Mining heavy load sprocket and wheel disc deep gap welding processing method

Abstract

The application provides a mining heavy load sprocket and a wheel disc deep slot welding processing method, in one aspect, the composition and proportion of the chain tooth and the shaft sleeve material are optimized, the preparation method of the chain tooth and the shaft sleeve is optimized, and the material performance is effectively improved. On the other hand, the shaft sleeve and the chain tooth are welded into a sprocket material by combining the wheel disc deep slot welding processing method, the sprocket is conveniently and low-cost replaced, and the overall service performance of the sprocket is greatly improved.

Description

Technical Field

[0001] This application relates to the field of metallurgical technology, specifically to a method for deep seam welding of the teeth and disc of a heavy-duty mining sprocket. Background Technology

[0002] Mining sprockets are core transmission components of heavy equipment such as underground scraper conveyors. They operate in extremely harsh environments, enduring enormous impact loads, intense abrasive wear, and corrosion. The performance and reliability of sprockets directly affect the production efficiency and operational safety of the entire coal mining operation.

[0003] Currently, the mining sprockets commonly used in the industry mainly adopt integral casting or forging integrated molding technology. That is, the sprocket teeth and bushings are machined as a single blank and put into use after heat treatment. While this traditional integrated structure ensures the integrity of the components, it exposes the following prominent defects in practical applications: 1. Extremely high maintenance costs: When some sprocket teeth fail due to excessive wear or impact fracture, because the teeth and bushings are an integral structure, they cannot be replaced individually. The entire sprocket assembly must be disassembled from the equipment and transported to the surface for overall replacement. This process not only consumes a lot of manpower, time, and transportation costs, but also results in a large number of undamaged parts (such as bushings) being discarded along with the sprockets, causing serious material waste and economic losses. 2. Difficulty in achieving both material properties: The working conditions of the teeth and bushings are different, creating an inherent contradiction in the requirements for material properties. The tooth surface requires extremely high hardness and wear resistance to resist wear, while the bushing needs excellent toughness to withstand impact and alternating loads. The integrated design forces manufacturers to choose a compromise in material composition and heat treatment process, resulting in insufficient wear resistance of the tooth surface or insufficient toughness of the tooth root / shroud, making it impossible to achieve optimal performance of both at the same time, thus limiting the overall life of the sprocket.

[0004] To address these issues, the industry has proposed a preliminary concept for split-type sprockets, which involves manufacturing the teeth and bushings separately and then connecting them. However, existing split-type solutions still suffer from the following technical bottlenecks: 1. Poor connection reliability: Under extreme downhole conditions, simple welded connections are prone to cracking in the weld seam and heat-affected zone due to stress concentration and material mismatch, leading to tooth detachment and ultimately lower reliability than integrated sprockets. 2. Lack of targeted optimization of materials and processes: While split-type designs should allow for the use of different materials and processes for the teeth and bushings, current solutions fail to fully leverage the potential advantages of split-type designs in terms of composition and heat treatment process control, resulting in limited performance improvements.

[0005] In conclusion, existing mining sprocket technologies, whether traditional integrated or early-generation split designs, have failed to fundamentally resolve the contradiction between high maintenance costs and high performance and long service life. Therefore, there is an urgent need for an innovative sprocket design, material system, manufacturing process, and supporting maintenance methods to truly achieve convenient and low-cost tooth replacement while ensuring reliable connection, and to significantly improve the overall service performance of the sprocket. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a deep-seam welding method for heavy-duty mining sprockets and discs. This application involves processing the sprocket teeth and bushings separately, and then welding them together to form a complete sprocket.

[0007] The heavy-duty mining sprocket includes chain teeth and bushings. By weight percentage, the chain tooth material comprises C: 0.40-0.45%, Si: 0.20-0.35%, Mn: 0.70-0.80%, Cr: 0.80-0.90%, Ni: 1.50-1.70%, Mo: 0.23-0.30%, Nb: 0.03-0.06%, V: 0.05-0.10%, Cu: 0.80-1.20%, Al: 0.01-0.025%, Ca: 0.001-0.003%, P≤0.010%, S≤0.005%; the remainder is Fe.

[0008] Furthermore, by weight percentage, the bushing material comprises C: 0.38-0.42%, Si: 0.20-0.35%, Mn: 0.70-0.90%, Cr: 0.90-1.20%, Ni: 0.10-0.30%, Mo: 0.30-0.40%, B: 0.001-0.003%, Ti: 0.01-0.02%, Al: 0.015-0.025%, P≤0.010%, S≤0.005%; the remainder being Fe.

[0009] Furthermore, the method for preparing the chain teeth is as follows: (1) Smelting and casting: The smelting process includes electric arc furnace melting, LF furnace refining, VD vacuum treatment, and calcium treatment in sequence. The ultimate vacuum degree of the VD vacuum treatment is ≤70Pa and the time is ≥15 minutes. In the calcium treatment step, 1.2-1.5kg / t of Ca-Si wire is fed in. The casting process uses argon protection to cast into steel ingots at a casting temperature of 1500-1550℃ and slow cooling after casting. (2) Forging: The steel ingot is heated in stages. The first stage is heated from room temperature to 650℃ at a heating rate of 100℃ / h; the second stage is heated to 1200℃ at a heating rate of 150℃ / h; the third stage is held at 1200-1250℃; isothermal die forging is performed using a die preheated to 950-1000℃, with an initial forging temperature of 1150-1180℃ and a final forging temperature of 950-980℃, and a deformation rate of 0.1-0.5S. -1 Total forging ratio ≥ 8; (3) Quenching: Transfer to the quenching tank for quenching within 15s after final forging. The cooling rate is 80-100℃ / s, and the quenching endpoint temperature is ≤50℃. (4) High-temperature tempering: Temper at 650-680℃ for 10-12 hours, then furnace cool to 300℃ and air cool; (5) Two-phase region quenching: Heat in an atmosphere furnace to the two-phase region of 790-810℃ above Ac1 and below Ac3, hold for 3-4 hours, and then oil quench to room temperature; (6) Final tempering: Temper at 200-240℃ for 8-10 hours, then air cool.

[0010] The two-phase quenching in this application refers to: heating the workpiece to a temperature range above the Ac1 phase transformation point and below the Ac3 phase transformation point for austenitization, holding at that temperature, and then quenching.

[0011] According to measurements, the Ac1 phase transition point of the chain tooth material of the present invention is 720-740℃, and the Ac3 phase transition point is 805-830℃.

