1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 1902 : Section 5.14 :
2、1992 Incorporating Amendment No. 1 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Methods of testing Refractory materials Part 5. Refractory and thermal properties Section 5.14 Determination of thermal expansion (temperatures up to 1500 C) (methods 1902-514)BS 1902 : Section
3、5.14 : 1992 Issue 2, January 1998 This British Standard, having been prepared under the direction of the Refractory Products Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 June 1992 BSI 1998 The following BSI references relate to the
4、work on this standard: Committee reference RPM/1 Draft for comment 90/47759 DC ISBN 0 580 20668 8 Amendments issued since publication Amd. No. Date Text affected 8740 January 1998 Indicated by a sideline in the margin Committees responsible for this British Standard The preparation of this British S
5、tandard was entrusted by the Refractory Products Standards Policy Committee (RPM/-) to Technical Committee RPM/1, upon which the following bodies were represented: British Ceramic Research Ltd. British Industrial Ceramic Manufacturers Association British Steel Industry Refractories Association of Gr
6、eat Britain Refractory Contractors Association Society of Glass TechnologyIssue 1, January 1998 BS 1902 : Section 5.14 : 1992 BSI 1998 a Summary of pages The following table identifies the current issue of each page. Issue 1 indicates that a page has been introduced for the first time by amendment.
7、Subsequent issue numbers indicate an updated page. Vertical sidelining on replacement pages indicates the most recent changes (amendment, addition, deletion). Page Issue Page Issue Front cover Inside front cover a b 1 2 3 4 2 2 1 blank 2 original 2 original 5 6 7 8 9 10 Inside back cover Back cover
8、original original original 2 1 1 original 2b blankIssue 2, January 1998 BS 1902 : Section 5.14 : 1992 BSI 1998 1 | | | | Contents Page Committees responsible Inside front cover Foreword 2 Methods 1 Scope 3 2 Designation 3 3 Definitions 3 4 Principle 3 5 Apparatus 3 6 Test pieces 6 7 Calibration 6 8
9、Procedure 6 9 Calculation and expression of results 7 10 Test report 7 Appendices A Requirement for accuracy 8 B Methods for testing investment casting shell moulds 8 Table 1 Thermal expansion reference data for polycrystalline alumina relative to 20 C 5 Figures 1 Horizontal dilatometer 3 2 Vertical
10、 dilatometer 4 B.1 Apparatus for testing investment casting shell moulds 92 BS 1902 : Section 5.14 : 1992 Foreword This Section of BS 1902 : Part 5 has been prepared under the direction of the Refractory Products Standards Policy Committee. The horizontal method given provides an increase in the tem
11、perature of use from 1100 C to 1500 C, when compared with that given in BS 1902 : Section 5.3 : 1990. The vertical method is essentially a scaled-down version of BS 1902 : Section 5.4 : 1989. NOTE. This Section is to be read in conjunction with BS 1902 : Section 5.0 Introduction and BS 1902 : Sectio
12、n 3.1 Guidance on sampling. Section 5.0 sets out the general arrangement of BS 1902 and lists the Sections of Part 5. Compliance with a British Standard does not of itself confer immunity from legal obligations. BSI 1998 3 Issue 2, January 1998 BS 1902 : Section 5.14 : 1992 Figure 1. Horizontal dila
13、tometer Methods | | | | | | 1 Scope This Section of BS 1902 : Part 5 describes two methods for determining the thermal expansion of refractory materials. The methods are applicable to products which have been fired to a temperature equal to or greater than the upper limit of intended testing, and ma
14、y also be used with oxidizable materials if the equipment is fitted with means to produce a reducing atmosphere. The maximum temperature for testing is 1500 C. NOTE 1. The methods may be used to determine the dimensional changes occurring during heating of unfired materials, which is not usually des
15、cribed as thermal expansion. NOTE 2. The titles of the publications referred to in this standard are listed on the inside back cover. Appendix B gives the method for testing investment casting shell moulds. This method is for determination of both thermal expansion and contraction as a function of t
16、emperature and time, and is applicable to all shell mould test pieces whether in a green or fired condition. 2 Designation The methods described in this Section may be referred to by the following designations: horizontal: method 1902 - 514/1 vertical: method 1902 - 514/2 3 Definitions For the purpo
17、ses of this Section of BS 1902 : Part 5, the following definitions apply. 3.1 thermal expansion The proportional extension which occurs when a material is heated. 3.2 thermal expansion coefficient The proportional extension which occurs when a material is heated over a temperature interval of 1 K. 3
