Forge damage?

Hey all,
I've been working a large Camp Knife made from a leaf spring and used
the forge to straighten it out and do a bit of shaping. I was sanding off
the grunge on the belt sander when I noticed there is a crack in the top
quarter of the blade that goes about half the thickness of the steel and
travels maybe a quarter to a half inch down from the back towards the edge.
Now this is a fairly huge piece of steel that was going to serve as a wood
chopping, bottle opening, all around heavy use camping blade. What I want
to know is if the experienced forging folk out there can tell me if this
kind of thing can be repaired? Should I hack the stock short at the crack
and start over? Should I just re-adjust the demensions of the blade to
grind out the crack? for the record, the steel appears to have some chromium
in it so I'm guessing 5160. This is the second time I have run into this
problem with what I think is similar material (based on appearence and
behavior). Is it possible to heat it up and repair the crack? On the last
piece of metal I tried folding the cold metal over in the vise at the crack
to see if it would break and it didn't, so I'm guessing this kind of thing
is localized. What is the opinion of the experts out there? It's all new
to me.
Greyangel
Reply to
Greyangel
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A fairly common problem with used springs. Stress fractures are common.
You could try forge welding it back together, but might be better off to work around the crack.
Reply to
Ernie Leimkuhler
I was wondering if forge weld was an option here but I can't see that it would be very easy without some folding. I think I've already made a different style of knife out of it in my head. You know, something with slimmer lines.
Greyangel
Reply to
Greyangel
It's not forge damage. It's typical of used springs. If you can get un-used spring cutoffs from a spring fab shop you'd be better off, but used springs are certainly the more common stock, and this is a common problem. I just moved my old truck springs closer to the shop, and chunks fell out of the middle of the stack - they became old springs because they had cracked in service, and some of the cracks went all the way though, so parts fell out. Other cracks may not become obvious until you start to work on them.
IMHO it's best to work around them, rather than to try and fix them. Some people say you should never use springs for this reason, but the price is right (I suppose not using them makes sense if you are a production smith - I'm not).
Reply to
Ecnerwal
Remember earlier I told you about ooold leaf springs? Microfractures... You can burn it together with a torch, or blaze it with an arc welder, but I haven't had all that much luck with hammering it into one once it cracks, crap gets into the crack and screws the fusion. It was probably too cold.
Charly
Reply to
Charly the Bastard
I went ahead and ground it out. It started life as an oversized Bowie style knife; now its sort of a Fantasy blade. I started with the idea of those "elven fighting knives" that you see on the commercial sites for Lord of the Rings weaponry and kind of let the design work itself out as I went at it on the grinder. Came out pretty cool. Lots of flowing curves. Still too much forge markes on it that need to be planed off on the belt sander but it should make a nice blade and the crack is gone.
At this stage for me I'm just sort of starting with a chunk of metal and seeing where it takes me. Not good enough yet to start and finish with the same idea. I am a bit worried about this crack thing though. As I said, it's not the first time this has happened and it's not the same source for the metal so I assumed I did something to it at the fire. I'm currently attempting to straighten and draw a rather large chuck of metal and I'm not going to be happy if it comes out with a bunch of cracks in it. Different steel though. I don't think there is any real alloy mix there so I'm hoping it'll behave for me. And yes I am making sure I don't work it too cold.
Greyangel
----- Original Message ----- From: "Ecnerwal" Newsgroups: alt.crafts.blacksmithing Sent: Thursday, May 06, 2004 6:38 AM Subject: Re: Forge damage?
Reply to
Greyangel
Been pretty careful about the cold thing. Thats what makes this frustrating; I don't really know what I did to it. Back up and punt. I ground it out and made a totally different style of blade out of it. Fortunately it was pretty oversized to begin with. It literally would split small rounds of fire wood. I've used it in the past to hack up dead trees for campfire wood.
Greyangel
Reply to
Greyangel
Are you still using the weed burner for heat that you wrote about in another thread? What exactly does it use for fuel? I'm thinking that you might not be 'keeping' enough of the heat to really get the temp in the box high enough. I ran into this with the gas, I wasn't pouring the heat in fast enough to overcome the 'leakage' out the top. Mixture has a LOT to do with it, maybe your fire is a bit on the rich side, which gives a cooler flame due to incomplete combustion. Getting 3000 degrees is not that easy, some days my gas rig won't get above cherry, no matter what I do, the air just won't support the heat.
Scientists say that fire is just numbers, but they're wromg. Fire is a live thing, and it has a personality. You've gotta make Fire your buddy, so he'll work for you. You'd be surprized what naming the forge will do towards making Fire your buddy. After I gave mine a name, things started going much more smoothly. All the big machines have names, maybe that's why the swords glow in the dark...
Charly
Reply to
Charly the Bastard
Folks have mentioned pre-existing cracks in old springs. I've seen a few but not many. There is another possibility: I was told by an instructor that you should never just re-heat after forging and quench for hardening. Get rid of any serious hammer marks with light hammering (hot). Reheat and let cool in air, i.e. "normalize". Then heat to "cherry" and quench, clean and temper.