[0012] Furthermore, the chain teeth obtained after final tempering undergo local heat treatment, with the root of the chain teeth being locally heated at a temperature of 650-700℃ for 3-5 minutes.

[0013] Furthermore, the welding surface of the chain teeth is pretreated. The pretreatment steps include: machining the welding surface to make its roughness Ra≤3.2 micrometers, then cleaning with acetone and drying at 120℃ for 2 hours.

[0014] Furthermore, a Ni layer is deposited by magnetron sputtering on the pretreated chain tooth welding surface, and the vacuum is reduced to ≤5*10⁻⁶. -3 Pa, high-purity argon gas is introduced to the working pressure of 0.5-1.0 Pa; deposition is carried out using a Ni target under the conditions of DC power of 300-500W, workpiece bias voltage of -50 to -100V, and uniform workpiece rotation, wherein the deposition temperature is 150-200℃, the deposition rate is 0.5-1.0 μm / h, the film thickness is 5-10 μm, and then vacuum annealing is performed.

[0015] Furthermore, the purity of the Ni target is ≥99.99%.

[0016] Furthermore, the specific steps of the vacuum annealing post-treatment are as follows: After deposition, the workpiece is annealed in a vacuum furnace, heated to 290-310℃ at a heating rate of ≤100℃ / h, held at that temperature for 2 hours, and maintaining a vacuum degree of 1*10 during the process. - 2 Pa, after the heat preservation is completed, it is cooled in the furnace to below 100°C and then removed from the furnace.

[0017] Furthermore, the method for preparing the bushing is as follows: (1) Smelting and casting: The smelting process includes electric arc furnace melting, LF furnace refining, and VD vacuum treatment, wherein the vacuum degree of the VD vacuum treatment is ≤100Pa; The casting process adopts argon-protected casting, the casting temperature is 1500-1550℃, and slow cooling is performed after casting. (2) Forging: The steel ingot is held at 1180-1220℃ for 5-8 hours; the initial forging temperature is ≥1050℃, the final forging temperature is ≥800℃, the total forging ratio is ≥7, and the forging is air-cooled or sand-cooled. (3) Normalizing treatment: The temperature is 870-880℃, the time is 7-9h, and after exiting the furnace, air cooling or mist cooling is adopted, the cooling rate is 5-10℃ / s, and the final cooling temperature is 50-100℃. (4) High-temperature tempering: The tempering temperature is 650℃, the holding time is 12-15h, and the furnace is cooled to 400℃ and then air-cooled. (5) Quenching treatment: Quenching temperature is 850-860℃, holding time is 5-7h, cooling rate is 30-50℃ / s, and final cooling temperature is ≤50℃. (6) Final tempering: Temper at 560-610℃ for 10-12 hours, then air cool.

[0018] Furthermore, the surface of the bushing obtained after final tempering is locally heated to a temperature of 900-980℃, and then the heated area is immediately spray-cooled at a cooling rate of not less than 50℃ / s, and the depth of the phase transformation hardened layer is 1.0-3.0mm; then low-temperature tempering is performed, in which the quenched area is heated to 180-250℃ using a heating device, held at that temperature for 2-4 hours, and then naturally cooled to room temperature.

[0019] This application provides a method for deep seam welding of a wheel disc, characterized by the following steps: (1) Preheating: Place the assembled chain teeth and bushings into a heating furnace for preheating at a temperature of 250-350℃ and hold for 2-4 hours; use mixed gas shielded welding for deep seam welding. The deep seam welding process is as follows: (2) Root pass welding: Solid wire is used, the welding current is 170-190A, the voltage is 20-23V, and a root pass with a thickness of 3-4mm is formed; (3) Filling welding: Gas shielded welding with flux-cored wire or double-wire submerged arc welding is used for filling and cover welding. The welding current is 210-230A, the voltage is 25-27V, and the thickness of each layer is 4-5mm. (4) Post-weld heat treatment: The welded sprocket is heat treated at a rate of 60-90℃ / h, and the temperature is raised to 200-250℃. After holding at the temperature for 5-8 hours, it is allowed to cool naturally.

[0020] Furthermore, in step (1), the preheating adopts a stepped heating method, with an initial heating rate of 50-80℃ / h. When the temperature reaches 100-120℃, it is kept at that temperature for 0.5-1 hour. Then, the temperature is increased to the final preheating temperature at a rate of 30-50℃ / h.

[0021] Furthermore, the shielding gas for mixed gas shielded welding is a mixture of argon and carbon dioxide, with argon accounting for 75-85% of the volume.

[0022] The beneficial effects of this application are as follows: 1. The chain teeth directly mesh with the chain, bearing severe impacts, contact fatigue, and abrasive wear. This application designs the chain teeth to ensure ultra-high toughness in the core while imparting extremely high surface hardness and wear resistance. C provides the basis for martensitic hardness, and its content range ensures high hardness while also taking into account a certain degree of toughness, avoiding excessive carbon content that leads to coarse and brittle carbides and a sharp increase in sensitivity to welding cold cracking. Cr, Ni, and Mo form a hardenability triangle. Cr and Mo significantly improve hardenability, ensuring that the core of large-section teeth can obtain martensitic / bainitic structure during quenching, avoiding the formation of soft ferrite bands. Mo can also effectively suppress high-temperature tempering brittleness. Ni does not form carbides and, when dissolved in ferrite, can significantly improve the low-temperature toughness of the matrix and reduce the ductile-brittle transition temperature. This is the key to the chain teeth bearing downhole impact loads without brittle fracture. During forging heating and austenitization, undissolved Nb and V particles effectively pin austenite grain boundaries, strongly inhibiting grain growth to obtain ultrafine-grained austenite. After quenching, ultrafine-grained martensite is obtained, which can improve strength and toughness. During tempering, Nb and V precipitate as fine carbonitrides, producing a strong precipitation strengthening effect, improving the material's strength, hardness, and resistance to tempering softening. Cu has a large solid solubility in ferrite, but during low-temperature tempering, it precipitates extremely fine, coherent copper-rich phases, producing significant precipitation strengthening to further enhance strength without significantly impairing toughness. Cu can moderately stabilize austenite, helping to obtain a small amount of thin-film, stable retained austenite in the final microstructure. These retained austenite particles distributed between martensite laths can relax stress, hinder crack propagation, and significantly improve fracture toughness and contact fatigue life. Al mainly acts as a deoxidizer; when controlling the lower limit, it is necessary to avoid excessive Al leading to embrittlement of the weld heat-affected zone. Ca can spheroidize long, harmful MnS inclusions into small, spherical CaS or calcium aluminate composite inclusions, greatly improving the isotropy of the material and significantly enhancing its transverse impact toughness and fatigue performance.

