1、Designation: A 923 08Standard Test Methods forDetecting Detrimental Intermetallic Phase in DuplexAustenitic/Ferritic Stainless Steels1This standard is issued under the fixed designation A 923; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 The purpose of these test methods is to allow detectionof the presence of intermetallic phases
3、in duplex stainless steelsto the extent that toughness or corrosion resistance is affectedsignificantly. These test methods will not necessarily detectlosses of toughness or corrosion resistance attributable to othercauses.1.2 Duplex (austenitic-ferritic) stainless steels are suscep-tible to the for
4、mation of intermetallic compounds duringexposures in the temperature range from approximately 600 to1750F (320 to 955C). The speed of these precipitationreactions is a function of composition and thermal or thermo-mechanical history of each individual piece. The presence ofthese phases is detrimenta
5、l to toughness and corrosion resis-tance.1.3 Correct heat treatment of duplex stainless steels caneliminate these detrimental phases. Rapid cooling of theproduct provides the maximum resistance to formation ofdetrimental phases by subsequent thermal exposures.1.4 Compliance with the chemical and mec
6、hanical 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 ASodium Hydroxide Etch Test forClassification of Etch Structures of Duplex Stainless Steels(Se
7、ctions 3-7).1.5.2 Test Method BCharpy Impact Test for Classificationof Structures of Duplex Stainless Steels (Sections 8-13).1.5.3 Test Method CFerric Chloride Corrosion Test forClassification of Structures of Duplex Stainless Steels (Sec-tions 14-20).1.6 The presence of detrimental intermetallic ph
8、ases isreadily detected in all three tests, provided that a sample ofappropriate location and orientation is selected. Because theoccurrence of intermetallic phases is a function of temperatureand cooling rate, it is essential that the tests be applied to theregion of the material experiencing the c
9、onditions most likelyto promote the formation of an intermetallic phase. In the caseof common heat treatment, this region will be that whichcooled most slowly. Except for rapidly cooled material, it maybe necessary to sample from a location determined to be themost slowly cooled for the material pie
10、ce to be characterized.1.7 The tests do not determine the precise nature of thedetrimental phase but rather the presence or absence of anintermetallic phase to the extent that it is detrimental to thetoughness and corrosion resistance of the material.1.8 Examples of the correlation of thermal exposu
11、res, theoccurrence of intermetallic phases, and the degradation oftoughness and corrosion resistance are given in Appendix X1and Appendix X2.1.9 The values stated in either inch-pound or SI units are tobe regarded as the standard. The values given in parenthesesare for information only.1.10 This sta
12、ndard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1
13、ASTM Standards:2A 370 Test Methods and Definitions for Mechanical Testingof Steel ProductsG48 Test Methods for Pitting and Crevice Corrosion Re-sistance of Stainless Steels and Related Alloys by Use ofFerric Chloride SolutionTEST METHOD ASODIUM HYDROXIDE ETCHTEST FOR CLASSIFICATION OF ETCHSTRUCTURES
14、 OF DUPLEX STAINLESS STEELS3. Scope3.1 The sodium hydroxide etch test may be used for theacceptance of material but not for rejection. This test methodmay be used with other evaluation tests to provide a rapid1These test methods are under the jurisdiction of ASTM Committee A01 onSteel, Stainless Ste
15、el and Related Alloys and are the direct responsibility ofSubcommittee A01.14 on Methods of Corrosion Testing.Current edition approved Oct. 1, 2008. Published October 2008. Originallyapproved in 1994. Last previous edition approved in 2006 as A 923 06.2For referenced ASTM standards, visit the ASTM w
16、ebsite, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Har
17、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.method for identifying those specimens that are free ofdetrimental intermetallic phases as measured in these othertests.3.2 The sodium hydroxide etch test may be used to screenspecimens intended for testing in Test Method B, Cha
18、rpyImpact Test for Classification of Structures of Duplex StainlessSteels, and in Test Method C, Ferric Chloride Corrosion Testfor Classification of Structures of Duplex Stainless Steels.3.3 Reference photomicrographs are provided to show clas-sifications of etch structures of a particular stainless
19、 steel typethat are equivalent to acceptable or to possibly unacceptableperformance for each practice. When Test Method A is used asa screening test for Test Method B or Test Method C,specimens having acceptable etch structures need not besubjected to Test Method B or Test Method C.3.4 Table 1 indic
