With the progress of science and technology and the vigorous development of foundry industry, different casting methods have different casting preparation contents . Taking the most widely used sand casting as an example, the preparation of casting mould includes two major tasks: preparation of moulding materials, moulding and core-making. Various raw materials used for moulding and coring in sand casting, such as casting raw sand, sand binder and other auxiliary materials, as well as moulding sand, core sand and coating made from them, are collectively called moulding materials. The task of preparing moulding materials is to select appropriate raw sand, binder and auxiliary materials according to the requirements of castings and the properties of metals, and then mix them into tools in a certain proportion. Molding sand and core sand with certain properties. Commonly used sand mixing equipment are grinding wheel mixer, counter-current mixer and continuous mixer. The latter is specially designed for mixing chemical self-hardening sand with continuous mixing and high mixing speed.
Modeling and core-making are based on the requirements of casting technology and the determination of moulding methods and preparation of moulding materials. The accuracy of castings and the economic effect of the whole production process mainly depend on this process. In many modern foundry workshops, moulding and coremaking have been mechanized or automated. Commonly used sand moulding core-making equipment are high, medium and low pressure moulding machine, air-punching moulding machine, box-less injection moulding machine, cold box core-making machine and hot box core-making machine, film-coated sand core-making machine, etc.
When the castings are taken out of the cooling mould, the castings with gate, riser, metal burr and slit still adhere to sand, so the cleaning process must be carried out. The equipment for this kind of work includes polisher, shot blasting machine, gate riser cutting machine, etc. Sand dropping cleaning of sand casting is a process with poor working conditions, so when choosing the moulding method, we should try our best to create convenient conditions for sand dropping cleaning. Because of special requirements, some castings have to undergo post-processing, such as heat treatment, shaping, rust-proof treatment, rough processing and so on.
Casting technology can be divided into three basic parts, namely, casting metal, casting preparation and casting treatment. Foundry metal refers to the metal material used in casting production. It is an alloy composed of one kind of metal element and other metal or non-metal elements. It is customarily called casting alloy, mainly cast iron, cast steel and cast non-ferrous alloy.
When the castings are removed from the cooling mould, there are gate, riser and metal burr slits. The sand casting also adheres to sand, so it must be cleaned up. The equipments for this kind of work are shot blasting machine, gate riser cutting machine, etc. Sand dropping cleaning of sand casting is a process with poor working conditions, so when choosing the moulding method, we should try our best to create convenient conditions for sand dropping cleaning. Because of special requirements, some castings have to undergo post-processing, such as heat treatment, shaping, rust-proof treatment, rough processing and so on.
Casting is a more economical method of blank forming, which can show more economy for parts with complex shapes. Such as automobile engine cylinder block and cylinder head, marine propeller and exquisite works of art. Some parts that are difficult to cut, such as nickel-based alloy parts of gas turbine, can not be formed without casting.
In addition, the size and weight of casting parts have a wide range of adaptability, and the types of metals are almost unlimited; while the parts have general mechanical properties, they also have comprehensive properties such as wear resistance, corrosion resistance and shock absorption, which can not be achieved by other metal forming methods such as forging, rolling, welding and punching. Therefore, the number and tonnage of the blank parts produced by casting method are still the largest in the machine manufacturing industry.
The materials often used in foundry production are various metals, coke, wood, plastics, gas and liquid fuels, moulding materials, etc. The required equipment includes various furnaces for smelting metals, various sand mixers for sand mixing, various moulding machines for core moulding, core moulding machines, sand blasting machines for cleaning castings, shot blasting machines, etc. There are also machines and equipment for special foundry, as well as many transportation and material handling equipment.
Foundry production has different characteristics from other processes, such as wide adaptability, more materials and equipment needed, and environmental pollution. Foundry production will produce dust, harmful gases and noise pollution to the environment, which is more serious than other mechanical manufacturing processes. Measures need to be taken to control the pollution.
The development trend of casting products is to require better comprehensive performance, higher precision, less margin and cleaner surface. In addition, the requirement of energy saving and the voice of society to restore the natural environment are also increasing. To meet these requirements, new casting alloys will be developed and new smelting processes and equipment will appear accordingly.
With the continuous improvement of mechanization automation in foundry production, more flexible production will be developed in order to expand the adaptability to different batches and varieties of production. New technologies that save energy and raw materials will be given priority, and new processes and equipment that produce little or no pollution will be given priority. Quality control technology will have new development in the detection and non-destructive testing of each process and stress measurement.
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