The cause of the caster tip explosion
In continuous casting and rolling production, the vertical plate is the key to the production of high-quality aluminum slabs, and the quality of the vertical plates directly affects the internal organization and surface quality of the aluminum slabs. In the vertical plate process, often after the vertical plate runs slag or out of the plate for a period of time, the casting nozzle position explodes, and the uncoagulated aluminum liquid splashes, resulting in damage to the lip of the casting plate, slag, oxide film upturned, inner cavity blockage, aluminum molten splash to the mouth roller gap, so that the casting and rolling process stops, increasing production costs.
In response to the problem of nozzle explosion, our company has successively taken measures such as punching holes in the surface of the nozzle plate, far infrared baking of the casting nozzle board, annealing furnace high-temperature baking of the casting nozzle board for a long time, etc., and achieved certain results, but every year to the rainy season, the phenomenon of casting nozzle(also called caster tips) explosion still occurs frequently.
1. The cause of the caster tip explosion
Caster tips explosion refers to the phenomenon that the gas in the casting area or nozzle escapes from the aluminum liquid instantaneously during the process of casting and rolling the vertical plate. There are two main forms of nozzle explosion, one is to explode in the direction of the roller gap, and the other is to explode in the gap between the nozzle rollers.
The casting nozzle explosion in the direction of the roller seam mainly occurs at the moment of release of the vertical plate, the high-temperature aluminum liquid flows out of the feed tube and comes into contact with the casting nozzle plate with high water content, and the wet roller surface, the moisture vapor instantly vaporizes, the volume expands thousands of times to form a water vapor mass, and the weak point of the aluminum liquid front near the inner cavity of the casting mouth or the mouth of the casting lip is instantly escaped, resulting in an explosion.
The small bubbles in the aluminum molten aluminum are continuously gathered in the casting area and the position of the lip, forming a large bubble with a certain pressure, and there are two ways for the large bubbles to escape, the first is that the large bubbles break through the aluminum between the gap between the mouth rollers, and the tension of the oxide film escapes from the gap between the mouth rollers, causing an explosion, and the second is that the internal pressure of the large bubbles is greater than the adhesion force of the nozzle plate, so that the nozzle plate is damaged and escapes, causing an explosion.
From the above cause analysis, it can be seen that the explosion of the casting nozzle is mainly caused by the vaporization of moisture and the inability to discharge from the inner cavity of the casting nozzle and the casting area in time after the gas is concentrated.