| 摘要 |
PROBLEM TO BE SOLVED: To provide a horizontal continuous heating furnace that is used in a horizontal continuous annealing apparatus which has a preheating oven, a horizontal continuous heating furnace and a reducing furnace, prevents heat from dissipating from the hearth roll, does not coarsen a crystal in the ends in a width direction of a steel sheet made from extra-low carbon steel even when the steel sheet is heated in the horizontal continuous heating furnace and then final-annealed in a reducing furnace of a subsequent stage, and secures product quality, and to provide a continuous annealing method using the same. SOLUTION: The horizontal continuous heating furnace 3 has an opening 9 arranged so as to longitudinally penetrate a heat insulation wall 7 which is installed on a hearth 8 of the horizontal continuous heating furnace 3 and covers the undersurface of a hearth roll 5. The opening 9 has an open area ratio of 30 to 90%, which is expressed by the equation: open area ratio (%)=cross section of the opening in furnace width direction/total cross section of heat insulation wall in furnace width direction including the opening×100. The continuous annealing method includes adjusting a passing speed of the sheet and/or a burner output of a direct flame burner 6 so that a temperature difference between a central part and an end in a width direction of a steel sheet (A) can be 70°C or lower in an outlet of the horizontal continuous heating furnace 3. COPYRIGHT: (C)2007,JPO&INPIT
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