20、ates the applicability and acceptance crite-ria for Test Method A. When Test Method A is specified as anacceptance test, specimens having other than acceptable etchstructures may, at the option of the producer, be tested by TestMethod B or Test Method C.3.5 The steel shall be tested in the final sol
21、ution heat treatedcondition or such other conditions as are agreed upon betweenthe producer and the user.4. Apparatus4.1 Source of Direct CurrentBattery, generator, or recti-fier capable of supplying approximately 15 V and 20 A.4.2 AmmeterRange from 0 to 30 A (see Note 1).4.3 Variable Resistance (se
22、e Note 1).4.4 CathodeA cylindrical piece of conductive metal.4.5 Large Electric Clamp, to hold the specimen to beetched.4.6 Metallurgical Microscope, for examination of etchedmicrostructures to 400 to 500 diameters.4.7 Electrodes of the Etching CellThe specimen to beetched is made the anode, and a c
23、ylindrical piece of metal aslarge as the specimen to be etched is made the cathode.4.8 Electrolyte, sodium hydroxide (NaOH), reagent grade.NOTE 1The variable resistance and ammeter are placed in the circuitto measure and control the current on the specimen to be etched.5. Preparation of Test Specime
24、ns5.1 For mill products, examination shall be made on alongitudinal or transverse section. For cast products, examina-tion shall be made on a separately cast test coupon which washeat treated in the same furnace load as the casting itrepresents. Unless otherwise specified, selection of the testcoupo
25、n size shall be at the discretion of the producer. Becausehigh temperature or mechanical deformation associated withparticular cutting processes may alter the structure of the steel,the cutting of the test specimen should be by a technique thatprevents these effects. Alternatively, after the specime
26、ns arecut, any material that may have been affected by high tempera-ture or deformation associated with the cutting should beremoved by machining or wet grinding prior to testing.5.2 For mill products, the specimen should allow for asurvey across the full thickness of the section or, in the case ofa
27、 heavy section, a survey from one surface through themid-thickness of the section. The specimen shall include themid-thickness.5.3 For cast materials, the specimen shall be taken atapproximately 1/4T.5.4 PolishingOn all materials, cross-sectional surfacesshould be polished to a metallographic finish
28、 suitable forexamination at 4003 after etching. Specimens containingwelds should include base metal, weld heataffected zone, andweld metal. The area to be etched may be prepared by grindingto an 80- or 120-grit finish on a grinding belt or wheel withoutexcessive heating and then by polishing on succ
29、essively fineremery papers, No. 1,12 ,10 ,20 ,30 , and finer. Other methodsof polishing may be acceptable.5.5 Etching SolutionThe solution for etching is preparedby adding 40 g of reagent grade sodium hydroxide (NaOH) to100 g of distilled water.5.6 Etching ConditionsThe polished specimen should beet
30、ched at approximately 1 to 3 V dc, for 5 to 60 s (see Note 2).NOTE 2When etching is performed at 1 to 3 V dc with a platinumcathode for 5 to 60 s, any intermetallic phase is revealed by yellow, thenbrown, staining, followed by staining of the ferrite.5.7 RinsingFollowing etching, the specimen should
31、 berinsed thoroughly in hot water and in acetone or alcohol,followed by air drying.6. Classification of Etch Structures6.1 The etched surface shall be examined on a metallurgicalmicroscope at 400 to 5003.6.2 The etched cross-sectional areas should be examinedthoroughly by complete traverse of the fu
32、ll sample and acrossall zones such as weld metal, weld-affected zones, and basemetal on specimens containing welds.6.3 The etch structures are classified into the followingtypes:6.3.1 Unaffected Structure (Fig. 1, Fig. 2)The ferrite hasbeen etched without revelation of intermetallic phase. Theinterp
33、hase boundaries are smooth.6.3.2 Possibly Affected Structure (Fig. 3, Fig. 4)Theferrite has been etched with isolated indications of possibleintermetallic phase. The interphase boundaries may show a finewaviness.6.3.3 Affected Structure (Fig. 5, Fig. 6)The indications ofan intermetallic phase are re
34、adily revealed before or simulta-neously with the staining of the ferrite during etching.6.3.4 Centerline Structure (Fig. 7)An intermetallic phaseis observed as a continuous or semi-continuous phase in theTABLE 1 Applicability and Acceptance Criteria forTest Method AGradeAcceptableEtch StructureNona
