| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and an apparatus for manufacturing a long steel material which prevents bending of the steel material due to cooling and which has excellent toughness or the like, when performing cooling from a tempering temperature after tempering in the heat treatment. SOLUTION: In the cooling after tempering treatment in the heat treatment to the long steel material composed of a bar steel or a steel pipe, a plurality of water-cooling nozzles 6 are provided to the upper and lower parts of the long steel material 2 in a cooling zone 4, the direction of the water-cooling nozzle 6 is made to have 20-45°with respect to the long steel material 2, and the water-cooling nozzle 6 has water volume enough to cool the surface of a red-heating part 3 of the long steel material 2 from the water-cooling starting temperature in the heat treatment to 250°C (preferably, 100°C) and a cooling rate is made≥400°C/s. With this apparatus, the cooling water is jetted onto the long steel material 2 at the water-flowing angle of 20-45°from the water-cooling nozzle 6 provided continuously at the upper and lower parts in the cooling zone 4 of the long steel material 2, and the cooling rate on the surface of the steel material is made≥400°C/s to cool the long steel material 2 from the heat-treatment temperature to 250°C (desirably 100°C). COPYRIGHT: (C)2011,JPO&INPIT |
