1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 28703:2011Fine ceramics (advancedceramics, advanced technicalceramics) Test method forthermal-shock resistance ofporous ceramicsBS ISO 28703:2011 BRITISH STANDARDNational
2、forewordThis British Standard is the UK implementation of ISO 28703:2011.The UK participation in its preparation was entrusted to TechnicalCommittee RPI/13, Advanced technical ceramics.A list of organizations represented on this committee can beobtained on request to its secretary.This publication d
3、oes not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2011ISBN 978 0 580 66466 3ICS 81.060.30Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority o
4、f theStandards Policy and Strategy Committee on 30 September 2011.Amendments issued since publicationDate Text affectedBS ISO 28703:2011Fine ceramics (advanced ceramics, advanced technical ceramics) Test method for thermal-shock resistance of porous ceramicsCramiques techniques Mthode dessai de la r
5、sistance au choc thermique des cramiques poreuses ISO 2011Reference numberISO 28703:2011(E)First edition2011-08-15ISO28703INTERNATIONAL STANDARDBS ISO 28703:2011ISO 28703:2011(E)COPYRIGHT PROTECTED DOCUMENT ISO 2011All rights reserved. Unless otherwise specified, no part of this publication may be r
6、eproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22
7、749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in Switzerlandii ISO 2011 All rights reservedBS ISO 28703:2011ISO 28703:2011(E)Contents PageForeword iv1 Scope 12 Normative references .13 Terms and definitions .14 Principle .25 Apparatus 25.1 Electric furnace 25.2 Coolin
8、g bath25.3 Temperature-measuring device .25.4 Vernier callipers .35.5 Micrometer callipers .35.6 Thermocouples 36 Test specimens 36.1 Shape and size .36.2 Pretreatment .36.3 Number of specimens 37 Procedure 38 Bending test 48.1 Bending strength .48.2 Mean bending strength 59 Thermal-shock resistance
9、 .510 Test report .5 ISO 2011 All rights reserved iiiBS ISO 28703:2011ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technic
10、al 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 work. ISO collaborates closely wi
11、th 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 International Standards. Draft Intern
12、ational 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 the elements of this document may b
13、e the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 28703 was prepared by Technical Committee ISO/TC 206, Fine ceramics.ISO 28703:2011(E)iv ISO 2011 All rights reservedBS ISO 28703:2011INTERNATIONAL STANDARD ISO 28703:2011(E)Fine cerami
14、cs (advanced ceramics, advanced technical ceramics) Test method for thermal-shock resistance of porous ceramics1 ScopeThis International Standard specifies a test method for determining the thermal-shock resistance of porous ceramics by water quenching using the bending strength. This test method ca
15、n be used for selection of materials during design.NOTE 1 There are three kinds of test methods for thermal shock, namely a rapid cooling method, a rapid heating method, and the rapid heating-cooling method. Ceramics are sensitive to tensile stress, and the surface region has many defects which act
16、as the starting points to which strength falls. For this reason, the rapid cooling method where the maximum tensile stress is generated on the surface serves as the severest test condition for ceramics. Therefore, this International Standard specifies the rapid cooling method.NOTE 2 In many thermal-
17、shock test methods, liquid or gas is needed as a cooling medium, and liquid is more efficient than gas in the cooling capability. Therefore, in this International Standard, water is specified as a cooling medium.2 Normative referencesThe following referenced documents are indispensable for the appli
18、cation of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 1101, Geometrical Product Specifications (GPS) Geometrical tolerancing Tolerances of form, orientation, location
19、 and run-outISO 3599, Vernier callipers reading to 0,1 and 0,05 mmISO 3611, Geometrical product specifications (GPS) Dimensional measuring equipment: Micrometers for external measurements Design and metrological characteristicsISO 4287, Geometrical Product Specifications (GPS) Surface texture: Profi
20、le method Terms, definitions and surface texture parametersISO 14704, Fine ceramics (advanced ceramics, advanced technical ceramics) Test method for flexural strength of monolithic ceramics at room temperatureISO 20507, Fine ceramics (advanced ceramics, advanced technical ceramics) VocabularyIEC 605
