HELP! I can't get 1084 hard

T

Theiskell

Joined
Nov 12, 2013
Messages
95
I know this stuff should be easy but it’s not working for me. I have very little experience heat treating. I have done some 4140 for tooling with good results, but that's about it. Here is what I have done and what I got.
USAknifemaker 1084 .250 thick X 1.5 wide
I have profiled and ground the knife down to 240 grit
I have a PID oven that the temperatures are reasonably accurate.( Checked with a fluke IR gun)
I put the knife in, blade edge up with the oven preheated to 1500. It takes about 7 minutes to become nonmagnetic. I let it soak for an additional 3 minutes
Remove from the oven immediately quench in canola oil heated to 125. Move the knife back and forth not side to side, until it’s too hot to touch but I am able to use a scrubby to get some of the scale off.
While it’s still warm (I'm guessing 150*) I am checking it on my hardness tester and it’s only showing around 42RC this is before tempering….what the heck am I doing wrong
I have calibrated the tester so it is reading correct. A file does not skate either.
 
Let it cool to room temp before checking hardness, as the "hardening" actually takes place between
around 450f (ms) and room temp (mf). also the sides of the piece being tested need to be parallel and free
of scale and decarb.
 
Also make sure you clean the blade before testing to bare metal and test on a flat surface on the blade
 
I didn't know about letting it cool to room temperature, but does that also explain the file? It almost seems softer than when I started. It's in the tempering oven now when that is finished I will remove all the scale, but I am afraid it will all be for nothing. This thing is killing me, it's by far the best blade (Looks) that I have made to date.
 
125 seems a little low for the oil, especially for such a thick piece of steel. I usually shoot for 140.
 
Gotta get use to them not turning out on occasion.

Like said you need to get rid of the top layer of steel. After I quench a blade if I am using oil I sat it on my anvil until cool to the touch then hit it with the file. The first pass or two with the file it will feel soft because of the decarb. After that it will start skating on the surface.

If I quench in water/brine I dont bother testing it until after the first temper. Too much risk, gotta get it in the oven as quick as possible.
 
Also make sure you clean the blade before testing to bare metal and test on a flat surface on the blade
 
What kind of grind are you doing on the 1/4" thick steel. I have found that with thick steel 1/4" and soaking times, that the geometry of the grinds is important. You might need to soak it for longer than the 3 minutes if the majority of the steel is 1/4" thick.
 
Along with the other suggestions, non-magnetic is not 1500°, it is only 1414°. Three more minutes over non-magnetic, in your particular oven, may not be enough time to increase the heat high enough to form a good homogenous solution of carbon and iron. Especially for a 1/4" blade. Your target quench temp should be between 1475° and 1500°, with a soak of about 5 minutes after reaching that temp.
 
TheWeatherman said:
What kind of grind are you doing on the 1/4" thick steel. I have found that with thick steel 1/4" and soaking times, that the geometry of the grinds is important. You might need to soak it for longer than the 3 minutes if the majority of the steel is 1/4" thick.
Click to expand...


This is after heat treat and tempering still measuring 42 at the tang
 
LRB said:
Along with the other suggestions, non-magnetic is not 1500°, it is only 1414°. Three more minutes over non-magnetic, in your particular oven, may not be enough time to increase the heat high enough to form a good homogenous solution of carbon and iron. Especially for a 1/4" blade. Your target quench temp should be between 1475° and 1500°, with a soak of about 5 minutes after reaching that temp.
Click to expand...
That was something I was concerned about but it looks like it should have hardened some at least. No??

Whetstone39 said:
Maybe it just isn't attracted to you? :D


(Somebody had to say it)
Click to expand...

Okay I deserved that:)
 
Does the edge also not skate a file? If not then either the whole thing didn't get hot enough or you took too long to quench. If the edge got hard but the rest not then it needed more time in the oven for the thicker sections.
 
Bet the edge is harder.

At 1/4" I'd soak longer 8-10 minutes. And not open door to check non-magnetic.

May have some decarb on the surface also.
 
oic0 said:
Does the edge also not skate a file? If not then either the whole thing didn't get hot enough or you took too long to quench. If the edge got hard but the rest not then it needed more time in the oven for the thicker sections.
Click to expand...

I didn't check the edge before tempering. I know, I was irritated.

Whats next? Can I normalize this and try to re-heattreat? Or do I make a nice letter opener?
 
That's a massive handle and a very thin blade. The mass of the handle could be soaking the heat from the blade. Drilling some holes to try to equalize the mass might help before heat treatment.
 
Bill - Actually, the mass of the handle can bleed heat into the blade, not suck heat from it. Too much mass right next to a thin blade ( such as a massive and thick spine) can keep the blade edge too hot too long and create pearlite in a quench using minimal oil.

What I read in these posts is:
1) Soak time isn't the same as temperature. They interrelate, but you still have to get to the target temp. Soaking for longer won't necessarily make it any hotter. Make sure the blade is fully at 1500F before removing it and quenching. Soak time STARTS when the blade is at temperature.
2) DO NOT open the oven door to check things unless you want to wait for the oven to re-bound and come back up to temperature.
3) Testing a blade before it is below 100F is a waste of time. Testing a blade that has not been prepared for testing is a waste of time. The blade needs to be clean, the surfaces tested parallel, and the decarb sanded/ground off before the testing.
4) Are you sure the steel is 1084? Things get mixed up in the shop, the wrong steel gets shipped, mistakes happen.....has any blade from this bar been successfully hardened?
5) Files are good to do a quick check that the blade hardened. You use a new/sharp file and give the edge a firm stroke at 45° to the bevels. It may bit on the first stroke, but it should skate on the second. If it is filing off steel after several strokes, something is wrong. The file won't tell you how hard the blade is, just that it got harder than it was.
6) If a HT run is in doubt, it can be re-done. If there is a concern that the temps are not right, try running it at 25°F higher. If that gets good results, the oven may be reading wrong, or you may have done something wrong in the earlier HT. Using a tempi-stick or temp-cones is a great way to check the ovens accuracy.
 
Bladsmth, Thank you for taking the time to list all of that. It's very helpful

I think I am going to give up on this bar. It is clearly labeled 1084. I cut 3 test pieces to play around with using various soak times and oven temperatures. It pretty constantly yields a 42 RC. It measures 32 before heat treating. this is baffling to me unless it was mislabeled.
 
Theiskell said:
Bladsmth, Thank you for taking the time to list all of that. It's very helpful

I think I am going to give up on this bar. It is clearly labeled 1084. I cut 3 test pieces to play around with using various soak times and oven temperatures. It pretty constantly yields a 42 RC. It measures 32 before heat treating. this is baffling to me unless it was mislabeled.
Click to expand...

Definitely Not 1084 there!

Where did you get it?
 
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