The most commonly used flame type for oxyfuel cutting is ______.

• A. An oxidizing flame
• B. A neutral flame
• C. A carburizing flame
• D. None of the above

Answer: (B)

In oxyfuel cutting, the preheat flame should heat the metal evenly without changing its surface chemistry. A neutral flame, which has a balanced mix of fuel and oxygen, provides clean, controlled heat that won’t add extra oxygen or carbon to the metal before ignition. This helps avoid premature oxidation or carburization of the edge while you bring it up to the ignition temperature. Once the metal is hot enough, you switch to the cutting action with a stream of pure oxygen to form and blow away the oxide.

An oxidizing flame would oversupply oxygen and cause unnecessary oxidation of the heated surface, while a carburizing flame would deposit carbon and alter the surface chemistry, both of which can worsen edge quality. That’s why the neutral flame is the most commonly used for oxyfuel cutting.