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1、BRITISH STANDARD BS 6043-4.8: 1991 Methods of sampling and test for Carbonaceous materials used in aluminium manufacture Part 4: Cold ramming pastes Section 4.8 Determination of electrical resistivity of baked rammed paste NOTEIt is recommended that this Section be read in conjunction with the gener
2、al information in BS 6043-4.0, published separately. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:28:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6043-4.8:1991 This British Standard, having been prepared under the direction of the Chemicals Standards Policy Committee, was published
3、under the authority of the Standards Board and comes into effect on 30 September 1991 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference CIC/24 Draft for comment 90/54848 DC ISBN 0 580 19732 8 Committees responsible for this British Standard The prepara
4、tion of this British Standard was entrusted by the Chemicals Standards Policy Committee (CIC/-) to Technical Committee CIC/24, upon which the following bodies were represented: Aluminium Federation British Ceramic Research Ltd. Chemical Industries Association Institute of Petroleum Refractories Asso
5、ciation of Great Britain Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:28:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6043-4.8:1991 BSI 10-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Princi
6、ple1 3Materials1 4Apparatus1 5Sampling1 6Preparation of test samples1 7Procedure1 8Calculation and expression of results2 9Test report2 Publication(s) referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:28:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6043-4.8:1
7、991 ii BSI 10-1999 Foreword This Section of BS 6043 has been prepared under the direction of the Chemicals Standards Policy Committee to provide a method of test for cold ramming pastes used in the production of aluminium. There is no corresponding International Standard; however, it is intended, up
8、on publication of this Section of BS 6043, that it be offered to the International Organization for Standardization (ISO) for possible adoption as an International Standard. It is essential to use BS 6043-4.1, BS 6043-4.6 and BS 6043-4.7 in conjunction with this Section of BS 6043. This standard des
9、cribes a method of test only, and should not be used or quoted as a specification defining the characteristics of a product. Reference to this Section should indicate that the method of test used is in accordance with BS 6043-4.8:1991. A British Standard does not purport to include all the necessary
10、 provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 an
11、d 2, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:28:06 GMT+00:00 2006, Uncontrol
12、led Copy, (c) BSI BS 6043-4.8:1991 BSI 10-19991 1 Scope This Section of BS 6043 describes a method for the determination, at ambient temperature, of the electrical resistivity of test pieces of baked rammed cold ramming paste used in aluminium manufacture. NOTEThe titles of the publications referred
13、 to in this standard are listed on the inside back cover. 2 Principle A baked test piece of known dimensions is produced from a test sample of cold ramming paste by ramming under regulated conditions followed by baking according to a defined programme. A constant direct electric current is passed lo
14、ngitudinally through the test piece and the electrical potential is measured between two longitudinally spaced points near the centre of the test piece using a bridge, potentiometer or voltmeter. 3 Materials 3.1 Copper gauze, approximately two threads per millimetre, bright, annealed. 3.2 Aluminium
15、foil, of thickness approximately 20 m. 3.3 Metallurgical or regular-grade petroleum coke, as described in 5.1 of BS 6043-4.7. 3.4 Refractory cement, for sealing the lid of the baking box. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Ramming apparatus, and the other apparatus described in clause
16、 4 of BS 6043-4.7:1991. 4.3 Test-piece holder, having two parallel metal plates electrically insulated from each other and capable of being clamped in contact with the full area of the end faces of the test piece, with connections for passing an electric current through the test piece. 4.4 Source of
17、 direct electric current, capable of being adjusted to pass a direct electric current of the order of 500 mA through the test piece, and capable of indicating and maintaining the set current with an accuracy of 0.5 %. 4.5 Potential measuring equipment, comprising a bridge, potentiometer or high-impe
18、dance voltmeter capable of measuring the potential developed on the test piece with an accuracy of 0.5 %. 4.6 Potential probe, having two sharp-pointed electrical contact pins set in an electrically-insulating body, at a fixed spacing of 50 0.1 mm. The actual spacing shall be checked and recorded at
19、 the start of each series of determinations. 4.7 Vernier callipers, capable of measuring lengths of not less than 150 mm, and having a vernier graduated in 0.1 mm or smaller units. 4.8 Electric oven, capable of being controlled at 110 5 C. 5 Sampling Prepare a representative laboratory sample of col
20、d ramming paste in accordance with BS 6043-4.1. 6 Preparation of test samples Prepare at least two test samples from the laboratory sample (see clause 5) by the method described in 7.1 and 7.3 of BS 6043-4.7:1991. 7 Procedure 7.1 Preparation of baked test pieces Prepare two test pieces by ramming th
