A two-dimensional model was established for the first time by coupling moving wire and arc in CMT-WAAM and GMAWWAAM process,revealing the temperature,potential and droplet transition behavior of droplet metal.The drop...A two-dimensional model was established for the first time by coupling moving wire and arc in CMT-WAAM and GMAWWAAM process,revealing the temperature,potential and droplet transition behavior of droplet metal.The droplet transition and the change of droplet transfer mode under different wire feeding speed were analyzed.The experiments and numerical simulation research found that droplet transition mode is projected transfer in GMAW-WAAM process under 150 A current,with a complete transition period is 14 ms.The droplet transition shows a short-circuit transition mode in CMT-WAAM process,with wire feeding speed of 5.5 m/min and a complete transition period is 20 ms.The droplet transition shows a mixture of droplet transfer and short-circuit transition mode in CMT-WAAM process,with wire feeding speed of 5.5 m/min and a complete transition period is 23 ms.Based on the theoretical research and experimental studies,the mechanism of droplet transfer mode in WAAM was studied,which can provide reference for optimizing parameters.展开更多
High-speed photography is utilized to capture an image of the arc area during the welding process.The variation in arc shape and droplet transfer behavior is compared when employing shielding gases of different compon...High-speed photography is utilized to capture an image of the arc area during the welding process.The variation in arc shape and droplet transfer behavior is compared when employing shielding gases of different components and proportions(e.g.,80%Ar+20%CO_(2),85%Ar+10%CO_(2)+5%O2,65%Ar+26.5%He+8%CO_(2)+0.5%O2)using a Ф1.2 mm welding wire under 360 A current.Furthermore,the effects of various shielding gas components on the stability of the welding process are discussed.It was determined that the addition of oxygen and helium changed the arc’s shape and the behavior of the droplet transfer,and the welding process stability increased.展开更多
In this paper, the droplet transfer in oscillating arc narrow gap gas metal arc （ GMA ） welding was studied. According to the experimental results, the oscillating arc has effect on the droplet transfer mode. The dr...In this paper, the droplet transfer in oscillating arc narrow gap gas metal arc （ GMA ） welding was studied. According to the experimental results, the oscillating arc has effect on the droplet transfer mode. The droplet transfer frequency in narrow gap groove is higher than that in bead-on-plate welding. Because of the change of arc location in narrow gap groove, the droplet transfer in oscillating arc narrow gap changes regularly. The droplet transfer frequency near groove sidewall is higher than that at the middle of narrow gap groove.展开更多
LF6 aluminum alloy plates with 4.5 mm thickness are welded in this experiment.Welding is carried out by using the CO_(2)laser-MIG paraxial hybrid welding in fiat position.The experimental results indicate that the inh...LF6 aluminum alloy plates with 4.5 mm thickness are welded in this experiment.Welding is carried out by using the CO_(2)laser-MIG paraxial hybrid welding in fiat position.The experimental results indicate that the inherent droplet transfer cycle time of conventional MIG arc is changed due to the interaction between CO_(2)laser beam and MIG arc in the short-circuiting mode of laser-MIG hybrid welding.Because of the preheating action of CO_(2)laser to electrode and base material,the droplet transfer frequency of MIG arc is increased in the hybrid welding process.When laser power is increased to a certain degree,the droplet transfer frequency is decreased due to the effect of laser-induced keyhole.Furthermore,through analyzing the MIG welding current and arc voltage waveforms and the characteristics of droplet transfer in the hybrid welding process,the effect of laser energy and the action point between laser beam and arc on the frequency of droplet transfer and weld appearance is investigated in details.展开更多
In order to study how welding parameters affect welding quality and droplet transfer, a synchronous acquisition and analysis system is established to acquire and analyze electrical signal and instantaneous images of d...In order to study how welding parameters affect welding quality and droplet transfer, a synchronous acquisition and analysis system is established to acquire and analyze electrical signal and instantaneous images of droplet transfer simultaneously, which is based on a self-developed soft-switching inverter. On the one hand, welding current and voltage signals are acquired and analyzed by a self-developed dynamic wavelet analyzer. On the other hand, images are filtered and optimized after they are captured by high-speed camera. The results show that instantaneous waveforms and statistical data of electrical signal contribute to make an overall assessment of welding quality, and that optimized high-speed images allow a visual and clear observation of droplet transfer process. The analysis of both waveforms and images leads to a further research on droplet transfer mechanism and provides a basis for precise control of droplet transfer.展开更多
