Page 491 of 561

AC/OX CUTTING/WELDING/BRAZING

The carburizing flame

The carburizing flame has an excess of Acetylene, and is recognized by a secondary flame zone between the inner cone and the flame envelope. This zone is less bright and more white in colour than the inner cone, but is considerably brighter than the flame envelope.

When igniting an Ac/Ox torch one normally opens fully for Acetylene and only slightly for Oxygen, obtaining a strongly carburizing flame. By adding Oxygen (and if necessary

reducing the Acetylene flow) the secondary zone will be reduced, and a neutral flame is obtained just as the secondary zone dissappears. Reducing the Oxygen flow slightly again will give a carburizing flame with a small secondary flame zone, approximately twice as long as the inner cone. This soft flame (also called a reducing flame) is used for welding of Aluminium and Aluminium alloys, and for soft soldering.

The oxidizing flame

5.01

490

By increasing the Oxygen flow slightly beyond the point where the secondary zone disappears one will obtain an oxidizing flame (with excess Oxygen). The flame will be shorter and sharper than the

neutral flame, with a shorter, more pointed inner cone. This flame is slightly hotter than the neutral flame, and is used for welding cast iron, brass, bronze and zinc alloys, and for brazing.