1、Designation: E 381 01 (Reapproved 2006)Standard Method ofMacroetch Testing Steel Bars, Billets, Blooms, andForgings1This standard is issued under the fixed designation E 381; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 Macroetching, which is the etchi
3、ng of specimens formacrostructural examination at low magnifications, is a fre-quently used technique for evaluating steel products such asbars, billets, blooms, and forgings.1.2 Included in this method is a procedure for rating steelspecimens by a graded series of photographs showing theincidence o
4、f certain conditions. The method is limited inapplication to bars, billets, blooms, and forgings of carbon andlow alloy steels.1.3 A number of different etching reagents may be useddepending upon the type of examination to be made. Steelsreact differently to etching reagents because of variations in
5、chemical composition, method of manufacture, heat treatmentand many other variables. Establishment of general standardsfor acceptance or rejection for all conditions is impractical assome conditions must be considered relative to the part inwhich it occurs.1.4 This standard does not purport to addre
6、ss 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. See the specificprecautionary statement in 5.3.2. Referen
7、ced Documents2.1 ASTM Standards:2E7 Terminology Relating to MetallographyE 340 Test Method for Macroetching Metals and AlloysE 1180 Practice for Preparing Sulfur Prints for Macrostruc-tural Examination2.2 ASTM Adjuncts:Photographs for Rating Macroetched Steel (3 plates)33. Terminology3.1 Definitions
8、For definitions of terms used in thismethod, 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 whereirregularly-shaped areas exhibit a different etch contrast thansurrounding areas. Sp
9、lash is normally associated with moltensteel which solidifies and oxidizes during initial pouring andwhich is not completely redissolved by the remaining moltensteel.3.2.1.2 butt tearssubsurface cracks normally parallel tothe surface of the ingot mold wall.3.2.1.3 flute crackscracks perpendicular to
10、 the surface ofthe ingot mold wall which may, or may not, extend to thesurface of the product.3.2.1.4 bursta single or multi-rayed crack normally lo-cated at the center of the wrought product.3.2.2 Definitions Applicable Only to Continuously CastProducts:3.2.2.1 chill zonerapidly cooled metal with a
11、 fine struc-ture at the surface of the product which is normally continuousaround that surface.3.2.2.2 chill zone crackany crack which is located par-tially or completely in the chill zone and may extend to thesurface of the product.3.2.2.3 diagonal cracka crack which lies completely orpartially in
12、the diagonal regions of a non-round product whereadjacent columnar or dendritic growth patterns intersect.3.2.2.4 subsurface cracka crack perpendicular to and justbeneath the chill zone.3.2.2.5 mid-radius cracka crack perpendicular to thesurface of the product located approximately halfway betweenth
13、e surface and center of the product.1This method is under the jurisdiction of ASTM Committee E04 on Metallog-raphy, and is the direct responsibility of Subcommittee E04.01 on SpecimenPreparation.Current edition approved Oct. 1, 2005. Published October 2006. Originallyapproved in 1968. Last previous
14、edition approved in 2001 as E 381 01.2For referenced ASTM standards, visit the ASTM website, 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.3Available from ASTM Hea
15、dquarters. Order Adjunct: ADJE038101 (Plate I),ADJE038102 (Plate II), and ADJE038103 (Plate III).1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.2.6 center cracka crack with an aspect ratio (length/width) of approximately 3 or gr
16、eater located at, or near, thecenter of the product.3.2.2.7 star cracka star-shaped or multi-rayed crack at thecenter of the product.3.2.2.8 scattered porositymultiple round or irregularly-shaped pores uniformly distributed about the central portion ofthe product.3.2.2.9 white banda light etching co
17、ntinuous band(s)parallel to the surface of the product usually located betweenthe one-quarter and three-quarter radius position, normallyassociated with electromagnetic stirring.3.2.2.10 columnar grainsa coarse structure of parallel,elongated grains formed by unidirectional growth duringsolidificati
18、on.3.2.3 Conditions Applicable to Both Ingot and ContinuouslyCast Product:3.2.3.1 nonmetallic inclusionsnonmetallic particlestrapped in the steel or the voids resulting when inclusions aredissolved by the macroetchant.3.2.3.2 patterna dark etching band, usually rectangular orsquare, enclosing the ce
19、ntral portion of the cross section,normally visible 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 unsoundnessmultiple round or irregularly-s
20、haped voids concentrated at the center of the product.3.2.3.5 dark centera dark etching area at the center of theproduct. Dark center is solid material and should not beconfused with center unsoundness.3.2.3.6 pinholessmall pores which lie at, or just beneath,the surface of the product.3.2.3.7 mold
