Heat Treat Woes!?

L

lostinthewoods

Joined
Dec 12, 2013
Messages
3
Hello all. I have been lurking here for quite some time and have learned ALOT from the members here already. I have made several knives over the past couple of years. I decided to make a few knives as Christmas gifts this year. I'm making a bushcraft style knife for my oldest son as a first "real" knife. The blade is of my own design and is about 4.38" long and 1/8" thick 1095 CRA steel.


{The center blade is the blade I'm concerned about, the top blade came out at 56 RW beautifully, the lower blade is 46 RW and is destined to be more of a display knife than a work horse so I'm not too worried about its hardness)


{This is the blade following HT prior to temper}



{This is the blade following the temper, by all rights I think it looks perfect in color etc.}

I heat treated the knife (as I have my past knives) with the following procedure:
1. Heated the blade in my forge to non-metallic (approx total time 3min 30sec)
2. Quenched the blade in 135* canola oil
3. Tempered the blade for 2 hrs @ 400* in oven, then cooled slowly to room temp and tempered again @400* for another 2 hrs.
4. Cleaned and polished the blade and is now ready for scales.


{this is the blade polished and ready for scales.....so I thought)

........ Today at work we had a NDE inspection guy from our inspection group come in to train a few of us. In his goodie bag he just happened to have a unltrsonic hardness tester. Through a little sweet talk I was able to twist his arm into testing my new made knife. I was expecting somewhere in the 50-65 range (a mill file dances nicely off of the blade) ......NOPE! 42 on the Rockwell scale (+/- 5 to 10%):confused::confused::confused:

Now I'm bummed! I would like this knife to become a family heirloom for my son but I've screwed something up. I don't like the idea of doing a brass rod test to clarify these results. I can re-HT the blade (although not fun, but dooable with no real damage to the blade) and just clean it up again. I think this is the best idea.

I have researched some more and think my soft blade may be from my tempering process as I think I may have over heated the blade during the temper.

Here is my plan as of now:
1. re HT the blade as before
2. temper in a 315-325* oven for 1 hr 3 times
3. then re-polish and then add scales and finish the knife

What do you think? I'm open to any questions, comments, or criticisms that you more seasoned bladesmiths may have.

Thanks in advance,
lost
 
Why don't you do as before at 400f but only do it once.
Ever thought about using clay on the edge to reduce the heat to it?
Although a drastic move, I once bought a toaster oven at a garage sale and cut a slot in it so it could hold the edge on the outside of the oven for most of the soak time.
I like to experiment!
 
My first question is; what did you test the 56 Rc hardness with? I don't remember the details, but as a "general" rule those ultrasonic hardness testers don't work very well for knife blades do to the thin blade. Since you've got the blade to this point, why don't sharpen and do the brass rod test?

BTW, just what is CRA steel? "Corrosion Resistance Steel"?

I don't think your tempering temperature is the issue, 400ºF should give a fully hardened 1095 62-63 Rc. Even at 650ºF would still give over 50 Rc.

Check this link for heat treating info on 1095: http://www.cashenblades.com/steel/1095.html ; Prof Kevin is pretty good at this knife stuff

Good luck, Ken H<
 
Simple. Your hardening heat was not high enough. Non- magnetic is only 1414°. You need to be at around 1475°, which is a full shade of red above non-magnetic. More of a red-orange in dim light. You will not get a good homogenous solution of iron and carbon at 1414°.
 
Sorry, but I just have to do it :)

I heat treated the knife (as I have my past knives) with the following procedure:
1. Heated the blade in my forge to non-metallic (approx total time 3min 30sec)
 2. Quenched the blade in 135* canola oil
3. Tempered the blade for 2 hrs @ 400* in oven, then cooled slowly to room temp and tempered again @400* for another 2 hrs.
4. Cleaned and polished the blade and is now ready for scales.


I think that is the problem....non-metallic for steel is above 5430F...the boiling point.

FWIW, the cooling between tempers is best done quickly by immersing the blade in water ( or sticking under the running faucet). Slow cooling is usually not suggested.
 
CRA stand for cold rolled annealled. Means that the steel is in its soft form when delivered.
HR stands for hot rolled
CRA is usually shiney due to rolling out the steel cold and hr will have a blueish black finish.

Im not sure it is a recipe issue. Your procedure sounds good. Might i ask what kind of forge you are using? I use a charcoal forge and it can get pretty hard to get an even heat. Perhaps one section reached critical temp but others did not?

Also if you did a file test and it seemed to have held it should be fine..... did you file test the entire length of the blade?

There seems to be an "edge quench" look in pic 4. I am not sure but perhaps only the edge was heated or only the edge placed in the quench? I am no expert in HT but i have done a few blades.

Also an unlikely case is that you were sold something other than 1095. It prob unlikely but it has happened before. where did you buy your steel?

lastly i like the design of your knife =) seems to flow well. Might i ask how you did the jimping and what kind of handles you intend to put on it?
 
I use a thermocouple and a heavy steel tube as a muffle in my gas forge, and have had good results.
 
Update.... First I'd like to thank everyone who responded with suggestions and comments.

I spoke to the fella with the hardness meter. It apparently is brand new and has YET TO BE CALIBRATED! I could scream!

Now to hush my own fears about the HT, I reluctantly did some testing of my own. I sharpened the knife. not to ridiculous but to nice paper slicing sharp. First I did the brass rod test. I was terrified that this would leave a horrible dink in the edge. On initial examination the edge did slightly flex but then went right back to where it belonged on the side glancing pressure test. Next I ran the knife down the rod like I was trying to peel the rod. No edge damage and it shaved of the brass nicely.



Next I closed my eyes and gritted my teeth and chopped at the rod (not like Conan the barbarian but you get the idea :3:) You can see the dink in the brass between the arrows.



Lastly I took and old hickory sledge hammer handle that I use in the shop to coax stubborn thing into places they generally don't wan to go and hacked at it with the blade. No Damage!



Then I tried to cut some curls from the handle, this handle is hard as nails and didn't want any part of releasing curls but there was no damage to the blade edge from this test either.



Boy I can't begin to express how happy this testing makes me! It may not be a totally awesome RW # but I do think that it will be good enough and will be a very serviceable blade. Again, thanks to everyone who commented and gave me advice. I will put it to use the next time I HT a blade but as for this one I think I'm going to leave well enough alone.

Thanks everyone!

Merry Christmas!
lost
 
ken1111 said:
CRA stand for cold rolled annealled. Means that the steel is in its soft form when delivered.
HR stands for hot rolled
CRA is usually shiney due to rolling out the steel cold and hr will have a blueish black finish.

Im not sure it is a recipe issue. Your procedure sounds good. Might i ask what kind of forge you are using? I use a charcoal forge and it can get pretty hard to get an even heat. Perhaps one section reached critical temp but others did not?

Also if you did a file test and it seemed to have held it should be fine..... did you file test the entire length of the blade?

There seems to be an "edge quench" look in pic 4. I am not sure but perhaps only the edge was heated or only the edge placed in the quench? I am no expert in HT but i have done a few blades.

Also an unlikely case is that you were sold something other than 1095. It prob unlikely but it has happened before. where did you buy your steel?

lastly i like the design of your knife =) seems to flow well. Might i ask how you did the jimping and what kind of handles you intend to put on it?
Click to expand...

My forge is a homebrew propane forge. Nothing fancy but it seems to do the job well. The steel is from Jantz supply. As for the jimping I cut it all with a needle file on this knife. The knife will have camo G10 micarta scales when finished. I'll be sure to post the pictures when its ready for Christmas.
 
You must log in or register to reply here.
Back
Top