MAGNETIC AND ELECTRICAL PROPERTIES OF POWDER METALLURGY IRON- PHOSPHORUS ALLOYS.

Iron Phosphorus alloys are the second most specified Powder Metallurgy soft magnetic material after pure iron. The alloys are produced by premixing pure iron with an iron-phosphorus intermetallic, which melts during sintering and diffuses into the iron, increasing the density of the sintered component.

Density is one of the key factors affecting the magnetic performance of the P/M components. With the density increase the saturation induction B max, permeability µ max and the residual saturation Br are increased, but the coercive force Hc is decreased.

The permeability (µ=B/H) is a measure of how easily a material may be magnetized and defined as the ratio of the flux density (induced magnetism B) to the applied field (H).

The iron-phosphorus alloys 45P (0.45%P) and 80P (0.80%P ) are patented products of AB Hoeganaes (Sweden) and Hoeganaes Corporation.


Typical Magnetic Properties of 45P and 80P Materials
Density, g/cc
Hc (Oe)
Br (kG)
Bmax (kG)
µmax
45P
6.84
1.75
9.7
11.1
2830
7.12
1.73
11.0
12.4
3290
7.27
1.71
11.8
13.2
3700
80P
6.86
1.50
11.8
11.9
3940
7.16
1.45
10.6
13.1
4520
7.34
1.45
11.8
12.9
4780

Oe, oersted- the unit of magnetizing force in c.g.s. system.
KG, kiloGauss-the unit of magnetic induction in c.g.s.system.

Due to residual porosity the electrical conductivity of the PM materials is less of wrought materials: higher the density - lower the porosity and higher the conductivity. There is no published data on the conductivity of 80-P material.
The conductivity of wrought soft steel is 16.05 microhms (cm 2 /cm).
Assuming that 80-P at full density has the same conductivity, the calculated conductivity as the function of density equal:

Electrical Conductivity of 80P Material
Density g/cc
% of Theoretical Density
Conductivity ,Microhms (cm2/cm)
6.86
6.86/7.87=0.87
0.87*16.05=13.99
7.16
7.16/7.87=0.90
0.90*16.05=14.6
7.34
7.34/7.87=0.93

0.93*16.05=14.97
The material conductivity data for sintering at higher temperature (100º C) and under hydrogen atmosphere is not available.
 
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