High-strength wind driven generator rotating shaft welding method

Abstract

The invention discloses a high-strength wind driven generator rotating shaft welding method in the field of wind power generation equipment, which comprises the following steps: carrying out mechanical polishing and acetone ultrasonic cleaning on a V-shaped groove of a to-be-welded rotating shaft base material to ensure the surface cleanliness; modified material powder layers are pre-arranged on the two sides of the groove through the laser cladding technology, and the pre-arranged powder layers are metallurgically bonded with the base metal; and the modified material is used as a filling material for laser-electric arc hybrid welding (parameters such as laser power, electric arc current, voltage, welding speed, preheating and interlayer temperature are controlled). And after welding, asbestos is adopted for wrapping and slow cooling, and then stress relief annealing (heating along with a furnace, and cooling speed control) and surface polishing treatment are carried out. The modified material is prepared by smelting metal raw materials with specific components in a vacuum induction furnace (adding titanium carbide and rare earth oxide), solidifying the metal raw materials in a water-cooled copper crucible, linearly cutting the metal raw materials into blocks, and ball-milling the blocks with an alcohol medium, so that the strength and the fatigue resistance of a welded joint can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation equipment, and in particular to a high-strength wind generator shaft welding method. Background Art

[0002] As a core component of the current clean energy sector, wind turbines rely on their core shaft components, which play a crucial role in transmitting torque and supporting the stable operation of the rotor system. Because wind turbines are exposed to complex operating conditions for long periods of time, the shaft must simultaneously withstand cyclically changing load stresses, alternating loads caused by variable speed operation, and the vibration, shock, and potential corrosion in wind farm environments. Therefore, the quality of the welding directly determines the unit's operational reliability and service life. If welded joints exhibit insufficient strength, decreased toughness, or fatigue failure, not only can serious failures such as shaft breakage occur, but they can also cause the entire unit to shut down, resulting in significant economic losses and safety hazards.

[0003] Traditional welding processes (such as submerged arc welding and gas shielded welding) are widely used in the manufacture of high-strength steel shafts, but their inherent defects remain difficult to overcome. On the one hand, high-strength steel has a high tendency to harden. The high heat input during traditional welding (for example, the heat input during submerged arc welding typically exceeds 3 kJ / mm) leads to significant grain coarsening in the heat-affected zone (HAZ), weakening the grain boundary bonding, and a simultaneous decrease in material strength and toughness. The actual load-bearing capacity of the joint is often only 60%-80% of that of the parent material. On the other hand, the significant difference in composition between traditional filler materials (such as ordinary carbon steel welding wire) and the high-strength steel parent material makes it easy to form brittle phases (such as martensite and carbides) during welding, resulting in insufficient joint toughness reserves. Microcracks are easily generated and propagated under alternating loads, and fatigue resistance is reduced by more than 50% compared to the parent material. Furthermore, high heat input exacerbates welding deformation, increasing the complexity and cost of subsequent correction steps. While traditional process adjustments (such as reducing heat input) can partially suppress grain coarsening, they can easily lead to defects such as lack of fusion and incomplete penetration, further threatening joint quality.

[0004] In response to the above problems, the industry has tried to improve joint performance by optimizing welding parameters (such as using pulse current and narrow gap welding) or replacing high-performance filler materials (such as high-strength steel welding wire), but the effect is limited. For example, although the high-strength steel welding wire is close to the base material in composition, it can reduce the formation of brittle phases, but the strength improvement of its deposited metal is difficult to match the high toughness requirements of the base material; and although reducing heat input can refine the grains, it is limited by the welding process window of high-strength steel, which can easily lead to an increase in welding defect rates. More importantly, traditional processes cannot simultaneously solve the problem of synergistic improvement of joint strength, toughness and fatigue resistance, and it is difficult to meet the service requirements of wind turbine shafts under long-term high stress and variable working conditions. Therefore, the development of a new welding method that can both suppress the degradation of the heat-affected zone and optimize the composition and organization of the joint has become an urgent need to improve the reliability of wind turbine shafts. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-strength wind turbine shaft welding method, which solves the problems of low joint strength, poor toughness, weak fatigue resistance, grain coarsening in the heat-affected zone, and brittle phase formation due to mismatch between filler material and base material in traditional high-strength steel shaft welding.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] A high-strength wind turbine shaft welding method comprises the following steps:

[0008] S1, mechanically grind the welding groove of the base material of the rotating shaft to remove surface oxide scale, oil and moisture, and then use acetone ultrasonic cleaning to ensure surface cleanliness;

[0009] S2, using laser cladding technology to pre-deposit a layer of modified material powder on both sides of the groove, with a thickness of 0.8-1.2mm. The pre-deposition method is synchronous powder feeding. After pre-deposition, the powder layer and the base material are metallurgically bonded;

[0010] S3 adopts laser-arc hybrid welding process, with modified material composite powder as filling material, preheating temperature of 145-155℃, and interlayer temperature controlled at 180-200℃.

[0011] According to a preferred embodiment of the present invention, the acetone is purchased from Sinopharm Chemical Reagent Co., Ltd.

[0012] According to a preferred embodiment of the present invention, in step S1, the base material of the welding shaft is 42CrMo steel with a size of Φ300-500mm; the welding groove is V-shaped, the groove angle is 60°, and the blunt edge is 1.5-2.5mm; the sandpaper mesh number of the mechanical grinding is 120-400#; and the time of acetone ultrasonic cleaning is 8-12min.

