TORSION DETERMINATION METHOD OF HOT SLAB WIDTH REDUCTION, HOT SLAB WIDTH REDUCTION METHOD AND MANUFACTURING METHOD OF HOT ROLLED STEEL SHEET

To provide a determination method of a hot slab width reduction which can determine whether it becomes a width reduction defective slab by torsion before performing width reduction.SOLUTION: A torsion determination method of a hot slab width reduction is given in which: when a width reducing device 12 performs the width reduction of a slab heated with a heating furnace by an edging rate γ(γ=ΔW/W0) that is the width reducing amount ΔW divided by the slab width W0 which is a width before reduction in a hot rolling line 30 where there is the width reducing device between the heating furnace 11 and a roughing mill 13, temperatures at the width end parts of both sides of the slab are acquired by, for example, numerical calculation or a temperature measuring device before the width reduction of the slab is performed by the width reducing device; temperature difference between the acquired temperatures at the width end parts of both sides of the slab is obtained as a width direction temperature deviation ΔT; and when a product by multiplying the width direction temperature deviation ΔT by the edging rate γ exceeds the constant value, torsion of the slab is determined to occur by the width reduction of the slab.SELECTED DRAWING: Figure 2 【課題】 熱間スラブの幅圧下において、ねじれにより幅圧下不良スラブとなるか否かを幅圧下前に判定する方法を提案する。【解決手段】 本発明に係る熱間スラブ幅圧下でのねじれ判定方法は、加熱炉１１と粗圧延機１３との間に幅圧下装置１２を有する熱間圧延ライン３０において、前記加熱炉で加熱されたスラブを、幅圧下量ΔＷを圧下前のスラブ幅Ｗ０で除した値である幅圧下率γ（γ＝ΔＷ／Ｗ０）で前記幅圧下装置にて幅圧下するにあたり、前記幅圧下装置でスラブを幅圧下する前に、例えば数値計算または測温機器によって、スラブの両側の幅端部の温度を求め、求めたスラブの両側の幅端部の温度差を幅方向温度偏差ΔＴとして定め、当該幅方向温度偏差ΔＴと前記幅圧下率γとの積が一定値を超えた場合に、スラブを幅圧下することによってスラブにねじれが発生すると判定する。【選択図】 図２