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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #16  
Old 10-24-2017, 01:16 PM
Rasmus Kristens Rasmus Kristens is offline
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Originally Posted by blitt214 View Post
I used canola oil I kept quenching but is wasn't getting hot, so I heated it up more and it hardened but I guess I got it too hot
I'm not completely sure i understand what you mean. Can you try to describe your process?
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  #17  
Old 10-24-2017, 04:49 PM
blitt214 blitt214 is offline
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Sorry I meant it wasn't getting hard so I kept reheating and quenching till I got to a temp that hardened the steel
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  #18  
Old 10-25-2017, 05:17 AM
Rasmus Kristens Rasmus Kristens is offline
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I think that if you have reheated and quneched the piece multible times, maybe you need to normalize or try another test piece.

It should be possible to get it to harden.

Try again :-) Preheat the oil to 130 F and be quick about the transfer from oven to quenching tank.
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  #19  
Old 10-28-2017, 06:45 PM
blitt214 blitt214 is offline
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Ok I think I did it, the grain looked just right and the file skates right off. Should the spine wind up as hard as the edge? I broke the blade to see what the grain was like and the edge snapped but some of the spine just bent is this ok?
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  #20  
Old 10-29-2017, 02:42 AM
Doug Lester Doug Lester is offline
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Depending upon the exact composition of the 1080 that you are using the soft spine with a hard edge could be due to the spine being too thick to form martensite while the edge was thin enough to harden. This can happen with the shallow hardening steels.

Doug


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  #21  
Old 10-29-2017, 07:40 AM
blitt214 blitt214 is offline
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Once I temper the blade would this be an issue
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  #22  
Old 10-29-2017, 01:51 PM
epicfail48 epicfail48 is offline
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Originally Posted by blitt214 View Post
Ok I think I did it, the grain looked just right and the file skates right off. Should the spine wind up as hard as the edge? I broke the blade to see what the grain was like and the edge snapped but some of the spine just bent is this ok?
Eh, it's not bad but it's not great either. Personally I like to see full hardness unless I'm intentionally trying for a soft spine, i.e clay coating the blade or similar.

Could be one of three things, the temperature of the steel is right at the edge of where it needs to be, you're taking too long to go from heat to quench and the steel is cooling, or your quenchant is just a hair too slow. The third one is the least likely of the three, warmed canola oil should be fast enough from most hypo-eutecoid steels (simple carbon, less than .8 carbon content). I'd bring the steel up just a touch higher in temperature, but just a touch, to give you a little more leeway in getting it to the quench, and make sure you can get into the quench as fast as safely possible
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  #23  
Old 10-29-2017, 03:38 PM
Doug Lester Doug Lester is offline
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Hardenability is a function of the alloying elements, primarily chromium, not carbon content as much. If the 1080 that is being used is more like the traditional alloy then no matter what you heat the spine to it will have too much mass to allow the formation of martensite. There is the possibility, however, that only the the edge of the blade was austenized in the forge before the quench and a little extra time was needed to equilize the temperature throughout the blade.

As far as the quenchant goes, maybe going to a fast commercial oil or gritting your teeth and using brine you might keep the steel in the spine from crossing the pearlite start line on the cooling curve but, depending on the exact alloy of the steel, you might not be able to prevent it.

I too prefer to have a fully hardened blade but be aware that there are many who think that a blade should have a soft spine and will go out of their way to create one with a hamom. If you are making a blade the the AKS performance test you pretty much have to make one with a soft spine.

Doug


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  #24  
Old 10-29-2017, 04:34 PM
blitt214 blitt214 is offline
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I bought on of those crayons that melts at 1500 so I'm pretty sure I'm right at 1500 so faster to the oil then!
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  #25  
Old 10-29-2017, 05:31 PM
epicfail48 epicfail48 is offline
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Originally Posted by blitt214 View Post
I bought on of those crayons that melts at 1500 so I'm pretty sure I'm right at 1500 so faster to the oil then!
I should clarify that when I say a touch I really do mean a touch, my experiments have shown that an extra 10f was all it took for me. The tiny bit of extra heat just gives you a bit of a buffer while you're getting to the quench. You still want to get there as fast as possible, but there's a world of difference between "fast" and "rush". You want the first, not the second
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  #26  
Old 10-29-2017, 05:52 PM
blitt214 blitt214 is offline
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I find it tough in the forge to judge the difference of 10 degrees all though doing it at night I was really able to see the difference as if was heating up it was pretty cool
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  #27  
Old 10-30-2017, 12:17 PM
Doug Lester Doug Lester is offline
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Learning to look for the decalesense is also a good way to see if the steel has austensized. It looks like a shadow that passes across the steel. There are some videos on some of these sites that show it. It is caused by the energy of the heat being used to cause phase conversion rather than light so you know when you see it you have at least achieved conversion to austenite.

As far as the faster oil goes, it may or may not solve your problem. As I said it depends on your exact alloy. If what you have is the 1080+ then it may well harden the blade all the way to the spine. If it's more like the classical 1080 with little more than iron, carbon, and manganese then the steel may not be hardenable to the thickness of the spine of the blade and will only harden part of the way up. This is seen more often in alloys like 1075 or 1095. It also depends on grain size with larger grain promoting hardenability, not something that you want.

Doug


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Last edited by Doug Lester; 10-30-2017 at 12:33 PM.
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1084, 1095, 52100, art, bee, blade, carbon, cold, edge, file, forge, forging, harden, heat, hot, knife, make, motor, problem, quenched, question, simple, steel, temper, water


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