Thermal Deformation Of Copper Stave And Copper Steel Composite Stave In Blast Furnace

Cooling stave’s campaign life in the bosh, belly and lower shaft region of blast furnace is a key factor that determines the campaign life of blast furnace. Copper staves are generally installed at the bosh, belly and lower shaft region of home and abroad blast furnace because of their good heat transfer performance, but the phenomena of cracks in the pipe-stave joint and damages near the hot-face of copper stave have been happened. However, there is a lack of quantitative analysis about the mechanisms of the cracks in the pipe-stave joint and damage near the hot-face of copper stave. There is a stress concentration problem near the copper steel interface of copper stave composite stave, which is designed aiming at decrease the cost of copper stave and overcome the pipe welding problem of copper stave, and the safty of copper steel composite stave in blast furnace has gradually becoming the restrictive factor that affects the popularization and application of copper steel composite stave. Therefore, thermal and mechanical behaviors of copper stave and copper steel composite stave for various operating conditions in blast furnace are studied.(1) Thermal deformation of copper stave without accretion is analysed by heat transfer and thermal elastic models for copper stave. Under considering the installed method of copper stave water pipes, the thermal stress distribution and thermal deformation of copper stave water pipes are investigated when there is a flexiable connection tube, a rigid connection tube between water pipes or a constraint of opening hole for shell on the water pipe. A reasonable diameter of opening hole for shell used for installation of copper stave water pipe is discussed.(2) Unsteady-stave heat transfer, thermal elastic-plastic and thermal fatigue models for copper stave are eastablished, and the thermal deformation and plastic accumulation of copper stave during the drop and reform of accretion are investigated with considering the welded construction near the roots of water pipes. The thermal fatigue life of copper stave is predicted, and the thermal fatigue behaviors of copper stave water pipes are analysed.(3) A mathematical model of heat transfer and thermal elastic of copper steel composite stave is used to investigate the heat transfer performance, thermal deformation and stress state of copper steel interface of copper steel composite stave with no accretion. The stress state of copper steel composite stave water pipes are analysed under considering the installed method of copper steel composite stave water pipes. The results show that copper steel composite stave has the same heat transfer performance as copper stave. The thermal deformation degree of copper steel composite stave is larger than that of copper stave, and there is a tensile force along the thickness of copper steel composite stave near the edge of copper steel interface. After optimization design, thermal deformation degree of copper steel composite stave is smaller than that of copper stave, and the copper steel interface is subjected to compression instead of subjected to tensile.(4) A thermal test is conducted for copper steel composite stave, and temperature and strain distribution of copper steel composite stave under different gas temperature are measured. The temperature and strain distribution of copper steel composite stave are calculated according to the thermal test. The calculated value basically agrees well with measured value, which verified the validity of the mathematical model.(5) Thermal elastic-plastic-creep model for copper steel composite stave is eastablished to investigate the thermal deformation of copper steel composite stave without accretion during the process of creep, and analyse the stress state of copper steel interface of copper steel composite stave during the process of creep. The effects of creep time and gas temperature on the thermal deformation and stress state of copper steel interface are investigated. The results show that the creep strain of copper steel composite stave during the process of creep increases rapidly and then increases slowly, but the stress decreases rapidly and then decreases slowly. The thermal deformation degree of copper steel composite stave after creep deformation increases, but it is still smaller than that of copper stave. After creep deformation, the stress concentration degree near the copper steel interface of copper steel composite stave decreases. The bending deformation degree and stress concentration degree near the copper steel interface of copper steel composite stave after creep deformation decrease with creep time increase. The bending deformation and stress concentration degree near the copper steel interface of copper steel composite stave after creep deformation increases with gas temperature, but the increasing amplitude is relatively small.