nozzle clogging with ladle shroud 4

[metudgn]

hi,

we are casting plain carbon grades in our continuous cating machine with 0,17-0,20 % C; 0,70-0,80 % Mn; 0,15-0,20 % Si; 0,030 % S; 0,010 % P. No Aluminium and Calcium wire addition is applied in ladle furnaces. Only 30 kg of Aluminium is added during EAF tapping.

During open casting, we do not have any probem of castability in tundish zirconia nozzles. However, when we apply ladle shroud between ladle and tundsh, clogging starts in our 18 mm zirconia nozzles. Even, we have very low Aluminium and Calcium content in our steel (0,003 % Al; 0,0005), analyze of clogging matrix shows alumina. We are searching the reason.

 

[TVP]

What is happening in the ladle? Are you using argon bubbling/rinsing/stirring? Synthetic slag? I would guess that the alumina is left over from the deoxidation process and remains in the ladle until pouring into the tundish. Are you sure that the substance clogging the nozzles is not a reaction product with the ladle refractory materials (Mg & Al spinel)?

 

[EdStainless]

I would start looking for refractory damage. You may be pulling it out of you lining somewhere else.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[steelmtllrgst]

Yes - examine refractory compositions. What is heat size for 30kg deox add? Soluble O may be attacking then oxide remains in liquid.

 

[MSUKeith]

Check on your tundish flow change after adding the shroud - you may be considerably changing tundish flow and distrubing tundish powder/surface. Lots can be seen through FEA of flow or water modelling.

Also, consider adding argon purge in ladle to tundish shroud (preferably just below ladle slide gate) if its not there already.

 

[metudgn]

One heat is around 110 tons. So, adding 30 kg of Al shall be very small quantity. We are stirring the steel with Argon plug underneath the ladle during Ladle Furnace operation. We are workig with Ca-silicate type ladle slag.

During CCM operation, Alumina type ladle shroud is used, and faced with nozzle clogging. When we take out ladle shroud from operation, no clogging occurs.

 

[mcguire]

This is a common problem with AK steel. Ca wire injections are required to liquify the aluminum oxide residue from deoxidation. This makes a calcium aluminum oxide with a lower melting point than the steel temperature at the nozzle.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[steelmtllrgst]

I agree with MCGUIRE, but be very careful with calcium treating grades that have any significant sulfur level - CaS can cause more problems that aluminates.