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Author: Site Editor Publish Time: 2025-01-16 Origin: Site
Cold heading and cold forging (cold extrusion) are both metal deformation processes performed under similar conditions, but there are significant differences in the way they operate. Cold heading is mainly suitable for forging deformation of small workpieces and is widely used in the fastener industry. In contrast, cold extrusion performs extrusion deformation on larger workpieces and has a wider range of applications. Next, let’s dig into the specific differences between cold heading and cold forging.
Cold heading is a metal forming process that uses the plasticity of metal at room temperature to apply pressure to the metal blank through molds and pressure equipment to cause local or overall plastic deformation of the metal blank to obtain parts or blanks of the desired shape. . In this process, the metal material mainly undergoes upsetting deformation. For example, under the action of a mold, one end of a cylindrical metal wire is upsetting into various shapes, such as hexagonal, circular, etc. This process is It's like turning a "slender" metal blank into a "short and fat" one.
From a mechanical point of view, cold heading utilizes the plastic deformation ability of the material below the yield strength. When the external pressure exceeds the yield limit of the material, the crystal structure inside the material will undergo phenomena such as slipping and twinning, causing the material to undergo irreversible plastic deformation and ultimately form the desired part shape. It is a non-cutting processing technology and can make full use of raw materials compared with traditional cutting processing.
High material utilization rate: Cold heading is a near-net forming process that manufactures parts by plastic deformation of metal blanks, with almost no material waste. For example, when producing bolts, compared with cutting, the cold heading process can convert almost all raw materials into part of the finished product, and the material utilization rate can be as high as 80% - 90% or more, greatly reducing production costs.
High production efficiency: Cold heading equipment (such as cold heading machines) works very fast and can achieve automated production. For example, in modern industrial production, some high-speed cold heading machines can produce dozens or even hundreds of parts per minute, and can mass-produce products that meet the requirements in a short time, especially suitable for mass production of products with high demand such as standard fasteners.
Good product quality: The cold heading process is formed in the mold, and the precision of the mold can ensure the dimensional accuracy and shape accuracy of the product. Moreover, since the processing is carried out at room temperature, the surface quality of the product is good, and the dimensional accuracy can be controlled within a very small tolerance range. For example, the dimensional accuracy of the bolts, nuts and other products produced can reach ±0.05mm or even higher precision requirements, and the surface roughness can also reach about Ra1.6 - Ra3.2μm.
Improved working conditions: The cold heading process is relatively clean, no chips are generated, and the pollution to the working environment is reduced. At the same time, due to the high degree of automation of the equipment, the workers mainly operate and monitor the equipment, and the labor intensity is low, which greatly improves the working conditions.
Good mechanical properties: During the cold heading process, after the metal material undergoes plastic deformation, work hardening will occur, which will increase the strength and hardness of the parts. For example, the tensile strength and yield strength of the bolts after cold heading are higher than those of the materials that have not been cold headed, which can better meet the mechanical performance requirements in actual use.
High cost of equipment and molds: The cold heading process requires special cold heading equipment, such as cold heading machines, which are expensive. Moreover, the manufacturing precision of cold heading dies is high, and its design and manufacturing also require a high cost. For example, the design and manufacturing costs of a set of high-precision cold heading dies may reach tens of thousands of yuan or even higher, and the service life of the dies is limited and needs to be replaced regularly, which increases the production cost.
Strict requirements on materials: The cold heading process requires metal materials to have good plasticity and low deformation resistance. Not all metal materials are suitable for cold heading. Some materials with high hardness and poor plasticity are prone to cracking and other defects during the cold heading process. For example, if high-carbon steel materials are not properly pretreated, it is difficult to form during cold heading. The material needs to be pretreated by spheroidizing annealing to improve its cold heading performance.
Limited product shape: Although the cold heading process can produce parts of various shapes, for some complex and special products, the cold heading process may not be realized or requires complex molds and multiple processes to complete. For example, some parts with complex internal structures or asymmetric shapes are difficult to form directly by relying solely on cold heading.
Fastener production: The main application area of cold heading process is the production of standard fasteners, such as bolts, screws, nuts, rivets, pins, etc. In the production of these products, cold heading can give full play to its advantages of high efficiency, high precision and high material utilization. For example, a large number of bolts and nuts in automobile engines, as well as various fasteners used in the construction industry, are produced by cold heading process.
Batch production of small parts: In addition to fasteners, cold heading is also suitable for the batch production of other small metal parts, which are relatively simple in shape and mainly obtain the required shape by upsetting deformation. For example, some small mechanical parts, such as small shafts, sleeves, etc., can also be produced by cold heading process to meet the needs of large-scale production.
