ASTM E768-99(2004)
(Practice)Standard Guide for Preparing and Evaluating Specimens for Automatic Inclusion Assessment of Steel
Standard Guide for Preparing and Evaluating Specimens for Automatic Inclusion Assessment of Steel
SCOPE
1.1 This guide covers two preparation methods for steel metallographic specimens that will be analyzed for nonmetallic inclusions with automatic image analysis (AIA) equipment. The two methods of preparation are offered as accepted methods used to retain nonmetallic inclusions in steel. This guide does not limit the user to these methods.
1.2 A procedure to test the suitability of the prepared specimen for AIA inclusion work, using differential interference contrast (DIC), is presented.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E768–99 (Reapproved 2004)
Standard Guide for
Preparing and Evaluating Specimens for Automatic
Inclusion Assessment of Steel
This standard is issued under the fixed designation E 768; 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.
1. Scope charged with an abrasive (usually 6 to 15-µm diamond par-
ticles), and used as the fine grinding operation in a metallo-
1.1 This guide covers two preparation methods for steel
graphic preparation procedure.
metallographicspecimensthatwillbeanalyzedfornonmetallic
inclusions with automatic image analysis (AIA) equipment.
4. Significance and Use
The two methods of preparation are offered as accepted
4.1 Inclusion ratings done either manually using Test Meth-
methods used to retain nonmetallic inclusions in steel. This
ods E 45 or automatically using Practice E 1122 or E 1245 are
guide does not limit the user to these methods.
influenced by the quality of specimen preparation. This guide
1.2 A procedure to test the suitability of the prepared
provides examples of proven specimen preparation methods
specimen for AIA inclusion work, using differential interfer-
that retain inclusions in polished steel specimens.
ence contrast (DIC), is presented.
4.2 This guide provides a procedure to determine if the
2. Referenced Documents prepared specimens are of suitable quality for subsequent
3 rating of inclusions. None of these methods should be con-
2.1 ASTM Standards:
strued as defining or establishing specific procedures or limits
E 3 Practice for Preparation of Metallographic Specimens
of acceptability for any steel grade.
E 7 Terminology Relating to Metallography
E 45 Test Methods for Determining the Inclusion Content
5. Preparation Methods
of Steel
5.1 Background:
E 883 Guide for Reflected-Light Photomicrography
5.1.1 The inclusions in the plane of polish must be fully
E 1122 Practice for Obtaining JK Inclusion Ratings Using
preserved and clearly visible. Preparation should not produce
Automatic Image Analysis
excessive relief around the perimeter of the inclusions that
E 1245 Practice for Determining the Inclusion or Second-
would exaggerate the size and number of inclusions on the
Phase Constituent Content of Metals by Automatic Image
plane of polish. In many cases, the preparation of specimens
Analysis
for inclusion rating is more readily performed after the
3. Terminology specimens have been hardened by a suitable heat treatment
procedure (austenize, quench to fully martensitic structure,
3.1 Definitions:
temper at a relatively low temperature).
3.1.1 For definitions used in this practice, refer to Termi-
5.1.2 Cleanliness is an important consideration in all stages
nology E 7.
of specimen preparation.
3.1.2 differential interference contrast microscopy—a com-
5.1.2.1 Heat-treated specimens should be wire brushed or
prehensive definition appears in Guide E 883, paragraph 11.8.
shot blasted or have the surface ground to remove adherent
3.2 Definitions of Terms Specific to This Standard:
scale.
3.2.1 rigid grinding disk—a non-fabric support surface,
5.1.2.2 After completing the grinding steps and before
such as a composite of metal/ceramic or metal/polymer,
performing the polishing steps, the specimens and specimen
holders must be cleaned to prevent contamination of the next
This test method is under the jurisdiction of ASTM Committee E04 on
preparationstep.Cleaningthespecimensandspecimenholders
MetallographyandisthedirectresponsibilityofSubcommitteeE04.01onSampling
between each grinding step can eliminate contamination of
Specimen Preparation, and Photography.
coarse abrasives to the following finer preparation step.
Current edition approved Nov. 1, 2004. Published November 2004. Orignally
approved in 1999. Last previous edition approved in 1999 as E 768–99. 5.1.2.3 After the preparation is complete, swab the surface
Supporting data have been filed at ASTM International Headquarters and may
carefully with cotton and a water/soap solution containing a
be obtained by requesting Research Report RR: E04–1002.
corrosion inhibitor such as a machine coolant or ethyl alcohol
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
solution to remove any films or other debris that would
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
interfere with the inclusion rating.
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E768–99 (2004)
5.1.2.4 It is advisable to perform the inclusion analysis as containing six 32-mm mounts, a force of approximately 87 N
soon as possible after preparation to minimize staining or other must be applied (see X1.4.2).
problems that can affect the analysis.