The method to detect droplet transfer by means of arc spectrum, while the experiment sets, testing principle and data processing procedure,are presented. The experiment and analysis results show that arc spectrum si...The method to detect droplet transfer by means of arc spectrum, while the experiment sets, testing principle and data processing procedure,are presented. The experiment and analysis results show that arc spectrum signal can be utilized to detect and measure the transfer procedure, the transfer modes and the transfer parameters. The arc spectrum signal enjoys excellent quality with high signal amplitude. Each transfer mode has its specific typical signal mode, and the pulse outline corresponds to an integrated transferring procedure of one droplet. All these features of arc spectrum signal can be easily applied hi the control of transfer procedure,the identification and stabilization of transfer mode and the measurement of transfer parameters.展开更多
A simulation system used in the arc welding short circuit transfer process and current waveform control process was developed in this paper. The simulation results are basically consistent with welding technical exper...A simulation system used in the arc welding short circuit transfer process and current waveform control process was developed in this paper. The simulation results are basically consistent with welding technical experiments. The simulation system can be used to simulate and test the current waveform control parameters with welding variables. By this simulation system, the influence regularities of the current waveform control parameters in the CO 2 arc welding droplet short circuit transfer process can be got. Moreover, the basic mode of real time current waveform control can be also established by the simulation testing.展开更多
The character of droplet transfer arc light sense signal is studied and validated in oscillating feed mode. And a novel mini photoelectric arc light sensor together with the controlling circuit used to automatically...The character of droplet transfer arc light sense signal is studied and validated in oscillating feed mode. And a novel mini photoelectric arc light sensor together with the controlling circuit used to automatically stabilize the signal range is developed. Further more the automatically identifying of the droplet transfer character signal from arc light is realized reliably.展开更多
In this paper, the droplet transfer behavior of the stainless steel coated electrode with double layer coating is researched by means of those experimental methods, such as high speed camera, collecting droplet in wa...In this paper, the droplet transfer behavior of the stainless steel coated electrode with double layer coating is researched by means of those experimental methods, such as high speed camera, collecting droplet in water, surfacing on the steel plate et al. The results show that the droplet transfer indexes of coated electrode are mainly controlled by the size of droplet, which affects the transfer behavior of droplet. The distribution characteristic of the droplet size of the electrode affects the numerical relationship among droplet transfer indexes. The metallurgical process of the coated electrode with double layer coating is carried out continuously in different zones. The main reason for the coated electrode with double layer coating gaining excellent usability quality is that the droplets realize the 'quasi flux wall guided transfer pattern'.展开更多
A new method and if.''principle .fi)r 's*ensin.q dry)Plet iran.5/dr in aide W ')/ steel and aluminum alloy have been researched in this paper. A practical arc light sensing and controlling system has b...A new method and if.''principle .fi)r 's*ensin.q dry)Plet iran.5/dr in aide W ')/ steel and aluminum alloy have been researched in this paper. A practical arc light sensing and controlling system has been developed. The reliability of the arc light characteristic signal that indicates droplet detachment and the control accuracy of the system have been verified using high-speed photography Based on the mathematical model set up in the paper, the mechanism of the signal and relative phenomena were analyzed The parameters, which influence arc light radiation were given and the limitation of this sensing method was discussed.展开更多
