The momentum of strong backward flowing melt jet and the thermal action from transferred droplets are two dominating factors affecting the formation of humping bead in high speed gas metal arc welding （GMAW）. Approp...The momentum of strong backward flowing melt jet and the thermal action from transferred droplets are two dominating factors affecting the formation of humping bead in high speed gas metal arc welding （GMAW）. Appropriate describing the influ- ence of the distribution mode of droplet heat content in the weld pool is essential to understand the physical mechanism of humping bead formation. Based on the exper- imental results, four kinds of droplet heat content distribution modes are proposed and employed to calculate the transient evolution of the temperature field and weld pool during high speed GMAW process. Through making comparison of predicted and measured weld bead dimensions, a suitable and adaptive distribution mode of droplet heat content is found, i.e., droplet heat content is distributed in bottom layer of gouging region at the front of weld pool, and is averagely distributed in the whole layer at the rear of weld pool. The proposed mode is also validated by experimental observation of the weld pool images and measured by geometric dimensions of the weld bead.展开更多
The developed mathematical model of humping formation mechanism in high-speed gas metal arc welding （GMAW） is used to analyze the effects of welding current and welding speed on the occurrence of humping bead. It co...The developed mathematical model of humping formation mechanism in high-speed gas metal arc welding （GMAW） is used to analyze the effects of welding current and welding speed on the occurrence of humping bead. It considers both the momentum and heat content of backward flowing molten jet inside weld pool. Three-dimensional geometry of weld pool, the spacing between two adjacent humps and hump height along humping weld bead are calculated under different levels of welding current and welding speed. It shows that wire feeding rate, power intensity and the moment of backward flowing molten jet are the major factors on humping bead formation.展开更多
Modern manufacturing industry demands low cost and high efficient welding processes to remain competitiveness in the time of globalization. In this study, conventional gas metal arc welding （GMAW） was modified, a do...Modern manufacturing industry demands low cost and high efficient welding processes to remain competitiveness in the time of globalization. In this study, conventional gas metal arc welding （GMAW） was modified, a double-electrode GMAW （DE-GMAW） system is developed and DE-GMAW process is implemented through optimization of the design and process parameters and suitable selection of igniting sequence of double arcs. High speed welding tests were carried out to examine the effects of different factors on occurrence of weld formation defects. Through observing the weld bead appearance in DE-GMA W, the values of critical welding speed were determined under different levels of welding current and welding speed.展开更多
During high-speed gas metal arc welding （GMAW）, the backward flowing molten jet with high momentum in the weld pool is considered to be responsible for the occurrence of humping bead. To suppress humping bead, an el...During high-speed gas metal arc welding （GMAW）, the backward flowing molten jet with high momentum in the weld pool is considered to be responsible for the occurrence of humping bead. To suppress humping bead, an electromagnetic device is developed and coupled with the welding system. By adjusting the conditions of external magnetic field, forward electromagnetic force is obtained to reduce the momentum of the backward flow of molten metal in weld pool. Consequently, the humping bead can be suppressed by adjusting the external magnetic field. Bead-on-plate welding experiment was conducted on mild steel plates, and the influence of magnetic flux density on the arc deflection angle and weld bead quality is investigated. It is found that external magnetic field can remarkably adjust the momentum of backward flow jet and significantly improve the quality of weld bead.展开更多
