| 摘要 |
PURPOSE:To decrease the disconnection during drawing and to improve the production efficiency and yield of an ultra-fine wire by subjecting a material after cold working including intermediate annealing to a heat treatment at a steep temp. gradient and at the temp. higher than the temp. in intermediate annealing then drawing the material. CONSTITUTION:An ingot is subjected to hot working, cold working and intermediate annealing and is then subjected to cold working at about 1-50% sectional area ratio. Such intermediate wire rod 2 is passed through a heating furnace 5. Cooling parts 6, 7 contg. cooling liquid are provided at both ends of the furnace 5. The wire rod 2 is cooled prior to heating in a heating part 8, and the atmosphere having the steep temp. gradient from the introducing part up to the max. temp. part is maintained therein. The max. temp. part is set higher than the temp. of the intermediate annealing. The wire rod 2 subjected to the heat treatment is taken up on a reel 9 and thereafter the wire rod is subjected to cold working at about >=99% reduction of area, by which the extra-fine wire is obtd.
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