Study On The Control Of Large Inclusions In IF Steel Continuous Casting Slab For Automobile Exposed Panels

The automobile exposed panels are extremely demanding on surface quality,with the acceletation of the pace of varieties structural adjustment by iron and steel enterprises.MaSteel increase the use of steel efforts in the development of auto panel,but for inclusion in the surface quality of cold rolled plate problems caused by metallurgical defects,become one of the main bottlenecks of automobile panel scale and brand.Through oxygen nitrogen analytic instrument and ASPEX inclusions automatic analytic instrument,the present quality of IF steel used in automobile panel of Masteel was analyzed and evaluated,and the flow field of tundish and mould in automobile plate production process was optimized by physical method.The flow field,temperature field and electromagnetic parameters in FC-moud were simulated and analyzed by mathematical simulation method.On the basis of this,the optimization effect of automobile panel production process was verified through industrial experiments.The results were as follows:The quality analysis of if steel used in automobile panel of Masteel shows that the surface inclusions of cold-rolled sheet are mold slag,bubble inclusions and Al₂O₃+Al₂O₃-TiOx.The proportion is 30%,35%and 25%,the ratio of metallurgical defects of 1100-1400mm section slab is as high as 10.53%.The optimization study of tundish flow field shows that for the rectangular tundish with the weir and dam combination,the steel flow channel between the retaining weir and dam have the greatest influence on the flow field of molten steel,The height of the dam is optimized to 300mm from the original design of 230mm.The distance from the bottom end of the retaining weir to the bottom of the middle envelope is optimized from the original design of 230 mm to 550 mm,and the horizontal spacing wall dam the original design of the 150mm is optimized for467mm,compared before and after optimization of average residence time increased49.33s,the dead volume is reduced by 6.17%;the inclusion removal rate increased by18.3%.The flow field optimization of the mould shows that it is not appropriate for the casting machine with 950-2150mm width to adopt the same type of nozzle for all sections.It is better to use different types of submerged nozzle according to950-1600mm?1600-1800 mm?1800-2150mm for comprehensive consideration of quality and field use.The study of flow field,temperature field and electromagnetic parameters in FC mould shows that the magnetic field intensity of FC-MOLD?is"hyperbolic"in the mold height direction.The application of magnetostatic magnetic field can change the flow direction of molten steel and influence the distribution of the upper and lower circulation region.The magnetic field strength of the upper and lower coils is kept at0.6-0.7:1,the shape of molten steel in mold is best;When the casting speed is lower than 1.6 m/min,the FC-MOLD may be not used,Based on argon flow rate,nozzle insertion depth of SEN,the width and casting speed.FC mould process control model are established.The production practice shows that:?1?the horizontal distance between the dam and the retaining weir is optimized by the original design 150mm is 467 mm,The average decrease value of total oxygen in steel from the end point of RH to the tundish steel was increased from 1.61ppm to 4.91 ppm;?2?the submerged nozzle is optimized from a single type to 950-1600mm?1600-1800mm?1800-2150mm according to the width of the slab.The proportion of surface defects of 1200mm?1600mm?1800mm slab corresponding to cold-rolled coil inclusions decreased by4.65%,3.10%,0.66%respectively compared with the same period of last year;?3?the casting speed is more than 1.6m/min.The FC mould process is used.The amount of inclusions smaller than 15um increases in the surface 5mm of salb.The size of inclusions in 15-50um has a tendency to decrease.?4?Mold powder with different casting speed and different performance indexes can significantly improve the quality and stability of IF steel continuous casting slab for automobile panel.?5?The rate is significantly lower than that of unscafing slab,Under the existing conditions,the scafing depth of 3-3.5mm is more economical and feasible.?6?after continuous casting process optimization.The sealing ratio for cold rolled panels fell from 6.18%in 2014 to 1.5%in 2017,and stability improved significantly.