Rail welding machine and method for refining weld grains

Abstract

The invention discloses a rail welding machine for refining weld grains, comprising a clamping mechanism, a heat source system, a convex pushing mechanism, an upset forging mechanism, an upset forging tailstock and a guiding mechanism; the components are interconnected into a whole, and also include a grain refinement mechanism, under the action of the grain refinement mechanism, relative movement is generated between the welding end faces of two to-be-welded rails, so that weld grains in a visco-plastic state or a molten state are kneaded and refined; the kneading method of the grain refinement mechanism is one or more of left-right kneading, up-and-down kneading, oblique kneading, swing kneading and circular track kneading; the rail welding machine only needs to replace a small number of parts such as a convex pushing knife, an electrode, a clamping block, etc., so that it can be applied to welding of various models and types of rails, and is a universal rail welding machine in the field of rail welding, realizing one machine with multiple uses; the types and quantities of welding machines are reduced, and the equipment investment cost in the field of railway rail welding is greatly saved.

Description

Technical Field

[0001] The invention relates to the technical field of rail welding, and in particular to a rail welding machine and method for refining weld grains. Background Art

[0002] With the continuous development and progress of rail transit technology, new demands such as higher speed, greater capacity, more energy-saving and environmental protection, and a faster and more comfortable riding experience have put forward higher and stricter requirements for railway rail welding technology. Rails, as the basis for train operation, guide the operation of locomotives and vehicles and bear the impact dynamic load of wheels. This requires that the rails on the line must have sufficient strength, toughness, smoothness, stability and wear resistance. The welded joints of rails on seamless lines have always been one of the weak links of rail lines. The quality of their welding is directly related to the service life of the rails and the safety of high-speed train operation.

[0003] At present, the world's main rail welding methods are flash welding, gas pressure welding and thermite welding. Their common feature is that the weld grains after welding are relatively coarse. For flash welding and gas pressure welding joints, my country's iron standard requires normalizing after welding, that is, using heat treatment process to refine the weld grains. Even so, the effect of refining the weld grains is very limited. Since the weld of thermite welding joint forms a casting structure with coarser grains, coupled with other reasons, it is even impossible to use normalizing method to refine the grains.

[0004] As we all know, grain refinement is the only way to improve both strength and toughness. Ultrafine grain structure has become a key technology urgently needed to be broken through in the field of materials science in various research institutes and universities due to its excellent comprehensive mechanical properties. At present, there are many methods for grain refinement in the fields of metallurgy and material processing, such as ultrasonic (electromagnetic) stirring of the molten pool, mechanical (ultrasonic) micro-casting and forging, changing material composition and process parameters, equal-diameter angular extrusion, high-ratio extrusion, hot forging, rapid cooling, etc. However, there are very few methods for grain refinement in the field of weld metal.

[0005] Patent CN109986189A discloses a process for refining the grains of rail flash welding welds. The core of the process is to apply and maintain sufficient pressure on the welded rail welds during the recrystallization process to increase the nucleation rate; extend the holding time until the recrystallization process is fully completed, thereby achieving weld grain refinement and an average grain size of 63 to 75 μm. Although the average grain size of the weld is reduced to a certain extent (maximum reduction of 15 μM), it is difficult to form welds with finer or even ultra-fine grain structures because no methods and means are used to further refine the weld grains; more importantly, this method is only suitable for short rail experimental welding and cannot be promoted and applied in long rail welding in on-site engineering construction.

[0006] The reason is that when welding short rails, the rails are not affected by external resistance, and the upsetting force of the flash welder during pressure maintenance is equal to the pressure maintenance force for grain refinement, which can be monitored and controlled; while when welding long rails during on-site construction, the length of the rails may be tens of meters, hundreds of meters, thousands of meters, or even longer. In addition, there are various resistances caused by various complex working conditions such as external friction resistance, long rail tensile stress, ramps, curves, etc. Since the two rails have become a whole during the pressure maintenance stage, coupled with the existence of various resistances, the actual effective pressure maintenance force for grain refinement becomes impossible to accurately monitor and even more impossible to accurately control. Therefore, this process lacks the feasibility of promotion and application in on-site engineering construction.

[0007] On the other hand, although several major steel mills in my country have made breakthrough progress in the development of high-toughness, high-strength, and high-wear-resistant rails, the weldability problem has not been solved, which seriously hinders and restricts the large-scale promotion and application of new material high-quality rails. For example, U20Mn bainite new material rails are currently recognized as the most difficult to weld high-toughness, high-strength, and high-wear-resistant rails. Flash welding and gas pressure welding have been explored and studied for a long time in relevant universities and research institutes, but no breakthrough has been made so far.

