The main equipment of billet continuous casting machine is usually the whole equipment from receiving the ladle to cutting the billet into fixed length and collecting it on the cooling bed. It includes ladle carrying equipment, tundish and tundish carrying equipment, mould and mould vibration device, secondary cooling device, withdrawal straightening machine, billet cutting device, billet conveying roller, cooling bed, billet collecting device, dummy rod and dummy rod storage equipment, etc. The main equipment involved in billet forming is described in detail below.
Mould and mould vibration device
The mould is a key component in the continuous casting system. The molten steel is rapidly cooled in the mould to form a primary billet shell with a certain thickness and the same shape as the inner cavity of the mould. Since the inner wall of the mould is in direct contact with the surface of the billet, the structural characteristics, cooling performance, and inner wall quality of the mould will directly affect the quality of the billet, and will also affect the service life of the mould itself. Therefore, the performance of the mould is subject to the following requirements:
- The material in contact with the molten steel must have good thermal conductivity and can quickly transfer heat to the cooling water outside to form a raw billet shell with sufficient thickness;
- The mould should have good structural rigidity and is not easy to deform when subjected to the impact of high-temperature molten steel;
- It should have good mechanical manufacturing processability and be easy to process, install and adjust. The selected material should have good wear resistance to achieve a longer service life;
- Reduce the weight as much as possible to reduce the load and impact force caused by the inertia of the mould vibration device.
According to the above requirements, most of the moulds used in small square billet continuous casting machines are tubular moulds. The mould of the large square billet continuous casting machine can be a copper tube type or an assembled type.
Common vibration modes of the mould vibration device include synchronous vibration, negative sliding vibration, and sinusoidal vibration. Its structure includes two basic parts: the part that realizes the mould motion trajectory (straight line or arc) and the part that realizes the mould vibration.
Secondary cooling device
Generally, the forming cooling of the billet by the mould is called primary cooling, and the cooling that continues to solidify after the billet leaves the mould is generally called secondary cooling. The equipment or device set for secondary cooling is generally called secondary cooling device. The secondary cooling device of the continuous casting machine has two basic functions:
- Forced cooling of the billet. According to the cooling requirements of different steel grades and different sections, the water volume of the nozzle is controlled to adjust the appropriate cooling intensity so that the billet is gradually and completely solidified;
- Support and guide the billet (including the dummy rod) so that the billet (or the dummy rod) can move according to the set trajectory (withdrawing or sending the dummy rod).
Withdrawal straightening machine
The functions and requirements of the withdrawal straightening machine can be summarized as follows.
- During the casting process, it can overcome the resistance of the mould and the secondary cooling device, and smoothly pull out and straighten the billet;
- It can adjust the pulling speed to adapt to different process requirements, such as changing the steel center and section. The billet drawing system that uses the adjustment of the pulling speed to automatically control the page of the mould should be able to achieve closed-loop control;
- It can achieve straightening of the fully solidified or liquid-phase billet, and ensure that the quality of the billet is not affected during the straightening process.
- Under the condition of meeting the process requirements, the structure should be simple and easy to install and adjust.
Dummy rod and dummy rod storage device
The function of the dummy rod is to block the lower opening of the mould before pouring, and solidify the molten steel at the head of the dummy rod, pull out the billet through the pulling roller, pass through the secondary cooling device, and after passing through the billet straightening machine, the dummy rod head is disconnected. Entering the normal billet withdrawing state, the dummy rod enters the storage device for the next casting.
