Preparation And Properties Of Anti-Oxidation Coating On Long Nozzle Surface Of Continuous Casting

The aluminum carbon long nozzle is used in the smelting of cutting steel for continuous casting production.The content of Al₂O₃ should be controlled during the smelting process.If the content of Al₂O₃ is too high,the steel will lose plasticity during the hot working process,resulting in the rupture of the billet.Therefore,a low-alumina,aluminum-free anti-oxidation coating on the surface of an aluminum carbon nozzle is prepared.The main raw materials used feldspar powder,clay powder,silica sand,borax and sodium oxide.Investigate the effect of different coating ratios on hemisphere temperature and oxidation resistance,and analyze the micro structure of the coating section.The results show that the ratio of low-aluminum anti-oxidation coating materials is 30%for clay powder,30%for feldspar powder,30%for silica sand and 10%for borax.The optimum conditions for the preparation of the coating slurry are 10 hours of ball milling time and the amount of water added is 100%of the mass of the solute.When the binder water glass solution is 30-40%,the spreading performance of the coating on the surface of the aluminum carbon nozzle is better.After water glass more is than 40%,the coating cannot wrap the aluminum carbon nozzle,and the oxidation weight loss rate increases.It can be seen from the SEM photograph that when the water glass solution is 40%,The coating and the substrate are integrated and firmly combined.The aluminum-free anti-oxidation coating was prepared by comparing the hemispheric temperature of silica sand with borax,silica sand with boron glass powder,silica sand with sodium oxide,silica sand with fluorite.Final determination of silica sand:borax=5:5,hemisphere temperature is791°C,in line with the use environment of aluminum carbon long nozzle,In order to improve its spread ability,when silica sand:borax=5:5,15%sodium oxide was added to the binary system,Further reduce the hemisphere temperature is 719℃.Comparing the effects of water glass solution,silica sol solution,sodium hexametaphosphate solution and sodium tripolyphosphate solution on the performance of the coating,the coating with 40%water glass solution has the lowest oxidation loss rate,The coating is tightly bonded to the aluminum carbon matrix.As the content of the additive boron glass powder increases,the oxidative weight loss rate decreases.According to the SEM photograph,when the boron glass powder is 25%,the coating is tightly bonded to the substrate,and there is no crack inside the coating.The optimal formulation of the aluminum-free anti-oxidation coating is 42.5%of silica sand,42.5%of borax,15%of sodium oxide,40%of water glass solution of binder,25%of boron glass powder,100%of water,and 0.1%of sodium bentonite.