| 摘要 |
PURPOSE:To soften the material of steel sheet which has been continuously annealed and hot-zinc dipped so as to improve the workability, by over-aging the steel sheet. CONSTITUTION:Steel sheet 4 which has been hot-zinc dipped by in-line type annealing process is heated while passing through an induction heating zone 1 of a heat treating furnace to a temp. of 425-460 deg.C. The steel sheet is maintained at the temp. at least for 2-4min. while passing through a soaking zone 2, then it is subjected to control-cooling in a control-cooling zone 3 at a rate near natural cooling. Or it is rapidly heated to about 300 deg.C while passing through the induction heating zone 1, maintained in the soaking zone 2, 3 at a temp. of 340-370 deg.C at least for 16min., and is allowed to cool. Application of the above-described heat cycle to a steel sheet softens the material and improves the workability of the steel sheet which has been hot-zinc dipped after continuous annealing. Either horizontal or vertical heat treating furnace may produce similar results. |
