1、Designation: A763 93 (Reapproved 2009)A763 14Standard Practices forDetecting Susceptibility to Intergranular Attack in FerriticStainless Steels1This standard is issued under the fixed designation A763; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 case of 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 Scope*1.1 These practices cover the following four tests:1.1.1 Practice WOxalic acid etch
3、test for detecting susceptibility to intergranular attack in stabilized ferritic stainless steelsby classification of the etching structures (see Sections 33 10 through 10).1.1.2 Practice XFerric sulfate-sulfuric acid test for detecting susceptibility to intergranular attack in ferritic stainless st
4、eels(Sections 1111 16 to 16).1.1.3 Practice YCopper-copper sulfate-50 % sulfuric acid test for detecting susceptibility to intergranular attack in ferriticstainless steels (Sections 1717 22 to 22).1.1.4 Practice ZCopper-copper sulfate-16 % sulfuric acid test for detecting susceptibility to intergran
5、ular attack in ferriticstainless steels (Sections 2323 29 to 29).1.2 The following factors govern the application of these practices (1-6)2:1.2.1 Practice W, oxalic acid test, is a rapid method of identifying, by simple,simple electrolytic etching, those specimens ofcertain ferritic alloys that are
6、not susceptible to intergranular corrosion associated with chromium carbide precipitation. PracticeW is used as a screening test to avoid the necessity, for acceptable specimens, of more extensive testing required by Practices X,Y, and Z. See Table 1 for a listing of alloys for which Practice W is a
7、ppropriate.1.2.2 Practices X,Y, and Z can be used to detect the susceptibility of certain ferritic alloys to intergranular attack associated withthe precipitation of chromium carbides or nitrides.1.2.3 Practices W, X, Y, and Z can also be used to evaluate the effect of heat treatment or of fusion we
8、lding on susceptibilityto intergranular corrosion.1.2.4 Table 2 lists the identification ferritic stainless steels for which data on the application of at least one of the standardpractices is available.1.2.5 Some stabilized ferritic stainless steels may show high rates when tested by Practice X bec
9、ause of metallurgical factorsnot associated with chromium carbide or nitride precipitation. This possibility must be considered in selecting the test method.Combinations of alloys and test methods for which successful experience is available are shown in Table 1. Application of thesestandard tests t
10、o the other ferritic stainless steels will be by specific agreement between producer and user.1.3 Depending on the test and alloy, evaluations may be accomplished by weight loss determination, microscopicalexamination, or bend test (Sections 30 and 31). The choices are listed in Table 1.1.4 This sta
11、ndard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use. For specific safety precauti
12、onary statements, see 3.2.5, Section 7, 13.1, and 19.1.2. Referenced Documents2.1 ASTM Standards:3A370 Test Methods and Definitions for Mechanical Testing of Steel Products1 These practices are under the jurisdiction ofASTM Committee A01 on Steel, Stainless Steel and RelatedAlloys and are the direct
13、 responsibility of Subcommittee A01.14on Methods of Corrosion Testing.Current edition approved April 1, 2009Oct. 1, 2014. Published April 2009October 2014. Originally approved in 1979. Last previous edition approved in 20042009 asA763 93 (2004).(2009). DOI: 10.1520/A0763-93R09.10.1520/A0763-14.2 The
14、 boldface numbers in parentheses refer to the list of references appended to these practices.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document S
15、ummary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recomme
16、nds that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
17、 West Conshohocken, PA 19428-2959. United States13. Apparatus3.1 Apparatus for Practice W, Oxalic Acid Etch Test:3.1.1 Source of DCBattery, generator, or rectifier capable of supplying 15 V and 20 A.3.1.2 Ammeter, range 0 to 30 A.3.1.3 Variable Resistance, for control of specimen current.3.1.4 Catho
18、deOne-litre stainless steel beaker or suitable piece of stainless steel.3.1.5 Electric Clamp, to hold etched specimen.3.1.6 Metallurgical Microscope, for examination of etched structures at 250 to 500.3.1.7 ElectrodesThe specimen is made the anode and the beaker or other piece of stainless steel the
