carbon migration in pattern welded steel

[Giuseppe Maresca]

There is something I can't understand about pattern welded steel.

I read somewhere that after folding few times a laminated billet, the carbon in it became homogeneus in the whole piece. This means that if I weld for example 5 layers of 1095 and 5 layers of 1010, I will make a pattern welded blade that works like an homogeneus piece of 1050, less some decarb.

So, if the carbon is well distributed in the steel, why does some layer get darker than other when I etch the blade? I talk only about steel with identical composition and different carbon content.

thank you

Giuseppe

[R.H.Graham]

Although carbon content can have a bearing on the etch, moreso it's a matter of differing alloy contents, for example, steels with more manganese tend to etch darker than steels with less, all other things being equal.

And alloying elements aside from carbon tend not to migrate between the steels, at least to a large degree.

 

What's kinda neat though is that even if you fold and weld one steel, you still get some pattern, I always thought it was because of decarb layers maybe or the weld zones themselves, it's just a guess though.

[Mike Blue]

...after folding few times a laminated billet, the carbon in it became homogeneus in the whole piece.

 

So, if the carbon is well distributed in the steel, why does some layer get darker than other when I etch the blade? I talk only about steel with identical composition and different carbon content.

 

It is a good thought problem and question though.

 

For the most part, by the time you've made four folds (implying welding heats), the carbon distribution is fairly homogenous. The only barrier to carbon migration, would be using a pure nickel shim between layers. Nickel alloys like 15N20 or L6 might have a measurable slowing on the migration process, but enough heat and time will even that out anyway since those are not pure boundaries.

 

The minor alloying elements can make a big difference in appearance as well as heat treatment etc. Those have all been discussed elsewhere. This can be especially true from lot-to-lot even from the same steel mill.

 

When I've used 1095/1010, there is still a subtle pattern that is quite attractive but without the usual help from nickle in one of the components. Others have attributed the darker color to a higher manganese level.

 

Then there is the weld line itself. Sometimes lighter, due to decarburization, sometimes dark from crud due to poor cleaning between welds, who knows?

[Beau Erwin]

Kinda the same thought with monosteel cable, that a small surface of each strand gets decarb, and turns to iron, which gives the patterning, but you'd kinda think the carbon would migrate back into those barriers.

[Giuseppe Maresca]

but you'd kinda think the carbon would migrate back into those barriers.

Exactly... This is another thing I can't understand.

 

I too thought that manganese was the thing, but this means that the lower carbon layer ger darker and that the high carbon layer remain brighter, and this is the opposite of what usually happen. Mn usually is more high in low carbon steel.

I've made a blade with A36 and 1080. A36 is recycled stuff, I know, but the impurities are relatively low (some bad S and P, and no Ni or Cr), and the Mn is pretty high. I etched the blade every time I folded and welded it, with no change of contrast from the first to the last weld, and A36 was always far brighter than 1080...

[daryl meier]

I've made a blade with A36 and 1080. A36 is recycled stuff, I know, but the impurities are relatively low (some bad S and P, and no Ni or Cr), and the Mn is pretty high. I etched the blade every time I folded and welded it, with no change of contrast from the first to the last weld, and A36 was always far brighter than 1080...

 

Unless you got a spec. sheet for the "A36", there is no telling what is in it. Cr,Ni,Si, and P all cause light color when etching.

Edited March 1, 2007 by daryl meier

[Giuseppe Maresca]

Here there is the chemical composition of A36. The Italian UNI code for it is Fe360. As you can see there aren't nickel and cromium, and there are small traces of sulphur and phosporus and some Mn. Pretty similar to 1080.

http://www.stefana.it/acciai.htm

http://www.falckacciai.it/ita/content/p-falk08.htm

[mete]

Giuseppe, Here in the USA we are suspicious as there is more and more 'junk' steel even with higher grades....The 360 doesn't do anything for you as far as a practical blade as the end result is the average carbon content of the two steels.... Carbon diffusion is determined by time at temperature and the number of folds . It will take more than a 'few' folds to make it homogeneous.

[Brian Vanspeybroeck]

I have used A36 for a lot of projects. Mostly harware and fittings but in the early days of learning to grind I ground out a few blades of A36. I have patinated/heat blued it and filed it and heat treated it and just done a lot of experimentation with what is classified as "A36" and never found any amount of consistancy in the steel even in the same bar.

 

If you etch it deeply or heat color it different sections of the same bar wll turn different colors at the same temp and often in an etch you will open up inclusions and even layers of stainless steel...all kinds of stuff.

 

There may be areas or places where there is a verifiable chemistry to A36 but where I'm at and with the steel I have been getting it is pretty much anything and everything remelted and rolled out into a bar and shipped. Oil hardening steel, air hardening stuff, small amounts of stainless and all kinds of stuff finds its way into A36.

