1、 ISO 2015 Carbonaceous materials for the production of aluminium Cathode block materials Part 1: Determination of the expansion due to sodium penetration with application of pressure Produits carbons utiliss pour la production de laluminium Blocs cathodiques Partie 1: Dtermination de lexpansion due
2、la pntration du sodium avec application de pression INTERNATIONAL STANDARD ISO 15379-1 Second edition 2015-05-15 Reference number ISO 15379-1:2015(E) ISO 15379-1:2015(E)ii ISO 2015 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2015, Published in Switzerland All rights reserved. Unless otherwi
3、se 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 bel
4、ow 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 15379-1:2015(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 Pr
5、inciple 1 4 Apparatus . 1 5 Reagents 2 6 Samples 3 7 Procedure. 3 8 Results . 4 8.1 Calculation 4 8.2 Precision . 4 9 Test report . 4 ISO 2015 All rights reserved iii Contents Page ISO 15379-1:2015(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of nati
6、onal 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. Internat
7、ional 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 intend
8、ed 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. www.iso.o
9、rg/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
10、in the Introduction and/or on the ISO list of patent declarations received. 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 relat
11、ed 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 production of primary alumi
12、nium. This second edition cancels and replaces the first edition (ISO 15379-1:2004), 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: Determination of the exp
13、ansion 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 15379-1:2015(E) Introduction Expansion due to sodium penetration is an important property of carbon cathod
14、e 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 which liquid aluminium
15、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 with materials allow
16、ing 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. Due to thermal and sodium expansion when heating up the cathode blocks in the
17、 electrolysis cells to operational temperature, the block will be subject to pressure from the steel shell; therefore, in the present method, 5 MPa is chosen as a realistic maximum pressure. ISO 2015 All rights reserved v Carbonaceous materials for the production of aluminium Cathode block materials
18、 Part 1: Determination of the expansion due to sodium penetration with application of pressure 1 Scope This part of ISO 15379 specifies a method that covers the determination of linear expansion under external pressure due to sodium penetration in cathode-block materials used in the production of al
19、uminium. 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 application. For dated references, only the edition cited ap
20、plies. 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 repeatability and reproducibility of a standard measurement
21、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 Techniques 3 Principle An anodic graphite crucible containing a cryol
22、itic bath with an initial cryolite ratio of 4,0 and with a cathode carbon sample placed in the crucible, as shown in Figure 1, is used for this experiment. The whole sample is immersed in a cryolitic bath with a graphite cylinder fitted as an extension from the sample. The crucible is placed in a cr
23、ucible support, which is connected to a hydraulic power cylinder. A constant pressure of 5 MPa is applied to the sample by pressing the graphite cylinder against a stop rod in the top of the furnace by the hydraulic power cylinder. The whole assembly is heated in a tubular furnace to (980 5) C and i
24、s then electrolyzed for 2 h with a current density of approximately 0,7 A/cm 2(see Clause 7 for precise setting). The expansion is measured by a probe, which is fastened to the frame of the furnace and measures the position of the crucible support. 4 Apparatus The principle of the apparatus for meas
25、uring sodium expansion is shown in Figure 1. 4.1 Furnace, capable of maintaining a temperature 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. INTERNATIONAL ST ANDARD ISO 15379-1:2015(E) ISO 2015 Al
26、l rights reserved 1 ISO 15379-1:2015(E) 4.3 Temperature-measuring device, i.e. a thermocouple, preferably of type K or S, capable of determining the temperature to 5 C at 980 C. The thermocouple should be calibrated in accordance with ASTM E 220. 4.4 Crucible, made of graphite, with an inner diamete
27、r of 90 mm and an inner height of 90 mm. The crucible acts as an anode. 4.5 Lid, made of graphite, which shall have a hole in the centre to allow the sample/graphite extension to reach above the lid. 4.6 Insulating ring, made of a ceramic material, which resists the temperature and the fluoride envi
28、ronment. The ring shall be placed in the hole of the graphite lid and act as an electrical insulation between the lid and the sample/graphite extension. The ring shall be large enough to allow the sample/graphite extension to move freely in the vertical direction. 4.7 Crucible support, made of heat-
29、resistant steel to conduct anodic current from the power supply to the crucible. 4.8 Stop rod, made of heat-resistant steel to conduct cathodic current to the top of the sample. The stop rod acts as a fixed reference point for the expansion measurements. The material for the steel support and the st
