Bret Posted March 8, 2008 Share Posted March 8, 2008 OK so Im new to melting steel. done some alum work so Im familiar with the basic process, but the equip is another story. I was looking online for crucibles with a temp rating high enough that I was confident I wasnt gonna have a melt down, and I ran across silicon-carbide and high purity Alumina crucibles. The Alumina are about twice as much and I was wondering if anyone had tried them and had any input on the subject. Link to comment Share on other sites More sharing options...
Greg Thomas Obach Posted March 8, 2008 Share Posted March 8, 2008 clay graphites work for me... and their cheaper.... just watch as there is carbon uptake the longer the steel is liquid.. had one SiC crucible... was expensive and broke after only one melt... maybe the brand i used sucked.. who knows.. --i'd find what your comfortable with and stick with it... they all have different characters... oh and follow the instruction for using them... some have to be cured let us know how you do Greg North Shore Forge & Ironworks Link to comment Share on other sites More sharing options...
JJH Posted March 8, 2008 Share Posted March 8, 2008 What do you guys this of a home-brew crucible the recipe is: 37.5% Fireclay 61% Grog 1.5% Potash Feldspar I was thinking of making a batch for doing wootz so they could be smashed to get the cake out. Also what could I substitute instead of potash feldspa, I know its a flux and to hand I have fluorspa, sal ammoniac or borax or a combination of all three. Link to comment Share on other sites More sharing options...
Bennett Posted March 9, 2008 Share Posted March 9, 2008 What do you guys this of a home-brew crucible the recipe is: 37.5% Fireclay 61% Grog 1.5% Potash Feldspar I was thinking of making a batch for doing wootz so they could be smashed to get the cake out. Also what could I substitute instead of potash feldspa, I know its a flux and to hand I have fluorspa, sal ammoniac or borax or a combination of all three. That looks good to me. I wouldn't use borax or flourspar in a crucible though. The melting point is too low. Plus it could eat up the crucible @ heat. Might be OK for a stack bloom lining though? Here is where I've been getting my crucibles lately. Not a bad price, as shipping is included. It shouldn't be that much more to the UK. http://www.budgetcastingsupply.com/busines...ist_11-1-07.pdf This place is a very good source for bulk refractory also.. http://www.refwest.com/ clay graphites work for me... and their cheaper.... just watch as there is carbon uptake the longer the steel is liquid.. had one SiC crucible... was expensive and broke after only one melt... maybe the brand i used sucked.. who knows.. --i'd find what your comfortable with and stick with it... they all have different characters... oh and follow the instruction for using them... some have to be cured let us know how you do Greg Yeah, the clay graphite are great and cheap, but I can't use them, as the 5000 degree liqiud iron, sucks up carbon at a furious rate. I would end up with cast iron It's not fair I tell ya. The SiC crucibles work very well, but they do have a tendancy to break on occasion. Be carefull with the addition of glass and such, as you will have to chip it out. The t-mite slag works great as a cover and does not seem to bond well to the SiC, even though they are both alumina. Oh, BTW, I dicovered that thermite slags are very desirous as a high heat refractory!! So John, be sure and tell Colin to save the black t-mite slags! I'm going to pulverize some and do testing. I think Chip was going to try something with them also. Jerry Link to comment Share on other sites More sharing options...
JJH Posted March 9, 2008 Share Posted March 9, 2008 What would happen if I left the potash feldspar out? Link to comment Share on other sites More sharing options...
Greg Thomas Obach Posted March 9, 2008 Share Posted March 9, 2008 maybe worth a looksee http://forums.swordforum.com/showthread.ph...ecanni+crucible i wish you luck in your attempts.. please keep us informed Greg North Shore Forge & Ironworks Link to comment Share on other sites More sharing options...
Jeff Pringle Posted March 9, 2008 Share Posted March 9, 2008 I used this recipe successfully once or twice, before I realized it is much cheaper to buy crucibles than to make them... Epk 40 Calcined Kaolin 20 Tennessee Ball Clay (OM #1) 20 Grog 10 Flint 10 Flint (silica) is here instead of feldspar; and it has a much lower melting point - must be the glue that makes the crucible hang together once it's been fired. Why it works (or not ), you'll have to ask at a ceramicist's forum, though most clay people don't go so hot the chemistry remains the same... Jomsvikingar Raða Ja! http://vikingswordsmith.com Link to comment Share on other sites More sharing options...
JJH Posted March 9, 2008 Share Posted March 9, 2008 So are you guys really saying cough up and buy crucibles? If so is the general consensus Silicon Carbide as there is no carbon to absorb though Fe eats them or adjust the carbon content of the wootz and use Clay graphite. Or neithe and go for a homebrew? Link to comment Share on other sites More sharing options...
Bennett Posted March 9, 2008 Share Posted March 9, 2008 ...I was thinking of making a batch for doing wootz so they could be smashed to get the cake out... If you want wootz, clay graphite is the way to go. Buy a type A, and you wont have to smash it. It will plop out upon cooling. So are you guys really saying cough up and buy crucibles? If so is the general consensus Silicon Carbide as there is no carbon to absorb though Fe eats them or adjust the carbon content of the wootz and use Clay graphite. Or neithe and go for a homebrew? Well, I have less experiance than Jeff or Greg at crucible steel, but I gave a go at homemade crucibles. I decided that the very little you save on money, is not worth the cussing and dissapointment of a faild crucible, or a contaminated cake. Not that you may be the guy to improve the comprimise, but it may just be good to shop around for a good price and pony up for a couple.... Link to comment Share on other sites More sharing options...