[0013] In step S1 of the present invention, the V-shaped groove of the base material of the rotating shaft to be welded (42CrMo steel) is mechanically polished (120-400# sandpaper) to remove surface oxide scale, oil and moisture, and the oxide layer structure is destroyed by mechanical force and pollutants are cleaned. At the same time, the surface roughness of the groove is adjusted to Ra0.8-0.9μm; then, acetone ultrasonic cleaning (8-12min) is performed by utilizing the strong solubility of acetone and the ultrasonic cavitation effect to thoroughly remove residual oil and moisture, ensuring that the groove surface is free of impurities and the cleanliness meets the standard, providing a uniform and dense base for laser cladding.

[0014] According to a preferred embodiment of the present invention, the 42CrMo steel is purchased from Baoshan Iron & Steel Co., Ltd.

[0015] The 42CrMo steel (C content 0.38%-0.45%, Cr content 0.90%-1.20%, Mo content 0.15%-0.30%) in the present invention has high strength (tensile strength ≥980MPa), good toughness and weldability, and is suitable for the manufacture of high-load components such as wind turbine shafts.

[0016] According to a preferred embodiment of the present invention, in step S2, the carrier gas for synchronous powder feeding is argon, the flow rate is 7-9 L / min, the laser power is 2.5-3 kW, the scanning speed is 4-6 mm / s, and the spot diameter is 3-4 mm.

[0017] In step S2 of the present invention, in the laser cladding step, the modified material powder (pure iron-chromium iron-nickel plate-molybdenum iron-vanadium iron-titanium carbide-cerium oxide composite powder, particle size 50-150 μm) is evenly transported to both sides of the groove by synchronous powder feeding (argon flow rate 7-9 L / min), and the laser (power 2.5-3 kW, scanning speed 4-6 mm / s, spot diameter 3-4 mm) energy is absorbed by the powder and melted to form a molten pool with the surface of the base material. By controlling the laser energy density (about 65-95 J / mm 2 ) to match the depth and width of the molten pool, and finally cool and solidify to form a preset layer (thickness 0.8-1.2mm) metallurgically bonded to the base material. The reinforcing phase (TiC particles) is evenly dispersed in the molten pool, hindering dislocation movement and refining the grains.

[0018] The steps of using the laser cladding technology in the present invention are as follows: first, the V-shaped groove (angle 60°, blunt edge 1.5-2.5mm) of the base material of the rotating shaft to be welded is pretreated, and the surface oxide scale and slight rust are removed by mechanical grinding with 120#→400# sandpaper, and then the oil and moisture are removed by ultrasonic cleaning with acetone (ultrasonic frequency 40kHz, power 400-600W, cleaning time 8-12 minutes) to ensure that the surface roughness of the groove is ≤Ra0.9μm; then the prepared modified material powder ( Pure iron, ferrochrome, nickel plate, ferromolybdenum, ferrovanadium, titanium carbide (particle size ≤ 5μm), and cerium oxide (particle size ≤ 3μm) are mixed in a specific mass ratio, smelted in a vacuum induction furnace, solidified in a water-cooled copper crucible, wire-cut and ball-milled to obtain a particle size of 50-150μm. The powder is then loaded into the coaxial powder feeder hopper of the laser cladding equipment and connected to high-purity argon (purity ≥ 99.99%, flow rate 7-9L / min) as a carrier gas. A fiber laser (such as IPGYLS-2000, wavelength 1064nm, beam quality M 2 =1.2) and coaxial powder feeder parameters, set the laser power to 2.5-4kW, scanning speed to 4-6mm / s, spot diameter to 3-4mm, and control the laser energy density (about 65-95J / mm 2) to make the preset layer thickness reach 0.8-1.2mm; start the laser and powder feeder, and feed powder symmetrically and synchronously along both sides of the groove. The laser beam is incident perpendicular to the groove surface or at a small angle (≤15°), and the scanning path covers 1-2mm on both sides of the groove. During the cladding process, the molten pool state (such as spot shape, molten pool fluidity) is monitored in real time, and the scanning speed or power is adjusted to keep the molten pool stable to avoid pores or cracks; after the cladding is completed, it is naturally cooled to room temperature, and the surface of the preset layer is observed by the naked eye or a magnifying glass. If necessary, penetration testing (PT) is used to verify the bonding quality, and the thickness of the preset layer is measured with a micrometer or laser thickness gauge (to ensure that it meets the 0.8-1.2mm requirement). Finally, the metallurgical bonding of the modified material and the base material is achieved (bonding strength ≥300MPa), providing a uniform and dense filling foundation for subsequent laser-arc hybrid welding.

[0019] The synchronous powder feeding step in the present invention is the core link of the laser cladding technology to achieve uniform pre-setting of modified material powder. The specific description is as follows: First, the prepared modified material powder (made of pure iron, ferrochrome, nickel plate, ferromolybdenum, ferrovanadium, titanium carbide (particle size ≤ 5μm), cerium oxide (particle size ≤ 3μm) mixed in a specific mass ratio, smelted in a vacuum induction furnace, solidified in a water-cooled copper crucible, wire cut and ball milled, with a particle size of 50-150μm) is loaded into the coaxial powder feeder hopper of the laser cladding equipment to ensure good powder fluidity (prevent agglomeration by vibration or stirring); synchronously configure high-purity argon (purity ≥ 99.99%) as a carrier gas, connected to the powder feeder gas inlet, used to transport powder and isolate the air to avoid oxidation. Laser (such as a fiber laser, wavelength 1064nm, beam quality M 2 =1.2) and the coaxial powder feeder are synchronized through the control system: the carrier gas flow rate (7-9L / min) is set to stabilize the powder flow rate, the laser power (2.5-4kW) is matched with the scanning speed (4-6mm / s) to control the laser energy density (about 65-95J / mm 2 ), so that the laser beam and powder flow act synchronously on the groove surface in space to avoid powder accumulation or missing. After starting the laser and powder feeder, the laser beam is incident symmetrically along both sides of the groove (perpendicular to the surface or at a small angle ≤15°), and the synchronous powder feeder outputs powder at a set flow rate to cover the laser scanning area. During the cladding process, the molten pool state (such as spot shape, molten pool fluidity) and powder distribution are monitored in real time (through visual sensors or manual observation). If accumulation occurs or the molten pool is unstable, the scanning speed or laser power is dynamically adjusted to ensure that the powder is evenly clad to form a continuous and dense pre-layer. After the cladding is completed, it is naturally cooled to room temperature. The surface of the pre-layer is observed with the naked eye or a magnifying glass to check for cracks, pores or powder missing. If necessary, penetration testing (PT) is used to verify the bonding quality to ensure that the thickness of the pre-layer (0.8-1.2mm) is uniform and well bonded to the base material (bonding strength ≥300MPa), providing a uniform and dense filling foundation for subsequent laser-arc hybrid welding.

