The way I've done it in the past is to fully seal the billet prior to forge welding. That is, once you make your sandwich, clamp it tightly in a vise and weld all the outer seams shut so that no oxygen can get in between the layers once you put it in the forge. You want clean mating surfaces free of any oxidation or other pollutants when you weld them. Once fully sealed shut, place the billet in the forge and let it soak for a few moments at a high welding heat, and then weld it much like you would a regular damascus billet, using steady, even hammer blows.

Steel selection is also important. A number of makers use 416 stainless for the outer layers, but I've also had success using 304 stainless, which has very high ductility and great corrosion resistance, making it pretty user friendly.

I'll piggyback/add to what Derrick said.....

These are things that I have discovered/do that makes my life much nicer when building stainless San-Mai.

1. I surface grind all the mating faces, and clean them with acetone just prior to stacking/MIG welding.

2. When I have the pieces ready to MIG weld, I have the forge running, and ready to go.... MIG weld the entire outside edges of the "sandwich"... Then get it into the forge right away. Something I learned early on with stainless San-Mai.....if you MIG weld it, and let it sit/cool, and you have ANY pin hole(s) in the MIG weld....as it cools, it will "suck" atmosphere in. I learned this the hard way by MIG welding a billet, then leaving it sit overnight.....next morning I forge welded it (at least I thought I did), and when I ground off the MIG, it literally fell into three pieces.....it was obvious what had happened. On the mating faces you could clearly see that there was a black line, beginning at the MIG weld(where there was a "pin" hole, and then spreading out over nearly all of the mating faces....it looked like a shiny black teflon all over the mating faces.

3. Once you have it forge welded, I don't recommend trying to do much forging to shape....the materials (both 416 and 304) have very different expansion/contraction properties then say a carbon steel, or Damascus core. You might get a little shaping done, but odds are it will come apart if you try to do to much forging on it after welding.

4. Neither 416 or 304 San-Mai will anneal like carbon steel. I tried a number of times to anneal it as I would carbon steel or carbon based damascus....in vermiculite. It simply doesn't work. The solution I came up with, was to put it in my paragon oven, set at 1350F for a 2 hour soak, then allow it to cool down in/with the oven overnight....and in some cases longer. My best annealing results come when I put a couple of larger chunks of steel in the oven with it.....when I do that, its often 24+ hours before the billet(s) are cool enough to remove from the oven, but they are well annealled, and MUCh easier to grind/work with.

5. There is going to be a huge amount of super tough scale....its just a by product of the temps used, and the duration in the forge. Speaking of that, personally, I dial my welding forge to 2370-2380F, and allow stainless San-Mai billets to soak for 7-10 mins AFTER the billets reach that temp. Back to the scale... After annealing, I grind all the MIG clean with an angle grinder, and if I've calculated/guessed correctly on the thickness of each initial piece in the billet, its not uncommon to remove approx. .100"+/- from each side to get rid of all the scale.

6. The majority of what I do after that is stock removal. I heat treat based on whatever material the core is.

7. Something you must keep in mind with stainless San-Mai, is that the stainless is not going to harden nearly to the level of the core material....this comes into play if you press fit guards on straight blades......meaning you need to file/fit much closer before press fitting. If you use the material for folders, you have to consider/plan for how soft the stainless is....meaning you have to think about wear surfaces if you use bearings in a folder (consider counterboring the blade instead of the liners/scales), or the size composition of washers. When used in a liner or framelock folder, you have to pay close attention to the amount of pre-load you put on lock bars, and the type of detent you use, otherwise the detent will gall the softer stainless along it's path of travel.... Personally this is where I use ceramic detent balls, and only pre-load lockbars to the point of positive engagement in the open position.

That's certainly not all there is to it, nor all the possibilities. Mr. Murphy is always lurking around when it comes to building Stainless San-Mai, and just waiting to jump on you. Its just another learning experience, and another step up the ladder of Bladesmithing. It took me a number of moths failing, and lot of talking to others before I managed my first success. But as with most thing we do, once you understand what's going on, and how to "work around" the problems, its not really all that difficult. These days I can achieve about an 80% success rate. The times I fail is almost always when I'm trying something "new", or get lazy and let my attention stray. <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' />

What thickness are you using for the middle section compared to the outside layers? From what you are saying I guess you are not using flux in between the layers? Thanks Kelly

For me, the thickness I use depends on what I want in the finished billet. Generally speaking my cores tend to be .080" to .125". Because there is so much loss on the outsides due to scale, and it's removal, I will generally go with .125" to .1875". If in doubt, go thicker.... you can always "grind it off", but you can't ever put it back. <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' />

No flux. The technique is generally referred to as "dry welding". The idea being that if you can eliminate oxygen, and the heat it correct, you can weld without the use of flux.

Thanks Ed going to try it soon.

Great info on san mai.

Where does one purchase .125-.1875 inch thick 416 stainless? I see Aldo has .250 and thicker.

Thank you!

Steve

Thats a good question..... I don't know. What I do is forge all the 416 I use. I generally get it in 1" and 1 1/4" round stock, then forge it to whatever end size/thickness I need. Every now and then I pick it up for free from a rifle barrel maker here in Montana (he saves his drops for me). If I have to purchase 416, round stock is much more readily available then other forms, and much cheaper too.

|quoted:

Great info on san mai.

Where does one purchase .125-.1875 inch thick 416 stainless? I see Aldo has .250 and thicker.

Thank you!

Steve

416 sheet is available through Texas Knife supply. http://www.texasknife.com/vcom/advanced_search_result.php?search_in_description=1&keywords=416&x=0&y=0

410 sheet is available through Jantz Supply. http://jantzsupply.com/

I think it was Karl Anderson that prefers the 410 to the 416, but I might be mistaken.

Admiral steel has 1/8, 3/16, 1/4 and 3/8.

Personally, I quit using 416 right at 4 years ago.

410/420 has been my choice since.

When it comes to forging, the added sulfur in 416 is not your friend.

Thanks Karl & Ed you guys are invaluable. I owe you both a drink at some point. Timber Tiger

Thanks for the tips gentlemen.

I just successfully forged my first stainless san mai yesterday.

My practice with high carbon and mild steel billets is to grind clean with a 120 grit belt, and as soon as possible wipe with WD-40. I just did the same with the components of my stainless san mai billet, and then sealed it up with the arc welder.

With san mai in general, I prefer to use 1/4" (or even thicker) stock for the pieces of the billets. This will hold the heat for welding better than a thinner piece, which can be beneficial.

My previous attempts at stainless san mai failed because I didn't get it hot enough (tough to do in most standard venturi burner forges it seems).

I used 416 for the cladding, and like Ed stated, it doesn't anneal normally. I didn't expect this. Anyway, it seemed fine for finishing after heat treating was complete, but I had to use a carbide bur to get the holes in the tang, before hardening.

I'll be looking into different options for the cladding just to see what might work better, but happy with the result over all.

Thanks.