ASTM A561-08(2014)
(Practice)Standard Practice for Macroetch Testing of Tool Steel Bars
Standard Practice for Macroetch Testing of Tool Steel Bars
ABSTRACT
This practice covers macroetch testing used for evaluating the quality of tool steel bars. This test shall be used as a quality control and inspection test to reveal by deep acid etching, the macrostructure in specimens cut from bars and to show the presence, absence, and severity of the following internal, surface, or subsurface conditions: pipe, bursts, carbide or alloy segregation, nonmetallic inclusion concentrations, porosity, cracks or thermal flakes, seams, laps, ingot corner segregation, pinholes, foreign material, and ingot pattern. Macroetching may be performed in a vessel of borosilicate glass, porcelain, corrosion-resistant metals, or some other acid resisting material. The etching reagent, specimen sampling, specimen preparation, and testing procedure including etching temperature, etching time, and macroetching technique are detailed.
SCOPE
1.1 This practice for macroetch testing has been found to be a useful and reliable method for evaluating the quality of tool steel bars. It is used as a quality control and inspection test to reveal by deep acid etching the macrostructure in specimens cut from bars and to show the presence of such conditions as pipe, cracks, porosity, segregation, or foreign material. The etched surface is generally examined visually, but magnification up to about 10× is occasionally employed.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: A561 − 08 (Reapproved 2014)
Standard Practice for
Macroetch Testing of Tool Steel Bars
This standard is issued under the fixed designation A561; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript 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 5. Sampling
1.1 This practice for macroetch testing has been found to be 5.1 The selection of specimens for macroetch testing must
a useful and reliable method for evaluating the quality of tool be done with care for interpretations to be of value.
steel bars. It is used as a quality control and inspection test to 5.1.1 Specimens are usually cut from hot-rolled annealed
reveal by deep acid etching the macrostructure in specimens bars, but may be cut from machined or ground bars if the bars
cut from bars and to show the presence of such conditions as are to be finish machined or ground.
pipe, cracks, porosity, segregation, or foreign material. The 5.1.2 Thespecimenshouldbelocatedatasufficientdistance
etched surface is generally examined visually, but magnifica- from the end of the bar to avoid end effects.
1 1
tion up to about 10× is occasionally employed. 5.1.3 For ease in handling, use specimens ⁄4 to ⁄2 in. (6.35
to 12.7 mm) thick.
1.2 The values stated in inch-pound units are to be regarded
5.1.4 Cut specimens to expose a transverse section of the
as standard. The values given in parentheses are mathematical
bar; however, the test is occasionally performed on a longitu-
conversions to SI units that are provided for information only
dinal section.
and are not considered standard.
5.1.5 Specimens may be taken from one or both ends of a
bar. Each bar may be sampled, or a few typical specimens may
2. Referenced Documents
be tested as representative of a large number of bars.
2.1 ASTM Adjuncts:
Six Photomacrographs
6. Specimen Preparation
3. Apparatus
6.1 In all cutting and grinding operations on the specimen,
care must be exercised to avoid heating the surface to an
3.1 Etching Containers—Macroetching may be performed
excessively high temperature. Specimens are cut from bars by
in a vessel of borosilicate glass, porcelain, corrosion-resistant
sawing, machining, abrasive wheel cutting, or other means.
metals, or some other acid-resisting material.
Cutting should be controlled to prevent smearing the cut face
4. Reagent and masking the structure.
6.1.1 The“as-cut”surfaceofaspecimenmaybesufficiently
4.1 Etching Reagent—A solution of equal volumes of con-
smooth to reveal the defects for which the examination is
centrated hydrochloric acid (HCl, sp gr 1.19) and water is
conducted. No additional surface preparation may then be
commonly used for macroetching tool steels. This solution
necessary.
must be used under a ventilating hood because HCl is volatile
6.1.2 Additional surface preparation may be required to
and the fumes are corrosive and irritating, although nontoxic.
remove cutting marks and to allow details to be revealed by
The solution may be reused within limits. With use, the
etching. In such circumstances, machining, grinding, or pol-
concentration of dissolved iron and other metals increases and
ishing may be necessary. Generally, the degree of surface
the acidity of the solution decreases retarding the etching
smoothness required is greater the finer the detail that must be
action.Spentsolutionshallbereplacedwithfreshsolution,not
resolved. When the action of the etchant is drastic, a coarser
replenished with concentrated acid.
surface finish may be used.
6.1.3 The surface must be free of adhering grease and oil.
This practice is under the jurisdiction of ASTM Committee A01 on Steel,
There should be no scale or oxide on the surface which will be
Stainless Steel and Related Alloysand is the direct responsibility of Subcommittee
examined after etching.
A01.29 on Tool Steels.
Current edition approved March 1, 2014. Published March 2014. Originally
approved in 1966. Last previous edition approved in 2008 as A561–08. DOI: 7. Procedure
10.1520/A0561-08R14.
7.1 Temperature for Macroetching—Etching characteristics
Available from ASTM International Headquarters. Order Adjunct No.
ADJA0561. Original adjunct produced in 1984. are influenced markedly by the temperature of the etchant.
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A561 − 08 (2014)
Thus, the reagent temperature should be controlled for mac- 8.1.1 Internal:
roetching if comparative results are desired. Tool steels are
8.1.1.1 Pipe,
generally macroetched at about 160°F (71°C). At this
8.1.1.2 Bursts,
temperature, the etching reaction is vigorous and solution
8.1.1.3 Carbide (see Note 1) or alloy segregation,
lo
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