最新刊期
卷 54 ， 期 9 ， 2024
- 摘要：With the rapid development of the rail transit industry, higher requirements have been put forward for the core indicators of trains. The strength level of materials used in vehicles continues to increase, the thickness continues to decrease, and the alloy composition becomes more complex, and the application of lightweight composite materials represented by carbon fiber in vehicle components is gradually expanding. The increasing demand for three-dimensional complex structures, ultra-thin walls and large differences in heterogeneous connections poses new challenges to the joining technology. This paper analyzes the shortcomings of traditional connection methods in terms of quality, cost and efficiency, and puts forward the development trend of rail passenger car connection technology. Through the development of high-energy-density heat source welding methods such as laser welding and laser-arc composite welding, the problem of high-strength, toughness and high-precision connection of long-walled and thin-walled components is solved; through the development of green welding technologies such as friction stir welding, induction brazing, ultrasonic welding, etc., the welding operation environment is improved and the welding energy consumption is reduced; with the rapid development of robots and information technology, digitalization, The intelligent connection manufacturing mode has gradually become the mainstream, and the heterogeneous connection problem under the multi-material system is solved through the comprehensive application of various connection methods such as welding, bonding, riveting, and bolting.关键词：railway vehicle;material;interconnection technique;welding
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发布时间：2024-10-11 - 摘要：The use of external magnetic field to improve the arc welding process has the advantages of low cost, low additional energy consumption and easy operation, which has become one of the hot spots in today's research. In order to solve the problems of poor weld forming and poor quality of welded joints during high-speed MIG welding, this paper carried out the welding process test of butt joints of aluminum alloy car body with large and thin wall profiles under different welding parameters to study the optimal welding process under high-speed welding conditions. It is found that for the weld of the aluminum alloy car body, the welding quality is the best when the excitation parameters are 8 A, 120 HZ, and the welding parameters are 265A, 23.5V, and 1.2 m/min. Metallurgical microscopy and backscatter electron diffraction (EBSD) were used to characterize the microstructure of welded joints under different welding parameters, and the effects of applied pulsed composite magnetic fields on the microstructure of welded joints were analyzed. The results show that under the condition of high-speed welding, the grain of the welded joint is significantly coarser compared with the conventional welding speed, and the width of the fusion zone is increased. However, with the introduction of pulsed composite magnetic fields, both the grain size and the width of the fusion zone are reduced to a level comparable to that of conventional welding. The results show that the mechanical properties of welded joints under different welding parameters are significantly improved, the average hardness of the weld zone is increased by 21.37%, and the average tensile strength of the joint reaches 187MPa, which is quite close to the 193MPa at the traditional welding speed. Under the condition of ensuring the forming quality of the weld and the mechanical properties of the welded joint, the welding speed was finally increased from 0.75m/min to 1.2m/min, and the high-quality and efficient welding process was realized.关键词：aluminum alloy;composite magnetic field;excitation parameters;magnetron arc welding;microstructure;mechanical properties;high efficiency welding
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发布时间：2024-10-11 - 摘要：In this paper, laser-MIG hybrid welding experiments were carried out on the 8mm thick 6005A-T6 aluminum alloy. The weld formations, microstructures, microhardness distributions and tensile properties with different groove shapes were comparative studied. The results indicated that both I-shape and Y-shape grooves could obtain high quality welds, but the arc action zone penetration of I-shape groove was larger. The weld centers of I-shape and Y-shape grooves were dendritic and had similar grain size. Compared with Y-shape groove, the columnar crystal zone width of I-shape groove weld was larger than that of Y-shape groove, and the grain size in the heat-affected zone of I-shape groove weld was coarse. The microhardness values in the weld zone and near the fusion of I-groove shape were both lower than those of Y-shape groove, and the microhardness of heat-affected zone was higher than that of Y-shape groove. The average tensile strengths of I-shape and Y-shape joints were 202.0 MPa and 205.2 MPa, respectively. The samples fractured near the fusion line, and the fracture paths were consistent with the fusion line. The fracture showed typical plastic fracture features.关键词：aluminum alloy;laser-MIG hybrid welding;groove shape;weld formation;mechanical properties