Considering the influence of backward flowing molten jet observed by experiments, a new pool surface deformation formula and droplets heat content model are used to investigate the humping formation mechanism during h...Considering the influence of backward flowing molten jet observed by experiments, a new pool surface deformation formula and droplets heat content model are used to investigate the humping formation mechanism during high-speed gas metal arc （GMA） welding. Three-dimensional geometry of the humping bead is numerically simulated only if some extra force and heat acted at the rear part of weld pool are taken into account in the model. It has proved that both the momentum and heat content of backward flowing molten jet must be appropriately treated to quantitatively analyze the physical mechanism of the humping phenomenon.展开更多
在熔化极气体保护焊(Gas metal arc welding,GMAW)过程中,当焊接速度超过临界值后,焊缝成形变差,出现咬边和驼峰焊道,无法满足生产要求。研究证明,熔池中动量很大的后向液体流是产生驼峰焊道的主要原因。自主研发外加磁场发生装置,向熔...在熔化极气体保护焊(Gas metal arc welding,GMAW)过程中,当焊接速度超过临界值后,焊缝成形变差,出现咬边和驼峰焊道,无法满足生产要求。研究证明,熔池中动量很大的后向液体流是产生驼峰焊道的主要原因。自主研发外加磁场发生装置,向熔池施加横向电磁力,对后向液体流进行主动干预,并调控熔池流态,从而抑制驼峰焊道的形成。在Q235低碳钢板上开展焊接工艺试验,获得了不同磁感应强度下的焊缝表面成形;采用高速摄像技术,拍摄焊接过程中的电弧和熔池图像,分析外加磁场对电弧形态、熔池流场和焊缝成形的影响规律,初步揭示外加磁场抑制驼峰焊道的机理。试验结果表明,外加横向磁场能明显调控熔池流态,减小后向液体流的动量,并能有效抑制驼峰焊道和咬边等缺陷,显著改善焊缝成形,提高临界焊接速度。展开更多
在熔化极气体保护焊(Gas metal arc welding,GMAW)过程中,当熔滴过渡转变为旋转射流过渡时,电弧不稳,焊缝成形变差。在Q235低碳钢上开展工艺试验,探究焊接过程中产生的飞溅和烟尘的形态及相结构。结果表明,高温熔融的金属被甩出雾化,雾...在熔化极气体保护焊(Gas metal arc welding,GMAW)过程中,当熔滴过渡转变为旋转射流过渡时,电弧不稳,焊缝成形变差。在Q235低碳钢上开展工艺试验,探究焊接过程中产生的飞溅和烟尘的形态及相结构。结果表明,高温熔融的金属被甩出雾化,雾滴在飞行过程中球化并快速凝固,飞溅颗粒表面具有特殊形貌,其成分以氧化物为主。电弧燃烧时,焊丝端部形成电流密度很高的斑点,斑点处温度很高,随着焊接电流的增大,金属蒸发量增加。金属蒸发带走了焊丝中大部分的Si、Mn等合金元素,而Si和Mn均是有效脱氧的元素。因此,金属蒸发带走了合金元素,影响O含量,进而影响焊缝性能。烟尘粒径与熔滴过渡方式有关,其粒度范围可达10^-1~10^2μm,分布概率较大的是10~60μm的粒子,它能通过人体上呼吸道进入肺部,对人体呼吸系统、神经系统等造成损伤。展开更多
运用自主研发的爬壁机器人研究焊接速度和焊接电流对竖向高速熔化极气体保护焊(gas metal arc welding,GMAW)驼峰焊缝的影响.结果表明,焊接速度或焊接电流超过某一临界值时,竖向高速GMAW会形成驼峰焊缝,且熔池中由电弧压力、熔滴冲击力...运用自主研发的爬壁机器人研究焊接速度和焊接电流对竖向高速熔化极气体保护焊(gas metal arc welding,GMAW)驼峰焊缝的影响.结果表明,焊接速度或焊接电流超过某一临界值时,竖向高速GMAW会形成驼峰焊缝,且熔池中由电弧压力、熔滴冲击力和重力作用下产生的动量很大的后向液体流是竖向高速GMAW形成驼峰焊缝的主要原因.同时,焊接速度和焊接电流显著影响驼峰焊缝形貌.当焊接电流不变时,随焊接速度提高,驼峰焊缝的驼峰间距和驼峰高度先稳定减小,后缓慢减小,而焊缝宽度则稳定减小;当焊接速度不变时,随焊接电流增加,驼峰焊缝的驼峰间距先增加后减小,驼峰高度则是先增加后不变,而焊缝宽度则稳定增加.此外,焊接速度过小或焊接电流过大均会造成金属液下淌.展开更多
基金supported by the project from the State Key Laboratory for Advanced Welding & Joining at Harbin Institute of Technology (No.09005)
文摘The momentum of strong backward flowing melt jet and the thermal action from transferred droplets are two dominating factors affecting the formation of humping bead in high speed gas metal arc welding （GMAW）. Appropriate describing the influ- ence of the distribution mode of droplet heat content in the weld pool is essential to understand the physical mechanism of humping bead formation. Based on the exper- imental results, four kinds of droplet heat content distribution modes are proposed and employed to calculate the transient evolution of the temperature field and weld pool during high speed GMAW process. Through making comparison of predicted and measured weld bead dimensions, a suitable and adaptive distribution mode of droplet heat content is found, i.e., droplet heat content is distributed in bottom layer of gouging region at the front of weld pool, and is averagely distributed in the whole layer at the rear of weld pool. The proposed mode is also validated by experimental observation of the weld pool images and measured by geometric dimensions of the weld bead.
文摘The developed mathematical model of humping formation mechanism in high-speed gas metal arc welding （GMAW） is used to analyze the effects of welding current and welding speed on the occurrence of humping bead. It considers both the momentum and heat content of backward flowing molten jet inside weld pool. Three-dimensional geometry of weld pool, the spacing between two adjacent humps and hump height along humping weld bead are calculated under different levels of welding current and welding speed. It shows that wire feeding rate, power intensity and the moment of backward flowing molten jet are the major factors on humping bead formation.
基金The authors wish to thank the financial support for this research from the National Natural Science Foundation of China （Grant No. 50675119）.
