1084 heat treat problem?

J

JonBishop

Joined
Oct 30, 2014
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Hello all. I’m in the process of making a machete out of .140 1084. I heat treated the blade today and it didn’t seem to get as hard as other blades I’ve made. Here are the variables: First purely stock removal blade that I have made, longest and widest blade I’ve attempted. My heat treat is in a gas forge 14” long. This blade is 23” with the handle. I quench in canola at 140f with candy thermometer verification. It came out of the quench with a bow. I corrected that on the anvil with a couple wood blocks. Then I put my file to it and it skated and kind of dug in. I went through the whole process twice with same results. Since this was a proof of concept project I went ahead and did some tests without tempering and no edge. Chopped some branches, some large ones, no bends or breaks. Edge, not sharpened, fine. So my question is should I go ahead and temper? It held up nicely to my tests. But when I take it down to the final edge does anyone think the edge could deform? I use made in Germany Pferd files to check hardness. It’s all I got. The picture will show the file marks. Thanks for any suggestions, Jon. Picture not showing.
 
I agree that the file test needs the de-carb removed. The multiple quench would make the decarb thicker.

What I don't get is your test in the full hard state. If you went out and whacked on stuff with an as-quenched hardness it should have easily chipped or broken (unless you were being pretty gentle in your chopping). Just dropping an as-quenched blade in 1084 on the floor can break it in half.

For a large blade, I would recommend 120°F for the canola oil and for a small blade no more than 130°F. I suspect you may have not got full hardness with a very large blade and too warm oil. It also probably auto-tempered a bit. You didn't say how much oil you used, but a blade that size needs 3 to 5 gallons of quenchant .
 
Thanks for the replies. I was not gentle in the chopping tests. I figured if it didn’t harden it would bend and if it did it would break. I went ahead and ground the de-carb off and the file caught some in spots. I also did two cycles at 400 degrees for an hour each. No noticeable difference on the file test after tempering. My quench tube is 6” pipe 24” tall. Has about 4.5 gallons in it about 3” from the top. Also my file test was with a Pferd no. 2 and a pferd plus file, not hardness files. I went with the short temper because I didn’t want any softer than it might already be. The temper didn’t seem to do much anyway. Should I just reheat treat? Could I do some more testing?

Thanks, Jon
 
i do not understand how you could have corrected a warp before tempering. i am worried it was not fully hardened. how are you judging that the blade is hot enough to put in the quench?
 
Yes, I too think it didn’t fully harden. The steel came from alpha knife supply. So I think the problem lies in me. I tried to do what I do with my other blades. Non-magnetic get a bit hotter and quench. My longest blade to this point was a hidden tang bowie with 7” blade. This blade is almost 10” longer than my forge. I could be wrong here but me running the blade in and out to get up to temp may have caused the “splotchy” hardness? Usually when I have the temp right in my forge the blade just about turns the same color as its surroundings when I let it set a little past magnetic. This was really a test piece to see if machetes were even feasible for me to do. I’ve had a lot of questions about them lately. I think I’ll try to heat treat one more time. If it doesn’t work out, well I’m not going to waste any more propane on it. I’ll have to figure the cost of sending out for heat treat on anything longer than about 12”.

Thanks, Jon
 
I’m guessing you only have a single burner in your forge, for a blade that size I’d use 2 or 3 burners to be able to get a more even heat while moving the blade through the forge.
 
Joshua Fisher said:
I’m guessing you only have a single burner in your forge, for a blade that size I’d use 2 or 3 burners to be able to get a more even heat while moving the blade through the forge.
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Hey, Joshua. It is a two burner. Venturi, vertical, square chamber. When the forge gets up to heat the chamber is evenly colored with no noticeable hot spots at all. I’ve had the forge for 8 years or so. I bought it from a place called rattlesnake forge or copperhead forge. It had some kind of snake name. It gets to welding heat. I have made one pattern welded blade with it. I will try one more heat treat. I’ll use a different technique though. What that is, I don’t know yet. If you or anyone else has any tips please share. I’m thinking about using hard fire bricks (their all I have) to extend the chamber. I don’t think it will work. The only way I see this plan working will use a lot of propane.

Thanks, Jon
 
Follow up on my last post. I also thought about cranking the forge up to welding heat. But I’m afraid I’ll get it too hot as DevinT said. Maybe not hot allover, just in spots. If that were to happen, then it seems to me tempering would be, well no reason to do it. Just re-heat treat. I didn’t get it too hot the first two times. I know I can get a good heat treat with my set up on smaller blades. This one has me stymied though.
 
If your entire chamber is open my guess is you are losing too much heat, what I do is narrow my chamber using some 2” thick firebricks set inside the chamber to close up the back of the chamber, for my forge this leaves me with a 2” wide opening through the forge, I pass my work piece through vertical with the edge up so it doesn’t warp from the weight of the blade I can run my forge at about 10psi with two burners and slowly bring my work piece to heat, I’ve heat treated 24” long blades this way without issues of hot spots or uneven heat.
 
Joshua Fisher said:
If your entire chamber is open my guess is you are losing too much heat, what I do is narrow my chamber using some 2” thick firebricks set inside the chamber to close up the back of the chamber, for my forge this leaves me with a 2” wide opening through the forge, I pass my work piece through vertical with the edge up so it doesn’t warp from the weight of the blade I can run my forge at about 10psi with two burners and slowly bring my work piece to heat, I’ve heat treated 24” long blades this way without issues of hot spots or uneven heat.
Click to expand...

Joshua, that was what I wanted to do, but my openings are only 2” tall. This blade is 2.5” tall. So I had to go horizontal. Hence the curve I got in the blade the first two times. I guess? And the uneven heat maybe?

Thanks, Jon
 
Is your whole forge made out of hard fire bricks? I noticed you mentioned hard fire bricks above. If that’s the case, that’s a problem. You want insulating firebricks for a forge. One burner should be fine for most knives.
 
I’m impressed that you could evenly heat a 23” blade in a 14” long forge... I’m pretty certain I couldn’t do that :)
 
Josh Rider said:
Is your whole forge made out of hard fire bricks? I noticed you mentioned hard fire bricks above. If that’s the case, that’s a problem. You want insulating firebricks for a forge. One burner should be fine for most knives.
Click to expand...
Hey, Josh. My forge has soft fire brick top and sides and a hard fire brick floor. The hard firebricks I mentioned were for extending the back of my forge temporarily to try and heat treat this blade. I’ve scrapped that idea. I’ve pretty much scrapped the whole idea of successfully heat treating this blade with my setup. I think it’s either send out long blades for heat treat, or build a dedicated heat treating forge. I have the materials to do it, just not a lot of free time on my hands.

Thanks, Jon
 
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