Proper quenching times

[Tehemton]

I'm a new knife maker and today I heat treated two blades in O1. I have a makeshift coal forge which is plenty hot to heat the blade (although doesn't really heat evenly and needs a lot of fidgeting). I quenched them properly in preheated sunflower oil.
I a minute after I got the knives out, they were still pretty hot to touch and I couldn't touch for more than a couple of seconds..
My question is, did I quench for long enough? And if not, how long do you guys quench and how do you know when it's completed.
P. S. They hardened alright I think, they passed the file test. And didn't warp too.

Conflict breeds creativity

 

[kuraki]

I think you'll see a lot of variety in the answers here, but what I've found to work best for me on oil quench blades austentizing around 1500F is to quench, edge first, agitating with the edge for a 3 or 4 count (depending on the size of the blade). At that point all of the steels I'm working with have passed the pearlite nose and are around 4-500 degrees. I pull them from the quench to check straightness as there is a minute or so at that temperature where I can straighten out any warping. If it's straight or after I've straightened it I go back into the oil until they are about 200 degrees. I let them air cool to room temp then go into the temper oven.

 

[Tehemton]

I think you'll see a lot of variety in the answers here, but what I've found to work best for me on oil quench blades austentizing around 1500F is to quench, edge first, agitating with the edge for a 3 or 4 count (depending on the size of the blade). At that point all of the steels I'm working with have passed the pearlite nose and are around 4-500 degrees. I pull them from the quench to check straightness as there is a minute or so at that temperature where I can straighten out any warping. If it's straight or after I've straightened it I go back into the oil until they are about 200 degrees. I let them air cool to room temp then go into the temper oven.

Thanks man. Exactly what I was looking for.
I'll try your method next time I'm heat treating. Also, how do you straighten any warps? Put it in a vice or lightly tap it with a hammer or maybe something else?

Conflict breeds creativity

 

[Stacy E. Apelt - Bladesmith]

You are fine.


With O-1, you need to hold the steel at 1500F for at least a few minutes. This hold is called a "soak". Ten minutes is the standard time. This is nearly impossible with a coal forge, so just get it as evenly heated to around 1500F and quench in the 130 degree oil.

Once in the oil, the steel cools rapidly to below 1000F. This drop is called the pearlite nose. If this is too slow, the steel becomes pearlite, and will not harden. If the steel cools quickly enough and "misses the nose" ( as it normally does), the steel will continue to drop to 400F where it begins to convert to martensite. This is the steel structure you want for a kife blade.It has to drop to room temperature for most carbon steels to finish this conversion. As long as it passed the pearlite nose, the rate of cooling to room temperature isn't important. It is best to be consistent and done within a few minutes.

After the quench, you need to temper the blades as soon as possible. Heat to 400-450F and bake for one to two hours. Cool off in water and put back in the oven for a second bake of one to two hours.Col off again with water and the blade is ready to finish.

 

[john april]

i straighten warps by counterbending on the second tempering cycle. if you try to do this before the first cycle, it will snap. lay the blade on a flat surface to see how large the warp is. i use a nickel/dime/quarter/penny in that space to gauge the warps size. make a mark on the blade with a magic marker at the warps highest point. then take two of whatever coin fit under the warp, and clamp the blade to a piece of angle iron, with the two coins at the magic marker mark, counter bending the warp in the opposite direction with two C clamps. the object is to counter bend twice the gap's size. tighten the clamps until the ends of the knife just touch the angle iron. keep one clamp about an inch back from the point/tip, it is much weaker there. temper for the second cycle, and quench in cool water before unclamping. 95% come straight on the first try. if there is still a warp, you can do it again. here is an example photo using a ruler as the blade with 2 quarters. there are a few methods to straighten blades, this one works for me.

 

[Tehemton]

Thanks for all the info.. So I needn't worry about it cooling after the pearlite nose.. Also I'm currently tempering at 3 one hour cycles at 425 degrees with air cooling post cycle.. I did soak the blade to a nice cherry red post sunset before quenching though.. And it's hardened pretty good.. Was just worried about pulling the blade out a bit sooner than I should've had.

Conflict breeds creativity

 

[kuraki]

Thanks man. Exactly what I was looking for.
I'll try your method next time I'm heat treating. Also, how do you straighten any warps? Put it in a vice or lightly tap it with a hammer or maybe something else?

Conflict breeds creativity

I leave a bench vise open about 1/2" and just stick it in there and push/pull where I want to straighten it. John's comment about breaking before the first temper cycle is true once the martensite conversion is finished. That minute out of the quench before hand the steel is very pliable and easy to straighten with little pressure.

