The cooling systems for continuous casting copper mould tube are mainly of the following types:
Classification by cooling medium
Water cooling system: This is the most commonly used cooling method. Using water as a cooling medium has the advantages of large specific heat capacity, high heat transfer efficiency, and low cost. Water circulates in the cooling channel of the crystallizer, absorbs the heat released when the molten steel solidifies, and then takes the heat away. According to the specific structure and water flow mode, it can be subdivided into many forms, such as the common water gap cooling structure, in which the cooling water flows from bottom to top at a high speed in the narrow water gap between the copper tube and the water jacket of the crystallizer to achieve efficient cooling; there is also a cooling structure in which a guide channel or a longitudinal water trough is set on the wall of the copper tube of the crystallizer, and the cooling water flows in the guide channel or the water trough for heat exchange.
Air cooling system: Use gas as a cooling medium, such as air, nitrogen, etc. Compared with the water cooling system, the air cooling system has a lower cooling intensity, but in some special cases, such as high requirements for the surface quality of the ingot and no residual cooling water, the air cooling system has certain advantages. The air cooling system usually sets gas channels or nozzles around the crystallizer so that the gas blows evenly on the surface of the crystallizer or the ingot to take away the heat.
Oil cooling system: Oil is used as the cooling medium. The cooling effect of oil is between that of water and air, and it has good lubricity and rust resistance. In some occasions where the cooling speed is not required but good lubrication and protection are required, the oil cooling system may be used. However, the cost of the oil cooling system is relatively high, and there are safety hazards such as oil leakage, so it is relatively less used.
Classification by cooling position and stage
Primary cooling system: mainly refers to the cooling inside the crystallizer, which is the first cooling of molten steel during the continuous casting process. Its function is to make the molten steel injected into the crystallizer solidify rapidly to form a billet shell of a certain thickness. The cooling effect of the primary cooling system directly affects the surface quality and initial solidification structure of the billet. For example, the primary cooling of the efficient continuous casting crystallizer generally adopts a water seam tube structure. Through the high-precision narrow water seam design and the appropriate copper tube inner cavity shape, the flow rate and uniformity of the cooling water are improved, and the heat transfer efficiency is increased.
Secondary cooling system: It is the further cooling of the billet in the secondary cooling zone after the billet leaves the crystallizer. The secondary cooling system usually uses water spraying or misting to spray cooling water on the surface of the billet so that the billet continues to solidify during the movement. The intensity and uniformity of secondary cooling have an important influence on the internal quality and overall solidification effect of the billet. Common ones include water spray cooling in the foot roll area and spray cooling of the corners of the billet in the multi-stage crystallizer.
Classification by cooling water flow
Straight-through cooling system: cooling water enters from one end of the crystallizer and flows directly out from the other end, and the water flows in a straight line in the cooling channel. This cooling system has a simple structure, but the cooling uniformity may be relatively poor, and it is easy to have insufficient or overcooling in some areas.
Circulating cooling system: cooling water circulates in the crystallizer, and the cooled water is re-delivered to the crystallizer inlet through water pumps and other equipment to achieve the reuse of cooling water. The circulating cooling system can better control the temperature and flow of cooling water, improve the cooling effect and uniformity, and is also conducive to saving water resources.
