最新刊期
期 1 ， 2023
- 摘要：In order to achieve favourable brazing between MnCuAl damping alloy and 430 stainless steel, the fillers with different Sn contents were designed and developed, and the effect and mechanism of Sn content on microstructures and melting characteristics of Cu-34Mn-6Ni filler were investigated. The results show that the saturated solid solubility of Sn in Cu-34Mn-6Ni alloy is about 6 wt. % at 720 ℃ and holding for 10 h. When the content of Sn exceeds 6% (including), the Sn-rich BCC Cu17Sn3 phases form among the matrix phase γ-(Cu,Mn). The amount of this Sn-rich phases gradually increases with the increasing Sn content, and its proportion in the filler will be higher than the matrix when the Sn content is 10%. The addition of Sn causes lattice distortion of the matrix phase. The lattice constant of the matrix phase gradually increases with the increasing Sn content, and the maximum swelling rate reaches 0.725 3%. With the increase of Sn content, the liquid point of filler decreases significantly. The liquid point of the Sn-rich phase is lower than that of the matrix phase, which makes the melting interval of the filler wider. The melting interval of the filler metal is the largest when the content of Sn is 6%, and then the width becomes smaller with the further increase of Sn content.关键词：Cu-Mn-Ni-xSn brazing filler metal;microstructure;melting characteristics;brazing of dissimilar metals
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发布时间：2023-02-04 - 摘要：As one of the most important components of a liquid rocket engine, the reliability and stability of welding quality are very important for the service performance of the engine and the reliable and safe operation of the rocket.In actual production, the weld defects are mainly identified by manual evaluation of film images, which generally have shortcomings such as low detection efficiency and strong dependence on manual experience. According to the characteristics of the digitized image of the liquid rocket engine thrust chamber film, the image sample set was constructed by performing image preprocessing such as size normalization and image enhancement on the original image.The YOLO algorithm was used to establish a self-identification model of fusion weld defects based on deep learning theory.The research results show that the trained YOLO neural network model can accurately identify four typical fusion weld defects such as pores, cracks, lack of fusion, and lack of penetration in digital film images, and the recognition accuracy can reach more than 90%. which has good industrial application prospects.关键词：non-destructive testing;brazing defects;X-Ray digital radiography;deep learning
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发布时间：2023-02-04 - 摘要：In the machinery equipment manufacturing industry, accidents caused by welding defects occur frequently. Welding hot crack is one of the typical welding defects. As common forms of hot cracks, liquation cracks can easily lead to metal structure failures and accidents. The objective evaluation and understanding of the liquation crack susceptibility of materials is particularly important. Liquation cracks are cracks caused by local grain boundary liquefaction due to the heat of the base metal or the reheating of the previous weld metal of the multi-pass weld. More than 140 test methods have been developed to evaluate the susceptibility of liquation crack in metal welding parts, among which thermal ductility test, programmierter verformungs test is widely used in pressure vessels, aerospace, petrochemical and other fields. In this paper, several kinds of widely-used method are reviewed, and the different test methods adopted by the susceptibility criterion have been discussed, which mainly includes temperature range and cracking length. However, the applicable conditions of different criteria are different, so it is particularly important to promote the optimization of liquation crack evaluation test of existing materials and the standardization of criterion results in the future, which will help to predict and prevent liquation cracking in machinery equipment and improve the service life of machinery and equipment.关键词：hot crack;liquation crack;test method;susceptibility criterion;heat affected zone
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发布时间：2023-02-04 - 摘要：Aiming at the problem of low accuracy of finite element simulation of welding deformation of thin-wall aluminum alloy, taking 2 mm profile T-joint of 6082-T6 aluminum alloy as the research object, the special heat source model of aluminum alloy MIG welding was studied by combining finite element simulation and actual sample checking. The morphology and deformation of weld pool of 2D Gaussian, double ellipsoid and 3D Gaussian are calculated. It is found that there is a gap between the size and deformation of molten pool calculated by the three typical heat source models and the actual sample. The heat flow of 2D Gaussian heat source is too small, and the width and depth of molten pool in the weld zone are significantly smaller than the actual molten pool size. The 3D Gauss heat source can reflect the effect of heat flow in the thickness direction, but the depth and width of the molten pool are slightly larger. The shape and width of the double ellipsoid heat source in the upper part of the pool are close to the actual ones, but the pool is shallow. Based on the characteristics of the three models, the optimized composite heat source model of "double ellipsoid +3D Gaussian" based on the typical heat source model is obtained by inverse calculation method. The weld pool size and offset are 90% consistent with the actual workpiece. The model is reliable and can be used for accurate simulation of MIG welding of thin-wall 6082 aluminum alloy T-joint.关键词：thin-wall aluminum alloy;finite element simulation;heat source model;offset;molten pool shape
