The Analysis And Control Of Submerged Nozzle Clogging For Ultra-low Carbon Steel Containing Titanium

Al₂O₃ inclusion is produced in IF steel by alumimum deoxidation during steelmaking,the addition of Ti influences the production of Al₂O₃ inclusion,which increases the chance of nozzle clogging.Analysis on the formation of clogging materials and blowing process are studied for nozzle clogging during ULC sreel containing Titanium steelmaking.Clogging materials are sampled from the inner wall of clogging SEN after continuous casting 4 heats of Ti-IF steel for SEM-EDS,the result of experiment suggests that the main component of clogging materials is Al₂O₃,and containing titanium oxide and other inclusions.Remnant inclusions after refining,inclusions by reoxidation,Al₂O₃ produced by reaction between steel and refractory and inclusion precipition because of temperature reduction are main sources of inclusions in steel during casting.These inlusions can not be removed during casting,and the process of argon stirring in nozzle is used to prevent the SEN from clogging.A 2:1 water model is engaged for stopper and tundish upper nozzle for argon blowing of 3# slab caster in that steel plant.The effects of argon blowing on molten steel flow both in nozzle and mould have been studied,and the analysis and summary of critical gas rates in different casting conditions will be effective to improve casting production in steel plant.The water mold study suggests that when blowing gas into the nozzle,with the gas rate increasing,the stirring area will extend downwardly and gradually become stable,and the stirring area ratio in the inner surface,the stirring volume ratio and the stirring strength are all increases.With the experimental casting speed of 0.85⁰.99m/min,and immersion depth is 120¹40mm,when the gas rate is critical,the stirring area is between the 1st to the 6th gas hole,the area ratio is about 20%⁵0%,and the volume ratio is between 20%⁹0%,but the stirring strength is difference.The starting stirring area will move downward at lower speed and deeper depth.The critical gas rates are different at all kinds of casting speed and immersion depth,and it is higher at lower speed and deeper depth.And the critical gas rate of nozzle is much higher than that of stopper.The gas injected into the mold makes the upper flow field move upward and towards the nozzle.The higher gas rate,the more intense level fluctuation and the lighter immersion depth on the narrow side of mold.