per mill, the flash current is set to be 1 and 11.0kA, and the maximum flash speed is 1 and 6.0 mm/s; the displacement limit 2 is 4.0mm, the phase control parameter 2 is 850 per mill, the flash current is set to be 2 to be 10.0kA, and the maximum flash speed 2 is 6.0 mm/s.

The first separation time of the short-circuit preheating stage is 1.2s, the heating time is 4.7s, the preheating pressure set value is 120kN, the phase control parameter is 510 per thousand, the heat conduction time is 1.5s, the separation distance is 3.0mm, the deformation limit is 1.2mm, and the preheating cycle number is 11.

The burning flash stage adopts 4 stages to carry out sectional control: the displacement limit 1 is 11.0mm, the phase control parameter 1 is 900 per mill, the flash current is set to be 1 to be 10.0kA, and the maximum flash speed is 1.0 mm/s; the displacement limit 2 is 14.0mm, the phase control parameter 2 is 850 per mill, the flash current is set to be 2 to 244.1kA, and the maximum flash speed is 2.0 mm/s; the displacement limit 3 is 17.0mm, the phase control parameter 3 is 750 per mill, the flash current is set to be 3 to be 244.1kA, and the maximum flash speed is 3 to be 2.4 mm/s; the displacement limit 4 is 19.0mm, the phase control parameter 4 is 800 ‰, the flash current is set to 4 to 244.1kA, and the maximum flash speed 4 is 2.5 mm/s.

In the upsetting stage, the time limit of quick upsetting is 0.4s, the displacement limit of quick upsetting is 23.0mm, the phase control parameter of quick upsetting is 270 per mill, the preset quick top control threshold is 2.7mm/s, the time limit of upsetting is 0.4s, the displacement limit of upsetting is 31.0mm, the set value of upsetting pressure is 512.0kN, and the set value of upsetting current is 30.0 kA.

The heat stage after pressure maintaining adopts 1 staged control: the heating time is 0.4s, the pressure setting value is 512kN, the phase control parameter is 270 per mill, and the displacement limit is 35 mm.

After the welding process is finished, the average current in the flash flat stage is 23.7kA, the current in the short circuit preheating stage is 56.8 kA-64.1 kA, and the average current in the burning flash stage is 14.1 kA. The time of the whole welding process was 148s, and the actual upset amount was 11.0 mm.

In the embodiment, the maximum deflection of the flash welding head of the steel rail is 23.9mm when the three-point static bending load is 2450kN, no fracture occurs, and the standard requirement is met. And breaking the statically bent steel rail joint by adopting a physical steel rail drop hammer testing machine, and observing the appearance of the fracture, wherein no gray spot defect is found.

Example 4

The test material of this example was a head hardened high strength heat treated pearlitic carbon rail of 136RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.81%, 0.53% and 1.19%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The early stage flashing stage adopts 1 stage to perform segmented control: the displacement limit is 6.0mm, the phase control parameter is 830 per mill, the flash current is set to be 10.0kA, and the maximum flash speed is 5.0 mm/s.

The first separation time of the short-circuit preheating stage is 1.0s, the heating time is 5.0s, the preheating pressure set value is 138.0kN, the phase control parameter is 500 per mill, the heat conduction time is 1.5s, the separation distance is 3.2mm, the deformation limit is 1.0mm, and the preheating cycle number is 12.

The burning flash stage adopts 4 stages to carry out sectional control: the displacement limit 1 is 11.0mm, the phase control parameter 1 is 850 per mill, the flash current is set to be 1 to be 9.0kA, and the maximum flash speed is 1 to be 2.0 mm/s; the displacement limit 2 is 14.0mm, the phase control parameter 2 is 850 per mill, the flash current is set to be 2 to 244.1kA, and the maximum flash speed is 2.0 mm/s; the displacement limit 3 is 18.0mm, the phase control parameter 3 is 850 per mill, the flash current is set to be 3 to be 244.1kA, and the maximum flash speed is 3 to be 2.1 mm/s; the displacement limit 4 is 19.0mm, the phase control parameter 4 is 980%, the flash current is set to 4 to 244.1kA, and the maximum flash speed 4 is 2.55 mm/s.

