On-line adaptive control of the hot rolling of steel sections

A section mill rolls a rectangular `slab´ or `bloom´ into an H-section beam while the steel is red-hot (around 1250°C). The universal group of stands rolls a roughly shaped `beam blank´ into an accurate `H´ of the required dimensions. There are typically three reversing stands in the universal group which roll the piece in tandem: two universal stands (universal rougher and universal finisher) and an edger stand. The former roll the piece between four rolls which form an H-shaped gap, while the edger reduces the flanges´ lengths by rolling their ends. Tight control increases efficiency in terms of scrap and savings on tolerances. To achieve the highest performance, a full set-up calculation is required. This demands complex mathematical models of the rolling process, which enable accurate prediction of the behaviour of the rolled metal and the mill. Experience in the rolling of flat products has proved that significant improvements in performance can be achieved by automatic correction of the models in an online adaptive system. Such techniques have been slow to find their way into the more complex area of section rolling, although activity in the offline modelling of the process is evident. This paper describes a multiloop adaptive control scheme for a beam mill which has already proven its worth on a state-of-the-art mill