How to normalize 1095?

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Chiro75

Chiro75

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Sorry to ask a basic question, but I searched and normalizing has been described as:
1) Heat to critical and let air cool
2) Heat to slightly above critical and air cool
3) Heat to slightly below critical and air cool

So, I'm a little confused. Nick Wheeler suggested 5-6 normalizing cycles of 1095 before HT'ing (I do stock removal and clay coated differential heat treats quenched in oil), but now I don't know what normalizing really means because Brian Goode said he thought it meant not heating to critical, then air cooling, but according to my reading in the search function it means anything and everything depending on who you ask. Sometimes the info even varies within a single post, so help me out! :D
 
The "ASTM Guidelines For the Heat treatment of Steel" calls out a normalizing temperature of 1550 °F for 1095 steel. Soak at temp long enough for homogenization (i.e long enough for complete austenization) and then rapid air cool to black heat.
 
Bring up to non-critical very slowly. By slow, I mean bring the tip up to heat, pull it out to cool dark, do it again and a little more of the tip will heat up at once. Keep doing this until the blade comes up to heat all at once (this basically keeps you from overheating the tip and allows some more heatin' time which doesn't hurt the blade at all.) Once it is all up to heat, swing it around or just hold it tip down until the "red" is out of the blade. Bring it up to heat like that 3 or 4 times and you're set.
 
Well, I don't claim to be an expert, but I have spent a heck of a lot of time getting this stuff to work for me.

I use a salt bath, which I know you don't have, but I'll give you some numbers anyway.

First off, what bladesmiths refer to as normalizing is not what is accepted as normalizing in industry.

I use the term rather loosely, as I use it to describe the thermal cycles I put blades though.

While I highly recommend following industry standards for the most part, so you don't have to reinvent the wheel... there are acceptions.

Doing the temps in the book will relieve stress and make a fairly fine grain.

However, if you want to create the optimal set-up for clay-hardening, I think the numbers need to be tweaked.

I first run the blade though the salt at 1600, then 1550, then 1500, 1450, and 1400 three times. This will set up the blade with an extremely fine grain, and actually reduce the hardenability. That's a good thing if you want a hamon.

A simple run of 1400X3 or 1450X3 will do... but the above works even better for me.

This knife was done that way, and chopped through 5 dry Alder branches (4.5" diam) and still shaved cleanly and would slice cigarette paper. It's W2, which I prefer to 1095, but they're pretty similar in make-up.

fikescamp.jpg


-Nick-
 
I'm no expert, but I once stayed at a Holiday Inn Express.

According to this spec sheet:
http://www.suppliersonline.com/propertypages/1095.asp

The hardening temp and annealing temp are the same for 1095 .... 1650 F.

'Normalizing' appears to be just a fancy term for annealing. I see nothing in the specs that refer to repeated annealing (or 'normalizing') prior to hardening 1095. (Although it does talk about pre and post heating during welding.)

It does, however, say:
"For cutting tools it is common practice to harden only the cutting edge by induction heating and quenching so as to retain the toughness of the steel behind the hardened edge."

'Induction heating' is defined as:
"The basic components of an induction heating system are an AC power supply, induction coil, and workpiece (material to be heated or treated). The power supply sends alternating current through the coil, generating a magnetic field. When the workpiece is placed in the coil, the magnetic field induces eddy currents (electric current circulating wholly within a mass of metal) in the workpiece, generating precise amounts of clean, localized heat without any physical contact between the coil and the workpiece."
http://www.ameritherm.com/aboutinduction.html

Interestingly, the spec sheet on 1095 also says to: "Temper at 700 to 1300 F. This steel is capable of a Rockwell C 55 hardness at the lower tempering temperature."
 
I wouldn't trust the numbers or information on that website. It looks to be way off.

Normalizing is done at above critical temperature with a fast air cooling. Annealing is done at/around critical temp and a slow controlled cool down. They are not the same nor are the names interchangable. The intent of normalizing is to refine the grain structure and the intent of annealing is to make the metal easier to machine.

The critical temperature of 1095 is about 1350°. Most people austenize at 1500° plus because 1095 is a very shallow hardening steel. You only have about 0.5 of a second to get the steel past the nose of the TTT curve (about 1000°). By austenizing at a higher than critical temperature, you give yourself a bit more time to get the blade into the quench and avoid making pearlite and other stuff.

Tempering temps are from 300 and up depending on the desired final hardness. As quenched hardness is supposedly a max of 65 HRC but I have never been able to get more than about 62 HRC.
 
I wouldn't trust the numbers or information on that website. It looks to be way off.
Click to expand...
Based on what?