Ted
Reply to
Ted Edwards
there are no mistakes in blade making,, just new blade designs ;o)
Reply to
bear
Hey GA, if the cracks were not there before you started then yeah it probably is something you did. Cracks often indicate forging too cold. If the cracks first appear like hairlines, usually running lengthwise, this is probably the case. Oil hardening steel (O-1) seems especially unforgiving of this sin. However if the surface of the steel is all gross and pitted and fissures or ruptures appear then this is caused by overheating and forging too hot. What kind of heat source you are using? Are you hand forging or power forging? Not that this matters much as you can always find ways to screw up when forging tools. There are two things you need to develop if you want to forge usable edged tools or weapons. The first is the ability to judge temperature by eye. At the very least, you must learn to recognize the high and low forging range. For spring steels and and similar plain carbon tool steels the upper limit is going to be around bright orange. Try and avoid frequent yellow heats. Hammering below dull red with all but very light blows is to be avoided. The second thing you need to develop is hammer control. Early on be most concerned with attaining smooth flat surfaces. Keep the anvil free of loose scale. Try wetting the anvil during the final light forging heats. This helps pop off heavy scale and will leave the surfaces quite glossy. This will make subsequent cold work a lot easier and quicker. For me, if a crack appears at any stage of making a blade, it goes directly to the scrap pile. I don't even think twice. Good luck Angel, develop good habits and it will pay off.
Glen G.
Reply to
glen
Cool, Good information. I have pretty much gotten over the temptation to keep hammering after the glow begins to fade. Bright orange is about the best my forge setup will manage and as soon as it gets to dull red the work goes back in the fire. The cracks I've seen are small lines that start at the edge and aim crosswise to the length of the piece (knive stock). The last one didn't even penetrate the thickness of the stock. I am sure that the damage was not there before the forging. I'm trying not to hit it too hard if I can help it now (hand hammering). The other problem with putting a lot of muscle into the hammer strokes is that you get a less even surface out of it. Been trying to straighten out a big heavy (about 1 inch square) piece of railroad steel (not rail). I've had to lay into it pretty hard to get any movement out of that stuff. Quite a shock transitioning from that to a smaller (1/4 inch or so) piece of metal. Way different approach to the forge work. I should get the big one drawn out soon so I expect it to get easier to work with as I progress.
Greyangel
Reply to
Greyangel
I'm at a pretty low altitude and the forge is working well enough to make me happy. I'm using a 5 gallon bottle of propane to feed the weed burner and it puts out a rather large hot fire. Depending on the air currents blowing up behind it the flame sometimes goes from bluish hard to see flames to more visible orange flames. Top heat inside the pile of brick is a really bright orange glow. after an half hour of heat the bricks start to hold that bright orange really well and the metal gets noticeably easier to work with less time in the reheat cycle. It's cool when the daylight fades away and I turn off the torch. the brick pile holds that bright orange inside for quite a while. Any rate I don't pull the metal out to work it till it gets full bright orange but as I said it does help when the forge gets up to full heat too.
Ahh forge theology! I may get there at some point :)
Reply to
Greyangel
Hmm. Sounds like hard, heavy brick? Lightweight Insulating Firebrick is much more fragile (and soft), but it will also come up to heat in no time flat (well, a minute or two at most, IME). On the other end, it does not hold much after it's shut down, but for the hobby work cycle, it can make life easier. The ceramic blanket insulation will do the same if you can get that in a convenient sized piece, but the lightweight brick is often easier to find in small quantities. Could be worth replacing some or all of your inner bricks with...
Reply to
Ecnerwal
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That's not set up to be a forge it's set up to get as even of heat as I can for heat treating knife blades. Regular fire bricks cost me 75c each and the insulated fire bricks cost me $2.45 each. They were the lightest to be had there/then.
Inside, on the floor, where you can't see, are two insulated fire bricks and simply surrounded by the ordinary fire-place-liner bricks to form the floor.
The insulated fire bricks are light weight almost like styrofoam. :)
No kidding on this, I did this and even showed it to others a couple times... picked up an insulated fire brick with my bare hand with one face of it glowing orange-yellow and turned that face toward myself and felt like I was going to singe my eyebrows. ;)
The first time fired it up after switching to the insulated fire bricks from the old ordinary fire place liner bricks I "almost melted" (non blacksmith ok?;) the O1 kitchen utility knife blade I was trying to heat treat. Not only was it much faster but so bright in there I missed seeing the arrest point and blew right past it. :) (i always heat treat at night)
I was using the same size of flame as before... since then cut it back to 1/4(?) and need to experiment with even cutting it back somemore.
I'd really like to see configurations of insulated fire bricks that are considered good forges by their user! So some day I could copy it. That's the thing about bricks you just re-configure as needed.
I melted and poured in four different melts, 315 pounds of lead using those bricks then put it back the way it is in the picture.