 

Pretty much mutt steel with no consistant working properties and characteristics. Some of it is pretty neat but 1018 is just as cheap and much more consistant from bar to bar and within the same run in my experience. So, it must be a different A36 than what you guys are getting in Italy, Giuseppe. A36 in the US is pretty much just junk steel.

 

Brian

[Giuseppe Maresca]

I think that it is the same junk.

this is the blade I made with this stuff and 1080. It has a good contrast, more than I expected...

http://i21.photobucket.com/albums/b268/Giu...86/DSCN1098.jpg

I have to change the example.

If I weld pure iron (100%Fe) and High carbon steel (99%Fe and 1%C), once the carbon homogeneusly migrate into the whole piece, will it show laminations?

[Mike Blue]

If I weld pure iron (100%Fe) and High carbon steel (99%Fe and 1%C), once the carbon homogeneusly migrate into the whole piece, will it show laminations?

 

That's a pretty blade Giuseppe, no matter what it's made of. I hope it cuts well.

 

But, to answer, the carbon will average out to 0.5% with those two materials. It will have laminations that are visible.

 

Mete: you said it'll take "more than a few folds" to make carbon homogenous throughout a bar. How many folds are necessary?

[mete]

If you take pure iron and iron with 1% C [ not steel] ,weld the two blocks together and heat above critical in a sealed container you eventually will get 1 block of .50 % C and no laminations showing. If you use 1 % C steel you will get laminations showing because the other elements will etch differently......It's not just the folds it's also the temperature .Forging at 1700F will require many more folds than at 1900F to get homogeneous. More time at temperature also speeds it up .Too many variables to give an exact answer.

[daryl meier]

If you take pure iron and iron with 1% C [ not steel] ,weld the two blocks together and heat above critical in a sealed container you eventually will get 1 block of .50 % C and no laminations showing. If you use 1 % C steel you will get laminations showing because the other elements will etch differently......It's not just the folds it's also the temperature .Forging at 1700F will require many more folds than at 1900F to get homogeneous. More time at temperature also speeds it up .Too many variables to give an exact answer.

 

All true. However with pure iron and 1095, if welded and drawn out at a temperature below the "Ac1" of the iron there will be little if any diffusion of carbon.

[Beau Erwin]

So how does it work with things like cable where the idea is the surface of the strands becomes iron from decarb, and the core stays steel?

[Giuseppe Maresca]

if you take pure iron and iron with 1% C [ not steel]

Isn't "iron with 1%C" steel???

 

All true. However with pure iron and 1095, if welded and drawn out at a temperature below the "Ac1" of the iron there will be little if any diffusion of carbon.

This is why san mai works. But if you weld 5 or more times you are working far above Ac1 for long time, and the when layers get very thin I think that the time required to diffuse C into steel decrease a lot.

Or I mistake?

Edited March 3, 2007 by Giuseppe Maresca

[mete]

Isn't "iron with 1%C" steel???

This is why san mai works. But if you weld 5 or more times you are working far above Ac1 for long time, and the when layers get very thin I think that the time required to diffuse C into steel decrease a lot.

Or I mistake?

Yes Fe+C is steel but I should have clarified that I meant ONLY Fe+C not with any other alloying element ......Yes with thin layers the time it takes to diffuse through a layer is shorter.......

[Giuseppe Maresca]

Fine... I was going in panic when I read [not steel].

 

About the blade, I'm glad that you like it Mike but it doesn't cut so well. I think that the carbon content get too low, from sparks I think that it is around 0,4 0,5%. Anyway it is just my sencond pattern welded blade, and the last time I use low carbon unknown stuff. It will became a letter opener for a lawyer.

[Don Hanson]

When I mix steel or iron with little or no cabon in my billets, I make sure that I use at lest 75% high carbon steel with 25% iron, 203E etc. .85 high carbon (1%+) to .15% low carbon is a good mix for me.

 

I recently welded up a billet with three 1'' thick bars of W2 and two 1/4'' thick bars of wrought iron. This mix put the carbon content at around .84 and at 3000+ layers, I got complete carbon migration. BTY, I did this with only 5 welding heats, so very little carbon loss. A blade of this mix cut very well also.

Edited March 4, 2007 by Don Hanson

[Giuseppe Maresca]

Of course... Was doing an experiment, I didn't expected to really came out with a blade, so I welded 4 layers of 1080 and 3 layers of junk iron. The carbon content of the starting billett was around 0,5; I added some steel after every fold, but the carbon loss make this useless...

Now I'm making a billett with 1080 and SK5S (1080 more 0,20Cr and 0,30Ni). I can see some contrast, so it's working for now, and the carbon loss is not a great problem.