Numerical Simulation Of Ingot And Concast Steel Reheating In Batch And Continuous Type Furnace To Optimize Energy Efficiency, Quality And Productivity

Abstract

Reheating of steel ingots in batch furnace like soaking pit and box furnace, and concast steel in continuous furnace like in walking beam, and pusher type furnace is an important step for further thermo-mechanical processing like forging and rolling operations. The slabs are heated up to 1100 – 1250 oC, and since this is a high temperature and energy intensive process, prolonged or excess heating time will cause productivity and energy loss, as well as oxidation and scale loss. On the other hand if it is heated very fast causing significant temperature difference between the surface and core temperatures, will lead to thermal stress generation, distortion and cracking. Furthermore, rapid heating of the surface to attain the specified temperature, without thermal homogenization of the slab can causes problems during hot rolling or forging operations, which may lead to cracking, roll stuck and forging problems. Therefore the aim of the heating process is to avoid any excessive thermal stress, particularly in the vulnerable ferrite to austenite phase transformation range, and also to minimize the time for thermal homogenization. To numerically simulate the process, a detailed two dimensional finite difference model is developed by using generalized Cartesian and cylindrical axi-symetric equation, and Crank-Nicholson technique. To accurately simulate the process we also have to consider all the complexities of the process like anomalous behaviour of thermal conductivity, change in density and specific heat due to phase transformation.