What have I done now?

O

Oldman57

Joined
Aug 19, 2017
Messages
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Recently I made a small veg. chopper from an old circular saw blade. I had my forge running for another project and decided to heat treat the chopper blade too. I got it to non magnetic and then quenched it in hot water. ( just to see what would happen) . The blade got a slight warp, so I straightened it with a couple taps with hammer on my anvil.
The file hardness test showed great, so proceeded to sand and polish. When I got to about 600 grit a pattern of circular microscopic “cracks” started showing up,radiating out from where I tapped it to take the warp out. Is this the martensite cracking, or what? Looks kinda cool but is the blade shot now?
 
You water quenched an unknown ( and probably air hardening) steel ... no surprise that it has cracks. It is likely just scrap steel now. Tapping on any hardened blade to straighten, and at any temperature lower than 400F, will likely destroy the blade.
 
Use it until it fails. It might last for years as is, or it may break before you finish the handle. Either way, you'll gather data and learn from it.
 
Stacy E. Apelt - Bladesmith said:
You water quenched an unknown ( and probably air hardening) steel ... no surprise that it has cracks. It is likely just scrap steel now. Tapping on any hardened blade to straighten, and at any temperature lower than 400F, will likely destroy the blade.
Click to expand...

I re-heated the blade in forge till quite hot before attempting to straighten it. Update: I went ahead with the hand sanding to 2000 grit. Somewhere between 800 and 1000 the “cracks” went away. The blade was free, I’m retired so it’s all good. I’m having fun trying and learning new things. I appreciate your feedback. I did metal fabrication and taught tig welding for 40 years before hanging it up.
 
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