Warming Quench Oil

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Wowndeye

Joined
Apr 15, 2014
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This may be a very basic question but I'm wondering how most of you guys that are heat treating at home, warm your quench oil to 130 degrees.

So I'm working with 1080 at home and quenching in Canola oil and my method has been to heat a piece of steel and insert in oil, swirl around till it's up to temp, then begin heating my blade and then quenching when the blade is up to temp. I had been using a meat thermometer to monitor the oil temp (which I didn't trust completely) but then bought a candy thermometer (which I think didn't work at all) so attempted to use my HF infared thermometer to determine the temperature (which I'm not sure I trusted either due to fluctuations in the readings even after removing the hot piece of steel).

Before actually trying to heat treat, I was playing around with warming the oil and seeing how fast it was cooling in the air to determine how much hotter I needed to make the oil so then when I was ready to quench, it would be right at 130. The problem was that I wasn't getting consistent readings with my IR thermometer and the change seemed to be happening too fast.

This is a step in the whole process I really want to dial in so I can determine what parts of my whole process need improvement. I've got my 1 3/4 gallons of Canola oil in a metal container and was considering using a hot plate underneath to hold a steady temperature but thought I would ask what you guys were doing.

Thanks!
 
i use the metal swirling in the oil technique. after some practice i got to know how long after removing the metal the oil would stay around the same temperature and therefore how long before quenching the blade i had to preheat the oil. for me it was nothing to scientific more trial and error to get the right temperature at the right time
 
Is the container sitting on concrete or a metal table? If so that surface is going to suck the heat right out of your oil. Use a wooden board under the container to act as an insulator. Of course a hot plate would eliminate that issue all together. But that's a trick you can use if you are doing multiple large blades and you're worried the oil is too hot, sit it on a concrete slab for a few minutes and watch the temp drop. :)

-edited-

Also, I actually heat up around 2qts of oil on in an old cooking pot on the stove to around 190F or so and then add it back to my quench tank which is around 2gal. This usually gets it right at the temp I need. Of course this pot isn't ever used for actual cooking.
 
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I use a dual element hot plate to warm the oil. Heats it up just a couple minutes. It only cost me $30 but I'm sure you could find one cheaper.

Make sure you stir the oil well, before you take the temperature. I use a meat thermometer to take the temperature and make sure the oil is at 130 degrees.

I believe that an IR thermometer would only take the temp of the surface of the oil. If it isn't stirred well, that may not be an accurate temp reading.
 
OK, first thing is to point out that Parks#50 should NOT be warmed unless it is cold in the shop. The normal range for it is 70-100F....room temp. Max is 120F and min is 50F.

The other quenching oils should be warm....120-130F is normal. This is a range, not an exact target. It can rise a bit or cool a bit with no problem. 110F is time to warm back up, and 150 needs to cool down. A trick to cool down the tank is to stick a 1 quart plastic bottle of oil or water in the freezer. When the tank gets too warm during multiple quenching , put the jug in the tank ( on a rope) and pull it up and down for a minute. It will drop the temp nicely.
Don't panic that the oil will cool off too fast while you attend to the blade being heated for quench. A couple gallons of oil ( you should always have 1 or more gallons of oil in the tank) won't cool off all that fast. Heat to 130F and tend to your blade...the oil will still be nice and warm when the blade is ready ( unless it is 30F out in the shop).

Stir the tank well before taking a reading. I find the small and cheap HF laser thermometers actually work pretty well on oil tanks and turkey fryers. Of course, a TC and a PID or other readout will be even better. Use a clad style TC for this task. Candy/frying thermometers with a clip to hold them on the pot work great.

A heated bar of steel works fine for warming the oil. I have a 1/2" rod with a 6" piece of 1" round welded on one end. I stick it in the forge and bring it to dull red, quench and stir, check the temp, repeat. When the oil is 130F it is ready. Don't het the tank warmer rod any higher than 1500F or you will scorch the oil when sticking the warmer bar in the oil.
Another good method if you have a large volume tank is a "drum heater" or "rod heater". These are plug in heating rods that often have a thermostat built in.
 
