AISI 1084 carbon steel

[Brian Madigan]

AISI 1084 composed of (in weight percentage) 0.80-0.93% Carbon ©, 0.60-0.90% Manganese (Mn), 0.04%(max) Phosphorus (P), 0.05%(max) Sulfur (S), and the base metal Iron (Fe).

 

 

ALDO's 1084 certs:

Chemistry/Certification

Certification: C- .876 Si- .274 Mn- .803 P- .0100 S- .0040 Cr- .153 Ni- .037 Mo-.007 V- .004 W- .003 Cu- .037 Sn- .0030 Al- .006 Annealed Structure: 95% spherodized carbides

 

0.60-0.90% Mn is important, as is the structure of 95% spherodized carbides.

 

Equipment: Evenheat w/rampmaster controller

Parks #50 Quench oil

Deep 18" black iron quench tank w/parts basket.

ATP-641 anti-scale coating

 

Normalize:

1700/still air (optional*)

1600/still air

1550/still air

 

Austentize:

1500 with 15 minute hold

Submerge fully, agitate

Cool to Mf (room temp, I usually scrub the blade clean in cold water at this point)

 

Temper:

420f/1 hour x 2. Sometimes 3.

Cool to room temp between tempering cycles.

 

Sometimes between tempering I like to do a final polish so I can hot blue it on the final heat.

 

I don't have a Rockwell tester, so I do edge deformation and chipping tests to verify the tempering results occasionally.

I use the same HT formula for 1084/15n20 Damascus, with the same result.

* With Damascus I do the extra normalizing step because I weld and forge much hotter and slower.

Edited May 24, 2013 by Brian Madigan

[Alan Longmire]

That's what I wanted to see, Thanks, Brian.

 

I use a lot of Aldo's 1084. Not having a kiln, I do it a bit differently.

 

For knives and other things that will fit, I use the old pipe-in-the-fire trick. About 18 inches of 2.5" black iron pipe, squashed to an oval shape about 1.5" x 3" and with one end welded shut goes in the forge. Once it comes up to heat I toss some charcoal in and push it to the very end. This creates a neutral to somewhat reducing atmosphere, preventing scale from forming. It also lets me watch the steel come up to heat. That is critical for my method, because I don't have a pyrometer. I judge the transformation temperature by watching the phase change in the steel.

 

Decalescence is the technical term, but when the crystalline structure shifts as the steel is fully austinitized, you can see what looks like shadows swirling inside the blade. As those shadows disappear starting at the edge and working towards the thicker sections they leave a distinct brighter color. That area of brighter color is fully austinitized and ready to harden, or to be pulled out of the pipe and left to cool in still air to normalize. After three normalization cycles to refine the grain I quench in veterinary-grade mineral oil warmed up to be uncomfortably hot to leave a finger in for long, about 130 degrees. It's not the best oil for the job (Brian's Parks 50 is MUCH better) but it does the job. I temper around 400 degrees as well, in either a toaster oven or a kitchen oven.

 

On tomahawk heads I can't use the pipe, plus since I do them as a composite construction of mild steel or wrought iron with a 1084 edge the whole thing does not need to be heated. For those I use an oxy-acetylene torch with a cutting tip. Using the cutting tip with low pressure and a bushy yellow flame rather than a welding tip adjusted for welding, I get a big soft even heat again without scaling the steel. Same oil quench.

 

While I could temper hawk heads in the toaster oven, I'd have to crank the heat up past 550 degrees F to get the temper I want for an axe-type tool. So, I polish the blackened oil off the edge with 400-grit sandpaper and wipe the oil film off with acetone (because the oil will affect the colors I'm about to describe), then gently start heating the middle of the head, NOT the edge, with a plain old propane torch. Since the body of the head is not hardenable, it is not affected much by tempering except as a stress relief. There isn't much stress to begin with though, since the body has been normalized a few times after forging. Anyway, slow gentle heat to the center of the head, turning it every few seconds to make sure it's even, I watch for the temper colors to start running up the edge. Slow heat means wide bands of color. If I used the acetylene torch the bands would be too narrow, possible leaving the blade behind the edge softer than I want. The edge will turn light straw yellow, then gold, then various reds and browns into purple until a beautiful light blue appears. That's the color I want on the whole edge. That corresponds to around 550 degrees F, for a hardness around Rc 52. This will cut a nail in two without chipping the edge.

 

So, there three ways of heat treating 1084 for various purposes.

 

On a related topic that bit about spheroidized structure Brian mentioned is very important if you are only grinding blades rather than forging them, because you will need to do a little soaking at heat to get those carbides redistributed. I, however, do not know enough about that to continue the topic. Forging a blade will involve enough heat cycles to distribute carbides and fracture grain boundaries (in a good way!) so that the full gamut of stuff they have to do in machine shops is not required.

