The selection of process parameter in the gas tungsten arc （GTA） welding of titanium alloy was presented for obtaining optimum grain size and hardness. Titanium alloy （Ti-6Al-4V） is one of the most important non-f...The selection of process parameter in the gas tungsten arc （GTA） welding of titanium alloy was presented for obtaining optimum grain size and hardness. Titanium alloy （Ti-6Al-4V） is one of the most important non-ferrous metals which offers great potential application in aerospace, biomedical and chemical industries, because of its low density （4.5 g/cm^3）, excellent corrosion resistance, high strength, attractive fracture behaviour and high melting point （1678℃）. The preferred welding process for titanium alloy is frequent GTA welding due to its comparatively easier applicability and better economy. In the case of single pass （GTA） welding of thinner section of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current process. Many considerations come into the picture and one needs to carefully balance various pulse current parameters to reach an optimum combination. Four factors, five level, central composite, rotatable design matrix were used to optimize the required number of experimental conditions. Mathematical models were developed to predict the fusion zone grain size using analysis of variance （ANOVA） and regression analysis. The developed models were optimized using the traditional Hooke and Jeeve＇s algorithm. Experimental results were provided to illustrate the proposed approach.展开更多
An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency...An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency and pulse on time were studied. The experiments were conducted based on a four-factor, five-level, central composite design matrix. The developed empirical relationship can be effectively used to predict the tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy joints at 95% confidence level. The results indicate that pulse frequency has the greatest influence on tensile strength, followed by peak current, pulse on time and base current.展开更多
Though the preferred welding process to weld aluminium alloy is frequently constant current gas tungsten arc welding (CCGTAW),it resulted in grain coarsening at the fusion zone and heat affected zone(HAZ).Hence,pulsed...Though the preferred welding process to weld aluminium alloy is frequently constant current gas tungsten arc welding (CCGTAW),it resulted in grain coarsening at the fusion zone and heat affected zone(HAZ).Hence,pulsed current gas tungsten arc welding(PCGTAW) was performed,to yield finer fusion zone grains,which leads to higher strength of AA6061 (Al-Mg-Si) aluminium alloy joints.In order to determine the most influential control factors which will yield minimum fusion zone grain size and maximum tensile strength of the joints,the traditional Hooke and Jeeves pattern search method was used.The experiments were carried out based on central composite design with 31 runs and an algorithm was developed to optimize the fusion zone grain size and the tensile strength of pulsed current gas tungsten arc welded AA6061 aluminium alloy joints.The results indicate that the peak current (Ip) and base current (IB) are the most significant parameters,to decide the fusion zone grain size and the tensile strength of the AA6061 aluminum alloy joints.展开更多
The interfacial reaction control of SiC_p/2124Al composites was investigated during pulsed argon arc welding. Meanwhile, the mechanical properties, the metallographic structure and interfacial microstructure of the in...The interfacial reaction control of SiC_p/2124Al composites was investigated during pulsed argon arc welding. Meanwhile, the mechanical properties, the metallographic structure and interfacial microstructure of the induced welding joint were tested and detected, respectively. The results reveal that the joint with excellent properties could be achieved by the proper selection of the special filling material and the addition of the pulse during welding. Moreover, the formation mechanism of the welding joint was discussed and the corresponding measures on further improving the quality of the welding joint of SiC_p/2124Al composites were put forward in the condition of pulsed argon arc welding.展开更多
Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardnes...Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardness profiles, microstructural features and residual stress distribution of aluminium alloy joints were reported. The use of pulsed current technique is found to improve the tensile properties of the weld compared with continuous current welding due to grain refinement occurring in the fusion zone.展开更多
The tenacity of heat-affected zone （HAZ） will decline and the size of grains will increase, because of the overheating on HAZ when submerged are welding （SAW） is ased to thick plate with high heat input. The shapi...The tenacity of heat-affected zone （HAZ） will decline and the size of grains will increase, because of the overheating on HAZ when submerged are welding （SAW） is ased to thick plate with high heat input. The shaping will worsen when SAW is used to thin plate with high current at high speed. A new SAW technology, the pulsed direct current （DC） automatic SAW, will be put forward in this paper in order to overcome the above shortcomings. And a pulsed controller with micro-controller unit （MCU） as the core, nixie tube （NT） and keyboard as the man-machine conversation interface is developed. The main functions of the pulsed controller include the output of pulsed welding current and the working with twinwire. The research has widely prospects in application with significant meanings in theory and practical engineering.展开更多
