MAIN TOPICS，ABSTRACTS & KEY WORDS

Effectsofpost-weldheattreatmentonfracturetoughnessofunderwaterwetfrictiontaperplugweldedjointsforX52pipelinesteel

Xiong Junzhen, Yang Xinqi, Tang Wenshen, Yuan Huixin

(Tianjin University, Tianjin 300350, China).p1-7

AbstractThe fracture behavior of underwater wet friction taper plug welded joints for X52 pipeline steel was investigated with crack tip opening displacement (CTOD) test. Effects of post-weld heat treatment on fracture toughness and microstructure characteristics of welded joints were discussed. The results showed that the average CTOD value of weld center was only 0.103 mm with significantly lower fracture toughness than that of parent metal, due to the obviously heterogeneous quenched martensite and a small amount of widmanstätten in weld center. With the tempered temperature increasing from 500 ℃ to 800 ℃, microstructure of weld center transformed into tempered martensite and become more homogeneous, which effectively improved the fracture resistance of weld center. The average CTOD value of weld center after 800 ℃ tempered temperature reached over 0.8 mm. However, after tempered with suitable temperatures, bonding zone could only get a limited improvement in fracture toughness, because of inclusions in bonding zone. The maximum CTOD value of bonding zone was 0.3 mm after 800 ℃ tempered temperature. The fracture resistance of bonding zone was a vital factor which affected the application of underwater wet friction taper plug welding technique.

Keywords:underwaterwetfrictiontaperplugwelding,post-weldheattreatment,fracturetoughness,pipelinesteel

Saliencydetectionalgorithmofweldinfraredimagebasedonfrequencytuning

Xia Weisheng1, Fang Xiangyao1, Yang Shuai1, Lin Fuming2, Yang Yunzhen2

(1. State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, China; 2. Wuhan University of Technology, Wuhan 430076, China).p8-12

AbstractWeld infrared on-line monitoring system was established for gas metal arc welding. A real-time detection algorithm of infrared weld saliency based on frequency domain was proposed. The frequency tuned (FT) algorithm was improved from three aspects of filter processing, color model and background suppression, so as to obtain better infrared weld saliency map. The improved FT algorithm was compared and analyzed with some typical saliency detection algorithms such as ITTI, GBVS, SR, FT, AC and HC. The results showed that the average running time of the improved FT algorithm was 0.075 s and no preprocessing was required, which effectively guaranteed the real-time performance of the detection process. Each algorithm was used to process the infrared image of the weld. The results showed that the improved FT algorithm could effectively suppress interfering pixels, such as background, noise and arc in the saliency map of the infrared weld, and also eliminate the interference of the heat affected zone. At the same time, the outline of the target weld in the saliency map was clear and the saliency was enhanced, which was beneficial to the feature extraction of the weld.

Keywords:gasmetalarcwelding,infraredmonitoring,visualsaliency,frequencytuned,featureextraction

RapidS-NcurvepredictionofQ460weldedjointsbasedonenergydissipation

Wei Wei1,2, Zou Li1,2, Yang Xinhua1,2

(1.Dalian Jiaotong University, Dalian 116028, Liaoning, China; 2. Liaoning Key Laboratory of Welding and Reliability of Rail Transportation Equipment, Dalian 116028, Liaoning, China).p13-18

AbstractIn view of the characteristics of the traditionalS-Ncurve requiring long test period and large number of samples, a three-parameterS-Ncurve rapid prediction model combined with the high cycle fatigue life, fatigue limit and statistics of welded joints was presented. Through determining the turning point of energy dissipation in stable temperature rise stage under gradually increasing of load, and this turning point was then regarded as an index for predicting the fatigue limit. Considering the cumulative damage threshold in the whole lifespan when the load was above the fatigue limit, a medianS-Ncurve prediction model based on the energy dissipation threshold was established. Then, combined with the maximum likelihood method, theS-Ncurve prediction with the survival probability of 95% was completed. To verify the validity of the proposed model, the predictedS-Ncurve was compared with the experimental data. Results showed that the experimental data were basically distributed between the medianS-Ncurve and theS-Ncurve with 95% survival probability, which verified the accuracy of the model.

