Designation:A604–93(Reapproved2003)
Standard Test Method for
Macroetch Testing of Consumable Electrode Remelted Steel Bars and Billets1
This standard is issued under thefixed designation A604;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript 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.Scope
1.1This test method2covers testing and inspection and is applicable to bars,billets,and blooms of carbon,alloy,and stainless steel which have been consumable electrode remelted.
1.2For the purpose of this test method,the consumable electrode remelting process is defined as a steel refining method wherein single or multiple electrodes are remelted into a crucible producing an ingot which is superior to the original electrode by virtue of improved cleanliness or lower gas content or reduced chemical or nonmetallic segregation.See Appendix X1and Appendix X2for descriptions of applicable remelting processes.
1.3This test method and the accompanying comparison macrographs3are generally applicable to steel bar and billet sizes up to225in.2in transverse cross section.
1.4The values stated in inch-pound units are to be regarded as the standard.The values given in parentheses are for information only.
1.5This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility 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.
editorial英文2.Referenced Documents
2.1ASTM Standards:
E381Method of Macroetch Testing Steel Bars,Billets, Blooms,and Forgings4
2.2ASTM Adjuncts:
ADJA0604
Adjunct to A604Test Method for Macroetch Testing of Consumable Electrode Remelted Steel Bars and Billet3 3.Description of Macroetch Testing
3.1Macroetch testing,as described herein,is a method for examining and rating transverse sections of bars and billets to describe certain conditions of macro segregation which are often characteristic of consumable electrode remelted materi-als.This test method is not intended to define major defects such as those described by Method E381.
3.2This test method employs the action of an acid or other corrosive agent to develop the characteristics of a suitably prepared specimen.After etching,the sections are compared visually,or at a
very low magnification,if necessary for clarification of conditions,to standard plates describing the various conditions which may be found.Materials react differ-ently to etching reagents because of variations in chemical composition,method of manufacture,heat treatment,and many other variables.
4.Application
4.1When material is furnished subject to macroetch testing and inspection under this test method,the manufacturer and purchaser should be in agreement concerning the following: 4.1.1The stage of manufacture at which the test shall be conducted,
4.1.2The number and location of the sections to be tested, 4.1.3The condition and preparation of the surface to be macroetched,
4.1.4The etching reagent,temperature and time of etching, or degree of etching including any special techniques which must be used,and
4.1.5The type and degree of conditions or combinations thereof that shall be considered acceptable or subject to metallurgical review.
1This test method is under the jurisdiction of ASTM Committee A01on Steel,
Stainless Steel,and Related Alloys and is the direct responsibility of Subcommittee
A01.06on Steel Forgings and Billets.
Current edition approved April10,2003.Published July2003.Originally
approved in1970.Last previous edition approved in1998as A604–93(1998).
2ASTM Committee A01gratefully acknowledges the help of the AISI Commit-
tee on General Metallurgy in preparing the appendix,assembling the macroetch
photographs,and assisting with the text of this test method.
3A complete set of the20macrographs on glossy paper is available at nominal
cost from ASTM Headquarters,100Barr Harbor Drive,W.Conshohocken,PA
19428.Request Adjunct ADJA0604.
4Annual Book of ASTM Standards,V ol03.01.
1
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
5.Sample Preparation
5.1Unless otherwise specified,the test shall be performed on specimens,usually1⁄4to1in.thick,cut to reveal a transverse surface.
5.2Disks for macroetch inspection may be removed from billets by a variety of methods including torch cutting,sawing, machining,or high-speed abrasive wheels.Adequate prepara-tion of the surface for macroetching must completely remove the effects of torch cutting or high-speed abrasive wheels. 5.3Due to the nature of the conditions to be detected, further surface preparation is usually required.
5.4When such further preparation is performed,grinding, machining,or sanding should be carried out in such a manner as not to mask the structure.
5.5The surface of the disk to be etched must be free of dirt, grease,or other foreign material which might impair the result of the test.
6.Etching Reagents
6.1The etching response and appearance is dependent upon the type and temperature of the etching reagent and the time of immersion.These details must be established by agreement between manufacturer and purchaser.
