Final answer:
The high temperatures necessary for welding produced by an oxyacetylene torch are generated by the inner cone of the flame, where acetylene combusts with oxygen in an exothermic reaction. This allows the torch to reach temperatures up to 3300°C.
Step-by-step explanation:
The part of an oxyacetylene torch flame that produces the high temperature needed for welding is the inner cone. This region exists where the acetylene and oxygen mix and burn to form a stable flame.
The combustion of acetylene in oxygen is an exothermic reaction, releasing energy that heats the metal to its melting point enabling welding and cutting processes. Acetylene torches are known for their ability to reach extremely high temperatures, up to around 3300°C due to the high heat of combustion for acetylene. It's not just in welding where acetylene plays a crucial role; the majority of manufactured acetylene is used to create chemical intermediates for products like vinyl, acrylics, and resins.