The first few years I was heat treating, that stack of fire bricks took on a dozen different configurations. :)
Alvin in AZ (dogs, beer, ribsteaks cooked over wood;) ps- still working on the spark testing... stalling for a known sample of something in between 1035 to 1060. pps- all I have are 4140 and 5160
Reply to
alvinj
Hey GA, from what you describe it is very possible that you are forging at to low a heat. I don't know how your finances are or how handy you are., but I would recommend putting together a decent forge. it doesn't have to be very big. A good atmospheric burner can be built for ten bucks! There are some companies that sell small amounts of fiber insulation and $50 or so should cover a knife makers forge. You will recover the cost in fuel savings in a very short time. Also, there is a blacksmiths tool called a "slick", some call it a "flatter". This is used as a finishing tool. It is basically a 3" square face with a shank. It is held on a handle and is designed to be struck with a sledge or heavy hand hammer. It can be awkward to use by yourself but it can be done and the results are dramatic. All but the deepest boo boos will be slicked down.
G.
Reply to
glen
Hmmm. If the metal is at color I don't see how this can be. It does seem to make a difference in overall work when the forge is fully soaked but still the metal is what is at issue here. As for me being handy... I'm new at this so mistakes are made. I'm learning though.
I kind of like my forge setup right now. I have a not quite assembled Riel burner in my garage That I plan on finishing and I do plan to do a forge chamber with Kaowool and.. whatever the name of the refractory sealant is. The two big drawbacks to my current setup is that the torch is probably not very conservative. Lots of air blowing around but I am out in the back yard without a shed for cover. The other is that I've never seen it at anything hotter than bright orange heat to slightly higher. Thinking about it though, I've never really opened up the torch valve beyond what I felt was needed so I don't really know what it will do. I try to idle it as much as possible to conserve fuel. On the plus side, I can set up and tear down in minutes. I don't know how big it will need to be untill I'm using it so it's inherently adaptable to blade size which is what I want it for anyway. Actually I like this feature so well I was thinking of just facing some bricks with refractory to make them more efficient for the interior spaces. I've also thought about making casted segments for the chamber that can be run end to end for the length needed for the blade that is being worked. This way I can just cap off the chamber or add sections on the fly. So, yeah I could have a more efficient set up but this works for me for now and untill I know what it is that I really want out of it
Sounds like cheating. Where can I find one? I like the idea. I'll be looking for a suitable piece of steel to make into one. After my experiences with working thick stuff I don't think I'm gonna try to forge anything that big. Hmmm, give me an idea. I've got a piece of railroad rail that I use as an anvil and I had a friend under cut the top rail so I've got a 6 inch length of the footing and webbing without the top. Still really heavy stuff. I've been working on sharpening the top so that it'll be a self standing hot cutoff. I'll bet a piece of that stuff would make a killer "flatter" since a lenth about 3 inches with the footter profiled a bit smaller (or not?) and the top flattend would make a killer stamping type tool. Ahh the wonders of railroad steel! Sorry, I'm rambling. Good Ideas! than's why I'm here.
Greyangel
Reply to
Greyangel
I prefer to buy material locally and the tan colored hard bricks are what I can get around here. So, what if I painted the interior bricks with ITC? Is ITC a lot better than plain refractory?
Greyangel
Reply to
Greyangel
That's what I'm talking about! I have just the tan bricks... So the insulated brick makes that big a difference in the interior heat? Guess I'll have to source some.
I keep playing with different designs than the one I have and I keep coming back to the original design. I would like to work out a double chamber system for heat treating where the torch flame travels to the end of the first and is bounced into a second chamber for lower more even heats
I'm with you on the working at night thing. I start in the late afternoon. Last night I was working it till it was almost too dark to see the rest of yard. You get an entirely different relationship with the forge and work after the sun goes down. Very nice!
So the HC spikes are a known 1030 anyway. Not close enough? I keep coming up with different samples of stuff. Been working a leaf spring lately and it seems to be pretty much the same thing as the cement/rail clips we were discussing. Which leads me to believe it's 5160 (shrug)? found another big heavy piece of railroad castoff the other day. shaped kind of like a splitting wedge with some extra details added on. Can't imagine what its used for.
Greyangel
Reply to
Greyangel
Ask your current supplier - they might be willing to order you a box. If no luck, check for "refractory materials" in the yellow pages. Any pottery supply will also have them.
Depending on how narrowly you define local, you should be able to get them locally. However, the good part about them if you actually can't find any locally is that they are lightweight to ship.
Web searching on insulating firebrick (or IFB) will result in various sources online. They may not be a good deal (alvinj reported a local price of $2.45, these are more expensive at $63 for 25 bricks, plus the shipping). But it's one source as an example, anyway.
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Those are 2300F bricks, there are others available up to 2600F (might be only one supplier for IFB at that temp - came across a page describing it as a novel process extending the IFB temp range from previous limit of 2500F, so 2500F is probably available from several suppliers). All should work fine for forging steel, and lower temp rating is probably cheaper.
Reply to
Ecnerwal

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