A couple of Questions on 1084

David Stifle

David Stifle

Joined
Nov 20, 2008
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Wow! This is the first time I've used 1084. I'm absolutely amazed at how easy it is to work. But, since it is the first time, just a few questions. First, I want a springy blade. I'm familiar with the technique of putting the blade in water and using a torch to draw back the spine, but I was wondering if the tempering could give me a flexible blade without drawing back? Would claying work? What should I temper it at to get a HRc of 55-58?

And finally, can this steel take a fast (park 50) quench, or should I use a slower oil such as canola?

Thanks, Folks!
 
Parks is great for 1084, and a clay hardened blade will give you a softer spine. I would think 55 hrc would be pretty low, even for a chopper. I would say maybe 57-59..? I'm not an expert in HT but thats what I would think. Of couse others with more knowledge will chime in :) Curious as to why you would be against doin a soft back draw..? Anf you can always just edge quench it. my $0.02 :rolleyes:

-Paul
_______________
(some of my knives etc. www.youtube.com/Lsubslimed)
 
Thanks Paul, good to know Parks is good. As for 55 hrc, it might be a mite soft, but many swords are right around that range. I'm not against doing a soft drawback, just wondering that other options might work. As for edge quenching, it's been so long since I've done that I practically forgot about it. I always do a vertical quench. An edge quench wouldn't work well in this case anyway due to the curvature of the blade.
 
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Tempering temperatures for 1084 vary from 375 to 450 Fahrenheit, depending on the final hardness you want, 400-420 being optimal, IMO.
 
Edge quenching makes for an inferior blade no matter how you look at it. Flexibility until you hit either yield or failure points is entirely controlled by geometry and cross section. Stress/strain deflection curves on identical cross section bars of steel, one dead soft annealed and one full hard are identical until the annealed bar hits its yield point and takes a permanent bend. What you are doing when you edge quench is creating a small area at the edge that is hardened, a transition zone of mixed structures, and a pearlitic spine. Your spine will have no strength and will take a permanent bend at much lower pressures than it should, basically transferring most of the actual stress to the hardened area at the edge. If for some reason you really feel the need for a soft spine do a torch draw, but really unless you plan for the knife to be batonned through firewood or car doors there is no need. If you want a hamon do the clay thing. Once again you have inferior mixed structure, but if done right if can be really beautiful. You can get a hamon with some 1084 alloys, but if you are looking to do a spectacular hamon you really want to be playing with W2 or 1095

-Page
 
To be clear what you get with a full hardened blade with a torch drawn spine is tempered martensite throughout the whole blade just a softer ( meaning lower yield point) spine. Martensite is the strong hard stuff you want a blade to be made out of, pearlite is not.

-Page
 
In order for high carbon steel to be springy it needs to be hardened and tempered back to 'spring' temper.

The thinner the material, the more flexible it will be.
 
sunshadow said:
Edge quenching makes for an inferior blade no matter how you look at it. Flexibility until you hit either yield or failure points is entirely controlled by geometry and cross section. Stress/strain deflection curves on identical cross section bars of steel, one dead soft annealed and one full hard are identical until the annealed bar hits its yield point and takes a permanent bend.
Click to expand...

What happens when a fully hardened blade hits its yield point?
 
GHEzell said:
What happens when a fully hardened blade hits its yield point?
Click to expand...
It breaks. Full (as quenched) hardness is not what you want, either. I agree with Page... tempered martensite is the way to go, unless you have a specific need for a blade that bends. I would rather have one that resists deformation. Admittedly, I am one of those guys that abuses knives. I need lateral strength and edge retention. Use geometry that is appropriate to the intended application of your knives and rock out, hard!
 
I never knew that about edge quenching (which is why I love this forum :) ) I have a question about the soft back draw to a fully hardened blade tho. Will is still be tempered martensite if you take the spine all the way to a dull blue, or even further.? I would've thought that it would just trasmform the tempered martensite back into pearlite of what have you. That would just be my guess, not sayin I read that somewhere or anything lol. Thanks :)

-Paul
_______________
(some of my knives etc. www.youtube.com/Lsubslimed)
 
As long as you stay below solutioning temps you should be fine. Blue oxide and blue-black oxide you should not have hit AF (critical) and your carbon should still be locked in the crystal structure with the iron. Once you hit AF (decoalescence) you are back to where you started.

Page
 
The short and simple answers are:
Fully harden the blade. In a knife blades, hardened martensite is stronger and better in virtually every parameter than pearlite.
Temper to the desired hardness. The harder it is the less bend until it breaks.
Thinness is what makes flex. 1/4" thick blades don't flex....1/16" blades flex a lot. Tapered blades have controlled flex.
 
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