MAIN TOPICS，ABSTRACTS & KEY WORDS

Laser-MAGhybridtransverseweldingforbackingweldofX80pipelinesteelinhorizontalposition

Miao Chunyu1, Jiao Xiangdong1,2, Zhu Jialei1, Li Jingyang3, Wang Kai2

(1. Beijing Institute of Petrochemical Technology, Beijing 102617, China; 2. Beijing University of Chemical Technology, Beijing 100029, China; 3. Yanshan Petrochemical Technology Co., Ltd., Beijing 100000, China).p1-6

AbstractTaking X80 petroleum pipeline steel as the research object, the mechanical properties of laser-MAG hybrid transverse welded joint were evaluated by tensile test, bending test and hardness test. The influence of laser-wire spacing on the weld formation of laser-MAG hybrid transverse welding was studied. The results showed that the best weld symmetry was obtained when the difference between laser and wires was 2 mm, the coupling performance of the hybrid heat source was the best, and the downward flow tendency of the weld pool was the smallest. Results of the tensile test, bending test and microhardness test of X80 pipeline steel welded joints met the requirements of API 5L standard.

Keywords:laser-MAGhybridtransversewelding,laser-wirespacing,hybridheatsource,X80pipelinesteel

MicrostructureandpropertiesofNi-Co-TiNcompositecoatingspreparedonthesurfaceofstubblecutters

Ma Chunyang,Li Huaxing, Xia Fafeng, Zhang Sidong

(Northeast Petroleum University, Daqing 163318, Heilongjiang, China).p7-14

AbstractIn order to improve surface hardness and corrosion resistance of stubble cutters, and then to extend their service life, the Ni-Co-TiN composite coatings were prepared by ultrasonic-assisted jet electrodeposition on the surface of 45 steel used in stubble cutters. The optimal process parameters for producing Ni-Co-TiN coatings were determined by orthogonal experiment. The microstructure, surface morphology, phase structure and elemental composition of the coatings were observed by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD) and energy dispersive spectrometer (EDS), respectively. Moreover, the microhardness and corrosion resistance of coatings were tested by microhardness tester and electrochemical workstation. The orthogonal experiment results demonstrated that the optimal process parameters for producing Ni-Co-TiN coatings were listed as follows, the jet speed of the plating solution 4 m/s, the ultrasonic power 120 W, the content of TiN nanoparticles 10 g/L and the electrode spacing of 8 mm. The nickel grain sizes of the Ni-Co-TiN coating prepared with the optimal process parameters were obviously refined and TiN particles were dispersed in the coating. The microhardness of the coating was as high as 489.82 HV, the self-corrosion potential (Ecorr) was -0.342 V and self-corrosion current density (Icorr) was 2.15×10-6A/cm2.

Keywords:stubblecutter,ultrasonic-assistedjetelectrodeposition,Ni-Co-TiNcompositecoating,microhardness,corrosionresistance

Preparationandfrictionpropertyofnickel-basedcoatingsbasedonmodificationbyCuandWS2

Zheng Guangzhi, Yuan Jianhui, Zhang Chen, Zhang Tianli, Liu Yao, Zhao Haoyang

(Shanghai University of Engineering Science, Shanghai 201620, China).p15-22

AbstractThree kinds of NiCr/TiC, NiCr/TiC-Cu and NiCr/TiC-Cu-WS2composite coatings were successfully prepared on the surface of 30CrMnSi manganese steel by laser cladding in order to improve wear resistance of the loader bucket. The microstructure and phase composition of the corresponding cladding layer were analyzed by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. The wear resistance and hardness of the coatings were comprehensively evaluated by friction and wear test and microhardness test. The NiCr/TiC coating had a dense structure without any obvious pores and cracks. The major components of this coating were γ-(Ni,Fe) solid solution, hard TiC and elemental Cr, and the hardness of the coating was about 2.5 times higher than that of the substrate. A large number of furrows were formed on the coating by wearing with the dual part, and the main wear mechanism was abrasive wear and fatigue wear. Due to the addition of soft metal Cu, the microhardness of NiCr/TiC-Cu composite coating decreased, and the friction coefficient and wear volume of the coating also decreased. Only a few furrows existed on the worn surface, and the main wear mechanism was adhesive wear. The NiCr/TiC-Cu-WS2coating contained γ-(Ni,Fe) solid solution, hard TiC and Cu, and also contained composite carbide (TiWC2) and a little of lubricating phase (CrxSy). Only a very weak furrows existed on the worn surface of the coating, and wear mechanism was adhesive wear and micro-plough wear. In the nickel-based composite coating prepared by laser cladding, the hardness of the coating was significantly improved due to the existence of TiC, and the lubrication performance of the coating was improved by the addition of Cu, and the lubrication performance of coatings was further improved by the synergistic effect of CrxSy, Cu and TiWC2. Among the three composite coatings, the NiCr/TiC-Cu-WS2coating obtained optimum anti-friction performance

