Quench Tanks

L

langchop

Joined
Jun 16, 2007
Messages
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Was just about hijacking someone elses thread so thought I'd make a new one:

I hear so much talk of how important the size of a quench tank it, and people talking about gallons upon gallons of capacity.

I understand that a blade at 1000*C is going to rapidly heat oil at 80*C. If you dunk it into a cup of oil it will get hotter and at a higher rate than if you dunk it into a swimming pool of oil.

However, at the end of the day, the heating is only for a few seconds and very localised that the outer reaches of any larger sized tank will have little to no influence. Logic tells me that as tank volume increases on a linear basis, the heat dissipation effects thereof will dramatically decrease exponentially, from anything more than a few litres.

If there was time for convection currents and long range heat transfer to be set up, I would understand a large tank.

If trying to keep a consistent temp throughout the quench is the goal, surely it would be more desireable to have a quickly agitated tank or have a recirculating pump and quench the blade in the stream of the pump output? This would have more effect than having a large tank?

Your opinions would be good to hear.

Lang
 
That is pretty much exactly how industrial mass quenching is done. The parts are passed through a spray of quenchant at high volume and pressure.
For big tanks,larger items, and multiple quenching, circulation pumps are the norm,too.

You are edging up to an important thing - Tank shape is perhaps more important than tank volume (assuming there is enough quenchant for the job). A 6" cylindrical tank may produce a better quench (at least more consistent) than a 1' square tank. The cylindrical tank should be 6-8" deeper than the blade and 2-3" wider. This will require a couple of gallons for normal length knives.
Stacy
 
I'm trying some 5" ID pipe for this reason, holds about a gallon per foot of length. Hopefully won't have to be an NBA center to get enough length/volume for moving the blade & cooling.
 
bladsmth said:
That is pretty much exactly how industrial mass quenching is done. The parts are passed through a spray of quenchant at high volume and pressure.
For big tanks,larger items, and multiple quenching, circulation pumps are the norm,too.

You are edging up to an important thing - Tank shape is perhaps more important than tank volume (assuming there is enough quenchant for the job). A 6" cylindrical tank may produce a better quench (at least more consistent) than a 1' square tank. The cylindrical tank should be 6-8" deeper than the blade and 2-3" wider. This will require a couple of gallons for normal length knives.
Stacy
Click to expand...

That's a really good point, Stacy, that the Industrial arena utilizes MOVING OIL! So, if you can't move the oil, you'd have to move the blade! This constantly keeps the blade in contact with new oil throughout the quench time. If you want to move the blade, then you'll need SPACE in the tank in which to MOVE IT!
Thus, a large tank.
 
kbaknife said:
That's a really good point, Stacy, that the Industrial arena utilizes MOVING OIL! So, if you can't move the oil, you'd have to move the blade! This constantly keeps the blade in contact with new oil throughout the quench time. If you want to move the blade, then you'll need SPACE in the tank in which to MOVE IT!
Thus, a large tank.
Click to expand...


Blade movement (or oil movement, for that matter) should also minimize vapor jacket, no?
 
MrPurple said:
Blade movement (or oil movement, for that matter) should also minimize vapor jacket, no?
Click to expand...
Precisely - that's the point.
If you just place the blade in the oil and hold it there, it becomes surrounded by the vapor jacket, inhibiting proper cooling of the blade.
Have you ever heard Agitate! Agitate! Agitate! That means move the blade! Which is difficult to do in a small tank.
 
My ten gallon tank has a recirculation pump that pumps the oil straight up from the bottom.
Stacy
 
Thanks for your views Stacy and all. Now thats what I was thinking would be the ideal Stacy... pump from bottom right to the top where you're quenching. Makes sense. Now, when you say that cylindrical tank is better than the cube one, is this on the theory that the oil will recirculate 'quicker' and so give you new, cooler oil sooner?

Maybe this is the source of my confusion: No tutorial or thread that I have read on quenching has mentioned rapidly agitating the blade. Is this one of those unmentioned things that is applicable in pretty much most cases? If this is thecase then a 'wider' tank would make perfect sense.

Stacy, question for you: If you quench in a still tank and then wanted a similar cooling rate on a recirculating stream in a tank, would you need to change to a different oil to counteract the additional cooling effect of the stream?

Lang
 
In a round tank the heat will dissipate in a more even fashion and you get an even quench. In a square tank heat builds up faster on the areas near a wall and stay cooler longer by the corners. IMHO the best quench tank is one that has a pump circulating the oil in a vortex around the blade. Has anyone ever tried a small heated ultrasonic parts cleaner for quenching?
 
You wouldn't want a vorex with it's axis of rotation centered on the blade, the trailing edges wouldn't get cooled at the same rate. I have however thought of a quench tank with the axis of rotation perpendicular to the blade.
 
No, I don't think the oil would need to change. The recirculation just allows the oil to do what it is supposed to do better and more evenly.
Stacy
 
When you "agitate" the blade, it's always from end to end - don't go side to side! This MAY/CAN cause one side to cool faster than the other causing warpage.
It's not a big deal. Just get a tank larger than you can heat up with the amount of blades you will normally be quenching during one heat treat operation.
 
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