摘要
Refractory coatings play a critical role in making defect.free castings using the lost foam casting process.Once a coating has been selected which gives the best overall casting results for a given part,the next step iS to develop consistent handling procedures and testing protocol SO that ideal property ranges for the coating can be maintained in a production environment.The coating properties which have the greatest impact on casting results are viscosity,percent solids,and permeability.If these properties are tested properly and maintained within predetermined ranges,casting results should reflect the coating consistency.Recommended testing protocol should include viscosity measurement using a Brookfield viscometer at multiple spindle speeds,%solids testing using a Mettler solids balance or equivalent method.permeability testing using the UAB method or screen permeability method and a check of wet and dry coating deposit weight.Consistent handling methods for coating should also be developed.These procedures should include pre-mixing,dip tank mixing,temperature control,and property testing methodology and frequency.Consistency,in preparation,use and property testing,is the key factor in making a coating formulation perform at optimum levels to provide the highest degree of casting qualitypossible.