JJH Posted March 9, 2008 Share Posted March 9, 2008 What do you mean the cakes plop out a friend has made wootz and every attempt destroyed the crucible or at least the ones I saw is that too much glass? I would definitely buy a crucible for casting purposes as I want max handling strength, but didn't want to keep throwing $60 away at a time on damaged crucibles. Was all may have a rethink, or join a pottery class and get 'em fired properly before use. Link to comment Share on other sites More sharing options...
Bennett Posted March 10, 2008 Share Posted March 10, 2008 (edited) What do you mean the cakes plop out a friend has made wootz and every attempt destroyed the crucible or at least the ones I saw is that too much glass? I would definitely buy a crucible for casting purposes as I want max handling strength, but didn't want to keep throwing $60 away at a time on damaged crucibles. Was all may have a rethink, or join a pottery class and get 'em fired properly before use. Yeah, I hear ya. I've found that using a lid made from insa wool, seald with saintinite or high cone clay, works well. You don't have to use much glass. Also I use a nifty tool to chip the slag and glass out. An old vibro engraver. Electric or pneumatic. It works just like a mini jack hammer. Just don't point it directly at the crucible, and take small nibbles near the walls. The type A sizes are a tapered ID. Hope I helped, Jerry Edited March 10, 2008 by Bennett Link to comment Share on other sites More sharing options...
JJH Posted March 11, 2008 Share Posted March 11, 2008 Will do once I've built the furnace. Link to comment Share on other sites More sharing options...
Greg Thomas Obach Posted March 11, 2008 Share Posted March 11, 2008 Jerry... thats a neat little tip... i'll have to give it a try... if you gently chip out an ingot... lots of times the clay graphite will go up to 8 uses and more.. making your own crucibles is something i'd love to do.. and didn't work out for me in the past...... but i was alway in a rush in the past... besides....i can't think of one thing that is cheep about making crucible steel.. .. if we could find a way to make the crucibles from local materials... that would be neat Greg North Shore Forge & Ironworks Link to comment Share on other sites More sharing options...
Matt Bower Posted March 13, 2008 Share Posted March 13, 2008 "If so is the general consensus Silicon Carbide as there is no carbon to absorb . . . " Uh, the chemical formula for silicon carbide is SiC. If you recall your periodic table, "C" is carbon. In other words, there's plenty of carbon in silicon carbide crucibles. And while I can't speak to this from personal experience, I'd be somewhat surprised if molten Fe couldn't suck up that carbon (and the silicon, too) fairly easily. The thing to experiment with for homemade steel crucibles is probably magnesium oxide. It seems to be the main component of most of the refractories used in commercial steel mills. As a starting point, various acids can act as binders for MgO. Link to comment Share on other sites More sharing options...
Bennett Posted March 13, 2008 Share Posted March 13, 2008 "If so is the general consensus Silicon Carbide as there is no carbon to absorb . . . " Uh, the chemical formula for silicon carbide is SiC. If you recall your periodic table, "C" is carbon. In other words, there's plenty of carbon in silicon carbide crucibles. And while I can't speak to this from personal experience, I'd be somewhat surprised if molten Fe couldn't suck up that carbon (and the silicon, too) fairly easily. The thing to experiment with for homemade steel crucibles is probably magnesium oxide. It seems to be the main component of most of the refractories used in commercial steel mills. As a starting point, various acids can act as binders for MgO. Yep. It does, but the carbon in SiC is not as available as graphite. Time and temperature make the rule. I have gotten only trace amounts from a SiC crucible, (spectro), with thermite. Link to comment Share on other sites More sharing options...
Dmitry.M Posted March 14, 2008 Share Posted March 14, 2008 (edited) I make my own crucibles. They last one melt and sometimes fail. There is nothing to reuse after the melt, the walls are so etched with the flux. I reuse the covers though, they might last for many melts if no flux or iron oxide gets on it. Ones iron oxide gets on the ceramic it etches it right through. My recipie is 2parts of Mullite and 1 part of EPK Kaolin. Sometimes I add some grog or graphite, but it seems like the most important thing is to pack the mixture in the mold up to the right density. Too tight and the crusible will crack, too loose and it will be etched through and you have a steel cake on the bottom of the furnace. Edited March 14, 2008 by Dmitry.M 1 www.artandknife.com Link to comment Share on other sites More sharing options...
Greg Thomas Obach Posted March 14, 2008 Share Posted March 14, 2008 thank you Dmitry that is some good information ! I believe its a good talent to have... to be able to make these crucibles ! Greg North Shore Forge & Ironworks Link to comment Share on other sites More sharing options...
Dmitry.M Posted March 15, 2008 Share Posted March 15, 2008 Thank you. This is one of my crucibles after successful melt (1) and not very succesful (2) www.artandknife.com Link to comment Share on other sites More sharing options...
JJH Posted March 16, 2008 Share Posted March 16, 2008 Goos Efforts! Any ideas what caused the failure, and do you fire the crucibles first in a potters kiln? Link to comment Share on other sites More sharing options...
Dmitry.M Posted March 16, 2008 Share Posted March 16, 2008 Any ideas what caused the failure, and do you fire the crucibles first in a potters kiln? I think it might fail because of wrong clay composition, or too much water in the clay or it was too dry. It also could be a result of cracks during drying. I do not fire the crucibles, just dry them to minimum humidity. Last step I do in my kitchen stove. Unfortunately this is pretty touchy stuff, sometimes i make 5-7 crucibles at ones and none of them fail. Sometimes some of them fail. Last time I made 3 and all of them failed. But crucibles fail different ways, this is just one example. I hade few crucibles exploded during the melt. www.artandknife.com Link to comment Share on other sites More sharing options...
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