Recently, due to the growing needs for clean steel and high performance steel products, the secondary refining conditions have become more severe in steelmaking plants. As a result, the damage of the steel teeming ladle refractories has increased remarkably, and ladle life has decreased. Spinel-forming monolithic refractories form spinel and the formation of spinel is accompanied by a large volume expansion of the refractory above 1200°C, and this volume expansion remains permanently. This spinel-related expansion causes stress in the refractory, along with cracks and spalling. In contrast, it is said that, in the refractoriness under load test, spinel-forming monolithic refractories show softening around 1200-1400°C, and that softening relaxes the stress caused by spinel expansion. Spinel-forming monolithic refractories may crack if the stress exceeds the relaxation that is provided by the softening. However few studies have considered these mechanisms in combination.
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