MAIN TOPICS，ABSTRACTS ＆ KEY WORDS

Application of friction welding in field of aviation

Zhou Jun1，Zhang Chunbo1，Du Miao2，Zhao Yushan1，Jiang Zixing1

(1.Harbin Welding Institute，China Academy of Machinery Science ＆ Technology，Harbin 150028，China; 2.China Welding Association，Harbin 150028，China) .p1-5

With the increasing improvement of civil and military aircraft performance and usage requirement，components and parts of civil aviation need to meet requirements of structure lightweight design，high reliability，long lifetime and economy.As the indispensable material processing technology in aviation industry，welding technology plays an important role in the development and production of the aviation parts.Inertia friction welding，friction stir welding and linear friction welding are typical friction welding process.Because of their technological superiority，friction welding processes had been successfully applied to manufacturing aero-engine rotor，aircraft structures，bladed disk and other aviation parts and components.The development of friction welding technologies will help aviation aircraft and aircraft engine to loss weight，promote the optimization design of aviation aircraft and aircraft engine structure，and enhance the performance of aircraft and aircraft engine．

inertial friction welding， friction stir welding， linear friction welding， aircraft

Cavitation erosion behavior of 316L steel welded joints at different heat input in liquid lead-bismuth alloy

Lei Yucheng，Zhang Bo，Guo Xiaokai

(School of Material Science and Engineering，Jiangsu University，Zhenjiang 212013，Jiangsu，China) .p6-9

In this paper，the cavitation erosion behavior of 316L welded joints at different heat input in the liquid lead bismuth alloy was studied．After the cavitation corrosion test for 80 hours，the surface morphology and roughness of the samples were analyzed by electron scanning electron microscopy (SEM) and atomic force microscopy (AFM) .Research showed the cavitation erosion resistance of 316L welded joints in liquid Pb-Bi depends on the austenite grain size.As welding heat input increases，the austenite grain size becomes larger，which leads to the poor corrosion resistance.The cavitation erosion resistance of 316L base metal is better than that of welded joints at the same cavitation erosion time．

cavitation erosion， 316L stainless steel， welded joint， lead-bismuth alloy

Sensing signal processing of narrow gap weaving arc welding

Ren Zhennan，He Junjie，Liu Wenji

(The Key Laboratory of modern mechanical and electrical equipment technology of Tianjin.Tianjin Polytechnic University，Tianjin 300387，China) .p10-13

Based on the existing arc sensing signal processing theory and method at home and abroad，taking into account the narrow gap weaving arc welding of the sensor signal susceptible to noise interference，a new combinatorial filtering method was proposed，which includes the clipping processing，the median filtering and the Fourier filtering.The collected current signals were filtered and simulated in Matlab.The results show that the proposed method can effectively improve the current waveform and the signal to noise ratio of the current signal.The welding experiments with different deviation conditions show that the proposed filtering method is feasible．

weaving arc， clipping， median filter， fourier filter

Microstructure and properties of TiN layer on Ti6Al4V prepared by nitrogen pulsed-arc

Wang Jiajie1，Xu Jianping1，Wang Huiwen1，Mo Shuhua1，Fan Yongbin2

(1.Department of Materials and Chemical Engineering，Heilongjiang Institute of Technology，Harbin 150050，China; 2.Harbin JianchengCompany Limited，Harbin 150030，China) .p13-16

By using nitrogen as the protective gas and reactant gas，pulsed nitrogen arc cladding technology was used to realize the synthesis of TiN layer on Ti6Al4V to improve surface characteristics.The microstructure and phase composition of TiN layer were investigated by metallurgical microscopy and X-ray diffraction (XRD) .The influence of the technological parameter on the properties of the TiN layer with pulsed arc mode were studied.The results show that compared with DC arc，the pulsed nitrogen arc technology improves the thickness and width of TiN layer.Due to the high concentration of the nitrogen ion，the thickness and microhardness of TiN layer by pulsed arc are much more than that by DC arc at the same welding heat input.TiN layer has the obvious (200) orientation.The diffraction peak of TiN is increased at pulsed arc mode．The microhardness of TiN layer is 2 600 HV at AC 200 A.The microhardness is about 7.4 times of the Ti6Al4V alloy．

