On Nov 21, 2009, at 5:58 AM, Erik Christiansen wrote: > On Sat, Nov 21, 2009 at 05:00:13AM -0700, Jeshua Lacock wrote: >> One of the beauties of casting with aluminothermic reactions is there >> is no crucible used (or furnace)! > > Would another beauty be that TiO2 is cheap enough to put in paint and > plastic, but Ti metal costs a mozza?
Indeed. > I can't quite get over that you're > casually extracting the metal from a most recalcitrant oxide, while > current industrial processes to do the same are horribly expensive. A considerable percent of commercial titanium reduced uses a similar reaction. The are several reasons why Ti costs "a mozza": 1. Marketing - they have you by the *alls - its Titanium!!! You know you want it! 2. It lasts forever - industries prefer you have to buy replacements - often! 3. Extremely difficult to machine and work with. 4. Raw materials still are not cheap. If you do the math for buying the TiO2, the aluminum powder, fluorite, etc, it would work out to around the going rate for raw titanium. Of course, if you order materials by the boat load, you can get the costs down. >> You plug the sprue (entry) going to the mold cavity with a thin sheet >> of metal (that is melted once the molten metal reaches it), and put >> the chemical on top. The slag melts to the top and the metal drains >> out into the mold.... > > Does it remain molten long enough to flow into a mould, if the > reaction > takes 20 minutes? The burning stage only lasts perhaps a couple minutes. But it keeps reacting for a good while afterwards. The burn rate is configurable by the size of the aluminum particle and the amount of flux used. Here is a pic of the actual combustion stage: <http://openosx.com/hotspring/TiFire.jpg> > Or was that just because you were melting a barrel of > the stuff? Even so, that wouldn't give a sound casting, just a pig for > remelting? If the plug and reaction rate is properly chosen, then you can get sound castings as I have. To get high purity Ti, one would have to re-melt the pig in an inert atmosphere (argon) and remove any slag that floats to top. That being said, I have made usable parts directly from Ti aluminothermic reactions. Cheers, Jeshua Lacock Founder/Programmer 3DTOPO Incorporated <http://3DTOPO.com> Phone: 208.462.4171 ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
