EN 820-2-2003 pdf download.Advanced technical ceramics – Methods of testing monolithic
ceramics – Thermo-mechanical properties – Part 2:Determination of self-loaded deformation.
4 Principle
The method involves determining whether or not test bars supported only at their ends deform at a series of temperatures, recording any self-loaded deformation observed, and recording the results graphically. The temperature of commencement of self-loaded deformation, taken from the graph, is reported.
This test is intended as a simple method of determining the upper use temperature of ceramic components in a self-loaded condition. The criterion is an upper limit of flexural distortion, The test is suitable for use on furnace construction materials and on any ceramic materials, from which components are subjected to further processing at high temperatures.
5 Apparatus
5.1 Measurement apparatus, of the type shown in Figure 1. The distance between the knife edge supports shall
be 160 mm ± 0,5 mm. The gauge for measuring deformation (sag or bow) shall be accurate to 0,01 mm.
NOTE The dial gauge shown in Figure 1 is an example only.
5.2 Steel bar, of dimensions as shown in Figure 2. with the top surface flat to ± 0,01 mm and parallel, to
± 0,01 mm, to the under surfaces in the regions of reduced thicknesses.
5.3 Laboratory furnace, capable of achieving 1600 °C, and of holding the temperature uniformly over the area occupied by the test pieces (see Figure 3) to within ± 5 °C. A controlled atmosphere, other than air, may be used if required. This shall be reported (see clause 10).
5.4 Two refractory supports, with square cross-section of approximately 12 mm (see Figure 3), made of material which is compatible with the test material at the test temperature. The supports shall be inspected alter each firing and where there is evidence of reaction with the test pieces, the supports shall be replaced.
5.5 Thermocouples (two), one to control the furnace and one to measure the temperature of the test pieces. The thermocouples shall be either type R, type S or type B in accordance with EN 60584-1.
C) thickness: 3,9 mm to 4,1 mm.
The test pieces shall be ground flat and parallel so that the thickness tolerance of a set of test pieces shall be
± 0.02 mm.
NOTE 1 A set is the number of test pieces which are required for the determinaflon of the temperature of commencement of self-loaded deformation.
Two pieces are required for each determination at a single temperature. Test pieces may be either cut from fired ceramic products or may be prepared especially for this method of test.
NOTE 2 In the latter case they should be tired before testing in a manner comparable to production tiring.
7 Procedure
1.1 SettIng up of measurement gauge
Check that the measurement gauge (see 5.1) probe is positioned at the mid-point between the two knife edges. as
shown in Figure 1. Place the steel bar (see 5.2) on the knife edges and adjust the gauge to read zero.
7.2 Marking of the test pieces
Mark the upper face of one end of the test piece with refractory paint, as the reference end. Draw a pencil line 8 mm from this reference end, across the top surface of the test piece, to act as a reference marker to be aligned with the knife edge of the reference gauge (see 7.3). Repeat the above procedure for the second test piece.
7.3 Measurement of test pieces before heat treatment
Place the test bar in the gauge, reference face uppermost so that the line across the width of the top surface (see 7.2) lies over a knife edge. Record the initial gauge reading (M1) to the nearest 0.01 mm and whether it is positive or negative. Repeat for the second test piece to be included in the heat treatment (see 7.4).
7.4 Heat treatment of test pieces
Support the two test pieces, approximately 6 mm apart. on the two square cross-section refractory supports (see 5.4), which are positioned 160 mm ± 0.5 mm apart on a refractory batt (see Figure 3). Place the test pieces so that the pencil lines marked across the width of the test pieces are facing upwards and lie over the inside edge of one of the square cross-section supports (see Figure 3). Place the refractory ball with the test pieces in the furnace and position the measuring thermocouple (see 5.5) adjacent to the test pieces. Raise the temperature of the test pieces in the furnace by 300 °C/h to the test temperature without exceeding it, and then maintain that temperature for 1 h. Cool the furnace to room temperature and remove the test pieces.EN 820-2-2003 pdf download.