Heat treat of San mai

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seanystrangle

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i have a question about heat treating San Mai it’s mild steel jacket with a layer of 15n20 on both sides and 1095 core. I was doing some reading and saw a lot of people seem to have them split after the quench. How should I go about this? Clay the spine? Edge quench? Do it like normal and do a full quench? Any help would be awesome thank you
 
Full quench. With good welds, I have never had a problem. I can't really understand any functional reason I would want to edge quench a san mai blade.
 
I wouldn’t do an edge quench to gain anything. I had read that it helps prevent splitting. I’m pretty sure my welds are good I haven’t seen any weld flaws while grinding but this is my first time having made San mai
 
I think you should full quench as advised, I think you would want to know if your welds are any good.
if the lamination is splitting then that is to be addressed,
 
joedhiggins said:
Full quench. With good welds, I have never had a problem. I can't really understand any functional reason I would want to edge quench a san mai blade.
Click to expand...

Welllllllll.....These welds were good right?

20180323_180743.jpg 20180323_180750.jpg

So good the jacket pulled that solid core of 1084 apart. Now, this was stainless, not mild steel, and apparently as the core grows in it's transformation to martensite, while the stainless doesn't because it didn't form martensite quenching from 1500F, so it's trying to hold it's current size while the 1084 is like puppies busting out of a sweater.

So edge quenching is one way around this. I didn't know if mild steel would act the same, but I know H HSC /// does a lot of this kind of cladding so if he hasn't had a problem, maybe it's no problem with mild steel.
 
kuraki said:
Welllllllll.....These welds were good right?

View attachment 970820 View attachment 970821

So good the jacket pulled that solid core of 1084 apart. Now, this was stainless, not mild steel, and apparently as the core grows in it's transformation to martensite, while the stainless doesn't because it didn't form martensite quenching from 1500F, so it's trying to hold it's current size while the 1084 is like puppies busting out of a sweater.

So edge quenching is one way around this. I didn't know if mild steel would act the same, but I know H HSC /// does a lot of this kind of cladding so if he hasn't had a problem, maybe it's no problem with mild steel.
Click to expand...

I do HT primarily laminated steels, san mai and multi layer, and I've never ever had a problem with splitting, and all quenched in water. However I do not make my own laminated steels. The bar stock I buy to forge is made in Japan with expensive equipment and I'm guessing on rolling mills.
 
I just HT for the core steel and full quench ( usually in Parks #50). Never had on separate.
 
kuraki said:
Welllllllll.....These welds were good right?

View attachment 970820 View attachment 970821

So good the jacket pulled that solid core of 1084 apart. Now, this was stainless, not mild steel, and apparently as the core grows in it's transformation to martensite, while the stainless doesn't because it didn't form martensite quenching from 1500F, so it's trying to hold it's current size while the 1084 is like puppies busting out of a sweater.

So edge quenching is one way around this. I didn't know if mild steel would act the same, but I know H HSC /// does a lot of this kind of cladding so if he hasn't had a problem, maybe it's no problem with mild steel.
Click to expand...
I wonder if stainless act same as clay act on carbon blade when you quench for hamon ?
 
I don't think so. Its coefficient of thermal transfer is a little slower than carbon steel but not like the difference between clay and steel.
 
kuraki said:
Welllllllll.....These welds were good right?

View attachment 970820 View attachment 970821

So good the jacket pulled that solid core of 1084 apart. Now, this was stainless, not mild steel, and apparently as the core grows in it's transformation to martensite, while the stainless doesn't because it didn't form martensite quenching from 1500F, so it's trying to hold it's current size while the 1084 is like puppies busting out of a sweater.

So edge quenching is one way around this. I didn't know if mild steel would act the same, but I know H HSC /// does a lot of this kind of cladding so if he hasn't had a problem, maybe it's no problem with mild steel.
Click to expand...

I imagine the carbon-to-carbon welds are more forgiving. But say it is an issue, edge quenching to a large degree defeats the purpose of an all carbon san mai. The hard and springy core with the reinforcement of ductile cladding. I understand the edge quench a bit more in stainless clad blades, as you just want a carbon steel cutting edge with stainless sides, but when it is all carbon, what else would be the point?
 
Well I have a bunch of hand sanding and some drilling before I heat treat it. I hope I’ll get to it Saturday I’ll do a full quench and see what happens thank you everyone
 
joedhiggins said:
I imagine the carbon-to-carbon welds are more forgiving. But say it is an issue, edge quenching to a large degree defeats the purpose of an all carbon san mai. The hard and springy core with the reinforcement of ductile cladding. I understand the edge quench a bit more in stainless clad blades, as you just want a carbon steel cutting edge with stainless sides, but when it is all carbon, what else would be the point?
Click to expand...

Only to prevent what I had happen (if it's a concern with mild given there is no martensite conversion to grow with the carbon core). But as far as the point, there's no point to san mai outside aesthetics in my opinion, so any mechanical advantage lost by edge quenching is moot to me.

But, it's apparently only a problem with stainless, as while I've never done mild, it's never caused me a problem with wrought iron either, and if you did want to through harden, you could also peen the cladding so it's in compression lengthwise before the quench, and then relaxes with the core growth as it converts to martensite.
 
kuraki said:
Only to prevent what I had happen (if it's a concern with mild given there is no martensite conversion to grow with the carbon core). But as far as the point, there's no point to san mai outside aesthetics in my opinion, so any mechanical advantage lost by edge quenching is moot to me.

But, it's apparently only a problem with stainless, as while I've never done mild, it's never caused me a problem with wrought iron either, and if you did want to through harden, you could also peen the cladding so it's in compression lengthwise before the quench, and then relaxes with the core growth as it converts to martensite.
Click to expand...
Mild and wrought are far more ductile than stainless, so it follows it would be less of an issue. Peening may help. A slower quench steel would probably also do it. 52100, 5160, O1, etc.

I don't necessarily disagree that san mai probably doesn't have a meaningful advantage over a differential temper in toughness. That being said, I can't speak definitively on the subject. Larin, maybe you can cover this at some point?

THere are some practical advantages from a blademaking standpoint to san mai. Blades are easier to straighten post quench, and they seem to hold up better to water quenches than do fully martensitic steels. They also allow some cool things like post heat treat texturing.
 
Whether san mai can make a mechanically superior blade or not wasn't my point. That's a can of worms I don't want to open (specifically when selling a knife). I meant I personally do not take the mechanical properties of san mai into account when I make a san mai blade. I do it for aesthetics. Maybe it's stronger, more flexible, whatever. Dunno. Don't care. Doesn't matter to me. It passes the testing I do before finishing or it doesn't, I'm confident it'll serve it's purpose or I'm not and it gets tossed, just like a mono-steel blade.
 
There are lots of advantages to san mai that aren't necessarily because/if it is "mechanically superior." Easier to straighten, easier to finish, corrosion resistance if using the right steels, etc.
 
....and there is less of the more expensive high carbon steel in the blade compared to a mono steel blade, which I think is the main reason san mai was invented all those years ago in the first place. I'm not so sure it was about toughness, but rather about economics. It's also much easier to thin if needed when sharpening.
 
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