ASTM E826-08(2013)
(Practice)Standard Practice for Testing Homogeneity of a Metal Lot or Batch in Solid Form by Spark Atomic Emission Spectrometry
Standard Practice for Testing Homogeneity of a Metal Lot or Batch in Solid Form by Spark Atomic Emission Spectrometry
SIGNIFICANCE AND USE
5.1 The purpose of this practice is to evaluate the homogeneity of a lot of material selected as a candidate for development as a reference material or certified reference material, or for a L/B selected for some other purpose (see Appendix X1-Appendix X4 for examples).
5.2 This practice is applicable to the testing of samples taken at various stages during production. For example, continuous cast materials, ingots, rolled bars, wire, etc., could be sampled at various stages during the production process and tested.
SCOPE
1.1 This practice is suitable for testing the homogeneity of a metal lot or batch (L/B) in solid form by spark atomic emission spectrometry (Spark-AES). It is compliant with ISO Guide 35—Certification of Reference Materials: General and Statistical Principles. It is primarily intended for use in the development of reference materials but may be used in any other application where a L/B is to be tested for homogeneity. It is designed to provide a combined study of within-unit and between-unit homogeneity of such a L/B.
1.2 This practice is designed primarily to test for elemental homogeneity of a metal L/B by Spark-AES. However, it can be adapted for use with other instrumental techniques such as X-ray fluorescence spectrometry (XRF) or atomic absorption spectrometry (AAS).Note 1—This practice is not limited to elemental analysis or techniques. This practice can be applied to any property that can be measured, for example, the property of hardness as measured by the Rockwell technique.
1.3 The criteria for acceptance of the test specimens must be previously determined. That is, the maximum acceptable level of heterogeneity must be determined on the basis of the intended use of the L/B.
1.4 It is assumed that the analyst is trained in Spark-AES techniques including the specimen preparation procedures needed to make specimens ready for measurements. It is further assumed that the analyst is versed in and has access to computer-based data capture and analysis. The methodology of this practice is best utilized in a computer based spreadsheet.
1.5 This practice can be applied to one or more elements in a specimen provided the signal-to-background ratio is not a limiting factor.
1.6 This practice includes methods to correct for systematic drift of the instrument with time. (Warning—If drift occurs, erroneous conclusions will be obtained from the data analysis.)
1.7 This practice also includes methods to refine estimates of composition and uncertainty through the use of a type standard or multiple calibrants.
1.8 It further provides a means of reducing a nonhomogeneous set to a homogeneous subset.
1.9 This 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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E826 − 08(Reapproved 2013)
Standard Practice for
Testing Homogeneity of a Metal Lot or Batch in Solid Form
by Spark Atomic Emission Spectrometry
This standard is issued under the fixed designation E826; 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.
1. Scope 1.7 This practice also includes methods to refine estimates
of composition and uncertainty through the use of a type
1.1 Thispracticeissuitablefortestingthehomogeneityofa
standard or multiple calibrants.
metallotorbatch(L/B)insolidformbysparkatomicemission
spectrometry (Spark-AES). It is compliant with ISO Guide
1.8 It further provides a means of reducing a nonhomoge-
35—Certification of Reference Materials: General and Statis-
neous set to a homogeneous subset.
tical Principles. It is primarily intended for use in the devel-
1.9 This standard does not purport to address all of the
opment of reference materials but may be used in any other
safety concerns, if any, associated with its use. It is the
application where a L/B is to be tested for homogeneity. It is
responsibility of the user of this standard to establish appro-
designed to provide a combined study of within-unit and
priate safety and health practices and determine the applica-
between-unit homogeneity of such a L/B.
bility of regulatory limitations prior to use.
1.2 This practice is designed primarily to test for elemental
homogeneityofametalL/BbySpark-AES.However,itcanbe
2. Referenced Documents
adapted for use with other instrumental techniques such as
X-ray fluorescence spectrometry (XRF) or atomic absorption
2.1 ASTM Standards:
spectrometry (AAS).