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发布时间：2024-10-11 - 摘要：The purpose of this study is to investigate the effects of welding speed on the microstructure and mechanical properties of 6082 aluminum alloy friction stir welding (FSW) joints, and to establish the regulation rules of FSW joint microstructure and properties based on welding speed. Metallographic observation, electron backscatter diffraction (EBSD) analysis, hardness testing, room temperature tensile and bending tests were used to characterize the microstructure and mechanical properties of FSW joints at four different welding speeds (500 mm/min, 750 mm/min, 1000 mm/min, 1 250 mm/min). The results show that with the increase of welding speed, the microstructure of FSW joints changes significantly. In the weld nugget zone (NZ), continuous dynamic recrystallization occurs, forming fine recrystallized grain structures, with the average grain size decreasing from 3.8 μm to 2.3 μm and the recrystallization fraction decreasing from 83% to 57.3%; In the thermomechanically affected zone (TMAZ), partial dynamic recovery and partial dynamic recrystallization occur, with a few fine equiaxed grains appearing at the grain boundaries and a large number of subgrain structures forming inside the grains. The proportion of substructure and the proportion of small-angle grain boundaries increase significantly, reaching 69.2% and 60.1% respectively; Due to the welding heat effect, the grain size in the heat-affected zone (HAZ) increases slightly compared to the base metal zone (BM), and the degree of recrystallization and grain boundary angle distribution are similar to those of the base metal. In terms of mechanical properties, with the increase of welding speed, the minimum hardness of FSW joints increases from 72.3 HV to 81.2 HV, the welding coefficient increases from 74.7% to 89%, and the heat-affected softening zone is significantly reduced. However, cracks occur in the back-bend specimen of FSW joints at a welding speed of 1 250 mm/min. Based on the welding speed control mode, the FSW joint has the best mechanical properties at a welding speed of 1 000 mm/min.关键词：6082 aluminum alloy;FSW;welding speed;microstructure;mechanical property
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发布时间：2024-10-11 - 摘要：To study the mechanism of welding hot cracking, the failed specimens of thin-walled 7003 aluminum alloy profile and 6111 aluminum alloy sheet MIG fillet weld cracks were taken as the research object, and the welding crack mechanism was analyzed by means of penetrant testing, metallographic observation, scanning electron microscope, energy spectrum analysis, hardness distribution and so on. The research results show that: the welding cracks 1 and 2 located on the sheet side are both liquefaction cracks, with lengths of 4 235.2 μm and 1 357.4 μm respectively, and the crack 2 is about 165 μm away from the nearest edge of the weld; the numerical variances of the hardness distribution on the profile side and the sheet side are 7.66 and 76.89 respectively, the sheet side fluctuates more and the maximum difference reaches 34.32HV, indicating that the sheet is more seriously deteriorated by the welding heat effect on the structure and performance; the energy spectrum analysis shows that the impurity phase around the crack is the brittle AlFeSi low melting point eutectic phase distributed along the grain boundary, which has a melting temperature lower than the melting point of aluminum alloy and will lead to the decrease of grain boundary toughness, and the formation of intergranular liquid film after melting is easily torn by the welding shrinkage stress, resulting in the initiation of intergranular liquefaction crack. By comparing and analyzing the three states of pre-welding, welding and post-welding, the effects of grain size, welding stress and low melting point impurity phase on the mechanism of aluminum alloy welding liquefaction crack were studied.关键词：dissimilar aluminum alloys;hot crack;welding liquefaction cracks;the low melting point impurity phase of AlFeSi;MIG welding
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发布时间：2024-10-11 - 摘要：To study the effect of repair welding times on the microstructure and properties of the 30CrMo alloy steel hollow shaft, a key component of the power locomotive bogie, and to optimize its repair welding process, three repair welding tests were conducted on the 30CrMo alloy steel hollow shaft. Static strength tests, metallographic tests, and fatigue tests were performed on the joints after each repair welding. Static strength tests included tension and bending tests. Metallographic tests observed the microstructure of various regions of the joint. Fatigue tests used rotating bending loading to determine the fatigue limit of the joint. The results showed that after multiple repair weldings, the joint had good tensile properties, and the tensile specimens broke at the base metal; the bending performance was good, and no fracture or crack occurred when the bending angle reached 180°; the impact properties at room temperature and low temperature decreased slightly after multiple repair weldings, meeting the standard requirements; the hardness of the weld after three repair weldings was between 330~340 HV, which was significantly higher than the hardness of the base metal and the heat-affected zone. Metallographic analysis showed that the microstructure of the hollow shaft base metal was tempered sorbite, upper bainite, and massive ferrite, the main microstructure of the heat-affected zone was tempered sorbite and a small amount of massive ferrite, the microstructure of the fusion zone was tempered sorbite, and the weld microstructure was tempered sorbite produced after quenching and tempering. The fatigue limit of the joint met the strength requirements, and the median fatigue limit was the highest in the third repair welding, which was 399 MPa at a specified life of 1×107 cycles. Post-weld quenching and tempering could effectively improve the effect of multiple repair weldings on joint properties. After multiple repair weldings, the 30CrMo alloy steel hollow shaft joint had good tensile, bending, and fatigue properties, and the fatigue strength of the joint increased gradually with the increase of repair welding times. This research result provides a theoretical basis for the optimization of the repair welding process of key components of the power locomotive bogie.