How much time for straightening after quench? 1080/1075 steel

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R.C.Reichert

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Jul 26, 2008
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Hello. I have some blades that I ground out of some 1080/1075 steel and I was wondering exactly how long after quenching do I have to straighten a blade. Say if I quench the blade and hold it in the quench for a count of 7 seconds (if that's good) and pull it out, how long do I have after this to straighten the blade up? ...A few seconds...a few minutes? I just don't want to over do it and damage the blade or something.
 
Never try to straighten a fully hardened blade. They are as brittle as glass.
 
I remember a few people on here saying there was a certain "window" of time after the quench that you could straighten a blade using gloved hands or a wood mallet and block, but I don't know how much of a window that is exactly. Is this wrong then?:confused:
 
If you do an interrupted quench as you described and pull the blade from the quench around the Martensite Start temperature then you should have enough time to work out any kinks before enough Martensite has formed to make it unworkable and brittle.
 
Given that air is actually a pretty good insulator I would say yeah a minute or two depending on ambient temperature.
 
I have found that 01, A2, oil quenched 10xx steels allow about 3 to 5 minutes time to hand straighten. I won't recommend it. You are on your own, but I've never broken a blade within that time frame, and most often am able to get them straight. I would not try that on a blade that is brine or water quenched.
 
OK,

When you quenched the blade from 1500F (approx), the blade was Austenite. Hopefully, it dropped from 1350F to below 1000F in less than one second, and remained Austenite ( and didn't start converting into Pearlite). The blade now has until it drops to about 400F to go before it converts to brittle as glass Martensite. Once you counted to 5 or 7 you had taken more than enough time, I use a three count. By removing the blade at that point, you are now dealing with rubbery Austenite. You can straighten it with gloved hands, or give it a few taps with a wooden mallet on the anvil. Place a piece of wood on the anvil to help slow down the cooling ( the anvil will suck the heat from the blade fast). When you feel the blade start to stiffen up and resist any more straightening attempts......STOP....or it will soon snap in two.

Here is my quench procedure for 1080/1084:
1) Austenitize to 1475F and hold for about two or three minutes to equalize.
2) Quench in 120-130F fast oil, and count to three. During the quench I move the blade rapidly up and down.
3) Remove the blade quickly and sight down the blade to check for warp and twist. The blade will smoke severely when you remove it and may even burst in flames...so do this in a well ventilated shop or outdoors. A quick wipe of the blade ( with an old towel) will remove much of the smoking oil. The blade is HOT, so wear heat treatment gloves.
4) Remove twist first. Have a vise opened a crack to drop the blade between the jaws and un-twist it. A 2X4/2X6 with a 1/4" slot sawn in it does even better.
5) Warp is easier. Use gloved hands or a few taps with a wooden mallet and a wooden anvil surface. Steel hammers and steel anvils will dent the soft steel easily as well as suck the heat out faster, so wood is good. An old piece of a baseball bat will work fine as a mallet. I call my wooden hammer a "swacker".
6) At some point in time the blade will start to stiffen. You will feel the difference easily. Quit all straightening attempts at this point. Once the blade gets to around 400F it starts converting to martensite. The percentage of martensite increases until about 200F when it is above 90% . At room temperature it should be near 100% martensite. Any straightening remaining in need will have to wait until after the temper cycles.I call this secondary straightening, and do it at 400F. You can heat the blade to 400F any time you wish ( as as many times as neded to get the job done) and gently straighten any remaining and newly discovered warpage. This will not affect the blade's temper at all. ( unless you tempered below 400F.)

