Abstract
In the conventional press and sinter process, dimensional change on sintering determines the precision of the final parts, providing that a good dimensional precision of green parts is ensured. Anisotropic dimensional change on sintering may be detrimental to the precision of Powder Metallurgy (PM) parts, and it should be considered in the design step. The effect of material and geometry on the anisotropic dimensional change is studied in this work. Four different iron alloys and five different geometries were considered. Dimensions were measured both on green and on sintered parts and the anisotropy of dimensional change was evaluated and correlated to the material and geometry. The effect of neglecting anisotropy in the design step was investigated, in terms of dimensional tolerances, which can be obtained with different process capabilities. A model to describe the effect of material and geometry on the anisotropic dimensional change is also being developed.
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Abbreviations
- Dext :
-
dimensional change in the external diameter normalized by the isotropic dimensional change
- Dint :
-
dimensional change in the internal diameter normalized by the isotropic dimensional change
- dN :
-
nominal dimension [mm]
- dg :
-
dimension of the green part [mm]
- ds :
-
dimension of the sintered part [mm]
- e:
-
process capability error
- H:
-
dimensional change in height normalized by the isotropic dimensional change
- h:
-
height of the part (disks - rings) [mm]
- hg :
-
height of the green part (disks - rings) [mm]
- hN :
-
nominal height [mm]
- hs :
-
height of the sintered part (disks - rings) [mm]
- K:
-
anisotropy parameter
- lg :
-
dimension in the green state [mm]
- R:
-
ratio between the internal and the external diameter in the green parts
- t:
-
wall thickness of the rings [mm]
- Vg :
-
volume of the green part (disks - rings) [mm3]
- Vs :
-
volume of the sintered part (disks - rings) [mm3]
- α :
-
geometrical parameter relating the dimensional changes in the internal and external diameters
- γ :
-
geometrical parameter relating R and α
- ΔV/Vg :
-
volume change
- ε d :
-
actual dimensional change
- ε h :
-
dimensional change in height
- ε iso :
-
isotropic dimensional change
- ε ref :
-
dimensional change relevant to a known reference geometry
- ε ϕ :
-
dimensional change in the external diameter for disks
- ε ϕ ext :
-
dimensional change in the external diameter for rings
- ε ϕ int :
-
dimensional change in the internal diameter for rings
- ϕ:
-
external diameter of the disks [mm]
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Cristofolini, I., Corsentino, N., Molinari, A. et al. Study of the influence of material and geometry on the anisotropy of dimensional change on sintering of Powder Metallurgy parts. Int. J. Precis. Eng. Manuf. 15, 1865–1873 (2014). https://doi.org/10.1007/s12541-014-0540-5
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DOI: https://doi.org/10.1007/s12541-014-0540-5