fluidsteel Posted August 11, 2011 Share Posted August 11, 2011 BP Building a freon tank forge. For now it'll be a venturi burner, but will be modifiable to be blown.. This is getting me by till I have the time to do a dual burner PID controlled temperature adjustable heattreat/forge. I didn't like that they weren't QUITE deep enough for a big 15-18" chopper blade. Also going to add angle iron to the back and make a firebrick back door for bigger/longer stock. Started with my shops scrap bin... Lookie here free(on) tanks! I picked out a couple....Applied the safety goggles and respirator....cut one in half with the angle grinder, and cut off the end of the other..... Then I stuck them together... Actually, I stuck them together BEFORE I cut the end off of the blue tank, it took me ten minutes to get them apart. I think that means they fit together nicely. Next, allowing for 2" of inswool and around 2" of 3200 degree refractory cement I centered my burner hole and drilled it with a hole saw...I put in an 1-1/2" BI nipple it's in there now with locknuts from an EMT conduit connector, but, it'll be welded when done. I made this burner... it's based on a Zoeller Z burner. I bought the parallel fitting, but the rest was scrap including the 1" SS 304 pipe. I'm going to forge a flare into the end of the SS.... Put it on the pipe rack and with the help of a hammer to keep it from kinking bent it to bring the burner in on a tangent.... Like a 6 on it's side... Next, I'm welding a couple 1" pipes to the side. Going to run a couple pieces of 1/2" rod through them with a 1/4" plate between for a tool/tong rest. Ordered and added a PID controller with a thermocouple, shield and a couple other items to get my temps set for normalizing, heat treat.. I'm a beginning bladesmith, and want to do blacksmithing as well.. I'm also adding angle iron to the front to allow a firebrick door that slides open left and right like a big aircraft hanger...Will weld it up this weekend. If the PID comes, I'll add the thermocouple too! What do you guys think? I'm a total newbie and am coming at this from HOURS of reading and researching... This is my version of slapping something together because I want to forge NOW! Brian Link to comment Share on other sites More sharing options...
Steven Fabrizio Posted August 11, 2011 Share Posted August 11, 2011 Looks good!!! Link to comment Share on other sites More sharing options...
ThomasPowers Posted August 11, 2011 Share Posted August 11, 2011 Tight at room temp and tight at hot temp are not the same; but a few self drilling self tapping metal screws through the overlap will make sure it won't work loose even when hot. Link to comment Share on other sites More sharing options...
pkrankow Posted August 11, 2011 Share Posted August 11, 2011 Thomas has a good point with the screws. You probably also want a pass thru out the backside, and having a slot for extra wide things is very nice too. You will like it I am sure. Phil Link to comment Share on other sites More sharing options...
MattBower Posted August 12, 2011 Share Posted August 12, 2011 Good work. 2" of castable is way too much, IMO. It'll take a very long time to get up to temp, and waste a lot of fuel, assuming you aren't planning to run this thing 16 hours a day. 1" is more than enough, and less would do fine. Are you planning to try to set your temps by adjusting the burner by hand? Link to comment Share on other sites More sharing options...
MattBower Posted August 12, 2011 Share Posted August 12, 2011 On further reflection, forget my last question. Regardless of how you're planning to set and hold the temps for heat treating, that forge isn't going to do it for you. I'm sorry to say it, because I know you've done a lot of hard work on this thing so far, but it's just not the thing for what you want to do. It'll be good for forging big stuff -- it'll work for forging blades as well, although it's excessively long for that. But the burner coming in the side like that is always going to create a hot spot, and because of that the temperature inside is going to vary a fair bit from one spot to another. The temperature your thermocouple reads will depend on where it's placed in the forge. For long, thin stuff like blades, you'll have serious problems obtaining even temps across the whole blade. It's the nature of the design. For heat treating, especially blades, you want as even a temperature as posslble throughout the entire interior of the furnace, and you want that temperature to be very close to the temperature you're trying to achieve in the steel. What you want is something like this:http://www.dfoggkniv...S/DrumForge.htm See how the burner comes in from the end and points down the long axis of the forge? No direct flame impingement on the side, or the blade itself, and the large interior volume lets the temperature even out. No hot spots. Link to comment Share on other sites More sharing options...
