Casting is the metal melting into that meet certain requirements and the liquid poured into the mold, the cooling and solidification, finishing after processing has a predetermined shape, size and properties of the casting process. Casting is the modern machinery manufacturing industry based on process.
Casting is the human grasp of the earlier one of hot metal processing technology, has a history of about 6000. China in about 1700 BC between 1000 before has entered the heyday of bronze casting, technology has reached a very high level. Chinese Shang Dynasty weighs 875 kg Si Mu Wu Fang Ding, the Warring States period, Ceng Houyi, disc, the transparent mirror, are ancient casting products on behalf of.
Early casting is mostly agricultural production, life, religion and other aspects of the tool or utensil, artistic strong color. The casting process with ceramic technology developed in parallel, greatly influenced by pottery.
China in 513 BC, cast out of the world's earliest found in written pieces of cast iron casting - Jin Ding, weighs about 270 kilograms. Europe in the eighth Century AD and also began producing iron castings. Cast iron castings, enlarges the application range. For example, in 15 ～ seventeenth Century, Germany, France and other countries successively laying a lot to the residents for drinking water cast iron pipe. Eighteenth Century after the industrial revolution, the steam machine, textile machine and railway industry is arisen, casting into industrial service in the new period, casting technology began to have great progress.
Enter twentieth Century, casting the development rate is very rapid, it is one of important factors is the product of advances in technology, requirements for casting various mechanical physical properties better, while still having good mechanical processing performance; another reason is the machinery industry and other industries such as chemical industry, instrument development, to casting industry has created favorable material condition. As the development of detection means, to ensure improve casting quality and stability, and to the casting theory development has provided the conditions; electron microscope of the invention, help people into metal micro world, exploration of metal crystal mystery, study of metal solidification theory, guiding casting production.
In this period of time to develop a large number of superior performance, a variety of new metal materials such as casting, ductile cast iron, malleable cast iron welding of ultra low carbon stainless steel, copper, aluminum, silicon, aluminum and magnesium alloy, titanium, nickel base alloy, and the invention of the grey iron inoculation treatment new the casting process, the more widely adaptability.
After 50 time, appeared in wet sand high pressure molding, the chemical hardening sand molding and core making, negative modeling and other special casting, shot blasting and other new technology, make the castings have high shape, dimensional accuracy and good surface finish, foundry working conditions and environmental health is also greatly improved.
Since twentieth Century, significant progress in foundry industry, gray cast iron, inoculation treatment and chemical hardening sand molding two this new process has a special significance. The two invention, break continue thousands of years of traditional methods, to casting technology has opened up a new field, to improve the competition ability of castings produced major effect.
Casting by the general modelling approach to classification, customarily divided into general and special casting sand casting. Sand casting including wet sand, dry sand, chemical hardening sand three class. Special casting by modeling of the different materials, and can be divided into two categories: one category with natural mineral sand as main materials, such as casting, shell mold casting, pressure casting, clay mold casting, casting, ceramic mold casting; a metal as the main mold material, such as metal type casting, centrifugal casting, continuous casting, pressure casting, low pressure casting.
Casting process can be divided into three basic parts, namely the casting metal preparation, mold preparation and casting processing. Casting metal refers to the casting production of cast metal material, it is a metallic element as a main component, and join the other metal or metalloid elements and the composition of the alloy, traditionally known as cast alloy, cast iron, cast steel and main nonferrous cast alloys.
Metal melting is not merely a melting, also including smelting process, so that the metal poured into the mold, temperature, chemical composition and purity are consistent with the expected requirements. Therefore, in the smelting process to be performed in order to control the quality for the purpose of testing, liquid metal at specified metrics before allowing the casting. Sometimes, in order to meet the higher requirements, the molten metal in the furnace and the furnace processing, such as desulfurization, vacuum degassing, refining, pregnant or modification. Smelting metal commonly used equipment cupola furnace, electric arc furnace, induction furnace, resistance furnace, such as furnace.
Different casting methods have different mold preparation content. The most widely used sand casting for example, mold preparation includes modeling material preparation and moulding core making two items of work. Sand casting is used to modeling the core making all kinds of raw materials, such as foundry sand, sand binder and other materials, as well as the mixture of sand, sand, paint and other known collectively as the molding material molding material preparation task is in accordance with the casting requirements, metal properties, select the appropriate raw sand, a binder and accessories, then according to the certain proportion mix them into a certain properties of the sand and core sand. Commonly used sand mixing device has a sand roller mill, counterflow type sand mixing machine and the blade groove type sand mixing machine. The latter is designed for mixed chemical self-hardening sand design, continuous mixing, fast speed.
Modelling core is based on the casting process requirement, in determining a good modeling method, ready to molding materials based on. Accuracy of casting and the whole production process of economic effects, depending on the procedure. In many modern casting workshop, molding core are realized mechanization or automation. Commonly used sand molding core equipment is high, low pressure molding machine, polishing, sanding machine, flaskless shoot squeeze molding machine, core shooting machine, hot and cold core box machine.
Casting casting casting from cooling after removal, a gate and riser, metal burr scull, sand casting casting also adhered sand, therefore must be cleaned process. The working device has shot blasting machine, gate cutting machine. Sand casting shakeout is labor conditions of poor working procedure, so the choice modeling method, should be taken into consideration for the shakeout to create convenient conditions. Some castings due to special requirements, but also the process of castings, heat treatment, such as plastic, anti-rust treatment, rough.
The casting is economical of blank forming method, for the shape of complex parts can show its economy. Such as automobile engine cylinder block and cylinder head, the ship propeller and exquisite works of art. Some hard cutting parts, such as gas turbine Ni-base alloy parts without casting method to form.
In addition, the cast part size and weight of the adapted to a wide range of metal type, almost without limit; parts in general mechanical performance at the same time, also has wear resistance, corrosion resistance, shock absorption performance, other metal forming methods such as forging, rolling, welding, punching and other do not. Therefore in machine manufacturing casting method for producing components, in the number and tonnage is still the most.
Casting production is often the material to be used with a variety of metal, plastic, wood, coke, gas and liquid fuel, modeling materials. The equipment required for a variety of metal smelting furnace, a sand mixing with various mixer, a molding core making use of a variety of molding machine, core making machine, cleaning out the casting shakeout machine, shot blasting machine. Also available for special casting machines and equipment as well as many transportation and material treatment equipment.
Casting production and other processes of different features, mainly adaptability, needed materials and equipment, environmental pollution. Foundry production will produce dust, harmful gas and noise pollution to the environment, compared to other machinery manufacturing technology to more serious, need to take measures to control.
Casting product development trend is the requirement of castings have better performance, higher precision, less volume and more smooth surface. In addition, the requirement of saving energy and society to restore the natural environment more and more is also high. In order to meet these requirements, the new cast alloy will be developed, smelting new technology and new equipment will occur.
Casting production of mechanization degree of automation in the rising at the same time, will be more to the flexible production development, to expand on the different batches and production of many varieties of adaptability. Save energy and raw materials of new technology will get preferential development, produce less or no pollution new technology new equipment will be the first attention. Quality control technology in the process of detection and non-destructive testing, stress testing, will have new development.
Foundry workers in electronic technology and testing means progress condition, will be on metal solidification and compaction theory for deeper exploration, research to improve casting properties and internal quality effective way. Robotic and computer in foundry production and management in the field of application, will be increasingly extensive
