A new hybrid welding process was successfully used to join aluminum alloy and stainless steel. In the MIG welding-brazing process, the lower thermal conductivity of steel can cause dramatic change of temperature gradi...A new hybrid welding process was successfully used to join aluminum alloy and stainless steel. In the MIG welding-brazing process, the lower thermal conductivity of steel can cause dramatic change of temperature gradient on steel surface, while the auxiliary TIG arc can change this phenomenon by heating the steel side. The auxiliary TIG improved the wettability of molten metal, resulting in the molten metal spreading fully on upper surfaces, front and back surface of steel, forming a sound brazing joint; the content of Cr and Ni elements in IMCs layer was increased, which can enhance the quality of the layer; and the microstructure of IMCs layer also was improved, increasing the bonding strength with the weld seam. The average tensile strength of the joint obtained with auxiliary TIG arc（146.7 MPa） was higher than that without auxiliary TIG arc（96.7 MPa）.展开更多
Twin-tungsten TIG welding was developed, in which two electrodes were placed in a single welding torch. In order to master this process, the arc physics characteristic was studied. The twin-tungsten coupling arc shape...Twin-tungsten TIG welding was developed, in which two electrodes were placed in a single welding torch. In order to master this process, the arc physics characteristic was studied. The twin-tungsten coupling arc shape was observed by using CCD camera, and the arc pressure was measured. The results show that the coupling arc includes two arcs that pull each other according to Lorentz force and one big coupling arc is formed; the coupling arc pressure is much lower than that of conventional TIG arc. In the end, a simple welding experiment was carried out. This proves that stable welding process can be achieved by twin-tungsten TIG at higher current than that of conventional TIG because of its low arc pressure and the high efficiency welding is realized.展开更多
Calculations have been made for weld depths occurring for TIG welding activated by a flux over the surface of the weld pool. In this case, the flux introduces an electrically insulating layer over the outer regions of...Calculations have been made for weld depths occurring for TIG welding activated by a flux over the surface of the weld pool. In this case, the flux introduces an electrically insulating layer over the outer regions of the weld pool surface. There is then an increase in the current density at the surface of the centre of the weld pool with a consequent increase in the J×B forces, which drive a strong convective flow of the molten metal downwards, tending to make a deep weld. For a flux which produces an insulating layer for all but a central region of radius 2 mm, the calculated weld depth is 7 mm, and an arc spot is predicted at the centre of the weld pool surface. As yet we have not resolved the reason for significant differences that exist between our measurements of weld depth and the theoretical predictions.展开更多
Methods of arc length control and visual image based weld detection for precision pulse TIG welding were investigated. With a particular all hardware circuit, arc voltage during peak current stage is sampled and inte...Methods of arc length control and visual image based weld detection for precision pulse TIG welding were investigated. With a particular all hardware circuit, arc voltage during peak current stage is sampled and integrated to indicate arc length, deviation of arc length and adjusting parameters are calculated and output to drive a step motor directly. According to the features of welding image grabbed with CCD camera, a special algorithm was developed to detect the central line of weld fast and accurately. Then an application system were established, whose static arc length error is ±0.1 mm with 20 A average current and 1 mm given arc length, static detection precision of weld is 0.01 mm , processing time of each image is less than 120 ms . Precision pulse TIG welding of some given thin stainless steel components with complicated curved surface was successfully realized.展开更多
TC4 alloy was welded by conventional TIG welding and arc-ultrasonic TIG welding respectively. The microstructure of joint was analyzed by means of optical-microscope, scanning electron microscope in order to study the...TC4 alloy was welded by conventional TIG welding and arc-ultrasonic TIG welding respectively. The microstructure of joint was analyzed by means of optical-microscope, scanning electron microscope in order to study the relationship between the macro-properties of joint and the microstructure. The results show that the joints were all welded successfully by conventional TIG welding and arc-ultrasonic TIG welding. With the increment of ultrasonic frequency and activated voltage, the width of joint became narrow step by step. The microstructure became more and more fine and was inclined to equiaxed crystal. Moreover, the dendrite depredation was not observed obviously. The properties of welded joint were improved markedly compared with that of conventional TIG welding.展开更多