If you want to experiment with the time you have and such, use a piece of 1080/1084 and heat it as if it was a blade. Quench and pull as noted above. Have one friend use one of those inexpensive HF laser pyrometers to check the temperature. Have another friend with a stop watch jot the time and temperatures down as the pyrometer person calls them out. Wipe off the blade and go through some bending and straightening procedures ( you will also discover how plastic austenite is), with the friend shooting readings as often as he can. Keep on "adjusting" the steel as the temperature drops and feel it stiffen. A little farther on it will snap like glass. You have tracked the cooling and conversion of the steel. This should give you a hands on feel of the different points on that curve.
Trying this in air only; using wooden straightening tools; and using a vise ,metal hammer, and steel anvil. This should teach you ( and your friends) about the ways these parameters affect the window of straightening time on this steel.

Now, the disclaimer - The procedures above for straightening are for 1080/1084. They should work for most low alloy steels in the .70 to 1.00 carbon range. I usually try and get it done in about 30 seconds.
High alloy steels have vastly slower conversion rates. On some steels you have many minutes to affect any straightening needed. Air hardening steels ,and steels like 5160 and O-1 are in this group. Use the same straightening procedure, but take your time.
 
R.C.Reichert said:
I managed to find some information with videos on interrupted quenching and blade straightening as demonstrated by Kevin Cashen. Here is the link....
http://www.straightrazorplace.com/forums/forge/51453-interupted-quench-2.html

So I guess this would mean I have about a minute or so to straighten a blade? Is that correct?
Click to expand...

With #50 oil you usually take around 7 seconds to get in the neighborhood of Mf and interrupt. How long you have to work any kinks out is not a matter of time, it is a matter of temperature. Martensite formation is not diffusion based so time has no bearing, it is all temperature driven as the steel cools enough to generate the strain energy required for the transformation. If you kept the blade in a 400F liquid you could bend it for hours if you liked, but your hands would not last nearly that long. So the only way that time is a factor is in measuring how long it takes for the blade to cool enough to make 60% or more martensite, at which point it may be best to leave it alone. You may have more time on a hot day than you will on a very cold day, but there are not set times only set temperatures. I personally apply the least amount of force to straighten the knife, and never apply sudden loading since there are some touchy mechanisms at work inside the steel at the transforming interfaces that could cause ugly things to happen. Gentle guidance with my gloved hands is all it needs.
 
The reason why I'm so concerned with the straightening thing is that I recieved a request from a potential customer about making him a Hudson Bay Camp knife. He said on a couple different occasions he had ordered and paid a substantial amount for custom hand made/hand forged knives from different makers, only to find that they were shipped with warped blades....not a lot, but enough to be noticeable if you looked close. I don't know how common of a thing this is, but he said it definitely caused him to think twice about ordering another custom knife....and I'm sure all his family, friends, etc...were made aware of his disappointment. One of the reasons why people buy expensive custom knives is that they expect to get something of better quality and worksmanship than what you can buy in a store or from a manufacturer. That is what I intend to do.
 
In my very humble and unqualified opinion, any blade that bends is a goner.
Obviously, this is because I'm just not good enough. People here can straighten bent blades like nothing and they are perfectly good blades afterwards. But they know what they are doing.
I use them for tests.
 
This whole messing with hot freshly quenched blades is a fascinating topic. I have done it, it works well. After quenching there is a "fudgey" stage where this works. You have to work fast. It is odd, but gloves tweaking a some-what warped blade seems so not precise, but it is amazing how welll it works. I tned to think that you are guiding the blade back to i where it was. If you over do it and take the blade to another place...well, muy malo. :eek::eek::eek:
 
Or just leave the warp in and tell people that is a feature of "GENUINE" Hudson Bay Camp Knives. The straight ones are poorly made. Then go into a dissertation about how the magnetic flux in the far northern areas causes steel curve toward magnetic north as it crosses the Cutie point on the way down from non-magnetic. After explaining the quenching speed of Bear Fat as the other reason for the warp, you will have the customer locked in for life.

Anyone can make a straight blade....it takes skill to make a properly warped blade.

(Just having some fun)
 
… about the time you get tired of holding the blade in the oil, take it out and straighten it right away,… works every time. :)
 
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