1、 Reference number ISO 14428:2005(E) ISO 2005INTERNATIONAL STANDARD ISO 14428 First edition 2005-08-15 Corrected version 2007-06-15 Carbonaceous materials for the production of aluminium Cold and tepid ramming pastes Expansion/shrinkage during baking Produits carbons utiliss pour la production de lal
2、uminium Ptes de brasquage froides et tides Expansion/rtrcissement durant la cuisson ISO 14428:2005(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are emb
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7、hed in Switzerland ii ISO 2005 All rights reservedISO 14428:2005(E) ISO 2005 All rights reserved iii 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
8、 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. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the w
9、ork. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare Int
10、ernational 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
11、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 14428 was prepared by Technical Committee ISO/TC 226, Materials for the production of primary aluminium. This corrected version of ISO 14428:2005 in
12、corporates the following correction: The publication date has been changed to 2005. ISO 14428:2005(E) iv ISO 2005 All rights reservedIntroduction The expansion/shrinkage of ramming pastes used in the production of aluminium is an important property, because excessive shrinkage can cause cracks in th
13、e baked paste serving as a lining material in alumina electrolysis cells. These cracks can cause leakage of the liquid bath, destroying the sidewall lining and the steel shell and thus leading to shut-down of the cell. Ramming pastes change phase from plastic to non- plastic between 400 C and 600 C
14、(200 C and 300 C for resin binders). The shrinkage which occurs between the temperature at which the paste becomes non-plastic and the operating temperature (950 C) is an important factor. Apparent shrinkage in the viscous range is due to slumping rather than actual shrinkage. INTERNATIONAL STANDARD
15、 ISO 14428:2005(E) ISO 2005 All rights reserved 1 Carbonaceous materials for the production of aluminium Cold and tepid ramming pastes Expansion/shrinkage during baking 1 Scope This International Standard specifies the determination of expansion/shrinkage during baking of cold and tepid ramming past
16、es used in the production of aluminium. 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 amendme
17、nts) applies. ISO 14422, Carbonaceous materials used in the production of aluminium Cold-ramming pastes Methods of sampling ISO 14427, Carbonaceous materials used in the production of aluminium Cold and tepid ramming pastes Preparation of unbaked test specimens and determination of apparent density
18、after compaction ASTM E220, Standard Test Method for Calibration of Thermocouples by Comparison Techniques 3 Principle The change in height of a rammed sample of paste is measured at temperatures increasing to 950 C, with a holding period of 3 h at the highest temperature. The shrinkage of the paste
19、 between the temperature at which the paste has become non-plastic and at 950 C (both before and after the holding period) is determined. 4 Apparatus and materials 4.1 Device for measuring the sample length, accurate to 0,1 mm. 4.2 Push-rod dilatometer, capable of determining changes in length of th
20、e specimen of 2 10 5l 0(i.e. 1 m for 50 mm length). The contact force of the extensometer shall not exceed 2 N. The expansion/shrinkage shall be measured vertically. An example of a vertical dilatometer is given in Figure 1. The dilatometer should preferably consist of a push rod and an outer tube m
21、ade of the same material. Vitreous silica is recommended as the material for the push rod and the outer tube. The gap between the outer tube and the sample shall not be less than 2 mm and not larger than 10 mm. If the sample-holding assembly is made of vitreous silica, see the precautions given in 6
22、.2. No irreversible changes should occur in the material in the temperature range 20 C to 950 C. ISO 14428:2005(E) 2 ISO 2005 All rights reservedKey 1 extensometer 2 lid 3 push rod 4 outer tube 5 carbon particles 6 disk 7 test specimen, 50 mm 8 thermocouple 9 furnace Figure 1 Example of quartz equip
23、ment for measuring thermal expansion/ shrinkage of ramming pastes samples having 50 mm diameter 4.3 Disk, preferably made of the same material as the outer tube, with the same diameter as the sample 0,1 mm and (2,0 0,5) mm thick, to be inserted on top of the sample. If the disk is made of vitreous s
24、ilica, see the precautions given in 6.2. 4.4 Carbon particles, used to support the sample during heating by filling the gap between the sample and the reference tube. ISO 14428:2005(E) ISO 2005 All rights reserved 3 The particle size shall be 1 mm. For example, the carbon material could be electroca
25、lcined anthracite or graphite. 4.5 Furnace, compatible with the dilatometer assembly, capable of attaining a temperature of 950 C, with a temperature gradient over the sample height of less than 10 C and with a furnace control device, suitable for the desired rate of increase in temperature of 3 C m
26、in 1 . 4.6 Temperature-measuring device, i.e. a thermocouple preferably type S (Pt/Pt10%Rh), capable of determining the temperature of the sample to 2 C in the temperature range 20 C to 950 C and calibrated in accordance with ASTM E220. 4.7 Inert gas, e.g. nitrogen 99,99 % pure. 4.8 Annealing furnac
27、e, capable of attaining a temperature of 1 100 C and with a furnace control device, suitable for the desired rate of decrease in temperature of 0,2 C min 1from 1 100 C to 900 C. 4.9 Reference sample, with shape and dimensions similar to those of samples usually tested in the test device, and certifi
28、ed by a national standards organization or laboratory. Vitreous silica, annealed according to 6.2, is recommended for the reference material. Care shall be taken to ensure that the thermal expansion behaviour of the reference material is not altered by the test. If the reference material is vitreous
