Author Topic: 1084 aldo steel  (Read 2330 times)

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Offline treez

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1084 aldo steel
« on: June 06, 2016, 11:31:56 AM »
So I picked up some 1084 steel (5/32) from NJ Steel Baron and will be making a few knives. I have made a few using O1, but my heat treat method seems to lend itself to 1084 right now.

From what I understand, to get the most out of O1 it needs to soak at a certain temp for like 10 minutes or something. I can't get that precise with my homemade firebrick forge.



I have a few questions.

1.) I have read a few places that people will heat to non-magnetic. Let cool to room temp and then heat to non-magnetic again and then quench. I guess this method helps relieve any stress brought on by the knife making process. Do you need to do this with 1084?

2) Any recommendations for tempering? With O1 I think I heated my blades at 350 for 2 hours if I remember right. Not sure what the RCH is, but seems like around 58 or 59.

Made this about 18 months ago and use it pretty regularly. Edge seems to hold up well.


3) Any tips from you guys in working with 1084. I am fairly in experienced. At this.

Offline Quenchcrack

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Re: 1084 aldo steel
« Reply #1 on: June 06, 2016, 12:07:54 PM »
PM sent.
I guess he'd rather be in Colorado.
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Offline treez

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Re: 1084 aldo steel
« Reply #2 on: June 06, 2016, 12:16:34 PM »
Got it. Thanks!

Offline wolfy

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Re: 1084 aldo steel
« Reply #3 on: June 06, 2016, 04:13:42 PM »
So, what is it......a secret or something? >:(
The only chance you got at a education is listenin' to me talk!
Augustus McCrea.....Texas Ranger      Lonesome Dove, TX

Offline wsdstan

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Re: 1084 aldo steel
« Reply #4 on: June 06, 2016, 05:29:40 PM »
Yes, enquiring minds want to know, and nosey ones too.   :-\
A man who carries a cat by the tail learns  something he can learn in no other way. 
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Offline Quenchcrack

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Re: 1084 aldo steel
« Reply #5 on: June 06, 2016, 05:49:00 PM »
It's just science.  Didn't want to offend anyone.  If Treez thinks it is worth sharing, he can post it.
I guess he'd rather be in Colorado.
-John Denver

Offline treez

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Re: 1084 aldo steel
« Reply #6 on: June 06, 2016, 07:18:26 PM »
Top secret stuff. Sorry.

When I figure out how to copy and paste the PM with the tap talk app I will share. But my wife is giving me a look right now. So will do later. It is our anniversary. I guess I should be paying attention to her or something. 

Offline treez

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Re: 1084 aldo steel
« Reply #7 on: June 06, 2016, 07:55:31 PM »
Alright.  So essentially what he told me was that when the two moons are at their peak on the second Tuesday of the 13th month, to quench the blades in the blood of unicorns. But that is only after heating them in a fire of orc bones. So pretty basic stuff.

Or if you can't get orc bones, try the following. 

Treez,  When steel is heated above the critical temperature, it transforms from room-temperature structures like pearlite, ferrite or martensite, and it becomes austenite.  Austenite is non-magnetic so when the steel is hot enough to be non-magnetic, you have formed austenite.  You must first create austenite to get any other structure upon cooling/quenching.  The recommended austenitizing temperature for 1084 is 1450F to 1500F which is a dull red.  You have only a few seconds to get the steel out of the furnace and down to room temperature so don't waste any time in the process.  Now if you want to improve the toughness, you can normalize it by heating it to about 1600 F, a bright red, and let is slow cool in still air.  This creates new and smaller grains in the steel.  This is important if the steel came to you annealed or if you forged it.  Small grains are much tougher than large grains.  Some bladesmiths normalize up to 3 times before austenitizing and quenching but they normalize at succeedingly lower temperatures to get finer and finer grains.  You probably don't have to do that 3 times.  For tempering, I would suggest a two hour temper at 350F, air cool, and a second two hour temper at 400F to 500F.  The double temper will get rid of retained austenite that commonly remains in high carbon steels and get you maybe another point of hardness.  Best of luck,

Offline wolfy

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Re: 1084 aldo steel
« Reply #8 on: June 06, 2016, 08:04:07 PM »
I appreciate you going public with that information, treez......I may never do it, but I do find it very interesting!  Never hurts to learn something once in a while! :P
The only chance you got at a education is listenin' to me talk!
Augustus McCrea.....Texas Ranger      Lonesome Dove, TX

Offline treez

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Re: 1084 aldo steel
« Reply #9 on: June 06, 2016, 08:12:13 PM »
 No problem. When I make my next knife I will do up a post on how it goes.

