Study on Stabilization of Welding Arc under Hyperbaric Condition

在高压TIG电弧焊接中，电弧趋于不稳定，因此难以获得良好的焊接。为此，本文研究了磁场和交变磁场频率对电弧现象和焊接效果的影响，主要结果如下：1）在高压下对焊接电弧施加磁场，电弧的收缩被释放，其直径增加。2）在高压下对电弧施加静磁场，防止电弧电压的不规则波动，但是电弧电压以大约0.5ms的周期振动。因此，电弧可以以2kHz的频率转动或振动。3）在高压下向电弧施加交变磁场，防止了电弧电压的波动，但是电弧电压根据激励电流的频率而振动。4）在高压下向电弧施加交变磁场，可以通过相对稳定的电弧获得直的和良好的焊接。但磁场频率对焊接效果的影响并不明显。5）在较高的磁场频率下，为了在较低的频率下获得相同的磁通密度，必须使用较高的励磁电流。6）La_2O_3-W电极的腐蚀比ThO_2-W电极小得多。在焊接过程中，在La2O3-W电极的尖端处，La2O3存在于表面处，并且其使功函数减小，并且防止电极尖端的弯曲。结果，电极的腐蚀可能变得比其它电极的腐蚀小。

In hyperbaric TIG arc welding, the arc tends to be unstable and accordingly it is difficult to obtain sound welds. Therefore the effects of magnetic field and the frequency of alternating magnetic field on the arc phenomena and welding results were investigated.Main results obtained are summarized as follows : 1)Applying magnetic field to a welding arc under high pressure, the constriction of the arc is released and its diameter increases.2)Applying static field to an arc under high pressure, irregular fluctuation of arc voltage is prevented, but the arc voltage vibrates in a period of 0.5ms approximately. Accordingly, the arc may turn or vibrate in a frequency of 2 kHz.3)Applying alternating magnetic field to an arc under high pressure, fluctuation of arc voltage is prevented, but the arc voltage vibrates depending on a frequency of excitation current.4)Applying alternating magnetic field to an arc under high pressure, straight and sound welds can be obtained by a relatively stable arc. However, effect of frequency of magnetic field on welding result is not observed.5)In a higher frequency of magnetic field, a higher excitation current must be used in order to obtain a same magnetic flux density in a lower frequency. As the result, the excitation coil has a tendency to be heated in operation.6)The erosion of La2O3-W electrode is much less than that of ThO2-W electrode. At the tip of the La2O3-W electrode during welding, La2O3 exists at the surface and it makes the work function decrease and prevents superheat of the electrode tip. As the result, erosion of the electrode may become smaller than those of other electrodes.