rwtf82 Posted December 11, 2011 Share Posted December 11, 2011 I've seen a lot of people talking about their forges and how they've lined them with Kaowool or a similar insulating material with a temperature rating of 2300 F. I've read that propane can burn at 3500 F in the air. Is it safe to use that sort of insulation with a propane forge? I've been having trouble finding any refractory or insulation rated above 3300 F. Will a propane forge not reach 3500 because of incomplete combustion or heat loss? Am I missing something here? I guess what I really want to know is how to decide what type of insulation is going to be safe for me to use (without a trial and error process). Thanks for your help in advance. Best, R Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted December 12, 2011 Share Posted December 12, 2011 Many propane forges do not reach 2300 degF welding temps as the cost of refractories tends to go way up with the temperatures they are good for I would start with one that is commonly used by smiths. The refractory in a forge is a consumable, expect to replace it if you use your forge a lot! Quote Link to comment Share on other sites More sharing options...
MattBower Posted December 12, 2011 Share Posted December 12, 2011 Theoretical adiabatic (without heat transfer) flame temp is what you see quoted in the flame temperature tables, and it's very different from what you can achieve in a forge or furnace in the real world. You would be really pushing the envelope to hit 3000 degress in a propane forge, I think, and many forges can't even hit the ballpark 2300 or 2400 you want for forge welding mild steel. In actual practice, 2300 degree fiber blankets hold up pretty well at forge temperatures (even forge welding), especially if they're protected with a thin layer of castable refractory as a hotface. What's more, overheated fiber blankets begin to shrink and lose some of their insulating value, but they remain usable well beyond the classification temperature. (At least the traditional ceramic fibers do. I've heard different concerning SuperWool.) I know of at least one guy who makes wootz -- which requires making molten high carbon steel) -- in a "furnace" composed of nothing more than a tube of several wraps of ceramic fiber blanket. I'm sure the stuff doesn't last long at those temps, but it illustrates the point. Quote Link to comment Share on other sites More sharing options...
WayneCoeArtistBlacksmith Posted December 12, 2011 Share Posted December 12, 2011 The previous answers pretty well cover it. You should use a ceramic blanket. It is a better insolator and weighs less. You should use a castable refactory to protect the blanket from the flame and flux and protect you from the floating ceramic fibers (read glass). You really dont want to be sucking glass fibers down deep in your lungs. Then paint an Infrared Reflective product (ITC 100 or Plistix) over the castable to increase the effencency of the forge. I have Inswool and Kast-0-Lite 3000 degree and 2600 degree castable and Plistix. I have not had anyone report to me any problems using either of these castables. Quote Link to comment Share on other sites More sharing options...
rwtf82 Posted December 16, 2011 Author Share Posted December 16, 2011 thanks guys. i didn't want to make any assumptions that could have caused problems down the line. cheers Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted December 16, 2011 Share Posted December 16, 2011 The biggest problems beginners tend to do is to 1: Want to pump a lot of money into something before they even try it out, (on another forum a guy is trying to sell an anvil he paid over $1000 for as he can't smith in his new place...) 2: Expect that what they start off with will be the one aspect of the craft they will do for the next several decades and so want to build a huge masonry forge when in reality they will probably be setting a small propane fore on top of it in a year or two. 3: Over think things; a simple hole in the ground has been used as a forge for thousands of years: Fancy != Better a lot of the times. 4: Try to reinvent the wheel: I've seen several folks posting to the effect that "I've never done *any* blacksmithing before; but I have designed a forge superior to others! (and then have the design such that it recycles exhaust into the burners producing massive amounts of CO) Yes you CAN make improvements; *but* you need to know how things work *first*! Quote Link to comment Share on other sites More sharing options...
