MAIN TOPICS，ABSTRACTS & KEY WORDS

Microstructuresandmechanicalpropertiesofthecoarse-grainedregioninweldedjointofEH40steelbyswingarcnarrowgapwelding

Fu Kuijun1, Ni Zhida2, Lin Sanbao2, Cai Xiaoyu2, Hu Fengya1

(1.Ansteel Group Corporation, State Key Laboratory of Metal Material for Marine Equipment and Application, Anshan 114001, Liaoning, China; 2. Harbin Institute of Technology, State Key Laboratory of Advanced Welding and Joining, Harbin 150001, China).p1-5，37

AbstractTwo welded joints of EH40 micro-alloyed steel were produced by narrow gap GMA welding with two welding parameters. The effect of filling thickness on the distribution of coarse-grained subregions in HAZ was analyzed and the mechanical properties of welded joints were studied. The research result showed that swing arc narrow gap MAG was suitable for narrow gap welding of microalloyed steel and good formation of weld was obtained without the defect, such as lack of fusion. Distribution of coarse-grained subregions was a periodic arrangement of UACG-HAZ, SCRCG-HAZ, IRCG-HAZ and CG-HAZ with a large filling thickness, while distribution of coarse-grained subregions was mainly a periodic arrangement of SCRCGHAZ and IRCGHAZ with a small filling thickness. All tensile specimens were broken at the base material, and the impact energy at room temperature could meet the requirements. The swing arc narrow gap MAG process could obtain MAG welded joint of EH40 steel with good mechanical properties.

Keywords:swingarc,narrowgapwelding,microstructures,fillingthickness

Highfrequencymicro-hammersystemandpreliminaryphysicalsimulationinarcadditivemanufacturingprocess

Hu Chaoxiong, Xiao Jun, Chen Shujun

(Beijing University of Technology, Engineering Research Centerof Advanced Manufacturing Technology for Automotive Components, Ministry of Education, Beijing 100124, China).p6-9

AbstractThe reduction of mechanical properties caused by internal defects, coarse grains and other factors was one of the main challenges in arc welding and additive manufacturing. Making the WAAM process supplemented by synchronized micro-area hammering and impacting would be a feasible way to solve the problem. Therefore, a micro-hammering technology based on compact and small linear actuators was proposed in the paper, which had advantages of small size, high displacement resolution, fast response speed, large output force and high frequency. The effect of synchronous hammering on the high-temperature solidification area was verified by the fixed-point welding and delayed hammering simulation, and the effect of the hammering oscillating molten pool was verified by the fixed-point welding and the hammering simulation nearby the welding point. The research result showed that after the hammering was added, grains were all refined to a certain extent, and it could be observed that coarse columnar crystals were transformed into fine equiaxed crystals. Both the hammering frequency and the hammering force had a great influence on the hammering effect.

Keywords:linearactuator,wirearcadditivemanufacture,hybridhammering,grainrefining

Processparameters,microstructuresandmechanicalpropertiesofKMNsteelbylaserwelding

Deng Dewei1,2, Lü Jie1, Ma Yushan3, Zhang Yong2, Huang Zhiye2, Tian Xin4

(1. Dalian University of Technology, Dalian 116024, Liaoning, China; 2. Shenyang Blower Works Group Corporation, Shenyang 110869, China; 3. Wuzhong Instrument Co., Ltd., Wuzhong 751100, Ningxia, China; 4. Sany Heavy Machinery Co., Ltd., Shanghai 201413, China).p10-16

AbstractThe effect of different welding parameters on the weld of KMN steel plate were studied through the orthogonal test of autogenous laser welding. The results showed that the laser spot diameter had the dominant effect on the weld penetration degree and the weld surface quality in the selected parameter range. The preliminary optimized welding parameters through orthogonal test were spot diameter of 0.8 mm, welding speed of 24 mm/s and laser power of 4.2 kW. Two sets of welding parameters with different energy density were selected to investigate the change of macroscopic morphology, microstructure and microhardness with welding parameters. It was found that the higher laser energy density gave rise to the deeper and wider weld, the coarser lath martensite and the lower hardness in the corresponding regions. Due to the differences between single-plate autogenous laser welding and butt autogenous laser welding, the practical welding parameters for butt-weld should be obtained by an appropriate adjustment. Laser butt welding was carried out with the adjusted welding parameters, and the mechanical properties between the obtained joint and TIG welded joint were compared. It was found that the laser welded joint had a higher tensile strength and elongation, but a lower impact toughness.

