HARDENING METHOD AND HARDENING APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide a hardening method in which the surface of a long material is hardened without oxidizing in a simple method. SOLUTION: While injecting non-oxidizing gas 34, 74, 84 from first gas injection tubes 30, a second gas injection tube 70 and a third gas injection tube 80, the surface 14 to be heated is heated to a hardening temperature with a first induction heating coil 20.