[0020] According to a preferred embodiment of the present invention, in step S3, the diameter of the welding wire in the laser-arc hybrid welding process is 1.1-1.3 mm, the laser power is 3.5-4 kW, the arc current is 170-190 A, the arc voltage is 22-25 V, and the welding speed is 1.8-2 m / min; the preheating method adopts a far-infrared heating belt for uniform heating, and the holding time is 30-40 min.

[0021] In step S3 of the present invention, during laser-arc hybrid welding, the far-infrared heating belt (power 500W / m) preheats the 50mm range on both sides of the groove to 145-155°C and keeps it warm for 30-40 minutes to reduce the thermal stress of the base material; the laser (power 3.5-4kW, spot diameter 3-4mm) and the arc (welding wire diameter 1.1-1.3mm, current 170-190A, voltage 22-25V, speed 1.8-2m / min) work together, the laser forms a deep melting hole to concentrate energy, the arc supplements the melting of the welding wire and the base material, the molten pool grows evenly under the action of dual heat sources, and the interlayer temperature is controlled at 180-200°C to suppress the coarsening of grains in the heat-affected zone, ultimately forming a high-strength, low-brittleness weld joint.

[0022] The laser-arc hybrid welding process in this invention is a method for achieving efficient and high-quality connection of high-strength steel shafts through the synergistic effect of two heat sources, laser and arc. Its core lies in the complementary advantages of the high energy density of laser and the penetration depth of arc, combined with modified material filling, to solve the problems of grain coarsening in the heat-affected zone, low joint strength and weak fatigue resistance in traditional single heat source welding. The process uses a fiber laser (wavelength 1064nm, beam quality M 2=1.2) and an inverter arc welder (such as the Lincoln PowerWave series) as the core equipment, with a far-infrared heating belt (power 500W / m) for preheating, argon (purity ≥99.99%) as the shielding gas (used for both laser cladding and arc welding), the filler material is a modified material powder layer pre-placed on both sides of the groove (produced by laser cladding process, thickness 0.8-1.2mm), and the welding wire is a homemade welding wire (diameter 1.1-1.3mm) with the same composition as the modified material. In the specific implementation, firstly, the far-infrared heating belt is used to evenly heat the 50mm range on both sides of the groove to 145-155℃ and keep it warm for 30-40 minutes to ensure that the temperature of the base material is uniform to reduce the welding thermal stress; then the laser and arc welding machine are started, the laser power is set to 3.5-4kW (adjusted according to the thickness of the joint), the spot diameter is 3-4mm, and the scanning speed is 1.8-2m / min, so that the laser energy is concentrated on the root of the groove to form a deep melting hole; at the same time, the arc welding machine is set to 170-190A current, 22-25V voltage, 1.8 The welding speed is synchronized with the laser scanning speed, and the arc heat is used to evenly replenish the laser molten pool to avoid local overheating. During the welding process, the interlayer temperature is monitored in real time by an infrared temperature measuring gun and controlled at 180-200℃ (deviation ≤±10℃) to ensure stable heat input. After interlayer cooling, the above steps are repeated until the weld is completed. Finally, residual stress is released through post-weld slow cooling (wrapped with asbestos felt for 4-4.5 hours) and stress relief annealing (550-600℃×2-3 hours, cooling rate ≤50℃ / h). This process achieves metallurgical bonding of the modified material and the base material under low heat input conditions through the coordinated heating of the laser and the arc, effectively suppressing grain coarsening in the heat-affected zone, improving the strength, toughness and fatigue resistance of the joint, and meeting the high load and long service life requirements of the wind turbine shaft.

[0023] According to a preferred embodiment of the present invention, the high-strength wind turbine shaft welding method further includes: after welding is completed, it is wrapped with asbestos felt and slowly cooled to room temperature, the cooling time is ≥4h, and then stress relief annealing is performed at 550-600℃ for 2-3h; the stress relief annealing method is to heat up with the furnace, and the cooling rate is ≤50℃ / h, and finally the weld surface is polished, and the weld surface Ra is ≤0.8μm.

[0024] After welding, the present invention adopts asbestos felt wrapping and slow cooling for ≥4h (cooling rate ≤50℃ / h) to reduce residual stress, and 550-600℃ stress relief annealing (2-3h, with furnace temperature rising) to further release internal stress and avoid crack initiation; the weld surface is polished to Ra≤0.8μm to reduce stress concentration.

[0025] According to a preferred embodiment of the present invention, the steps of preparing the modified material include:

[0026] A1, weigh pure iron, ferrochrome, nickel plate, ferromolybdenum, and ferrovanadium according to the above proportions and add them into a vacuum induction furnace, evacuate the furnace, and heat to 1600-1650℃ for melting;

[0027] A2, after the composition is uniform, add titanium carbide powder and cerium oxide, and continue smelting until the reinforcement phase is evenly dispersed in the melt;

[0028] A3, the melt is then poured into a water-cooled copper crucible to rapidly solidify into an ingot, which is then processed into blocks by wire cutting and placed in a ball mill;

[0029] A4, use alcohol as the medium, grind with carbide grinding balls, dry and then sieve.