In the upsetting stage, the time limit of quick upsetting is 0.5s, the displacement limit of quick upsetting is 25.0mm, the phase control parameter of quick upsetting is 275 per thousand, the preset quick top end control threshold is 3.0mm/s, the time limit of upsetting is 0.6s, the displacement limit of upsetting is 35.0mm, the set value of upsetting pressure is 520.0kN, and the set value of upsetting current is 31.0 kA.

The heat stage after pressure maintaining adopts 1 staged control: the heating time was 0.5s, the pressure setting was 520kN, the phase control parameter was 275% o, and the displacement limit was 38 mm.

After the welding process is finished, the average current in the flash flat stage is 26.7kA, the current in the short circuit preheating stage is 58.1 kA-66.8 kA, and the average current in the burning flash stage is 11.6 kA. The time of the whole welding process is 150s, and the actual upset amount is 18.9 mm.

In the embodiment, the maximum value of the hardness of the longitudinal section of the steel rail flash welding head is 381.1HB, and the minimum value is 338.3HB, so that the standard requirement is met; the maximum width of the macroscopic heat affected zone is 41.0mm, and the standard requirement is met.

Example 5

The test material of this example was a standard strength carbon steel rail of 115RE profile specified in AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.82%, 0.55% and 1.15%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The first separation time of the short-circuit preheating stage is 1.0s, the heating time is 5.0s, the preheating pressure set value is 140.0kN, the phase control parameter is 510 per mill, the heat conduction time is 1.6s, the separation distance is 2.4mm, the deformation limit is 1.0mm, and the preheating cycle number is 7.

After the welding process is finished, the average current in the flash flat stage is 37.5kA, the current in the short circuit preheating stage is 46.1 kA-63.6 kA, and the average current in the burning flash stage is 15.5 kA. The time of the whole welding process is 98s, and the actual upsetting amount is 11.4 mm.

In the embodiment, the maximum deflection of the three-point static bending of the steel rail flash welding head is 23.5mm when the load is 1960kN, no fracture occurs, and the standard requirement is met. And breaking the statically bent steel rail joint by adopting a physical steel rail drop hammer testing machine, and observing the appearance of the fracture, wherein no gray spot defect is found.

Example 6

The test material of this example was a standard strength carbon steel rail of 115RE profile specified in AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.83%, 0.54% and 1.19%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The first separation time of the short-circuit preheating stage is 1.0s, the heating time is 4.8s, the preheating pressure set value is 240.0kN, the phase control parameter is 490 per thousand, the heat conduction time is 1.5s, the separation distance is 3.0mm, the deformation limit is 1.0mm, and the preheating cycle number is 8.

After the welding process is finished, the average current in the flash flat stage is 26.8kA, the current in the short circuit preheating stage is 45.7 kA-63.7 kA, and the average current in the burning flash stage is 16.1 kA. The time of the whole welding process was 152s, and the actual upset amount was 13.4 mm.

In the embodiment, the maximum deflection of the three-point static bending of the steel rail flash welding head is 23.7mm when the load is 1960kN, no fracture occurs, and the standard requirement is met. And breaking the statically bent steel rail joint by adopting a physical steel rail drop hammer testing machine, and observing the appearance of the fracture, wherein no gray spot defect is found.

Example 7

The test material of this example was a standard strength carbon steel rail of 115RE profile specified in AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.81%, 0.54% and 1.18%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The first separation time of the short-circuit preheating stage is 1.2s, the heating time is 4.7s, the preheating pressure set value is 145.0kN, the phase control parameter is 450 per mill, the heat conduction time is 1.5s, the separation distance is 3.0mm, the deformation limit is 1.2mm, and the preheating cycle number is 9.

In the upsetting stage, the time limit of quick upsetting is 0.4s, the displacement limit of quick upsetting is 23.0mm, the phase control parameter of quick upsetting is 270 per mill, the preset quick top control threshold is 2.7mm/s, the time limit of upsetting is 0.4s, the displacement limit of upsetting is 31.0mm, the set value of upsetting pressure is 520.0kN, and the set value of upsetting current is 30.0 kA.

The heat stage after pressure maintaining adopts 1 staged control: the heating time is 0.4s, the pressure setting value is 520.0kN, the phase control parameter is 270 per mill, and the displacement limit is 35 mm.

After the welding process is finished, the average current in the flash flat stage is 38.1kA, the current in the short circuit preheating stage is 46.8 kA-63.4 kA, and the average current in the burning flash stage is 15.1 kA. The time of the whole welding process is 108s, and the actual upsetting amount is 15.6 mm.