[0008] With the continuous increase in the operating speed of high-speed railways and the use of rail welds in extreme environmental conditions such as the Sichuan-Tibet Railway, extremely stringent safety requirements have been placed on line welds. There is an urgent need for a welding device and method that can produce welds without internal and external defects, with excellent fatigue resistance, high strength, stable wear resistance, good low-temperature toughness, and comprehensive mechanical properties close to, equal to, or even exceeding those of the parent rails being connected.

[0009] Due to the limitations of existing technologies and equipment, they are unable to solve and meet the high requirements of rail weld quality, such as high strength, high toughness, high wear resistance, and good low-temperature toughness. It is urgent to solve the key technical problems of weld quality during the on-site laying and welding of rails, such as low comprehensive mechanical properties of welds and difficulty in adapting to extreme environmental conditions. Summary of the invention

[0010] The purpose of the present invention is to provide a rail welding machine and a method for refining weld grains in view of the above-mentioned deficiencies. The rail welding machine can not only completely solve the problem of weld grain refinement, but also can be well promoted and applied in the on-site welding construction process of railway rails.

[0011] The present invention is achieved through the following scheme:

[0012] A rail welding machine for refining weld grains, comprising a clamping mechanism, a heat source system, a convex pushing mechanism, an upset forging mechanism, an upset forging tailstock and a guide mechanism; each component is interconnected into a whole, and is characterized in that it also includes a grain refining mechanism, under the action of which a relative movement is generated between the welding end faces of two to-be-welded rails, so that weld grains in a visco-plastic state or a molten state are kneaded and refined.

[0013] Preferably, the kneading method of the fine crystal mechanism is one or more of left-right kneading, up-and-down kneading, oblique kneading, swing kneading, and circular trajectory kneading.

[0014] Preferably, the crystal refining mechanism includes a clamping cylinder, a crystal refining cylinder, a movable housing, a crystal refining mechanism body, a clamping cylinder seat, a connecting rod and a clamping arm; the cylinder barrel of the clamping cylinder is fixedly connected to the clamping cylinder seat, the piston rod of the clamping cylinder passes through the clamping cylinder seat, the lower end of the piston rod of the clamping cylinder is fixedly connected to the crystal refining mechanism body, the connecting rod is respectively hinged to the clamping cylinder seat and the clamping arm, a rotating shaft is provided on the clamping arm, and is rotatably connected to the crystal refining mechanism body through the rotating shaft, and the connecting rod and the clamping arm are provided in pairs.

[0015] Preferably, the crystal thinning mechanism body is movably arranged inside a mobile shell, the mobile shell is provided with a through hole for the clamping arm to pass through and move, the cylinder barrel of the crystal thinning cylinder is fixedly connected to the mobile shell, and the crystal thinning cylinder barrel is sleeved on the piston rod of the clamping cylinder.

[0016] Preferably, a kinematic pair is provided between the movable housing and the crystal refining mechanism body; rail accommodating grooves are provided on the movable housing and the crystal refining mechanism body, and the rail accommodating grooves on the movable housing and the crystal refining mechanism body match the rail accommodating grooves on the fixed housing.

[0017] Preferably, a upset tailstock is provided on one end of the movable housing away from the fixed housing, and the upset mechanism is arranged on the upset tailstock; the upset mechanism includes upset cylinders, which are arranged in pairs on the upset tailstock, the upset cylinders are arranged close to the rails, and the piston rod end of the upset cylinder is fixedly connected to the movable housing.

[0018] Preferably, the clamping mechanism is also provided with a rail transverse centering adjustment cylinder.

[0019] Preferably, the heat source system can be a flash resistance heating system, an electromagnetic induction heating system, a gas combustion heating system, a friction heating system, an arc heating system, a physical and chemical reaction heating system, an electron beam heating system, a laser heating system, etc., or a combination of some of them, to heat the end face of the rail to be welded, forming a completely thermoplastic state or a completely molten state on the entire welding interface, and having a high-temperature metal layer of a certain thickness.

[0020] The present invention also provides a method for refining weld grains, that is, adding a grain refining kneading step during the welding process;

[0021] The step of fine grain kneading is as follows: when the welding heat source system heats the entire welding interface to form a completely thermoplastic state or a completely molten state, and has a high-temperature metal layer of a certain thickness, a certain upsetting force is applied or maintained along the normal direction of the welding interface, so that the thermoplastic or molten metal at the welding interface is squeezed out of the weld; the motion mechanism is started to generate relative movement between the interfaces to be welded of the two weldments, and the kneading action of grain refinement is formed on the welding interface in combination with the upsetting force or the extrusion force; as the kneading action continues, the grains of the weld zone tissue are continuously kneaded and fined; at the same time, the temperature of the entire welding interface is further uniformed, and the temperature gradient along the weld axis and the interface is further reduced to form a stable temperature field distribution; when the entire welding interface forms a stable temperature field and reaches the time set for grain refinement or the shortening amount of the weldment, the kneading action is quickly stopped, and the weldment is immediately aligned; at the same time, the upsetting force is maintained or a larger upsetting force is applied, and the pressure is maintained until the grain recrystallization and recrystallization process of the weld zone grains are fully completed, thereby obtaining a high-quality weld joint with fine grains and ultrafine grain structures.

