Question about A2 steel

[KSCATTRAPR]

A few years ago I was given a couple pieces of A2 to try out and I constructed a couple really nice blades from the pieces. Being new to making knives, which I am still really new to the art, I just assumed you heat treated all steel the same. Back then I made all my knives out of old files and didn't use any other steel. When I heat treated the blade, I heated it up until it was non magnetic, then quenched it in old motor oil. After the blade cooled, I used a torch to "chase the colors" on the blade. After this was done I finished the blade out. This knife holds a tremendous edge, much better than any other knife I have made and over the last few years has cleaned a lot of animals. I thought it might be a fluke but both blades have been put through a lot of work and held up wonderfully. I gutted and skinned a deer this last weekend with it and after all the cutting I did with this blade, hair, meat, and some bone, the edge was still sharp, not quite shaving sharp, but it could have easily cleaned a few more deer. This got me to thinking....

My questions are:
Is it ok to quench A2 in oil and still get a good knife?

If A2 is supposed to be air hardened, why does this blade hold an edge the way it does?

Being curious about this steel I have read up on it and some makers heat the blade up to a certain temp then let it air cool. Is this the proper way to heat treat A2?

I thought maybe the steel was something other than A2 but after checking with my cousin who I received it from, he was certain that is was in fact A2. Any help or explanation would be appreciated, I know a little about different metal make ups and how to treat different steels but this one is beyond my knowledge. Thanks.

[kbaknife]

This might be a really goofy answer - and I may be way off the mark - but I don't think so.
A2 is an air hardening steel. It has so much chromium that it takes a long time for the austenite/martensite conversion to take place, so, in fact, the method of cooling is not critical, as far as quick speed is concerned, to avoid the steel reverting back to pearlite.
Truth is, used motor oil is pretty worthless as a quenching oil and is not efficient in quickly lowering steel temp. So, you did not, actually, accomplish much in the way of reducing heat with the used oil.
So, ultimately, you simply sped up the cooling process faster than air, but no so fast as to induce problems into the mix.
Had you quenched in a fast metallurgical steel quenching oil, you may very well have ended up with a whole bunch of little knives.  
To get A2 into austenite before air quenching, so it can turn into martensite, it needs to soak a bit around 1750-1800 degrees for maybe 10 minutes to get the carbon into solution through all that chromium. So, you also escaped problems there by not having a fully austenized blade to begin with.
As well, it's really hard to say what you have as a result.

[kbaknife]

Used motor oil is not designed to be subjected to 1500 temps.
That is not how it is designed.
So when you place a piece of hot steel into it, there instantly becomes what is called a "vapor jacket" surrounding the blade.
The fluid simply vaporizes because of the intense heat, and, in fact, the blade is not touching the oil at all.
It's simply surrounded by a vapor, which does not extract heat well at all.
So the steel is basically cooling in "air" anyway.
That's what makes quenching oils extract heat - they have additives that eliminate that vapor jacket and the fluid is in direct contact with the quenching oil which is really sucking the heat out of the steel quickly so as to inhibit the austenitic steel from reverting back to pearlite, which is worthless and soft.
Your motor oil did little to change anything. But you would not have had austenite very much to begin with unless you were up near 1800 degrees.
Non-magnetic is about 1418.

[kbaknife]

https://www.crucible.com/eselector/general/generalpart2.html

[kbaknife]

duplicate post

[KSCATTRAPR]

Thanks Karl, I appreciate the response.