Acidic and alkaline binders for magnesium aggregates in tundish coatings play an important role in the field of refractory materials. Their selection directly affects the performance and use effect of the coating. The following is a detailed analysis of these binders:
Acidic binders
Among magnesium aggregates, a typical representative of acidic binders is magnesium sulfate (MgSO4). Magnesium sulfate is acidic at low temperatures and combines very well with the alkaline aggregate MgO. At high temperatures, magnesium sulfate decomposes into MgO (solid) and SO3 (gas). Some of the remaining MgO is the same as the oxide crystal nucleus. This combination not only does not corrode the material, but also makes it easy to remove the slag shell. Therefore, magnesium sulfate is considered to be an excellent acidic binder in magnesium aggregates.
Alkaline binders
For alkaline binders, although sulfates such as calcium sulfate (CaSO4), sodium sulfate (Na2SO4) and potassium sulfate (K2SO4) have also been studied, their bonding strength with MgO aggregate is relatively weak and does not form a strong bond like magnesium sulfate. This may be because their chemical properties are not as well matched to MgO as magnesium sulfate.
Other binders
In addition to sulfate binders, there are other types of binders that can be used in magnesium aggregates. For example, phenolic resins, boric acid, and boric anhydride are also used as binders for tundish dry materials. These binders can form a dense bond under specific process conditions, improving the strength and corrosion resistance of the coating.
When selecting a binder for magnesium aggregate in tundish coatings, it is necessary to comprehensively consider factors such as the performance requirements of the coating, construction conditions, and cost. Acidic binders such as magnesium sulfate bind well with MgO at low temperatures and have stable performance at high temperatures, making it a good choice. However, under certain specific conditions, other types of binders or additives may be required to meet specific performance requirements.
The acidic and alkaline binders used for magnesium aggregates in tundish coatings have their own characteristics. Magnesium sulfate performs well as an acidic binder in magnesium aggregates, while alkaline binders such as calcium sulfate, sodium sulfate, and potassium sulfate are relatively weak. In actual applications, the appropriate binder should be selected according to specific needs, and other ingredients may need to be added to optimize the overall performance of the coating.
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