ISO/FDIS 4653

ISO/TC 155/WG 15
Secretariat: AFNOR
Date: 2026-05-1909-17
Ferronickel — Determination of carbon, sulfur, silicon, phosphorus,
nickel, cobalt, chromium, and copper contents — Spark emission
spectrometric method
FDIS stage
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ii
Contents
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 3
5 Apparatus . 3
6 Sampling . 3
7 Procedure . 3
7.1 Calibration procedures . Error! Bookmark not defined.
7.2 Surface preparation . 3
7.3 Analysis . 6
8 Determination and expression of analysis results . 6
8.1 General. 6
8.2 Acceptance of final results from duplicate measurements in the laboratory . 6
8.3 Interlaboratory precision and agreement assessment . 7
8.4 Determination of trueness . 7
9 Interlaboratory test data of precision and trueness . 8
9.1 General. 8
9.2 Interlaboratory test . 8
9.3 Precision data . 8
9.4 Trueness data . 11
10 Test report . 14
Annex A (informative) Analytical spectral lines . 15
Annex B (informative) Some theoretical principles in calibration . 17
Annex C (normative) Procedure for obtaining the final results . 18
Annex D (informative) Compositions of the samples used for the validation test . 19
Annex E (informative) Graphical representation of the precision data. 20
Bibliography . 33

iii
Foreword
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iv
Ferronickel — Determination of carbon, sulfur, silicon, phosphorus,
nickel, cobalt, chromium, and copper contents — Spark emission
spectrometric method
1 Scope
This document specifies a method for the determination of carbon, sulfur, silicon, phosphorus, nickel, cobalt,
chromium, and copper contents in ferronickels by spark optical emission spectrometry (S-OES). This method
cannot be used for arbitration analysis.
The methodThis document is applicable to the following content ranges (in % mass fraction) given in
Table 1.):
Table 1 — Content ranges
Content range
Element
% (mass fraction)
Carbon 0,030 to 2,5
Sulfur 0,018 to 0,27
Silicon 0,13 to 4,2
Phosphorus 0,007 to 0,04
a
Nickel 14,3 to 25,0
Cobalt 0,13 to 2,2
Chromium 0,08 to 2,3
Copper 0,019 to 0,26
NOTE  Table note.
a
The values from 25,0 % to 48,3 % are indicative.
— carbon: 0,030 to 2,5
— sulfur: 0,018 to 0,27
— silicon: 0,13 to 4,2
— phosphorus: 0,007 to 0,04
— nickel: 14,3 to 25,0
— cobalt 0,13 to 2,2
— chromium: 0,08 to 2,3
— copper: 0,019 to 0,26
This method document cannot be used for does not apply to arbitration analysis.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 8049, Ferronickel shot — Sampling for analysis
ISO 8050, Ferronickel ingots or pieces — Sampling for analysis
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1
reference material
RM
material, sufficiently homogeneous and stable with respect to one or more specified properties, which has
been established to befitbe fit for its intended use in a measurement process
[SOURCE: ISO GUIDE 30:2015, 2. ISO 33400:2026, 3.1.1, modified — the"in a measurement process" added.
Notes to entry have been deleted.]
3.2
certified reference material
CRM
reference material (RM)(3.1) characterized by a metrologically valid procedure for one or more specified
properties, accompanied by an RM certificate that provides the value of the specified property, its associated
uncertainty, and a statement of metrological traceability
[SOURCE: ISO GUIDE 30:2015, 2.1.2, modified — the Notes to entry have been deleted.]
3.3
test sample
representative quantity of material for testing purposes
3.4
drift control samples
series of homogeneous materials that contain all the elements which have been calibrated and that cover the
low, mid and high points of the calibration range for each element, used to detect variations over time in these
points
Note 1 to entry: Drift control samples can also be used for statistical process control (SPC) of the instrument.
3.5
recalibration samplessample
samplessample at botheither a low and high pointspoint of the calibration ranges used to recalibrate the
spectrometer
Note 1 to entry: These Recalibration samples are measured during the calibration procedure, and the intensities obtained
are stored in the computer according to the manufacturer's instructions.
Note 2 to entry: No chemical analyses are necessary, but the homogeneity of thesethe recalibration samples should be
carefully evaluated.
