Optimum size for a quench vessel?

C Craft

Well-Known Member
In an effort to conserve money I am rethinking the idea of a quench vessel. I need something that will do up to approx. a 24" in length of blade for a knife I am going to make. :what!:

With 6" and about 28" in depth I can get by with a little over 3 gallons of quench oil!

With 8" and about 28" in depth I can get by with a little over 6 gallons of quench oil!

My present tank is 10.5" and about 28" in depth it will take a little over 10 gallons of quench oil!

So here is the $50,000 dollar question what diameter of pipe am I looking at. Can I get away with a 6" diameter pipe or is that to small to stab into. I will be running a pump on it too circulate the oil and won't be doing too many multiple quenches.

Anyone got any ideas on this subject or care to share info on what they are using it would be greatly appreciated. :biggrin:
 
It is going to depend on how many knives you are going to be quenching at a time. If you regularly do several blades in a batch you might want to consider going to a 6 gallon volume. If you only do 2-4 max and rarely the high end, I'd go with the 3 gallon size. Of course, the length of the blade is going to figure into it too.

Doug
 
It is going to depend on how many knives you are going to be quenching at a time. If you regularly do several blades in a batch you might want to consider going to a 6 gallon volume. If you only do 2-4 max and rarely the high end, I'd go with the 3 gallon size. Of course, the length of the blade is going to figure into it too.

Doug

I do not do a big volume at one time! So what your saying Doug I really don't need to worry about the diameter of the vessel the quench oil is in it is more about the quantity of the quench oil within the vessel! Is that correct?
I can get the depth I need by using the 6" diameter and going with the 28" depth and still hold the oil down to approximately 3 gallons. Still not cheap considering the cost of good quench oil! I was just concerned about the 6" diameter for the opening, that means a straight down plunge basically but a pump to circulate should help to elevate any problems!
 
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What I've found out about tubular quench vessels; there's no place to move the blade. Moving the blade into and through cooler oil is a must, especially for large blades.

When hot metal is quenched, a vapor envelope is initially formed around the hot metal as it is immersed in the oil. The stability of this vapor envelope—and thus the ability of the oil to harden steel—is dependent on the metal surface irregularities, the presence of oxides, surface wetting agents (which accelerate the wetting process and destabilize the vapor envelope), and the presence of other oil degradation by-products.

Upon further cooling, the vapor envelope collapses, resulting in so-called nucleate boiling, which is the fastest heat transfer.

Nucleate boiling is a type of boiling that can take place under certain conditions. It is the process of forming steam bubbles within liquid in micro cavities adjacent to the wall if the wall temperature at the heat transfer surface rises above the saturation temperature while the bulk of the liquid is sub-cooled. The bubbles grow until they reach some critical size at which point they separate from the wall and are carried into the main fluid stream. There the bubbles collapse because the temperature of bulk fluid is not as high as at the heat transfer surface where the bubbles were created. Heat and mass transfer during nucleate boiling has a significant effect on the heat transfer rate. This heat transfer process helps to quickly and efficiently carry away the energy created at the heat transfer surface. When the temperature of the hot steel interface is less than the oil’s boiling point, nucleate boiling will stop and convective cooling will begin.

I've found a longer thinner quench tank allows this envelope to quickly collapse around the blades hot surface alloying proper quenching to take place.

Something to think about, Fred
 
Optimum anything is a tough determination. I cut the tops off two junked fire extinguishers that measure ~ 10" diameter and 24" tall. You can get extinguishers in just about any size you need and you don't have to worry about a liquid tight weld at the bottom. Are they optimum - I don't know. Do they work - Yes. One is filled with water and the other is filled with Canola oil.

ps Don't sweat heating the quenchant up too much with the first blade or two. You are preheating the quenchant anyway - preheat shy of your target, split the difference and quench with impunity.
 
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Six inches is plenty.
I use large fire extinquishers which are six inches wide and have no problem even with wide bowie blades. Cut the tops off and set in buckets of vermiculite and you're done. Although I don't do swords so keep that in mind. The more volume of oil, the better...so you don't over heat it.

Rudy
 
The point of the volume is that it absorbs more of the heat without changing temperature that much. You could undoubtedly get by with even less than 3 gallons if you are only doing one short blade and not have to worry about overheating the oil and altering the cooling rate. You might even be able to do it with one gallon of quenchant. Give it a try with some test knives and monitor the oil temp with a thermometer to see if it's staying in range.

Doug
 
I use piece of 4" PVC drainage pipe with a toilet flange expoxied to the bottom for a base. It holds just about exactly 1 gallon, give or take.

Granted, I only do a couple knives at a time, and if it's a larger knife, I only do one. I'll eventually get a bigger tank just for more volume. I probably wouldn't use something so small for a sword though.
 
I use a 4" pvc pipe for water and a 4" steel pipe for Parks 50. I used to use a garbage can for canola but the change in temp split the seams.

I regularly heat treat a couple of small knives and then a 27" dao (single-edge like katana only a little wider).

more than 2 knives and a sword, and I would have to let the Parks cool a little before quenching something else, but that would be like quenching 10 knives one after the other.

kc
 
I used to use a garbage can for canola but the change in temp split the seams.


kc
I will bet that was one _ _ ell of a mess, when the garbage can split!

Thanks KC and everyone else that has chimed in on this thread. Since I first opened this thread you all have helped to work through a lot of misinformation that is out there!
 
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