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Main Boards => Hunting Knives and Crafters => Topic started by: agd68 on March 10, 2010, 07:10:00 AM
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Is normalizing nessessary for the stock remaval method ?
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Some will say yes.... they have to me anyway when I asked that question. But not everybody (in fact most I think) would agree with that. Hopefully some of the more experienced will chime in.
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I would normalize. Even if there was no stress, which I think there is, I would want to reduce the grain size of the steel before I quench to harden. If there is stress it can cause the blade to warp in the quench. Lin
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I always normalize. For the reason Lin stated and you never know what stresses the milling and processing at the factory created in the steel.
Normalizing is cheap insurance.
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That makes sense. I've been annealing the steels before grinding, so I'm guessing that would achieve the same purpose? Assuming that you don't stress it out too much during the grinding process???
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Yes, annealing will help, but also normalize before you harden the blade. That's your last chance to reduce grain. Lin
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Originally posted by mossanimal:
That makes sense. I've been annealing the steels before grinding, so I'm guessing that would achieve the same purpose? Assuming that you don't stress it out too much during the grinding process???
Thanks, Lin, for the reference to grain size.
On any new steel, it would behoove the maker to thermal cycle the steel a few times to get all of the alloy into solution in the steel matrix.
I know a guy - And Lin knows him as well - who once etched a brand new bar of steel and could actually see the profile of a FILE!! in the steel! The file hadn't even been melted before they poured out their recycled batch of "NEW" steel.
Who knows where it came from - Indiana? Pakistan? Hungary?
Steel is bought and sold as a commodity, and it hits the market all under the same name no matter where it came from.
Annealing and normalizing are two things that are only DONE in the same room - they create entirely different results.
And, there are two completely separate "annealing" procedures.
Be careful of tossing that name - "annealing" - around. There is a full anneal and a sub-critical spherodizing anneal.
One is done above "critical", (not non-magnetic), and the other is done well below non-mag at around 1300.
They are dramatically different.
And BOTH are done at a slow cool, whereas "normalizing" is done in a reducing heat process and cooled quickly to reduce grain size.
If you don't have really, really, really good control over the full anneal, and get too hot, you'll dramatically increase grain size, and only emphasize the need for proper normalizing steps prior to hardening.
For example, non-magnetic is at 1414, which is the reaction of heat to the iron ore, no matter what grade of steel. "Critical", say for 5160 is over 1525.
Over normalize, and you can reduce grain size so small that you'll minimize hardening depth.
At that point, one would actually need to OVER heat the steel once more to increase grain size, and then start over with normalizing.
But beyond all that, do what works best for you with your chosen steel type, and don't forget to have fun!
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Thanks... I've been taking it to just above non-magnetic when I anneal. I have accidentally taken something too far above, so I intuitively started normalizing.
How do you over-normalize???? Too many cycles???
Great stuff... thank you...
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Scott, when you are referring to "annealing" and you take it above non-magnetic, what do you do with it then?
To be what one wold call an "anneal", it would need to then be sloooooooooooooowly cooled from that temp.
I know a lot of folks think that by sticking into some "stuff" to insulate it they are annealing it, but not really. Maybe a little bit if you go to some real extremes with that process.
But it's probably cooling so fast it's not much more than a normalizing cycle.
And, a proper normalizing sequence is done in "reducing heats'.
The first cycle would be at about the forging temp if the steel has been forged. Here we're talking about anywhere from 1600-1800 degrees.
You want it as hot as you have been forging.
Then cooled to a black heat - about 900-1000 degrees.
Then a second heat to right at about critical for that steel. Just make sure yo are WELL ABOVE non-magnetic, like 1500 - 1550 degrees, and then back to a black heat.
Then right back in the forge and up to a dull red, sort of right about where the steel ALMOST acts like it wants to go non-magnetic, but not quite.
Now all during these cycles you want the heat EVEN all throughout the blade. Not yellow at the edge and orange at the spine, but even throughout. Otherwise you end up with different structures throughout the blade.
