1、 ISO 2015 Carbonaceous materials for the production of aluminium Cathode block materials Part 2: Determination of the expansion due to sodium penetration without application of pressure Produits carbons utiliss pour la production de laluminium Blocs cathodiques Partie 2: Dtermination de lexpansion d
2、ue la pntration du sodium sans application de pression INTERNATIONAL STANDARD ISO 15379-2 Second edition 2015-05-15 Reference number ISO 15379-2:2015(E) ISO 15379-2:2015(E)ii ISO 2015 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2015, Published in Switzerland All rights reserved. Unless othe
3、rwise 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
4、below or ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org ISO 15379-2:2015(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3
5、 Principle 1 4 Apparatus . 1 5 Reagents 2 6 Sampling 2 7 Procedure. 3 8 Results . 3 8.1 Calculation 3 8.2 Precision . 3 9 Test report . 4 ISO 2015 All rights reserved iii Contents Page ISO 15379-2:2015(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of
6、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. Inte
7、rnational 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 in
8、tended 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 document should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.is
9、o.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the docu
10、ment 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 an
11、d expressions related to conformity assessment, as well as information about ISOs 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 226, Materials for the producti
12、on of primary aluminium. This second edition cancels and replaces the first edition (ISO 15379-2:2004), which has been technically revised. ISO 15379 consists of the following parts, under the general title Carbonaceous materials for the production of aluminium Cathode block materials: Part 1: Deter
13、mination of the expansion due to sodium penetration with application of pressure Part 2: Determination of the expansion due to sodium penetration without application of pressureiv ISO 2015 All rights reserved ISO 15379-2:2015(E) Introduction Expansion due to sodium penetration is an important proper
14、ty of carbon cathode blocks. As soon as alumina electrolysis starts, sodium penetrates into the carbon cathode blocks causing swelling of these blocks. This increase in volume creates mechanical stresses within the blocks and/or bulging of the bottom block plate. This can lead to cracks through whic
15、h liquid aluminium and/or liquid electrolyte can flow, reaching the thermal insulation beneath the blocks and destroying these ceramic materials. In such a case, the electrolysis cell has to be relined, resulting in loss of aluminium production and high expenses. Therefore, cathode blocks produced w
16、ith materials allowing only low sodium penetration and having the lowest possible expansion due to sodium penetration are preferred. The study can be supplemented by measuring electrical resistivity (see ISO 11713) before and after the test. ISO 2015 All rights reserved v Carbonaceous materials for
17、the production of aluminium Cathode block materials Part 2: Determination of the expansion due to sodium penetration without application of pressure 1 Scope This part of ISO 15379 specif ies a met hod t hat covers t he determinat ion of linear ex pansion under ex ternal pressure due to sodium penetr
18、ation in cathode-block materials used in the production of aluminium. The linear expansion of the blocks depends on the sampling direction due to anisotropy. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its
19、 application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results Part 2: Basic method for the determination of
20、 repeatability and reproducibility of a standard measurement method ISO 8007-1, Carbonaceous materials used in the production of aluminium Sampling plans and sampling from individual units Part 1: Cathode blocks ASTM E 220, Standard Test Method for Calibration of Thermocouples By Comparison Techniqu
21、es 3 Principle An anodic graphite crucible containing a cryolitic bath with an initial cryolite ratio of 4,0 and with a cathode carbon sample suspended in the bath, as shown in Figure 1, is used for this experiment. The whole assembly is heated to (980 5) C and is then electrolyzed for 2 h with a cu
22、rrent density of approximately 0,7 A/cm 2(see Clause 7). The expansion is measured by a probe, which is inserted into a hole that is drilled into the sample. 4 Apparatus The principle of the apparatus for measuring sodium expansion is shown in Figure 1. 4.1 Furnace, capable of maintaining a temperat
23、ure of 980 C, with a temperature gradient over the melt of less than 10 C. 4.2 Furnace control device, suitable for holding the temperature at (980 5) C. 4.3 T emperature-measuring device, i.e. a thermocouple, preferably type K or S, capable of determining the temperature to 5 C at 980 C. The thermo
24、couple should be calibrated in accordance with ASTM E 220. INTERNATIONAL ST ANDARD ISO 15379-2:2015(E) ISO 2015 All rights reserved 1 ISO 15379-2:2015(E) 4.4 Crucible, made of graphite, with an inner diameter of 90 mm. The crucible acts as an anode. 4.5 Copper pipe, with an outer diameter of 14 mm a
25、nd an inner diameter of 12 mm. The pipe acts as a sample holder and as a fixed reference for the expansion measurements. It also conducts current from the power supply to the sample. The pipe shall be threaded at one end and shall be long enough to extend out of the furnace when the sample is placed
26、 on the bottom of the crucible. 4.6 Inconel 1)rod, with a diameter of 5 mm, which is used to measure the expansion of the sample. The rod shall be placed inside the hole in the sample and shall reach out of the copper pipe. 4.7 Extensometer, connected to a computer or data recorder , with a measurin