[0023] Through the synergistic effect of the above elements, the chain tooth material of this application finally obtains a multiphase structure with ultrafine lath martensite as the main component, containing a small amount of stable residual austenite and uniform precipitates, thus achieving an excellent match between hardness and toughness.

[0024] 2. The bushing primarily bears torque, bending stress, and compressive stress, and as the base material, it needs to be welded to the chain teeth. The bushing design in this application maximizes its weldability while ensuring sufficient strength and excellent toughness, ensuring the safety of the welded joint. The carbon content is slightly lower than that of the chain teeth, achieving better ductility and toughness while maintaining strength, significantly reducing the carbon equivalent and improving weldability. Mo improves hardenability and high-temperature strength, and enhances resistance to tempering softening. Trace amounts of boron segregate at the austenite grain boundaries, significantly delaying ferrite nucleation at the grain boundaries and greatly improving hardenability. This allows the bushing to achieve an ideal bainitic / martensite microstructure in the large cross-section without relying on large amounts of expensive alloying elements, thus achieving uniform performance. Ti has a strong affinity for N, preferentially forming fine, thermally stable TiN particles. These TiN particles can still partially exist at the high welding temperatures, effectively pinning the austenite grain boundaries in the heat-affected zone (HAZ) and preventing excessive grain growth. Fine HAZ grains are key to ensuring the toughness of the weld joint, fixing free N in the steel and avoiding embrittlement caused by the formation of free AlN or BN. Al is controlled at a low level, mainly for deoxidation, avoiding the formation of large amounts of AlN, which dissolves during the welding thermal cycle and precipitates at the grain boundaries of the HAZ, causing embrittlement of the weld heat-affected zone. Cr provides basic hardenability and strength, Mn solid solution strengthening improves hardenability, and a small amount of Ni helps improve the toughness of the matrix.

[0025] Through the synergistic effect of the above elements, the bushing obtains a uniform microstructure mainly composed of bainite or tempered sorbite, which has excellent plasticity and toughness.

[0026] 3. The chain tooth preparation method of this application fully unleashes the potential of material composition design through innovative processes, resulting in significant improvements in chain tooth hardness, wear resistance, toughness, fatigue performance, and microstructure uniformity. Vacuum treatment (VD) deeply removes gases from the molten steel, greatly reducing the risk of hydrogen-induced cracking (white spots) and oxide inclusions, thus improving material density and fatigue life. Calcium treatment significantly improves the isotropy, transverse impact toughness, and fatigue strength of the material by removing long, harmful MnS or complex inclusions, which is crucial for chain teeth subjected to multi-directional impacts. Argon-protected casting and slow cooling prevent secondary oxidation, reduce casting defects, and slow cooling eliminates internal stress, avoiding ingot cracking. In the forging process, low-temperature forging inhibits grain growth and promotes dynamic recrystallization; isothermal forging achieves ultrafine-grained austenite. Post-forging residual heat quenching completes deformation heat treatment, fixing the ultrafine microstructure and directly transforming the ultrafine, high-dislocation-density austenite microstructure obtained by isothermal forging into equally ultrafine, high-density lath martensite. This process avoids grain coarsening caused by reheating austenitization, achieving a seamless connection between forging and quenching, and significantly improving both strength and toughness simultaneously. High-temperature tempering restores the microstructure and spheroidizes carbides, eliminating the enormous internal stress from post-forging quenching, preventing cracking during subsequent machining, and decomposing the unstable quenched martensite into tempered sorbite. Carbides begin to aggregate and spheroidize, providing a stable, softened, easily machinable microstructure with uniform carbide distribution for subsequent dual-phase quenching, ensuring controllable austenitization during reheating. In the dual-phase quenching step, the microstructure consists of undissolved ferrite and newly formed austenite coexisting. After quenching, the newly formed austenite transforms into martensite, while the undissolved ferrite is retained, resulting in a dual-phase microstructure of martensite (hard phase, providing strength, hardness, and wear resistance) and ferrite (soft phase, providing plasticity and toughness), exhibiting continuous yield characteristics, high work hardening rate, and excellent crack propagation resistance. Ferrite effectively blunts crack tips, making the chain teeth less prone to catastrophic brittle fracture under impact, resulting in excellent impact fatigue resistance. The final low-temperature tempering process achieves stress relief and nanoprecipitation, eliminating residual stress formed during quenching in the two-phase region. ε-carbides precipitate in the martensite, causing secondary hardening. In this temperature range, Cu elements in the material precipitate a coherent, nanoscale, copper-rich ε-Cu phase, resulting in strong precipitation strengthening, further enhancing strength without significant loss of toughness. This also promotes the transformation of a small amount of unstable residual austenite into tempered martensite or lower bainite, stabilizing the microstructure.

[0027] 4. The manufacturing method of the bushing in this application ensures excellent strength, toughness, hardenability, and uniform microstructure of the material. Building upon this foundation, the friendliness of subsequent welding processes was improved, achieving an optimal balance between performance, reliability, and economy through process control. Specifically, in the forging process, high-temperature, long-term holding ensures sufficient diffusion, homogenizes chemical composition, and eliminates as-cast segregation; controlling the final forging temperature avoids plastic deformation in the blue brittle zone, preventing plasticity reduction and cracking risks due to dynamic strain failure; controlling the total forging ratio fully breaks down as-cast dendrites, welding internal voids to densify the microstructure, significantly improving the material's transverse properties and toughness; post-forging cooling yields a refined pearlite-ferrite microstructure, preparing the microstructure for subsequent heat treatment while avoiding excessive internal stress. Normalizing eliminates the inhomogeneity of the forging microstructure and refines the grains, resulting in a pearlite + ferrite microstructure with uniform composition and fine grains. Controlled cooling rates prevent excessive precipitation of proeutectoid ferrite along grain boundaries, making the microstructure even finer and more uniform, laying the foundation for austenite homogenization during subsequent quenching. High-temperature tempering effectively eliminates residual stresses generated during normalizing and pre-processing, significantly reducing material hardness, greatly improving machinability, and preparing the material for final quenching in a soft state. During quenching, carbide dissolution and uniform composition are ensured, while excessively high temperatures leading to grain coarsening are avoided. A suitable cooling rate is used to achieve high hardenability, avoiding the nose of the CCT curve and suppressing the formation of non-martensitic structures, ensuring the entire cross-section is predominantly lath martensite. The final tempering process is conducted in the high-temperature tempering zone, where quenched martensite fully decomposes into tempered sorbite. This microstructure maintains high yield strength and tensile strength while exhibiting extremely high plasticity and impact toughness. The microstructure after high-temperature tempering has moderate hardness and a low carbon equivalent angle, greatly reducing the material's sensitivity to welding cold cracking, allowing for more lenient welding preheating temperature requirements, and minimizing performance degradation in the heat-affected zone.

