ASTM A904-98
(Specification)Standard Specification for 50 Nickel-50 Iron Powder Metallurgy (P/M) Soft Magnetic Alloys
Standard Specification for 50 Nickel-50 Iron Powder Metallurgy (P/M) Soft Magnetic Alloys
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.
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Designation: A 904 – 98
Standard Specification for
50 Nickel-50 Iron Powder Metallurgy (P/M) Soft Magnetic
Parts
This standard is issued under the fixed designation A 904; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope Electronic Hysteresigraphs
B 328 Test Method for Density, Oil Content and Intercon-
1.1 This specification covers the magnetic properties of 50
nected Porosity of Sintered Powder Metal Structural Parts
nickel-50 iron parts fabricated by powder metallurgy tech-
and Oil-Impregnated Bearings
niques and is intended for parts that require high magnetic
E 1019 Test Methods for Determination of Carbon, Sulfur,
permeability, high electrical resistivity, low coercive field
Nitrogen, and Oxygen in Steel and in Iron, Nickel and
strength, and low hysteresis loss. It differs from the wrought
Cobalt Alloys
alloy specification (see Specification A 753) because these
parts are porous. A number of magnetic properties such as
3. Terminology
permeability are proportional to the sintered density.
3.1 The terms and symbols used in this specification are
1.2 This specification deals with P/M parts in the sintered or
defined in Terminology A 340.
annealed condition. Should the sintered parts be subjected to
any secondary operation that causes mechanical strain, such as
4. Ordering Information
machining or sizing, they should be resintered or annealed.
4.1 Orders for parts conforming to this specification shall
1.3 The values stated in either customary (cgs-emu and
include the following information.
inch-pound) units or SI units are to be regarded separately as
4.1.1 Reference to this standard and year of issue/revision.
standard. Within the text, the SI units are shown in brackets.
4.1.2 Reference to an applicable part drawing.
The values stated in each system are not exact equivalents;
4.1.3 Quantity required.
therefore, each system shall be used independently of the other.
4.1.4 A critical cross section of the part shall be defined and
Combining values from the two systems may result in noncon-
so indicated on the applicable part drawing. The location of the
formance with this specification.
critical section is by mutual agreement between the purchaser
2. Referenced Documents and producer (see 6.2).
4.1.5 Magnetic property requirements if they are other than
2.1 ASTM Standards:
stated in 7.5.
A 34/A 34M Practice for Sampling and Procurement Test-
2 4.1.6 Certification of chemical analysis or magnetic prop-
ing of Magnetic Materials
erty evaluation, or both (Sections 5 and 7).
A 340 Terminology of Symbols and Definitions Relating to
2 4.1.7 Marking and packaging requirements (Section 12).
Magnetic Testing
4.1.8 Exceptions to this specification or special require-
A 596/A 596M Test Method for Direct-Current Magnetic
ments such as functional testing as mutually agreed upon by
Properties of Materials Using the Ballistic Method and
2 the producer and purchaser.
Ring Specimens
A 753 Specification for Nickel-Iron Soft Magnetic Alloys
5. Chemical Composition
A 773/A 773M Test Method for Magnetic Properties of
5.1 The chemical composition of the parts shall conform to
Materials Using Ring and Permeameter Procedures with
the requirements prescribed in Table 1.
5.2 Determination of metallic constituents shall be by a
method acceptable to both producer and purchaser. Analysis of
This specification is under the jurisdiction of ASTM Committee A06 on
Magnetic Properties and is the direct responsibility of Subcommittee A06.02 on
Material Specifications.
Current edition approved April 10, 1998. Published December 1998. Originally
published as A 904–90. Last previous edition A 904–90. Annual Book of ASTM Standards, Vol 02.05.
2 4
Annual Book of ASTM Standards, Vol 03.04. Annual Book of ASTM Standards, Vol 03.06.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
A904–98
TABLE 1 Chemical Requirements (in Weight Percent)
7.6 Since magnetic properties are strongly affected by
Element % process conditions, refer to the appendixes for typical values
and explanatory notes.
Nickel 46 -51
Carbon 0.02 max
Oxygen 0.10 max 8. Workmanship, Finish and Appearance
Nitrogen 0.01 max
A 8.1 The parts shall be uniform in composition and uniform
Others 0.5 max
B
Iron balance in density within critical sections.
A
8.2 If parts are sectioned or fractured, there shall be no
Others refers to trace elements that are to be regarded as incidental and not
deliberate additions.
readily recognizable defects.
B
Iron is the balance by difference. Quantitative analysis of this element is not
required.
9. Sampling
9.1 A lot shall consist of parts of the same form and
carbon, nitrogen, sulfur, and oxygen shall be done in accor-
dimensions, produced from a single mixed powder batch and
dance with Test Methods E 1019.
from an unchanged process, without discontinuity in produc-
tion, and submitted for inspection at one time.
6. Sintered Density Requirements
9.2 The purchaser and producer shall agree upon a repre-
6.1 Magnetic and residual induction of P/M parts strongly
sentative number of specimens for testing.
depend on density. The density of P/M parts is determined by
the compressibility of the powder, the compacting pressure,
10. Rejection and Rehearing
and sintering practice (temperature, time, and atmosphere).
10.1 Parts that fail to conform to the requirements of this
6.2
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