In the embodiment, the maximum value of the hardness of the longitudinal section of the steel rail flash welding head is 327.9HB, and the minimum value is 286.1HB, so that the standard requirement is met; the maximum width of the macroscopic heat affected zone is 29.8mm, and the standard requirement is met.

Example 8

The test material of this example was a high-strength pearlitic rail for heavy haul railways having a 136RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.80%, 0.70% and 0.81%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The first separation time of the short-circuit preheating stage is 1.0s, the heating time is 5.0s, the preheating pressure set value is 108.0kN, the phase control parameter is 480 per mill, the heat conduction time is 1.3s, the separation distance is 2.4mm, the deformation limit is 1.0mm, and the preheating cycle number is 12.

After the welding process is finished, the average current in the flash leveling stage is 24.1kA, the current in the short-circuit preheating stage is 57.1 kA-65.6 kA, and the average current in the burning flash stage is 14.5 kA. The time of the whole welding process was 145s, and the actual upset amount was 11.9 mm.

In the embodiment, the maximum deflection of the three-point static bending of the steel rail flash welding head is 22.3mm when the load is 2400kN, no fracture occurs, and the standard requirement is met. And breaking the statically bent steel rail joint by adopting a physical steel rail drop hammer testing machine, and observing the appearance of the fracture, wherein no gray spot defect is found.

Example 9

The test material of this example was a high-strength pearlitic rail for heavy haul railways having a 136RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.79%, 0.69% and 0.91%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The early stage flashing stage adopts 1 stage to perform segmented control: the displacement limit is 6.0mm, the phase control parameter is 800 per mill, the flash current is set to be 10.0kA, and the maximum flash speed is 6.0 mm/s.

The first separation time of the short-circuit preheating stage is 1.0s, the heating time is 5.0s, the preheating pressure set value is 100.0kN, the phase control parameter is 470 per mill, the heat conduction time is 1.3s, the separation distance is 2.4mm, the deformation limit is 1.0mm, and the preheating cycle number is 12.

The burning flash stage adopts 4 stages to carry out sectional control: the displacement limit 1 is 10.0mm, the phase control parameter 1 is 900 per mill, the flash current is set to be 1 to be 10.0kA, and the maximum flash speed is 1.6 mm/s; the displacement limit 2 is 15.0mm, the phase control parameter 2 is 800 per mill, the flash current is set to be 2 to be 244.1kA, and the maximum flash speed is set to be 2 to be 1.6 mm/s; the displacement limit 3 is 16.0mm, the phase control parameter 3 is 750 per mill, the flash current is set to be 3 to be 244.1kA, and the maximum flash speed is 3 to be 1.7 mm/s; the displacement limit 4 is 17.0mm, the phase control parameter 4 is 800 ‰, the flash current is set to 4 to 244.1kA, and the maximum flash speed 4 is 2.7 mm/s.

In the upsetting stage, the time limit of quick upsetting is 0.2s, the displacement limit of quick upsetting is 22.0mm, the phase control parameter of quick upsetting is 275 per thousand, the preset quick top end control threshold is 3.0mm/s, the time limit of upsetting is 0.2s, the displacement limit of upsetting is 38.0mm, the set value of upsetting pressure is 480.0kN, and the set value of upsetting current is 32.0 kA.

The heat stage after pressure maintaining adopts 1 staged control: the heating time is 8.0s, the pressure setting value is 480kN, the phase control parameter is 0 per mill, and the displacement limit is 38 mm.

After the welding process is finished, the average current in the flash flat stage is 24.1kA, the current in the short circuit preheating stage is 56.1 kA-64.6 kA, and the average current in the burning flash stage is 14.5 kA. The time of the whole welding process was 145s, and the actual upset amount was 9.9 mm.

In the embodiment, the maximum deflection of the flash welding joint of the steel rail is 22.9mm when the three-point static bending load is 2450kN, no fracture occurs, and the standard requirement is met. And breaking the statically bent steel rail joint by adopting a physical steel rail drop hammer testing machine, and observing the appearance of the fracture, wherein no gray spot defect is found.

