不同水深水下湿法焊接电弧等离子体数密度研究

Study on the Number Density of Underwater Welding Arc Plasma Under Different Water Depth

水下湿法焊接技术应用日益广泛,由于特殊的焊接条件,导致深水下其焊接质量亟待改善。通过搭建水下湿法焊接实验平台,压力罐调节气压分别模拟0.3,20和40 m水深,界定焊接引弧阶段,分别采集三个水深环境条件下焊接引弧阶段的光谱信息及电压电流数据,采集光谱信息时利用光谱仪的延时触发功能,分别采集引弧5,10,15,20和25 ms时刻的光谱数据,对采集到的电弧光谱数据整理后进行诊断分析。诊断分析时结合NIST原子光谱数据库以及特征谱线的相关数据,得到各元素粒子的识别结果。对于高价态的元素离子态,因为其电离能比较大,激发电离程度会受到电弧温度变化的影响,不能仅靠光谱图进行识别诊断,还需要进一步对其组分进行数密度计算。结合水下湿法焊接电弧光谱诊断的信息和水下湿法焊接反应过程,确定出计算中要考虑的电弧等离子组分的18种粒子,求解由沙哈方程、解离电离方程、准中性方程、气体压力平衡方程等组成的方程组,采用牛顿迭代法对方程组进行联立求解,对于求解非线性方程组,采取分段赋值的方法,得到等离子体组分在三个水深环境下的数密度,并对其变化规律进行分析,探究不同水深环境对焊接电弧等离子体数密度影响及因素。研究表明各个粒子数密度在不同水深条件下的变化是非线性的,随着水深加大电弧数密度变化幅度也快速增大。随着水深的增加,电弧会受到压缩,但电弧不能无限制被压缩;粒子的电离受温度的影响,温度越大电离作用越强烈,但当温度升高到一定程度时,各个电离作用有其电离极限,粒子数密度也不会无限增大。通过不同水深条件下焊接电弧引弧阶段数密度的计算,对水下焊接电弧引弧阶段粒子产生的机理进行了研究,为提高水下焊接电弧稳定性及电弧模拟仿真计算等提供了理论依据。

The application of underwater wet welding technology is becoming more and more extensive.Due to the special welding conditions,the welding quality in deep water should be improved.This paper simulates water depths of 0.3,20 and 40 m respectively by building an underwater wet welding experiment platform and adjusting air pressure by pressure tank.After defining the arc initiation stage,the spectral information and voltage and current data of the welding arc initiation stage under three water depth environmental conditions were collected.When collecting spectral information,the delay trigger function of the spectrometer is used to collect the spectral data at the time of arc initiation of 5,10,15,20 and 25 ms,respectively,and the collected arc spectral data is analyzed for diagnosis after sorting out.In the diagnostic analysis,the recognition results of each element particle were obtained by combining the relevant data of the NIST atomic spectral database and characteristic spectral lines.For the elemention state of high price state,the degree of excitation ionization will be affected by the change of arc temperature due to its large ionization energy.Therefore,it is not only necessary to identify and diagnose its components by spectrogram,but also need to calculate the number density of its components.Eighteen kinds of particles of arc plasma components to be considered in the calculation are determined by combining the spectral diagnosis information of underwater wet welding arc and the reaction process of underwater wet welding.The number density of the plasma component under three water depths is obtained by solving the equations composed of the Saha equation,dissociation ionization equation,quasi-neutral equation and gas pressure equilibrium equation.The variation law was analyzed to explore the influence of different water depth on the number density of welding arc plasma and its factors.The results show that the variation of particle number density is nonlinear under different water depth,and the variation amplitude of arc number density increases rapidly with the increase of water depth.As the water depth increases,the arc will be compressed,but the arc cannot be compressed indefinitely.The ionization of particles is affected by the temperature.The higher the temperature is,the stronger the ionization will be.However,when the temperature rises to a certain degree,each ionization has its ionization limit,and the particle number density will not increase indefinitely.Based on the calculation of arc number density,the mechanism of underwater welding arc is studied,which provides theoretical basis for improving welding stability and arc simulation.