GMAW电弧等离子体平衡成分计算及其在光谱学中的应用

计算了常压下3 000～25 000 K范围内熔化极气体保护焊(GMAW)保护气体Ar，CO₂，82%Ar-18%CO₂及其与Fe蒸汽的混合物的平衡成分。上述气体被看作一种Ar-CO₂-Fe等离子体，等离子体中的39种粒子被分为5种主元粒子和34种非主元粒子。根据化学方程，非主元粒子由主元粒子表示以减少未知数的个数和求解量，再利用牛顿迭代法对平衡方程进行求解，最终实现了成分求解。计算结果表明，Ar气随着温度升高依次发生一次电离和二次电离，CO₂气体除了在高温时发生原子电离外，在低温时(T<8 000 K)还存在CO₂，O₂，CO等分子的解离，82%Ar-18%CO₂混合气则既有解离又有电离。Fe的加入会增加等离子体的电子密度，特别是在15 000 K以下。等离子体成分的确定为GMAW电弧等离子体辐射属性计算以及电弧中Fe蒸汽浓度的光谱测定奠定了基础。

Computation of Equilibrium Compositions of GMAW Arc Plasmas and Its Applications in Spectroscopy

This article is devoted to the computation of equilibrium compositions of the shielding gases in gas metal arc welding (GMAW) Ar, CO₂, and 82%Ar-18%CO₂ as well as their mixtures with Fe metal vapour at atmospheric pressure between 3 000 and 25 000 K. The above gases were treated as a type of Ar-CO₂-Fe mixture with 39 particles. These particles were divided as two categories: 5 basis particles and 34 non-basis particles. The particle number densities of non-basis particles were expressed by that of basis particles based on chemical equation, thus reducing the unknowns and the computation. Finally, the conservation equations were solved by Newton’s method to obtain the number density of each particle. The results indicate that primary and secondary ionization occur in pure argon with the increase of temperature, the dissociation of molecules of CO₂, O₂ and CO at low temperature (T＞8 000 K) occur in pure CO₂ besides the ionization at high temperature, and both ionization and dissociation exist in the 82%Ar-18%CO₂ mixture. It also found that the addition of Fe can increase the electron number density, especially at temperature below 15 000 K. The determination of chemical compositions built a solid foundation for the calculation of radiative properties of GMAW arc plasmas and for the spectroscopic measurement of iron vapour concentration in arcs.