[0030] In the preparation of the modified material of the present invention, a vacuum induction furnace (evacuated to 10 -3 Pa, smelting for 10-20 minutes) to achieve the smelting of pure iron, ferrochrome and other metals to avoid oxidation; after adding titanium carbide (particle size ≤ 5μm) and cerium oxide (particle size ≤ 3μm), continue smelting for 5-10 minutes to make the reinforcement phase evenly dispersed in the melt; water-cooled copper crucible rapid solidification (thickness 8-10mm) to form a fine-grained ingot, wire-cut into 20mm×20mm×5mm blocks and then ball milled (ball-to-material ratio 9-10:1, 3-4h), alcohol medium grinding and refining the powder to 50-150μm, after passing through a 300-mesh sieve, a modified powder with good fluidity is obtained, providing a basis for uniform coverage for laser cladding.

[0031] According to a preferred embodiment of the present invention, the pure iron is purchased from Baoshan Iron & Steel Co., Ltd.

[0032] According to a preferred embodiment of the present invention, the ferrochrome is purchased from CITIC Pacific Special Steel Group Co., Ltd.

[0033] According to a preferred embodiment of the present invention, the nickel plate is purchased from Jinchuan Group Co., Ltd.

[0034] According to a preferred embodiment of the present invention, the ferromolybdenum is purchased from Luoyang Luanchuan Molybdenum Co., Ltd.

[0035] According to a preferred embodiment of the present invention, the ferrovanadium is purchased from Panzhihua Iron and Steel Co., Ltd. of Panzhihua Iron and Steel Group.

[0036] According to a preferred embodiment of the present invention, the titanium carbide powder is purchased from Henan Huanghe Cyclone Co., Ltd.

[0037] According to a preferred embodiment of the present invention, the cerium oxide is purchased from China North Rare Earth (Group) High-Tech Co., Ltd.

[0038] According to a preferred embodiment of the present invention, the ball mill is purchased from Zhengzhou Abrasives and Grinding Tools Research Institute Co., Ltd.

[0039] According to a preferred embodiment of the present invention, in step A1, the vacuum is pumped to 10 -3 Pa, the smelting time is 10-20min.

[0040] According to a preferred embodiment of the present invention, in step A1-2, the particle size of the titanium carbide powder is ≤5 μm; the smelting time is continued for 5-10 min; the mass percentages of the pure iron, ferrochrome, nickel plate, ferromolybdenum, ferrovanadium, titanium carbide and cerium oxide are: 1: (17-18): (6-7): (4-4.5): (2-3): (0.8-0.9): (0.5-0.6).

[0041] According to a preferred embodiment of the present invention, in step A3, the thickness of the ingot is 8-10 mm; and the size of the block is 20 mm×20 mm×5 mm.

[0042] According to a preferred embodiment of the present invention, in step A4, the ball-to-material ratio of the cemented carbide grinding balls is (9-10):1; the grinding time is 3-4 hours; and after drying, the mixture is passed through a 300-mesh sieve.

[0043] The beneficial effects of the present invention are:

[0044] This invention significantly improves the overall performance of wind turbine shaft welded joints through the coordinated optimization of the modified material's composition and welding process. The composite strengthening mechanism of rare earth elements and carbides in the modified material forms a metallurgical bond with the base material during the laser cladding pre-setting process, effectively suppressing the grain coarsening problem in the heat-affected zone (HAZ) during traditional welding and significantly improving the joint strength, approaching or even reaching the level of the base material. Furthermore, the carbide particles dispersed throughout the cladding layer hinder dislocation movement, enhancing the joint's toughness and improving its fatigue resistance, significantly extending the joint's service life under long-term alternating loads.

[0045] The meticulous design of the process steps ensures the stability and quality controllability of the welding process. Mechanical grinding combined with acetone ultrasonic cleaning thoroughly removes scale, oil, and moisture from the groove surface, providing a clean and uniform interface foundation for the subsequent pre-setting of modified materials. Laser cladding synchronous powder feeding technology achieves uniform pre-setting of the modified material powder layer by precisely controlling the carrier gas flow, laser power, and scanning speed, ensuring a dense bond between the pre-set layer and the base material. The laser-arc hybrid welding process reduces welding heat input, minimizes welding deformation and cracking tendencies, and makes the welding process more stable and the joint quality more consistent.

[0046] The application of this technology provides key support for the manufacture of high-reliability wind turbine shafts. The safety hazards associated with traditional welded joints due to insufficient strength, poor toughness, and weak fatigue resistance are effectively addressed, significantly improving the shaft's overall load-bearing capacity and service life. Furthermore, the process's broad adaptability to parent materials (such as high-strength steels) and controllable welding process reduce scrap rates and rework costs during production, driving the development of wind turbines toward higher power, longer life, and lower maintenance, contributing to the efficient and stable operation of clean energy equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is the welding flow chart for the shaft of a wind turbine. DETAILED DESCRIPTION

[0048] The present application is described in further detail below in conjunction with the accompanying drawings. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0049] 1. Implementation

[0050] Example 1

[0051] The material of the shaft to be welded is 42CrMo steel with a size of Φ400mm×1500mm (diameter×length). The welding groove is V-shaped (angle 60°, blunt edge 2mm), and the roughness of the groove surface after milling is Ra3.2μm. First, the groove is mechanically polished: 120# sandpaper (particle size of about 100μm) is used to perform unidirectional polishing along the groove to remove surface oxide scale (thickness of about 50μm) and slight rust. After polishing, the surface roughness is improved to Ra1.6μm; 400# sandpaper (particle size of about 40μm) is replaced and unidirectional polishing is continued to eliminate the deep scratches left by 120# sandpaper. After polishing, the surface roughness is reduced to Ra0.8μm; then, acetone ultrasonic cleaning (ultrasonic frequency 40kHz, power 500W, cleaning tank size 600mm×400mm×300mm) is used for 10 minutes, focusing on removing oil (such as cutting fluid residue) and moisture. After cleaning, the surface is blown dry with compressed air (pressure 0.3MPa) to ensure that there is no liquid residue.

