SIST EN ISO 18265:2014
(Main)Metallic materials - Conversion of hardness values (ISO 18265:2013)
Metallic materials - Conversion of hardness values (ISO 18265:2013)
This International Standard specifies the principles of the conversion of hardness values to equivalent values in other hardness scales and to estimates of tensile strength. It gives general information on the use of the conversion tables. The conversion tables in Annexes A to G apply to - unalloyed and low alloy steels and cast steel, - steels for quenching and tempering, - steels for cold working, - high speed steels, - tool steels, - hardmetals, and - non-ferrous metals and alloys. Converted values obtained using this International Standard are only directly applicable to the exact material tested. For all other materials, they provide an indicator only. In all cases, the converted values are not intended as replacements for values obtained by the correct standard method. In particular, tensile strength estimates are the least reliable converted values in this International Standard.
Metallische Werkstoffe - Umwertung von Härtewerten (ISO 18265:2013)
Diese Internationale Norm legt die Grundlagen zur Umwertung von Härtewerten in äquivalente Werte anderer Härteskalen und in Näherungswerte für die Zugfestigkeit fest. Sie gibt allgemeine Informationen zur Anwendung von Umwertungstabellen.
Die in den Anhängen A bis G dieser Norm enthaltenen Umwertungstabellen gelten für
- unlegierte und niedriglegierte Stähle und Stahlguss,
- Vergütungsstähle,
- Kaltarbeitsstähle,
- Schnellarbeitsstähle,
- Werkzeugstähle,
- Hartmetalle sowie
- Nichteisenmetalle und legierungen.
ANMERKUNG 1 Die Umwertungstabellen in den Anhängen B bis G dieser Norm basieren auf experimentellen Ergebnissen, die mittels Regressionsanalyse ausgewertet wurden. Für die Umwertungstabelle im Anhang A dieser Norm lagen für diese Auswertung nicht genügend Messergebnisse vor.
ANMERKUNG 2 Anhang H gibt Informationen über die Auswirkungen von Änderungen im Prüfverfahren, das in den entsprechenden Normen festgelegt ist.
Eine direkte Anwendung der Werte, die durch eine Härteumwertung nach dieser Internationalen Norm ermittelt wurden, ist nur auf genau gleiche Werkstoffe möglich. Für alle anderen Werkstoffe dienen diese Werte lediglich als allgemeiner Indikator. In allen Fällen sind die Ergebnisse der Umwertung nicht als Ersatz für die nach den zutreffenden genormten Verfahren ermittelten Werte vorgesehen. Am wenigsten zuverlässig sind die nach dieser Internationalen Norm abgeschätzten Zugfestigkeitswerte.
Abschnitte dieser Internationalen Norm sind mit der Genehmigung von ASTM nachgedruckt, und stammen aus ASTM E140 Standard Hardness Conversion Tables for Metals Relationship among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Harness, Knoop Hardness, and Scleroscope Hardness.
Matériaux métalliques - Conversion des valeurs de dureté (ISO 18265:2013)
L'ISO 18265:2013 spécifie les principes de conversion des valeurs de dureté en des valeurs équivalentes dans d'autres échelles de dureté et en des estimations de la résistance à la traction. Elle donne des informations générales sur l'utilisation des tables de conversion.
Les tables de conversion des Annexes A à G s'appliquent à des aciers non alliés et faiblement alliés et aciers moulés, aciers pour trempe et revenu, aciers pour formage à froid, aciers rapides, aciers à outils, métaux durs, et métaux et alliages non ferreux.
Les valeurs converties obtenues au moyen de l'ISO 18265:2013 ne sont directement applicables qu'au matériau exact soumis aux essais. Pour tous les autres matériaux, elles fournissent seulement un indicateur. Dans tous les cas, les valeurs converties ne sont pas destinées à remplacer les valeurs obtenues par la méthode normalisée correcte. En particulier, les estimations pour la résistance à la traction sont les valeurs converties les moins fiables de l'ISO 18265:2013.