21、slaginclusions which are normally associ-ated with entrapped fused mold powder and are normallylocated at, or just beneath, the surface of the product. They areusually found in continuously cast or bottom poured products.3.2.3.8 flakesshort discontinuous internal cracks attrib-uted to stresses produ
22、ced by localized transformation andhydrogen solubility effects during cooling after hot working. Inan etched transverse section, they appear as short, tightdiscontinuities which are usually located in the midway tocenter location of the section. They are also known as shattercracks or hairline crack
23、s.3.2.3.9 gassyirregularly-shaped voids which may, or maynot, be uniformly distributed throughout the cross section.These may be located anywhere from the near surface region ofthe product to the center of the product, depending on thesource and severity of the condition.3.2.3.10 dendritica “tree-li
24、ke” pattern with branches (pri-mary, secondary, and tertiary arms) due to compositionaldifferences that arise during solidification. For a specificcomposition, a weak dendritic structure is associated with alow superheat while a strong dendritic structure is associatedwith a high superheat during ca
25、sting. Compositional differ-ences also influence the clarity of the dendrites.3.2.3.11 refilled crackA defect formed during the solidi-fication of continuously cast steel, either external (bulging) orinternal (shrinkage) forces result in the separation of crystal-lites so as to permit solute rich li
26、quid to refill the gap as itforms.4. Significance and Use4.1 Macroetching is used in the steel industry because it isa simple test that will provide information about the relativehomogeneity of the sample. The method employs the action ofan acid or other corrosive agent to develop the macrostructura
27、lcharacteristics of a suitably prepared specimen. The nameimplies that the etched surface is examined visually, or at lowmagnifications (usually 103).4.2 Macroetching will show: (1) variations in structure suchas grain size, dendrites, and columnar structure; (2) variationsin chemical composition su
28、ch as segregation, coring, andbanding; 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 theinquiry, contract, order or specifications, forgings, billets,blooms, etc., are to be produced subject to
29、 macroetch testingand inspection, the manufacturer and the purchaser should bein agreement concerning the following: (1) the stage ofmanufacture at which the test shall be conducted; (2) thenumber and locations of the sections to be examined; (3) thenecessary surface preparation prior to etching of
30、the specimen;(4) the etching reagent, temperature, and time of etching; and,(5) the type, size, number, location, and orientation of condi-tions that are to be considered injurious.4.4 When not specified, the procedures of the test may beselected by the manufacturer to satisfy the requirements of th
31、egoverning specification.4.5 When agreed upon by purchaser and producer, sulfurprinting of as cast-sections, if continuously cast, is an accept-able alternative to macroetching. Sulfur printing shall beperformed in accordance with Practice E 1180. Examinationand rating of specimens shall be in accor
32、dance with Sections10 and 11 of this (E 381) standard.4.6 Steel from ingots shall be examined according to pro-cedures described in Section 9. Continuously cast steel bloomsand billets, in the as cast condition, shall be examinedaccording to the procedures described in Sections 10 and 11.With reduct
33、ions over a 3:1 area ratio, wrought product fromcontinuously cast steel may be examined according to Section9.5. Reagents5.1 The most common reagent for macroetching iron andsteel is a 1:1 mixture, by volume, of concentrated hydrochloricacid (HCl) and water. The hydrochloric acid need not bereagent
34、grade. Commercial quality hydrochloric acid (alsoknown as muriatic acid) is satisfactory. The etching solutionshould be clear and free from scum. It should be hot, 70 to80C (160 to 180F). The reagent should be used under a fumehood, or some other means of carrying off the corrosive fumesmust be prov
35、ided. The solution may be heated without seriouschange in concentration. The etching solution may be reused ifit has not become excessively contaminated or weakened.NOTE 1The addition of hydrogen peroxide (H2O2) may be necessaryE 381 01 (2006)2in order to provide sufficient reaction to properly etch
36、 some types ofproduct. This should be added to an etching bath that is operating at roomtemperature.5.2 A second macroetching solution, favored by some asproducing a clearer structure, is composed of concentrated HCl(38 volume %), sulfuric acid, H2SO4(12 volume %) and water,H2O (50 volume %). (See 5
37、.1 with respect to acid quality,heating, and ventilation.)5.3 Observe caution in mixing macroetch solutions. Theacids are strong and they can cause serious chemical burns.Add acid slowly to water with stirring. This is especially truefor sulfuric acid. Mix solutions and macroetch under a fumehood.5.
