Performance Analysis Of Raw Material Of Lost Foam And Its Application Study On Ductile Iron Casting

Foam patterns are pre-expanded and formed from beads of polymer materials such asEPS, STMMA. Foam beads of higher performance is very important to ductile iron lostfoam casting.In this paper, with methods of thermal gravimetric analysis, differential thermalanalysis, metallographic analysis,scanning electron microscope and pouring comparativeexperiments, research and evaluation of performance of foam beads are made, includingChinese STMMA material, Japanese STMMA material. From differential thermal analysis,Japanese STMMA is softening and easier deformed compared with Chinese STMMA; thedecomposition temperature of Japanese STMMA is higher than the Chinese STMMA of27.5℃, so Chinese STMMA cracks more easily with releasing heat. Pouring test showedthat, compared to EPS, Japanese STMMA and Chinese STMMA can significantly reducethe carbon defects of ductile iron casting. Chinese STMMA is more difficult topre-expand and form, and its price is lower, so it is suitable for the production of largeparts; Japanese STMMA is easy to pre-expand and form, and its price is very high, so it issuitable for the production of small pieces.In this paper, the use of ordinary EPS, Japanese STMMA and Chinese STMMA inthe application of ductile iron lost foam casting in China is analyzed and summarized.There are carbon inclusion defects in the production of fire hydrants and diaphragm valvewith ordinary EPS, so it is need to improve the pouring temperature, improve the feedsystem and change raw material to STMMA. For complex vehicle differential case,reducer shell, There are wrinkled skin and carbon inclusion defects with ordinary EPSeasy to produce wrinkled skin.The carbon defects of vehicle differential case,reducershell can be significantly reduced with Chinese STMMA, one-piece casting process and1580℃pouring temperature.There are carbon inclusion defects in the production of highelongation ductile iron QT400-18 of automotive bracket with Chinese STMMA, eventhough making ductile iron matrix of more than 95% ferrite. Carbon defects leaded to lowelongation of test bars. So, rational process is needed to be explored, such as raising thecast pouring temperature, using a smooth bottom gating system and slag riser to eliminatethe carbon inclusion defects.