In order to analyze the influence of the distance between heat sources(D_(LA))on the welding process,the effects of D_(LA)on the droplet transfer behavior,weld formation characteristics and weld formation mechanism of...In order to analyze the influence of the distance between heat sources(D_(LA))on the welding process,the effects of D_(LA)on the droplet transfer behavior,weld formation characteristics and weld formation mechanism of AH36 in laser and cable-type welding wire gas metal arc welding arc hybrid welding were studied.Real-time photography was conducted using a high-speed camera to determine the droplet transfer and arc behaviors;the surface morphology and macroscopic cross-section of the weld obtained from the experiment were observed and analyzed.The arc height decreases with the increase in the DLA,the arc width shows the opposite change,and the welding current decreases.The allure of the laser to the arc increases with the increase in the D_(LA).The frequency of droplet transfer increases with the increase in the D_(LA),but the growth rate decreases.The continuous increase in the D_(LA)leads to the tendency of the droplet size to decrease first and then increase,and the minimum value is obtained when the D_(LA)is 4 mm.The D_(LA)has obvious influence on the weld formation.The weld penetration and reinforcement change similarly,increasing first and then decreasing as the D_(LA)increases,and the laser area of the weld also increases first and then decreases.展开更多
Thin walls of an AZ91 magnesium alloy with fine equiaxed grains were fabricated via cold arc-based wire arc additive manufacturing(CA-WAAM),and the droplet transfer behaviours,microstructures,and mechanical properties...Thin walls of an AZ91 magnesium alloy with fine equiaxed grains were fabricated via cold arc-based wire arc additive manufacturing(CA-WAAM),and the droplet transfer behaviours,microstructures,and mechanical properties were investigated.The results showed that the cold arc process reduced splashing at the moment of liquid bridge breakage and effectively shortened the droplet transfer period.The microstructures of the deposited samples exhibited layered characteristics with alternating distributions of coarse and fine grains.During layer-by-layer deposition,the β-phase precipitated and grew preferentially along grain boundaries,while the fineη-Al_(8)Mn_(5)phase was dispersed in the α-Mg matrix.The mechanical properties of the CA-WAAM deposited sample showed isotropic characteristics.The ultimate tensile strength and elongation in the building direction(BD)were 282.7 MPa and 14.2%,respectively.The microhardness values of the deposited parts were relatively uniform,with an average value of HV 69.6.展开更多
Metal device rapid prototyping with welding is one of the research interests at present. A controlled inertial droplet transfer MAG welding (CIDTMAGW) process was developed for the 3D steel device rapid prototyping wi...Metal device rapid prototyping with welding is one of the research interests at present. A controlled inertial droplet transfer MAG welding (CIDTMAGW) process was developed for the 3D steel device rapid prototyping with metal deposition. In this process, by using a special designed wire feeder, a controlled inertia is imposed on the droplet formed on the wire tip and combines with the arc force to make it detached. Thus, according to the requirements of rapid prototyping, the arc heat and the droplet detaching force can be separately controlled to attain a stable and satisfactory metal deposition process. A CIDTMAGW system and a testing manipulator for the 3D steel device rapid prototyping are presented. The required software is completed as well. The experiments proved that the geometric formation of the rapid prototyping device with welding deposition is well agreed the data of the device CAD modeling. The surface of the deposited device is comparatively smooth.展开更多
The high-speed camera system and data acquisition system of welding parameters were created in tandem MIG welding of high strength aluminum alloy. The experiments were carried out in order to obtain the photos of drop...The high-speed camera system and data acquisition system of welding parameters were created in tandem MIG welding of high strength aluminum alloy. The experiments were carried out in order to obtain the photos of droplet transfer under different welding parameters in pulsed mode. The droplet transfer mode of “one pulse one droplet” becomes the preferred selection during welding process because of its stable procedure and sound weld form. The parameter ranges for corresponding transfer mode were experimentally achieved, among which the stable droplet transfer mode of “one pulse one droplet” can be realized. These efforts brave the way for control weld heat input and weld formation in the future.展开更多
