Graphite crucible is widely used in smelting of alloy tool steel and smelting of non-ferrous metals and their alloys in metallurgy, casting, machinery, chemical industry and other industrial sectors due to its high temperature resistance, small coefficient of thermal expansion, certain strain resistance against thermal shock, strong corrosion resistance to acid and alkaline solution, and excellent chemical corrosion resistance stability Economic effect. Graphite crucible is mainly made of graphite, which is a kind of allotrope of carbon.
The periphery of each carbon atom is connected with another three carbon atoms (arranged in honeycomb like hexagon) to form covalent molecules by covalent bond. Most of the graphite crucibles are carbon and some of them are air, so that the graphite crucibles are prone to oxidation, relaxation and falling off at high temperature. A new type of anti-oxidation coating researchers found that the graphite material began to oxidize at about 500 ℃, with the increase of the temperature of graphite crucible, the oxidation rate showed a geometric growth, and the oxidation was intensified. There are three kinds of graphite materials under high temperature, including graphite electrode, graphite mold and graphite crucible.
Under high temperature, graphite is prone to oxidation and combustion reaction, resulting in the increase of porosity and structure porosity of carbon layer on the surface of the material, affecting the service life. Taking the conventional baking of ladle as an example, the decarburized loose layer of more than 15mm is produced on the surface of carbon (graphite) refractories after baking, and the decarburized layer is quickly eroded after being filled with steel. At this time, most of the graphite crucibles adopt high-temperature resistant sealing coating, which has high temperature resistance. With special high-temperature solution, the temperature resistance can reach 1800 ℃, and can withstand open fire barbecue for a long time.
The coating material adopts nano scale structure, which has good compactness and effectively prevents the diffusion of oxygen under high temperature. The hardness can reach 7-8h, which is higher than the hardness of metal. High temperature resistant sealing coating is applied on the graphite crucible to form a dense coating, which has strong anti rust and anti-corrosion, high temperature resistance, anti oxidation, anti discoloration, wear resistance and other characteristics. High temperature resistant sealing coating is applied on kiln, graphite, metal, etc. to prevent the oxidation rate under high temperature can reach more than 80%, and the energy-saving utilization rate of graphite crucible material can reach more than 95%.
The graphite electrode used in the high temperature oxidation environment will undergo partial sublimation oxidation due to the high temperature arc, which will cause the continuous consumption of the graphite crucible, even fracture and damage. The loss rate of graphite crucible can reach 40-60%. The new high temperature resistant sealing coating is mainly used for anti-oxidation protection of graphite electrode, graphite crucible and graphite parts under high temperature environment, delaying oxidation speed, increasing material strength and improving service life. It effectively reduces the probability of fracture, breakage and falling off of graphite electrode. After the graphite crucible is impregnated and coated with anti-oxidation coating, the high-temperature ZS-1011 graphite transition coating liquid can infiltrate into the pores of the graphite crucible, and the residual air in the graphite crucible can be emptied.
An anti-oxidation protective film is formed on the pores and the surface of the graphite crucible. It is this protective film that can effectively insulate the air from direct contact with the graphite crucible and produce oxidation reaction. The graphite crucible impregnated with the anti-oxidation coating will not crack and fall off in the high temperature upheaval, so it can effectively delay the oxidation of the graphite crucible and extend the service life of the graphite crucible. Graphite crucible anti-oxidation coating, water-based inorganic environmental protection coating, no volatile matter produced at high temperature and normal temperature. The high temperature resistant coating is acid and alkali resistant, and does not react with the quenching medium. It can effectively protect the graphite crucible from chemical reaction at high temperature, and can effectively prevent the oxidation rate of the graphite crucible at high temperature from reaching more than 95%.