PLASMA-ENERGY TRANSFER IN GAS-SHIELDED WELDING ARCS
High-current welding arcs are influenced by the selfmagnetic field produced within the discharge acting to compress or pinch the conducting plasma. The thermal expansion of the plasma opposes the magnetic compression. The geometric form of the discharge is controlled by the interaction of these opposing forces. An axial pressure gradient occurs, occasioned by the magnetic compression when the radius of the plasma varies throughout its length. The magnetic pressure is proportional to the square of the current and varies inversely with the cross-sectional area of the plasma. The product of the plasma temperature, particle density and gas constant determines the opposing pressure of the gas expansion. The thermal conductivity which varies with the gas composing the plasma is an influential factor determining the radial temperaturc gradient and effective pressure of the arc. Arcs shielded by low- thermalconductivity gases manifest the magnetic compression at lower current values than high-thermal conductivity gases. Those in the former group known to form readily a compressed plasma are xenon, mercury, and argon. Helium is representative of the latter group. The various modes of heat conduction comprising the total thermal-conductivity coefficient for several gases are described. The magnetic-pinching mechanism is analyzed and shown to be effective in assisting the transfer of metal through the arc. In the absence of the magnetic compression metal transfers more slowly and less uniformly, constituting what is known as globular transfer. (auth)
- Research Organization:
- Westinghouse Research Labs., Pittsburgh
- NSA Number:
- NSA-13-018165
- OSTI ID:
- 4231438
- Journal Information:
- Welding J., (N.Y.), Vol. Vol: 38; Other Information: Orig. Receipt Date: 31-DEC-59
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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