High alumina brick refractory material for steel ladle working lining
At present, ladles used for out-of-furnace refining can generally be divided into two types: processing ladles and refining ladles. The former has no temperature compensation function, and is mainly used for degassing, desulfurization, forming control and changing the shape of inclusions in molten steel in a short refining time. etc.; the latter has a temperature compensation function, so the refining temperature is high and the processing time is long, and it is mainly used for the refining of high alloy steel and special steel.
With the increasing proportion of out-of-furnace refining and alloying processes in the steelmaking process, the importance of refractory materials for ladle working linings has become more and more prominent. Therefore, the physical and chemical properties of the refractory material for ladle working lining itself and its reaction with molten steel and slag are the most concerned directions in the research of ladle lining refractory materials. Precise control and improvement of molten steel quality are also crucial. With the gradual improvement of steel quality requirements in modern industry, the refining methods of molten steel tend to be diversified.
In order to meet the refining needs in different periods, the development of refractory materials for ladle working linings has also undergone several important changes. Below, we will discuss from high alumina brick series, carbon composite series, corundum-spinel castable series and calcium oxide The characteristics, development trajectories and research status of four typical refractories are reviewed and summarized.
High Alumina Brick Refractories
Clay brick (mainly composed of aluminosilicate) has been the main choice of refractory material for ladle working lining in my country from the early 1960s to the late 1970s, but its service life is low and the consumption is large. In the same period, foreign ladle has begun to High-alumina bricks are used as the main lining bricks. From the late 1970s to the early 1990s, with the improvement of my country's steelmaking process and the development of smelting technology to a certain extent, high-alumina bricks have been gradually adopted by steel mills. The acquisition is mainly based on natural bauxite. Under the condition that the use conditions are not too harsh at that time (no refining or the refining treatment time is very short), the life of the high-alumina brick lining is only about 20 to 30 times.
In order to improve the service life of the working lining of ordinary high-alumina bricks, people adopt methods such as increasing the content of Al2O3 or adding zircon and andalusite powder. Compared with ordinary high-alumina bricks, the service life of this kind of high-alumina bricks is increased. The improved high-alumina bricks will form corundum and mullite after contact with molten steel. The high melting point reaction layer of the main minerals, but also contains a high amount of liquid phase at high temperature. These shortcomings lead to the high alumina bricks being easily penetrated by molten steel and slag during the service process in the face of thermal shock, forming thicker bricks. The permeable layer is easy to hang slag and peel off, resulting in uneven damage to the lining. Subsequently, researchers have successively introduced chemically bonded high-alumina bricks, phosphoric acid or phosphate-bonded high-alumina ramming materials and high-alumina castables to improve the The anti-spalling properties of the material further increase the service life of the high-alumina ladle lining, but these treatment methods often adversely affect the quality of the molten steel, such as the introduction of phosphoric acid or phosphate into the steel.
With the increase of refining temperature and the prolongation of refining time, the problem of low service life of high-alumina bricks gradually becomes insurmountable. In addition, SiO2 in high-alumina brick-based refractories will inevitably lead to the increase of molten steel during service [Si ], and its typical reaction is as follows:
3( SiO2 ) + 4[Al]→2( Al2 O3 ) + 3[Si] (1)
At the same time, high-alumina brick-based refractories will also interact with CaO in the slag, and the reaction process can be expressed by the following reaction equation:
(CaO) + (SiO2) = (CaO·SiO2) ( 2)
(CaO) + 2( SiO2 ) + ( Al2 O3 ) = (CaO·Al2 O3·2SiO2 )(3)
2( CaO) + ( SiO2 ) + ( Al2 O3 ) = ( 2CaO·Al2 O3·Si )(4)
The melting points of the reaction products wollastonite (CaO·SiO2), anorthite (CaOAl2O3·2SiO2) and mayorite (2CaO·Al2O3·SiO2) are 1540, 1550 and 1590 °C, respectively, which are all lower than the refining temperature. Therefore, these The product is easily affected by scouring and enters the molten steel and becomes the corresponding inclusions.
Due to the limitation of short service life and polluted molten steel, high-alumina brick-based refractory materials are gradually replaced by other refractory materials in the field of ladle working lining.
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