GB1258802A - - Google Patents

Abstract

1,258,802. Automatic temperature control systems. WESTINGHOUSE ELECTRIC CORP. Feb.3, 1969 [Feb. 14, 1968], No. 5644/69. Heading G3R. A control system for a multizone reheat furnace for metal slabs comprises a means for providing a signal representing the speed of slab movement and for controlling the speed, means for detecting the temperature and controlling the heat input in each zone, also a control means responsive to speed and temperature signals to effect a predetermined slab heat energy content by controlling both the speed of the furnace and the heat input. The arrangement is controlled by a computer 10 into which information is fed regarding slab thickness etc. and time required, which time is dependent on the anticipated period for rolling mills following the furnace to clear previously heated slabs. This time may be adjusted manually during passage of any slab to allow for predicted and unpredicted delays. Speed and temperature set points are then set by the computer which set points are then updated periodically so that the slab emerges at the predicted time and temperature. The characteristics of a slab are determined from curves derived empirically and experimentally and which are stored in the computer. The furnace has three zones, pre-heat, heat and soak, heat to each slab being added incrementally so that the final temperature is not reached until the slab reaches the exit of the heat zone. The soak zone is provided merely to redistribute the heat evenly throughout the slab. Signals may be of analogue form converted in digital converters for use in the computer, and digital output signals from the computer may be reconverted. At each slab discharge, computer 10 adjusts the speed and temperature set points for the slab following. During passage of any slab the computer may adjust the speed and/or heat input to ensure attainment of a desired temperature at the furnace exit point, and further movement may be prevented until the desired heat content has been absorbed. In such conditions a suitable warning is given. A similar condition would also apply if a slab had not remained in the soak zone for a sufficient time. In the Specification it is envisaged that approximately 80% of the heat will be added in the heat zone. A logical flow diagram for the computer is given in Fig. 3 (not shown) included in this circuit is an arrangement 190 to determine whether the mill following the furnace is operating at full capacity.