ASTM A839-15(2023)

Standard Specification for Iron-Phosphorus Powder Metallurgy Parts for Soft Magnetic Applications

ABSTRACT
This specification covers parts produced from pressing and sintering of iron-phosphorus powders. The specification does not cover parts produced by metal injection molding. These parts are used in magnetic applications requiring higher permeability and electrical resistivity and lower coercive field strength than routinely attainable in parts produced from unalloyed iron powder. Two powder types are covered: Type I containing nominally 0.45% phosphorus, and Type II containing nominally 0.8% phosphorus. Apart from chemistry, parts produced to this specification shall have a minimum sintered density and maximum allowable coercive field strength. The minimum sintered density shall be 6.8 g/cm3 (6800 kg/m3) in the magnetically critical section of the part. Three grades with increasing maximum allowable coercive field strength are defined for each powder type. Detailed appendices showing the effect of sintering conditions on the magnetic and mechanical properties of parts made from both powders are included in this specification.
SCOPE
1.1 This specification covers parts produced from iron-phosphorus powder metallurgy materials. These parts are used in magnetic applications requiring higher permeability and electrical resistivity and lower coercive field strength than attainable routinely from parts produced from iron powder.  
1.2 Two powder types are covered; Type I containing nominally 0.45 wt.% phosphorus, and Type II containing nominally 0.8 wt.% phosphorus.  
1.3 This specification deals with powder metallurgy parts in the sintered or annealed condition. Should the sintered parts be subjected to any secondary operation that causes mechanical strain, such as machining or sizing, they should be resintered or annealed.  
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to customary (cgs-emu and inch-pound) units, which are provided for information only and are not considered standard.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Apr-2023
• ICS: 77.160 - Powder metallurgy
• Technical Committee: A06 - Magnetic Properties
• Drafting Committee: A06.02 - Material Specifications

Relations

• Refers: ASTM B962-15 - Standard Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes’ Principle
• Effective Date: 01-Apr-2015
• Refers: ASTM B962-14 - Standard Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes’ Principle
• Effective Date: 01-Sep-2014
• Refers: ASTM B962-13 - Standard Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes’ Principle
• Effective Date: 01-Apr-2013
• Refers: ASTM A34/A34M-06(2012) - Standard Practice for Sampling and Procurement Testing of Magnetic Materials
• Effective Date: 01-Nov-2012
• Refers: ASTM E1019-11 - Standard Test Methods for Determination of Carbon, Sulfur, Nitrogen, and Oxygen in Steel, Iron, Nickel, and Cobalt Alloys by Various Combustion and Fusion Techniques
• Effective Date: 15-Mar-2011
• Refers: ASTM A596/A596M-95(2009)e1 - Standard Test Method for Direct-Current Magnetic Properties of Materials Using the Ballistic Method and Ring Specimens
• Effective Date: 01-Nov-2009
• Refers: ASTM A773/A773M-01(2009) - Standard Test Method for dc Magnetic Properties of Materials Using Ring and Permeameter Procedures with dc Electronic Hysteresigraphs
• Effective Date: 01-May-2009
• Refers: ASTM E1019-08 - Standard Test Methods for Determination of Carbon, Sulfur, Nitrogen, and Oxygen in Steel, Iron, Nickel, and Cobalt Alloys by Various Combustion and Fusion Techniques
• Effective Date: 01-Nov-2008
• Refers: ASTM B962-08 - Standard Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes<span class='unicode'>’</span> Principle
• Effective Date: 01-Nov-2008
• Refers: ASTM A34/A34M-06 - Standard Practice for Sampling and Procurement Testing of Magnetic Materials
• Effective Date: 01-Nov-2006
• Refers: ASTM A596/A596M-95(2004)e1 - Standard Test Method for Direct-Current Magnetic Properties of Materials Using the Ballistic Method and Ring Specimens
• Effective Date: 01-Oct-2004
• Refers: ASTM A596/A596M-95(2004) - Standard Test Method for Direct-Current Magnetic Properties of Materials Using the Ballistic Method and Ring Specimens
• Effective Date: 01-Oct-2004
• Refers: ASTM E1019-03 - Standard Test Methods for Determination of Carbon, Sulfur, Nitrogen, and Oxygen in Steel and in Iron, Nickel, and Cobalt Alloys
• Effective Date: 01-Oct-2003
• Refers: ASTM E1019-02 - Standard Test Methods for Determination of Carbon, Sulfur, Nitrogen, and Oxygen in Steel and in Iron, Nickel, and Cobalt Alloys
• Effective Date: 10-Oct-2002
• Refers: ASTM A34/A34M-96 - Standard Practice for Sampling and Procurement Testing of Magnetic Materials
• Effective Date: 10-Oct-2001

Overview

ASTM A839-15(2023) is an international standard developed by ASTM International that specifies requirements for iron-phosphorus powder metallurgy (PM) parts intended for soft magnetic applications. These parts are manufactured by pressing and sintering iron-phosphorus powders and are engineered to deliver enhanced magnetic properties-such as high permeability, increased electrical resistivity, and reduced coercive field strength-compared with components produced from unalloyed iron powder. The specification addresses two powder types, Type I with approximately 0.45% phosphorus and Type II with approximately 0.8% phosphorus, and defines criteria for chemical composition, sintered density, magnetic properties, and mechanical integrity.

