Failure mechanism of blast furnace tuyeres
The damage of a blast furnace tuyere, requiring its replacement, disturbs normal operation of the blast furnace and reduces the economic efficiency of production. In this paper, the failure mechanism of blast furnace tuyeres was investigated by metallographic examination of sections cut from failed tuyeres and laboratory experiments directed towards a simulation of tuyere operation and failure. The obtained results revealed a complex failure mechanism which consists of two main phases: the phase of local damage by corrosion and the phase of melting of damaged areas. The corrosion of tuyeres is caused by the presence of aggressive chemical compounds in the blast furnace, primarily chlorinecontaining compounds. The corrosive attack on a tuyere results in the formation of intergranular cracks and microporosity in the tuyere copper. Such defects affect severely the cooling of the copper in the affected areas. Thermal load on the tuyere surface through the splashing of hot metal and slag and reduced thermal conductivity of the copper in the areas affected by corrosion lead to the overheating and finally localized melting of the tuyere. This process can take place repeatedly until the tuyere is completely damaged, which is accompanied by leakage of water into the furnace.
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