Kovinski materiali - Pretvorbe vrednosti trdote (ISO 18265:2013)
Ta mednarodni standard določa načela za pretvorbe vrednosti trdote v primerljive vrednosti drugih lestvic trdote in približkov natezne trdnosti. Podaja splošne informacije o uporabi tabel s pretvorbami. Tabele s pretvorbami v dodatkih A–G veljajo za – nelegirana in malolegirana jekla ter jeklene litine; jekla za kaljenje in popuščenje; – jekla za hladno preoblikovanje; – visoko hitrostna jekla; – jekla za orodje; – trde kovine; in – železne in neželezne kovine in zlitine. Vrednosti, pretvorjene s tem mednarodnim standardom, se uporabljajo le neposredno za material za testiranje. Za vse ostale materiale so zgolj smernice. Pretvorjene vrednosti v nobenem primeru niso zamenjava za vrednosti, pridobljene s pravo metodo standarda. Ocene natezne trdnosti so najmanj zanesljive pretvorjene vrednosti v tem mednarodnem standardu.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 18265:2014
01-junij-2014
1DGRPHãþD
SIST EN ISO 18265:2004
Kovinski materiali - Pretvorbe vrednosti trdote (ISO 18265:2013)
Metallic materials - Conversion of hardness values (ISO 18265:2013)
Metallische Werkstoffe - Umwertung von Härtewerten (ISO 18265:2013)
Matériaux métalliques - Conversion des valeurs de dureté (ISO 18265:2013)
Ta slovenski standard je istoveten z: EN ISO 18265:2013
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
SIST EN ISO 18265:2014 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 18265:2014
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SIST EN ISO 18265:2014
EUROPEAN STANDARD
EN ISO 18265
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2013
ICS 77.040.10 Supersedes EN ISO 18265:2003
English Version
Metallic materials - Conversion of hardness values (ISO
18265:2013)
Matériaux métalliques - Conversion des valeurs de dureté Metallische Werkstoffe - Umwertung von Härtewerten (ISO
(ISO 18265:2013) 18265:2013)
This European Standard was approved by CEN on 3 August 2013.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2013 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18265:2013: E
worldwide for CEN national Members.
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SIST EN ISO 18265:2014
EN ISO 18265:2013 (E)
Contents Page
Foreword .3
2
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SIST EN ISO 18265:2014
EN ISO 18265:2013 (E)
Foreword
This document (EN ISO 18265:2013) has been prepared by Technical Committee ISO/TC 164 "Mechanical
testing of metals" in collaboration with Technical Committee ECISS/TC 101 “Test methods for steel (other
than chemical analysis)” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by April 2014, and conflicting national standards shall be withdrawn at the
latest by April 2014.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 18265:2003.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 18265:2013 has been approved by CEN as EN ISO 18265:2013 without any modification.
3
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SIST EN ISO 18265:2014
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SIST EN ISO 18265:2014
INTERNATIONAL ISO
STANDARD 18265
Second edition
2013-10-01
Metallic materials — Conversion of
hardness values
Matériaux métalliques — Conversion des valeurs de dureté
Reference number
ISO 18265:2013(E)
©
ISO 2013
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Principles of conversion . 1
3 Application of conversion tables . 4
3.1 General . 4
3.2 Converting values . 7
3.3 Designation of conversion results . 9
3.4 Notes on use of conversion tables .10
Annex A (informative) Conversion table for unalloyed, low alloy steels and cast steel .12
Annex B (informative) Conversion tables for steels for quenching and tempering .17
Annex C (informative) Conversion tables for steels for cold working .37
Annex D (informative) Conversion tables for high speed steels .48
Annex E (informative) Conversion tables for hardmetals .61
Annex F (informative) Conversion tables for non-ferrous metals and alloys .65
Annex G (informative) Conversion tables for tool steels .76
Annex H (informative) Remarks on the effect of the changed test conditions .80
Bibliography .84
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directives
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received. www.iso.org/patents
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT), see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 164, Mechanical testing of metals, Subcommittee
SC 3, Hardness testing.
This second edition cancels and replaces the first edition (ISO 18265:2003) which has been
technically revised.
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
Introduction
The hardness conversion values given in Table A.1 were obtained in interlaboratory tests by the Verein
Deutscher Eisenhüttenleute (VDEh) (German Iron and Steel Institute) using verified and calibrated
hardness testing machines. Statistically reliable information cannot be given on the uncertainty of these
values because the test conditions were not reproducible, and the number of results used to calculate
the mean hardness values is not known. The conversion values in this table are in accordance with the
information presented in IC No. 3 (1980) and IC No. 4 (1982) of the European Coal and Steel Community,
as well as in ISO 4964:1984 and ISO/TR 10108:1989.
Annexes C, D and E contain – in a revised format – the extensive results on the conversion of hardness
values presented in TGL 43212/02 to 43212/04, standards published by the former East German
standards body, the Amt für Standardisierung, Meßwesen und Warenprüfung (ASMW). The values
presented in Annex B had also been determined by the ASMW, but were published in a report of the
[1]
Physikalisch-Technische Bundesanstalt (PTB), the German national institute for science and technology,
not in a TGL standard.
