What defects often occur during the metal powder metallurgy compaction process?
During the metal powder metallurgy pressing process, compact defects may occur due to various reasons, resulting in powder metallurgy parts being scrapped. So, what defects often occur during the metal powder metallurgy compacting process?
1. The compact density does not meet the design requirements
In the production of metal powder metallurgy parts, the higher the density of the material, the higher its physical and mechanical properties. In other words, the density and distribution of the compacted metal powder metallurgy parts will determine the performance of the product. Therefore, during the debugging and pressing process of metal powder metallurgy molds, the density of the compact is an item that must be tested. During density testing, it should be noted that compacts with different structures and requirements should be treated differently.
2. The size of the compact does not meet the requirements
2.1 Unqualified radial size or unqualified hole spacing
There may be a problem with the mold design or manufacturing. If the error can be eliminated by adjusting the process (that is, by adjusting the powder composition, compact density, sintering process, etc.). It can also be remedied, otherwise the mold will only be scrapped.
2.2 Unqualified axial dimensions
For stepless cylindrical compacts, the axial size can be adjusted and stabilized by adjusting the powder loading, changing the pressing pressure or extending the holding time. For step compacts, the step height can be changed by adjusting the forming position of the combined die punch, the powder loading ratio of each station, and the operating speed of the floating die punch.
3. Geometric tolerance is out of tolerance
Reasons for excessive straightness include: excessive straightness of the mold, uneven density distribution of the compact, uneven wall thickness of the compact, etc.
Reasons for excessive parallelism include: excessive parallelism of the mold, uneven powder loading, etc.
Reasons for excessive coaxiality include: excessive mold accuracy, low accuracy of pressing tooling and equipment, mold installation that does not meet requirements, uneven decoration, etc.
When the powder flow rate is appropriate, the mold accuracy meets the design requirements, and the pressing tooling and equipment accuracy meets the installation requirements, the geometric tolerance is mainly related to the density distribution of the compact. When the pressing method is determined, the density distribution of the compact is directly related to It is related to the powder filling effect.
4. Unsatisfactory appearance
High roughness, excessive burrs, dropped edges, rough edges, cracks, etc. are all common appearance defects of the compact.
The above is an introduction to the defects produced during the metal powder metallurgy compaction process. There are many defects in metal powder metallurgy compactions, but the hard-to-find defects that can cause the product to be scrapped are: uneven density and compaction cracks, so everyone must pay attention.
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