What are the requirements for molds in cold heading parts processing?

The skill level of cold heading in the process of processing is as follows 5 points:
1, cold heading should not be processed with high strength material, need to use large tonnage press, because cold kneading of the deformation resistance of the blank is large, need to use hundreds of tons or even thousands of tons of press. Because the cost of cold kneading mold is high, usually only applicable to large-scale production of parts. It is suitable for small batches of 5-100,000 pieces.
2, the rough before kneading the appearance of treatment. This not only increases the process, needs to occupy a larger production area, and difficult to achieve production automation.
3. Cold heading process has high demand for die. During cold kneading, the deformation resistance of the blank in the die increases obviously because of the three-dimensional compressive stress, which makes the stress of the die much larger than that of the usual stamping die. In addition to the mold needs to have high strength, but also to meet the impact toughness and wear resistance.
4. The severe plastic deformation of the metal blank in the mould will make the mould temperature rise to 250 ° C ~ 300 ° C, therefore, the mould material needs the necessary tempering stability.
5, cold kneading die life is much lower than the stamping die. The ductility and impact toughness of cold-kneaded parts become worse, and the residual stress of parts becomes larger, which will lead to the decrease of deformation and corrosion resistance (stress corrosion) .
 
How does the metal move in the cold heading process? There are several common extrusion methods in the cold heading process:
1. Forward extrusion. During extrusion, the direction of metal flow is consistent with the direction of convex-transverse motion. Positive extrusion is divided into solid parts positive extrusion hollow parts positive extrusion two. Positive extrusion method can be cold heading processing out of a variety of shapes of solid parts and hollow parts, such as screws, mandrel, tubes and shells.
2. Reverse extrusion. During extrusion, the flow direction of gold chips is opposite to the movement direction of punch. The reverse extrusion method can produce cup-shaped parts with various cross-section shapes, such as cold heading instrument shell, universal joint bearing sleeve, etc. .
3. Compound extrusion. During extrusion, one part of the blank flows in the same direction as the punch, while the other part flows in the opposite direction, the composite extrusion method can be used to manufacture double cup type parts, and can also be used for cold heading of cup rod type parts and rod rod type parts.
From this, it can be seen that the decision to process a qualified cold upsetting piece is not a simple matter, so the price has a reason. It will not be fake if you pay a penny for the goods. Once again, I appeal to you not to neglect the quality, pay attention to craftsmanship.