Forge damage?

GA, You are using a big ass torch tip in open air now, right? Your idea of "baffles and chambers" is not needed. You need to think differently about forges. Think of the interior of a forge as very even, controllable, volume of heat energy. When you use a heat source in open air it is nearly impossible to control the atmosphere surrounding the steel you are working with. Even if you can manage an even heat on the entire knife blank the steel is probably suffering a lot of undesired oxidation. Think of a knife makers forge as a box with a 6"w x5"h x 10"l interior holding an even, non oxidizing, volume of gases at 2300?f. You really don't want the torch or burner directly impinging on the steel. You can do this with brick but the most efficient way to do this is with fiber blanket insulation like "Kaowool" The downside of refractory brick (hard or soft) is that, while very durable and heat resistant, it is also a VERY poor insulator. This means that it requires a lot of BTU's to get it hot, and to KEEP it hot. Every brick you put in a forge will be acting as a heat magnet.

There is really no comparing brick to thermal fiber insulators (like Kao-Wool) These materials reflect almost all of the heat energy and absorb almost none. Put 2"- 3" in a sheet metal tube and it will get to welding heat in 15 minutes and the outer surface temp will only be about

500?f. The forge will also be stone cold in and hour or two. The downside of fiber is that it is very susceptible to abrasion. In my mind a good gas forge will use as much blanket as is practical with some brick or castable refractory to toughen up high wear areas like doors and floors Using an expensive liquid coating like ITC100 on hard brick is pretty much a waste of money unless you are trying to hold molten metal, like in an iron cupola. ITC100 encapsulates and slightly toughens the surface of the fiber insul. It is also resistant to welding flux which, btw eats through fiber like gasoline through styrofoam.

Greyangel, there is no such thing as cheating when it comes to using tools. It's how you use them mate. A better description of the flatter would be to think of a hammer about 1-1/2" square one face flared to 3" square with the other left plain.

Good luck, GG

GA, do yourself a favor, read that again, only slower this time. ;)

I forgot to "jump" you about something. ;)

You mentioned your flame had yellow tips, right? :(

If so... your setup sucks. ;)

Yellow flame is showing you it's too cool and/or doesn't have enough air (oxygen) to burn the -carbon- the way you want it to be burning it.

The "easier to burn" hydrogen is burning and leaving behind the carbon.

Just like coal/coke, charcoal or oil-fired, "it's the carbon". :)

If your flame doesn't have yellow tips... well then... ooops. ;)

And not forced air from a blower or special ventury setup for top heat/temperature which is a product of the -mixture- and its

-speed-.

If you want to read up on it, when you get close, you'll find what you're looking for under- "explosive mixtures". I looked into several sources but by far the best one was my old 50's Encyclopedia Britanica. Went through it like you knew nothing, at the speed like you knew it all. Just the way I like it. ;)

More modern Encyclopedia's sucked. :/

That's just a guess tho, right? :)

Alvin in AZ

I picked mine up at the brick yard, they are stored under a shed and the display for them was indoors they had four levels of "insulated fire brick".

The higher temperature ones aren't as insulated but feel like they are heavier and stronger than mine, mine are the lightest, and at the time didn't care about anything higher than ~2000F.

KaoWool is one thing I don't know anything about, but;) like another poster said I suspect it to be a better insulator than my bricks... but not as much as he described, I believe he was comparing kaowool to regular fireplace brick.

There's sure enough one way to find out tho ;) a regular fire brick is pretty much the same temp front to back... when it comes to picking one up with your bare hand. ;)

The type of bricks I have are exactly the same material as what is in the electric-ceramics-firing-kilns. You could go by a ceramics shop and ask about it and see it and feel it first hand.

I did that early on and I was given an old kiln. ;) It was in really bad shape, left outside for years, they just never got around to hauling it to the dump... salvaged some bricks from it and the controller. I took then some ceramic shelves/plates(?) for stacking ceramics for firing in return.

My bricks look and feel and "sound" like cream-colored stryofoam.

The higher temp bricks are more glassy looking and heavier.

