ASTM A904-98 - 10.4.1998
 
1. Scope

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.

 
2. Referenced Documents

A773/A773M-21

Standard Test Method for Direct Current Magnetic Properties of Low Coercivity Magnetic Materials Using Hysteresigraphs

A753-21

Standard Specification for Wrought Nickel-Iron Soft Magnetic Alloys (UNS K94490, K94840, N14076, N14080)

A34/A34M-06(2021)

Standard Practice for Sampling and Procurement Testing of Magnetic Materials

B328-96

Standard Test Method for Density, Oil Content, and Interconnected Porosity of Sintered Metal Structural Parts and Oil-Impregnated Bearings

A340-23a

Standard Terminology of Symbols and Definitions Relating to Magnetic Testing (Includes all amendments and changes 12/19/2023).

A596/A596M-21

Standard Test Method for Direct-Current Magnetic Properties of Materials Using the Point by Point (Ballistic) Method and Ring Specimens

E1019-24

Standard Test Methods for Determination of Carbon, Sulfur, Nitrogen, and Oxygen in Steel, Iron, Nickel, and Cobalt Alloys by Combustion and Inert Gas Fusion Techniques

B962-23

Standard Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes’ Principle