DOMO?

[Bruce Macmillan]

I'm a little sheepish about asking this after 30+ years of metal working....Lately I've had bad luck getting steel hard in oil......Is dirty old motor oil a bad choice for this? I've had lots of successes with it in the past but lately not so much.....I'm not looking for allot of technical info aside from which oil would be best....just a simple yes or NO you IDIOT will do......

[JNewman]

What kind of steel?

[Grant]

I think most oils work best when heated to 100º or so. Getting cold there, is it?

[David Einhorn]

...Lately I've had bad luck getting steel hard in oil..

The answer is, "it depends". If you are trying to harden plain structural steel/mild steel in oil, that will not work. Mild steel does not have enough carbon in it to allow it to be hardened in plain oil or water. To harden mild steel you will have to use a formula called "Super Quench". To harden steel such as tool steel, which are designed and formulated to be hardened, you would use the liquid recommended for that specific type of steel.

If you want more useful answers, then you will need to provide us with specifically what type of steel you are trying to harden, *and* the application of the finished product because different tools/products require different hardening **and** tempering.

[Bruce Macmillan]

Question answered, nobody said DOMO is the choice of idiots.....That being more or less established I'll continue to use it.
I learned quickly that mild steel can't be hardened, unless you don't want it to, eg; after forging an ornamental element in ''A36'' you make the mistake of quenching it in water.....Then it breaks when you bend it cold.........Back in the 70's when I started a36 was 36, now it's a crap shoot as to what's in it, so beware....and let it air cool....
The term ''steel''was too broad, myself like many others jack around without knowing exactly what you're dealing with......
The event that promted this question was after seeing a thread at IFI on RR track cutters it re perked my interest in the several I've had kicking around forever. The one I decided to fool with has ""alloy''stamped in it so I decided to employ my usual routine, cut off the ends (which left me with the hammer shape I wanted), and test the drops. First air, then oil, then water. When I tried that on the test chunk the oil didn't work so on to water....It cracked, so what then........In my frustration I figured skrew it maybe the larger mass will prevent cracking??? Hammer head to water. It got kinda hard but didn't crack, so I decided to leave it as and use it....Maybe the stars aren't aligned??? It was around 1500* when I quenched it.....I hate chasing my tail...........I loathe rhubarb too.

[JNewman]

There was a recent article in Industrial Heating magazine about using vegetable based oils as a quenchant. I only got around to skimming the article, but it mentioned that vegetable based oils were a faster quench than mineral oil quenchants. I don't know where motor oil falls in quenching speed. http://www.industrialheating.com/Art...00000001097301

[Greg Obach]

i use canola for alot of knife steels... but then again knives are a thin cross section and its not too difficult to remove the heat from it
- to be honest, you have to know the alloy make up of the steel to guess whether water,oil, or air would be a good quench... and then do not forget to temper it after to relieve some stress ...lose some hardness in return for some toughness....

myself, i don't have anything good to say about old motor oil..

i'd rather use old peanut oil from the chip stand... at least it'll smell better when you quench


Greg

[Francis Cole]

years ago I ran across an blend of diesel fuel 1 part and used motor oil 2 parts it has worked very good for me.

[Grant]

Many years ago I worked in an old (Norwegian) blacksmith shop and we had a tank of fish oil. Read some technical stuff later that rated it very highly for a quench oil, gave very consistent (and fast) results over a wide temperature range. Only a Norwegian could appreciate the aroma!

[Gene C]

ya sure you betcha