How does protective grease provide lubrication?
Release time:
2020-07-29
During casting, the crystallizer vibrates up and down, and the billet moves downward, causing friction between the surface of the solidified shell and the copper wall, causing the shell to adhere to the copper wall, increasing the pulling resistance, and possibly leading to shell cracking, or even shell cracking. Therefore, lubrication must be applied between the shell and the copper wall, and this effect can only be achieved through protective slag to achieve.
To ensure good lubrication, there must be a layer of liquid slag film with appropriate properties and uniform thickness between the solidified shell and the copper wall. protective slag The liquid slag layer on the surface of the mold steel is the source of the continuous supply of the liquid slag film. Therefore, it is necessary to ensure that the liquid slag flows into the channel between the billet shell and the copper wall near the meniscus of the crystallizer without being blocked by the slag ring around the copper wall.
So protective slag how does it lubricate ? When molten steel is poured into the crystallizer, a primary billet shell is formed. When protective slag powder is added to the liquid surface, protective slag the powder melts to form a layer of liquid slag, and the liquid slag near the copper wall cools to form a slag ring. As the crystallizer moves downward, the slag is gradually squeezed between the billet shell and the copper wall, thus completely filling the slag. The copper wall temperature is low, and the slag shell near the copper wall is still solid slag skin, while the surface temperature of the solidified shell is high, and the slag near the shell is a liquid slag film with fluidity. In this way, the copper wall and shell of the crystallizer are lubricated by the liquid slag film, the liquid slag film is consumed during billet pulling, and the solid slag skin adhering to the copper wall is basically not consumed during crystallizer vibration. When protective slag the film is continuously consumed, the liquid slag on the steel surface is continuously replenished downward through the meniscus channel, forming a stable liquid protective slag film.
The thickness of the slag film is related to factors such as slag viscosity, casting speed, and mold vibration. Knowing that the viscosity of the slag is constant, the casting speed increases, and the slag film thickness increases; however, when the pulling speed is unchanged and the viscosity increases, protective slag the film thickness decreases. protective slag The film thickness is generally 50 ~ 200 microns, and the slag consumption is 0.4 ~ 0.6 kg/ton. Therefore, in order to make protective slag the lubrication of the film to the solidified shell is in the optimal state, protective slag the film thickness, slag consumption, and slag viscosity should be appropriately matched. When the crystallizer vibration is unchanged, the viscosity () and casting speed (V) should be appropriately matched, while low viscosity and low casting speed, or high viscosity and high casting speed are undesirable. The product V is used as an indicator to evaluate the lubrication conditions. If V is too small or too large, it means protective slag the film thickness and consumption are inappropriate, and the lubrication conditions are poor.
More about protective slag questions can be consulted from Luoyang Turner High Temperature Instrument Co., Ltd.
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