Ti6Al4V alloy， TiN， nitrogen arc

Effects of welding speed on microstructure and weld appearance quality of fiber laser beam welded joints of Mg-Mn magnesium alloy

Zhang Qiumei，Hou Juncai

(School of Materials Science and Engineering，Shaanxi University of Technology，Hanzhong 723003，Shaanxi，China) .p17-20

Mg-Mn magnesium alloy with the thickness of 4 mm was laser beam welded by using the high power fiber laser to investigate the effect of welding velocity on the weld appearance quality and microstructure.The results showed that the sound joints without porosity were obtained in the range of the welding speed from 1 500 ～ 1 800 mm/min.The columnar grains were observed near the fusion zone.And the grains were changed into fine equiaxed dendrite near the weld center.The α-Mg matrix，massive Mn phases，Mg8Ce inter-metallic compounds were observed in the joint.The greater difference of the microstructures of the joints was detected at the different welding speed.The weld width and the grain size of the joint were decreased with the increase of welding speed．

grain size， dendrite， exquiaxed grain， weld with， porosity

Recognition of molten pool morphology in CO2 welding based on convolution neural network

Qin Ke1，Liu Xiaogang1，Ding Lixin2

(1.Guangxi Colleges ＆ University Key Laboratory Breeding Base of Robot ＆ Welding Technology，Guilin University of Aerospace Technology，uilin 541004，Guangxi，China; 2.State Key Laboratory of Software Engineering，Wuhan University，Wuhan 430072，China) .p21-26

A kind of convolution neutral network CNN-M was proposed to recognize the morphology of molten pool in CO2 welding.A simple pretreatment of the molten pool image was adopted as the input vector in CNN-M，which avoids the adverse effects brought by the subjectivity of artificial extraction of molten pool image features.In order to decrease the possibility of network over-fitting caused by the sparse training data set，several methods including ReLU activation function，random Dropout and SVM classifier were used in CNN-M.The experimental results show that CNN-M has better performance in recognition rate and recognition speed than the BP neural network does，which adopt the characteristic values of the molten pool as the input vector.The performance of CNN-M is able to meet the requirement of the on-line moltenpool monitoring．

CO2 welding molten pool， convolution neutral network， state recognition

Study on piezoelectric actuator based GMAW welding decoupling control method and its mechanism

Zhu Xiaoxiang，Liu Jia，Bai Lilai

(College of Mechanical Engineering and Applied Electronics Technology，Beijing University of Technology，Beijing 100124，China) .p26-29

The piezoelectric actuator based welding stick return mechanism combined with DSP coring control system was adopted to research the effect of extra force on droplet transfer.With high-speed shooting on welding process，the effects of different parameters on droplet transfer were studied.The results indicated that extra separating force was applied to droplet by using of piezoelectric actuator based welding stick return mechanism，and the droplet transfer was realized.The longer the return time，the greater the welding current，the bigger the wire feeding speed，and the easier the realization of droplet transfer.There was almost no spatter during the welding process; droplet transfer was realized with non-short circuiting transfer at low current．

piezoelectric actuator， return， droplet transfer

Numerical simulation of flow field and temperature field in reverse polarity plasma cutting

Zheng Shida，Krivtsun Igor，Han Shanguo，Cai Detao

(Guangdong Welding Institute (China-Ukraine E.O.Paton Institute of Welding) ，Guangzhou 510650，China) .p30-34

The numerical model for thermodynamic and dynamic characteristics of reverse polarity plasma cutting was established.The results show that the plasma is heated and accelerated in the compressed channel of gun body，and the temperature and velocity of plasma reach the peak value，but the temperature and velocity of plasma are nearly constant for the diffusion region and the cutting cavity of the workpiece.The geometry of plasma gun body (nozzle diameter and compression channel length) ，process parameters (current，ion flow and nozzle height)have important effects on the temperature and velocity of plasma．

reverse polarity plasma cutting， geometry for gun， plasma temperature， plasma velocity

Review on welding technology of thick austenitic stainless steel

Li Haixin，Zhang Linlin，Zhang Jing，Du Yongpeng，Yang Zhenlin，Yin Ziqiang

(Shandong Provincial Key Laboratory of Ocean Environmental Monitoring Technology，Institute of Oceanographic Instrumentation，Shandong Academy of Sciences，Qingdao 266001，Shandong，China) .p35-38

