A forging method uses a punch or punch to press a blank placed in a concave die to make it flow plastically, so as to obtain a product corresponding to the shape of a die hole or concave-convex die. In the process of extrusion, the blank produces three-dimensional compressive stress, and even the blank with low plasticity can be extruded. Extrusion, especially cold extrusion, has the advantages of high material utilization rate, improving material structure and mechanical properties, simple operation and high productivity. It can be used to manufacture parts with long rods, deep holes, thin walls and special sections, and is an important machining process with less cutting. Extrusion is mainly used for the forming of metals, and can also be used for the forming of nonmetals such as plastics, rubber, graphite and clay blanks. /kloc-in the 0/7th century, the French used a manual screw press to extrude lead pipes for water pipes, which was the beginning of cold extrusion. At the end of 19, the cold extrusion of zinc, copper and copper alloys was realized, and it was extended to the extrusion of aluminum and aluminum alloys at the beginning of the 20th century. In 1930s, the Germans invented the phosphating saponification surface antifriction and lubrication treatment technology, which made the cold extrusion of steel successful, and was originally used to extrude steel casing. After World War II, cold extrusion of steel was extended to other countries, and its application scope was expanded. In 1950s, molten glass lubrication method was adopted, and hot extrusion of steel was applied and developed in metallurgical and mechanical industries. Classification extrusion can be divided into three types according to blank temperature: hot extrusion, cold extrusion and warm extrusion. The extrusion (see plastic deformation) of metal blank above recrystallization temperature is hot extrusion; Room temperature extrusion is cold extrusion; Extrusion above normal temperature but not above recrystallization temperature is warm extrusion. According to the plastic flow direction of billet, extrusion can be divided into forward extrusion with the same flow direction and pressure direction, reverse extrusion with opposite flow direction and compound extrusion with bidirectional flow of billet. Hot extrusion is widely used to produce pipes and profiles of non-ferrous metals such as aluminum and copper, which belongs to metallurgical industry. Hot extrusion of steel is not only used to produce special pipes and profiles, but also used to produce solid carbon steel and alloy steel parts with holes (through holes or not) that are difficult to form by cold extrusion or warm extrusion, such as thick-headed bars, cylinders and containers. The dimensional accuracy and surface smoothness of hot extrusion parts are better than those of hot die forgings, but the matching parts still need finishing or cutting. At first, cold extrusion was only used to produce pipes and profiles of lead, zinc, tin, aluminum and copper, as well as toothpaste hoses (lead-coated tin), dry battery casings (zinc), shell casings (copper) and other products. In the mid-20th century, cold extrusion technology began to be used in carbon structural steel and alloy structural steel parts, such as bars and rod-shaped parts with various sections, piston pins, wrench sleeves, spur gears and so on. Later, it was used to extrude some high carbon steel, rolling bearing steel and stainless steel parts. Cold extrusion parts have high precision and smooth surface, and can be directly used as parts without cutting or other finishing. Cold extrusion operation is simple, and it is suitable for mass production of smaller parts (the diameter of steel extruded parts is generally less than 100 mm). Warm extrusion is an intermediate process between cold extrusion and hot extrusion. Under suitable conditions, warm extrusion can have both advantages. However, warm extrusion needs to heat the blank and preheat the die, and the high-temperature lubrication is not ideal, and the die life is short, so it is not widely used. Process characteristics Extrusion processing has certain process characteristics in blank treatment, extrusion pass, extrusion force, die life, extrusion equipment and so on, depending on the requirements of blank and extruded parts. In order to reduce the hardness, deformation resistance and improve plasticity of hard aluminum, copper and steel, it is necessary to soften and anneal the blank first. Hot extrusion does not require annealing treatment. Lubrication and surface treatment In order to reduce the extrusion force and the wear rate of the die and prevent the thermal bonding between the metal blank and the die surface, good lubrication is needed in the extrusion process. In order to prevent grease from being extruded under high pressure, it is necessary to reduce friction and lubricate the blank surface. The most common method is phosphating to form a rough and porous phosphate surface layer, and then coating soap-based materials (such as zinc stearate and sodium stearate) on the surface layer to fill the pores. During extrusion, the phosphating layer releases soap continuously, which plays an effective role in lubrication. Warm extrusion and hot extrusion are not suitable for phosphating-saponification lubrication because of their high temperatures. Generally, glass powder (high temperature melting), molybdenum disulfide, graphite and other oils are used for lubrication. The deformation degree of extrusion pass and extrusion deformation degree are expressed by the reduction rate of cross-sectional area of blank before and after deformation. The ultimate deformation degree of crack-free blank at the initial deformation is called allowable deformation degree. When the blank is extruded under triaxial compressive stress, the allowable deformation degree is high. The allowable deformation degree of low carbon steel is more than 75% in cold forward extrusion, but it can reach more than 90% in hard aluminum, copper and brass, and it is slightly lower in reverse extrusion. In the hot state, the allowable deformation degree can be greatly improved, and the increase range increases with the increase of temperature. The deformation degree is large, the required extrusion force is also large, and the die wear is accelerated and easy to be damaged, so the limit value of allowable deformation degree is generally not adopted, for example, when cold extruding carbon steel, 60% of the deformation limit value is used as the allowable degree of primary deformation. If the total deformation from the blank to the finished product is great, it will be extruded several times and gradually formed. In the process of cold extrusion, softening annealing is needed between processes. The allowable deformation degree of hot extrusion and warm extrusion is larger, which is beneficial to reduce extrusion force and extrusion pass. Extrusion force Extrusion force is the main factor that determines the strength of die and selects the nominal pressure of extruder. Extrusion force is related to extrusion area of punch, mechanical properties of blank