Something isn't right, but what???

N

Ninja Blacksmith

Joined
Aug 26, 2012
Messages
136
I've recently gathered materials to build a newer, larger cylinder propane forge for heat treatments, and have given it 3 test runs to make sure it was up to the task of heating blades longer than 20". The forge itself it about 25" from end to end, and has open ends (with some blocked to help retain heat) to allow me to pass sword-sized blades through. Test run #1 and #2 were successful, with rods of 1018 steel and W1 tool steel inserted and reaching austenization temps (1500+ F) between 12 - 23 minutes depending on rod diameter 3/8" and 1". Test run #3 was done using a 1018 (as far as I can tell) wallhanger katana blank that I keep around for dimensional reference. Here is where I noticed something that baffled me...It had been over 20 minutes with all the lights out in the shop, and nowhere on the blank did I see even a hint of dark red heat. I increase the gas feed more than I did during the previous trials, and 35 minutes later temperature is still clearly not past the triple digits!?!? Trying not to panic, I brought out the two rods again and did the same test, with the same results I got the first round; 12 - 23 minutes to crit temp.

This is the first time I've experienced this problem, though I'm reluctant to say it was the blank, but other evidence doesn't point to the forge as the problem...I'm putting all heat treatments on standby until I figure out what happened. I came here to shop talk hoping that some senior/master smiths could help me identify the culprit.:confused:
 
I'm no master smith but imho some pictures of your setup might help. What are you using for burners?
 
@Ozark: It's a weedburner that I have had untainted success with in the past - today, not so much. I think (think being the keyword here) the problem has been found; the nozzle isn't jetting the flame at a shallow enough angle into the cylinder, preventing the flame vortex needed to help spread the heat. I can go back and fix this in 1 hour or less in the morning. I did try something new, however, that doesn't APPEAR to hinder the forge's efficiency, but could be another issue hiding right under my nose. At both ends of my cylinder I have welded small half-ellipses to leave rectangular slots. Could this rectangular slot design be another problem? I'm a bit new still to heat-treatable steels and even newer to designing gas forges. Also, While I have been able to get by just fine without ceramic insulation/Kaowool, I'm seriously considering ordering a roll of it. If you've used it before, would you recommend it?
 
I suspect that your forge is too large and your burner too ineffective. And what's with not insulating your forge body? You're wasting a LOT of fuel that could be put to use. Please post pics of what you're working with as well as filling out your profile with a location....there may be members who can help you right around the corner.
-Mark
 
Besides the wrong burner type, only one burner, and an uninsulated large forge, I don't have any idea why this isn't working perfectly.

Look at some of the forge and burner building plans in the stickies. At 24", most will go to two or three burners. The burners need to be proper venturi type, or even better - blown burners. A large and long forge will need at least a 1" wool liner ( 2" is better) coated with 1/4" of satanite and then a coating of ITC-100. Once brought up to heat, this type forge will quickly bring a large bar or billet up to forging temp, and will also be able to hit welding temps.
 
http://ronreil.abana.org/design1.shtml

http://www.instructables.com/id/how-to-build-a-gas-forge-burner/?ALLSTEPS
http://makingcustomknives.com/how-to-build-a-propane-forge-burner-video/

Here are a few links to everything you ever wanted to know about the reil burner and its construction. Very efficient, and cheap to build using readily available plumbing supplies.

As Stacy already mentioned, insulation is a must. If using something as large as a propane tank (I assume your using a standard 20lb LP tank), I'd recommend AT LEAST 2 inches of ceramic fiber insulation, as the larger you make your cavity, the more you're going to be wasting in heat and fuel. In other words, don't make the cavity any larger they you think you are likely to need.

Also, do not neglect coating the insulation with satanite, and if you can swing the initial cost, ITC-100. You can also get a product called Plistix 900 that, while not as efficient as ITC-100, is quite a bit cheaper, and better than relying on satanite alone.

You probably are going to want at leat two burners in your forge as well.
 
Also, fill out your profile. Depending on where your located, there may be an experienced bladesmith nearby that can help you with your build, or at the very least can recommend nearby sources for parts and materials.
 
Well, I'm definitely ordering some Kaowool, and while the new one is the same diameter as the small forge (6") I'm guessing that the length is a big part of what's been killing the heat retention - which should be fixed in 2-4 days depending on UPS.

@:knife to a gunfight: I've never come across that video in my searches, it's much appreciated - thanks. While I've not found any welding supply stores in Hazard KY, there is a Lowe's and Tractor Supply here, and I know they have non-galv iron pipe, but I don't recall seeing any brass tubing or fuel regulators at either place.

Everyone; I'm really grateful for the advice and will get on putting this into action when I can, and thanks for helping this starting smith weed out the culprits.
 
Ninja Blacksmith said:
Well, I'm definitely ordering some Kaowool, and while the new one is the same diameter as the small forge (6") I'm guessing that the length is a big part of what's been killing the heat retention - which should be fixed in 2-4 days depending on UPS.

@:knife to a gunfight: I've never come across that video in my searches, it's much appreciated - thanks. While I've not found any welding supply stores in Hazard KY, there is a Lowe's and Tractor Supply here, and I know they have non-galv iron pipe, but I don't recall seeing any brass tubing or fuel regulators at either place.

Everyone; I'm really grateful for the advice and will get on putting this into action when I can, and thanks for helping this starting smith weed out the culprits.
Click to expand...

right hand threaded Brass pipe fittings can be found in Home Depot

Feul fitting and other left hand thread fittings as well as Regulators can be found in your local welding store.
 
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