Strip thickness control device for hot rolling mill

Abstract

The present disclosure provides a strip thickness control device for a hot rolling mill that can reliably pass a leading end of a material-to-be-rolled without raising equipment cost even in a case of rolling the material-to-be-rolled extremely thinly. The strip thickness control device for a hot rolling mill includes a strip thickness meter installed at a delivery side of a last one of rolling stands in a series direction, a gap calculating unit that calculates a gap between rolls in each of the rolling stands, the gap being larger than a product target strip thickness of the material-to-be-rolled and corresponding to a passable strip thickness that enables a leading end of the material-to-be-rolled to be passed stably, a gap setting unit that sets the gap calculated by the gap calculating unit for each of the rolling stands, an automatic strip thickness control unit that executes automatic strip thickness control of minimizing a strip thickness deviation between a strip thickness measured value of the strip thickness meter and the passable strip thickness, and a target strip thickness changing unit that changes the passable strip thickness to the product target strip thickness by adding a strip thickness bias to the strip thickness deviation at a predetermined ramp rate after the leading end of the material-to-be-rolled is passed through the last one of the rolling stands.

1 . A strip thickness control device for a hot rolling mill in which a plurality of rolling stands are provided in series, and a heated material-to-be-rolled is rolled successively by the plurality of rolling stands, comprising:
 a strip thickness meter that is installed at a delivery side of a last one of the rolling stands in a series direction and measures a strip thickness of the material-to-be-rolled;   a gap calculating unit that calculates a gap between rolls in each of the rolling stands, the gap being larger than a product target strip thickness of the material-to-be-rolled and corresponding to a passable strip thickness that enables a leading end of the material-to-be-rolled to be passed stably;   a gap setting unit that sets the gap calculated by the gap calculating unit for each of the rolling stands;   an automatic strip thickness control unit that executes automatic strip thickness control of minimizing a strip thickness deviation between a strip thickness measured value of the strip thickness meter and the passable strip thickness; and   a target strip thickness changing unit that changes the passable strip thickness to the product target strip thickness by adding a strip thickness bias to the strip thickness deviation at a predetermined ramp rate after the leading end of the material-to-be-rolled is passed through the last one of the rolling stands.   
     
     
         2 . The strip thickness control device for a hot rolling mill according to  claim 1 , wherein the target strip thickness changing unit is configured to change the product target strip thickness to the passable strip thickness by adding the strip thickness bias to the strip thickness deviation at the predetermined ramp rate before a tail end of the material-to-be-rolled is passed through a first one of the rolling stands in the series direction.