MAIN TOPICS，ABSTRACTS & KEY WORDS

Microstructureandmechanicalpropertiesof6082-T651aluminumalloycruciformweldedjoints

Qi Guangbin1, Hao Xiaohu1, Dong Honggang1, Xu Chenling2, Jiao Xinggui2, He Jianwei2

(1. Dalian University of Technology, Dalian 116024, Liaoning, China; 2. Dalian Huicheng Aluminum Co., Ltd., Dalian 116105, Liaoning, China).p1-8

AbstractCruciform welded joints of 15 mm thick 6082-T651 aluminum alloy plates were obtained by metal inert gas welding. The influence of welding parameters on formation of weld, tensile properties and microhardness of cruciform welded joints was studied, and the element distribution in different zones of the joint was analyzed. The results showed that with the increase of wire feeding speed and welding current, the reinforcement of the weld decreased while the penetration and weld width increased. The edge of the weld was a columnar crystal microstructure, and the center of the weld was a mixed microstructure of dendrites and equiaxed crystals. The grain boundary liquation extended from fusion line to the inside of heat-affected zone. Alloy elements such as Mg, Si, Fe and Mn segregated in the weld to form intergranular precipitates. The tensile strength of cruciform welded joints was up to 239 MPa, and the fracture mode was ductile fracture. The microhardness of the joint symmetrically distributed on the web side and the wing side, and the microhardness of the heat-affected zone decreased with the increase of welding heat input, even lower than that of weld zone.

Keywords: 6082aluminumalloy,cruciformweldedjoint,elementdistribution,tensilestrength

PreparationandpropertiesofultrasonicassistedlasercladdingNi-TiNcoatingonsurfaceofN80steelforoilpipeline

Xia Fafeng, Li Qiang, Li Chaoyu, Ma Chunyang, Li Huaxing

(Northeast Petroleum University, Daqing 163318, Heilongjiang, China).p9-12

AbstractNi-TiN coatings were prepared on the surface of N80 steel for oil pipeline by ultrasonic assisted laser cladding in this paper. The effects of different ultrasonic powers on the surface morphology, microhardness and wear resistance of Ni-TiN coatings were studied by scanning electron microscope, X-ray diffractometer, microhardness tester and friction and wear tester. The results indicated that when the ultrasonic power was 300 W, size of TiN particles in the Ni-TiN coating was smaller, and its average particle size was 16.7 μm. The nickel diffraction peak of the coating became low and wide, testifying the refinement of the metal grains in the coating. Furthermore, the microhardness of the coating was the largest, and the average microhardness was 833 HV. When the ultrasonic power was 0 W, the friction coefficient of the Ni-TiN coating was the largest, and its average value was 0.57. However, when the ultrasonic power was 300 W, the friction coefficient of the coating was the smallest, and its average value was 0.42.

Keywords:ultrasonicassistedlasercladding,Ni-TiNcoating,surfacemorphology,wearresistance

High-temperaturetensilepropertiesofHAZinQ345FREhighNbfire-resistantsteelbysimulation

Cui Qiang1, Liu Pan2, Meng Lingming1, Wang Honghong2

(1. Nanjing Iron and Steel Group Co., Ltd., Nanjing 210035, China; 2. Wuhan University of Science and Technology, Collaborative Innovation Center for Advanced Steels, Wuhan 430081, China).p13-18,33

AbstractTensile tests of HAZ in Q345FRE fire-resistant steel at 600 ℃ under conditions of different peak temperatures in single pass, different peak temperatures in multiple passes and differentt8/5times were carried out on Gleeble-3500 tester by thermal simulation method. The high temperature tensile properties, secondary high temperature tensile properties and their variations in the heat affected zone under different conditions were studied. The results showed that in the HAZs of single pass and double pass, the incomplete recrystallization zone at 870 ℃ peak temperature was simulated and its high temperature yield strength and tensile strength at 600 ℃ were the lowest. The coarse-grained zone at 1 320 ℃ peak temperature was simulated and its high temperature yield strength and tensile strength at 600 ℃ were the highest and higher than those of parent metal. The effect of welding heat input(t8/5) on high temperature yield strength and tensile strength at 600 ℃ was not obvious the incomplete recrystallization zone at 870 ℃ simulation peak temperature. The strength of the incomplete crystallization zone after secondary overheating by thermal simulation of did not decrease att8/5≤80 s.

