Jump to content

First steps in pattern welding

Arno Visser

Recommended Posts

Hi everyone,


After waiting what seemed like a year (in reality a few weeks), I finally had my long awaited class in pattern welding yesterday.

Since there is only so much you can do in one day, we didn't have the time to make a big billet with so many layers, but still, I'm now the proud owner -and creator- of a nice piece of san mai.

The first few hours of the day were spend on a theoretical part. For me this proved very useful. Still have some questions, but I'm getting to that part later.

After that it was hammer time....We were told we were 'only' going to do a three layer billet. But we were given the most difficult weld to perform (according to the teacher). We were going to do a weld of iron to a 1,2% carbon steel. And he was going to make it easier for us by putting the iron plates on the outside. Since apparently iron heats up slower than this carbon steel. Anyway, the result is there. To a lot of you guys this may seem like nothing special, but this was mt first time..... B)

I have taken some of the material from the side with a grinder and it seems like all went well. In the light you can see the color difference between the layers. I'm still thinking of what I'm going to make from this......


Now to my question. When I was in school to become a goldsmith, I had to learn a lot of theoretical things. Calculating the weight of the components you need to make a certain alloy (say, 18 carat yellow gold) was one of those things. So, I'm very into that stuff.


What we were told was that making a billet is like creating a new metal. You have to think well. You need to have a clear picture of what you want to create and what you are going to use to create it with. Carbon migration and carbon loss are two things you have to think about, otherwise you might end up with a metal that has to less carbon to do a HT.


Every welding cycle causes 0,03% of carbon loss. By the way....correct me when you think I'm wrong. I'm only repeating what I was taught.

Also carbon migration causes a decrease in carbon. The example was like this. When you weld a piece of 1,2% C steel to a 0,3% piece, you'll end up with:

(1,2+ 0,3)/2 = 0,75 and if you perform 5 welding cycles that leaves you with 0,75 - (0,03*5)= 0,6% carbon in your end product.

Now, it's this first part that I have some questions about. I can understand that carbon migration causes one part to absorb the carbon of the other part. But I think that in this example the calculation is only correct when the two parts are equal in mass. When you take 1,2% C steel of 8mm thickness and 0,3% C of 4mm (the two pieces have the same length and width) , I don't think you'll end up with 0,75 (or 0,6 after 5 welding cycles). How does this work?

Also, is my 0,3% piece after welding now suddenly 0,6% C throughout the whole piece or only in the zone closest to the fusion bond?

Again, how does this work?


Learning only raises more questions....... :wacko:



Link to comment
Share on other sites

Nice piece. I'll let others more knowledgeable comment on the carbon loss and such but the numbers do seem extreme. If you keep the atmosphere reducing you shouldn't lose much at all. You will get an average of the carbon content after a fair bit of folding though.

Beau Erwin


Custom knives

Bcarta Composites

Stabilized Woods

Link to comment
Share on other sites

Well, I'm not the metallurgist in the group, so the Ric Furrers, Peter Johnssons, Mick Maxens of the forum may disagree with me (and I'd go with their thoughts over mine), but I'm having a hard time buying the carbon loss for each weld stat that you quote. I've folded steel a LOT of times and it has still has seemed to hardened up just like the factory steel would have.


Don Fogg told me he once folded a blade to 6 MILLION layers. Not sure how many welding passes that is, but I'm sure he would have mentioned if it lost so much carbon as a result of the folding that it didn't harden.


The carbon migration question: I recently heard that it takes four welds on average for a billet to fully migrate carbon. I have not heard of overall carbon loss from migration, but rather an averaging of the carbon content.


What kind of steel is the middle layer?


I'd just forge it to shape, grind an edge and see what happens. You may be over thinking this.


Congratulations on the weld, and good luck!




"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood, who strives valiantly; who errs and comes short again and again; because there is not effort without error and shortcomings; but who does actually strive to do the deed; who knows the great enthusiasm, the great devotion, who spends himself in a worthy cause, who at the best knows in the end the triumph of high achievement and who at the worst, if he fails, at least he fails while daring greatly." -- Theodore Roosevelt


Link to comment
Share on other sites

Thanks guys...


I understand carbon migration and the averaging that causes, but does that mean that my iron plates that are on the outside have turned into steel that can take a HT?


Dave: Thanks for your encouragement (the rest of you guys as well of course) according to this theory, a 6 million layer would be still possible I think. If you would only use high carbon steel......then you would only suffer from the 0,03% loss each welding cycle. And if you start a billet with a lot of layers...that is just one welding cycle. The averaging of the carbon content is what I was talking about. The only overall carbon loss (0,03%) is apparently because of getting the material up to welding temp. (I'm just repeating what I've been told).


My middle layer is a 1,2% Carbon steel. Something like O2 or so.

Using this calculation my san mai billet should contain something like ((1,2+0,3+0,3)/3)-0.03 = 0,57% Carbon. Good enough for HT.


I've always been getting high marks in chemistry when I was still in school, 'twas my favorite subject next to history. so with these things I always like to know the scientific facts. If there is something to explain or calculate this, I'm just very interested to know about it. With this billet the only concern that I have might be that I cannot decide which of the ideas I'm having I'm going to carry out...........just too many ideas...... :P


And....over thinking. ahh..well maybe. Over engineering....definitely. I'm always making it too difficult for myself. wait till you see the box-bellows I have just built...... ;)



Edited by Arno Visser
Link to comment
Share on other sites

The rate of carbon diffusion is related to time, temperature, and distance. The skins on your three layer billet are not steel. They are still iron. When you grind into it, if you polish and etch you will see visual evidence of the carbon diffusion along the weld zone. Fold it and weld it four more times, and things are pretty well homogenized for carbon content, assuming "normal" forge welding practice and temperatures.


And congatulations! Wlcome to a very habit forming, obsession feeding, pocketbook depleting craft. :)

Edited by Howard Clark
Link to comment
Share on other sites

If anyone will run the carbon loss testing I will donate a 32 million layer billet to the experiment.

I bet less than a smidgen of carbon will be lost....migration yes, but loss...very little.


Welcome to the wonderfully annoying world of pattern-welding Arno.



Richard Furrer

Door County Forgeworks

Sturgeon Bay, WI

Link to comment
Share on other sites

Thanks guys.....Howard, Ric

What you are saying is what I thought I knew ( a bit) before Howard, but this carbon migration and loss story got me confused a bit. So, should I decide to fold my billet a few times, only then the carbon has migrated so much that it is divided equally through the billet.

And congatulations! Wlcome to a very habit forming, obsession feeding, pocketbook depleting craft. :)
that is all probably very true.


To me it's just to new to be annoying yet Ric. But when I continue like this that feeling will probably come all to soon......

As for carbon migration: is there a formula with which you can calculate the carbon content you are going to end up with? or are you like....don't worry too much about the whole carbon migration stuff. just do your thing and have fun.......or something like that.



Link to comment
Share on other sites


As for carbon migration: is there a formula with which you can calculate the carbon content you are going to end up with? or are you like....don't worry too much about the whole carbon migration stuff. just do your thing and have fun.......or something like that.



Now, you could always start doing all high-carbon pw, in which case you can pretty much forget all the average-carbon stuff. I find L6/1084 heat-treats just like regular L6 steel, is maybe more forgiving/less likely to air harden, but holds an edge great after 2 welding cycles or 8.

Edited by Al Massey
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Create New...