21、84-1, Thermocouples Part 1: Reference tables3 Terms and definitionsFor the purposes of this document, the terms and definitions in ISO 20507 and the following apply.3.1porous ceramicsceramics with a porosity of typically 30 % to 60 % and a pore diameter of 1 m to 100 m, for applications such as filt
22、ers, catalyst carriers, humidity sensors or molecular sieves, excluding structural honeycomb cellular channels ISO 2011 All rights reserved 1BS ISO 28703:20113.2thermal shockphenomenon generating impulsive thermal stress due to the large temperature difference in a material by rapid heating or cooli
23、ng3.3thermal-shock temperature differencetemperature difference between a material and the environment at thermal shock3.4residual bending strengthbending strength of a material after the thermal-shock test3.5decreasing ratio of residual bending strengthratio of the amount of reduced bending strengt
24、h after testing to the mean bending strength before testing3.6maximum permissible temperature differencemaximum thermal-shock temperature difference that does not significantly reduce the residual bending strength after thermal-shock testing4 PrincipleThe resistance of a material to thermal shock is
25、 estimated by the maximum thermal-shock temperature difference which the material can withstand without its residual bending strength being significantly affected. The data such as residual bending strength and maximum permissible temperature difference shall not be used directly for the design of m
26、aterials and components.5 Apparatus5.1 Electric furnaceSpecimens are heated in a electric furnace with a temperature accuracy of 2 K (2 C). When multiple specimens are heated at the same time, the temperature of the furnace shall be able to be controlled uniformly around the location where the speci
27、mens are situated.The design of the furnace shall allow a rapid and smooth transfer of the heated specimens from the hot furnace chamber to the cooling bath. When a furnace such as the rapid radiation type is used, it is important for good accuracy of the results to minimize the temperature differen
28、ces of the locations where specimens are set.5.2 Cooling bathThe cooling bath shall use a controller to maintain uniform water temperature within 2 K (2 C) during the test. Mechanical mixing or agitation shall ensure uniformity in a water temperature within 2 K (2 C) throughout the bath.NOTE Tempera
29、ture differences in the water influence the stress at a thermal shock. Therefore, in this International Standard, only the cooling bath with apparatus to control the water at a uniform temperature is allowed.5.3 Temperature-measuring deviceTemperature-measuring devices which are used to measure the
30、temperature of specimens in the electric furnace and to control the electric furnace itself shall have the temperature sensors (thermocouples, etc.) located in the position nearest to the specimens.ISO 28703:2011(E)2 ISO 2011 All rights reservedBS ISO 28703:20115.4 Vernier callipersVernier callipers
31、 with the same accuracy of minimum reading of 0,05 mm as specified in ISO 3599, or more, shall be used.5.5 Micrometer callipersMicrometer callipers for measurement of external dimensions with the same accuracy as specified in ISO 3611, or better, shall be used.5.6 ThermocouplesThermocouples with the
32、 same accuracy as Type K Class 1 specified in IEC 60584-1, or better, shall be used.6 Test specimens6.1 Shape and sizeSpecimens are made by cutting out from actual components or by a particular process. A particular process must guarantee specimens made by it to be equivalent to those made by cuttin
33、g from actual components, and the process must be the same as that used in making the components. The shape of the specimen shall be a rectangular prism with a rectangular cross-section. The standard dimensions of the specimen are b = (8,0 0,1) mm in width, h = (6,0 0,1) mm in thickness and L = 70 m
34、m or more in length. Parallelism of the upper and lower surfaces shall be under 0,02 mm as specified in ISO 1101. The surfaces of specimen shall be finished by a grindstone with a grain number of #800 or finer. Four corners of longitudinal direction are chamfered with c = 0,1 mm 0,3 mm. In spite of
35、the former provision, chamfering can be neglected for specimens with grains larger than 0,1 mm.Lhbc45Figure 1 Specimen dimensions and chamfering of ridge line6.2 PretreatmentContamination by wax, if any, should be removed by organic solution or by heating at 773 K (500 C) for 1 h to evaporate wax.6.