21、e test samples (see clause 7) by the method described in 8.2 of BS 6043-4.7:1991 using the ramming apparatus (4.2). If the cold ramming paste requires pre-curing before baking, pre-cure the test pieces in accordance with 8.3 of BS 6043-4.7:1991. Bake the test pieces by the method described in 8.4 of
22、 BS 6043-4.7:1991. 7.2 Determination 7.2.1 On each of the baked test pieces (see 7.1) carry out the operations described in 7.2.2 to 7.2.6. 7.2.2 Dry the test piece by heating it for 2 h in the oven (4.8), controlled at 110 5 C, then place it in a desiccator to cool to ambient temperature. Keep the
23、test piece in the desiccator until it is required for testing. 7.2.3 Measure the diameter of the test piece in the central region using the vernier callipers (4.7), making two measurements mutually at right angles. Measure to the nearest 0.1 mm and calculate the mean of the two measurements to the n
24、earest 0.1 mm. 7.2.4 Place the test piece (7.1) in the holder (4.3) with a flat pad comprising several thicknesses of the copper gauze (3.1) or the aluminium foil (3.2) between each end face of the test piece and the corresponding parallel metal plate of the holder. Clamp the test piece in the holde
25、r, using the minimum force necessary to ensure reliable electrical contact over the whole area of the end faces of the test piece. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:28:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6043-4.8:1991 2 BSI 10-1999 7.2.5 Pass an electric current
26、(see 4.4) through the test piece, selecting a magnitude for the current which allows the developed potential to be measured by the potential measuring equipment (4.5) with a limit of error in the reading of less than 0.5 %, e.g. for a digital voltmeter reading to 0.01 mV, a minimum reading of 2.00 m
27、V is obtained. Ensure that the selected magnitude of the current is not sufficient to cause any detectable change in the resistance of the test piece due to electrical heating during the test. Record the current used to a precision of 0.5 %. 7.2.6 Using the potential probe (4.6) connected to the pot
28、ential measuring equipment (4.5), take four readings of the developed potential at approximately 90 circumferential spacing, with the pins of the probe positioned longitudinally with respect to the test piece in its central region. Calculate the mean of the four readings to a precision of 0.5 %. 7.3
29、 Validation of data If the range of the four potential readings (7.2.6) is greater than 5 % of the mean value, repeat the measurements in accordance with 7.2.6 with the probe positioned at new locations close to the original positions and calculate a new mean value to a precision of 0.5 %. If the ra
30、nge of the new set of readings is less than 5 % of the mean, take the data as valid. Persistently anomalous or fluctuating values indicate the presence of a major inhomogeneity in the test piece; in this case discard the test piece, reject the result and repeat the determination, by following the op
31、erations described in 7.1 and 7.2.2 to 7.2.6 with a new test piece. Take the mean of the four validated readings of the potential to calculate the electrical resistivity of the test piece. 8 Calculation and expression of results Calculate the electrical resistivity, E, of the test piece, in 7m, from
32、 the following equation: where: Calculate the electrical resistivity for each test piece (see 7.1) to three significant figures. If the results obtained for the two test pieces differ by more than 10 % of the lower value, reject the results and the test pieces and repeat the procedure starting with
33、fresh test samples (see clause 6). Express the mean electrical resistivity of the two test pieces (see 7.1) to three significant figures. NOTETypical values generally fall in the range 5 7m to 100 7m. 9 Test report The test report shall include the following information: a) a complete identification
34、 of the test pieces including details of the cold ramming paste and of its compaction, baking and any other treatment; b) a reference to this British Standard, i.e. BS 6043-4.8:1991; c) the value of the mean electrical resistivity of the two test pieces, calculated and expressed in accordance with c
35、lause 8; d) any unusual features noted during the determination; e) any operation not included in this British Standard or regarded as optional. Vis the mean validated potential (see 7.3) (in mV); Dis the mean diameter of the test piece (see 7.2.3) (in mm); Cis the current passing through the test p
36、iece (see 7.2.5) (in A); Lis the distance between the pointed tips of the potential probe (4.6) (in mm). E V D/2()2 CL - -= Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:28:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6043-4.8:1991 BSI 10-1999 Publication(s) referred to BS 6043, Meth
37、ods of sampling and test for carbonaceous materials used in aluminium manufacture. BS 6043-4, Cold ramming pastes. BS 6043-4.0, General introduction1). BS 6043-4.1, Methods of sampling. BS 6043-4.6, Determination of maximum rammed apparent density. BS 6043-4.7, Preparation of baked rammed test piece
38、s and determination of baked apparent density, change in volume and loss in mass. 1) Referred to on the front cover only. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:28:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6043-4.8: 1991 BSI 389 Chiswick High Road London W4 4AL BSI British
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