JPS5633118A - Automatic controlling method for wall thickness of seamless steel pipe - Google Patents

Abstract

PURPOSE:To improve the accuracy of shape and size, by deciding the draft distribution for each pass depending on the draft distribution model, by setting the roll gap for the first pass according to the forecast rolling load, and by setting the roll gap for the second pass depending on the increment of the wall thickness at the groove bottom in the first pass and the increment of the forecast rolling load for the second pass. CONSTITUTION:When the pipe blank to be rolled is held just in front of the plug mill, the draft distribution for each pass is decided depending on the draft distribution model to be obtained from the specified formula. The temperature of the pipe blank 22 rolled by the elongator 3 is measured by the thermometer 4, and its length is measured by the length meter 5. The forecast rolling load for each pass is obtained from the rolling load forecast model made in consideration of above measured values of the temperature and length, and the roll gap for the first pass is corrected by the learning control depending on the actual rolling performance in the former pass by the same plug and on the aim size. Besides, the increment of the wall thickness at the groove bottom is obtained from the actually measured rolling load in the first pass and the forecast rolling load; and the increment of the forecast rolling load for the second pass is obtained from the actually measured pipe blank's temperature in the first pass and the forecast rolling temperature; hereby, the roll gap for the second pass is corrected.