Hamon questions.

[nateman_doo]

I heat treated 1095 like I normally do in canola oil. First, I will show you what I know to be good results:

This is just a sand blasted finish. The fact that the edge is still shiny, means its harder then the glass beads I am using to blast it with.

Now on to the piece in question:

There are a few "shiny" spots that I know to be hard, but if you look close enough, there is a hamon on there. To me, it means some form of differential hardening happened. The gunk on the spine is still remnants of the clay

Here is a closer view:

A file slightly bites into it, but its not easy. Perhaps there is a harder layer just slightly under the surface?

Has this happened to anyone else?

 

[Stacy E. Apelt - Bladesmith]

Shiny vs dull isn't a real indication of much.

Until you sand/grind the surface decarb and scale off, you don't know what you have. Clean it up and dip it in FC and then you will know.

Hypereutectoid steels will often form an auto-hamon when quenched in canola. It is fast enough for the edge, but may not fully covert the thicker areas. Using Parks #50 will get deeper hardening.

 

[nateman_doo]

describe the term surface decarb... because I am looking at bare metal. I glass bead blasted the edge and got to bare metal. I thought surface decarb WAS all the junk on the metal after the quench.

What I know of metal hardness, is that softer things dont scratch harder things. So having a shiny edge with the blasting means its harder then the media.

I will dunk it in the FC to see if it is darker.

 

[Stacy E. Apelt - Bladesmith]

Decarb is metal. It is the surface of the steel where the carbon has been reduced by oxidation. It has low to no carbon, and it isn't hardened steel.

 

[stezann]

Yes, you shouldn't confuse scale/gunk with decarburated steel.
Under the scale there is a thin (hopefully thin) layer of steel whose carbon had been lost to the oxygen during the heat treatment. That layer will act like iron (or very low carbon steel) and won't harden... it is that little bite of your file, underneath, hardened steel will prevent the file to dig deeper.
Features like the Hamon will suffer and be disguised by the decarburated layer, so you have to sand through it to reveal the actual appeareance of the hamon.
Often the clay will shield and protect somewhat the steel from decarburation and what does look like an hamon at first it's just the decarburation pattern, so the real hamon might look like different both in placement and activity

 

[nateman_doo]

Yes, you shouldn't confuse scale/gunk with decarburated steel.
Under the scale there is a thin (hopefully thin) layer of steel whose carbon had been lost to the oxygen during the heat treatment. That layer will act like iron (or very low carbon steel) and won't harden... it is that little bite of your file, underneath, hardened steel will prevent the file to dig deeper.

These are the droids I have been looking for.