fluidsteel Posted August 12, 2011 Author Share Posted August 12, 2011 A couple questions Matt, One, it's not obvious from the picture, as I didn't show an After picture, but, the burner inlet was bent on the tank to cause tt to come in on an angle like a b on it's side. I was told that will help the flame roll through the forge. Do yo think that will help keep the temps even? I was going with the thicker refractory because I my research said that it will help keep the temps more stable, More mass does take longer to heat, but it also retains it's heat longer. Thoughts? I could easily scrap this plan if it's a waste of my time. For now, all I'm forging is 1084. No soak time at temp is needed. 1475 and into the Parks 50. Normalizing also needs no time at temp. So it seems that I should be able to hit my temps w/o too much trouble? My other option, and what I planned on doing, is to scrap the tank as is, do another with two burner ports. And make a high low solenoid/PID controlled dual burner blown forge... It would have a Low burner that when running would get the temps to say 1400 degrees max. The high burner controlled by the PID would boost the tempt to whatever temp I set. The PID's fuzzy logic figures out how long the burner needs to stay on, and will "learn" to correct for overshoots. Option B. Make a blown forge w/PID so I can read the thermocouple, and us it for forging, and buy an Evenheat to do my heat treat. I want to do some stock removal kitchen knives with some PG O-1 and that needs the 5-6 minute soak times. I need a smaller, somewhat portable forge now. I don't have the space for a drum forge. Besides, that drum forge would have 3 times the mass to heat than my freon tank wouldn't it? Even if they only added a skim coat of refractory to keep the ceramic blanket from being damaged? Link to comment Share on other sites More sharing options...
MattBower Posted August 12, 2011 Share Posted August 12, 2011 Let me just say that I do my heat treating in a solid fuel forge because I also don't have the room for a drum forge, and I have not been satisfied with the propane forges that I've tried for blades. Even using a pipe muffle in a propane forge, I have never been able to achieve the sort of gentle, even heat that I want for heat treating. But I have not tried one exactly like what you're planning, so perhaps I shouldn't have been so forceful in saying it won't give the results you want. I don't think it will, but that's just speculation on my part. Not entirely uninformed speculation, but speculation nevertheless. WIth that said . . . Even with the burner coming in on a tangent to create a swirl, you're going to have direct flame impingement on the interior that's going to create a hot spot. So while the rest of the forge is heating by conduction/convection, you'll have an area there that will be putting off a lot of radiant heat, and the closer you get to that spot the hotter it'll be. The hot spot may be bigger than with a burner that's oriented toward the center axis of the forge, and you won't get direct flame impingement on the blade, both of which are good things. But it'll still be a hot spot, and I think it'll still cause you problems. However, as I said, that's just informed speculation. I could be wrong. I have given some thought to how to reproduce the effect of a drum forge in a smaller package, but all my ideas are untested theory so I'm a little reluctant to throw them out. I will offer one suggestion that you might try if your design doesn't work out as hoped. I have tried a muffle in a propane forge with poor success -- the muffle just developed a hot spot where the hot spot in the forge was -- but the muffle was fairly thin. A thicker muffle might do better, especially with your design. I have considered a ceramic muffle of some sort, but the prices of mullite and similar tubes are pretty intimidating just for experimentation. You might be able to do it with castable refractory. The drum forges usually don't have any castable in them. Just some ridigizer to lock own the fiber particles. (I suspect the rigidizer is just sodium silicate or something similar.) I'll try to get to your other questions later. Link to comment Share on other sites More sharing options...
Dodge Posted August 12, 2011 Share Posted August 12, 2011 Rolling the burner flame helps IMHO, but there's still a hot spot. Two smaller burners can produce more BTUs than one large burner and be able to spread out your heat. There will be two hotspots but if they are aimed correctly, the overall result is more even heat. Still maybe not critical enough for exotic alloys but for overall forging you'd be happier. I'd also cut a back door. That's just me, but being able to heat the middle of long material comes in handy at times. Edit: I was still typing when Matt posted, but what he said. As for mufflers or baffles, I believe this is how many glass furnaces work; a short wall between the burner(s), often ribbon type in design, and the main business area of the furnace. Link to comment Share on other sites More sharing options...
