Study On Preparation And Properties Of Water Soluble Fine Ceramic Cores For Casting Aluminum Alloys

With the rapid development of China’s auto and aerospace industries,the demand of market for aluminum alloy precision castings with complex internal cavities and holes is increased.The use of high-strength,high-precision,environmentally-friendly ceramic cores,and core-in-one castings have become the trend in the production of such aluminum alloy castings.However,the current ceramic cores for aluminum alloy castings have poor collapsibility that the core removal methods mainly through chemical corrosion and external forces,which often causing damage to the surface of precision aluminum castings.The water-soluble ceramic core has a good application prospect in the production of aluminum alloy because of its easy removal and cleaning.In this paper,325 mesh fused corundum powder was used as refractory aggregate,and NaCl,Na₂CO₃ and K₂CO₃ were used as binders.The blanks were formed by compression molding and injection molding respectively,and then sintered to prepare water-soluble ceramic cores.The forming method and bonding were studied.The effect of the agent,pore-forming agent,and sintering process on the core structure,mechanical properties,water disintegratability,and storage properties were verified.When the blank is formed by pressing and the amount of the single component binder is20%,the NaCl binder core can be completely collapsed after standing in room temperature water for 5 minutes,the water-soluble collapsibility reaches Class Ⅳ across the s standard in the paper,and the bending strength reached the peak that is 4.75MPa at the sintering temperature of 825℃.adding 1%200 mesh wood powder in the green compact,can increase the strength of the core after sintering,and maintain the water-soluble collapsibility of the core.The highest bending strength of Na₂CO₃ binder core is about 2 times higher than that of NaCl binder core.When the sintering temperature is lower than 850℃,the water disintegratability of core is higher than grade ⅡI.The highest bending strength of K₂CO₃ binder core is about 3times higher than that of NaCl binder core,and the water-soluble collapsibility is lower than grade Ⅱ.When the binder content of the two components is 15%,the bending strength of the NaCl-Na₂CO₃ binder core can reach 11.32 MPa when sintered at 725℃,and the water-soluble collapsibility is ⅡI grade.The NaCl-K₂CO₃ binder core,when K₂CO₃ is added in an amount of2%,is sintered at 775℃ and 825℃,has a flexural strength of 7.02MPa,a water-soluble collapsibility of Class ⅡI or higher,and when K₂CO₃ is added in an amount of 20%,When sintered at 750℃,the flexural strength reached 13.27 MPa,and the water-soluble collapsibility was grade I.After 1%200 mesh wood flour was added to the NaCl-K₂CO₃（1:4）-20%-750℃ binder core compact,the core collapse performance did not improve,and the flexural strength increased by 8%.After adding 3%200 mesh activated carbon powder,the bending strength decreased by 60%and the porosity increased by about 25%.In the single-component adhesive core,the order of the moisture absorption rate from small to large is a NaCl binder core,a Na₂CO₃ binder core,and a K₂CO₃ binder core.In the range of 15%to 20%,the amount of the two component cores added is in the range of 15%to20%.With the increase of the amount of binder added,the moisture absorption rate increases,and the moisture absorption rate of the primary relative core in the binder has an important influence.Adding Na₂CO₃ or K₂CO₃ two-component adhesive to NaCl reduces the moisture absorption rate of the core.When the core storage time is within 5 days,precipitation treatment can effectively prevent moisture absorption;when the storage time exceeds 5 days,the addition of wood powder has better anti-hygroscopic effect.When the addition amount of binder is 20%,the tensile strength of the NaCl binder core is only 1.32 MPa,which is lower than that of the press-molded sample,but the water-soluble collapsibility and compression The molded sample is equivalent.The manufacturing unit binder core round rods were sampled and placed in cast cast aluminum alloy castings.The dissolution test results showed that stirring can significantly improve the water-soluble disintegration efficiency of the core.NaCl-K₂CO₃ binder core prepared by injection molding sintering,when NaCl:K₂CO₃ is 1:4,addition amount is 20%,sintering temperature is 750℃,bending strength is 15.98 MPa,water disintegratability and compression molding sample quite,level Ⅰ.