Examples10

The test material of this example was a high-strength pearlitic rail for heavy haul railways having a 136RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.79%, 0.60% and 0.89%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The first separation time of the short-circuit preheating stage is 1.2s, the heating time is 5.0s, the preheating pressure set value is 120kN, the phase control parameter is 450 per mill, the heat conduction time is 1.5s, the separation distance is 3.0mm, the deformation limit is 1.2mm, and the preheating cycle number is 10.

The burning flash stage adopts 4 stages to carry out sectional control: the displacement limit 1 is 8.0mm, the phase control parameter 1 is 900 per mill, the flash current is set to be 1 to be 10.0kA, and the maximum flash speed is 1.0 mm/s; the displacement limit 2 is 14.0mm, the phase control parameter 2 is 850 per mill, the flash current is set to be 2 to 244.1kA, and the maximum flash speed is 2.0 mm/s; the displacement limit 3 is 15.0mm, the phase control parameter 3 is 750 per mill, the flash current is set to be 3 to be 244.1kA, and the maximum flash speed is 3 to be 2.4 mm/s; the displacement limit 4 is 17.0mm, the phase control parameter 4 is 800 ‰, the flash current is set to 4 to 244.1kA, and the maximum flash speed 4 is 2.5 mm/s.

In the upsetting stage, the time limit of quick upsetting is 0.4s, the displacement limit of quick upsetting is 23.0mm, the phase control parameter of quick upsetting is 270 per mill, the preset quick top control threshold is 2.7mm/s, the time limit of upsetting is 0.1s, the displacement limit of upsetting is 31.0mm, the set value of upsetting pressure is 480.0kN, and the set value of upsetting current is 30.0 kA.

The heat stage after pressure maintaining adopts 1 staged control: the heating time is 0.4s, the pressure setting value is 500.0kN, the phase control parameter is 270 per mill, and the displacement limit is 35 mm.

After the welding process is finished, the average current in the flash flat stage is 23.7kA, the current in the short circuit preheating stage is 51.8 kA-60.1 kA, and the average current in the burning flash stage is 14.1 kA. The time of the whole welding process is 136s, and the actual upset amount is 9.5 mm.

In the embodiment, the maximum deflection of the three-point static bending load of the steel rail flash welding head is 21.7mm when 2350kN is achieved, no fracture occurs, and the standard requirement is met. And breaking the statically bent steel rail joint by adopting a physical steel rail drop hammer testing machine, and observing the appearance of the fracture, wherein no gray spot defect is found.

Example 11

The test material of this example was a high-strength pearlitic rail for heavy haul railways having a 136RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.80%, 0.67% and 0.87%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. Immediately after the welding process has started, the joint is provided with a gas shield using a gas conveying device, the gas medium being nitrogen.

The first separation time of the short-circuit preheating stage is 1.0s, the heating time is 4.5s, the preheating pressure set value is 110.0kN, the phase control parameter is 510 per mill, the heat conduction time is 1.2s, the separation distance is 3.2mm, the deformation limit is 1.0mm, and the preheating cycle number is 11 times.

The burning flash stage adopts 4 stages to carry out sectional control: the displacement limit 1 is 11.0mm, the phase control parameter 1 is 850 per mill, the flash current is set to be 1 to be 9.0kA, and the maximum flash speed is 1 to be 2.0 mm/s; the displacement limit 2 is 14.0mm, the phase control parameter 2 is 850 per mill, the flash current is set to be 2 to 244.1kA, and the maximum flash speed is 2.0 mm/s; the displacement limit 3 is 16.0mm, the phase control parameter 3 is 850 per mill, the flash current is set to be 3 to be 244.1kA, and the maximum flash speed is 3 to be 2.1 mm/s; the displacement limit 4 is 17.0mm, the phase control parameter 4 is 980%, the flash current is set to 4 to 244.1kA, and the maximum flash speed 4 is 2.55 mm/s.

In the upsetting stage, the time limit of quick upsetting is 0.5s, the displacement limit of quick upsetting is 20.0mm, the phase control parameter of quick upsetting is 260 per mill, the preset quick top control threshold is 3.0mm/s, the time limit of upsetting is 0.5s, the displacement limit of upsetting is 35.0mm, the set value of upsetting pressure is 510.0kN, and the set value of upsetting current is 31.0 kA.

