ASTM A561-71(2004)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:A 561–71 (Reapproved 2004)
Standard Practice for
Macroetch Testing of Tool Steel Bars
This standard is issued under the fixed designation A 561; 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 5.1.1 Specimens are usually cut from hot-rolled annealed
bars, but may be cut from machined or ground bars if the bars
1.1 This practice for macroetch testing has been found to be
are to be finish machined or ground.
a useful and reliable method for evaluating the quality of tool
5.1.2 Thespecimenshouldbelocatedatasufficientdistance
steel bars. It is used as a quality control and inspection test to
from the end of the bar to avoid end effects.
reveal by deep acid etching the macrostructure in specimens
1 1
5.1.3 For ease in handling, use specimens ⁄4 to ⁄2 in. (6.35
cut from bars and to show the presence of such conditions as
to 12.7 mm) thick.
pipe, cracks, porosity, segregation, or foreign material. The
5.1.4 Cut specimens to expose a transverse section of the
etched surface is generally examined visually, but magnifica-
bar; however, the test is occasionally performed on a longitu-
tion up to about 103 is occasionally employed.
dinal section.
2. Referenced Documents
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
2.1 ASTM Adjuncts:
be tested as representative of a large number of bars.
Twelve Photomacrographs
6. Specimen Preparation
3. Apparatus
6.1 In all cutting and grinding operations on the specimen,
3.1 Etching Containers—Macroetching may be performed
care must be excercised to avoid heating the surface to an
in a vessel of borosilicate glass, porcelain, corrosion-resistant
excessively high temperature. Specimens are cut from bars by
metals, or some other acid-resisting material.
sawing, machining, abrasive wheel cutting, or other means.
4. Reagent
Cutting should be controlled to prevent smearing the cut face
and masking the structure.
4.1 Etching Reagent—A solution of equal volumes of con-
6.1.1 The “as-cut” surface of a specimen may be sufficiently
centrated hydrochloric acid (HCl, sp gr 1.19) and water is
smooth to reveal the defects for which the examination is
commonly used for macroetching tool steels. This solution
conducted. No additional surface preparation may then be
must be used under a ventilating hood because HCl is volatile
necessary.
and the fumes are corrosive and irritating, although nontoxic.
6.1.2 Additional surface preparation may be required to
The solution may be reused within limits. With use, the
remove cutting marks and to allow details to be revealed by
concentration of dissolved iron and other metals increases and
etching. In such circumstances, machining, grinding, or pol-
the acidity of the solution decreases retarding the etching
ishing may be necessary. Generally, the degree of surface
action. Spent solution shall be replaced with fresh solution, not
smoothness required is greater the finer the detail that must be
replenished with concentrated acid.
resolved. When the action of the etchant is drastic, a coarser
5. Sampling
surface finish may be used.
6.1.3 The surface must be free of adhering grease and oil.
5.1 The selection of specimens for macroetch testing must
There should be no scale or oxide on the surface which will be
be done with care for interpretations to be of value.
examined after etching.
This practice is under the jurisdiction of ASTM Committee A01 on Steel,
7. Procedure
Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee
A01.29 on Tool Steel. 7.1 Temperature for Macroetching—Etching characteristics
Current edition approved September 1, 2004. Published January 2005. Originally
are influenced markedly by the temperature of the etchant.
approved in 1966. Last previous edition approved in 1999 as A 561 – 71 (1999).
Thus, the reagent temperature should be controlled for macro-
Available from ASTM International Headquarters. Request Adjunct
etching if comparative results are desired. Tool steels are
ADJA0561.
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A 561–71 (2004)
generally macroetched at about 160°F (71°C).At this tempera- 8.1.1 Internal:
ture, the etching reaction is vigorous and solution losses
8.1.1.1 Pipe,
through evaporation are not excessive. The solution may be
8.1.1.2 Bursts,
heated on a gas or electric hot plate
...