6.2For illustrative purposes some of the commonly used etching reagents are as follows:
6.2.1Hydrochloric Acid—A solution of1part commercial concentrated hydrochloric acid(HCl,sp gr1.19)and1part water is more generally used than any other macroetching reagent.This solution may be heated without significant change in concentration,and may be reused if it has not become excessively contaminated or weakened.Etching is generally done with the solution at a temperature of approxi-mately160°F.
6.2.2Hydrochloric Acid-Sulfuric Acid Mixture—A mixture containing50%water,38%commercial concentrated HCl, and12%commercial concentrated sulfuric acid(H2SO4,sp gr 1.84)is sometimes used in place of the previously mentioned 50%HCl solution.The statements in the previous paragraph regarding reuse and temperature of etchant are applicable to this reagent.
6.2.3Aqua Regia—A solution consisting of1part concen-trated nitric acid(HNO3,sp gr1.42)and2parts concentrated HCl is used on corrosion and heat-resistant materials of the 18%chromium,8%nickel type and higher alloy types.This reagent is used at room temperature.
N OTE1—The reagents in6.2.1,6.2.2,and6.2.3should be used under ventilating hoods or with some provision to remove the corrosive fumes.
6.2.4Nitric Acid—This etchant consists of5%HNO3 solution in alcohol or water,and is generally used at room temperature.When this reagent is used,the etch disk must have a smooth surface.
7.Etching Containers
7.1Macroetching must be done in containers that are resistant to attack from the etching reagents.Caution must be exerted to prevent the occurrence of electrolytic couples which can cause uneven attacks and misleading results.
8.Preparation of Etched Surface and Examination
8.1Upon completion of etching,surfaces of disks should be cleaned by either chemical or mechanical methods that do not affect the macroetch quality.Care should be taken to prevent rusting of the etched
surface.
9.Interpretation of Conditions Found by Macroetching 9.1Four distinct classes of conditions are defined and described under this method:
9.1.1Class1:Freckles—Circular or near-circular dark etching areas generally enriched with carbides and carbide-forming elements.
9.1.2Class2:White Spots—Light etching areas,having no definitive configuration or orientation which are generally reduced in carbide or carbide-forming elements.
9.1.3Class3:Radial Segregation—Radially or spirally oriented dark etching elongated areas occurring most fre-quently at mid-radius which are generally carbide enriched. This condition may be easily confused with freckles in some materials.
9.1.4Class4:Ring Pattern—One or more concentric rings evidenced by a differential in etch texture associated with minor composition gradients and ingot solidification.
9.2Macroetch photographs show examples of each of the conditions revealed by macroetch testing,withfive degrees of severity,identified as A,B,C,D,and E for each condition. Degree A exhibits th
e minimum occurrence of each condition detectable by visual examination of the etched surface,while degrees B,C,D,and E represent increasing severity of occurrence.
9.3For each condition,or combination of conditions,rat-ings shall be obtained by comparing each macroetched section with the standard photographs.Bar or billet sections to225in.2 cross-sectional area may be rated against these standards. Larger sizes may be rated by agreement between manufacturer and purchaser,but caution must be exercised in interpretation of such results.Figs.1-20have been reduced44%in area from the standard photographs.
9.4If the appearance of a given condition does not exactly match one of thefive standard photographs,it shall be assigned the rating of the standard that it most nearly matches.
9.5No standards for acceptance are stated or implied in these illustrations.The extent to which each condition may be permissible varies with the intended application,and such standards should be stated in the applicable product specifica-tion,or may be the subject of negotiation between manufac-turer and
purchaser.
FIG.1Class1—Freckles—Severity A
FIG.2Class1—Freckles—Severity B
FIG.3Class1—Freckles—Severity C
FIG.4Class1—Freckles—Severity D
FIG.5Class1—Freckles—Severity E
FIG.6Class2—White Spots—Severity A
FIG.7Class2—White Spots—Severity B
FIG.8Class2—White Spots—Severity C

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