1、Designation: E381 01 (Reapproved 2012)E381 17Standard Method ofMacroetch Testing Steel Bars, Billets, Blooms, andForgings1This standard is issued under the fixed designation E381; 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 Scope*1.1 Macroetching, wh
3、ich is the etching of specimens for macrostructural examination at low magnifications, is a frequently usedtechnique for evaluating steel products such as bars, billets, blooms, and forgings.1.2 Included in this method is a procedure for rating steel specimens by a graded series of photographs showi
4、ng the incidenceof certain conditions. The method is limited in application to bars, billets, blooms, and forgings of carbon and low alloy steels.1.3 A number of different etching reagents may be used depending upon the type of examination to be made. Steels reactdifferently to etching reagents beca
5、use of variations in chemical composition, method of manufacture, heat treatment and manyother variables. Establishment of general standards for acceptance or rejection for all conditions is impractical as some conditionsmust be considered relative to the part in which it occurs.1.4 This standard do
6、es not purport to address all of the safety concerns, 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. See the specific precautionary state
7、ment in 5.3.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Ba
8、rriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E7 Terminology Relating to MetallographyE340 Practice for Macroetching Metals and AlloysE1180 Practice for Preparing Sulfur Prints for Macrostructural Evaluation2.2 ASTM Adjuncts:Photographs for Rating Macroetched Steel (3 pl
9、ates)33. Terminology3.1 DefinitionsFor definitions of terms used in this method, see Terminology E7.3.2 Definitions of Terms Specific to This Standard:3.2.1 Terminology Applicable Only to Ingot Cast Product:3.2.1.1 splasha nonuniform etch pattern where irregularly-shaped areas exhibit a different et
10、ch contrast than surroundingareas. Splash is normally associated with molten steel which solidifies and oxidizes during initial pouring and which is notcompletely redissolved by the remaining molten steel.3.2.1.2 butt tearssubsurface cracks normally parallel to the surface of the ingot mold wall.3.2
11、.1.3 flute crackscracks perpendicular to the surface of the ingot mold wall which may, or may not, extend to the surfaceof the product.3.2.1.4 bursta single or multi-rayed crack normally located at the center of the wrought product.1 This method is under the jurisdiction of ASTM Committee E04 on Met
12、allography and is the direct responsibility of Subcommittee E04.01 on Specimen Preparation.Current edition approved Oct. 1, 2012June 1, 2017. Published October 2012June 2017. Originally approved in 1968. Last previous edition approved in 20062012 asE381 01(2006).(2012). DOI: 10.1520/E0381-01R12.10.1
13、520/E0381-17.2 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 Summary page on the ASTM website.3 Available from ASTM Headquarters. Order Adjunc
14、t: ADJE038101 (Plate I), ADJE038102 (Plate II), and ADJE038103 (Plate III).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
15、depict all changes accurately, ASTM recommends 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 Interna
16、tional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2 Definitions Applicable Only to Continuously Cast Products:3.2.2.1 chill zonerapidly cooled metal with a fine structure at the surface of the product which is normally continuous aroundthat surface.3.2.2
17、.2 chill zone crackany crack which is located partially or completely in the chill zone and may extend to the surface ofthe product.3.2.2.3 diagonal cracka crack which lies completely or partially in the diagonal regions of a non-round product whereadjacent columnar or dendritic growth patterns inte
18、rsect.3.2.2.4 subsurface cracka crack perpendicular to and just beneath the chill zone.3.2.2.5 mid-radius cracka crack perpendicular to the surface of the product located approximately halfway between thesurface and center of the product.3.2.2.6 center cracka crack with an aspect ratio (length/width
19、) of approximately 3 or greater located at, or near, the center ofthe product.3.2.2.7 star cracka star-shaped or multi-rayed crack at the center of the product.3.2.2.8 scattered porositymultiple round or irregularly-shaped pores uniformly distributed about the central portion of theproduct.3.2.2.9 w
