ASTM A904-98

1.1 This specification covers the magnetic properties of 50 nickel-50 iron parts fabricated by powder metallurgy techniques and is intended for parts that require high magnetic permeability, high electrical resistivity, low coercive force and low hysteresis losses. It differs from the wrought alloy because parts are generally porous (see Specification A753). Porosity can cause some of the magnetic properties to differ from the wrought grade because some magnetic properties are directly proportional to the sintered density.

1.2 The 50 nickel-50 iron parts shall have a typical chemistry as shown in Table 1. Magnetic properties are affected significantly by the sintering process. Magnetic properties of as-sintered products vary greatly with respect to carbon, nitrogen, oxygen, and sulphur content. The levels of these elements should be agreed upon between the producer and user. Parts made through powder metallurgy techniques, including metal injection molding are generally to configuration of the desired part.

1.2.1 If secondary or machining operations are required, which may stress the part, an anneal should be provided to restore magnetic properties to the as-sintered condition, as defined in this specification.