Effect Of Composite Fiber Content On Dispersion Of Gypsum Slurry And Properties Of Gypsum Mold

As a kind of near net shape technology,plaster investment casting is widely used in the manufacture of aviation enterprises such as the large complex thin-walled castings.The gypsum slurry has good flowability,so it is easy to produce the small thin-walled castings.But the thermal conductivity and permeability of plaster are very poor,which greatly limits its application in the large thin wall parts.Therefore,finding a new technology which can improve its thermal conductivity and permeability,and can guarantee the strength has important practical significance for the study of the properties of plaster mold.The influence rule of the content of composite fiber on fiber dispersion and the properties of plaster mold is studied,which has certain guiding function for the production of high quality gypsum mold.In this paper,ceramic and nylon composite fiber are used as reinforcements.The composite fibers with different content are added to the gypsum powder and scattered by ball-milling and the fiber dispersion.Then the powder is reacted with the solvent,which can produce the plaster mold.The influence rule of the content of composite fibers on the fiber dispersion and the various properties of plaster mold was studied,and the strengthening mechanism of the composite fiber was analyzed.The experimental result can be showed as follows:(1)when the fiber content is 0 %~0.5 %,the dispersion is the best;at0.5 %~0.75 %,the dispersion is better;at 0.75 %~1.25 %,the effect of fiber dispersion is poor.(2)When the fiber content changes at 0 %~1.25 %,with the increase of fiber content,the bending strength of the embryo of the gypsum type generally increased firstly and then decreased,the bending strength after roasting was decreased firstly,then increased and finally decreased.When the content of fiber is 1 %,the flexural strength of the embryo reached the maximum,4.086 MPa,which increases by 18.5 %compared to the gypsum mold without fiber.When the fiber content is 0.75 %,the strength after roasting is the largest in the gypsum type of adding fiber,0.447 MPa,and the strength does not change more than the plaster type without fibers.(3)With the increase of fiber content,the thermal conductivity of gypsum type first increased and then decreased;permeability increased gradually;the penetrationincreases,the standard deviation of the penetration decreased firstly and then increased;thermal shock resistance was improved obviously.When the fiber content is 0.75 %~1 %,the thermal conductivity is the best.When the fiber content is 1.25 %,the air permeability is the best.When the fiber content is 0.75 %,the penetration is medium and the standard deviation is the smallest.Through the study of ball-milling composite fiber and gypsum powder to disperse fiber and fiber content on the performance of plaster,the effects of fiber dispersion and fiber content on the properties of gypsum.The results provide theoretical guidance and technical support for the preparation of high performance plaster mold and the production of large thin-wall parts.