ASTM A1084-13
(Test Method)Standard Test Method for Detecting Detrimental Phases in Lean Duplex Austenitic/Ferritic Stainless Steels
Standard Test Method for Detecting Detrimental Phases in Lean Duplex Austenitic/Ferritic Stainless Steels
SIGNIFICANCE AND USE
4.1 Test Method A shall only be used to supplement the results of Test Methods B and C. It shall not be used as a rejection criterion, nor shall it be used as an acceptance criterion. Test Methods B and C are intended to be the procedures giving the acceptance criteria for this standard.
4.2 Test Method A can reveal potentially detrimental phases in the metallographic structure. As the precipitated detrimental phases can be very small, this test demands high proficiency from the metallographer, especially for thinner material.
4.3 The presence of detrimental phases is readily detected by Test Methods B and C provided that a sample of appropriate location and orientation is selected.
4.4 The tests do not determine the precise nature of the detrimental phase but rather the presence or absence to the extent that the normally expected toughness and corrosion resistance of the material are significantly affected.
4.5 This standard covers testing of samples taken from coil, coil- and plate mill plate, sheet, tubing, piping, bar and deformed bar, though some of these products might not be suitable for testing according to Method B (see Test Method B for further details). Other product forms have thus far not been sufficiently tested and documented to be an integral part of this standard, though the standard does not prohibit testing of these product forms according to the three test methods. For these other product forms, this standard gives only limited and non-exhaustive guidance as to interpretation of result and associated acceptance criteria.
4.6 Testing on product forms outside the present scope of this standard shall be agreed between purchaser and supplier.
SCOPE
1.1 The purpose of this test method is to allow detection of the presence of detrimental chromium-containing phases in selected lean duplex stainless steels to the extent that toughness or corrosion resistance is affected significantly. Such phases can form during manufacture and fabrication of lean duplex products. This test method does not necessarily detect losses of toughness nor corrosion resistance attributable to other causes, nor will it identify the exact type of detrimental phases that caused any loss of toughness or corrosion resistance. The test result is a simple pass/fail statement.
1.2 Lean duplex (austenitic-ferritic) stainless steels are typically duplex stainless steels composed of 30-70 % ferrite content with a typical alloy composition having Cr > 17 % and Mo Table 1. Similar test methods for some higher alloyed duplex stainless steels are described in ASTM A923, but the procedures described in this standard differ significantly for all three methods from the ones described in A923.TABLE 1 List of the Lean Duplex Grades Covered by this Standard
Grades
UNS S32101, UNS S32304
1.3 Lean duplex stainless steels are susceptible to the formation of detrimental chromium-containing compounds such as nitrides and carbides and other undesirable phases. Typically this occurs during exposures in the temperature range from approximately 300 to 955°C (570 to 1750ºF) with a maximum susceptibility in the temperature range around 650 to 750°C (1200 to 1385ºF). The speed of these precipitation reactions is a function of composition and the thermal or thermo-mechanical history of each individual piece. The presence of an amount of these phases can be detrimental to toughness and corrosion resistance.
1.4 Because of the low molybdenum content, lean duplex stainless steels only exhibit a minor susceptibility to sigma or other types of molybdenum containing intermetallic phases. Heat treatment, that could lead to formation of small amounts of molybdenum containing intermetallics, would result in a large amount of precipitation of detrimental nitrides or carbides – long before any signs of sigma and similar phases would be observed.
