Abstract:
The last decade has seen a considerable growth in the exploitation of
deep sea mineral reserves. Accompanying these developments has come the
need for suitable underwater repair and uainten-nce techniques. one such
technique involves the use of fusion welding processes in localised dry
high pressure environments created around weldments. Pressure chambers
at Cranfield have been employed to simulate this sitiu. ation. These have
been used to investigate the influence of ambient pressure (1 to 45 bars)
on gas-tungsten arcs.
The study has been of a basic nature with emphasis on arc characteristics
and arc structure. Special attention is given to the argon TIG arc
although helium TIG arcs and constricted argon-tungsten arcs have also
been examined. Arc characteristics are reported in terms of arc
appearance and modes, electrical characteristics and weld bead studies.
The investigation of arc structure is concerned with gaining an
understanding of observed characteristics. This has involved experimental
and theoretical developments. Experimental techniques used include,
electrostatic probes, calorimetry and the measurement of total power
radiated from an arc. Models developed here have successfully explained
many of the experimental findings and special emphasis has been directed
at understanding gas flow in the column and arc stability.
Much of the work included in this thesis has implications for the
development of underwater welding procedures. Results presented should
also contribute to gaining a better understanding of arcs operating under
normal ambient conditions. However, these aspects are not discussed in
any detail as the main emphasis has been placed on documenting and explaining the influence of pressure on gas-tungsten arcs.
