最新刊期
期 6 ， 2023
- 摘要：Porosity defects are often occurred in electron beam welded locked butt joint of aero-engine. A 3D numerical model of the transient keyhole and molten pool dynamics during electron beam welding was established to simulate the welding process. By comparing the experimental results with simulation results, the reason of porosity formation is the cavity from collapse of unstable keyhole captured by the solidified front. The simulation of pulsed electron beam welding proved that, the higher the pulsed frequency, the more stable the keyhole. When the frequency is 1000 Hz, the keyhole was dynamically stable, and porosity defect was effectively suppressed. The results provide a theoretical basis for the suppression of porosity defects in non-penetration electron beam welding.关键词：electron beam welding;keyhole behavior;porosity;pulsed beam;numerical simulation
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发布时间：2023-06-25 - 摘要：According to the requirements of the electron beam wire melting material increase manufacturing process on the long-term stability and reliability of the equipment, the control circuit of the acceleration power supply is designed in the form of voltage double closed-loop to realize the long-term stable output of the acceleration voltage when the grid voltage and load characteristics change; By means of asynchronous switching on/off and current sharing control, the three-way parallel operation of the accelerating power supply is realized, the EMI generated by the circuit under the output power of 30 kW is reduced, and the reliable operation of the accelerating power supply under the high-power state for a long time is realized. On this basis, the design of the filament power supply, the bias power supply and the bombardment power supply are completed, and the development of the high-voltage power supply for electron beam wire melting material increase is realized. The characteristics of the developed high-voltage power supply are verified. It can work stably for 20 hours under the condition of 60 kV output voltage and 30 kW output power, which meet the requirements of electron beam wire melting material increase manufacturing process.关键词：electron beam;fuse additive manufacturing;voltage double closed-loop;asynchronous switching on/off;current sharing control
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发布时间：2023-06-25 - 摘要：Selective laser sintering (SLM) was considered as one of the most potential metal additive manufacturing technologies. The formation and improvement of the side surface quality of 316L thin-walled parts formed by SLM was studied in this paper. The results show that the surface defects including sticking powders, depression (pore), and the wall thickness deviation of SLMed metal thin-walled parts have the similar piecewise change trends with the increase of bulk energy density. It could be inferred that there are three sintering modes of molten pool including solid-state sintering, steady-state conduction and unstable keyhole. Under different bulk energy density, the different coupling effects of the thermal and dynamic behavior of molten pool makes the distribution, morphology and formation mechanism of various surface defects changed. And then the formation mechanism of three kinds of surface ripples was also analyzed innovatively. The above research could provide some experimental and theoretical experience for improving the surface quality of complex thin-walled structures formed by SLM.关键词：SLM;surface defects;molten pool;metal thin-wall parts
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发布时间：2023-06-25 - 摘要：ZM6 magnesium alloy castings with large size and complex structure are prone to produce defects such as cracks, porosity and inclusions. The development of high-quality welding repair technology will help promote its wider application. In this paper, the argon arc welding technology was used to repair ZM6 cast magnesium alloy with different sizes of circular grooves using optimized pre welding preheating measures, welding process parameters and post welding heat treatment processes. The weld characteristics, microstructure and mechanical properties of argon arc welding repair joints were analyzed. The results showed that for the grooves with diameter of 10~40 mm, the repair welding joint without cracks, pores and incomplete fusion defects was obtained by preheating at 200 ℃ for 1 hour before welding and welding with 160 A current. The grain in the weld area of the repair welding joint was refined, and the grain size was 30~40 μm. The width of the heat affected zone was narrow, but the grains grow and the cluster-like precipitates were significantly reduced. Therefore, the hardness of the heat-affected zone was the lowest. With the increase of groove size, the hardness of weld zone and heat affected zone decreased, and the tensile strength of the sample also decreased. The tensile specimen mainly breaks in the heat affected zone, and the average tensile strength and elongation could reach 93.7% and 95.1% of that of the base metal.关键词：ZM6 cast magnesium alloy;argon arc welding;weld characteristics;microstructure feature;mechanical properties