3.6
type recalibration samplessample
reference samplessample or internally developed standard samplessample, with the same matrix and
comparable composition as the test sample (3.3samples)
3.7
quality control sample
sample with known composition which is analysed in the same way as the test sample (3.3) to check the
trueness of the analytical results
4 Principle
The method described in this document involves applying an electrical discharge between the sample, which
serves as one electrode, and an inert counter-electrode to generate a spark, and then measuring the intensity
of the radiation emitted by this spark, whose wavelength corresponds to the characteristic radiation of each
element of interest.
The content of each element is determined by relating the measured intensities of test samples to calibration
curves prepared from reference materials.
5 Apparatus
5.1 Optical emission spectrometer.
Spectrometer with spark source capable of measuring the intensities of the optical radiation emitted at
specific wavelengths by the elements present in the material.
The wavelengths generally used are given in Annex A.
5.2 Apparatus for sample surface preparation.
The most common surface preparation techniques for ferronickel are milling and grinding or turning,
provided that the composition of the surface shall not be influenced.
The lathe, milling machine or any other machines used for surface preparation shall be able to produce a
surface that conforms to the requirements of 7.1.
WARNING — The appropriate safety recommendations for the use of mechanical apparatus shall be
observed. These operations shall be carried out only by properly trained personnel wearing
appropriate personal protective equipment.
6 Sampling
Sampling shall be carried out in accordance with ISO 8049 or ISO 8050, as appropriate.
The sample shall be sufficiently homogeneous with regard to spark impact. The measuring surface should be
free of imperfections.
7 Procedure
7.1 Surface preparation
7.1.1 The surface of the sample shall be prepared so that it is sufficiently flat and smooth to tighten the
sample chamber and shall be reasonably free of contaminants, pores, cracks, inclusions, and shrinkage cavities
that maycan otherwise affect the analytical results.
In order to avoid variation of results due to the influence of surface finish, the same method of preparation
shall be used for all samples.
To avoid cross-contamination between different sample materials, all relevant components of the machine
shall be thoroughly cleaned before use or separate tools shall be used.
Once the surface has been prepared, avoid any contamination, (e.g. fingerprints.).
Measurements shall be carried out soon after surface preparation. Samples should be stored, until the time of
later measurement, in a desiccator.
7.1.2 The milling, grinding or turning shall be carried out at a suitable speed to avoid undue heating of the
sample surface, which willcan otherwise possibly lead to bias in analysis.
Any lubricants (e.g. propanol) used shall be selected to ensure that they do not affect the analytical result.
7.2 Calibration procedures
7.2.1 General
7.2.1.1 Calibration process
The calibration process is subdivided into calibration and drift compensation by recalibration.
7.2.1.2 Range of calibration
The range of calibration for an element shall extend well below the minimum content reported in the list of
alloys composition and above the maximum content reported in the same list, taking into account that the
lowest limit should be at least equal to the quantification limit.
7.2.1.3 Number of sparks on calibration samples
The number of sparks carried out on each certified reference material (CRM) or reference material (RM) for
calibration shall not be less than four. The spark areas shall be distributed over the prepared surface. Centre
and border of the sample shall be avoided. All measurements shall be examined; if any measurement is
obviously defective, further sparks shall be carried out to obtain the minimum four acceptable measurements.
The average of the four acceptable measurements is used for calibration.
The influence of temperature is very important for direct measurement methods. The sample should be cooled
to ambient temperature between each spark.
7.2.2 Calibration
The calibration of the spectrometer is carried out by using a series of certified reference materials (CRMs) or
reference materials (RMs) which have the same or at least similar matrix and metallurgical structure as the
samples to be analysed, in order to calculate the calibration functions from which the analysis of test samples
can be obtained. The content range of the certified reference materialsCRMs used shall cover that of all the
samples to be analysed within each specific analytical program. For each element in each CRM or RM, the mean
intensity is correlated to the corresponding certified content, and a regression is calculated.
Calibration CRMs or RMs should span the composition ranges and types of materials expected. Extrapolation
is prohibited. It is recommended that theThe number of CRMs and RMs used for each curve isshould be twice
the number of coefficients to be determined by regression. This includes, including the curve parameters and
any correction coefficients. Minimally, there should be at least one more data point than the number of
coefficients or constants in the equationformula. The proportion of CRMs in the analytical curve shall be at
least 60 %.
