Gauge Variations Of Strips Causedby ROUingLarger Slabs

Abstract

Slabs tend to become larger and larger for improving the rolling capacity and the yield. In paralled therewith, the gauge and quality of the strip coil are susceptible to variations and would give rise to discussions on the equipment.
Gauge variations alone are discussed here. There are many factors which cause gauge variations. When larger slabs are rolled, however, it is the variation of deformation resistance due to a temperature difference that mainly causes gauge variations.
As the thickness of a bar leaving the rougher is 3/4-1 nch, the larger slab becomes the longer bar on the delay table. The temperature difference between the top and the tail of the bar is larger and causes the gauge variations owing to the mill spring. These gauge variations are due to a difference of rolling speed between the rougher and the finisher.
If the roughers are composed of two stands and the rolling speed of the last roughers is controlled in proportion to the finisher, the temperature difference is reduced without spoiling the roping capacity.
Skid marks too tend to become larger. In order to reduce the skid marks, it is effective both for design and opperation of a furnace to make the heat-liberating distribution as higher as possible on the charging side of the slab-reheating furnace.