The cracking of zirconia refractory tubes under hot shock

The evolution of stresses and strains in a zirconia-containing refractory t ube subjected to a hot shock on the outer surface and convective cooling at the inner surface is analysed with the method of finite elements. To accou nt for the temperature-induced phase transformation in the zirconia as well as the overall thermal expansion, a coefficient of total dilatation is int roduced. The parameters that control the time-dependent stress and strain r esponses are identified by performing finite element calculations that span the range of variables relevant to steel making. The effects of tube thick ness, hot shock duration, initial temperature, temperature dependence of el astic modulus, and transformation amplitude on stress and strain distributi ons are discussed, and heating and process strategies to eliminate surface cracking are suggested. (C) 2000 Kluwer Academic Publishers.