| The waste shell of investment casting is a kind of industrial waste produced in the process of casting.The discharge of this waste will pollute water resources and soil,which does not meet the requirements of "energy saving and emission reduction,green casting".Because of the complex composition of waste shell in investment casting,there are many problems such as difficult recovery,low added value of recovered products,poor stability and poor economic benefits.At the same time,although the artificial spherical sand for casting has the advantages of high fire resistance,low linear expansion and reusability,it can not be widely used in industrial production due to the high manufacturing cost.In order to solve these problems,in this paper,the use of casting waste mold shell to separate electric fused white corundum and manufacture artificial spherical sand not only solves the problem of recycling investment casting waste mold shell,but also greatly reduces the manufacturing cost of artificial spherical sand.In this paper,a treatment technology of waste shell in investment casting is studied,which can effectively separate and recover surface sand and electrofusion white corundum,and prepare a new type of original sand artificial spherical ceramsite sand for casting.The research work includes two aspects:recovery of surface sand and electrofusion white corundum from waste shell in investment casting by mechanical ball milling method,and preparation of artificial spherical ceramsite by process design and composition optimization Sand can improve the surface morphology and properties of ceramsite sand.The conclusions are as follows.(1)The processing method of waste shell of investment casting has the advantages of high economic benefit,zero discharge of solid waste and green environmental protection,which effectively solves the problem of polluted water resources and soil caused by the discharge of waste.(2)The high-value fused white corundum particles in the waste shell of investment casting were separated effectively by mechanical ball milling,and the high-value fused white corundum particles with the weight of 7～8%and the particle size of 109-270μm were obtained.(3)It is found that the remaining powder can be milled for 10-12h to obtain more than 90%of the powder with particle size less than 13 μm.the alumina silica ratio is adjusted to be 2.32 by adding bauxite.After mechanical granulation,it is sintered at 1550℃for 2～3h and the content of mullite is more than 83.25%.(4)TiO2 and CaO were added as spherical sintering aids.When 1%TiO2 was added alone,the sintering temperature was reduced to 1500℃ and kept warm for 2～3 h.The basic properties of ceramsite sand were as follows:the bulk density was 1.68g/cm3,the true density was 3.058g/cm3,the apparent porosity was 10.6%,and the crushing rate was 1.58%.When 7%CaO was added alone,the sintering temperature was reduced to 1375℃ and kept warm for 2-3 h,and the basic properties of ceramsite sand were as follows:the bulk density 1.71g/cm3,true density 2.834g/cm3,apparent porosity 6.03%,crushing rate 1.47%.At the same time,adding 1%TiO2+7%CaO as sintering aid,the sintering temperature can be reduced to 1340℃,the sintering holding time is 2～3h,adding 2.0%resin,and the cold core strength is 1.85MPa in 24h.(5)Artificial spherical ceramsite sand is applied to the surface sand of precision casting,and the 304 and 316 stainless steel castings are prepared by mold shell,which can meet the surface quality requirements of castings. |
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