at extrusion temperature, deformation degree, die shape, lubrication effect and other factors. In cold extrusion of hard aluminum, copper and other materials, the extrusion force per unit area is generally below 1000 N/cm2; Carbon steel and alloy steel are generally above 1000 N/cm2 during cold extrusion, and the height can reach 2500 ~ 3000 N/cm2. Because of the large extrusion force per unit area, most female dies subjected to expansion stress adopt 2 or 3 layers of prestressed structure to improve their strength and rigidity, so that wear only occurs in the innermost layer, which is beneficial to the repair of the die (only replacing the inner layer of the female die). Prolonging die life is an important factor to reduce extrusion processing cost. The size and shape errors of extrusion parts may exceed the allowable values due to the longitudinal cracks of the die or the wear of the forming cavity and hole. The former can be avoided by correct design and manufacture; The latter can be slowed down by correctly selecting the die material and its heat treatment and surface treatment process, and correctly determining the extrusion process and lubrication, thus prolonging its service life. The small extrusion parts of extrusion equipment are generally extruded by general mechanical presses, hydraulic presses and screw presses. Large extrusion parts and long extrusion parts are often extruded by special extrusion machines. Since the second half of the 20th century, hydrostatic extrusion technology has appeared. Static pressure extrusion adopts normal temperature extrusion. The blank is extruded from the die hole under the longitudinal and circumferential static pressure of high-pressure liquid injected into the die. The hydrostatic friction coefficient between the periphery of the blank and the extrusion cylinder wall is extremely low, and the ratio of transverse compressive stress in the deformation zone of the blank increases under general extrusion conditions, which reduces the resistance of extrusion deformation and further improves the plasticity of the blank. High strength and low plasticity metal materials such as high speed steel, titanium alloy, zirconium alloy and nickel-based alloy can be formed by static extrusion without cracks. However, the problem of high-pressure sealing needs to be improved, and hydrostatic extrusion is still in the further research stage. Loss caused by slight bending of optical fiber when it is squeezed. Drilling machine
Stamping is a production technology that makes the sheet material directly subjected to deformation force in the die with the help of the power of conventional or special stamping equipment, so as to obtain product parts with certain shape, size and performance. Sheet metal, die and equipment are the three elements of stamping. Stamping is a cold deformation processing method of metal. Therefore, it is called cold stamping or sheet metal stamping for short. It is one of the main methods of metal plastic working (or pressure working) and also belongs to material forming engineering technology. The die used for stamping is called stamping die, or stamping die for short. Stamping die is a special tool for batch processing materials (metal or nonmetal) into required stamping parts. Stamping die is very important in stamping. Without the required stamping die, it is difficult to carry out mass stamping production. Without advanced stamping die, advanced stamping technology cannot be realized. Stamping technology, die, stamping equipment and stamping materials constitute the three major elements of stamping processing, and only by combining them can stamping parts be obtained. Compared with other mechanical processing and plastic processing methods, stamping has many unique advantages both technically and economically. The main performance is as follows. (1) The stamping production efficiency is high, the operation is convenient, and it is easy to realize mechanization and automation. This is because stamping depends on stamping die and stamping equipment to complete the processing. The number of strokes of an ordinary press can reach dozens of times per minute, and the high-speed pressure can reach hundreds or even thousands of times per minute. Every stroke of stamping may be punched. (2) During stamping, because the die ensures the accuracy of the size and shape of the stamping parts, it generally does not damage the surface quality of the stamping parts, and the die life is generally long, the stamping quality is stable, the interchangeability is good, and it has the characteristics of "identical". (3) Parts with large size range and complex shapes can be processed by stamping, such as stopwatches as small as clocks and watches, as large as automobile longitudinal beams and panels. In addition, the cold deformation hardening effect of materials in the stamping process makes the stamping strength and stiffness higher. (4) Stamping generally does not produce chips and waste materials, requires less materials, and does not need other heating equipment. It is a material-saving and energy-saving processing method, and the cost of stamping parts is low. Because stamping has such advantages, stamping is widely used in all fields of national economy. For example, aerospace, aviation, military industry, machinery, agricultural machinery, electronics, information, railways, posts and telecommunications, transportation, chemical industry, medical equipment, household appliances, light industry and other industries all have stamping processes. Not only is it used in the whole industry, but everyone is directly related to stamping products. There are many large, medium and small stamping parts on airplanes, trains, cars and tractors. Body, frame and rim are all stamped. According to relevant survey statistics, 80% of bicycles, sewing machines and watches are stamped parts; 90% of televisions, tape recorders and cameras are stamped parts; There are also food metal cans, steel boilers, porcelain bowls and stainless steel tableware, all of which are products stamped with molds; Even the hardware of the computer needs stamping parts. However, the dies used in stamping are generally special, sometimes a complex part needs several sets of dies to be processed and formed, and the dies have high manufacturing accuracy and high technical requirements, so they are technology-intensive products. Therefore, only mass production of stamping parts can fully reflect the advantages of stamping and obtain better economic benefits. Of course, there are also some problems and shortcomings in stamping. Mainly manifested in the noise and vibration produced by stamping, and the safety accidents of operators occur from time to time. However, these problems are not entirely due to the stamping process and the die itself, but mainly due to the traditional stamping equipment and backward manual operation. With the progress of science and technology, especially the development of computer technology and electromechanical integration technology, these problems will be solved as soon as possible.
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