Abstract
A new method for evaluation of iron powders is suggested. Ultimate tensile strength is chosen as a base parameter, and the relations between this property and compacting pressure and raw material cost, respectively, are shown. For this purpose it has been necessary to deduce two supplementary parameters, Relative Pressure Response (Pr) and Relative Raw Material Requirement (Mr), which are functions of compacting pressure and ultimate tensile strength, and of compacting pressure and density, respectively.
It is shown that the importance of compressibility of iron powders is overrated in current opinion and, consequently, that it is misleading to judge the overall merits of an iron powder according to its compressibility.
Raw material costs of sintered steels are lower, if sponge-iron powders are used instead of atomized powders, even if the price of all iron powders were equal. This tendency is more strongly emphasized at low densities, where the sponge-iron powder with the lowest apparent density value is preferable. The differences are beginning to lessen and disappear gradually at densities approaching or exceeding 7·0–7·2 g/cm3 (for single-pressed and single-sintered materials).
Alloy composition has a stronger influence on raw-material costs than the choice of iron-powder grades. Close and reliable control of carbon contents and avoidance of oxidation of manganese is essential for lowering of costs in the PM structural-component manufacturing industry.
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