38、4 An ammonium persulfate solution, a 10 to 20 % aque-ous solution, is used primarily on longitudinal sections todetect certain types of ghost lines, segregation, flow lines, etc.A freshly made solution is necessary for best results. Thesolution should be swabbed on the finished surface at roomtemper
39、ature. Inspection is most effective when done while thepiece is still wet.5.5 A nitric acid solution, 5 % or 10 % nitric acid in alcoholor water, is used to detect local overstraining, grinding cracks,overheated areas, and depth of carburized or decarburizedsurface zones. The use of this reagent nec
40、essitates a smoothsurface. The reagent is used at room temperature by immersionor swabbing.5.6 Many other reagents have been used for special appli-cations. When the use of a reagent other than those describedin 5.2-5.5 is desired, it should be by agreement between thepurchaser and the manufacturer.
41、 (See Test Method E 340 forother etching solutions.)6. Sampling6.1 When macroetching is used as an inspection procedure,sampling should be done at an early stage of manufacture sothat, if the material is inadequate, the minimum amount ofunnecessary processing is done (or the processing can bemodifie
42、d to salvage the material). For ingot cast product, thespecimen is usually taken after ingot breakdown. Billets orblooms going into small sizes are sampled after the initialbreakdown. Sampling of continuously cast product is usuallydone in the as-cast condition, or after intermediate or finalprocess
43、ing, depending on size and preference. Random sam-pling of the finished product may be performed if the locationswithin the cast are not known.6.2 Normally, the specimens are disks cut from the ends ofbars, billets or blooms. Enough material should be discardedbefore taking the specimen to eliminate
44、 any extraneous effectsof rolling such as “fish tails.” Specimens may be cut cold byany convenient means; saws and abrasive cut-off wheels areparticularly effective. Torch cutting or other hot cutting willmaterially affect the structure of the specimen and may be usedonly when necessary to remove a
45、larger piece prior to cuttingto size by cold methods. Sufficient torch cut material should beremoved by cold cutting to eliminate the thermal effects oftorch cutting.6.3 The macroetch test, as applied to the inspection of steelproducts of this specification, is carried out on slices, usually13 to 25
46、 mm (12 to 1 in.) in thickness. Disks or specimens areusually cut to reveal a transverse surface, but the requirementsof the specification, contract, or order may include the prepa-ration and examination of a longitudinal surface.6.4 When the test is conducted on single pieces (bar, billet,bloom, et
47、c.), the purchaser may specify that the specimen disksbe cut to represent both ends, or only one end, of the piece.6.5 When the test is conducted on a number of pieces madefrom a heat of steel, the purchaser may require that each piecebe individually tested; or, a representative method of samplingma
48、y be agreed upon by the manufacturer and the purchaser.6.6 For the indication of certain internal types of disconti-nuities, such as thermal cracks or flakes, the purchaser mayspecify that disks for macroetch inspection be taken a certainminimum distance from the ends of the specimen. In the caseof
49、forgings, depending upon prior agreement, this may beaccomplished by adding excess metal for discard on the ends orends of the forging; or, by forging in multiple lengths andremoving the test disk between individual pieces when cuttingup the multiple forging.7. Preparation7.1 Specimen preparation need not be elaborate. Anymethod of preparing smooth surfaces with a minimum amountof cold work should be satisfactory. Disks may be faced on alathe or a shaper. The usual procedure is to take a roughing cut,then a finishing cut. This will generate a smooth surf
