Cold forging of aluminum alloys
Compared with hot forging, cold forging technology has many advantages. It has high workpiece accuracy, good strength, low material consumption, and low energy consumption. Other advantages are low total processing cost, high production efficiency, and ease of automation.
But there are also some disadvantages too. Cold forging equipment requires large tonnage, rigidity, and precision. The strength and toughness of the mold material are required to be high. The mold structure is complex and difficult to manufacture. The scope of application of the material is narrow as most materials cannot be cold forged due to poor plasticity and deformation resistance.
Additionally, the pretreatment process of the material is complex, and most cold forging materials need to be annealed and softened, phosphating -saponification treatment. Although these problems have limited the promotion and application of aluminum alloy cold forging technology to a certain extent, with the development of science and technology, there are more and more measures to overcome these technical problems.
The cold forging technology of pure aluminum was developed earlier. This is because pure aluminum has little deformation resistance and good plasticity at room temperature. The processing hardening is not strong when deforming. So the cold forging performance is very good, which is an ideal cold forging material. Pure aluminum cold forgings have been widely used.
Anti-rust aluminum with a low degree of alloying (such as 5A02, 3A21, etc.) also has a good cold forging performance. But compared with pure aluminum, anti-rust aluminum has a higher hardening tendency. It requires larger equipment for cold forging, and the current application range is expanding.
Other aluminum alloys also cold forged
Among other series of aluminum alloys in the main applications of cold forging technology are 2A11, 2A12, 2A14, 2A50, 6061, 6082, and other alloys. Compared with steel in the annealed state, the deformation resistance of these alloys in the annealed state is slightly smaller. But the plasticity is slightly worse, which is easy to produce cracks. However, after the blank is annealed and phosphating saponified, the friction conditions are improved. So the shape can be smoothly formed.
The technical measures of aluminum alloy cold forging mainly include:
(1) The aluminum alloy is annealed before cold forging to reduce the cold forging force and improve the plasticity of the material. For duralumin alloys, the hardness after annealing is not as low as possible. Generally, the hardness of the blank should be HBS49~50 when the positive extrusion is positive. Similarly, the hardness of the blank should be HBS46~50 when the anti-extrusion is used.
(2) Duralumin should be oxidized -saponified before cold forging, and the blank is placed in a NaOH solution of 50 °C ~ 70 °C (containing NaOH 40g ~ 60g per liter of solution) for 1min to 3 min so that a layer of the crystalline oxide film is formed on the surface. Then heated in industrial soap or sodium stearate to 60 ° C ~ 70 ° C for 20min ~ 30min. It is then naturally dried or dried. Pure aluminum and anti-rust aluminum generally do not carry out this surface treatment when cold forging.
(3) Aluminum alloy can use soybean oil or industrial vegetable oil to lubricate the mold in cold forging. It can also use industrial lard. With the development of lubricants, many companies now produce special aluminum alloy cold forging lubricants, and the lubrication effect is better.
If you would like to know more about forging production technology, please contact us.