1. Hot forging process:
The process of plastic deformation of metal materials by heating them above the recrystallization temperature is called hot forging.
Due to the fact that heating devices generally use furnace heating methods such as coal-fired reverberatory furnaces and heavy oil furnaces, the temperature of the billet is difficult to control, the heating is uneven, the heating time is long, and it is easy to cause overburning and oxidation decarbonization, which is the main reason for poor quality of the formed parts.
2. The forging force is only 1/4~1/3 of the cold heading force, and equipment with lower nominal pressure can be selected.
3. Difficulty in cooling the mold cavity. The mold can withstand a temperature of around 100 ℃ for the blank, and areas that cannot be cooled are prone to softening and cracking, causing damage to the mold.
Cold heading process:
Cold heading (extrusion) belongs to the category of metal pressure machining and is one of the non cutting metal pressure machining processes.
In production, external force is applied to the metal at room temperature to form it in a predetermined mold. This method is usually called cold heading (extrusion).
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 other processing techniques, cold extrusion has the following advantages:
1. High utilization rate of steel. Cold heading (extrusion) is a minimal and non cutting processing method, such as machining hexagonal bolts and cylindrical internal hexagonal screws for rods. By using cutting processing method, the steel utilization rate is only 25% to 35%, while using cold heading (extrusion) method, its utilization rate can be as high as 85% to 95%, with only some process consumption of material head, material tail and cutting hexagonal head edge.
2. Good mechanical performance. Parts processed by cold heading (extrusion) method have much better strength than those processed by cutting because the metal fibers are not cut.
3. Suitable for automated production. Fasteners (including some irregular parts) suitable for cold heading (extrusion) production are basically symmetrical parts, suitable for high-speed automatic cold heading machine production, and are also the main method for mass production.
4. 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%.
5. 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.