A-TIG焊中氧含量对熔池流动方式影响的数值模拟

建立了三维移动热源作用下焊接熔池的数学模型,模拟了不同氧含量下熔池中的速度场和温度场.结果表明,氧化物活性剂中的氧元素改变了熔池中的表面张力温度系数,从而影响熔池中的流动方式,是熔深和深宽比增加的重要原因;随着氧含量的增加,深宽比和熔深急剧增加,熔宽减小.当氧含量超过150×10-6时,增加氧量,熔池表面最高温度减小,并逐渐趋于一定值;当氧含量超过200×10-6时,深宽比、熔深和熔宽趋于一定值;氧含量小于300×10-6时,熔池表面最高温度高于正表面张力温度系数作用的温度范围,正、负表面张力温度系数在熔池中同时存在.当氧含量超过300×10-6时,熔池表面最高温度处于正表面张力温度系数作用的温度范围之内,熔池中的表面张力温度系数为正值;随着氧含量的增加,在熔池中出现数目、大小、方向、位置不同的涡流,当两个涡流的方向均由熔池边缘流向熔池中心的环流时,涡流有效地把电弧能带到熔池底部,产生较大的熔深和深宽比.

Modeling of the Effects of Oxygen Content on Flow Patterns in A-Tig Welding

A 3D mathematical model was developed to calculate the temperature and velocity distributions in a moving A-TIG weld pool with different oxygen concentrations. It is shown that the oxygen element, which changes the temperature dependence of surface tension coefficient from a negative value to a positive value, can cause significant changes in the weld penetration and depth/width ratio (D/W) of the weld pool. When the oxygen content increases, the weld bead penetration and $ D/W increases sharply while the weld metal width decreases. When oxygen content exceeds 150 10-6, the surface temperature decreases and then remains a constant. When the oxygen content increased beyond 200 10-6, the increase in oxygen content did not effect the weld pool size and shape. As the oxygen content is less than 300 10-6, negative and positive exist at the same time in the weld pool. The increase of oxygen content and the decrease of surface temperature can extend the region of positive surface tension coefficient and increase the depth of the pool. As the oxygen content exceed 300 10-6 the temperature at the maximum surface tension increases beyond the simulated maximum surface temperature, andis positive. Depending upon the oxygen concentrations, three, one, or two vortexes with different positions, strengths, and directions may be found in the weld pool. The contrary vortexes can efficiently transfer the thermal energy from the arc, creating a deep weld pool.