The pitting corrosion characteristics of pulse TIG welded Ti-6Al-4V titanium alloy in marine environment were explained. Besides the rapid advance of titanium metallurgy, this is also due to the successful solution of...The pitting corrosion characteristics of pulse TIG welded Ti-6Al-4V titanium alloy in marine environment were explained. Besides the rapid advance of titanium metallurgy, this is also due to the successful solution of problems associated with the development of titanium alloy welding. The preferred welding process of titanium alloy is frequently gas tungsten arc(GTA) welding due to its comparatively easier applicability and better economy. In the case of single pass GTA welding of thinner section of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current process. The benefit of the process is utilized to obtain better quality titanium weldments. Four factors, five levels, central composite, rotatable design matrix are used to optimize the required number of experiments. The mathematical models have been developed by response surface method(RSM). The results reveal that the titanium alloy can form a protective scale in marine environment and is resistant to pitting corrosion. Experimental results are provided to illustrate the proposed approach.展开更多
This study investigated multi-response optimization of the pulse metal active gas-tungsten inert gas( PMAG-TIG) twin arc hybrid root welding process for an optimal parametric combination to yield favorable back bead g...This study investigated multi-response optimization of the pulse metal active gas-tungsten inert gas( PMAG-TIG) twin arc hybrid root welding process for an optimal parametric combination to yield favorable back bead geometry of welded joints using grey relational analysis and Taguchi method.Eighteen experimental runs based on an orthogonal array following the Taguchi method were performed to derive objective functions to be optimized within the experimental domain.The objective functions were selected in relation to parameters of PMAG-TIG twin arc root welding back bead geometry: back bead width to root reinforcement ratio and deposited metal height.The Taguchi approach was followed by grey relational analysis to solve the multi-response optimization problem.The significance of factors on overall quality characteristics of the weld joint was also evaluated quantitatively using analysis of variance.Optimal results were verified through additional experiments,and showed to feasibility of applying grey relation analysis in combination with Taguchi technique for continuous improvement of product quality in the manufacturing industry.展开更多
Based on the extended application of COMSOL multiphysics, a novel dual heat source model for pulsed laser-gas tungsten arc （GTA） hybrid welding was established. This model successfully solved the problem of simulati...Based on the extended application of COMSOL multiphysics, a novel dual heat source model for pulsed laser-gas tungsten arc （GTA） hybrid welding was established. This model successfully solved the problem of simulation inaccuracy caused by energy superposition effect between laser and arc due to their different physical characteristics. Numerical simulation for pulsed laser-GTA hybrid welding of magnesium alloy process was conducted, and the simulation indicated good agree- ments with the measured thermal cycle curve and the shape of weld beads. Effects of pulse laser parameters （laser-excited current, pulse duration, and pulse frequency） on the temperature field and weld pool morphology were investigated. The experimental and simulation results suggest that when the laser pulse energy keeps constant, welding efficiency of the hybrid heat source is increased by increasing laser current or decreasing pulse duration due to the increased ratio of the weld bead depth to width. With large laser currents, severe spatters tend to occur. For optimized welding process, the laser current should be controlled in the range of 150-175 A, the pulse duration should be longer than 1 ms, and the pulse frequency should be equal to or slightly greater than 20 Hz.展开更多
A novel ultrafast-convert hybrid pulse variable polarity gas tungsten arc welding process （HPVP-GTAW） is developed. High frequency pulse square-wave current which has a frequency of more than 20 kHz is exactly integ...A novel ultrafast-convert hybrid pulse variable polarity gas tungsten arc welding process （HPVP-GTAW） is developed. High frequency pulse square-wave current which has a frequency of more than 20 kHz is exactly integrated in the positive polarity current duration. The effects of pulse current parameters on arc characteristics and weld penetration have been studied during the HPVP-GTAW process using Al-5. 8 Mg alloy plates. The arc characteristics studied by arc voltage and its profile, weld penetration noted by the ratio of weld depth to width have been found to be influenced significantly by the pulse current. The experimental results show that the HPVP-GTA W process can improve the arc profile predominantly and obtain the higher weld penetration with lower heat input. The observation may help in understanding the weld characteristics with respect to variation in the pulse current parameters which may be beneficial in using the novel HPVP-GTAW process to produce the better weld quality of aluminum alloy plates.展开更多
Pulsed tungsten inert gas （TIG） welding is widely used in industry due to its superior properties, so the measurement of arc telnperature is important to analyse welding process. Arc image of spectral line in 794.8 ...Pulsed tungsten inert gas （TIG） welding is widely used in industry due to its superior properties, so the measurement of arc telnperature is important to analyse welding process. Arc image of spectral line in 794.8 nm is captured by high speed camera; both the Abel inversion and the Fowler-Milne method are used to calculate the temperature distribution of the pulsed TIG welding. Characteristic of transient variation in arc intensity and temperature is analyzed. When the change of current happens, intensity and temperature of arc jump as well, it costs several millisoconds. The flirther the axial position from the tungsten is, the greater the intensity jumps, and the smaller the temperature changes.展开更多