High efficiency welding has always been one of the hot research subjects at home and overseas. Aiming at the problem of unstable droplet rotating spray transfer process in 450 A thin wire metal active gas arc(MAG) wel...High efficiency welding has always been one of the hot research subjects at home and overseas. Aiming at the problem of unstable droplet rotating spray transfer process in 450 A thin wire metal active gas arc(MAG) welding, a three-dimensional arc-droplet coupled model is established in this paper on the base of fluid dynamics to conduct numerical analysis for droplet transfer behavior with external magnetic controlled MAG welding, and used high-speed camera system to verify the simulation results. The results indicate that without external magnetic field, the droplet is transferred by the way of rotating spray, the arc is changeable and the spatter is serious. The electromagnetic force accelerates the radial liquid beam rotation under direct current(DC) magnetic field, and increases the angle between liquid beam and welding wire axis. Meanwhile, the rotation frequency of the liquid beam reaches 400 Hz, the area of arc column and heat loss increase under DC magnetic field. Based on the alternating magnetic field, the arc is the “bell shaped”, the arc stiffness raises, its temperature achieves 26 000 K, and the maximum speed of the liquid stream beam can reach 500 m/s. And the droplet transfer is more stable, the spatter significantly reduces, and welding quality is effectively improved.展开更多
Short-arc pulsed gas metal arc welding(P-GMAW)was used to solve the dificulties of molten pool spreading and droplet transfer of Ni-based welding wire.Suppression of short-circuit current was used to reduce spatter.Ar...Short-arc pulsed gas metal arc welding(P-GMAW)was used to solve the dificulties of molten pool spreading and droplet transfer of Ni-based welding wire.Suppression of short-circuit current was used to reduce spatter.Arc length stabilizer was used to acquire a proper and stable arc length maintained at the critical position where short circuit starts to occur.Short-arc P-GMAW with or without arc length stabilizer was compared.The droplet transfer,arc behaviors and weld bead profiles were investigated and compared based on the high-speed photography and observation of weld cross-section.When the arc length stabilizer was deactivated,the arc length was unstable and too short.The droplet transfer mode was mainly short circuit partial transfer,with only a small part of the droplet transferred into the molten pool,with the characteristics of no obvious necking,a few spatters,small droplet impact,long short circuit duration and high short-circuit current.There was also a small proportion of short circuit complete transfer with obvious necking,larger droplet impact,shorter short-circuit duration and lower short-circuit current.With arc length stabilizer,droplet transfer modes were short circuit complete transfer and spray transfer.The spray transfer had the largest droplet impact,no short circuit and no spatter.With the arc length stabilizer activated,a deep penetration,a high penetration ratio,a small reinforcement and a large reinforcement factor were acquired.This provides an innovative method to solve the difficulties of droplet transfer and molten pool spreading and eliminate the incomplete fusion in the GMAW of 9%Ni steel with nickel-based alloy welding wire.展开更多
Based on the high speed video system with electrical signals collecting and wavelet analyzing, the welding processes under three different median currents with the same median time were detected. The experimental resu...Based on the high speed video system with electrical signals collecting and wavelet analyzing, the welding processes under three different median currents with the same median time were detected. The experimental results show that, when the median current is higher, the input peak energy is lower. And the droplet transfer is almost in spray mode. The welding process is the stablest.展开更多
The heat input from arcs to weld pool in twin-arc gas metal arc welding （GMAW） with a common weld pool is investigated by high-speed photography. The characteristics of arc shapes and droplet transfer are studied an...The heat input from arcs to weld pool in twin-arc gas metal arc welding （GMAW） with a common weld pool is investigated by high-speed photography. The characteristics of arc shapes and droplet transfer are studied and then the models for heat flux distribution on top surface of weld pool and enthalpy distribution of metal droplets transferred into weld pool are established. By using the model, 3-D geometries of weld pools in twin-arc GMAW with a common weld pool are predicted. Corresponding welding experiments on mild steel plates are carried out and the results indicate that the predicted shape of weld bead on cross section shows good agreement with measured one.展开更多
With the background of the control of additional mechanical force droplet transfer in MIG/MAG welding, regarding the AC servo motor as core, a novel oscillating wire feeding system has been developed with excellent pe...With the background of the control of additional mechanical force droplet transfer in MIG/MAG welding, regarding the AC servo motor as core, a novel oscillating wire feeding system has been developed with excellent performances of control and dynamic acceleration which is tested. System constitution and operation principle are introduced in this paper. Influences of parameters on dynamic acceleration performance are analyzed and discussed emphatically, such as oscillating frequency, oscillating amplitude and draw-back speed. Experimental result indicates that according to the technique of welding control, the novel wire feeding system responds rapidly to various kinds of control orders of wire feeding and draw-back, and realizes flexible control of welding wire axial movement, including dynamic shifting,oscillating and so on.展开更多
