Figure 11.
Oxyacetylene flames.
(1) Neutral flame.
{a) The welding flame should be adjusted to neutral before either the
carburizing or oxidizing flame mixture is set. There are two clearly defined zones
in the neutral flame. The inner zone consists of a luminous cone that is bluish-
white. Surrounding this is a light blue flame envelope or sheath. This neutral
flame is obtained by starting with an excess acetylene flame in which there is a
"feather" extension of the inner cone. When the flow of acetylene is decreased or
the flow of oxygen increased the feather will tend to disappear. The neutral flame
begins when the feather disappears.
(b) The neutral or balanced name is obtained when the torch mixed gases
consist of approximately one volume of oxygen and one volume of acetylene. It is
obtained by gradually opening the oxygen valve to shorten the acetylene flame until
a clearly defined inner cone is visible. For a strictly neutral flame no whitish
streamers should be present at the end of the cone. In some cases it is desirable
to leave a slight acetylene streamer or "feather" (1/16- to 1/8-inch long) at the
end of the cone to insure that the flame is not oxidizing. The volume ratio of
oxygen to acetylene in forming a neutral flame is 1.04 to 1.14. This flame
adjustment is used for most welding operations and for preheating during cutting
operations. When welding steel with this flame the molten metal puddle is quiet
and clear. The metal flows easily without boiling, foaming, or sparking.
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