19、 cathode.3.1.8 ElectrolyteOxalic acid (H2C2O42H2O) reagent grade, 10 weight % solution.TABLE 1 Methods for Evaluating Ferritic Stainless Steels for Susceptibility to Intergranular CorrosionAlloy Time of Test, hEvaluation CriteriaWeight Loss MicroscopicalExaminationBend TestPRACTICE WOXALIC ACID ETCH
20、 TEST439 0.025 NA AA NA18Cr-2Mo 0.025 NA AA NAXM27 0.025 NA AA NAXM33 0.025 NA AA NA26-3-3 0.025 NA AA NAPRACTICE XFERRIC SULFATE - SULFURIC ACID TEST430 24 AB,C A NA446 72 AC A NAXM27 120 AD AC NA29Cr-4Mo 120 NAE AC NA29Cr-4Mo-2Ni 120 NA AC NAPRACTICE YCOPPER-COPPER SULFATE - 50% SULFURIC ACID TEST
21、446 96 AC A NAXM27 120 AD AC NAXM33 120 AD AC NA2633 120 AD AC NA29-4C 120 AD AC NA29Cr-4Mo 120 NA AC NA29Cr-4Mo-2Ni 120 NA AC NAPRACTICE ZCOPPER-COPPER SULFATE - 16% SULFURIC ACID TEST430 24 NA NA no fissures434 24 NA NA no fissures436 24 NA NA no fissures439 24 NA NA no fissures18Cr-2Mo 24 NA NA n
22、o fissuresA Polished surface examined at 250 to 500 with a metallurgical microscope (see 3.1.6). All other microscopical examinations are of the corroded surface under 40binocular examination (see Section 27).B A = Applicable.C Preferred criterion, these criteria are the most sensitive for the parti
23、cular combination of alloy and test.D Weight loss measurements can be used to detect severely sensitized material, but they are not very sensitive for alloys noted with this superscript and may not detectslight or moderate sensitization.E NA = Not applicable.TABLE 2 Steels for Which Test Results are
24、 AvailableUNS Designation Alloy Practice(s)S43000 430A X, ZS43400 434A ZS43600 436A ZS43035 XM8 ZS44400 18Cr-2Mo W, ZS44600 446A X, YS44626 XM33 W, YS44627 XM27 W, X, YS44660 2633 YS44700 29Cr-4Mo X, YS44735 29-4C YS44800 29Cr-4Mo-2NI X, YA Types 430, 434, 436, and 446 are nonstabilized grades that
25、are generally notused in the as-welded or sensitized condition in other than mildly corrosiveenvironments. In the annealed condition, they are not subject to intergranularcorrosion. For any studies of IGAonTypes 430, 434, 436, or 446, the indicated testmethods are suggested.A763 1423.2 Aparatus Comm
26、on to Practices X, Y, and ZThe apparatus common to Practices X,Y, and Z is listed below. SupplementarySuplementary requirements are noted as required.3.2.1 The apparatus used is shown in Fig. 1.NOTE 1No substitution for this equipment may be used. The cold-finger type of condenser with standard Erle
27、nmeyer flasks may not be used.3.2.2 Allihn or Soxhlet Condenser, four-bulb (minimum) with a 45/50 ground-glass joint. Overall length shall be about 330 mm(13 in.)in.), with condensing section,section 241 mm (912 in.).3.2.3 Erlenmeyer Flask, 1-Lwith a 45/50 ground-glass joint. The ground-glass openin
28、g is somewhat over 38 mm (112 in.) wide.3.2.4 Glass Cradles (Note 2), (Note 2) can be supplied by a glass blowing shop. The size of the cradles should be such that theycan pass through the ground-glass joint of the Erlenmeyer flask. They should have three or four holes in them to increasecirculation
29、 of the test solution around the specimen.NOTE 2Other equivalent means of specimen support such as glass hooks or stirrups may also be used.3.2.5 Boiling Chips, must be used to prevent bumping. It has been reported that violent boiling resulting in acid spills can occur.It is important to ensure tha
30、t the concentration of acid does not become more concentrated and that an adequate number of boilingchips (which are resistant to attack by the test solution) are present.43.2.6 Silicone Grease, is recommended for the ground-glass joint.3.2.7 Electrically Heated Hot Plate, or other device to provide
31、 heat for continuous boiling of the solution.4. Preparation of Test Specimens4.1 The preparation of test specimens is common among Practices X, Y, and Z. Additional requirements are noted wherenecessary.4.2 A specimen having a total surface area of 5 to 20 cm2 is recommended for Practices X, Y, and
32、Z. As-welded specimensshould be cut so that no more than 13 mm 12 (in.) width of unaffected base metal is included on either side of the weld andheat-affected zone.4 Amphoteric alundum granules, Hengar Granules, from the Hengar Company, Philadelphia, PA have been found satisfactory for this purpose.