Key Topics

• Material Types: The standard delineates two iron-phosphorus powder compositions:

  • Type I: Contains 0.40–0.50% phosphorus by weight
  • Type II: Contains 0.75–0.85% phosphorus by weight

• Sintered Condition: Parts must be in the sintered or annealed state. If secondary operations such as machining or sizing are performed, resintering or annealing is required to restore optimum material properties.

• Density Requirements: A minimum sintered density of 6.8 g/cm³ in the part’s magnetically critical section is essential. This ensures reliable and consistent magnetic performance.

• Magnetic Properties: The specification defines maximum allowable coercive field strengths for three grades per powder type, supporting varying application needs for magnetic softness.

• Testing and Certification: Standards for chemical and magnetic property testing, density determination, sampling, certification, and packaging are included, promoting material traceability and consistency.

Applications

Iron-phosphorus powder metallurgy parts covered by ASTM A839 are primarily used in soft magnetic applications where improved magnetic permeability and reduced coercive force are critical. Key sectors and uses include:

• Electric Motors: Components with minimized hysteresis and eddy current losses.
• Transformers and Inductors: Parts requiring high electrical resistivity to reduce losses and improve efficiency.
• Sensors and Electromagnetic Actuators: Applications necessitating soft magnetic response and stability under alternating fields.
• Automotive Components: Use in hybrid vehicle electronics, fuel injection systems, ABS sensors, and similar systems.
• Industrial Automation: In equipment like relays and switchgear, where precise magnetic properties are essential for reliable operation.

The ability to tailor the phosphorus content and select from defined magnetic grades enables designers and manufacturers to optimize magnetic characteristics for demanding industrial and automotive environments, achieving higher efficiency and reliability.

Related Standards

Many ASTM and international standards interface with or support the requirements of ASTM A839-15(2023). Notable related standards include:

• ASTM A34/A34M: Practice for sampling and procurement testing of magnetic materials
• ASTM A596/A596M: Test method for direct-current magnetic properties using the point-by-point (ballistic) method and ring specimens
• ASTM A773/A773M: Test method for measuring DC magnetic properties of low coercivity materials using hysteresigraphs
• ASTM B962: Test methods for determining the density of compacted or sintered PM products
• ASTM E1019: Test methods for determining carbon, sulfur, nitrogen, and oxygen content in steel, iron, nickel, and cobalt alloys

Compliance with ASTM A839 facilitates reliable qualification of soft magnetic parts in international markets, supporting standardization and quality across the global powder metallurgy and soft magnetic materials industry.