29、 silica, it shall be annealed (or re-annealed) in accordance with 6.2 before certifying its properties. 4.10 Fine abrasive material, e.g. silicon carbide on paper or fabric. 5 Samples Sample the ramming paste in accordance with ISO 14422. Prepare the sample in accordance with ISO 14427. Keep the sam
30、ple in a closed box if it is not used within 1 h. The expansion/shrinkage measurement should preferably be started within 48 h after sample preparation. 6 Procedure 6.1 Cleaning Clean all the surfaces (push rod, reference tube, disk, support and extensometer holder) by removing binder condensate and
31、 coked material. If necessary, remove solid coating from the surface of the support with a fine abrasive material (4.10). Ensure the end surfaces of the sample-holding assembly are clean and smooth. If the sample-holding assembly is made of vitreous silica, it will gradually devitrify and thus shoul
32、d be changed regularly. 6.2 Preparation of vitreous silica materials Anneal the vitreous silica reference sample (4.9) and equipment made of vitreous silica (4.2, 4.3) before they are used for the first time, by first heating the vitreous silica to 1 100 C for 7 h in a suitable furnace (4.8) and the
33、n cooling it from 1 100 C to 900 C at a constant rate of 0,2 C min 1 . Then allow the vitreous silica to cool to room temperature. For the reference sample, perform this procedure before determining and certifying its properties. ISO 14428:2005(E) 4 ISO 2005 All rights reserved6.3 Calibration Calibr
34、ate the equipment. In order to correct the measured length, change, l meas (T), with respect to irregular thermal expansion of the different parts of the dilatometer (4.2), the test procedure laid down in 6.4 shall be carried out on a reference material with certified thermal expansion (4.9). Determ
35、ine the measured change in length of the reference material by making at least three separate determinations in accordance with 6.4, and calculate the average change in length, l ref (T). Perform the calibration at least each time any part of the equipment is changed. 6.4 Test procedure Measure the
36、length of the sample, 0 l , at room temperature with an accuracy of 0,1 mm. Insert the sample into the dilatometer (4.2) and fill the gap between the sample and the outer tube with carbon particles (4.4). Place a disk (4.3) on top of the sample and mount the rest of the equipment. Wait until the sig
37、nal from the extensometer is stable. Ensure that all parts of the dilatometer are able to move freely in the vertical direction, because any undesired contact will influence the expansion/shrinkage. Place the thermocouple (4.6) close to the sample. Determine the position of the dilatometer at the in
38、itial temperature, t 0 , and take this reading as zero for the uncorrected change in length, l meas (T), which will be measured. Heat the furnace (4.5) at a rate of 3 C min 1from room temperature to (950 5) C under an inert atmosphere (4.7). Keep the furnace at the highest temperature for 3 h (holdi
39、ng time) and then allow it to cool to room temperature. Record the temperature, T, and the related change in length, l meas (T), at least every 5 min. NOTE Coke packing could hinder shrinkage, especially for wet paste. Coke packing could hinder measurement of CTE by cooling. 7 Results 7.1 Calculatio
40、n of the correction term Calculate the correction term for each temperature from the following equation: corr ref real () () () lTlTlT = (1) where l corr (T) is the correction term at temperature T, in mm; l ref (T) is the measured change in length of the reference material at temperature T, in mm;
41、l real (T) is the actual change in length at temperature T supplied by the certifier, in mm. 7.2 Calculation of the expansion/shrinkage Calculate the expansion or shrinkage for each temperature from the following equation. () () ( ) meas corr 0 100 lTlT LT l = (2) ISO 14428:2005(E) ISO 2005 All righ
42、ts reserved 5 where L(T) is the expansion/shrinkage at temperature T, in %, rounded off to the nearest 0,01 %; l meas (T) is the uncorrected change in length at temperature T, in mm; l corr (T) is the correction term at temperature T, in mm; l 0is the initial sample length, in mm. Plot a curve of th
43、e expansion, L(T), versus the temperature, T (see Figure 2). Using the curve and the calculated data, determine the following (see Figure 2): a) the expansion, in %, (plateau or maximum), L A , at the temperature at which the paste has become non- plastic usually between 400 C and 600 C (200 C and 3
44、00 C for resin binders) with the corresponding temperature, T A , in C; b) the expansion at the highest temperature before the holding period, L B , in %; c) the expansion after 3 h of holding at top temperature, L C , in %. Calculate the maximum thermal shrinkage before hold, L before , in %, from
45、the following equation: before A B L LL = (3) Calculate the maximum thermal shrinkage after the hold period, L after , in % from the following equation: after A C L LL = (4) Key X temperature, C Y expansion, % Figure 2 Example of a record of change in length versus temperature ISO 14428:2005(E) 6 IS
46、O 2005 All rights reserved8 Test report The test report shall include the following information: a) a reference to this International Standard, i.e. ISO 14428:2005; b) all details necessary for identification of the sample; c) sample size; d) the temperature used for sample preparation; e) the resul
47、ts of the test: the expansion (plateau or maximum) at the temperature at which the paste has become non-plastic, usually between 400 C and 600 C (200 C and 300 C for resin binders), L A , in %, with the corresponding temperature, T A , in C, the maximum thermal shrinkage before hold, L before , in %
48、, the maximum thermal shrinkage after the hold period, L after , in %, the curve of L(T) versus temperature, T; f) the date of the test; g) details of any unusual features noted during the determination; h) details of any operation not included in this International Standard or regarded as optional. ISO 14428:2005(E) ICS 71.100.10 Price based on 6 pages ISO 2005 All rights reserved