18、.3 mean thermal expansion coefficient The average value of thermal expansion coefficient over a temperature range T 1 to T 2 . 4 Principle A test piece is heated at a specified, uniform rate and its change in length and temperature measured either continuously or at regular and frequent intervals du
19、ring the heating. The thermal expansion, relative to ambient temperature, is calculated for the temperature of the test piece and the results either plotted as a graph or expressed as a mean coefficient of expansion for a given temperature range. In the horizontal method, the test piece is a bar or
20、cylinder with the temperature being measured at the mid-point of the upper surface. In the vertical method, the test piece is a vertically mounted hollow cylinder with the temperature being measured at its geometric centre. 5 Apparatus 5.1 Furnace, capable of heating the test piece evenly such that
21、the temperature variation along the length of the test piece is not greater than 5 K. The assembly of test piece and measuring device for the horizontal method is illustrated diagrammatically in figure 1. NOTE. Equipment is available which performs the horizontal method in a vertical mode, which is
22、outside the scope of this standard. The assembly of the test piece and measuring device for the vertical method is illustrated diagrammatically in figure 2.4 BS 1902 : Section 5.14 : 1992 Figure 2. Vertical dilatometer5 BS 1902 : Section 5.14 : 1992 For both methods, the construction materials for t
23、he test piece holder, push rod and measuring tubes shall be an alumina ceramic of at least 99.8 % Al 2 O 3 content and with a minimum density of 3.70 g/cm 3 . For the vertical method only, such a material shall also be used for the spacers and restraint shown in figure 2. The upper end of the inner
24、sensing tube is restrained by means of a cylinder of alumina, 35 mm in diameter and 17 mm to 50 mm in height, placed on top of the upper spacer. The height of the restraint, and hence its mass, is determined by the strength of the spring in the measuring device (5.2). The expansion of the alumina tu
25、bes is taken up by a floating mechanism in the measuring device. 5.2 Measuring device, for measuring changes in the length of the test piece which may be one of the following. a) A dial gauge with jewel bearings with a minimum range of 5 mm and a scale graduated to 0.002 mm. b) A digital displacemen
26、t indicator with a minimum range of 5 mm reading to an accuracy of 0.002 mm. c) A linear transducer with a minimum range of 5 mm and linearity of 0.1 % or better, with a millivolt-meter of suitable range and linearity of 0.1 % or better. d) A linear transducer for automatic recording, with a minimum
27、 range of 5 mm, linearity of 0.1 % or better and an X-Y recorder which has linearity and repeatability better than 0.1 % of full-scale deflection and variable control of sensitivity on ranges. 5.3 Instrumentation, for controlling the furnace and measuring the temperature of the test piece via the th
28、ermocouple (5.4) consisting of one of the following. a) For a manual recording system, a ramp generator/controller with PID (proportional, integral, derivative) control, with digital temperature display, a range of at least 20 C to 1500 C and an accuracy of temperature measurement of 0.3 % of full s
29、cale. b) For an automatic recording system, a ramp generator/controller as specified in (a) with analogue signal output for connection to the X-Y recorder (5.2(d). 5.4 Thermocouple, platinum-13 % rhodium/platinum, Type R in accordance with BS 4937 : Part 2. The thermocouple is used as part of the fu
30、rnace temperature control system and also as an indicator of the temperature of the test piece. 5.5 Vernier callipers, complying with BS 887. 5.6 Reference material, used to obtain the calibration data to correct the measured change in length of a test piece (see clause 7). The correction to be appl
31、ied is obtained by calibration using a test piece prepared (preferably) from polycrystalline alumina of at least 99.8 % Al 2 O 3 and with a minimum density of 3.70 g/cm 3 . Thermal expansion reference data for this material are given in table 1. The use of any reference material other than this shal
32、l be reported, together with the reference data used. Table 1. Thermal expansion reference data for polycrystalline alumina relative to 20 C Temperature Relative expansion C % 20 0.000 50 0.018 100 0.049 200 0.117 300 0.190 400 0.270 500 0.354 600 0.442 700 0.532 800 0.625 900 0.720 1000 0.818 1100
33、0.920 1200 1.018 1300 1.112 1400 1.211 1500 1.305 NOTE. For the purposes of achieving the overscale accuracy levels of this method, the data given in table 1 are considered adequately accurate without certification of reference specimens. If there is any doubt concerning the origin or quality of the
34、 reference material, it should be certified independently.6 BS 1902 : Section 5.14 : 1992 6 Test pieces 6.1 Horizontal method The size and shape of the test piece shall be between 35 mm and 50 mm long and have a 10 mm 2m m diameter or octagonal cross section. NOTE. Octagonal cross-sectional test pie
