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8:24 pm
NWBA Member
June 12, 2010
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I am ready to build a ribbon burner forge........just wanted to know what is the best refractory to use for the floor of the forge? I just came back from H-W in Clackamas. They didn't have any info on resistance to welding flux (borax). Thanks all
11:21 pm
March 22, 2010
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I made the floor of mine hard brick and figure on putting a consumable kaowool liner in the bottom. I think if you want to dO castable mizzu is the best choice
Whatever you are, be a good one.
Abraham Lincoln
1:22 am
NWBA Member
April 19, 2010
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I have had excellent long term luck with alumina (ceramic?) bricks. last long time.....a little spendy, over sized, but very tough and heat resistant.
1:40 am
April 21, 2010
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these guys are just on the other side of the mountains and are pretty decent prices from what I am told.
2:44 am
August 2, 2010
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Coincidentaly I was just down at my local Harbison Walker distribution center today to pick up an order of refractory board and a couple of bags of castable. At my last visit one of their technical sales people recommended that I use use Kastolite 30 LI plus for a replaceable forge bottom when I described the problem of Borax flux. I'm hoping that he's right. These next few forges I'll finally be able to finish since I got the last sheet metal parts for them should get a serious workout in a school situation so it will be a good test of his recommendation. In my little freon bottle forges I use a single 1 1/4" thick hard fire brick as a floor over 2" of inswool lining and use a coating of Greenset 94P over the exposed inswool areas. Unfortunately none of it is cheap- well the castable isn't too bad but the board, no way. Steve G
5:25 am
SGensh;5715 wrote: Coincidentaly I was just down at my local Harbison Walker distribution center today to pick up an order of refractory board and a couple of bags of castable. At my last visit one of their technical sales people recommended that I use use Kastolite 30 LI plus for a replaceable forge bottom when I described the problem of Borax flux. I'm hoping that he's right. These next few forges I'll finally be able to finish since I got the last sheet metal parts for them should get a serious workout in a school situation so it will be a good test of his recommendation. In my little freon bottle forges I use a single 1 1/4" thick hard fire brick as a floor over 2" of inswool lining and use a coating of Greenset 94P over the exposed inswool areas. Unfortunately none of it is cheap- well the castable isn't too bad but the board, no way. Steve G
FWIW, having done a fair amount of forge welding in a natural gas fired forge, no refractory is going to hold up to the flux. In order to mitigate the damage to the forge, I have found that: One, make a forge for forge welding only and it need not be as large as the forge you would normally use in everyday use. 12" long is more than enough. Two, use hard brick on the bottom, and design/build the forge so that the hard brick extends the thickness (2.5" laid on its side) up from the floor. ( This protects the Kaowool from the immediate effects of the flux.) Three, use ITC 100 on the Kaowool. Four, build a dam and pour a 1" layer over the hard brick floor using Mizzou.
If you forge weld a lot, expect that your forge is expendable and design it so that parts that fail can be replaced easily. I use a ribbon burner and the burners are subject to cracking over time at welding temps. I keep the original wooden casting box/accessories on hand for the inevitable. Keep the flux build up on the forge floor chipped out when possible.
Your forge is a tool like any other. Use it, abuse it. When it passes away, build another one. I have found that the knowledge gained with each generation of forge building makes building/using the new forge better than the last.
John
6:23 am
March 22, 2010
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I don't forge weld now a days, just use a castable refractory forge for small work.
I heard of one smith using fire brick rubble "hammered up fire brick" for the floor of the forge, when flux globbered it up it was removed and more rubble put on the forge floor.
No experience in this but it sounded like a good idea.
Had a good Christmas, roasted a reindeer, tastes like chicken.:smoke::smoke::smoke:
3:43 pm
NWBA Member
November 8, 2010
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If I were serious about daily forge welds, I'd build a vertical knifemakers' forge with the kitty litter bottom to catch the flux. Plans for this style of forge are out in e-space somewhere, probably on the knife-sites.
I have laid a loose half-brick inside of my atmospheric pipe forges to catch flux and it's a cheap sacrificial fix to replace that vs. a whole new liner. For initial forge construction I like rolling a layer of fiber-board (1/4" semi-rigid wool) on the inside of the pipe first, then insert sono-tube and cast. As said- everyone's got their favorite blends of how to do it.
