tundish cover powder? 3

[djemba]

hello everybody

i always read from forum pages but this is my first writing..

my question about tundish slag fluxes..in continues casting process for preventing corrosion of tundish plaster which type of slag flux should we use?
as far as i read from an article basic slag is the best for MgO base plasters..

any practical answers about usage of those materials would be great?

cem

 

[unclesyd]

Not on your particular application I've seen MgO wash, Kaolin wash, and graphite wash used for slag and molten metal problems.

I've used products fro ZYP for some very high temperature molten refractory slag/glass problems. You might want to them a call.

http://www.zypcoatings.com/index.htm

 

[arunmrao]

Tundish coatings are provided to avoid lining erosion by slag,produce clean steels,easy removal of skull,reduce thermal losses. The trend now is to move away from monolithic linings towards insulating boards which offer all these advantages. However a basic wash/coating will be beneficial as suggested by unclesyd.

Learn the rules,so you know how to break them properly.
Dalai Lama

_____________________________________

 

[steelmaking]

For the basic lining MgO slags are usefull, but it depend also what steel are you cast (carbon content), if you are casting special steels, the cover slag needs to has and chemical activity in order to catch non-metallic inclusions.

 

[Ron]

Be careful of MgO slags if you are recycling the slag for aggregate or fill purposes....bad actor due to expansion and conversion to Brucite.

 

[djemba]

thank you for everyone who consider about this subject..

our carbon content is usually between 0,10- 0,25
recently we made some experiments i can also write about the slag analysis if somebody wants to talk about it..

i want to discuss about the results a little (if you see somethings wrong in this discussion directly correct me if its possible)

when no slag powder used, after 3 or 4 heat tundish created its own slag which was acidic (by the way we are not using shroud) and after 22 heat linings were cut..

then we used acidic powder we had a creamy slag under a brittle thin slag crust but again linings are not good after 22 heat..

with a high CaO content basic powder we can create a basic slag, and we observed that it was so good with catching non metallic inclusions and after 22 heat our linings was still in a good position..
but our problem with basic slag was it became solid very fastly and its quite hard to broke it for sampling..

as far as from my searchings fluidity of the slag is not related with acidity or basicity.. "Fluidity of slag comes from low melting point eutectics in CaO-Fe2O3 and CaO-FeO(about 1200 C) due to iron oxide on top of the steel melt."

so what should i add for fluidity..
should i throw some FeO powder on to slag or what?

 

[Compositepro]

This is just a guess, but borax is in many fluxes. Perhaps also sodium carbonate.

 

[arunmrao]

fluorspar (CaF2) is added to make the slag thin. Can you get a copy of Biswas Bashforth on steel making. You can understand the slag chemistry well.

Learn the rules,so you know how to break them properly.
Dalai Lama

_____________________________________

 

[unclesyd]

arunmrao,
This comes from a long time ago.

Aren't some of the feldspar's used to flux slag?

 

[arunmrao]

They are also used in welding rod(sticks) coating,to provide a fluid slag.

Learn the rules,so you know how to break them properly.
Dalai Lama

_____________________________________

 

[steelmaking]

Dear colleague, you must avoid high FeO content into the slag, it means that you have high [o] into the steel. I dont know what type of deoxidizer you use Al, Si or SiCa,
but adding of Feo into the slag will decrease content of these elements in the steel. Al203 will bock FNC nozles and you will have problems with casting. For me it is usefull to add fluspar CaF2, or SiCa prowder in order to reduce Fe0, Si02 will decrease melting temperature of cover slag.

 

[deadrange]

Under no circumstance should you be adding FeO to your slag. As the above poster has mentioned the addition of FeO will simply add oxygen to your system. Based on what you have described above, you are pouring open into an open tundish. The slag that you mention being "created after 3-4 heats" is likely a combination of ladle slag carryover and re-ox product from your open pour operation.

Have you done an analysis on the ladle slag to compare its composition to the tundish slag.

arunmrao: flourospar is indeed used in many cases to help flux in the slag.

 

[mineraltrader]

Deadrange and steelmaking are right. Fluorspar is really a killer to all type of refractory lining and banned in some countries due to enviormental reasons.
But it is almost impossible to give right advice over the net without knowing all the facts. There are at least 10 - 15 facts to be clearified before correct advice can be given.
For example: Type of steel cast, length of sequence, open cast or ladle shroud, quantity of carry over slag from ladle, thickness and composition of tundish spray. precise despriction of tundish cover (Rice Husk Ash?). Solutions depend on plant conditions. R u able to slag off, for example? I suggest you invite you supplier of tundish spray and/or cover for consulting. If they know there job, they should be able to make proper suggestions.