20、hite banda light etching continuous band(s) parallel to the surface of the product usually located between theone-quarter and three-quarter radius position, normally associated with electromagnetic stirring.3.2.2.10 columnar grainsa coarse structure of parallel, elongated grains formed by unidirecti
21、onal growth during solidification.3.2.3 Conditions Applicable to Both Ingot and Continuously Cast Product:3.2.3.1 nonmetallic inclusionsnonmetallic particles trapped in the steel or the voids resulting when inclusions are dissolvedby the macroetchant.3.2.3.2 patterna dark etching band, usually recta
22、ngular or square, enclosing the central portion of the cross section, normallyvisible only in wrought product. In ingot cast product, it is sometimes called ingotism or ingot pattern.3.2.3.3 pipe or center voida single large cavity located at, or near, the center of the product.3.2.3.4 center unsoun
23、dnessmultiple round or irregularly-shaped voids concentrated at the center of the product.3.2.3.5 dark centera dark etching area at the center of the product. Dark center is solid material and should not be confusedwith center unsoundness.3.2.3.6 pinholessmall pores which lie at, or just beneath, th
24、e surface of the product.3.2.3.7 mold slaginclusions which are normally associated with entrapped fused mold powder and are normally located at,or just beneath, the surface of the product. They are usually found in continuously cast or bottom poured products.3.2.3.8 flakesshort discontinuous interna
25、l cracks attributed to stresses produced by localized transformation and hydrogensolubility effects during cooling after hot working. In an etched transverse section, they appear as short, tight discontinuities whichare usually located in the midway to center location of the section. They are also k
26、nown as shatter cracks or hairline cracks.3.2.3.9 gassyirregularly-shaped voids which may, or may not, be uniformly distributed throughout the cross section. Thesemay be located anywhere from the near surface region of the product to the center of the product, depending on the source andseverity of
27、the condition.3.2.3.10 dendritica “tree-like” pattern with branches (primary, secondary, and tertiary arms) due to compositional differencesthat arise during solidification. For a specific composition, a weak dendritic structure is associated with a low superheat while astrong dendritic structure is
28、 associated with a high superheat during casting. Compositional differences also influence the clarityof the dendrites.3.2.3.11 refilled crackAdefect formed during the solidification of continuously cast steel, either external (bulging) or internal(shrinkage) forces result in the separation of cryst
29、allites so as to permit solute rich liquid to refill the gap as it forms.4. Significance and Use4.1 Macroetching is used in the steel industry because it is a simple test that will provide information about the relativehomogeneity of the sample. The method employs the action of an acid or other corr
30、osive agent to develop the macrostructuralcharacteristics of a suitably prepared specimen. The name implies that the etched surface is examined visually, or at lowmagnifications (usually 10).4.2 Macroetching will show: (1) variations in structure such as grain size, dendrites, and columnar structure
31、; (2) variations inchemical composition such as segregation, coring, and banding; and, (3) the presence of discontinuities such as laps, seams, cracks,porosity, bursts, pipe. and flakes.4.3 When, in accordance with the requirements of the inquiry, contract, order or specifications, forgings, billets
32、, blooms, etc.,are to be produced subject to macroetch testing and inspection, the manufacturer and the purchaser should be in agreementconcerning the following: (1) the stage of manufacture at which the test shall be conducted; (2) the number and locations of thesections to be examined; (3) the nec
33、essary surface preparation prior to etching of the specimen; (4) the etching reagent,temperature, and time of etching; and, (5) the type, size, number, location, and orientation of conditions that are to be consideredinjurious.E381 1724.4 When not specified, the procedures of the test may be selecte
34、d by the manufacturer to satisfy the requirements of thegoverning specification.4.5 When agreed upon by purchaser and producer, sulfur printing of as cast-sections, if continuously cast, is an acceptablealternative to macroetching. Sulfur printing shall be performed in accordance with Practice E1180
35、. Examination and rating ofspecimens shall be in accordance with Sections 10 and 11 of this (E381) standard.4.6 Steel from ingots ingots, in the wrought condition, shall be examined according to procedures described in Section 9.Continuously cast steel blooms and billets, in the as cast condition, s