[0028] 5. This application employs pretreatment of the chain tooth welding surface, magnetron sputtering of a Ni layer, and vacuum annealing to fundamentally reconstruct and optimize the welding interface. This pre-constructs a high-performance, highly compatible welding interface transition layer for the chain teeth, simplifying the complex metallurgical problem of on-site welding into a more reliable connection issue. Pretreatment provides a uniform and moderately rough surface, increasing the actual surface area, improving mechanical interlocking, and providing uniform nucleation sites for subsequent Ni layer deposition, which is beneficial for obtaining a dense and strongly bonded film.

[0029] Under high vacuum and ion bombardment conditions, the deposited Ni atoms possess high energy and activity, forming a strong metallurgical bond with a bonding strength far exceeding that of traditional plating methods such as electroplating. The pure Ni layer (face-centered cubic structure) exhibits excellent plasticity, toughness, and low yield strength. During welding and service, this Ni layer acts as a soft, plastic buffer, effectively absorbing and relaxing stress concentrations caused by differences in thermal expansion coefficients between the chain teeth and bushings, welding residual stress, and external loads, preventing crack initiation and propagation at the hard and brittle interface. When high-carbon / high-alloy chain teeth are directly welded to medium-carbon bushings, carbon diffuses from the chain teeth to the bushings under welding thermal cycles, forming a carbon-depleted soft band on the chain tooth side and a high-carbon brittle martensitic band in the heat-affected zone near the fusion line, severely weakening the joint. The Ni layer, acting as a carbon diffusion barrier, has a much lower affinity for carbon than iron. The insertion of a pure Ni layer significantly hinders long-distance carbon atom diffusion, ensuring the stability of the microstructure on both sides of the interface. Furthermore, the Ni layer exhibits good compatibility and wettability with most iron-based welding materials. During on-site welding, the molten welding material can spread and fuse better on the Ni layer surface, reducing defects such as incomplete fusion and undercut, resulting in a dense and continuous weld. Vacuum annealing promotes interfacial interdiffusion, creating a gradient transition and providing sufficient kinetic energy for Ni and Fe atoms to diffuse in the solid state. This forms an Fe-Ni interdiffusion zone at the original sharp interface, where the composition and properties gradually change from pure Ni to the base steel, achieving a smooth gradient transition and enhancing the bonding strength. Annealing also eliminates the stress accumulated inside the Ni layer during magnetron sputtering, preventing subsequent peeling and flaking of the film, resulting in a more stable grain structure and more uniform properties for the Ni layer.

[0030] 6. After final tempering, the chain teeth undergo local heat treatment, which reduces the hardness of the affected area while keeping the hardness of the tooth surface and core unchanged. Through rapid local heating, the martensite in this area is further decomposed, and the carbides aggregate and grow to obtain tempered sorbite and pearlite structures. The softening effect is significant. In actual use, the old teeth can be cut quickly and smoothly through the softened area, with neat cuts, reduced heat input requirements, and reduced risk of thermal damage to the bushing.

[0031] 7. This application describes the surface treatment of the bushing after final tempering, which locally hardens and toughens the bushing surface. This extends the service life of the bushing, enabling it to resist daily wear and withstand accidental severe impacts, thus preventing catastrophic failures such as tooth breakage. The hardened surface effectively resists brief accidental contact with flame during chain tooth replacement cutting operations, protecting the bushing body from damage. Its good toughness reduces the risk of surface cracking due to improper operation. Rapid heating of the bushing surface causes the spherical carbides in the thin layer to redissolve, and the microstructure transforms back into fine austenite. Subsequent rapid cooling transforms this austenite into high-hardness martensite, resulting in a several-fold increase in wear resistance. This achieves an ideal gradient structure with a hard outer layer and a tough inner layer. Phase transformation occurs only in the surface layer (1-3 mm deep), while the core retains tempered sorbite, preserving its high strength, toughness, and plasticity. This provides strong toughness support for the hardened surface layer, preventing brittle collapse under heavy impact. A region with a smooth transition in hardness and microstructure is formed between the hardened layer and the core, avoiding abrupt changes in properties, facilitating stress transfer, and preventing interfacial delamination. Low-temperature tempering can eliminate quenching stress and improve crack resistance. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the heavy-duty mining sprocket structure in this application.

[0033] Among them: 1. bushing, 2. chain teeth, 3. welding position. Detailed Implementation

[0034] Unless otherwise specified, the raw materials and instruments used in the following examples are all commercially available products.

[0035]

Example 1

[0036] The method for preparing chain teeth is as follows: (1) Smelting and casting: The smelting process includes electric arc furnace melting, LF furnace refining, VD vacuum treatment and calcium treatment in sequence. The ultimate vacuum degree of VD vacuum treatment is 70 Pa for 15 minutes. In the calcium treatment step, 1.2 kg / t of Ca-Si wire is fed in. The casting process uses argon protection to cast into steel ingots at a casting temperature of 1500℃ and slow cooling after casting. (2) Forging: The steel ingot is heated in stages. The first stage is heated from room temperature to 650℃ at a heating rate of 100℃ / h; the second stage is heated to 1200℃ at a heating rate of 150℃ / h; the third stage is held at 1200℃ for 8 hours; isothermal die forging is performed using a die preheated to 1000℃, with an initial forging temperature of 1150℃ and a final forging temperature of 980℃, and a deformation rate of 0.5 s. -1 The total forging ratio is 8; (3) Quenching: Transfer to the quenching tank within 15s after final forging for quenching, with a cooling rate of 80℃ / s and a quenching endpoint temperature of 50℃. (4) High-temperature tempering: Temper at 650℃ for 12 hours, then furnace cool to 300℃ and then air cool; (5) Two-phase region quenching: Heat to 790℃ in an atmosphere furnace to the two-phase region above Ac1 and below Ac3, hold for 4 hours, and then oil quench to room temperature; (6) Final tempering: Temper at 240℃ for 8 hours, then air cool.