Here's another source on 1095:
"SAE 1095 Carbon Tool Steel:
Normalizing: Heat to 1575°F (855°C) cool in air. (note no holding time).

Annealing: "As is generaly true for all high carbon steels, the bar stock is supplied by mills in spheroidized condition. . . . . When parts are machined from bars in this condition no normalizing or annealing is required."

Forgings should be normalized.

Anneal by heating to 1475°F (800°C). Soak thoroughly. Furnace cool to 1200°F (650°C) at a rate not exceeding 50°F (28°C) per hour. From 1200°F (650°C) to ambient temperature, cooling rate is not critical.

Hardening: Heat to 1475°F (800°C), Quench in water or brine. OIL QUENCH sections under 3/16" (1.59mm).

Tempering: As quenched hardness as high as 66 HRC. Can be adjusted downward by tempering."
http://www.anvilfire.com/FAQs/heat_faq_index.htm

The point is, where's the data that supports people's positions? If it's 'fact' then there should be some manufacturers data that states as much ...as opposed to the wealth of black magic and alchemy that floats around the knife world.

And ...what it appears is that for 1095 steel, they recommend that it be tempered to a maximum of 55 RC so that it is not so brittle, a combination of toughness and strength ...hence the high tempering temps of 700 F+.

Has anyone tried induction heating with a current and magnetic field? That process may be what folks are stumbling onto with all the 'normalizing' cycles and clay hardening tactics.
 
At 700° the HRC will be around 47. If you want to temper a small blade at 700° or temper it down to 55 HRC be my guest, but it will not perform the way you want it to. Unless you wanted to make a pry bar.

I am pulling my information from the "ASTM Heat Treaters Guide" not my Alchemy book. It is called a "guide" for a reason. I would tend to have more faith in the information contained in the ASTM publication than on some website.

How does induction heat treating relate to clay hardening and normalizing?

Here is a picture of a piece of 1095 that was normalized once at non magnetic, quenced in warm oil, and tempered at 375° resulting in an HRC of 58 to 59. This was a blade for one of my prototype balisongs and I broke the "tang" of the knife when trying to press fit in the tang pin. So I decided to break it further down the blade to get a pic of the coarse grain structure.

micro.jpg
 
How does induction heat treating relate to clay hardening and normalizing
Click to expand...
Because it's a method of 'differential' hardening/tempering. And if 'normalizing' cycles are part of your hardening process, then it's the same ball of wax.

What it actually appears to be about is that steels vary by manufacturer ...the 'same' steel (in this instance 1095) varies in its properties from one manufacturer to another ...hence the differing numbers. There is no one set of numbers (or 'guide') that applies across the board.
It also appears that the blade shape affects the process too, and using the same exact process on two different blade shapes will result in two different finished products.
One would have to experiment with the exact blade shape they are going to be using to come up with consistent results. Otherwise it's a crap shoot.

As for the photo ..that's all well and good. But the results would be different with either a different steel source and/or a different blade shape. Break some different ones and take a peek.
(Not to mention the fact that if it broke pressing in a pin at "58/59" hardness ...then that would lead one to believe that it was indeed too brittle.)
 
jiminy said:
Because it's a method of 'differential' hardening/tempering. And if 'normalizing' cycles are part of your hardening process, then it's the same ball of wax.
Click to expand...

Induction heating is not a method that most knife makers could readily use. Induction equipment is very expensive. Along the lines of $10,000 for a 2.5 kW unit. Plus there is the whole deal on what frequency your supply runs at as to what thickness of metal you can heat. "Low" frequency for deep penetration and "high" frequency for surface heating. Clay hardening and normalizing are techniques that are independant from the equipment used to generate the heat.

Blade thickness would make a difference in the heat treat results, but I doubt blade shape would.

10-4 on each batch of steel being different. I think Nick mentioned a bit ago (in a different post) that he tests a blade to destruction (or close to it) on every new batch of steel he gets.
 
Jiminy those numbers are way OFF for knife blades, they may work for some other type of tool but not knives.

Guys listen to Nick Wheeler, he's right.

For 1095 I normalize 3 time at 1400-1500 F, heat to 1400-1500, quench in warm oil and temper 350- 400 1 hour twice depending on the knife. At the lower quench temps I let soak a little longer than at the higher temp.

Don Hanson lll sunfishforge.com
 
jiminy said:
(Not to mention the fact that if it broke pressing in a pin at "58/59" hardness ...then that would lead one to believe that it was indeed too brittle.)
Click to expand...

Not absolutly true. The next blade was sucessful at the same hardness. The difference being I opened up the hole size by 0.0005. The steel was not too brittle, the hole was too small. Or yes, the steel (on the one that broke) was too brittle for that size pin going through that hole.

