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ASTM A262 2015 奥氏体不锈钢晶间腐蚀敏感性检测标准方法.pdf
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- ASTM A262 2015 奥氏体不锈钢晶间腐蚀敏感性检测标准方法.pdf
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1、Designation: A262 15Standard Practices forDetecting Susceptibility to Intergranular Attack in AusteniticStainless Steels1This standard is issued under the fixed designation A262; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、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.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1 These practices cover t
3、he following five tests:1.1.1 Practice AOxalic Acid Etch Test for Classificationof Etch Structures of Austenitic Stainless Steels (Sections 4 to13, inclusive),1.1.2 Practice BFerric Sulfate-Sulfuric Acid Test for De-tecting Susceptibility to Intergranular Attack in AusteniticStainless Steels (Sectio
4、ns 14 to 25, inclusive),1.1.3 Practice CNitric Acid Test for Detecting Suscepti-bility to Intergranular Attack in Austenitic Stainless Steels(Sections 26 to 36, inclusive),1.1.4 Practice ECopperCopper SulfateSulfuric AcidTest for Detecting Susceptibility to Intergranular Attack inAustenitic Stainles
5、s Steels (Sections 37 to 46, inclusive), and1.1.5 Practice FCopperCopper Sulfate50 % SulfuricAcid Test for Detecting Susceptibility to Intergranular Attackin Molybdenum-Bearing Austenitic Stainless Steels (Sections47 to 58, inclusive).1.2 The Oxalic Acid Etch Test is a rapid method ofidentifying, by
6、 simple etching, those specimens of certainstainless steel grades that are essentially free of susceptibilityto intergranular attack associated with chromium carbideprecipitates. These specimens will have low corrosion rates incertain corrosion tests and therefore can be eliminated(screened) from te
7、sting as “acceptable.” The etch test isapplicable only to those grades listed in the individual hot acidtests and classifies the specimens either as “acceptable” or as“suspect.”1.3 The ferric sulfate-sulfuric acid test, the coppercoppersulfate50 % sulfuric acid test, and the nitric acid test are bas
8、edon weight loss determinations and, thus, provide a quantitativemeasure of the relative performance of specimens evaluated. Incontrast, the coppercopper sulfate16 % sulfuric acid test isbased on visual examination of bend specimens and, therefore,classifies the specimens only as acceptable or nonac
9、ceptable.1.4 The presence or absence of intergranular attack in thesetests is not necessarily a measure of the performance of thematerial in other corrosive environments. These tests do notprovide a basis for predicting resistance to forms of corrosionother than intergranular, such as general corros
10、ion, pitting, orstress-corrosion cracking.NOTE 1See Appendix X1 for information regarding test selection.1.5 The values stated in SI units are to be regarded asstandard. The inch-pound equivalents are in parentheses andmay be approximate.1.6 This standard does not purport to address all of thesafety
11、 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. Some specifichazards statements are given in 10.1, 20.1.1, 20.1.9, 31.3, 34.
12、4,53.1.1, and 53.1.10.2. Referenced Documents2.1 ASTM Standards:2A370 Test Methods and Definitions for Mechanical Testingof Steel ProductsA380/A380M Practice for Cleaning, Descaling, and Passi-vation of Stainless Steel Parts, Equipment, and SystemsD1193 Specification for Reagent WaterE3 Guide for Pr
13、eparation of Metallographic Specimens2.2 ASME Code:3ASME Boiler such use is outside the scope of this practice.4.2 This test is intended to be used in connection with otherevaluation tests described in these practices to provide a rapidmethod for identifying qualitatively those specimens that arecer
14、tain to be free of susceptibility to rapid intergranular attackin these other tests. Such specimens have low corrosion rates inthe various hot acid tests which require from 15 to 240 h ofexposure. These specimens are identified by means of theiretch structures, which are classified according to the
15、criteriagiven in Section 11.4.3 The Oxalic Acid Etch Test may be used to screenspecimens intended for testing in Practice BFerric Sulfate-Sulfuric Acid Test, Practice CNitric Acid Test, PracticeECopper-Copper Sulfate16 % SulfuricAcid Test, and Prac-tice FCopper-Copper Sulfate50 % Sulfuric Acid Test.
16、4.4 Each of these other practices contains a table showingwhich classifications of etch structures on a given stainlesssteel grade are equivalent to acceptable or suspect performancein that particular test. Specimens having acceptable etchstructures need not be subjected to the hot acid test. Specim
17、enshaving suspect etch structures must be tested in the specifiedhot acid solution.4.5 There are two classes of specimens to be considered:base metal, and process-affected metal.4.5.1 Process-affected metal contains any condition thataffects the corrosion properties of the material in a non-uniformw
18、ay, such as (but not limited to) welds; carburized. nitrided, oroxidized surfaces; mechanical deformation; and areas affectedby heat. Base metal has none of these conditions.4.5.2 Because Practices B, C, and F involve immersing theentire specimen and averaging the mass loss over the totalspecimen ar
19、ea, and because welding, carburization, mechanicaldeformation, and the like affect only part of a specimen, thepresence of process-affected metal in a specimen can affect thetest result in an unpredictable way depending on the propor-tions of the area affected.4.5.3 If the presence of these or other
20、 localized conditions isa concern to the purchaser, then tests that do not average themass loss over the total specimen surface area, such as PracticeA, the OxalicAcid EtchTest, or Practice E, the CopperCopperSulfateSulfuric Acid Test for Detecting Susceptibility toIntergranular Attack in Austenitic
21、 Stainless Steels, should beconsidered.5. Summary of Practice5.1 A specimen representative of the material to be evalu-ated is polished to a specified finish and over-etched usingoxalic acid electrolytically. The etched specimen is thenexamined using a metallurgical microscope. The etched struc-ture
22、 is compared with reference photographs to determinewhether the material is acceptable or suspect. Suspect materialis then subjected to the specified hot acid immersion test.6. Significance and Use6.1 Use of the etch test allows rapid acceptance of specificlots of material without the need to perfor
23、m time-consumingand costly hot acid immersion tests on those lots.7. Apparatus7.1 Etching Cell:7.1.1 An etching cell may be assembled using componentsas described in this section. Alternatively, a commercialelectropolisher/etcher (as used for metallographic samplepreparation) may be used for small s
24、pecimens provided thecurrent density requirement of 10.2 is met.7.1.2 Source of Direct CurrentBattery, generator, or rec-tifier capable of supplying about 15 V and 20 A.7.1.3 AmmeterFor direct current; used to measure thecurrent on the specimen to be etched.7.1.4 Variable ResistanceUsed to control t
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