With the increasing application of thick austenitic stainless steel，more and more attention has been paid to the welding technology of thick austenitic stainless steel.In this paper，the research results and development status of welding technology of thick austenitic stainless steel were analyzed in detail.The research situation of the conventional arc welding，submerged arc welding，narrow gap welding，electron beam welding and laser welding in the welding of thick austenitic stainless steel were introduced emphatically，from the development of welding technology，welding material selection，welding parameters selection and evaluation of welding quality.Furthermore，and the current welding problems and future development direction of welding technology of thick austenitic stainless steel has been put forward，which is of great signification．

austenitic stainless steel， thick plate， welding

Development of flux-cored wire for repairing 5CrNiMo hot-working die with CO2-gas shielding arc welding

Li Yu，Yu Shengfu

(School of Materials Science and Engineering，Huazhong University of Science and Technology，Wuhan 430074，China) .p39-43

The effect of NaF content on the stability of CO2-gas shielding arc was studied by using high-speed photograph.The results show that the welding process can be improved by adding NaF into the flux-cored wire.While NaF content is added to 1.5%，the welding process is the best stable，which has the least spatter based on the small particles.The quality of deposited metal is high and welding defects is free on the top surface.Besides，the microstructures and mechanical properties were studied in this paper.The results show that the deposited metal has high hardness because of the high content of martensite and great stability at high temperature.There are few differences of yield strength and tensile strength while the experiments are carried on at the room temperature and 600 ℃.Compared to the as-forged 5CrNiMo steel，the deposited metal has better wear resistance.The experiments show that the wear rate of deposited metal is 18.75%，which is less than that of the 5CrNiMo forged at 600 ℃ and can be used to repair the die．

5CrNiMo hot-working die， flux-cored wire， welding process， deposited metal

Welding experiments on thin-wall part of T250 cobalt free maraging steel

Yao Chunchen1，Wang Haiyun1，Xu Jie1，Zeng Li2，Cao Junmin3，Chang Hai1，Liu Tianyu1

(1.Jiangnan Industries Group，Xiangtan 411207，Hunan，China; 2.Hunan Vocational College of Science＆Technology，Xiangtan 411207，Hunan，China; 3.Xiangtan University School of mechanical engineering ，Xiangtan 411105，Hunan，China) .p44-46

For ensuring the welding workmanship and reliability of thin-wall cylindrical pressure vessel of T250 cobalt free maraging steel，GTAW welding experiments were carried out with a thin-wall cylindrical sample and a corner weld sample.The results indicated that T250 steel has good weldability，cold cracking in GTAW joint of the thin-wall part little occurs，and neither pre-heat before welding nor heat treatment for removing stress after welding are required.In welding process，the welding current should be controlled strictly to prevent the weld defects.Besides，the strength of welded joint is not high after welding，so it is necessary to improve the joint strength to reach the similar strength of ultrastrength steel by ageing or quench annealing + aging treatment．

maraging steel， thin-wall part， pressure vessel， GTAW， ageing

Study on laser cladding technology with side feeding powder

Jia Yazhou，Xiao Jun ，Chen Shujun ，Wang Liwei

(College of Mechanical Engineering ＆ Applied Electronics Technology，Beijing University of Technology，Beijing 100124，China) .p47-50

By using Q235 steel as the substrate，the laser scanning cladding system with paraxial powder feeding type was built based on the IPGYLS-4000 type fiber laser and the paraxial powder feeder，and the deposition experiments were carried out on the Q235 steel substrate．The effects of laser power，scanning velocity and amplitude on the sizes and microstructures of the deposited layer were studied.The results show that the laser power and scanning speed are the main process parameters affecting cracks in the deposited layer.With the increase of laser power，the melting amount of iron based alloy powder increases，the thickness of single layer of deposited metal significantly increases.The influence of scanning speed on the deposited layer width and thickness is larger，with the decrease of the scanning speed，the width and thickness of the deposited layer increase.Through optimizing process parameters，good and crack-free deposited layer can be obtained，which provide theoretical and technical basis for the next step research of laser scanning technology without (small) distortion．

paraxial synchronous powder feeding， laser scanning cladding， crack， cladding layer

Influence of high frequency induction heat treatment on residual stress in 2219 aluminum alloy TIG welded joint