 

Any other methods out there? I'm sure I'll be editing my post as other things occur to me, especially the reasons why I do certain things. After all, it's good to know what you need to do, but if you know why it has to be that way you can tweak things a bit for different effects. Like, say, hamon... Which, by the way, can't be done well on 1084 due to the manganese content which makes it too deep-hardening for the full effect to be seen. Differential heat treatment for hard edge/soft back yes. beautiful aetherial cloudy hamon with all the microstructure, not so much.

[Christopher Price]

My method is even more hick. I don't have a thermocouple, and I don't have Parks.

 

I'll eyeball the normalization and practice it thrice, but without high precision. I probably overheat just a bit, but not to an excessive bright orange or yellow. Spotted blades are the tell-tale for that little mistake.

 

I quench almost everything in a 10 year old batch of Goddard's Goop, which is an even mix of transmission fluid, lard, and paraffin wax. Sets up solid at room temperature, and I usually melt some down with a scrap bar, a trough or all of it depending on the piece, which gives me a nice hot oil bath for my blades. Upon quenching, the mixture shouldn't quite want to burst into flames, though if that happens you know the combination of oil preheat and the temp of the blade is too much. Large, thick blades exacerbate this, since they carry much more thermal mass into the bread pan I'm using.

 

What I learned with Aldo's 1084 is that it will not tolerate multiple quenches, as I'd been experimenting with in other alloys at the time... the manganese and vanadium do a good enough job at grain refinement, that a second quench just puts too much stress into the system, and it lets go. Proper normalization, and one good quench, and you should be fine. I temper in the toaster oven with a thin (1 inch) firebrick as a heat sink for 2 hours, set to 450-475* F.

 

In an edge, or partial quench (as opposed to a full quench) I can get a nice smooth transition line to appear, not always conforming to the liquid surface, depending on how the heat was distributed in the blade, and the blade geometry itself... but it's usually not my goal and I only do minor work to show it, if it's appropriate on the piece in question.

[Gary LT]

Thanks everyone, but Alan your input was especially helpful for me. Three various treaments....three different applications. Kevin talked about watching the shadows in one of his replies. My forge is propane, and heats up very fast, almost too quickly, as I usually go to orange with very little pause in reds. Of course starting at the thinner distal taper first. Now I am using a piece of square mild steel tubing as a shield as it's helped.

Great stuff!

 

GT

[Brandon Buford]

That's what I wanted to see, Thanks, Brian.

 

I use a lot of Aldo's 1084. Not having a kiln, I do it a bit differently.

 

For knives and other things that will fit, I use the old pipe-in-the-fire trick. About 18 inches of 2.5" black iron pipe, squashed to an oval shape about 1.5" x 3" and with one end welded shut goes in the forge. Once it comes up to heat I toss some charcoal in and push it to the very end. This creates a neutral to somewhat reducing atmosphere, preventing scale from forming. It also lets me watch the steel come up to heat. That is critical for my method, because I don't have a pyrometer. I judge the transformation temperature by watching the phase change in the steel.

 

Decalescence is the technical term, but when the crystalline structure shifts as the steel is fully austinitized, you can see what looks like shadows swirling inside the blade. As those shadows disappear starting at the edge and working towards the thicker sections they leave a distinct brighter color. That area of brighter color is fully austinitized and ready to harden, or to be pulled out of the pipe and left to cool in still air to normalize. After three normalization cycles to refine the grain I quench in veterinary-grade mineral oil warmed up to be uncomfortably hot to leave a finger in for long, about 130 degrees. It's not the best oil for the job (Brian's Parks 50 is MUCH better) but it does the job. I temper around 400 degrees as well, in either a toaster oven or a kitchen oven.

 

On tomahawk heads I can't use the pipe, plus since I do them as a composite construction of mild steel or wrought iron with a 1084 edge the whole thing does not need to be heated. For those I use an oxy-acetylene torch with a cutting tip. Using the cutting tip with low pressure and a bushy yellow flame rather than a welding tip adjusted for welding, I get a big soft even heat again without scaling the steel. Same oil quench.

 

While I could temper hawk heads in the toaster oven, I'd have to crank the heat up past 550 degrees F to get the temper I want for an axe-type tool. So, I polish the blackened oil off the edge with 400-grit sandpaper and wipe the oil film off with acetone (because the oil will affect the colors I'm about to describe), then gently start heating the middle of the head, NOT the edge, with a plain old propane torch. Since the body of the head is not hardenable, it is not affected much by tempering except as a stress relief. There isn't much stress to begin with though, since the body has been normalized a few times after forging. Anyway, slow gentle heat to the center of the head, turning it every few seconds to make sure it's even, I watch for the temper colors to start running up the edge. Slow heat means wide bands of color. If I used the acetylene torch the bands would be too narrow, possible leaving the blade behind the edge softer than I want. The edge will turn light straw yellow, then gold, then various reds and browns into purple until a beautiful light blue appears. That's the color I want on the whole edge. That corresponds to around 550 degrees F, for a hardness around Rc 52. This will cut a nail in two without chipping the edge.