[0022] The movement of the movement mechanism is a plane movement parallel to the welding interface, or a space movement forming a certain angle with the welding interface.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The equipment and method solve the feasibility problem of achieving weld grain refinement in on-site long rail welding construction.

[0025] 2. Ultrafine grain material organization, due to its excellent and super comprehensive mechanical properties, has always been a key technology in the field of materials science, and key scientific research institutes and universities are working hard to tackle and seek breakthroughs. This technical solution makes it easier to obtain fine grain and ultrafine grain weld organization through mechanical fine grain kneading movement, so that the comprehensive mechanical properties of the weld are close to, equal to, or even exceed the connected parent material rail, providing strong weld quality assurance for the extremely stringent safety requirements that the rail welds must meet under high-speed railway speed-up and extreme environmental conditions.

[0026] 3. The welding machine can be equipped with a variety of different welding heat source systems, such as flash resistance heating system, electromagnetic induction heating system, gas combustion heating system, friction heating system, arc heating system, physical and chemical reaction heating system, electron beam heating system, laser heating system, etc. or a combination of some of them, providing an open comprehensive research platform for the future development and innovation of new processes and technologies for various new rail welding.

[0027] 4. This welding machine can be applied to welding of various models and types of rails by only replacing a small number of parts such as push-convex knives, electrodes, clamping blocks, etc. It is a universal welding machine in the field of rail welding, which can achieve multiple uses of one machine; it reduces the types and number of welding machines, and greatly saves the equipment investment cost in the field of railway rail welding.

[0028] 5. Compared with various existing rail welding methods, it does not require gas protection, is energy-saving and environmentally friendly, has a narrow weld heat-affected zone, and has a small amount of rail loss; the hardness of the parent material, weld, and heat-affected zone is evenly distributed; it not only completely solves various welding defects such as slag inclusion, pores, and looseness in fusion welding; it also solves the long-standing welding defects that cannot be eradicated, such as gray spots in flash welding and light spots in gas pressure welding; it also solves the "hump" problem caused by uneven hardness distribution in high-speed rail welds; it greatly improves the welding quality of the weld. The weld structure obtained by the welding machine and its method is fine-grained and ultra-fine-grained structure, and the average grain size of the weld is refined from 60 to 120 μm in flash welding and gas pressure welding to about 10 to 20 μm.

[0029] 6. This method has achieved excellent welding results through experiments, and obtained defect-free ultra-fine-grained weld structures with comprehensive mechanical properties exceeding those of the parent material. It also cleverly avoids the problem of complicated debugging of welding process parameters due to the sensitivity of the material and the combined influence of multiple welding parameters in flash welding; it also avoids the huge impact of uncontrollable and difficult-to-control factors such as environmental wind force, human experience, gas quality, and cleanliness of the rail welding end face on the welding quality of gas pressure welding. It greatly reduces the difficulty of welding quality control and assurance; it avoids the influence of human factors and uncontrollable factors on welding quality to a large extent; it also reduces the sensitivity of welding to the material of the weldment, and solves the weldability problems of various high-strength, high-wear-resistant rails, heterogeneous material rails, and other high-performance, new materials, and high-quality rails. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall three-dimensional structure of the present invention;

[0031] Figure 2 It is a schematic diagram of the overall internal structure of the present invention;

[0032] Figure 3 It is a schematic diagram of the overall main structure of the present invention;

[0033] Figure 4 It is a schematic diagram of the overall right view structure of the present invention;

[0034] Figure 5 It is a schematic diagram of the main structure of the present invention after removing the movable housing and the fixed housing;

[0035] Figure 6 This is the microscopic morphology of the fine-grained weld zone of the present invention (material: U75VG rail)

[0036] Figure 7 This is the hardness distribution diagram of the rail top along the longitudinal direction of the rail in the fine-grained weld zone of the present invention (material: U20Mn bainite rail)

[0037] Figure 8 This is the microscopic morphology of the fine-grained weld zone of the present invention (material: U20Mn bainite rail)

[0038] In the figure: 1. Clamping mechanism; 2. Flash welding heat source system; 4. Fine grain mechanism; 5. Guide mechanism; 6. Lateral horizontal centering adjustment cylinder; 11. Clamping cylinder; 12. Clamping cylinder seat; 13. Connecting rod; 14. Clamping arm; 15. Fixed shell; 16. Clamping arm support; 31. Upsetting tailstock; 32. Upsetting cylinder; 41. Clamping cylinder; 42. Fine grain cylinder; 43. Moving shell; 44. Fine grain mechanism body; 45. Through hole. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0041] Example 1