关键词：30CrMo alloy steel hollow shaft;Different welding repair times;microstructure;mechanical property;fatigue
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发布时间：2024-10-11 - 摘要：This study explores the potential of magnetic resistance spot welding technology to improve the welding quality and joint performance of high-strength stainless steel materials for railway vehicles, which are prone to problems such as prominent indentation, large fluctuations in nugget diameter, and shrinkage holes in the center of the nugget. By adding annular permanent magnets to existing resistance spot welding equipment and utilizing the electromagnetic stirring effect of the external magnetic field on the molten metal, magnetic resistance spot welding was found to significantly improve the quality of the weld and joint performance. Compared to traditional resistance spot welding, magnetic spot welding can reduce indentation height by 80.6%, increase nugget diameter by 12.0%, and improve the dendrite proportion in the isometric zone of the nugget from 29% to 6%. Additionally, the tensile shear fracture load of the magnetic spot welded joints is increased by 11.8%, and fatigue strength is also enhanced. Microstructure observations reveal that magnetic spot welding can effectively refine the nugget grains, significantly reduce the dendrite proportion, thereby improving the surface strength of the joint and reducing indentation depth. Fatigue test results show that the fatigue life of magnetic spot welded joints is significantly improved, and the fracture mode changes from the interfacial fracture of traditional spot welding to a high-toughness button fracture mode. This study provides experimental data support for the application of magnetic resistance spot welding technology in the manufacturing of stainless steel railway vehicles and offers valuable references for the high-reliability and mark-free spot welding of unpainted vehicles.关键词：magnetic resistance spot welding;high strength stainless steel;railway vehicles;mechanical properties;welding quality
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发布时间：2024-10-11 - 摘要：This article uses BAg34CuZnSn composite brazing material and induction brazing technology to braze the TP2Y2 copper pipe sleeve joint. Through analysis and testing methods such as OM, SEM, EDS, and tensile tests, the morphology of the composite brazing joint, the filling depth of the brazing material, the interface structure of the brazing joint, and the mechanical properties of the brazing joint were studied. The influence of brazing thermal cycle on the microstructure and properties of the copper pipe was analyzed. The results show that using output power (40 kW), brazing current (100 A), and brazing time (40 s) can ensure that the brazing material was completely and effectively filled, achieving sealed high-strength connection of TP2Y2 copper pipe sleeve joint. The appearance of the brazing joint is smooth and continuous, and the base material has no concave melting corrosion. The brazing seam mainly consists of Ag solid solution and Cu solid solution, and the microstructure of the brazing seam is continuous and dense, without defects such as pores and cracks. The brazed joint of purple copper tube has an average shear strength of 222.7 MPa, which can meet the reliable connection of large penetration copper tube structures.关键词：copper pipe;induction brazing;microstructure;shear strengths
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发布时间：2024-10-11 - 摘要：In the process of intelligent welding of locomotive steel structure, affected by heat input, material deformation and other factors, the actual position and shape of the weld will change. When tracking the weld, the current visual frame difference method is easy to ignore the position information and the position deviation of the weld trajectory, resulting in large tracking error. In this regard, a seam tracking method for locomotive steel structure welding robot based on visual features is proposed. Based on the "checkerboard&Stripe" mixed image, the stereo vision position of the locomotive steel structure welding robot is calibrated, and the centerline feature of the laser stripe of the welding robot is captured; The Roberts operator is used to extract the weld edge information, and the Hough transform is introduced to determine the weld centerline to realize the weld identification. The weld coordinates are transformed and mapped to the basic coordinate system of the locomotive steel structure welding robot, and the weld trajectory is constructed in three-dimensional space; Based on the current position information of the welding torch and the calculation of the position deviation of the weld trajectory, the weld trajectory data is corrected in real time by cubic uniform rational B-spline, and the real-time tracking of the weld seam of the locomotive steel structure welding robot is realized. The experimental results show that the proposed method can effectively improve the seam tracking accuracy of the locomotive steel structure welding robot.关键词：visual features;locomotive steel structure;welding robots;weld seam tracking
