ASTM A923 - 23 检测锻制双重奥氏体/铁素体不锈钢中有害金属间相的标准试验方法

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Designation: A923 −23
Standard Test Methods for
Detecting Detrimental Intermetallic Phase in Duplex
Austenitic/Ferritic Stainless Steels
1
This standard is issued under the ﬁxed designation A923; 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 The purpose of these test methods is to allow detection
of the presence of intermetallic phases in certain duplex
stainless steels as listed in Table 1, Table 2, and Table 3 to the
extent that toughness or corrosion resistance is affected signiﬁ-
cantly. These test methods will not necessarily detect losses of
toughness or corrosion resistance attributable to other causes.
Similar test methods for other duplex stainless steels are
described in Test Method A1084, but the procedures described
in this standard differ signiﬁcantly from Test Methods A, B,
and C in A1084.
1.2 Duplex (austenitic-ferritic) stainless steels are suscep-
tible to the formation of intermetallic compounds during
exposures in the temperature range from approximately 600 to
1750 °F (320 to 955 °C). The speed of these precipitation
reactions is a function of composition and thermal or thermo-
mechanical history of each individual piece. The presence of
these phases is detrimental to toughness and corrosion resis-
tance.
1.3 Correct heat treatment of duplex stainless steels can
eliminate these detrimental phases. Rapid cooling of the
product provides the maximum resistance to formation of
detrimental phases by subsequent thermal exposures.
1.4 Compliance with the chemical and mechanical require-
ments for the applicable product speciﬁcation does not neces-
sarily indicate the absence of detrimental phases in the product.
1.5 These test methods include the following:
1.5.1 Test Method A—Sodium Hydroxide Etch Test for
Classiﬁcation of Etch Structures of Duplex Stainless Steels
(Sections 3–7).
1.5.2 Test Method B—Charpy Impact Test for Classiﬁcation
of Structures of Duplex Stainless Steels (Sections 8 – 13).
1.5.3 Test Method C—Ferric Chloride Corrosion Test for
Classiﬁcation of Structures of Duplex Stainless Steels (Sec-
tions 14 – 20).
1.6 The presence of detrimental intermetallic phases is
readily detected in all three tests, provided that a sample of
appropriate location and orientation is selected. Because the
occurrence of intermetallic phases is a function of temperature
and cooling rate, it is essential that the tests be applied to the
region of the material experiencing the conditions most likely
to promote the formation of an intermetallic phase. In the case
of common heat treatment, this region will be that which
cooled most slowly. Except for rapidly cooled material, it may
be necessary to sample from a location determined to be the
most slowly cooled for the material piece to be characterized.
1.7 The tests do not determine the precise nature of the
detrimental phase but rather the presence or absence of an
intermetallic phase to the extent that it is detrimental to the
toughness and corrosion resistance of the material.
1.8 Examples of the correlation of thermal exposures, the
occurrence of intermetallic phases, and the degradation of
toughness and corrosion resistance are given in Appendix X1
and Appendix X2.
1.9 The values stated in either inch-pound or SI units are to
be regarded as the standard. The values given in parentheses
are for information only.
1.10 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 appro-
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.11 This international standard was developed in accor-
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
2
1
These test methods are under the jurisdiction of ASTM Committee A01 on
Steel, Stainless Steel and Related Alloysand are the direct responsibility of
Subcommittee A01.14 on Methods of Corrosion Testing.
Current edition approved May 15, 2023. Published June 2023. Originally
approved in 1994. Last previous edition approved in 2022 as A923 – 22. DOI:
10.1520/A0923-23.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. 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
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.
1