Keywords:fire-resistantsteel,weldingheataffectedzone,hightemperaturetensileproperties

Effectofnickelinterlayeronmicrostructureandmechanicalpropertiesof304/5052laser-MIGhybridweldedjoint

Peng Cong, Liu Guiqian, Liu Xiuhang, Zhang Nanfeng, Gao Xiangdong

(Guangdong University of Technology, Guangdong Provincial Welding Engineering Technology Research Center, Guangzhou 510006, China).p19-23

AbstractThe deep penetration lap welding of 304 stainless steel/5052 aluminum alloy was carried out with laser-MIG hybrid welding. The effects of nickel interlayer with different penetration on cross section morphology, microstructure and mechanical properties of interface layer were studied. Experimental results showed that the addition of nickel interlayer would worsen the 304/5052 joint under the condition of low penetration. Under the condition of medium penetration and high penetration, the addition of nickel interlayer could effectively inhibit the formation of Fe-Al intermetallic compounds (IMCs) and reduce the thickness of IMCs in the interface layer. Nickel atom could replace some iron atoms to form Al3Ni, which could reduce the brittleness and hardness of IMCs. After adding nickel interlayer, the tensile strength of the joints with low penetration became lower, the tensile strength of the joints with medium penetration increased but the increase range was not obvious, and the tensile strength of the joints with high penetration increased obviously.

Keywords:laser-MIGhybridwelding,deeppenetrationlapwelding, 304stainlesssteel, 5052aluminumalloy

Solidstatequasi-equalstrengthrepairingforweldingdefectsof2195Al-Lialloys

Liu Li’an1, Chen Sihao1,2, Zhao Yaobang1, Meng Xiangchen2, Huang Yongxian2

(1. Shanghai Aerospace Precision Machinery Institute, Shanghai 201600, China; 2. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China).p24-27

AbstractAiming at the keyhole defects after friction stir welding (FSW) of 2195 Al-Li alloys, the solid state quasi-equal strength repairing based on filling friction stir welding (FFSW) was performed. This method was characterized by low heat input, sufficient friction and material flow and high strength of interfacial bonding. The results showed that introducing the additional filling stud could make the sufficient filling of the keyhole, while the friction stir processing was beneficial to the second forging effects on the repairing regions. By optimizing the welding parameters, when the rotating velocity was 1 600 r/min, the tensile strength of the repaired joint was 358.1 MPa, up to 90.7% that of high quality FSW joint, while its elongation was 3.17%, up to 90.6% that of high quality FSW joint. It realized the solid state quasi-equal strength repairing of 2195 Al-Li alloys.

Keywords: 2195Al-Lialloy,fillingfrictionstirwelding,keyholerepairing,interfacialbonding

Heatsourcemodelofplasma-MIGhybridweldingbasedonarcdeflection

Huang Jiming, Jin Cheng

(Dalian Jiaotong University, Dalian 116028, Liaoning, China).p28-33

AbstractThe interaction between MIG arc and plasma flow in plasma-MIG hybrid welding was analyzed. The heat source model of the hybrid welding was revised in combination with the observation of the shape of the hybrid arcs. Considering the repulsion between the reverse plasma flow and the MIG current in hybrid welding, the hybrid welding process with the introduction of arc deflection angle was simulated and calculated, the influence of the deflection angle on the temperature field was analyzed, and the calculation results were compared with the experimental measurement. The comparison results showed that the calculation results of the heat source model formula after introducing the arc deflection angle could better describe the physical process of hybrid welding, which had a certain practical application value for optimizing its welding process parameters.

Keywords:plasma-MIGhybridwelding,couplingarc,arcdeflection,heatsourcemodel

Researchstatusofqualitycontroltechnologyforunderwaterwetweldedjoint

Zhou Chao1, Li Haixin1, Yang Zhenlin1, Jiang Fengchun1, Wang Qichen2, Zhang Wenjie3

(1. Yantai Research Institute and Graduate School of HEU, Yantai 264010, Shandong, China; 2. CIMC Offshore Engineering Institute, Yantai 264000, Shandong, China; 3. Weihai Donghai Shipyard Co., Ltd., Weihai 264200, Shandong, China).p34-39,60

AbstractTo explore underwater wet welding in the field of modern industry application prospect, common problems of underwater wet welding were briefly introduced, such as hydrogen induced crack, poor quality of welded joint and unstable welding process. Improving principles and methods of underwater wet welded joint quality were introduced. The research progress of controlling the diffused hydrogen content of underwater wet welded joint, improving strength of the joint and the stability of welding process were mainly introduced. Underwater wet welding process for the future development was prospected in engineering practice.

