ASTM B935-20

Standard Guide for Steam Treatment of Ferrous Powder Metallurgy (PM) Materials

SIGNIFICANCE AND USE
5.1 The performance and quality of steam-treated materials depends upon the surface cleanliness of the material prior to steam treatment and the adequacy of the processing. Steam treatment can be used as a decorative coating, producing a blue-gray to a blue-black appearance. It can reduce the susceptibility of ferrous PM materials to further oxidation and corrosion, thus providing better shelf life. More significantly, improvements in apparent hardness, compressive strength, wear characteristics, and some mechanical properties (see Appendix X1) can be observed due to steam treatment. The hardness of magnetite (Fe3O4) formed during steam treatment is typically equivalent to 50 HRC, and when present in sintered materials, their wear resistance can be improved significantly. Steam treatment is also used to seal parts or provide a base material for additional coatings. Steam treated ferrous PM materials are used in many industries, including automotive, marine, home appliances, and lawn and garden applications.
SCOPE
1.1 This guide is intended as an aid in establishing and maintaining a procedure for the steam treatment, also referred to as steam blackening, of sintered ferrous PM materials and the appropriate use and evaluation of these materials. Additional information concerning the effect of this process on ferrous PM material properties is contained in Appendix X1.  
1.2 Units—With the exception of the values for density and the mass used to determine density, for which the use of the gram per cubic centimetre (g/cm3) and gram (g) units is the longstanding industry practice, the values in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.3 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.  
1.4 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: 30-Sep-2020
• ICS: 77.160 - Powder metallurgy
• Technical Committee: B09 - Metal Powders and Metal Powder Products
• Drafting Committee: B09.05 - Structural 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: B935 − 20
Standard Guide for
Steam Treatment of Ferrous Powder Metallurgy (PM)
1
Materials
This standard is issued under the fixed designation B935; 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* atmosphere;(3)heattheloadtotheprocessingtemperatureand
maintain the temperature for the duration of the processing
1.1 This guide is intended as an aid in establishing and
cycle; and (4) cool the load to a temperature suitable for
maintaining a procedure for the steam treatment, also referred
handling. This process will produce a layer of black iron oxide
to as steam blackening, of sintered ferrous PM materials and
(magnetite) on the surface of the parts and on the surfaces of
the appropriate use and evaluation of these materials. Addi-
the interconnected porosity by the reaction.
tional information concerning the effect of this process on
ferrous PM material properties is contained in Appendix X1. 3Fe14H O ~gas!↔Fe O 14H ~gas!
2 3 4 2
1.2 Units—With the exception of the values for density and 3.2 For continuous steam treatment, parts are transported
through the furnace on a continuous mesh belt, and the thermal
the mass used to determine density, for which the use of the
3
gram per cubic centimetre (g/cm ) and gram (g) units is the profileofthefurnace(temperaturesettingsofthevariouszones
and the speed of the mesh belt) is set to ensure that parts are
longstanding industry practice, the values in inch-pound units
are to be regarded as standard. The values given in parentheses clean and at the appropriate temperature before they are
exposed to the superheated steam.
are mathematical conversions to SI units that are provided for
information only and are not considered standard.
4. Terminology
1.3 This standard does not purport to address all of the
4.1 Definitions of powder metallurgy (PM) terms can be
safety concerns, if any, associated with its use. It is the
found in Terminology B243.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
5. Significance and Use
mine the applicability of regulatory limitations prior to use.
5.1 The performance and quality of steam-treated materials
1.4 This international standard was developed in accor-
depends upon the surface cleanliness of the material prior to
dance with internationally recognized principles on standard-
steam treatment and the adequacy of the processing. Steam
ization established in the Decision on Principles for the
treatment can be used as a decorative coating, producing a
Development of International Standards, Guides and Recom-
blue-gray to a blue-black appearance. It can reduce the
mendations issued by the World Trade Organization Technical
susceptibility of ferrous PM materials to further oxidation and
Barriers to Trade (TBT) Committee.
