Continuous casting, also known as strand casting, is the process where a metal is heated until it liquefies. The molten metal is then allowed to solidify until it becomes a semi-finished slab that is later rolled in the finishing mill. It is used to cast metals of uninterrupted lengths. In this process, the molten metal is continuously supplied to the mold. The mold has an indeterminate length. When the molten metal is cast through a mold, it keeps travelling downward increasing in its length as the time passes by. The molten metal is continuously passed through the mold, at the same rate to match the solidifying casting. This results in casting of long strands of metal. The whole process of continuous casting is a precisely deliberated process that can produce astounding results.
Unlike other processes of casting, the time line of steps in continuous casting is entirely different. While in other casting processes, each step of casting heating of the metal, poring of the molten liquid into casts, solidification and cast removal are a sequential process, in continuous casting all steps occur congruently and hence it saves a lot of processing time.
Continuous casting is a method that was invented to enhance the production of metals. The continuity of the casting helps to lower the cost of the casted steel. Further, it helps in the standardized production of steel cast. Further, the carefully controlled process also reduces errors leading to better quality steel casts. They increase the productivity and produce better yields.
Continuous casting eliminates some of the problems of traditional casting methods. For example, they eliminate piping, structural and chemical variations that are common problems of ingot casting method. All the casting products manufactured by continuous casting possess uniform properties. The solidification rate of the molten metal is also ten times faster than the solidification of the metal in ingot casting method.
Continuous casting has several advantages but it is also a process that needs distinct resources. This is the reason why this process is employed only in industries that require high yield of steel cast. The metal is first liquefied and poured into a tundish, which is a container that leads to the mold that will cast the steel. The tundish is placed about 80-90 feet above the ground level and the whole process of casting sues gravity to operate. The tundish is constantly supplied with molten steel to keep the process going. The whole process is controlled to ensure there is smooth flow of molten steel through tundish. Further, the impurities and slag are filtered in tundish before they move into the mold. The entrance of the mold is filled with inert gases to prevent reaction of molten steel with the gases in the environment like oxygen. The molten metal moves swiftly through the mold and it does not completely solidify in it.The entire mold is cooled with water that flows along the outer surface. Typically, steel casting solidifies along the walls of the casting and then gradually moves to the interior of the steel casting. The metal casting moves outside the mold with the help of different sets of rollers. While one set of rollers bend the metal cast, another set will straighten it. This helps to change the direction of flow of the steel slab from vertical to horizontal.