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发布时间：2024-10-11 - 摘要：The text discusses the reparation of commonly used 5083 aluminum alloy materials for railway transportation using Al-Mg-Sc-Zr high-strength aluminum alloy welding wires. The study compares the microstructure and mechanical properties of different process-repaired samples using pulse CMT (CMT-P) and pulse MIG (MIG-P) melting pole arc welding, as well as non-melting pole arc welding with variable polarity TIG (TIG-V).Resultsshow that the repaired areas formed by different arc repairprocesses using Al-Mg-Sc-Zr high-strength aluminum alloys are distributed with a large number of Al3(Sc,Zr) particles, which significantly refine the grain structure of the repaired area. In addition, all repaired specimens have tensile strengths above 90% of the base materials. Among them, CMT-P has the smallest heat input, causing minimal loss to matrix strength due to thermal cycling, at only 1.3%. The repaired 5083 aluminum alloy using this method gets a tensile strength as high as 293 MPa, which reaches 94% of the base material's strength; TIG-V and MIG-P have relatively larger heat inputs and achieve 283 MPa and 290 MPa tensile strengths after being repaired respectively. However, both methods result in greater losses to matrix strength due to thermal cycling, about 16% and 8.7% respectively.关键词：Al-Mg-Sc-Zr high strength aluminum alloy;arc additive repair process;microstructure;mechanical properties
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发布时间：2024-10-11
High-performance Welding Manufacturing of Rail Vehicles
- 摘要：The manufacturing process and quality of water turbine blades are directly related to their service life and operation safety. The influence of tempering temperature on the microstructure and properties of 0Cr13Ni4Mo stainless steel in CMT arc additive manufacturing 0Cr13Ni4Mo stainless steel was studied by optical microscope (OM), scanning electron microscope (SEM), 0 ℃ impact test and hardness test under fixed heat input, interlayer temperature and other welding process parameters. The results show that the 0Cr13Ni4Mo stainless steel material manufactured by CMT arc additive is tempered at different temperatures, and its microstructure is typical slatted martensite. With the increase of tempering temperature, the martensite phase weakens, a large number of adjacent martensite slats are fused, the trend of martensitic slats merger intensifies, and the content of contravariant austenite increases. The impact specimens were mainly ductile fractures, and the ductile fractures at the fractures were obvious, and a large number of tenements were distributed. With the help of SEM, the inclusions at the bottom of the ligament fossa could be clearly observed, and EDS analysis showed that the round particles were mainly Mn and Si oxides. The impact toughness increases with the increase of tempering temperature, and the hardness first increases and then decreases. The comprehensive study shows that the specimen tempered at 610 ℃ and kept warm for 8h has excellent comprehensive mechanical properties to meet the actual needs of the project.关键词：CMT additive manufacturing;tempering temperature;0Cr13Ni4Mo stainless steel;microstructure and performance
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发布时间：2024-10-11 - 摘要：The strength matching form and corrosion resistance of girth welds are crucial for the reliable operation of pipelines. In this paper, shielded metal arc welding was used on D1219×18.4 mm X80 spiral welded pipes with low strength matching, equal strength matching, and high strength matching. The weld joints were subjected to hydrogen-induced cracking (HIC) tests, and the effects of different strength matching on the HIC resistance of X80 pipeline steel girth welds were analyzed comprehensively, including chemical composition, microstructure, joint strength, and toughness. The results show that the HIC resistance of the X80 pipeline steel weld joints under the three matching forms can meet the relevant requirements. Moreover, the crack length sensitivity ratio (CLR), crack thickness sensitivity ratio (CTR), and crack sensitivity ratio (CSR) of the weld joints increase with the increase of matching strength. The content of C, P, and S in the weld metal has a significant impact on HIC sensitivity, and reducing the content of these elements helps to improve the HIC resistance of the weld. Microstructure observation indicates that the type and morphology of the weld metal also have an important influence on HIC sensitivity. A thermodynamically balanced and stable small tissue is an ideal tissue for HIC resistance.关键词：Strength match;X80 pipeline steel;girth weld;HIC