kraythe Posted December 27, 2011 Share Posted December 27, 2011 I've seen a lot of people talking about their forges and how they've lined them with Kaowool or a similar insulating material with a temperature rating of 2300 F. I've read that propane can burn at 3500 F in the air. Is it safe to use that sort of insulation with a propane forge? I've been having trouble finding any refractory or insulation rated above 3300 F. Will a propane forge not reach 3500 because of incomplete combustion or heat loss? Am I missing something here? I guess what I really want to know is how to decide what type of insulation is going to be safe for me to use (without a trial and error process). Thanks for your help in advance. Best, R Use Safe wool and coat it with a half inch layer of Kastolyte 30. Both can be obtained from the hitemp refractory store on ebay. If you exceed that with common burners then I would be amazed. 3500 degrees farenheit is pour temp for cast iron. There is most likely no way in heck your forge will ever get that hot. If it does you will have other massive safety problems unless you know that you are doing. The biggest forge problems for smiths is actually boric acid decomposition of refractory materials. Most fluxes eat refractory materials, even the expensive stuff. When forge welding make a disposable 1/4 inch steel catch pan with a spout at one end to catch the borax and let it drip out of the forge into a catch bucket. The stuff is molten at near 1000 degrees so a catch bucket lined with refractory is in order. When that pan corrodes due to oxidation ( and it will ), throw it away and put in another. Quote Link to comment Share on other sites More sharing options...
MattBower Posted December 27, 2011 Share Posted December 27, 2011 3500 F is way beyond the pour temp for cast iron, actually. In fact it's quite a bit hotter than the pour temp for cast steel! Quote Link to comment Share on other sites More sharing options...
kraythe Posted December 27, 2011 Share Posted December 27, 2011 Appears you are right. I didn't know steel was that low. I have only poured aluminum but cast steel for thin wall pours at 3092 farenheit according to this table. At any rate there is no way in heck he gets his forge up to even 2600 with standard burners. A ribbon might be able to hit 2800 but it would be a BIG burner and use a ton of fuel. Quote Link to comment Share on other sites More sharing options...
MattBower Posted December 27, 2011 Share Posted December 27, 2011 I agree. 3000 might be doable with a serious preheat of the combustion air, but I don't think it'd be an easy build. Quote Link to comment Share on other sites More sharing options...
Big Lake Forge Posted December 28, 2011 Share Posted December 28, 2011 my buddy gave me a burner that he was going to use in his grill( he had a old chicken grill thing). But it shot a propane flame out 4 foot and in my forge it burnt through 4 inches of kaowool and the side of the forge(about 1/4'' thick) in about 5 mins.So i think it was alot hotter than 3000. Quote Link to comment Share on other sites More sharing options...
kraythe Posted December 28, 2011 Share Posted December 28, 2011 Possibly. The flame temp of propane can reach in excess of 3900 degrees. It sounds like the burner was to large for the forge. Quote Link to comment Share on other sites More sharing options...
MattBower Posted December 28, 2011 Share Posted December 28, 2011 my buddy gave me a burner that he was going to use in his grill( he had a old chicken grill thing). But it shot a propane flame out 4 foot and in my forge it burnt through 4 inches of kaowool and the side of the forge(about 1/4'' thick) in about 5 mins.So i think it was alot hotter than 3000. What you describe does not necessarily indicate an exceptionally high temperature in the forge. Was the Kaowool lined with hard refractory? Quote Link to comment Share on other sites More sharing options...
Big Lake Forge Posted December 31, 2011 Share Posted December 31, 2011 well, does satanite count? Quote Link to comment Share on other sites More sharing options...
MattBower Posted December 31, 2011 Share Posted December 31, 2011 Close enough. Very interesting. Quote Link to comment Share on other sites More sharing options...
MattBower Posted January 1, 2012 Share Posted January 1, 2012 Disregard. Quote Link to comment Share on other sites More sharing options...
PJames Posted January 7, 2012 Share Posted January 7, 2012 I have ordered plistix, but it has not come in yet. Is it wise (read SAFE) to fire a forge without coating with the hardener. Can the reflective coating be applied any time? I used a couple inches of kaowool and covered that coating of refractory cement. It has been drying all week. I even put it in the kitchen oven to bake out moisture. It's not like I plan to breathe the air coming out of the forge, but I don't want particles of ceramic wool/refractory filling the air either.. Quote Link to comment Share on other sites More sharing options...
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