[0042] See also Figures 1 to 5 , the present invention provides a technical solution:

[0043] A rail welding machine for refining weld grains, comprising a clamping mechanism 1, a flash welding heat source system 2, a convex pushing mechanism, an upset forging mechanism, an upset forging tailstock 31, a grain refining mechanism 4 and a guide mechanism 5; each component is interconnected to form a whole; the clamping mechanism 1 is used to clamp the steel rail to be welded at the fixed shell end; the flash welding heat source system 2 is used to provide the required heat for welding, so that the end surface of the steel rail to be welded forms a metal layer in a viscoplastic state or a molten state;

[0044] The push-out mechanism is used to remove the weld nodules produced by welding upset forging or extrusion; the upset forging mechanism provides the required upset force and extrusion force for the welding of the two steel rails to be welded and provides the power for the movement required for welding;

[0045] The grain refinement mechanism 4 is used to extrude and knead the end face of the rail to be welded, which has been heated to a visco-plastic state or a molten state by the flash welding heat source system 2, so that most of the visco-plastic state and molten state metal is squeezed out of the weld under the action of the upsetting force or the extrusion force to form a weld nodule; as the kneading movement continues, the high-temperature visco-plastic state metal at the welding interface continuously undergoes plastic deformation, and the original grains of the parent material are continuously crushed and refined to form fine-grained and ultra-fine-grained weld structures.

[0046] The guide mechanism 5 is used to provide high-precision guiding effect for the reciprocating motion of the whole formed by the movable shell 43, the fine grain mechanism 4 and the rail clamped by the fine grain mechanism 4 along the axis of the rail, so that the two rails to be welded can always keep the working edges aligned during the upsetting and pressure holding process in the final stage of welding.

[0047] In this embodiment, the kneading method of the fine crystal mechanism 4 is one or more of left-right kneading, up-and-down kneading, oblique kneading, swing kneading, and circular trajectory kneading; the fine crystal mechanism 4 is electrically and hydraulically connected to the external control system, and under the joint action of mechanical, electrical and hydraulic control systems, a precisely controlled kneading movement is achieved.

[0048] The clamping mechanism 1 includes a clamping cylinder 11, a clamping cylinder seat 12, a connecting rod 13, a clamping arm 14, a fixed shell 15 and a clamping arm support 16; the cylinder barrel of the clamping cylinder 11 is fixedly connected to the clamping cylinder seat 12, the connecting rod 13 is hinged to the clamping cylinder seat 12 and the clamping arm 14 respectively, a rotating shaft is arranged on the clamping arm 14, and the clamping arm 14 is rotatably connected to the rotating shaft, both ends of the rotating shaft are movably connected to the fixed shell 15, and the connecting rod 13 and the clamping arm 14 are arranged in pairs; the lower end of the clamping arm 14 clamps the left and right rail waist parts of the to-be-welded rail respectively; the clamping arm support 16 is arranged between the four clamping arms, and the clamping arm support and the clamping arm are rotatably connected through the rotating shaft, and the rotating shaft passes through the clamping arm support; the lower end of the piston rod of the clamping cylinder 11 is fixedly connected to the clamping arm support.

[0049] In this embodiment, the clamping cylinder seat 12 is hinged to the four connecting rods 13 respectively, and the four connecting rods 13 and the four clamping arms 14 are hinged respectively. When the clamping cylinder 11 is actuated, the clamping arms 14 are driven to rotate to clamp or release the rails. When the clamping cylinder 11 drives the connecting rods 13 to move downward, the clamping arms 14 will rotate around the rotation axis through transmission to clamp the rails. Conversely, when the clamping cylinder 11 drives the connecting rods 13 to move upward, the clamping arms 14 will rotate in the opposite direction around the rotation axis through transmission to release the rails.

[0050] When the clamping cylinder 11 clamps the rail, the clamping oil pressure in the lower chamber of the cylinder is kept unchanged, and the clamping arms 14 arranged in pairs firmly clamp the rail.

[0051] The fixed shell 15 is provided with a plurality of guide holes and a rail receiving groove. The rail receiving groove is used to guide the rail into the welding machine for clamping the rail. The guide hole is used for the guide mechanism 5 to pass through and be fixed. The guide mechanism 5 is electrically isolated (insulated) and fixedly connected to the fixed shell 15.