I was told by the knowledgable folks at Seattle Pottery that for flux resistance you want a high-alumina refractory. I never researched it but it could be the same kao-lite or mizzou we've been using all along.
What I wasn't told is the firebricks I'd been paying out the @ss to them for are available at typically any home despot store for about 1/2 the price.
They only remember you when you SCREW UP~!!!
4:16 pm
NWBA Member
July 9, 2010
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Ron Reil suggested using a high-alumina refractory "Kiln Shelf" for the floor. The pottery supply houses have them at not too high a price. We bought one of a size to make three forge floors. Cut it with a masonary blade. I put a stainless steel sheet in the forge when we weld so I can't tell you how resistant the shelf is really.
My son is the Blacksmith
5:02 pm
November 4, 2010
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Cybo;5719 wrote: If I were serious about daily forge welds, I'd build a vertical knifemakers' forge with the kitty litter bottom to catch the flux. Plans for this style of forge are out in e-space somewhere, probably on the knife-sites.
I have laid a loose half-brick inside of my atmospheric pipe forges to catch flux and it's a cheap sacrificial fix to replace that vs. a whole new liner. For initial forge construction I like rolling a layer of fiber-board (1/4" semi-rigid wool) on the inside of the pipe first, then insert sono-tube and cast. As said- everyone's got their favorite blends of how to do it.
I was told by the knowledgable folks at Seattle Pottery that for flux resistance you want a high-alumina refractory. I never researched it but it could be the same kao-lite or mizzou we've been using all along.
What I wasn't told is the firebricks I'd been paying out the @ss to them for are available at typically any home despot store for about 1/2 the price.
I made a vertical forge just as you describe, except that I made the sacrificial floor of a mix of kaolin and vermiculite, in a sort of bowl made from dense firebrick. Unfortunately I don't get to use it much, since I've suspended most of my backyard smithing activities in order to keep peace with the neighbors. (Now I do most of my work at the guild's shop.)
Alumina is indeed flux resistant (but not flux-proof). All the common refractories that I hear of smiths using are primarily composed of alumina and silica. (The steel industry uses a lot of basic refractories -- basic as in "acids and bases" -- composed of stuff like magnesia, but those are a whole different animal.) Clays are mainly alumina and silica, too. What varies in refractories and clays is the ratio. Generally, flux resistance and temperature resistance both increase as the alumina:silica ratio goes up. You also want minimal impurities -- mainly metallic oxides other than silica and alumina -- which tend to act as fluxes at high temps. (When it comes to commercial refractories, the impurities aren't such an issue -- the temp rating tells you most of what you need to know. The impurities issue comes into play if you're looking at a raw clay body.)
For comparison, the 3000 F degree castables like Mizzou and Kast-O-Lite 30 tend to run around 50%-60% alumina by weight. Super Heatcrete 32, which is produced by a company not too far from me, is 70% alumina and rated to 3200 F. Super Heatcrete 33 (3300 F) is 95% alumina. Cordierite, a common kiln shelf material, is around 33% alumina by weight. High alumina kiln shelves are maybe a bit under 50% alumina. The alumina content in hard firebricks varies from I don't know where up to around 85%. The common ones you get at your masonry supplier for under $2 each probably aren't very high in alumina.
Alumina is considerably more expensive than silica (silica is the most abundant mineral in the Earth's crust), and that's reflected in prices.
5:15 pm
bed of ash in a side draft resists most heat and flux. no wait ALL heat and flux;)
but they are antique , they won't work these days.
:cloud9:
5:19 pm
Gene C , dave thompson has some of those old broken bits in his forge. also refractory clay chunks made when he had too much for a project. they do catch the flux though it can still melt down to where gravity takes it.
they do seem to create a more even heat by creating a more chaotic air flow.
5:49 pm
August 2, 2010
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Hey Jack, Do you mean I can't weld in my coal forge anymore? When did that happen? Maybe mine still works cause it's a bottom blast (grin). Actually I love working in coal and most of my forge welding has been done that way.
