Selection of electric furnace gunning refractory materials for electric furnace lining maintenance
The electric furnace adopts the gunning material maintenance to effectively delay the damage time of the lining, improve its service life; reduce the large and medium repair costs, ensure the continuous production of the electric furnace, thereby improving the production efficiency of the electric furnace; the spray filling process is simple, easy to use, short production cycle, saving energy and strong adaptability.
Therefore, the choice of electric furnace spray materials usually has the following criteria:
(1) Raw materials selection. At present, the aggregate of electric furnace gunning material mainly uses magnesia, magnesium dolomite, magnesia-chromite, magnesia carbon and magnesium dolomite carbonaceous raw materials, and at the same time, an appropriate amount of additives such as Si, Al, Mg and other low-melting metal powders, are added to the material. During gunning, the metal oxide oxidation exotherm helps to increase the temperature, and forms harmless oxides in the spray material, which is beneficial to improve the adhesion of the spray material; adding spinel , Cr203, SiC, B4C, Si3N4, etc. to improve the oxidation resistance and corrosion resistance of the material; the addition of organic explosion-proof fiber is beneficial to the discharge of moisture in the binder, which can prevent the castable from bursting during use; adding metal fiber for The tapping port part is used to improve the anti-flaking property of the spray material; adding a small amount of metallurgical slag can improve the adhesion and corrosion resistance of the spray material.
(2) The binder is classified into two types: an organic binder and an inorganic binder. Most of the organic binders are thermosetting resins and water-soluble phenolic resins; inorganic binders include CaO and MgO and their hydration products, as well as phosphates, water glass, chlorides, sulfates, and so on. In practice, organic binder composite inorganic binder or several inorganic binders are used in combination, in particular, phosphate binder and magnesium spraying material with proper amount of hardening agent and plasticizer are used in electric furnaces.
(3) Optimize particle gradation. The particles are large, the rebound rate is high, the fluidity is poor, but the erosion resistance is good; the particles are small, although the rebound rate can be reduced, the porosity of the spray material is high, which is not conducive to the corrosion resistance of the materials. Generally, the critical particle size of the semi-dry spray material is 3 mm. The critical particle size of the flame gunning materials is 1 mm.