Abstract: Cross sectional dimensions of an intermediate product of sectional steel are measured in the course of rolling, by simultaneously, horizontally reciprocating, in the direction transverse to a conveyance line of the sectional steel, two laser range finders which are disposed vertically opposite to each other. The method and apparatus are capable of determining, precisely and automatically, a sectional shape of the H-beam in an on-line manner, thereby improving product quality and yield.

Abstract: In the size measurement of steel sections, a pair of two-dimensional rangefinders and a pair of one-dimensional rangefinders are arranged so as to sandwich a steel section consisting of a pair of flange portions and a web portion in a widthwise direction of the flange portion and face to each other, whereby a vertical distance ranging from the two-dimensional rangefinder to the flange portion and a vertical distance ranging from the one-dimensional rangefinder to the web portion are measured, respectively to calculate a deviation at center, a flange width and a web thickness from the above measured values. In this case, a laser rangefinder is used as each of the two-dimensional rangefinder and one-dimensional rangefinder.

Abstract: In a steel rolling mill, (a) a calibration of a thickness in the output side which is calculated from a rolling force at a lock-on position in the present pass is performed depending upon a fluctuation from a predetermined thickness at the lock-on in the last pass, a deformation resistance of a slab and a mill constant; and (b) a constant lock-on level is given to be a predetermined thickness in the present pass as the same with a thickness in the output side given by a plastic characteristic curve of the rolled slab on the predetermined thickness at the lock-on in the last pass and an elastic characteristic curve of a rolling mill on a screw position in the present pass; and then, (c) an adjusting degree of a screw gap of the press-down screw is obtained depending upon the thickness fluctuation from the predetermined thickness in the last pass, the mill constant and a differential coefficient in a rolling load function from the predetermined thickness in the present pass; and (d) the press-down screw positio