Building a small propane heat treating oven

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Ok so I decided this would be a fun little project to make knives with.I have one question before I can actually get started, is a gas powered forge better with an open tunnel or a sealed back end?
Reply:A suggestion...you might also post your question over on the blacksmithing website, www.iforgeiron.comYou'll need to sign up there just like this forum to be able to exchange info.They have a lot of gas forge and knife making experts over there and tons of online articles about knife making.
Reply:Ok, so I went through with the project. No welding yet, but I promise its coming.So far I have core drilled out a few bricks with a hole saw. What a pain that was. I can't find any suppliers for soft fire bricks, so I have the hard kind that needs masonry bits/tools.I am not sure I like how the bricks turned out so uneven from cutting them with an angle grinder, and I don't have access to a large wet saw for clean cutting. I think I may pick up a few more bricks and just keep the full size of the brick and drill a pair of holes overlapping for a larger forge interior. That or I will just use full bricks with the same hole in the middle so everything is nice and clean on the edges. Attachment 750281Attachment 750291This was my first burner attempt. I'm using a low psi BBQ line for this. I have a high pressure 0-20psi line on the way this week. Should at least double the intensity and hopefully give me that jet flame.Attachment 750301This is my new burner design I made today. Its 1/4" larger to begin with diameter wise and definitely seems to look promising sorry no pics of that one. Its basically a bunsen burner on steroids.Attachment 750311Attachment 750321Last edited by BrooklynBravest; 06-22-2014 at 09:00 PM.
Reply:Down side of those hard bricks is that they are going to soak up a ton of heat and use a good bit of fuel to come up to temp. I learned that the hard way when I bough a bunch of them to build my brick pile gas forge. The other thing is since they heat up, you'll have to make sure they aren't up against anything that might be flammable.I've pretty much dumped the brick gas forge idea. I look at it as money wasted because I didn't do enough research 1st to understand the down sides of the materials. While they were easy to purchase and readily available, I'd have been much better off going with Kaowool insulation or at least looking for the correct insulating fire bricks. I'll have a lot more money into it than a commercial forge by the time I get done if I continue, and I may just write it off as a learning experience and just buy a gas forge eventually rather than keep throwing good money after bad..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Def what DSW said, you'll spend more fuel getting and keeping those hard bricks up to temp that actually heating the knives. Also are you just heat treating or actually forging blades? http://www.indfirebrick.com/soft-fire-brick.html I got bricks from these guys and they shipped in a couple weeks no problem. Hole saws cut these real easy and I even shaped em with a spoon. Use an unwanted spoon. Those hard bricks are going to crack and these soft bricks will crack as well so you will want to make (weld) a frame to keep it all together.Kaowool might be cheaper and easier to obtain and is a little easier to work with. you can use a coffee can as a shell.
Reply:thanks for the brick links! huge help. Gonna order a few.The hard bricks do get very hot I noticed that when I messed with them and a plumbers torch.I'm probably only going to be heat treating. Maybe heating something to bend it here and there im not looking to be a blacksmith.I also considered getting this http://www.amazon.com/Rutland-12-5-l...ble+refractory   and building a wooden form for it, followed by a metal shell.Last edited by BrooklynBravest; 06-23-2014 at 05:58 AM.
Reply:I'm pretty sure that castable refractory is rated at too low a temp for what you are going to do. I'd have to dig thru the links I was reading about when I was looking at doing my forge, but I believe the lower rated Kaowool breaks down with a gas burner like you have fairly rapidly and it's rated at 2600F not 2200 F.It's not that it won't "work" only that the liner will quickly begin to deteriorate where the burner is pointed in the furnace. There are coatings that can be applied like ITC IIRC that can help prolong the liners. Your best bet is to go to a place like Shortfuse suggested, like Iforgeiron and talk to those guys some.http://www.iforgeiron.com/ They are very familiar with exactly what you are doing since quite a few of those guys have built their own gas forges, casting furnaces of alum and brass, as well as heat treating ovens for treating blades. They can point you towards all the info on liners, coatings etc as well as all the pitfalls. BE aware a few of those guys don't tolerate guys who just show up and ask the same old question that's been answered dozens of times before. Take a bit and look at some of the older posts in the "blueprint" section where they walk guys thru the process as do a bit of searching first and show you have some what of a clue, and you'll get better results..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:so do the soft bricks stay cooler on the outside ? What breaks down faster i thought the bricks were the liner ?
Reply:The castable says it's rated to 2000 degrees.  Its $30 shipped for 3 of the soft bricks. $17 for shipping...But the entire container of castable makes like one brick.
Reply:If you want to heat treat, then you need an electric oven with temperature control. Here's a nice homemade oven build:http://www.machinistweb.com/forum/sh...eat+treat+ovenAlso see:http://www.practicalmachinist.com/vb...t-oven-237514/http://www.practicalmachinist.com/vb...ne-off-199644/"USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:Originally Posted by OldendumIf you want to heat treat, then you need an electric oven with temperature control. Here's a nice homemade oven build:http://www.machinistweb.com/forum/sh...eat+treat+ovenAlso see:http://www.practicalmachinist.com/vb...t-oven-237514/http://www.practicalmachinist.com/vb...ne-off-199644/
Reply:I also agree that you will want higher rated furnace cement. 3000 degree cement or higher if you can find it. If you're making very advanced knives then an oven with controls will be more sophisticated but if you are just mucking around then the propane burner will be fine. And you can upgrade later if you need to anyways.
