The most used materials in casting technology. 【 Sand casting technology takes sand as profile, and sands with different compositions can be subdivided into wet sand casting technology and dry sand casting technology, etc., but not all sands can be used for casting. The advantage is that the cost is lower, because the sand used in the mold can be reused; The disadvantage is that the mold is time-consuming, and the mold itself cannot be reused, and the finished product can only be obtained after it is destroyed. Die-casting method uses metal with higher melting point than raw materials to make molds. Among them, it is subdivided into gravity casting, low pressure casting and high pressure casting. Limited by the melting point of the mold, the metal that can be cast is also limited. Investment casting (lost wax casting) This method can be external film casting and solid casting. First, the article to be cast is copied with wax, then it is immersed in a pot filled with ceramics and dried, so that the wax copy is covered with a ceramic outer film, and the above steps are repeated until the outer film is enough to support the casting process (about 1/4 inches to 1/8 inches), then the wax in the mold is melted and the mold is taken out. After that, the mold needs to be heated several times to enhance the hardness before casting. This method has good accuracy and can be used for casting high melting point metals (such as titanium). However, because ceramics are expensive, they need to be heated many times, and the production is complicated and the cost is quite expensive. Taking sand casting, which is the most widely used, as an example, mold preparation includes two major tasks: preparation of molding materials, modeling and core making. All kinds of raw materials used for modeling and core-making in sand casting, such as casting raw sand, molding sand binder and other auxiliary materials, as well as molding sand, core sand and coatings prepared from them, are collectively called modeling materials. The task of preparing molding materials is to select suitable raw sand, binder and auxiliary materials according to the requirements of castings and the properties of metals, and then mix them into molding sand and core sand with certain properties according to a certain proportion. Commonly used sand mixing equipment includes drum mixer, counter-current mixer and continuous mixer. The latter is specially designed for mixed chemical self-hardening sand, with continuous stirring and fast sand mixing speed. On the basis of determining the modeling method and preparing modeling materials, modeling and core-making are carried out according to the casting process requirements. The precision of castings and the economic effect of the whole production process mainly depend on this process. In many modern foundry workshops, modeling and core-making have been mechanized or automated. Commonly used sand mold core-making equipment includes high, medium and low pressure molding machines, air impact molding machines, boxless injection molding machines, cold core box core-making machines, hot core box core-making machines, coated sand core-making machines and so on. After the casting is taken out of the pouring cooling mold, there are gates, risers, metal burrs and joints, and sand is still attached to the casting cast by sand mold, which must be cleaned. The equipment for this kind of work includes polishing machine, shot blasting machine, pouring and riser cutting machine, etc. Sand removal and cleaning of sand castings is a process with harsh working conditions, so when choosing the molding method, we should try our best to create convenient conditions for sand removal and cleaning. Due to special requirements, some castings need post-treatment, such as heat treatment, shaping, rust prevention, rough machining and so on. The casting process can be divided into three basic parts, namely, casting metal preparation, mold preparation and casting treatment. Casting metal refers to the metal material used to pour castings in casting production. It is an alloy with a metallic element as the main component and other metallic or nonmetallic elements. Traditionally called cast alloy, it mainly includes cast iron, cast steel and cast nonferrous alloy. After the casting is taken out of the pouring cooling mold, there are gates, risers and metal burrs, and sand is still attached to the casting cast by sand mold, which must be cleaned up. The equipment for this kind of work includes shot blasting machine, gate and riser cutting machine, etc. Sand removal and cleaning of sand castings is a process with harsh working conditions, so when choosing the molding method, we should try our best to create convenient conditions for sand removal and cleaning. Due to special requirements, some castings need post-treatment, such as heat treatment, shaping, rust prevention, rough machining and so on. Casting is an economical blank forming method, which can show its economy for parts with complex shapes. Such as cylinder block and cylinder head of automobile engine, propeller of ship and exquisite works of art. Some difficult-to-machine parts, such as nickel-based alloy parts of gas turbines, cannot be molded without casting. In addition, the size and weight of castings are widely applicable, and the types of metals are almost unlimited; Parts not only have general mechanical properties, but also have comprehensive properties such as wear resistance, corrosion resistance and shock absorption, which cannot be achieved by forging, rolling, welding, stamping and other metal forming methods. Therefore, the number and tonnage of blank parts produced by casting in machinery manufacturing industry are still the largest. The materials often used in casting production are various metals, coke, wood, plastics, gas and liquid fuels, modeling materials and so on. The required equipment includes various furnaces for smelting metals, sand mixers for mixing sand, molding machines for making cores, core-making machines, sand mixers for cleaning castings and shot blasting machines. There are also machines and equipment for special casting and many transportation and material handling equipment. Casting production is different from other processes, such as wide adaptability, many materials and equipment, and great environmental pollution. Foundry production will produce dust, harmful gas and noise pollution to the environment, which is more serious than other mechanical manufacturing processes and needs to be controlled by measures. The development trend of casting products is to require better comprehensive performance, higher precision, less allowance and smoother surface. In addition, the demand for energy conservation and the call for social restoration of the natural environment are getting higher and higher. In order to meet these requirements, new casting alloys will be developed, and new smelting processes and new equipment will also appear accordingly. With the continuous improvement of mechanization and automation of foundry production, more flexible production will be developed to expand the adaptability to different batches and varieties of production. Give priority to the development of new technologies that save energy and raw materials, and give priority to the development of new technologies and equipment that are less polluting or pollution-free. Quality control technology will make new progress in detection, nondestructive testing and stress determination of each process.