[0037] By weight percentage, the bushing material comprises C: 0.38%, Si: 0.20%, Mn: 0.90%, Cr: 1.20%, Ni: 0.10%, Mo: 0.30%, B: 0.003%, Ti: 0.01%, Al: 0.015%, P: 0.008%, S: 0.003%; the remainder is unavoidable impurities and Fe.

[0038] The manufacturing method of the bushing is as follows: (1) Smelting and casting: The smelting process includes electric arc furnace melting, LF furnace refining, and VD vacuum treatment. The vacuum degree of VD vacuum treatment is 100Pa. The casting process adopts argon protection casting, the casting temperature is 1550℃, and slow cooling is performed after casting. (2) Forging: The steel ingot is held at 1180℃ for 8 hours; the initial forging temperature is 1050℃, the final forging temperature is 800℃, the total forging ratio is 7, and it is air-cooled after forging; (3) Normalizing treatment: The temperature is 870℃, the time is 9h, and after exiting the furnace, air cooling is adopted with a cooling rate of 5℃ / s and a final cooling temperature of 100℃. (4) High-temperature tempering: The tempering temperature is 650℃, the holding time is 12h, and the furnace is cooled to 400℃ and then air-cooled. (5) Quenching treatment: Quenching temperature is 850℃, holding time is 7h, cooling rate is 30℃ / s, and final cooling temperature is 50℃. (6) Final tempering: Temper at 610℃ for 10 hours, then air cool.

[0039]

Example 2

[0040] The method for preparing chain teeth is as follows: (1) Smelting and casting: The smelting process includes electric arc furnace melting, LF furnace refining, VD vacuum treatment and calcium treatment in sequence. The ultimate vacuum degree of VD vacuum treatment is 60Pa and 20 minutes. In the calcium treatment step, 1.5kg / t of Ca-Si wire is fed in. The casting process uses argon protection to cast into steel ingots at a casting temperature of 1550℃ and slow cooling after casting. (2) Forging: The steel ingot is heated in stages. The first stage is heated from room temperature to 650℃ at a heating rate of 100℃ / h; the second stage is heated to 1200℃ at a heating rate of 150℃ / h; the third stage is held at 1250℃ for 3 hours; isothermal forging is performed using a die preheated to 950℃, with an initial forging temperature of 1180℃ and a final forging temperature of 950℃, and a deformation rate of 0.1 s. -1 The total forging ratio is 10; (3) Quenching: Transfer to the quenching tank for quenching within 15s after final forging. The cooling rate is 100℃ / s and the quenching endpoint temperature is 40℃. (4) High-temperature tempering: Temper at 680℃ for 10 hours, then furnace cool to 300℃ and air cool; (5) Two-phase region quenching: Heat to 810℃ in an atmosphere furnace to the two-phase region above Ac1 and below Ac3, hold for 3 hours, and then oil quench to room temperature; (6) Final tempering: Temper at 200℃ for 10 hours, then air cool.

[0041] By weight percentage, the bushing material comprises C: 0.42%, Si: 0.35%, Mn: 0.70%, Cr: 0.90%, Ni: 0.30%, Mo: 0.40%, B: 0.001%, Ti: 0.02%, Al: 0.025%, P: 0.007%, S: 0.002%; the remainder is unavoidable impurities and Fe.

[0042] The manufacturing method of the bushing is as follows: (1) Smelting and casting: The smelting process includes electric arc furnace melting, LF furnace refining, and VD vacuum treatment. The vacuum degree of VD vacuum treatment is 90Pa. The casting process adopts argon protection casting, the casting temperature is 1500℃, and slow cooling is performed after casting. (2) Forging: The steel ingot is held at 1220℃ for 5 hours; the initial forging temperature is 1100℃, the final forging temperature is 850℃, the total forging ratio is 8, and it is air-cooled after forging; (3) Normalizing treatment: The temperature is 880℃ and the time is 7h. After exiting the furnace, air cooling combined with mist cooling is used. The cooling rate is 10℃ / s and the final cooling temperature is 50℃. (4) High-temperature tempering: The tempering temperature is 650℃, the holding time is 15h, and the furnace is cooled to 400℃ and then air-cooled. (5) Quenching treatment: Quenching temperature is 860℃, holding time is 5h, cooling rate is 50℃ / s, and final cooling temperature is 40℃. (6) Final tempering: Temper at 560℃ for 12 hours, then air cool.

[0043]

Example 3

[0044] The method for preparing chain teeth is as follows: (1) Smelting and casting: The smelting process includes electric arc furnace melting, LF furnace refining, VD vacuum treatment and calcium treatment in sequence. The ultimate vacuum degree of VD vacuum treatment is 50 Pa for 25 minutes. In the calcium treatment step, 1.3 kg / t of Ca-Si wire is fed in. The casting process uses argon protection to cast into steel ingots at a casting temperature of 1530℃ and slow cooling after casting. (2) Forging: The steel ingot is heated in stages. The first stage is heated from room temperature to 650℃ at a heating rate of 100℃ / h; the second stage is heated to 1200℃ at a heating rate of 150℃ / h; the third stage is held at 1230℃ for 5 hours; isothermal die forging is performed using a die preheated to 980℃, with an initial forging temperature of 1160℃ and a final forging temperature of 960℃, and a deformation rate of 0.3S. -1 The total forging ratio is 9; (3) Quenching: Transfer to the quenching tank for quenching within 15s after final forging. The cooling rate is 90℃ / s and the quenching endpoint temperature is 30℃. (4) High-temperature tempering: Temper at 670℃ for 11 hours, then furnace cool to 300℃ and air cool; (5) Two-phase quenching: Heat to 800℃ in an atmosphere furnace to the two-phase region above Ac1 and below Ac3, hold for 3.5h, and then oil quench to room temperature; (6) Final tempering: Temper at 220℃ for 9 hours, then air cool.

[0045] By weight percentage, the bushing material comprises C: 0.40%, Si: 0.28%, Mn: 0.80%, Cr: 1.05%, Ni: 0.20%, Mo: 0.35%, B: 0.002%, Ti: 0.015%, Al: 0.020%, P: 0.005%, S: 0.003%; the remainder is unavoidable impurities and Fe.