The effects of pulsing current parameters on weld pool geometry namely front height, back height, front width and back width of pulse current gas tungsten arc welded （GTAW） titanium alloy was analysed. Four factors,...The effects of pulsing current parameters on weld pool geometry namely front height, back height, front width and back width of pulse current gas tungsten arc welded （GTAW） titanium alloy was analysed. Four factors, five levels, central composite design were used to develop empirical relationships, incorporating pulsed current parameters and weld pool geometry.展开更多
文摘The selection of process parameter in the gas tungsten arc （GTA） welding of titanium alloy was presented for obtaining optimum grain size and hardness. Titanium alloy （Ti-6Al-4V） is one of the most important non-ferrous metals which offers great potential application in aerospace, biomedical and chemical industries, because of its low density （4.5 g/cm^3）, excellent corrosion resistance, high strength, attractive fracture behaviour and high melting point （1678℃）. The preferred welding process for titanium alloy is frequent GTA welding due to its comparatively easier applicability and better economy. In the case of single pass （GTA） welding of thinner section of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current process. Many considerations come into the picture and one needs to carefully balance various pulse current parameters to reach an optimum combination. Four factors, five level, central composite, rotatable design matrix were used to optimize the required number of experimental conditions. Mathematical models were developed to predict the fusion zone grain size using analysis of variance （ANOVA） and regression analysis. The developed models were optimized using the traditional Hooke and Jeeve＇s algorithm. Experimental results were provided to illustrate the proposed approach.
文摘An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency and pulse on time were studied. The experiments were conducted based on a four-factor, five-level, central composite design matrix. The developed empirical relationship can be effectively used to predict the tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy joints at 95% confidence level. The results indicate that pulse frequency has the greatest influence on tensile strength, followed by peak current, pulse on time and base current.
基金Naval Research Board (NRB),Ministry of Defence,New Delhi for the financial support to carry out this investigation through sponsored project No.DNRD/05/4003/NRB/67.
文摘Though the preferred welding process to weld aluminium alloy is frequently constant current gas tungsten arc welding (CCGTAW),it resulted in grain coarsening at the fusion zone and heat affected zone(HAZ).Hence,pulsed current gas tungsten arc welding(PCGTAW) was performed,to yield finer fusion zone grains,which leads to higher strength of AA6061 (Al-Mg-Si) aluminium alloy joints.In order to determine the most influential control factors which will yield minimum fusion zone grain size and maximum tensile strength of the joints,the traditional Hooke and Jeeves pattern search method was used.The experiments were carried out based on central composite design with 31 runs and an algorithm was developed to optimize the fusion zone grain size and the tensile strength of pulsed current gas tungsten arc welded AA6061 aluminium alloy joints.The results indicate that the peak current (Ip) and base current (IB) are the most significant parameters,to decide the fusion zone grain size and the tensile strength of the AA6061 aluminum alloy joints.
文摘The interfacial reaction control of SiC_p/2124Al composites was investigated during pulsed argon arc welding. Meanwhile, the mechanical properties, the metallographic structure and interfacial microstructure of the induced welding joint were tested and detected, respectively. The results reveal that the joint with excellent properties could be achieved by the proper selection of the special filling material and the addition of the pulse during welding. Moreover, the formation mechanism of the welding joint was discussed and the corresponding measures on further improving the quality of the welding joint of SiC_p/2124Al composites were put forward in the condition of pulsed argon arc welding.
文摘Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardness profiles, microstructural features and residual stress distribution of aluminium alloy joints were reported. The use of pulsed current technique is found to improve the tensile properties of the weld compared with continuous current welding due to grain refinement occurring in the fusion zone.
文摘The tenacity of heat-affected zone （HAZ） will decline and the size of grains will increase, because of the overheating on HAZ when submerged are welding （SAW） is ased to thick plate with high heat input. The shaping will worsen when SAW is used to thin plate with high current at high speed. A new SAW technology, the pulsed direct current （DC） automatic SAW, will be put forward in this paper in order to overcome the above shortcomings. And a pulsed controller with micro-controller unit （MCU） as the core, nixie tube （NT） and keyboard as the man-machine conversation interface is developed. The main functions of the pulsed controller include the output of pulsed welding current and the working with twinwire. The research has widely prospects in application with significant meanings in theory and practical engineering.
