For  hardening, what type should you use?  I was wondering if motor oil (used or new) or something like canola???   Thanks for help.

Check out the heat treating section, this is well covered, keep off motor oils especially used, loads of additives and potential toxins.

Every now and then I pump out a knife shaped object. I don't let any thing near them that isn't food grade. Personally a food grade oil would probably be your best bet.

WHAT ARE YOU TRYING TO HARDEN?  Knife, sword, ANVIL. tooling?   Alloy and Size of the object do make a difference.  Do you need a fast oil or a slow one?

 

But as mentioned stay away from used motor oil; not only the toxins from quenching but it's not very nice if you plan to use a kitchen oven to draw temper.

Is used canola oil ok or does it contain unwanted impurities?  Using to harden 5160.

There is proper quenching oil. Different cooling rates. I have drums of two different grades.

Drop over and get some. :) :)

 

Neil

used fry oil is generally ok; you will want to use it warmed to about 140 degF  Should be OK for 5160---what size item?  You will need a LOT of it for large items.  Beware of flare up when quenching hot steel---get in under the surface fast!  Make sure it's in a metal container and have a lid to cover it to put out a fire.

If you search the forum using the keyword quenchant you'll get a lot of good hits including ideas for a quench tank.  Learning how to use the search facility makes everyone's life easier.

I use canola to quench my 5160 blades.  If it's fairly new and clear, should be good; if it's dark and kind of murky, better to get fresh.  Preheat a bit to around 120 to 130 Fahrenheit.  You can also use mineral oil, and preheat closer to 150 to 160.  The mineral oil's a bit faster, but canola seems to harden nicely on 5160.

Thanks for responses everyone.  I lost the thread after it was moved.  This is indeed for blades and thickest would be around 3/16".  I have an old CO2 tank from mig welding that has been retrofitted into my quench tank.  Have been using used motor oil, but you guys have enlightened me and I will be switching to canola most likely.  Tank holds around three gallons, so the commercial ones can get pricey!

Kayakersteve,

If I remember correectly  you posted this in the blacksmithing threads. I was not sure exactly what you were going to quench and I sent you a private message asking you..After a day or so without a response i moved the thread on a wild guess it was about knife blades.

A lot of folks post incorreectly in the blacksmithing area. Maybe it is because it is the first place on the home page.

A good reason to look before posting is that some folks just follow certain areas as that is where they look and respond. 

This thread had good responses and seems like it answered your needs.

 

moderator51 - You are correct that I seem to have posted in wrong area - I am still getting used to site and it took a few days to even find that I had a PM from you.  - I appreciate your directing me and will review more moving forward to save you guys from doing unneeded work.

here are a few quenchants and their relative speeds

• Brine, 5-6 seconds

• Canola oil, 10-11 seconds

• Chevron Quenching oil 70, 10.5 seconds

• Citgo Quenching Oil 0510, 14.5 seconds

• Drasta 119S, 13-16 seconds

• Drasta 117S, 8-12 seconds

• Duratherm G, 11 seconds

• Duratherm Superquench 70, 10 seconds

• Gloc Quench A, 11 seconds

• Gulf Super Quench 70, 11 seconds

• Houghton G quench, 10-11 seconds

• Houghton K, 7-9 seconds

• HP Metaquench 39 14.6 seconds

• HP Metaquench 42 14.2 seconds

• HP Metaquench 43 12. seconds

• HP Metaquench 44 8.9 seconds

• McMaster quench all, 28 seconds

• McMaster quench fast, 11 seconds

• Parks 50, 7-9 seconds 280°F

• Parks AAA; 10-11 seconds 340°F

 

 

Mr. Sells Sir,

Your chart is marvelous.  Thank you very much for it.

SLAG.

Yes, thanks much for the list.  One question of clarification though.  What does the time rating represent?  Is it time from quenching temperature to quench medium temperature or to another point in the sub-critical curve?

The ideal quenchant is one that exhibits little or no vapor stage, a rapid nucleated boiling stage and a slow rate during convective cooling.  This is why most experienced smiths advocate the use of commercial quenchants over used fryer oils.

Quenchant speeds are a standard measurement based on the time it takes to cool a 7/8 inch (22mm) diameter nickel ball from 1625°F to 670°F (885°C to 355°C).

 

this has been another teaser from my new book Knifemaking 2.0

 

Thanks for the teaser (answer).  Looking forward to the new book. 

But do any of the commercial quenchants make you shop smell like a deli or doughnut shop?

On the serious side. Drats, I reread your post and you answered my only serious question in the last sentence. You reading my mind again?

Thanks Steve.

Frosty The Lucky.

On 8/15/2018 at 12:41 PM, Steve Sells said:

Parks 50, 7-9 seconds 280°F

Parks AAA; 10-11 seconds 340°F

Forgive me Mr Sells if this was covered elsewhere and I have not found it yet or if this is something you would rather I read form your book, but how would I know what works best for the steel I am using and the project I am working on? If it is elsewhere could you help me find it? I am struggling to find what I am looking for using the search. I was wondering if there was a chart somewhere that equates the speed of quench to the hardness for different steels? Or is it really just use certain quenchants for certain steels?

the spec sheet you can get when you order steel should  have information about how fast you need to cool the steel for proper hardening.

Its  over simplification but as a general rule oil hardening steels are more than 10 seconds,  water hardening steels less than 10 sec

On 5/4/2020 at 10:20 AM, Steve Sells said:

the spec sheet you can get when you order steel should  have information about how fast you need to cool the steel for proper hardening.

Darn I was hoping there was something like the steam tables From thermodynamics. I am pretty broke and most of my stuff is found metal. I occasionally know the series but not much else. I was hoping to narrow down some of it with some quench tests and cross referencing. 

Thank you so much for your help and for your knowledge! I really appreciate everything you bring to this environment! 

remember when quenching thin objects such as knife blades these times will be much faster, which again, is why we have a separate area for heat treatment of blades in the first place

Yes; when hardening thin cross sections; alloys often shift "one quenchant over"   Why so many people get surprised to find their oil quench steel  air hardening when they didn't want it to!

Gurus out there -- if I have this wrong, feel free to chime in...

There is a simple test procedure for figuring out mystery steels' quenching/hardening types:

• Quench it in air (let it air cool), then test with a file, if the file skates across the steel without cutting into it, it's hard -- i.e., an air-quench steel. If not, move to water.
• Quench in water, test with a file -- if it skates, it's a water-quench steel. If not, move to oil.
• Quench in oil, test with a file -- if it skates, it's an oil-quencher. 

If none of the above work, you probably have mild steel that won't harden. Use it for mild steel applications. The test procedure above is a quick way to roughly identify mystery steel's hardenability and quenchant 'preference.' Beyond those too-simple steps, it gets into the weeds with exactly which quenchant you'll need for the specific steel (and thickness / cross section) you're quenching -- keep experimenting, or just get the correct data for known steels.

Yanni, if this testing is being done on the same sample, I’d go: Air, Oil, and then water. If it will harden in oil, it will harden in water and possibly be destroyed. (The argument can be made that testing the same sample over and over with change the result, but if you going this route, you’re only looking at basic “it got hard!”)
 

Keep it fun,

David

edit: not a guru, just my two cents…