Did I Ruin a Blade?

CDHumiston

KNIFE MAKER
Last night I was heat treating an AEB-L blade. My wife got me sidetracked and I missed taking it out of the oven after the 1925 soak time. By the time I remembered the oven had cooled to 1500 degrees. I took the blade out and cooled it with my aluminum plates and went ahead and tempered it.

What say you all? Should I do the heat treat over, leave it or is it ruined?
 

fitzo

Gold Membership
Last night I was heat treating an AEB-L blade. My wife got me sidetracked and I missed taking it out of the oven after the 1925 soak time. By the time I remembered the oven had cooled to 1500 degrees. I took the blade out and cooled it with my aluminum plates and went ahead and tempered it.

What say you all? Should I do the heat treat over, leave it or is it ruined?

What does the HRC say about how it hardened? If it's hard, put it in service in the home kitchen and compare...
 

CDHumiston

KNIFE MAKER
I haven't tested it yet, that was going to be the first thing I did. It was late last night and I just got home from work.
 

CDHumiston

KNIFE MAKER
What does the HRC say about how it hardened? If it's hard, put it in service in the home kitchen and compare...

It tests at 58.5 HRC. I usually get around 61 on AEB-L. I think it will be okay. I'm going to go ahead and finish it...
 

fitzo

Gold Membership
Well, then, you know immediately it's not quite right and the excursion had an effect of some sort. How much of what effect? Well, micrographs would be interesting, but not worth the money IMO. If you re-HT, you'll still never be certain you removed all effects of the excursion.

So, I agree. Finish and put into service where you can gauge it's performance and then you'll have an important piece of information for yourself.

My opinion. Others may vary.
 

52 Ford

Well-Known Member
Well, then, you know immediately it's not quite right and the excursion had an effect of some sort. How much of what effect? Well, micrographs would be interesting, but not worth the money IMO. If you re-HT, you'll still never be certain you removed all effects of the excursion.

So, I agree. Finish and put into service where you can gauge it's performance and then you'll have an important piece of information for yourself.

My opinion. Others may vary.

Well, not ideal, but you could snap the tip of the knife off and look at the grain structure compared to that of your other HT'd blades. Take note of the elastic and plastic deformation as you break it.


Ooooooorrrrr, just use it and accept that it's a lil different.

Sent from my Champion Forge using Tapatalk
 

CDHumiston

KNIFE MAKER
Well, not ideal, but you could snap the tip of the knife off and look at the grain structure compared to that of your other HT'd blades. Take note of the elastic and plastic deformation as you break it.


Ooooooorrrrr, just use it and accept that it's a lil different.

Sent from my Champion Forge using Tapatalk

This particular cleaver design has been a jinx to me! The first one warped and I broke it, the second on I ground too thin pre-heat treat and now this one was forgotten in the oven!

I think I'll give it a whirl on the grinder before I decide to break it...who knows maybe the 3rd time is still the charm?
 

fitzo

Gold Membership
I would recommend against breaking it. The types of changes you'd be looking for are microscopic differences that would thus need micrography to evaluate. You didn't heat it hot enough for grain growth.

What might be interesting for learning's sake is 1) what happens to HRC if frozen overnight in a regular freezer?, &, 2) What happens if it's then subjected to cold (dry ice ) or cryo (LN).
 

fitzo

Gold Membership
Maybe it's time to buy a SEM? :)


Sent from my Champion Forge using Tapatalk

I thought about a metallograph a couple times. Used one daily my first year of employment, a carbide tool company, and it definitely has a cool geek appeal. Used carbon electrodes for the light source. Bigger than a business desk, though! LOL
 

52 Ford

Well-Known Member
You forgot to add the suspenseful music!

As far as durability goes, looks like that woulda made one heck of a knife! You can still get a few small blades out of it.

I believe that being "scientific" about those bend tests requires going "full send" on the first attempt. If you bend to 45 and return, then 50 and return, then 55 and return, etc. You're work hardening the blade.

In any case, I think the heat treat is fine. Go ahead and glue the knife back together and carry on with the finish grinding :D

Edit: If you wanted to get sorta fancy with the bending set up, you could film straight on with the edge of the blade and slowly pull the blade over till it breaks (maybe use a rope to get out of the danger zone? Take a screen shot of the moment the blade fails, then measure that angle.
 
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52 Ford

Well-Known Member
I thought about a metallograph a couple times. Used one daily my first year of employment, a carbide tool company, and it definitely has a cool geek appeal. Used carbon electrodes for the light source. Bigger than a business desk, though! LOL

Now, I'm no metallographicalologist - at least not since that accident... :rolleyes:

Anyway, it looks like you can get one for a few hundred dollars on Ebay. Like small-ish bench top model. Doesn't use carbon arc lamps for light... so that's kinda lame. Uses LEDs. Where's the fun in that? Wouldn't you rather have all the lights in the house dim when you cut your fancy microscope on?
 
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