Safety - Quenching with oil

Hey guys, I'm on the safety committee for our tool and die shop, and I've got a question about quenching parts with oil.

Recently the MSDS sticker burned off the oil container, and now we arne't sure what's in it. This is bad, I know, but we only use this to harden very small parts maybe once a month. The same oil has been in the container for probably a decade at this point.

My questions:

1. Is there are a type of professional or industrial oil quenching canister? Something made specifically for this? Everything I see online appears to be just whatever container you can find.

2. What oil do you use for all-purpose hardening of tool steel. We almost exclusively work with A2, D2, 420, H13 and O1 and probably go about 45Rc, nothing critical in terms of hitting exact hardness.

3. Any general safety tips? Most of our old school veterans have retired, and some of the young guys using the oil really don't know anything beyond "put hot part in oil".

Thanks guys

Well I can tell you from experience, if you don't get the part fully submerged it will ignite. It makes one hell of a mess when it does, I cleared the shop for an hour on that one. I would think to keep something like sand or similar to put out if you do have a fire, with an extinguisher close by as well. I don't think I would use the extinguisher as first choice since I (guessing here) think it might spray the burning oil over a larger area?

Mike1974 said:

Well I can tell you from experience, if you don't get the part fully submerged it will ignite. It makes one hell of a mess when it does, I cleared the shop for an hour on that one. I would think to keep something like sand or similar to put out if you do have a fire, with an extinguisher close by as well. I don't think I would use the extinguisher as first choice since I (guessing here) think it might spray the burning oil over a larger area?

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I'm guessing a special extinguisher wouldn't spray the oil but your intuition on a normal one spraying oil is pretty good, that's what my intuition tells me as well.

Regarding the quench oil itself. I believe there are special oils with flame retarders in them designed specifically for quenching that reduce the fire risks. In college when I had to harden some stuff they had a "quench container" which was essentially a square metal tub with a basket that could be lowered down into the oil and pulled back up to let the oil drain. The oil they had was specially marked (factory markings) as a quenching oil and came in a steel 5-gallon bucket. Outside of that I can't tell you much about the oil other than the fact that it didn't smoke or flash as easily as normal motor oil. When I was working overseas all I could get for quenching O1 was motor oil and that stuff flashes pretty easily compared to the quench oil.

It would make sense to have a quenching vat with a lid that comes down automatically in the event of a fire like you get on a degreasing tank.

I've got a safety can that was made for rags. Sitting inside that is a separate
metal can that holds about 2 gallons of quench oil ( fast quench ).
I step on the cover opening lever for the safety can and then dip/swirl
my parts.
If unlucky enough to get a fire, just drop the lid.
I only do small parts.
David

Beside my forge I have a metal trash can with a foot pedal to open the lid (the same thing you see in bathrooms and kitchens everywhere). It was not completely leak proof so I put a galvanized bucket inside the trash can. I step on the pedal and it opens up. I quench, release pedal and go on about my business. I have always just used motor oil and yes it has flashed a few times. It always goes out immediately when I release the pedal and drop the lid back on however. It works well because I usually have both hands full.

You don't say how big your parts are. My answer pertains to parts that generally weigh a half a pound or less as that is the size I work with most of the time in my shop. My metal oil container is about 1/2 gallon in size.

I have had the canola oil I use to quench parts flame occasionally. As pointed out above, that only happens if I pull the the still-very-hot part up into the vaporized oil cloud above the container. The part is no longer hot enough to ignite the oil after just a few seconds in the oil. If the oil ignites it can usually be stopped just by letting the part cool enough to no longer need up and down agitation, this causes the vapor to no longer be generated. Since the oil in the container is not hot, it burns weakly and often will self extinguish or I just give it a good puff of breath and blow it out. No, I don't blow oil all over the shop causing a massive fire 3-alarm fire. The other option would be to just put the metal cap back on the metal quench oil container which works just as well. So, this whole ignition event is actually a non-event. That said, I do take care to have a medium-sized dry powder ABC extinguisher which is approved for oil fires. https://en.m.wikipedia.org/wiki/ABC_dry_chemical

What I relate above is the practical reality in my view. In a setting requiring a formal write-up for safety committees and oversight, I would be replacing your unknown oil with a low-vaporization proprietary quench oil. Here Petrofer provides a summary of the various quenchants we offer. Even so, the oil is still likely to flame under the circumstances listed above and the main message to the trainees should be not to panic and run, but just use common sense to help it go out. It is very easy to extinguish and can barely keep itself going.

