ASTM B849-02

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Designation: B 849 – 02
Standard Specification for
Pre-Treatments of Iron or Steel for Reducing Risk of
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Hydrogen Embrittlement
This standard is issued under the fixed designation B 849; 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.
INTRODUCTION
When atomic hydrogen enters steels and certain other metals, for example, aluminum and titanium
alloys, it can cause a loss of ductility, load carrying ability, or cracking (usually as submicroscopic
cracks) as well as catastrophic brittle failures at applied stresses well below the yield strength or even
the normal design strength for the alloys. This phenomenon often occurs in alloys that show no
significant loss in ductility, when measured by conventional tensile tests, and is referred to frequently
as hydrogen-induced delayed brittle failure, hydrogen stress cracking, or hydrogen embrittlement.The
hydrogen can be introduced during cleaning, pickling, phosphating, electroplating, autocatalytic
processes, porcelain enameling, and in the service environment as a result of cathodic protection
reactions or corrosion reactions. Hydrogen can also be introduced during fabrication, for example,
during roll forming, machining, and drilling, due to the breakdown of unsuitable lubricants as well as
during welding or brazing operations. Parts that have been machined, ground, cold-formed, or
cold-straightened subsequent to hardening heat treatment are especially susceptible to hydrogen
embrittlement damage.
The results of research work indicate that the susceptibility of any material to hydrogen
embrittlement in a given test is related directly to its trap population. The time-temperature
relationship of the heat treatment is therefore dependent on the composition and structure of steels as
well as plating metals and plating procedures. Additionally, for most high-strength steels, the
effectiveness of the heat treatment falls off rapidly with a reduction of time and temperature.
1. Scope parts, such as the cleaning procedures prior to electroplating,
autocatalytic plating, porcelain enameling, and other chemical
1.1 This specification covers procedures for reducing the
coating operations.
susceptibility or degree of susceptibility to hydrogen embrittle-
ment or degradation that may arise in electroplating, autocata-
NOTE 1—1 MPa = 145.1 psi.
lytic plating, porcelain enameling, chemical conversion coat-
1.3 This specification has been coordinated with ISO/DIS
ing, and phosphating and the associated pretreatment
9587 and is technically equivalent.
processes.This specification is applicable to those steels whose
1.4 The values stated in SI units are to be regarded as the
properties are not affected adversely by baking at 190 to 230°C
standard.
or higher (see 6.1.1).
1.2 The heat treatment procedures established herein have
2. Referenced Documents
been shown to be effective for reducing the susceptibility of
2.1 ASTM Standards:
steel parts of tensile strength 1000 MPa or greater that have
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A 919 Terminology Relating to Heat Treatment of Metals
been machined, ground, cold-formed, or cold-straightened
B 242 Practice for Preparation of High-Carbon Steel for
subsequent to heat treatment. This heat-treatment procedure is
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Electroplating
used prior to any operation capable of hydrogen charging the
3
B 322 Practice for Cleaning Metals Prior to Electroplating
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B 374 Terminology Relating to Electroplating
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This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
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B08.02 on Pre Treatment. Discontinued 1999; see 1999 Annual Book of ASTM Standards, Vol 01.02.
Current edition approved Dec. 10, 2002. Published January 2003. Originally Replaced by Terminology A 941.
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approved in 1994. Last previous edition approved in 1994 as B 849 – 94. Annual Book of ASTM Standards, Vol 02.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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B849–02
TABLE 1 Classes of Stress Relief Requirements for High- mass, or design parameters, some parts may perform satisfactorily with no
Strength Steels (See Sections 4 through 6 for Details on the
stress relief treatment. Class SR-0 treatment is therefore provided for parts
Use of Table 1)
that the purchaser wishes to exempt from treatment.
NOTE 3—The use of inhibitors in acid pickling baths is not necessarily
Stress-Relief Heat-Treatment Classes for High-Strength Steels
guaranteed to minimize hydrogen embrittlement.
Class
Steels of Tensile
...