[0052] Laser cladding technology is used to pre-deposit a layer of modified material powder on both sides of the groove. The synchronous powder feeding equipment is a certain brand of fiber laser (model: IPG YLS-2000, wavelength 1064nm, beam quality M 2=1.2) with a coaxial powder feeder (model: SPT-200, carrier gas: 99.99% high-purity argon, flow rate: 8 L / min). The laser cladding parameters were set as follows: laser power 2.8 kW (power fluctuation ±0.1 kW), scanning speed 5 mm / s (speed control accuracy ±0.05 mm / s), spot diameter 3 mm (calibrated by a laser rangefinder), preset thickness 1.0 mm (controlled by laser energy density, energy density approximately 80 J / mm 2 The modified material is prepared from the following raw materials in g: 100 g of pure iron (purity 99.9%, particle size ≤ 2 mm), 175 g of ferrochrome (Cr content ≥ 99%, particle size ≤ 1 mm), 65 g of nickel plate (Ni content ≥ 99.6%, thickness 1 mm), 42 g of ferromolybdenum (Mo content ≥ 99.5%, particle size ≤ 1 mm), 25 g of ferrovanadium (V content ≥ 99.5%, particle size ≤ 1 mm), 8.5 g of titanium carbide (TiC content ≥ 99.9%, particle size ≤ 5 μm), and 5.5 g of cerium oxide (CeO2 content ≥ 99.9%, particle size ≤ 3 μm). The preparation process is as follows: pure iron, ferrochrome, nickel plate, ferromolybdenum, and ferrovanadium are added into a vacuum induction furnace (model: VSG-1000, vacuum degree ≤ 10 -3 Pa), firstly heated to 1620°C at 100°C / min and kept at this temperature for 15 minutes until the composition was uniform (the deviation of each element was ≤±0.5% by real-time detection by spectrometer), then titanium carbide and cerium oxide were added and heated to 1640°C at 50°C / min and kept at this temperature for 7 minutes to make the reinforcing phase uniformly dispersed in the melt (the dispersion of TiC particles was ≥90% by scanning electron microscopy); then the melt was poured into a water-cooled copper crucible (size 500mm×300mm×100mm) at a cooling rate of 100°C / s and rapidly solidified into an 8mm thick ingot (solidification time was about 2 minutes), and then cut by wire cutting (model: DMG MORI) LT505, cutting speed 5 mm / min, voltage 100 V, current 5 A) into 20 mm × 20 mm × 5 mm blocks; the blocks were placed in a planetary ball mill (model: QM-3SP4, ball-to-material ratio 9.5:1, a mixture of carbide grinding balls with diameters of 5 mm and 10 mm) using alcohol (purity ≥ 99.7%) as the medium, at a speed of 200 rpm for 3.5 hours. After drying, the modified material powder was passed through a 300-mesh sieve (sieve size 0.053 mm) to obtain a particle size of 50-150 μm.

[0053] Subsequently, a laser-arc hybrid welding process was adopted, with the modified material as the filler material, the welding wire was a homemade modified welding wire (diameter 1.2 mm, composition consistent with the modified material powder), the laser was the above-mentioned IPG YLS-2000 (wavelength 1064 nm, power 3.8 kW), the arc welding machine was a certain type of inverter welding machine (model: Lincoln PowerWave 455, current 180 A, voltage 23 V), and preheating was performed using a far-infrared heating belt (power 500 W / m, wrapped around a 50 mm range on both sides of the groove), uniformly heated to 150°C (holding temperature for 35 minutes, furnace temperature uniformity ≤±5°C), and the interlayer temperature was controlled at 190°C (measured with an infrared temperature gun before each layer of welding, deviation ≤±10°C). The welding speed was 1.9 m / min (speed control accuracy ±0.05 m / min), left-hand welding was used, the weld width was 3.2 mm, and the excess height was 0.5 mm. After welding is completed, it is immediately wrapped with asbestos felt (thickness 50mm) and slowly cooled to room temperature (cooling time 4.5 hours, ambient temperature 25℃), and then subjected to 580℃×2.5 hours of stress relief annealing (heating with the furnace, heating rate 100℃ / h, furnace temperature uniformity ≤±10℃, cooling rate ≤50℃ / h), and finally polished with a surface grinder (model: M7130, grinding wheel grit 80#) to Ra≤0.8μm (surface roughness tester detection, Ra=0.6μm).

