Casting is a metal thermal processing technology that has been mastered by humans for a long time. It has a history of about 6,000 years. China has entered the heyday of bronze castings between about 1700 and 1000 BC, and the process has reached a fairly high level. The Shang dynasty of China’s Shang dynasty, weighing 875 kilograms, was founded by Zeng Houyi, the Zeng Houyi of the Warring States period, and the translucent mirror of the Western Han Dynasty. Most of the early castings were tools or tools for agricultural production, religion, and life, and the art was strong. The casting process at that time was developed in parallel with the ceramics process and was greatly influenced by pottery.
In 513 BC, China cast the world's first cast iron piece in the world, which was about 270 kilograms. Europe also began producing cast iron parts around the eighth century. The emergence of cast iron parts has expanded the range of applications for castings. For example, in the 15th and 17th centuries, Germany, France and other countries have laid a number of cast iron pipes that supply drinking water to residents. After the industrial revolution of the 18th century, industries such as steam engines, textile machines and railways rose, castings entered a new era of service for large industries, and casting technology began to develop.
In the 20th century, the development speed of casting is very fast. One of the important factors is the advancement of product technology, which requires various mechanical and physical properties of castings to be better, while still having good mechanical processing performance. Another reason is the mechanical industry itself and others. The development of industries such as chemicals and instruments has created favorable material conditions for the foundry industry. Such as the development of testing methods, to ensure the improvement and stability of casting quality, and to provide conditions for the development of casting theory; the invention of electron microscopy, etc., to help people penetrate into the microscopic world of metal, explore the mystery of metal crystallization, study the theory of metal solidification To guide casting production.
During this period, a large number of new cast metal materials with superior performance and rich variety, such as ductile iron, weldable malleable cast iron, ultra-low carbon stainless steel, aluminum-copper, aluminum-silicon, aluminum-magnesium alloy, titanium-based, nickel-based alloy, etc. And invented a new process for the inoculation of gray cast iron, making the casting more adaptable.
After the 1950s, there were new technologies such as wet sand high pressure molding, chemical hardening sand molding and core making, negative pressure molding and other special casting and shot blasting, which made the castings have high shape, dimensional accuracy and good surface finish. The working conditions and environmental sanitation of the foundry were also greatly improved. In the significant progress of the foundry industry since the 20th century, the two new processes of gray cast iron gestation treatment and chemical hardening sand molding have special significance. These two inventions have broken through the traditional methods that have lasted for thousands of years, opening up new fields for the casting process and having a major impact on improving the competitiveness of castings.
Casting is generally classified according to the modeling method, and is customarily divided into ordinary sand casting and special casting. Ordinary sand casting includes three types: wet sand type, dry sand type and chemically hardened sand type. Special castings can be divided into two categories according to different modeling materials: one is natural mineral sand as the main modeling material, such as investment casting, shell casting, negative pressure casting, clay casting, solid casting, ceramics. Type casting, etc.; one type of metal is used as the main casting material, such as metal casting, centrifugal casting, continuous casting, pressure casting, low pressure casting, and the like.
The casting process can be divided into three basic parts, namely casting metal preparation, mold preparation and casting processing. Cast metal refers to the metal material used for casting castings in casting production. It is an alloy composed mainly of a metal element and added with other metal or non-metal elements. It is customarily called cast alloy, mainly cast iron. Cast steel and cast non-ferrous alloys.
Metal smelting is not only a simple melting process, but also a smelting process that allows the metal to be poured into the mold to meet the expected requirements in terms of temperature, chemical composition and purity. For this reason, various inspection tests for the purpose of controlling quality are carried out during the smelting process, and the liquid metal can be allowed to be poured after reaching various specified indexes. Sometimes, in order to achieve higher requirements, the molten metal is treated outside the furnace after being discharged, such as desulfurization, vacuum degassing, refining outside the furnace, gestation or deterioration treatment. Commonly used equipment for melting metal is cupola, electric arc furnace, induction furnace, electric resistance furnace, reverberatory furnace and the like.
Different casting methods have different mold preparation contents. Taking the most widely used sand casting as an example, the mold preparation includes two major tasks: modeling material preparation and modeling core making. Various raw materials used for molding cores in sand casting, such as foundry sand, sand binders and other excipients, as well as molding sand, core sand, paints, etc., which are formulated by them, are collectively referred to as modeling materials. The task of preparing materials is to follow castings. The requirements, the nature of the metal, choose the appropriate raw sand, binder and auxiliary materials, and then mix them into a certain type of molding sand and core sand in a certain proportion. Commonly used sand mixing equipment include a roller type sand mixer, a counter flow type sand mixer and a blade groove type sand mixer. The latter is designed for mixed chemical self-hardening sand, continuous mixing and fast speed.