This work mainly articulated the effects of nozzle structure on arc characteristics in gas pool coupled activating TIG （GPCA-TIG） welding process by using Fluent Software. Different models were set up to adapt the d...This work mainly articulated the effects of nozzle structure on arc characteristics in gas pool coupled activating TIG （GPCA-TIG） welding process by using Fluent Software. Different models were set up to adapt the different torch structure during computer progress. The specific configuration of the welding torch made the gas flow in outer gas passage constrained. The nozzle structure has great influence on outer gas distribution because of the changing of coupling region between the outer active gas and molten pool surface. When the coupling degree is reduced or the outer gas passage become smaller, the oxygen in outer gas penetrates into the arc plasma and spreads to the arc region more easily. Owing to its cooling effects, the morphology of arc is contracted, and the arc temperature is increased. When the inner wall and the outer wall of outer gas passage are not parallel, the wide top and narrow bottom nozzle shape can bring more oxygen into the arc plasma, the arc is contracted and the peak temperature of arc rises a little more comparing to the narrow top and wide bottom one.展开更多
In order to study the arc force distribution of ultrasonic assisted tungsten inert gas （U-TIG） welding and compare it with the conventional tungsten inert gas （TIC） welding, a series of experiments have been carri...In order to study the arc force distribution of ultrasonic assisted tungsten inert gas （U-TIG） welding and compare it with the conventional tungsten inert gas （TIC） welding, a series of experiments have been carried out, using our self- designed welding and testing system. The distribution of arc pressure is studied, under conditions as radiation distance, which is the distance between the ultrasonic horn tip and workpiece, and welding current. The values of arc pressure generally increase as the current increases. Other experimental phenomena are also accounted for in detail in this paper. Welding parameters are thought to be responsible for enhancing the welding efficiency and improving the appearance of weld.展开更多
The arc spectrum of TIG welding in high pressure was analyzed by Stark broadening. Using the characteristic line of Arl in welding arc, a study of electron density in high pressure revealed that the electron density o...The arc spectrum of TIG welding in high pressure was analyzed by Stark broadening. Using the characteristic line of Arl in welding arc, a study of electron density in high pressure revealed that the electron density of the welding arc had an upward trend with the pressure increase. According to data analysis, a curve of relationship between electron density alwl environmental pressure was established. It has a universal significance for change of electron density in high pressure. Through the analysis of electron density changing in time-domain in different pressure, a theoretical basis was provided for the problem of poor arc stability in high pressure.展开更多
The influence of laser parameters on are beharior of laser-TIC, dauble-side welding was investigated by utilizing CCD sensor and intage processing methods. It was found that are images had an obvious transformation fr...The influence of laser parameters on are beharior of laser-TIC, dauble-side welding was investigated by utilizing CCD sensor and intage processing methods. It was found that are images had an obvious transformation from laser preheating to laser plasma ejected from the keyhole bottom, resulting in the phenomena of arc column convergence and arc root constrictian. The attraction phenomenon of the laser and the arc is also found in laser-TIG double-side welding. More noteworthy is that the behavior of arc attraction or constriction became much obvious at a lower current or laser plasma ejected from the keyhole bottom. The decrease in arc voltage had a certain relation u＇ith the improvement of arc stabilio.展开更多
文摘A new hybrid welding process was successfully used to join aluminum alloy and stainless steel. In the MIG welding-brazing process, the lower thermal conductivity of steel can cause dramatic change of temperature gradient on steel surface, while the auxiliary TIG arc can change this phenomenon by heating the steel side. The auxiliary TIG improved the wettability of molten metal, resulting in the molten metal spreading fully on upper surfaces, front and back surface of steel, forming a sound brazing joint; the content of Cr and Ni elements in IMCs layer was increased, which can enhance the quality of the layer; and the microstructure of IMCs layer also was improved, increasing the bonding strength with the weld seam. The average tensile strength of the joint obtained with auxiliary TIG arc（146.7 MPa） was higher than that without auxiliary TIG arc（96.7 MPa）.
文摘Twin-tungsten TIG welding was developed, in which two electrodes were placed in a single welding torch. In order to master this process, the arc physics characteristic was studied. The twin-tungsten coupling arc shape was observed by using CCD camera, and the arc pressure was measured. The results show that the coupling arc includes two arcs that pull each other according to Lorentz force and one big coupling arc is formed; the coupling arc pressure is much lower than that of conventional TIG arc. In the end, a simple welding experiment was carried out. This proves that stable welding process can be achieved by twin-tungsten TIG at higher current than that of conventional TIG because of its low arc pressure and the high efficiency welding is realized.
文摘Calculations have been made for weld depths occurring for TIG welding activated by a flux over the surface of the weld pool. In this case, the flux introduces an electrically insulating layer over the outer regions of the weld pool surface. There is then an increase in the current density at the surface of the centre of the weld pool with a consequent increase in the J×B forces, which drive a strong convective flow of the molten metal downwards, tending to make a deep weld. For a flux which produces an insulating layer for all but a central region of radius 2 mm, the calculated weld depth is 7 mm, and an arc spot is predicted at the centre of the weld pool surface. As yet we have not resolved the reason for significant differences that exist between our measurements of weld depth and the theoretical predictions.