E135Terminology Relating to Analytical Chemistry for
NOTE 1—This practice is not limited to elemental analysis or tech-
Metals, Ores, and Related Materials
niques.Thispracticecanbeappliedtoanypropertythatcanbemeasured,
E177Practice for Use of the Terms Precision and Bias in
for example, the property of hardness as measured by the Rockwell
ASTM Test Methods
technique.
E178Practice for Dealing With Outlying Observations
1.3 Thecriteriaforacceptanceofthetestspecimensmustbe
E634Practice for Sampling of Zinc and Zinc Alloys by
previously determined. That is, the maximum acceptable level
Spark Atomic Emission Spectrometry
of heterogeneity must be determined on the basis of the
E716Practices for Sampling and Sample Preparation of
intended use of the L/B.
Aluminum and Aluminum Alloys for Determination of
1.4 It is assumed that the analyst is trained in Spark-AES
Chemical Composition by Spectrochemical Analysis
techniques including the specimen preparation procedures
E1329PracticeforVerificationandUseofControlChartsin
needed to make specimens ready for measurements. It is
Spectrochemical Analysis
further assumed that the analyst is versed in and has access to
E1601Practice for Conducting an Interlaboratory Study to
computer-baseddatacaptureandanalysis.Themethodologyof
Evaluate the Performance of an Analytical Method
this practice is best utilized in a computer based spreadsheet.
E1806Practice for Sampling Steel and Iron for Determina-
1.5 This practice can be applied to one or more elements in
tion of Chemical Composition
a specimen provided the signal-to-background ratio is not a
2.2 ISO Standard:
limiting factor.
ISO Guide 35Certification of Reference Materials: General
1.6 This practice includes methods to correct for systematic
and Statistical Principles
drift of the instrument with time. (Warning—If drift occurs,
erroneousconclusionswillbeobtainedfromthedataanalysis.)
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This practice is under the jurisdiction ofASTM Committee E01 on Analytical contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ChemistryforMetals,Ores,andRelatedMaterialsandisthedirectresponsibilityof Standards volume information, refer to the standard’s Document Summary page on
Subcommittee E01.22 on Laboratory Quality. the ASTM website.
Current edition approved April 1, 2013. Published August 2013. Originally Available from International Organization for Standardization (ISO), 1, ch. de
approved in 1981. Last previous edition approved in 2008 as E826–08. DOI: la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://
10.1520/E0826-08R13. www.iso.ch.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E826 − 08 (2013)
3. Terminology 4.4 This practice requires that there be an absence of
outliers in the data (Practice E178). (Warning—The use of
3.1 Definitions—For definitions of terms used in this
Practice E178 dealing with outliers should be done with
practice,refertoTerminologyE135,andPracticesE177,E178,
extreme care to ensure that values are not discarded that may
E1329, and E1806.
be valid for the analysis.)
3.2 Definitions of Terms Specific to This Standard:
4.5 Variability introduced by sample preparation may influ-
3.2.1 ANOVA (analysis of variance)—a statistical means of
ence the findings of this practice.
partitioning the variance of a data set into contributing com-
ponents.
5. Significance and Use
3.2.2 batch—a set of specimens to be tested for
homogeneity, often a subset of a lot.
5.1 The purpose of this practice is to evaluate the homoge-
neity of a lot of material selected as a candidate for develop-
3.2.3 between-unit homogeneity—homogeneitywithrespect
ment as a reference material or certified reference material, or
to the various specimens in the candidate L/B (see Section 8).
for a L/B selected for some other purpose (see Appendix
3.2.4 drift—a gradual, systematic change in instrument
X1-Appendix X4 for examples).
readings with time.