文摘Modern manufacturing industry demands low cost and high efficient welding processes to remain competitiveness in the time of globalization. In this study, conventional gas metal arc welding （GMAW） was modified, a double-electrode GMAW （DE-GMAW） system is developed and DE-GMAW process is implemented through optimization of the design and process parameters and suitable selection of igniting sequence of double arcs. High speed welding tests were carried out to examine the effects of different factors on occurrence of weld formation defects. Through observing the weld bead appearance in DE-GMA W, the values of critical welding speed were determined under different levels of welding current and welding speed.
基金The authors are grateful to the financial support for this research from the National Natural Science Foundation of China，the Research Fund for the Doctoral Program of Higher Education of China
文摘During high-speed gas metal arc welding （GMAW）, the backward flowing molten jet with high momentum in the weld pool is considered to be responsible for the occurrence of humping bead. To suppress humping bead, an electromagnetic device is developed and coupled with the welding system. By adjusting the conditions of external magnetic field, forward electromagnetic force is obtained to reduce the momentum of the backward flow of molten metal in weld pool. Consequently, the humping bead can be suppressed by adjusting the external magnetic field. Bead-on-plate welding experiment was conducted on mild steel plates, and the influence of magnetic flux density on the arc deflection angle and weld bead quality is investigated. It is found that external magnetic field can remarkably adjust the momentum of backward flow jet and significantly improve the quality of weld bead.
基金The authors are grateful to the financial support for this project from the National Natural Science Foundation of China under grant No. 50675119.
文摘Considering the influence of backward flowing molten jet observed by experiments, a new pool surface deformation formula and droplets heat content model are used to investigate the humping formation mechanism during high-speed gas metal arc （GMA） welding. Three-dimensional geometry of the humping bead is numerically simulated only if some extra force and heat acted at the rear part of weld pool are taken into account in the model. It has proved that both the momentum and heat content of backward flowing molten jet must be appropriately treated to quantitatively analyze the physical mechanism of the humping phenomenon.
文摘在熔化极气体保护焊(Gas metal arc welding,GMAW)过程中,当焊接速度超过临界值后,焊缝成形变差,出现咬边和驼峰焊道,无法满足生产要求。研究证明,熔池中动量很大的后向液体流是产生驼峰焊道的主要原因。自主研发外加磁场发生装置,向熔池施加横向电磁力,对后向液体流进行主动干预,并调控熔池流态,从而抑制驼峰焊道的形成。在Q235低碳钢板上开展焊接工艺试验,获得了不同磁感应强度下的焊缝表面成形;采用高速摄像技术,拍摄焊接过程中的电弧和熔池图像,分析外加磁场对电弧形态、熔池流场和焊缝成形的影响规律,初步揭示外加磁场抑制驼峰焊道的机理。试验结果表明,外加横向磁场能明显调控熔池流态,减小后向液体流的动量,并能有效抑制驼峰焊道和咬边等缺陷,显著改善焊缝成形,提高临界焊接速度。
文摘在熔化极气体保护焊(Gas metal arc welding,GMAW)过程中,当熔滴过渡转变为旋转射流过渡时,电弧不稳,焊缝成形变差。在Q235低碳钢上开展工艺试验,探究焊接过程中产生的飞溅和烟尘的形态及相结构。结果表明,高温熔融的金属被甩出雾化,雾滴在飞行过程中球化并快速凝固,飞溅颗粒表面具有特殊形貌,其成分以氧化物为主。电弧燃烧时,焊丝端部形成电流密度很高的斑点,斑点处温度很高,随着焊接电流的增大,金属蒸发量增加。金属蒸发带走了焊丝中大部分的Si、Mn等合金元素,而Si和Mn均是有效脱氧的元素。因此,金属蒸发带走了合金元素,影响O含量,进而影响焊缝性能。烟尘粒径与熔滴过渡方式有关,其粒度范围可达10^-1~10^2μm,分布概率较大的是10~60μm的粒子,它能通过人体上呼吸道进入肺部,对人体呼吸系统、神经系统等造成损伤。
文摘运用自主研发的爬壁机器人研究焊接速度和焊接电流对竖向高速熔化极气体保护焊(gas metal arc welding,GMAW)驼峰焊缝的影响.结果表明,焊接速度或焊接电流超过某一临界值时,竖向高速GMAW会形成驼峰焊缝,且熔池中由电弧压力、熔滴冲击力和重力作用下产生的动量很大的后向液体流是竖向高速GMAW形成驼峰焊缝的主要原因.同时,焊接速度和焊接电流显著影响驼峰焊缝形貌.当焊接电流不变时,随焊接速度提高,驼峰焊缝的驼峰间距和驼峰高度先稳定减小,后缓慢减小,而焊缝宽度则稳定减小;当焊接速度不变时,随焊接电流增加,驼峰焊缝的驼峰间距先增加后减小,驼峰高度则是先增加后不变,而焊缝宽度则稳定增加.此外,焊接速度过小或焊接电流过大均会造成金属液下淌.
