What is the principle of resistance furnace?

An industrial furnace that uses electric current to heat the electric heating element or heating medium in the furnace to heat the workpiece or material. Resistance furnaces are used in the mechanical industry for metal forging pre-heating, metal heat treatment heating, brazing, powder metallurgy sintering, glass ceramic baking and annealing, low melting point metal melting, sand mold and paint film drying, etc.