Does flame cutting use a neutral flame or slightly oxidizing flame?

Answer 1

Assuming that you are using the Oxygen-Acetylene cutting process; both, depending at what stage/phase of the cutting process you are in. What we encounter is a gas flow differential problem. With the cutting torch flame properly adjusted (the acetylene valve opened to the point where the un-mixed acetylene flame is burning without producing any smoke but still in contact with the cutting tip of the torch, the oxygen valve is slowly opened until you have adjusted the flame to a neutral quality or setting. Press the cutting oxygen lever; typically the flame will become slightly carburizing ("feathers" will appear at the ends of the pre-heat flames) this phenomonom occurs because of the drop in line pressure due to the high flow of oxygen through the cutting tube or orifice. With the oxygen lever remaining depressed, readjust the flame to a neutral setting. This will cause the flame to become slightly oxidizing when the cutting lever is released; since an oxidizing flame burns slightly hotter than a neutral flame the pre-heat of the metal that is being cut is faster. When the metal is at the proper pre-heat or kindling temperature (1600 F for pure iron - various steel alloys will be slightly different; beginning to turn bright red is a good indicator) depress the cutting oxygen lever, the flame will revert to "neutral" and the cut can then begin. Weld. Prof.