After the welding process is finished, the average current in the flash flat stage is 26.7kA, the current in the short circuit preheating stage is 58.1 kA-65.8 kA, and the average current in the burning flash stage is 11.6 kA. The time of the whole welding process is 140s, and the actual upset amount is 14.9 mm.

In the embodiment, the maximum value of the hardness of the longitudinal section of the steel rail flash welding head is 387.1HB, and the minimum value is 347.0HB, so that the standard requirement is met; the maximum width of the macroscopic heat affected zone is 38.4mm, and the standard requirement is met.

Comparative example 1

The test material of this comparative example was a head hardened high strength heat treated pearlitic carbon rail of 136RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.82%, 0.55% and 1.18%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. No gas delivery device was used to provide gas shielding for the joint after the welding process was initiated.

The early stage flashing stage adopts 1 stage to perform segmented control: the displacement limit is 4.0mm, the phase control parameter is 800 per mill, the flash current is set to be 12.0kA, and the maximum flash speed is 7.0 mm/s.

The first separation time of the short-circuit preheating stage is 1.0s, the heating time is 4.5s, the preheating pressure set value is 120.0kN, the phase control parameter is 450 per mill, the heat conduction time is 1.2s, the separation distance is 4.0mm, the deformation limit is 1.0mm, and the preheating cycle number is 10.

The burning flash stage adopts 3 stages to carry out sectional control: the displacement limit 1 is 12.0mm, the phase control parameter 1 is 750 per mill, the flash current is set to be 1 to be 10.0kA, and the maximum flash speed is 1 to be 2.5 mm/s; the displacement limit 2 is 15.0mm, the phase control parameter 2 is 850 per mill, the flash current is set to be 2 and 250.0kA, and the maximum flash speed 2 is 1.8 mm/s; the displacement limit 3 is 18.0mm, the phase control parameter 3 is 850%, the flash current is set to be 3 to be 250.0kA, and the maximum flash speed is 3 to be 1.0 mm/s.

The rapid upsetting time limit in the upsetting stage is 0.5s, the rapid upsetting displacement limit is 26.0mm, the rapid upsetting phase control parameter is 277 permillage, the preset rapid top end control threshold value is 2.7mm/s, the upsetting time limit is 0.4s, the upsetting displacement limit is 40.0mm, the upsetting pressure set value is 530.0kN, and the upsetting current set value is 30.0 kA.

The comparative example did not take post-dwell heating measures. After the welding process is finished, the average current in the flash flat stage is 25.6kA, the current in the short circuit preheating stage is 57.9 kA-67.2 kA, and the average current in the burning flash stage is 16.4 kA. The time of the whole welding process was 148s, and the actual upset amount was 11.3 mm.

In the comparative example, the maximum deflection of the flash welding joint of the steel rail is 10.3mm when the three-point static bending load is 1570kN, and the flash welding joint of the steel rail is broken and does not meet the standard requirement. The fracture is observed, and the foot area of the steel rail has the defect of long-strip-shaped outcrop gray spots of 10mm multiplied by 1.5 mm.

Comparative example 2

The early stage flashing stage adopts 1 stage to perform segmented control: the displacement limit is 4.0mm, the phase control parameter is 850 per mill, the flash current is set to be 9.0kA, and the maximum flash speed is 4.0 mm/s.

The first separation time of the short-circuit preheating stage is 1.5s, the heating time is 5.2s, the preheating pressure set value is 120.0kN, the phase control parameter is 520 per mill, the heat conduction time is 2.0s, the separation distance is 3.5mm, the deformation limit is 1.2mm, and the preheating cycle number is 13.

The burning flash stage adopts 3 stages to carry out sectional control: the displacement limit 1 is 13.0mm, the phase control parameter 1 is 700 per mill, the flash current is set to be 1 to be 12.0kA, and the maximum flash speed is 1 to be 2.0 mm/s; the displacement limit 2 is 17.0mm, the phase control parameter 2 is 800 per mill, the flash current is set to be 2 and 200.0kA, and the maximum flash speed is 2.5 mm/s; the displacement limit 3 is 20.0mm, the phase control parameter 3 is 950 ‰, the flash current is set to be 3 at 200.0kA, and the maximum flash speed 3 is 3.0 mm/s.

