This article describes several structural forms and properties of continuous casting crystallizers.
Key words: continuous casting; mold; structure; performance
What are the types of continuous casting crystallizer structure
According to the different types of continuous casting machine, the crystallizer can be divided into two categories: straight and arc. Divided according to the specifications and shapes of billets, there are billets, blooms, slabs and special-shaped billet crystallizers. According to the structure of the crystallizer itself, it can be divided into 3 types:
Tubular crystallizer: It is made of a copper tube with a wall thickness of 6-12mm to make the required section. Outside the copper tube, a sleeve is placed to form a cooling water passage of 5-7mm to ensure that the cooling water flow rate is per minute 6 ~ 10m. The crystallizer has a simple structure and is easy to manufacture, and is widely used in billet continuous casting machines.
Integral crystallizer: It is made by planing a whole piece of copper ingot, and there are many small holes drilled around its inner cavity for cooling water. This kind of crystallizer has good rigidity, easy maintenance, and long service life, but it has high manufacturing cost and consumes a lot of copper, so it has not been used in recent years.
Combined crystallizer: It is composed of 4 copper plates to form the required inner cavity. Plan a groove on a 20-50mm steel plate and connect it with a steel plate, and the cooling water passes through the groove. Both bloom and slab casters use this form of mold.
What properties should the continuous casting crystallizer have
Mold is an important part of continuous casting machine. The molten steel is solidified and shaped in the crystallizer, forming a shell with a certain thickness and being pulled out continuously into the secondary cooling zone.
A good crystallizer should have the following properties:
(1) Good thermal conductivity can make molten steel solidify quickly. Every 1kg of molten steel is poured into a slab and cooled to room temperature, the heat released is about 1340kJ/kg, and the crystallizer takes away about 5-10%, that is, 67-134kJ/kg. If the slab size is 250×1700mm, the casting speed is At lm/min, the crystallizer can take away as much as 200,000 kJ of heat per minute. And the crystallizer length is relatively short, generally no more than 1m, in such a short distance to be able to take away a lot of heat, it must have good thermal conductivity. If the thermal conductivity is poor, the slab shell coming out of the mold will become thinner. In order to prevent leakage, the casting speed has to be reduced. Therefore, good thermal conductivity of the mold is an important prerequisite for achieving high casting speed.
(2) The structural rigidity is better. The inner wall of the crystallizer is in contact with high-temperature metal, and the outer wall passes through cooling water, and its wall thickness is very thin (only 10-20mm), so the temperature gradient in its thickness direction is extremely large, and the thermal stress is considerable. Its structure must have a relatively Large rigidity to accommodate large thermal stress.
(3) Easy assembly, disassembly and adjustment. In order to quickly change the size of the billet or quickly repair the mold to increase the production capacity of the continuous casting machine, modern molds have adopted integral hoisting or online width adjustment technology.