Denis

I did work in a tool and die shop for a while and they did have a commercial quenching oil. Who knows were they got the stuff, like yours it was probably decades old. For small parts it probably does not matter what type. You do need to agitate the parts while they are submersed in oil. The oil in contact will get hot and not cool as fast or worse make a gas bubble surrounding the part (this happens when you see smoke boiling out of the oil). That smoke boiling out will be extremely flammable. Swirling the parts as mentioned prevents that as well as doing a better hardening.

dgfoster said:

You don't say how big your parts are. My answer pertains to parts that generally weigh a half a pound or less as that is the size I work with most of the time in my shop. My metal oil container is about 1/2 gallon in size.

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The parts are small, generally 1" to 3" diameter bushings.

Ah yes, fond memories of nearly burning the shop down. One of our toolmakers made a pedal operated "hot can" out of a 55 gallon drum, some metal, a mig welder and some ingenuity. Inside that drum was a 35-40 gallon metal trash can surrounded by lava rock. I don't know what the oil was, I think someone told me it was hydraulic but I doubt that because of the detergents in hydraulic oil. Might have been whale oil from before the great depression by the way it looked.

Tell them not to mess around submerging it. Don't "drop" it in the oil, use the tongs to get it under then let it go.

I always use tie-wire or a coat hanger wire to suspend the part and make sure to vigorously agitate in an up and down motion the part while it cools from red hot to a few hundred degrees. Just dropping it into the oil allows oil vapor to coat and insulate the part leading to slow and uneven cooling. Agitation is important. I have tested non-agitated parts vs agitated parts. The non-agitated parts often don't achieve full hardness. Bryson talks about the importance of agitation (as do almost all authors writing about the subject) in his book on heat treating.

Denis

Added later: If I am making a smallish part that does not have a through-hole or appendage for convenient wire suspension, I often turn and mill the part but leave it attached to the tool steel rod by a thin neck. This makes it easy to hold the rod and heat just the part as heat does not conduct through the the thin neck well into the rod. Then I just hold the rod and dunk and agitate the part in the oil. Then I just saw off the he part or bend it back and forth to snap it off the rod. A touch of the grinder removes the nib.

A lot of knife guys use Canola.Cheap, easy to source, high flash, non toxic, easy to dispose of. bb

Quench Oil

Something like this is what I use. I fabricated a 20 gallon tub and use a round french fry basket with a wire handle to submerge my parts. After they cool, I hang the basket on a hook above the tub on a drip shelf and let it drain. I can unwrap the foil and never get a drop of oil on the floor.

cyberslick18 said:

The parts are small, generally 1" to 3" diameter bushings.

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Sounds like you don't need anything larger then 15-20 gallon fluid tank as the only steel you mention in the original post are air harden steels. The O-1 is oil quench, where I worked we had 4 vats 200 gal. Each for quenching. 2 were for oil quench and the other 2 were brine for water quench, the oil vats had covers in case of a surface fire but as long as the oil temp is not very high there was no concern. All 4 vats had circulaters in them and all 4 had chillers and were held at a specified temp. We ran 40-50 tons of steel
Through the heat treating room each year, and there were chain hoists from the furnaces to the vats for transferring the work.

Back when we did a lot of oil quenching, it was in a quench furnace. Not cheap unless you do a lot (1/2 ton loads).

We used Mobil Fenso 51. IIRC, smallest quantity was 55 gal drums.

Canola oil is actually one of the easier burning oils. Corn oil, soybean oil, and safflower oil are all better in ascending order.
JR

JRIowa said:

. <Snip>

Canola oil is actually one of the easier burning oils. Corn oil, soybean oil, and safflower oil are all better in ascending order.
JR

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You sure about that? See flash points here. Page not found | Baseline of Health. Not that burning tendency matters much as noted in posts above.

Denis

Just remember that if your parts are small, you can superheat the oil if the batch numbers are large, and the tank isn't big enough. A well known blacksmith in the Seattle area burned his large shop about three months ago due to a quenching accident.

E.F. Thumann said:

Just remember that if your parts are small, you can superheat the oil if the batch numbers are large, and the tank isn't big enough. A well known blacksmith in the Seattle area burned his large shop about three months ago due to a quenching accident.

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I agree that it is not hard to overheat the oil in a production situation, so it's prudent to keep an eye on the oil temp. I have had to use larger containers in that situation,

If you and I are thinking of the same fire in Seattle, that was due to sleeper sparks from welding per reports of the owner that he posted on list that I am a member of. Monster Metal Shop Fire :: Northwest Blacksmith Association

Denis

A2 and D2 are air quench steels, we don't use oil at all for them ...

I use peanut oil for O1, has a high flash point and it makes the shop smell good.

And I don't fret about dumping it in the compost bin when I'm done. Just a quart or so a year though--high volume would be a different story.