 

So, there three ways of heat treating 1084 for various purposes.

 

On a related topic that bit about spheroidized structure Brian mentioned is very important if you are only grinding blades rather than forging them, because you will need to do a little soaking at heat to get those carbides redistributed. I, however, do not know enough about that to continue the topic. Forging a blade will involve enough heat cycles to distribute carbides and fracture grain boundaries (in a good way!) so that the full gamut of stuff they have to do in machine shops is not required.

 

Any other methods out there? I'm sure I'll be editing my post as other things occur to me, especially the reasons why I do certain things. After all, it's good to know what you need to do, but if you know why it has to be that way you can tweak things a bit for different effects. Like, say, hamon... Which, by the way, can't be done well on 1084 due to the manganese content which makes it too deep-hardening for the full effect to be seen. Differential heat treatment for hard edge/soft back yes. beautiful aetherial cloudy hamon with all the microstructure, not so much.

 

Alan, I use coal to forge in. If I use that pipe trick, can I throw a piece of coke in or does it have to be charcoal? What's the ready to buy charcoal I can get at lowes, home depot, etc?

[Alan Longmire]

I actually prefer a little piece of wood. Some charcoal spits at you in the pipe.

nothing big, maybe an inch of half-inch dowel or the equivalent size scrap.

[Brandon Buford]

Awesome. Wood I have. Can't wait to try this out. I am glad someone posted a video a few weeks ago on decalescence. Helps me visualize that process.

[Brandon Buford]

Well, I guess that video I was referencing was actually Recalescence. So I still need a visual. But, Alan, you described it well, so I think I can figure it out.

[Alan Longmire]

It's the same thing, but in reverse. As long as you're in the dark when you do it, you'll see it just fine.

[Austin crist]

Has anyone ever used 1080+ i got a 2-1/4 inch knife i just made out of it i was gonna heat treat it as if it was 1084 but its got .6 Chromium and .2 vanadium In it so im afraid the extra alloys will effect it some the knife is for my fother hes a dear hunter and likes his knives really hard yet not hard to sharpen mostly because he hates making me do it for him lol it goes up to 65hrc so it makes me nervous ive had it sitting in my garage for a few years and never used it but im hoping it makes exactly what my dad wants he loves 1095 knives but i dont got that and need to finish it sometime tomorrow any suggestions would be really appreciated thanks

[Austin crist]

Has anyone ever used 1080+ i got a 2-1/4 inch knife i just made out of it i was gonna heat treat it as if it was 1084 but its got .6 Chromium and .2 vanadium In it so im afraid the extra alloys will effect it some the knife is for my fother hes a dear hunter and likes his knives really hard yet not hard to sharpen mostly because he hates making me do it for him lol it goes up to 65hrc so it makes me nervous ive had it sitting in my garage for a few years and never used it but im hoping it makes exactly what my dad wants he loves 1095 knives but i dont got that and need to finish it sometime tomorrow any suggestions would be really appreciated thanks

[Alan Longmire]

That sounds like 80CRV2. Treat it just like 5160 and you'll be happy with it.

[Connor J. Myers-Norton]

Hardening should be about the same, maybe a tiny extra soak for good measure. And tempering should be similar as well, maybe a little hotter, like by 10-20*

[Alan Longmire]

A PM from a new guy made me revisit this thread, especially since I just got back from Ashokan where I heard a most excellent lecture from Kevin Cashen on heat treating stuff. Here is what I said, and I think it needs broader exposure since this is starting to happen a fair bit these days:

 

First, have you read this? http://www.bladesmit...showtopic=26523 (note: that is this very topic, don't click the link!)

 

Second, there's a whole book about that by Dr. Paul Verhoeven called "steel metallurgy for the non-metallurgist."

 

Third, did you look at this:http://www.cashenbla...ttreatment.html , http://www.cashenbla...steel/1084.html, http://www.cashenbla...metallurgy.html

 

Finally, here's the short version:

 

Nonmagnetic occurs at 1417.73 degrees F in iron alloys, because magnetism is a physical property unrelated to alloy content (except, of course, for 300-series stainless steels which are not magnetic to begin with). The critical temperature is a crystalline phase transformation which depends entirely on the alloy involved, which is why that pipe trick mentioned in that first link works so well. You can SEE it happen, so you don't need a magnet. This is a good thing because critical for 1084 is around 1475 degrees F, a little over nonmagnetic. Critical for 5160 is 1660 F, a LOT over nonmagnetic. Magnets are not your friend.

