ASTM B935-05(2009)e1
(Guide)Standard Guide for Steam Treatment of Ferrous Powder Metallurgy (P/M) Materials
Standard Guide for Steam Treatment of Ferrous Powder Metallurgy (P/M) Materials
SIGNIFICANCE AND USE
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 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
Relations
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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
´1
Designation: B935 − 05(Reapproved 2009)
Standard Guide for
Steam Treatment of Ferrous Powder Metallurgy (PM)
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.
´ NOTE—P/M was changed to PM editorially in December 2009.
1. Scope wear characteristics, and some mechanical properties (see
Appendix X1) can be observed due to steam treatment. The
1.1 This guide is intended as an aid in establishing and
hardness of magnetite (Fe O ) formed during steam treatment
3 4
maintaining a procedure for the steam treatment, also referred
is typically equivalent to 50 HRC, and when present in sintered
to as steam blackening, of sintered ferrous PM materials and
materials, their wear resistance can be improved significantly.
the appropriate use and evaluation of these materials. Addi-
Steam treatment is also used to seal parts or provide a base
tional information concerning the effect of this process on
material for additional coatings. Steam treated ferrous PM
ferrous PM material properties is contained in Appendix X1.
materials are used in many industries, including automotive,
1.2 This standard does not purport to address all of the
marine, home appliances and lawn and garden applications.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Apparatus
priate safety and health practices and determine the applica-
4.1 The material can be processed in either a batch-type
bility of regulatory limitations prior to use.
furnace or a continuous belt-type furnace. The furnace must be
capable of heating the load, maintaining it at the processing
2. Summary of Guide
temperature, and maintaining a steam atmosphere free of air
2.1 A normal sequence of steps is: (1) preheat the load; (2)
leaks. Both batch type and continuous furnaces must meet the
introduce a superheated steam-rich atmosphere; (3) heat the
same criteria described in the following procedure section.
load to the processing temperature and maintain the tempera-
When both batch and continuous furnaces are operated to meet
ture for the duration of the processing cycle; and (4) cool the
the same processing times, temperatures, and atmosphere, the
load to a temperature suitable for handling. This process will
results should be similar.
produce a layer of black iron oxide (magnetite) on the surface
of the parts and on the surfaces of the interconnected porosity
5. Procedure
by the reaction.
5.1 Place the load in the furnace and heat in air until the
3Fe14H O ~gas!Fe O 14H ~gas!
2 3 4 2
temperature of the entire load is above 100°C (212°F) without
exceeding 430°C (800°F).
3. Significance and Use
5.2 Once the load is preheated, introduce superheated steam
3.1 The performance and quality of steam-treated materials
into the furnace until all of the air is purged from the furnace
depends upon the surface cleanliness of the material prior to
or processing zone.This steam atmosphere must be maintained
steam treatment and the adequacy of the processing. Steam
until the processing cycle is complete.
treatment can be used as a decorative coating, producing a
NOTE 1—The temperature of the parts must be in excess of 100°C
blue-gray to a blue-black appearance. It can reduce the
(212°F) before the superheated steam is introduced. If it is not, water will
susceptibility of ferrous PM materials to further oxidation and
condense on the parts and rust spots will form. The temperature must not
corrosion, thus providing better shelf life. More significantly,
exceed 430°C (800°F) before the superheated steam is introduced or the
improvements in apparent hardness, compressive strength,
parts will be covered with a smooth even coating of rust caused by air in
the furnace atmosphere.
5.3 Raise the temperature of the furnace to the processing
This guide is under the jurisdiction of ASTM Committee B09 on Metal
temperature of between 430°C (800°F) and 590°C (1100°F)
Powders and Metal Powder Products and is the direct responsibility of Subcom-
while maintaining the atmosphere of superheated steam.
mittee B09.05 on Structural Parts.
NOTE 2—The processing temperature depends on the desired proper-
Current edition approved Nov. 1, 2009. Published December 2009. Originally
approved in 2005. Last previous edition approved in 2005 as B935 – 05. DOI: ties. Lower temperatures result in deeper oxide penetration while higher
10.1520/B0935-05R09E01. temperatures produce a thicker surface oxide layer.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
B935 − 05 (2009)
NOTE 3—Processes that decrease the amount or the size of the
batch-type furnace, the furnace should be flushed with nitrogen
interconnected porosity such as copper infiltration, grinding, vibratory
or an inert gas unless the parts and furnace are cooled to below
finishing, sizing, machining, burnishing, shot peening, or polishing will
the auto ignition point of hydrogen while still in the steam
reduce the effectiveness of the steam treatment by limiting the ability of
atmosphere.
steam to penetrate the part. Increasing the density reduces the pore size,
which reduces penetration unless sufficiently large porosity is available to
7.2 Foreign material can interfere with steam treatment and
maintain a pathway for the steam. Copper infiltration also coats the
possibly pose a serious health threat. Some chemical com-
surface of iron particles with copper, which prevents steam from reacting
pounds, for example, chlorinated hydrocarbons, decompose
with the iron and decreases the effectiveness of steam treatment as a
surface treatment. into products that cause materials to rust during processing.All
c
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.