San Mai layer question

[Daniel Sheets 16]

15n20 core with 1084 on the outside.

Is it normal for the layer line to look like this or did the forge weld fail?

[billyO 411]

Hard to tell from the pic.  How much did you grind off and how much of the bevel did you forge in (or is all that ground from a flat bar?)

 

[Daniel Sheets 16]

It's all ground from a flat bar that I forge welded.

 

Although I can see the line, I can't feel it. To my fingers it's a perfectly smooth surface.

[billyO 411]

What about your fingernail or can you catch a needle in the crack?  It looks a bit large from the picture, but it's hard to tell.  It is possible to see the seam when grinding, but usually it's pretty hard to see and not that obvious.

 

[Daniel Sheets 16]

Can't catch a fingernail in it. Haven't tried a needle.

 

I'll probably keep on with it since I've came this far. If it grinds out then good. If not then it's experience under my belt.

[Francis Gastellu 270]

It's hard to be sure from the low resolution photo. I think this may just be carbon migration from the 1084 to the 15n20 layer, but I can't tell for sure. What makes me doubt that it's a delamination is that it runs the length of the blade and stops at the ricasso area, which would make sense if you left that part of the knife out of the quench (unhardened steel does not etch the same). Otherwise, you'd need to have messed up almost the entire length of the billet.

 

Here's a photo of a couple delamination areas on one of my blades:

 

 

And here's a photo of carbon migration. As you can see, this is much more consistent throughout the length of the blade. It is also perfectly smooth, as you describe:

 

 

Again it's hard to tell given the resolution, but I think this is the latter. I personally like this effect, and use it to add contrast to my patterns.

Edited May 4, 2021 by Francis Gastellu

[Alan Longmire 3,682]

Is that etched?  If the line was invisible while you were grinding you're probably good.  

[Daniel Sheets 16]

That is slightly etched. But the line was visible while grinding. Just not as visible as it is now.

[billyO 411]

It's normal to be able to see the lines between the layers (on low layer patterns) as you grind.  To me, they look like what you might see when you draw a line on a stack of paper, and then look at the second or third sheet down where you'll see the line scored in the paper slightly.  Often, you will only be able to see the lines when you have the reflection right, but it goes away when you shift the angle of the blank.  

Edited May 4, 2021 by billyO

[Alan Longmire 3,682]

You're probably good to go.  

[Daniel Sheets 16]

So here it is after quenching and a bit of grinding. The welds didn't take all the way.

 

Question... If I finish this just for seeing what it looks like, does it still need to be tempered?

 

https://flic.kr/p/2kWGfw6

Edited May 4, 2021 by Daniel Sheets

[Jerrod Miller 593]

You should have tempered before any grinding.  Always temper immediately after hardening.  Not only does it make grinding easier, but more importantly there can be stresses in the blade that cause failure in the blade while it just sits there.  

[Daniel Sheets 16]

Ahhh. Noted.

 

Guess I'll trash, call it experience and start again.

Edited May 5, 2021 by Daniel Sheets

[Alex Middleton 831]

If you want to finish it out as a practice blade, I say go for it.  Throw it in the oven at 400 for a couple hours to help insure it doesn't completely break on you, and then go to town.  Another good use would be to snap it and take a look at the grain.  Itll tell you a lot about your heat treat process and whether or not you have it dialed in.

[Daniel Sheets 16]

I think I'll go for the second option.

[billyO 411]

and you have a good example of what good, welded lines look like compared to un-welded.