The shape core is based on the requirements of the casting process, based on the determination of the modeling method and the preparation of the molding material. The accuracy of the casting and the economics of the entire production process depend mainly on this process. In many modern foundry workshops, the styling core is mechanized or automated. Commonly used sand-type molding core equipments include high, medium and low pressure molding machines, sand blasting machines, boxless injection molding machines, core shooting machines, cold and hot core boxes.
After the casting is taken out of the cast-cooled mold, there are gates, risers and metal burrs, and the sand-cast castings adhere to the sand, so it must be cleaned. Equipment for performing such work includes a shot blasting machine, a gate riser cutter, and the like. The sand falling of sand castings is a process with poor working conditions. Therefore, when selecting the modeling method, it should be considered to create convenient conditions for the falling sand cleaning. Some castings are subject to special post-processing requirements such as heat treatment, shaping, anti-rust treatment, roughing, etc.
Casting is a relatively economical method of forming blanks, which is more economical for parts with complex shapes. Such as the cylinder block and cylinder head of the car engine, ship propellers and fine art. Some hard-to-cut parts, such as nickel-base alloy parts of gas turbines, cannot be formed without casting.
In addition, the size and weight of the cast parts are wide, and the metal types are almost unlimited. The parts have general mechanical properties, and also have comprehensive properties such as wear resistance, corrosion resistance and shock absorption. Other metal forming methods such as forging , rolling, welding, punching, etc. can not be done. Therefore, the number of blank parts produced by the casting method in the machine manufacturing industry is still the largest in terms of quantity and tonnage.
Casting production has different characteristics from other processes, mainly due to its wide adaptability, the need for materials and equipment, and pollution of the environment. Casting produces dust, harmful gases and noise that pollute the environment. It is more serious than other mechanical manufacturing processes and requires measures to control it.
The trend in casting products is to require castings with better overall performance, higher precision, less headroom and a smoother surface. In addition, the requirements for energy conservation and the voice of society to restore the natural environment are also increasing. In order to meet these requirements, new casting alloys will be developed, and new smelting processes and new equipment will emerge.
While the degree of mechanization automation of foundry production is increasing, it will be more developed to flexible production to expand the adaptability to different batches and varieties. New technologies for energy and raw materials will be given priority, and new processes and new equipment with little or no pollution will be given priority. Quality control technology will have new developments in the detection and stress measurement of various processes.
Casting workers will further explore the theory of metal crystallization solidification and sand compaction under the conditions of continuous advancement of electronic technology and testing methods to study effective ways to improve the performance and internal quality of castings. The application of robots and computers in the field of foundry production and management will also become increasingly widespread.
In 513 BC, China cast the world's first cast iron piece in the world, which was about 270 kilograms. Europe also began producing cast iron parts around the eighth century. The emergence of cast iron parts has expanded the range of applications for castings. For example, in the 15th and 17th centuries, Germany, France and other countries have laid a number of cast iron pipes that supply drinking water to residents. After the industrial revolution of the 18th century, industries such as steam engines, textile machines and railways rose, castings entered a new era of service for large industries, and casting technology began to develop.
In the 20th century, the development speed of casting is very fast. One of the important factors is the advancement of product technology, which requires various mechanical and physical properties of castings to be better, while still having good mechanical processing performance. Another reason is the mechanical industry itself and others. The development of industries such as chemicals and instruments has created favorable material conditions for the foundry industry. Such as the development of testing methods, to ensure the improvement and stability of casting quality, and to provide conditions for the development of casting theory; the invention of electron microscopy, etc., to help people penetrate into the microscopic world of metal, explore the mystery of metal crystallization, study the theory of metal solidification To guide casting production.
During this period, a large number of new cast metal materials with superior performance and rich variety, such as ductile iron, weldable malleable cast iron, ultra-low carbon stainless steel, aluminum-copper, aluminum-silicon, aluminum-magnesium alloy, titanium-based, nickel-based alloy, etc. And invented a new process for the inoculation of gray cast iron, making the casting more adaptable.
After the 1950s, there were new technologies such as wet sand high pressure molding, chemical hardening sand molding and core making, negative pressure molding and other special casting and shot blasting, which made the castings have high shape, dimensional accuracy and good surface finish. The working conditions and environmental sanitation of the foundry were also greatly improved. In the significant progress of the foundry industry since the 20th century, the two new processes of gray cast iron gestation treatment and chemical hardening sand molding have special significance. These two inventions have broken through the traditional methods that have lasted for thousands of years, opening up new fields for the casting process and having a major impact on improving the competitiveness of castings.
