Strange Pitting after HT?

colu41

colu41

Joined
Dec 24, 2014
Messages
1,598
So this will be my.......18th knife I believe. :rolleyes: And I've heat treated all of them at home without a problem. I hand sand most my blades to 400 grit pre heat treat.
After HT, I continued with 400 grit to remove scale, and to move on to 600 grit. But I noticed a strange pitting on both sides of the blade. I kept going with 400 thinking it was just some strange haze or something and it did nothing. I moved back down to 220 and it got rid of most of it, but its still visible (in certain lighting). Did something go wrong? Or do I just need to keep sanding away?

Sorry no pics, my phone is currently out of commish until I get my replacement tmrw.... drop it on my concrete floor as I was sanding the blade. Now theres spiders all over my screen!:foot:
 
Yes answering Shane's questions will help us understand what has happened.
But if i have to guess, the first thing crossing my mind is decarburation, and if it the case, yes, do continue sanding it away until you only have omogeneus steel.
Decarburation is a different thing than scaling, so it may go unnoticed until the higher finishing and then shows like an haze of a slight different color.
 
& a picture?

I grind the crust off ofter heat treating. Could not imagine starting with 400 hand sanding after heat HTing???
 
Stacy E. Apelt - Bladesmith said:
That is half an answer...what is your HT regime.
Click to expand...

I heat in brick forge until non magnetic. I then stick it back into the forge for another minute or 2, or until the entire blade goes up another shade in glowing red, and then I quench in 120-130 canola. Tempered at 400 in (2) 1 hour intervals.
 
Don Hanson III said:
& a picture?

I grind the crust off ofter heat treating. Could not imagine starting with 400 hand sanding after heat HTing???
Click to expand...

I will try to get a pic after I get my new phone hooked up. I sanded it to 400 pre heat treat, so Post HT it is surprisingly easy (for me) to get the blackened "scale" or "decarb" off and get down to my original 400 grit finish. Going back to 220 would probably be a little quicker, that's just how I've been doing it. Remind you guys, I still have a lot to learn. Been only 4 months into the hobby. :o
 
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