The effect of nonmetallic inclusions in the droplet of the stainless steel covered electrode on the porosity was researched.The result shows that the nonmetallic inclusions in the droplet are spherical,their compositi...The effect of nonmetallic inclusions in the droplet of the stainless steel covered electrode on the porosity was researched.The result shows that the nonmetallic inclusions in the droplet are spherical,their composition is different from the one of slag and the inclusions have the character of “inner formation”.When the ratio of rutile to ilmenite in the coated material is increased, the droplet becomes coarse, the content of nonmetallic inclusion in the droplet decreases,and the porosity sensitivity in the weld metal also decreases.When the ratio of fledspar to ilmenite in the coated material is increased, the droplet becomes fine,the content of nonmetallic inclusion in the droplet increases, and the porosity sensitivity in the weld metal increases. When the ratio of Fe_2O_3 to ilmenite in the coated material is increased, the droplet becomes fine, the content of nonmetallic inclusion decreases, while the porosity sensitivity does not reduce.展开更多
文摘A two-dimensional model was established for the first time by coupling moving wire and arc in CMT-WAAM and GMAWWAAM process,revealing the temperature,potential and droplet transition behavior of droplet metal.The droplet transition and the change of droplet transfer mode under different wire feeding speed were analyzed.The experiments and numerical simulation research found that droplet transition mode is projected transfer in GMAW-WAAM process under 150 A current,with a complete transition period is 14 ms.The droplet transition shows a short-circuit transition mode in CMT-WAAM process,with wire feeding speed of 5.5 m/min and a complete transition period is 20 ms.The droplet transition shows a mixture of droplet transfer and short-circuit transition mode in CMT-WAAM process,with wire feeding speed of 5.5 m/min and a complete transition period is 23 ms.Based on the theoretical research and experimental studies,the mechanism of droplet transfer mode in WAAM was studied,which can provide reference for optimizing parameters.
文摘High-speed photography is utilized to capture an image of the arc area during the welding process.The variation in arc shape and droplet transfer behavior is compared when employing shielding gases of different components and proportions(e.g.,80%Ar+20%CO_(2),85%Ar+10%CO_(2)+5%O2,65%Ar+26.5%He+8%CO_(2)+0.5%O2)using a Ф1.2 mm welding wire under 360 A current.Furthermore,the effects of various shielding gas components on the stability of the welding process are discussed.It was determined that the addition of oxygen and helium changed the arc’s shape and the behavior of the droplet transfer,and the welding process stability increased.
基金They also thank the National Natural Science Foundation of China for its financial support
文摘In this paper, the droplet transfer in oscillating arc narrow gap gas metal arc （ GMA ） welding was studied. According to the experimental results, the oscillating arc has effect on the droplet transfer mode. The droplet transfer frequency in narrow gap groove is higher than that in bead-on-plate welding. Because of the change of arc location in narrow gap groove, the droplet transfer in oscillating arc narrow gap changes regularly. The droplet transfer frequency near groove sidewall is higher than that at the middle of narrow gap groove.
文摘LF6 aluminum alloy plates with 4.5 mm thickness are welded in this experiment.Welding is carried out by using the CO_(2)laser-MIG paraxial hybrid welding in fiat position.The experimental results indicate that the inherent droplet transfer cycle time of conventional MIG arc is changed due to the interaction between CO_(2)laser beam and MIG arc in the short-circuiting mode of laser-MIG hybrid welding.Because of the preheating action of CO_(2)laser to electrode and base material,the droplet transfer frequency of MIG arc is increased in the hybrid welding process.When laser power is increased to a certain degree,the droplet transfer frequency is decreased due to the effect of laser-induced keyhole.Furthermore,through analyzing the MIG welding current and arc voltage waveforms and the characteristics of droplet transfer in the hybrid welding process,the effect of laser energy and the action point between laser beam and arc on the frequency of droplet transfer and weld appearance is investigated in details.
基金This work was supported by National Natural Science Foundation of China （ No. 50875088） Natural Science Foundation of Guangdong Province, China （ No. 07006479）.
