Physical And Numerical Simulationon Large Inclusions Control In The Continuous Casting Process

With the extensive use of bearing steel,the quality of bearing steel is more and more strict.The content of inclusions in bearing steel is an important index to judge its quality,because the inclusions seriously affect the fatigue life of bearing steel,especially the point of inclusions.Therefore,how to control the inclusions in the continuous casting process is the key to improve the quality of bearing steel.The subject focuses on the problem that the small inclusions in the bearing steel are locally agglomerated is seriously affected.Taking Tundish?SEN?Mold as the research.Using the method of physical and numerical simulation.Based on the assessment of the quality of slab,the clogging,the flow field of tundish and mold in the production process,it is to find the source of the inclusion.From three aspects of controlling inclusions content,it is to solve the slab of quality problems in the continuous casting process.First,the structure of the turbulence inhibitor and the flow field of tundish are optimized in order to reduce the corrosion of the refractory material and and promote the removal of inclusions in tundish.Second,the SEN structure is optimized in order to reduce the clogging.Finally,the related parameters of the mold in order to promote the removal of inclusions.The results of the bearing steel slabs quality and process show that the composition,morphology,size and phase of the inclusions in the slab are very similar to the SEN clogging.The current flow pattern is unreasonable and has a short flow and death in the tundish.The condition of clogging is serious in the double and four sides outlet SEN with inner diameter of 45 mm.In addition,the upward circulation flow is weak in the mold and the removal rate of inclusions is low.The case is best with the angle of 15°double hole baffle + dam height 350 mm +turbulence inhibitor height 360 mm in different casting speeds.Compared with the present tundish,there are no short flow,extending stimulus response time by8.8s,increasing the removal rate of inclusions 9%-18% in different sizes and uniform distribution of temperature field and velocity field in the optimized tundish.Under the same casting speed,the uniformity of the outlet velocity distribution of the elliptical outlet is stronger than that of the rectangular outlet,which is more beneficial to reduce the clogging.From the surface fluctuation,the impacting depth,the flow field,the slag layer cover,the inclusions removal rate comprehensive evaluation,the inner diameter of40 mm SEN meets the indexes,and the number of clogging on the double and four sidesoutlets of the 40 mm diameter SEN was reduced by 13.1% and 23.5% compared with the current diameter of 45 mm.The industrial experiment show that the thickness of th clogging of the optimized SEN is 55.6-62.5% lower than the current SEN,and the content of MgO in clogging was also reduced by 55.7%.What is more,the flow pattern in the tundish is more reasonable,the removal of the inclusions is increased and the erosion of the turbulence inhibitor is reduced.The clogging is divided into three layers.The outer layer is mainly composed of Al₂O₃.The intermediate layer is a mixture of MgO·Al₂O₃ particles and CaO-Al₂O₃?-MgO?.CaO-Al₂O₃?-MgO?composite inclusions have low melting point and have sintering effect,and the granular MgO·Al₂O₃ inclusions are tightly bonded to form stable adsorption.The inner layer is composed of flaky Al₂O₃ and spherical iron,and there is no laminated structure between the MgO·Al₂O₃ and MgO·Al₂O₃ in the clogging.