Continuous casting is the final step in the rail’s transformation from liquid to solid. During this process, it’s crucial to ensure that the high-temperature molten steel doesn’t lose temperature rapidly and isn’t affected by air. Today, we’ll explore the fascinating transformations of mold powder on the surface of molten steel at 1500°C within the continuous casting mold.
01 State of the Continuous Casting Mold
The mold slag structure in the mold is generally divided into three layers: the original (solid) slag layer, the sintered layer, and the liquid slag layer. When added to the mold surface, the mold slag is a solid powder, covering the molten steel to form a loose original slag layer. Upon heating, the lower portion of the original slag layer softens and sinters to form the sintered layer. As the temperature rises, it melts to form the liquid slag layer. During the casting process, this multi-layered structure maintains a dynamic equilibrium as new mold slag is continuously added.
Schematic diagram of the state of protective slag in the copper mould tube
02 Influence of melting rate of continuous casting mold powder
The melting process of protective slag is complex and orderly, and its melting rate determines the extent to which it can play a role in the crystallizer.
(1) An appropriate melting rate can ensure that the surface of the molten steel in the crystallizer is continuously covered with a stable liquid slag layer, giving full play to its lubrication and heat transfer functions;
(2) If the melting is too fast, the liquid slag layer will be too thick and easy to roll up, affecting the quality of the ingot;
(3) If the melting is too slow, the liquid slag layer will be insufficient, making it difficult to meet the process requirements, and also damaging the quality of the ingot and operational stability.
03 The core role of continuous casting protective slag
The core role of continuous casting protective slag is mainly in the following aspects:
(1) Isolate the air and prevent the secondary oxidation of the molten steel;
(2) Absorb non-metallic inclusions in the molten steel;
(3) Lubricate the ingot and reduce friction resistance;
(4) Control the heat transfer of the crystallizer and adjust the cooling rate of the ingot;
(5) Stabilize the liquid level of the molten steel in the copper mould tube.
