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Continuous Casting

Introduction: Continuous casting is the process whereby molten metals solidifies into continuous forms of strips and billets that can be further worked upon in the finishing mills. These "semi finished" billet, bloom, or slab are casted by using open ended mold and water spray technique. The continuous casting process was developed only in 1950, before that steel was poured into a stationary mold to form 'ingots'.

Sir Henry Bessemer, the inventor of Bessemer converter got the patent for casting the metal between two contra rotating roller. This casting process helps in eliminating many steps in the casting process like ingot teeming, stripping, primary rolling, etc. To now this method is used to casting steel strips.

Continuous Casting Process: A seemingly simple process, the continuous casting is a technically sophisticated process that could be developed properly only 50 years age, while the casting industry has a history of more than 5000 years old. In continuous casting, molten metal is poured into an open-ended mold that can be made of graphite or copper. Graphite molds are widely used both in vertical and horizontal continuous casting. Most molds are made from isostatically pressed graphite. However, extruded graphite molds can also be used for vertical casting of large ingots.

The metal is first melted in a furnace and poured into a ladle. From the ladle the hot metal is transferred into the tundish. The hot metal is poured into the continuous casting machine from the tundish. The mold is water cooled. When the hot metal is poured into the furnace, the metal near the walls cool first forming a skin like thin strip. While the meal to the inside is still molten.

The thin shell like solidified metal withdraws from the mold and pass through a straightening roller. In the chamber the strand is water sprayed which prevents porosity. The thin strip, now called a strand, rolls on a rotating roller. After solidification, predetermined lengths of strands are cut into pieces using mechanical shears or travelling oxyacetylene torches. The cast size are are called strips, billets, slabs etc.

Continuous casting can be better controlled by making the process automated. The two common types of continuous casting are horizontal and vertical continuous casting. Long shapes of simple cross section like round, square and hexagonal rods can be done in a short, bottomless, water cooled metal mold.

Application of Continuous Casting: A great tonnage of continuous casting is done using cast steel. Other metals that are continuous casting are copper, aluminum, grey cast irons, white cast irons, aluminum bronzes, oxygen-free copper, etc. Metals are cast as ingot for rolling, extrusion, or forging, and long shapes of simple cross section are cast as round, square, hexagonal rods, etc.

Advantages of Continuous Casting:
  • Cost effective, time saving, casting process
  • A highly productive process that can be fully automated
  • High quality castings can be done.