Heat treatment furnace, heating device, manufacturing method of wire electrode and heat diffusion treatment method

A heat treatment furnace, which moves an element wire having been zinc-galvanized at a predetermined speed and heats the element wire to perform a heat diffusion treatment, comprising:

• a first rotary electrode, a second rotary electrode and a third rotary electrode to which a voltage is applied;
• a motor that rotationally drives the first rotary electrode, the second rotary electrode and the third rotary electrode;
• and a control device;
• wherein the first rotary electrode, the second rotary electrode and the third rotary electrode are arranged in a manner that the element wire is laid in a V-shape or an I-shape in an order of the second rotary electrode, the first rotary electrode and the third rotary electrode from the upstream side in a travel direction of the element wire;
• wherein the motor is driven according to a command from the control device to cause the element wire to travel, a voltage is applied to the first rotary electrode, and a voltage having a sign opposite to that of the first rotary electrode is applied to the second rotary electrode and the third rotary electrode;
• and
• wherein a current flows through and heats the element wire which travels in a first heating section between the second rotary electrode and the first rotary electrode and in a second heating section between the third rotary electrode and the first rotary electrode.