In daily life and industry, many metal products are made by casting technology. It can be said that casting is a kind of metal hot processing technology that humans mastered relatively early. With the continuous development of science and technology, casting technology has also developed in types according to different needs, including sand casting, pressure casting, low-pressure casting, centrifugal casting, metal mold casting, vacuum die casting, extrusion casting, lost foam casting, continuous casting, and investment casting.
Forging is also commonly called forging, a common metal processing technology. Specifically, it refers to the impact force or static pressure generated by tools or molds on forging equipment to cause partial or complete plastic deformation of the blank to obtain forgings with certain geometric shapes, sizes, quality and mechanical properties.
Classification of forging:
• According to temperature, it is divided into: cold forging and hot forging.
• According to whether the mold is used for forming, it is divided into: free forging, die forging and tire die forging.
• According to the processing method, it is divided into: manual forging and mechanical forging.
The following introduces the concepts of each forging process.
• Cold forging: a forging process that presses metal materials at room temperature;
• Hot forging: a forging process that presses metal materials when they are heated to a state above the recrystallization temperature and below the solidus;
• Free forging: refers to the process in which the metal blank receives pressure from the upper and lower irons during forging, and produces free plastic deformation in all directions (horizontally). The basic processes of free forging include upsetting, drawing, punching, cutting, bending, twisting, shifting and forging, etc.;
• Die forging: the heated metal blank is fixedly placed in the forging die on the die forging equipment for forging. The plastic deformation of the metal blank is limited by the die cavity and is "unfree";
• Die forging: refers to a forging method that uses a movable die on a free forging equipment to produce die forgings. It is a process between free forging and die forging;
• Manual forging: A traditional processing method, such as forging weapons in ancient times;
• Mechanical forging: a modern processing method, performed by mechanical equipment.
• The advantages and disadvantages of forging are as follows:
• Advantages a/ Can eliminate internal defects of parts or blanks b/ Good shape and dimensional stability of forgings c/ Good toughness, good mechanical properties, high strength d/ Great production flexibility Disadvantages a/ Cannot be directly forged into parts with more complex shapes b/ The dimensional accuracy of forgings is not high enough c/ The heavy machinery and equipment and complex tools and molds required for forging production have high requirements for factory foundations and high initial investment costs.
Extrusion is also called extrusion, which is also called extrusion in plastics, extrusion in rubber, and extrusion in metals. The basic principle of extrusion is to heat and melt plastics, rubber, metals and other materials, and then apply pressure to continuously pass the materials from the specified extrusion barrel through a shaped mold. The materials are extruded and cooled to form, thereby obtaining a blank or part that conforms to the cross-section of the die hole. For example, the familiar aluminum alloy profiles.
Common extrusion methods include: forward extrusion, reverse extrusion, compound extrusion, and radial extrusion.
Extrusions can be divided into profiles and plates according to their uses after forming.
• Extruded plates: refers to products that are flat plates with a certain thickness.
• Extruded profiles: refers to a state with a certain shape compared to plates. Such as cylinders, round shapes, concave shapes, convex shapes, grooves, etc. Such as pipes, home decoration right-angle materials, plastic profiles, industrial aluminum profiles, guide rails, connectors, etc.
Applications of extruded parts: doors and windows, metal tubular objects, structural parts, panels, automotive parts, etc.
The advantages and disadvantages of extrusion are as follows:
• Advantages Precise dimensions, smooth surface, often with complex shapes such as thin walls, deep holes, and special-shaped sections. Generally, cutting is not required, which saves a lot of metal materials and processing time, and has high production efficiency. Due to the work hardening effect of the extrusion process, the strength, hardness, and fatigue resistance of the parts are significantly improved, which is conducive to improving the plasticity of the metal. Extrusion parts have high production efficiency and high consistency. Disadvantages Extrusion can only be processed continuously in one direction, and it is impossible to make workpieces with more complex requirements.
Stamping is one of the metal plastic processing methods, also known as sheet metal stamping. It is a process method that uses a mold to separate or plastically deform metal sheets under pressure to obtain the required workpiece. Stamping processing can achieve stretching, bending, punching and shearing processes using different molds.
• Stretching: Place the sheet (blank) to be processed on the die, apply a certain pressure to it with a pressure plate, and then use the punch to apply force downward to stretch it into shape. Most metal containers are formed by stretching.
• Bending: The blank is placed on the die, and pressure is applied to the punch. Under the joint action of the die and the punch, the blank is bent into the required shape. Bending can be divided into sheet bending and wire bending.
• Punching and shearing: During processing, the blank is placed on the die, and impact force is applied to the punch. Under the joint action of the die and the punch, part of the metal is sheared off. The sheared shape depends on the shape of the die.
Application of stamping technology: automobiles, home appliances, electronic product housings, hardware tools, construction, etc.
Classification of stamping
• According to the stamping processing temperature, it is divided into hot stamping and cold stamping.
• According to the processing function of stamping, it can be divided into punching and forming.
The concept of each stamping is introduced below.
• Hot stamping: suitable for sheet metal processing with high deformation resistance and poor plasticity. Cold stamping can produce thin-walled parts with complex shapes, small mass and good rigidity. Its surface quality is good, and the dimensional accuracy meets the general interchangeability requirements without cutting. As a result of work hardening after cold deformation, the strength and rigidity of stamping parts are improved. However, the rigidity of thin-walled stamping parts is slightly lower, and the application of stamping parts is limited for some parts with high shape and position accuracy requirements;
• Cold stamping: It is carried out at room temperature and is a commonly used stamping method for thin plates;
• Blanking processing: also known as separation processing, including punching, blanking, trimming, cutting, etc.;
• Forming processing: It is to make the material plastically deformed, including bending, drawing, curling, etc. If the two types of processes are completed in the same mold, it is called composite processing.
