ASTM B935-16

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 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 30-Sep-2016
• ICS: 77.160 - Powder metallurgy
• Technical Committee: B09 - Metal Powders and Metal Powder Products
• Drafting Committee: B09.05 - Structural Parts

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: B935 − 16
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* 3.2 For continuous steam treatment, parts are transported
through the furnace on a continuous mesh belt, and the thermal
1.1 This guide is intended as an aid in establishing and
profile of the furnace (temperature settings of the various zones
maintaining a procedure for the steam treatment, also referred
and the speed of the mesh belt) is set to ensure that parts are
to as steam blackening, of sintered ferrous PM materials and
clean and at the appropriate temperature before they are
the appropriate use and evaluation of these materials. Addi-
exposed to the superheated steam.
tional information concerning the effect of this process on
ferrous PM material properties is contained in Appendix X1.
4. Terminology
1.2 With the exception of the values for density and the
4.1 Definitions of powder metallurgy (PM) terms can be
mass used to determine density, for which the use of the gram
found in Terminology B243.
3
per cubic centimetre (g/cm ) and gram (g) units is the long-
5. Significance and Use
standing industry practice, the values in inch-pound units are to
be regarded as standard. The values given in parentheses are
5.1 The performance and quality of steam-treated materials
mathematical conversions to SI units that are provided for
depends upon the surface cleanliness of the material prior to
information only and are not considered standard.
steam treatment and the adequacy of the processing. Steam
1.3 This standard does not purport to address all of the treatment can be used as a decorative coating, producing a
safety concerns, if any, associated with its use. It is the blue-gray to a blue-black appearance. It can reduce the
responsibility of the user of this standard to establish appro- susceptibility of ferrous PM materials to further oxidation and
priate safety and health practices and determine the applica- corrosion, thus providing better shelf life. More significantly,
bility of regulatory limitations prior to use. improvements in apparent hardness, compressive strength,
wear characteristics, and some mechanical properties (see
2. Referenced Documents
Appendix X1) can be observed due to steam treatment. The
hardness of magnetite (Fe O ) formed during steam treatment
3 4
2.1 ASTM Standards:
is typically equivalent to 50 HRC, and when present in sintered
B243 Terminology of Powder Metallurgy
materials, their wear resistance can be improved significantly.
Steam treatment is also used to seal parts or provide a base
3. Summary of Guide
material for additional coatings. Steam treated ferrous PM
3.1 A normal sequence of steps for batch processing is: (1)
materials are used in many industries, including automotive,
preheat the load; (2) introduce a superheated steam-rich
marine, home appliances and lawn and garden applications.
atmosphere;(3)heattheloadtotheprocessingtemperatureand
maintain the temperature for the duration of the processing
6. Apparatus
cycle; and (4) cool the load to a temperature suitable for
6.1 The material can be processed in either a batch-type
handling. This process will produce a layer of black iron oxide
furnace or a continuous belt-type furnace. The furnace must be
(magnetite) on the surface of the parts and on the surfaces of
capable of heating the load, maintaining it at the processing
the interconnected porosity by the reaction.
temperature, and maintaining a steam atmosphere free of air
3Fe14H O gas ↔Fe O 14H gas
~ ! ~ ! leaks. Both batch type and continuous furnaces shall meet the
2 3 4 2
same criteria described in the following procedure section.
While comparable performance may be obtained from batch
1
This guide is under the jurisdiction of ASTM Committee B09 on Metal and continuous furnaces, the process conditions used may not
Powders and Metal Powder Products and is the direct responsibility of Subcom-
be exactly the same.
mittee B09.05 on Structural Parts.
Current edition approved Oct. 1, 2016. Published October 2016. Originally
7. Procedure
ɛ1
approved in 2005. Last previous edition approved in 2009 as B935 – 05(2009) .
DOI: 10.1520/B0935-16. 7.1 Batch Processing
*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

---------------------- Page: 1 ----------------------
B935 − 16
7.1.1 Place the load in the furnace and
...

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.
´1
Designation: B935 − 05 (Reapproved 2009) B935 − 16
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
ε NOTE—P/M was changed to PM editorially in December 2009.
1. Scope 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 With the exception of the values for density and the mass used to determine density, for which the use of the gram per cubic
3
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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
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
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 typically equivalent to 50 HRC, and when present in sintered materials, their wear resistance can be
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 Nov. 1, 2009Oct. 1, 2016. Published December 2009October 2016. Originally approved in 2005. Last previous edition approved in 20052009
ɛ1
as B935 – 05.B935 – 05(2009) . DOI: 10.1520/B0935-05R09E01.10.1520/B0935-16.
*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

---------------------- Page: 1 ----------------------
B935 − 16
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.
6. Apparatus
6.1 The material can be processed in either a batch-type furnace or a continuous belt-type furnace. The furnace must be capable
of heating the
...