prEN ISO 6508-1

Metallic materials - Rockwell hardness test - Part 1: Test method (ISO/DIS 6508-1:2022)

ISO 6508-1:2016 specifies the method for Rockwell regular and Rockwell superficial hardness tests for scales A, B, C, D, E, F, G, H, K, 15N, 30N, 45N, 15T, 30T, and 45T for metallic materials and is applicable to stationary and portable hardness testing machines.
For specific materials and/or products, other specific International Standards apply (for instance, ISO 3738‑1 and ISO 4498).

Metallische Werkstoffe - Härteprüfung nach Rockwell - Teil 1: Prüfverfahren (ISO/DIS 6508-1:2022)

Dieser Teil der ISO 6508 legt die Härteprüfung nach dem Standard Rockwell  und Superrockwell Verfahren für die Skalen A, B, C, D, E, F, G, H, K, 15N, 30N, 45N, 15T, 30T und 45T für metallene Werkstoffe fest und gilt für ortsfeste und mobile Härteprüfmaschinen.
Für Sonderwerkstoffe und/oder  erzeugnisse gelten andere besondere Internationale Normen (z. B. ISO 3738 1 und ISO 4498).

Matériaux métalliques - Essai de dureté Rockwell - Partie 1: Méthode d'essai (ISO/DIS 6508-1:2022)

L'ISO 6508-1 :2016 spécifie la méthode d'essai de dureté Rockwell normale et de dureté superficielle Rockwell pour les échelles A, B, C, D, E, F, G, H, K,15N,30N,45N,15T,30T et 45 T pour les matériaux métalliques. Elle s'applique aux machines d'essai de dureté fixes et portables.
Pour des matériaux et/ou produits spécifiques, d'autres Normes internationales spécifiques s'appliquent (par exemple ISO 3738‑1 et ISO 4498).

Kovinski materiali - Preskus trdote po Rockwellu - 1. del: Preskusna metoda (ISO/DIS 6508-1:2022)

General Information

• Status: Not Published
• Publication Date: 26-Nov-2024
• ICS: 77.040.10 - Mechanical testing of metals
• Technical Committee: ECISS/TC 101 - Test methods for steel (other than chemical analysis)
• Drafting Committee: ECISS/TC 101 - Test methods for steel (other than chemical analysis)
• Current Stage: 4599 - Dispatch of FV draft to CMC - Finalization for Vote
• Start Date: 04-Jul-2023
• Completion Date: 04-Jul-2023
• Ref Project: oSIST prEN ISO 6508-1:2023 - Metallic materials - Rockwell hardness test - Part 1: Test method (ISO/DIS 6508-1:2022)

Relations

• Revises: EN ISO 6508-1:2016 - Metallic materials - Rockwell hardness test - Part 1: Test method (ISO 6508-1:2016)
• Effective Date: 15-Dec-2021

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN ISO 6508-1:2023
01-januar-2023
Kovinski materiali - Preskus trdote po Rockwellu - 1. del: Preskusna metoda
(ISO/DIS 6508-1:2022)

Metallic materials - Rockwell hardness test - Part 1: Test method (ISO/DIS 6508-1:2022)

Metallische Werkstoffe - Härteprüfung nach Rockwell - Teil 1: Prüfverfahren (ISO/DIS

6508-1:2022)

Matériaux métalliques - Essai de dureté Rockwell - Partie 1: Méthode d'essai (ISO/DIS

