Microcomputer-Based Controls for Continuous Casting

The continuous casting of steel eliminates many processing steps, thus allowing savings in time, energy, and processing costs. In this process a moving strand of steel is partially solidified in a water-cooled mold and subsequently cooled to complete solidification by intensive-cooling water sprays. Control of the cooling sprays is complex, requiring distributed control techniques, which are not readily implemented by analog means. Therefore, digital computer control systems have been developed for this purpose. In the past these systems have used a minicomputer in a supervisory control mode to provide optimum water-flow setpoints to conventional proportional plus integral analog controllers. This approach has given satisfactory results, but initial hardware and software costs have been high, and maintenance requirements, particularly in the computer/controller interface hardware, have been excessive. US Steel is currently testing a microcomputer-based control system which has the potential for resolving these problems. This system provides all the control features normally used as well as direct digital control (ddc) of cooling water flows, thus eliminating the need for analog controllers. Experience to date indicates that this new approach will provide increased reliability along with a significant reduction in equipment and maintenance costs.