1st Attempt at San Mai Billet

K

Ken H>

Joined
Dec 31, 2011
Messages
4,580
OK, here' my first attempt at a San Mai billet. It's got a .093" thick 15N20 (high carbon) with a .100" layer of mild steel on outside. Clamped in vise, stick welded all way around, put in forge got hot (bright orange) and started pecking away. The trick seems to be light steady taps, not hard whams. The black is the 15N20 core that's been etched, with the whitish part the mild steel outside. Best I can tell there are no delaminations visible. I'll most likely cut this up looking for delams inside rather than make a blade from it. I didn't take photos of making the billet because I didn't expect it to turn out this good.

1st-San-Mai-Blade-Profile-s.jpg


This is the top edge - the core seems to be fairly well centered and no delams visible on top.
1st-San-Mai-Blade-Edge-s.jpg
 
Only way to know is to cut a knife profile out of it and see if the center welded. I would be concerned about "Bright Orange". You need to weld at yellow heat. Drawing is ar orange heat. Colors are based on the observer, and may appear different depending on the smith and the light, so you may be fine.

I like to stick a piece of coat hanger in the forge, pull it out after a few seconds and stick it in some borax, then out it back in and push it against the surface of the billet. If it is at welding temp, the wire will stick. Just twist it to remove and it will pop off.
 
Perhaps "bright orange" isn't the right color I actually saw - it was more to the point of next color would have been whitish looking. It's hard to determine color in sunshine. With the TC tip right at the edge of the insulation in forge the temp was around 2200°F. If I pushed the tip more toward the center of forge the temp is over 2400°F. Moving billet around inside forge to get an even color over the total billet I figure the temp was in the +2200F range. I should have tried that coat hanger trick - I'll do that next time.

I had planned to cut up the billet looking for delams, but perhaps profiling a blade would would be just as good. "IF" it does happen to be clear of delams no reason it wouldn't make a decent blade.
 
Hi Ken. Make sure you post a picture.

I'm curious to the contrast between the mild steel and 15N20. I did a santoku a year ago out of 3 layers (O1 core, 15N20 and mild steel on the outside) and there isn't much contrast between the mild and 15N20.
Entro9T.jpg
4hr0QrG.jpg


I'm not sure if I didn't forge it out enough so I ground through the all the mild, did I forge it off center, or if I didn't sand it enough before etching to get a good contrast, or if I sanded it too fine before etching, or did I sand it too much after etching, or....

If I'm remembering correctly, it's likely that I didn't forge the billet thin enough and ground through most of the mild.
 
You can see the contrast in my profile photo. Remember, this billet is NOT HT'd yet and the nice dark black of the 15N20 would come off pretty easy I'd expect. I'm in the process of profiling out a blade now. Once I get it worked up I'll be etching the edges looking for any delams that might be exposed.

That blade looks good. I see what you mean by sanding too much of mild steel away, it's left islands of cladding - I like it. BTW, what handle wood is that? My wife LOVES the spalted woods. Of course, each new wood (or new knife I make for her) becomes her favorite.... until the next knife anyway. {g}
 
OK, I got the profiled blade shaped, ground, and etched. With all the grinding I did no delams showed up so I'm pretty happy with my first San Mai attempt. Now to HT, finish grinds and put handle on knife. With the 15N20 core it should work good, but boy I'll bet that mild steel cladding will rust just looking at it! My 2nd attempt on a gut hook, my first was in the first year of making knives and didn't really like putting them in. Still don't, but wanted to try again.

1st-San-Mai-Gut-Hook-Blade-Profile-s.jpg
 
Ken H> said:
BTW, what handle wood is that?
Click to expand...

It's the same wood as all but one of my knives, spalted maple from my trees.

The handle is one of the reasons why I haven't tried to redo the finish
 
The mild steel cladding wil not rust any easier than the 15N20. It takes a lot moren than 2% nickel to become rustproof.
 
Thanks for info Stacy - I normally work with SS and forget how quickly carbon steel can rust. It just seemed like the mild steel cladding was rusting so fast. Is there a trick to getting that black oxide coating on the 15N20 to stay black with use? I've not HT'd the blade yet so maybe it will be better after HT?

Thanks again for the help on this forum.

Ken H>
 
Glad it welded up fully.

The black is just a surface oxide. If the knife is sanded, buffed, or used … it will rub off.
 
That reminds me of a question I've been wanting to try out, but as it's now been almost a year since I've been able to do anything in the shop....
Because the oxide on sanded/buffed steel gest rubbed off quicker, is there a rougher grit finish that will still allow the oxides to wipe off the 15N20 easily but not the rest? Especially on San Mai knives where you can't etch to get topography like on standard damascus.
Thanks
 
THe best way to keep a black edge or other area is to sand and finish the whole knife and then give it a quick etch. Rinse and neutralize well and then carefully hand buff only the part you want silvery with something like the 3M pink sheets, or 0000 steel wool.

Any spots on the dark areas that need touching up in the future can be quickly done with a Q-tip and FC. Remember to wash off the FC and neutralize before oil again.
 
You must log in or register to reply here.
Back
Top