Ladle is a necessary equipment to receive molten steel and conduct continuous casting. As many kinds of steel need to be refined in the ladle, including argon blowing temperature regulation, fine adjustment of alloy composition, powder injection refining and vacuum treatment of continuous caster, the working conditions of ladle lining are getting worse and worse, so the requirements for all refractory bricks, castables and other refractory materials are also getting higher and higher.
Working environment of ladle refractory
(1) The temperature of molten steel is higher than that of mould cast steel ladle.
(2) The residence time of molten steel in the ladle is extended.
(3) The ladle lining volatilizes itself under high temperature and vacuum and is subject to the agitation of molten steel.
(4) The impact on the lining when it receives molten steel.
(5) Erosion of lining by slag.
Requirements for ladle refractories
(1) High temperature resistance, can withstand high temperature molten steel for a long time without melting and softening.
(2) Heat resistant impact, can repeatedly bear the loading and unloading of molten steel without cracking and peeling.
(3) It is resistant to the erosion of slag and can withstand the erosion of slag and slag alkalinity change on the lining.
(4) It has sufficient high-temperature mechanical strength and can withstand the agitation and scouring of molten steel.
(5) The lining has certain expansibility. Under the action of high-temperature molten steel, the lining is closely contacted to form a whole.
Selection conditions and types of common ladle refractories
Selection conditions of ladle refractory
(1) Working conditions of ladle, such as tapping temperature, residence time of molten steel, pouring steel grade, whether refining treatment is carried out, etc.
(2) The position of ladle refractory in the ladle.
(3) Basicity of slag.
(4) Working conditions and economic ladle age of ladle building, ladle dismantling and ladle baking in the steel plant.
(5) Economy.
Types of commonly used ladle refractories
(1) Clay fire bricks. The content of Al2O3 in clay brick is generally between 30%~50% and the price is low. It is mainly used for permanent layer and bottom of ladle.
(2) High alumina brick. The Al2O3 content in the brick is between 50%~80%, which is mainly used for the working layer of the ladle.
(3) Wax stone brick. The brick is characterized by high SiO2 content. Generally, w (SiO2) >80%, which is better than clay brick in terms of corrosion resistance and integrity, and does not hang slag. It is commonly used in ladle wall and bottom.
(4) Zircon brick. This brick is mainly used for ladle slag line. The content of zr2o3 in bricks is generally between 60%~65%. It is characterized by good erosion resistance, but the price is high, so it is not often used.
(5) Magnesia carbon brick. The brick is mainly used for ladle slag line, especially for multi furnace continuous casting. The content of MgO in bricks is generally about 76%, and the content of C is between 15%~20%. It is characterized by low corrosion of molten slag and good corrosion resistance and spalling resistance.
(6) Aluminum magnesium castable. The castable is mainly used for ladle. It is characterized by the reaction of MgO and Al2O3 in the castable to produce alumina magnesium spinel under the action of molten steel, which improves the flooding resistance and thermal resistance of the lining.
(7) Alumina magnesia carbon brick. This brick is a ladle lining developed on the basis of aluminum magnesium castable, and its service life is long.
(8) Do not burn bricks. At present, almost all materials used for ladle fired bricks can be made into corresponding unburned bricks. It is characterized by relatively simple manufacturing process and low price. The brick itself has certain mechanical strength and corrosion resistance, which is convenient for construction and masonry.
If the ladle itself is also used for refining, mgo-cr2o3-al2o3 and mgo-cao-c refractories can also be selected, mainly including magnesium chromium brick, magnesium chromium aluminum brick, dolomite brick, etc.
When using bricks containing graphite as ladle lining, it is better to apply a layer of anti-oxidation coating on its surface to prevent the lining surface from being oxidized and loose during baking, which will affect its service life.