bad day in the shop

wmhammond

wmhammond

Well-Known Member
Today I started a shortened Chef's knife (8") out of .108" 1095 that I purchased expressly for that purpose. Why 1095? well, a Hamon, of course. Well, I cut it out, perfected the profile, drilled the pin holes and ground it down to 220 grit. I left the edge as thick as I could (about .05"). Then I applied my clay and let it dry thoroughly dry. Heated it up and quenched the blade in 140* 20% brine solution for 3 seconds and then into 140* Canola Oil until "cool". Laid it out on a towel to soak up the oil and then put it on my concrete shop floor to really cool, Came back in 15 minutes and it looked like a potato chip with about 5 cracks on the blade edge. I'm going to try it again tomorrow and my only thought is to heat treat it before I grind it at all. Got any suggestions? Thanks,

Wallace
 
Man that stinks! Do you think you just ground it too thin? Did you notice is start warping during the quenches or only after is completely cured? I feel fortunate I guess, my day is coming I'm sure, but I have yet to have a blade warp during heat treat. So, when it happens to someone else, I always listen for clues and tips so it doesn't happen to me. Got any pics of the first try?
 
I don't think that I would have laid it down on the shop floor. I put my blades on a cooling rack to air cool.

Doug
 
As soon as I read the "brine" part, I knew what was coming! OUCH! I totally agree with Doug..... that concrete floor is a giant heat sink. The other suggestion I would make is....that as soon as the blade is cool enough to handle, into the temper oven it goes.
 
I also think laying it on the cold floor had something to do with it,I also use a rack on top of the warm oven and as soon as its cool enough to handle it gets tempered.
 
Just to backup what's been said, I'll tellyou what I did ONCE..... was hardening 2 nice Bowie blades of 52100. I finished quenching just about the time my Mrs. got home from work... I left those blades laying on the bench, with the tempering oven warming up, and totally forgot about them until after supper (about 2 hours later). I ran back to the shop, thinking I would get them in the oven.....NOT....both had multiple fractures all along the edge, about 1/3 the width of the blade..... learned my lesson! :)
 
EdCaffreyMS said:
As soon as I read the "brine" part, I knew what was coming! OUCH! I totally agree with Doug..... that concrete floor is a giant heat sink. The other suggestion I would make is....that as soon as the blade is cool enough to handle, into the temper oven it goes.
Click to expand...

Ed, should Wallace not have used the brine solution?
 
Jason:
Personally, I don't recommend brine quenching for any "knife" steel..... its generally a 50/50 chance of destroying something....at least in my experience. The other part of the equation is to get a blade into the tempering oven ASAP after hardening. Quenching any type of hardenable steel introduces a great amount of stress into the material, and if allowed to linger, those stresses do nothing but create problems....on the mild end would be warping, but often it causes stress cracks/fractures. which is what I suspect occurred in this case.
 
Hey guys, here are some pics of the blade. I always temper as soon as I can handle them but occasionally when I take them out of the oil they are still to hot to handle. I have done several knives this way and have only had problems when the knives were bigger, thinner kitchen knives. As I mentioned, I was clayed up and shooting for a Hamon. I thought I had to go brine/oil to bring out the Hamon on 1095. Can I get the Hamon without the brine. The other picture os of a thicker knife (.188") that I HT'ed the same way and it came out unscathed. Thanks for all the help.

Wallace

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Way back when I got some 1095 from Admiral that would not harden in oil, I think that I was using Goddard's Goop at the time, and I could only get it to harden in oil. If I had known more about heat treating I would have thrown out the Goop and gotten some canola oil which might have worked. Now there are makers out there who really love brine for quenching with the steels that they use but I'm with Ed, it doesn't make sense to add more stress to the system than is needed to get the job done. I also have my tempering oven, my kitchen oven, ready to receive the blades before I start quenching.

Doug
 
Here you have another trade off. As I understand it brine will give a better hamon than canola oil will but brine will give you more broken blades unless you are very careful in your prep to reduce stress risers. Another, and probably better, route would be to get some professional quenching oils that are designed for shallow hardening steel, something like Parks #50. There are other quick oils out there but Parks is the only one that comes to mind. Maybe some other makers could add to the list. Of course you could also look at a different alloy, something like Aldo's 1075 which is good at producing a hamon. Or you could pass on the hamons and get an alloy with more hardenability.

Doug
 
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