ASTM A247-06

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Designation:A 247–06
Standard Test Method for
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Evaluating the Microstructure of Graphite in Iron Castings
This standard is issued under the fixed designation A 247; 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 the sample being evaluated. It does not indicate except in a
very broad way the origin of the graphite, or the suitability of
1.1 This test method covers the classification of graphite in
the iron-carbon alloy for a particular service.
cast irons in terms of type, distribution, and size. This test
method is intended to be applicable for all iron-carbon alloys
5. Test Specimens or Samples
containing graphite particles, and may be applied to gray irons,
5.1 The preferred sample is a section cut from an actual
malleable irons, and the ductile (nodular) irons.
casting that is being evaluated. When this is impractical, a test
1.2 The reference standards included in this test method are
lug or projection often can be cast attached to the casting and
in no way to be construed as specifications. In an appropriate
sawedorbrokenofftobeusedasthesample.Ifneitherofthese
specification for a specific material where graphite microstruc-
methodsisconvenient,microscopicaltestcoupons,suchasthat
ture is an important consideration this test method may be used
recommended by the Ductile Iron Research Committee (12K)
as a reference to define concisely the graphite microstructure
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of the American Foundrymen’s Society should be cast from
required.
metal representative of the castings poured.
1.3 These standards are offered primarily to permit accurate
reporting of microstructures of cast irons and to facilitate the
6. Polishing
comparisonofreportsbydifferentlaboratoriesorinvestigators.
6.1 Grinding and polishing may follow the usual accepted
1.4 This standard does not purport to address all of the
metallographic procedures as covered in MethodsE3, except
safety problems associated with its use. It is the responsibility
that care must be taken that the graphite is retained at the
oftheuserofthisstandardtoconsultandestablishappropriate
polished surface and not torn or dragged out. Use of diamond
safety and health practices and determine the applicability of
powder polishing compound in one of the final stages of
regulatory limitations prior to use.
polishing is very effective in retaining the graphite at the
polished surface.
2. Referenced Documents
2.1 ASTM Standards:
7. Classification of Graphite Form with Chart
E3 Guide for Preparation of Metallographic Specimens
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7.1 The graphite form type chart (Plate I) is used as a
reference standard by scanning the polished specimen under
3. Summary of Test Method
the microscope and noting the graphite forms in the micro-
3.1 The reference diagrams included in this standard form
structure that more nearly correspond to type designations on
the basis for classification. Characteristic features of graphite
the chart.
particles are designated by numerals and letters. Type, distri-
7.2 Type I is the normal and usually desirable graphite form
bution, and size of observed graphite are compared with the
in ductile iron, although the presence of Type II graphite forms
idealized microstructures in the standard charts and rated
has little or no adverse effect on properties. Graphite forms
accordingly as closely as possible to the equal or similar
represented by Types IV through VI often occur in ductile iron
microstructures in the charts.
in conjunction with Types I and II. The percentages of each
4. Significance and Use graphite type are estimated by observation, or better, by
counting the particles of each type. Types present in a sample
4.1 The comparison of observed graphite particles with the
are to be reported in percentages to total 100. Any convenient
structures shown in the charts give only purely descriptive
magnification that clearly reveals the graphite form may be
informationonthetype,distribution,andsizeofthegraphitein
used.
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This test method is under the jurisdiction of ASTM Committee A04 on Iron
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Castings and is the direct responsibility of Subcommittee A04.21 on Testing. Transactions, American Foundrymen’s Society, 1960, p. 655.
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Current edition approved Nov. 15, 2006. Published December 2006. Originally Plates I, II, and III may be obtained from ASTM Headquarters. Order
approved in 1941. Last previous edition approved in 1998 as A 247 – 67 (1998). ADJA0247.
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