| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for preventing a coil-break of a hot-rolled steel sheet developed in the case of un-coiling a hot-rolled coil which is still under a hot-rolled state. SOLUTION: In un-coiling the hot-rolled coil with an un-coiler for hot-rolled coil provided with a pressure roll, the amount of push-downδof the pressure roll and the distance L from a position starting the un-coiling of the steel sheet to a position where the pressure roll is pushed down are controlled so that a cross sectional yield ratioαof the following equation (3), which is expressed by a bending curvatureκapplied to the steel sheet with the pressure roll in the following equation (1) and an elastic limit curvatureκ<SP>e</SP>of the steel sheet in the following equation (2), becomes 0.4<α<0.6,κ=m(δ+h)/L<SP>2</SP>...(1),κ<SP>e</SP>=2σ<SB>y</SB>/(hE)...(2),α=1-κ<SP>e</SP>/κ...(3), whereinκ: the bending curvature of the steel sheet, m: constant (4 to 8),δ: the push-down amount, h: the sheet thickness, L: the distance from the position starting the un-coiling of the steel sheet to the position where the pressure roll is pushed down,κ<SP>e</SP>: the elastic limit curvature,σ<SB>y</SB>: yield stress, E: Young's modulus andα: the cross sectional yield ratio. COPYRIGHT: (C)2004,JPO
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