Mathematical And Physical Simulation On Application Process And Optimization Of Structure And Performance Of Purging Plug In Refining Ladle

As a valid metallurgical technology, ladle with bottom blowing become a metallurgical technology over the years, which is seriously concerned by metallurgical science and technology workers. Many experts and scholars have used mathematical and physical modeling approach, primarily by improving location of purging plug and gas flow rate to get a shorter mixing time and better refining effect. Currently purging plug with slits are the main blowing component of refining ladle in China. But the purging plugs were easy to prematurely cross destroyed, severe lower refining efficiency. To extend the service life of ladle, avoid refractories of secondary pollution, maximum cleaning steel fluid, the effect of slits size and distribution on molten steel purity and the effect of gas blowing parameters on erosion and corrosion have to be explored.In this paper, according to practical parameters of 300t refining ladle, the mathematical simulation and physical modeling methods were combined, the effects of the parameters of single-blowing and double-blowing on refinement were studied, the effects of slits size and distribution of purging plug on mixing time and inclusion removal rate were explored. The finite element method was adopted, the temperature and thermal stress of purging plug in service process were analyzed. Combined with the physical properties of purging plug, the cross-damage factors in the actual service conditions were discussed. The erosion model of refining ladle lining material was established, the effect of blowing parameters on wear of refining ladle lining were studied by mathematical simulation. Based on the above studies, micro magnesia binder was applied, the high performance purging plug was prepared.Thesis reached the following conclusions:1. The main factors of refining ladle refractory lining erosion rate are erosion angle, inclusion size, velocity and the porosity of refractories. The relation of erosion angle and erosion rate presents single peak, the others are exponential relationship. Regression analysis was applied, the associated expression on erosion of inclusion and molten steel were fittied out, the erosion model of refining ladle lining material was established.2. The molten steel flow characteristics and inclusion removal rate in refining ladle with different blowing patterns, the results show that: in case of the mixing time and inclusion removal rate, single-blowing is inferior to double-blowing. In view of lager critical slag-entrapment gas flow rate of single-blowing, it can be improved by increasing the gas flow rate. When gas flow rate was 1.45m3/h and steadily, the mixing time was only 82.44s and the inclusion removal rate was 62.86%, the need of ladle stirred and puried could be satisfied.3. The effect of outer slits of purging plug on molten steel refinement are larger. But the change of the slit width main impact the particle size distribution of inclusion removal, the small and big width of the slit respectively in favor of removal of large size and small inclusions. The optimized PB5 purging plug is applied, the total inclusion removal rate is remarkable increased, reached 67.21%. Because the removal rate of micro inclusions and more than 100 eye inclusions both are improved. In order to guarantee good refinement, the distance of the purging plug lacation from centre of circle should be greater than 0.4R.4. For different blowing conditions, the corrosion and erosion of the ladle refractory lining was mathematical simulated, the following conclusions: Compared with double-blowing condition, the corrosion and erosion of the ladle refractory lining are smaller and the wear area is fewer. The refractories in slag line main bear more corrosion and erosion. Follow the increasing of gas flow rate, the corrosion and erosion of the ladle refractory lining become deteriorated. And the location of purging plug is too far from circle centre, the wear of some parts of ladle refractory lining could occurred too quickly. So we should try to choose a small bottom-blown eccentricity to ensure blowing refinement, and avoid short board effect.5. The cataclysm of temperature-stress of purging plug in service process follow the change of the gas flow rate, some parts of purging plug may bear the thermal stress alternating, especially the areas near work face are easy to peeling. The periodic rapid heating and cooling in condition of oxygen burning can cause cross wear of purging plug, but the slit width is more narrower the axial thermal stresses are more smaller. it can significantly improve the axial thermal stress distribution of purging plug in oxygen burning condition through improving slits distribution and reducing thermal expansion coefficient.6. The micro magnesia binder was applied, the high performance purging plug was prepared. Compared with the original material, the optimized material with lower thermal expansion coefficient, which is not easily clogging, is better to avoid long oxygen burning treatment and resist the thermal stress alternating in bottom blowing and oxygen burning processing, effectively avoiding cross-damage.