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

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  #1  
Old 04-24-2023, 02:08 PM
Bill R Bill R is offline
 
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1095 not Annealing

I am a new knife maker. I got ahead of myself and heat treated my blades before I drilled holes for the scales. I d## a great job heat treating but now I can't anneal the blades to be able to drill them. I have tried several normalizing sessions. I have taken the blades to critical temp an allowed to cool very slowly. It doesn't seem to matter what I do, it almost seems like these blades are only getting harder. I am using a forge so my temps are estimations at best and am mostly going by sight and color of metal. I took a few of the blades and let them soak at critical temp for about 15-20 minutes before letting them slowly cool. The blades seems even harder. The file still skates across it like it d## after the quench for heat treating. Any ##eas?
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  #2  
Old 04-25-2023, 06:52 AM
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Crex Crex is offline
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How are you judging critical temp? Put a sprinkle of rock salt on the steel - when it melts you are in the right ballpark. Magnets only tell you that you're close to CT.
How are you handling the blades after taking them out of the forge? If you have cool air flow (fan or breeze), lay the blade on a cool to cold surface or clamp in a cold vise it's going to harden some as well.
I've used a lot 1095 and never had a problem softening for drill work. Also might make sure your drill bit is sharp.
Are you sure it is 1095? Possible source mix up?


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  #3  
Old 04-25-2023, 06:19 PM
Doug Lester Doug Lester is offline
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You could also try Tempilstiks to help judge your temperature. They come at various temperature ratings and, like the rock salt, melt when in contact with metal of a given temperature. Another thing that you can do to just draw the temper in the tang of the knife is to insert the blade in a can of wet sand and heating the tang with a torch. The wet sand servers as a heat sink that will protect the blade from having it's temper drawn.

Another thing that you could try is a carb##e tipped drill bit.

Doug


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Old 04-26-2023, 05:49 AM
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Something doesn't sound right, if using 1095. It ought to soften with normalizing temps. However, most high eutecto## steels don't respond well to repeated quenches - should soften ok but the next hardening quench becomes iffy grain structure wise.
Also, if properly drawing the temper after the quench, the file should bite not skate for most practical blade applications.

Lot of unknowns not in the OP.

I usually soften the tang as you suggested Doug, but use heavy 1/4" angle jaw inserts in my big vise as heat sinks instead of sand. Less mess for me. Still works very well.


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  #5  
Old 05-01-2023, 07:30 AM
Kevin R. Cashen Kevin R. Cashen is offline
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Quote:
Originally Posted by Bill R View Post
I am a new knife maker. I got ahead of myself and heat treated my blades before I drilled holes for the scales. I d## a great job heat treating but now I can't anneal the blades to be able to drill them. I have tried several normalizing sessions. I have taken the blades to critical temp an allowed to cool very slowly. It doesn't seem to matter what I do, it almost seems like these blades are only getting harder. I am using a forge so my temps are estimations at best and am mostly going by sight and color of metal. I took a few of the blades and let them soak at critical temp for about 15-20 minutes before letting them slowly cool. The blades seems even harder. The file still skates across it like it d## after the quench for heat treating. Any ##eas?

1095 is a hypereutecto## steel, which means that any carbon in excess of roughly around .8% will create leftover iron carb##e (pro-eutecto## cementite). How you cool above “critical” will determine the form that this carb##e will take. It is the “slow cool” that is the problem here or, more specifically, the slow cool from full solution. It is for these reasons that 1095 is normally a bit more of a challenge as a first steel choice.

When slow cooled from full solution, i.e. above “critical”, the extra .1% carbon will come out of solution on carb##e sheets and form networks in the grain boundaries. This will make drilling all but impossible and will also embrittle the steel, as well as lead to unstable edge retention due to microchipping. Thus, it is very important that you do not slow cool from full solution for annealing, air cooling in normalizing is all right but any slower is bad.

Normalize to dissolve the carb##e sheets and then subcritical anneal. Heat to around 1300°F, but no hotter, and simply air cool. This will ball up the carb##e, rather than creating lamellar sheeting, making it more manageable and easier to cut.
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Old 05-01-2023, 07:33 AM
Kevin R. Cashen Kevin R. Cashen is offline
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Odd this forum doesn't seem to like the letters "I" or "D" when put together in a sentence. Hmmm.
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  #7  
Old 05-01-2023, 02:30 PM
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Excellent info!

That letter sequence is the censored because of the spammers that post for fake I-D documents.


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Old 05-01-2023, 04:31 PM
Doug Lester Doug Lester is offline
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Kevin, I feel that I should know this, but could one simply not heat the tang up to critical along with the blade and then quenching the knife or would that be inviting a steel failure? Or would that be a way to allow the steel in the tang to remain pearlite?

Doug


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  #9  
Old 05-02-2023, 09:34 AM
Kevin R. Cashen Kevin R. Cashen is offline
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Quote:
Originally Posted by Doug Lester View Post
Kevin, I feel that I should know this, but could one simply not heat the tang up to critical along with the blade and then quenching the knife or would that be inviting a steel failure? Or would that be a way to allow the steel in the tang to remain pearlite?

Doug
If one is going for maximum strength in the tang they may be hesitant to do this, but I think it is a moot point unless you are using damascus, when the aesthetics come into play on a differential HT. But there is the question as to how one keeps the heat off the tang. I leave 1/3 of most of my tangs unhardened but I have the option of simply leaving the unhardened area above the surface of the high temp salts, those working in a forge or kiln may have a more difficult time keeping the heat entirely off the tang. But there is no concern for steel failure in simply leaving the tang unhardened.
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