The advantages and disadvantages of stamping are as follows:
Advantages High production and sales rate, high product size accuracy, good surface quality, easy to realize automation and mechanization, low processing cost, low material consumption, suitable for mass production. Stamping has high production efficiency, high finished product qualification rate and material utilization rate, uniform product size, smooth surface, mechanization and automation, suitable for mass production, low cost, widely used in aviation, automobile, instrumentation, electrical appliances and other industrial sectors and daily necessities. Disadvantages: It is only suitable for plastic material processing, and cannot process brittle materials such as cast iron and bronze, and is not suitable for processing parts with complex shapes.
Machining is the abbreviation of mechanical processing, which refers to the processing technology of removing materials through mechanical precision processing. It is a processing process in which the excess metal layer thickness is directly cut off on the blank with a tool during the production of parts, so that it meets the technical requirements of dimensional accuracy, shape and position mutual accuracy, surface quality, etc. required by the drawing. For example, most Apple computers and consumer electronic products use metal machining technology.
Machining mainly includes manual processing and CNC processing.
• Manual processing refers to the method of processing various materials by mechanical workers manually operating mechanical equipment such as milling machines, lathes, drilling machines and sawing machines. Manual processing is suitable for small batch and simple parts production.
• CNC machining is the well-known CNC, which uses CNC equipment for machining, including machining centers, milling centers, EDM wire cutting equipment, thread cutting machines, etc. Most machining workshops use CNC machining technology. Through programming, the position coordinates (X, Y, Z) of the workpiece in the Cartesian coordinate system are converted into program language. The CNC controller of the CNC machine tool controls the axis of the CNC machine tool by identifying and interpreting the program language, automatically removing materials as required, and thus obtaining a finely machined workpiece. CNC machining processes workpieces in a continuous manner, which is suitable for large quantities of parts with complex shapes.
CNC is the main equipment for prototype production. The processing method is to carve various types of metal materials such as aluminum, copper, stainless steel, and various plastics into the physical samples we need. The samples processed by CNC have the advantages of large molding size, high strength, good toughness, and low cost, and have become the mainstream of prototype production.
The advantages and disadvantages of CNC are as follows:
Advantages a/High processing accuracy and high processing quality b/Multi-coordinate linkage can be performed, and parts with complex shapes can be processed. When the processed parts are changed, generally only the CNC program needs to be changed, which can save production preparation time c/The machine tool itself has high precision and high rigidity, and can choose favorable processing dosages, with high productivity (generally 3 to 5 times that of ordinary machine tools). The machine tool has a high degree of automation, which can reduce labor intensity d/Batch production, and product quality is easy to control.
Disadvantages a/The quality requirements for operators are low, and the technical requirements for maintenance personnel are high. However, its processing route is not easy to control, unlike ordinary machine tools. It is inconvenient to maintain and has high technical requirements b/The process is not easy to control.
Welding must be familiar to everyone, also known as welding. Welding is a process technology that joins metals or other thermoplastic materials by heating, high temperature or high pressure. At present, the more advanced welding technologies include laser welding, cold spray welding, ultrasonic welding, etc.
The characteristics of welding include
• Welded products are lighter than riveted parts, castings and forgings, which can reduce the weight of transportation vehicles and save energy;
• Welding has good sealing properties and is suitable for manufacturing various containers;
• Developing joint processing technology to combine welding with forging and casting can produce large, economically reasonable cast-welded structures and forged-welded structures with high economic benefits;
• The use of welding technology can effectively utilize materials, and welded structures can use different performance materials in different parts.
MIM, or metal powder injection molding, is known as the fifth generation of metal forming technology. This process is a newly developed technology based on plastic injection molding combined with powder metallurgy. It is used to produce small and complex products with significant advantages.
MIM can make the geometric design of parts with unequal thickness possible (increasing the degree of design freedom), and can also significantly reduce the cost of complex precision structural parts in mass production. In addition, the advantages include: easy mass production, improved precision, excellent product strength and other inherent properties, and a wide range of material selection.
MIM is different from other metal forming processes. It is somewhat similar to the plastic injection molding process. The metal powder and the binder are first mixed to form the feed (particles), and then injection molding is performed. After that, the binder is removed (degreasing process), sintered at high temperature, and post-processed. Product design, mold design and manufacturing are required before production, and the subsequent process flow is shown in the figure below:
3D printing is a type of rapid prototyping technology. It is a technology that uses a digital model file as the basis, uses powdered metal or plastic and other bondable materials, and constructs objects by printing layer by layer.
Application of 3D: 3D printing is usually achieved using a digital technology material printer. It is often used to make models in the fields of mold manufacturing, industrial design, etc., and then gradually used for the direct manufacturing of some products. There are already parts printed using this technology. This technology is used in jewelry, footwear, industrial design, architecture, engineering and construction (AEC), automobiles, aerospace, dental and medical industries, education, geographic information systems, civil engineering, guns and other fields.
In general, 3D printing is expensive. Products after 3D printing often have poor surface effects and need to be reprocessed. At present, it is only suitable for some small-scale manufacturing, especially high-end customized products, such as automotive parts manufacturing. Although the main material is still plastic, metal materials will definitely be used in 3D printing in the future, and the scope of application will become wider and wider in the future.