Alvin in AZ

From...what..you...were... saying... (huh? oh sorry) So let me get this straight. If the inside of the forge gets to glowing bright orange and the metal gets to bright orange that should put me in the right range, right? Jumping ahead of the message a bit, the orange flames that I mentioned happens only when the wind blows up the ...uh mouth of the forge where I have the torch. You saw the picture I posted right? At normal operation there is no orange flame. When the wind is not messing with the mix then it's hard to say that there is a color to the flame at all. I understand that there are rich and lean mixtures that happen in the forge but no doubt I don't understand what I am seeing as well as I should. If I kick up the flow on the needle valve for the torch I can get a richer and by venturi hotter mix going. The normal that I run at is because I've found that it will keep a nice conservative but (I think) adaquate heat going in the forge chamber. As the chamber starts to get heat soaked so does the propane tank start to chill and the pressure begins to back off a bit. It has seemed to me that this was a fortuitous natural adjustment to less required fuel since by this time the brick is starting to radiate pretty good and all I want is to keep it at temperature.

I would say that I have a very transparent blue cone from a couple of inches out from the torch out to about 12 to 16 inches. The cone kind of expands outward as it get farther from the torch. I figure I have an optimum area of about 10 inches or so before the main heat starts to slack off At the back of the forge where I have it partially open (to prevent heat from blasting back at the torch) there are definately orange flame escaping but that is probably the mixing with fresh air as it escapes the chamber. I have tried blowing air in behind the torch and this gives me a bunch of orange flame (same as a gust of wind). Kind of backwards from what I would expect but I'm guessing this is because the extra draft is not mixing well with the gas when so far removed from the source? I know, sounds like I don't know what I'm talking about. That's 'cause I don't really. It's all part of the grand experiment. I'm learning all kinds of things about forging and knifemaking and it all takes time to put it together.

Call it a behavioral study. It's a lot of experimentation right now and I've been falling into rhythms that seem to work. As for optimum forging heat I sort of have to go by the color of the metal but how it gets there could probably be tuned up. Everything I have read suggests that I really don't want to forge it into the white heats I can and will experiment with kicking the forge gas up see how that goes. As a friend of mine mentioned, I really need to visit a working setup at the local college to get a visual on what folks who know what they are doing are doing. I will finish the Riel Burner soon as well and check the difference in operation.

Back to earlier conversations on Railroad steel: Found another gem laying beside the tracks here in town. It's a wedged shaped thing that weighs at least a couple of pounds. A bit like a splitting wedge but with a longer tapir. Probably 12 to 14 inches long with a half round hollow along one side and a much thinner ridge of steel sticking out from the opposite side with a bunch of 1/4 inch or so holes drilled through it. It has a cross section of about 2 inches and about 3 or four inches wide at the big end. Kind of too big to consider trying to shape it much but then again it would make a great wood splitter or a hammer head or it could be pounded out to an ax head... oh my! ;). I spark tested it and it appears to be the same material as those little formed lumps of steel I found earlier. Really dark orange spark; really short and curly cue shaped. Weird stuff. I'll have to experiment to see if it can be hardend but if so then its got serious potential.

"GA"

Thats about the gist of it ;)

Actually I'm working up to something about 36 inches long...

Read several designs. Shooting for a Riel setup in the near future. Kind of curious though, I think it is Dan Fogg who has the design for the upright tube chamber that he passes the steel all the way through it and only gets about 6 or 8 inches of actual forge heat on the steel at a time? This would seem to cause problems with the heat soaking off the ends but then I've seen his work and he's doing what he does very well.

Less fuel would be good.

Understood. Ron Riels reciepe calls for coating the entire inner surface with ITC. A round chamber will also circulate the heat better than sqare brick.

I was joking ;). Actually I thought to myself "what a wonderful idea!" I have a left over piece of railroad rail without the top rail that I cut off my rail anvil and got to thinking that a piece of that with webbing forming the part you hammer on and the footing cut down to shape would make an excellent flatter.

GA

Orange reddish flame indicates too lean, bright yellow indicates too rich. Think about what you're actually seeing. The color of an open flame tells you how energetic the reaction is. The more energetic the reaction, the more energy is liberated into the surrounding environment, that's why blue stars are hotter than yellow or red ones. (We covered the chemistry of combustion extensively back in airplane mechanic's school, of course there's a two-page formula that goes with this lecture...) You can't make horsepower by pumping air, you've gotta burn fuel. Quit worrying about the mileage and get the temp up. If you're having real expansion cooling problems, set the tank in a bucket of room temp water to keep the propane warm.

