Presice MIM Process MIM Factory Auto Gears

Material: iron
Density: ≥ 7.6g/cm3
Hardness: 40-45HRC
Tensile strength: 300mpa
Yield strength: ≥180mpa
Surface treatment: vibrate grinding + polishing

Here we introduce the powder metallurgy process peformance and defect.

1.The compact density does not meet the design requirements.

In the production of powder metallurgy parts, the higher the density of materials, the higher the physical and mechanical properties. In other words, the compact density and distribution of powder metallurgical parts will determine the performance of the final product. Therefore, in the process of debugging and pressing of powder metallurgy dies, the density of compacts must be tested. In density testing, attention should be paid to the different structure and requirements of the compacts to be treated differently.

2. Compacted blank size does not meet the requirements

2.1 Unqualified radial dimension or hole spacing

It may be that there is a problem with the design or manufacture of the die. If the error can be eliminated by adjusting the process (that is, by adjusting powder composition, compact density, sintering process, etc.). It can also be remedied, otherwise only scrap moulds.

2.2 Axial Dimensions Unqualified

For non-step cylindrical billet, the axial dimension can be adjusted and stabilized by adjustin powder loading, changing pressing pressure or prolonging holding time. For step blanks, adjusting the forming position of the combined die, the powder loading ratio of each stage and the running speed of the floating die can change the step height size.

3. Excess tolerance of form and position

3.1 Straightness

The causes of straightness overshoot are as follows: die straightness overshoot, uneven distribution of compact density, uneven wall thickness of compact, etc.

3.2 Parallelism

The reasons for the parallelism overshoot are: the parallelism overshoot of the die and the uneven powder loading.

3.3 coaxiality

The causes of coaxiality overshoot are: the precision of die is overshoot, the precision of pressing tooling and equipment is low, the installation of die does not meet the requirements, and the dressing is not uniform.

When the powder flow rate is appropriate, the die precision meets the design requirements and the pressing tooling and equipment accuracy meets the installation requirements, the shape and position tolerance is mainly related to the density distribution of the compact. When the pressing mode is determined, the density distribution of the compact is directly related to the filling effect.

4. Unqualified Appearance

High roughness, excessive burr, edge drop, roughening and crack are common exterior defects of compacts.