[0052] The fine crystal mechanism 4 includes a clamping cylinder 41, a fine crystal cylinder 42, a movable housing 43, a fine crystal mechanism body 44, a clamping cylinder seat 12, a connecting rod 13, a clamping arm 14 and a clamping arm support 16; the cylinder barrel of the fine crystal cylinder 42 is fixedly connected to the movable housing 43; the piston rod of the clamping cylinder 41 passes through the clamping cylinder seat 12, the connecting rod 13 is hinged to the clamping cylinder seat 12 and the clamping arm 14 respectively, a rotating shaft is provided on the clamping arm 14, and the clamping arm 14 is rotatably connected to the rotating shaft, the clamping arm support 16 and the clamping arm 14 are rotatably connected through the rotating shaft, the rotating shaft passes through the clamping arm support 16, and both ends of the rotating shaft are fixedly connected to the fine crystal mechanism body 44, the connecting rod 13 and the clamping arm 14 are arranged in pairs; the lower end of the clamping arm 14 clamps the left and right rail waists of the rail to be welded at the end of the movable housing respectively.

[0053] The clamping arm support 16 is arranged between the four clamping arms, and the clamping arm support 16 and the clamping arm 14 are rotatably connected via a rotating shaft, the rotating shaft passes through the clamping arm support 16, and both ends of the rotating shaft are fixedly connected to the fine crystal mechanism body 44; the lower end of the piston rod of the clamping cylinder 41 is fixedly connected to the clamping arm support 16.

[0054] The crystal thinning mechanism body 44 is arranged inside the movable housing 43, and the movable housing 43 is provided with a through hole 45 for the clamping arm 14 to penetrate and move. The cylinder barrel of the crystal thinning cylinder 42 is fixedly connected to the movable housing 43, and the crystal thinning cylinder barrel is sleeved on the piston rod of the clamping cylinder 41, that is, the clamping cylinder 41 and the crystal thinning cylinder 42 share a piston rod;

[0055] When in use, first keep the piston rod in the fine-crystal cylinder 42 fixed; by changing the oil inlet and outlet direction of the clamping cylinder 41, the cylinder barrel of the clamping cylinder 41 and the clamping cylinder seat 12 as a whole rise or fall together; when the cylinder barrel of the clamping cylinder 41 and the clamping cylinder seat 12 as a whole fall, the clamping arm 14 will rotate around the rotation axis through the transmission action of the connecting rod 13 to clamp the rail; conversely, when the cylinder barrel of the clamping cylinder 41 and the clamping cylinder seat 12 as a whole rise, the clamping arm 14 will rotate in the opposite direction around the rotation axis through the transmission action of the connecting rod 13 to loosen the rail;

[0056] When the clamping cylinder 41 clamps the rail at one end, the clamping cylinder 41, the clamping cylinder seat 12, the connecting rod 13 and the clamping arm 14 are in a clamping state, the position remains constant, and the clamped rail forms a whole through the clamping force; at this time, the fine crystal cylinder 42 is introduced into the alternating pressure oil with continuous reversal, and the piston rod of the fine crystal cylinder 42 drives the entire fine crystal mechanism 4 (except the moving shell 43) and the clamped rail to reciprocate up and down, forming a fine crystal kneading action. Since the cylinder barrel of the fine crystal cylinder 42 is fixedly connected to the moving shell 43, and the fine crystal cylinder 42 and the clamping cylinder 41 share a piston rod, the reversing pressure oil is introduced into the fine crystal cylinder 42, and the shared piston rod can move up and down in the fine crystal cylinder 42, thereby driving the entire fine crystal mechanism 4 (except the moving shell 43) and the clamped rail to move up and down, so the alignment function of the upper and lower working edges of the rail can also be realized. In the above two cases, the movable housing 43 and the cylinder barrel of the fine-crystal oil cylinder 42 do not move along with the up-and-down movement of the piston rod.

[0057] The movable housing 43 and the fine grain mechanism body 44 are both provided with rail receiving grooves for the rails to pass through, and the grooves match the rail receiving grooves on the fixed housing 15 .

[0058] An upsetting tailstock 31 is arranged on one end of the movable housing 43 away from the fixed housing, and the upsetting mechanism is arranged on the upsetting tailstock 31; the upsetting mechanism includes an upsetting cylinder 32; the upsetting cylinders 32 are arranged in pairs on the upsetting tailstock 31, and the upsetting cylinders 32 are arranged close to the rails, and the upsetting tailstock 31 is fixedly connected to the end of the guide mechanism 5, and the piston rod of the upsetting cylinder 32 is fixedly connected to the movable housing 43, and the cylinder barrel of the upsetting cylinder 32 is fixedly connected to the upsetting tailstock 31, and the movable housing 43 is driven to reciprocate along the guide mechanism 5, i.e., the axis (longitudinal direction) of the rail, by the piston rod of the upsetting cylinder 32, and at the same time, upsetting force or extrusion force can be provided to the welding end face of the rail to be welded;

[0059] The movable housing 43 can reciprocate along the guide mechanism 5 under the action of the upsetting cylinder 32. The guide mechanism 5 is a plurality of independent guide shafts, which pass through the guide holes on the fixed housing 15 and the movable housing 43. The movable housing 43 and the guide mechanism 5 can be connected by sliding or rolling.