If all else fails, try reducing the volume of the box. Pack the heat in as small a space as you can get away with.

Charly

Hey GA, Weld a longish handle parallel with the web of the rail section and that should make a usable flatter. The face of the tool should be, well.......FLAT.

36" long forge? That's huge. keep in mind the more voulume the more burners/fuel you will need. I have a huge commercial brick pile forced air forge with 5 burner ports, 500k BTU's. It's great if you want to heat 30" of 2" square bar but for most work it is an absolute waste of energy. A small frax forge will do 90% of the work I do and costs very little to run.

GG

The more I read what you're setup's like, the more sure I am you aren't getting hot enough for forging.

At night, bright orange -to me- is about 1600F. YMMV

The insides of my insulated fire brick heat treating furnace gets a full yellow color in no time and I'm using 1/4 the flame you are.

Funny how this must sound to you. :)

Efficientcy is key here, propane is a marginal fuel.

You are pouring propane in there so fast your bottle is chilling down. How can it not be hot enough?

I was doing and thinking the same as you right up until my change to insulated fire bricks. (insulation)

Now, the propane lasts forever and the whole thing is very subdued and pleasant instead of sounding like a jet-engine -and- I'm getting more heat. BTW, I'm just heat treating, not forging, and the extra heat was helpful.

Whatever type of insulation you decide to use, you'll like it. At least that's what I see from here.

Alvin in AZ

And smooth. Every imperfection in the surface will be faithfully transfered to the work.

Three feet of box? You're gonna need more Fire. Think about another burner for the back half.

Charly

wrote in message news:c7tlqg$kc1$ snipped-for-privacy@reader2.panix.com...

Ok, having listened (really) to all the arguments I fired up the brick pile and looked really hard at how it behaved. I tried closing the end of it off and a lot of kickback came out at the burner. Kind of scary and the stupid weed burner still has some zinc coating left on it that I immediatly noticed was putting a nasty irritating vapor into the immediate area. I pulled the end cap off and vacated the vicinity for a minute. Examining the interior of the forge at normal operation I decided that the only part of the chamber that is getting any good heat is where the blue portion of the flame is dominant. The brick is soaking off the heat fairly rapidly elswhere. There are indeed little yellow salamanders dancing around in the chamber most of the time though not so much once it all starts to warm up. I took a knife that I made out of some of that railroad scrap and tried to harden it. in order to get a reasonably even heat to it it pretty much has to be in the torch blast zone. This was a polished piece of metal and through a couple of normalizations it put on a lite film of scale. I then heat it to bright orange and stuck it edge wise into some mineral oil. Big thin flakes of scale drifted off into the oil. After it was cooled to the point where I could handle it, I took some sanding paper (500 grit) and buffed off most of the carbon/scale. The scale was only a light film really. I checked it for hardness with a file and was dissappointed to find that I scratched it pretty easily. Ok back to the forge. This time I set the pan of oil on the hot bricks on top of the forge and let it heat up to maybe a little over 100 degrees. Not hot enough to burn me when I stuck my finger in it but really warm. Having moved the oil off to the side but a bit closer than before, I then fired up the torch again and heated the knife up to a good solid bright orange and stuck it in the oil edgewise but fully submerged and swished it around for a bit giving it plenty of time to cool. When I check it with the file this time it did resist a lot better but still seemed to have softer spots. I didn't really want to scratch the hell out of it if I could help it. I got the impression that the hardness is not very evenly distributed. Just to be on the safe side I put it in toaster oven at 325 for an hour. Figure I'll put a sharp edge on it and beat up a two by four to see how it holds up. If it doesn't hold an edge well up and down the blade then I'm thinking of trying a water quench. Just for the record, the blade is about an eighth inch thick or a little more at the thickest part.

So what did I conclude from all this? Yeah, the forge setup runs dirty and doesn't hold heat worth a damn. The torch needs to be replaced with a better design and I'll be buying some Kaowool soon. Guess its time to put together that Riel burner that I've got half built in the garage. Still got questions about the blowback though. Seems like without an escape hole the fire wants to come back on the torch. Then I guess any gas forge has two openings. One for the torch and one for sticking the metal in and out.

