ISO 5940-2:2007

INTERNATIONAL ISO
STANDARD 5940-2
First edition
2007-05-01
Carbonaceous materials used in the
production of aluminium — Pitch for
electrodes —
Part 2:
Determination of the softening point
(Mettler softening point method)
Produits carbonés utilisés pour la production de l'aluminium — Brai
pour électrodes —
Partie 2: Détermination du point de ramollissement (Point de
ramollissement par la méthode Mettler)

Reference number
©
ISO 2007
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Foreword
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(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
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ISO 5940-2 was prepared by Technical Committee ISO/TC 226, Materials for the production of primary
aluminium.
ISO 5940 consists of the following parts, under the general title Carbonaceous materials used in the
production of aluminium — Pitch for electrodes:
⎯ Part 1: Determination of the softening point by the ring-and-ball method (will replace ISO 5940:1981)
⎯ Part 2: Determination of the softening point (Mettler softening point method)

Introduction
This part of ISO 5940 is based on DIN 51920 Testing of carbonaceous materials — Determination of the
Mettler softening point — Binding and impregnating materials, prepared by NMP 281 "Prüfverfahren für
Kohlenstoff und Graphit" and published by DIN, Deutsches Institut für Normung e.V., Berlin.
Coal-tar pitch is used as a binding and impregnating agent in the production of carbon anodes for primary
aluminium metal production. When heated, pitch transforms gradually from a solid to a liquid. The analytical
determination of a softening point described in this method is useful for characterizing this thermal behaviour
of the coal-tar pitch when used as binder. The softening point is expressed as a temperature, in degrees
Celsius (°C).
Annex A gives an approximate comparison with softening points determined by other methods.

iv © ISO 2007 – All rights reserved

INTERNATIONAL STANDARD ISO 5940-2:2007(E)

Carbonaceous materials used in the production of aluminium —
Pitch for electrodes —
Part 2:
Determination of the softening point (Mettler softening point
method)
1 Scope
This part of ISO 5940 specifies a method to determine the softening point of pitches by the Mettler method,
within the range of 50 °C to 180 °C.
It can be used for other organic materials that are used as binder and impregnating agents, where they have a
Mettler softening point within the range of 50 °C to 150 °C.
2 Normative references
The following referenced documents are indispensable for the application 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
DIN 1333, Presentation of numerical data
DIN 51848-1, Testing of mineral oils — Precision — General introduction, definitions and application to
specifications
3 Principle
A test portion of pitch is placed within a cylindrical sample cup with an outlet diameter of 6,35 mm. The
temperature is increased under constant conditions in air, until softened material issues from the outlet and
interrupts a light barrier 19 mm below.
4 Apparatus and reagents
1)
4.1 Test apparatus (see Figure 1) consisting of the parts given in 4.1.1 to 4.1.7.
4.1.1 Electrically heated furnace.
4.1.2 Sample cup (see Figure 2), made from chrome-plated yellow brass or chrome nickel-steel.
4.1.3 Resistance thermometer, capable of measuring temperatures from 50 °C to 180 °C.
4.1.4 Cup holder.
4.1.5 Light barrier, capable of sensing the material as it issues from the sample cup.
4.1.6 Control unit, with a temperature indicator for the thermometer (4.1.3), and an indicator to show the
operational status of the machine.
4.1.7 Collector, for the softened material.
4.2 Bowl, made of porcelain, Teflon or metal with a volume of about 50 ml.
4.3 Plate, with a smooth surface, e.g. made of metal or glass.
4.4 Knife or spatula.
4.5 Release agent for cup, e.g. a mixture of glycerine and dextrin, ratio 1:1.
4.6 Electro-hydraulic press, as described in ASTM D3104, or another suitable press for filling the sample
cup with grindable binder.
4.7 Punch, suitable for pressing grindable pitch.
4.8 Balance, capable of weighing grindable pitch to an accuracy of 0,1 g.

1) Available from Mettler Toledo Inc. http://www.mt.com. Further information on sources of supply can be obtained from:
DIN-Bezugsquellen für normgerechte Erzeugnisse of DIN Deutsches Institut für Normung e. V., Burggrafenstraße 6,
D-1000 Berlin 30. This information is given for the convenience of users of this part of ISO 5940 and does not constitute
an endorsement by ISO of this apparatus.
2 © ISO 2007 – All rights reserved
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