| 摘要 |
PURPOSE:To obtain an annealed steel material having excellent quality by passing a steel material previously through a preceding heating furnace at a temp. lower than the A1 transformation point in a reducing atmosphere, and then sending the steel material into an annealing furnace wherein the steel material is annealed at elevated temp. in annealing the steel material. CONSTITUTION:When a steel material such as billets and wire-rod coils is annealed, the steel material is firstly introduced into an inlet purging chamber 7 which is evacuated, and then the vacuum is turned off by introducing a reducing protective gas. The steel material is then carried into a preceding heating furnace 1 wherein a reducing protective gas is introduced, and heated with a radiant tube to 670 deg.C which is lower than the A1 transformation point to reduce the oxides on the surface of the steel material. The steel material is subsequently carried in an intermediate purging chamber 9 which is evacuated to purge the gas in the preceding heating furnace 1, and the vacuum is turned off by supplying a protective gas. The steel material is then carried into an annealing furnace 2, heated to 740 deg.C in a heating zone 2a in a protective gas atmosphere, and annealed. The steel material is then slowly cooled in a slow-cooling zone 2b to 680 deg.C by a radiant tube through which the external air is passed, and taken out to the outside through an outlet purging chamber 10. |
