Research On The Filling Capacity And Casting Process Of Supper Alloy Thin-Walled Casting

The filling capacity and solidification structure control of super alloythin-walled casting has been studied through the combination of differentexperimental methods and numerical simulation techniques in thisdissertation. With synchrotron radiation X-ray imaging technology thedendrite growth and evolution of Al-20%Cu model alloy thin-walledfeatures were observed in situ and the dendrite formation mechanism ofthin-walled castings was analyzed. And through the numerical simulationand experimental validation of K4169alloy thin-walled castingsbottom-gate investment casting process, the principle of filling andbottom-gate investment casting solidification under gravity was studied indetail, an innovative method and apparatus of adjust pressure castingapplied for super alloy thin-walled castings was put forward. The mainresults as follows:Firstly, the dendrite evolution of Al-20%Cu model alloy thin-walledfeatures were observed in situ by synchrotron radiation X-ray imagingtechnique. The dendrite growth of2mm and5mm thickness thin-walledsamples was characterized on the whole in that the first nucleationappeared on both sides, and then the dendrites formed and grow graduallytoward the center portion. The mobile trajectory of eutectic forefront wastracked and found when the plate thickness(2mm) was thinner, the dendritenetwork formation time and solidification time were faster and the eutecticforefront moved forward as massive structure; When the platethickness(5mm) was thicker, the dendrite network formation time andsolidification time were slower and the eutectic forefront moved forward as the concave curves.Secondly, through numerical simulation method the impact of castingprocess parameters on the melt filling flow and solidification principle ofK4169alloy melt in the bottom-gate investment casting process werestudied. The results showed that in a certain range, pouring temperature,the pouring flow and shell temperature is linearly increasing relationshipwith K4169thin-walled castings pouring flow rate and solidificationproperty. And when the casting speed was respectively2kg/s,3kg/s and thepouring temperature is1550℃or upon, the thin-walled castings to beable to fill the mold completely and feed solidification well. At the sametime, we should avoid less than1.5mm thin-walled castings in the designof large complex thin-walled castings.Then, through the bottom-gate investment casting experiments underthe gravity conditions, the results showed that the experimental resultswere generally consistent with the numerical simulation results about theimpact of pouring temperature and mold shell temperature on the fillingrate and the solidification structure of the thin-walled castings. Thesolidification structure the different thickness thin-walled castings werecomparative analyzed, it showed that the arrangement and phase ofdendrites of thin-walled castings were more uniform and dendrites grew byboth sides to the center, which verifies the observation of synchrotronradiation imaging.At last, the numerical simulation of super alloy thin-walled castingsfilling and solidification process under adjusted pressure casting(APC)showed that K4169thin-walled castings alloy melt filled smoothly, theCasting Solidification order was more regular because of larger feedingchannel is conducive to the feeding of the thin-walled castings. So the APCare more suitable for the filling and solidification well of super alloythin-walled casting. Besides, according to the features ofAPC, the impact ofhold pressure to thin-walled castings feeding can be verified.