Spinel products are a type of refractories, the main component of which are compounds containing oxides of divalent and trivalent metals.
Spinels are a group of compounds whose composition can be expressed by the general formula R+2R+304. Spinels crystallize, as a rule, in the cubic system and are considered as chemically complex compounds, in which R + 2 can be in the form of Mg , Fe, Zn, Mn , less often Co and Ni, and R + 3 can be in the form of 4Fe, Al, Cr , Mn .
Spinel products are obtained from a mixture of sintered magnesite and technical alumina. They are produced pressed with subsequent firing or cast. Pressed products are produced from a mixture containing about 30% magnesite, pre-fired at a temperature of 550-650 ° C, and 70% technical alumina. The binder is magnesite. To speed up the synthesis reaction, 0.5–1.0% boric anhydride B 2 O 3 or chromite is added to the mixture.
Cast products are obtained from a melt prepared in electric furnaces. They have a very high density and extremely high slag resistance up to 1600 °C. However , it should be taken into account that at temperatures above 1600°C, spinel products are quickly destroyed by ferruginous slags. The limiting temperature of their service is 1600-1700 ° C, thermal resistance is 3-5 water heat cycles.
One area of spinel use is molded refractories for slag belts and concretes for steel pouring ladles. An important condition for the service of such materials is their high inertness, heat resistance, low infiltration by melts, and optimal thermal properties. The latter parameters are controlled by a directional change in the refractory porosity.