The traditional foundry coating only acts as a barrier and isolation between the casting and the mold to achieve the purpose of anti-sticking sand, but ordinary casting coatings are likely to cause sticky sand on the casting due to poor adhesion, low strength, poor fire resistance, and large gas evolution at high temperatures , Blisters, pores, carbon slag and other defects. Casting sticks to sand because the coating does not effectively block and isolate it, or the coating reacts chemically with the high-temperature metal liquid.
1. Poor paint adhesion: the paint will peel off when the sand is filled and shaken, causing the casting to stick to sand
2. The coating expansion coefficient is large: when the coating is in contact with high-temperature metal liquid, the thermal volume expansion of the coating separates from the mold, which causes the casting to stick to the sand.
3. The high-temperature liquid metal is oxidized and chemically reacts with the coating and the mold to form metal oxides, both for coating and sand Extremely strong adhesion, can firmly adhere the molding sand to the surface of the casting to form a series of low melting point compounds (in thick walls and corners of the casting, there are more low melting points, and the sand layer is more behind), causing the casting to stick Sand, although sometimes there is no sticky sand, but a layer of paint that is difficult to remove on the surface of the casting, and sticky dust is produced.
Causes of casting blisters:
1. There is sand falling in the mold
2. The paint has low strength, poor fire resistance, and cannot withstand the erosion of high temperature liquid metal, and the molding sand is drawn into the casting. There are many reasons for the porosity of castings. The most common reason is that there are more substances with large gas emission in the mold, the gas is fast, the paint or sand has poor air permeability, and the gas is not removed in time. The new casting coating developed is improved and adjusted on the basis of the traditional casting coating. It does not crack or fall off at high temperature, and has high strength. It can effectively prevent high-temperature liquid metal from oxidizing, and it is not chemically chemical in contact with mold and high-temperature liquid metal. reaction. At the same time, it can prevent the production of nitrogen, sulfur, carbon and other gases. So as to completely solve the casting sand sticking, casting sand holes, rough castings, casting pores, casting inclusions (slag), nodular iron variation, cast steel vulcanization cracks, carburization defects, etc.
The castings produced by the shell casting method have high dimensional accuracy and low surface roughness, which can save a lot of metal cutting consumption and machining man-hours, and the changes in the amount of sand and the change in molding methods have created conditions for the mechanization and automation of casting production, which are especially suitable It is suitable for producing castings with larger batches and higher precision requirements.
The process difference between shell-shaped stainless steel casting and cast iron using hot box coated sand process is that the process difference between shell-shaped stainless steel casting and cast iron is that the content of raw sand is different, and the content of SiO2 in cast iron is 90%. Cast steel is more than 95%, and the precision of shell casting is lower than that of wax die casting.
Qingdao Sanzhuji Equipment Manufacturing Co., Ltd. specializes in the production of Green Sand Molding Line,Self-hardening sand molding line,foundry machines,Sand molding machine,Sand casting equipment,sand mixer,GS high efficiency rotary mixer,Resin sand mixer,no-bake resin sand mixer,Jolt squeeze molding machine/Jolt-squeezing moulding machines,Multi- Piston Moulding Machine/Hydraulic multi-piston moulding machine,sand casting molding machine,sand reclamation equipment，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.
