oldgeek said:
Should i still use the following flux recipe, or is there a better flux mix for my application?
(3) parts waste material
(1 ½) parts silica sand
(3 ½) parts soda ash
(1/2) part fluorspar
(2) parts borax
*(1/2) part "collector" of choice
I know i need a low viscosity flux, but i do not really know HOW to mix one. I have all of the ingredients listed above, so i would like to stick with them if possible.
Sure. Stick with them, and if you find it's not working exactly as you'd hope, start making alterations. Remember, none of this is carved in stone---and my circumstances were very different from yours.
Also, should the flux "parts" be weighed or measured out? I suspect i should weigh them out.
In my case, it was all done by volume. I chose a small container that represented a reasonable amount, then used it for everything. The very pleasant surprise I received was when I added water. I knew I'd have a terrible problem with blowing soda ash and borax away, along with some of my values. In my case, I melted directly in the furnace, with no crucible, so the entire charge was subject to the violence of the blower and ensuing flame.
Back to the pleasant surprise----I added water, in my case it was about 600 ml, and stirred to mix things well. To my surprise, in short order, the mixture started setting. I discovered that I could mix everything, stir well, then pour to a form and allow the material to set hard. I had a number of plastic ice cream bucket lids handy, so I chose them as my form. The mixture was stiff enough to create a thick section in the center, so I'd pour until the edge of the lid was filled, then allow them to firm up. They could be removed after a couple hours, then I'd allow them to dry fully. Once dry, a smack in the center with a hammer reduced them to four or five small pie shaped sections that would be easily charged to my furnace. The good part was that the process eliminated dusting completely. The hard pieces would transform from solid to molten with perfect tranquility.
I encourage you to do a few test lots, playing with ratios. No harm done if they don't turn out perfect, for you'll just send it to the furnace anyway.
The formula I used yielded exceptional results, but keep in mind, my material was laden with silver chloride (to act as a collector) and was primarily silica in nature. Much of my waste material was fiber glass (filters from my fume hood that had been incinerated). Silica is very easy to process. I added yet more silica in the way of (silica) sand to help reduce the attack on the furnace lining. In spite of using a 94% alumina, the interface between the top of the slag and the combustion chamber was rapidly eroded. The furnace required repair after three days of operation. That's the nature of using an aggressive flux.
Fluorspar serves to thin your slag---you may wish to use more or less. Using less will reduce the amount of destruction, but soda ash alone serves to dissolve things, so it can't be avoided totally.
I had my slag assayed to determine if I was achieving the hoped for results. While I don't recall the numbers now, the slag contained so little value that it was not accepted by a company that specialized in recovering small amounts of values from slag. It was their opinion that it should be discarded. That was all the evidence I needed to know that I was on the right track.
Sure enough! I hope some of this will be useful to you.
Harold