Deng Lifen1，Li Qingqing1，Han Guoliang1，Xiao Hong1，Li Weili2

(1.Tianjin Long March Launch Vehicle Manufacturing Co.Ltd.，Tianjin 300462，China; 2.School of Material Science and Engineering，Harbin Institute of Technology，Harbin 150001，China) .p51-54

The tungsten inert gas(TIG) welding was used to weld 8 mm-thick 2219 aluminum alloy，the high frequency induction heat treatment was carried out to welded joint at 90 ℃，140 ℃ and 190 ℃，respectively，and X ray diffraction method was used to measure welding residual stress before and after heat treatment，then microstructure and mechanical properties were analyzed.The results showed that effects of heat treatment on welding residual stress at 140 ℃ and 190 ℃ are significant，while that at 90 ℃ is relatively poor.Compared with the samples without heat treatment，no obvious change is observed in microstructure，tensile properties and distribution of hardness of welded joint．

residual stress， welding， 2219 aluminium alloy， induction heat treatment

Analysis of deposited metal tension properties EQNiCr －3 welding strip for nuclear power

Du Ning1，Huo Shubin2，Chen Yan2，Guo Xiao2，Han Bo2，Zhang Jiaqing3

(1.Harbin Electric Corporation (Qhd) Heavy Equipment Company Limited，Qinhuangdao 066206，China; 2.Harbin Well Welding Co．Ltd.，Harbin 150028，China; 3.Xiamen University Tan Kah Kee College，Xiamen 363105，Fujian，China) .p54-56

The nuclear steam generator primary surface of tube-sheet needs the cladding with EQNiCr-3，but sometimes the tension strength and elongation can not meet the requirement of specification.Through analyzing of EQNiCr-3 deposited metal under the different conditions，it was found that the intergranular crack is the main reason for failure of deposited metal tension properties and the distribution of Nb second phase maybe is the important factor on the brittleness．

intergranular crack， energy spectrum analysis， the second phase

Research on double spindle phase friction welding for assembling of drive shaft

Xue Xiaoyun，Zhu Hai，Shen Hongqiao，Sun Long，Sun Jinrui

(College of Electromechanical Engineering，Northeast Forestry University，Harbin 150040，China) .p57-60

According to the phase accuracy and length precision of the miniature automobile drive shaft，combined with the characteristics of friction welding，a double spindle phase friction welding machine was designed.The machine can complete two welds at the same time to achieve the shaft pipe welding.Through the small batch welding experiment and the comprehensive evaluation of the welding parts，it is verified that the machine can realize the welding accuracy and stability of the shaft pipe，improve the production efficiency and reduce the production cost．

double spindle， phase friction welding， drive shaft， displacement control

Microstructure and microhardness of laser overlap welded joint of high strength steel sheets

Liu Qingyong，Du Yanbing，Guo Jian，Xia Mingsheng

(Technology Center，Tangshan Iron ＆ Steel Group，Tangshan 063016，Hebei，China) .p61-65

Dual-phase steel DP780 + Z and low alloy high strength steel HC420LA are commonly used in automobile industry，the research about laser overlap welding was carried out in this paper by using fiber laser welding system.The microstructure and microhardness near theweld were analyzed，and the influence of different welding speed on microhardness of weld were also studied.Results show that the microstructure of the joint mainly includes fusion zone，heat affected zone and base material.The microhardness of HC420LA steel shows the increasing trend from base material to weld at constant laser power.However the changing trend of DP780 + Z is first increasing and then decreasing．With the increase of welding speed，the microhardness of HC420LA increases，and that of DP780 + Z first increases and then decreases．

laser welding， overlap joint， welding speed， microhardness

Design of laser welding system for medical calipers

Shao Fengxiang，Li Kunquan

(School of Mechanical Engineering，Henan Institute of Engineering，Zhengzhou 451191，China) .p65-68

The laser welding system was designed to weld the medical calipers to connecting rod.The profiling fixture of calipers and connecting rods were designed for precision positioning the welding track.The air cylinder of the bilateral driving mechanism takes the profiling fixtures to close and compress simultaneously，and then welding was carried out.The practical production results indicate that the system meets the requirements of product，and has high welding efficiency．

medical calipers， laser welding， location， system designment