35、cceptableEtch StructureS31803, S32205,S32750, S32550,S32520, J92205,J93404unaffectedstructure (Fig. 1,Fig. 2)possibly affectedstructure (Fig. 3, Fig. 4)affected structure (Fig. 5,Fig. 6)centerline structure (Fig.7)A923082FIG. 1 Unaffected Structure in S31803: (a) Longitudinal Sectionand (b) Transver
36、se Section (5003 Magnification BeforeReproduction)FIG. 2 (a) J92205: Unaffected Structure-Statically Cast (4003Magnification)FIG. 2 (b) J92205: Unaffected Structure-Centrifugally Cast (4003Magnification) (continued)FIG. 3 Possibly Affected Structure in S31803: (a) LongitudinalSection and (b) Transve
37、rse Section (5003 Magnification BeforeReproduction)A923083mid-thickness region of the product, with or without theaffected structure outside of the mid-thickness region, indica-tive of segregation.7. Interpretation and Use of the Etch StructureClassifications7.1 When Test Method A is used as a scree
38、ning test, the useof these etch structures depends on the test method for whichthe specimens are being screened. Important characteristics ofeach of the test methods are described as follows.7.2 Test Method BThe Charpy impact test detects reduc-tions in toughness from that of the optimal composition
39、 andprocessing. Such reductions may be attributable to intermetal-lic phases or to other causes not necessarily detectable by TestMethod A. A Possibly Affected Structure is likely to beassociated with a loss of Charpy impact toughness rangingfrom slight to severe. An Affected Structure is associated
40、 witha severe loss of Charpy impact toughness. A CenterlineStructure may or may not be detected by a Charpy test,depending on the orientation of the Charpy specimen.7.3 Test Method CThe ferric chloride corrosion test is a24-h test in 10 % ferric chloride. It will detect a loss ofcorrosion resistance
41、 associated with local depletion of chro-mium and molybdenum as a result of the precipitation ofchromium-rich and possibly molybdenum-rich phases, notlimited to intermetallic phases. An Affected Structure is asso-ciated with significant weight loss in the corrosion test. APossibly Affected Structure
42、 is likely to be associated withsignificant weight loss in the corrosion test.TEST METHOD BCHARPY IMPACT TEST FORCLASSIFICATION OF STRUCTURES OFDUPLEX STAINLESS STEELS8. Scope8.1 This test method describes the procedure for conductingthe Charpy impact test as a method of detecting the precipita-tion
43、 of detrimental intermetallic phases in duplex stainlessFIG. 4 (a) J92205: Possibly Affected Structure-Statically Cast(4003 Magnification)FIG. 4 (b) J92205: Possibly Affected Structure-Centrifugally Cast(4003 Magnification) (continued)FIG. 5 Affected Structure in 8a S31803: (a) Longitudinal Sectiona
44、nd (b) Transverse Section (5003 Magnification BeforeReproduction)A923084steels. The presence or absence of an indication of intermetallicphase in this test is not necessarily a measure of performanceof the material in service with regard to any property other thanthat measured directly. The Charpy p
45、rocedure as here appliedis different from that as commonly applied for the determina-tion of toughness and should not be used when characterizationof material toughness is the purpose of the testing.8.2 The Charpy impact test may be used to evaluate mill andcast products, provided that it is possibl
46、e to obtain a specimenof relevant location and geometry.8.3 Table 2 indicates the applicability and acceptance crite-ria for Test Method B.9. Rapid Screening Test9.1 Before testing by the Charpy impact test, specimens ofthe steel may be given a rapid screening test in accordance withthe procedures o
47、f Test Method A, Sodium Hydroxide Etch Testfor Classification of Etch Structures of Duplex Stainless Steels.Preparation, etching, and the classification of etch structuresare described therein. Specimens having an etch structuredescribed as Unaffected Structure in Test Method A will beessentially fr
48、ee of detrimental effect on impact toughnessrelated to the formation of intermetallic phase. Other mecha-nisms for loss of toughness may occur independently but arebeyond the scope of this test method. Specimens showingUnaffected Structure in Test Method A are acceptable withrespect to the absence o
49、f intermetallic phases, without thenecessity of performing the Charpy test as described in TestMethod B. All specimens having other than Unaffected Struc-ture shall be tested by the Charpy impact test.10. Apparatus10.1 The test apparatus shall be as described in TestMethods and Definitions A 370.11. Preparation of Test Specimens11.1 The test specimen shall be as described in Test Meth-ods and Definitions A 370.11.2 An impact test for the purpose of detecting intermetal-lic phases shall consist of a single specimen taken from theproduct piece or lot to be
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