Keywords:underwaterwetwelding,weldedjoint,diffusivehydrogen,researchstatus

EffectofweldingprocessmeasuresonmechanicalpropertiesofL555Mpipegirthweldedjoint

Sui Yongli1, Sun Zhe2, Xu Weizhang3, Feng Dayong1

(1. China Petroleum Pipeline Research Institute Co., Ltd., National Engineering Laboratory for Pipeline Safety, Langfang 065001, Hebei, China; 2. No.1 Branch Company of China Petroleum Pipeline Engineering Co., Ltd., Langfang 065001, Hebei, China; 3. Gas Branch Company of China Petroleum Pipeline Engineering Co., Ltd., Langfang 065001, Hebei, China).p40-47

AbstractIn this paper, through the research on the effect of FCAW welding process measures, such as preheating temperature, inter-pass temperature and girth weld pass number, it was found that welding process measures such as preheating, inter-pass temperature and multi-layer and multi-pass welding were adopted to improve the microstructure of weld and heat affected zone and prevent coarse grains, and then to improve bending performance and low temperature impact toughness of girth welded joints. At the same time, there was a reasonable range of preheating temperature, inter-pass temperature and the optimal number of weld passes with different wall thicknesses, which should be determined through welding process qualification to ensure the stability of the comprehensive mechanical properties of girth welded joint.

Keywords:L555Mpipeline,girthweldedjoint,weldingprocess,preheat,inter-passtemperature

Optimizationofweldingprocessandmechanicalpropertiesoffrictionpullplugweldedjointon2219aluminumalloysheet

Zhao Huihui1, Gao Han1, Hu Lan1, Dong Jiyi1, Yin Yuhuan1, Cui Lei2,3

(1. Shanghai Aerospace Equipment Manufacturing General Factory Co., Ltd., Shanghai 200245, China; 2. Tianjin University, Tianjin 300072, China; 3. Tianjin Key Laboratory of Advanced Joining Technology, Tianjin 300072, China).p48-55

AbstractIn this paper, the friction pull plug welding process and mechanical properties of 2219 aluminum alloy with 5.5 mm thickness were studied. Four kinds of plug with different geometrical shapes were designed, and the optimal plug geometry and size were determined through experiments, the plug was circular (R=50 mm), the diameter of little end was 32 mm, and the length of conical section was 16.17 mm. Under the rotation speed of 7 000 r/min, axial tension force of 30 kN and axial feed of 10 mm, defect-free welded joints could be obtained. The microstructure analysis showed that the interface between plug and base material was good, and the grains on the side of the base material adjacent to the interface had dynamic recrystallization, and the grains in the thermal-mechanical affected zone were elongated along the extrusion direction of the plug. The orthogonal test and analysis results showed that among the three main welding parameters such as rotation speed, axial tension force and axial feed, the rotation speed, had the greatest influence on the tensile strength of the joint, the axial tension force was the second, and the axial feed was the least. When the rotation speed reached more than 7 000 r/min, the tensile strength of the joint could be improved by increasing the axial tension force. The highest tensile strength of the joint obtained in this paper could reach 357 MPa, which was equivalent to 76.7% of the base material. Under the condition of good bonding interface, the tensile fracture location of the joint was the thermal-mechanical affected zone, and the fracture surface showed toughness characteristics.

Keywords: 2219aluminiumalloy,frictionpullplugwelding,weldingprocess,mechanicalproperties

D-Archighefficiencyweldingprocessofhighstrengthsteelthickplateforconstructionmachinery

Tan Xing, Ni Chuanhao, Jiang Yaping

(Zoomlion Heavy Industry Science & Technology Co., Ltd., Chinese National Engineering Research Center of Concrete Machinery, Changsha 410013, China).p56-60

AbstractWelding experiments of butt joint and T joint of Q690D thick plate for construction machinery were performed with D-Arc welding technology. Formation of weld, microstructure and microhardness of welding samples were analyzed. And the mechanical properties of tensile test, bending test and impact test were also carried out. The results showed that, compared with conventional gas shielded welding, butt joint with 25 mm thickness plate and T joint with 30 mm thickness plate by D-Arc welding technology could reduce the weld by more than one third. The depth of fusion obviously increased, and formation of weld was good. The microstructure of D-Arc joint with large current parameter was not exceptionally coarsened. The maximum hardness in heat-affected zone and the minimum hardness of softening zone were not outliers compared with the base metal hardness. The tensile test, bending test and impact test were qualified.

Keywords:constructionmachinery,highstrengthsteel,D-Arcwelding,thickplatewelding