- Time:Jul 21, 2022
Ladle refractory properties The ladle is an important supporting equipment in the process of steelmaking and continuous casting. Its process position is between the steelmaking furnace and the tundish. It receives molten steel from the steelmaking furnace, and then transports it to the tundish for continuous casting. The working lining bricks of the ladle are divided into clad bricks, clad bottom impact zone bricks, molten pool bricks and slag line bricks according to the masonry parts. The sla...
Ladle refractory properties
The ladle is an important supporting equipment in the process of steelmaking and continuous casting. Its process position is between the steelmaking furnace and the tundish. It receives molten steel from the steelmaking furnace, and then transports it to the tundish for continuous casting. The working lining bricks of the ladle are divided into clad bricks, clad bottom impact zone bricks, molten pool bricks and slag line bricks according to the masonry parts. The slag line is an important part of the ladle, which is subject to chemical erosion and thermal scouring by alkaline melting. This part of the bricks is a high-grade product in the entire ladle; the second is the impact zone at the bottom of the ladle, which is mainly used to withstand the mechanical action of molten steel during tapping. ; The thermodynamic effect of molten pool bricks and bottom-clad bricks is relatively small, and the corrosion damage mechanism is also different. According to the different parts of use, different batching processes are adopted.
Ladle refractories must have the following properties:
Good strength at room temperature, high temperature and resistance to slag erosion and penetration at high temperature. During the process of pouring steel, the liquid level of molten steel gradually decreases, the refractory of the clad wall is scoured and eroded by the molten steel and slag, and the refractory at the ladle slag line is affected. The erosion of steel slag is particularly serious, and at the same time, the refining process damages the refractory material on the clad wall, and the refractory material at the bottom of the ladle is impacted and eroded by the molten steel during use.
Ladle refractory lining should have the conditions
Ladle working lining is an important part in contact with molten steel and slag. It is affected by the erosion, erosion, melting and thermal shock damage of molten steel and slag during use. Therefore, the following conditions should be met during use:
(1) The work lining should strive for simple equipment and convenient construction in the construction project, which can reduce labor intensity and improve labor productivity. It must have good baking adaptability, reduce the energy consumption of the baking ladle, and at the same time increase the utilization rate of the ladle, prolong the service life of the ladle, and reduce the number of spare ladles.
(2) It should have good high temperature performance under high temperature use conditions. Not only high refractoriness and certain high temperature strength are required, but also good chemical stability to ensure that secondary oxidation of molten steel will not occur under high temperature conditions. , will not pollute the molten steel, and will not reduce the quality of the billet.
(3) It should have good resistance to slag erosion and penetration during use, as well as resistance to molten steel and slag scouring, which is conducive to improving the service life of the ladle working lining, reducing the consumption of ladle refractory materials, and reducing the impact of refractory materials on refractory materials. Contamination of molten steel.
(4) The working lining should have good thermal shock resistance and good volume stability, and will not burst when in contact with molten steel to ensure good integrity of the ladle.
(5) The ladle working lining should also have low thermal conductivity and good thermal insulation performance, which can reduce the heat loss of the tundish and keep the temperature of the molten steel in the tundish stable.
(6) The working lining after use should be easy to unpack, and the working layer and the layer are easy to detach, which can reduce the damage of the working lining refractory material to the ladle lining and help prolong the service life of the ladle.
Reasons for Damage of Ladle Refractories and Measures to Improve Service Life
Causes of damage to ladle refractories
Chemical action:
1) Erosion of refractory materials by molten steel composition.
2) Erosion of slag components to refractory materials.
3) Under the action of high temperature, the damage caused by the reaction of the refractory material itself, such as the volume effect caused by the phase change caused by the generation of new minerals and the volatilization under the action of vacuum, etc.
Physical effect:
1) The scouring effect of molten steel on refractory materials.
2) The thermal shock caused by the repeated action of molten steel on the refractory material causes the cracking and spalling of the refractory material of the continuous caster.
3) Damage caused by the thermal expansion effect of the refractory itself.
4) The erosion effect of high temperature molten steel on refractory materials.
Man-made causes:
1) Inappropriate selection and matching of refractory materials.
2) Improper use of refractory materials. Such as masonry methods, baking methods are not suitable.
3) The ladle turnover period is too long, resulting in cold ladle.
4) Improper unpacking will damage the steel cladding.
5) No repair measures have been taken.
Main measures to improve the service life of ladle
(1) Choose refractory materials with high temperature resistance, erosion resistance and thermal shock resistance as lining.
(2) Correctly select and match refractory materials to achieve balanced construction.
(3) Understand the properties of the selected refractory materials, and reasonably formulate the use conditions of the ladle, such as the formulation of the baking system.
(4) Speed up the use cycle of the ladle as much as possible and achieve the "red envelope" work. ’
(5) For the damaged part of the lining refractory material, carry out gunning treatment in time.
Cleaning the ladle maintenance lining
Steps
(1) After the casting of the previous furnace is completed, the remaining steel residue in the ladle shall be poured out as soon as possible.
(2) Clean up the cold steel residue in the package mouth in time.
(3) If there is cold steel at the bottom of the ladle, the ladle must be laid horizontally, and the cold steel must be melted and removed with oxygen.
(4) Check the damage of the ladle slag line, the bottom of the bag, the wall of the bag and the brick, and repair and maintain it in time:
a. Due to the quality of masonry or lining bricks, the ladle will cause local damage during use. Therefore, after removing the residual steel residue, the severely eroded parts should be repaired.
b. In order to improve the service life of the ladle and prevent steel leakage, hot repair should be carried out in time. Such as hot-filling brick joints: The hot-filling brick joint method is to use a relatively dilute fire brick powder-water glass slurry (or other refractory powders and binders) to fill the brick joints, because the water glass is heated Foaming, so it is often necessary to make up several times in a row. Hot-filling holes: The method of hot-filling holes is to use thicker fire brick powder-sodium silicate paste (or other refractory powders mixed with a binder) to fill up, and beat them appropriately. Hot-filling block: The method of hot-filling the block is the same as the method of hot-filling the hole. Repair should be carried out after the nozzle is installed, and the nozzle should be blocked with an iron cover equal to the outer diameter of the nozzle brick to prevent the mud from falling on the nozzle.
c. When there is a large area of erosion, refractory bricks can also be used for hot repair. Before repairing, the residual steel and residue should be cleaned up.
(5) Quickly replace the sliding nozzle of the ladle, and send the ladle hot.
(6) Hang the ladle to the baking position for baking or stand-by.
Precautions
(1) The residual steel residue in the bag must be completely removed.
(2) Be careful not to damage the cladding and other equipment when removing the residual steel slag.
The role of removing the residual steel residue from the ladle
To remove the residual steel residue in the ladle, the residual steel residue in the used ladle must be completely removed, otherwise it will seriously affect the quality requirements of the next batch of steel, the specific performance is as follows:
(1) Lower the temperature of molten steel. When the molten steel and slag at the bottom of the ladle are melted, a large amount of heat must be absorbed from the molten steel, especially for small-capacity ladle.
(2) The molten steel is contaminated by residues. The slag is gradually melted by the molten steel. If it cannot float up completely, it will become inclusions in the steel. At the same time, the iron oxide in the slag will increase the oxygen content in the steel and the oxidation loss of alloying elements.
(3) Too much molten steel at the bottom of the package will also cause major accidents of low-temperature steel, and for alloy steel, it will also cause excessive changes in the composition of the molten steel in the next furnace or even be scrapped.