6508-1:2022)
Ta slovenski standard je istoveten z: prEN ISO 6508-1
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
oSIST prEN ISO 6508-1:2023 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 6508-1:2023
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oSIST prEN ISO 6508-1:2023
DRAFT INTERNATIONAL STANDARD
ISO/DIS 6508-1
ISO/TC 164/SC 3 Secretariat: DIN
Voting begins on: Voting terminates on:
2022-11-03 2023-01-26
Metallic materials — Rockwell hardness test —
Part 1:
Test method
Matériaux métalliques — Essai de dureté Rockwell —
Partie 1: Méthode d'essai
ICS: 77.040.10
This document is circulated as received from the committee secretariat.
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
ISO/CEN PARALLEL PROCESSING
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
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BEING ACCEPTABLE FOR INDUSTRIAL,
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USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 6508-1:2022(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. © ISO 2022
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oSIST prEN ISO 6508-1:2023
ISO/DIS 6508-1:2022(E)
DRAFT INTERNATIONAL STANDARD
ISO/DIS 6508-1
ISO/TC 164/SC 3 Secretariat: DIN
Voting begins on: Voting terminates on:
Metallic materials — Rockwell hardness test —
Part 1:
Test method
Matériaux métalliques — Essai de dureté Rockwell —
Partie 1: Méthode d'essai
ICS: 77.040.10
This document is circulated as received from the committee secretariat.
COPYRIGHT PROTECTED DOCUMENT
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© ISO 2022
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NOT BE REFERRED TO AS AN INTERNATIONAL

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POTENTIAL TO BECOME STANDARDS TO
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NATIONAL REGULATIONS.
Website: www.iso.org ISO/DIS 6508-1:2022(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
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NOTIFICATION OF ANY RELEVANT PATENT
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PROVIDE SUPPORTING DOCUMENTATION. © ISO 2022
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oSIST prEN ISO 6508-1:2023
ISO/DIS 6508-1:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Principle ........................................................................................................................................................................................................................ 1

4 Symbols, abbreviated terms and designations ................................................................................................................... 2

5 Testing machine....................................................................................................................................................................................................4

6 Test piece ..................................................................................................................................................................................................................... 5

7 Procedure ....................................................................................................................................................................................................................5

8 Uncertainty of the results .......................................................................................................................................................................... 7

9 Test report .................................................................................................................................................................................................................. 7

10 Conversions to other hardness scales or tensile strength values ...................................................................7

Annex A (normative) Special HR30TSm and HR15TSm test for thin products ......................................................8

Annex B (normative) Minimum thickness of the test piece in relation to the Rockwell

hardness ....................................................................................................................................................................................................................... 9

Annex C (normative) Corrections to be added to Rockwell hardness values obtained on

convex cylindrical surfaces ...................................................................................................................................................................12

Annex D (normative) Corrections to be added to Rockwell hardness C scale values obtained

on spherical test surfaces of various diameters .............................................................................................................15

Annex E (normative) Daily verification procedure ...........................................................................................................................16

Annex F (normative) Inspection of diamond indenters ...............................................................................................................19

Annex G (informative) Uncertainty of the measured hardness values .......................................................................20

Annex H (informative) CCM — Working group on hardness ...................................................................................................25

Annex I (informative) Rockwell hardness measurement traceability .........................................................................26

Bibliography .............................................................................................................................................................................................................................29

iii
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oSIST prEN ISO 6508-1:2023
ISO/DIS 6508-1:2022(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 (see 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 (see 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 World Trade Organization (WTO) principles in the

Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html .

The committee responsible for this document is ISO/TC 164, Mechanical testing of metals, Subcommittee

SC 3, Hardness testing.

This fourth edition cancels and replaces the third edition (ISO 6508-1:2015), of which it constitutes a

minor revision in order to clarify the scope of this part of ISO 6508.

ISO 6508 consists of the following parts, under the general title Metallic materials — Rockwell hardness

test:
— Part 1: Test method
— Part 2: Verification and calibration of testing machines and indenters
— Part 3: Calibration of reference blocks
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oSIST prEN ISO 6508-1:2023
DRAFT INTERNATIONAL STANDARD ISO/DIS 6508-1:2022(E)
Metallic materials — Rockwell hardness test —
Part 1:
Test method
1 Scope

This part of ISO 6508 specifies the method for Rockwell regular and Rockwell superficial hardness

tests for scales A, B, C, D, E, F, G, H, K, 15N, 30N, 45N, 15T, 30T, and 45T for metallic materials and is

applicable to stationary and portable hardness testing machines.

