PURPOSE: To remove the projecting part of the weld bead without discharging chips or cutting chips by rolling down the bead when the bead temperature after the welding is in the prescribed temperature range.
CONSTITUTION: The bead is rolled down when the bead temperature after the welding is in the temperature range of 400-750°C. The projecting part of the weld bead formed on the outer surface is rolled down to be smooth and flat, and no chips or cutting chips are discharged. The projecting part is rolled down when the bead temperature after the welding is ≥400°C, and the rolling- down force is not so large, the bead of high temperature and small deformation resistance are concentratedly rolled down, and this work can be achieved by a compact rolling-down equipment. For example, when the bead temperature is ≤350°C, the deformation resistance of a steel tube is remarkably increased, and the bead height can not be set within the allowable range. When the bead temperature is ≥800°C, a recessed part is generated due to the defective welds or the shrinkage during the cooling. When the bead is rolled down in the range of 400-750°C, the bead height can be set within the allowable range, and the welded steel tube for a column free from any defective welds can be manufactured.
FUKUMOTO TADASHI
SAWA MIKIO