This is one more reason to throw those coffee can forges in the river - they are WAAAAAAAAAY too hot in a small area and don't allow for evenly controlled temps.
Just do yourself a favor and build a little bigger forge. Get a longer body and larger diameter, it truly doesn't take any more time or dollars to build a bigger one and the result will make you a much happier knife maker.
Yes, over normalizing is the result of thinking you might be doing the steel a favor by giving it s few more cycles and you're just creating a situation of reducing hardenability.
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Karl.... I now anneal by burying it in vermiculite that has a couple of smoking hot pieces of metal in it to 'pre-warm' it. When I've done this with farrier files, I can take the rasp teeth off reallll easy. Not to say that I'm getting an even heat though. That is the bugger right now... but I don't THINK it's because my forge is too small... I THINK it's because the forge is to big for my single burner. I don't have a coffee can size forge. I think when I made some posts on this in the beginning, I was going that route. But I ended up making a forge out of an air compressor cylinder that is approx. 12" in diameter and about 24" long. I put a single burner in, but left room further back for when I can afford another burner.... and a bigger propane tank. Those 20# tanks sure don't last long....
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I used to do the same thing, and it's a better way to go. I would get two pieces of heavy wrought iron really hot and lay my heated blade between them and cover them with lime.
Even better than vermiculite is lime, it's a much better insulator.
But it's obvious you are doing as much as you can with what you have.
I have a pretty big forge and only one burner and weld damascus in it all the time! Which means about 2300 degrees. It's 12 by maybe 22 I think and I can shoot flames out the door a foot long! You don't need two burners.
Darren Ellis sells coupling hoses where you can connect more than one tank at a time, which will help to keep a 20#er from freezing.
That might help until you can a 100#er.
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I appreciate it Karl. I've actually been out to my forge between these posts working on a skinner and I'm starting to experiment with where to place the steel during my heats. I now realize one of my problems: I put a false back-wall in to minimize the heating area of the forge since I have a bunch of space in the back (going with the theory of leaving space for another burner). I just now figured out that I can get a much more even heat by knocking that false wall back further and pushing the steel further back. Seems like common sense, but I was working under the idea that I needed the smaller area to build up heat. Nonsense.
Thanks adg68 for asking.
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Cool. More important than size is how well you have it insulated.
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I've got two inches of ceramic wool and a layer of plistix on that. The question I have... is how much ventilation do you need on the back side of the forge to allow air flow? I'm wondering if I can reduce the size of the hole I have back there to provide less heat escape....
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Originally posted by mossanimal:
I've got two inches of ceramic wool and a layer of plistix on that. The question I have... is how much ventilation do you need on the back side of the forge to allow air flow? I'm wondering if I can reduce the size of the hole I have back there to provide less heat escape....
I've been gone for two days in Madison and the computer at the hotel was worthless.
Not sure what you mean by "ventilation"?
Are you not using a blower on your burner?
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No... mine is a venturi.
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I've made my three forges and all of them are with forced air blowers.
They are also the only kind I've ever worked with at hammer-ins, other maker's shops, etc. so I'm of little or no help on this one.
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You don't want air to flow in :) All the oxygen you need is coming in through the intake on your burner. The only reason to have a hole in the back is if you're planning on forging long pieces. Mine does have an opening in the back, but it's closed off with a kiln brick and wool until I actually need it.
I have all the pieces for two new venturi burners in the shop... I think I feel a build along coming.
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Jeremy, a build along would be great. I have an old LP tank for a grill (#20) that I think I'm going to try and build a gas forge out of. I still have some more research to do though. Not to get off topic here but can the fire bricks you use in a fireplace (not the soft kiln bricks) be used in a forge? I'm assuming they can and my neighbor is a mason and can get me some for free.