For specific materials and/or products, other specific International Standards apply (for instance,

ISO 3738-1 and ISO 4498).
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 6508-2, Metallic materials — Rockwell hardness test — Part 2: Verification and calibration of testing

machines and indenters

ISO 6508-3, Metallic materials — Rockwell hardness test — Part 3: Calibration of reference blocks

3 Principle

An indenter of specified size, shape, and material is forced into the surface of a test specimen under two

force levels using the specific conditions defined in Clause 7. The specified preliminary force is applied

and the initial indentation depth is measured, followed by the application and removal of a specified

additional force, returning to the preliminary force. The final indentation depth is then measured and

the Rockwell hardness value is derived from the difference, h, in the final and initial indentation depths

and the two constants N and S (see Figure 1, Table 1, and Table 2) as shown in Formula (1):

Rockwell hardness=−N (1)
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oSIST prEN ISO 6508-1:2023
ISO/DIS 6508-1:2022(E)
4 Symbols, abbreviated terms and designations
4.1 See Table 1, Table 2, Table 3, and Figure 1.
Table 1 — Rockwell Regular scales
Rockwell Hardness Type of indenter Preliminary Total Scaling Full Applicable
symbol force force Constant Range range
Regular
of application
hardness Unit F F S Constant
(Rockwell
scale
Regular
hardness scales)
A HRA Diamond cone 98,07 N 588,4 N 0,002 mm 100 20 HRA to
95 HRA
B HRBW Ball 1,587 5 mm 98,07 N 980,7 N 0,002 mm 130 10 HRBW to
100 HRBW
C HRC Diamond cone 98,07 N 1,471 kN 0,002 mm 100 20 HRC to
70 HRC
D HRD Diamond cone 98,07 N 980,7 N 0,002 mm 100 40 HRD to
77 HRD
E HREW Ball 3,175 mm 98,07 N 980,7 N 0,002 mm 130 70 HREW to
100 HREW
F HRFW Ball 1,587 5 mm 98,07 N 588,4 N 0,002 mm 130 60 HRFW to
100 HRFW
G HRGW Ball 1,587 5 mm 98,07 N 1,471 kN 0,002 mm 130 30 HRGW to
94 HRGW
H HRHW Ball 3,175 mm 98,07 N 588,4 N 0,002 mm 130 80 HRHW to
100 HRHW
K HRKW Ball 3,175 mm 98,07 N 1,471 kN 0,002 mm 130 40 HRKW to
100 HRKW

The applicable range of application can be extended to 10 HRC if the surfaces of the diamond cone and spherical tip are

polished for a penetration depth of at least 0,4 mm.
Table 2 — Rockwell Superficial scales
Rockwell Hardness Type of Preliminary Total Scaling Full Applicable
Superficial symbol indenter force force Constant Range range
hardness Constant of application
Unit F F S
scale (Rockwell
Superficial
hardness scales)
15N HR15N Diamond cone 29,42 N 147,1 N 0,001 mm 100 70 HR15N to
94 HR15N
30N HR30N Diamond cone 29,42 N 294,2 N 0,001 mm 100 42 HR30N to
86 HR30N
45N HR45N Diamond cone 29,42 N 441,3 N 0,001 mm 100 20 HR45N to
77 HR45N
15T HR15TW Ball 1,587 5 mm 29,42 N 147,1 N 0,001 mm 100 67 HR15TW to
93 HR15TW
30T HR30TW Ball 1,587 5 mm 29,42 N 294,2 N 0,001 mm 100 29 HR30TW to
82 HR30TW
45T HR45TW Ball 1,587 5 mm 29,42 N 441,3 N 0,001 mm 100 10 HR45TW to
72 HR45TW
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oSIST prEN ISO 6508-1:2023
ISO/DIS 6508-1:2022(E)

Scales using indenter balls with diameter 6,350 mm and 12,70 mm may also be used, if specified in the

[11]

product specification or by special agreement. See ASTM E18 for additional scales using these ball

sizes.

NOTE 1 For certain materials, the applicable range of application might be narrower than those indicated.