Is the container sitting on concrete or a metal table? If so that surface is going to suck the heat right out of your oil. Use a wooden board under the container to act as an insulator. Of course a hot plate would eliminate that issue all together. But that's a trick you can use if you are doing multiple large blades and you're worried the oil is too hot, sit it on a concrete slab for a few minutes and watch the temp drop.

-edited-

Also, I actually heat up around 2qts of oil on in an old cooking pot on the stove to around 190F or so and then add it back to my quench tank which is around 2gal. This usually gets it right at the temp I need. Of course this pot isn't ever used for actual cooking.
Click to expand...

Good call on the surface the container was sitting on. It was on a metal base and I'll definitely set it on wood from now on. Didn't even cross my mind so thanks!

I use a dual element hot plate to warm the oil. Heats it up just a couple minutes. It only cost me $30 but I'm sure you could find one cheaper.

Make sure you stir the oil well, before you take the temperature. I use a meat thermometer to take the temperature and make sure the oil is at 130 degrees.

I believe that an IR thermometer would only take the temp of the surface of the oil. If it isn't stirred well, that may not be an accurate temp reading.
Click to expand...

OK, first thing is to point out that Parks#50 should NOT be warmed unless it is cold in the shop. The normal range for it is 70-100F....room temp. Max is 120F and min is 50F.

The other quenching oils should be warm....120-130F is normal. This is a range, not an exact target. It can rise a bit or cool a bit with no problem. 110F is time to warm back up, and 150 needs to cool down. A trick to cool down the tank is to stick a 1 quart plastic bottle of oil or water in the freezer. When the tank gets too warm during multiple quenching , put the jug in the tank ( on a rope) and pull it up and down for a minute. It will drop the temp nicely.
Don't panic that the oil will cool off too fast while you attend to the blade being heated for quench. A couple gallons of oil ( you should always have 1 or more gallons of oil in the tank) won't cool off all that fast. Heat to 130F and tend to your blade...the oil will still be nice and warm when the blade is ready ( unless it is 30F out in the shop).

Stir the tank well before taking a reading. I find the small and cheap HF laser thermometers actually work pretty well on oil tanks and turkey fryers. Of course, a TC and a PID or other readout will be even better. Use a clad style TC for this task. Candy/frying thermometers with a clip to hold them on the pot work great.

A heated bar of steel works fine for warming the oil. I have a 1/2" rod with a 6" piece of 1" round welded on one end. I stick it in the forge and bring it to dull red, quench and stir, check the temp, repeat. When the oil is 130F it is ready. Don't het the tank warmer rod any higher than 1500F or you will scorch the oil when sticking the warmer bar in the oil.
Another good method if you have a large volume tank is a "drum heater" or "rod heater". These are plug in heating rods that often have a thermostat built in.
Click to expand...

I've got a single element plate I think should work fine and will start with that and see if I can get it to hold a reasonable, steady temperature. In addition I think before I do my next heat treat I'm just going to spend a little time playing around with the quench oil to see how it's going to behave so I'm better prepared for the next.

Thank you Stacy for the info on the temp range for the quenching oil. That will help me from worrying about it being precisely the 130 I was shooting for although I'll try and keep the temp right there in the middle. I also didn't think about the temperature of the steel I was heating to warm the oil in regards to getting it too hot and scorching the oil so I'm glad you shared that as well so I can get the most use out of it.

I'll also play around with each of my thermometers and see if I can get a consistent reading between the three. I just lost confidence in them all because they were each so different so I didn't know which to trust. Now that I have a couple seconds to do some searching I'm going to look for a little $5 thermocouple thermometer from Ebay I had read about somewhere along all my reading that everyone seemed to love and make it dedicated to my quench tank.

You guys are awesome, thanks again for the help! :)
 
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