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1084 Heat treat question


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I made my first blade out of 1084 today and I'm having some trouble tempering it. I'll explain what I did so that you have a good understanding.

I use minimal equipment and do not have a digital oven. After the blade was forged I heated the blade in an LP forge, to an orange color and placed it in a container of vermiculite for several hours until it was cool. The blade was then rough ground.

Once the blade was ready for heat treat, I heated the blade to an orange color and let it sit at that temperature for approximately ten minutes. The, I let it cool to room temperature. I then reheated the knife to an orange red color, soaked again for approximately ten minutes, and let it cool to room temperature once more. Again the blade was heated, this time until it was red in color. It was held at this color/temperature for another ten minutes and then was cooled to room temperature.

Now, I was ready to harden the blade. I brought the knife blade to an orange/red color. I was aiming for a bright red color, but it went a little hotter by mistake. I held the blade at that color for around 3 minutes then quenched in McMaster-Carr 11 second quench oil. I let the blade cool to room temperature and placed it in the oven for one hour at 300. I let the blade cool again to room temperature. A file would still glide over the edge. I tempered for another hour at 350. Same results. So, I tempered again at 400 for an hour. A file still glides over the edge, but cuts just a little. The spine is soft.

Is it possible that there is a carbide buildup on the surface? Should I grind with a heavy belt and see what the steel is like below the surface? I was not sure if I should continue to raise the temperature on the oven and re-temper until I have the desired results?

Any help would be great and I thank you in advance.

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If you didn't manage the atmospheric contact with the blade, there will be a decarburized skin on the blade which should be removed. However, I can't really tell what you don't like about the blade. A file barely cutting on the edge along with a soft spine could make a very good blade, depending on final purpose.

You didn't mention using one but a magnet can be a great help in finding critical temperature - when the blade loses its attraction, you have reached austenitizing temps. Memorize that color, with your eyes, in your environment, for reference.

Lots of great blades have been made and will continue to be made without measuring equipment - especially with simple carbon steels such as 1084.

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Well it is a larger knife and I was looking for a softer edge that would hold up well to chopping without chipping. I suppose I should just take it to the belt ginder and then try it out. I did use a magnet, it was slightly hotter than I was aiming for.

I should have reworded my first sentance. I just re read it an it sounds like I made my first knife today. It was simply my first knife that I made out of 1084. It's probably my 20th knife or higher. I suppose that I'll grind it and test it out.

Thank you for the information Sir.

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The ten minute soaks are longer than 1084 needs for hardening, and for normalizing. For normalizing, all you need to do is kiss the target temperature -- no soak -- remove the blade from the heat and air cool it well into the black. Target temps should be -- roughly, here, since you're eyeballing it -- a shade above non-magnetic, then a half-shade, then just non-magnetic. For hardening, a very short soak (1-2 minutes) is enough with 1084.

I'd be a little concerned that with ten minute soaks and spotty temperature control, you may have grown the grain some.

Full hard 1084 will be about RC 65. Tempering at 400 will get you down to around 60-61 or so. That's still darned hard. (And kitchen ovens are notoriously inaccurate when it comes to temperature, so if that's what you used I wouldn't count on having hit the desired temperature exactly.) That's likely why your file is barely cutting. (Is it a sharp file? Good quality?) If you want it softer, temper higher. 1084 shouldn't form many carbides, if any, so I doubt that's your problem.

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Hi I temper 1084 for 3 one hour cycles at 375 to 425 with cooling to room temp between cycles. 400 degrees should be about what you want but you may need longer than one hour at that temp. I would grind then test before you put the handle on. then you could always re temper.

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Paper like newsprint will char and begin to burn at about 375f, Matts thought about your oven not being off is likely a problem..if you put blade in oven for a half hour or 45 minutes at 375 and wipe it with newsprint the paper should char failry quick if it does not yoiu need to up the temp a bit. Dont get to crazy with all the normalizing and soak times. this is a great steel for blades and simple methods work well. One time normalizing as they said above then harden and temper/ Clean all scale off then test with a file..I hardly ever have to do a second temper cycle on this steel. If you start a paper fire in your house I did not say that was ok.

