In oxy-acetylene flame terminology, the carburizing flame results from which condition?

• A. Excess acetylene
• B. Excess oxygen
• C. Balanced mix
• D. No acetylene

Answer: (A)

Carburizing flame is the fuel-rich, reducing flame in oxy-fuel operations. It occurs when there is more acetylene than oxygen, so not all of the acetylene can be burned; the flame becomes smoky with soot and can deposit carbon on the workpiece. This is why excess acetylene is the condition that produces a carburizing flame. If there were excess oxygen, the flame would be oxidizing, typically blue and less sooty, tending to oxidize the surface. A neutral flame results from a balanced mix, producing minimal soot. Without any acetylene, you wouldn’t have a carburizing flame at all.