MattBower Posted August 12, 2011 Share Posted August 12, 2011 OK, a few other thoughts. First, drum forges are mainly for heat treating swords. I think the design is scalable to a certain extent for smaller blades; if you're planning on doing 10" Bowies or kitchen knives you wouldn't need a 55 gallon drum. You might be able to apply the same principle to a smaller burner in a 5 gallon steel bucket lined with an inch of ceramic wool. As for the thicker refractory stabilizing the temps, I guess that's true, although something the size of a blade doesn't really suck out all that much heat. But it'd also make the temps slower to adjust. (It occurs to me that with a really massive forge you might actually be able to run it up to temp, cut the burner off, and use the residual heat in the forge to HT with. But I've never tried it, or had a forge that massive to experiment with!) I'm not quite sure I follow what you mean about hitting your temps with 1084. Yes, it's fairly easy to HT well, but hot spots will still cause problems. 1084 will benefit from a short soak at austenitizing temps (1-2 min. at the temps you're talking about). If you really want a near-zero soak you'll want to go a bit hotter, more like 1525. 1084 will still make a good blade with what you're planning. Frankly, there's always a certain amount of soak time built into the process, because you're bound to spend a little time eyeballing the blade and deciding whether it is fully up to critical. Roman Landes (German metallurgist) has a post about soak times for 1084 over on hypefreeblades.com. Roman is one of a few people I pay very careful attention to when it comes to the metallurgy of heat treating. If you really want the best of both worlds I think your option B is it. Forges aren't ideal for heat treating, and heat treating furnaces aren't ideal for forging. If you leave heat treating out of the equation it becomes much simpler to design a good propane forge. A thermocouple on the forge seems like overkill to me, but it won't hurt anything. It is possible to build your own electric heat treating furnace, BTW, and it should be quite a bit cheaper than the commercial HIT furnaces I've seen, which are all quite expensive by my standards. Plus, DIY would let you choose the dimensions to suit what you want to do. All the commercial furnaces I've seen seem more or less oversized for blades, even most of the Paragon ones designated as being for knifemakers. (Although having a little extra capacity for HTing tooling and the like isn't necessarily a bad thing.) Link to comment Share on other sites More sharing options...
fluidsteel Posted August 12, 2011 Author Share Posted August 12, 2011 Long term I would plan on building a salt pot, and getting an oven as well. For now, I'm stuck with a forge. I'm going by the shop today. I might pick up a solenoid and put together a couple new tanks and make a blown forge instead. I honestly don't have much time or money in the venturi burner or the tank itself. More time doing the WIP post actually.... Maybe buy a box of crayons too.... and make a ribbon forge burner... I'm ADD... Can't stay on, look at that anvil, topic long... It's easy to change direction for me if it's not the best choice for what I want to do. Thanks for the link on the heat treat. I greatly respect Kevin Cashen.... I soak up all the info I can on heat treating..! This is a short reply.. I'll think about all this and decide which way to go. Link to comment Share on other sites More sharing options...
MattBower Posted August 12, 2011 Share Posted August 12, 2011 I'm pretty interested in ribbbon burners, too, but according to folks here who've built and/or used them, they don't tune down well. So that's not really what you want for HTing, if that's still your plan. Link to comment Share on other sites More sharing options...
pkrankow Posted August 12, 2011 Share Posted August 12, 2011 Here's a tip from someone else with ADD, build the FORGE now, worry about HEAT TREAT later. If you just spin your wheels trying to build a device to do everything with, then you will end up doing nothing! Second point, build a smaller forge that can open up for irregular shapes (a slot down the side that can be plugged) and you will be happier if you do anything that requires a lot of bending. Your current forge is rather big for one burner, but you can always choke it down more later with a backstop. I think you are on a good path, stay the course. Build a uni-tasker heat treat oven when you are ready for serious, high quality heat treating. Phil Link to comment Share on other sites More sharing options...
pkrankow Posted August 12, 2011 Share Posted August 12, 2011 BTW, my forge is 150 cu inches. It gets melting hot and sips propane. Phil Link to comment Share on other sites More sharing options...
RockingCWelding Posted December 21, 2011 Share Posted December 21, 2011 Brian, Where did you find the parallel fitting at? I have looked everywhere and can't seem ti find one. Link to comment Share on other sites More sharing options...
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