The generation mechanism of the slag circle:
The temperature of the protective slag at the meniscus near the slag crystallizer is only 1200~1300°C, and so-called slag circles often appear during casting. The formation of the slag ring is caused by the adhesion of the sintered layer and the semi-molten layer of the mold slag in contact with the copper wall to produce a paste layer. With the vibration of the mold, the paste layer becomes thicker and thicker, forming a slag ring. When casting aluminum killed steel, the mold flux absorbs Al2O3, the viscosity increases, and the slag ring grows quickly. This point has been confirmed when casting high aluminum steel.
The hazards of excessively growing slag circles:
Slag ring, also called slag stick or slag rope. Generally, the mold slag layer on the molten steel surface of the mold contacts the mold wall, and adheres to the mold wall after solidification. A smooth “slag circle” is formed along the periphery of the crystallizer, commonly known as “slag strip” and “slag rope”. The slag ring is generally thin and brittle under normal conditions. It will not affect the smooth progress of pouring, and once the slag circle grows due to this special reason.
During the negative slippage of the mold vibration, the slag ring may block the passage between the liquid flowing into the slab shell and the mold, which reduces the lubrication and heat transfer effects of the protective slag film, and makes the casting slab prone to longitudinal cracks and even lead to breakout accidents.
The excessively thick slag ring formed on the mold slag and the mold wall not only brings trouble to the operation, but also often causes slag inclusion and slag embedding on the surface of the casting billet, which may cause steel leakage in severe cases. If the page fluctuates greatly, when the liquid level drops, a slag circle will appear near the wall of the meniscus, and the slag will generally fall toward the center of the crystallizer. If the operation is too late to remove it, the liquid level will rise again quickly. It is possible to involve the slag ring, causing uneven cooling of the surface, and the risk of steel leakage.
For a long time, the growth of mold protective slag is a common and more troublesome problem in continuous casting production. The phenomenon of slagging is frequent. Operators continue to pick up the slag, which increases the labor intensity of operators, and this behavior is serious. Affect the surface quality of the cast slab.