Keywords:laserwelding,KMNsteel,orthogonaltest,energydensity,mechanicalproperties

Efficiencyandjointqualityanalysisbetweenmulti-layermulti-passweldingandmulti-layerweavebeadweldingforInvarsteelthickplate

Hao Ju1, Li Yuyang1, Zhu Yongmiao1, Zhang Jiahao2, Zhan Xiaohong2

(1.Xi’an Aircraft Industrial Company Limited, Xi’an 710089, China; 2. Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China).p17-23

AbstractButt welding tests were carried out on Invar steel with thickness of 19 mm by multi-layer multi-pass welding and multi-layer weave bead welding, and power consumption and efficiency of these two processes were calculated and analyzed. By observing and measuring the microstructure and microhardness of Invar steel weldment, the quality of the welded joint with the two welding methods was compared. The results indicated that when connecting thick plate Invar steel, multi-layer weave bead welding had less welding time, higher efficiency, and lower power consumption due to its less welding passes than that of multi-layer and multi-pass welding. The interlayer remelting zone in multi-layer weave bead welding was well fused, while obvious incomplete fusion defects were observed in multi-layer multi-pass welded joints. The width of heat affected zone of multi-layer weave bead welding was much smaller than that of multi-layer multi-pass welding. The average grain size and microhardness of multi-layer weave bead welding were slightly larger than that of multi-layer multi-pass welding.

Keywords:Invarsteel,multi-layermulti-passwelding,weavebeadwelding,weldingefficiency,jointquality

Ultrasonicwelding-rivetinghybridjoiningprocessof30%carbonfiberreinforcedPA6compositematerials

Zhang Guotao1, Wang Yao1, Yang Ruibin2, Liu Zhongxia1

(1.Zhengzhou University, Key Laboratory of Materials Physics, Ministry of Education, Zhengzhou 450052, China; 2. Zhengzhou University of Technology, Zhengzhou 450015, China).p24-30

AbstractIn this study, a specially designed rivet with double flange structure was used to fabricate ultrasonic welding-riveting hybrid joints of 30% carbon fiber reinforced PA6 composite materials. The macro appearance, cross-section, failure mode, shear strength and peel strength of hybrid joints were investigated, and improvement mechanism of mechanical properties of hybrid joints was analyzed. The results showed that the hybrid joining process of ultrasonic welding-riveting consisted of five stages, coulomb friction phase, upper workpieces riveting phase, lower workpieces riveting phase, melting phase and solidification phase of materials on the faying surface. The double-flange rivets avoided the formation of flash in riveting site, resulted in the excellent mechanical interlocked of flanges of the rivets with the workpieces and the formation of the weld around the rivets. Therefore, the shear strength, peel strength and energy absorption ability of hybrid joints were improved. Compared with shear strength, ultrasonic welding-riveting process improved the peel strength more significantly. Compared with the ultrasonic welded joints, the ultrasonic welded-riveted hybrid joints that were produced with optimum parameters increased the shear strength, peel strength by 29.9% and 39.2%, respectively. The improvement of shear strength and peel strength of the hybrid joints attributed to the combination effect of the mechanical interlock of the rivet flange with the workpieces and the weld around the rivets.

Keywords:carbonfiberreinforcedPA6compositematerials,ultrasonicwelding-rivetinghybridjoining,jointstructure,shearstrength,peelstrength

Ultrasonicspotweldingtechniqueanditsapplicationinthelithium-ionbatterymanufacturing

Ni Zenglei1, Yang Jiajia1, Li Shuai1, Wang Xingxing1, Ye Fuxing2

(1. North China University of Water Resources and Electric Power, Zhengzhou 450045, China; 2. Tianjin University, Tianjin 300072, China).p31-37

AbstractIn this paper, advantages of ultrasonic spot welding were introduced, in comparison with that of resistance spot welding and laser welding. And its welding equipment, welding mechanism and investigation status in the lithium-ion battery manufacturing were demonstrated. Meanwhile, the key effects on the macroscopic appearance, microstructure and mechanical properties were systematically illustrated. To obtain the sound robustness and good quality of ultrasonic spot welded joint, a real-time controller and a new tool geometry design for the sonotrode were effective methods, but numerous unsolved issues existed. In addition, some perceptions on how to further enhance the process robustness of ultrasonic spot welded joint were proposed in this paper.

Keywords:ultrasonicspotwelding,weldinginterface,microstructure,mechanicalproperties,robustness

Researchprogressandapplicationofmagneticallyimpelledarcbuttweldingtechnologyintubeswelding

Liu Hongbing1, Peng Mingjian1, Liu Xu2, Yang Jin1, Xuan Yang1

(1. Shanghai University of Engineering Science, Shanghai 201620, China; 2. Yangzhou Dongsheng Automotive Co. Ltd., Yangzhou 211403, Jiangsu, China).p38-42

AbstractThe technological characteristics and principle of magnetically impelled arc butt welding were introduced. The research progress and application of magnetically impelled arc butt welding were reviewed on welding procedure test, welding performance test, welding quality evaluation and welding process simulation. The research result showed that there are many welding parameters in magnetically impelled arc butt welding, and the parameters affected each other. Different material thickness, solid or hollow would influence magnetic flux density, change arc velocity, and then affect welding quality. The magnetic flux density had a great influence on magnetically impelled arc butt welding, and it was only suitable for welding of magnetic materials, but hardly used in non-magnetic materials. Finally, the future research and development direction of magnetically impelled arc butt welding were prospected.

