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The Newbies Arena Are you new to knife making? Here is all the help you will need.

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  #1  
Old 11-24-2012, 06:21 AM
Afterburner Afterburner is offline
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Heat treatment and tempering?

Hi everyone, im new to the forum and knife making.

Just started on my first knife a while back, and used the 316 grade stainless steel.

I've cut the steel to profile (scrollsaw) and filed the edge sharp-ish.

How do i go about from here? Do i heat treat? Temper?
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  #2  
Old 11-24-2012, 08:24 AM
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Ray Rogers Ray Rogers is offline
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Actually, you're done. 316 stainless is not a blade steel, it won't harden. What you have now is something that looks like a knife but isn't. It will cut if you sharpen it but won't hold an edge for long. You might finish it just for the practice and then use it as a letter opener. Even if it had been a hardenable stainless you would have had to send it out for the heat treatment unless you have your own heat treat oven. Stainless cannot be hardened properly with a torch or in a forge.....


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Old 11-24-2012, 09:10 AM
Afterburner Afterburner is offline
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Ah, i see. Just wanted to test how workable metal is before spending money on knife making.

I guess i'll buy one of the more recommended steel types after im done with this then!
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Old 11-24-2012, 10:15 AM
Doug Lester Doug Lester is offline
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Try 440C. It's one of the cheaper steels as far as stainless goes, easy to find, makes a decent blade, and just about any heat treater will know how to handle it. It will take a regulated kiln to austinize it, if you are wanting to do your own heat treating, but you can temper it in a kitchen oven.

Doug


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Old 11-24-2012, 10:43 AM
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Ray Rogers Ray Rogers is offline
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Funny thing about that workable metal test: 316 is kind of nasty to work with. Not as bad as 303 but not as good as 440C or most any of the carbon steels. In other words, what you did is probably a little more difficult than it would have been with a good blade steel.

As Doug said, use 440C if you want stainless. Send it to Texas Knifemakers for heat treatment, they charge about $5 for one blade and they do it all - heat treat and tempering. If you want to do your own heat treatment with a torch or a forge then get some 1084 ....


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Old 11-25-2012, 09:44 AM
Afterburner Afterburner is offline
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I live more then 10,000 kilometers away from Texas...

But anyway, that aside, how exactly does the treatment process go for metals like the 10xx series?

Was reading, and still confused on the need to heat treat, then temper (sounds like heat treating at a lower temperature to me)
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Old 11-25-2012, 11:26 AM
Imakethings Imakethings is offline
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Alright, there's a lot of science behind doing a heat treatment and tempering.
One of the blacksmiths that taught me the basics of doing this and explained it like this.
"Hardening makes it as hard as it can be, tempering softens it up a bit and lets it bend rather than break."

So here's a slightly longer explanation:
When you heat treat a blade you're trying to get the carbon and other stuff in the steel to distribute evenly throughout the metal, this is why it can take so long with some of the more exotic steels, those extra elements take longer to dissolve and distribute through the material.
So imagine it like this (not entirely accurate, but it works for visualization/understanding). So when a piece of steel is fully annealed it's like a pack of ping-pong balls all stacked and shrink wrapped nicely and organized. They take up more space like this, but there is more space for them to move around, compress, and bend.
When you apply heat it's like unwrapping the ping-pong balls and dumping them in a box, they tumble on to each other and even if the box is the same volume when they're not nicely stacked, they will take up less space, but there isn't as much space between them to bend and flex.

Tempering is basically adding in some of that organization so there is space for it to bend and flex.
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Old 11-25-2012, 12:32 PM
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Ray Rogers Ray Rogers is offline
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QUOTE: I live more then 10,000 kilometers away from Texas...

Uh huh, and if you filled out your profile we'd know where you were and could adjust our responses to your questions to be more useful to you.

Annealing is making a hard piece of metal into a soft piece of metal.

Heat treating makes a soft piece of metal as hard as it can possibly be.

Tempering softens heat treated metal just a little bit so that it becomes tough as well as hard ...


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Old 11-25-2012, 02:21 PM
Doug Lester Doug Lester is offline
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Ok, here's a little better picture. Iron atoms form a nice matrix of inter connected atoms in the form of crystals. At below 1328? F. (720? C. ) these are in the form of interlinked cubes with an atom of iron in the middle and at each corner, a body centered cube. At above 1328? the atoms rearrange themselves into interlinked cubes with iron atoms at each corner and the middle of each face without an iron atom in the middle of the mass, a face centered cube. In this hot form the iron can dissolve much more carbon than the cool form can; 0.77% as opposed to just under 0.02%.

Now the fun starts. When you heat the steel to complete the change to from a face centered cube to a body centered cube, depending on the alloy that is going to be 1475? or higher, and give it enough time carbon, bound up in carbides, dissolves into this carbon matrix. When allowed to cool in still air and form back into a body centered cube the carbon can escape from the iron matrix and reform carbides. If you cool the steel too quickly for this to happen, and to a point around 400? depending on the alloy, then the carbon gets trapped in the iron matrix and forms a body centered tetrahedron by physically not allowing the iron atoms to move back together and this stresses the bonds between them and gives the steel hardness and brittleness.

The problem is that it's far too brittle, in most cases, to be used for anything. That's where tempering comes in. You heat the steel back up a little bit and allow the carbon to move slightly and allow a portion of it to escape the iron matrix and reduce the stress on the bonds between the iron atoms and decrease the brittleness. A little hardness will also be be lost but that's a trade off that can't be avoided. You will find that in working with steel you will be faced with one trade off after another.

The reason that 316 will not work is not that it does not have carbon in it; it does not have enough carbon in it. You pretty much have to have to have 0.40% carbon to hold an edge and even at that level it won't do it well. For the most part you want to be above 0.60%.

There's one important exception to what I've written above that I need to mention and that air quenching steel. Those are steels that will harden when cooled in still air which takes in all stainless steels. Highly complex steels are full of alloying elements like chromium, nickel, vanadium, and the like that will decrease the temperature takes for steel to convert from a face centered cube to a body centered cube or tetrahedron and the temperature gets too low for the carbon atoms to travel fast enough to escape. This is just a thumbnail sketch of what goes on and is way, way oversimplified. I have two books on the subject that are 200 pages and they're just Cliff Notes on the subject. Universities offer undergraduate and graduate degrees in metallurgy.

Doug


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Old 11-25-2012, 05:09 PM
Imakethings Imakethings is offline
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Doug's explanation is better than mine, listen to him.
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Old 11-25-2012, 09:47 PM
Bowman Bowman is offline
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Afterburner,

I'm going to assume that you are Canadian as you mentioned distance in kilometers. I would check out Canadian Knifemaker Supply in Sundre, Alberta for supplies and heat treating service.

Last edited by Bowman; 11-26-2012 at 12:07 AM.
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