LFC Aluminum Casting Process Research And Hole Defect Control

Because of excellent physical properties, aluminum alloy gets the favor ofthe automobile and aerospace fields. It is gradually replacing part of the iron andsteel, achieved“lightweight”purpose. And the lost foam casting is becoming anew method of aluminum alloy forming because of its process characteristics.However, aluminum alloy via LFC have some disadvantages, such as seriousporosity defects like pinhole and blowhole, low mechanical properties. Thesedisadvantages limit the development and application of aluminum alloy lostfoam casting technology. Therefore, aiming at low mechanical properties andserious porosity defects of aluminum alloy castings, the paper investigatesystematically the effects of various process factors on the hardness and porositydefects of aluminum alloy castings, and by optimizing the process parameters toachieve the purpose of improving hardness and reducing porosity defects.Firstly, by the orthogonal experiment, the paper investigate the effects ofpouring temperature, coating thickness, vacuum degree and pattern density onthe hardness of ZL102aluminum alloy via LFC, and obtain the best processparameters. Under the condition of best process parameters, the experimentsinvestigate the effects of different modifiers on the hardness of ZL102aluminumalloy. The results show that: in the condition of pouring temperature is760℃,coating thickness is0.3mm,vacuum degree is0.02MPa,pattern density is16kg/m3,the hardness of castings is best. The modification efficiency of sodiumsalt modifier is better, and the hardness of castings increases.Secondly, the morphology of porosity defects is investigated in the sectionand microstructure of sample. The effects and regulars of coating property,coating thickness, pouring temperature, vacuum degree, pattern density on theporosity defects of aluminum alloy lost foam casting are investigated separately.The results show that: the porosity defects of aluminum alloy casting viaLFC are serious. For the capability of lost foam aluminum alloy coating, theexcellent sorption of coating is beneficial to improve castings density. Thecastings density decreases with the coating thickness and pattern density increasing. To improve castings density，there should be a suitable pouringtemperature and vacuum degree.Finally, through orthogonal experimental, the paper observe the influenceof pattern density, pouring temperature, coating thickness and the vacuumdegree on the porosity defects of aluminum alloy lost foam casting, and obtainthe optimal process parameters. The castings defects appearing in someexperiments are analyzed and some corresponding control measures are putforward. The results show that: pouring temperature is the biggest influencefactor on the porosity defects of aluminum alloy castings, secondly is vacuumdegree，coating thickness and pattern density is least. Optimal conditions forexperiment: pattern density is16kg/m3,pouring temperature is760℃,coatingthickness is0.3mm, vacuum degree is0.02MPa. In the process of aluminumalloy lost foam casting, pinhole, sticky sand and short run defects occur easily.