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发布时间：2024-10-11 - 摘要：A finite element simulation study was conducted on the prediction and control of welding deformation during the welding process of steam generating unit. Based on the sequential coupling thermal elastic-plastic finite element method, welding process of typical pipe-sheet structures was simulated and analyzed under different welding sequences by using ABAQUS software. The welding temperature field, stress distribution, and deformation were calculated using a combined heat source verified with metallographic examination to apply heating flux. The results show that using a combination of Gaussian and ellipsoidal heat sources can accurately simulate the morphology of the melt pool. There is stress concentration in the weld area of the pipe-sheet structure, and the stress peak is located in the clamped area, with a magnitude of 631.2 MPa, exceeding the material yield limit. The stress distribution of a single circumferential weld joint along different special paths exhibits complex fluctuations due to the influence of heat input from the surrounding weld joint. Adopting a symmetrical welding sequence from top to bottom can effectively reduce welding deformation, providing a reference basis for process optimization.关键词：finite element simulation;titanium alloy pipe-sheet welding;combined heat source;sequential coupling;welding sequence
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发布时间：2024-10-11 - 摘要：In recent years, the equal load-carrying calculation method for fillet welds has played a significant role in the low-cost design of fillet weld sizes. At the same time, this method has also posed new requirements for the quantitative calculation of the shear performance of the deposited metal. In this paper, the simulation and experimental study on the shear properties of deposited metal from low alloy steel welding wire are carried out by using the lap joint fillet weld. A new formula for calculating the shear strength of fillet weld is proposed, and a recommended method for evaluating the shear properties is given based on the research results. The results show that the shear cracking angle of fillet weld is around 22.5°, and the existence of penetration does not affect the cracking angle, but equal to the increasing of weld size. The test should adopt the general size, multi-pass welding method, so as to obtain the representative shear strength of the deposited metal. In addition, it is recommended to calculate the sum size of the fracture surface to obtain the shear strength. Although the shear strength will be reduced by about 10%, the influencing factors can be much less and the general applicability of the calculation results can be effectively increased by directly defining the cracking angle as the theoretical angle and the width of the fracture surface as "weld size plus penetration".关键词：deposited metal;shear property;shear membrane stress;cracking angle
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发布时间：2024-10-11 - 摘要：For 800 MPa high strength steel welding wire, the deposited metal was prepared by MAG welding assisted by applied transverse magnetic field. The arc shape and droplet transition characteristics under the action of applied transverse magnetic field were observed and analyzed by high-speed camera method. The microstructure of deposited metal with or without external transverse magnetic field was analyzed by OM and EBSD, and the mechanical properties of deposited metal were tested. The results show that the addition of transverse magnetic field can deflect the arc shape and melt drop, and the average grain size of the deposited metal is refined by 9.3% compared with that without magnetic field, and the texture types change to {111}<110>, {111}<112>, {110}<112>, {001}<100>. Compared with no magnetic field, the tensile strength of the deposited metal is increased by 4.65%, the elongation is increased by 3.4%, and the low temperature impact toughness is increased by 28%.关键词：transverse magnetic field;deposited metal;arc shape;grain refinement;mechanical properties
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发布时间：2024-10-11
Welding Technology
- 摘要：Wire rope rigging plays a crucial role in machinery, bridges, and lifting equipment, and its reliability mainly depends on the brazing quality of the wire rope ends and joints. The traditional ZnCu6 brazing material has issues such as high temperature during the brazing process leading to the softening and strength reduction of the steel wires, while at low temperatures, the poor fluidity of the brazing material makes it difficult to achieve good filling, affecting the joint strength. In light of this, appropriately reducing the melting point of the brazing material used without affecting the joint strength has become a feasible direction for research. This paper adds the rare earth element Yb to the ZnCu1.7 eutectic alloy to refine the grains, and improves the strength of the brazed joint with an appropriate amount of Ag component, developing a new type of ZnAg2Cu1.7Yb brazing material for wire rope joint brazing, and the performance characterization of ZnAg2Cu1.7Yb brazing material was carried out through methods such as melting point testing, mechanical property testing, grain size analysis, flowability and porosity testing. The experimental results show that the brazing temperature of the new brazing material is 80 ℃ lower than that of ZnCu6, effectively reducing the thermal impact on the wire rope, while the joint strength is increased by 9.5%; in addition, the grains of the ZnAg2Cu1.7Yb brazing material are refined, the fluidity is enhanced, and the porosity inside the joint is significantly reduced.关键词：brazing filler metal;mechanical properties;breaking force;porosity
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发布时间：2024-10-11
Welding Material
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