Casting is generally classified according to the modeling method, and is customarily divided into ordinary sand casting and special casting. Ordinary sand casting includes three types: wet sand type, dry sand type and chemically hardened sand type. Special castings can be divided into two categories according to different modeling materials: one is natural mineral sand as the main modeling material, such as investment casting, shell casting, negative pressure casting, clay casting, solid casting, ceramics. Type casting, etc.; one type of metal is used as the main casting material, such as metal casting, centrifugal casting, continuous casting, pressure casting, low pressure casting, and the like.
The casting process can be divided into three basic parts, namely casting metal preparation, mold preparation and casting processing. Cast metal refers to the metal material used for casting castings in casting production. It is an alloy composed mainly of a metal element and added with other metal or non-metal elements. It is customarily called cast alloy, mainly cast iron. Cast steel and cast non-ferrous alloys.
Metal smelting is not only a simple melting process, but also a smelting process that allows the metal to be poured into the mold to meet the expected requirements in terms of temperature, chemical composition and purity. For this reason, various inspection tests for the purpose of controlling quality are carried out during the smelting process, and the liquid metal can be allowed to be poured after reaching various specified indexes. Sometimes, in order to achieve higher requirements, the molten metal is treated outside the furnace after being discharged, such as desulfurization, vacuum degassing, refining outside the furnace, gestation or deterioration treatment. Commonly used equipment for melting metal is cupola, electric arc furnace, induction furnace, electric resistance furnace, reverberatory furnace and the like.
Different casting methods have different mold preparation contents. Taking the most widely used sand casting as an example, the mold preparation includes two major tasks: modeling material preparation and modeling core making. Various raw materials used for molding cores in sand casting, such as foundry sand, sand binders and other excipients, as well as molding sand, core sand, paints, etc., which are formulated by them, are collectively referred to as modeling materials. The task of preparing materials is to follow castings. The requirements, the nature of the metal, choose the appropriate raw sand, binder and auxiliary materials, and then mix them into a certain type of molding sand and core sand in a certain proportion. Commonly used sand mixing equipment include a roller type sand mixer, a counter flow type sand mixer and a blade groove type sand mixer. The latter is designed for mixed chemical self-hardening sand, continuous mixing and fast speed.
The shape core is based on the requirements of the casting process, based on the determination of the modeling method and the preparation of the molding material. The accuracy of the casting and the economics of the entire production process depend mainly on this process. In many modern foundry workshops, the styling core is mechanized or automated. Commonly used sand-type molding core equipments include high, medium and low pressure molding machines, sand blasting machines, boxless injection molding machines, core shooting machines, cold and hot core boxes.
After the casting is taken out of the cast-cooled mold, there are gates, risers and metal burrs, and the sand-cast castings adhere to the sand, so it must be cleaned. Equipment for performing such work includes a shot blasting machine, a gate riser cutter, and the like. The sand falling of sand castings is a process with poor working conditions. Therefore, when selecting the modeling method, it should be considered to create convenient conditions for the falling sand cleaning. Some castings are subject to special post-processing requirements such as heat treatment, shaping, anti-rust treatment, roughing, etc.
Casting is a relatively economical method of forming blanks, which is more economical for parts with complex shapes. Such as the cylinder block and cylinder head of the car engine, ship propellers and fine art. Some hard-to-cut parts, such as nickel-base alloy parts of gas turbines, cannot be formed without casting.
In addition, the size and weight of the cast parts are wide, and the metal types are almost unlimited. The parts have general mechanical properties, and also have comprehensive properties such as wear resistance, corrosion resistance and shock absorption. Other metal forming methods such as forging , rolling, welding, punching, etc. can not be done. Therefore, the number of blank parts produced by the casting method in the machine manufacturing industry is still the largest in terms of quantity and tonnage.
Casting production has different characteristics from other processes, mainly due to its wide adaptability, the need for materials and equipment, and pollution of the environment. Casting produces dust, harmful gases and noise that pollute the environment. It is more serious than other mechanical manufacturing processes and requires measures to control it.
The trend in casting products is to require castings with better overall performance, higher precision, less headroom and a smoother surface. In addition, the requirements for energy conservation and the voice of society to restore the natural environment are also increasing. In order to meet these requirements, new casting alloys will be developed, and new smelting processes and new equipment will emerge.
While the degree of mechanization automation of foundry production is increasing, it will be more developed to flexible production to expand the adaptability to different batches and varieties. New technologies for energy and raw materials will be given priority, and new processes and new equipment with little or no pollution will be given priority. Quality control technology will have new developments in the detection and stress measurement of various processes.
Casting workers will further explore the theory of metal crystallization solidification and sand compaction under the conditions of continuous advancement of electronic technology and testing methods to study effective ways to improve the performance and internal quality of castings. The application of robots and computers in the field of foundry production and management will also become increasingly widespread.
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