For iron castings, surface wrinkles are the most common defect. Because free carbon does not easily penetrate into the surface of the casting, but is deposited on the surface of precision casting and molds. Sanzhuji found through observation and statistics of the casting process of cooperative customers that ES type and molten metal will be decomposed into gaseous, liquid and P-mode solid components during casting. The gaseous state is mainly composed of CO, CO: 2, H, methane, styrene and its derivatives; the liquid is mainly composed of liquid hydrocarbon groups such as benzene, toluene, styrene and glassy polystyrene; the solid state is mainly formed by the pyrolysis of polystyrene The bright carbon and coke residue group. The following is the combination of sanzhuji''''s characteristics of investment sand casting and the experience summarized by the foundry. I hope it will be helpful to friends who use investment sand casting.
The residual solid carbon between the liquid metal surface and the mold forms a wrinkle defect. Some high temperature carbon accumulates too much locally, causing the casting surface to be rough, which is called wrinkle defect.The bright carbon in the phase forms a melt adhesive with the gas phase and the liquid phase, and the liquid phase will also decompose at a certain rate to form the secondary gas phase and solid phase.Dimers, trimers and repolymers in liquids often produce a viscous bituminous liquid. The liquid decomposition remains on the inside of the coating, part of it is absorbed by the coating, and part of the a-corrugated wrinkle) b) drops into a thin film between the casting and the coating, and this part of the film forms fine flake or dander-like crystalline residual carbon in the reduced (O) C atmosphere, that is, the wrinkled skin is formed.Some of them gather on the surface of castings and show irregular coarse particles, forming droplet-like wrinkles and slag-like wrinkles, that is, in the process of pouring, liquid metal is involved in non-gasified polystyrene solid products. after cooling and solidification in precision casting, these soot-like carbon ash are mixed on the surface of castings to form irregular slag wrinkle defects.
In the part of liquid metal flow, the residual liquid phase due to surface tension) cold end e) cold insulation wrinkle d) the slag-like wrinkle shrinks to form wrinkle defect ESP softens and shrinks during the wrinkle defect process of producing pyrolysis products or tar-like residue, which thickens the diaphragm of the thin honeycomb tissue in the original foam plastic by thousands of times,destroys the foam-like tissue and forms a very thick hard film. The liquid or hard film polystyrene residue floats on the liquid metal surface or adheres to the mold wall in a glassy state. Therefore, under the boundary J: wrinkle defects can be divided into corrugated wrinkle, tumor-like wrinkle, cold barrier wrinkle and slag wrinkle according to their appearance. Generally, the depth of corrugated wrinkle is shallow, and the latter three are deeper. The depth is 0.1.1mm, and the serious one is about 10mm. The surface of this kind of precision casting defects is often covered with light and shiny carbon sheets, and the depressions of the defects are filled with soot and carbon, which are surface carbon defects. The wrinkle defect often occurs when the liquid ESP, from the metal is too late to gasify in the process of hot metal condensation, which causes shrinkage because the surface tension is different from that of the molten iron. After the liquid metal is cooled and solidified, it forms a non-liquid and finally flows to the part or the "cold end" of the liquid flow.Continuous corrugated wrinkle defects and cold insulation wrinkles.
The pulsating flow process produces wrinkle defects ES liquid metal P and rapid gasification after contact, producing a large amount of gas.In the early stages of pouring.The metal head is large, and the liquid metal filling is smooth.But with the precision casting.Due to the certain air permeability of the coating and the mold, the pressure at the air gap increases gradually, so it is bound to reach a balance between the metal head and the air gap at a certain moment. The formation mechanism of wrinkle defect is a complex process, which involves the heating of the model.
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Qingdao Sanzhuji Equipment Manufacturing Co., Ltd. specializes in the production of sand reclamation equipment,foundry machines,Sand casting equipment,GS high efficiency rotary mixer,no-bake resin sand mixer,Jolt squeeze molding machine/Jolt-squeezing moulding machines,Multi- Piston Moulding Machine/Hydraulic multi-piston moulding machine,foundry molding machine,flaskless moulding machine,shot blasting machine,dust collector,according to the amount of old sand recovered Carry out plan customization, and provide sand reclamation equipment installation, commissioning, and training. Welcome guests to visit the factory.