NOTE 2 The numbers representing the test forces were originally based on units of kgf. For example, the total

test force of 30 kgf has been converted to 294,2 N.
Table 3 — Symbols and abbreviated terms
Symbol/
Abbreviated Definition Unit
term
F Preliminary test force N
F Additional test force (total force minus preliminary force) N
F Total test force N
S Scaling constant, specific to the scale mm
N Full range constant, specific to the scale
h Permanent depth of indentation under preliminary test force after removal of
additional test force (permanent indentation depth)
HRA
HRC Rockwell Regular hardness =100−
0,002
HRD
HRBW
HREW
HRFW
Rockwell Regular hardness =130−
HRGW 0,002
HRHW
HRKW
HRN
Rockwell Superficial hardness =100−
0,001
HRTW
4.2 The following is an example of the designation of Rockwell hardness.
EXAMPLE

NOTE 1 Previous versions of this part of ISO 6508 allowed the use of steel indenter balls, which required the

suffix S.

NOTE 2 For the HR30TSm and HR15TSm scales defined in Annex A, a capital S and a lower-case m is used

indicating the use of steel indenter balls and a diamond spot specimen holder.
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oSIST prEN ISO 6508-1:2023
ISO/DIS 6508-1:2022(E)
Key
X time 4 permanent indentation depth, h
Y indenter position 5 surface of specimen
1 indentation depth by preliminary force, F 6 reference plane for measurement
2 indentation depth by additional test force, F 7 position of indenter

3 elastic recovery just after removal of additional test force, F 8 indentation depth vs. time curve

Figure 1 — Rockwell principle diagram
5 Testing machine

5.1 Testing machine, shall be capable of applying the test forces for some or all of the Rockwell

hardness scales as shown in Table 1 and Table 2, performing the procedure defined in Clause 7, and

complying with all of the requirements defined in ISO 6508-2.

5.2 Spheroconical diamond indenter, shall be in accordance with ISO 6508-2, with an included

angle of 120° and radius of curvature at the tip of 0,2 mm. Diamond indenters shall be certified for use

for either
— only the regular Rockwell diamond scales,
— only the superficial Rockwell diamond scales, or
— both the regular and the superficial Rockwell diamond scales.

5.3 Ball indenter, shall be tungsten carbide composite in accordance with ISO 6508-2, with a

diameter of 1,587 5 mm or 3,175 mm (see NOTE 1 and NOTE 2).

NOTE 1 Ball indenters normally consist of a spherical ball and a separate appropriately designed holder. Single-

piece spherically tipped indenters are allowed, provided that the surface of the indenter that makes contact with

the test piece meets the size, shape, finish, and hardness requirements for the calibration and verification of the

ball indenter as defined in ISO 6508-2, and meets the performance requirements for the indirect verification of

the ball holder assembly as defined in ISO 6508-2.
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oSIST prEN ISO 6508-1:2023
ISO/DIS 6508-1:2022(E)

NOTE 2 Attention is drawn to the fact that the use of tungsten carbide composite for ball indenters is the

standard type of Rockwell indenter ball. Steel indenter balls can only be used when performing Rockwell

HR30TSm and HR15TSm tests according to Annex A.
6 Test piece

6.1 The test shall be carried out on a surface which is smooth and even, free from oxide scale, foreign

matter and, in particular, completely free from lubricants, unless specified otherwise in product or

materials standards.

An exception is made for reactive metals, such as titanium, which might adhere to the indenter. In such

situations, a suitable lubricant such as kerosene may be used. The use of a lubricant shall be reported on

the test report.

6.2 Preparation shall be carried out in such a way that any alteration of the surface hardness due to

excessive heating or cold-working for example, is minimized.

This shall be taken into account, particularly in the case of low-depth indentations.

6.3 The thickness of the test piece, or of the layer under test (minimum values are given in Annex B),

shall be at least 10 times the permanent indentation depth for diamond indenters and 15 times the

permanent indentation depth for ball indenters, unless it can be demonstrated that the use of a thinner

test piece does not affect the measured hardness value.

In general, no deformation should be visible on the back of the test piece after the test, although not all

such marking is indicative of a bad test.

