JUDGING METHOD FOR GENERATING SOURCE OF THICKNESS DEVIATION OF SEAMLESS STEEL PIPE

PURPOSE:To judge on line the generating source of thickness deviation of a seamless steel pipe, by measuring the change of rolling conditions continuously in rolling a pipe-material to analyze a wave form obtained from the measured result. CONSTITUTION:Rolling load signals, obtained only in rolling, are read in fixed sampling period according to a timing signals T by a load sensing relay 13, by sending detected signals of both sided load cells 6, incorporated into a rolling mill, to a signal treating device 11 through amplifiers 10, and a total signal, summed up rolling loads on both sides, is computed to obtain a frequency power spectrum at the time of the completion of rolling. On the other hand, the phase difference between the signals of both sides, and further, the phase and gain for every frequency, are obtained to be sent to the 1st arithmatic unit 12. These signals, rolling time T' from the load sensing relay 13, and the pipe length L and dia. D of the pipe-material sent from a length meter 14 and outer dia. meter 15 of elongator, are given to the unit 12 so as to compute the gain for every angle alpha. The contents obtained from said computing is analyzed by an arithmatic unit 16 to obtain the degree and cause of the thickness deviations, thereby indicating the degree for every cause by an indicator 17.