BS ISO 21736:2020 Refractories — Test methods for thermal shock resistance

BS ISO 21736:2020 Refractories — Test methods for thermal shock resistance. 5.2 Principle In the conditions of the specified testing temperature and cooling medium, the test piece with the specified shape and dimensions suffers thermal shocks. At the end of each thermal shock, a rupture test with a certain bending stress (load) or a blowing burst test is conducted on the test piece. The experienced thermal shock cycle of the test piece is adopted to describe the thermal shock resistance. 5.3 Equipment 5.3.1 Experimental furnace. Use an electric furnace whose temperature can be controlled in accordance with the specifications in 5S. The temperature distribution of the test piece loading area shall be uniform to ensure the temperature difference between two random points on the hot end surface is lower than 10 °C. The uniform temperature zone shall be able to hold at least three test pieces simultaneously. One end of the thermocouple shall be sealed. Temperature record and display devices shall be equipped to control, record and display the furnace temperature continuously. 5.3.2 Blowing device, with a nozzle of 8 mm diameter and 5 mm length. 5.3.3 A steel board (400 mm x 250 mm x 20 mm), with positional pins for test piece fixing. The position of the pins shall he proper to let the nozzle target the centre of the test piece according to the dimensions of the test piece. 5.3.4 Tester of cold modulus of rupture. The curvature radius of the contacts shall he 5 mm ± 0,5 mm. The distance between the two lower contacts shall be 100 mm ± 1 mm. The other requirements shall be in accordance with the specifications of ISO 5014. 5.3.5 Insulating pincher to hold the heated test pieces. 5.3.6 Drying oven, from room temperature to 300 °C. 5.4 Test pieces 5.4.1 Sampling Sampling of shaped refractory products and monolithic refractories shall be conducted in accordance with ISO_5022 and ISOJ9272, respectively, or negotiated by corresponding parties. 5.4.2 Shape, dimensions and preparation of test pieces Rectangular test pieces with dimensions of (114 ± 3) mm x (64 ± 2) mm x (64 ± 2) mm shall be adopted. The two surfaces along the length direction shall be parallel. The allowable deviation of the parallelism between the tensed surface and the compressed surface shall not be larger than 0,5 mm and the allowable deviation of the parallelism between the two opposite edges of...