Opening leakage refers to the leakage caused by molten steel flowing out from the connection between the dummy head and the billet during the opening process of pouring.
What are the causes of opening leakage?
Poor sealing: The head of the dummy rod is not sealed well. After pouring, the molten steel may flow into the gap between the dummy rod and the crystallizer, causing leakage. The dummy rod is not firmly assembled and loose, and the molten steel may flow out of the crystallizer.
Crystallizer problem: The corner seam of the crystallizer is too large. When pouring, the molten steel is easy to leak from the corner seam or cause hanging leakage. The scratches, deformation or inappropriate taper of the crystallizer copper plate will affect the uniform growth of the billet shell and the lubrication between the crystallizer and the billet shell, resulting in insufficient strength of the billet shell or increased resistance to billet drawing, which will cause leakage.
Molten steel: The higher the superheat of the molten steel, the thinner the shell thickness. If the pouring and emergence time is too short at this time, the molten steel in the dovetail groove cannot be completely solidified. Under the static pressure of the molten steel in the crystallizer, the shell is easy to expand and rupture, causing steel leakage. If the temperature of the molten steel is too low, it will cause poor slag slagging of the protective slag, increase the viscosity, and cause a fault in the liquid slag film between the shell and the crystallizer. The crystallizer is poorly lubricated and the shell cannot be removed. The shell and the copper plate are bonded and leaking.
Operational factors:
â‘´ The pouring and starting speed is too fast, the primary shell of the casting is thin, and the liquid slag film in the crystallizer cannot be replenished in time, which increases the friction between the primary shell and the copper plate of the crystallizer, which is easy to cause bonding and leakage.
⑵ The protective slag is added incorrectly. If too much is added at one time and concentrated in the inner arc, it will be sloped, which will cause uneven filling of liquid slag, affecting the lubrication and uniform heat transfer between the crystallizer and the shell.
⑶ The pouring flow of the tundish is eccentric, resulting in uneven heat transfer, uneven thickness of the solidified billet shell, reduced strength at the weak part of the billet shell, and difficulty in withstanding the static pressure of the molten steel, resulting in steel leakage.
â‘· Insufficient emergence time leads to the inability of the molten steel in the dovetail groove to solidify completely. Under the static pressure of the molten steel in the crystallizer, the billet shell is easy to expand and rupture, resulting in steel leakage.
⑸ Blasting during the pouring process. Due to excessive water content during the pouring process, blasting during the pouring process will cause the asbestos rope and asbestos cloth that block the ingot to be flushed out, resulting in steel leakage in the gap.
⑹ The pouring operation is not standardized, the pouring operation is varied, and the operation is random, which greatly increases the probability of steel leakage during the pouring.
⑺ The starting material box is an important process part to ensure the strength of the billet head in the initial stage of pouring. If the design is not appropriate, the strength is insufficient, or the solidification cannot be fully filled during pouring, it will cause the pouring to start and then cause steel leakage.
Equipment factors: Unstable vibration during the pouring process, the stopper mechanism cannot control the flow and other abnormal conditions will affect the pouring. Improper or untimely handling will cause pouring failure; the design of the ingot head is unreasonable, the dovetail groove is shallow, and the ingot cannot be guaranteed for pouring
How to prevent steel leakage during pouring?
Production preparation: Before production, production preparation work must be done fully, such as the inspection of the nozzle centering should be done in advance, and it cannot be confirmed after the baking package; the materials used for plugging the ingots must be confirmed to be dry in advance.
Blocking the ingots: When sending the ingots, pay attention to the centering of the ingot rod. If it is not centered, send the ingot again; before blocking, the ingot rod and the inside of the crystallizer must be blown clean to ensure dryness and no moisture; the asbestos rope and asbestos cloth used for blocking must be pounded solid without gaps; for some dovetail groove ingot heads, the inclined surface is the focus of blocking and needs to be protected; the iron pins covering the gaps must be kept dry and uniform, and the particles cannot be too large; after blocking, check well, and before pouring, confirm whether the ingot rod has slipped, etc.
The inspection of the crystallizer should be done after the last pouring. For the copper plate combination type, the corner seam of the crystallizer should be checked. If the corner seam is too large, the crystallizer should be replaced in time; if the corner seam is less than 0.35mm, iron mud should be applied when sealing the ingot rod; for the copper tube type, it is necessary to check whether the inner wall of the crystallizer has coating shedding, steel sticking, etc.
Molten steel: Strengthen the coordination with refining and control the temperature and composition of molten steel. For some high-aluminum steels and high-S steels, it is necessary to pay attention to the use of special protective slag.
For the pouring operation, according to the equipment conditions of each continuous casting machine, the pouring operation should be solidified, and the starting time and starting pulling speed should be accurately controlled through standard operating techniques; at the same time, the protective slag should be added correctly, and it should be kept uniform and added in appropriate amounts to avoid adding too much at one time or concentrating in one place.
Equipment inspection: Before pouring, the plugging mechanism, vibration, radiation source monitoring and other equipment must be checked, and if conditions permit, they must be tested in advance.