The converted hardness values in the above-mentioned TGL standards were obtained in statistically
reliable hardness and tensile tests. The hardness tests were performed using ASMW normal testing
machines on plane-parallel, polished specimens of various materials in different heat treatment
conditions. Tensile strength was tested on machines whose force measuring and extension measuring
systems had been calibrated immediately before testing. The tensile test method used is equivalent to
that specified in ISO 6892-1, and the calibration procedures conform with those specified in ISO 7500-1
and ISO 9513.
Annex G contains the results on the conversion of hardness values of two tool steels with the assistance
of the Verein Deutscher Eisenhüttenleute (VDEh) which were obtained in the year 2007.
Users of this International Standard should take note of Clause 2, especially the concluding warning.
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SIST EN ISO 18265:2014
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SIST EN ISO 18265:2014
INTERNATIONAL STANDARD ISO 18265:2013(E)
Metallic materials — Conversion of hardness values
1 Scope
This International Standard specifies the principles of the conversion of hardness values to equivalent
values in other hardness scales and to estimates of tensile strength. It gives general information on the
use of the conversion tables.
The conversion tables in Annexes A to G apply to
— unalloyed and low alloy steels and cast steel,
— steels for quenching and tempering,
— steels for cold working,
— high speed steels,
— tool steels,
— hardmetals, and
— non-ferrous metals and alloys.
NOTE 1 The conversion tables in Annexes B to G are based on empirical results which were evaluated by
means of regression analysis. Such analysis was not possible in the case of the values given in Annex A because a
sufficient number of results was not available.
NOTE 2 Annex H gives information about the effects of changes of the test procedure in the standards specifying
the hardness tests.
Converted values obtained using this International Standard are only directly applicable to the exact
material tested. For all other materials, they provide an indicator only. In all cases, the converted values
are not intended as replacements for values obtained by the correct standard method. In particular,
tensile strength estimates are the least reliable converted values in this International Standard.
Sections of this International Standard are reprinted, with permission of ASTM International, from
ASTM E140 Standard Hardness Conversion Tables for Metals Relationship among Brinell Hardness, Vickers
Hardness, Rockwell Hardness, Superficial Harness, Knoop Hardness, and Scleroscope Hardness.
2 Principles of conversion
Hardness testing is a form of materials testing that provides information on the mechanical properties
of a material with limited destruction of the specimen and within a relatively short period of time. In
practice, it is often desirable to use hardness results to draw conclusions on the tensile strength of the
same material if tensile testing is too involved or the piece to be examined is not to be destroyed.
Since the means of loading in hardness testing is considerably different from that in tensile testing, it is
not possible to derive a reliable functional relationship between these two characteristic values on the
basis of a model. Nevertheless, hardness values and tensile strength values are positively correlated,
and so it is possible to draw up empirical relationships for limited applications.
Often it is necessary to check a given hardness value against a value gained by a different test method.
This is especially the case if only a certain method can be used due to the particular specimen or coating
thickness, the size of the object to be tested, surface quality, or the availability of hardness testing machines.
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
Conversion of hardness values to tensile values makes it possible to carry out hardness measurement
in place of the measurement of tensile strength taking into account that these tensile strength values
must be seen as being the least reliable form of conversion. Likewise, with conversion between hardness
scales, a hardness value can be replaced with a value obtained using the desired method.
Sometimes a conversion relationship is drawn on a single-case basis to gain information on properties
other than hardness, most often to obtain a good estimate of tensile strength. Special relationships
are sometimes drawn for hardness-to-hardness conversions. This may be done as long as the following
conditions are fulfilled.
— The hardness test method used is only employed internally, and the results obtained will not be
compared with those of other methods, or the details of the test procedure are defined precisely
enough so that results can be reproduced by another laboratory or at another time.
— The conversion tables used shall have been derived from a sufficiently large number of parallel
experiments using both scales and carried out on the material in question.
— Converted results are to be expressed in such a manner that it is clear which method was used to
determine the original hardness value.
However, the conversion values in this International Standard are informative only. A measurement
made according to the correct hardness (or tensile) standard for the scale being reported shall always
take precedence over a hardness (or strength) value derived from a conversion table within this
International Standard. Similarly, a value derived by conversion shall not provide sufficient grounds
either for a complaint or for proof of meeting an acceptance criterion.