Keywords: Iron-phosphorus, powder metallurgy, soft magnetic materials, ASTM A839, sintered density, magnetic permeability, coercive field strength, electrical resistivity, magnetic parts.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: A839 − 15 (Reapproved 2023)
Standard Specification for
Iron-Phosphorus Powder Metallurgy Parts for Soft Magnetic
Applications
This standard is issued under the fixed designation A839; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This specification covers parts produced from iron- 2.1 ASTM Standards:
phosphorus powder metallurgy materials. These parts are used A34/A34M Practice for Sampling and Procurement Testing
in magnetic applications requiring higher permeability and of Magnetic Materials
electrical resistivity and lower coercive field strength than A596/A596M Test Method for Direct-Current Magnetic
attainable routinely from parts produced from iron powder. Properties of Materials Using the Point by Point (Ballistic)
Method and Ring Specimens
1.2 Two powder types are covered; Type I containing
A773/A773M Test Method for Direct Current Magnetic
nominally 0.45 wt.% phosphorus, and Type II containing
Properties of Low Coercivity Magnetic Materials Using
nominally 0.8 wt.% phosphorus.
Hysteresigraphs
1.3 This specification deals with powder metallurgy parts in
B962 Test Methods for Density of Compacted or Sintered
the sintered or annealed condition. Should the sintered parts be
Powder Metallurgy (PM) Products Using Archimedes’
subjected to any secondary operation that causes mechanical
Principle
strain, such as machining or sizing, they should be resintered or
E1019 Test Methods for Determination of Carbon, Sulfur,
annealed.
Nitrogen, and Oxygen in Steel, Iron, Nickel, and Cobalt
Alloys by Various Combustion and Inert Gas Fusion
1.4 The values stated in SI units are to be regarded as
standard. The values given in parentheses are mathematical Techniques
conversions to customary (cgs-emu and inch-pound) units,
3. Ordering Information
which are provided for information only and are not considered
standard. 3.1 Purchase orders for parts conforming to this specifica-
tion shall include the following information:
1.5 This standard does not purport to address all of the
3.1.1 Reference to this specification and year of issue/
safety concerns, if any, associated with its use. It is the
revision.
responsibility of the user of this standard to establish appro-
3.1.2 The type of powder to be used (see 4.1 and Table 1).
priate safety, health, and environmental practices and deter-
3.1.3 Reference to an applicable part drawing.
mine the applicability of regulatory limitations prior to use.
3.1.4 Quantity required.
1.6 This international standard was developed in accor-
3.1.5 A critical cross section of the part shall be defined and
dance with internationally recognized principles on standard-
so indicated on the applicable part drawing. The location of the
ization established in the Decision on Principles for the
critical section is by mutual agreement between the user and
Development of International Standards, Guides and Recom-
the producer (see 5.2).
mendations issued by the World Trade Organization Technical
3.1.6 Magnetic property requirements if they are other than
Barriers to Trade (TBT) Committee.
stated in Table 2.
3.1.7 Whether certification of chemical analysis or magnetic
property evaluation is required (see Sections 4 and 6).
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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 15, 2023. Published April 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1985. Last previous edition approved in 2015 as A839 – 15. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/A0839-15R23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A839 − 15 (2023)
TABLE 1 Chemical Composition Requirements (in Weight
A34/A34M. The ring specimen(s) shall be produced from the
Percent)
same mixed lot of powder used to produce the parts.
Element Type I Type II
6.3 The dc magnetic properties shall be determined in
Phosphorus 0.40/0.50 0.75/0.85
accordance with Test Methods A596/A596M or A773/A773M.
Carbon, max 0.03 0.03
Oxygen, max 0.10 0.10
6.4 For the purpose of this specification, only the coercive
Nitrogen, max 0.01 0.01
A
field strength determined from a maximum applied magnetic
Iron balance balance
A field strength of 1200 A/m (15 Oe) needs to be determined.
Iron is the balance by difference. Quantitative analysis of this element is not
required.
Other magnetic properties may be specified by mutual agree-
ment between the user and the producer.
6.5 Coercive Field Strength Requirements—Three grades,
TABLE 2 Maximum Coercive Field Strength Requirements
defined by coercive field strength, are stipulated by this
Grade Powder Type I Powder Type II
specification and are listed in Table 2. The coercive field
(0.45 wt.% P) (0.8 wt.% P)
strength requirements for Type I are based on an interlabora-
1 110 A/m (1.4 Oe) 100 A/m (1.2 Oe)
tory study conducted by ASTM Committee B09. The require-
2 140 A/m (1.8 Oe) 110 A/m (1.4 Oe)
3 160 A/m (2.0 Oe) 140 A/m (1.7 Oe)
ments for Type II are based on both interlaboratory study and
technical literature.
6.6 Magnetic Aging—Nitrogen introduced during sintering
3.1.8 Marking and packaging requirements (see Section 11).
can cause time-dependent degradation of magnetic properties.
3.1.9 Whether testing for magnetic aging is required.
Therefore, when requested by the user, the producer shall test
3.1.10 Exceptions to this specification or special require-
for aging. To determine the susceptibility of the parts to aging,
ments such as functional testing, as mutually agreed upon
the test ring(s) should be heated in air for either 100 h at 150 °C
between the producer and the user.
or 600 h at 100 °C and the coercive field strength remeasured.
A change in coercive field strength of 10 % or more of the
4. Chemical Composition
original value is evidence that aging has occurred.
4.1 The chemical composition of the parts shall conform to
6.7 Since magnetic properties are strongly affected by
the requirements prescribed in Table 1.
process conditions, refer to the Appendix X1 – Appendix X3
4.2 Chemical analysis for phosphorus shall be determined
for typical values and explanatory notes.
by wet chemistry in accordance with a method to be agreed
7. Workmanship, Finish, and Appearance
upon between the user and the producer. Analysis of carbon,
oxygen, and nitrogen shall be done in accordance with Test
7.1 The parts shall be uniform in composition and uniform
Methods E1019.
in density within critical sections.
7.2 If parts are sectioned or fractured, there shall be no
5. Sintered Density Requirements
readily recognizable defects.
5.1 Magnetic and residual induction of powder metallurgy
parts strongly depend on density. The density of powder
8. Sampling
metallurgy parts is determined by the compressibility of the
8.1 A lot shall consist of parts of the same form and
powder, the compacting pressure, and sintering practice
dimensions, produced from a single mixed powder batch and
(temperature, time, and atmosphere).
from an unchanged process, without discontinuity in
5.2 Parts produced in conformance with this specification
production, and submitted for inspection at one time.
shall have a minimum sintered density of 6.8 Mg/m in the
8.2 The user and the producer shall agree upon a represen-
critical section of t
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