In the upsetting stage, the time limit of quick upsetting is 0.1s, the displacement limit of quick upsetting is 200mm, the control parameter of a quick upsetting phase is 280 per mill, the preset quick top end control threshold is 3.0mm/s, the time limit of upsetting is 1.0s, the displacement limit of upsetting is 30.0mm, the set value of upsetting pressure is 500.0kN, and the set value of upsetting current is 30.0 kA.

The heat stage after pressure maintaining adopts 2 stages to carry out sectional control: the heating time 1 is 1.0s, the pressure setting value 1 is 500kN, the phase control parameter 1 is 270 permillage, the heating time 2 is 0.5s, the pressure setting value 2 is 500kN, the phase control parameter 2 is 100 permillage, and the displacement limit is 40 mm.

After the welding process is finished, the average current in the flash flat stage is 23.7kA, the current in the short circuit preheating stage is 61.1 kA-73.5 kA, and the average current in the burning flash stage is 13.6 kA. The time of the whole welding process was 155s, and the actual upset amount was 16.6 mm.

In the comparative example, the maximum deflection of the flash welding head of the steel rail is 11.3mm when the three-point static bending load is 1670kN, and the flash welding head of the steel rail breaks and does not meet the standard requirement. The fracture is observed to find that the triangular area at the rail bottom of the steel rail has the circular gray spot defect of 5mm multiplied by 1 mm.

Comparative example 3

The test material of this comparative example was a standard strength carbon steel rail of 115RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.82%, 0.55% and 1.18%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. No gas delivery device was used to provide gas shielding for the joint after the welding process was initiated.

The comparative example did not take post-dwell heating measures. After the welding process is finished, the average current in the flash flat stage is 25.6kA, the current in the short circuit preheating stage is 57.9 kA-67.2 kA, and the average current in the burning flash stage is 16.4 kA. The time of the whole welding process is 98s, and the actual upsetting amount is 10.5 mm.

In the comparative example, the maximum deflection of the flash welding joint of the steel rail is 10.3mm when the three-point static bending load is 1570kN, and the flash welding joint of the steel rail is broken and does not meet the standard requirement. The fracture is observed, and the foot area of the steel rail has the defect of 3mm multiplied by 2mm circular exposed dust spot.

Comparative example 4

After the welding process is finished, the average current in the flash flat stage is 23.7kA, the current in the short circuit preheating stage is 61.1 kA-73.5 kA, and the average current in the burning flash stage is 13.6 kA. The time of the whole welding process is 130s, and the actual upsetting amount is 16.6 mm.

In the comparative example, the maximum value of the hardness of the longitudinal section of the flash welding joint of the steel rail is 305.1HB, and the minimum value is 241.4HB, so that the standard requirement is not met; the maximum width of the macroscopic heat affected zone is 50.6mm, and the requirement of the standard is not met.

Comparative example 5

The test material of this comparative example was a high-strength pearlitic rail for heavy haul railways having a 136RE profile specified in the AREMA standard. The mass fractions of carbon, silicon and manganese measured by the solid chemical components of the steel rail are respectively 0.79%, 0.70% and 0.81%. Welding tests were carried out using a GAAS80/580 rail mounted flash welder. No gas delivery device was used to provide gas shielding for the joint after the welding process was initiated.

The first separation time of the short-circuit preheating stage is 1.0s, the heating time is 4.0s, the preheating pressure set value is 95.0kN, the phase control parameter is 510 per mill, the heat conduction time is 1.2s, the separation distance is 4.0mm, the deformation limit is 1.0mm, and the preheating cycle number is 9.

The comparative example did not take post-dwell heating measures. After the welding process is finished, the average current in the flash flat stage is 25.6kA, the current in the short circuit preheating stage is 57.9 kA-67.2 kA, and the average current in the burning flash stage is 16.4 kA. The time of the whole welding process is 130s, and the actual upset amount is 9.0 mm.

In the comparative example, the maximum deflection of the steel rail flash welding head is 10.5mm when the three-point static bending load is 1370kN, and the joint is broken and does not meet the standard requirement. 3 gray spots are found by observing the fracture, the largest size of the gray spots is located in the foot area of the steel rail, and the size of the gray spots is 10mm multiplied by 1.5 mm.

Comparative example 6

In the comparative example, the maximum deflection of the flash welding joint of the steel rail is 12.5mm when the three-point static bending load is 2045kN, and the flash welding joint of the steel rail is broken and does not meet the standard requirement. The fracture is observed, and the triangular area at the rail bottom of the steel rail has the defect of circular gray spots of 4mm multiplied by 1 mm.