文摘In order to study how welding parameters affect welding quality and droplet transfer, a synchronous acquisition and analysis system is established to acquire and analyze electrical signal and instantaneous images of droplet transfer simultaneously, which is based on a self-developed soft-switching inverter. On the one hand, welding current and voltage signals are acquired and analyzed by a self-developed dynamic wavelet analyzer. On the other hand, images are filtered and optimized after they are captured by high-speed camera. The results show that instantaneous waveforms and statistical data of electrical signal contribute to make an overall assessment of welding quality, and that optimized high-speed images allow a visual and clear observation of droplet transfer process. The analysis of both waveforms and images leads to a further research on droplet transfer mechanism and provides a basis for precise control of droplet transfer.
基金This project is supported by National Natural Science Foundation of China (No. 59575059)
文摘The method to detect droplet transfer by means of arc spectrum, while the experiment sets, testing principle and data processing procedure,are presented. The experiment and analysis results show that arc spectrum signal can be utilized to detect and measure the transfer procedure, the transfer modes and the transfer parameters. The arc spectrum signal enjoys excellent quality with high signal amplitude. Each transfer mode has its specific typical signal mode, and the pulse outline corresponds to an integrated transferring procedure of one droplet. All these features of arc spectrum signal can be easily applied hi the control of transfer procedure,the identification and stabilization of transfer mode and the measurement of transfer parameters.
文摘A simulation system used in the arc welding short circuit transfer process and current waveform control process was developed in this paper. The simulation results are basically consistent with welding technical experiments. The simulation system can be used to simulate and test the current waveform control parameters with welding variables. By this simulation system, the influence regularities of the current waveform control parameters in the CO 2 arc welding droplet short circuit transfer process can be got. Moreover, the basic mode of real time current waveform control can be also established by the simulation testing.
基金ThispaperissupportedbyNationalNaturalScienceFoundation (No .5 9775 0 62 )
文摘The character of droplet transfer arc light sense signal is studied and validated in oscillating feed mode. And a novel mini photoelectric arc light sensor together with the controlling circuit used to automatically stabilize the signal range is developed. Further more the automatically identifying of the droplet transfer character signal from arc light is realized reliably.
文摘In this paper, the droplet transfer behavior of the stainless steel coated electrode with double layer coating is researched by means of those experimental methods, such as high speed camera, collecting droplet in water, surfacing on the steel plate et al. The results show that the droplet transfer indexes of coated electrode are mainly controlled by the size of droplet, which affects the transfer behavior of droplet. The distribution characteristic of the droplet size of the electrode affects the numerical relationship among droplet transfer indexes. The metallurgical process of the coated electrode with double layer coating is carried out continuously in different zones. The main reason for the coated electrode with double layer coating gaining excellent usability quality is that the droplets realize the 'quasi flux wall guided transfer pattern'.
文摘A new method and if.''principle .fi)r 's*ensin.q dry)Plet iran.5/dr in aide W ')/ steel and aluminum alloy have been researched in this paper. A practical arc light sensing and controlling system has been developed. The reliability of the arc light characteristic signal that indicates droplet detachment and the control accuracy of the system have been verified using high-speed photography Based on the mathematical model set up in the paper, the mechanism of the signal and relative phenomena were analyzed The parameters, which influence arc light radiation were given and the limitation of this sensing method was discussed.
基金This work is supported by the National Natural Science Foundation of China(Grant No.51905231)China Postdoctoral Science Foundation(Grant No.2020M670943)Graduate Student Scientific Research Innovation Projects in Jiangsu Province(Grant No.KYCX22_3788).