WARNING — In practice, an attempt is often made to establish a strong relationship between the
original and converted values without taking the characteristics of the material under test into
consideration. As Figures 1 and 2 show, this is not possible. Therefore, users of this International
Standard should ensure that all conditions for conversion are met (see also References [2] and [3]).
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
Key
X Hardness HV 30
Y Tensile strength, R in MPa
m
1 untreated, soft annealed, normalized
2 quenched and tempered
Figure 1 — HV 30/R curves for quenching and tempering steels in various heat treatment
m
conditions
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
Key
X Hardness HV30 3 R /R =0,70 to 0,79 normal annealed
e m
Y Tensile strength, R in MPa 4 R /R =0,70 to 0,79 heat treated
m e m
1 R /R =0,45 to 0,59 5 R /R =0,80 to 0,89
e m e m
2 R /R =0,60 to 0,69 6 R /R =0,90 to 0,99
e m e m
Figure 2 — Mean HV 30/R curves for quenching and tempering steels with different R /R ratios
m e m
3 Application of conversion tables
3.1 General
Conversion from one hardness value to another or from a hardness value to a tensile strength value
involves uncertainties which must be taken into account. Extensive investigations have shown that it
is not possible to establish universally applicable conversion relationships between hardness values
obtained by different methods, no matter how carefully the tests had been carried out. This lies in the
fact that there is a complex relationship between the indentation behaviour of a material and its elastic
and plastic deformation. For this reason, the given conversion relationship provides greater equivalency
the more similarity there is between the elasticity of the tested material and that of the material used
to establish the relationship. Likewise, a better equivalency can be expected for methods with similar
indentation processes (i.e. where the differences in the force application-indentation procedures and
the test parameters is minimal). Therefore, conversion from hardness values to tensile values must be
seen as being the least reliable form of conversion.
NOTE In many cases, the yield strength or the 0,2 % proof strength provides information on the elastic
behaviour of a material.
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
Measurement best practice shall be defined by the hardness test adopted.
It should be noted that each hardness determination is only applicable to the immediate area of the
indentation. Where hardness varies, e.g. at an increasing distance from the surface, Brinell or Vickers
hardness values, or even tensile strength values can deviate from the converted values solely as a result
of the different rate of elongation within the area under consideration. Different geometry indentations
are affected differently by these effects and so conversions from one hardness scale to another may no
longer be consistent even in the same sample.
Hardness values shall only be converted when the prescribed test method cannot be used, for example
because a suitable machine is not available, or if the required samples cannot be taken. A suitable test
method can be selected with the aid of Figures 3 and 4.
Converted values shall not be used as the basis for proof of compliance (or not) to a specification or
contract (any necessary exceptions therefore require specific agreement between the parties concerned).
If hardness or tensile strength values are determined by conversion in accordance with this International
Standard, this shall be stated, as shall the hardness test method (ISO 6506-1, ISO 6507-1, ISO 6508-1) used.
The basis of conversion shall be the mean of at least three individual hardness values.
To ensure an acceptable uncertainty of measurement, the specimen surfaces shall be sufficiently smooth;
depending on the hardness test method and the test force a suitable method of surface preparation has to
be selected, e.g. machine-finishing (for macro hardness) up to polishing (for low-force and micro hardness).
The uncertainties of the values given in the conversion tables here comprise the confidence interval of
the hardness conversion curves calculated by means of regression analysis, and the uncertainty of the
hardness or tensile strength value to be converted. The confidence interval of the regression function is
a parameter that cannot be influenced by the user and is calculated as a function of hardness.
The uncertainty associated with the hardness values to be converted is influenced by the repeatability
of the testing machine, the quality of the specimen surface, the uniformity of the specimen’s hardness,
and the number of indentations used to determine hardness. It is thus dependent on the test conditions
of the person doing the conversion. This conversion is to be carried out on the basis of the tables given
in this International Standard for various groups of materials. These tables give hardness values for
various scales and, in some cases, the relevant tensile strength.
When only comparing the values in these tables without actually carrying out hardness testing, the
uncertainty of the converted value is reduced to the confidence interval of the calculated hardness
conversion curve. When using the tables, it is not significant which value is taken as the measured value
and which as the converted one.
The determination of the uncertainty of converted values, as well as the specification of a permissible
level of uncertainty may be agreed, in which case the converted values are to be established on the basis
of the mean of five individual values.
