Straitening of Continuous Casting Billet
Straightening is the process of making flat rolling stock—in particular, structural shapes such as angles, channels, beams, squares, tubes, and other miscellaneous sections—true and straight in all directions. In the case of continuous cast billets, the heat of the casting process is transferred to the exterior surface of the billet. As this heat passes through the steel from the outside to the center of the billet, thermal stresses are created in the billet, causing it to twist and bow. The straitening process is designed to counteract these thermal stresses and return the billet to a straight and true condition before it goes on to its end use.
Straightening of a continuous cast billet begins with heating the billet to a preheat temperature, which is the temperature at which meaningful straightening can begin. This temperature is typically about 600 - 650°F for steel. Once the billet is up to preheat temperature, it is ready to enter the straightener. A straightener is a machine built with rolls that the billet is fed through while being rotated or twisted. As the billet is passed through the rolls, each roll applies a small amount of pressure to the billet, gradually straightening it. It is important to note that the billet is not subject to high pressure in the straightener, as this could cause it to develop internal stresses or even break. It is also important to avoid over straightening the billet, as this can also cause internal stresses and can alter the metallurgical properties of the steel.
Once the billet has been straightened, it is then ready to move on to its end use. This will typically involve some type of secondary operation, such as rolling or extruding, to give it a finished shape. In some cases, the billet may be ready for a finished part without an additional operation, but in most cases some type of secondary operation will be required.
The straitening process for continuous cast billets is an important part of the process that must not be overlooked. Without this process, there would be significant defects in a finished product that would cause it to be unusable. Straightening should be done carefully and thoughtfully in order to get the best possible results, and to ensure that the finished product has the desired properties and performance.