[0046] The manufacturing method of the bushing is as follows: (1) Smelting and casting: The smelting process includes electric arc furnace melting, LF furnace refining, and VD vacuum treatment. The vacuum degree of VD vacuum treatment is 80Pa. The casting process adopts argon protection casting, the casting temperature is 1520℃, and slow cooling is performed after casting. (2) Forging: The steel ingot is held at 1200℃ for 6 hours; the initial forging temperature is 1050℃, the final forging temperature is 900℃, the total forging ratio is 10, and it is air-cooled after forging; (3) Normalizing treatment: The temperature is 875℃ and the time is 8h. After exiting the furnace, air cooling combined with mist cooling is used. The cooling rate is 8℃ / s and the final cooling temperature is 80℃. (4) High-temperature tempering: The tempering temperature is 650℃, the holding time is 13h, and the furnace is cooled to 400℃ and then air-cooled. (5) Quenching treatment: Quenching temperature is 855℃, holding time is 6h, cooling rate is 40℃ / s, and final cooling temperature is 30℃. (6) Final tempering: Temper at 580℃ for 11 hours and air cool.

[0047]

Example 4

[0048]

Example 5

[0049] A Ni layer was deposited by magnetron sputtering on the pretreated chain tooth welding surface, and the vacuum was reduced to ≤5*10⁻⁶. -3The working pressure was increased to 0.5 Pa by introducing high-purity argon gas. A Ni target with a purity ≥99.99% was used for deposition under conditions of 300 W DC power, -100 V workpiece bias, and uniform workpiece rotation. The deposition temperature was 150 °C, the deposition rate was 1.0 μm / h, and the film thickness was 10 μm. After deposition, the workpiece was annealed in a vacuum furnace by heating to 290 °C at a rate of 100 °C / h and holding for 2 hours, maintaining a vacuum of 1*10⁻⁶ Pa. -2 Pa, after the heat preservation is completed, it is cooled to below 100°C in the furnace and then removed from the furnace.

[0050]

Example 6

[0051] The surface of the chain teeth after local heat treatment is pretreated. The pretreatment steps include: machining the surface to make its roughness Ra≤3.2 micrometers, then cleaning with acetone and drying at 120℃ for 2 hours.

[0052] A Ni layer was deposited by magnetron sputtering on the pretreated surface, and the vacuum was reduced to ≤5*10⁻⁶. -3 The working pressure was increased to 1.0 Pa by introducing high-purity argon gas. A Ni target with a purity ≥99.99% was used for deposition under conditions of 500 W DC power, -50 V workpiece bias, and uniform workpiece rotation. The deposition temperature was 200℃, the deposition rate was 0.5 μm / h, and the film thickness was 5 μm. After deposition, the workpiece was annealed in a vacuum furnace by heating to 310℃ at a rate of 80℃ / h and holding for 2 hours, maintaining a vacuum of 1*10⁻⁶ Pa. -2 Pa, after the heat preservation is completed, it is cooled to below 100°C in the furnace and then removed from the furnace.

[0053]

Example 7

[0054]

Example 8

[0055] The surface of the chain teeth after local heat treatment is pretreated. The pretreatment steps include: machining the surface to make its roughness Ra≤3.2 micrometers, then cleaning with acetone and drying at 120℃ for 2 hours.

[0056] A Ni layer was deposited by magnetron sputtering on the pretreated surface, and the vacuum was reduced to ≤5*10⁻⁶. -3 The working pressure was increased to 0.8 Pa by introducing high-purity argon gas. A Ni target with a purity ≥99.99% was used for deposition at a DC power of 400 W, a workpiece bias voltage of -80 V, and uniform workpiece rotation. The deposition temperature was 180 °C, the deposition rate was 0.7 μm / h, and the film thickness was 7 μm. After deposition, the workpiece was annealed in a vacuum furnace by heating to 300 °C at a heating rate of 90 °C / h and holding for 2 hours, maintaining a vacuum of 1*10⁻⁶ Pa. -2 Pa, after the heat preservation is completed, it is cooled to below 100°C in the furnace and then removed from the furnace.

[0057] Based on Example 3, the surface of the bushing obtained after final tempering is locally heated to a temperature of 980°C, and then the heated area is immediately spray-cooled at a cooling rate of not less than 50°C / s, with a phase transformation hardening layer depth of 3.0mm; then low-temperature tempering is performed, in which the quenched area is heated to 250°C using a heating device, held at that temperature for 2 hours, and then naturally cooled to room temperature.

[0058]

Example 9

[0059]

Example 10

[0060]

Example 11

[0061]

Example 12

[0062] Comparative Example 1 The difference from Example 1 is that the chain tooth material includes C: 0.41%, Si: 0.23%, Mn: 0.56%, Cr: 0.80%, Ni: 1.30%, Mo: 0.19%, with the remainder being unavoidable impurities and Fe.

[0063] Comparative Example 2 The difference from Example 1 is that the chain tooth material includes C: 0.40%, Si: 0.20%, Mn: 0.70%, Cr: 0.90%, Ni: 1.50%, Mo: 0.23%, Al: 0.025%, P: 0.006%, S: 0.005%, with the remainder being unavoidable impurities and Fe.

[0064] [Performance Characterization] 1. Hardness: Refer to GB / T 39536 and use a hardness tester to test the hardness; 2. Mechanical properties: Tensile test bars were prepared in accordance with GB / T228.1 standard for tensile testing of metallic materials, and tensile tests were conducted using a universal testing machine; 3. Impact test: Prepare impact test blocks according to GB / T229 standard for Charpy impact test of metallic materials, and conduct impact test using a metal pendulum. 4. Friction and wear test: Prepare the specimens according to GB / T 12444.2 Metal wear test method standard, and wear them for 2 hours under a load of 250N using a friction and wear tester. The wear pair uses GCr15 steel balls and the rotation speed is 200rpm.

[0065] Examples 4, 6, 7, and 8 only applied the above tests to the partially treated materials. The mechanical and impact properties of the bushings in Examples 7 and 8 are difficult to test, therefore these tests were not performed.

[0066] Table 1 Test Results 1

[0067] Analyzing the experimental data in Table 1, this application innovates the material design by using multi-element micro-alloying composite reinforcement. Elements such as Cu, Nb, and V are added to the chain tooth material to improve the material strength, and the refined microstructure also contributes to toughness.

[0068] This application innovates the preparation method. The innovative process combines forging residual heat quenching, high-temperature tempering, two-phase zone quenching, and low-temperature tempering to achieve the peak of the material's triple properties of strength, toughness, and wear resistance.