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发布时间：2023-06-25 - 摘要：To study the application value of TIP-TIG (TT) welding technology in 9Ni steel welding of Liquefied Natural Gas storage tanks, in this paper, the charpy impact toughness test and crack tip opening displacement (CTOD) test were carried out on the welded joints of SAW and TT of 9Ni steel according to national standard. The microstructure and fracture of CTOD sample were analyzed. The results show that the average low-temperature impact energy absorption of TT weld and heat-affected zone is much higher than that of SAW, and the low-temperature impact toughness is better. The average CTOD eigenvalues of TT weld and heat affected zone are 0.455 mm and 0.744 mm respectively, and SAW weld zone and heat affected zone are 0.621 mm and 0.391 mm respectively. The CTOD eigenvalues are far higher than the requirements of common engineering standards. The fracture of CTOD samples are all ductile pits, and the fracture form is ductile fracture. TT welding, the push and pull vibration wire feeding function of wire feeder to achieve the mixing of molten pool, making the weld metal composition more uniform, refine the grain, but also reduce the production of porosity in the welding process; On the other hand, TT welding adopts pendulum swing mode, the swing of welding gun is also conducive to grain refinement, thus improving the low temperature toughness of welding joints. TT welding technology applied to 9Ni steel welding, compared with the traditional arc welding method, not only can obtain high-quality welding joints, but also can solve the problems of root cleaning and large amount of grinding, save considerable welding material quantity and labor cost, so as to achieve efficient and high-quality welding.关键词：9Ni steel;TT;SAW;low temperature toughness;CTOD
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发布时间：2023-06-25 - 摘要：Hot Isostatic Pressing (HIP) is one of the effective methods to eliminate the internal clearance of the molded parts. In this paper, TC4 titanium alloy specimens prepared by Selective Electron Beam Melting(SEBM) are taken as the research object. Hot isostatic pressing experiments are carried out in the furnace to study and analyze the microstructure and mechanical properties of the alloy after hot isostatic pressing treatment. The experimental results show that the density of TC4 titanium alloy specimen after hot isostatic pressing reaches more than 99% by drainage method, and it is almost completely dense. The tensile test was carried out on the tensile specimen at room temperature. After hot isostatic pressing treatment, the tensile strength of the specimen decreased and the plasticity increased. The tensile strength was 640.49 MPa, which was lower than 760 MPa of SEBM formed parts, and the elongation at break reached 19.95%. The fracture surface of the specimen shows elongated cup and cone shape and a few large and deep dimples, which indicates that the plasticity of the specimen is improved and the strength is reduced. After hot isostatic pressing, the specimen presents a basket structure, which is uniform and fine as a whole, and consists of coarsened strips α Phase and larger equiaxed α Grain composition with a small amount β Grain size.关键词：HIP;SEBM;Ti-6Al-4V;mechanical property
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发布时间：2023-06-25
Important Issuse
- 摘要：Friction stir welding technology is used to splice aluminum alloy profiles in the production of rail train body. Traditional welding control requires real-time manual adjustment of welding depth and position. When the welding stroke becomes longer, the labor intensity of workers is increased, and the welding efficiency is low and so is the quality. Therefore, the auxiliary welding technology is needed to upgrade the welding control: constant pressure control technology is used to automatically detect the welding depth and make adaptive adjustment to realize the automatic control of the welding Z-direction depth; laser tracking technology is used to detect and adjust the welding Y-direction position in real-time; finally, by combining NC programming, the automatic welding of rail train body products can be realized. Practical applications have shown that the welding time of a single product has been shortened from 1 hour to 40 minutes, and the welding quality qualification rate has increased from about 87% to about 95%.关键词：rail train body;friction stir welding;automatic;laser tracking technology;constant pressure control technology
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发布时间：2023-06-25
Welding Equipment
- 摘要：M390 high carbon martensitic stainless steel and 304 austenitic stainless steel are joined by Tungsten Inert Gas arc welding (TIG) experiments in the manufacturing of high-end cutting tools. The mechanical properties and microstructure of the welded joint were characterized by tensile experiment, vickers microhardness test, Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS). Analysis of phase composition in each location using X-ray diffraction. The grain sizes in different areas on M390 side are measured and joining mechanism of the welded joint was revealed. The results show that: M390 high carbon martensitic stainless steel and 304 austenitic stainless steel TIG welding joints with beautiful weld appearance, no holes, no inclusions and other defects can be achieved. The best welding process parameters are welding current of 120 A, welding voltage of 16 V, welding speed of 3.3 mm/s, the corresponding tensile strength can reach 266 MPa. The weld metal is composed of martensitic、M23C6 and M7C3. The grain size in weld metal is the largest, which can reach an average grain size of 17.96 μm. Because the weld metal matrix is martensitic, with the highest grain size, cleavage fracture occurs in the weld metal. The carbides in M390 side and weld metal are mainly (Cr, V) carbides. The carbide morphology gradually evolves from block shape to long strip shape from M390 base metal to the coarse-grained region.关键词：M390 high carbon martensitic stainless steel;TIG;microstructure;mechanical properties
