All the cool kids are doing it, water quench

B

Brad Lilly

Moderator and Awards Boss
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Can you see that stupid little line?
I had a small tool box given to me full of various odds and ends one of which was a worn out black diamond file. A bunch of helpful knife dogs gave me their opinion that this file was most likely w2. So I thought this would be a great item to try and get a hamon line on, before I waste a bunch of money on quality steel. I ground the teeth out and forged the knife to shape, rough ground it and put it on my shelf for a month or two. Finally I decided I should heat treat this thing and see what happens. I use veterinarian grade mineral oil heated to 120 deg for quenching. Some day I hope to get the real stuff but I have had zero luck trying to get commercial quench oil. I could not find any of the proper clay for the coating so I used Home hardware brand furnace cement. The first time I quenched the blade I had a great hamon line roughly 1/8" from the edge. I scratched my head for a while and thought I must have extended the cement too close to the edge. Back to the forge to normalize and try again. I kept the cement a little further back but I had the same result. Maybe I did not soak the blade long enough, try again same result. I tried coating a little less, heat a little longer and I still could not get this blade to harden any more than 1/8". After the fourth unsuccessful try I decided to try water, I figured my oil was not fast enough to quench the blade in. I did a interrupted quench 3 seconds in 120 degree water and 10 minutes in oil. I think I got it finally to hardened up. The moral of the story Files are evil things:) Oh and some times pigheaded determination pays off.

I hope to do a WIP on the handle.
 
Yep, I see it... should make for a great looking blade and way to stick with it on the HT!
 
What is happening is that you are using a shallow hardening steel. With something the thickness of a knife blade, less than 1/4" or 6.35mm, there is little difference in the rate of cooling between the inside and the outside of the steel. The big difference is between the thin and thick parts of the blade. Towards the edge the steel is thin enough that it will cool quickly enough to form martensite. Towards the thick parts of the blade, the spine and the tang, it will not cool quickly enough to form martensite due to the mass that has to be cooled and will form pearlite. It's not going to matter where you put the clay with this steel unless you get really close to the edge. If you are wonder why then did the file harden, it was because it was thick enough, approximately greater than 1/4" or so, that there was a greater difference between the rate of cooling of the outside and the inside of the bar and you ended up with a martensetic jacket around a pearletic core.

Doug
 
blacks diamond files arnt really W2..Ive seen several spec tests results done on them..Its a fairly basic carbon steel but with way more carbon than W2..Upwards of 1.27% on the ones Ive seen..
Something like this..(credit to Matt Bower for this reading)
C:1.28 | Mn:0.34 | P: 0.016 | S:0.015 | Si:0.15 | Cu: 0.02 | Cr:0.14 | Mo:0.005 | Ni: 0.02 | Sn: 0.002
 
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The reference material that I have for the W series of steels as having carbon from 0.6% to 1.40% so, without the vanadium, what you are showing is W1 with just a tad bit of silicon; for deoxidation and depth of hardening and tensile strength, and chromium; for depth of hardening. If you use it I'd watch the temperature and soak time to reduce the retained austinite.

Doug
 
I normally shoot for about 1440-1450 and a 5 minute soak for these steels..W1,W2 and 1086M as well as files when we use them..Ive also found that most of these (good quaility) file steels will produce a very nice, very active hamon with this heat treat with almost no effort..Like Don Hanson told me "less heat, less clay" then howard Clark told me "less etch, more polish" Both are very true in my exp..
Here is a plain working knife made from a black diamond file..Wasnt even trying for a hamon really..No clay, just temp control..Not even polished, just a machine finished to 400 grit and polished with a med grit scotch brite belt..No etch either and still the hamon pops with activity..I would have like to seen it hand polished..
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Despite not being a space age quenchant, water works great. Nice looking blade btw.
 
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