最新刊期
期 2 ， 2022
- 摘要：Hybrid laser-MIG welding of 8 mm thick Q345 steel plates was carried out using different laser-to-arc heat input ratio (QRLA). The effects of QRLA on the cross-sectional macro-morphology and the microstructures in the hybrid welded joint were investigated. Development of temperature field distribution in the welding process and residual stress distribution in the welded joint under different QRLA were also analyzed. The results show that the weld bead width decreases while peak temperature in the welding process increases with elevated QRLA. The microstructure of coarse grained HAZ is mostly martensite due to the high welding speed, and the amount of martensite increases with elevated QRLA. The stress levels of equivalent residual stress, longitudinal residual stress, transverse residual stress and through-thickness stress all reduce moderately as laser power increases with QRLA in the range of 0.72~1.0. However, the stress levels of the four stresses increases slightly as laser power increases with QRLA in the range of 1.0~1.18.关键词：hybrid laser arc welding;laser-to-arc heat input ratio;microstructure;temperature field;residual stress filed
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发布时间：2022-05-06 - 摘要：To meet the requirements of weight and cost reduction at the same time, the titanium/aluminum composite structure has a good application prospect, but because of the great physical and chemical performance difference between titanium alloy and aluminum alloy, adopts the traditional welding method is difficult to form a reliable connection, and friction stir spot welding technology has great advantage in connecting dissimilar metals, current research on titanium/aluminium alloy friction stir spot welding is very little. Spot welding experiments were carried out on 2 mm thick TC4 titanium alloy and 6061 aluminum alloy by refill friction stir spot welding. Based on the response surface method, the second-order response model of welding process parameters and tensile-shear fracture load was established, and the effect of process parameters on the joint was studied. The influence of process parameters on the tensile-shear fracture load of joints was studied, and the tensile-shear fracture load of spot joints was predicted through optimization of process parameters. The experimental results show that the response model is very accurate, and the average error between the predicted value and the experimental value is about 2.41%. The best welding process parameters obtained are the welding tool speed 1 052.9 r/min, the plunge depth 2.19 mm, and the welding time 3.01s .关键词：refill friction stir spot welding;dissimilar metal;response surface method;process parameters optimization
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发布时间：2022-05-06 - 摘要：In this paper, an effective prediction method is proposed to predict the FSW weld deformation for the large-size structures using partition mapping of inherent strain under the local-global mapping frame. The contact state between fixtures and weldment is considered by contact constraints in the thermoelastic-plastic simulation of local structure. The detailed partition scheme is determined by the distribution characteristics of residual plastic strain on the basis of the prediction results of local structure, and the partition scheme is implemented to the global structure for the partition mapping of inherent strain. For the welding of small-size 6061-T6 aluminum alloy sheet, the weld deformations are predicted under the contact and fixed constraint states by thermoelastic-plastic simulation, and these results are analyzed and compared with the experimental data. The results show that the prediction results considering contact constraints are closer to the experimental data and can capture actual asymmetric deformation, thus it is necessary that the contact constraints between fixtures and weldment are modeled in the local structure. The proposed method is applied to the welding of large-size 6061-T6 aluminum alloy plates, and the prediction results are compared with those obtained by thermoelastic-plastic method considering the contact constraints between fixtures and weldment. The results show that the proposed method can effectively predict the welding FSW deformation of large-size plates.关键词：friction stir welding;inherent strain;partition mapping;contact constraint;welding deformation
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发布时间：2022-05-06 - 摘要：Laser scanning welding is a highly efficient new laser welding technology, with unique laser beam positioning, wide scanning range, high flexibility, long working distance and other advantages, compared to traditional laser welding, its multi-point welding characteristics can largely enhance the welding efficiency. Overview of the working principle and classification of laser scanning welding technology, focusing on the laser scanning welding characteristics and research status of several common alloys such as aluminum, magnesium, titanium, copper and copper alloys, and aluminum-steel. The stirring effect of the scanning laser beam on the molten pool can effectively improve the defects in the aluminum alloy weld, the microstructure of small holes and the force changes in the welding process is a breakthrough point for future research on scanning laser welding of aluminum alloys. Laser scanning welding can significantly improve the quality of weld forming of magnesium alloys, optimization, control, adjustment of different laser scanning welding process parameters operating window and the development of relevant process specifications, as well as how to control the formation of the intermediate phase and its content is the focus of research on scanning welding magnesium alloys need to break through. An important difficulty in laser scanning welding of titanium alloys is the instability of the keyhole during the welding process, which largely affects the weld formation. The stability of the keyhole depends on its force state, so the first step is to control the movement of the laser beam (such as scanning trajectory, scanning amplitude, scanning frequency, etc.). The low absorption and high thermal conductivity of copper and copper alloys require higher laser power for scanning welding copper. The required equipment, high cost and possible inclusions limit the diffusion of the process, and more research is still needed to understand the mechanism of scanning welding of copper alloys and to overcome the problems of low process stability, large spatter and high porosity during welding. Laser scanning welding of other heterogeneous alloys such as magnesium - aluminum, aluminum - copper, magnesium - titanium, titanium - aluminum alloy will also be the focus of future laser scanning welding research. Finally, for the shortcomings in the existing research proposed laser scanning welding challenges and future development trends.关键词：laser scanning welding;scanning trajectory;scanning frequency;welding spatter;porosity
