i would like to build a furnace w sic elements...

[nicko0]

would someone translate that to ohm mm2/m

[PyroChixRock]

You guys are making me want to build a furnace.

[brads]

Resist that urge, lol.

[nicko0]

im still working on this. just didnt want anyone to get too discouraged and feel all for not.

[brads]

I just wanted to revisit this thread for those sceptics who seemed to think I pulled the SSR control system for my 200 lb, 3 phase glass furnace out of my ass, or that it is inferior because it wasn't designed by a real industrial engineer. Not only was this method of control designed by an engineer, it appeared in "Solid-State Relay Handbook, with Applications", a book of SSR applications published by Crydom in 1988 and reprinted in '90, '94, and '97, and written by Anthony Bishop, their Applications Engineering Manager. Crydom is one of the largest SSR manufacturers in the world.

Here's a copy of the page (pg. 140) that originally gave me the idea for using this method:



Although I think I paid $25 or $30 for the book when I bought my copy in 1991 or '92, it can now be downloaded for free here. Even if there had been nothing else in the book of value to me aside from this control design, that alone served me very well for 14 years, so my original book purchase was well worth it. (It would still be serving me well, but I no longer have a shop with 3 phase power.)

[nicko0]

i totally believe you, the design you use is spot on. its exactly the design recommended by the element manufacturers and is the only reliable proven equipment and design ive found, and the only type of build i see commercialized to any extent.

at temps above 2400 it appears more control is recommended but i feel like this design can be arranged to accommodate higher temps.

[brads]

I'm not entirely sure what you mean by "more control", as this system provides excellent control, in spite of its simplicity. I've personally used it on my own furnace to 2550F. But I can understand potentially needing more of a power cushion to deal with SiC aging at higher temps than 2500 or 2600F, which could present some problems doing it this way.

But getting back to your original question, I still agree with Draconis that moly elements are your best bet for batching low COE boro if you want to melt electrically. I also think that Sky (somewhere) had a good point about considering gas instead of electric melting. The technology is well understood and the question of element material becomes moot. Then you can concentrate on what the hell you're going to use for a crucible at those temperatures. Whatever you choose, I can pretty much guarantee you won't like the price.