Constant temperature closed cooling system for Casting mill machine
In aluminum strip continuous casting and rolling process, casting machine always runs through casting crystallization and pressure process. During aluminum crystallization, there is carrying out strong hot exchange between aluminum liquid and casting roll. Thus,in order to achieve aluminum strip continuous stable rolling, there must be enough circulating cooling water to cool roll sleeve.
The former circulating cooling water systems used in casting machine are all open system. It means water directly contact air to exchange heat, which will bring dust into circulating water in large quantities, gradually it will increase the hardness and turbidity of circulating water, the scaling speed of roller core and easily block the filler of cooling tower. And each time when it stops to maintenance the pump and pipe, the pipe inner surface would be oxidized by as the pipe network is empty, thus leading to fast corrosion and the short lifespan of the pipe system. Moreover, the replaced roller can not be drained completely that will certainly cause the roller core channel blockage due to precipitation. When reinstalled in the casting mill, the roller cant get cooled due to the blockage, causing the roller longitudinal thermal crown and thus causing equidistant horizontal groove defects on the casting strips. Its necessary to take off shell to clean the roller, this can not only increase maintenance costs, but also decrease the production efficiency.
Now, most new casting machines adopt closed circulating cooling system, and there are many manufacturers reform their old opensystem into closed system and gain good results. There are three characteristics of this system as follows:
1.Closed circulating cooling system means the cooling water is in closed circulating, the water is not direct contacted with the air . So itwill not be polluted and the soft water is stable, this will eliminate the possibility of roller core scaling formation and ensure the rollersdesigned service life. Moreover, when there is need stop the pump to maintenance , the pipe is full of water and there will be impossible for the pipe inner surface to be oxidized by air, thus it could prolong the service life of pipe network.
2.Closed circulating cooling system can achieve constant temperature control of the water, that is to ensure the temperature difference of the water that enter the casting roller within 0.5℃ of the set temperature, this will be benefit to remain the up and down casting roller thermal crown. The set temperature can be adjusted in a certain range according to different alloy compositions, the range is from 5℃ to 60℃. Constant temperature is achieved by the water linear distribution characteristic of pneumatic or electric three way control valve, thus making the roller temperature is in a predetermined temperature range. Its advantage is that the supping water temperature will not vary according to climates thus ensuring the casting plate qualit . And it can also adjust temperature so as to adapt to different .temperature requirements for rolling different alloys
3.Closed cooling system is fully closed cycle, the pressure loss is small.It can increase 30% circulating water compared with the open circulating system under the same power. It also reduce the circulating water temperature difference between entrance and exit, this can significantly reduce the thermal crown change of up and down roller and reduce the difference of same casting strip
.There is great significance for ensuring strip shape and improving strip quality
1、0.4 -0.6MPa； Working pressure: 0.4-0.6MPa
2、200m3/h；Circulation water: 200m3/h
3、Temperature range:32℃-60℃ in summer, it can be decreased in other seasons
4、Temp Accuracy: basic set offset is ±0.5℃
The cooling system components : take a set of cooling system for 1003*1850 casting machine used under the environmentof wet bulb temperature 27℃ as an example.
It should pay special attention to air circulation during the installation of cooling tower. The best site of installation is rooftop or ground surface with good air circulation far away from wall and barrier. If the cooling tower is put inside well type partition, closed or near the high wall , the cooling tower layout should be properly considered in order to avoid hot airre floback w phenomenon. If the hot humid air discharged by the cooling tower flow into the fresh air inlet, it would cause hot air re flow phenomenon. It would increase the inlet air temperature thus causing the outlet water temperature can not reach the set temperature and influence the heat exchange efficiency . In order to reduce the hot air re flow possibility , it isadvisable to use ventilator heighten the air outlet top to the same level of the wall top It should be avoided that the setting the cooling tower air outlet is at or near the inlet of the architecture during equipment installation.