A370 Test Methods and Deﬁnitions for Mechanical Testing
of Steel Products
A1084 Test Method for Detecting Detrimental Phases in
Lean Duplex Austenitic/Ferritic Stainless Steels
G48 Test Methods for Pitting and Crevice Corrosion Resis-
tance of Stainless Steels and Related Alloys by Use of
Ferric Chloride Solution
TEST METHOD A—SODIUM HYDROXIDE ETCH
TEST FOR CLASSIFICATION OF ETCH
STRUCTURES OF DUPLEX STAINLESS STEELS
3. Scope
3.1 The sodium hydroxide etch test may be used for the
acceptance of material but not for rejection. This test method
may be used with other evaluation tests to provide a rapid
method for identifying those specimens that are free of
detrimental intermetallic phases as measured in these other
tests.
3.2 The sodium hydroxide etch test may be used to screen
specimens intended for testing in Test Method B, Charpy
Impact Test for Classiﬁcation of Structures of Duplex Stainless
Steels, and in Test Method C, Ferric Chloride Corrosion Test
for Classiﬁcation of Structures of Duplex Stainless Steels.
3.3 Reference photomicrographs are provided to show clas-
siﬁcations of etch structures of a particular stainless steel type
that are equivalent to acceptable or to possibly unacceptable
performance for each practice. When Test Method A is used as
a screening test for Test Method B or Test Method C,
specimens having acceptable etch structures need not be
subjected to Test Method B or Test Method C.
3.4 Table 1 indicates the applicability and acceptance crite-
ria for Test Method A. When Test Method A is speciﬁed as an
acceptance test, specimens having other than acceptable etch
structures may, at the option of the producer, be tested by Test
Method B or Test Method C.
3.5 The steel shall be tested in the ﬁnal solution heat treated
condition or such other conditions as are agreed upon between
the producer and the user.
4. Apparatus
4.1 Source of Direct Current—Battery, generator, or rectiﬁer
capable of supplying approximately 15 V and 20 A.
4.2 Ammeter—Range from 0 to 30 A (see Note 1).
4.3 Variable Resistance (see Note 1).
4.4 Cathode—A cylindrical piece of conductive metal.
4.5 Large Electric Clamp, to hold the specimen to be
etched.
4.6 Metallurgical Microscope, for examination of etched
microstructures to 400 to 500 diameters.
4.7 Electrodes of the Etching Cell—The specimen to be
etched is made the anode, and a cylindrical piece of metal as
large as the specimen to be etched is made the cathode.
4.8 Electrolyte, sodium hydroxide (NaOH), reagent grade.
NOTE 1—The variable resistance and ammeter are placed in the circuit
to measure and control the current on the specimen to be etched.
5. Preparation of Test Specimens
5.1 For mill products, examination shall be made on a
longitudinal or transverse section. For cast products, examina-
tion shall be made on a separately cast test coupon which was
heat treated in the same furnace load as the casting it
represents. Unless otherwise speciﬁed, selection of the test
coupon size shall be at the discretion of the producer. Because
high temperature or mechanical deformation associated with
particular cutting processes may alter the structure of the steel,
the cutting of the test specimen should be by a technique that
prevents these effects. Alternatively, after the specimens are
cut, any material that may have been affected by high tempera-
ture or deformation associated with the cutting should be
removed by machining or wet grinding prior to testing.
5.2 For mill products, the specimen should allow for a
survey across the full thickness of the section or, in the case of
a heavy section, a survey from one surface through the
mid-thickness of the section. The specimen shall include the
mid-thickness.
5.3 For cast materials, the specimen shall be taken at
approximately 1/4T.
5.4 Polishing—On all materials, cross-sectional surfaces
should be polished to a metallographic ﬁnish suitable for
examination at 400× after etching. Specimens containing welds
should include base metal, weld heat–affected zone, and weld
metal. The area to be etched may be prepared by grinding to an
80- or 120-grit ﬁnish on a grinding belt or wheel without
excessive heating and then by polishing on successively ﬁner
emery papers, No. 1,
1
⁄
2
,
1
⁄
0
,
2
⁄
0
,
3
⁄
0
, and ﬁner. Other methods of
polishing may be acceptable.
5.5 Etching Solution—The solution for etching is prepared
by adding 40 g of reagent grade sodium hydroxide (NaOH) to
100 g of distilled water.
5.6 Etching Conditions—The polished specimen should be
etched at approximately 1 to 3 V dc, for 5 to 60 s (see Note 2).
NOTE 2—When etching is performed at 1 to 3 V dc with a platinum
cathode for 5 to 60 s, any intermetallic phase is revealed by yellow, then
brown, staining, followed by staining of the ferrite.
5.7 Rinsing—Following etching, the specimen should be
rinsed thoroughly in hot water and in acetone or alcohol,
followed by air drying.
TABLE 1 Applicability and Acceptance Criteria for
Test Method A
Grade Acceptable
Etch Structure
Nonacceptable
Etch Structure
S82441, S31803,
S32205, S32750,
S32760,
S32550,S32520,
J92205, J93404
unaffected
structure (Fig. 1,
Fig. 2)
possibly affected
structure (Fig. 3,Fig. 4)
affected structure (Fig. 5,
Fig. 6)
centerline structure (Fig.
7)
A923 − 23
2

6. Classiﬁcation of Etch Structures

6.1 The etched surface shall be examined on a metallurgical

microscope at 400 to 500×.

6.2 The etched cross-sectional areas should be examined

thoroughly by complete traverse of the full sample and across

all zones such as weld metal, weld-affected zones, and base

metal on specimens containing welds.

6.3 The etch structures are classiﬁed into the following

types:

6.3.1 Unaffected Structure (Fig. 1,Fig. 2)—The ferrite has

been etched without revelation of intermetallic phase. The

interphase boundaries are smooth.

6.3.2 Possibly Affected Structure (Fig. 3,Fig. 4)—The

ferrite has been etched with isolated indications of possible

intermetallic phase. The interphase boundaries may show a ﬁne

waviness.

6.3.3 Affected Structure (Fig. 5,Fig. 6)—The indications of

an intermetallic phase are readily revealed before or simulta-

neously with the staining of the ferrite during etching.

6.3.4 Centerline Structure (Fig. 7)—An intermetallic phase

is observed as a continuous or semi-continuous phase in the

mid-thickness region of the product, with or without the

affected structure outside of the mid-thickness region, indica-

tive of segregation.

7. Interpretation and Use of the Etch Structure

Classiﬁcations

7.1 When Test Method A is used as a screening test, the use

of these etch structures depends on the test method for which

the specimens are being screened. Important characteristics of

each of the test methods are described as follows.

7.2 Test Method B—The Charpy impact test detects reduc-

tions in toughness from that of the optimal composition and

processing. Such reductions may be attributable to intermetal-

lic phases or to other causes not necessarily detectable by Test

Method A. A Possibly Affected Structure is likely to be

FIG. 1 Unaffected Structure in S31803: (a) Longitudinal Section

and (b) Transverse Section (500× Magniﬁcation Before Reproduc-

tion)

FIG. 2 (a) J92205: Unaffected Structure-Statically Cast (400× Mag-

niﬁcation)

FIG. 2 (b) J92205: Unaffected Structure-Centrifugally Cast (400×

Magniﬁcation) (continued)

A923 − 23

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标签： #检测锻制 #双重奥氏体 #铁素体

摘要：

ASTM A923-2023 Standard Test Methods for Detecting Detrimental Intermetallic Phase in Wrought Duplex Austenitic/Ferritic Stainless Steels 检测锻制双重奥氏体/铁素体不锈钢中有害金属间相的标准试验方法

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ASTM A923 - 23 检测锻制双重奥氏体/铁素体不锈钢中有害金属间相的标准试验方法

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