[0069] Examples 9 and 10, and Comparative Examples 1 and 2, adjusted the material composition of the chain teeth and bushings. Examples 11 and 12 adjusted the manufacturing process of the chain teeth and bushings, which affected the performance of the materials.

[0070] Examples 5, 6, and 8 show that depositing a Ni layer is beneficial for improving wear resistance or connection performance. Examples 7 and 8 show that treating the surface of the bushing yields an extremely hard wear-resistant layer, achieving an ideal structure that is hard on the outside and tough on the inside.

[0071] 5. Ni layer bonding strength test: Refer to ASTM C1624 scratch test to determine the critical load Lc of the bond between the Ni layer and the chain tooth substrate. From the chain tooth welding surface area where the Ni layer has been deposited, a 20*20mm sample is cut using a water-cooled precision cutter. The surface is sanded and polished until the Ni layer reaches a mirror finish with no visible scratches. Then, a scratch tester is used to test the sample, and the average critical load Lc1 is recorded.

[0072] Table 2 Test results of Ni layer bonding strength

[0073] The Ni layer prepared in this application exhibits strong adhesion to the chain tooth substrate, resulting in enhanced peel resistance during subsequent welding. The coating is less prone to detachment and can sustainably provide multiple functions including wear resistance, corrosion prevention, and improved weldability. Example 8 demonstrates the highest bonding strength, indicating that the localized heat treatment process of the substrate significantly contributes to improving the bonding strength.

[0074] 6. Chain tooth cutting performance: Use a water-cooled cutting machine to cut chain tooth samples with a size of 100*50mm. Use a flame cutting machine and a propane torch to fix the sample on the test table. Cut the sample in a straight line with the cutting path perpendicular to the sample. Record the maximum stable cutting speed and the cutting time per unit length after cutting.

[0075] Table 3 Test data on chain tooth cutting performance

[0076] Local heat treatment of the chain tooth material softens the material, improves its thermal conductivity, makes it easier to reach the ignition point, and produces more fluid oxidized slag. This significantly reduces cutting resistance and increases cutting speed.

[0077] Example 8, based on localized heat treatment, adds a magnetron sputtered Ni layer, lowering the surface ignition point and making cutting initiation and maintenance easier. The Ni-containing slag has lower viscosity and better flowability, making it easier to blow away.

[0078] 7. Shaft sleeve surface cut resistance verification: Point the welding torch flame at the shaft sleeve surface and burn it for 15 seconds. When the local temperature reaches 1200℃, immediately cool it with water mist. Repeat the above "burning-cooling" cycle 3 times. Observe whether there are molten pits, spalling or radial cracks visible to the naked eye at the burning point, and record the depth of the molten pit.

[0079] Table 4. Test data on the cutting resistance of the bushing tooth surface

[0080] Example 8 has a deeper hardened layer and better microstructure uniformity, which improves the material's resistance to ablation at high temperatures and makes the melting zone shallower.

[0081] Example 8: The deeper hardened layer avoids interfaces with abrupt performance changes, and the higher tempering temperature reduces material brittleness. Together, these factors effectively relax thermal stress during rapid cooling, thus preventing the formation of macroscopic cracks. Example 8: The bushing, after minor burning, only develops very shallow craters without initiating cracks, extending the effective lifespan of the component and reducing replacement costs.

[0082] 8. On-site welding simulation test: The deep seam welding method using a rotary disc is as follows: (1) Preheating: The chain tooth material and bushing material are placed in a heating furnace for preheating at 300℃ and held for 3 hours; deep seam welding is performed using mixed gas shielded welding (a mixture of argon and carbon dioxide, with argon accounting for 80% of the volume). The deep seam welding process is as follows: (2) Root pass welding: ER100S-G solid core welding wire is used, the welding current is 180A and the voltage is 20V; (3) Filling welding: Gas shielded welding with flux-cored wire (E91T1-G) is used for filling and cover welding. The welding current is 220A and the voltage is 25V. Multi-layer, multi-pass, symmetrical segmented welding is used. (4) Post-weld heat treatment: The welded material is heat treated at a rate of 80℃ / h, and the temperature is raised to 200℃. After holding at the temperature for 6 hours, it is allowed to cool naturally.

[0083] The following tests were performed on the welded position after welding: 1. Mechanical properties: Tensile tests on welds were conducted in accordance with GB / T 2651; 2. Bending test: The bending test shall be conducted in accordance with GB / T 2653; 3. Impact toughness: Tested according to GB / T 2650.

[0084] Table 4 Welding performance test data

[0085] The data comparison and analysis above show that the tensile strength and impact toughness of Examples 5 and 8, which have Ni layers, are significantly improved. As a plastic buffer zone and carbon diffusion barrier, the Ni layer effectively inhibits the formation of brittle phases in the weld fusion zone and transforms stress concentration into plastic deformation, thereby improving the welding performance of bushings and chain teeth.

[0086] The changes in the composition of the bushing material in Examples 9 and 10, and the changes in the composition of the chain tooth material in Comparative Examples 1 and 2, will affect the welding performance of the bushing and chain tooth; the changes in the chain tooth preparation method in Example 11 and the changes in the bushing preparation method in Example 12 will also affect the welding performance of the bushing and chain tooth.

[0087] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0088] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A heavy-duty mining sprocket, characterized in that, The chain includes chain teeth and bushings, which are welded together to form a heavy-duty mining sprocket. By weight percentage, the chain tooth material comprises: C: 0.40-0.45%, Si: 0.20-0.35%, Mn: 0.70-0.80%, Cr: 0.80-0.90%, Ni: 1.50-1.70%, Mo: 0.23-0.30%, Nb: 0.03-0.06%, V: 0.05-0.10%, Cu: 0.80-1.20%, Al: 0.01-0.025%, Ca: 0.001-0.003%, P≤0.010%, S≤0.005%; the remainder being Fe. The chain tooth preparation method is as follows: (1) Smelting and casting; (2) Forging: The steel ingot is heated in stages. The first stage is heated from room temperature to 650℃ at a heating rate of 100℃ / h; the second stage is heated to 1200℃ at a heating rate of 150℃ / h; the third stage is held at 1200-1250℃; isothermal die forging is performed using a die preheated to 950-1000℃, with an initial forging temperature of 1150-1180℃ and a final forging temperature of 950-980℃, and a deformation rate of 0.1-0.5S. -1 Total forging ratio ≥ 8; (3) Quenching: Transfer to the quenching tank for quenching within 15s after final forging. The cooling rate is 80-100℃ / s, and the quenching endpoint temperature is ≤50℃. (4) High-temperature tempering: Temper at 650-680℃ for 10-12 hours, then furnace cool to 300℃ and air cool; (5) Two-phase region quenching: Heat in an atmosphere furnace to the two-phase region of 790-810℃ above Ac1 and below Ac3, hold for 3-4 hours, and then oil quench to room temperature; (6) Final tempering: Temper at 200-240℃ for 8-10 hours, then air cool.