5.2.2.1 Low pressures are recommended to ensure the
5.1.3 The two methods that follow have been found to be retention of an assortment of inclusion types found in a variety
reliable procedures for retaining inclusions in steel and achiev-
of steel grades. The relatively low pressures suggested in this
ing the desired results when evaluated by DIC. There are other procedure will not necessarily result in a satisfactory polish for
methods that will result in a quality specimen as revealed by
etching and the further evaluation of the specimen’s general
DIC. Each laboratory should develop preparation procedures microstructure. The pressures used in the following rigid disk
for their materials so that the prepared surfaces meet the
procedure are more likely to result in a surface more satisfac-
requirements presented in 6 of this guide. tory for revealing general microstructures.
5.1.4 As described in Prractice E 3, the specimens may be
5.2.3 Grind the specimens on ANSI 80 grit (P80 FEPA)
sectioned and mounted to ease handling during preparation. It
silicon carbide paper to ensure all sectioning artifacts and
is advisable to use a mounting medium that is hard enough to
deformation damage have been removed and the entire speci-
preserve edges and maintain flatness.
men surface is co-planar to the grinding surface.
5.1.5 Abrasive grit size designations in this guide are
NOTE 2—If the sectioning method resulted in a smooth face and little
expressed in theAmerican National Standards Institute (ANSI)
deformation damage, and if after securing the specimens in a fixture for
or Coated Abrasives Manufacturers Institute (CAMI) system
polishing,theentiresurfaceofinterestisco-planartothegrindingsurface,
units with the corresponding Federation of European Abrasive
then finer grit papers, such asANSI 180 to 240 (P180 to P240 FEPA) can
Procedure (FEPA) numbers in parentheses. Table 1 provides a
be used for the initial grinding step.
correlation between these two systems and the approximate
5.2.3.1 An adequate flow of water should remove all loos-
median particle diameter for a given grit size in micrometres.
ened abrasive and grinding debris from the paper during the
5.1.6 Most preparation systems apply pressure on the speci-
grinding procedure. The flow of water should ensure the
mens being processed. The best pressure to be used for each
specimen is kept cool during grinding.
preparation step should be determined experimentally. Conver-
5.2.4 Continue grinding through the sequence of silicon
sions between applied force and pressure are discussed in the
carbide papers listed in Table 2. It may be necessary to clean
Appendix X1.
the samples between every grinding step to prevent contami-
NOTE 1—Care must be taken to protect the polished specimen surface
nation of the next preparation step.
from scratches or contaminants when using a specimen leveling device.
5.2.5 After completing the entire grinding operation, clean
5.2 Silicon Carbide Procedure: the specimens thoroughly, using ethyl alcohol and cotton, then
5.2.1 A summary of the silicon carbide procedure can be
rinse and dry. Ultrasonic cleaning can be used.
found in Table 2.
5.2.5.1 The use of a soap and water solution in an ultrasonic
5.2.2 When using a semi-automatic polishing equipment,
cleaner can attack non-metallic inclusions in some carbon and
grinding and polishing should be performed using approxi-
low alloy steels, leading to an exaggeration in the inclusion’s
mately 18 kPa pressure per specimen. (For a specimen holder
apparent size. Adding an inhibitor (such as that used as a
machining coolant) may reduce this size exaggeration.
5.2.6 Polish the specimens using 3-µm diamond abrasive on
TABLE 1 Comparison of ANSI (CAMI) versus FEPA versus
a low nap cloth, such as woven wool, for 50 s. Clean and dry
Median Diameter of Grit Size in Micrometers
the specimens as described in 5.2.5.
A B C
ANSI (CAMI) FEPA Approximate Median
5.2.7 Polish the specimens using a 1-µm diamond abrasive
Diameter
on a high nap cloth for 50 s. Clean and dry the specimens as
(µm)
described in 5.2.5.
60 P60 250
80 P80 180
5.2.8 A final manual polishing step may be added, using
100 P100 150
0.25-µm diamond abrasive on a low nap cloth for 10 to 20 s,
120 P120 125
using relatively high pressure. Clean and dry the specimens as
150 P150 90
180 P180 75 described in 5.2.5.
220 P220 63
5.2.8.1 Ultrasonic cleaning is not recommended after the
240 P240 58.5
final manual or automatic polishing step. Ultrasonic cleaning
P280 52.2
280 P320 46.2
can cause cavitation damage, ultimately distorting the inclu-
320 P360 40.5
sion sizes.
P400 35.0
360 P500 30.2
NOTE 3—Dependingonthematerial,itmaybeadvisabletoavoidwater
400 P600 25.8
after polishing.
P800 21.8
500 P1000 18.3
5.3 Rigid Grinding Disk Procedure:
600 P1200 15.3
800 P2400 8.4
5.3.1 Asummaryoftherigidgrindingdiskprocedurecanbe
D
1200 P4000 3.0
found in Table 3.
A
ANSI - American National Standards Institute
5.3.2 Semi-automatic grinding equipment is required, with
B
CAMI - Coated Abrasives Manufacturers Institute
C specimens contained in a circular fixture for the entire proce-
FEPA - Federation of European Abrasive Producers
D
Not a FEPA designation dure. For 5.3.2-5.3.5, a pressure of 42 kPa should be applied
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.