China's Refractories

Abstract: To prevent dense chromium oxide covers from cracking during firing, such as internal cracking, surface cracking and fracture, the firing process of dense chromium oxide products was simulated, and the performance parameters at several specific temperatures before and after densification of chromium oxide green bodies were tested. The temperature difference and the stress difference of chromium oxide green bodies were calculated by Finite Element Software at heating and cooling rates of 10, 20, 30 and 40 ℃·h^-1, respectively. The results show that large temperature difference and thermal stress difference are the main causes of internal cracking, surface cracking and fracture of the brick. Suitable heating rates reduce or avoid internal cracking of the brick. When the heating rate is 30 ℃·h^-1 below 1 450 ℃ and 10 ℃·h^-1 above 1 450 ℃, the temperature difference and the thermal stress difference in the brick are below 4 ℃ and 4 MPa, respectively, and there is no internal crack in the brick after firing. The initial cooling stage is the key stage that causes cracking or fracture of bricks. When the cooling rate is 20 ℃·h^-1 above 1 450 ℃, the thermal stress difference in the brick is less than 4 MPa, which can significantly reduce the surface cracks and fracture of the brick.

Key words: finite element, dense chromium oxide, cracking, temperature difference, stress difference