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发布时间：2023-02-04 - 摘要：According to the different stress distribution under interfacial fracture mode and button pull-out mode, the maximum force on high strength steel spot-welded joints for two kinds of failure modes were analysised and calculated based on Mises criteria and ultimate stress theory.The critical weld diameter
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发布时间：2023-02-04
Important Issuse
- 摘要：When aluminum alloy is welded by arc welding process, it is easy to cause coarse grain in the weld zone and produce defects such as pores and cracks. The laser oscillation welding tests of 1.0 mm thick 5A01 aluminum alloy sheet were carried out, and the microstructure and mechanical properties of the joint were studied. The results show that under the condition of surface focusing, when the robot speed is 40 mm/s, laser power is 1 600 W, pulse frequency is 5 000 Hz, swing frequency is 110 Hz, and swing amplitude is 0.5 mm, the joint with good formability can be obtained. It was found that the columnar grains grow mainly along the fusion zone and the weld center is mainly composed of fine equi-axed crystal. The hardness gradually decreases from the base metal zone to the weld zone. The tensile strength of the joint is about 66% of the base metal, and the elongation is about 41% of the base metal. The fracture form of the joint is dimple fracture. The mechanical properties of the joints are significantly reduced, mainly due to the stress concentration easily generated at the porosity and the concentrated energy of laser welding, resulting in uneven heating of the thin plate generating large internal stresses.关键词：5A01 aluminum alloy;laser welding;microstructure;mechanical properties
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发布时间：2023-02-04 - 摘要：The exact characterization of rail fatigue cracks growth ability under the creep load is the basis for formulating reasonable rail grinding plan, these cracks located in 5~25 mm below the rail tread. In this paper, fatigue crack growth rate of base metal and joints under different stress ratio were tested, real-time strain characteristics were captured by using DIC (Digital Image Correlation) technology, fatigue crack growth abilities between base metal and joints and characteristics of crack flanks and tips were analyzed. The results show that the fatigue crack growth ability of joint is weaker than that of base metal, obvious characteristics of plasticity-induced crack closure are shown under condition of small stress ratio. Then, a local stress model around crack flanks and tips led by a plastic zone is established based on the results of strain characteristics in the samples got by DIC technology.关键词：welded rail;fatigue crack growth;sub surface;DIC technology;growth rate
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发布时间：2023-02-04 - 摘要：Pitch gear ring is one of the core component of wind turbine, mostly processed and manufactured by 42CrMo. The hardened layer of gear teeth are prone to be worn after running a long time, which need to be repaired on-line in the tower. In order to solve the problem, the repair process of 42CrMo pitch gear was tested by using gas tungsten arc weld (GTAW) with H27. Before the welding, ultra-audio frequency induction heating equipment was used for heating. And the treatment of temper bead welding (TBW) for slow cooling was used after the welding. Some experiments including effective hardness layer, wear resistance, metallographic structure and simulation run mode were carried out to assess the reliability of the repair. The results show that this repair process greatly reduces the probability of cracks, pores and other defects after 42CrMo welding, which can be applied to the on-line operation and maintenance of wind turbines. In this way, the cost is decreased and good economic benefits are achieved.关键词：wind turbine;pitch gear ring;on-line repair;reliability assessment;GTAW
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发布时间：2023-02-04 - 摘要：Titanium alloy blades usually bear different degrees of fretting wear in actual working conditions. In order to improve the wear resistance of titanium alloy blades, it is necessary to prepare wear-resistant and impact resistant wear-resistant layers on them. Studying the fretting wear performance of wear-resistant layers plays an important role in the working reliability and service life of blades. WC wear-resistant layer was brazed on TC4 substrate by induction brazing using titanium based brazing filler metal. The effects of different loads, displacements and frequency vibrations on fretting wear properties of wear-resistant layer were studied. The results show that under the condition of small load, the change of displacement and frequency has little effect on the average friction coefficient of the wear-resistant layer; under the condition of medium and high load, the change of frequency has little influence on the average friction coefficient of the wear-resistant layer while the change of displacement has a great influence on it. Under the condition of small displacement, the average friction coefficient of wear-resistant layer decreases with the increase of load, while under the condition of medium and large displacement, the change of load has little effect on the average friction coefficient of wear-resistant layer. The change of displacement amplitude has a significant influence on the wear volume of the wear-resistant layer. The wear mechanisms of the wear-resistant layer are abrasive wear and adhesive wear.关键词：WC wear-resistant layer;fretting wear;friction coefficient;wear volume;surface morphology