35、ces can be prepared by grinding off the four corners of a square section specimen. The apparatus shall be calibrated (see clause 7) using a piece of reference material of the same length as the test piece. 6.2 Vertical method The test piece shall be a hollow cylinder, 35 mm 0.5 mm in diameter and 50
36、 mm 0.5 mm in height with a bore between 12 mm and 13 mm extending throughout the height of the test piece and co-axial with the outer cylindrical surface. The ends of the test piece shall be plane and parallel, ground if necessary, and shall be perpendicular to the axis of the cylinder. The surface
37、 of the cylinder shall be free from visible cracks. Measurements of the height at any two points made using the callipers (see 5.5) shall not differ by more than 0.2 mm. When one face of the test piece is placed on a plane surface and a set square also in contact with the surface is brought into con
38、tact with any part of the periphery of the test piece, the gap between the side of the test piece and the end of the set square shall not exceed 0.5 mm. 7 Calibration 7.1 General It is necessary to correct the measured change in length of a test piece for the following: a) the effect of differential
39、 expansion in the apparatus which acts in opposition to the measured change in length of the test piece; b) systematic errors arising from the design of the apparatus and its method of use as described in clause 8. 7.2 Procedure for calibration Measure the change in length of a test piece of the ref
40、erence material (5.6) of dimensions given in either 6.1 (horizontal method) or 6.2 (vertical method) using the procedure described in clause 8. If it is not possible to obtain reference material of the dimensions given in 6.2, it is permitted to use a thin-walled cylinder of height 50 mm 0.5 mm and
41、approximate mean diameter of 24 mm. Record the difference, positive or negative, between the measured change and that obtained by calculation using the reference data (see table 1) at corresponding temperatures, for the full temperature range of calibration. In a test, correct the measured change in
42、 length of a test piece by inclusion of the data obtained by calibration at corresponding temperatures. 7.3 Frequency of calibration The calibration procedure (see 7.2) shall also be carried out: a) at intervals not exceeding 10 test runs; b) if the apparatus has been out of use for a period greater
43、 than 4 weeks; c) whenever the apparatus is serviced or parts replaced; d) at intervals of 6 months if none of (a) to (c) applies. Where the apparatus is supplied with more than one furnace, calibration data shall be obtained and identified for each furnace. If furnaces are interchanged without reca
44、libration they shall be positioned to within 1 mm of their previous position. Records of calibration shall be kept. NOTE. The frequency of calibration will depend on the equipment, its rate of use and the types of material tested. 8 Procedure NOTE. For a required accuracy, additional measurement cri
45、teria are necessary (see appendix A). 8.1 Ensure that the apparatus is positioned for use in an environment where the temperature, at the start of the test, has been stable at 20 C 3 C for at least 2 h. 8.2 Dry the test piece at 110 C 5 C to constant mass and cool in a desiccator to ambient temperat
46、ure. In the horizontal method (see 6.1), measure the length of the test piece to an accuracy of 0.1 mm with the vernier callipers (5.5) between the extreme points of contact on the end faces. In the vertical method (see 6.2), measure the height of the test piece at four locations equally spaced roun
47、d its periphery to an accuracy of 0.1 mm with the vernier callipers (5.5). Record the mean of the four readings as the initial length of the test piece. 8.3 Ensure that the apparatus, especially the surfaces in contact with the test piece, is free from any adherent debris. Insert the test piece in t
48、he apparatus. In the horizontal method, adjust the thermocouple (5.4) so that its junction is positioned to be in contact with the surface of the test piece, at a point midway along the length of the test piece. In the vertical method, adjust the thermocouple (5.4) so that its junction is positioned
49、 at the geometric centre of the test piece. Adjust the measuring device (5.2) to make contact with the assembly as shown in either figure 1 or figure 2 in such a way as to record both expansion and contraction. Record the initial measurement and the temperature. 8.4 Allow the temperature of the test piece to stabilize before the commencement of a test run, so that subsequent measured changes in length relate to an initial temperature of 20 C 3 C.7 BS 1902 : Section 5.14 : 1992 8.5 If manual recording is carried out, note the initial reading of the
