Differential HT, or more importantly, water quenching help

J

James Hall

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Sep 18, 2013
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I'll start by saying that after messing up 1095 in the past trying for a hamon, I've done a bunch of research.

I've got some of Aldo's 3/32" by 2"1095 and I'm trying to make a 6" funayuki/small gyuto style blade. As much as I'd like to clay up a blade, I realize that I'm not quite ready yet. I took a blade through some thermal cycles tonight and I'm getting much more confident with bringing it up to temp slowly and uniformly. My limiting factor at the moment is budget, which won't allow for Parks 50 or other engineered oils right now.

After some reading, I understand that regardless of clay or no, differential or full hardening, the most important factors are temperature and time. Assuming I can get those to an acceptable precision along with proper blade prep (finish, no stress risers, etc.), is there anything I can do to prevent cracking during quench?

My goal is just to get a good heat treatment to get the foundations down. The blade will be unground, and if I even go for a hardening line it will be unclayed. Despite the thin stock, I'm assuming that supermarket oils are still out of the question, however would a quench in water be enough to get under the curve before moving to oil? Or should I just man up and keep it moving in the water until it's cool? Or am I overthinking everything? I've read a ton of posts on this, but they all have slightly different information and are usually for thicker knives. As always, I appreciate any help. You guys are awesome.
 
When trying to avoid cracks in thin 1095/W2 blades and water quench, I find that prayer helps. :)

Seriously, you will loose a lot of blades to start with. It will get better, but it never really gets to be a guarantee. I think in the beginning, clay helps. Also, water is a term..it is actually a brine quench.

Switching to Parks #50 and clay is where most folks go to stop the broken blades.

Get the lowest Mn alloy you can find. Aldo no9w has Hitachi Blue...which is really nice for a Japanese blade.
 
Thanks for the advice. On the plus side, thinner stock means new blanks are easier to cut after you mess up.
I'm assuming you mean a thin clay on the whole blade as opposed to thick hamon clay for preventing cracks?
 
I have messed around with water quenching....

To start off, I agree with Stacy. I have broken and cracked lots and lots of blades to water and trying to get something to work. Once you pull the trigger on some Parks 50 you will wonder why it took you so long to do so. But having said that I hate being told not to do something when it should work so here is what I learned with water quenching:

What seemed to help was using hot water, for me at least. But that doesn't take away the cracks just helps bring it up to a 50:50, for me.

I have also tried the interrupted quench. If you do that right you also get away from some of the cracks but you still loose blades. ( I am not very good at the interrupted quench, I lost a lot of blades chasing that)

Another thing you could do is use the hot water, get the steel under the temp that you need it to get under in the time it needs and then put it between some Aluminum plates. I have had good luck with that as well. ( Helps with some warp issues as well)
 
I have found 3 seconds in, 3 seconds out, 3 seconds back in, then take out any warps by hand. Alternatively, 3 seconds in, 3 seconds out, then finish the quench in heated canola. I use DT-48 now, which is basically the same as parks 50.
 
Thanks for the help, I've got two blanks coated with a thin slurry. I'll HT tomorrow and let you know how it turns out.
 
Well, both blades survived the quench and skated a file really well. I heated a bit past non magnetic and quenched for about 4 seconds in 3 gallons of warm 9% brine, 3 seconds out, and finished the quench in heated veg oil. The first blade had clay about as thick as the steel. The second had only the slurry and warped significantly (probably because I went back into the brine with it). It also cooled as I was trying to straighten and snapped near the tip.

On the bright side, the grain was pretty fine and the edge was super hard. I don't think a 50% success rate is too bad to start.
Thanks again for the tips.
 
James Hall said:
I'll be getting around to it. is there somewhere you'd recommend buying from?
Click to expand...

Maxim Oil. Parks 50.

I am curious about what you did to straighten it. I have had to straighten a Sh*t ton of blades and haven't broken any and some of them were bananas.
 
I have a 1/4" by 2" piece of steel that has a bend at one end. Clamping the blade to the flat during temper gets rid of gradual warping and using the curve helps with anything drastic. I don't clamp during the first temper cycle, and if it needs more straightening I just tweak it and put it in for another cycle. I'm curious about what method you use though.
 
James Hall said:
I have a 1/4" by 2" piece of steel that has a bend at one end. Clamping the blade to the flat during temper gets rid of gradual warping and using the curve helps with anything drastic. I don't clamp during the first temper cycle, and if it needs more straightening I just tweak it and put it in for another cycle. I'm curious about what method you use though.
Click to expand...

It sounds like I do something similar to what you do.

I temper the first cycle with now clamping or whatever. Let cool. Then I use angle iron, c-clamps, and spare change to make shims. I shim the bent/warped area and then clamp it right onto the change and then use the other clamps to bend just past straight and temper it for two hours. I take it out and let cool to room temp and then unclamp it. I might have to do it two times but I have been having really good results doing it that way.
 
No need to let it slowly cool to room temp. Better if the whole clamped up jig is dunked or rinsed with water. This sets the martensite a bit firmer and avoids any other transformations. It is not a quench as in HT ( which may cause warp or cracks), but a rapid cooling from temper, which is actually beneficial.
 
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