27、g range of 10 mm and an accuracy of 1 m over the whole range, to observe the expansion due to sodium penetration. 4.8 Crucible holder or supporter, made of heat-resistant steel to conduct current from the power supply to the crucible. 4.9 Graphite powder, may be used to improve the electrical connec
28、tion between the crucible and the crucible holder. 4.10 Power supply, capable of supplying (54 1) A DC, with a current density of the cathode that shall be approximately 0,7 A/cm 2 . 5 Reagents 5.1 Argon, welding-grade quality. 5.2 Cryolite, Na 3 AlF 6 , natural, 99,7 % by mass or synthetic, 97 % by
29、 mass. 5.3 S odium fluoride, NaF, purum, 99 % by mass. 5.4 Calcium fluoride, CaF 2 , precipitated pure, 97 % by mass. 5.5 Alumina, Al 2 O 3 , extra pure, 98 % by mass. 5.6 Bath composition, which shall have a cryolite ratio of 4,0 and consist of the following: 71,5 % Na 3 AlF 6 , 14,5 % NaF , 5,0 %
30、CaF 2 , 9,0 % Al 2 O 3 . The bath is crushed to 2 mm using a jaw crusher and shall have a mass of 765 g. 6 Sampling Sample the material in accordance with ISO 8007-1. The diameter of the sample shall be (30,0 0,1) mm. The length shall be 100 mm. Drill a hole (6 mm ) centrally in the sample to a dept
31、h 10 mm above the bottom. The centred hole shall be threaded to a depth of (25 5) mm, i.e. the distance between the measuring points shall be (65 5) mm. The threaded hole shall have a diameter fitting the copper pipe. 1) Inconel is an example of a suitable product available commercially. This inform
32、ation is given for the convenience of users of this part of ISO 15379 and does not constitute an endorsement by ISO of this product.2 ISO 2015 All rights reserved ISO 15379-2:2015(E) 7 Procedure Mount the sample on the copper pipe (4.5). Determine the difference in position, l 0 , between the bottom
33、 end of the copper pipe and the bottom of the hole in the sample at room temperature. Prepare the bath in accordance with the conditions given in 5.6. Place the cryolitic bath components in the crucible (4.4). Place the crucible in the crucible holder (4.8). Graphite powder (4.9) can be used to impr
34、ove the electrical connection between the crucible and the crucible holder. Place the crucible and the holder in the furnace (4.1). Place the sample, which is attached to the copper pipe, above the bath allowing the sample to preheat together with the crucible. Insert the Inconel rod (4.6) through t
35、he copper pipe down to the bottom of the hole in the sample. Place the thermocouple (4.3) close to the crucible near the centre of the melt height. Heat the furnace to (980 5) C with an argon (5.1) flush. After reaching a stable temperature, insert the sample until the bottom end of the sample is 30
36、 mm above the bottom of the crucible. Place the extensometer holder on top of the copper pipe. The extensometer (4.7) shall rest on top of the Inconel rod (4.6). Detect the change in position between the copper pipe and the Inconel rod. Leave the sample to be heated by the bath until no further ther
37、mally induced movement can be detected in the sample and apparatus. Measure the difference in position between the copper pipe and the Inconel rod and take this reading as the zero reference for subsequent measurements of the change in length, l meas (t). Connect the power supply (4.10) to the cruci
38、ble holder and the copper pipe. Electrolyze the system for 2 h with a constant current of (54 1) A. Record the change in length, l meas (t), every minute. Then turn off the electrolysis. Remove the sample from the bath. Allow the furnace to cool down to room temperature. 8 Results 8.1 Calculation Ca
39、lculate the relative expansion of the sample for each recording using Formula (1): (1) where L(t) is the relative expansion, in percent, at time, t; l meas (t) is the measured change in length, in millimetres, at time, t; l 0 is the difference in position, in millimetres, between the bottom end of t
40、he copper pipe and the bottom end of the Inconel rod 1)at room temperature. Plot the relative expansion, L(t), versus time. Determine the maximum relative expansion, L max . Round the results to the second decimal place. 8.2 Precision The precision is calculated in accordance with ISO 5725-2. ISO 20
41、15 All rights reserved 3 ISO 15379-2:2015(E) The repeatability is calculated from Formula (2): (2) where L is the maximum average expansion; 0,03 is in absolute %. EXAMPLE Material A has a maximum average expansion equal to 0,70 %. The repeatability is then 0,22 0,70 + 0,03 = 0,18, in % absolute. Th
42、e reproducibility is calculated from Formula (3): (3) where the parameters are the same as for Formula (2). The degrees of freedom, i.e. number of laboratories (e.g. 4) times the number of samples (e.g. 3), is equal to 12. 9 Test report The report shall include the following information: a) referenc
43、e to this part of this International Standard (e.g. ISO 15379-2:2004); b) all details necessary for identification of the sample; c) direction of the sample relative to the extrusion or vibration direction; d) results of the test, including the maximum expansion, L max , in percent, due to sodium pe
44、netration and a plot of the relative expansion, L(t), due to sodium penetration versus time, t; e) date of the test; f) details of any unusual features noted during the determination; g) details of any operation not included in this part of ISO 15379 or regarded as optional.4 ISO 2015 All rights res
45、erved ISO 15379-2:2015(E) Dimensions in millimetres Key A Inconel 1)rod B sample holder (copper) C thermocouple (type K or S) D steel container E sample F graphite crucible G cryolite melt H graphite powder Figure 1 Apparatus for measuring expansion due to sodium penetration ISO 2015 All rights reserved 5 ISO 15379-2:2015(E) ISO 2015 All rights reserved IC S 71.100.10 Price based on 5 pages
