Prevention of contact tube melting in arc welding
We have discovered that catastrophic melting of the contact tube (due to wire feed blockage and other problems) in continuously fed consumable electrode arc welding can be prevented. In our laboratory, we have found that there is a delay near 0.1 s between electrode feed blockage and melting of the contact tube, a time sufficient to detect this problem and interrupt the power. Blockage of the electrode feed, running out of electrode, or any other condition that would cause the wire feed st stop in a continuous electrode process upsets the stable heating/melting rate balance at the tip of the electrode. As a result, the arc to grow until it reaches the contact tube. At this point, the contact tube may be destroyed and the weld contaminated with the contact tube alloy. The change in the arc length and the electrode extension also changes the respective voltage drops in the electrical circuit. A simple voltage sensor can detect these changes (a voltage increase that typically exceeds 5 V within 0.1 s) due the electrode feed blockage. We show plots of the electrode extension (length of electrode beyond the contact tube) versus voltage, after the electrode feed is interrupted. Relatively simple circuitry can respond to the change in the voltage and interrupt the welding current before contact tube melting occurs.
- OSTI ID:
- 115552
- Report Number(s):
- CONF-9404233--
- Country of Publication:
- United States
- Language:
- English
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