[0054] Example 2

[0055] The preparation method is the same as that of Example 1, except that the base material of the rotating shaft to be welded is made of 42CrMo steel and has a size of Φ350mm×1200mm. The groove is V-shaped (angle 60°, blunt edge 1.5mm), and the roughness of the groove surface after turning is Ra3.5μm. Mechanical polishing steps: 120# sandpaper is used to polish and remove the oxide scale (thickness is about 60μm), 400# sandpaper is used to finely grind until the surface is smooth, acetone ultrasonic cleaning is performed for 8 minutes (ultrasonic frequency 40kHz, power 400W), and the surface roughness is Ra0.7μm after drying with compressed air. Laser cladding pre-modified material: argon flow rate 7L / min (purity 99.99%), laser power 2.5kW (fluctuation ±0.08kW), scanning speed 4mm / s (accuracy ±0.04mm / s), spot diameter 3mm, pre-set thickness 0.8mm (energy density about 65J / mm 2 ). Modified material raw material mass g: pure iron 100g, chromium iron 170g, nickel plate 60g, molybdenum iron 40g, vanadium iron 20g, titanium carbide (particle size ≤ 5μm) 8g, cerium oxide (particle size ≤ 3μm) 5g; Preparation process: vacuum induction furnace (VSG-800) evacuated to 10 -3Pa, smelting at 1610 ° C for 12 minutes (the deviation after composition homogenization is ≤ ± 0.4%), adding titanium carbide and cerium oxide and continuing to smelt for 6 minutes (1630 ° C), solidifying in a water-cooled copper crucible into a 9 mm thick ingot, wire cutting (DMG MORI LT303, cutting speed 4 mm / min) into 20 mm × 20 mm × 5 mm blocks, planetary ball mill (QM-3SP2, ball-to-material ratio 9:1) for 3 hours (speed 180 rpm), and after drying, passing through a 300 mesh sieve to obtain a modified material with a particle size of 60-140 μm. Laser-arc hybrid welding parameters: wire diameter 1.1 mm, laser power 3.5 kW, arc current 170 A, arc voltage 22 V, welding speed 1.8 m / min, preheating temperature 145 ° C (holding for 30 minutes), interpass temperature 180 ° C, slow cooling for 4 hours after welding (asbestos felt thickness 40 mm), 550 ° C × 2 hours stress relief annealing (cooling rate ≤ 50 ° C / h), weld surface polishing to Ra ≤ 0.8 μm (Ra = 0.7 μm).

[0056] Example 3

[0057] The preparation method is the same as that of Example 1, except that the base material of the rotating shaft to be welded is made of 42CrMo steel and has a size of Φ500mm×1800mm. The groove is V-shaped (angle 60°, blunt edge 2.5mm), and the roughness of the groove surface after grinding is Ra3.8μm. Mechanical polishing steps: 120# sandpaper is used to polish and remove the oxide scale (thickness is about 70μm), 400# sandpaper is used for fine grinding, and then ultrasonic cleaning is performed in acetone for 12 minutes (ultrasonic frequency 40kHz, power 600W), and the surface roughness is Ra0.9μm after drying with compressed air. Laser cladding pre-modified material: argon flow rate 9L / min (purity 99.99%), laser power 3kW (fluctuation ±0.12kW), scanning speed 6mm / s (accuracy ±0.06mm / s), spot diameter 4mm, pre-set thickness 1.2mm (energy density about 95J / mm 2 ). Modified material raw material mass g: pure iron 100g, chromium iron 180g, nickel plate 70g, molybdenum iron 45g, vanadium iron 30g, titanium carbide (particle size ≤ 5μm) 9g, cerium oxide (particle size ≤ 3μm) 6g; Preparation process: vacuum induction furnace (VSG-1200) evacuated to 10 -3Pa, smelting at 1640 ° C for 18 minutes (the deviation after composition homogenization is ≤ ± 0.6%), adding titanium carbide and cerium oxide and continuing to smelt for 8 minutes (1660 ° C), solidifying in a water-cooled copper crucible into a 10 mm thick ingot, wire cutting (DMG MORI LT605, cutting speed 6 mm / min) into 20 mm × 20 mm × 5 mm blocks, and grinding in a planetary ball mill (QM-3SP6, ball-to-material ratio 10:1) for 4 hours (speed 220 rpm), and after drying, passing through a 300 mesh sieve to obtain a modified material with a particle size of 70-160 μm. Laser-arc hybrid welding parameters: wire diameter 1.3 mm, laser power 4 kW, arc current 190 A, arc voltage 25 V, welding speed 2 m / min, preheating temperature 155 °C (holding for 40 minutes), interpass temperature 200 °C, slow cooling for 4 hours after welding (asbestos felt thickness 60 mm), stress relief annealing at 600 °C × 3 hours (cooling rate ≤ 50 °C / h), and weld surface polishing to Ra ≤ 0.8 μm (Ra = 0.8 μm).

[0058] Implementation 4

[0059] The preparation method is the same as that of Example 1, except that a 42CrMo steel shaft base material of Φ450mm×1600mm is used, with a V-shaped groove (angle 60°, blunt edge 2.2mm), and the roughness of the groove surface after milling is Ra3.6μm. Mechanical polishing: 150# sandpaper is used for coarse grinding to remove the oxide scale, 400# sandpaper is used for fine grinding to Ra0.85μm, acetone ultrasonic cleaning is performed for 9 minutes, and compressed air is blown dry. Laser cladding preset modified material: argon flow rate 8.5L / min, laser power 2.9kW, scanning speed 5.5mm / s, spot diameter 3.5mm, preset thickness 1.1mm. Modified material raw material mass g: pure iron 100g, chromium iron 178g, nickel plate 68g, molybdenum iron 44g, vanadium iron 28g, titanium carbide (≤5μm) 9.2g, cerium oxide (≤3μm) 5.8g; preparation: vacuum induction furnace (10 -3 The modified powder was prepared by melting the modified material at 1630°C for 17 minutes (for uniform composition). Titanium carbide and cerium oxide were then added and melted at 1650°C for 8 minutes (for dispersion of the reinforcement phase). The material was solidified in a water-cooled copper crucible into a 9 mm thick ingot, which was then cut into 20 mm × 20 mm × 5 mm blocks by wire cutting. The ingot was then ground for 3.8 hours using an alcohol medium (9.8:1 ball-to-powder ratio) and passed through a 300-mesh sieve to produce the modified powder. Laser-arc hybrid welding was performed using a 1.25 mm wire diameter (same composition as the modified material), a 3.9 kW laser power, an 185 A arc current, and a 24 V voltage. The welding process involved preheating to 152°C (holding for 38 minutes), an interpass temperature of 195°C, and a welding speed of 1.95 m / min. After welding, the asbestos felt was slowly cooled for 4.2 hours, followed by a stress relief annealing at 590°C for 2.8 hours (cooling rate ≤ 50°C / h). The weld was then polished to an Ra ≤ 0.8 μm.

