? about tempering 1095

[shortstroke 91]

How do I know if I've tempered correctly? I brought the steel up past nonmagnetic and held for about 5 minutes then went right into vegetable oil that was 130 degrees. I then ran 2 cycles of 400 degree soaks for an hour each. My new Nicholson file will take off steel but not easily. When you guys say "scate off the steel" do you mean that it won't take off anything? Just a little concerned before I start putting the handle on.  
I'm also a little confused about "burning the steel", would it hurt to leave the blank in the forge for another 10 minutes or would I even gain anything? Any tips on knowing the actual steel temp for us guys without a thermometer that goes up to 1500 degrees?
Thanks,

[Wampus]

The file should skate when you first take it out of the oil and it's dead hard.  Once you run the 400 degree temper cycles, you've reduced the hardness to a less brittle working hardness and a file will bite it a little.  Keeping it above non-magnetic longer will burn out the carbon near the surface, but usually you will remove enough of the surface layer during finishing to get down to high carbon steel again.  
The worst part about keeping it above magnetic for a long time is it will cause grain growth. It shouldn't be a huge problem if it's just barely above magnetic, but when you get a little too hot for a little too long, you get large grain structure and the steel isn't as strong or wear resistant as small grain structure.  For thin sections like knives, there's no need to soak for a long time before quenching.  Those soak times in heat treating manuals are mostly for big machine parts that may be several inches thick.  Better to get it just above magnetic and cool it off a couple of times to reduce the grain size before the final heat and quench.  There are some other threads on thermal cycling and grain reduction you can search for more info.

[kbaknife]

Above is good avice, but I would also pay particular attention to the oil you are using.
1095 is a shallow hardening steel, and as such, needs to drop from around 1500 to about 950 - depending on carbon content - in 3-5 seconds, or the steel will/may return to pearlite, or at minimum, only give you a partial martensitic transformation.
That's the risk you run with using a shallow hardening steel and a non-standard quench media.
Thicker sections of 1095 - 3/16+ - are designed to be quenched in water/brine - it is that fast.
When I quench my 1095, right out of the tank it is like GLASS.
File doesn't even touch it.
Fully hardened 1095 can attain hardness of 66 RC.
Then you adjust accordingly with temper.
Two one hour tempers are not nearly enough for fully hardened 1095. More like 2 at 2 hours minimum.

[kbaknife]

I will also give our new friend here - Matt Lamey - to you as a one to whom you should listen.
Matt spends a LOT of time with 1095.
Let's start bugging him for some info as well.

[shortstroke 91]

Thanks guys, I'm using 3/16" so I'll put it back in the forge tonight and try the water\\brine instead and do 2 soaks for 2 hours. Thanks for the help, I'll be on tomorrow and we'll see how it went.
On the brine is there a specific ammount of salt/water ratio I need or anything else?

[kbaknife]

Let you know in advance that the success ratio on brine quenched KNIFE BLADES is about 50:50.
On these thin geometries, get accustomed to failures.
Rule of thumb is enough salt to raise the specific gravity enough to float a raw egg.
If you are up for experimenting, you can quench for a few seconds in the brine to really suck the heat out, yank it out quick and then quench into your oil to sort of eeeeeaaaaaase it on down.
How brave are ya'?

[Lamey]

why thanks for the kind words Karl.  Your right, ive spent ALOT of time with 1095, at first because its what I could afford, then later it was what I liked after trying umpteen different steels.  Im sure youve done the same thing!

Couple quick things,  in your initial post it seems you did everything right.  Im just wondering what if anything at all is the problem with the blade?    If you dont have a way to rockwell test, just use the good ole file method.   A brand new "high" quality single cut file should cut into the edge with light pressure.  A "dull" file should barely cut, if at all with moderate pressure, this is AFTER your tempering cycle.  I dont even check my blades before tempering, I like to get them into a tempering cycle ASAP, so as soon as I check/correct for straightness I get them in that 425 oven!   I run 2-3 tempering cycles, after the first I clean off the blade @120 grit, at this point I investigate the steel a bit more, check for hardnesss, check again for striaghtness, cupping etc...  do at least 1 more cycle, maybe 2 after that (totaling 2-3 cycles sometimes ramping up temps).

1095 will tell you ALOT by just looking at it,  take it to 220-400 grit and you may see evidence of a "temperline" even if you werent trying to get one.  As Karl says, its a shallow hardening steel, and fast.

I would recomend that you stick to warmed (125+/-) veg. oil over a brine solution.    I used veg. oil with about 25% olive oil for the first 8-9 years I made knives and had good success.   The key is warming the oil as stated and getting a thorough heat  on your blade.   I highly suggest getting a pyrometer so you know exactly what temp your at before quinch.   Yes, you can use your eyeball,  and you still will even with a pyro,  just the pyro "helps" your eyeball.  

Also if you have a controlled heat treat oven (meaning you KNOW the temp. and have a degree of control over it),  dont be afraid to experiment with soak times.    Especially if you start messing with thicker stock,  I use alot of round bar and 3/8" stock,  so my spines at times are 3/8+".    You will get completely different results when you soak at temp for 3-5 minutes then you will quinching at the apex of your desired heat with no soak.

Hope this helps some,  i wouldnt abandon that blade as it is right now,  im still not sure there is anything "wrong".

[kbaknife]

Thanks a bunch, Matt.
I, myself, will be using more of the 1095 I have, as well.
I'm liking the way my last one turned out.

[shortstroke 91]

Matt, thanks for the info. What do you mean "You will get completely different results when you soak at temp for 3-5 minutes then you will quinching at the apex of your desired heat with no soak". I went ahead and did the "old" file method and got almost no grab at all so I think I'm alright. I glued up the handle last night and hopefully will get her finished by the weekend.

[Steve Nuckels]

Great questions and great information provided!

Matt, I love your work!

Thanks!

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IN GOD WE TRUST

[Lamey]

shortstroke,   ive found that when you do a short cycle soak, lets say 3-5 minutes at your desired temp. (1475 for me),  you will get a deeper conversion than if you quinch when you hit 1475.   This is especially true with 1095, W2, the shallower hardening/faster steels.

thanks Steve,  i work hard at it, and at times really love it !

[Lin Rhea]

I just got some Parks 50 oil in and will be posting some results myself soon. Lin

[Lamey]

Lin, the parks 50 works great.   I believe its  a tad faster than the Houghton (same thing as "Tuff Quinch" from Texaco) that im using now.