| 摘要 |
PURPOSE:To prevent the formation of oxide film on the surface of steel material so as to prevent the fall in cooling effect during quenching, by, in hardening of the steel material, installing a seal chamber using an inert gas between a heating furnace and a cooling unit for the steel material. CONSTITUTION:A steel material 8 is heated in a heating furnance 1 to a hardening temp., then it is delivered to a cooling unit 2, where it is quenched and hardened with cooling medium sprayed through cooling medium spray nozzles 6. In that case, a seal chamber 3 is arranged between the heating furnace 7 and the cooling unit 2. Inert gas such as nitrogen is introduced into the seal chamber 3 through an inlet 4. Hot steel material 8 which passes from the heating furnace 1 to the cooling unit 2 proceeds through the seal chamber 3, where it does not come into contact with air, hence no oxide coating is formed on the surface. Consequently, the steel material 8 is quenched and hardened uniformly all over the material because no decrease in cooling effect due to the oxide coating is caused. |