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
Key
X Vickers hardness HV30 1 non-ferrous metal
Y Rockwell hardness 2 steel
1
Y Brinell hardness 3 hardmetal
2
a
Brinell hardness, determined with steel ball (HBS)
b
Brinell hardness, determined with hardmetal ball
(HBW)
This figure is intended only as an aid in selecting an alternative test method and is not to be used for conversion
purposes.
2
NOTE The designation “HB5D ” corresponds to the force-diameter ratio according to ISO 6506-1.
Figure 3 — Various hardness scales compared to the Vickers scale
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
Key
X Brinell hardness HB/ Vickers hardness HV 1 HB10/1 000
1
X Rockwell hardness, HR according to its different 2 HB10/500 and HB 5/250
2
scales
Y Indentation, depth, µm 3 HB5/125 and HB 2,5/62,5
4 HB2,5/62,5
Figure 4 — Indentation depth as a function of hardness for various test methods
3.2 Converting values
3.2.1 Limits of error
Depending on the measurement conditions in practice, measured value/converted value pairs (e.g.
HV/HRC, HRC/HV, HRA/HRN, HB/R ) can be taken from the tables in Annexes A to G. Essential criteria
m
which should be taken into account when selecting a hardness test method are discussed in this clause.
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
The example below illustrates the conversion of values together with their limits of error using Table C.2.
Given hardness value: (300 ± 30) HV
Desired scale: HRC
Converted values from table: 270 HV ≙ 26,9 HRC
300 HV ≙ 31,0 HRC
330 HV ≙ 34,6 HRC
+36,
The converted value, 31 HRC, for the nominal value 300 HV no longer represents the mean of the upper
−41,
and lower limits in HRC because of the nonlinear relationship between HV and HRC values (see Figure 5).
The confidence interval of the hardness conversion curve may be disregarded for such estimations.
Key
X HV 30
Y HRC
Figure 5 — Shift of the nominal value when converting hardness values
3.2.2 Uncertainty
The uncertainty of a converted value should be taken from the curves associated with the conversion
table used, as shown in the figures in Annexes B to E for various types of material.
The families of curves given in the annexes represent the uncertainty, u, for a probability level of 95 %
as a function of the hardness value H for various reproducibility limits, R. ( H is the corrected
K K
arithmetic mean of five individual values.) The curves have been arranged so that interpolation between
neighboring curves is possible. The reproducibility, R, is to be calculated on the basis of five measurements
as shown in 3.4.2 for various hardness test methods.
The uncertainty curves only take account of the effects of the random errors of the measured value on
the converted value. However, they do not take account of the systematic error of the testing machine
used, as this can lead to exceedingly high errors in the converted result, even if the systematic error lies
within the permissible range specified for the machine; this is explained in 3.4. For this reason, hardness
testing machines are to be verified, using calibrated blocks, at least within the time interval specified
in the relevant standards. The systematic error determined in this manner is to be compensated by
correcting the measured mean hardness value. This is especially important in the case of Rockwell
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
hardness testing. Figure 6 illustrates the determination of the uncertainty, u, of a converted hardness
value (dashed line) according to the example below.
EXAMPLE
— 500 HV
Measured, corrected mean hardness H
K
— Converted value as in Annex C 49,5 HRC
— Calculated reproducibility limit, R 2,0 %
— Uncertainty of converted value, u ± 0,7 HRC
Key
X
H in HV 30
K
Y u in HRC
Figure 6 — Determining uncertainty of a converted hardness value (example)
3.3 Designation of conversion results
Conversion results shall be reported in a manner that clearly indicates which method was used to
determine the original hardness value. In addition, the relevant annex to this International Standard or
the table used shall be given.
EXAMPLE 1
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SIST EN ISO 18265:2014
ISO 18265:2013(E)
EXAMPLE 2 If it is agreed that the uncertainty of the converted value is to be given, this is included in the
result as follows:
EXAMPLE 3 Conversions into tensile strength values are expressed as follows:
3.4 Notes on use of conversion tables
3.4.1 Selection of alternative hardness test methods
3.4.1.1 In Figure 3, hardness scales for non-ferrous metals, hardmetals and selected steels are compared.
The relationship of each scale to the Vickers scale is illustrated, and by comparison with Rockwell and
Brinell scales (y-axes), information is gained as to the hardness ranges covered by each method. This
figure is intended solely as an aid to selection and is not to be used for conversion purposes.
3.4.1.2 Figure 4 shows indentation depths as a function of hardness for various test methods. This
should facilitate selection of a suitable test method on the basis of specimen or coating thickness.
3.4.1.3 Another cr
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Questions, Comments and Discussion
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