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发布时间：2022-05-06 - 摘要：With the rapid development of modern intelligent manufacturing, Robots and other automation equipment are widely used in metal additive manufacturing, green remanufacturing, welding and other fields. Visual sensing is a key link in robot intelligent manufacturing. This article addresses the above requirements, Designed and calibrated a set of vision sensors based on laser structured light, and independently developed a machine vision system for the robotic laser additive manufacturing process. This method realizes the internal and external parameter calibration of the camera through the Matlab camera calibration toolkit, uses Labview programming to extract the pixel coordinates, fits the laser plane equation in the camera coordinate system according to the least square method, and realizes the conversion from pixel coordinates to laser plane coordinates. Finally, the "Eye-in-Hand" system of the vision sensor and the robot realizes hand-eye calibration, and obtains the conversion of pixel coordinates to the three-dimensional base coordinates of the robot. Experiments show that the developed vision sensor has high positioning accuracy.关键词：additive manufacturing;machine vision;line structured light;Eye-in-Hand calibration
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发布时间：2022-05-06 - 摘要：The electrode arc stability is the main factor that affects its manufacturability. In order to avoid the impact of SMAW on the evaluation of arc stability due to differences in welder skills, and it is difficult to make a true and objective evaluation of the electrode process stability. Based on the electrode welding robot, the welding electrical parameters of the E308L-16 electrode is tested through the arc analyzer, and combining the high-speed camera and other synchronous detection platforms, the characteristic information related to the metal transfer shape is extracted, and the arc stability of E308L-16 electrode is studied. The results show that by controlling the feedback control arc voltage of the welding robot, the E308L-16 electrode can achieve two different transition modes: short circuiting transfer and flux-wall guided transfer. At19 V, the main form of metal transfer is short circuiting transfer of large particles. During the welding process, the sleeve depth is small and the welding current is large. At 21 V or above, the main form of metal transfer is flux-wall guided transfer. Compared with welding current, feedback control arc voltage is the dominant factor to determine the metal transfer form. The arc stability is better when the medium and long arc operation is adopted in the test.关键词：E308L-16 electrode;process performance;arc stability;metal transfer;electrode welding robot
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发布时间：2022-05-06
Important Issuse
- 摘要：Numerical simulation analysis has been widely used in temperature and material flow study relate to FSW process. In this paper, three numerical simulation analysis methods—— Computational Fluid Dynamics method, Arbitrary Lagrangian Eulerian method, Couple Eulerian Lagrangian method——widely used in recent years is reviewed. The three methods have their own characteristics. The CFD method was adopted earlier, but this method ignores the hardening behavior of the base metal and the peeling behavior . ALE method avoid excessive distortion of the mesh during solution, but are still essentially Lagrangian meshes. The CEL method using Euler analysis is more consistent with the prediction of base metal flow, but the calculation cost is relatively high.The researcher should select the model according to the focus。Some issues in FSW study with numerical simulation method are pointed out. Finally, the development trends of numerical simulation in FSW study were also predicted.关键词：friction stir welding;numerical simulation;Computational Fluid Dynamics;Lagrangian formulation;Eulerian formulation
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发布时间：2022-05-06 - 摘要：Weld OVERLAY technology is to add corrosion-resistant materials on the basis of the original design wall thickness to change the stress state of the original inner surface, thereby inhibiting the generation or expansion of cracks. It can be used for in-service maintenance or preventive maintenance. The technology is widely used abroad, and has some application cases of CRDM repairing in China. However, the lack of systematic and complete technical research restricts the popularization of the technology. This article systematically sorts out the classification and standard evolution of Weld OVERLAY technology, compares and analyzes the application scope and characteristics by ASME standards and literature studying. This article introduces the Non mandatory Appendix Q of ASME BPVC.XI-2005, Weld Overlay Repair of Classes 1, 2, and 3 Austenitic Stainless Steel Piping Weldments, summarizes the evolution process, analyzes the key standard clauses, and provides technical support for the promotion of this technology and the formulation of standards.关键词：nuclear power plant;weld OVERLAY;ASME-Ⅺ;standard study
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发布时间：2022-05-06 -
Effect of Heat Treatment on Microstructure and Properties of SUS304 Stainless Steel TIG Welded Joint