Hardware tool manufacturing: In the hardware tool industry, cold heading is also widely used. For example, some parts of simple hand tools, such as wrench heads, screwdriver rods, etc., are partially manufactured by cold heading process, which can improve production efficiency and product quality.
Cold forging, also known as cold bulk forming and cold extrusion, is both a manufacturing process and a processing method. Similar to the stamping process, cold forging is also composed of three key elements: materials, molds and equipment. The difference between the two is that the materials used in stamping are mainly plates, while the materials used in cold forging are mainly disc wires. In the Japanese Industrial Standard (JIS), this process is called cold forging (abbreviated as cold forging); in the Chinese National Standard (GB), its term is cold heading; and in some screw manufacturers, it is accustomed to calling it heading.
Cold forging refers to various types of bulk forming operations performed below the recrystallization temperature of the metal. According to metallurgical theory, the recrystallization temperature of different metal materials is different, and the calculation formula is T recrystallization = (0.3~0.5)T melt. Taking ferrous metals and non-ferrous metals as examples, their minimum recrystallization temperatures are different. At room temperature or normal temperature, the forming of lead and tin does not belong to the category of cold forging, but should be classified as hot forging; however, the forming of iron, copper and aluminum at room temperature can be called cold forging.
In the actual production process, compared with cutting, hot forging, powder metallurgy and casting, cold forging has many significant advantages:
High material utilization rate: The material consumption in the cold forging process is very small, and basically no waste is generated, which greatly saves material costs and avoids the pollution to the environment caused by the hot billet.
Excellent production efficiency: The cold forging machine runs at a very fast speed, reaching 60 to 600 PCS per minute.
Improving part performance: The strength performance of the parts after cold forging is excellent, which is due to the work hardening effect generated during the cold deformation process, which effectively improves the comprehensive performance of the parts.
High processing accuracy: Cold forging is a precision forming technology that can ensure that the workpiece meets a high precision standard.
Great potential for technological development: With the continuous advancement of technology, cold forging technology continues to innovate, processing methods are increasingly sophisticated, and gradually expand into the field of high-difficulty products.
Strict mold requirements: The processing of cold forging molds is extremely difficult, not only the cost is high, but also the processing cycle is long.
Not suitable for small-batch production: Due to the high initial investment cost, the cold forging process is difficult to reflect cost-effectiveness in small-batch production.
High material requirements: During the cold forging process, the material usually needs to be softened annealed or surface phosphating and lubricated. This is because the deformation resistance of cold forging is large. For larger-sized products, larger equipment is required for processing.
Definition of cold forging processing
Cold forging processing is based on the principle of plastic deformation of metal materials. At room temperature, the cut metal material is fed into the mold cavity of the cold forging machine. Under the combined action of strong unit extrusion pressure and a certain speed, the metal blank is forced to undergo plastic deformation in the mold cavity, thereby obtaining parts with specific shapes, sizes and certain mechanical properties. Cold forging is a volume plastic forming process for metals at room temperature. Its main deformation methods include upsetting and extrusion.
With the continuous progress of society and the rapid development of the market, product demand has shown a trend of diversification. In order to adapt to this change, cold forging technology continues to explore and innovate, actively explore new market areas, and gradually move towards information products. At present, products such as iron cores, shafts (round, flat), shafts (punching), shafts (grooving), screws, etc. can basically be produced and manufactured through cold forging.
Cold heading and cold forging are not the same thing. Although they are both metal pressure processing processes, there are many differences:
Processing object size: Cold heading is usually used for forging deformation of smaller workpieces, which is common in the fastener industry, such as the manufacture of small parts such as bolts and nuts; cold forging is generally used for extrusion deformation of larger workpieces, and has a wider range of applications. It is not only used for common parts, but also in the manufacture of some large parts with high precision and performance requirements.
Operation method: Cold heading mainly applies impact force or pressure to the blank through the mold, so that the blank is upset and deformed in the mold cavity to form the desired shape; cold forging covers a variety of deformation methods, in addition to upsetting similar to cold heading, there are also extrusion, drawing, etc. Through different molds and process combinations, the metal material undergoes plastic deformation in the mold to achieve the target shape and size.
Process characteristics: Cold heading has high production efficiency and is suitable for mass production of standard parts. It can effectively utilize materials and reduce waste. Cold forging can produce parts with complex shapes and high precision. The strength and hardness of parts are improved after cold forging, but the mold design and manufacturing requirements are high and the cost is also high.
Application areas: Cold heading is mainly used to produce various fasteners, such as bolts, nuts, rivets, etc.; cold forging is more widely used in the automotive, aerospace, machinery manufacturing and other industries, and is used to manufacture key parts such as engine parts and transmission parts.