36、hall be examined according to the procedures described inSections 10 and 11.With reductions over a 3:1 area ratio, wrought product from continuously cast steel may be examined accordingto Section 9.5. Reagents5.1 The most common reagent for macroetching iron and steel is a 1:1 mixture, by volume, of
37、 concentrated hydrochloric acid(HCl) and water. The hydrochloric acid need not be reagent grade. Commercial quality hydrochloric acid (also known as muriaticacid) is satisfactory. The etching solution should be clear and free from scum. It should be hot, 70 to 80C (160 to 180F). Thereagent should be
38、 used under a fume hood, or some other means of carrying off the corrosive fumes must be provided. The solutionmay be heated without serious change in concentration. The etching solution may be reused if it has not become excessivelycontaminated or weakened.NOTE 1The addition of hydrogen peroxide (H
39、2O2) may be necessary in order to provide sufficient reaction to properly etch some types of product.This should be added to an etching bath that is operating at room temperature.5.2 A second macroetching solution, favored by some as producing a clearer structure, is composed of concentrated HCl (38
40、volume %), sulfuric acid, H2SO4 (12 volume %) and water, H2O (50 volume %). (See 5.1 with respect to acid quality, heating,and ventilation.)5.3 Observe caution in mixing macroetch solutions. The acids are strong and they can cause serious chemical burns. Add acidslowly to water with stirring. This i
41、s especially true for sulfuric acid. Mix solutions and macroetch under a fume hood.5.4 An ammonium persulfate solution, a 10 to 20 % aqueous solution, is used primarily on longitudinal sections to detect certaintypes of ghost lines, segregation, flow lines, etc. A freshly made solution is necessary
42、for best results. The solution should beswabbed on the finished surface at room temperature. Inspection is most effective when done while the piece is still wet.5.5 A nitric acid solution, 5 % or 10 % nitric acid in alcohol or water, is used to detect local overstraining, grinding cracks,overheated
43、areas, and depth of carburized or decarburized surface zones. The use of this reagent necessitates a smooth surface. Thereagent is used at room temperature by immersion or swabbing.5.6 Many other reagents have been used for special applications. When the use of a reagent other than those described i
44、n 5.2 5.5 is desired, it should be by agreement between the purchaser and the manufacturer. (See Test Method E340 for other etchingsolutions.)6. Sampling6.1 When macroetching is used as an inspection procedure, sampling should be done at an early stage of manufacture so that,if the material is inade
45、quate, the minimum amount of unnecessary processing is done (or the processing can be modified to salvagethe material). For ingot cast product, the specimen is usually taken after ingot breakdown. Billets or blooms going into small sizesare sampled after the initial breakdown. Sampling of continuous
46、ly cast product is usually done in the as-cast condition, or afterintermediate or final processing, depending on size and preference. Random sampling of the finished product may be performedif the locations within the cast are not known.6.2 Normally, the specimens are disks cut from the ends of bars
47、, billets or blooms. Enough material should be discarded beforetaking the specimen to eliminate any extraneous effects of rolling such as “fish tails.” Specimens may be cut cold by any convenientmeans; saws and abrasive cut-off wheels are particularly effective. Torch cutting or other hot cutting wi
48、ll materially affect thestructure of the specimen and may be used only when necessary to remove a larger piece prior to cutting to size by cold methods.Sufficient torch cut material should be removed by cold cutting to eliminate the thermal effects of torch cutting.6.3 The macroetch test, as applied
49、 to the inspection of steel products of this specification, is carried out on slices, usually 13to 25 mm (12 to 1 in.) in thickness. Disks or specimens are usually cut to reveal a transverse surface, but the requirements of thespecification, contract, or order may include the preparation and examination of a longitudinal surface.6.4 When the test is conducted on single pieces (bar, billet, bloom, etc.), the purchaser may specify that the specimen disks becut to represent both ends, or only one end, of the piece.6.5 When the test is conducted on a nu
