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ASTM C424-93(R2020) pdf free download

ASTM C424-93(R2020) pdf free download.Standard Test Method for Crazing Resistance of Fired Glazed Whitewares by Autoclave Treatment
1. Scope
1.1 This test method covers the determination ofthe crazing resistance of fired glazed whitewares using the autoclave treatment and under the conditions specified in this test method. 1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4. Number of Specimens
4.1 The crazing test shall be made on at least ten identical uncut specimens having facial dimensions up to and including 6 by 6 in. (152 by 152 mm) or 6 by 8 in. (152 by 200 mm). For larger specimens, specifically tile products, five samples will suffice and these may be cut to facilitate entry into the autoclave. However, all cut pieces should be as large as possible and all cut pieces are to be tested.
5. Procedure
5.1 Placement of Specimens in the Autoclave—Place a sufficient amount ofdistilled water in the autoclave so that after the test a slight excess of water will remain. Place all specimens on a suitable support at least 2 in. (51 mm) above the water line within the autoclave at room temperature. Fasten the autoclave head securely in place. 5.2 Operation ofAutoclave—Gradually heat the water in the bottom of the autoclave. Keep the blow-off valve open for several minutes after steam begins to escape, thereby expelling most of the air. After closing the blow-off valve, increase the steam pressure at a uniform rate until the desired pressure is reached within a period of not less than 45 min nor exceeding 1 h. Apply sufficient heat to maintain the indicated pressure constant (62 psi (14 kPa)) for an additional hour. Shut off the heat source and release the steam pressure immediately by opening the blow-off valve. 5.2.1 If it is desirable to ascertain whether failure occurs as a result of rehydration only, the blow-off valve should be cracked only and the steam released slowly over a period of 30 min. If this method of steam release is used, the report shall so state. 5.3 Removal of Specimens From Autoclave—Loosen the autoclave head and allow the specimens to cool in place for 30 min. Remove the specimens and allow to cool at room temperature for an additional 30 min before examination. 5.4 Examination of Specimens for Crazing Failures—Use oblique lighting and the application of a suitable ink or dye solution upon the glazed surfaces to aid in the detection and examination of crazing failures. Consider only those failures visible to the naked eye. 5.5 Pressure Schedule—Make 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, ifnecessary, at increasing intervals of50 psi until all specimens have crazed or until a pressure of 250 psi (1.7 MPa) has been reached. Successive tests shall be separated by a time interval not exceeding 24 h. If it is desired to use this procedure in conjunction with a product specification, the test may be limited to one or more of these specified pressures.

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