Understanding Gas Welding Flame Temperature

Gas welding uses a flame produced by burning a fuel gas (like acetylene) with an oxidizer (usually oxygen). The flame has different zones, each with a specific temperature. These zones are created as the gases mix and burn.

The main zones in a typical gas welding flame, especially a neutral flame (most commonly used for welding), are:

• Inner Core (or cone): This is the small, bright, sharply defined cone at the torch tip. This is where the primary combustion of the fuel gas occurs.
• Reducing or Intermediate Zone: This zone surrounds the inner core.
• Outer Envelope: This is the outermost part of the flame, where secondary combustion with atmospheric oxygen takes place.

Each zone has a different temperature, and the hottest part of the flame is crucial for melting metals during welding.

Temperature of the Inner Core Flame Zone

The inner core of the gas welding flame is where the fuel gas undergoes its initial, most intense combustion reaction with the oxygen supplied by the torch. This primary combustion releases a large amount of heat in a concentrated area.

Due to this highly exothermic reaction occurring in a small volume, the inner core reaches the peak temperature of the entire flame. For an oxy-acetylene flame, which is very hot, the temperature in the inner core can reach approximately:

\(\text{Temperature of Inner Core} \approx 3100^{\circ}\text{C}\) to \(3200^{\circ}\text{C}\)

While the intermediate and outer zones are also hot, their temperatures are lower than the inner core.

Therefore, the inner core of the flame in gas welding has the highest temperature compared to the other zones.

Gas Welding Flame Temperature Distribution Revision

Additional Information on Gas Welding Flame Types and Temperature

The exact temperature distribution also depends on the type of fuel gas used (e.g., acetylene, propane, methane) and the ratio of oxygen to fuel gas, which determines the flame type (neutral, oxidizing, or carburizing).

• Neutral Flame: Equal volumes of oxygen and acetylene (after primary combustion). Used for most welding. Has a clear inner cone.
• Oxidizing Flame: More oxygen than acetylene. Shorter, sharper inner cone. Hotter than neutral flame but can oxidize metals.
• Carburizing (Reducing) Flame: More acetylene than oxygen. Has a feathery edge around the inner cone. Cooler than neutral flame, adds carbon to metal.

Regardless of the flame type, the inner core (or the region closest to the primary combustion) is generally the hottest part because that is where the most energetic reaction occurs.