Casted versus forged steel

For a better understanding of the main differences between the processes of foundry and forgering, Fupresa has prepared a detailed techinical documentation.

Limitations and Considerations

The first consideration to be made is that, steel parts originally projected to be produced by conventional metalurgical methods, can rarely be produced by sintering without modifications.

In order to obtain maximum sintering process advantages (high dimensional precision and superficial finishing excellence), it's necessary to adequately project the modifications to be made to the part itself, considering the limitations that the compression operation itself (fundamental process operation) poses.

The sintering techniques (powder metallurgy) works well with items which do not present considerable variations in its transversal sections. Therefore, corners, and sharp edges, very thin walls, or any such particularity must be avoided, for the powder, under the effect of pressure, does not flow as liquid does, which prevents the adequate fulfilment of the recesses in the matrices cavities.

The product designer must bear in mind a series of rules which restrict the sintered parts project and, must also consider the supplementary machining operation if the finished product so demands.

Such rules may be summarized as below:

• Avoid parts shapes and contours which prevent the extraction of the part from the matrice. Lateral holes, negative draft angles, bolt threads, etc, are impossible to mould, these product geometrical particularities, if really necessary, can only be obtained by supplementary machining;
• Avoid thin walls, sharp edges and such particularities which by making difficult the inflow of powder into the matrice leads to an increase in production costs and originate material with defective physical characteristics. Such product geometrical particularities, if really necessary, can only be obtained by supplementary machining;
• Avoid abrupt changes in wall thicknesses, because it may result in bending and irregular density during the sintering process, leading therefore, to an increase in the amount of scrap parts;
• Due to the small variety of metallic powder, select just within the limited “menu”.