The following fusion welding process utilizes a flame.

The fusion welding process that utilizes a flame is oxy-fuel welding. This method employs a combination of fuel gas and oxygen to create a flame that melts the base material, allowing for the joining of metals through fusion. The process is characterized by its versatility and the ability to weld a variety of metals and thicknesses.

Oxy-fuel welding can be adjusted for different heat requirements by varying the ratio of oxygen to fuel gas, making it excellent for applications where control over the heat input is critical.

In contrast, other welding processes listed do not primarily use a flame for fusion. Shielded metal arc welding relies on an electric arc between a coated electrode and the workpiece, while gas metal arc welding uses an electric arc and a continuous wire feed as the electrode. Gas tungsten arc welding also focuses on an electric arc but uses a non-consumable tungsten electrode, rather than a flame, to produce the weld. Thus, oxy-fuel welding stands out for its use of a gas flame as the primary heat source.