5.2 This practice is applicable to the testing of samples
3.2.5 fair (fairness)—the assurance for a participant in a
taken at various stages during production. For example, con-
proficiencytestprogramthatallofthematerialfromwhichthe
tinuous cast materials, ingots, rolled bars, wire, etc., could be
participants’ test materials are taken is sufficiently homoge-
sampled at various stages during the production process and
neous so that any results later identified as outliers should not
tested.
be attributed to any significant test item variability.
3.2.6 homogeneity—as defined in this practice, statistically
6. Summary of the Test Method
acceptable differences between means in the test.
6.1 General—This practice is based on J. W. Tukey’s HSD
3.2.7 solid form—specimensareinaformequivalenttothat
(honestly significant difference) procedure for pairwise com-
described in 6.4.4 of Practice E1806.
parisons among means (8). It uses the ANOVA technique to
3.2.8 type standard—as defined in this practice, calibrant
partition the variation into contributing components, then
similar in composition to the candidate for homogeneity
eliminates contributions from sources other than heterogeneity
testing.
and random processes. The model used is:
3.2.9 unit—specimen to be tested, referred to as a disk,
x 5 µ1β 1τ 1ε (1)
ij i j ij
regardless of the actual shape.
where:
3.2.10 within-unit homogeneity—homogeneity with respect
to an individual specimen (see Section 8). x = the result of the ith burn on the jth P/S,
ij
µ = the “true” mean of the population of all possible burn
4. Summary of Practice
results,
β = the variation in the ith burn due to the measurement
4.1 This practice, which is based on statistical methods
i
process,
(1-8), consists of stepwise instructions for testing the homo-
τ = the variation in the jth P/S due to heterogeneity, and
geneity of a candidate L/B. The candidate specimens are j
ε = the variation due to random or randomized processes.
selected as described in Section 10, and then measured by ij
Spark-AES (Section 11). The resultant data are corrected for
6.1.1 The data are then arranged inabbyt matrix (where b
instrumental drift, if desired (see Sections 13-15), and then
isthenumberofburnsperP/Sandtisthenumberofpositions
tabulated (see Tables2, X1.3, and X1.4) to facilitate the
or specimens) and rowwise statistics taken. These statistics
statistical calculations that are performed according to Section
allowtheestimationandeliminationofthevariationduetothe
12.
measurement process, leaving only the contributions from
heterogeneity and random processes. The maximum contribu-
4.2 The homogeneity of the L/B is determined from the
results of the data analysis consisting of a one-way analysis of tion of random error is estimated and a critical value (w)
determined. If the difference between any two pairs of means
variance (ANOVA).
is less than the critical value, then the set of positions or
4.3 This practice requires that repeated measurements on
specimens is considered homogeneous. In practice, the “ best”
the same position or specimen (P/S) have sufficient precision
difference is between the maximum and the minimum. If we
(that is, repeatability) through appropriate selection of instru-
call this value T, then if T is less than or equal to w, the set is
mental parameters so that any significant difference within or
considered homogeneous at the selected level of confidence
between positions or specimens can be detected with confi-
(usually 95% or 99%). If T is greater than w, then the set is
dence. This is best done through the use of drift management:
considered heterogeneous.
standardization, control charts (Practice E1329),
normalization, and drift monitoring.
6.2 Multiple Determinations—The reason for taking mul-
tiple determinations on each P/S is to obtain a gage of the
variation associated with the measurement process and the
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard. material being tested.
E826 − 08 (2013)
6.3 Randomized Testing—Randomizing the measurement 7.3 Regardless of shape, individual specimens must be
sequences randomizes any systematic error(s) not accounted dimensionally compatible with common analytical methods.
for with instrument, process, and drift controls. 7.3.1 Mostsolidformtechniquesrequireaspecimentohave
NOTE 2—It is possible to extend this to any population that can be put
at least one flat analytical face.
in this form. This means that this technique can be applied to lab data
7.3.2 If the shape of a specimen is too irregular, it will be
generated by an interlaboratory study. Currently, interlaboratory studies,
too difficult to “clamp” to Spark-AES spark stand.
even with the aid of h and k statistics (Practice E1601), only allow the
7.3.3 The preferred form is cylindrical, but any form that
administrator to request corrections or perhaps eliminate certain data
based on judgement calls. The application of this approach would allow satisfies the above criteria is acceptable.
the option of systematic elimination through the use of an accepted
7.3.4 Typical forms are round, elliptical, rectangular, or
statistical method.
hexagonal disks, truncated cones, etc.
