Specialized metallurgical processes – compositions for use therei – Compositions – Loose particulate mixture containing metal particles
Patent
1994-03-22
1996-04-09
Wyszomierski, George
Specialized metallurgical processes, compositions for use therei
Compositions
Loose particulate mixture containing metal particles
75231, 75252, C22C 3302, H01F 1147
Patent
active
055057608
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an iron-based powder composition containing Sn and P for manufacturing components with stringent demands in respect of soft magnetic properties and low eddy current losses.
One of the major advantages gained from powder-metallurgical manufacture of components as compared with conventional techniques is that it permits manufacturing components in long series with high dimensional accuracy. In such manufacture, an iron base powder is mixed e.g. with additions of pulverulent alloying substances and a lubricant. The alloying substances are added to give the finished component the desired properties, whilst the lubricant is added primarily to reduce the tool wear when compacting the powder mixture. The compacting of the powder mixture into the desired shape is followed by sintering.
Powder-metallurgical manufacture of components for soft magnetic purposes is today performed primarily by compacting and high-temperature sintering, meaning temperatures above 1150.degree. C. High-temperature sintering is relied on above all since it is known that the soft magnetic properties are improved when the sintering temperature is raised. It is above all the particle growth, but also such factors as a more homogeneous distribution of alloying substances and higher density that entail enhanced soft magnetic properties in these materials as compared with materials sintered at lower temperatures.
The major iron-based tonnage for soft magnetic purposes is manufactured with the addition of Si, both to enhance the soft magnetic properties and to increase the resistivity so as to reduce the eddy current losses in AC applications. Powder-metallurgical manufacture of Si-alloyed materials necessitates high-temperature sintering, since otherwise Si would oxidise and not be dissolved into the iron. High-temperature sintering however results in substantial shrinkage during sintering, which gives rise to difficulties in maintaining the dimensional accuracy on the components.
Components for soft magnetic purposes can also be manufactured in powder metallurgy by adding P to iron-based materials. The addition of P enhances the soft magnetic properties as compared with pure Fe and also improves the resistivity to some extent, that is, reduces the eddy current losses in AC applications. Moreover, the process technique is simple in that the components can be sintered in a belt furnace where the temperature is maximised to about 1150.degree. C. P-alloyed materials, on the other hand, have considerably lower resistivity than today's Si-alloyed materials, both after sintering in a belt furnace and after sintering at a high temperature (t>1150.degree. C.).
The object of the present invention therefore is to provide an iron-based powder composition which after compacting and sintering exhibits iron-based powder-metallurgical materials;
Moreover, this powder composition should after compacting and sintering exhibit currently known iron-based powder-metallurgical materials when sintering is performed in a belt furnace, i.e. at a maximum temperature of about 1150.degree. C.;
According to the invention, the desired properties can be obtained by means of an iron-based powder composition which, in addition to a substantially non-alloyed Fe-powder, comprises Sn and P, optionally lubricant and at most 1.0% by weight of impurities, wherein
a) Sn and P are present as an SnP-alloy in powder form, or wherein
b) Sn is present in the form of a metallic powder and P is present in the form of a ferrophosphorous powder, Fe.sub.3 P, the Sn-content, based on the total iron-based powder composition, being at least 4.5% by weight and the individual particles, which contain Sn and P, being present as particles substantially separate from the particles in the non-alloyed Fe-powder, or wherein
c) Sn and P are present as an SnP-alloy in powder form, and Sn is additionally present as a metallic powder, and wherein, optionally, P is also present as a ferrophosphorous powder Fe.sub.3 P.
In powder compositions according to Alternatives a) and
REFERENCES:
patent: 4093449 (1978-06-01), Svensson et al.
patent: 4643765 (1987-02-01), Takajo
patent: 5256185 (1993-10-01), Semel et al.
patent: 5290336 (1994-03-01), Luk
Hoganas AB
Wyszomierski George
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