The role of continuous casting slag protection
Release time:
2022-01-16
The mold flux is a crucial element in the initial stage of casting. The liquid mold flux layer not only protects the casting from air, but also ensures that the mold flux layer forms between the mold copper tube and the metal billet shell, significantly affecting heat transfer, the formation of vibration marks, and the surface quality of the casting. Vibration marks are an inevitable product of the mold's up and down vibrations. Understanding the causes of vibration marks and reducing their harm is a crucial aspect of controlling the surface quality of castings. Let's explore this further. Continuous casting mold flux and its functions.
There are many explanations for the causes of vibration marks, but they seem somewhat different from what is observed on-site. After years of observation and reflection, it is proposed that while the mold flux forms a protective layer by coating the copper tube wall with liquid mold flux, the vibration marks are formed by the mold flux layer produced during the up and down vibrations of the mold. This explains and analyzes the function of the slag, the formation of the outer slag protective layer of the billet, the mechanism of vibration mark generation, and its impact on the surface quality of the billet.
The role of continuous casting mold flux
The true meaning of casting is not merely the formation of a certain thickness of liquid mold flux layer on the top of the molten steel in the mold, isolating the atmosphere from the liquid metal. After completing this task, a certain thickness of protective slag layer is wrapped around the surface of the billet. On the slag interface in the mold, a non-metallic mold shell is first formed, and then the liquid metal adheres to the inner cavity of the mold shell to form a nascent metal mold shell, gradually developing and increasing its thickness, away from the mold copper tube, forming a mold shell with sufficient safety thickness, so that the internal molten steel, figuratively speaking, is wearing a tight-fitting garment on the outer wall of the mold shell. This molten mold shell acts as a separation between the high-temperature mold shell and the copper tube, playing the following roles.
Continuous casting mold flux can improve the frictional relationship: It changes the contact friction between the metal billet shell and the inner surface of the copper tube to the contact friction between the slag shell composed of non-metallic mold flux and the copper tube. This is a stable frictional contact relationship, greatly reducing the wear of the copper tube and significantly increasing the service life of the copper tube.
Continuous casting mold flux can reduce molten steel fluctuations: From the perspective of open casting, the molten steel pouring surface fluctuates greatly, but in protective casting, due to the certain thickness of the slag, its self-weight acts on the molten steel pouring surface, greatly reducing the fluctuation of the molten steel. Of course, due to the relatively large immersion depth of the submerged entry nozzle, a stable surface is sometimes formed. Therefore, the vibration marks formed on the protective slag are regular.
Continuous casting mold flux can change the heat transfer method and efficiency of the casting: The close combination of the slag shell formed by the slag and the surface of the metal shell creates conditions for the stable heat transfer of the entire shell, which is conducive to the uniform generation and development of the shell.
Continuous casting mold flux is beneficial for gap filling: The matrix shrinks during the transition from liquid to solid, causing local depressions in the matrix and forming gaps. The molten mold flux is pressed into the gaps by the mold pulling action, filling the gaps and maintaining the continuous and stable heat transfer of the mold flux layer.
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