36、3 Number of specimensUse a minimum of five specimens for each thermal condition.NOTE Ceramics are materials with a large scatter in strength. When the smallest number of specimens is used in the thermal-shock test, a large scattering is obtained for the temperature difference for the reduction of re
37、sidual strength. Therefore, the number of specimens for each temperature condition is specified to be at least five in this International Standard. However, around the temperatures for determining the maximum permissible temperature difference, it is desirable for the number of test specimens to be
38、10 or more.7 Procedure7.1 Measure the width b and thickness h of the test specimens in advance, using a vernier calliper or micrometer.ISO 28703:2011(E) ISO 2011 All rights reserved 3BS ISO 28703:20117.2 After setting the test specimen in a uniform temperature region in the electric furnace, heat th
39、e test specimen to the testing temperature at a rate between 10 K/min (10 C/min) and 30 K/min (30 C/min).NOTE In the heating process, it is necessary to consider the heating rate at which thermal stress does not occur in the test specimen, and to avoid rapid heating.7.3 After holding for 15 min to 3
40、0 min at a predetermined temperature, the test specimen is put into a cooling-water tub quickly and is cooled promptly. The temperature of water which is a cooling medium is maintained at (293 3) K (20 3) C.NOTE The test specimen is generally thrown or dropped into the cooling water, and quenched.7.
41、4 The test specimen under the cooling water is taken out from the water after cooling for 5 s to 10 s. When taking out the next test specimen and putting it into a cooling bath at a specific time, more than a 10 min interval is needed after the temperature of the cooling water is constant.7.5 First
42、determine a value of thermal-shock temperature difference for which the average value of the residual bending strength does not decrease. Repeat the test with increased values of thermal-shock temperature difference until the decrease in the average value of residual bending strength is 30 % or more
43、. Use at least five specimens for each temperature difference.8 Bending testThe test specimen that was given a thermal shock shall be dried out at 383 K (110 C) for 2 h. Next, the four-point bending test shall be conducted on the test specimen, the residual bending strength is measured, and the aver
44、age value is calculated. The four-point bending fixture of similar construction to that shown in ISO 14704 shall be used (see Figure 2). A distance between the outer supporting points L2shall be (60,0 0,5) mm, and a distance between the inner supporting points L1shall be (30,0 0,5) mm. The radius of
45、 curvature at the inner and outer supports shall be 4,0 mm to 6,0 mm, and its surface roughness, Ra, as specified in ISO 4287, shall be, at most, 0,40 m. The crosshead speed of the testing machine shall be 0,5 mm/min.8.1 Bending strengthThe bending strength sBis calculated from the measured value P
46、of the destructive load acquired by the four-point bending test. P is the maximum load at which the test specimen breaks.B=( )322 12P L Lbh(1)where b is the width of the test specimen, and h is the thickness of the test specimen (see Figure 1).ISO 28703:2011(E)4 ISO 2011 All rights reservedBS ISO 28
47、703:201112L1/2L2/2 L2/2L1/2b46Lh12Key1 inner supports2 outer supportsFigure 2 Four-point bending fixture8.2 Mean bending strengthThe average value smof the bending strength is calculated by the arithmetic average.9 Thermal-shock resistanceThe maximum permissible temperature difference is used as the
48、 evaluation index of thermal-shock resistance. This maximum value of Tcis calculated by averaging the value of T1for which the averaged strength-decreasing ratio is less than 5 % and the value of T2for which the decreasing ratio of the averaged residual strength is greater than 10 % to 15 %. The dec
49、reasing ratio s* of residual strength is calculated by the following equation. * =mo mthmo(2)Here, smois the average value of the bending strength on test specimens which were not subjected to any thermal shock, and smthis the mean value of the residual bending strength on the test specimens after a thermal shock.Calculate the maximum permissible temperature difference Tcaccording to the following equation. TT Tc=+1 22(3)In a thermal-shock test, many test specimens for the tes
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