The Research And Control On The Edge Defect Of Low Carbon-aluminum Steel

Low-carbon-aluminum steel slab of high-quality and high additional value such assilicon-steel,appliance-steel is the main product in some steel plant.Owing to theincreasing casting speed and the decreasing rolling temperature, the defect rate of edgein the later processes increased to4.04%and it had an effect on the hot rollingproduction and the quality of low-carbon-aluminum steel slab.From the comparision of the edge of the low-carbon-aluminum steel slab,the edgedefect of steel sheet is developed from the slag inclusions rolled. The defect resultsanalyzed from SEM and Energy Dispersive Spectrdmeter (EDS),the main reason for theslag inclusion occured on the slab surface is the slag entrapment and poor removal ofAl2O3inclusions, therefore,the optimizition of mold flow field is necessary. Through thenumerical simulation, physical simulation researches and industrial experiments,theconclusions can be drawed as follows:(1)After blowing Ar in mold, the upward center is closer to narrow surface andmoves up,then a smaller reflux one is formed on the liquid surface which is close tonozzle.(2)Enlarging the side angle of nozzle,the liquid surface fluctuation is less and theimpact deepth of stream is a little larger; enlarging the side expansion angle ofnozzle,the liquid surface fluctuation and impact deepth of stream both decrease;the bestside angle of nozzle is20°.(3)With increasing the inserted deepth of nozzle,the liquid surface fluctuationdecreases apparently, but the impact deepth of stream increases;with the Ar blowingamount increasing, the impact deepth of stream decreases for a little, but the slagentrapment possibility becomes larger for the impact of Ar bubbles on the mold surfaceis larger; the best inserted deepth of nozzle is150mm and the blowing Ar amount is15~20L/min(4) Crystallization vibration mode using high-frequency and small-amplitude canreduces the incidence of edge defect.(5) After using the inserted nozzle which has been optimized and the castingparameters, the edge defect decreased from22.4to7.4%.