I responded to the thread mostly because I thought Bert's HW meant that his Harbison Walker outlet wasn't giving him the information I got from mine. I don't actually do all that much forge welding for my work but sometimes it seems the only proper way to go. Since I started making burners for sale I've been doing a lot more gas forge welding than I used to. The first question a potential buyer always asks is "Will it weld?" (or maybe the second after "How much?") It helps to be able to demonstrate that it will. That makes keeping in practice a good thing- . The little gas forges I supplied for the teaching tent at the Abana conference this year all had single brick floors and they survived the forge welding sessions just fine although there was lots of flux depositied on those bricks.
I like a replaceable floor in my own gas forges since even if you aren't welding it will eventually get messed up and I don't want to replace the whole forge when one piece is damaged. I've used castable and kiln shelves both for that purpose but a kiln shelf is completely flat while I can cast a replaceable bottom with ramped edges to protect the side walls of the forge too. Even industry replaces furnace linings when necessary so all we can hope for is a flux resistant floor not an impervious one. Use it while you can and then replace it when you need to. Steve G
9:00 pm
NWBA Member
June 12, 2010
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Sounds like it would be simpler (and less expensive) to just make a floor from the hard firebrick. I tried a kiln shelf tile, the flux ate it in very little time. 😡 Stainless steel has to be thicker than 20ga sheet, cuz the forge will melt that. :timebomb: For the time being I am going to make a floor pan from 1/4" ss plate. I'll let you know how that works. I'm guessing that it will warp, just don't know how much. Thanks for all the input. :bounce:
1:34 am
June 24, 2010
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Larry,
I'm a little late reading this, but in a post yesterday you mentioned that you planned to use a sacrificial layer of kaowool. That brought to mind Monte Python's Scottish Kamikaze Regiment.
The kaowool would certainly sacrifice itself, but would it really protect anything else?
5:01 am
December 10, 2010
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What about using an ITC product??
Keep on Forgin
The difference between stupidity and genius is that genius has its limits.
Albert Einstein
5:23 am
June 10, 2010
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It has been years since I made any and at the time it was an A.P. Green product and I think they are long gone, a Moleite ramable (SP?). We would get a box of the material it was sort of premixed and hammer it down into a form we had made for the forge floors. It was great stuff we were using lots of borax and we made the floor as a trough so the flux would run out the door into a can. The borax didn't do much damage but the guys that were doing pattern welding were replacing the floor once a year or so. I do remember that they had a chemist in their research department that advised use to use it, and pretty cheep compared to the alternatives.
3:44 pm
"Hey Jack, Do you mean I can't weld in my coal forge anymore? When did that happen? Maybe mine still works cause it's a bottom blast (grin). Actually I love working in coal and most of my forge welding has been done that way."
LOL Sure you can. no problems . Glad to see you use coal. BUT if the blade don't fit .. get a side draft.
The bed of the side draft does not get in the way as a pot does.
It allows the blade or other object to be passed through the fire without having to bend the piece to get it in the fire.
If you want to drive an etsel don't let me stop you;)
I would sell the etsel to a tool collector and get me a decent rig.
Though, to be honest, mine end up looking like skoda patched together with any bits of sheet I can weld into a box.
3:55 pm
March 22, 2010
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Mike B;5731 wrote: Larry,
I'm a little late reading this, but in a post yesterday you mentioned that you planned to use a sacrificial layer of kaowool. That brought to mind Monte Python's Scottish Kamikaze Regiment.
The kaowool would certainly sacrifice itself, but would it really protect anything else?
Well I have a firebrick floor with a layer of rigidized kaowool on top with a kiln shelf on top of that... the kaowool is disposable, If I weld in the big forge I pull the kaowool and put in a new chunk, its sucked up the flux like a rag.... I have an advantage in that I got three big trash bags full of free kaowool to use for such things..
I have a small forge specifically for welding that has a hard brick bottom with a castable liner over it, I still find if I throw a chunk of kaowool on the floor of the forge when welding it catches most if not all of the flux, the trick is as soon as the forge is cool you pull it out and throw it away, if you leave it in there I think the flux would eat it and get into the floor in a hurry
Whatever you are, be a good one.
Abraham Lincoln
3:59 pm
NWBA Member
Board Member
April 26, 2010
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Daryl;5740 wrote: It has been years since I made any and at the time it was an A.P. Green product and I think they are long gone, a Moleite ramable (SP?).
A.P. Green's product line was bought out by "A.N.H." A lot of the A.P. Green stuff can still be had. Don't know about the mullite, though.
No matter where you go... there you are.
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