The process of taking the precision casting out of the mold, removing the excess parts outside the body, and polishing the internal and external surfaces of the casting.
Core removal and surface cleaning:
It can be divided into dry process and wet process. Dry cleaning is the use of mechanical equipment to clean castings. It has the advantages of simple equipment, high production efficiency, great adaptability to different types of castings and effective surface cleaning as well as core removal. The disadvantage is that the dust is flying, the noise is large and the environment is polluted. There is no dust in wet cleaning, but the surface of casting is easy to rust because of water as medium. In the process of operation, a large amount of sewage and cement sand are produced, which brings problems such as sand and water regeneration and sludge treatment.
Common dry and wet cleaning methods in production include:
① Drum cleaning. The casting and Star iron are put into the circular drum together. When the drum rotates, the internal and external sand of the casting is removed by the impact and friction between the casting, Star iron and waste sand, the surface of the casting is polished, and the flash burr can also be partially removed. This kind of equipment is suitable for cleaning small and medium-sized castings with simple shape and thick wall.
② Shot blasting. Use the impact force of high-speed moving steel shot, iron shot and abrasive flow to remove the core, stick sand and polish the casting surface. In addition, the commonly used shot blasting equipment includes shot blasting table and shot blasting room. The shot blasting machines used for continuous production include chain plate shot blasting roller, continuous shot blasting table, hanging continuous production shot blasting room, etc. The operation and maintenance cost of this kind of equipment is high.
③ Hydroblasting. The high-pressure water is injected into the treated casting from the nozzle of the spray gun through the pipeline, and the core and the sand sticking of the casting are removed by the kinetic energy and scouring effect of the water flow. Hydraulic sand cleaning is usually equipped with an open cleaning chamber composed of section steel and steel plate. A rotary table is set at the bottom, and the spray gun is installed on the side wall, which can move up and down and rotate, so that the high-pressure water can shoot to any part except the bottom of the casting. Sometimes, in order to improve the efficiency of removing the sand sticking on the surface of the precision casting, quartz sand and other abrasives are introduced into the proper position of the spray gun to obtain high-speed water sand flow. This method is generally called water sand cleaning.
④ Water blasting and sand cleaning. After casting, when the casting is cooled to the specified temperature, it is boxed and immediately immersed in the pool. The water penetrates into the mold through all the cracks and vaporizes and explodes rapidly in contact with the high-temperature metal. The shock wave can basically remove the sand adhered inside and outside the casting. With the advantages of short operation time and high efficiency, water blasting is widely used in steel casting workshop in China. It is generally used to process steel castings with simple shapes with carbon content less than 0.35%.