Research Of Wear-Resistant Parts Of Impeller-head That Based On Composite Shell Of Investment Casting And Related Equipments

Impeller-head is the key component to realize the shot-blast cleaning and strengtheningtechnology, which use the kinetic energy of high-speed to achieve the purpose of cleaning andstrengthening parts. In this process, points pills round and blade are sports strong friction wearparts and they get the most serious failure, especially for the blade, even if the surface hassmall defects such as a blow hole or sand hole, the material will generate cracks in this placeand get failure rapidly. These wear-resistant parts were made through common clay sandcasting by using high chromium cast iron. But, because of the clay sand mold cavity does notgive the average compactness, the casting parts often easily get defects, and their sizeaccuracy is also not so good. Thus, improving the surface quality, size accuracy and servicelife of these wear parts become widespread concern.In view of this situation, this article put forward composite shell by using the investmentcasting method to make the wear parts of impeller-head, and made much research work on thecharacteristics of composite shell of precision investment casting technology and relatedequipments. From the selection of high chromium cast iron material to process parameters ofthe investment casting, as well as the conditions of related equipments and problems thatshould be noted in actual production.Technique of the composite shell using colloidal silica and sodium silicate, the surfaceand transition layer using the silicon sol shell process, and the back layer using sodiumsilicate shell process. Quartz sand and powder guarantee high surface quality of shell cavity,and mullite keep shells have enough high temperature strength and good thermal stability aswell as thermal expansion. Experiments have proved that this composite shell precisioninvestment casting process is better than that only using colloidal silica. It reducesmanufacturing cost, shortens the cycle and gets equivalent quality standard at the same time.This method is suitable to produce wear parts of impeller-head.The using of some main equipment improves the efficiency of wear parts production, sothis article also discusses some related equipment so as to continue reduce the cost. Thisprocess has already been used in Shandong Kaitai Shot-blasting Machinery CO, LTD. Itsproducts have bright and clean surface, standard quality and hardness, which meet the requirements of operation. Production practice have showed that using this process couldchange casting position of liquid metal and the way of filling, so the solidification order of theliquid metal changes at the same time, in this way, the quality of these wear-resistant partsalso improved. The service life of these wear parts have increased from150~230hours toabout600hours.