2. The heavy-duty mining sprocket according to claim 1, characterized in that, The smelting process in step (1) of the chain tooth preparation method includes, in sequence, electric arc furnace melting, LF furnace refining, VD vacuum treatment, and calcium treatment. The ultimate vacuum degree of the VD vacuum treatment is ≤70Pa and the time is ≥15 minutes. In the calcium treatment step, 1.2-1.5kg / t of Ca-Si wire is fed in. The casting process uses argon protection to cast into steel ingots at a casting temperature of 1500-1550℃, followed by slow cooling after casting.

3. A heavy-duty mining sprocket according to claim 1, characterized in that, After final tempering, the chain teeth are subjected to local heat treatment, with the root of the chain teeth being locally heated at a temperature of 650-700℃ for 3-5 minutes.

4. A heavy-duty mining sprocket according to claim 1, characterized in that, The welding surface of the chain teeth is pretreated. The pretreatment steps include: machining the welding surface to make its roughness Ra≤3.2 micrometers, then cleaning with acetone and drying at 120℃ for 2 hours. A Ni layer was deposited by magnetron sputtering on the pretreated chain tooth welding surface, and the vacuum was reduced to ≤5*10⁻⁶. -3 Pa, high-purity argon gas is introduced to the working pressure of 0.5-1.0 Pa; deposition is carried out using a Ni target under the conditions of DC power of 300-500W, workpiece bias voltage of -50 to -100V, and uniform workpiece rotation, wherein the deposition temperature is 150-200℃, the deposition rate is 0.5-1.0 μm / h, the film thickness is 5-10 μm, and then vacuum annealing is performed.

5. A heavy-duty mining sprocket according to claim 4, characterized in that, The purity of the Ni target is ≥99.99%; The specific steps of the vacuum annealing post-treatment are as follows: After deposition, the workpiece is annealed in a vacuum furnace, heated to 290-310℃ at a heating rate of ≤100℃ / h, held for 2 hours, and the vacuum degree is maintained at 1*10 during the process. -2 Pa, after the heat preservation is completed, it is cooled to below 100°C in the furnace and then removed from the furnace.

6. A heavy-duty mining sprocket, characterized in that, The sprocket comprises chain teeth and bushings, which are welded together to form a heavy-duty mining sprocket. By weight percentage, the bushing material comprises: C: 0.38-0.42%, Si: 0.20-0.35%, Mn: 0.70-0.90%, Cr: 0.90-1.20%, Ni: 0.10-0.30%, Mo: 0.30-0.40%, B: 0.001-0.003%, Ti: 0.01-0.02%, Al: 0.015-0.025%, P≤0.010%, S≤0.005%, with the remainder being Fe. The bushing is prepared as follows: (1) Smelting and casting; (2) Forging: The steel ingot is held at 1180-1220℃ for 5-8 hours; the initial forging temperature is ≥1050℃, the final forging temperature is ≥800℃, the total forging ratio is ≥7, and the forging is air-cooled or sand-cooled. (3) Normalizing treatment: The temperature is 870-880℃, the time is 7-9h, and after exiting the furnace, air cooling or mist cooling is adopted, the cooling rate is 5-10℃ / s, and the final cooling temperature is 50-100℃. (4) High-temperature tempering: The tempering temperature is 650℃, the holding time is 12-15h, and the furnace is cooled to 400℃ and then air-cooled. (5) Quenching treatment: Quenching temperature is 850-860℃, holding time is 5-7h, cooling rate is 30-50℃ / s, and final cooling temperature is ≤50℃. (6) Final tempering: Temper at 560-610℃ for 10-12 hours, then air cool.

7. A heavy-duty mining sprocket according to claim 6, characterized in that, The smelting process in step (1) of the preparation method of the bushing includes electric arc furnace melting, LF furnace refining, and VD vacuum treatment, wherein the vacuum degree of the VD vacuum treatment is ≤100Pa; the casting process adopts argon protection casting, the casting temperature is 1500-1550℃, and slow cooling after casting.

8. A heavy-duty mining sprocket according to claim 6, characterized in that, After final tempering, the surface of the bushing is locally heated to 900-980℃, and then the heated area is immediately spray-cooled at a rate of not less than 50℃ / s, with a phase transformation hardening layer depth of 1.0-3.0mm. Then, low-temperature tempering is performed, in which the quenched area is heated to 180-250℃ using a heating device, held at that temperature for 2-4 hours, and then naturally cooled to room temperature.

9. A method for deep seam welding of a wheel disc, characterized in that, The deep seam welding method for the wheel disc is used to prepare the heavy-duty mining sprocket according to any one of claims 1-8, and the steps are as follows: (1) Preheating: Place the assembled chain teeth and bushings into a heating furnace for preheating at a temperature of 250-350℃ and hold for 2-4 hours; use mixed gas shielded welding for deep seam welding. The deep seam welding process is as follows: (2) Root pass welding: Solid wire is used, the welding current is 170-190A, the voltage is 20-23V, and a root pass with a thickness of 3-4mm is formed; (3) Filling welding: Gas shielded welding with flux-cored wire or double-wire submerged arc welding is used for filling and cover welding. The welding current is 210-230A, the voltage is 25-27V, and the thickness of each layer is 4-5mm. (4) Post-weld heat treatment: The welded sprocket is heat treated at a rate of 60-90℃ / h, and the temperature is raised to 200-250℃. After holding at the temperature for 5-8 hours, it is allowed to cool naturally.

10. A method for deep seam welding of a wheel disc according to claim 9, characterized in that, Step (1) Preheating adopts a stepped heating method. The initial heating rate is 50-80℃ / h. When the temperature reaches 100-120℃, it is held for 0.5-1 hour. Then, the temperature is increased to the final preheating temperature at a rate of 30-50℃ / h. The shielding gas for mixed gas shielded welding is a mixture of argon and carbon dioxide, with argon accounting for 75-85% of the volume.

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