1、Designation:C42493(Reapproved 2016)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 revision,t
2、he 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 the autoclav
3、etreatment 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 with its use.
4、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 moisture expansi
5、on.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 of atleast 275 psi(1.
6、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 gaugemeasuring pressure above atmospheric pressure with an accu-racy of 65 psi(34 kPa),and a source of heat of sufficientcapacity to ensure a c
7、onstant 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,specifically tile products,five samples wi
8、llsuffice 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 autoclave so that afterthe test a sli
9、ght 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 in thebottom of the autoclave.Keep the blow-off val
10、ve 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 exceeding1 h.Apply sufficient heat to maintain the i
11、ndicated 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,the blow-off valve should becracked only and the
12、steam released slowly over a period of30 min.If this method of steam release is used,the report shallso state.5.3 Removal of Specimens from AutoclaveLoosen theautoclave head and allow the specimens to cool in place for30 min.Remove the specimens and allow to cool at roomtemperature for an additional
13、 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 those failuresvisible to the naked eye.5.5 Pressure S
14、cheduleMake the initial test at 50 psi(345 kPa).If any or all of the specimens show no crazing,repeat the test on the uncrazed pieces at 100 psi(689 kPa)and,if necessary,at increasing intervals of 50 psi until all specimens1This test method is under jurisdiction of ASTM Committee C21 on CeramicWhite
15、wares and Related Products and is the direct responsibility of SubcommitteeC21.03 on Methods for Whitewares and Environmental Concerns.Current edition approved Nov.1,2016.Published November 2016.Originallyapproved in 1958.Last previous edition approved in 2012 as C424 93(2012).DOI:10.1520/C0424-93R1
16、6.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 have crazed or until a pressure of 250 psi(1.7 MPa)has beenreached.Successive tests shall be separated by a time intervalnot 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 spec
