As an alternative to Kanthal (which reaches up to 1200-1300C chamber temperature) I found a hotter alternative up till 1600 C for an electric cast iron furnace. I found 'Globar' SiC elements: https://www.kanthal.com/en/products...ng-elements/silicon-carbide-heating-elements/ On ebay I found some listings: https://www.ebay.com/sch/i.html?_dl...ftrt=901&_ftrv=1&_nkw=globar+heating+elements Many people here have experience with Kanthal wire, including myself, but does somebody have experience with these elements ?
No experience with these units but....... I'd have to have a real need before I'd consider them. Same material furnace igniters are made from and they are fragile and picky. A fingerprint can shorten their life considerably.
I don't know about those specific units at the links but I took a pretty hard look at it some time ago. SiC and MoSi2 are the most common materials for high temp electric furnace elements. Some claim up to 1500c but most will back off that to 1400c for continuous use and life caveats. The elements can be pricey, undergo significant changes in resistance while heating and require controlled heating and cooling schedules to avoid fracture during the temp cycle both up and down causing some concerns about furnace use, ie removing a crucible. Consequently, they require more sophisticated/complex electrical controls and temperature sensing compared to resistive wire. They can be fragile. Most are straight or U-tubes hung from the top of the furnace wall. Furnace materials and electrical conductors to connect to the elements also take special attention. If you splatter metal on the element it will fail, which is true of Kanthal too, but can be more difficult to avoid de-slagging iron. Though I didn't/haven't completely written it off, I did decide against pursuing it for then/now. Already have a big backlog of aluminum parts to cats! Best, Kelly
@Kelly Alumina: I know these issues about Kanthal Super (MoSi2): expensive and requires a well controlled heating up schedule, i.e. heating up very quickly to above 1000 C as it is very brittle below 1000 C, but I did not know about SiC elements. Until induction furnace become affordable for amateurs, I stick to propane melting for cast iron and arc melting for (small quantities of) stainless steel.
Not sure if all SiC and MoSi2 element control schemes are the same, but, I looked at a few commercial ovens and their control schemes. The SiC was better as far as complexity of power control but still not simple on/off control. Either way, when pressed the manufacturers about continuous operating temps and melting furnace duty, I concluded they would be marginal at best when it came to iron temps and with that, I thought there was little to be gained for me because bronze temps were probably already within reach with resistive wire, and if I was going to put that kind of effort into building a power supply and control scheme, I'd probably do that (or just buy) for an induction system. For me, at minimum, I would want an A20 (minimum) to A60 melt capacity, aluminum at high end but any metal at low end. Some of the Chinese sourced induction systems are within the realm of the possible $, and, making the power available to do so is doable with effort, but it would mean a dedicated foundry space that I don't have and would be unwilling to dedicate permanently........but sure would be nice. My furnace is on wheels and functions and stores wherever I desire but I have a drop cord with 6ga conductor. Problem is, Only 240vac single phase, and that means a lot of current for say a 50kw+ induction power source. I was thinking the SiC or MoSi2 system would be a power compromise versus melt time and still potentially portable on wheels. a 50kw drop cord wasn't a comforting feeling for me. Not now, might build a smaller A10 sized induction system one day. That still covers a lot of ground. Best, Kelly
Long time no see, gents. In my experience, MoSi2 are EXTREMELY fragile vs Kanthal. At work we have a decent sized box oven that uses those and they're expensive and easily broken. Globar SiC elements are detailed in this book which is a treasure trove of cool stuff (more chemistry related but has some details on resistance furnace builds): https://library.sciencemadness.org/library/books/brauer_ocr.pdf Kelly, a 50 kW induction melter will do some decent sized iron/steel melts (I'd imagine about 35-50 lb heats) without much issue at all. I have a 35 kW Inductotherm and it melts steel/cast iron like ice cubes in August.
