Study On Failure And Refining Effect Of Purging Plug With Different Slits

As the cornerstone of the national economy,the iron and steel industry not only provides critical raw materials for national infrastructure but also strongly supports the development of related industries.But at present,the output of high quality steel in our country can't meet the increasing material demand,so it is urgent to develop and improve the ladle furnace technology.Purging plug is an important functional component in ladle furnace that is a technology for producing high-quality steel,which service lifespan determines the downtime and efficiency of the whole ladle.In this paper,the interaction law of flow/deformation/heat transfer between argon and purging plug in the refining process was investigated by the fluid-solid coupling method.Then the heat transfer,thermal stress and thermal deformation behavior of purging plug in service were discussed,so as to find an approach to alleviate and optimize the thermal stress distribution,which can prolong the service lifespan of purging plug.The main work of this paper is as follows:Firstly,the transient temperature distribution of purging plug in service was obtained by applying fluid-solid conjugate heat transfer modeling.Then,the thermomechanical behaviour of purging plugs with rectangular slit was analysed.The results showed that there is an intense heat exchange between argon and the slit wall,and the temperature distribution is depended on the change of the heat transfer coefficient.The tensile stress is mainly concentrated at about 0.323 m away from the bottom of the purging plug,which indicated that transverse fracture is most likely to occur at this location.The position where the temperature changes most dramatically with time at the center axis is close to the position where the maximum tensile stress occurs.Furthermore,the central axis of purging plug is in the compressive stress state,so the transverse fracture can't easy occurs here.It is also found that the simulation results are in good agreement with the actual usage by comparing to the new purging plug to a used one.Therefore,it is indicated that the combination of experiment and fluid-solid coupling heat transfer method is an effective method to study the thermomechanical behavior of purging plug.Secondly,it is found that the circular slits can effectively alleviate the stress concentration compared with the rectangular slits by the finite plate with holes model.Then the thermomechanical behavior and refining effects of the purging plug with a rectangular slit were compared to that of the purging plug with a circular slit.The results showed that the temperature distribution of purging plug with circular slits is more even than the purging plug rectangular slits,that result from circular slits was uniformity arranged in purging plug.Furthermore,the circular slit can effectively alleviate the stress concentration of the purging plug and reduces the maximum axial tension stress of purging plug,which prolongs its service lifespan.The physical model experiment showed that when the gas flow rate is less than 6.02 NL/min,the mixing time of purging plug with circular slits is shorter,and the inclusion removal rate is about 10% higher than that of purging plug with rectangular slits.Then,the Drucker-Prager model was employed to compare and analyze the irreversible mechanical behavior of purging plugs with the different slit in service.The simulation results showed that no matter the value of shear and tensile plastic deformation as well as the influence area,purging plug with a rectangular slit are always greater than that of purging plug circular slit,which because the life of purging plug the circular slit is longer than that of purging plug with the rectangular slit.The plastic deformation of the purging plug with circular slit always concentrates around the slits.The plastic deformation of purging plug with rectangular slits not only concentrates around slits but also there is plastic deformation above the cross-section y=0.323 m,which is one of the reasons for the spalling of purging plug.Meanwhile,the irreversible mechanical analysis provides a new way of predicting the service life of the purging plug and other refractories.Finally,the refining effect of purging plugs with varying different slit geometries was investigated by applying a physical model in this paper.The experimental results showed that when the gas flow rate was less than 6.02 NL/min,with the slit angle increases,the angle of the bubble bundle decreases,and the bubble collision probability increases,that resulting in an increase in bubble size and the mixing time decreases.When the gas flow rate is less than 5.26 NL/min,with the diameter of the slit increases,the bubble size increases,the mixing time diminishes,the inclusion removal rate also decreases,that owing to the specific surface area of the bubble decreases.With the size of slits increasing,the slag area increases,and the slit angle is proportional to the slag area.