文摘The pitting corrosion characteristics of pulse TIG welded Ti-6Al-4V titanium alloy in marine environment were explained. Besides the rapid advance of titanium metallurgy, this is also due to the successful solution of problems associated with the development of titanium alloy welding. The preferred welding process of titanium alloy is frequently gas tungsten arc(GTA) welding due to its comparatively easier applicability and better economy. In the case of single pass GTA welding of thinner section of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current process. The benefit of the process is utilized to obtain better quality titanium weldments. Four factors, five levels, central composite, rotatable design matrix are used to optimize the required number of experiments. The mathematical models have been developed by response surface method(RSM). The results reveal that the titanium alloy can form a protective scale in marine environment and is resistant to pitting corrosion. Experimental results are provided to illustrate the proposed approach.
基金supported by the National Natural Science Foundation of China(Grant No.11375038)Science Fund for Creative Research Groups of NSFC(Grant No.51621064)
文摘This study investigated multi-response optimization of the pulse metal active gas-tungsten inert gas( PMAG-TIG) twin arc hybrid root welding process for an optimal parametric combination to yield favorable back bead geometry of welded joints using grey relational analysis and Taguchi method.Eighteen experimental runs based on an orthogonal array following the Taguchi method were performed to derive objective functions to be optimized within the experimental domain.The objective functions were selected in relation to parameters of PMAG-TIG twin arc root welding back bead geometry: back bead width to root reinforcement ratio and deposited metal height.The Taguchi approach was followed by grey relational analysis to solve the multi-response optimization problem.The significance of factors on overall quality characteristics of the weld joint was also evaluated quantitatively using analysis of variance.Optimal results were verified through additional experiments,and showed to feasibility of applying grey relation analysis in combination with Taguchi technique for continuous improvement of product quality in the manufacturing industry.
基金This work was supported by the Natural Science Foundation of Liaoning Province of China （Grant Nos. 201602391 and 20170540460）.
文摘Based on the extended application of COMSOL multiphysics, a novel dual heat source model for pulsed laser-gas tungsten arc （GTA） hybrid welding was established. This model successfully solved the problem of simulation inaccuracy caused by energy superposition effect between laser and arc due to their different physical characteristics. Numerical simulation for pulsed laser-GTA hybrid welding of magnesium alloy process was conducted, and the simulation indicated good agree- ments with the measured thermal cycle curve and the shape of weld beads. Effects of pulse laser parameters （laser-excited current, pulse duration, and pulse frequency） on the temperature field and weld pool morphology were investigated. The experimental and simulation results suggest that when the laser pulse energy keeps constant, welding efficiency of the hybrid heat source is increased by increasing laser current or decreasing pulse duration due to the increased ratio of the weld bead depth to width. With large laser currents, severe spatters tend to occur. For optimized welding process, the laser current should be controlled in the range of 150-175 A, the pulse duration should be longer than 1 ms, and the pulse frequency should be equal to or slightly greater than 20 Hz.
基金The research is supported by the National Natural Science Foundation of China （ No. 50975015 and No. 51005011 ） the China Postdoctoral Science Foundation （No. 20090460186）.
文摘A novel ultrafast-convert hybrid pulse variable polarity gas tungsten arc welding process （HPVP-GTAW） is developed. High frequency pulse square-wave current which has a frequency of more than 20 kHz is exactly integrated in the positive polarity current duration. The effects of pulse current parameters on arc characteristics and weld penetration have been studied during the HPVP-GTAW process using Al-5. 8 Mg alloy plates. The arc characteristics studied by arc voltage and its profile, weld penetration noted by the ratio of weld depth to width have been found to be influenced significantly by the pulse current. The experimental results show that the HPVP-GTA W process can improve the arc profile predominantly and obtain the higher weld penetration with lower heat input. The observation may help in understanding the weld characteristics with respect to variation in the pulse current parameters which may be beneficial in using the novel HPVP-GTAW process to produce the better weld quality of aluminum alloy plates.
基金the National Natural Science Foundation of China （No. 51275299）
文摘Pulsed tungsten inert gas （TIG） welding is widely used in industry due to its superior properties, so the measurement of arc telnperature is important to analyse welding process. Arc image of spectral line in 794.8 nm is captured by high speed camera; both the Abel inversion and the Fowler-Milne method are used to calculate the temperature distribution of the pulsed TIG welding. Characteristic of transient variation in arc intensity and temperature is analyzed. When the change of current happens, intensity and temperature of arc jump as well, it costs several millisoconds. The flirther the axial position from the tungsten is, the greater the intensity jumps, and the smaller the temperature changes.
文摘The effects of pulsing current parameters on weld pool geometry namely front height, back height, front width and back width of pulse current gas tungsten arc welded （GTAW） titanium alloy was analysed. Four factors, five levels, central composite design were used to develop empirical relationships, incorporating pulsed current parameters and weld pool geometry.