See Annex A for special requirements for testing very thin sheet metal using the HR30TSm and

HR15TSm scales.
6.4 For tests on convex cylindrical surfaces and spherical surfaces, see 7.11.
7 Procedure

7.1 This part of ISO 6508 has been developed with a laboratory temperature requirement of

10 °C to 35 °C.

For environments outside the stated requirement, it is the responsibility of the testing laboratory to

assess the impact on testing data produced with testing machines operated in such environments. When

testing is performed outside the recommended temperature limits of 10 °C to 35 °C, the temperature

shall be recorded and reported.

NOTE If significant temperature gradients are present during testing and/or calibration, measurement

uncertainty can increase and out of tolerance conditions can occur.

7.2 The daily verification defined in Annex E shall be performed before the first test of each day for

each scale to be used.
The condition of diamond indenters should be checked according to Annex F.

7.3 After each change, or removal and replacement, of the indenter, indenter ball, or test piece

support, perform at least two tests and discard the results, then determine that the indenter and the

test piece support are correctly mounted in the machine by performing the daily verification process

defined in Annex E.
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oSIST prEN ISO 6508-1:2023
ISO/DIS 6508-1:2022(E)

7.4 The diamond or ball indenter shall have been the indenter used during the last indirect

verification.

If the indenter was not used during the indirect verification and is being used for the first time, it shall

be verified in accordance with the daily verification given in Annex E using at least two test blocks (one

from the low and high ranges as defined by the table in ISO 6508-2 titled “Hardness ranges for different

scales”) for each Rockwell scale that is normally used. This does not apply to replacing a ball.

7.5 The test piece shall be placed on a rigid support and supported in such a manner that the surface

to be indented is in a plane normal to the axis of the indenter and the line of the indenting force, as well

as to avoid a displacement of the test piece.

Products of cylindrical shape shall be suitably supported, for example, on centering V-block or double

cylinders made of material with a Rockwell hardness of at least 60 HRC. Special attention shall be given

to the correct seating, bearing, and alignment of the indenters, the test piece, the centering V-blocks,

and the specimen holder of the testing machine, since any perpendicular misalignment might result in

incorrect results.

7.6 Bring the indenter into contact with the test surface and apply the preliminary test force, F ,

without shock, vibration, oscillation, or overload.

The preliminary force application time should not exceed 2 s. The duration of the preliminary test force,

F , shall be 3 s.
NOTE The requirements for the time durations are given with asymmetric limits.

EXAMPLE 3 s indicates that 3 s is the ideal time duration, with an acceptable range of not less than

1 s (3 s - 2 s) to not more than 4 s (3 s + 1 s).
7.7 Measure the initial indentation depth.

For many manual (dial-indicator) machines, this is done by setting the indicating dial to its set-point or

zero position. For many automatic (digital) machines, the depth measurement is made automatically

without the user’s input and might not be displayed.

7.8 Apply the additional force F without shock, vibration, oscillation, or overload to increase the

force from F to the total force, F.

For the regular Rockwell scale tests, apply the additional test force, F , in not less than 1 s and not

more than 8 s. For all HRN and HRTW Rockwell superficial test scales, apply the additional test force,

F , in less than or equal to 4 s. It is recommended to perform the same test cycle used during indirect

verification.

NOTE There is evidence that some materials might be sensitive to the rate of straining which causes small

changes in the value of the yield stress. The corresponding effect on the termination of the formation of an

indentation can make an alteration in the hardness value.

7.9 The total test force, F, shall be maintained for a duration of 5 s. Remove the additional test

force, F , and, while the preliminary test force, F , is maintained, after 4 s, the final reading shall be

1 0
made.

As an exception for test materials exhibiting excessive plastic flow (indentation creep) during the

application of the total test force, special considerations might be necessary since the indenter will

continue to penetrate. When materials require the use of a total force duration that exceeds the 6 s

allowed by the tolerances, the actual extended total force duration used shall be reported following the

test results (for example, 65 HRF/10 s).
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oSIST prEN ISO 6508-1:2023
ISO/DIS 6508-1:2022(E)

7.10 Measure the final indentation depth while the preliminary test force is applied.

The Rockwell hardness number is calculated from the permanent indentation depth, h, using the

formula given in Formula (1) and the information given in Table 1, Table 2, and Table 3. For most

Rockwell hardness machines, the depth measurement is made in a manner that automatically calculates

and displays the Rockwell hardness number.
The derivation of the Rockwell hardness number is illustrated in Figure 1.