Keywords:weldedjoints,fatiguelimit,energydissipation,S-Ncurve

Microstructureandmechanicalpropertiesof316Lcompositeformedbylasermetaldepositionandcoldmetaltransfer

Cui Xin1, Xue Fei1,2, Song Chunnan3, Peng Na3, Li Mian3

(1. Xi’an Jiaotong University, Xi’an 710049, China; 2. Guangdong Add-Substance Technology Co., Ltd., Foshan 528234, Guangdong, China; 3. National Additive Manufacturing Innovation Center, Xi’an 710075, China).p19-24

AbstractIn order to achieve the complementary advantages of cold metal transfer (CMT) forming with high efficiency and laser metal deposition (LMD) forming with precision, it was proposed to combine CMT and LMD processes to manufacture parts with complex structures and high precision requirements in production. For 316L stainless steel material in this paper, the CMT formed block samples were used as the base and the LMD formed composite samples were used on its different surfaces. The two additive manufacturing processes, microstructure and mechanical properties of the hybrid interface were compared through experiments. The results showed that the dendrite microstructures of the LMD and CMT formed samples appeared obvious epitaxial growth characteristics, and the primary dendrite spacing of LMD microstructure was significantly smaller than that of CMT microstructure. When the deposition directions of the two additive processes were parallel/vertical, a good metallurgical bond was formed at the hybrid interface.The tensile samples at the composite forming interface all fractured at the CMT part, which indicated that the mechanical properties at the hybrid interface were better than the CMT forming part.

Keywords:lasermetaldeposition,coldmetaltransition,microstructure,mechanicalproperties

Effectofweldingtemperatureonmicrostructureandpropertiesoftitaniumalloydiffusionweldedjoints

Yu Kang1,2, Zhou Jun1,2, Zhou Jie1,2

(1. Shanghai Institute of Space Propulsion, Shanghai 201112, China; 2. Shanghai Engineering Research Center of Space Engine, Shanghai 201112, China).p25-27,44

AbstractIn order to solve problems of large brittleness, difficult processing and many defects of Ti-Zr-Ni-Cu intermediate layer, liquid phase diffusion welding technology of TC4 with Ni foil intermediate layer was studied. Welding temperature selection was based on Ni-Ti eutectic point and phase transition temperature of TC4 material. When welding temperature was below eutectic point 942 ℃, solid phase diffusion process occurred in the interface, there were larger pores in the joint, and Ni foil intermediate layer remained. When welding temperature was higher than eutectic point 942 ℃, solid-liquid diffusion process occurred in the interface. When welding temperature was 970 ℃, holding time was 120 min and welding pressure was 0.1 MPa, the titanium alloys with Ni foil intermediate layer could achieve effective joining, the tensile strength of welded joints reached 946 MPa, which was close to the tensile strength of the base metal.

Keywords:titaniumalloy,diffusionwelding,Nifoilintermediatelayer

StrengthcharacteristicsandfailureanalysisoflargeareasolderedjointforLTCCcircuitsubstrate

Wang Tianshi, Zhang Yi, Wang Qingbing, Liao Xu, Yue Shuaiqi, Zhou Jiewen

(The 29th Research Institute of CETC, Chengdu 610036, China).p28-34

AbstractSoldering process was used to join LTCC circuit substrate and package carrier, the strength and failure characteristics of soldered joint of large size LTCC circuit substrate and package carrier were analyzed. The results showed that the average shear strength of large area soldered joint of LTCC circuit substrate (Au/Pt/Pd pad) and package carrier (surface coating Au 0.5 μm) with Sn63Pb37 eutectic solder was 28.21 MPa, while the shear strength of abnormal samples were about 30% of the average value. The LTCC pads were loose with dense perforating holes. Sn elements of Sn-Pb solders entered into LTCC pads through holes after soldering. Some Sn elements reached the interface of LTCC pads and LTCC circuit substrate, and then formed a large area of non-dendritic AuSn4inside the LTCC pads. Compared to the normal samples, the sintering bonding strength between LTCC pads and LTCC circuit substrate of abnormal ones was lower, which was the main reason of interface failure and decreasing shear strength.

