JPS6411072A - Method for cutting cast slab - Google Patents

Abstract

PURPOSE:To improve the cutting efficiency of a cast slab by detecting the temperature of a preheating part and blowing out oxygen for cutting from blowpipes when the detected temperature attains a prescribed value to start the cutting of the slab and performing sure notching thereon. CONSTITUTION:When the blowpipes 71 and 72, beam generators 81 and 82 and beam detectors 91 and 92 stop at the other edge of the cast slab 1, gases for preheating are blown out from the blowpipes 71 and 72 and both side edges of the cast slab are preheated by gas flames. Modulated laser beams, etc., are projected on the preheating part from the beam generators 81 and 82 and the scattered beams reflected from the preheating part are detected by the beam detectors 91 and 92. A thermometer 11 catches the transition from a stable state to an unstable state of the outputs of the beam detectors 91 and 92 from the rate of change of the outputs or the rate of change of amplitude and detects that the preheating temperature attains an almost lower limit of the proper preheating temperature range. The preheating part temperature detected by the thermometer 11 is inputted to a control part 12 and compared with the threshold temperature and when it attains the threshold value, a control signal is sent from the control part 12 to a control valve 13 and the oxygen for cutting is blown out from the blowpipes 71 and 72.