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发布时间：2023-06-25 - 摘要：With increasing requirements for the strength of metal materials, the performance of single metal materials has great limitations, and it is difficult to meet the growing needs of people. In recent years, the connection of Cu/W dissimilar metals has played an increasingly important role in the welding field. In this paper, Cu/W dissimilar metal welded joints are produced by cold welding technology. The results show that the cold welding current has an obvious influence on the forming of the joint. At 160 A, there are many holes and unwelded defects at the interface, and the fracture occurs at the interface junction. Undercut appears at 170 A, and pores gather near the fusion line in the weld, where the fracture occurs. At 180 A, the weld seam is formed more evenly, the interface bonding is compact, the diffusion degree of Cu and W is the largest, the joint strength is the highest, and the fracture occurs on the tungsten base metal. At 190 A, solder joints overlap and the connection area changes greatly. There are large pores at the interface and weld, and the quality of the weld is unstable. The joint strength first increases and then decreases with the increase of current, reaching a peak value of 77.78 MPa at 180 A, and the quality of the welded joint is the best. The hardness of tungsten side after welding is not significantly different from that before welding, and the hardness of weld is extremely low. The hardness of heat affected zone is between copper base metal and weld, and the hardness of interface decreases with the increase of current. Except for 170 A, the joint has no obvious softening zone under other current parameters.关键词：Cu/W;dissimilar metals;cold welding;microstructure of welded joint;mechanical property
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发布时间：2023-06-25 - 摘要：The welding process of L-joint of Q345 thick plate is taken as the research object, and the V-bead structure of thick plate is extracted for analysis. Based on the double ellipsoidal power density distribution body heat source model as the input heat source, the mesh model is established by using the visual environment finite element software, and the calculation file of welding heat process is established. The temperature field of thick plate under different welding parameters was simulated and analyzed by numerical simulation of the welding thermal process of V bead of a straight plate structure, and the influence of different effective heat power and welding speeds on the welding temperature field was studied. Combined with the infrared laser test data of V-shaped plate welding test, the simulation results of temperature cloud section are compared to prove that the simulation effect of temperature field data is consistent with the actual, and the data of numerical simulation are accurate. At the same time, the size changes of different temperature ranges of the welding temperature field under different thermal efficiencies and welding speeds are analyzed. The calculation results show that the size of low temperature zone becomes smaller, which proves that the heat dissipation effect of thick plate is better than that of thin plate. Several sets of simulation data show that increasing the heat input of the weld decreases in the high temperature region, confirming that the requirement of the V bead for heat input is higher than that of the double V bead. The larger the welding speed is, the smaller the volume of the high-temperature zone and the low-temperature zone is. Compared with the temperature field cross-section of the weld with different welding speeds, the reduction ratio of the width of the high-temperature zone is greater than that of the depth, that is, the influence of the welding speed on the low-temperature zone is more obvious than that on the high-temperature zone.关键词：V bead;welding speed;temperature field;heat source model;numerical simulation
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发布时间：2023-06-25 - 摘要：The deformation of the welding fan of the main generator rotor of a certain type of diesel locomotive is dispersive after welding. In order to study the influence of welding deformation on the fatigue life of the fan, the assembly stress caused by the installation caused by different deformations of the floor of the welding fan is tested, and then the fatigue test of the fan is carried out by using the real load spectrum, three improved schemes to reduce welding deformation by changing welding process are compared. The results show that the fan deformation caused by welding will produce assembly stress in the installation process. The larger the deformation is, the larger the assembly stress is. The deformation is approximately nonlinear with the assembly stress. The fatigue fracture occurs at the weld toe of fan blade. The larger the welding deformation is, the smaller the fatigue life of blade is. Welding deformation can be controlled by anti-deformation tooling. When the welding deformation is less than 0.35 mm, it can meet the design life requirements.关键词：welding deformation;stress test;force simulation;fatigue test