文摘In order to analyze the influence of the distance between heat sources(D_(LA))on the welding process,the effects of D_(LA)on the droplet transfer behavior,weld formation characteristics and weld formation mechanism of AH36 in laser and cable-type welding wire gas metal arc welding arc hybrid welding were studied.Real-time photography was conducted using a high-speed camera to determine the droplet transfer and arc behaviors;the surface morphology and macroscopic cross-section of the weld obtained from the experiment were observed and analyzed.The arc height decreases with the increase in the DLA,the arc width shows the opposite change,and the welding current decreases.The allure of the laser to the arc increases with the increase in the D_(LA).The frequency of droplet transfer increases with the increase in the D_(LA),but the growth rate decreases.The continuous increase in the D_(LA)leads to the tendency of the droplet size to decrease first and then increase,and the minimum value is obtained when the D_(LA)is 4 mm.The D_(LA)has obvious influence on the weld formation.The weld penetration and reinforcement change similarly,increasing first and then decreasing as the D_(LA)increases,and the laser area of the weld also increases first and then decreases.
基金supported by the National Natural Science Foundation of China(No.51805265)the Fundamental Research Funds for the Central Universities,China(No.30922010921).
文摘Thin walls of an AZ91 magnesium alloy with fine equiaxed grains were fabricated via cold arc-based wire arc additive manufacturing(CA-WAAM),and the droplet transfer behaviours,microstructures,and mechanical properties were investigated.The results showed that the cold arc process reduced splashing at the moment of liquid bridge breakage and effectively shortened the droplet transfer period.The microstructures of the deposited samples exhibited layered characteristics with alternating distributions of coarse and fine grains.During layer-by-layer deposition,the β-phase precipitated and grew preferentially along grain boundaries,while the fineη-Al_(8)Mn_(5)phase was dispersed in the α-Mg matrix.The mechanical properties of the CA-WAAM deposited sample showed isotropic characteristics.The ultimate tensile strength and elongation in the building direction(BD)were 282.7 MPa and 14.2%,respectively.The microhardness values of the deposited parts were relatively uniform,with an average value of HV 69.6.
文摘Metal device rapid prototyping with welding is one of the research interests at present. A controlled inertial droplet transfer MAG welding (CIDTMAGW) process was developed for the 3D steel device rapid prototyping with metal deposition. In this process, by using a special designed wire feeder, a controlled inertia is imposed on the droplet formed on the wire tip and combines with the arc force to make it detached. Thus, according to the requirements of rapid prototyping, the arc heat and the droplet detaching force can be separately controlled to attain a stable and satisfactory metal deposition process. A CIDTMAGW system and a testing manipulator for the 3D steel device rapid prototyping are presented. The required software is completed as well. The experiments proved that the geometric formation of the rapid prototyping device with welding deposition is well agreed the data of the device CAD modeling. The surface of the deposited device is comparatively smooth.
文摘The high-speed camera system and data acquisition system of welding parameters were created in tandem MIG welding of high strength aluminum alloy. The experiments were carried out in order to obtain the photos of droplet transfer under different welding parameters in pulsed mode. The droplet transfer mode of “one pulse one droplet” becomes the preferred selection during welding process because of its stable procedure and sound weld form. The parameter ranges for corresponding transfer mode were experimentally achieved, among which the stable droplet transfer mode of “one pulse one droplet” can be realized. These efforts brave the way for control weld heat input and weld formation in the future.
基金Major Scientific and Technological Project of Gansu Province(No.22ZD6GA008)the National Natural Science Foundation of China(No.51775256).
文摘High efficiency welding has always been one of the hot research subjects at home and overseas. Aiming at the problem of unstable droplet rotating spray transfer process in 450 A thin wire metal active gas arc(MAG) welding, a three-dimensional arc-droplet coupled model is established in this paper on the base of fluid dynamics to conduct numerical analysis for droplet transfer behavior with external magnetic controlled MAG welding, and used high-speed camera system to verify the simulation results. The results indicate that without external magnetic field, the droplet is transferred by the way of rotating spray, the arc is changeable and the spatter is serious. The electromagnetic force accelerates the radial liquid beam rotation under direct current(DC) magnetic field, and increases the angle between liquid beam and welding wire axis. Meanwhile, the rotation frequency of the liquid beam reaches 400 Hz, the area of arc column and heat loss increase under DC magnetic field. Based on the alternating magnetic field, the arc is the “bell shaped”, the arc stiffness raises, its temperature achieves 26 000 K, and the maximum speed of the liquid stream beam can reach 500 m/s. And the droplet transfer is more stable, the spatter significantly reduces, and welding quality is effectively improved.
