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Spray Arc Welding
By raising the welding current and voltage
still further, the metal transfer will become a true spray arc. The
minimum welding current at which this
occurs is called the transition current. Table
1-2 shows typical values of
transition current for various filler metals and shielding gases. As seen in this
table, the transition current depends
on the metal wire diameter and shielding gas. However, if the shielding gas for
welding carbon steel
contains more than about 15% CO2 there is
no transition from globular transfer to spray transfer. Figure
1-3 shows the typical fine arc column and pointed wire of the spray arc. The molten
drops from the wire
are very small, affording good arc stability. Short circuiting is rare. Little
spatter is associated with this welding
technique. Spray
arc welding can produce high deposition rates of weld metal. This welding technique
is generally used for
joining materials 3/32 in. (2.4mm) and greater in thickness. Except when welding
aluminum or copper, the
spray arc process is generally restricted to welding in the flat position only
because of the large weld puddle.
However, mild steel can be welded out of position with this technique when small
weld puddles are used;
generally with a .035 in. (.89mm) or .045 in. (1.1mm) diameter wires.
Figure 1-3
Spray Arc Welding
Technique