Keywords:lowtemperatureco-firedceramic,circuitsubstrate,largeareasoldering,shearstrength,failureanalysis

CharacterizationofmetaltransfermodesofGMAWbasedonmetallurgicalreaction

Sun Xian

(Institute of Welding Consumables, Taiyuan University of Technology, Taiyuan 030024, China).p35-44

AbstractThe characteristics of droplet transfer modes of GMAW involving welding metallurgy reactions were reviewed. The results showed that the main metallurgical reactions in the arc had different effects on the dominant force acting on the droplet. The relationship between the metallurgical reaction of welding wire and the mode of droplet transfer depended on the mechanical conditions of droplet transfer. When the metallurgical reaction increased theFsor decreased theFh, the droplet transfer mode could be improved. For flux cored wire, increasing the content of TiO2, Si-Fe, Al2O3and SiO2additives in the flux core, increasing the welding current, increasing the Ar content in the shielding gas and increasing the filling rate of the flux core could improve the droplet transfer moge. For solid wire, the coating composition of copper-free wire, as well as increasing the welding current, reducing the wire diameter, increasing the Ar content in the shielding gas, and using direct current electrode positive could improve the droplet transfer mode.

Keywords:metallurgicalreaction,droplettransfer,dominantforceofdroplettransfer,gasmetalarcwelding

Internationalweldingstandardsystemandapplicationinweldingmanufacturingfield

Qian Qiang1, Shao Hui1, Du Na2

(1. Harbin Welding Training Institute, Harbin 150046, China; 2.Yankuang Donghua Heavy Industry Co., Ltd., Jining 273500, Shandong, China).p45-51

AbstractThe content and system of international welding standards have been increasingly improved, which is resulted from the advancement of welding technology itself. It also greatly promotes the continuous development of welding technology and its application in engineering. The welding standard system in the manufacturing field with the ISO 3834 standard as the core, summarizes the control elements for welding quality into 9 related aspects systematically, namely, base metal and welding consumables, welding process specification (WPS) and welding process qualification (WPQR), personnel qualification, welding joint inspection, qualification and acceptance, welding process (preparation, welding and post welding), welding consumables manufacturing and supply, and environment, health and safety. This system can help professional and technical personnel fully understand the application of international welding standards in the field of engineering technology and improve their international level.

Keywords:weldingmanufacturing,internationalstandardsystem,application

Effectofrootdefectontensilepropertiesoffrictionstirweldedjoint

Zhou Ping1，Dai Qilei2，Zhang Yuanjie3

(1. Jiangxi University of Engineering, Xinyu 338000, Jiangxi, China; 2. Hwaway Technology Co., Ltd., Zhuji 311800, Zhejiang, China; 3. Xinyu Iron and Steel Co., Ltd., Xinyu 338000, Jiangxi, China).p52-56

Abstract6082-T6 aluminum alloy welded joint with root defect by friction stir welding was analyzed through DIC observation combined with SEM observation to reveal effect of root defects of welded joint on the tensile properties of aluminum alloy friction stir welded joint. The results showed that with the increase of welding speed, the root of the joint was prone to defects and the severity of defects would increase. Due to the root defect, the tensile properties of friction stir welded joint of 6082-T6 aluminum alloy was significantly reduced, and the bearing capacity and strength of the welded nugget zone were reduced. The tensile fracture morphology was step-like with brittle fracture morphology, and there were shallow and small dimples on the step surface.

Keywords:frictionstirwelding,rootdefect,tensile,fracturemorphology

WelddefectdetectionofcomplexstructurebasedonultrasonicC-scan

Hu Wengang, Liu Wei, Zhu Ruican, Yu Bo, Luo Zhiwei

(Capital Aerospace Machinery Corporation Limited, Beijing 100076, China).p57-61

AbstractAffected by the structure, the electron beam weld with complex structure didn’t have the condition of radiographic testing. However, it could be effectively detected by ultrasonic C-scan testing. The lack of penetration could be located, and the weld penetration could be measured. It was an effective method for the internal quality inspection of weld. Through the simulation of ultrasonic sound field, the probe parameters were optimized to obtain a strong sound field in the weld area. The reliability of the method was verified by ultrasonic C-scan testing of welding specimens, and the testing sensitivity could reach the defect equivalent ofφ3 mm-9 dB. The results showed that the ultrasonic C-scan technology was possessed of high detection rate and high sensitivity for the lack of penetration. Combined with the ultrasonic C-scan image, the weld penetration could be detected accurately. Compared with the destructive test, the defect location are accurate, the detection error of weld penetration was about 4%, and the result was reliable.

Keywords:electronbeamwelding,ultrasonicC-scan,lackofpenetration,weldpenetration,testingsensitivity