I know it's a long way so I try to paint a good picture ;)

I was thinking on using it like a punch for more control. Might do one of each to see what works best for me.

I expect to build up to this for swords but it's not necessary for smaller items. NEVER 2" sqare stock. Long and low and narrow would be appropriate. Too much work to start with material that oversized. Actually I was thinking on building tubular segments out of refractory lined with Kaowool with maybe brick for an exoskeleton. Do it in two brick lengths that can be fitted together or capped off depending on the immediate need? All it needs is a quick connect for the desired number of torches and an insulated plug for the back end. I'm also thinking on a fairly easy tear down since I don't have a proper shop.

YeeeHaaaaw! :) Some of us might have been "shown". :( But... I'll bet most of us fiNgured it out by ourselves, just that way. :)

If you weren't kept up all night coughing then you didn't get a bad dose of it. :)

Oooops. :/

That part sounds good.

Speed is very important. Certain steels when coupled with certain quench mediums... there is no such thing as "fast enough".

You've got to learn to see the arrest point. :)

One way to help you find the arrest point is to use a magnet? :/ Austenite is non-magnetic.

I don't like the magnet method for heat treating knife blades. You could try it out at first as a learning tool tho?

My favorite way to see it is to get an old file and get it really hot (too hot) and pull it from the fire at night and watch it cool.

The file will grow duller and duller then all of a sudden the outside edges will "flash" brighter for a second then the center will do the same a few seconds later. It doesn't all go down through the arrest point and release its "extra heat energy" all at once unless you control it's cooling rate somehow. But the demonstration is best in the air so you get a double shot at seeing it.

After seeing that you can more easily recognize it as you heat it up, which is not as obvious.

The outside edges of the file will prob'ly go through the arrest point un-noticed but then the edges will begin to brighten back up again and when the center actually cools some, that's when it's easy to see and you won't mistake its look. It is soaking up the extra heat energy that it will release later when it drops back down through the arrest point.

It'll have a cooled down looking "shadow" in the center or in the case of a knife blade the thicker sections will have a "shadowy look" to them. Heat the piece just until the color evens out and quench it... it'll get full hard if you get it in the quench tank quick enough and it's the right quenchant. ;)

The steel itself shows you when it's ready for quenching.

Cool huh? :)

Quench some of that railroad junk in brine at least for learning. If it warpes on you no sweat just get the process seen and learned then try switching to oil for a more gentle quench for your thin stuff.

Oil should be able to harden the thin edge, if there is one, but prob'ly won't do a good job on that thickness of plain medium to high carbon steel.

I've heard it said "that it might be called a water-quench but they always really mean brine".

I'm sure you're going to like it. :)

I don't know if it can be seen in my picture or not but the brick at the rear isn't sealing off the end of the oven, there's a gap for exhaust. I vary how that last brick sets depending on which way the air outside is moving from. Also I've found if I want high heat for the entire length it's best to turn up the fire a little and open the "exhaust port" wider.

There. :) I believe I've typed out here on a.c.b everything I (think I) know about my heat treating furnace. :) I'm sure there is a lot more to know that I may never figure out. :)

Except for one more little detail. I heat up the "handle" of the knife through a little "side slot" between the bricks very close to the burner. I stick the thick handle part of the (thinly hollow ground) knife blade in there and get it to glowing good, pull it out and grab it with my pliers, for the rest of the heat treating process.

See? The dangged ol' thick part needs a head start or it won't get to quenching temperature when the thin part does. Pretty obvious after it's spelled out like that huh? :/ I want the handle to be hard at least half way up for the slab handled kitchen knives I make.

"it's easy when you know how" -my best friend

Good job at that, no kidding. :)

Alvin in AZ

Howard Clark used to start with 3/4" round because that's all he could get -real- L6 (4370) in was rounds.

Alvin in AZ

...snip...

Why? I'll argue than an ideal situation for a knife is the edge hard, and the bulk of the knife not hard. Or, if it be hardened evenly, the edge kept cooler while the rest is tempered quite a bit higher than the edge - more or less the same result either way, subject to more argument. Harder edge, springier body. Can't say I've done all that much with making this work perfectly in practice, but it seems like the place to be aiming for.