基金the MARK III Materials Research Project of Ministry of Industry and Information Technology of China。
文摘Short-arc pulsed gas metal arc welding(P-GMAW)was used to solve the dificulties of molten pool spreading and droplet transfer of Ni-based welding wire.Suppression of short-circuit current was used to reduce spatter.Arc length stabilizer was used to acquire a proper and stable arc length maintained at the critical position where short circuit starts to occur.Short-arc P-GMAW with or without arc length stabilizer was compared.The droplet transfer,arc behaviors and weld bead profiles were investigated and compared based on the high-speed photography and observation of weld cross-section.When the arc length stabilizer was deactivated,the arc length was unstable and too short.The droplet transfer mode was mainly short circuit partial transfer,with only a small part of the droplet transferred into the molten pool,with the characteristics of no obvious necking,a few spatters,small droplet impact,long short circuit duration and high short-circuit current.There was also a small proportion of short circuit complete transfer with obvious necking,larger droplet impact,shorter short-circuit duration and lower short-circuit current.With arc length stabilizer,droplet transfer modes were short circuit complete transfer and spray transfer.The spray transfer had the largest droplet impact,no short circuit and no spatter.With the arc length stabilizer activated,a deep penetration,a high penetration ratio,a small reinforcement and a large reinforcement factor were acquired.This provides an innovative method to solve the difficulties of droplet transfer and molten pool spreading and eliminate the incomplete fusion in the GMAW of 9%Ni steel with nickel-based alloy welding wire.
基金This work was supported by National Natural Science Foundation of China （ Grant No. 50575074 and 50875088 ） and Guangdong Science Foundation （ Grant No. 07006479）.
文摘Based on the high speed video system with electrical signals collecting and wavelet analyzing, the welding processes under three different median currents with the same median time were detected. The experimental results show that, when the median current is higher, the input peak energy is lower. And the droplet transfer is almost in spray mode. The welding process is the stablest.
基金Supported by National Natural Science Foundation of China （ No. 50575074） and the Scientific Research Foundation of QUST.
文摘The heat input from arcs to weld pool in twin-arc gas metal arc welding （GMAW） with a common weld pool is investigated by high-speed photography. The characteristics of arc shapes and droplet transfer are studied and then the models for heat flux distribution on top surface of weld pool and enthalpy distribution of metal droplets transferred into weld pool are established. By using the model, 3-D geometries of weld pools in twin-arc GMAW with a common weld pool are predicted. Corresponding welding experiments on mild steel plates are carried out and the results indicate that the predicted shape of weld bead on cross section shows good agreement with measured one.
基金NationalNatureScienceFoundation (No .5 9775 0 62 )
文摘With the background of the control of additional mechanical force droplet transfer in MIG/MAG welding, regarding the AC servo motor as core, a novel oscillating wire feeding system has been developed with excellent performances of control and dynamic acceleration which is tested. System constitution and operation principle are introduced in this paper. Influences of parameters on dynamic acceleration performance are analyzed and discussed emphatically, such as oscillating frequency, oscillating amplitude and draw-back speed. Experimental result indicates that according to the technique of welding control, the novel wire feeding system responds rapidly to various kinds of control orders of wire feeding and draw-back, and realizes flexible control of welding wire axial movement, including dynamic shifting,oscillating and so on.
文摘The effect of nonmetallic inclusions in the droplet of the stainless steel covered electrode on the porosity was researched.The result shows that the nonmetallic inclusions in the droplet are spherical,their composition is different from the one of slag and the inclusions have the character of “inner formation”.When the ratio of rutile to ilmenite in the coated material is increased, the droplet becomes coarse, the content of nonmetallic inclusion in the droplet decreases,and the porosity sensitivity in the weld metal also decreases.When the ratio of fledspar to ilmenite in the coated material is increased, the droplet becomes fine,the content of nonmetallic inclusion in the droplet increases, and the porosity sensitivity in the weld metal increases. When the ratio of Fe_2O_3 to ilmenite in the coated material is increased, the droplet becomes fine, the content of nonmetallic inclusion decreases, while the porosity sensitivity does not reduce.