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发布时间：2023-06-25 - 摘要：In order to obtain the rule of transient deformation process in thin plate welding and the influence of specimen size on the deformation after welding. Based on the three-dimensional optical surface scanning measurement system, the transient deformation process of weld area and key points in Q235 sheet welding was analyzed. According to the test, the finite element model was modified, and the influence law and mechanism of specimen size on the out-of-plane welding deformation of Q235 thin plate were discussed in detail by using the developed finite element model. The analysis of the modified finite element model is consistent with the experimental test results. The simulation results show that when the thin plate length is fixed, the longitudinal bending degree decreases with the increase of the width of the plate, and the change of the Angle deformation is not obvious. When the width of the thin plate is constant, the longitudinal bending degree and angular deformation increase with the increase of the length of the plate. The ratio of length to width of the test plate has little influence on the size and distribution of the longitudinal plastic strain of the weld, but has great influence on the transverse strain distribution range and size of the weld. This study provides effective guidance for judging and reducing post-welding deformation in industrial production.关键词：three-dimensional optical surface scanning measurement system;thin plate;welding deformation;finite element simulation;mechanism
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发布时间：2023-06-25 - 摘要：A three-dimensional repair welding model of X80 steel was established by using the finite element software ABAQUS. Considering the influence of welding residual stress and microstructure inhomogeneity, the temperature field, stress field and hydrogen diffusion of plate repair welding were coupled by using the sequential indirect coupling method. The variation of residual stress in repair welding under different heat input conditions was studied. The results show that the maximum residual stress after repair welding occurs in the weld zone, the peak stress of transverse residual stress S11 increases by 55%, and the longitudinal residual stress S22 exceeds the yield strength of the material. The S11 is greatly affected by different heat input of repair welding. When there is no residual stress, hydrogen diffusion presents a gradient distribution. When there is stress, hydrogen concentration is large in the residual stress concentration area, and the residual stress promotes the diffusion and enrichment of hydrogen.关键词：X80 steel;repair welding;residual stress;hydrogen diffusion
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发布时间：2023-06-25 - 摘要：Based on the measured stress and strength data, the static strength reliability assessment of Inconel 690-321 dissimilar metal welded joints was carried out, and the static strength reliability of the welded joints and the reliability safety factor of the welded joints were studied by applying the stress strength interference model. The results show that the static strength reliability of the welded joint in the hydrostatic test condition is 0.99993 under the condition that the stress and strength follow the normal distribution, and on the other hand, the reliability safety factor of the welded joint under the condition of R=0.9999 is 1.1. Based on the measured data, the established static strength reliability assessment method of welded joints can be popularized and applied to the strength design and evaluation of similar welded joints, so as to achieve the purpose of refined design of safety factor and structural weight reduction.关键词：reliability evaluation;dissimilar metal welds;stress strength interference model;XRD
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发布时间：2023-06-25 - 摘要：In order to verify the influence of different system welding materials (American standard and Russian standard) on the fracture performance of repair welds of composite steel pipe in typical nuclear power plants, mature welding processes and different system welding materials were used to prepare composite steel pipe maintenance samples, and the fracture performance of the deposited zone and heat affected zone were tested respectively. The results show that the fracture resistance of the deposited zone of the repair weld with American standard welding materials is significantly higher than that of Russian standard welding materials; The fracture resistance of the heat affected zone of the weld repaired by the two systems are similar; The fracture resistance of the heat affected zone of the repair weld with Russian standard welding materials is significantly higher than that of the deposited zone; Judging from the trend, with the increase of crack growth, the J resistance curve of heat affected zone of American standard welding material repair weld is significantly higher than that of deposited zone, and there is little difference in the conditional crack initiation toughness between the deposited zone and heat affected zone of American standard welding material repair weld is not different.关键词：composite steel pipe;load separation;resistance curve;fracture resistance
