ISO INTERNATIONAL 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 I'aluminium - Brai pourélectrodes Partie 2: Détermination du point de ramollissement (Point de ramollissement par la methode Mettler) Reference number ISO 5940-2:2007(E) ii 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 International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. 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. 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 aluminiumPitch 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) ii Introduction Kohlenstoff und Graphit" and published by DIN, Deutsches Institut fur Normung e.V., Berlin. 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 Carbonaceous materials used in the production of aluminium Pitch for electrodes - Part 2: Determination of the softening point (Mettler softening point method) 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 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. Apparatus and reagents 4.1 Test apparatus1) (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