Reply:Originally Posted by BrooklynBravestNo you don't. Electric is just another option. You only need to be able to heat the specific metal to it's specified heat treating temperature and remove it.
Reply:Originally Posted by OldendumRamping, soaking and even heating to a specific temperature with a manually operated gas oven won't be easy.  To just eyeball a temperature, quench and temper a carbon steel knife blade isn't so bad. That can be done on a charcoal fire. Seen it done dozens of times.
Reply:Originally Posted by BrooklynBravestI'm just heating it carefully until it loses its magnetic properties.The actual temper I will do in an oven.
Reply:Originally Posted by OldendumI have no problem with simple heat treating.  I just wish I had known a bit more what to look for when I worked with a 70 year old blacksmith in Thailand.  That man knew his stuff.  I still wish I knew what he used for a "magic mud" slurry to wash onto the blades prior to heating and quenching.  I think it was some local mud that would prevent oxidation so he could then easily see the temper colors when he drew the temper.  It was a very thin slurry, sort of like a watery flux.
Reply:Il get some pics up soon. I have some parts soaking in muriatic right now they were all rusty from the steel yard.Basically I ordered 4, 2600 degree fire bricks which I will cut in half and drill a 2.5" hole in for the forge-way.I was only planning on spending $25 for a piece of tubing to make the shell out of, but the only piece the yard would sell me a cut off was from the scrap pile. What I needed was a 5" square piece, 12" long with .250 wall.I ended up having to buy a $44 piece of 5/16" wall, 25" long from the scrap pile. So now I have twice what I need, maybe il make a second one after and sell it for a couple hundred if it's nice.Last edited by BrooklynBravest; 06-24-2014 at 05:33 PM.
Reply:I'm late to the dance but plastic firebrick might have been simpler. You can form it into any shape you need and it works well over ceramic insulating board if you need to reduce the overall mass you will be heating.This looks like this is their superior product  http://www.sparref.com/uploadedFiles...1214342481.pdf  insulating board here http://www.indfirebrick.com/ceramic-fibers.html. Check your local directory for refractory companies near you or get friendly with the furnace guys at the local foundry.---Meltedmetal
Reply:Ok so heres where I am at so far. It isn't much to look at yet.I also picked up some 1" tube to make the base and some sch 40 pipe to make a burner mount on the side.I only cut the end cap shown here so far. The other end I need to make a bigger piece to work off of. The end in the photo will be welded on, the other side will have 4 holes tapped for bolts so it can be removed to replace bricks/service the inside if ever needed.Attachment 751811Attachment 751821
Reply:Had an hour to kill so I got started on the base.Attachment 752411
Reply:Here is where I am at so far.Reluctantly I goofed a bit. When I placed the base on the body of the forge, I forgot to actually square it up to the base I only centered it. So the body is probably out of level with the base by 1/8" which im a little bummed over but this isn't a precision instrument so it is what it is. Not worth cutting it apart to fix that.I also probably put a little bit too much welding into the design for 1" tube in such a small space. It did bend the tube inward about 1/8" at the center of the length but its uniform on both sides so it looks like a little cool design anyway.Overall. I think it came out just "ok" so far. I'm not the most pleased with some of the welds I did. One bead I forgot to turn the gas on, another bead my 10lb spool finally ran out on me and it's just too humid out to not get frustrated working out in the garage with every little thing.Attachment 752981Attachment 752991Attachment 753001Attachment 753011Last edited by BrooklynBravest; 06-26-2014 at 04:15 PM.
Reply:Cut and drilled the bricks. I cut them down from a pair of 2600 degree rated 9" kiln bricks. That line scored across the top I had to make to accommodate the weld bead inside the tube.Have to go back to the drawing boards a bit with the heat source. The design I went with didn't work too great.Attachment 755181Attachment 755191Attachment 755201
Reply:Just about coming to the end of this project. I would have had the front plate on today, but the cheap DeWalt tap for the holes snapped.I went with an offset burner to allow for a vortex/swirling flame that you can clearly see in the video. Really happy with how the whole thing came out overall and its definitely cool to play with as dangerous as it is. Steel is orange heat within a minute or two of firing the forge up, I haven't even tried max burner heat yet it doesn't seem necessary.Attachment 758951Attachment 758961Attachment 758971Attachment 758981Attachment 758991
Reply:Attachment 759001Attachment 759011Attachment 759021Video
Reply:Attachment 761831Attachment 761841Attachment 761851Welded on the rear cap. Think I've reallyImproved on my outside corners but I'm a little bummed I messed up on one side had to stop and restart before reaching the end. My finger was propped too close and if I kept going it would have burnt me.Brooklyn,Looks like you built yourself a pretty nice little heat treat oven there.  Good job man.
Reply:Finished.Attachment 763151