ISO 5940-1:2019

INTERNATIONAL ISO
STANDARD 5940-1
First edition
2019-10
Carbonaceous materials for the
production of aluminium — Pitch for
electrodes —
Part 1:
Determination of softening point by
the ring-and-ball method
Produits carbonés utilisés pour la production de l'aluminium — Brai
pour électrodes —
Partie 1: Détermination du point de ramollissement par la méthode
bille et anneau
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 1
6 Apparatus . 2
7 Procedure. 3
7.1 Preparation of test portion . 3
7.2 Preparation of the apparatus . 3
7.3 Determination . 3
8 Expression of results . 3
8.1 Method of calculation . 3
8.2 Precision . 4
9 Test report . 4
Annex A (normative) Thermionic devices for temperature sensing and output .5
Annex B (normative) Melting of pitch samples . 6
Foreword
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electrotechnical standardization.
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different types of ISO documents should be noted. This document was drafted in accordance with the
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.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 226, Materials for the production of
primary aluminium.
This first edition of ISO 5940-1 cancels and replaces ISO 5940:1981, which has been technically revised.
The main changes compared to the previous edition are as follows:
— 5.1.6 has changed to 6.1.2 which has been modified so that mercury thermometers are no longer
required.
— Annex A has been modified.
A list of all parts in the ISO 5940 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 5940-1:2019(E)
Carbonaceous materials for the production of
aluminium — Pitch for electrodes —
Part 1:
Determination of softening point by the ring-and-ball
method
1 Scope
This document specifies the ring-and-ball method, a method of using the ring-and-ball apparatus for
the determination of the softening point (softening temperature) of pitch used in the production of
aluminium.
The method is applicable to pitches having softening points equal to or greater than 30 °C.
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 6257, Carbonaceous materials used in the production of aluminium — Pitch for electrodes — Sampling
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle
Prepare a disc-shaped test piece by moulding a test portion in a ring, fitting the prepared ring into a
heated bath and placing a steel ball on the upper surface of the test piece.
Determine the temperature at which the test piece, on heating at a prescribed rate, softens sufficiently
to sag to a specified depth under the mass of the ball.
This temperature corresponds to the softening point (softening temperature).
5 Reagents
During the analysis, use only reagents of recognized analytical grade and distilled water, or water of
equivalent purity, freshly boiled and cooled.
5.1 Glycerol, for use with pitches having softening points greater than 85 °C.
5.2 Water, for use with pitches having softening points in the range 30 °C to 85 °C.
6 Apparatus
Ordinary laboratory apparatus and
6.1 Ring-and-ball apparatus (see Figure B.1 for assembled apparatus), comprising:
6.1.1 Rings, brass, tapered (see Figure B.2), having the dimensions:
— depth: 6,4 mm ± 0,1 mm;
— internal diameter at bottom: 15,9 mm ± 0,1 mm;
— internal diameter at top: 17,5 mm ± 0,1 mm;
— external diameter above shoulder: 20,6 mm
...