1、Designation: C424 93 (Reapproved 2012)Standard Test Method forCrazing Resistance of Fired Glazed Whitewares byAutoclave Treatment1This standard is issued under the fixed designation C424; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the crazingresistance of fired glazed whitewares using t
3、he autoclavetreatment and under the conditions specified in this testmethod.1.2 The values stated in inch-pound units are to be regardedas the standard. The values given in parentheses are forinformation only.1.3 This standard does not purport to address all of thesafety concerns, if any, associated
4、 with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Significance and Use2.1 This test method is particularly useful for porous mate-rials that can exhibit
5、moisture expansion.2.2 This test method is a primary test method that is suitablefor use in specifications, quality control, and research anddevelopment. It can also serve as a referee test method inpurchasing contracts or agreements.3. Apparatus3.1 AutoclaveAn autoclave built for a steam pressure o
6、f atleast 275 psi (1.9 MPa), and preferably with sufficient capacityto contain at least ten specimens. The apparatus shall beequipped with a safety valve, a blow-off valve, pressure gagemeasuring pressure above atmospheric pressure with an accu-racy of 65 psi (34 kPa), and a source of heat of suffic
7、ientcapacity to ensure a constant steam pressure within theautoclave.4. Number of Specimens4.1 The crazing test shall be made on at least ten identicaluncut specimens having facial dimensions up to and including6 by 6 in. (152 by 152 mm) or 6 by 8 in. (152 by 200 mm). Forlarger specimens, specifical
8、ly tile products, five samples willsuffice and these may be cut to facilitate entry into theautoclave. However, all cut pieces should be as large aspossible and all cut pieces are to be tested.5. Procedure5.1 Placement of Specimens in the AutoclavePlace asufficient amount of distilled water in the a
9、utoclave so that afterthe test a slight excess of water will remain. Place allspecimens on a suitable support at least 2 in. (51 mm) abovethe water line within the autoclave at room temperature. Fastenthe autoclave head securely in place.5.2 Operation of AutoclaveGradually heat the water inthe botto
10、m of the autoclave. Keep the blow-off valve open forseveral minutes after steam begins to escape, thereby expellingmost of the air. After closing the blow-off valve, increase thesteam pressure at a uniform rate until the desired pressure isreached within a period of not less than 45 min nor exceedin
11、g1 h. Apply sufficient heat to maintain the indicated pressureconstant (62 psi (14 kPa) for an additional hour. Shut off theheat source and release the steam pressure immediately byopening the blow-off valve.5.2.1 If it is desirable to ascertain whether failure occurs asa result of rehydration only,
12、 the blow-off valve should becracked only and the steam released slowly over a period of 30min. If this method of steam release is used, the report shall sostate.5.3 Removal of Specimens from AutoclaveLoosen theautoclave head and allow the specimens to cool in place for 30min. Remove the specimens a
13、nd allow to cool at roomtemperature for an additional 30 min before examination.5.4 Examination of Specimens for Crazing FailuresUseoblique lighting and the application of a suitable ink or dyesolution upon the glazed surfaces to aid in the detection andexamination of crazing failures. Consider only
14、 those failuresvisible to the naked eye.5.5 Pressure ScheduleMake the initial test at 50 psi (345kPa). If any or all of the specimens show no crazing, repeat thetest on the uncrazed pieces at 100 psi (689 kPa) and, ifnecessary, at increasing intervals of 50 psi until all specimenshave crazed or unti
15、l a pressure of 250 psi (1.7 MPa) has beenreached. Successive tests shall be separated by a time interval1This test method is under jurisdiction of ASTM Committee C21 on CeramicWhitewares and Related Products and is the direct responsibility of SubcommitteeC21.03 on Methods for Whitewares and Enviro
16、nmental Concerns.Current edition approved April 1, 2012. Published April 2012. Originallyapproved in 1958 . Last previous edition approved in 1999 as C424 93 (2006).DOI: 10.1520/C0424-93R12.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United St
17、ates.not exceeding 24 h. If it is desired to use this procedure inconjunction with a product specification, the test may belimited to one or more of these specified pressures.6. Report6.1 Report the following information:6.1.1 Identification of specimens.6.1.2 Number of specimens tested.6.1.3 Identi
18、fication of ink or dye solutions used in exami-nation of specimens.6.1.4 Table listing each steam pressure, in pounds persquare inch (or pascals), with the number of specimens failingat each pressure,6.1.5 Average failure pressure, calculated by multiplyingeach pressure by the number of specimens fa
19、iling at thatpressure and dividing the sum of these products by the totalnumber of pieces tested (specimens having withstood the200-psi (1.4-MPa) test shall be said to have failed at 250 psi(1.7 MPa) for the purpose of calculation), and6.1.6 Time consumed for steam release, if the pressure wasnot re
20、leased immediately at the conclusion of each test.7. Precision and Bias7.1 Duplicate determinations should not differ by more than50 psi (0.34 MPa).7.2 Bias has not been determined.8. Keywords8.1 autoclave; crazing; crazing resistanceASTM International takes no position respecting the validity of an
21、y patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to rev
22、ision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your
23、 comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyr
24、ighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).C424 93 (2012)2
