Heat treating 1084 for the first time! I need some help!

SkagSig40

SkagSig40

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Feb 1, 2001
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Ok so I finally got a few decent blades ground that deserve to be hardened and tempered. These are my first knives I have ever made and need a little push to get my confidence up! I have an Atlas mini forge to bring the 1084 up to critical and some canola oil to quench the blade in. SO if I understand this correctly I heat the blade up to cherry red when a magnet wont stick any more and then leave in the forge about 10 more seconds and then quickly dunk the blade in the oil. Is this all correct?

How long do I leave the knife in the oil for? When checking for hardness how much pressure do I apply to the file and at what angle do I put the file to blade?

I have a pizza oven to temper but it only goes to 450 degrees. I could buy one that goes hotter if needed. What temperature do I use to temper the blade to 58-59rc and what is the exact process? Do I pre-heat the oven to the proper temp and then put the knife in and start the timer? How many tempering cycles will the knife need and for how long? Does it fully cool at room temp between cycles?

Thanks guys and I'll post pictures when I finish her up! Many thanks for all the help!!!!
 
Looks like you have the basics. Here is the normal method for I recommend for 1084:

Heat blade evenly to non-magnetic. The blade will stop sticking to the magnet at around 1420 F.
Pay attention to the edge, it is part you want at the exact temperature. If you can get the whole blade at the exact same color, great, but don't overheat the edge while trying to get the spine hot enough. Pull blade and check against the magnet (a welding magnet stuck to side of forge works perfect).

Once the magnet stops sticking, heat just a shade of red brighter. It may take 10-15 seconds in an average forge. Keep the blade moving and watch that the edge doesn't get too bright. The desired temperature for the quench is 1485-1500F.

Immediately quench in 120-130F canola oil. For an average size knife, you want at least a gallon of oil, and 2 gallons is even better. Put the oil in a metal container, and have a lid of some sort to cover it if needed. The tank should be at least 4" deeper than the blade length, and 4" wide at a minimum. The simplest way to warm the oil is to heat a bar of steel up and quench a few times, stirring the oil with the bar. A cheap $15 laser thermometer from HF will read the oil temperature accurately.

Plunge the blade straight down in the oil point first. Plunge completely under the oil. Move the blade up and down, and in slicing motions from edge to spine and back. Do not move from side to side.

The steel passes the pearlite nose in only a few seconds. This is about 1000F, and if the blade cools fast enough, it will continue as austenite until about 400F when it starts to convert to hard martensite. After five to eight seconds, you can pull the blade out and check for any warp. You have about 20-30 seconds to easily straighten the blade. The blade is rubbery soft until it hits 400F, so you can straighten it with gloved hands or with a slotted straightening board. Once you have sighted down the blade from tip to butt, and from butt to tip, and are OK with any warp corrections, you can just hang the blade from the magnet by the butt and let it cool in the air. if the blade starts to get stiff while straightening - STOP. It is starting to convert and will become very brittle. Any further straightening needs to be done during the second temper

Once the blade is at room temperature, temper immediately at 400-450F for an hour. Cool in running water and temper a second hour. Cool in running water and the blade is ready to start finish sanding.
 
ETA Stacy typed faster than I did so rather than duplicate I'll just leave this part:

Your pizza oven will work to temper but you should add some thermal mass to it and also use another thermometer to check it's temperature and not trust the dial. I use a $8 one from Walmart. Like a digital heat thermometer. Thermal mass will help keep the temperature constant. Like a pizza ceramic stone or a piece of plate steel. This will also keep your blade from being directly exposed to the heating element.

Let the oven come up to temp and hold it for 30 minutes before putting your knife in. I generally temper 1084 at 400 degrees which should be around 60 RC. 415-425 or so would give you 59 ish. I temper everything twice for two hours at a time unless the recommendation is higher (like some super steels 3 times, etc).

Temper immediately after the quench and checking with a file, or as close to it as feasible. It's not an emergency but you don't want to wait hours if you don't have to. You won't hurt anything by tempering 2.5 hours or 1.75 hours, at that point time is a little less critical.

If you need to straighten a warp you did not straighten out of the quench, I try to do it in the first tempering cycle by clamping the blade flat to another heavier piece of steel. When doing this I generally extend the tempering time for the added mass. If it doesn't come out straight, on the second temper I counter bend it with a shim under the warp. I've had very good luck with this process. 100% success at removing warps and no breakages.
 
If there is a slight warp, is it apropriate to use a carpenters vise mounted vertically with heavy alloy plates fitted to it and use that to straighten after the first temper cycle?
 
When straightening a warp, you want the blade fully tempered. After the second temper, but before you cool it off, straighten while hot. Merely clamping it in a straight vise won't remove the warp. You have to use shims of some sort to over correct the warp and let it cool in that reverse bend. If it needs more correction, re-heat to the temper point as many times as you need to and continue to correct. A large woodworking vise with hardwood jaws is great for this.