7.3.5 Spark-AES requires a specimen to be at least 6 mm
7. Lot or Batch Forms
thick to minimize heating effects.
7.1 Lots or batches may be cast or wrought.
NOTE 3—When considering the use of cast material, the analyst must
7.1.1 Acastmateriallotisgenerallypresentedintheformof
consider the possibility that microscopic cast structures may cause
ingot(s) or linked pieces.
problems with the measurement technique. It is best to use a casting
7.1.2 A wrought material lot is generally presented in the
technique that will produce “well behaved” specimens such as chill
form of bar stock.
casting.
7.2 Lots or batches may be contiguous, piecewise, or a
8. The Sampling Model
combination.
7.2.1 A contiguous lot might be a single ingot or bar. 8.1 General—The proposed sampling system is based on
7.2.2 A piecewise lot might be a set of pieces having been cylindrical geometry. That is, most lots or batches tested
cut from bar(s), ingot(s), or linked piece casting(s). In this last present themselves in some variant of cylindrical geometry.
case, even if the pieces have not been separated, it can be Roundbarstockisfairlyobvious.Butevensquare,rectangular,
considered a piecewise lot since they are already defined. hexagonal,orothersuchgeometriesworkunderthisapproach.
7.2.3 Acombined lot would be a set of contiguous portions 8.1.1 ConsiderthecylinderdisplayedinFig.1.Thecylinder
such as a set of bars from a single heat. is sitting on a flat plane. For convenience, suppose the plane
FIG. 1
E826 − 08 (2013)
corresponds to zero height. Further, suppose the axis of the
cylinder defines the origin of an XYZ coordinate system. The
zaxiscorrespondstothecylinderaxis.The xand yaxescanbe
oriented as one chooses. Let the x axis correspond to an angle
of zero degrees. Then, every point in the cylinder can be
described by its height from the plane (H ≥ Z), its distance
fromthecentralaxis(R),anditsanglewithrespecttothe xaxis
(Θ).
8.1.2 Given the cylindrical geometry described in 8.1.1
(Fig. 1), homogeneity can be defined in axial, radial, and
circumferential terms.Axial homogeneity refers to the unifor-
mity of the material from one end to another. Radial homoge-
neity refers to the uniformity of the material from the center
outward.Circumferentialhomogeneityreferstotheuniformity
of the material around a concentric circle.
8.1.3 At any level (Z) the latter two are measured by
selecting a number of positions on the analytical face of each
sampletobesocharacterized.Thenumberandpositionofeach
isarationalizationbetweenthesizeandshapeoftheanalytical
face and the size of Spark-AES burn spot.Asufficient number
of spots are chosen to represent a reasonable sampling of the
surface.
FIG. 3
8.1.4 Two common forms encountered are demonstrated in
Figs. 2 and 3.Arationalization of sample size versus spot size
total number of positions. Four such sequences are run. The
dictates a seven-position strategy for round samples in the
resultant data are derandomized and presented as a 4×n
range of 25 mm to 50 mm in diameter and a nine-position
matrix. The resultant matrix is processed in accordance with
strategy for square samples in the range of 25 mm to 50 mm
Section 12.
across.Fortheroundgeometry,circumferentialhomogeneityis
8.1.6 If this process is applied at any level (Z), then the
covered with Positions 1–6. Comparisons of these to Position
entire solid can be characterized.
7coversradialhomogeneity.Forthesquaregeometry,circum-
ferentialhomogeneityiscoveredwithPositions1–8.Compari-
8.2 Within-Unit Homogeneity (R, Θ)—For
...
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