Keywords:magneticallyimpelledarcbuttwelding,tubes,magneticfield,researchprogress,application

Weldingparametersmeasurementandanalysisofrotaryaxisultrasonicwelding

Li Ping, Chen Qiyu, Li Xiaomin, Huang Dong, Wang Yu

(Guangdong Institute of Intelligent Manufacturing, Guangzhou 510651, China).p43-47

AbstractThrough methods of orthogonal test, welding parameters of rotary axis ultrasonic welding were studied. The test value of each welding parameter was measured by instruments, and the bonding force of non-woven fabric welding pattern was taken as the welding quality index. By means of range method and variance method, the influence of welding parameters on welding quality was analyzed and the optimal welding parameters were obtained. The results indicated that the welding amplitude had the most significant effect on the bonding quality of welding patterns in non-woven fabric, and the optimal welding parameters were 31.85 r/min of rotary axis speed, 0.3 MPa of welding pressure and 48 μm of welding amplitude.

Keywords:medicalheatingblanket,ppnon-wovenfabric,ultrasonicwelding,orthogonaltest

Effectoflasercleaningonsurfaceandweldingqualityof30Cr3ultra-highstrengthsteel

Xia Ling, Liu Jingtao, Pan Lihua, Shan Xiufeng

(Shanghai Space Propulsion Technology Research Institute, Shanghai 201108, China).p48-52

AbstractIn order to research the effect of laser cleaning pretreatment on the welding quality of 30Cr3 ultra-high strength steel, surface morphology, element composition and matrix microstructure were observed by scanning electron microscope before and after cleaning. The results showed that the proper laser cleaning process could effectively remove the oxide layer on the surface of 30Cr3 ultra-high strength steel, which made the surface smoother without damaging the base material. The test samples after laser cleaning were welded by electron beam. After welding, it was observed that the weld surface was well formed without undercut, depression and other defects, and the internal quality and mechanical properties of the weld fulfilled the requirements. Then welded joints were made into metallographic specimen to observe its microstructure and morphology. After laser cleaning pretreatment, welded joints were fully formed without crack, undercut and other defects under low power mirror. Through high power observation, grains in the center of the weld were fine and uniform. Therefore, the laser cleaning pretreatment of 30Cr3 ultra-high strength steel could effectively remove the contaminated layer on the surface, and the welding quality met the requirements.

Keywords: 30Cr3ultra-highstrengthsteel,lasercleaning,weldquality,microstructureandmorphology

Microstructureandpropertiesofresistancespotweldedjointofdissimilaraluminumalloys

Liu Lala, Liu Zhuhuan, Shi Tao, Guo Chunfei, Wang Yong

(Tianjin 707 Hi-Tech Co., Ltd., Tianjin 300409, China).p53-56

AbstractThe resistance spot welding process was used to overlap weld 5182 aluminum alloy and 5754 aluminum alloy with a thickness of 2 mm. The metallurgical characteristics were observed with a metallurgical microscope. And the mechanical properties are tested by the tensile tester and the microhardness tester. The results showed that the welded joint was composed of three typical zones, base metal, heat affected zone and nugget zone. The nugget zone of the welded joints mainly consisted of edge columnar grains and central equiaxed grains, and the volume of central equiaxed crystal zone accounts for about 90% of the entire nugget zone. In the heat affected zone of 5182 aluminum alloy, there appeared many large precipitates and liquefied cracks. However, there existed no obvious precipitates and liquefied cracks in the heat affected zone of 5754 aluminum alloy. The fracture form of the welded joint was a button fracture, and the nuggets on the 5754 aluminum alloy side were peeled off. The hardness of the columnar zone in the nugget was higher than that of the equiaxed crystal zone, and the hardness of the heat-affected zone on both aluminum alloys was higher than that of the corresponding base metal.

Keywords: 5182aluminumalloy, 5754aluminumalloy,resistancespotwelding,microstructure,mechanicalproperties

Weldingtechnologyforguidebeamscompositionoflongrailwaywagons

Jin Zhaohui, Sun Haitao, Zhang Zhongyu, Feng Baozhu

(CRRC Qiqihar Rolling Stock Co., Ltd., Qiqihar 161002, Heilongjiang, China).p57-60

AbstractBased on the analysis of the structure of the guide beam composition that was an important part of long railway wagons, the overall welding process was planned. According to the irregular shape of its spatial structure, the special process equipment was adopted to determine the assembly process benchmark. The material of the components was analyzed and identified. In accordance with the welding of WEL-TEN780A low alloy high strength steel and different materials, the corresponding welding method was selected, and the welding materials and welding parameters were determined. The main welding deformation was analyzed, and reasonable and effective measures and methods were taken to correct it. A reasonable welding and machining sequence was made to ensure the position and size of the guide sleeve. The welding process problems were solved such as welding quality assurance of guide beam composition under heavy load and complex structure, welding quality assurance of WEL-TEN780A low alloy high strength steel and different materials, welding deformation control and post-weld correction of medium and heavy plate and location dimension assurance of main parts. Finally, the requirements of geometrical tolerance and dimension of guide beam composition were met, and the overall welding quality requirements were guaranteed.

Keywords:weldingtechnology,longrailwaywagons,guidebeamcomposition,WEL-TEN780Aalloysteel,deformationcontrol