Rapid Manufacturing Process Research Of Low Thermal Conductivity And High Strength Graphite/Ceramic Composite Type

Sodium silicate sand is a common casting material.It is widely used in the production of steel castings.However,its recycling rate is low and will cause deep pollution to the environment.Therefore,it is urgent to find a substitute for sodium silicate sand.Eliminate pollution sources and reduce pressure on environmental protection.To this end,this article integrates selective laser sintering technology and vacuum pressure impregnation strengthening technology together to quickly develop a low thermal conductivity(<2W/(m·K)),high strength(>10MPa)graphite/ceramic composite type,with Replace water glass sand type.The research work of this paper mainly includes the following aspects:(1)Complete the graphite/ceramic composite structure design based on the series heat conduction model.The composite type is designed as a gradient functional structure of a loose thermal insulation layer and an impregnated strengthened layer.The former ensures that the composite type has lower thermal conductivity,and the latter gives the composite type higher mechanical properties.First,establish a"sandwich"laminate heat conduction model,derive the relationship expression between the thermal conductivity and volume ratio of the loose thermal insulation layer and the impregnated strengthened layer,and then select five suitable design schemes according to the expression,and finally pass the Abaqus finite element The method of simulation determined the second design plan as the research plan of this article(loose insulation layer:1.33<₁<2(W/(m.K)),₁>6.5MPa;impregnation strengthening layer:₂>1(W/(m.K)),₂>12.32MPa)).(2)Quickly prepare graphite/ceramic composite loose thermal insulation layer,and adjust its thermal conductivity and mechanical properties by optimizing the composition of the material formula.Firstly,the influence of the amount of thermosetting phenolic resin powder on the molding process of graphite/ceramic composite blanks was studied.The study found that the appropriate amount of phenolic resin(25 wt%?35 wt%)helps to ensure the composite blank Forming accuracy and flexural strength;then studied the effect of the addition of high-purity silicon powder and expandable graphite on the thermal conductivity and compressive strength of the loose thermal insulation layer.The study found that with the increase in the amount of high-purity silicon powder,the looseness The thermal conductivity and compression performance of the thermal insulation layer show an increasing trend.With the increase of the amount of expandable graphite added,the thermal conductivity and compression performance of the loose thermal insulation layer show a decreasing trend.The final results show that when the phenolic resin powder,high-purity silicon powder and expandable graphite powder are added in 30 wt%,25 wt%and 1 wt%respectively,the thermal conductivity of the loose thermal insulation layer impregnated and strengthened layer is 1.42W/(m K),the compressive strength is 7.24 MPa,which meets the aforementioned design requirements for the performance of the loose thermal insulation layer.(3)Prepare the graphite/ceramic composite impregnation strengthening layer,and adjust its thermal conductivity and mechanical properties by optimizing the impregnation process parameters.The effect of impregnation parameters(impregnation time,impregnation times,vacuum degree)on the compound weight gain rate and impregnation depth was studied in detail.Research shows that:when the applied pressure is 0.1MPa,the vacuum degree is 0.1MPa,the immersion time is 45s,and the immersion times is 2 times,the impregnation weight gain rate of the composite mold is the largest,reaching 25%,and the impregnation depth is 5mm.The thermal conductivity is 2.78 W/(m K),and the compressive strength is 14.78 MPa,which meets the aforementioned performance design requirements for the impregnated strengthened layer.(4)Based on the manufacturing basis of the loose thermal insulation layer and the impregnated strengthening layer,prepare the cup-shaped graphite/ceramic composite type and conduct the pouring verification experiment.First,by studying the size shrinkage rate of the pouring cup-shaped mold,the accuracy deviation of the actual mold and the design size are determined,and then the verification experiment is carried out and the quality analysis of the cast steel parts is carried out.The results show that the graphite/ceramic composite pouring cup has excellent comprehensive performance,low thermal conductivity(1.89 W/m·K)and high compressive strength(10.54 MPa),and the number of successful pourings has reached 28.Under certain conditions,it is possible to replace the water glass sand casting mold.