Re-Heat Treat 1084

[Colby L.]

Hi All -

I am concerned I may have overheated my most recent knife during HT. With no way to be certain without breaking the blade, to play it safe I have decided I'd like to re-do the heat treat. I have been looking around and it seems like I can just go straight to normalizing without annealing correct? The steel in question is 1084.

 

[Stacy E. Apelt - Bladesmith]

How much did you overheat it? 1084 is the eutectoid steel and is pretty forgiving, since it has no surplus carbon and very little alloying.
What is the issue that makes you think it was overheated?

I would make a quick edge and do a brass rod test first. If the edge is chippy, then redo the HT.

If you think you greatly overheated the blade for a long time, do a few normalization or grain refinement cycles.
If you think it was just a bit too hot, just redo the HT at the proper temperature.

 

[Colby L.]

How much did you overheat it? 1084 is the eutectoid steel and is pretty forgiving, since it has no surplus carbon and very little alloying.
What is the issue that makes you think it was overheated?

I would make a quick edge and do a brass rod test first. If the edge is chippy, then redo the HT.

If you think you greatly overheated the blade for a long time, do a few normalization or grain refinement cycles.
If you think it was just a bit too hot, just redo the HT at the proper temperature.

I was having a hard time getting the ricasso area heated enough so I spent more time in the forge than normal. Call it 30-60 seconds longer once the main portion of the blade was a bit past non magnetic. I was being careful, pumping in and out of the heat. I didn't notice any wild changes in color at the edge/tip but I was admittedly focused in the ricasso.

After the quench the blade was very hard but I had more decarb than normal. When cleaning up the blade post temper the surface had what appeared to be baked oil or like clear smashed bubbles if that makes sense?

For a brass rod test do I need to grind my bevels in first? Or just grind down to an edge at like 45 degrees. I have been grinding post HT.

 

[Stacy E. Apelt - Bladesmith]

Temper the blade as planned. For 1084 425°F-450°F is a good range. For a high harness blade, 400°F is fine.
Grind an edge on the blade (no need to clean up the bevels) at a somewhat acute angle, around 15-20DPS. No need to make it hair popping sharp .. 400 grit will do.
Place on a 1/4" brass rod that is epoxied (or clamped) to a board.
Apply some sideways pressure while pushing down slightly. You can tilt the knife a bit if needed.
Watch the edge as you do this. What you are trying to see is a slightly deflection of the edge. If you can't make it deflect at all, re-sharpen at a lower angle.
Lift the blade and inspect the edge ( a magnifier helps).
If the edge more or less returned to straight - Good
If the edge deflected and slightly chipped out - it is too hard and needs a higher temper.
If it just snapped away as you deflected it - the HT is probably bad, Do a grain refinement series and re-HT.
If the edge deflected and stayed bent - the temper is too high . It will need to be re-HTed.

 

[Colby L.]

Temper the blade as planned. For 1084 425°F-450°F is a good range. For a high harness blade, 400°F is fine.
Grind an edge on the blade (no need to clean up the bevels) at a somewhat acute angle, around 15-20DPS. No need to make it hair popping sharp .. 400 grit will do.
Place on a 1/4" brass rod that is epoxied (or clamped) to a board.
Apply some sideways pressure while pushing down slightly. You can tilt the knife a bit if needed.
Watch the edge as you do this. What you are trying to see is a slightly deflection of the edge. If you can't make it deflect at all, re-sharpen at a lower angle.
Lift the blade and inspect the edge ( a magnifier helps).
If the edge more or less returned to straight - Good
If the edge deflected and slightly chipped out - it is too hard and needs a higher temper.
If it just snapped away as you deflected it - the HT is probably bad, Do a grain refinement series and re-HT.
If the edge deflected and stayed bent - the temper is too high . It will need to be re-HTed.

OK thank you Stacy. I will give it a shot and report back.

 

[Colby L.]

Temper the blade as planned. For 1084 425°F-450°F is a good range. For a high harness blade, 400°F is fine.
Grind an edge on the blade (no need to clean up the bevels) at a somewhat acute angle, around 15-20DPS. No need to make it hair popping sharp .. 400 grit will do.
Place on a 1/4" brass rod that is epoxied (or clamped) to a board.
Apply some sideways pressure while pushing down slightly. You can tilt the knife a bit if needed.
Watch the edge as you do this. What you are trying to see is a slightly deflection of the edge. If you can't make it deflect at all, re-sharpen at a lower angle.
Lift the blade and inspect the edge ( a magnifier helps).
If the edge more or less returned to straight - Good
If the edge deflected and slightly chipped out - it is too hard and needs a higher temper.
If it just snapped away as you deflected it - the HT is probably bad, Do a grain refinement series and re-HT.
If the edge deflected and stayed bent - the temper is too high . It will need to be re-HTed.

Ok I ended up grinding full bevels as I am trying to learn freehand grinding (sorry N Natlek !). I then sharpened it on a coarse dmt stone. I ran the brass rod test and no chipping! I seem to be in the "more or less returned to straight" zone. Visually it seems like it essentially goes back to straight. However after I run the test along a portion of the blade it almost feels like there is a tiny burr is formed opposite the side that the pressure was applied too. Is that normal?
There could actually be a tiny burr left since I sharpened it pretty fast. It still cleanly cuts news paper so I don't think the edge is permanently deforming.

Edit: I went back and re inspected and I can feel slight dimples in a couple spots. Does that mean it's too soft? I tempered at 400-415 so it shouldn't be super soft. Does how thin I grind it before sharpening make a difference? I ground it to sub 0.01" before I sharpened. It seems the steel would stay permanently deformed if it's thin enough no matter the heat treat.

 

[Stacy E. Apelt - Bladesmith]

That sounds pretty much normal for a brass rod test. There is usually some amount of deflection. I would say to finish it up and do some real use testing. Cut some rope and cardboard, whittle some wood, cut some veggies, etc.

 

[Colby L.]

That sounds pretty much normal for a brass rod test. There is usually some amount of deflection. I would say to finish it up and do some real use testing. Cut some rope and cardboard, whittle some wood, cut some veggies, etc.

Thanks Stacy, that is my plan at this point. I appreciate the help/advice as always!

 

[Natlek]

Ok I ended up grinding full bevels as I am trying to learn freehand grinding (sorry N Natlek !).

Whatever works for you my friend ,whatever works.............show to us what you did so far .Who knows, one day maybe you will be the one who will accept my challenge

 

[Colby L.]

...Who knows, one day maybe you will be the one who will accept my challenge

Ha perhaps someday! I am just happy to get through a grind while minimizing how much hand sanding I have to do. I am working on trying to get steady enough to do some belt finished hunting knives. I am close but my off hand still needs some work. I just posted one of my first freehand ground blades over in the whats going on in your shop thread.