For each element in every reference materialRM, a regression curve is generated by relating the measured
intensity to the certified content. The calibration functions are usually stored withinin a computer, connected
st nd
to the spectrometer. These calibration functions are 1 first or 2 second order polynomials. Verification of the
quality of the adjustment is done by means of the regression residuals graph, as explained in Clause B.1, and,
if possible, by a normal probability plot of the regression residuals. Abnormal behaviour of the points indicates
the necessity of either excluding or including new CRM or RM, or both; (e.g. the choice of other calibration
functions and adjustment in the content range, for instance.). When the calibration range of any particular
element is large, two calibration curves covering different parts of that range may be used.
The calibration shall be in accordance with the spectrometer manufacturer's instruction manual.
The trueness of the analytical procedure is checked by measuring a set of certified reference materialsCRMs
or—, if not available—, a set of reference materialsRMs not used in the calibration. These reference
materialsRMs shall cover at least the low, mid, and high points of the calibration range for each element. The
difference between the analysis value of each element and the certified value should not exceed ±2σ (σ is the
uncertainty or standard deviation of the certified value of each element of the standard sample). If the
measurement results do not match the certified values, the cause shall be identified, and the calibration curve
shall be redrawn or optimized.
Some theoretical principles related to calibration are provided in Annex B for reference.
7.2.3 Recalibration
Drift of the spectrometer readings shall be corrected using a recalibration procedure as described in the
manufacturer's instruction manual. Recalibrations can be done either for all analytical channels (global
recalibration),) or only for individual analytical channels (selective recalibration).
Recalibration can either be done periodically or due to a deviation from statistical process control (SPC) limits
(see 7.3.4). When a periodical recalibration procedure is used, the period depends on the stability of the
spectrometer and shall be established by a stability check of the spectrometer. The stability check shall be
repeated at appropriate intervals.
NOTE The same set of check samples can be used both for drift control and for statistical process controlSPC of the
spectrometer.
After recalibration, a set of reference materialsRMs shall be measured for confirmation. The reference
materialsRMs used shall cover at least the low, mid, and high points of the elements being analysed. The
difference between the analysis value of each element and the certified value should not exceed ±2σ (σ is the
uncertainty or standard deviation of the certified value of each element of the standard sample). If the
measurement result of the reference materialsRMs does not match the certified values, the cause shall be
identified, and recalibration shall be carried out again.
7.2.4 Type recalibration
Type recalibration offers a further possibility of correcting instrument drift and, in addition, for matrix
influences. In this process, one or two type recalibration samples are analysed alongside the test sample.
Subsequently, through linear correction, the contents of the test sample are correlated with the certified
values of the type recalibration sample(s). This operation should be conducted in accordance with the
instrument software's type recalibration procedure.
nd
NOTE This practice cannot be employed if the calibration function is a 2 second order one, unless the element to
be calibrated has a content very close to that of the type recalibration sample.
7.3 Analysis
7.3.1 Preparation of analytical programs
Analytical programs can be prepared either by measuring only the intensities of all the elements concerned,
or by taking into account the ratios between the measured intensity for each element and the intensity
corresponding to the "“matrix element"” taken as internal standard.
In principle, intensity measurements are used for trace analysis purposes (e.g. phosphorus), whilstwhile
rationed measurements are taken for the determination of other levels of content.
During the preparation of an analytical program, the possible optical interferences or the inter-elements
effects, or both, shall also be carefully investigated, and suitable corrections shall be made. Possible
interferences or effects are given in Annex A.
The preparation of analytical programs shall be in accordance with the spectrometer manufacturer's
instruction manual.
7.3.2 Analytical method
The method used shall be in accordance with the spectrometer manufacturer's instruction manual.
7.3.3 Number of sparks on test samples
The spark areas shall be distributed over the prepared surface, and whenever possible, approximately midway
between the centre and the border, thereby avoiding the centre of the sample. The number of sparks carried
out on a test sample shall be at least two. All the measurements shall be examined. If the two sparks are
inconsistent, a third or fourth measurement is required and shall follow the procedure given in Annex C.
7.3.4 Status check of the apparatus
Any change from the original status of the spectrometer (e.g. drifts) shall be checked at regular intervals by
analysing drift control samples or quality control samples in accordance with the spectrometer
manufacturer's instruction manual. It is common practice to document the status of the spectrometer using
control charts. The difference between the results of these checks and their reference values are plotted
regularly on a control chart. If the points of the control charts present different behaviours from the expected
pattern (see ISO 7870-2), then further actions (e.g. recalibration, type recalibration, further checks, new
calibration) shall be taken.
