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Forge welding stainless to high carbon?


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Did some looking here, but haven't found much.  Did some looking on youtube as well and there are a couple of videos of some folks successfully forging stainless to high carbon, but not much on the actual process or how they did it.

Anyone here do it?  Is it terribly difficult?  Are there any benefits to it?  I'm kind of more curious about it than anything.  The examples I've seen made for some beautiful knives.  

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Most of the pieces of this type that I have seen have been san mai blades, with a stainless cladding and high carbon core. You would benefit from having a mostly stainless blade (any exposed non-stainless steel will still oxidize) and a quality blade steel at the edge. 

 

It's not that hard if the proper steps are taken. The chromium in the stainless forms oxides that inhibit the forge welding process, that's your major challenge to overcome. There are some fluxes I have heard about that will take care of this. But if I remember correctly, the more effective they are, the more toxic they are, usually.

 

Welding the pieces in a canister is another option. 

 

Probably the easiest way to do this is to stack up your pieces and TIG weld the edges completely shut, so no oxygen can get to the inside of the billet and form chromium oxides on the bonding surfaces. Any welding process should work, I'm just partial to TIG because of the precision and control you have. 

 

It's also possible to pattern weld with stainless, its easiest if put non stainless steel as the outer pieces on both sides of your initial billet, so each fold has non stainless bonding to non stainless. Then the only hard part is getting the initial billet to stick. The above advice of welding the edges completely shut would still apply to the initial forge welding of the billet. I'm not sure what effect carbon diffusion has between stainless and non stainless steels, but I'm sure it would still be an issue to contend with.

 

Hope this helps. 

 

 

Edited by Will Wilcox
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Makes perfect sense.  Sounds like it's a little tedious with having to seal things up to prevent chromium oxide.  And yes, a san-mai construction is what I've seen. Carbon migration looks to be visible in the region where the two metals are welded and the bevels ground on the blade (and that is part of what makes them look so nice).

It would also seem that the right flavor of stainless is needed too.  I looked at some coefficients of linear thermal expansion for carbon and stainless steels.  While the plain chromium grades have similar CTE values as carbon steels, the austenitic grades are around 1.5 times higher.  Also, thermal conductivity for stainless is a bit less than carbon steel, so that could be a big problem with warping or cracking during a quench.  I could see the carbon steel core possibly pulling completely loose or maybe even splitting.  I'd say an edge quench would be the way to go.

 

However, even with what sounds like a recipe for doom, some folks are doing it and making some awesome looking knives.   Lol, I guess there's a couple ways to go about this...read more, see what other info I can find...or just go try it!  

 

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I have done it once and it worked okay, I used a cheapo stick welder to seal the billet.

the biggest piece of advice I can give, is that your pieces of steel need to be close to finished thickness.

the combo of stainless with carbon steel is so different that forging it to shape just causes all kinds of problems. I ended up cutting in the tip and tang. becuase forging it on edge just caused the material to split.

 

when done properly it looks really good, so could be worth the extra effort.

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I've made several  of the SS clad billets for San Mai blades.  I use 416SS, but have heard 410 is better since 410 has less sulfur (.03% vs .15%).  I've read the sulfur can make cracking a tad worse, but I've not had a problem using 416SS for the billets I've made.  I use 1095 for core with 416SS cladding.  I clean (grind clean) each piece of steel used in the billet, then clamp in vise, then seal weld all the way around the billet.   Weld handle on, heat in forge to around 2200°F to 2300°F, then lightly hammer to fully set welds.  I'll do this 3 or 4 times to be sure before drawing billet out to thickness desired - usually around .150", then surface grind to final thickness usually around .100" for kitchen knives.

 

Good luck and have fun.

Edited by KenH
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