Heat Transfer during Continuous Casting of Steel Jun19

Heat Transfer during Continuous Casting of Steel...

Heat Transfer during Continuous Casting of Steel During continuous casting (CC) of steel, careful control of the strand cooling and growth of the shell along the CC machine is of great importance. These factors play an important role on the formation of cracks and other defects which can be formed in the cast steel product. To ensure defect free cast steel products, the strand is to be cooled down according to a pattern which depends on steel grade, steel product dimensions, casting speed, and CC machine design. On the other hand, the control of the liquid pool length is a key element in optimizing the casting speed with respect to good productivity. So, the heat transfer plays a very important role in the operation of the CC machines, especially when casting crack sensitive steel grades. In fact, many diverse phenomena simultaneously control the complex sequence of events which govern heat transfer in the CC process. The temperature of liquid steel in the tundish is typically 30 deg C to 50 deg C higher than the liquidus temperature. At the beginning of the continuous casting process, the liquid steel is cooled in a water cooled mould to form a solidified shell which can support the liquid pool at the mould exit. Typical temperature at the end of the mould is1100 deg C and that in the center of the strand is 1550 deg C. Since steel does not solidify at a fixed temperature, but over a range of temperature, there is a mushy region where the steel is neither completely solid nor completely liquid. Steel grades used in continuous casting are completely solid below a temperature ranging from 1350 deg C to 1500 deg C, and the solidification starts at a temperature ranging from 1450...