Heat Treating 1084 or 1080 - Here is another way

BossDog

KnifeDogs.com & USAknifemaker.com Owner
Staff member
Note: this has been edited on the temper temperatures. In researching I found two different temper recipes from ASM. The original temper temperatures seemed too high. I am revising the temperatures down to reflect the second set of temperatures I found from ASM that seems to be more in line with what we see in the real world.

I am working on updating heat treat information on my supply site so I thought I would throw it up here for reference as well. Feel free to add anything in.

Heat Treating 1080 or 1084
Reference data: ASM Book: Practical Heat Treating by Boyer
Written by Tracy Mickley
www.USAknifemaker.com

1080 or 1084 is a high carbon steel with .80% carbon (the 80 in 1080) and is proven, good quality knife steel with good edge retention. 1080/1084 is slow close together the industry specifications overlap to the degree that 1084 could be closer to the 1080 and vice versa when tested. You will hear about 1084fg which has a bit of vanadium added to reduce grain size. I have never hear anyone testing for a difference in performance between 1080 and 1084 and it is generally assumed they perform so similarly they are practically the same steel despite slightly different specifications. We will just call it 1080 to keep it simple.
Normalizing: Normalize by bringing to 1600F, soak for 4 minutes and allowing to cool in still air. Normalizing steel allows the crystalline structure to be reset and redistributes the carbides back to uniformity in the structure of the metal. Steel doesn’t like uneven structure. If the carbides have gotten all bunched up and oversized from forging, the steel won’t hold an edge as it potentially could. Bar stock from the mill probably shouldn’t have to be Normalized, especially if it has been annealed. Material that has been forged could probably benefit. Basically, heat it in your forge or oven and let it air cool. Done.
Annealing: Anneal by heating to 1500F and cool at a rate no faster than 50F per hour. Generally, most guys heat to temperature in their forge as the last heat of the day, turn off the forge and let the steel cool in the forge overnight. If you have other work you want done, I use a half size trash can full of vermiculite. I heat a couple large bars of scrap steel to add mass/heat. I heat the steel to temperature and put it all in the vermiculite to cool down slowing using the vermiculite as an insulator. Cooling slower in the forge works better but cooking in the vermiculite works fairly well also. Some guys use lime instead of vermiculite.
Hardening: Heat to 1500F or past non-magnetic which is around 1425F. Generally, in a forge, this means heating it until a magnet doesn’t stick and then “just a little more” to get the extra heat into the steel past non-magnetic. A few minutes at this temperature will not grow grain but does allow the carbon to get “into solution”. Overheating steel into the 1550F 1600F range and beyond and soaking it will grow grain. Simple, heat it to non-magnetic, give it another minute or so to heat a bit more, quench. You will see somewhere, a lot of places in fact, that the steel really needs to be cooled off at a high rate, like 1 to 2 seconds and that is absolutely true. That doesn’t mean you only have 1 second to get from your heat source to your quench. Moving a blazing hot piece of steel from heat to oil is where a lot of fires get started. A guy knocks over the oil, drops the red hot steel into the oil and instant fire! The steel will retain heat and survive a few seconds in the air as you move from heat to quench. Do this safely and be prepared for a flare up of fire and a large amount of smoke. Always be prepared for a fire.
Tempering: If you did everything right quenching, your steel is around 65RC and fragile as glass. If you drop it now, it will shatter. You want to temper it as soon as it gets to room temperature. I have a left a piece of steel overnight untempered and found it cracked the next day from the stress hardening puts into the steel. It’s rare but it happens. Temper twice at 2 hours each allowing the steel to cool back to room temperature between cycles.

(note edited temps below from original post revised data from ASM Heat Treater Guide Practices and Procedures for Iron and Steels.)

  • 400F yields approximately 57RC. This seems to be the most used temperature.
  • 500F yields approximately 55RC
  • 600F yields approximately 50RC

Cryo Treatment: Cryo treatment, soaking steel after hardening but before tempering at temperatures at least minus -90F (dry ice range) to minus -290F (liquid nitrogen range) for eight hours. Most high carbon steels are generally not cryo treated as the benefit to carbon steels is usually not as significant as it is with the newer super stainless steels. Many people will say a properly heat treated steel should not need any cryo treatment as it only “makes up for a poor heat treat” This sounds good but isn’t necessarily true. Cryo treatment is an industry recognized practice in heat treating and simply wouldn’t exist as an unnecessary expense if wasn’t a legitimate extension of the heat treat, quench and temper process. Big business doesn’t waste money on steps on heat treating it doesn’t need to do. Having said all that, most don’t cryo treat carbon steels but you can if you want. Soak it in liquid nitrogen overnight or even a cooler full of dry ice. You will read about guys using acetone in dry ice. Acetone is crazy flammable. Avoid it please. Use Kerosene or even diesel fuel if you feel you need a liquid medium but just putting your blade under a block of dry is all you need to do. Some guys do one low temper heat at at 300F to 350F sometimes called a “snap temper” to take some of the stress out of a hardened blade before cryo. This lowers the chance of cracking the blade. I have never had one crack from cryo treating a blade after quenching but that just means I have been lucky. Eventually I will, it is just a matter of time.
Austempering: This is a process of hardening steel into Bainite, something we knife guys generally don’t use. We are after Martinsite steel.
 
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Doug Lester

Well-Known Member
Tracy, my only real problem is with your tempering temperatures. Granted, I don't have a hardness meter but the hardness for the temperatures that you have posted seems to be higher than I have seen from other sources. I temper my 1084 at 400° and I don't have any chipping or indentation with the wire cut.

Doug
 

BossDog

KnifeDogs.com & USAknifemaker.com Owner
Staff member
To be honest, they look a bit high to me also. I interpreted the tempering graph as best I could from the ASM Practical Heat Treating Guide. Personally, I might start at 50F lower. On the other hand, the ASM people are tempering to what they believe is a perfect heat treat with high martinsitic steel so the higher temp would make sense in a way. Us mere human knife makers may not quite get the full conversion a professional heat treat factory might and so a lower tempering temperature would get the results we are looking for...
 

Knifemaker.ca

Dealer - Purveyor
I have to agree with the tempering concerns Boss. I tend to stick to Kevin Cashen's charts and get results very close to what they predict. 400F x 2 hrs x 2 usually within a half point of 60. I haven't done it but I suspect 500F just might result in a pretty "easy to sharpen" blade. :34:

As you suggested, this may be one of those times the standard practices don't fit our special circumstances
 

BossDog

KnifeDogs.com & USAknifemaker.com Owner
Staff member
I found another ASM publication with completely conflicting data, which is disappointing. The ASM is supposed to be the premier authority on heat treating and their data from one publication doesn't match in this case. Just another indicator that heat treating data is all over the place and two apparently conflicting points of view maybe correct.
 
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