摘要：After the impact and vibration test of rail transit vehicles, some equipment 304 stainless steel welded parts appeared fracture failure. In order to improve the mechanical properties of 304 stainless steel after welding, in this paper, by means of metallographic microscope, scanning electron microscope, hardness and tensile test, the effects of medium and low temperature heat treatment process on the microstructure and mechanical properties of 2 mm thick 304 stainless steel plate TIG welded joints were studied. It is found that the microstructure of the untreated weld is composed of γ-austenite and δ-ferrite after heat treatment at 400 ℃ for 30 min, and δ-ferrite mainly distributes in the Cr-rich zone and appears as a worm, and the content of δ-ferrite decreases to some extent after heat treatment. After heat treatment, the hardness of welded joints is lower than that of untreated ones. The yield strength of welded joints after welding is 189.5 MPa, and the strain is 64.5%. After heat treatment, the yield strength is 221 MPa, the strain is 72.7%, and the yield strength is increased by 16.6%, reaching the yield strength of base metal. The fracture surface shows ductile fracture characteristics and no significant welding defects, mainly showing deep dimples, and the dimples are distributed with second phase particles, which hinder the slip and cause stress concentration and produce micro-pits, which become one of the main craters of cracks.关键词：SUS304;TIG welding;low temperature heat treatment;microstructure;mechanical properties- 58
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发布时间：2022-05-06 - 摘要：Mainly introduced the Sanya stadium project in the space spherical bearing complex node production process, before there have been many people from the design and on-site installation to interpret, but the introduction of the factory to make spherical bearing nodes is relatively insufficient, this article through the joint bearing node production process supplement, the application of spherical bearing nodes in the field of steel structure, from the design, production, installation of three steps of organic combination, to help related practitioners smooth construction. By analyzing the production process of spherical bearing nodes, starting from the three aspects of assembly, welding and inspection, we will solve the difficult problems in the production of nodes. Through the welding process evaluation, the welding parameters and groove angle of the oblique T-shape small angle position are determined, so that the quality of the weld of this type is guaranteed; the plug welding and groove welding measures are used to solve the deformation problem after the hot-dip galvanizing of the bearing ear plate reinforcement patch; the precision of the joint bearing node is effectively guaranteed by adding support and pin shaft testing inspection process; the production idea of the joint bearing node plate is mainly put forward, and the rest of the components are secondary, which is convenient for production and inspection. Mainly by controlling the production process of complex nodes of spherical bearings, the assembly accuracy and welding deformation of complex nodes of space spherical bearings are controlled, which ensures the quality of node production, improves the installation accuracy of plates, and obtains qualified quality installation accuracy, which provides reference experience for other similar projects.关键词：process measures;welding procedure specifications;deformation control;quality acceptance
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发布时间：2022-05-06 - 摘要：Based on the Alibaba Cloud Internet of Things platform and MQTT (Message Queue Telemetry Transmission) communication protocol technology, a set of resistance spot welding data with STM32F103VET6 microcontroller as the main control core and Alibaba Cloud IoT Studio (Internet of Things Application Development) webpage as the monitoring interface is designed The monitoring system realizes online monitoring of resistance spot welding process and remote real-time display of welding current and electrode pressure curve. The design of the monitoring system is divided into two parts: hardware and software. The main content includes sensors, data signal processing modules, main control modules, wireless transmission networks, and Alibaba Cloud Internet of Things platform. The actual measurement results show that the system can accurately realize remote real-time monitoring of welding data, with stable performance, and the data transmission packet loss rate is less than 1%, which provides technical support for intelligent welding under the Internet of Things.关键词：resistance spot welding;real-time monitoring;internet of things;MQTT
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发布时间：2022-05-06 - 摘要：Pressure resistance welding and TIG welding were used to weld the welding joint between the uncoated/Cr-coated zirconium alloy cladding tube and the end plug. The microstructure and corrosion resistance of the welded joint were evaluated. Testing corrosion property of welding specimen using high temperature and high pressure water. The surface morphology of the welded joint specimen after etching and the longitudinal section morphology of Cr coating cladding tube welded joint specimen were studied by means of SEM. The composition of the interface was identified by EDS. The longitudinal section microstructure of welded joint specimen was observed by using microscope. Results prove that when the zirconium alloy cladding tube with Cr coating was welded by TIG welding method, the alloying phenomenon of Cr and Zr metals appeared in the welded joint, and many pores and cracks appeared in the joint. However, the presence of Cr coating did not have a negative effect on the welded joints when using pressure resistance welding method, and the welded joints maintained good welding performance and had a good resistance to high temperature water corrosion.关键词：pressure resistance welding;tungsten inert gas protection welding;Cr-coated cladding tube;metallographic structure
