A2 or S7 for a Katana?

Since this is back to the steel. 1050-1080 will produce the best katana that a home smith can do. The steel is forgiving,takes a wicked edge, can be tempered to a great amount of spring,and produces a heart stopping hamon.With all deference to those who use L-6, A-2 and 440 (yuck)....The heart of a sword is in the steel, and the soul is in the fire.10XX steel is the one you want if you want a sword with heart and soul.Why accept or settle for less!
Stacy
 
As Phill hartsfield does it, the entire blade is hardened to a hardness of who knows what, and then in the 2nd and 3rd tempering phases the blade is drawn down to 58/59 leaving the rest of the cutting edge 60/61. I have tried to oil harden A2, but since it is air hardening, the rest of the blade practically gets as hard as the oild quenched part. So when you go to temper it the first time almost, the whole blade ends up the same hardness practically throughout. You just have to figure out WHAT mr. hartsfield use on the edge to protect it from being drawn down in the 2nd and 3rd tempering phases as i know he tempers A2 3 times (for a reason). I don't believe A2 is a very good choice as a katana for someone who is a beginner as i don't believe many if any make a katana out of a2 as again it is air hardening.
 
I know Phill Hartsfield since 92 and he definitely air hardens his A2. jack76 is right, the spine of his katanas is about 58RC. Why differentially temper A2?
Years back I was in Phills shop when Sensei Yamazaki came in with his katana for Phill to repair. There were slight chips on the leading edge, he told Phill he accidentally missed his target, and cut the iron stand!! I saw the iron stand with my own eyes and there was indeed a nice deep cut. Sensei Yamazaki has been cutting for many years and stated that if it had been a traditional sword, it definitely would have broken instead of chipped, no ifs or buts.
Phill believes that even if differentially tempered by a few points, it helps when cutting heavy duty targets like thick walled bamboo and 2 by 4s.
Nobody knows how he does a temper line on A2 and I doubt anybody will. And he did some amazing hamon patterns in the 80s that he will not duplicate again.
His 1st katana was made in 1982, which is long before anyone else.
 
I have made a few katana via stock removal and prefer 5160 in various types of heat treat scenareos. Mostly thru hardened as I disagree strongly with some who feel that a katana *must* have a hamon. Having done them with hamon and without I find that most folks who handle a well done katana (either tactical, pseudo traditional, or totally traditional) don't really worry about it. If it is well done the work stands on it's own, hamon or not but that is a matter of personal taste. :D

Yachoricasso1.jpg


This is a tactical style katana in 5160. No hamon, paracord and black steel mounts.

If you want to use A2 and send it out to someone who specializes in air hardening steels I'd think that would be cool as heck done right. Me personally? I'd use 1/4" 5160 (I *do* use 5160...) bar stock and send it out for heat treat to a reputable guy.

A lot of steels make dandy katana if you can live without a hamon and in my opinion a good 10XX steel tempered to the mid 50's rc will give outstanding performance and is easily done on a small belt grinder and cleaned up with paper and files.

5mmsori.jpg


A 5160 katana done *with* hamon in a very nearly traditional mount and saya...

Good luck!

Brian
 
To answer your original question regarding A2 or S7, S7 has 3 times the impact resistance that A2 does, at a minimum. With A2, either at Rc60 or 57, you get a Charpy C notch test (imoact breaking strength, basically, of 41 ft lbs. With S7, at Rc 59, you get a Charpy C notch of 85 ft lbs. At Rc 57, it goes to 125 ft lbs. Due to impact on a sword, I'd opt for S7 over A2 anyday. I'd probably opt for 1060 or 1070 over either.

Gene
 
I was bitten by the Japanese blade bug several years back and exposed myself to months of frustration attempting to create a katana blade via the traditional ht methods. It seemed like a stright forward process. Take a piece of shallow hardening steel (w2, 1060 etc) clay coat it and quench in brine or fast oil.

I cracked several blades before I was able to get one hardened in one piece. I was able to get the "look" (nice hamon) I wanted but never was able to get the cutting performance where it should be. I finally decided to try a through hardened 5160 blade and my first try resulted in a blade that would really cut and is tough as nails.

The traditional HT methods are very much an art-form and would probably work if you are willing to invest a lot of time and money in getting the process down.

I think the bottom line is:

If you must have the asthetics of a traditional blade plus cutting performance, you would be well served by purchasing a blade from one of the known blade smiths like Randal Graham or Rick Barrett. They have perfected the art form to the point where they can produce blades that look good and perform well.

If you want to do it yourself and are mainly interested in performance 5160 or a2 would produce excellent cutters.

Jim
 
I would like to throw in that I have cut Tameshigiri with a sword made through marsquenching (hope i an saying the right one) to form banite. I must say that while I agree with the looks and function of a hamon this sword cut as well if not better than any traditional sword I have cut with. I however do not have a 400 degree salt bath yet. For a competition sword I have been thinking alot about a that juicy banite but you cant beat the looks of a nice hamon.
 
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