Quenching: Water or Oil?

[bigfootnampa]

About the oil mix,
The oils you mention earlier I have not seen anywhere here. But then again, we don't have stores like Brownell's here.
I have a couple of liters of sunflower oil at hand. Someone on another forum said to use a mix of 50% sunflower oil and 50% mineral oil. Why the mineral oil? or would simple sunflower oil be fine?
I have seen different grades of viscosity, I think this goes for mineral oils as well. would it be better to use to use an oil with a low (like 5W-30) or high (like 15W-50) viscosity, or doesn't viscosity matter with mineral oil? Or would it be better to use mineral oil entirely?

Here I go with all my questions again But the whole mineral oil / viscosity thing got me thinking now.

Louis

I have used linseed oil which worked very well, and motor oil which is also fine... I can't see why sunflower oil wouldn't work well. Temperature has at least as much effect as viscosity rating. My advice is to use what you have.

[Mainely,Bob]

For safety you need to be concerned about the ignition temp(flash point) more than anything else.
I was using peanut oil and some folks I know use canola oil but I`ve since gone to marine hydraulic fluid as it is fire resistant and I got it for free.It seems to be working very well but doesn`t smell as good as the cooking oil.

[MattBower]

As long as you're using at least a gallon of oil per pound of steel (which appears to be the standard recommendation in the industry), and letting the oil cool back to a proper quenching temp between uses, I don't see any reason to get wrapped up around flash point. Most commercial quench oils seem have flashpoints in the 280 F to 450 F range. Your quench tank should be metal with a fireproof lid, so you can snuff out any flare-ups that do occur, and it should be something that won't tip over easily. That said, although a little surface flare during the quench isn't uncommon (or a lot of surface flare if you're into edge quenching -- which BTW is very hard on your quenchant), it'd take some pretty severe abuse to get a full tank to sustain a burn. I personally don't let flash point drive my decision making about quench oil; my first concern is whether it has the right cooling characteristics. Obviously I don't use materials with absurdly low flash points -- gasoline might have a great cooling curve, but obviously that's just not gonna work -- but anything in the ballpark of 300 F or up is OK with me.

[pkrankow]

As long as you're using at least a gallon of oil per pound of steel (which appears to be the standard recommendation in the industry), ...

I've never encountered this statement. I have been looking to estimate how much oil I need for general tasks and never found a recommendation.

Phil

[MattBower]

I got that from Scott MacKenzie, who's the technical guy (metallurgist) for quenchants at Houghton. But I'm sure I've also seen it in writing elsewhere. In any event, Scott's a very reliable source. The bottom line is that you want sufficient volume of oil to prevent an excessive temperature rise during the quench. Apparently a gallon per pound is usually enough, though I typically use more. (I have a three gallon tank and I rarely quench anything that weighs three pounds.)

[30cal_Fun]

I've never encountered this statement. I have been looking to estimate how much oil I need for general tasks and never found a recommendation.

Phil

Me neither, but I have wondered about it often. Good to know.
I have never weighed my blades, but since I only forge small blades up to Tanto size, I think I would hardly need more than one gallon.

Having read all of the above posts, I think I will stick with my sunflower oil. My backyard will smell like French fries when I am done quenching.

Louis

[MattBower]

I have a couple of liters of sunflower oil at hand. Someone on another forum said to use a mix of 50% sunflower oil and 50% mineral oil. Why the mineral oil? or would simple sunflower oil be fine?

Sorry, I missed this question at first.

Aim for about four liters of quenching oil per 500g of steel.

Generally speaking, a lower viscosity oil will be a faster quenchant than a higher visosity oil. If you were quenching shallow hardening steels you'd want to stay away from viscous oils. (One reason we normally preheat quench oil is to decrease the viscosity.) But 5160 does not require an especially fast quench. As I said in an earlier post, I suspect its popularity for blades may have something to do with the fact that it will harden reasonably well in relatively slow quenchants (which describes a lot of the junk people sometimes quench in).

As best I can tell, sunflower oil is probably a pretty fast quenchant. Cutting it with mineral oil will slow it down some. For 5160 that might not be such a bad thing.

[30cal_Fun]

Hi Matt,

Thanks for the reply.
Oh, and don't worry about gallons to liters or anything, google solves whatever I might not know

In addition, I might try interrupted quenching to aid the clay coated blade in differential hardening.
I hope the weather gets better this week, I can't wait to start building my forge!
Here is a drawing of what I intend to build. Every square is 2x2 inches, so the scale is 1:10.


Louis