Help Please! I have bubbles after normalizing?

[Adam S.]

Hi all!
This is my first real knife I've tried to make and today I was trying to normalize in my homemade TS8000t firebrick forge and when I pulled the blade out a minute or so after it was non-magnetic I have these "bubbles" on the blade? I sanded it with 220 on a spot to see how deep it went and it's in there deeper than I expected. So........is this just deep scale or did I overheat the blade?
Pics for reference:

Sanded
Unsanded
Whole Blade

Any help would be greatly appreciated, as I mentioned I'm a super noob!

 

[A.McPherson]

Looks like you got it too hot. In those small forges with no temp control, you really have to keep the blade moving as you heat it up. If not you'll get uneven heating.

 

[Adam S.]

Looks like you got it too hot. In those small forges with no temp control, you really have to keep the blade moving as you heat it up. If not you'll get uneven heating.

Thanks for letting me know that's what it seemed like to me after reading up a little bit. I assume this blade is trash? I think it was probably a little ambitious to make a bigger bowie as my fist knife and the small forge with uneven heating definitely didn't help.
Oh Well

 

[daizee]

Probably not "trash", but check how hard the edge (and spine got). You can do a rough finish instead of polishing it out, put a handle on it, and beat on it to learn something.

A big knife in a small forge IS ambitious. Also with your first knife.
But that ambitious will take you places eventually.
I have a small Atlas forge and learned that I can harden about 7" of steel in it reliably, and that's it. And that's blade-shaped ground steel, not full-thickness stock.
Also yeah, don't leave it sitting in the forge like they do on TV.

 

[A.McPherson]

Eh, you can possibly salvage it... Try thermal cycling it a few times, then re-quench it.
So heat it, till just barely below non-magnetic 3 times, air cooling till black between each heat. Then heat it till just over non-magnetic ( do this in the dark) it should be in the low orange side of things. If it's yellow, it's too hot. Then quench in oil and continue shaping.

All the effort might not pay off though, but the experience will on later knives!! If you're going to heat treat by color, you have to get good at recognizing the colors!

 

[Adam S.]

I actually did not get to the quench this was just the first normalizing cycle and I notice the "bubbles" when it was cooling. I think the middle may have gotten yellow.
,

 

[daizee]

Then you might have grain growth if you left it in there too long. If you're forging, it's a good idea to thermo-cycle it a few times when you're done shaping regardless. It only takes a few minuets. Very short minuets - that only last minutes.

 

[12345678910]

You may find more info if you call those blisters instead of bubbles.

Heat colour temps are hard to read.
do it in the dark.
Bright daylight biases you too hot.