熱間タンデム粗圧延機における張力測定法と張力制御の効果

抄録

In hot rolling such as that in a hot strip mill, a section mill or a bar mill, the tandem rolling, in which a slab is rolled at the same time by more than two stands, is put into operation mainly for the improvement of productivity, quality and yield. For the purpose of the improvement of the gauge accuracy of the strip width, the inter-stand tension should be controlled at zero or near zero value because the strip elasticity band is narrow. This slight tension control is called the “Tension Free Control”. The main technical problem of such control is to detect the inter-stand tension without touching the strip. The tension measurement method shown in this paper is a method which, uses the motor torque and the rolling force of each stand. The inter-stand tension is calculated from the difference of the G/P ratios of two neighbering stands, where G/P ratio is the ratio of the motor torque to the rolling force of the stand.
By this method, the inter-stand tension is detected with an accuracy of 1t/°C in case the strip temperature varies. The measuring error is one half that of the convenuional methods which estimates the tension from the motor torque and the rolling force of a stand. Consequently, when controlling the inter-stand tension with this method, the controlled error was less than 5t. Experimenting with a strip mill in operation, the effect of the tension on the gauge of a strip was shown to be 0.05mm/t of the thickness, and 0.5mm/t of the width. Therefore, it became clear that tension free control is an effective gauge control.