Let ‘s just cut into the case.
What is cold extrusion?
Cold extrusion of cold extrusion workpiece is to place metal blank in the cold extrusion die cavity. At room temperature, pressure is exerted on the blank through the fixed punch on the press, so that the metal blank can produce plastic deformation and the processing method of parts is made. Obviously, cold extrusion processing relies on the die to control the metal flow, and depends on the large volume of metal to rotate. Move to form parts. In terms of extrusion equipment, our country has the ability to design and manufacture various tonnage extrusion press. In addition to general mechanical press, hydraulic press and cold extrusion press, friction press and high-speed and high-energy equipment are successfully used for cold extrusion production.
If the blank is extruded without heating, it is called cold extrusion. Cold extrusion is one of the processing technologies for parts without chips and with few chips, so it is an advanced processing method in the plastic processing of metal chips. If the blank is heated to the 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 technology with high precision, high efficiency, high quality and low consumption. It is widely used in the large-scale production of small and medium forgings. Compared with hot forging and warm forging, it can save 30%-50% of material and 40%-80% of energy. It can also improve the quality of forgings and the working environment. At present, cold extrusion technology has been widely used in fasteners, machinery, instrumentation, electrical appliances, light industry, aerospace, shipping, military and other industrial sectors, and has become one of the indispensable important processing means in metal plastic volume forming technology. With the progress of science and technology and the continuous improvement of technical requirements for products in automobile, motorcycle, household appliances and other industries, cold extrusion production technology has gradually become the development direction of fine production of small and medium forgings. Cold extrusion includes forward extrusion, backward extrusion, compound extrusion and radial extrusion.
Advantages of cold extrusion process
1. Save raw material cold extrusion is to use metal plastic deformation to make the required shape parts, which can greatly reduce cutting processing and improve material utilization. The material utilization rate of cold extrusion can generally reach more than 80%. 2. Improving labor productivity by using cold extrusion instead of cutting to manufacture parts can increase productivity several times, tens of times or even hundreds of times. 3. The parts with ideal surface roughness and dimensional accuracy can reach IT7-IT8 and R0.2-R0.6. Therefore, parts processed by cold extrusion are seldom re-machined, and only need to be grinded at a particularly high level. 4. Improving the mechanical properties of the parts after cold extrusion, hardening the metal after cold working, and forming a reasonable fiber streamline distribution inside the parts, so that the strength of the parts is much higher than that of the raw materials. In addition, reasonable cold extrusion process can form compressive stress on the surface of parts and improve fatigue strength. Therefore, the cold extrusion process can be omitted for some parts which need to be strengthened by heat treatment. Some parts need to be manufactured with high strength steel. After cold extrusion process, the steel with lower strength can be used instead. 5. Machinable parts with complex shapes, such as special section, complex inner cavity, inner teeth and invisible inner grooves on the surface, which are difficult to cut. 6. Reduce the cost of parts because the cold extrusion process has the advantages of saving raw materials, improving productivity, reducing the amount of cutting parts, and using poor materials instead of high-quality materials, so that the cost of parts is greatly reduced.
What is cold heading?
Cold upsetting process for cold heading workpiece is one of the new processes for pressure processing of few or no cutting metals. It is a kind of processing method that makes use of the plastic deformation of metal under the action of external force and makes the volume of metal redistribute and transfer by means of die, thus forming the required parts or blanks. Cold heading process is most suitable for the production of standard fasteners such as bolts, screws, nuts, rivets, pins and so on. The common equipment used in cold heading process is special cold heading machine. If the production is not large, crank press or friction press can be used instead. Because of its high productivity, good product quality, greatly reducing material consumption, reducing production cost and improving working conditions, cold heading process is more and more widely used in mechanical manufacturing, especially in the production of standard fasteners. The most representative product produced by multi-station cold heading machine is bolt. Screws and nuts.
Advantages of cold heading process
1. Cold upsetting is carried out at room temperature. Cold heading can improve the mechanical properties of metal parts. The tensile strength of cold upsetting is about 10% higher than that of cutting, and some can even be increased by 20%. This is because the metal fibers of cold heading products will not be cut off, the internal structure of the metal will be compacted, and accompanied by the existence of work hardening, so the mechanical properties of the metal have been improved. 2. Cold heading process can improve material utilization rate. Taking the cold heading bolt as an example, the material utilization rate of the new technology “concave” hexagonal head bolt can reach more than 99%. Except for the loss of material head and tail, no cutting has been achieved. For cutting, the material utilization rate is only 40%. The material utilization rate of cold heading nut can also reach about 80%, while that of cutting nut is only 54%. 3. Cold heading process can greatly improve productivity. For example, compared with the original cutting process, the productivity of cold heading nut is increased by 25-30 times. 4. Because of the use of multi-station cold heading machine, all processes are processed simultaneously on one machine tool, which reduces the investment of equipment, reduces the production site occupied by equipment, reduces the transportation of semi-finished products between different processes, especially reduces the labor intensity of workers, and improves the working conditions. 5. Cold heading process can improve product surface finish and ensure product accuracy. For mass production of bolts, nuts and so on, the accuracy can be fully guaranteed.
Is cold heading the same as cold extrusion? What’s the difference?
Cold upsetting and cold extrusion are basically deformation processing under the same conditions, but the operation mode is different. Cold pier belongs to forging deformation of small workpiece and is often used in fastener industry. Cold extrusion belongs to the extrusion deformation of larger workpieces and has a wide range of applications. Cold upsetting is equivalent to a branch of cold extrusion. Simply speaking, in the process of making bolts, hexagonal head forming belongs to cold upsetting, and rod diameter reduction belongs to cold extrusion (forward extrusion). Non-trimmed hexagonal flange bolts (multi-station forming) have both cold upsetting and cold extrusion. The front side of hexagonal nuts is cold upsetting, while the back process is cold extrusion (forward and backward extrusion).