Keywords:lasercladding,nickel-basedalloy,wear-resistantcoating,wearmechanism

Interfacialmicrostructureandmechanicalpropertiesofvacuumbrazed3003aluminumalloyhoneycombpanel

Li Yunyue1, Shen Yuanxun1, Li Xiupeng1, Pei Yinyin1, Wang Luyi1, Long Weimin1,2

(1. Zhengzhou Research Institute of Mechanical Engineering Co., Ltd., State Key Laboratory of Advanced Brazing Filler Metals and Technology, Zhengzhou 450001, China; 2. China Innovation Academy of Intelligent Equipment (Ningbo) Co., Ltd., Ningbo 315700, Zhejiang, China).p23-28

AbstractVacuum brazing of 6063/3003/6063 sandwich aluminum honeycomb panel was carried out with 4004 brazing filler metal. The effect of brazing temperature on microstructure and mechanical properties of brazed interface was studied. The results showed that microstructure of the brazed interface of 6063/3003/6063 honeycomb plate was sensitive to brazing temperature, and good metallurgical bonding could be formed at 580～595 ℃. Microstructure of brazing seam consisted of Al rich phase, AlSi eutectic phase and Al(Mn,Fe)Si phase. However, with the increase of brazing temperature, the corrosion degree of the base metal increased, and the base metal was almost completely dissolved at 595 ℃. The results of flat pressure test showed that the bending deformation of honeycomb core aluminum foil led to unstable collapse, the fracture occurred in the middle of honeycomb core during flat tension test, which indicated that the strength of brazed interface was high, and the fracture did not occur at the brazed joint.

Keywords:aluminumhoneycombpanel,vacuumbrazing,brazingtemperature,interfacemicrostructure,mechanicalproperties

EffectofNionmicrostructureandpropertiesofSMAWdepositedmetalonQ690steel

Chen Jianguo1,2,3, Yang Yongmei1, Li Liqun3, Wang Zejun2, Xiao Huiying1

(1. Tianjin Yongchang Welding Wire Co., Ltd., Tianjin 300300, China; 2. Tianjin Special Equipment Inspection Institute, Tianjin 300192, China; 3. Harbin Institute of Technology, Harbin 150001, China).p29-33,40

AbstractThe welding consumables of Q690 high-strength steel were taken as the research object, effects of Ni content on the microstructure and mechanical properties of deposited metal by shielded metal arc welding (SMAW) were studied by means of optical digital microscope, scanning electron microscope and fracture analysis. The results showed that the solution strengthening and fine grain strengthening were the main strengthening mechanism of deposited metals. The addition of Ni could effectively modify the microstructure and mechanical properties of the deposited metal. With the increase of Ni content, the tensile strength of the deposited metal increased while the impact performance decreased. Appropriate amount of Ni addition could cause the increase of acicular ferrite. However, excessive addition of Ni resulted in the decrease of acicular ferrite, and the formation of lath bainite and martensite, which caused the deterioration of the impact properties of the deposited metal.

Keywords:microstructure,mechanicalproperties,Q690steel,Nicontent

Mesoscopicsimulationofvibrationreductionofresidualstressinaluminumalloywelding

Du Song, Jin Cheng

(Dalian Jiaotong University, Dalian 116028, Liaoning, China).p34-40

AbstractIn view of the welding residual stress, the finite element software ABAQUS was used to simulate the welded joint of thin sheet aluminum alloy under several groups of welding parameters. According to the EBSD data of welded joints under different welding parameters, the macroscopic model and the mesoscopic model were established respectively. In the mesoscopic model, the temperature field and residual stress field were calculated by the face-centered cubic model based on the crystal cell structure of aluminum alloy. On this basis, non-resonant vibration was used to reduce the residual stress. The changes of residual stress in the macroscopic model and the mesoscopic model with different initial crystal orientations were compared, and the influence of crystal orientations on the stress relief effect under the different initial stress was compared. Results showed that the residual stress reduction effect of the mesoscopic model was better than that of the macroscopic model. The polycrystalline model with large crystal orientation difference had the highest stress reduction effect. The mesoscopic model could effectively simulate the reduction of longitudinal residual stress, and it was in accordance with the experimental results.