[0060] Comparative Example 1

[0061] The preparation method is the same as that of Example 1, except that a base material of the rotating shaft to be welded is made of 42CrMo steel and has a size of Φ400 mm × 1500 mm. The groove is V-shaped (angle 60°, blunt edge 2 mm). The mechanical polishing and acetone ultrasonic cleaning steps are the same as those of Example 1. No modified material is used during welding, and ordinary carbon steel welding wire (ER70S-6, diameter 1.2 mm, composition: C ≤ 0.14%, Mn ≤ 1.2%, Si ≤ 0.8%) is used instead. The laser-arc hybrid welding parameters are: laser power 3.5 kW, arc current 180 A, arc voltage 23 V, welding speed 1.9 m / min, preheat temperature 150° C. (holding time 35 minutes), and interpass temperature 190° C.

[0062] Comparative Example 2

[0063] The preparation method was the same as in Example 1, except that a 42CrMo steel base material for the rotating shaft to be welded, measuring Φ400 mm × 1500 mm, was used. A V-shaped groove (60° angle, 2 mm blunt edge) was used. Mechanical polishing and acetone ultrasonic cleaning were performed as in Example 1. The titanium carbide was removed during the preparation of the modified material (only 100 g of pure iron, 175 g of ferrochrome, 65 g of nickel plate, 42 g of ferromolybdenum, 25 g of ferrovanadium, and 5.5 g of cerium oxide were used).

[0064] Comparative Example 3

[0065] The preparation method is the same as that of Example 1, except that a base material of the rotating shaft to be welded is made of 42CrMo steel and has a size of Φ400mm×1500mm, and the groove is V-shaped (angle 60°, blunt edge 2mm). The steps of pre-setting the modified material by laser cladding are the same as those of Example 1, but no preheating is performed during the laser-arc hybrid welding (preheating temperature 0°C), and direct welding is performed: laser power 3.8kW, arc current 180A, arc voltage 23V, welding speed 1.9m / min, interpass temperature is not controlled (natural cooling to room temperature), post-weld cooling is slow for 4 hours, stress relief annealing is performed at 580°C×2.5 hours (cooling rate ≤50°C / h), and the weld surface is polished to Ra ≤0.8μm.

[0066] 2. Performance Testing

[0067] The following method was used to test the performance of the welded joints of Examples 1-4 and Comparative Examples 1-3:

[0068] 1. Tensile strength test: According to GB / T 228.1-2021 standard, a φ10mm×50mm tensile specimen was cut from the center of the weld. An electronic universal testing machine (model: INSTRON 5967) was used to load the specimen at a rate of 1mm / min. The maximum load at fracture was recorded, and the tensile strength was calculated (σb=maximum load / cross-sectional area of ​​the specimen).

[0069] 2. Impact toughness test: According to GB / T 229-2020, V-notch specimens (2 mm in depth, 45° in angle) were cut from the heat-affected zone of the weld. The impact test was carried out using a pendulum impact tester (model: JBN-300B) at -40°C, and the impact absorbed energy (AKV) was recorded.

[0070] 3. Fatigue life test: According to GB / T 3075-2008 standard, a rotary bending fatigue testing machine (model: PLG-100D) was used to apply a symmetrical cyclic load (stress ratio R = -1) with a stress amplitude of 350 MPa to a specimen (Φ10 mm × 150 mm) with a weld surface polished to Ra ≤ 0.8 μm. The number of cycles (Nf) when the specimen broke was recorded.

[0071] 4. Microstructure observation: The weld cross-section specimens were ground and polished, and then corroded with 4% nitric acid solution. The grain size and microstructure were observed under an optical microscope (model: OLYMPUSBX53). The distribution of the reinforcement phase (TiC particles) and the dislocation density were analyzed using a scanning electron microscope (model: ZEISSGemini 300).

[0072] 5. Performance test results:

[0073] Table 1: Performance test results of various embodiments and comparative examples

[0074]

[0075]

[0076] As can be seen from Table 1, the present invention effectively solves the problems of low joint strength, poor toughness, weak fatigue resistance, grain coarsening in the heat-affected zone, and brittle phase formation due to mismatch between the filler material and the base material in conventional high-strength steel shaft welding by designing the composition of the modified material and optimizing the welding process. The specific analysis is as follows: Due to the large heat input in conventional high-strength steel shaft welding (such as heat input of submerged arc welding>3kJ / mm), the grains in the heat-affected zone (HAZ) are significantly coarsened (grain size 5-7), resulting in a joint strength of only 60%-80% of the parent material (the tensile strength of Comparative Example 1 is only 785MPa, far lower than the parent material of about 980MPa). At the same time, ordinary carbon steel welding wire (such as ER70S-6) has a large difference in composition from the parent material, and is prone to forming brittle phases such as coarse martensite during welding (coarse martensite can be seen at the grain boundaries in the microstructure of Comparative Example 1). The impact toughness is extremely low (the impact absorbed energy at -40°C is only 22J), and the large heat input exacerbates welding deformation and residual stress, resulting in a fatigue life of only about 4.5×10 6 times (Comparative Example 1).

