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 the 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

摘要： 为了解决烧成过程中致密铬盖板砖坯的内裂、表面开裂和断裂等问题,模拟了致密铬产品的烧成工艺过程,测试了氧化铬坯体致密化前后特殊温度点的各项性能参数,采用有限元模拟软件分析了升、降温速率分别为10、20、30和40 ℃·h^-1时氧化铬砖坯的温度差和应力差。结果表明:较大的温度差和热应力差是引起砖坯开裂、内裂或断裂的主要原因;合适的升温速率可减少或避免砖坯内裂的产生,1 450 ℃前和1 450 ℃后升温速率分别为30和10 ℃·h^-1时,坯体内的温度差和热应力差分别在4 ℃和4 MPa以下,烧成后砖坯无内裂;降温初期是砖坯开裂或断裂的关键阶段,1 450 ℃前,降温速率小于20 ℃·h^-1时,砖坯内的热应力小于4 MPa,可显著降低砖坯的开裂和断裂。

关键词: 有限元, 致密铬, 开裂, 温度差, 应力差