文摘Methods of arc length control and visual image based weld detection for precision pulse TIG welding were investigated. With a particular all hardware circuit, arc voltage during peak current stage is sampled and integrated to indicate arc length, deviation of arc length and adjusting parameters are calculated and output to drive a step motor directly. According to the features of welding image grabbed with CCD camera, a special algorithm was developed to detect the central line of weld fast and accurately. Then an application system were established, whose static arc length error is ±0.1 mm with 20 A average current and 1 mm given arc length, static detection precision of weld is 0.01 mm , processing time of each image is less than 120 ms . Precision pulse TIG welding of some given thin stainless steel components with complicated curved surface was successfully realized.
文摘TC4 alloy was welded by conventional TIG welding and arc-ultrasonic TIG welding respectively. The microstructure of joint was analyzed by means of optical-microscope, scanning electron microscope in order to study the relationship between the macro-properties of joint and the microstructure. The results show that the joints were all welded successfully by conventional TIG welding and arc-ultrasonic TIG welding. With the increment of ultrasonic frequency and activated voltage, the width of joint became narrow step by step. The microstructure became more and more fine and was inclined to equiaxed crystal. Moreover, the dendrite depredation was not observed obviously. The properties of welded joint were improved markedly compared with that of conventional TIG welding.
基金supported by National Natural Science Foundation of China(Grant No.51265029)
文摘This work mainly articulated the effects of nozzle structure on arc characteristics in gas pool coupled activating TIG （GPCA-TIG） welding process by using Fluent Software. Different models were set up to adapt the different torch structure during computer progress. The specific configuration of the welding torch made the gas flow in outer gas passage constrained. The nozzle structure has great influence on outer gas distribution because of the changing of coupling region between the outer active gas and molten pool surface. When the coupling degree is reduced or the outer gas passage become smaller, the oxygen in outer gas penetrates into the arc plasma and spreads to the arc region more easily. Owing to its cooling effects, the morphology of arc is contracted, and the arc temperature is increased. When the inner wall and the outer wall of outer gas passage are not parallel, the wide top and narrow bottom nozzle shape can bring more oxygen into the arc plasma, the arc is contracted and the peak temperature of arc rises a little more comparing to the narrow top and wide bottom one.
基金This study was supported by National Natural Science Foundation of China （51105109）, the Major State Basic Research Development Program of China （973Program） （No. 2013CB035500）and Natural Scientific Research Innovation Foundation in Harbin Institute of Technology （ HIT. NSRIF. 201006）.
文摘In order to study the arc force distribution of ultrasonic assisted tungsten inert gas （U-TIG） welding and compare it with the conventional tungsten inert gas （TIC） welding, a series of experiments have been carried out, using our self- designed welding and testing system. The distribution of arc pressure is studied, under conditions as radiation distance, which is the distance between the ultrasonic horn tip and workpiece, and welding current. The values of arc pressure generally increase as the current increases. Other experimental phenomena are also accounted for in detail in this paper. Welding parameters are thought to be responsible for enhancing the welding efficiency and improving the appearance of weld.
基金Acknowledgement The authors wish to thank the financial support for this research from the National High Technology Research and Development Program of China （863 Program） （Grant No. 2002AA602012） and the National Natural Science Foundation of China （Grant No. 40776054）.
文摘The arc spectrum of TIG welding in high pressure was analyzed by Stark broadening. Using the characteristic line of Arl in welding arc, a study of electron density in high pressure revealed that the electron density of the welding arc had an upward trend with the pressure increase. According to data analysis, a curve of relationship between electron density alwl environmental pressure was established. It has a universal significance for change of electron density in high pressure. Through the analysis of electron density changing in time-domain in different pressure, a theoretical basis was provided for the problem of poor arc stability in high pressure.
文摘The influence of laser parameters on are beharior of laser-TIC, dauble-side welding was investigated by utilizing CCD sensor and intage processing methods. It was found that are images had an obvious transformation from laser preheating to laser plasma ejected from the keyhole bottom, resulting in the phenomena of arc column convergence and arc root constrictian. The attraction phenomenon of the laser and the arc is also found in laser-TIG double-side welding. More noteworthy is that the behavior of arc attraction or constriction became much obvious at a lower current or laser plasma ejected from the keyhole bottom. The decrease in arc voltage had a certain relation u＇ith the improvement of arc stabilio.