[0060] By independently arranging the forging cylinder 32 on the forging tailstock 31, the forging cylinder 32 can be arranged as close to the rail to be welded as possible. The distance between the forging cylinder 32 and the rail can be reduced during forging, thereby reducing the strength and rigidity requirements of the frame during forging and reducing the strength requirements of the material; under the condition of the same forging force, the wall thickness of the frame can be reduced, thereby reducing the weight of the welding machine.

[0061] The clamping mechanism 1 is also provided with a transverse horizontal centering adjustment cylinder 6, which is arranged in pairs at both sides of the rails to be clamped, or a single cylinder is arranged at one side of the rails to be clamped. The transverse horizontal centering adjustment cylinder 6 can be used to move and adjust the transverse position of the rails to be welded, so that the top sides of the two rails to be welded are aligned, thereby improving the rail alignment accuracy of welding. The piston rod of the transverse horizontal centering adjustment cylinder is fixedly connected to the clamping arm support 16, and the transverse horizontal centering adjustment cylinder pushes the clamping arm support to make the clamping mechanism move horizontally as a whole, thereby realizing the transverse movement alignment adjustment of the rails clamped by the clamping mechanism.

[0062] The flash welding heat source system 2 is disposed between the fixed housing 15 and the movable housing 43 to heat the rail to be welded.

[0063] The convex pushing mechanism in this solution is an existing weld nodule removing mechanism, and this solution does not make any improvement to the convex pushing mechanism.

[0064] The flash welding heat source system in this scheme is only one type of heat source system. The heat source system can also be a gas combustion heating system, an electromagnetic induction heating system, a friction heating system, an arc heating system, a physical and chemical reaction heating system, an electron beam heating system, a laser heating system, or a combination of some of them, which heats the end face of the rail to be welded, forming a completely thermoplastic state or a completely molten state at the entire welding interface, and having a high-temperature metal layer of a certain thickness.

[0065] The working process of the present invention is as follows:

[0066] Step 1: Preparation before welding, rust removal of rails, remove all loose rust and oxide scale on the end faces of the two rails to be welded, as well as loose rust and oil stains around the end faces. For flash welding, it is also necessary to remove all loose rust, oil stains and oxide scale on the contact parts of the conductive electrodes of the rails.

[0067] Step 2: The rail welding machine is lowered, and the position of the welding machine is adjusted along the rail axis (longitudinal direction) so that the rail seam is in a suitable longitudinal position of the welding machine; the welding machine is continued to be lowered, and the rail to be welded is introduced into the rail clamping mechanism so that the rail top reference block of the welding machine contacts the rail top surface of the rail.

[0068] Step 3: The clamping pressure of the welding machine hydraulic system is set to a low pressure state, and the rail is pre-clamped with a small pressure. The alignment of the working edge of the rail is checked and adjusted. After the upper and lower working edges and the left and right working edges are aligned, the control system records the initial position of the rubbing end rail. The clamping pressure of the hydraulic system is set to a high pressure state, and the rail is clamped with all its strength. After the rail clamped by the fixed housing end is aligned, it remains fixed relative to the frame during the entire subsequent welding process.

[0069] Step 4: Start the welding heat source system to heat the two rail ends to be welded. After a series of mechanical movements and the joint action of the electrical and hydraulic systems, the metal at the weld interface gradually reaches a viscoplastic state or a molten state. When a completely thermoplastic state or a completely molten state is formed on the entire welding interface and a high-temperature metal layer with a certain thickness is formed, turn off the welding heat source system.

[0070] Step 5: Start the grain refinement mechanism to rub and refine the grains. After the welding heat source system is turned off, immediately apply or maintain a certain upsetting force along the normal direction of the welding interface, so that most of the thermoplastic or molten metal at the welding interface is squeezed out of the weld to form a weld nodule; at the same time, quickly start the grain refinement mechanism, which drives the clamped rail to make a small periodic movement, and works together with the upsetting force or extrusion force to form a rubbing action on the welding interface to refine the grains; as the rubbing movement continues, the weld thermal field distribution gradually becomes uniform, and the high-temperature viscous-plastic metal remaining at the welding interface continues to undergo plastic deformation, and is continuously squeezed out of the weld under the action of the upsetting force and rubbing movement, and the weld nodule continues to increase; the original grains of the parent material are continuously crushed and rubbed, and the high-temperature metal atoms at the interface of the two rails to be welded diffuse with each other, recrystallize and recrystallize. At the same time, the temperature of the entire welding interface is further uniformed, the temperature gradient along the axis of the weldment and the interface is further reduced, and a stable temperature field distribution is gradually formed.