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发布时间：2022-05-06 - 摘要：According to the lap joint structure of the upper and lower sidewall panels of a stainless steel vehicle, the spot welding technology based on conductive sealant is adopted to realize the structural connection, and ensure the vehicle sealing. To verify the reliability of the procedure, the three types of lapping structure were carried out welding tests respectively by resistance spot welding based on conductive sealant. Then, tests on spot welded joint were carried out for the three types of lapping structure according to the product standard after welding,and the visual testing, shear testing, shear tensile testing, metallographic examination are included.Moreover, the test results of the dent size on the spot welded joint surface,nugget diameter,tensile shear force,cracks inside nugget,shrinkage hole were analyzed. The test results show that performance of resistance spot welded joint can meet the demands for the structure,and the resistance spot welding technology based on conductive sealant applied in the stainless steel carbody is feasible; and the spot welding parameters are verified reasonable,which can provide the data support for the resistance spot welding technology based on conductive sealant applied in the stainless steel carbody.关键词：resistance spot welding;conductive sealant;stainless steel carbody
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发布时间：2022-05-06 - 摘要：Steel catenary riser (SCR) is the main component of floating platform. It is extremely prone to fatigue damage under service conditions due to the influence of various environmental factors such as ocean waves, tides and typhoons. In order to solve the problem about fatigue failure of steel catenary riser（SCR）affected by cyclic load in deep water environment, full-automatic GMAW welding process and mechanical tests were developed by using cold metal transition（CMT）for root pass and pulse mode for fill and cap pass for SCR S-lay. The test results of mechanical properties meet the requirements of SCR welding specification. The fatigue properties of all test welds meet or exceed the 95% level of confidence based on BS7608(1993) D mean curve as OD and E mean curve as ID.Because cold metal transition for root pass without backing is the technology of single side welding and double side forming, it has the advantages of smaller welding heat input and no spatter, ensuring the smooth transition between weld root forming and base metal, so as to reduce stress concentration and improve the fatigue resistance of SCR welds.关键词：steel catenary riser (SCR);GMAW;cold metal transition (CMT);weld properties
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发布时间：2022-05-06 - 摘要：When austenitic stainless steel works in corrosive medium, it is easy to generate stress corrosion crack if residual stress exists in welded joint, so stress relief treatment is needed. The influence of different stress relieving methods and their combinations on residual stress of 304L stainless steel welded joint are studied experimentally. The results show that both the simple stress relief annealing method and the mechanical vibration aging treatment can effectively relieve the peak stress of the weld and weld toe, the stress peak drops are equivalent, and the stress relief annealing method relieves stress more uniformly. Compared with the simple vibration aging treatment, the decrease of stress peak of vibration aging + stress relief annealing method are not obvious, compared with the vibration aging after the first annealing, the stress peak of the weld reduces slightly. Compared with the simple stress relief annealing method, the stress relief annealing + vibration aging method results in a significant decrease in the stress peak.关键词：stress relief annealing;304L stainless steel;residual stress;vibration aging
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发布时间：2022-05-06 - 摘要：According to the national standard GB/T1591-2018 "Low-alloy High-strength Steel" and the examples of steel structure construction, this paper analyzes the essential difference between Q355 and Q345 based upon the chemical composition of the steel. It further expounds upon the characteristics of Q355 low carbon, micro-alloy, pure purification and fine grain with the concept of carbon equivalent, which illustrates the objective fact that Q355 is a typically new type of fine grain steel. Based on the analysis, this paper only considers that the strength and grain refinement of the welded joints of high-strength steel are directly related to the micro-alloyed elements of steel. The welding thermal cycle will cause the loss of alloying elements. Therefore, the loss of alloying elements will increase after one more thermal cycle, which is unfavorable to the quality of welded joint and will inevitably reduce the comprehensive properties of the welded joint. This is the key to welding Q355 steel.关键词：high-strength steel;chemical composition;alloy series;carbon equivalent;welding technique
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发布时间：2022-05-06
Welding Technology
- 摘要："Welding Structure Manufacturing" is a required course for the welding direction of material forming and control engineering major. Its main content are the technology and equipment of typical welding structure products in the manufacturing process. It is the core course of "product manufacturing" in the "product R&D chain" oriented course system of this major. In this paper, the manufacturing process of welding structures is taken as the carrier. According to the general manufacturing process of typical welding structure (mainly: spherical pressure vessel), the typical work tasks of welding structure manufacturing are analyzed and sorted out, learning situation is created, the teaching content is organized in the way of project-driven task, and the teaching system of “welding structure manufacturing” course is reconstructed in order to promote the reform of teaching mode and improve the quality of teaching.关键词：teaching model;project-driven;teaching system reconstruction;typical welding structure
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发布时间：2022-05-06
Welding Education
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