Cooling down your quenching oil….any tricks for that?

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godogs57

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Apr 16, 2004
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Had a half dozen carbon steel blades to heat treat in the forge Wednesday. Quenching with P50. “Room temp” is traditionally the temp I quench, like everyone else. Thermometer in the P50 said 80 degrees just before quenching the first blade. Second blade in raised the temp over 150 and I backed off on the next few blade’s ht until the oil cooled down. I turned off the forge, let the oil cool for a few hours and worked on other blades. Fired up the forge again and ht blades three and four and had to shut it down again to cool down. There has to be some shortcut to cool the oil down other than just shutting things down and waiting on it to cool on its own. I threw a couple of tongs in one of my deep freezes in my shop for about an hour, swished em around in the P50 and dropped the temp back down quickly.

Any other tricks out there to cool the oil down? It makes no sense to me to quench a subsequent blade if the oil is say, 150 degrees or so, when it needs to be room temp. I usually only ht two or so blades at any time. Me doing six blades Wednesday was out of the ordinary for me.

Thanks in advance.
 
What volumr are you working with? I have a 5 gallon container and I can do quite a few blades before the temp of the oil exceeds where I would like it to be.

As I was reading your post, what came to my mind was what you mentioned, throw something with some mass in the freezer the night before and cool the oil down that way. A frozen quench plate would do the trick, I am willing to bet, along with anything like it.

But, yes, 150°F is in the extreme upper range of P50 working temps, room temp through 100°F works quite well.
 
I have a friend at a machine shop make me a stainless tube with a flat bottom welded on so it stands upright. It’s very steady. The tube is about 4”-5” inside diameter, 18 or so inches tall and holds about a gallon, gallon and a half.

Good idea on the plate aluminum. He has a good bit of scrap for recycling after projects and I might ask for a piece about a half to 3/4” thick, 3” wide, foot long. That would suck the life right out of some hot oil I’m sure.
 
You need a larger volume of oil, 5 gallons is really what I consider the minimum for batches, when I was mostly working with carbon steel blades and heat treating batches of 20-30+ I have a drum with 15-16 gallons of parks 50 in it. One thing to be careful of with your current method of cooling is condensation, you do not want any water getting into the oil. I spoke with one of the technicians at maxim oils that sells parks 50 and other similar products and asked if I could cool a block of steel and dunk that in the oil to cool it and they said yes but only if you wipe it dry immediately before putting it in the oil. Can’t remember all of the reasoning but they made a point to stress not getting water in the oil. If you can’t use a larger volume of oil then put your quench container in a bucket with ice water to cool the outside of the container and reduce the temp that way.
 
Volume will take care of the issue for most makers who only quench a few knives at a time.

IF you do large volume quench sessions, you can actually make an oil cooler from junkyard or auto parts store stuff.
You need a transmission oil cooling radiator, a 12VDC cooling fan from a car radiator, a cooling fan temperature switch with thermostat, a 12VDC fuel pump, and some gas/oil line tubing to connect the parts.
Either add ports to your quench tank or use an old 5-gallon water heater as the quench tank. Run the oil from the top of the quench tank ... to the temperature switch ... to the pump ... to the radiator ... and back to the bottom of the quench tank. You can use an old car battery charger for the 12VDC power supply or use a car battery. Set the switch for around 130°F and put the TC in the quench oil tank. When the tank reaches 130°F the switch will turn the pump and fan on and circulate the oil. The oil coming up from the bottom also creates a better quench.

I used a new 5 -gallon and a 10-gallon water heater to make these quench tanks for a friend. The tank heater was set at 120°F and the cooling pump switch at 130°F. You have to be aware of where the element sticks out in the tank when quenching a long blade, but besides that it was a very good quench setup for someone doing many quenches in a row. I made a piece of copper tubing that came out of the bottom port and had a 90° elbow on the end to send the stream of oil straight up the center of the tank.
 
Make a copper tube coil. Attach hose, one to tap and another to drain. When hot, dip the coil in. In a minute temp is good again.
 
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JoeBusic said:
Make a copper tube coil. Attach hose, one to tap and another to drain. When hot, dip the coil in. In a minute temp is good again.
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Ah, the old wort chiller design :p just don't use it for your home-brew afterwards

godogs57 said:
he tube is about 4”-5” inside diameter, 18 or so inches tall and holds about a gallon, gallon and a half.
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226 to 353 cubic inch, or 3.7 to 5.8L. I have a similar one for oil that's ~1.2m (48 inch) and it's still too small really
Giving it a good stir after each knife may help a bit, you're probably getting a warm layer at the top
 
I used to used frozen water bottles to cool down film developer in the back of a radiography rig during summer months. Just dropped them in the tanks. If you can’t immediately go to more oil volume, you may be able to use something similar for your purposes. If you don’t like the idea of condensation/water in your oil then any large steel chunks kept in your freezer until needed can act as a chiller when submerged. Thermal mass is what you are looking for.
 
Bühlmann said:
If you don’t like the idea of condensation/water in your oil then any large steel chunks kept in your freezer until needed can act as a chiller when submerged. Thermal mass is what you are looking for.
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Unless you live in a dry climate, you'll have to wipe the steel off before dropping it in the oil because there will be condensation on it.
 
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