In the ASTM C554-93 standard published by the American Society for Testing and Materials (ASTM), a test for determining the resistance of baked, glazed, ceramic white goods to cracking when residual stresses after glossy firing cause a tendency to crack, triggered by factors other than moisture expansion. method is defined.
This test method is not designed to cause moisture expansion. Another ASTM standard, ASTM C424, defines another test method for determining resistance to cracking caused by moisture expansion (ASTM C424-93 Standard test method for autoclave cracking resistance of baked glazed white goods).
The use of this standard is generally limited to testing unglazed and semi-glazed ceramic white goods. Because these products are subject to such expansion. For white goods with negligible moisture expansion, such as glassy and waterproof products, the thermal shock method described here is generally preferred.
The resistance of fired glazed white goods to cracking is determined when exposed to thermal stresses. The samples are initially heated at 120 degrees and quenched with water. This cycle is repeated three times. If cracking does not occur, three cycles are repeated in increments of 4 degrees to 230 degrees. Failure is defined as the temperature at which cracking is observed. ASTM recommends testing five samples.
Unless there is a harmony between glaze and body expansions, all glazed white goods may contain residual stresses from firing that binds the glaze to the body. In addition, white goods are increasingly exposed to thermal stresses in service. Therefore, an important use criterion for glazed white goods is adequate resistance to repeated sudden thermal changes. In most cases, cracks occur in the glaze as a result of insufficient resistance to thermal shock. These cracks are detected by examining them with oblique lighting and applying a suitable paint.
Among the numerous tests, measurements, analyses, and evaluations our organization provides for businesses in various sectors, we also offer standard testing services for the crack resistance of fired glazed ceramic white goods using the thermal shock method, within the scope of the ASTM C554-93 standard, thanks to our trained and expert staff and advanced technological equipment.
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