The influence of the melting point of continuous casting slag protection
Release time:
2023-01-16
The thickness of the slag layer is related to the consumption of continuous casting slag. Continuous casting slag The lower the viscosity, the higher the flow rate, the better the lubrication effect on the slab, and the higher the melting speed required. Even in the same mold, the thickness of the slag layer varies at different locations. Usually located deep at the outlet, wider and thinner surfaces and thinner and narrower surfaces. Currently, there is little research on interfacial tension, but it is one of the factors that must be considered in the development of slag protection. Increasing viscosity is also beneficial for increasing surface tension, but it is not conducive to heat conduction, which can be solved by lowering the melting point of the continuous casting slag. The following introduces the influence of the melting point of continuous casting slag:
1. Melting temperature
The melting temperature of the flux has a great influence on the slag film thickness and mold heat flow. The slag film at the bottom of the crystallizer is thicker than that at the top, but the thickness increases with the increase of the melting point. The melting temperature of the continuous casting slag directly affects the thermal resistance of the slab and the slag film. The higher the melting point, the better the heat resistance of the slag film. In addition, as the temperature of the protective slag increases, the thickness of the protective slag film decreases, and the melting temperature of the crystallizer is extremely high, which is related to the critical thickness and drawing speed of the billet. For a given critical billet thickness, the faster the drawing speed, the lower the melting temperature.
2. Melting rate
Continuous casting slag not only controls the thickness of the slag layer, but also determines the depth of the slag layer, and determines the speed at which the continuous casting slag flows into the gap between the slab and the mold. High melting speed and unstable slag layer thickness will cause the steel surface to be exposed to intermittent air, which will not only increase heat loss and lead to the formation of "floaters", but also promote the thickening of the slag film and the solidification of the molten steel on the meniscus. If the melting speed is too low, there is insufficient liquid slag, and it may not even be able to enter the gap evenly, resulting in defects such as cracks on the surface of the steel billet, or even leakage. To ensure sufficient lubrication, the thickness of the liquid slag layer is generally 6～12mm, and the thickness of the high-speed slag layer should be maintained above 20mm, and an appropriate melting point is required. As the traction force increases, the heat flow and melting rate increase. Although the slag layer thickness decreases at the beginning with the increase of the drawing speed, the subsequent stable thickness is still greater than the initial value.
3. Viscosity
Viscosity has a great influence on the performance and quality of the inventory. Low viscosity will also cause the molten steel in the molten steel to flow at the molten steel interface, and the steel slag in the molten steel will disperse and produce inclusions. Therefore, it is very important to choose the appropriate viscosity. In the continuous casting process, the frictional resistance of the continuous casting slag to the outer shell of the steel billet not only affects the frictional resistance of the steel billet, but also affects the deformation and drawing resistance of the steel billet, that is, the total resistance of the steel billet. Starting from the minimum value of the total mold resistance, the basic relationship between the slurry viscosity, vibration parameters, and speed is obtained. The choice of viscosity also changes with the matching of vibration parameters and drawing speed.
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