Undoubtedly, the continuous casting machine has gained a lot of popularity lately because it guarantees high precision as well as superior finish qualities. Plus, it ensures smooth operations, trouble free maintenance including optimum performance. Better yet, it offers high energy and time savings. The machine provides fully automated cooling control which is very essential in solidifying the molten metal into semi-finished slab or bloom or billet that can further be processed at the finishing mills.
Even though a billet continuous casting machine offers improved control practices as well as techniques, there are a number of factors that may affect its productivity. However, these factors have greatly been dealt with by developing new equipment designs including operating concepts. They include:
- Electromagnetic stirring – it is suitable for increasing the speed of casting. This in turn increases productivity.
- Downward insertion or top fed dummy bar – it helps in reducing preparation time.
- Sequence casting – this also helps in reducing the preparation time.
- Split or divided moulds – they help in reducing mould inventory as well as mould changing time. Also, it increases the casting rate.
- Use of modern moulds – there are moulds having variable width adjustment lately. This helps in reducing mould changing time.
- Slitting cast product – this helps in reducing mould’s frequency from changing. It also reduces mould’s inventory.
The amount of heat injected to the machine without interfering with the dummy bar’s insertions differ greatly. This may be attributed by size of production, state of entry nozzles, and presence of nozzle clogging including other troubles or damages in teeming systems. The entire preparation work or process involves mould sealing, dummy bar insertion, changing tundish and extraction of the finished piece. It is imperative to extract the finished piece with caution to prevent bleeding or prevent molten slag exiting the upper end. This is done by shortening the preparation time. Usually, downward-inserting type (an example of dummy bar insertion) is chosen since it makes it easy to insert dummy bar and at the same time extracting the finished piece. That cannot happen if upward-insertion type is chosen and also the preparing time will be longer.
It is true that the billet continuous casting machine offers unbeaten product quality but that will entirely depend of the casting practices employed. Now, it is essential to watch closely the chemical as well as physical factors that may affect the overall quality. For example, there are different defects that may affect the productivity of the casting machine. They include:
- Internal defects – They include porosity, segregation, cracks, inclusions and many more.
- Subsurface defects – They include blowholes, cracks, inclusions, pinholes and many more.
- Surface defects – They include laps, slag, entrapped inclusions, oscillation marks, cracks, deformed cross sections and many more.
These cracks may be reduced by:
- Mould coatings
- Mould lubrication
- Mould wear control
- Casting speed and machine alignment
- Secondary and mould cooling
- Electromagnetic stirring
- Compression casting
- Multipoint straightening
- Inline reductions
When the right continuous casting machine is used and other factors closely monitored, then miners can be rest assured of improved productivity.