[0071] Step 6: When the entire welding interface forms a stable temperature field and reaches the kneading time or weld shortening amount set for grain refinement, the kneading action is stopped immediately and the weld is aligned forged immediately. That is, the grain refinement mechanism drives the kneaded end rail to immediately return to the initial alignment state of the rail working side, that is, the initial position; at the same time, the original forging force is maintained or a greater forging force is applied, and pressure maintenance begins.

[0072] Step 7: After a certain delay, the convex pushing mechanism is activated to complete the tumor pushing work.

[0073] Step 8: Keep the pressure until the diffusion, recrystallization and recrystallization of the weld metal atoms are fully completed, forming a high-quality weld joint with fine and ultra-fine grain structure. At this point, the welding process is completed.

[0074] Step 9: When the pressure holding time is reached, the clamping knob is turned to the loose state, the rail clamping mechanism is loosened, the lower rail is released, the welding machine rises, and the welding process is completed. Prepare for welding the next pair of rails.

[0075] Example 2

[0076] This solution provides a method for refining weld grains, using a rail welding machine for refining weld grains as described in Example 1, including a rail clamping step, a working edge alignment step, a heating step, a grain refining kneading step, and an alignment top forging step:

[0077] The rail clamping step specifically includes: respectively introducing two rails to be welded into two rail clamping mechanisms of the welding machine, and pre-clamping them with a relatively small clamping force.

[0078] The working edge alignment step is specifically as follows: aligning and adjusting the end faces of the two rails to be welded, aligning the working edges of the rail top surface and the side face of the rail head, and fully clamping the rails after the working edges are aligned.

[0079] The heating step specifically comprises: utilizing a flash resistance heating system, an electromagnetic induction heating system, a gas combustion heating system, a friction heating system, an arc heating system, a physical and chemical reaction heating system, an electron beam heating system, a laser heating system, or a combination of some of them to heat the end face of the rail to be welded, so as to form a high-temperature metal layer having a certain thickness in a completely thermoplastic state or a completely molten state at the entire welding interface.

[0080] The step of fine grain kneading is specifically as follows: a certain upsetting force is applied or maintained along the normal direction of the welding interface, so that most of the thermoplastic or molten metal at the welding interface is squeezed out of the weld to form a weld nodule; at the same time, a residual thin layer of high-temperature thermoplastic or molten metal is formed at the welding interface. The fine grain mechanism is quickly started, and the relative movement between the two rail ends to be welded, combined with the upsetting force and the extrusion force, forms a kneading action on the welding interface. The kneading motion is a planar motion parallel to the welding interface, or a spatial motion at a certain angle to the welding interface; as the kneading motion continues, the original grains of the parent material at the interface of the weld area are continuously crushed and fined, and the welding interface formed by the end face of the rail to be welded is continuously kneaded away to form a new interface. The metal atoms on both sides of the center of the weld diffuse with each other, gradually forming fine grains and ultrafine grain structures, and the closer to the center of the weld, the finer the grains, the softened metal is continuously squeezed out of the weld, the weld nodule continues to increase, and a small amount of kneading shortening occurs on the two rails. At the same time, the temperature of the entire welding interface is further uniformed, the temperature gradient along the weld axis and the interface is further reduced, and a stable temperature field distribution is gradually formed.

[0081] The alignment upsetting step is specifically as follows: when the two rails to be welded reach a certain amount of rubbing (shortening) or a certain time, the temperature and temperature distribution of the weld zone reach a stable state, and the rubbing action stops quickly; the rail at the rubbing end is reset to align the working edges of the two rails to be welded under the drive of the fine grain mechanism, while maintaining the upsetting force or applying a greater upsetting force, and then maintaining the pressure until the mutual diffusion, recrystallization and recrystallization process of metal atoms in the weld zone are fully completed. Thus, a high-quality weld joint with fine grain and ultrafine grain structure is obtained.

[0082] Example 3

[0083] This example provides some specific experimental data of this method. Figures 6 to 8The following is the test result of welding with this method. The materials welded in the experiment are: U75VG high-speed rail and U20Mn bainite new material rail. U20Mn bainite rail is currently recognized as the most difficult to weld high-strength and high-wear-resistant rail. Flash welding and gas pressure welding have been explored and studied for a long time in relevant universities and research institutes, but no breakthrough has been made so far. However, this method has achieved excellent welding results and obtained defect-free ultra-fine-grained weld structure with comprehensive mechanical properties exceeding those of the parent material.

[0084] pass Figure 6 The microscopic morphology of the fine-grained weld zone of the present invention shows that after using the method, the grains in the weld zone have been basically completely refined; Figure 7 The distribution diagram of the longitudinal hardness of the rail top in the fine-grained weld zone of the present invention shows that after using the method, the longitudinal hardness distribution of the rail top along the rail tends to be uniform, so that when the rail is put into long-term railway operation after welding, the strength and wear of the rail weld zone and the rail parent material are basically consistent, avoiding the occurrence of the "hump" phenomenon in the weld zone, ensuring the stability and safety of the train during operation, and reducing the workload and frequency of maintenance and grinding of the rail weld joints of the operating line to eliminate the "hump" disease of the high-speed rail, thereby improving the service life of the rail and saving the maintenance cost of the high-speed rail.