The period between checking the spectrometer status depends on its stability and the analytical assignment
and can be derived from the control charts.
8 Determination and expression of analysis results
8.1 General
This clause specifies the procedures for calculating, expressing, and verifying the acceptability of analytical
results obtained by this method.
Results are expressed in percentages (mass fractions).
8.18.2 Acceptance of final results from duplicate measurements in the laboratory
Having computed the duplicate results, compare them with the repeatability limit (r) from Table 32 or
Table 43, using the procedure given in Annex C, and obtain the final laboratory result.
8.28.3 Between-laboratoryInterlaboratory precision and agreement assessment
8.3.1 General
This clausesubclause specifies the procedure for assessing the agreement between final results reported by
two laboratories, assuming both have followed the method described in this document.
8.2.18.3.2 Calculation of the mean value in two laboratories
Calculate the mean of the two final results by using Formula (1):
𝜇𝜇 +𝜇𝜇
1 2
𝜇𝜇  =
1,2
(1)
where
μ is the final result reported by laboratory 1;
μ is the final result reported by laboratory 2;
µ1,2 is the mean of final results.
8.2.28.3.3 Calculation of precision standard deviation
Using µ as the content value, obtain the reproducibility limit (R) and repeatability limit (r)
1,2
from Table 32 or Table 43, as applicable.
Then calculate the following standard deviations:
— Reproducibility standard deviation by using Formula (2):
𝜎𝜎 =𝑅𝑅/2,83 (2)
𝑅𝑅
— Repeatability standard deviation by using Formula (3):
𝜎𝜎 =𝑟𝑟/2,83 (3)
𝑟𝑟
— Between-laboratoryInterlaboratory standard deviation by using Formula (4):
2 2
𝜎𝜎 =�𝜎𝜎 −𝜎𝜎 (4)
𝐿𝐿 𝑟𝑟
𝑅𝑅
8.2.38.3.4 Critical difference for agreement
Calculate the critical difference P by using Formula (5):
2 2
𝑃𝑃 = 2,83�𝜎𝜎 +𝜎𝜎 /2 (5)
𝑟𝑟
𝐿𝐿
The absolute difference between the two laboratory results, |𝜇𝜇 −𝜇𝜇 |, shall not exceed P. If this condition is
1 2
met, the results are considered to be in agreement.
8.38.4 Determination of trueness
This clausesubclause specifies the procedure for assessing the trueness of the analytical method by comparing
the average measurement result from duplicate analyses against the certified value of a reference materialRM.
The trueness is verified by analyzinganalysing a certified reference material (CRM) or a reference material
(RM) and comparing the average of two measurement results to its certified value.
The absolute difference between the average value of the two measurement results and the certified value
¯
|𝑋𝑋−𝜇𝜇 | shall not exceed the critical difference CD (, as per Formula (6)formula 6) or C (, as per
0.,95
Formula (7)formula 7).
NOTE At the 95 % probability level, the critical difference CD0,95 of the absolute value of the difference between the
average value of the two measurement results and the certified value is calculated according to Formula (6)formula (6)::

2 2
CD = �𝑅𝑅 −𝑟𝑟 /2 (6)
0,95
√
where
R is the reproducibility limit, obtained from Table 32 or Table 43;
r is the repeatability limit, obtained from Table 32 or Table 43.
When the uncertainty of the CRM or RM cannot be ignored, the critical difference, C, can be calculated
according to Formula (7)formula (7)::
𝐶𝐶 = 𝐶𝐶𝐷𝐷 +𝑈𝑈 (7)
�
0,95
where U is the uncertainty of the CRM or RM.
9 Interlaboratory test data of precision and trueness
9.1 General
This clause presents the data and statistical evaluation from an interlaboratory validation test, conducted to
establish the precision and trueness of the method specified in this document.
9.19.2 Interlaboratory test
Fourteen laboratories in five countries participated in an interlaboratory validation test, involving three
determinations of eight elements at ten contents (samples). The chemical composition of the samples used in
the interlaboratory test is given in Annex D.
Each laboratory carried out two determinations under repeatability conditions as defined in ISO 5725-1, i.e.
one operator, same apparatus, identical operating conditions, same calibr
...