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发布时间：2023-02-04 - 摘要：Tantalum is widely used in electronics and chemical industries because of its excellent properties such as high density, high melting point and corrosion resistance. However, Ta is not only scarce and unevenly distributed in the earth's crust, but also more difficult to extract, which directly leads to the expensive price of Ta and huge application costs. Therefore, the connection with other metals to form composite components has become a hot spot for research. 304L stainless steel has become one of the common structural materials due to its good heat resistance, corrosion resistance, weldability, thermal stability and forming properties. This research first of all, Ta and 304L stainless steel weldability analysis, followed by a review of welding methods for Ta and stainless steel in recent years, comparing the advantages and disadvantages of different welding methods, and finally the Ta and stainless steel welding methods put forward the prospect.关键词：tantalum;stainless steel;heterogeneous material;welding technology;research status
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发布时间：2023-02-04 - 摘要：To explore the applicability of high entropy alloys as structural materials, the CoCrFeMnNi high-entropy alloys sheet samples with the thickness of 2 mm were welded by laser beam welding and gas tungsten arc welding, respectively. And the microstructure observation, hardness test and tensile property test were carried out on the welded joints.. The results show that the grain morphology transformation of the weld zone by laser beam welding and gas tungsten arc welding is basically the same in the solidification process, which is composed of cellular dendrites perpendicular to the fusion line and equiaxed crystals in the middle of the weld. But the grain of laser beam welding specimens is finer. The hardness of the weld obtained by the two welding processes is both higher, but the strength and ductility of the welded joint are slightly lower than that of the base metal. This study has certain reference significance for the application of high entropy alloys in the future.关键词：high-entropy alloys;laser beam welding;gas tungsten arc welding;microstructure;mechanical property
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发布时间：2023-02-04 - 摘要：According to the wear failure requirements of electric winch roller, the multi-layer and multi-pass laser cladding was used to fill the groove symmetrically, the microstructure, hardness, tensile and impact properties of joint made of the same material as roller by powder laser cladding were studied. The results of 30CrMnSiA laser cladding test show that the joint hardening phenomenon occurs in the heat affected zone, the maximum hardness reaches 450 HV0.5, the hardness of cla-dding zone is about 380 HV0.5, and the average tensile strength and average yield strength of cladding joint are 1 176 MPa and 1 049 MPa respectively, both of them are 104% of the base metal, and the tensile fracture occurs in the base metal. The impact toughness of 30CrMnSiA additive-30CrMnSiA forging (115.8 J/mm2) far exceeds the standard value (49 J/mm2) of forging and meets the performance requirements of roller material. The repair performance can meet the use requirements.关键词：laser cladding;30CrMnSiA alloy steel;repair;microstructure;mechanical properties
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发布时间：2023-02-04 - 摘要：In this paper，aiming at the problems of poor metal Inert gas Welding （MIG） weld forming and low joint coefficient of 7A52 medium-thickness plate , taking 7A52 aluminum alloy as the research object, semi-automatic MIG was used to conduct weld bead forming tests on ER5356 wire under different welding parameters. After the test, weld bead forming characteristics such as weld penetration, weld width, weld bead remaining-height, weld wetting angle under different welding processing parameters were measured. Optimize the optimal processing parameters. The optimized process parameters was used to weld the deposited metal and butting joint. After the welding, through the testing methods include X-ray detection, mechanical property test, microstructure observation, the performance of welding butting joint using ER5356 wire was studied. The results show that the average tensile strength for butting joint is 302.5 MPa and the joint coefficient is 0.74 respectively. The fracture position of the butting joint located in the weld zone. The bending performance of the butting joint is good, without cracks and other defects. The hardness value of the weld zone is the lowest, indicating that the weld zone is the weak zone of the welding joint, which is consistent with the fracture position of the tensile test specimen. The mechanical properties and welding properties of butting joints and deposited metals are good.关键词：processing parameters;joint coefficient;welding bead forming;tensile strength
