Slyfox Posted May 24, 2017 Share Posted May 24, 2017 Hello all, I've got some questions for everyone who's more knowledgeable in forge building. I built my own forge several years ago but only in the past few months have I been starting to use it most days as I'm trying to turn this hobby into a business. Anyways I find my current forge lacking in some ways, the openings are a bit too small for the things I want to put in, the chamber is a bit big for what does go in (currently a double burner setup) and the refractory coating on the kaowool has been patched several times and in need of it again. So I figure its about time I make a new one more suited for what I'm doing now. The plus side is I have a bunch of SuperWool and Kast-o-lite 30 leftover from making my HT oven that I was thinking about using those as the lining. My current idea is to make a chamber roughly 9"x7"x4.5" (subject to change a little), the lining would be 2" of the SuperWool and then I'd cast up some 1"ish plates of the Kast-o-lite 30 for the "coating". I know the SuperWool has a rating of 2300~ degrees F but with the 1" of cast able refractory, rated for 3000 degrees F, between it and the heat how long would the SuperWool last going up to forge welding tempts? I know the refractory will act as somewhat of a heat sink but I'm willing to take that efficiency loss to protect the SuperWool if it can and move from a double burner to a single. Quote Link to comment Share on other sites More sharing options...
WayneCoeArtistBlacksmith Posted May 24, 2017 Share Posted May 24, 2017 Check out the Build a Gas Forge. It will tell you about casting the interior of a forge. With your concerns for wanting to forge larger pieces this design will help. Let me know how I can help you Thank you, Wayne Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 24, 2017 Share Posted May 24, 2017 You might want to read the gas forge section of Iforge as well. Your questions have been answered many times. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted May 25, 2017 Share Posted May 25, 2017 Well, I do like the idea of casting the hard refractory in separate plates; that will cut down a lot on possible cracks. BTW, that is a semi-insiating castable, so it should do a lot to add to the life of your ceramic wool. If you add rigidizer to the blanket, I would give the insulation a year with daily use at welding temperatures. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted May 26, 2017 Share Posted May 26, 2017 Heat reflection by re-radiation from the refractories hot face will also do a lot to keep temperatures down in the ceramic wool, while doing a lot to keep temperature up within the forge interior; a win, win, situation. Quote Link to comment Share on other sites More sharing options...
timgunn1962 Posted May 27, 2017 Share Posted May 27, 2017 I am surmising that your concern is over the Superwool's ability to handle the temperature it might see at the interface with the Kast-O-Lite, given its classification temperature of "only" 1200 degC/2192 degF and continuous use temperature of 1000 degC/1832 degF? It is entirely possible to calculate the theoretical interface temperature and make the Kast-O-Lite layer thick enough to bring the interface temperature down to whatever you decide is appropriate. I did something similar a long time ago for a waste gas burner we built at work and found it a PITA, involving some pretty daunting math, a lot of iterative calculation and many, many hours reading textbooks. The main reason I'd not do it for a forge though is that it needs real numbers that few of us have: I'd be pretty surprised to find that more than 10% of smiths could tell you their forge temperature within about 20 degrees, for example. Most of us basically just copy what others have done until we build up enough experience and understanding to work out how to improve things ourselves and, if we do a good enough copying job on a good enough initial design, improvement is not always needed. The Superwool does not melt at 1201 degC, or even close to it, so exceeding the classification temperature, even by some considerable margin, is not going to leave you with a dribbly mess and no working forge. In your shoes, I'd have no qualms at all about using an inch of Kast-O-Lite 30 over rigidized Superwool. In reality, I'm inclined to suspect that the biggest issue you'll have to contend with in respect of longevity is getting the forge properly dried out before first firing. Incomplete drying causes the water trapped in the refractory to flash off to steam causing cavities which greatly weaken the structure.These cavities seem to join up with temperature cycling. "Build it Saturday, use it Sunday" seems to be a recipe for a short-lived forge. "Build it June, use it August" seems rather closer to the mark, though climate is obviously a big factor. In some locations, it may even be necessary to take steps to slow the drying (though Astoria, OR probably isn't one of them). I'd build it, use it for six months, see what needs changing and build the next one as soon as possible so it can be dried fully before needing to use it. It's worth pointing out that the single biggest non-human factor in determining how well or badly a given forge works is the burner. Be prepared to spend at least as much time researching burners as you do researching the structural parts of the forge and do not make the mistake of costing the burner separately from the forge: A burner made from pipe fittings might look like a huge saving against the cost of a commercial item. However, once you factor in things like taps and tapping drills, the construction materials for the forge, any coating used, the regulator, hose and first fill of gas, the overall percentage saving tends to look at lot less impressive. If the pipe-fittings burner will do what you need it to do, great, that's the way to go. Mention of an HT oven and the size of forge given in the OP is suggestive of bladesmithing to me and I'd expect a burner with air:fuel ratio adjustment to be advantageous in that application. Quote Link to comment Share on other sites More sharing options...
Slyfox Posted May 27, 2017 Author Share Posted May 27, 2017 Thanks for all the responses. I've been trolling about the forums for a bit trying to discover what others had found. I wasn't so much worried about the SuperWool melting per say, more crumbling. I used a bit to block up one end of my forge for a bit and after a week or so pulled it back out to find it had hardened up and became a bit brittle. I just wanted to make sure that didn't happen too quickly in this new forge where I couldn't tell it was happening. And yes I initially started out making knives by stock removal and used a torch and some soft fire bricks originally for heat treating. Lucky for me my shop is full of all kinds of CNC tooling so building burners isnt too much of an issue. Got a lot of pipe and fitting parts leftover from when the compressed air system was installed around the building. Was going to put together another 3/4" sidearm burner, the only thing I'm missing for it at the moment is the reducing tee. And if I need to I can hook up a small blower I have at times to crank up the heat. Quote Link to comment Share on other sites More sharing options...
Frosty Posted May 27, 2017 Share Posted May 27, 2017 How about either making a gun (blown) burner or a naturally aspirated one? Mixing and matching different types of equipment doesn't usually work out very well. You're concerned enough to build the forge liner right why not the burner too? Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
john so what its my name Posted June 17, 2019 Share Posted June 17, 2019 I have sat and read till my eyes water. How-ever I still am unsure of what is need to build a forge that will allow me to make a few knifes. Im just starting and would like to build my own. Im just using 1065 -1095 material. I don't however want to limit my self to this. At this time Ive just staked some light brick on my welding table and a torch. I would like a phone # to call and talk to a person and order the wool and brick and 30 or what ever it is. Yea, Im that easy. Or should I say new-y in a old school way. A phone number to a store or a person.? Quote Link to comment Share on other sites More sharing options...
Frosty Posted June 17, 2019 Share Posted June 17, 2019 Try reading in the "Forges 101" sub section, we've been discussing how to build efficient and effective propane forges for quite a while. If you wish to try making a burner, "Burners 101" has that covered pretty well too. No need to read them all, skim the subject lines then skim the subject lines in the posts. There is NO secret formula nor blue print level instructions for the perfect . . . anything. If you're looking for something like a forge kit you need to buy a commercially built one. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted June 17, 2019 Share Posted June 17, 2019 59 minutes ago, john so what its my name said: sat and read Have you read this yet? READ THIS FIRST It will help you get the best out of the forum. You can buy most of the supplies through this forum. https://www.iforgeiron.com/forum/254-gas-forge-refractories-and-supplies/ Quote Link to comment Share on other sites More sharing options...
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