Marangoni convection and weld shape variations in Ar-O2 and Ar-CO2 shielded GTA welding
Marangoni convection and weld shape variations in Ar-O2 and Ar-CO2 shielded GTA welding
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DOI：
10.1016/j.msea.2004.05.057
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发表时间：
2004-08-25
期刊：
影响因子：
6.4
通讯作者：
Nogi, K
中科院分区：
文献类型：
--
作者：
Lu, SP;Fujii, H;Nogi, K
当氧气或二氧化碳浓度低于0.6Vol时，增加氩基保护气体中的氧或二氧化碳浓度会导致焊缝金属氧含量的增加。%在保护气体中。而当Ar基保护气体中O-2或CO2浓度高于0.6vol.%时，焊缝金属氧保持在200ppm-250ppm左右。当焊缝金属氧含量大于100ppm时，熔池中发生向内Marangoni对流模式。当小于100ppm时，Marangoni对流将向外转变，焊缝形状由深窄变浅宽。O-2和CO2浓度对深层渗透的影响范围是相同的。当保护气体中O-2或CO_2浓度大于0.6%时，会形成较厚的氧化物层。根据Fe、Si、Cr、Mn与铁液中氧的平衡反应的热力学计算，得到了FeO、SiO_2、Cr2O_3、MnO的氧化物产物和焊缝金属的实验氧含量，在焊接过程中，可能在弧柱下熔池表面的外围区域形成了Cr2O_3和SiO_2氧化物。提出了一个模型来解释高温下氧化层在熔池表面Marangoni对流中的作用。重氧化层抑制了Marangoni对流引起的流体流动，并成为熔池吸氧的障碍。(C)2004爱思唯尔B.V.保留所有权利。
Increasing the oxygen or the carbon dioxide concentration in the argon-based shielding gas leads to an increase in the weld metal oxygen content when the oxygen or carbon dioxide concentration is to be lower than 0.6 vol. % in the shielding gas. However, when the O-2 or CO2 concentration is higher than 0.6vol.% in the Ar-based shielding gas, the weld metal oxygen is maintained around 200ppm-250ppm. An inward Marangoni convection mode in the weld pool occurs when the weld metal oxygen content is more than 100 ppm. When it is lower than 100 ppm, the Marangoni convection would change to the outward direction and the weld shape varies from a deep narrow to a shallow wide shape. The effective ranges of O-2 and CO2 concentrations for deep penetration are same. A heavy layer of oxides is formed when the O-2 or CO2 concentration in the shielding gas is more than 0.6 vol.%. Based on the thermodynamic calculation of the equilibrium reactions of Fe, Si, Cr and Mn with oxygen in liquid iron for the oxide products, FeO, SiO2, Cr2O3 and MnO and the experimental oxygen content in the weld metal, Cr2O3 and SiO2 oxides are possibly formed at the periphery area of the liquid pool surface under the arc column during the welding process. One model is proposed to illustrate the role of the oxide layer on the Marangoni convection on the pool surface at elevated temperature. The heavy oxide layer inhibited the fluid flow induced by the Marangoni convection and also became a barrier for the oxygen absorption into the molten weld pool. (C) 2004 Elsevier B.V. All rights reserved.