Cause Analysis and Measures of Blasting of Caster tip
Causes of nozzle explosion
Nozzle explosion means that during the process of casting and rolling the vertical plate, the gas in the casting and rolling area or the nozzle escapes from the molten aluminum instantaneously.
There are two main forms of casting nozzle explosion: one is to explode toward the roll gap direction; the other is to explode to the nozzle-roll gap.
(1) The explosion of the casting nozzle in the direction of the roll gap mainly occurs at the moment when the vertical plate is released, and the high-temperature aluminum liquid is self-feeding from the feeding pipe
When the outflow touches the Caster tip with high water content and the wet roller surface, the water vaporizes instantly, and the volume expands thousands of times.
The water vapor air mass breaks through the inner cavity of the casting nozzle or the weak part of the aluminum liquid front near the casting lip mouth and escapes instantly, resulting in
(2) The small air bubbles in the molten aluminum continue to gather in the casting area and the lip position, forming a large bubble with a certain pressure.
Bubbles, there are two ways for large bubbles to escape. The first is for large bubbles to break through the aluminum liquid between the nozzle and roll the gap and vaporize.
Membrane tension escapes from the nozzle roller gap, causing an explosion. The second is that the internal pressure of the large bubble is greater than the viscosity of the casting Caster tip.
The joint force makes the Caster tip damaged and escape, causing an explosion
Influencing Factors of Nozzle Explosion
1. The influence of the water content of the casting Castertip and the water content of the bonding glue of the casting Caster tip;
2. The influence of wet roller surface:
In the stage of graphite on the roller surface of the vertical plate, if the amount of graphite sprayed by the spray gun is large, the moisture in the graphite emulsion cannot be volatilized in time,
A large area of fine water droplets will be formed on the roller surface, and even a string of water droplets will be formed. When the air humidity is high and the roller surface meets low temperature, the liquid capacity
easy to forms water droplets;
When the vertical plate runs slag, the wet roll surface encounters high-temperature aluminum liquid, the water vapor is instantly vaporized and expands rapidly, and it is easy to follow the roll gap
The direction explodes forward; due to the slow temperature rise of the roll surface during the slag running process of the vertical plate, a large amount of water vapor after gasification meets the roll again
It condenses into fine water droplets, which are easy to drip on the lip between the nozzle rolls, increasing the water content of the casting lip.
3. The influence of gas content in molten aluminum;
During the stand-up process, since the liquefied gas combustion product contains a large amount of water vapor, at the same time the liquefied gas is compressed in the air
Combustion under the action of compressed air continuously blows the aluminum oxide film on the surface of the launder, accelerating the moisture and aluminum in the air
The reaction speed of the liquid makes the hydrogen content in the aluminum liquid increase significantly; when the hydrogen ions in the aluminum liquid are in the inner cavity of the nozzle, on the one hand, the hydrogen
The ions form hydrogen gas, on the other hand, during the condensation process in the casting and rolling area, as the temperature decreases, the hydrogen ions rich in the aluminum liquid
Precipitation forms hydrogen gas, which makes many small bubbles form in the casting and rolling area, and finally explodes.
Measures to prevent nozzle explosion
1. Reduce the water content of the nozzle
2. Reduce the humidity of the casting roll surface
3. Reduce the hydrogen content in the discharged aluminum liquid
4. Optimize the process operation of the vertical board
① Slag running process control: The slag running speed should be higher when the narrow board vertical board is higher than the wide board, and the narrow board vertical board
The slag running a temperature should be higher than that of the wide plate, and the slag running time should be as long as possible to make the gas escape as much as possible.
②Publishing process control:
After the vertical board is out of the board, let the board surface be in a continuous hot state, which is beneficial to the inner cavity area of the casting nozzle
Tiny air bubbles continue to escape from the tropics in small amounts, reducing the chance of nozzle explosion.