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发布时间：2023-06-25 - 摘要：In order to study the effect of anti-spatter fluid overuse and accumulation during welding process, overlaying tests are implemented to analyze the state changes of different types and accumulation of anti-spatter fluid in the welding process and its effect on molten pool fluidity, arc stability and weld geometry. The results show that once the accumulated amount of oil-based anti-spatter fluid is greater than 0.045 mL·cm-2, some of the anti-spatter fluid will enter into the molten pool, which in turn reduces the fluidity of the molten pool, resulting in the accumulation of molten metal behind the arc, while the anti-spatter fluid will be in direct contact with the arc. The water-based anti-spatter fluid moves forward and evaporates rapidly under the arc heat plus pressure and does not enter into the molten pool even at accumulation of 0.227 mL·cm-2, thus it has no influence on the fluidity of the molten pool. The arc stability of the water-based anti-spatter fluid is significantly better than that of the oil-based anti-spatter fluid, especially when the accumulated amount is less than 0.09 mL·cm-2. Under the influence of two types of anti-spatter fluids, the overall weld geometry is basically the same and only weld penetration is about 0.5 mm lower than that without anti-spatter fluids, while the weld reinforcement and width have no evident changes.关键词：anti-spatter fluid;molten pool fluidity;arc stability;weld geometry
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发布时间：2023-06-25 - 摘要：In this paper, 6 mm-thick 2219 aluminium alloy were welded by friction stir welding. The results of both the X ray image and the metallographic structure observed at transverse and longitudinal direction were compared and analyzed. A obvious bright line could be observed at the advanced side in the joint and crescent shaped white inclusions could be observed along the weld longitudinal direction with periodic intermittent distribution. It was the combined influence of both thermal mechanical effect and plastic material flow during FSW that cause the abnormal aggregation and growth of strengthening phase at the advanced side in the joint. Under the influence of the size and the distribution characteristics of the strengthening phase of the material, it formed an uneven crescent-shaped inclusion.But the inclusion thickness is thin and formed a metallurgical bond with the matrix. The aggregated phase has no significant effect on the joint mechanical properties.关键词：2219 aluminum alloy;friction stir welding;X Ray;aggregated phase
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发布时间：2023-06-25 - 摘要：In order to promote the engineering application of PAUT technology in ferrite steel thin-plate butt welds of nuclear power plant, this paper compared and analyzed the major requirements of the domestic and foreign common PAUT standards which are applicable to ferrite steel thin-plate butt welds, ISO 13588—2019, DL/T 1718—2017, and NB/T 47013.15—2021 are more suitable as reference standards for phased array ultrasonic testing of thin-plate butt welds in nuclear power plants. The application of phased array ultrasonic testing of ferritic steel thin-plate butt welds in nuclear power plants can refer to the requirements of NB/T 47013.3—2015 for testing sensitivity and acceptance standards. This conclusion can provide reference for the engineering application of phased array ultrasonic testing technology for ferrite steel thin-plate butt welds of nuclear plant.关键词：ferrite steel thin-plate;butt welds;phased array testing;nuclear plant;standard
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发布时间：2023-06-25 - 摘要：The low temperature impact energy of welding joint does not meet the requirements of welding standard or is with a large dispersion as robot automatic welding specification developing. In order to solve this problem, this paper formulate different welding schemes according to the factors that may affect the low temperature impact toughness of the robot automatic welding joint, carried out the low temperature impact energy of the joints after welding, and analyzed the dispersion of the obtained data. It is found that different influencing factors have different effect on the low temperature impact toughness of welding joints. Finally, a welding scheme for robot automatic welding with the highest construction efficiency was designed. According to this scheme, experiments were carried out. The results show that the low temperature impact energy of the joint is acceptable by the welding standard at -40 ℃.关键词：offshore engineering steel structure;robot automatic welding;low temperature impact toughness;welding specification
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发布时间：2023-06-25 - 摘要：Through the phased array inspection of the fillet weld of the directly buried temperature casing on the main steam pipe of the thermal power unit, it is found that there are a lot of buried defects exceeding the standard in the weld. During the excavation of the defect parts of the fillet weld, a large number of slag inclusion, porosity and non fusion defects were found in the weld, which matched well with the defect positions detected by the phased array. The weld defects were successfully repaired by formulating reasonable welding process and post weld heat treatment process. It is concluded that the phased array inspection should be carried out on the fillet welds of the directly buried temperature casing of the high-temperature pipelines of the in-service units with running time of more than 100,000 hours; At the same time, for the directly buried temperature casing structure, if the casing, weld and main pipe are of the same material or the same material, the internal quality of fillet weld can generally operate safely and stably after passing the inspection.关键词：phased array detection;internal weld defect;temperature sleeve;directly buried structure;welding repair
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发布时间：2023-06-25
Welding Technology
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