1.5 Correct heat treatment of lean duplex stainless steels can el...
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Designation: A1084 − 13
StandardTest Method for
Detecting Detrimental Phases in Lean Duplex Austenitic/
1
Ferritic Stainless Steels
This standard is issued under the fixed designation A1084; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope of molybdenum containing intermetallics, would result in a
largeamountofprecipitationofdetrimentalnitridesorcarbides
1.1 The purpose of this test method is to allow detection of
– long before any signs of sigma and similar phases would be
the presence of detrimental chromium-containing phases in
observed.
selectedleanduplexstainlesssteelstotheextentthattoughness
or corrosion resistance is affected significantly. Such phases
1.5 Correctheattreatmentofleanduplexstainlesssteelscan
can form during manufacture and fabrication of lean duplex
eliminate or reduce the amount and alter the characteristics of
products.Thistestmethoddoesnotnecessarilydetectlossesof
these detrimental phases as well as minimizing Cr-depletion in
toughness nor corrosion resistance attributable to other causes,
the matrix phase in the immediate vicinity of these phases.
nor will it identify the exact type of detrimental phases that
Adequately rapid cooling of the product from a suitable
caused any loss of toughness or corrosion resistance. The test
annealing temperature provides the maximum resistance to
result is a simple pass/fail statement.
formation of detrimental phases by subsequent thermal expo-
sures. For details of the proper annealing temperature recom-
1.2 Leanduplex(austenitic-ferritic)stainlesssteelsaretypi-
mendations for the alloy and product in question, the user is
cally duplex stainless steels composed of 30-70% ferrite
referredtotherelevantapplicableASTMproductspecification.
contentwithatypicalalloycompositionhavingCr>17%and
Mo < 1% and with additions of Nickel, Manganese, Nitrogen
1.6 Compliance with the chemical and mechanical require-
and controlled low carbon content as well as other alloying
ments for the applicable product specification does not neces-
elements. This standard test method applies only to those
sarilyindicatetheabsenceofdetrimentalphasesintheproduct.
alloys listed in Table 1. Similar test methods for some higher
1.7 These test methods include the following:
alloyed duplex stainless steels are described in ASTM A923,
1.7.1 Test Method A—Etch Method for detecting the pres-
buttheproceduresdescribedinthisstandarddiffersignificantly
enceofpotentiallydetrimentalphasesinLeanDuplexStainless
for all three methods from the ones described in A923.
Steels
1.3 Lean duplex stainless steels are susceptible to the
1.7.2 Test Method B—Charpy V-notch Impact Test for
formation of detrimental chromium-containing compounds
determiningthepresenceofdetrimentalphasesinLeanDuplex
such as nitrides and carbides and other undesirable phases.
Stainless Steels.
Typicallythisoccursduringexposuresinthetemperaturerange
1.7.3 Test Method C—Inhibited Ferric Chloride Corrosion
from approximately 300 to 955°C (570 to 1750ºF) with a
TestfordeterminingthepresenceofdetrimentalphasesinLean
maximumsusceptibilityinthetemperaturerangearound650to
Duplex Stainless Steels.
750°C (1200 to 1385ºF). The speed of these precipitation
1.7.4 Examples of the correlation of thermal exposures, the
reactions is a function of composition and the thermal or
occurrence of detrimental phases, and the degradation of
thermo-mechanical history of each individual piece. The pres-
toughness and corrosion resistance are given in Appendix X2,
ence of an amount of these phases can be detrimental to
Appendix X3 and the References.
toughness and corrosion resistance.
1.8 Guidelines for the required data needed for subcommit-
1.4 Because of the low molybdenum content, lean duplex
tee A01.14 to consider listing a lean duplex stainless steel in
stainless steels only exhibit a minor susceptibility to sigma or
this standard test method are given in Annex A1.
other types of molybdenum containing intermetallic phases.
Heat treatment, that could lead to formation of small amounts
1.9 The values stated in SI units are to be regarded as
standard. The values given in parentheses are mathematical
1 conversions to other units that are provided for information
This test method is under the jurisdiction of ASTM Committee A01 on Steel,
Stainless Steel and RelatedAlloys and is the direct responsibility of Subcommittee only and are not considered standard.
A01.14 on Methods of Corrosion Testing.
1.10 This standard does not purport to address all of the
Current edition approved June 1, 2013. Published July 2013. DOI: 10.1520/
A1084–13 safety c
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