Heat treading to hot?

Welcome to Bladeforums!

I moved this to Shop Talk, where the knifemakers hang out. :)
 
That looks pretty normal if it was done in a forge. Remember that you nearly always re-grind after Heat treat to remove the surface decarb.
 
It's kind of tought to say just from a picture. can you tell us what kind of steel it is? What did you use to heat treat it? How did you judge when it was hot enough? How did you quench it and temper it?
 
The steel is O1. I used a magnet to see if i reached the right temp. But i noticed that the "bubbles" where there before i quench it. I used an simple homemade charcoal furnace.
 
Well, today i re-grinded the blade and it turned out OK. The where a few tiny cracks showing on the surface but nothing to worry about, i thought.. So, i fitted the handle and etched a nice logo. Then in the finale stage of finishing, ... The blade broke! :eek: A lot of work for nothing. Ok, not for nothing because i learned a lot making my first knife.

Here are some pictures where you can see the cracks are deeper then i thought.

http://picasaweb.google.com/mcgaag/20100806MesKapot#5502374876606136034

http://picasaweb.google.com/mcgaag/20100806MesKapot#5502374860750620722

http://picasaweb.google.com/mcgaag/20100806MesKapot#5502374856637685714

http://picasaweb.google.com/mcgaag/20100806MesKapot#5502374846304066850

http://picasaweb.google.com/mcgaag/20100806MesKapot#5502374868667589618

So, what happened here??? What did i do wrong?

I heated the blade in a charcoal furnace till it was non magnetic. Then used brine to quench it. Then tempered in my kitchen oven for 2 hours at 430F.

I am working on a new blade and don't want to make the same mistake again. :)
 
I'm going to say based on the first picture that yes, you got it too hot and you also probably could have used a more reducing atmosphere in the forge. When I used to heat treat in a forge, the only scale I generated at HT time was just a light, dusty kind of scale. If it was anything more than that, I knew I had gone too hot.

Also, if you're seeing surface cracking when you begin to clean it up, that's a sign that something, somewhere, was probably not OK. O-1 is a tough steel to really get right, even if you have a kiln. If you're HTing with a forge, you might want to think of using a simpler steel like 1084. It will be much more forgiving in HT.

-d
 
I'm going to take a guess that maybe brine is a little too violent for O1. The "O" is for 'Oil Quenching'.

I like your attitude about lessons learned. You'll be a fine knife maker! :thumbup:

Rob!
 
its hard to really tell by the picture of the broken blade but i would say the brine made the blade too hard. you need to get some heat treat oil and some scrap pieces to experiment on before trying to heat treat another blade. the bubbles or spots look like the blade might have been overheated.
 
I use a crude charcoal forge and get blisters on the 1095 steel that I've been using. On another thread the probable explanation was the following from Sunshadow,

"your surface blisters are either just overheating the surface, or possibly getting surface infusion of carbon (kind of like case hardening) which lowers the melting temperature at the surface where the charcoal then touches the blade and spot overheats it."

http://www.bladeforums.com/forums/showthread.php?t=760489

I want to continue using charcoal but think I need to make a better forge than the coffee can I'm currently using.

What does your forge look like?

LonePine
AKA Paul Meske, Wisconsin

Good luck
 
lonepine said:
What does your forge look like?
Click to expand...

Just a simple old cooking pan and a flowerpot with a hole in the bottom for adding air with my wife's hairdryer:D

DSCF9589.JPG


DSCF9590.JPG


DSCF9588.JPG


Simple but it works..

I plan on building this though. For around $100 you can get the electronics on ebay.
http://www.viddler.com/explore/rashid11/videos/3/
 
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