San Mai help

David Stifle

David Stifle

Joined
Nov 20, 2008
Messages
10,188
Hi guys,

I took my first shot at making a san mai blade, and failed. I had sandwiched a 3/16's 1095 billet between 2 pieces of 1/16th 15N20. For the life of me, I couldn't get the metals to merge. Is there a tutorial on making a san mai blade? Or can some of you fine folks give me some pointers? Much appreciated.

Dave
 
It's just like any other forge welding really. First thing I see that raised your level of difficulty was putting the thin stock on the outside. If possible, you want to have thicker stock on the outside of the billet. I'm guessing that you saw the 15n20 bowing out from the 1095 as it heated right? I could type here for hours, but seeing as Ive done a good bit of that typing already on my website I'll refer you there for now. Everything that applies to pattern welding applies to san-mai. It's just a 3-layer billet.

Feel free to drop me an email or post back here with any specific questions, etc and I'll do the best I can to help you. Some things that would be helpful to diagnose what went wrong are:

  • What type of forge are you using?
  • What type of flux are you using?
  • how did you prepare the billet?
  • What was your heating/welding process?
  • How did it fail? What type of behavior did you see as you worked?

-d
 
like deker said the thin stock on the outside was a big part of the problem. Also the thin 15n20 will be mostly scaled away bt the time that you gat anything forged from it. But try this it should work for you. Put three pieces of the 1/16th 15n20 on each side of the 1095 press tightly together and weld all the way around the billetso that all the seems are covered with weld. before you weld the last end. soak the billet in kerosene (let things cool to room temp first) or number one diesel fuel for ten to fifteen minutes. The reason to do the short side/end of the billet is that you dont want all the kerosene to burn out of the billet while your welding. If you are a good enough welder that you can weld 100% with no leaks then drill a small hole in one end of the billet so that any pressure caused by the kerosene burning can escape. If your not that good of a welder don't worry about it because your probly going to have a small hole in the weld. Put your piec in the forge and bring it up to welding temp let it soak at temp for a MINIMUM of 15 minutes. take it out and squeeze or hammer it together. A six inch long billit should only take 30 seconds or so to do both sides. don't play with it look it over or pick your nose just take it out cover both side with firm even blows and get it back in the fire. let it return to welding temp and soak again ten to fifteen minutes. now you can take it out and start to draw it out. I like to work the whole length of the billet the first few times. ie., take it out and forge one side reheat, take out and forge the other side etc.. I know this is a little bit different welding proceedure but it will work for this thin stock that you are triing to use. By the way 15n20 makes at least as good of a cutting edge as 1095 and is way less picky about quench speed than 1095. I would probably use 15n20 for the cutting edge and the 1095 for the sides, then add clay for a hamon and harden in parks 50 or water. But that is just me.
 
I recently made one with the exact set-up you used and it worked fine. First, I gound any mill scale off the steel so the steel was clean. I used wire to hold the 15n20 on the outside while heating. I used borax for flux and hand hammered it to weld. The welds took fine and having the 15n20 so thin, I forged it very close to shape to avoid grinding the outside layer off. It worked, but I agree with the others that thicker stock on the outside would make things considerably easier. I only used the thin 15n20 because it is what I had on hand.
Good luck.

Mike

Here is a pic:
picture.php
 
I have found with the san mai, that in order to keep the center steel along the cutting edge the entire length of the blade, you should have the center steel (1095 in your case) fairly thick. What I do is 1/4" of outer steel, followed by two 1/4" center steel then a final layer of 1/4" outer steel. The entire billet is 1" thick and 1 1/4" wide. I usually cut them about 2 1/2" long, and I get a 10 inch billet out of it. The extra steel in the center allows you to keep the center steel along the cutting edge without much trouble. I tried it only using a single layer of center steel, and the outer steels stayed too close to the edge and occasionally touched the cutting edge, which was unacceptable for me.
 
Guys,

Thanks for all the information. I prepared the steel as Deker illustrates on his website, I ground it all nice and clean, wired it up good and tight, put it in the forge (coal) and got it to a good orange, took it out and started to hammer. The 15N20 bowed and slide on me, rather than sticking. I did not use any flux (should I have put some flux between the layers before heating?). I tried flipping the billet to hammer the 15N20 sides, and now wonder it I should have focused on one side, then move on to the other as a sepate process.

The 1095 seemed to move easier than the 15N20, because it was thicker. I think next time I will put the 15N20 in the middle, the thicker 1095 on the outside. I didn't dip it in kerosence or diesel, but I won't forget next time.

I'm not able to get back into my shop until the weekend, hope it works out better this time.
 
define 'good orange'.

you are going to run into trouble trying to weld without flux, and i'm not so sure you are at an appropriate welding heat.

what is the kerosene or diesel for?
 
Listen to what Bill Wrote! He's spot on with how it's done. Oxygen is your enemy in any forge welding operation. The diesel/kerosene IS basically the flux. It burns, consuming the oxygen, and negates any oxides forming on the facing surfaces. Don't just "dip" the billet...let it SOAK in the diesel or kerosene for a minimum of the time Bill suggested.

Two things you mentioned in your last post throw up red flags for me...fist the wiring part. Wiring a billet together CAN work, but because the wires heat up and expand, causing the billet to "loosen up", it makes thing much more difficult than they have to be. Tack welding the edges of a billet works MUCH better. Next, I doubt your heat was high enough. If your going to use color as a guide, your going to want to be in the yellows, and in some cases whites to achieve good welds. Temp wise, that's going to be in the 2300F+ area. Personally, when welding, I bring my forge to 2350F before I ever put the billet in. When Bill was talking about "soaking", it means that once the billet achieves the same temp as the forge....then start your soak time.

It's going to take some experimenting to discover how it works, but once you get there, it will seem easy.
 
Thanks Ed.

I agree with Ed. it sounds like your too low on your temps, and if you have a welder weld the billet together.

Also it was mentioned above about keeping the edge steel on the edge. this gets more difficult as the core gets thinner. good forging practices will go a long way ie.. not just hitting the steel on both sides but moving the steel the same amount on both sides. Another little trick is to get all the rough forging done, the profile and the bevels started. then let the blade cool grind around the profile just enough to get the scale off and then do a quick dip in ferric long enough so that you can see he core. Mke sure that it is in the middle, if not reheat and forge the blade so that the core is in the center of where the edge will be. If/when the core is where you want it then finish forge the blade bevels and you are done.
 
I think I got it, thanks to you guys. Yes, the wiring was an issue, and I agree I didn't got a high enough heat. Can't wait until next time. Thanks again, guys. Hope to post pics if I get it right.

Dave
 
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