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Spinel

Description

Spinel is a type of refractory material whose main component consists of compounds containing oxides of divalent and trivalent metals. Spinels are a group of compounds whose composition can be expressed by the general formula R²⁺R³⁺₂O₄. As a rule, they crystallize in the cubic system. R²⁺ can be Mg, Fe, Zn, Mn, and less commonly Co and Ni, while R³⁺ can be Fe, Al, Cr, Mn.

Spinel products are obtained from a mixture of sintered magnesite and technical alumina. They are produced either pressed with subsequent firing or cast. Pressed products are manufactured from a mixture containing about 30% magnesite, pre-fired at 550–650 °C, and 70% technical alumina; magnesite serves as the binder. To accelerate the synthesis reaction, 0.5–1.0% boric anhydride B₂O₃ or chromite is added to the mixture.

Cast products are obtained from a melt prepared in electric furnaces. They have very high density and extremely high slag resistance up to 1600 °C. At temperatures above 1600 °C, spinel products are rapidly destroyed by ferruginous slags. Their maximum service temperature is 1600–1700 °C, and thermal shock resistance is 3–5 water-heat cycles.

Advantages

  • High mechanical strength and hardness – capable of withstanding significant mechanical loads in linings and structures.
  • Low thermal expansion coefficient – minimal deformation on heating, preserving product geometry.
  • Good corrosion resistance – resistance to chemical attack by slags and aggressive media over a wide temperature range.
  • High thermal resistance – operable at temperatures up to 1600 °C (short-term up to 1700 °C) in the absence of ferruginous slags.
  • High material purity – allows the production of refractories without extraneous impurities, which is especially critical in demanding metallurgical processes.

Applications

  • Shaped refractories for slag belts of steel pouring ladles.
  • Concretes for lining steel pouring ladles.
  • Other refractory structures where high inertness to melts, thermal resistance, and low slag infiltration are crucial.
  • Products requiring controlled variation in porosity to adjust thermal properties.

FAQ

Spinel is a refractory material based on compounds of oxides of di- and trivalent metals (spinels). The raw materials are sintered magnesite and technical alumina. Products are obtained by pressing with firing or by casting from a melt.

Pressed products are formed from a powder mixture and fired. Cast products are obtained by melting raw materials in electric furnaces and pouring into molds; they are characterized by very high density and maximum slag resistance up to 1600 °C, but are destroyed by ferruginous slags above this temperature.

The maximum service temperature is 1600–1700 °C. At temperatures above 1600 °C, cast spinel products are rapidly destroyed by ferruginous slags. Thermal shock resistance is at the level of 3–5 water-heat cycles.

High purity makes it possible to obtain refractories without extraneous impurities, which is critically important in metallurgy: it prevents the introduction of non-metallic inclusions into steel and increases the reliability of the lining.