It should be particularly noted that the various components or steps in the above embodiments can be mutually intersected, replaced, added or deleted, and therefore, the combination formed by the reasonable permutation and combination conversion shall also belong to the protection scope of the present invention, and the protection scope of the present invention shall not be limited to the embodiments.

The above is an exemplary embodiment of the present disclosure, and the order of disclosure of the above embodiment of the present disclosure is only for description and does not represent the merits of the embodiment. It should be noted that the discussion of any embodiment above is exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, of embodiments of the invention is limited to those examples, and that various changes and modifications may be made without departing from the scope, as defined in the claims. The functions, steps and/or actions of the method claims in accordance with the disclosed embodiments described herein need not be performed in any particular order. Furthermore, although elements of the disclosed embodiments of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.

Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, of embodiments of the invention is limited to these examples; within the idea of an embodiment of the invention, also technical features in the above embodiment or in different embodiments may be combined and there are many other variations of the different aspects of an embodiment of the invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, substitutions, improvements, and the like that may be made without departing from the spirit and principles of the embodiments of the present invention are intended to be included within the scope of the embodiments of the present invention.

Claims

1. A gas delivery device for providing a shielding gas during welding of a workpiece, the device comprising a first conduit and a second conduit, wherein

The two openings of the first pipeline are respectively butted with the two openings of the second pipeline, so that the first pipeline and the second pipeline form a closed pipeline, the inner wall of the closed pipeline is provided with an air outlet, and the outer wall of the closed pipeline is provided with an air inlet.

2. The apparatus of claim 1, wherein the workpiece is a rail, the shape of the inner wall of the closed conduit is adapted to the cross-sectional shape of the rail, and the cavity defined by the inner wall of the closed conduit comprises a first enlarged portion corresponding to the head of the rail, a second enlarged portion corresponding to the foot of the rail, and a constricted portion corresponding to the waist of the rail.

3. The apparatus of claim 2 wherein said air outlet aperture is provided on an inner wall at said constricted portion and said air inlet aperture is provided on an outer wall at said second enlarged portion.

4. The apparatus of claim 2,

the inner diameters of the first pipeline and the second pipeline are 25-30 mm; and/or

When the closed pipeline and the steel rail are concentrically arranged, the gap between the closed pipeline and the steel rail is 20-25 mm; and/or

The aperture of the air outlet is 4-8 mm; and/or

The aperture of the air inlet hole is 18-20 mm.

5. A steel rail flash welding method comprises the following steps: the method comprises the following steps of an early stage flash flattening stage, a short circuit preheating stage, a burning flash stage, an upsetting stage and a pressure maintaining post-heating stage;

the method further comprises the following steps: providing a shielding gas to shield the welding area using the gas delivery device of any of claims 1-4.

6. The method of claim 5,

the early stage flash level stage adopts 1 ~ 2 to carry out segmentation control stage by stage, to every stage: the displacement limit is 5.0 mm-6.0 mm, the phase control parameter of the voltage is 800-850%, the flash current is 10.0-11.0 kA, and the maximum flash speed is 3.0-6.0 mm/s; and/or

7. The method of claim 6,

in the short circuit preheating stage, the preheating cycle time is 11-12 times, the time of each heating is 4.7-5.1 s, the pressure applied each time is 108.0-140.0 kN, the phase control parameter of the voltage is 470-510 per mill, and the time of each separation for heat conduction is 1.3-1.6 s; or

8. The method of claim 5,

in the short-circuit preheating stage: the deformation limit is 0.8mm to 1.2mm each time, and/or the separation distance is 2.4mm to 3.5mm each time; and/or

9. The method of claim 5,

after the heat stage is finished after the pressure maintaining, directly placing the welding joint in the air and naturally cooling to room temperature; and/or

After the upsetting phase is finished, the supply of the protective gas is stopped.

10. The method of claim 5,

after the welding process is finished, the average current of the early stage flash leveling stage is 23.0 kA-41.0 kA, the current of the short circuit preheating stage is 46.0 kA-68.0 kA, and the average current of the burning flash stage is 10.0 kA-17.0 kA; and/or

The time of the whole welding process is 98 s-155 s, and the actual upsetting amount is 9.0 mm-20.0 mm.