A MOBILE CONTACTLESS TEMPERATURE-MEASURING DEVICE FOR LAMINAR COOLING PROCESS OF HOT STRIPS

摘要

Laminar cooling is also called runout table cooling. As one of the most important stages of the entire hot rolling process, it plays a key role in the grain structure and mechanical properties of the final product. The aim of laminar cooling is to control cooling water sprays to achieve uniform temperature throughout the hot strip and attain a specified target coiling temperature, within a tolerance as strict as possible.1 In order to accurately predict the temperature of hot strips during the laminar cooling process, the thermal models used in the laminar cooling temperature setting control, which can describe the heat transfer and metallurgical behaviors of hot strips, need the temperature measurement data in the laminar cooling section as the initial boundary conditions. Moreover, the coiling temperature control (CTC), which is actually implemented in the laminar cooling section to attain a specified target coiling temperature, also requires the precise temperature of the strip surface as the feedforward and feedback signals.2 To some extent, the temperature-measuring precision has direct influence on setting and control accuracy of laminar cooling. At present, the temperature measurement of hot strips in the laminar cooling section is carried out by the infrared pyrometers installed in the zones without cooling water, after the finishing mill or before the down coiler. Nevertheless, new steel products, such as dual-phase steel, transformationinduced plasticity steel, and ferrite–bainite steel, are developed and applied as advanced materials in the automobile industry; all of them feature two-stage cooling techniques in the laminar cooling section.3,4 To meet the requirements of cooling control for the new steel products, additional infrared pyrometers are fixed at some intermediate positions between the main cooling region and the finish cooling region. But the temperature measurement at these points is imprecise because of the radiation effect of steam and cooling water over the strip.