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I usually take my blades to an almost finished state(400 grit or so) and after a couple hardenings i clean it up again and then go to the oven at about 350F and watch diligently for color change(Straw color or light bronze) this usually does the trick quite nicely. After I usually clean off all temper colors and then grab a wet rag and put the blade edge down in the vise with about 2/3 blade exposed and then soften the back. I use the wet rag so I don't haul the hardness out of the edge. This has worked great for me. Hope this helps. Cheers

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The ten minute soaks are longer than 1084 needs for hardening, and for normalizing. For normalizing, all you need to do is kiss the target temperature -- no soak -- remove the blade from the heat and air cool it well into the black. Target temps should be -- roughly, here, since you're eyeballing it -- a shade above non-magnetic, then a half-shade, then just non-magnetic. For hardening, a very short soak (1-2 minutes) is enough with 1084.

I'd be a little concerned that with ten minute soaks and spotty temperature control, you may have grown the grain some.

Full hard 1084 will be about RC 65. Tempering at 400 will get you down to around 60-61 or so. That's still darned hard. (And kitchen ovens are notoriously inaccurate when it comes to temperature, so if that's what you used I wouldn't count on having hit the desired temperature exactly.) That's likely why your file is barely cutting. (Is it a sharp file? Good quality?) If you want it softer, temper higher. 1084 shouldn't form many carbides, if any, so I doubt that's your problem.


Most excelent information. Today I'll do some hardening samples and break them to see if I have excessive grain growth with the hardening I'm using. I completely take your word on shorter soak times, I just like to see how bad I mess things up, ya know... I'm going to get a more accurate thermomiter this morning and check the oven temp.


Hi I temper 1084 for 3 one hour cycles at 375 to 425 with cooling to room temp between cycles. 400 degrees should be about what you want but you may need longer than one hour at that temp. I would grind then test before you put the handle on. then you could always re temper.


I'll grind and test it, I'll also retemper it at 400 twice once I get a goo thermomiter.


Paper like newsprint will char and begin to burn at about 375f, Matts thought about your oven not being off is likely a problem..if you put blade in oven for a half hour or 45 minutes at 375 and wipe it with newsprint the paper should char failry quick if it does not yoiu need to up the temp a bit. Dont get to crazy with all the normalizing and soak times. this is a great steel for blades and simple methods work well. One time normalizing as they said above then harden and temper/ Clean all scale off then test with a file..I hardly ever have to do a second temper cycle on this steel. If you start a paper fire in your house I did not say that was ok.


Great information. I like the paper trick!


By the way, is this Aldo's 1084? If so, the vanadium tends to pin the grains, so triple normalizing may indeed be too much.


I don't believe so. It was purched from USAknifemaker.com It's my first time dealing with them so I'm not sure who they get material from. Aldo sells his own stuff though, no?


I usually take my blades to an almost finished state(400 grit or so) and after a couple hardenings i clean it up again and then go to the oven at about 350F and watch diligently for color change(Straw color or light bronze) this usually does the trick quite nicely. After I usually clean off all temper colors and then grab a wet rag and put the blade edge down in the vise with about 2/3 blade exposed and then soften the back. I use the wet rag so I don't haul the hardness out of the edge. This has worked great for me. Hope this helps. Cheers


That is similar to what I do. I just want to be sure to have a proper hardness edge.... without a large grain structure.
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The 1084 Tracy Mickley sells through USAKnifemaker also has vanadium added; that's why he calls it 1084fg (for "fine grain"). Same deal. You probably don't need more than two normalizing cycles with that stuff unless you badly overheated it during forging. One cycle might do fine. (Crucible's Cru Forge V steel has a healthy dose of vanadium in it, and I'm sure part of the rationale is that the V makes it a little harder to screw up the steel during forging and heat treating.)

With regard to the soaks, let me add that the time concerns me less than temperature. (I'm always a little suspicious of propane forges when it comes to dialing them back to moderate temps and getting them to hold those temps reasonably accurately.) If you're confident that you can tune your forge down to around 1500 F, and hold it there, then soaking for a little extra time probably won't do any harm.

