Traditional welding methods are limited in low heat input to workpiece and high welding wire melting rate. Twin-wire indirect arc（TWIA） welding is a new welding method characterized by high melting rate and low heat...Traditional welding methods are limited in low heat input to workpiece and high welding wire melting rate. Twin-wire indirect arc（TWIA） welding is a new welding method characterized by high melting rate and low heat input. This method uses two wires one connected to the negative electrode and another to the positive electrode of a direct-current（DC） power source. The workpiece is an independent, non-connected unit. A three dimensional finite element model of TWIA is devised. Electric and magnetic fields are calculated and their influence upon TWIA behavior and the welding process is discussed. The results show that with a 100 A welding current, the maximum temperature reached is 17 758 K, arc voltage is 14.646 V while maximum current density was 61 A/mm2 with a maximum Lorene force of 84.5 ~tN. The above mentioned arc parameters near the cathode and anode regions are far higher than those in the arc column region. The Lorene force is the key reason for plasma velocity direction deviated and charged particles flowed in the channel formed by the cathode, anode and upper part of arc column regions. This led to most of the energy being supplied to the polar and upper part of arc column regions. The interaction between electric and magnetic fields is a major determinant in shaping TWIA as well as heat input on the workpiece. This is a first study of electromagnetic characteristics and their influences in the TWIA welding process, and it is significant in both a theoretical and practical sense.展开更多
采用激光-MAG(Metal active gas arc welding)复合焊接工艺,以焊缝表面成形、焊缝纵截面形貌和熔深波动程度为工艺稳定性评价依据,借助高速摄像系统和图像处理方法,对焊接过程中飞溅和等离子体两种关键过程信息进行特征识别和定量化表征...采用激光-MAG(Metal active gas arc welding)复合焊接工艺,以焊缝表面成形、焊缝纵截面形貌和熔深波动程度为工艺稳定性评价依据,借助高速摄像系统和图像处理方法,对焊接过程中飞溅和等离子体两种关键过程信息进行特征识别和定量化表征,系统地研究激光功率从5 kW提高到30 kW时,焊接过程关键特征信息与焊接过程稳定性之间的关系。结果表明,随着激光功率的增加,焊缝表面成形出现周期性“上凸-下凹”现象,焊缝内部裂纹和熔深变化特征也随之周期性变化;等离子体面积和飞溅面积均随激光功率的提高呈增加趋势,且两者波动程度和熔深波动程度均呈正相关;等离子体面积增加会导致激光传输过程中能量衰减程度的加剧,使焊缝熔深增加趋势逐渐变缓,其波动程度是影响焊接过程稳定性的关键因素之一。展开更多
Thermal sprayed Ni-5wt.% Al coating was fabricated on the substrate of 6061-T6 aluminum alloy by twin-wire arc spraying. Experimental results indicated that the average value of bond strength was around 46. 90 MPa, th...Thermal sprayed Ni-5wt.% Al coating was fabricated on the substrate of 6061-T6 aluminum alloy by twin-wire arc spraying. Experimental results indicated that the average value of bond strength was around 46. 90 MPa, the average hardness was 240 HV and the average value of surface roughness was about O. 14 mm. Friction and wear test results showed that the dry friction coefficient of Ni-5wt.% Al coating firstly decreased, and then tended to a slight increase after 200 cycles. In the early abrasion stage, adhesion wear played the key role for wear mechanics of Ni-5wt.% Al coating, but gradually abrasive wear became to replace adhesion wear.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51171093)
文摘Traditional welding methods are limited in low heat input to workpiece and high welding wire melting rate. Twin-wire indirect arc（TWIA） welding is a new welding method characterized by high melting rate and low heat input. This method uses two wires one connected to the negative electrode and another to the positive electrode of a direct-current（DC） power source. The workpiece is an independent, non-connected unit. A three dimensional finite element model of TWIA is devised. Electric and magnetic fields are calculated and their influence upon TWIA behavior and the welding process is discussed. The results show that with a 100 A welding current, the maximum temperature reached is 17 758 K, arc voltage is 14.646 V while maximum current density was 61 A/mm2 with a maximum Lorene force of 84.5 ~tN. The above mentioned arc parameters near the cathode and anode regions are far higher than those in the arc column region. The Lorene force is the key reason for plasma velocity direction deviated and charged particles flowed in the channel formed by the cathode, anode and upper part of arc column regions. This led to most of the energy being supplied to the polar and upper part of arc column regions. The interaction between electric and magnetic fields is a major determinant in shaping TWIA as well as heat input on the workpiece. This is a first study of electromagnetic characteristics and their influences in the TWIA welding process, and it is significant in both a theoretical and practical sense.
文摘采用激光-MAG(Metal active gas arc welding)复合焊接工艺,以焊缝表面成形、焊缝纵截面形貌和熔深波动程度为工艺稳定性评价依据,借助高速摄像系统和图像处理方法,对焊接过程中飞溅和等离子体两种关键过程信息进行特征识别和定量化表征,系统地研究激光功率从5 kW提高到30 kW时,焊接过程关键特征信息与焊接过程稳定性之间的关系。结果表明,随着激光功率的增加,焊缝表面成形出现周期性“上凸-下凹”现象,焊缝内部裂纹和熔深变化特征也随之周期性变化;等离子体面积和飞溅面积均随激光功率的提高呈增加趋势,且两者波动程度和熔深波动程度均呈正相关;等离子体面积增加会导致激光传输过程中能量衰减程度的加剧,使焊缝熔深增加趋势逐渐变缓,其波动程度是影响焊接过程稳定性的关键因素之一。
文摘Thermal sprayed Ni-5wt.% Al coating was fabricated on the substrate of 6061-T6 aluminum alloy by twin-wire arc spraying. Experimental results indicated that the average value of bond strength was around 46. 90 MPa, the average hardness was 240 HV and the average value of surface roughness was about O. 14 mm. Friction and wear test results showed that the dry friction coefficient of Ni-5wt.% Al coating firstly decreased, and then tended to a slight increase after 200 cycles. In the early abrasion stage, adhesion wear played the key role for wear mechanics of Ni-5wt.% Al coating, but gradually abrasive wear became to replace adhesion wear.
