Inclusions removal in a tundish with argon purging

The effect of argon purging site and argon flow rate in a tundish,in particular argon purging in injection flow area,on steel cleanliness was investigated by field test.The results show that bubbling at injection flow area with suitable argon flow can improve steel cleanliness,while bubbling at the corner site in casting area and nearby the stopper has no obvious effect on steel cleanliness.The suitable argon flow rate is 6 L·min^-1 when purging at injection flow area,and compared with no argon bubbling,the removal rate of total oxygen and inclusions in steel can be decreased about 10%.But large argon flow with 15 L·min^-1 will obviously increase total oxygen and inclusions in steel.Inclusions removal in the argon purging tundish may be explained as that when argon purging at injection flow area,bubbles will be smashed into a smaller size by the strong turbulence intensity.A large number of diffusive bubbles in molten steel not only accelerate the collision between inclusions,but also increase the probability of bubbles to capture inclusions,which result in the increase of inclusion size and accelerating inclusions floating up and being removed.On the other hand,the distance from injection flow area to the tundish nozzle is the longest,and when argon purging at injection flow area,the grown-up inclusions have the longest time to be removed from steel.These two factors make purging at injection flow area have significant impact on inclusions removal.