Keywords:weldingresidualstress,crystalplasticity,polycrystallinemodeling,mesoscopicsimulation,nonresonantvibration

Researchanddevelopmentofweldingwithlocalcooling

Xiao Xiucheng1, Yang Zhanli1, Yang Zekun1, Zhao Bao1, Jiang Hongpeng2, Xue Yong2

(1. Harbin Welding Institute Co., Ltd., Harbin 150028, China; 2. Fushun Machinery Manufacturing Co., Ltd., Fushun 113122, Liaoning, China).p41-47,61

AbstractTrends of residual stress and strain, heat-affected zone width, crack susceptibility and weld microstructure of welded joints with local cooling were reviewed in the article. The influence of the four characteristic parameters of cooling medium, the distance between the cooling source and the center of the molten pool, the action width of the cooling source and the cooling termination temperature on the cooling effect of the cooling source was analyzed. It was hoped to provide a reference for the application of welding with local cooling technology in actual engineering.

Keywords:weldingwithlocalcooling,coolingrate,microstructureofweldedjoint,stress,strain

Insightsonheattreatmenttoimprovemechanicalpropertiesofweldedjoints

Li Yunfu1, Fang Wunong1, Li Zhenhua2

(1. Hefei General Machinery Research Institute Co., Ltd., Hefei 230031, China; 2. Harbin Welding Institute Huatong (Changzhou) Welding Industry Co., Ltd., Changzhou 213000, Jiangsu, China).p48-52

AbstractThe common heat treatment process of pressure vessel was introduced. The effect of post-weld heat treatment on mechanical properties of welded joints of V improved steel (2.25Cr-1Mo-0.25V), P91 steel and 07MnNiMoDR steel was described. The effect of heat treatment aboveAc3line on the impact toughness of hot forming head weld and electroslag welded joint was emphasized. The improvement of other properties of welded joints (weld metal) by post-weld heat treatment was introduced from aspects of fracture toughness, creep property, stress corrosion resistance and fatigue strength. It was hoped that the customary term of “heat treatment to improve the mechanical properties of materials” in relevant standards would be changed to “heat treatment to improve the mechanical properties of welded joints”.

Keywords:post-weldheattreatment,aboveAc3lineheattreatment,improvingmechanicalproperties

HotrepairweldingtechnologyofZG15Cr1Mo1Vcasting

Ma Zhibao1,Li Fengqiang2,Chen Xin1,Gao Dawei1,Liu Yanru1,Guo Derui1

(1.Datang North China Electric Power Experimental Research Institute,Beijing 100040;2. Datang International Power Generation Co., Ltd., Beijing Gaojing Thermal Power Plant, Beijing 100041,China).p53-56

AbstractThe cracking position of ZG15Cr1Mo1V casting was determined as angle R position of the combined valve body.The composition, microstructure and mechanical properties of the parent material around the defect were tested,and the casting was qualified for repair welding.The weldability and key points of repair welding of ZG15Cr1Mo1V steel were analyzed.The repair welding of ZG15Cr1Mo1V casting of medium pressure reheat combined control valve of a power plant was successfully carried out with the same material hot repair welding and the integral heat treatment. It has been running safely and stably for 4 years.

Keywords:ZG15Cr1Mo1V,hotrepairwelding,integralheattreatment,casting

Applicationoflaserweldinginsteadofprojectionweldinginskylightstandardparts

Fang Yingze, Yang Huangrui

(Dongfeng (Wuhan) Industrial Co.,Ltd., Wuhan 430056, China).p57-61

AbstractFor the skylight reinforcement ring and its matching standard parts, 5 sets of tests were designed, involving the collocation between different plates and different standard parts. remote laser self-fusion welding was used to carry out welding tests, andthe appearance and penetration of the welds wereobserved, and then the ejection force of standard parts were tested.The results showed thatgood welding results were obtainedin different plates and different types of standard parts. The ejection force of the welding nut exceeded 25kN, which was more than 3 times that of the standard requirements. The ejection force of the welding screw exceeded 17kN, which was morethan 3.5 times that of the standard requirements. Considering the comprehensive performance,cost and industrialization,laser welding of skylight standard parts had application prospects.

Keywords:Laserwelding,skylightreinforcementring,standardparts,ejectionforce