Author: Site Editor Publish Time: 19-09-2019 Origin: Site
1. Inter-particle shift:
The interparticle bonding is initially formed mainly by plastic deformation and powder block motion. Under ideal conditions, the densification process is bidirectional, symmetrical and synchronous, and there is no interparticle displacement. The shift after the densification process The bit motion prevents the formation of bonds between the particles and can destroy the bonds that have formed in the early stages of forming.
2. High tension, shear force:
In the state of powder metallurgy, if the tensile force generated by the external or internal action of the shaped body is higher than the green strength of the shaped body itself, cracks will occur.
3. Wrong material integration:
For various reasons, metal powders use additives. For example, adding a suitable lubricant for mixing increases the compressibility and reduces the release force. However, adding too much lubricant to the mixed iron powder inhibits the formation of bonds between the particles and bonds. Agents, impurities and even residual air can have a negative effect on bond formation.
4. During the abnormal plastic strain separation forming process:
The particles will undergo irreversible plastic deformation. In addition, recoverable plastic deformation will occur. After the final forming stage, the associated pressure will decrease and eventually fall to zero during the demolding process. At the moment when the forming pressure is released, the compressive stress is released. The shaped body embryo will suddenly change from plastic to elastic stage. If the internal stress is greater than the strength limit of the shaped body, cracks will be generated.