Offline Unknown

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Re: 1084 aldo steel
« Reply #10 on: June 06, 2016, 08:53:18 PM »
Does double tempering get rid of retained austenite or would it be more accurate to say, helps to reduce retained austenite?

I heard a story about an old time traditional smith who's practice became not to sell a knife until it was at least 20 years old. Or, something like that.

Offline 1066vik

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Re: 1084 aldo steel
« Reply #11 on: June 06, 2016, 10:17:23 PM »
I do a double temper at 400 with 1084.
my understanding is that the first temper cycle does stress relief on the martensite and helps convert the remaining austenite.
the second temper cycle stress relieves the "new" martensite that was converted during the first bake.

Offline Quenchcrack

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Re: 1084 aldo steel
« Reply #12 on: June 07, 2016, 03:38:22 AM »
The first temper will transform most of the retained austenite to martensite and the second temper will reduce the hardness of that new martensite. There will probably always be a small percentage of  austenite left in the microstructure.  Double, or even triple tempering is most critical in applications like bearings where high loads are encountered.  Retained austenite will transform to martensite under load or impact.  This can lead to cracking and reduced service life. The main benefit in a blade is a bit of extra hardness.
I guess he'd rather be in Colorado.
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Offline RickM

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Re: 1084 aldo steel
« Reply #13 on: September 08, 2016, 06:53:45 PM »
I know I'm late to the party...
Quenchcrack has made all the necessary points. I would like to suggest that you ALWAYS thermal cycle your steel whether you forge or stock remove... and to start those cycles a bit higher, like 1650F-1700F to make sure everything gets into solution. Especially with Aldo's highly spheroidized steels. I would also like to explain why 1084 is such a good beginner steel. First off, that title does not give 1084 its due credit. 1084 is better described as the "perfect eutectoid".

There are 3 types of carbon steel. Hypoeutectoid, Eutectoid and Hypereutectoid. At its most basic, Eutectoid contains .80 - .83% carbon. Hypoeutectoid has less, Hypereutectoid has more. Even more simply put... Eutectoid steel WANTS to go into solution... Hypo and Hyper need a little coaxing for different reasons but I won't get into that. Eutectoid steels reach their critical temperature quicker without the need for soaking or elevated heat. Essentially, get it red and quench. That is why 1084 is often suggested to beginners.

Back to thermal cycling... I like to set things up BEFORE the final heat treat so I don't have to mess with extended soaks or high temperatures. That means getting the grain refined and the carbides sufficiently distributed.

Here is my 1084 regime(after forging)...

- Heat to 1650F-1700F, cool to magnetic
- Heat to 1550F, cool to magnetic
- Heat to 1475F, Quench in oil(to lock it all in)
- Heat to 1300F (dull red but still magnetic), two or three times(this is a sub-critical anneal that makes it easier to cold work... filing, grinding, drilling, etc...)

When I am ready to do my final HT, I will bring the blade up to 1300F(very dull red) let it cool and check for straightness... this is a stress relieve cycle. Then I heat slowly to 1500F and quench in warm oil. I have found that I need to temper between 425F and 450F to get my desired hardness   
« Last Edit: September 10, 2016, 05:01:10 PM by RickM »
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Offline 1066vik

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Re: 1084 aldo steel
« Reply #14 on: September 09, 2016, 09:52:00 PM »
Rick!
good to see you here!

Offline Quenchcrack

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Re: 1084 aldo steel
« Reply #15 on: October 08, 2016, 06:28:51 AM »
Rick, thanks for the additional info in 1084.  You point out that 1084 is a eutectoid steel meaning the carbon content coincided with the eutectoid point on the iron-carbon phase diagram.  This point represents a unique point where the the steel transforms to austenite at a single temperature.  All other carbon compositions transform over a range of temperatures from the lower to upper critical temperature.  The phase diagram does not indicate the physical condition of the iron carbides, however.  If they are large from fully annealing, they require some time at temperature to dissolve.  Normalizing will help refine the carbide size and distribution.  Fully conditioned austenite is critical to developing full hardness and that means a bit of soak time. You can certainly skip the soak and get most of the hardness however.
I guess he'd rather be in Colorado.
-John Denver