33、FIG. 1 Test ApparatusA763 1434.3 The intent is to test a specimen representing as nearly as possible the surface of the material as used in service. Only suchsurface finishing should be performed as is required to remove foreign material and obtain a standard, uniform finish as specified.For very he
34、avy sections, specimens should be prepared to represent the appropriate surface while maintaining reasonable specimensize for convenience in testing. Ordinarily, removal of more material than necessary will have little influence on the test results.However, in the special case of surface carburizati
35、on (sometimes encountered, for instance, in tubing when carbonaceouslubricants are employed) it may be possible by heavy grinding or machining to remove the carburized layer completely. Suchtreatment of test specimens is not permissible, except in tests undertaken to demonstrate such surface effects
36、.4.4 Sensitization of Test Specimens:4.4.1 Specimens from material that is going to be used in the as-received condition without additional welding or heat treatmentmay be tested in the as-received condition without any sensitizing treatment.4.4.2 Specimens from material that is going to be welded o
37、r heat treated should be welded or heat treated in as nearly the samemanner as the material will experience in service.4.4.3 The specific sensitizing or welding treatment, or both, should be agreed upon between the supplier and the purchaser.4.5 For Practice W, a cross section of the sample includin
38、g material at both surfaces and a cross section of any weld and its heataffected zones should be prepared. If the sample is too thick, multiple specimens should be used. Grind the cross section on wetor dry 80 or 120-grit abrasive paper followed by successively finer papers until a number 400 or 3/0
39、 finish is obtained. Avoidexcessive heat when dry-grinding.4.6 For Practices X, Y, and Z, all surfaces of the specimen including edges should be ground on wet or dry 80 or 120-gritabrasive paper. Avoid excessive heat when dry-grinding. Do not use sand- or grit-blasting. All traces of oxide scale for
40、med duringheat treatment must be removed. To avoid scale entrapment, stamp specimens for identification after heat treatment and grinding.4.7 Degrease and dry the sample using suitable nonchlorinated agents.PRACTICE WOXALIC ACID ETCH TEST FOR DETECTING SUSCEPTIBILITY TO INTERGRANULARATTACK BY CLASSI
41、FICATION OF MICROSTRUCTURE FOR SCREENING OF CERTAIN FERRITICSTAINLESS STEELS5. Scope5.1 The oxalic acid etch test is intended and may be used for screening of certain ferritic stainless steels to precede or precludethe need for corrosion testing as described in Practices X, Y, or Z. Specimens with u
42、nacceptable microstructures should besubjected to Practices X, Y, or Z to better determine their susceptibility to intergranular attack. See Table 1 for a listing of alloysfor which Practice W is appropriate.6. Etching Conditions6.1 The polished specimens should be etched at 1 A/cm2 for 1.5 min. Thi
43、s may be accomplished with the apparatus prescribedin 3.1 by adjusting the variable resistance until the ammeter reading in amperes equals the immersed specimen area in squarecentimetres. Immersion of the specimen-holding clamp in the etching solution should be avoided.7. Etching Precautions7.1 Etch
44、ing should be carried out under a ventilating hood. Gas evolved at the electrodes with entrained oxalic acid is poisonousand irritating. The temperature of the etching solution, which increases during etching, should be kept below 50C by using twobeakers of acid, one of which may be cooled while the
45、 other is in use.8. Rinsing Prior to Examination8.1 Following etching, the specimen should be rinsed in hot water then acetone or alcohol to avoid oxalic acid crystallizationon the etched surface during forced air-drying.9. Examination9.1 Examine etched specimens on a metallurgical microscope at 250
46、 to 500 as appropriate for classification of etchedmicrostructure type as defined in Section 10.10. Classification of Etched Structures10.1 Acceptable structures indicating resistance to chromium carbide-type intergranular attack:10.1.1 Step structureStructureSteps only between grainsno ditches at g
47、rain boundaries (see Fig. 2).10.1.2 Dual structureStructureSome ditches at grain boundaries in addition to steps, but no single grain completelysurrounded by ditches (see Fig. 3).10.2 Unacceptable structures requiring additional testing (Practices X, Y, or Z):10.2.1 Ditch structureStructureOne or mo
48、re grains completely surrounded by ditches (see Fig. 4).A763 144PRACTICE XFERRIC SULFATE-SULFURIC ACID TEST FOR DETECTING SUSCEPTIBILITY TOINTERGRANULAR ATTACK IN FERRITIC STAINLESS STEELS11. Scope11.1 This practice describes the procedure for conducting the boiling ferric sulfate-sulfuric acid test
49、 which measures thesusceptibility of ferritic stainless steels to intergranular attack. This test detects susceptibility to intergranular attack associated withthe precipitation of chromium carbides and nitrides in stabilized and unstabilized ferric stainless steels. It may also detect thepresence of chi or sigma phase in these steels. The test will not differentiate between intergranular attack resulting from carbidesand that due to intermetallic phases. The ferric sulfate-sulfuric acid solution may also selectively attack titanium
