Thread: San Mai exercise

I decided to do a san mai exercise in order to practice my welding and to learn about core distortion during extreme drawing.

I started with a piece of 1095 1/4" x 1" x 5" and two equal size pieces of A36. My goal was a 3" x 6" cleaver plus a tang.

The first thing that I learned is that drawing out that much width while gaining minimal length was not practical for me without upsetting the the length and by the time that this was apparent the blank was too thin to upset effectively. So I ended up with a 2.5" x 7" cleaver plus a tang.

During all of the drawing I got no indication that there was any problem with the weld, but when I started grinding I uncovered welding flaws that were now ~ four times their original size. One of them near the heel was deep enough that I decided to cut it out resulting in a 2.5" x 5" cleaver.

When I cut down the san mai cleaver and continued thinning the blade I ran into another welding flaw on the other side of the blade, but the grinding is cleaning it up pretty well. I think I will get some cool figuring on that side where the core is unevenly exposed.

I've still got more thinning and shaping to do, butI wanted to write some of my thoughts while they are still fresh in my mind.

The first is that all of the welding flaws were in the inboard half of the billet. This is the side that I welded first, taking another heat to do the second half. I think that the second half welded better because there was more time for the heat to get into the center of the billet. I will try to do a longer soak before the first weld next time.

I didn't have too much of a problem finding and exposing the core at the cutting edge, but I feel like I may have just been lucky

Trying to draw a 3/4" x 1" x 5" billet into a 3" x 6" cleaver is too hard, so the next time I try this I will try upsetting the billet to 4" before drawing out the width. The upsetting should expose any problems in the weld much sooner in the process saving a lot of work if there are problems.

Using a 1/4" x 1" x 5" piece of 1095 along with two pieces of A36 is a ridiculous way of making a large cleaver, but it does really test a lot of smithing skills. I can hardly wait to try it again. I will need to make another set of tongs first that are able to hold the billet while I'm upsetting.

One of the billets I had done at Charlies did the same thing, I wasn't patient enough to let it heat throughout. Post some pics of it if you have any...or if you are like me you planned on pics, but were too wrapped up in the moment to remember them.

Here is a picture of the bad spot before cutting it out.

Originally Posted by ScottGoodman

One of the billets I had done at Charlies did the same thing, I wasn't patient enough to let it heat throughout. Post some pics of it if you have any...or if you are like me you planned on pics, but were too wrapped up in the moment to remember them.

What I'm having trouble getting my head around is 'If I can take a second heat to do the other half of a billet, why can't a subsequent heat weld a spot that did not weld the first time?' I did 3 or 4 heats at welding temperature with brushing and flux between.

I've only done a couple of san mai before and they were with 1084 and wrought iron. I have had little success with A36 forge welding while doing hawks and axes. Seems A36 is recycled and a "wonder what'n hell's in it" mix. Some will weld fine, some won't weld for anything, and that could be in the same 20' bar. I've had very good luck with 1018 and high carbon though. As an aside I found out a long time ago that grinding between folds has eliminated a lot of issues for me.

Originally Posted by bluesman7

What I'm having trouble getting my head around is 'If I can take a second heat to do the other half of a billet, why can't a subsequent heat weld a spot that did not weld the first time?' I did 3 or 4 heats at welding temperature with brushing and flux between.

From what little I know of forge work and welding, I'd surmise that while it was being worked scale formed in between the layers. At that point without a proper cleaning fluxing can only do so much. The forged welds I've made that didn't take were mostly in places where I could grind them then re-flux them. At that point it could be re-welded, but without the ability to get to clean steel I've not had great success with trying to flux and re-weld layers.

What helps me the most when forge welding is to grind everything clean before stacking or folding. And a dip in diesel fuel will act as an oxygen barrier to the point I've welded stacks of damascus up with no flux, just a dip in diesel while cold. Another thing that helps is don't wait till the billet is glowing orange to flux, I like to put a dab of flux on cold and when it starts to melt and the billet is not yet even glowing I'll add more. Another thing I've found is if working by hand to work from the center outward, or from one end to the other with overlapping hammer blows to work any slag or flux out. I've had issues in the past where I'd trap a spot of flux and it'd bubble up and make a blister, no way to get it to weld except cut or drill a hole to allow the flux out. No reason you can't weld something partially and then weld more later, just as long as a bunch of scale hasn't built up, or your trapping flux or scale. That's another issue I've had with A36, depending on what's in the mix sometimes it scales horribly. Hope this helps.

I'm pretty sure that the problem was due to trapped flux.