Cold heading belongs to the category of metal pressure processing, which is one of the non cutting metal pressure processing technologies. In the formation process of fastening parts, cold extrusion heading is a main process. The cold extrusion process is the most suitable for production of bolts, screws, nuts, rivets.
What is Cold Extrusion?
Cold heading is an important part of precision plastic forming technology. Cold extrusion refers to putting metal blank into the mold cavity in the cold state. Under the effect of strong pressure and a certain speed, the metal material is forced to produce plastic flow, so as to obtain the required shape, size and some extrusion parts with certain mechanical properties.
Obviously, cold extrusion processing is to control metal flow by molds, and a large amount of metal volume is transferred to form parts. In fact, the forming of any fastener can be realized not only by cold heading, but also is accompanied by a variety of deformation methods such as extrusion, punching and rolling.
Advantages Of Cold Extrusion
1. Saving raw materials.
Cold extrusion adopts plastic deformation of metal to make the required parts, so it can reduce cutting process and improve the material utilization rate. The utilization rate of cold extrusion materials can generally reach more than 80%.
2. Improve labor productivity
Manufacturing parts produced by cold extrusion process instead of cutting processing, which can increase productivity several times, or even dozens of times.
3. The parts can obtain the ideal surface roughness and size accuracy.
The parts that are processed with cold extrusion are rarely re-cutting process, and only need to be grinded for the particularly high requirements.
4. Improve the mechanical properties of parts
The cold work hardening of metal through cold extrusion processing and a reasonable fiber streamline distribution inside the parts, making the strength of the parts much higher than the strength of the raw materials. In addition, a reasonable cold extrusion process can form compression stress on the surface of the parts to increase fatigue intensity. Therefore, some parts that require heat treatment enhancement can save the heat treatment process adopting the cold extrusion process.
5. Machinable parts with complicated shapes and difficult to cut processing.
Such as irregular section, complex inner cavity and teeth, and invisible inner grooves.
6.Reduce production cost
Because the cold extrusion process has the advantages of saving raw materials, increasing productivity, reducing the amount of cutting processing, and using inferior materials instead of high-quality materials, which can greatly reduce cost.
Difficulties In Application of Cold Extrusion Technology
1. High requirements for molds
When cold extruding, the deformation resistance of metal blank is significantly increased under the pressure stress in the mold, which makes the stress suffered much larger than the general stamping mold. In addition to high-intensity, the mold also needs sufficient impact toughness and high wear resistance.
2.Requiring a large tonnage press machine
Due to the large deformation resistance of the blank during cold extrusion, hundreds of tons or even thousands of tons of press machine are needed.
3.Only applicable to a large scale of production
Due to the high cost of cold extrusion molds, it is generally only applicable to the production for parts of large quantities. Its minimum number is 50000 pieces.
4. The surface treatment must be performed in advance
The surface treatment not only increases the procedures and occupy a large production area, but also it is also difficult to achieve automation.
5.Not suitable for high-intensity materials processing
6. Part deformation and reduction of corrosion resistance
The plasticity and impact toughness of cold extruded parts have become worse, and the residual stress of the parts is large, which will cause parts deformation and produce stress corrosion.
Development Trend of Cold Extrusion Technology
1.With the increasingly serious energy crisis, people will pay more attention to the quality of the environment, and the increasing market competition will promote the development of forging production in the direction of efficient, high-quality, refinement, energy saving and material-saving. Therefore, the output of the refined forging parts produced by extruding forming and other processes will be developed in market competition
2.The car has developed towards the directions of light, high-speed, and stable. It has put forward higher requirements for the size accuracy, weight accuracy and mechanical properties of forging parts, which will promote the development of refined production technology.
3. Specialized and large-scale organizational production is still the development trend of cold extrusion production.
4. Extrusion machine will become a development trend. With the refined production development of small and medium-sized forging parts and the application of cold extrusion technology, multi station cold extrusion machine, precision press, and special machine designed and manufactured for some forged parts will be vigorously developed.
Cold extrusion technology is an advanced production technology with the characteristics of high-precision, high-efficiency, high-quality and low-consumption, which is mostly applied in large scale production of medium and small forging parts.