30、eel stop rod should have minimal deformation at a pressure of 5 MPa. NOTE The steel quality Sanicro 31HT 1) , X 10 NiCrAlTi32.20 has been shown suitable for the crucible support rod and the stop rod. If other steel grades are used, it has to be verified that they do not deform significantly versus t
31、he length change of the sample. 4.9 Alumina disk, capable of covering the bottom of the crucible and capable of acting as electrical insulation between the crucible and the sample. The disk should preferably have a centring slot to help position the sample in the centre of the crucible. 4.10 Graphit
32、e cylinder, which shall be used as an extension to the sample and shall have a diameter of (30,0 0,1) mm and a length of (40 1) mm. 4.11 Hydraulic power cylinder, capable of applying a constant pressure of 5 MPa 0,1 MPa during the whole experiment independent of the expansion of the sample. 4.12 Ext
33、ensometer, connected to a computer or data recorder , with a measuring range of 10 mm and an accuracy of 1 m over the whole range, in order to observe the expansion due to sodium penetration. 4.13 Power supply, capable of supplying 39,6 A DC, with a current density of the cathode which shall be 0,7
34、A/cm 2 . 5 Reagents 5.1 Argon, welding-grade quality. 1) Sanicro 31HT is an example of a suitable product available commercially. This information 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 reser
35、ved ISO 15379-1:2015(E) 5.2 Cryolite, Na 3 AlF 6 , natural, 99,7 % by mass or synthetic, 97 % by 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 ha
36、ve a cryolite ratio of 4,0 and consist of the following: 71,5 % Na 3 AlF 6 , 14,5 % NaF , 5,0 % 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 Samples Sample the material in accordance with ISO 8007-1. The diameter of the sample shall be (3
37、0,0 0,1) mm. The length shall be (60 1) mm. 7 Procedure Assemble the crucible support (4.7) with the crucible (4.4) and the sample so they can be pressed together with a hydraulic power cylinder against a heat-resistant steel stop rod (4.8) conducting the cathodic current to the top of the sample (s
38、ee Figure 1). The stop rod (4.8) acts as a fixed reference point for the expansion measurements. Place the alumina disk (4.9) in the bottom of the crucible (4.4). Measure the length, l 0 , of the sample at room temperature with an accuracy of 0,1 mm. Place the sample on the alumina disk in the centr
39、e of the crucible. Place the graphite cylinder (4.10) on top of the sample. Fill the crucible with the bath prepared in accordance with 5.6. Place the lid (4.5), with an insulating ring (4.6) around the graphite extension, on top of the crucible. Lift the crucible by the hydraulic power cylinder ( 4
40、.11) until the sample touches the stop rod (4.8) inside the furnace (4.1). Adjust the hydraulic pressure to 5 MPa. Place the thermocouple close to the crucible near the centre of the melt height. Place the extensometer (4.12) underneath the base of the crucible holder outside the furnace. Heat the f
41、urnace to (980 5) C with an argon (5.1) flush, and measure the change in the length of the sample and the apparatus. Wait until no further thermally induced movement can be detected in the sample and apparatus. Determine the position of the crucible support and take this reading as the zero referenc
42、e for subsequent measurements of the change in length, l meas (t). Connect the power supply (4.13) to the crucible support and the stop rod. Electrolyze the system for 2 h with a constant current of 39,6 A. Record the change in length, l meas (t), every minute. Then, turn off the electrolysis. Relea
43、se the pressure, but keep the crucible inside the furnace. Allow the furnace to cool down to room temperature. ISO 2015 All rights reserved 3 ISO 15379-1:2015(E) 8 Results 8.1 Calculation Calculate the relative expansion of the sample for each recording using Formula (1): (1) where L(t) is the relat
44、ive expansion, in percent, at time, t; l meas (t) is the measured change in length, in millimetres, at time, t; l 0 is the initial sample length, in millimetres. Plot the relative expansion, L(t), versus time. Determine the maximum relative expansion, L max . Round the results to the second decimal
45、place. 8.2 Precision The precision is calculated in accordance with ISO 5725-2. The repeatability is calculated from Formula (2): (2) where L is the maximum average expansion; 0,02 is in absolute %. EXAMPLE Material A has a maximum average expansion equal to 0,56 %. The repeatability is then 0,20 0,
46、56 + 0,03 = 0,15, in % absolute. The 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
47、 following information: a) reference to this part of this International Standard (e.g. ISO 15379-1:2015); 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
48、 max , in percent, due to sodium penetration and a plot of the relative expansion, L(t), due to sodium penetration versus time, t;4 ISO 2015 All rights reserved ISO 15379-1:2015(E) e) date of the test; f) details of any unusual features noted during the determination; g) details of any operation not
49、 included in this part of ISO 15379 or regarded as optional. ISO 2015 All rights reserved 5 ISO 15379-1:2015(E) Dimensions in millimetres Key A heat-resistant steel stop rod G graphite crucible B insulating ring H sample C thermocouple (type K or S) I alumina disk D graphite lid J heat resistant steel crucible support E graphite cylinder (sample extension) K hydraulic power cylinder F cryolite melt L