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Matt,

He had two steels listed. 1084fg and 1084. I purchased the regular 1084, unles he just forgot to put fg after the first few that he listed. I can set the forge to keep steel at basicly any range between just dull red on up. The problem is knowing what the actual temperature is. I would love to purchase or build an oven but it's just not possable for me right now. I just purchased a thermometer that reads 400deg at room temperature.... quality. I'm headed out to buy an infared thermometer now.... That should help with the tempering I think, and let me know if that's where the issue lies or not. Once i have a few more pennys saved I'll see if I can get a high temp one that reads above 1600 deg. I would assume that would help me narrow down the forge temps.

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I recently picked up a lab thermometer at the fleamarket for my oil quenches after a student listened to me tell him to preheat the oil to just above "can touch the side of the tank" and then found that he had heated the oil up to boiling and wondered why his blade wasn't hardening correctly---the oil being above the tempering temperature will do that... Now I can tell them a set temperature for the quench oil and live with the whining about overshoot/undershoot as they try to get it *EXACT*, Sigh.

Those optical pyrometers are the bee's knees!

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OK, I didn't realize he was also selling regular 1084.

Do you use a magnet to help check your hardening temperature? The magnet method is far from perfect in general, but for a very simple eutectoid steel like 1084 it's actually a pretty good solution.

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Matt,
Yes I did. The blade is plenty hard. It's jjust slightly softer than when quenched it seems.... I just cant seem to get it soft. I checked the oven, temp was only ten deg low. I put it back in for two more tempers at 400. I only got it once at 400, but that should have don it anyway... I don't know...

So far it has been tempered at 300, 350, and 400, each for one hour. I'll give it another go at 400 then raise the temp again.

Thomas,
Oil was warm and viscous but not extremely hot. Just warm maybe slightly hot to the touch. I'm saving for one of them high temp ones. That should help lots.

Thank you all very much for the help so far. I even learned some stuff!

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I really don't think you have anything to worry about in terms of hardness, from the sound of it. Your blade got really hard. It's supposed to do that! Now it's just a few points softer than a file, so your file is cutting slowly. Again -- sounds about right. Just increase the tempering temp a bit until you get the hardness you want.

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  • 4 weeks later...

The smaller the grain size, the lower the hardenability of the steel. If it's done correctly, normalizing can lower grain size. (There is some finite limit on how far you can go with this.) I know bladesmiths -- who I trust to know what they're doing -- who have normalized a particular blade so many times that it wouldn't harden properly, presumably because the grain had gotten too fine. They were able to fix the problem by deliberately growing the grain a little.

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normalisation certainly does alter hardenability. this can be used to advantage when you are trying to get a hamon in a steel that would normally through harden . successive normalisations will chase the hamon down towards the thinner edge

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  • 3 months later...
  • 2 years later...

I been forging for a few years and my slack tub has water.   Haven't really needed oil so far... mostly.   Just tried knifemaking with 1084.   2" x 5/32"   I used a full bevel across the full 2" on a kitchen knife about 6" long.  No forging, all stock removal on a 2x72".  

 

Is there any issue with a water quench?   I should be able to hit the right temps with my gasser or coal forge and a magnet.  

 

Do I need oil for the quench?  

 

Right now we are in the 90sF in Louisiana so my water aught to be in the upper 80s.   I understand in colder times that a 40F quench in water can make a difference...    If oil is preferred can I instead heat the water somewhat instead?  Or is water just a bad idea.  During grinding I kept the 1084 cool without overheating.

 

Just trying to be clear if I need an oil quench set up or can I do just fine with water?

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After heat treat did you do all the normal shop tests to make sure it was hard?,,,and then after you tempered did you again test? And how did you know the blade was at the correct heat to quench?

All the answers are here in the heat treat stickiews and knfe making lessons.

If you google specifications for 1084 steel  you will find what the maker suggests for quenchant...and for any other steel by number also in different searches.

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Rich, you may be a journeyman now.   You may not have read my post or perhaps your reply is to a previous post.  

 

I did google the quenchant and it sounds like quenching in water below 1/4" might be a bad idea.   And it would need to be heated to perhaps 130+...   depending on who you talk to.      Sounds like oil is better and give a better quench but even then from what I read it also needs to be heated.

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