Continuous casting (CC) is a method of producing an infinite solid strand from liquid steel by continuously solidifying it as it moves through a Continuous casting machine. It is a modern steel plant which links steel-making and hot rolling including horizontal continuous casting machine and vertical continuous casting machine.
Types of Continuous Casting machines
CCM has evolved from the strictly vertical type of machine to curved machines in order to limit the installation height while still using high casting speeds. In recent years, CCM of the more sophisticated mechanical design is being constructed. These machines apply several techniques for achieving higher casting speeds and higher outputs and are with progressive straightening or progressive bending over a liquid core. The main types of continuous casting machines which are in operation these days are given below.
- Simple vertical continuous casting machine with a straight mould and cutoff in the vertical position
- Vertical continuous casting machine with a straight mould along with single point bending and straightening
- Vertical CCM with a straight mould along with progressive bending and straightening
- Bow type machine with curved mould and straightening
- Bow type machine with curved mould and progressive straightening
One important characteristic in continuous casting is the removal of nonmetallic inclusions from the liquid steel. Owing to their lower density compared to the liquid steel, the inclusions are able to float up from the liquid. In the straight continuous casting machine, the inclusions can float up more easily to the meniscus (liquid surface near the mould wall) than in the bow type CCM machines. This is because in the bow type CCM machines some inclusions can attach to the inner arc of the strand shell when they are flowing up. This can be seen as a higher amount of inclusions but also as an uneven distribution of the inclusions in the cast strand. So, the vertical or vertical bending type continuous CCM has the advantage that inclusions can float up better to the meniscus than in bow type CCM.
Horizontal continuous casting machines have some advantages of low height and low construction costs over the conventional CCM machines. These kinds of CCM machines have been used for the continuous casting of many metals such as copper and copper alloys, but for steel, the technology is so complex that it is not widely used for the continuous casting of liquid steel.
The choice between the types of casting machines depends on a complex optimization of the specific facility requirements for the continuous casting machine’s productivity, product quality, machine complexity, and cost. With the introduction of the newer designs, there has been an increasing adoption of the bow type CCM machines with curved moulds for CCM of slabs and to a lesser extent for CCM of billets and blooms.
Continuous Casting Machine Composition
The main equipment of a continuous casting machine constitute
(i) ladle turret along with turret weighing system and ladle cover manipulator,
(ii) tundish and tundish car along with tundish weighing system, tundish preheater and dryer,
(iii) mould and mould oscillation along with mould level control and electromagnetic stirrer,
(iv) secondary cooling consisting of strand cooling, strand containment and guiding,
(v) withdrawal and straightener,
(vi) dummy bar, dummy bar parking and dummy bar disconnect roll unit,
(vii) pinch roll and torch cut off the unit,
(viii) Product identification system, and
(ix) Roller table and product discharge system.
