Heat treating Hitachi San Main Blue Paper Steel

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theblademaker

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I have a question about quenching San Mai Blue Paper Steel or any San Mai in fact. I know the required temps for my steel however when quenching it I didn't do any grinds on the knife and simply profiled the billet. Meaning the harden-able core wasn't exposed during the quench but rather remained jacketed. Is that a proper way of heat treat? I file tested it with the hardness tester kit and gave me a hardness between 60 and 65 after tempering and exposing the hardenable edge. However the customer is saying it's not retaining the edge very well. So should I expose the harden-able edge before quenching?
 
How thick was the steel? What did you quench it in? What are the measurements on the edge geometry? How did you sharpen the edge? How is the customer sharpening the edge? What is he/she cutting? What kind of cutting board?
 
It was a 3.3 mm billet that I quenched in Canola oil. I took the grinds to create an edge with almost no thickness at around 12 degrees for the bevels. I did a double beveled skiving knife basically that the customer uses to cut leather. I sharpened it on a tormek t8. But in terms of heat treatment does leaving the core jacketed actually harden it? I used an oven to reach the temp required which I believe was 815 C .
 
Hitachi blue does better in parks50 or DT-48, but you can get an extra Rc point in brine. You risk broken blades in brine. I did some experiments a few years back. Heat treat at 1475-1485, quench, and temper to desired hardness. I don’t remember tempering temps off hand. Search old threads to find them.

if you don’t grind in the bevels, the risk of breaking is lessened.
 
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theblademaker said:
I have a question about quenching San Mai Blue Paper Steel or any San Mai in fact. I know the required temps for my steel however when quenching it I didn't do any grinds on the knife and simply profiled the billet. Meaning the harden-able core wasn't exposed during the quench but rather remained jacketed. Is that a proper way of heat treat? I file tested it with the hardness tester kit and gave me a hardness between 60 and 65 after tempering and exposing the hardenable edge. However the customer is saying it's not retaining the edge very well. So should I expose the harden-able edge before quenching?
Click to expand...
just to be clear.................did you grind bevels and put edge on right side ? Of course if this is what you have ........
Construction: Core layer is Hitachi Blue Paper No 2 high carbon steel
16 layer low carbon steel outer layers(8 layers per side).
Blue Paper steel core extends only to middle of bar and spine will be soft.
Click to expand...
 
It seems like with any San Mai using high carbon core and low carbon cladding you'd want as fast a quench as possible because the low carbon cladding is going to slow the quench of core a good bit. It seems that brine would be a very good quench medium. Has anyone had cracked or broken blades from quenching any low carbon clad San Mai?

I'm asking because I KNOW I do not have the experience to determine.
 
I don't have the experience, either. I've heat treated a few of the Dictum/Workshop Heaven billets with both Blue paper and White paper steel cores. (not the suminigashi, but rather the billet that has wrought iron as a jacket, where the core steel goes completely from one edge of the billet to the other). I always pre ground those blades to expose the core steel to the quench medium, Parks 50 oil, and would be my recommendation. Blue and White paper steels are very shallow hardening, especially White, and just personally speaking I would want that bevel pre ground to expose the whole edge "area", not just the 1mm thick edge on a profiled blank.
 
You're right, if the blade has bevels ground to expose core material pre-HT'ing I would expect to HT based on needs of core material. The question asked by OP and my response above was based on a profiled only blade with NO core material exposed, other than the edges. It seems the low carbon cladding would slow the quench a good bit thus requiring about the fastest possible quench available with no worries of cracking the core material. I'm hoping Larrin, Hoss, or other knowledgeable folks will chime in on this with comments.
 
I've regularly quenched laminated steels (perhaps 250 blades) in straight water and never have had a cracked or delaminated blade, thousands of blades are done regularly at Carter Cutlery this way. The bevels are never pre ground in. The material is always quenched with the full cladding, with no core material exposed (except at the spine and profile edge)

those of you who are concerned about straight water and cracking etc should try it, it works fine and works well.

The concern about the customer saying it doesn't hold the edge well is subjective and I think we need more details on that....
 
I agree with Harbeer the core does harden just fine, but the thickness of the cladding and core also factor in. If the cladding is left too thick it could be possible it would slow the quench too much - my thinking anyway. The only laminated blades I've quenched are <1/8" with a pretty thin core and cladding.
 
The effectiveness of the quench would still be related to the thickness of the steel whether there is cladding or not. Laminated steel has roughly the same heat conductivity because it is a solid piece.
 
OK, that makes sense. That means the core is HT'd the same with low carbon cladding as the middle of blade of same thickness would be if a single layer. Thanks Larrin.
 
Update:
I HT'd a scrap piece I had exactly the same way I did it the first time and then ground it to expose the core. I then used a hardness tester file and the 65 was skating a bit and biting a bit. The 60 was completely skating and didn't bite at all. I then left it without tempering it and came back the next day to find the piece split in half lol. But anyways I think using water would be a better option and grinding the bevels pre HT on this thickness of a billet isn't really necessary.
 
I flash temper laminated steel in the Forge within seconds of the quench. You can use a tempilstik temperature marking
 
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