It's not always perfect though, sometimes it continues to warp as it continues cooling. At that point John's method in the 2nd temper is your best bet.

 

[E.Carlson]

It's not always perfect though, sometimes it continues to warp as it continues cooling. At that point John's method in the 2nd temper is your best bet.

I discovered that if you hang the blade rather than lay it down on a table or something it greatly reduces the "after the fact warping". I guess it leads to more even cooling. i have a little chain and hook hanging over my quench tank that I hang the blade on and let it cool/drip into the tank.

 

[JTknives]

i straighten warps by counterbending on the second tempering cycle. if you try to do this before the first cycle, it will snap. lay the blade on a flat surface to see how large the warp is. i use a nickel/dime/quarter/penny in that space to gauge the warps size. make a mark on the blade with a magic marker at the warps highest point. then take two of whatever coin fit under the warp, and clamp the blade to a piece of angle iron, with the two coins at the magic marker mark, counter bending the warp in the opposite direction with two C clamps. the object is to counter bend twice the gap's size. tighten the clamps until the ends of the knife just touch the angle iron. keep one clamp about an inch back from the point/tip, it is much weaker there. temper for the second cycle, and quench in cool water before unclamping. 95% come straight on the first try. if there is still a warp, you can do it again. here is an example photo using a ruler as the blade with 2 quarters. there are a few methods to straighten blades, this one works for me.

I will have to disagree with you on this in a way. You use a spacer and counter bend the blade on your second temper. I clamp the blade straight onto a thick steel bar that has been flat ground. I use a few c clamps and clamp the blade so it's perfectly straight. No counter over bending using shims and I do it befor the first heat treat. I then pre heat the oven and then pop the blade and steel bar in the oven. Give it 2 hrs and out it comes and what do you know perfectly straight. You have to most power over straightening in the first tempering. Each temper after that will require shims and over bending and it gets to a point if you keep trying and tempering that nothing happens and the bend is set.

I use to pull the blade out hot and straighten by hand and eye but now I don't even try. I let it cool in the oil till it does not smoke any more then I pull it out and let the oil drip off back into the tank. I then wipe it down and let it air cool the rest of the way. Then I go to the cryo tank if the steel needs it then temper or I go straight to tempering. I love to cryo my steels because it gives my heat treat oven time to cool down and stabilize.

This cutlas blade had a bow and a bad twist.

I clamped it straight to a 1.5" square stainless bar used the c clamps to straighten the twist.

And abracadabra straight after a 2hr temper.

Straightening a sword is tricky and busting a sword blade trying to straighten it was what put me down this path of finding a better way.

 

[kuraki]

I discovered that if you hang the blade rather than lay it down on a table or something it greatly reduces the "after the fact warping". I guess it leads to more even cooling. i have a little chain and hook hanging over my quench tank that I hang the blade on and let it cool/drip into the tank.

That's a good idea. I will give it a go next time I HT something with holes in it.

 

[MBurks]

I will have to disagree with you on this in a way. You use a spacer and counter bend the blade on your second temper. I clamp the blade straight onto a thick steel bar that has been flat ground. I use a few c clamps and clamp the blade so it's perfectly straight. No counter over bending using shims and I do it befor the first heat treat. I then pre heat the oven and then pop the blade and steel bar in the oven. Give it 2 hrs and out it comes and what do you know perfectly straight. You have to most power over straightening in the first tempering. Each temper after that will require shims and over bending and it gets to a point if you keep trying and tempering that nothing happens and the bend is set.

I use to pull the blade out hot and straighten by hand and eye but now I don't even try. I let it cool in the oil till it does not smoke any more then I pull it out and let the oil drip off back into the tank. I then wipe it down and let it air cool the rest of the way. Then I go to the cryo tank if the steel needs it then temper or I go straight to tempering. I love to cryo my steels because it gives my heat treat oven time to cool down and stabilize.

This cutlas blade had a bow and a bad twist.

I clamped it straight to a 1.5" square stainless bar used the c clamps to straighten the twist.

And abracadabra straight after a 2hr temper.

Straightening a sword is tricky and busting a sword blade trying to straighten it was what put me down this path of finding a better way.

How do you allow for the taper in the blade when clamping? Seems like it would create a bend of your clamping to something dead flat, especially if you had a tapered tang as well.

Not doubting your methods just trying to get my head around it.

Also, you say you clamp before the first temper so do you just clamp every blade every time?

Edit to add
Really not doubting you but this sounds like a way to avoid warps all together so I want to make sure I fully understand the process before I try it and screw up.