Quench Oil Preheat Questions

MTBob

Well-Known Member
I'm about to change my quench oil from using only Canola to both Parks 50 and Parks AAA depending on which steel I'm using. I understand from USAKnifemaker website that Parks AAA works best with oil pre-heated to around 120°F. I also read that Parks 50 should not be allowed to exceed 120°F", but nothing is mentioned about a minimum temperature.
So, here are my questions:
- What is the workable temperature range for Parks AAA - Low to High? Can I start the oil at say,100 and go to 130... or some other range?
- What is the workable temperature range for Parks 50? I read the instructions to mean that I can start at room temperature and go to as high as 120? Is that right?
- During multi-blade quenching cycle is it practical to use a chunk of cold steel to absorb heat (a heat sink) if the upper temperature limit is exceeded?
 

Kevin R. Cashen

Super Moderator
Park Metallurgical/Heatbath AAA should be heated to the 120°F to 130°F range, I would not go much cooler and would get concerned if it got to 150°F. The challenge of keeping it cool is why I never recommend buying quenchants in less than 5 gallons. I personally don't believe sellers should offer it in less than 5 gallons, as it is just setting folks up for failure. Park Metallurgical/Heatbath #50 should be used in a range from 57°F to 120°F and should not be pushed beyond that. I have found a sweet spot in its cooling curve between 98°F and 108°F.

I have worked with clients that circulated the oil through radiator type assemblies for production work, but for our small time shops may I suggest a very easy, and cheap, option that would be very effective. Any makers out there that are also hobby zymurgists would be very familiar with a immersion wort chiller. It is this simple- go to the hardware and get 10 to 20 feet of 1/4" to 3/8" soft copper line, wrap it around a cylinder that is just smaller than the inside of your quench tank, leaving a foot of either end coming off the top of this coil. Attach fittings to connect a water hose to these and then run cold water through the coil while immersed in your quenchant. This setup takes about six minutes to bring 5 gallons of boiling beer wort to 65°F, so it can bring your oil back in line quite well.
 

MTBob

Well-Known Member
Park Metallurgical/Heatbath AAA should be heated to the 120°F to 130°F range, I would not go much cooler and would get concerned if it got to 150°F. The challenge of keeping it cool is why I never recommend buying quenchants in less than 5 gallons. I personally don't believe sellers should offer it in less than 5 gallons, as it is just setting folks up for failure. Park Metallurgical/Heatbath #50 should be used in a range from 57°F to 120°F and should not be pushed beyond that. I have found a sweet spot in its cooling curve between 98°F and 108°F.

I have worked with clients that circulated the oil through radiator type assemblies for production work, but for our small time shops may I suggest a very easy, and cheap, option that would be very effective. Any makers out there that are also hobby zymurgists would be very familiar with a immersion wort chiller. It is this simple- go to the hardware and get 10 to 20 feet of 1/4" to 3/8" soft copper line, wrap it around a cylinder that is just smaller than the inside of your quench tank, leaving a foot of either end coming off the top of this coil. Attach fittings to connect a water hose to these and then run cold water through the coil while immersed in your quenchant. This setup takes about six minutes to bring 5 gallons of boiling beer wort to 65°F, so it can bring your oil back in line quite well.
Kevin: First, thanks for your excellent reply. To summarize my understanding: Parks AAA Min 120 - Max 150 F (target 120-130). Parks 50 Min 57 - Max 120 (target of 98-108).
Now, regarding maintaining the temperature during multiple knife quench cycles... that is an issue, and you got me thinking. I understand the desire to use 5 gal of oil in order to create a heat sink, that makes sense. But Parks oil is expensive... and I'm cheap. Buying 4 "extra" gallons of oil (each) seems unnecessary if the heat sink effect can be achieved in a simple less costly way. Your tubing heat exchanger idea is one approach.
As a non-production / small shop, that will likely only HT 1-5 knives in a batch, I'm thinking something simpler might do the trick. Here's what I have in mind - mount the oil quench tanks (4" industrial gas tanks in this case, that 1 gallon of oil will fill) inside a 5 gallon container and fill it with water. The question then is whether the heat in five 15-1600 degree knife blades will be sufficient to raise the oil temperature 10 - 20 degrees. This is a great heat transfer question, and easily tested. I'm thinking of heating up 5 low carbon 1/8"x2"x16" stock pieces and test this with Canola oil to see how many knives it takes to raise the temperature above the maximum limit. In that process I would use a disk type plunger to attempt to equalize the oil temperature from top to bottom prior to immersing the steel.
Thoughts?
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tkroenlein

Well-Known Member
I think you can get by with 3 gallons. But if you're buying 3 gallons, it's probably cheaper to just buy the bucket. My container holds 3 with enough head space. It's what I had to build at the time. I can do about 5 smaller knives before the oil temp gets too high. I am going to build a bigger one and it will hold 6 plus about 1 gallon head space. I have no doubt that Kevin recommends 5 minimum for good reasons. Very specific, data driven reasons.

The biggest practical concerns with the 1 gallon quench is the physical size of the quench container and the inability to absorb the heat from one blade, let alone multiples. With the size, you cannot adequately agitate the blade because of the size constraint of the container. And, depending on that container, you may not even be able to get the whole blade covered adequately, and that causes flame ups.
 

Greg Rice

Well-Known Member
Observation: I have never see a question around heat treating, quenching - where Mr. Cashen himself didn't show up to share his vast knowledge he has spent a lifetime acquiring.

Thank you sir - just know it does not go unnoticed and inspires others to also share what we too know... so awesome...
 

MTBob

Well-Known Member
With the size, you cannot adequately agitate the blade because of the size constraint of the container. And, depending on that container, you may not even be able to get the whole blade covered adequately, and that causes flame ups.
I agree, the 3 7/8" ID size tank I've shown is very limiting. It's about 22 inches high so there is some room for up / down motion during quenching. They just happen to be some tanks I use for other projects. Clearly, this size would only be possibly used on smaller knives. It's interesting to note USAKnifemaker sells a 4" square tank that holds 1 gallon of oil.
I'm just a tinkerer / maker and curious whether there is a practical work around for larger size oil tanks. Part of the practical limits of fiddling with oil heat control is the amount of time multiple blades can be kept in their prescribed soak times while at the same time trying to keep the oil temperature set correctly. Unless I can figure out a way to make an automated heat controlled oil container, I think the fatal flaw in using a small tank may be the oil temperature "fiddle factor" while trying to maintain proper steel temperature in an oven with more than 1 or 2 knives. I can envision making a heating control system that works somewhat like a tempering oven that uses a PID controller to allow water to flow in a container around the oil tank, something similar to what Kevin referenced.
 
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