MMPA STANDARD No. 0100-00
STANDARD SPECIFICATIONS FOR PERMANENT MAGNET MATERIALS
MAGNETIC MATERIALS PRODUCERS ASSOCIATION

IRON-CHROMIUM-COBALT MAGNETS (FeCrCo)

1.0 CHEMICAL COMPOSITION
These alloys are primarily of the Iron-Chromium-Cobalt (FeCrCo)composition. Some grades may also contain additions of vanadium, silicon, titanium, zirconium, manganese, molybdenum or aluminum.

2.0 MANUFACTURING METHODS
The Iron-Chromium-Cobalt alloys are formed either by casting to size or by casting in the form of an ingot which is then rolled and/or drawn either to final shape or to form which can then be cut. Heat treatment is essential to develop the magnetic properties. The magnetic properties can be increased in a preferred direction by applying a magnetic field during heat treatment.
Although this alloy is hard and brittle in its fully heat treated condition, it is sufficiently ductile to be rolled, drawn, machined, turned or threaded prior to its final heat treatment.

3.0 MAGNETIC PROPERTIES
The magnetic properties of the commercial grades of Iron-Chromium-Cobalt alloys are listed in Table V-l.

4.0 DIMENSIONS AND TOLERANCES
Standard tolerances for cast, rolled and drawn IronChromium-Cobalt magnets are listed in Table V-2.

5.0 MECHANICAL CHARACTERISTICS
The following general specifications are for mechanical characteristics and visual conditions.
5.1 Surface Conditions
There should be no cracks, chips, burrs or other conditions that would interfere with the proper functioning of the end use device.
5.2 Chips
5.2.1 Magnets shall be free of loose chips or imperfecttions which will result in loose chips under normal handling and shipping conditions.
5.2.2 A chipped edge or surface shall be acceptable if not more than 10% of the edge or 5% of the surface is removed.
5.3 Visual Standards The use of mutually agreed upon visual standards is recommended in cases where such properties are critical.
5.4 Inspection Methods Inspection methods such as the use of penetrants, magnetic particle analysis, ultrasonics or x-ray shall not be acceptable methods for judging the quality of cast, rolled or drawn Iron-Chromium-Cobalt magnets except in cases where the magnet is expected to withstand abnormal conditions. In those cases the service conditions must be specified and a mutually acceptable service test devised.

6.0 PHYSICAL PROPERTIES
Typical values for density, thermal expansion, thermal conductivity and electrical resistivity are listed in Table V-3.

7.0 THERMAL PROPERTIES
Typical values for the reversible temperature coefficients of residual induction and intrinsic coercive force, Curie temperature and maximum service temperature are listed in Table V-4.

8.0 INSPECTION AND TESTING
8.1 Unless otherwise agreed upon by the manufacturer and the user, all lots of bulk magnet material and individual magnets will be inspected by the use of a statistical sampling plan. Such plans may be derived from, Quality Planning And Analysis: From Product Development Through Use, J.M. Juran and F. M. Gryna, 3rd Edition, McGraw Hill (1993), Chapter 19. ISBN 0-07-033183-9
8.2 A method of magnetic tests shall be chosen which causes the magnet to operate at one or more points on its major and/or minor hysteresis loops as indicated by the operating points of the magnet in its final magnetic circuit. The acceptance limits chosen shall be mutually agreeable to both the manufacturer and user. A magnet shall be chosen to serve as a calibration reference.
Acceptability of a magnet will then be judged solely by comparison to the reference magnet, tested under identical conditions.