EPC foundry processing
casting machinery
EPC foundry process
lost foam casting processing
EPC is a kind of foundry techniques nearly without machining allowance and can mold with precision, which is easy to achieve the purpose of cleanness, mass production and provides abundant freedom to design complex structures of castings. The mobile phase front of molten metal is the product of thermolysis evanescent mode (gas or liquid), which can react with molten metal and influence the quality of molten metal. If in the process of molding, the thermolysis products can not be removed, it will cause defects, such as air hole, cockle and carbonization, etc. so the technicians must grasp the principle of EPC casting mould, design casting system correctly and make rational technique scheme. Though cost of integrating casting is very low, it is better to mass produce in order to gain optimal economical benefit.
1.Process and techniques:
The pouring process of EPC dry sand casting is the process which molten metal replaces the mould. Pouring channel must be full of molten steel. If it is not full, because of intensity of coating is limited, it is very easy to cause sand mixture sink and entering air which can arise defects of castings. As to common castings, workers must control upward movement of molten metal, that is bottom pouring , which is favorable to steadily molding and can avoid making a very big cavum. As portative force and gravity of subpressure casting, molding speed of molten steel is very fast and the vertical casting gate is not suitable to big. The molten steel of EPC is very different from that of traditional sand molding casting: the traditional sand casting adopts opentop, while EPC adopts subpressure close type and the part below runner cup must be close. The reason is that avoid air enter pouring channel. During pouring, runner cup must keep full. Molten steel enters mould, begins to liquefy and burn, then gasifies and disappears. In front of molten steel , a short distance forms temporary cavum. In order to avoid forming cavum when molten steel radiates and melts other casting moulds, so speed of molding of molten steel must be correspondent with that of disappearance of foam mould. The place of vertical casting (ingate) is the lowest of whole box of casting, usually section of vertical casting is 40 mm×40mm. in order to prevent casting mould transfiguring and melting when the distance between castings and pouring channel is too near, pouring channel must a little faraway from castings. Dimension of cross gate section is 50 mm×50mm. When pouring, there must be runner cup. The diameter of back cut of runner channel must longer than 200mm, section surface is equal to vertical casting, height is about 300mm. the main function of runner cup is amassing molten steel in order to make vertical casting full instantaneously and molten steel quickly run downward steadily. Pay attention to adjust and control subpressure vacuity fluctuating within a limit when pouring. After pouring keep 10 or 20 minutes under a certain subpressure condition, subpressure stops, molten steel is condensed then took out.
2. Announcements:
Workers should pour molten steel steadily and quickly. Instantaneously molten steel fulfills runner cup and run down fast and continuously. Keep runner cup full all the time. If it is not continuous casting, it may absorb air and has the defects such as sand collapse or more airholes that we may have a scrap products. As portative force of subpressure vacuum, heat of molten steel in sand box will lose, and that foam mould gasifies also need heat, so temperature of molten steel must be 30-100°C higher than that of traditional sand casting.