Some folks clamp all blades in the quench plates to cool straight right out of the quench oil. That helps a bit, but won't remove all warp and twist.
 
Thanks again guys! So I was planning on getting a Coleman stove or hot plate and placing the steel container on that to het the oil to 120-130 degrees. Would this work well? Also I'm having a hard time finding a metal container for holding the oil. My ideas are a steel ammo can(might not be deep enough? Cutting a 20lb gas grill tank in half and using the bottom half, maybe a gas cylinder that you would use for argon or helium and cut it to length? Would a 8" pipe welded to a steel plate work?
 
SkagSig40,

Your last two ideas will work well for a quench tank. The steel ammo can will work but make sure it is a larger can. As Stacy mentioned it is recommended to hold at least a couple of gallons of quenchant. I get out of spec CO2 cylinders from my local compressed gasses supplier for free. I cut them to the length I want and weld a couple of rebar handles near the top to aid in moving it around. It gets kinda heavy when it's full of oil.
 
I use a crappy old jerry can I cut part of the top off of. I've seen people use ammo cans. Mortar cans are nice and long and deep.
Many people don't heat their oil externally. They heat up a chunk of steel and drop it in. Repeat until at temp.
 
There was a long discussion about that a while ago. It's a minimum amount most people feel necessary to prevent the work from heating the oil up enough, quickly enough, to actually make it ineffective at quenching.

Of course that depends a lot on the thermal mass of what you're quenching, but it's a pretty good rule of thumb.
 
kuraki said:
There was a long discussion about that a while ago. It's a minimum amount most people feel necessary to prevent the work from heating the oil up enough, quickly enough, to actually make it ineffective at quenching.

Of course that depends a lot on the thermal mass of what you're quenching, but it's a pretty good rule of thumb.
Click to expand...

ok, I'll look it up
I guess the amount depends on several things, how many, how big, how often,
seems that more oil is the conservative approach here
 
I quench everything in Parks 50. No preheating that way. Less space. I know it's faster than recommended for some steels but it's never caused me any issue.
 
I'm going to get an old argon cylinder and cut it to length and weld a base plate to it to stabilize it. I plan on using 1084 to start out with but could I quench 1084 in Parks 50 oil so I don't have to pre-heat the oil? I'm not familiar with the different quench oils and how they work exactly. Will Parks 50 work with all steels and not need to be pre heated?
 
I use a rectangular deep fryer . It has its own heating element, you can set it to the proper temp, it is made to hold oil. It holds about 1.75 gallons.
Also using it for steel is better for me than using it for hush puppies.
 
Stagnant straight water for laminated blades in this steel 5 gallon. And 11 second quench oil In this 4" pipe with welded base for 1095 and W1

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Sent from my iPhone using Tapatalk
 
SkagSig40 said:
I'm going to get an old argon cylinder and cut it to length and weld a base plate to it to stabilize it. I plan on using 1084 to start out with but could I quench 1084 in Parks 50 oil so I don't have to pre-heat the oil? I'm not familiar with the different quench oils and how they work exactly. Will Parks 50 work with all steels and not need to be pre heated?
Click to expand...

Some people will say it's too fast for some steels and you might risk cracking them. I've not experienced that myself, and I believe Stacy quenches only in Parks 50 as well. As far as I'm concerned it will quench all oil quench steels. It does not need preheating because it's fast enough for even W2 or Hitachi white at room temp.
 
How many seconds do I quench 1084 in canola oil preheated to 130° for? Right now I'm using quarter inch thick steel with only a 3 to 4 inch blade so I imagine I won't get any warping.
 
SkagSig40 said:
How many seconds do I quench 1084 in canola oil preheated to 130° for? Right now I'm using quarter inch thick steel with only a 3 to 4 inch blade so I imagine I won't get any warping.
Click to expand...

I gave you that in your original request:
....The steel passes the pearlite nose in only a few seconds. This is about 1000F, and if the blade cools fast enough, it will continue as austenite until about 400F when it starts to convert to hard martensite. After five to eight seconds, you can pull the blade out and check for any warp. You have about 20-30 seconds to easily straighten the blade. The blade is rubbery soft until it hits 400F, so you can straighten it with gloved hands ...."
 
In response to the question about oil volume, it is a ratio that has to do with thermal conductivity and thermal mass. For a small knife, one gallon will work, but more is better. For large knives, two gallons is just barely enough, and three to five is best. Multiple knives also require larger volume of oil. Anything that can increase the transfer of heat is a benefit. Circulating the oil, distance to the tank walls, and volume of oil are how it is optimized. The quench is the thing that will determine if the knife is made of hardened steel. It deserves your utmost attention and the best environment possible .... so don't skimp on the oil.
You might compare it to anvils. By impulse ( hammer) to resistive mass (anvil) ratio, a 75# anvils is more than sufficient for forging a knife with a three pound hammer. However, the general consensus is that a larger anvil is a better choice.
 
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