To suppress bending of steel bars in the vicinity of a sheared surface and crushing of the sheared surface without lowering productivity and needing complicated structure during shearing in a refining line and a machining line, in the cooling bed of a steel bars hot rolling line.
On the rear surface of the cooling bed of the rolling line, the steel bar is sheared after a sheared portion is locally heated to a blue brittleness temperature area. A shearing machine is provided with a mechanism to exert a force on a material to be sheared from two directions different from each other. First, a force from the first direction is applied, a shearing portion is brought into a yield state and a force is applied from the second direction for shearing. A notch having depth of 1.0 mm or more is formed in the portion to be sheared and the notch position is sheared. Shearing is effected with the steel bar on a fixed blade pressed by a press means with a press force being 1/3-1 as much as a yield stress. Thus, a need for a straightening work and a defective part cutting work after shearing is eliminated and further a load during shearing can be relieved.
SHINOHARA MITSUNORI
SATO TATSUYA
