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Cold extruded workpiece ↑
Cold extrusion is a processing method that places a metal blank in a cold extrusion mold cavity, applies pressure to the blank through a fixed convex mold on a press at room temperature, and causes plastic deformation of the metal blank to produce parts. Obviously, cold extrusion processing relies on the mold to control the flow of metal and the large transfer of metal volume to form parts. In terms of extrusion equipment, China has the ability to design and manufacture various tonnage extrusion presses. In addition to using general mechanical presses, hydraulic presses, and cold extrusion presses, friction presses and high-speed high-energy equipment have also been successfully used for cold extrusion production.
If the blank is extruded without heating, it is called cold extrusion. Cold extrusion is one of the advanced processing techniques for chip free and chip less parts, making it an advanced method in metal chip plastic processing. If the blank is heated to a temperature below the recrystallization temperature for extrusion, it is called warm extrusion. Warm extrusion still has the advantage of less chips.
Cold extrusion technology is an advanced production process technology with high precision, efficiency, high quality and low consumption, which is widely used in the large-scale production of small and medium-sized forgings. Compared with hot forging and warm forging processes, it can save 30% to 50% of materials, 40% to 80% of energy, and improve the quality of forgings and the working environment.
At present, cold extrusion technology has been widely used in industrial sectors such as fasteners, machinery, instruments, electrical appliances, light industry, aerospace, shipbuilding, and military industry, and has become an indispensable and important processing method in metal plastic volume forming technology. With the advancement of technology and the continuous improvement of product technology requirements in industries such as automobiles, motorcycles, and household appliances, cold extrusion production technology has gradually become the development direction for refined production of small and medium-sized forgings.
Cold extrusion can also be divided into forward extrusion, reverse extrusion, composite extrusion, radial extrusion, etc;
▲ Advantages of Cold Extrusion Process
1. Save raw materials
Cold extrusion is the use of metal's plastic deformation to produce parts of the desired shape, which can significantly reduce cutting processing and improve material utilization. The material utilization rate of cold extrusion can generally reach over 80%.
2. Improve labor productivity
Using cold extrusion technology instead of cutting to manufacture parts can increase productivity by several times, tens of times, or even hundreds of times.
3. The workpiece can achieve ideal surface roughness and dimensional accuracy
The accuracy of the parts can reach IT7~IT8 level, and the surface roughness can reach R0.2~R0.6. Therefore, parts processed by cold extrusion are generally rarely cut and only require precision grinding in areas with particularly high requirements.
4. Improve the mechanical properties of parts
The cold work hardening of the metal after cold extrusion, as well as the formation of a reasonable fiber streamline distribution inside the part, make the strength of the part much higher than that of the raw material. In addition, a reasonable cold extrusion process can create compressive stress on the surface of the parts and improve fatigue strength. Therefore, some parts that originally required heat treatment strengthening can be eliminated through cold extrusion technology, while some parts that originally needed to be made of high-strength steel can be replaced with lower strength steel after cold extrusion technology.
5. Parts with complex shapes that are difficult to machine by cutting
Such as irregular cross-sections, complex internal cavities, internal teeth, and invisible grooves on the surface.
6. Reduce component costs
Due to the advantages of cold extrusion technology, such as saving raw materials, improving productivity, reducing the cutting amount of parts, and using inferior materials to replace high-quality materials, the cost of parts is greatly reduced.
▲ What is cold heading
Cold heading workpiece ↑
Cold heading technology is one of the new processes for pressure machining of rare and uncut metals. It is a processing method that utilizes the plastic deformation of metal under external force, and uses a mold to redistribute and transfer the volume of the metal, thereby forming the required parts or blanks. Cold heading technology is suitable for producing standard fasteners such as bolts, screws, nuts, rivets, and dowels. The commonly used equipment for cold heading process is a dedicated cold heading machine. If the production volume is not too large, a crank press or friction press can also be used as a substitute.
Cold heading technology is increasingly widely used in mechanical manufacturing, especially in the production of standard fasteners, due to its high productivity, good product quality, greatly reduced material consumption, lowered production costs, and improved working conditions. Representative products produced by multi station cold heading machines are bolts, screws, and nuts.
▲ Advantages of cold heading process
1. Cold heading is carried out under normal temperature conditions. Cold heading can improve the mechanical properties of metal parts. The tensile strength after cold heading processing is about 10% higher than that of cutting processing, and some can even increase by 20%. This is because the metal fibers of cold heading processed products are not cut, the internal structure of the metal is compacted, and the presence of work hardening phenomenon is accompanied, so the mechanical properties of the metal are improved.
2. Cold heading technology can improve material utilization efficiency. Taking cold heading bolts as an example, the new process of "concave hole" hexagonal head bolts can achieve a material utilization rate of over 99%. Except for the loss of material heads and tails, it has achieved complete zero cutting processing. If cutting is used, the material utilization rate is only 40%. The material utilization rate of cold heading nuts can also reach about 80%, while the material utilization rate of cutting nuts is only 54%.
3. Cold heading technology can greatly improve productivity. Compared with the original cutting process, the productivity of cold heading nuts is increased by about 25-30 times.
4. Due to the use of multi station cold heading machines, each process can be processed simultaneously on one machine tool, thereby reducing equipment investment, minimizing the production space occupied by equipment, reducing the transportation of semi-finished products between processes, especially reducing the labor intensity of workers and improving working conditions.
5. Cold heading technology can improve the surface smoothness of products and ensure product accuracy. For mass production of bolts, nuts, etc., their accuracy can be fully guaranteed.
Are cold heading and cold extrusion the same thing? What's the difference?
Cold heading and cold extrusion are basically deformation processes under the same conditions, but their operating methods are different. Cold pier belongs to the forging deformation of smaller workpieces and is commonly used in the fastener industry. Cold extrusion belongs to the deformation of larger workpieces and has a wide range of applications; Cold heading is equivalent to a branch of cold extrusion. Simply put, in the process of making bolts, hexagonal head forming belongs to cold heading, and rod diameter reduction belongs to cold extrusion (positive extrusion). Non cut hexagonal flange bolts (multi station forming) have both cold heading and cold extrusion. The front forming of hexagonal nuts only has cold heading, while the later process of hole extrusion belongs to cold extrusion (forward and backward extrusion).
(Source: Cold heading Home)