[0085] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A rail welding machine for refining weld grains, comprising a clamping mechanism, a heat source system, a convex pushing mechanism, an upsetting mechanism, an upsetting tailstock and a guide mechanism; each component is interconnected into a whole, characterized in that: It also includes a grain refinement mechanism, under the action of which, relative movement is generated between the welding end faces of the two steel rails to be welded, so as to knead and refine the weld grains in a visco-plastic state or a molten state; The fine crystal mechanism comprises a clamping cylinder, a fine crystal cylinder, a movable housing, a fine crystal mechanism body, a clamping cylinder seat, a connecting rod and a clamping arm; the cylinder barrel of the clamping cylinder is fixedly connected to the clamping cylinder seat, the piston rod of the clamping cylinder penetrates the clamping cylinder seat, the connecting rod is hinged to the clamping cylinder seat and the clamping arm respectively, a rotating shaft is provided on the clamping arm, and the rotating shaft is connected to the fine crystal mechanism body, and the connecting rod and the clamping arm are arranged in pairs; The main body of the crystal thinning mechanism is movably arranged inside a movable shell, and a through hole is arranged on the movable shell for the clamping arm to penetrate and move. The cylinder barrel of the crystal thinning cylinder is fixedly connected to the movable shell, and the cylinder barrel of the crystal thinning cylinder is sleeved on the piston rod of the clamping cylinder.

2. A rail welding machine for refining weld grains according to claim 1, characterized in that: The kneading method of the fine crystal mechanism is one or more of left-right kneading, up-and-down kneading, oblique kneading, swing kneading, and circular trajectory kneading.

3. A rail welding machine for refining weld grains according to claim 2, characterized in that: A kinematic pair is provided between the movable housing and the main body of the grain thinning mechanism; rail receiving grooves are provided on the movable housing and the main body of the grain thinning mechanism, and the rail receiving grooves on the movable housing and the main body of the grain thinning mechanism match the rail receiving grooves on the fixed housing.

4. A rail welding machine for refining weld grains according to claim 3, characterized in that: A forging tailstock is arranged on one end of the movable housing away from the fixed housing, and the forging mechanism is arranged on the forging tailstock; the forging mechanism includes forging cylinders, which are arranged in pairs on the forging tailstock, and the forging cylinders are arranged close to the rails, and the piston rod end of the forging cylinder is fixedly connected to the movable housing.

5. A rail welding machine for refining weld grains according to claim 4, characterized in that: The clamping mechanism is also provided with a rail horizontal centering adjustment cylinder.

6. A rail welding machine for refining weld grains according to claim 5, characterized in that: The heat source system can be a flash resistance heating system, an electromagnetic induction heating system, a gas combustion heating system, a friction heating system, an arc heating system, a physical and chemical reaction heating system, an electron beam heating system, a laser heating system or a combination of some of them, which heats the end face of the rail to be welded, forming a completely thermoplastic state or a completely molten state at the entire welding interface, and having a high-temperature metal layer of a certain thickness.

7. A method for refining weld grains, characterized in that: During the welding process, a fine grain kneading step is added; The step of fine grain kneading is as follows: when the welding heat source system heats the entire welding interface to form a completely thermoplastic state or a completely molten state, and has a high-temperature metal layer of a certain thickness, a certain upsetting force is applied or maintained along the normal direction of the welding interface, so that the thermoplastic or molten metal at the welding interface is squeezed out of the weld; the motion mechanism is started to generate relative movement between the interfaces to be welded of the two weldments, and the kneading action of grain refinement is formed on the welding interface in combination with the upsetting force or the extrusion force; as the kneading action continues, the grains of the weld zone tissue are continuously kneaded and fined; at the same time, the temperature of the entire welding interface is further uniformed, and the temperature gradient along the weld axis and the interface is further reduced to form a stable temperature field distribution; when the entire welding interface forms a stable temperature field and reaches the time set for grain refinement or the shortening amount of the weldment, the kneading action is quickly stopped, and the weldment is immediately aligned; at the same time, the upsetting force is maintained or a larger upsetting force is applied, and the pressure is maintained until the grain recrystallization and recrystallization process of the weld zone grains are fully completed, thereby obtaining a high-quality weld joint with fine grains and ultrafine grain structures.

8. A method for refining weld grains according to claim 7, characterized in that: The movement of the movement mechanism is a plane movement parallel to the welding interface, or a space movement forming a certain angle with the welding interface.

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