corrosion, thus providing better shelf life. More significantly,
2. Referenced Documents
improvements in apparent hardness, compressive strength,
2
wear characteristics, and some mechanical properties (see
2.1 ASTM Standards:
B243 Terminology of Powder Metallurgy Appendix X1) can be observed due to steam treatment. The
hardness of magnetite (Fe O ) formed during steam treatment
3 4
3. Summary of Guide
is typically equivalent to 50 HRC, and when present in sintered
3.1 A normal sequence of steps for batch processing is: (1) materials, their wear resistance can be improved significantly.
preheat the load; (2) introduce a superheated steam-rich
Steam treatment is also used to seal parts or provide a base
material for additional coatings. Steam treated ferrous PM
1
This guide is under the jurisdiction of ASTM Committee B09 on Metal materials are used in many industries, including automotive,
Powders and Metal Powder Products and is the direct responsibility of Subcom-
marine, home appliances, and lawn and garden applications.
mittee B09.05 on Structural Parts.
Current edition approved Oct. 1, 2020. Published November 2020. Originally
6. Apparatus
approved in 2005. Last previous edition approved in 2016 as B935 – 16. DOI:
10.1520/B0935-20.
6.1 The material can be processed in either a batch-type
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
furnace or a continuous belt-type furnace. The furnace must be
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
capable of heating the load, maintaining it at the processing
Standards
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: B935 − 16 B935 − 20
Standard Guide for
Steam Treatment of Ferrous Powder Metallurgy (PM)
1
Materials
This standard is issued under the fixed designation B935; 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*
1.1 This guide is intended as an aid in establishing and maintaining a procedure for the steam treatment, also referred to as steam
blackening, of sintered ferrous PM materials and the appropriate use and evaluation of these materials. Additional information
concerning the effect of this process on ferrous PM material properties is contained in Appendix X1.
1.2 Units—With the exception of the values for density and the mass used to determine density, for which the use of the gram per
3
cubic centimetre (g/cm ) and gram (g) units is the longstanding industry practice, the values in inch-pound units are to be regarded
as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and
are not considered standard.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 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.
2. Referenced Documents
2
2.1 ASTM Standards:
B243 Terminology of Powder Metallurgy
3. Summary of Guide
3.1 A normal sequence of steps for batch processing is: (1) preheat the load; (2) introduce a superheated steam-rich atmosphere;
(3) heat the load to the processing temperature and maintain the temperature for the duration of the processing cycle; and (4) cool
the load to a temperature suitable for handling. This process will produce a layer of black iron oxide (magnetite) on the surface
of the parts and on the surfaces of the interconnected porosity by the reaction.
3Fe14H O ~gas!↔Fe O 14H ~gas!
2 3 4 2
3.2 For continuous steam treatment, parts are transported through the furnace on a continuous mesh belt, and the thermal profile
1
This guide is under the jurisdiction of ASTM Committee B09 on Metal Powders and Metal Powder Products and is the direct responsibility of Subcommittee B09.05
on Structural Parts.
Current edition approved Oct. 1, 2016Oct. 1, 2020. Published October 2016November 2020. Originally approved in 2005. Last previous edition approved in 20092016
ɛ1
as B935 – 05B935 – 16.(2009) . DOI: 10.1520/B0935-16.10.1520/B0935-20.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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B935 − 20
of the furnace (temperature settings of the various zones and the speed of the mesh belt) is set to ensure that parts are clean and
at the appropriate temperature before they are exposed to the superheated steam.
4. Terminology
4.1 Definitions of powder metallurgy (PM) terms can be found in Terminology B243.
5. Significance and Use
5.1 The performance and quality of steam-treated materials depends upon the surface cleanliness of the material prior to steam
treatment and the adequacy of the processing. Steam treatment can be used as a decorative coating, producing a blue-gray to a
blue-black appearance. It can reduce the susceptibility of ferrous PM materials to further oxidation and corrosion, thus providing
better shelf life. More significantly, improvements in apparent hardness, compressive strength, wear characteristics, and some
mechanical properties (see Appendix X1) can be observed due to steam treatment. The hardness of magnetite (Fe O ) formed
3 4
during steam treatment is typica
...