 

1084 is a simple alloy and has the exact amount of carbon that can go into solution with none left over, which is why it is such a good steel for those of us with less-than-high-tech setups. It requires no soak at temperature (the instructions Brian gave in the first link are in per inch of thickness, and since knives are thin you can safely ignore soak times on simple alloys. By the time you see the transformation it's soaked enough). It doesn't require a spheroidized anneal because there's not enough extra carbon to form carbide clumps that wreck drill bits, and the vanadium content is just enough to pin the grain boundaries so you don't have as much problems with excessive grain growth unless you soak the hell out of it or overheat it. Which leads me to your exact questions...

 

Heating 1084 to 100 degrees above nonmagnetic is what you want to do.

 

Letting it cool in still air leaves a small grain size and evenly distributed carbon. This is normalization.

 

Leaving it in the forge to slow cool can result in massive grain growth and severe decarburizing if it is too hot. Carbon prefers oxygen to steel, and will leak off the surface at high heats, especially if held there for a long time. It's just a bad idea and you will not find anyone who knows what they are talking about recommend that you do this.

 

Putting it in a bucket of hot ash is called a lamellar anneal. The carbon will precipitate into the grain boundaries and form sheets of pure carbide, which actually make it more difficult to grind, file, or drill. The iron part will be soft, but the carbon in the grain boundaries will be crunchy, which leads to ragged holes and tearout when filing.

 

So: A triple normalization from descending heats (way hot, a bit hot, and barely critical) will make your grain size uniform and small with evenly distributed carbon. This is what you want. The result will not be quite as soft as a spheroidized anneal, but neither you nor I have the equipment to do that and the difference is not enough to bother with for the things we do. If we were working with 4" thick blocks, then yes, it'd be slightly better for machineability to spheroidize it, but for simple filing, grinding, or drilling normalization is all you need.

[Shmuel]

Awesome thread, thanks. And it's really useful to know that this is way off mark for 5160 because I hope to pick up some unused leaf spring soon.

[Brian C Madigan]

Good info as always Alan!

I probably don't need the 15 minute hold time. Once the probe reads the temp, the steel is probably the same temp. But I don't know how even 'Evenheat' ovens really are, especially when I have radiant heat on multiple blades side by side. For example, if there are 3 blades in the oven, the middle one doesn't get direct radiant heat from the elements, and is visibly cooler than the two blades that ARE getting direct heat. They're basically shielding the middle one from radiation. So the hold time is more to get all the heat even in the oven than to follow the soak time/inch that is recommended.

Also, to prevent decarb in the electric oven (which is seriously bad because there's no gas to prevent it), I use either foil or ATC coating.

[Robert D.]

interesting info on the 5160, as Kevin lists 1525 as the hardening temp on his site, but that could easily be out of date.

on another note, I think I might be ordering some 1084 in the near future to do a side by side beat down test with my current 5160 stock, to see which one does better.

[MacCrea]

What are some other good quench oils for 1084?...For low tech shop

[Wes Detrick]

Canola oil is great and easy to find. Get is hot to the touch (but not too hot), and it will work wonderfully.

Mineral oil, and Peanut oil work great as well from what I have been told. Never used them though, but I know others have.

[Connor J. Myers-Norton]

I've used peanut oil, it's a bit thick so heat it up good (I used to heat up the quench tank with a rose bud but that may be a bit too hot for this). At home I use an ammo can full of ATF (automatic transmission fluid) and it works well, but different manufacturers of automotive fluids have different specs so I may have lucked out. The only advantage to synthetic oils is that they don't go bad but natural oils are the same no matter who you get them from.

[Wes Detrick]

I've used peanut oil, it's a bit thick so heat it up good (I used to heat up the quench tank with a rose bud but that may be a bit too hot for this). At home I use an ammo can full of ATF (automatic transmission fluid) and it works well, but different manufacturers of automotive fluids have different specs so I may have lucked out. The only advantage to synthetic oils is that they don't go bad but natural oils are the same no matter who you get them from.

 

I would also worry about some of the additive chemicals in things like ATF or motor oil...

[MacCrea]

If my pea brain is processing correctly 1084 is definitely a steel to be air cooled when tempering?

[Wes Detrick]

30 minutes ago, MacCrea said:

If my pea brain is processing correctly 1084 is definitely a steel to be air cooled when tempering?

By tempering, do you mean heat treating?  if so, then no, 1084 is a oil hardening steel, so you would want to use an oil for your quench medium.  You would, however, let the steel cool in air when you are normalizing before your quench.  Post quench, you would temper it in an oven at around 400 degrees F to draw some of the brittleness out.

[MacCrea]

I understand you need to oil quench for the hardening process. My question was after tempering in an oven is it better to air cool? I've seen some quenched, but what is best for 1084

[Alan Longmire]

All steels benefit from slow air cooling after the tempering step.  It may only be a miniscule benefit, but it's better than quenching.