Also good info. on here about the normalizing. I've been doing two cycles of normalizing before quenching. My problem is I think I'm overheating the blade at quenching. I did a couple of blades the other day along with a scrap piece. After finishing I broke the scrap piece to see how it looked inside. A little coarse. Not as smooth looking as the examples I've seen here. Oh well, Rome wasn't built in a day!
Aaron
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I've heard it both ways Jeremy... I think it was on Zoeller's site that I saw to make sure to include air flow through the back? I will try it without and see how she performs...
I'm putting a choke plate on mine this week... any experience playing with those? I will need to reducing conditions for forge welding tomahawks soon....
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Another question on normalizing. Karl, you talked about doing three cycles of normalizing on forged steel to reduce the stresses. Would three cycles, as you described, be necessary when simply doing stock removal? Just wondering. There wouldn't be any stresses from hammering, just cutting and grinding. Would one or two cycles be sufficient? Thanks.
Aaron
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Nope, I don't think I said anything about relieving stresses - did I?
It's mostly for even distribution of alloys and grain refinement. In that respect, yes there are stresses, but it's stresses from uneven distribution of the alloys creating different steel structures throughout the blade.
Truth of the matter is, you have NO IDEA of the condition of that steel. NO IDEA of what mill it came from or how it was treated.
When you thermal cycle in three REDUCING HEAT steps, with good heat control for EVEN heating of the target steel, you DISSOLVE the alloy for even distribution and in the cooling process enhance grain refinement.
I always think of different steel types as different types of cakes with different ingredients.
We have "simple" tool steels and we have "high alloy" steels.
A simple cake would only have flour, egg, water, just basic ingredients.
Wouldn't take much to get all of that dissolved and evenly distributed.
But as soon as you begin to make a more complex cake, with a lot more ingredients, the more stirring, the more heat and the more TIME is needed to evenly distribute the ingredients and the more time in the oven to get it cooked.
For example, to austenize 1084 for hardening, you barely need to get it much more than non-magnetic (1414) and quench in something wet! It has very few ingredients.
But, to do it properly, 5160, because of all the chromium and other alloys, needs to soak at 1525-1550 for a GOOD! 20 minutes.
A LOT more heat and a LOT more time.
I know I'm going on here, but just to delineate between simple steels and complex steels.
Is it important to thermal cycle blade steels?
I can come up with a lot more reasons to do it than to not do it.
But make sure to do it in REDUCING HEATS!!
If a subsequent heat cycle goes ABOVE the previous cycle, then you just lost overything you were trying to gain!
Go HOT on that first one to dissolve all the alloy and let cool to black, then right back in the heat.
Heat the second time to a nice even orange color well above non-mag, but not as hot as the first time. Once again, just back to a black heat, which will be about 900 degrees.
On the third one, just to non-mag and let cool to room temp.
It's a really basic procedure, but better than NOT doing it.
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I agree with Karl. It dont hurt to do it, but it may hurt NOT to.
A lot of testing and time have been spent trying to figure out the magic (not literally magic :D ) number and, from what I have read, three is it. Three times. After that the returns are deminshing and may even have negative effects. This does not mean you cant thermocycle more than one session of three during the whole forging, grinding, heat treat process. You can and thermocycling generally will help each following step up to the quench.
This information is just what I and Karl as well as many others gather while at the Hammer Ins and classes. It's not to say that it's the final word. But it does seem to work well. Lin
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Sorry, didn't mean to raise any hackles. I guess I read it wrong. Thanks for the info.
Aaron
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No hackles were raised - to the contrary - you just gave us another opportunity to discuss what we enjoy!
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Where can a guy come up with a color chart to see differant heats of steel? Ever seen any? Thanks Mark
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Yes. But I cant remember where. :biglaugh:
After I said it, I thought about how little help that is. Lin
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Scroll towards the bottom of this LINK (http://www.knives.com/heatreat.html)
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Thanks, Ill copy that. Mark
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Yep, that's where I saw it. Lin
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The machinists Handbook has color charts in it that make for great references when forging / normalizing / hardening your steel.