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发布时间：2023-02-04 - 摘要：Continuous drive friction welding method was used for typical embedded steel bars in nuclear power plant, and the macroscopic morphology, microstructure and mechanical properties were analyzed. The results show that the upper and lower flying edges of the T-shaped friction welding joint are asymmetrically distributed due to the uneven heat dissipation during welding process, and the metal of the reinforcement side has obvious strain deformation during welding process. Through high magnification metallographic observation and scanning analysis, it is confirmed that the "black line" at the weld interface is normal metal organization rather than welding defect. Dynamic recrystallization occurrs in the weld nugget zone, which is fine ferrite and bainite, and carbides in the microstructure of the heat affected zone begin to precipitate after heating. The upset forging quantity can be used to measure the tensile quality of the joint. When the upset forging quantity of reinforcement exceeds a certain value, the tensile qualification rate of the joint can reach 100%. Through small-size tensile and hardness tests, it is found that the weakest area of friction weld joint is steel base metal, and the index affecting the fracture position of T-joint is seaming ratio, which is related to welding parameters (upset forging quantity) and pre-welding cleaning.关键词：embedded steel bars;T-joint;continuous drive friction welding;flying edges;microstructure
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发布时间：2023-02-04
Welding Technology
- 摘要：The header is an important part of the power station boiler system. In order to solve the problems of numerous materials and different sizes of the header, 3D vision technology is adopted to realize the automatic welding of the header by positioning the bead and combining the size parameters of the pipe socket groove, so as to improve the efficiency and welding quality of the boiler header pipe socket welding test. Based on this, an intelligent welding test workstation is developed for the header pipe seat, and a process expert software is developed including 3D graphical interface display, process intelligent planning and other functional modules, and the welding of the header dense pipe joint is completed. The practical application shows that the welding workstation has a high degree of intelligence and the welding quality meets the process requirements.关键词：boiler header;tube base;Robot welding;offline programming technology software
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发布时间：2023-02-04 - 摘要：The arc behavior have a significant effect on the forming of the weld. In this paper, the arc shape and arc pressure between 2 Hz to 15 000 Hz were studied with the high-speed camera system and water-cooled copper plate force test system. The results indicated that there were significant differences in the effect of frequency on the arc in different frequency ranges. (1)As the frequency increased from 2 Hz to 50 Hz, the arc force was stable at 80 Pa, and the width of the arc was stable at 8.15 mm; (2) As the frequency increased from 50 Hz to 5 000 Hz, the arc force had a positive linear relationship with the natural logarithm of the frequency, and the arc width had a negative linear relationship with the natural logarithm of the frequency; (3) As the frequency increased from 5 000 Hz to 15 000 Hz, the arc pressure was basically stable at 155 Pa, and the arc width was stable at 5.70 mm. In engineering applications, the arc force and arc width can be controlled by adjusting the frequency in the range of 50 Hz to 5 000 Hz.关键词：high-frequency pulse TIG welding;high-speed camera system;pulsed frequency;arc shape;arc pressure
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发布时间：2023-02-04
Welding Equipment
- 摘要：ENiCrMo-6 electrode is mainly used for welding LNG plant made by 9%Ni steel on land and ship. Its long-term dependence on import leads to high production cost and limited technology development, so it's necessary to realize the localization. In this paper, the development of domestic ENiCrMo-6 electrode is introduced. The pure nickel core and CaO-CaF2-TiO2 slag system are selected as the base slag system of the electrode coating to make the electrode meet the requirements of engineering application with suitable for alternating welding, all position welding and excellent manufacturability. The manufacturability, microstructure and mechanical properties of the developed ENiCrMo-6 electrode are studied. The results show that its technology level is equivalent to that of imported electrode, and the strength, plasticity and toughness of the deposited metal and the welded joint are excellent and can meet the design and construction requirements of the 9%Ni steel LNG plant. The impact absorbed energy at -196 ℃ is far higher than the technical requirements, which can be applied to practical projects and solve the situation that this electrode depends on imports for a long time.关键词：9%Ni steel;ENiCrMo-6 electrode;deposited metal;mechanical properties;all position
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发布时间：2023-02-04
Welding Material
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