Best SS alloy to use in molten aluminum for skimmers and ladles

[semisolid]

I am looking for the best stainless steel alloy to use for molten aluminum alloy (380, 390 369)foundry tools. I would like to know why a particular alloy is more resistant to attack than others. How do the inconel alloys do in this application?

 

[mcguire]

Stainless steels certainly have the ability to withstand the temperatures of molten aluminum, but all grades are attacked corrosively by molten aluminum. The protective oxide on the surface that makes stainless stainless is reduced by the aluminum and the iron base of stainless readily alloys with and is dissolved by molten aluminum resulting in disappearing tools.
If you had a way to protect the stainless from contact with the aluminum, e.g. a coating, an austenitic would be the best choice since they retain their strength better at high temperature. 304 or 316 are common grades that would work. Inconel costs lots more and has the same drawbacks.
There is data on these grades at

http://www.stainlesscenter.com

 

[arunmrao]

With a refractory coating on the skimmers 304 grade of stainless steel will suffice. The higher grades may not be cost beneficial. I have seen many a foundries using plain ms material with a thick coating of refractory,preheated to cure the coating and used.Ofcourse the life will be shorter.

 

[Bugman]

Have you thought about using a coating on your stainless steel? Something like a ceramic coating that is resistant to molten aluminium like boron nitride (

http://www.azom.com/details.asp?articleID=78).

You may be able to thermally spray a coating onto the stainless steel. While I'm not an expert on this topic you could go to

http://www.azom.com/experts.asp?expertid=43

and this person may be able to assist you. There is also information available on this site on various grades of stainless steel.