7.11 For tests on convex cylindrical surfaces and spherical surfaces, the corrections given in Annex C

(Table C.1, Table C.2, Table C.3, or Table C.4) and in Annex D (Table D.1) shall be applied.

The correction values shall be reported on the test report.

In the absence of corrections for tests on concave surfaces, tests on such surfaces should be the subject

of special agreement.

7.12 Throughout the test, the apparatus shall be protected from shock or vibration.

7.13 The distance between the centres of two adjacent indentations shall be at least three times the

diameter of the indentation. The distance from the centre of any indentation to an edge of the test piece

shall be at least two and a half times the diameter of the indentation.
8 Uncertainty of the results
[3]

A complete evaluation of the uncertainty should be done according to ISO/IEC Guide 98-3.

A guideline for the determination is given in Annex G.
9 Test report

The laboratory shall record at least the following information and that information shall be included in

the test report, unless agreed by the parties concerned:
a) a reference to this part of ISO 6508, i.e. ISO 6508-1;

b) all details necessary for the complete identification of the test piece, including the curvature of the

test surface;
c) the test temperature, if it is not within the limits of 10 °C to 35 °C;
d) the hardness result in the format defined in 4.2;

e) all operations not specified in this part of ISO 6508, or regarded as optional;

f) details of any occurrence which might have affected the result;

g) the actual extended total force duration time used, if greater than the 6 s allowed by the tolerances;

h) the date the test was performed;

i) if conversion to another hardness scale is also performed, the basis and method of this conversion

[12]
shall be specified (see ISO 18265 ).
10 Conversions to other hardness scales or tensile strength values

There is no general process for accurately converting Rockwell hardness into other scales, or hardness

into tensile strength. Such conversions, therefore, should be avoided, unless a reliable basis for

[12]
conversion can be obtained by comparison tests (see also ISO 18265 ).
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oSIST prEN ISO 6508-1:2023
ISO/DIS 6508-1:2022(E)
Annex A
(normative)
Special HR30TSm and HR15TSm test for thin products
A.1 General

This test is applicable to thin sheet metal products having a maximum thickness of 0,6 mm to the

minimum thickness indicated in the product standards, and of a maximum hardness of 82 HR30TSm

or 93 HR15TSm. The product standard shall specify when the Special HR30TSm or HR15TSm hardness

test is to be applied.

This test is carried out under conditions similar to those in the HR30TW or HR15TW test defined in

this part of ISO 6508. The appearance of deformation on the bottom of the test pieces below the indent

is permitted.

NOTE 1 The Sm in the scale designations indicates that a steel ball indenter and a diamond spot specimen

holder are used for this testing.

NOTE 2 Prior to testing, hardness tests should be made on thin sheet samples of a known hardness to verify

that the specimen holder surface does not affect the measurement results.

The following requirements shall be met, in addition to those specified in this part of ISO 6508.

A.2 Ball indenter

A hardened steel ball indenter, that meets the requirements of ISO 6508-2, with a diameter of

1,587 5 mm shall be used for this testing.
A.3 Test piece support

The test piece support shall comprise a polished and smooth flat diamond surface approximately

4,5 mm in diameter. This support surface shall be approximately centred on the axis of the indenter

and shall be perpendicular to it. Care shall be taken to ensure that it is seated correctly on the machine

table.
A.4 Test piece preparation

If it is necessary to remove material from the test piece, this should be done on both sides of the test

piece. Care shall be taken to ensure that this process does not change the condition of the base metal,

for example, by heating or work hardening. The base metal shall not be made thinner than the minimum

allowable thickness.
A.5 Position of the test piece

The distance between the centres of two adjacent indentations or between the centre of one of the

indentations and the edge of the test piece shall be at least 5 mm, unless otherwise specified.

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