Study On Graphite Cruicble Oxidation Resistance

Graphite is being used more and more widely in refractory products because of its excellent property such as chemical stability,high thermal conductivity and low thermal expansion coefficient etc.Graphite crucible is a typical example of carbon composites and is one of absolutely necessary tools for modern coloured metallurgy.With development of coloured metal smelt tecnics,its using condition increasingly severe, the oxidation of graphite has become a urgently solved problem. In this study the graphite crucible substrate sample is adopted and its self-healing behavior,impregnation process and methods of oxidation resistant coating are studied.Studying Self-healing oxidation resistant on graphit crucible sample,we study mostly reviews the influences on oxidation resistant when Al,Si and SiC added in.The analyzed results show a small quantity of Al,Si and SiC additives can not obviously improve the oxidation resistibility of the samples and the better addictive quantity of Al,Si and SiC as follows: 25%,20%,20%.For the high charge of materials, it is believed that the three as oxidation resistant additives are not practical significance.Studying impregnation oxidation resistant on graphit crucible sample, we quest for the influence of constitutes of impregnants and impregnation process,it can be found that better oxidation resistant effect under 1000℃is achieved in the graphite crucible samples when applying hyperacid aluminium phosphate with Al/P equal to 1/2 and controlling the impregnation process temperature in 90℃.In the study of oxidation resistant coating the influences of different binders, monolayer and two-doubled coatings of different constitute are studied.The results show that phenolic resin and aluminium dihydric phosphate composite binder can make the coating and the substrate integrate well and thesample with Si-rich coating inside and B-rich coating outside has better oxidation resistibility.In this paper the combination of the three methods to the oxidation resistance of graphite crucible and its feasibility are also studied and by optimization and combination of different methods the excellent graphite crucible product has been gained.The results of oxidation test show that the loss-in-weight rate of oxidation of the sample is only 1.21%,and surface layer has not decarbonized zone when heated from room temperature to 1300℃and warm keeping one hour,after the process of adding a spot of oxidation resistant additives in it,impregnating in aluminium dihydric phosphate and coating Si-rich coating inside and B-rich coating outside.