I think you are going to have one heck of a time convincing any body that 58 to 59 HRC on a 1095 blade is too brittle. Taking into consideration, of coarse, smallish blades not swords or camp knives.
 
It's not about who's 'right' or 'wrong' ...it's about where's the source for your information, particularly pertaining to the numerous normalizing cycles?

As for the temps, for anyone knows that could be the proper specs for attaining 55 Rc with the 1095 steel they supply.
Did you happen to notice the spreads in the percentages of the elements that make up 1095? (and other steels for that matter) Quite a bit of wiggle room in there. I imagine that the 1095 made from all the low percentages of the scale would be quite a different beast from a 1095 made from all the higher percentages.

Here's something else to mull over. I've noticed that some high carbon steels anneal (soften) during forging ...simply by going repeatedly thru the heat/cool cycles of forging. Some don't.
 
jiminy said:
It's not about who's 'right' or 'wrong' ...
Click to expand...

I agree, but you were quoting some info from a website that is erroneous and I don't think that wrong info should be spread.

Every maker is going to do things a bit different and there is not one single correct answer.
 
I first got the idea for the multiple thermal cycles from reading archived posts from SwordForums by Howard Clark, Don Fogg, Randal Graham, and Darryl Meir. Add some more names like Jimmy Fikes, and you are looking at the men that know heat-treating blades inside and out.

I am not into hocus pocus, chicken blood, or witches brew. I started with numbers in books, and the word of men like I mentioned above.

I have tested to destruction something like 130 blades.

That is why I think what I do works.

I have tried just a couple thermal cycles at the higher temps, and the blades did not hold an edge very well, deformed rather easily, and broke easily. When I looked at the crystalline structure, it was coarse like raw sugar.

When I break blades done the way I described above, they look like they don't even have grain. It's a very very fine grey... These blades hold an edge well, are much tougher, and much more difficult to break.

I'm not saying I'm right-

What I'm saying is if you make a blade the way I described, it will work well.

As Sean mentioned, coil heat treating is very cool, but not very realistic for most knifemakers.

Chiro, to get back to answering your question.

Without the equipment I have, I would take the blade up to the point that it loses the all shadows. This can really only be seen in a completely dark shop... so doing it at night really helps.

I would recommend you do that at least 3 times, letting it cool to black between each heat. I think you would be impressed with your results if you took a few more minutes and did it 2 or 3 additional heats.

Of course you don't HAVE to, it's just a suggestion ;)

:D -Nick- :D
 
See, that is what this place is about. Sharing the info. So now I get to try Nick's normalizing method and compare it to mine. It might be better, and it can't hurt to try it.

Chiro- Shoot me an email or give me a call and I can give you some more input on how I built my salt pot.
 
Fair enough ...that's all I was asking.

Does the heat/cool cycles of forging have a similar propensity to refine the grain structure?

If what you're saying is the case, then a forged blade would be a better 'quality' blade, and have a more refined steel structure, then a stock removal blade ...all things being equal and both blades 'normalized' only one or two times prior to hardening.

And if the blades were each six times normalized prior to hardening, then wouldn't the forged blade be even better still, after having gone thru numerous heat/cool cycles during forging ...having an even more refined structure then the stock removal blade?
 
jiminy-

I'm a pretty firm believer that's the reason why the "forged blades are better" thing started. Smiths were essentially taking their blades though many thermal cycles, while many stock removal makers were going directly to austentizing heat and quenching.

You can still make a good blade that way. But I feel you can make it even better with thermal cycling.

I have done extensive testing with O1 this way as well. When you buy O1, it is supplied with a speroidal anneal. This means it's butter soft and easy to machine... but the grain is not super fine. When I take O1 and put it through thermal cycles prior to hardening, I can achieve a super fine grain and get better performance from the blade.

I want to add that there are many other smiths that are now on my "A" list like Kevin Cashen... it's just the above mentioned guys were the ones I found info from when I started... and still respect just as much today.

-Nick-

my great uncle likes to say, "It's okay if you disagree with me. You just have to remember that you're wrong."

LOL, j/k :D
 
jiminy said:
Hardening: Heat to 1475°F (800°C), Quench in water or brine. OIL QUENCH sections under 3/16" (1.59mm).
Click to expand...

Please note that this Faq has errors that are evident not only through experience, but in measure and conversion as well.

When was the last time you saw something that was 3/16th thick that was also 1.59 MM?

That Faq is made up of posts compiled from another forum, and is sure to have some error.

Not to step on toes, but I'd stick to knifemakers for advice on knife blades, and ask the blacksmiths about making leaves and fireplace tools

Tony
 
Yes, but one would think the steel supplier would have accurate information for the product(s) they are distributing as well.
 
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