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How does thermite joining produce superheated liquid metal?

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Welder in a blue uniform and protective helmet using shielded metal arc welding to join metal pieces, with bright sparks and smoke visible at the welding point. — welding Shielded metal arc welding.

Thermite joining, also known as the aluminothermic process, produces superheated liquid metal through a highly exothermic chemical reaction.1

The process utilizes a powdered mixture consisting of finely divided aluminum and a metal oxide, such as iron oxide. When this mixture is ignited, the aluminum acts as a powerful reducing agent, chemically combining with the oxygen from the metal oxide. This rapid chemical reaction releases an enormous amount of heat, which is sufficient to melt the metal and produce a superheated liquid at temperatures reaching approximately 2,400 °C to 2,800 °C (4,400 °F to 5,000 °F).12

Because the reaction is completed quickly—typically within 30 seconds to two minutes—it is particularly effective for joining large, compact cross-sections of ferrous metals, with a mold used to contain the resulting molten material.1