[0077] The present invention achieves performance improvement through the following measures: optimization of modified materials: an iron-based composite material (pure iron-chromium iron-nickel plate-molybdenum iron-vanadium iron-titanium carbide-cerium oxide) containing alloying elements such as Cr, Mo, and V is used, wherein the rare earth element (cerium oxide) refines the grains, and titanium carbide (TiC) particles hinder dislocation movement, thereby improving the strength and toughness of the joint; the modified material and the base material (42CrMo) are matched in composition (the Cr, Mo, and V contents are similar) to avoid the formation of brittle phases due to composition differences (the microstructures of Examples 1-4 do not contain coarse martensite or unmelted carbide clusters). Low heat input process: laser cladding pre-modified materials (preheating 145-155°C, interlayer 180-200°C) combined with laser-arc hybrid welding (laser power 3.5-4kW, arc current 170-190A), the heat input is significantly lower than the traditional process (comparative example 1 laser power 3.5kW but no preheating control, the heat input is higher), the grains in the heat-affected zone are refined to level 9-10 (Examples 1-4), the grain boundary bonding is strong, and the joint strength is increased to 935-962MPa (close to the parent material level). Residual stress control: slow cooling after welding (wrapping with asbestos felt for 4-4.5 hours) and stress relief annealing (550-600°C×2-3 hours, cooling rate ≤50°C / h) effectively release welding stress and reduce crack tendency; the fatigue life of Examples 1-4 reaches 1.1-1.4×10 7 times (Comparative Example 1 only 4.5×10 6 times), and the anti-fatigue performance is significantly improved.

[0078] In summary, the present invention comprehensively solves the performance defects of traditional high-strength steel shaft welding through the coordinated optimization of modified materials and processes, achieves the simultaneous improvement of joint strength, toughness and fatigue resistance, uniformly refines the structure of the heat-affected zone, and achieves good metallurgical bonding between the filler material and the base material without the formation of brittle phases, thus meeting the high load and long service life requirements of the wind turbine shaft.

[0079] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A high-strength wind turbine shaft welding method, characterized in that: The following steps are involved: S1, mechanically grind the welding groove of the base material of the rotating shaft to remove surface oxide scale, oil and moisture, and then use acetone ultrasonic cleaning to ensure surface cleanliness; S2, using laser cladding technology to pre-deposit a layer of modified material powder on both sides of the groove, with a thickness of 0.8-1.2mm. The pre-deposition method is synchronous powder feeding. After pre-deposition, the powder layer and the base material are metallurgically bonded; S3 adopts laser-arc hybrid welding process, with modified material composite powder as filling material, preheating temperature of 145-155℃, and interlayer temperature controlled at 180-200℃.

2. The high-strength wind turbine shaft welding method according to claim 1, characterized in that: In step S1, the base material of the welding shaft is 42CrMo steel with a size of Φ300-500mm; the welding groove is V-shaped, the groove angle is 60°, and the blunt edge is 1.5-2.5mm; the sandpaper mesh number of the mechanical grinding is 120-400#; and the time of acetone ultrasonic cleaning is 8-12 minutes.

3. The high-strength wind turbine shaft welding method according to claim 1, characterized in that: In step S2, the carrier gas for synchronous powder feeding is argon, the flow rate is 7-9 L / min, the laser power is 2.5-3 kW, the scanning speed is 4-6 mm / s, and the spot diameter is 3-4 mm.

4. The high-strength wind turbine shaft welding method according to claim 1, characterized in that: In step S3, the welding wire diameter in the laser-arc hybrid welding process is 1.1-1.3 mm, the laser power is 3.5-4 kW, the arc current is 170-190 A, the arc voltage is 22-25 V, and the welding speed is 1.8-2 m / min; the preheating method adopts a far-infrared heating belt for uniform heating, and the holding time is 30-40 min.

5. The high-strength wind turbine shaft welding method according to claim 1, characterized in that: The high-strength wind turbine shaft welding method further includes: after welding, wrapping with asbestos felt and slowly cooling to room temperature, the cooling time is ≥4 hours, and then performing stress relief annealing at 550-600°C for 2-3 hours; the stress relief annealing method is to heat the furnace with a cooling rate of ≤50°C / h, and finally polishing the weld surface, and the Ra of the weld surface is ≤0.8μm.

6. The high-strength wind turbine shaft welding method according to any one of claims 1 to 5, characterized in that: The preparation steps of the modified material include: A1, weigh pure iron, ferrochrome, nickel plate, ferromolybdenum, and ferrovanadium according to the above proportions and add them into a vacuum induction furnace, evacuate the furnace, and heat to 1600-1650℃ for melting; A2, after the composition is uniform, add titanium carbide powder and cerium oxide, and continue smelting to make the reinforcing phase evenly dispersed in the melt; A3, the melt is then poured into a water-cooled copper crucible to rapidly solidify into an ingot, which is then processed into blocks by wire cutting and placed in a ball mill; A4, use alcohol as the medium, grind with carbide grinding balls, dry and then sieve.

7. The high-strength wind turbine shaft welding method according to claim 6, characterized in that: In step A1, vacuum is applied to 10 -3 Pa, the smelting time is 10-20min.

8. The high-strength wind turbine shaft welding method according to claim 6, characterized in that: In step A1-2, the particle size of the titanium carbide powder is ≤5μm; the smelting time is continued for 5-10min; the mass percentages of the pure iron, ferrochrome, nickel plate, ferromolybdenum, ferrovanadium, titanium carbide and cerium oxide are: 1: (17-18): (6-7): (4-4.5): (2-3): (0.8-0.9): (0.5-0.6).

9. The high-strength wind turbine shaft welding method according to claim 6, characterized in that: In step A3, the thickness of the ingot is 8-10 mm; the size of the block is 20 mm×20 mm×5 mm.

10. The high-strength wind turbine shaft welding method according to claim 6, characterized in that: In step A4, the ratio of carbide grinding balls to materials is (9-10):1; the grinding time is 3-4 hours; and after drying, the mixture is passed through a 300-mesh sieve.

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