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...

Understanding the Process of Continuous Casting of Steel Jun07

Understanding the Process of Continuous Casting of Steel...

Understanding the Process of Continuous Casting of Steel Continuous casting (CC) of steel is a process whereby liquid steel is solidified into a semi-finished steel product (billet, bloom, beam- blank, round or slab) for subsequent rolling in the rolling mills. The basic operation of a CC machine is to convert liquid steel of a given composition into a strand of desired shape and size through a group of operations like mould operation, spray cooling zone, straightener operation, etc. For successful continuous casting, it is necessary to understand the process behaviour under different conditions for these operations. The process of continuous casting basically comprised of the following sections. A tundish, located above the mould, to receive the liquid steel from steel teeming ladle and to feed it to the mould at a regulated rate. A primary cooling zone consisting of water cooled copper mould through which the liquid steel is fed from the tundish for generating a solidified outer steel shell sufficiently strong enough to maintain the strand shape as it passes into the secondary cooling zone. A secondary cooling zone in association with a containment section positioned below the mould, through which the steel strand (still mostly liquid) passes and is sprayed with water or a mix of water and air (air mist) for further solidifying of the steel strand. A section for the unbending and straightening of steel strand. This section is not there in the straight vertical casting machines. A cutting section consisting of cutting torches or mechanical shears for the cutting of the solidified steel strands into desired lengths for removal. A run out table to cooling beds or directly to a product transfer area. In the CC process, liquid steel flows from the steel teeming ladle, through a tundish into...