Hell, 3/4 round would be the next best thing to flat stock for a knife or sword man with a forge. Now Railroad scrap, now thats work! ;)

Greyangel

Naw, I don't think so. I don't really know what it's supposed to do to you but understand that it's bad. I vacated the vicinity quickly and it was out in open air anyway.

??? The mineral oil by the way is as good as I had heard from an ease of use standpoint. Some flame but not enought to worry about (kind of like holding a burning stick). No smoke, no smell and it wipes off really easy. I would highly recommend it as an oil quench.

The refrigerator magnet melted in my hand... Just kidding. Haven't got one of those telescopic magnets yet.

Seems to be the training tool of choice.

Sounds like fun.

Bingo! This is what I was looking at! I figured with the shadow still lurking in it's heart that results would be unpredictable.

I was advised by another person on this group to preheat the oil to something like 200 degrees for 5160 (which is what I've pretty much decided this metal must be). Going by my last experience, Cold didn't work well; Warm worked better, Hot should be just right. The cool part is I can use the top of the brick pile as a warming table for the oil pan. I just need to guage the temperature of the oil.

Well since the best pieces of the railroad material is probably plain carbon steel (excepting the spring clips) A water quench would probly be appropriate for larger knives and such. You recall I earlier talked about doing a test quench in crank case oil. I had used a piece of the spring clip material rough forged into a flat bar and it took a couple tries to get that hard but it worked. The knife I'm trying to harden now is the same material but thinner. I changed quenchant so I suppose this is a good demonstration of the difference in quenches.

Well it helps when folks say what they mean :)> I'm always trying to convince my boy of that. Makes the English language work right. Actually though, I think it is question of how rapid you want the cooling. Call it what you want but if all my reading is worth anything then water cools faster than brine and brine faster than oil, etc. I think the object is to cool it as slowly as will get the job done, to prevent stress on the steel. That's my take anyway.

hmm, yeah, I've been bouncing this one around in my head (ktink, ktink). I haven't quite figured out how to get the blade to not heat faster in places. With a better insulation this should get better but usually the metal closest to the torch will heat up a lot faster than what is farther away. With a blade it pays to put the thinnest spots farthest from the torch. Maybe a hole that I could poke the sharp end into or a slot in the bottom to seat the edge... hmm yes... how about a heat treating "rack"? A smallish piece of brick with a groove to set the knive blade upright into and slide th whole thing into the forge? I like it! It would keep the blade standing on edge without having a pair of tongs attached to it. You're a genious!

Greyangel

Depends on the purpose of the blade. My own opinion is that differential hardening is great for big ugly general destruction blades (my preferred type) but if you want a cutter then by God make it hard as you can without shattering it. Especially for Kitchen knives!

GA (See you guys got me doing it now!)

If he were getting a hard case that would be cool I guess. :) Didn't sound like it was working out so good, so far tho.

That all might change after he gets the arrest-point figured out? :)

Because my knives are thin bladed "old hickory" kitchen style knives. There has to be "some" heat treating up inside the handle otherwise the knife will bend where the metal meets the wood and stay bent. :/

I agree, if you are speaking for yourself, and aren't saying it has to be "ideal" for me too. ;)

I'm weird, I make them different from most everyone else, for sure different hardnesses and toughness than the factories "have to" with their lifetime guarantees and all.

No arguement coming from here. :)

I'm weird, we got that straight at least? ;) What I'm all about is getting the hardest and best edge holding I can get and not the least bit interested in making more tough, thick, clunky knives... the "world is full of 'em" and don't feel like I need to make more of those. YMMV :)

Alvin in AZ

I don't know, but figure, that work is going to get a lot easier when you get your new, hotter forge going. ;)

What I need to figure out is a way to take rounds and laser cut or EDM(?) them into nice, clean, thin (3/32") flats. If I felt sure about that part I could get some steel I've always wanted to make pocket knife blades from-> F2! :)

F2 tool steel:

1.25% C (minimum) 0.25% Mn and Si (nice and low:) 3.50% W and either 0.30% Mo or 0.30% Cr

Fracture grain size = #10 looks kind of like flint when it breaks. :)

O7 tool steel is another that I'd like to get but haven't found in rounds or anything else. :/

Alvin in AZ