harder than hard?

[Coutel]

Hi guys...I wonder if someone could help explain something for me...

I know some makers quench in oil, some in water and some in a mixture of both.
I am a bit confused.

Some makers say they like to quench in water because it makes the steel 'harder'.

I dont understand 'harder'?....If I am quenching in oil then tempering and getting between a 58 and 60 on the RC scale surely thats hard enough?....any harder would defeat sharpening and may cause edge chipping.

So WHY do some makers quench in different mediums to get an exceptionaly 'hard' blade only to reduce this hardness by tempering to equal what others are doing with a blade that wasnt quenched quite so hard!!!!!... what is the definition of 'hard'.

I have never quenched in water...I use warm peanut oil and I always seem to get good results.....

:confused:

Thanks.

Kevin.

[Gabe Newell]

Selecting a quenching medium isn't a function of eventual hardness so much as it is the steel being used (since, as you point out, the goal is the same hardness range).

Different steels need to be cooled at different rates in order to effect matensite formation.

O-1 is typically quenched in oil. W-2 is typically quenched in water. A-2 is quenched in air.

Of course there are a zillion people here who can give both a more detailed and more accurate explanation.

A favorite resource of mine on metallurgy is:

Kevin Cashen Metallurgy Article

[Coutel]

Gabe.

Thanks for your reply and the link you posted.
I need to read it and take it all in before I ask any other questions

Thanks again.

kevin.

[Philip Lee]

Hi Gabe,

Greetings from Fiji.

Yes there is alot to be said about quench medium,. when we say water some steels like 1095 needs to be cool below 900F in 1/2 second otherwise you would get pearlite than martensite. Thus using water heated to 180F would give you a better chance of forming martensite. Obviously the design and the size of the blade has alot to do with quenching medium. I personally have used Brine, water and oil for 1095, i find with brine and water the steel is harder , the knife if tempered at the same temp for oil quench would produce a harder blade and the knife would be great for slicing and slicing, definitely not for chopping.

I made my wife a knife out of an oil Nicholson file , i quenched in oil then did two temper cycles of 1/2 hour each. The blade is holding its edge exceptional well even vigorous cutting for 2 months through meat , vegetables everyday.

Typically 1095 is brine quenched, I cracked a few blades with water simply the temp of the water was too cold. Before the quench i hone a razor edge on the blade so when i harden it i don't have to work hard to sharpen it.

Good luck and i just wanted to give you my thoughts.

Philip Lee