mono vs. sanmai, spring vs. differential

This Forum is a place for students of swordsmanship to ask advice from moderators Paul Champagne & Scott M. Rodell on how to practice test cutting in a manner consistent with how swords were historically used in combat. Readers use this Forum at their own risk.

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B.Ko
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mono vs. sanmai, spring vs. differential

Post by B.Ko » Sat Sep 16, 2006 3:01 pm

I posted a similar question on SFI but will do so here to hear from an expert smith like Paul.



I've spoken to Laoshi about the difference in resonance of sanmai vs. mono steel. I also wonder about spring temper mono steel vs. differential hardened mono steel...some one has posted on SFI that differentially hardened steel is more prone to lateral bending.



I've also heard Laoshi talk about resilience of the old laminates but wonder how this translates to actual use. Does this apply only to cutting or also parrying?



This is the point I am most interested in, since few if any of us fight with our swords, do we know how sound they are for parries? Also would the above constructions and heat treatments affect the sword's ability to endure parries?

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Post by PaulC » Thu Oct 05, 2006 3:12 pm

I'm going to start with a simple and short answer to your question, then I will follow with more detail to show how it may not be so simple to answer -short and simply.



the simple

Using the same steel for the construction method, making the blades to the same dimensions and tempering to the same hardness a differentially hardened blade (edges hardened while the center/back is left unhardened) will tend to take a set easier than one that is hardened and tempered evenly throughout the entire blade. A blade hardened all the way though will be more prone to breaking than a differentially hardened one.

When deflecting the true 'springy' blade will hold up to more abuse without bending. It has the ability to return to true. This also helps when a cut is 'off'. It is easier to use a well made sword of modern steel for the beginning student. There is less chance of your blade bending and needing some TLC. I have a friend who is well versed in Japanese swords. He understands that even a well made, traditional katana can take a set with a poor cut or bad technique, he likes traditional blades, he owns traditional blades and he still prefers a modern steel springy katana for test cutting! He is also practical and doesn't have a sword straightener living down the street. Does this mean that a sword made from modern steel and spring tempered is' better' than a traditional steel sword.....?



The not so simple *stop here unless you want more questions instead of less*

A very complex question. Mainly due to the fact that the exact same steel given to 2 different smiths and both told to made a similar sword using similar construction and heat treament techniques can give wildly varying results. With that said lets try to break it down to some more basics and generalities. (oh…remember I said generalities)



traditional steels

The old steels were very simple in chemical makeup compared to modern steels. They were basically iron and carbon with some traces of other element depending upon the ores used in their smelting.The smiths were concerned with varying the carbon content to affect the attributes of the steel, though they did not know that 'carbon' per se, was what was affecting the system.



modern steels

are made to specific formulas each devised to give steels with various properties when heat treated in a certain way. Iron and carbon are the main ingredients just like the traditional steels, but alloying elements such as chrome, and manganese are added to greatly affect the properties of the steel during heat treatment. Modern steels are made by cultures that dont fight with swords anymore. They use jets, tanks guns and missiles. Not one of the modern steels was designed with military swords in mind. Modern smiths find the steels with the potential qualities they want in their blades and go from there.



The main difference is how easily the blades will harden.

Most modern steels will harden all the way to the center of your average sword thick section. They can do this when quenched in oil- a generally gentler quench than water.

The tradition steels were very ' shallow hardening' meaning they required the fast drastic quench that a water quench would give. They may not harden all the way to the center of a thicker cross section.



What does it mean to a swordsman/swordswoman?

It means that with tradition steel it would be a lot more difficult to get a true springy sword hardened all over the surface and inside of the blade like we take for granted today. This means that the traditional blades were more prone to bending than breaking. This is not necessarily a defect or deficiency of traditional steels. When we look at the construction methods of various cultures, we see that they are VERY concerned about a blade breaking and seem to have come to terms with them bending. In fact they designed them to do so. A thousand years ago various cultures knew how to harden and use steel for the edge of a chisel. They could have made a full sword of this edge type steel and fully hardened the entire thing - but I havent seen that done in any of the pieces I've seen or studied. In my examination of Japanese, Viking, Norman pre-1400 European, Chinese, etc swords, I have found this to be true of them all. In fact many blades would be considered very soft (except for some of the edges) by todays standards. Remember - a bent sword can be straightened a broken one is.. well..broken.



Effect of construction methods

A construction method is how a sword is assembled from various pieces of steel. Is it made from one piece of steel all the way through? Perhaps its has one piece used for the edges and center and 2 other pieces for the outside 'skin' (sanmei) Notice I am not differentiating whether the steel used for the parts of the sword are modern or traditional, both can be used in similar construction methods. Construction methods are ways to impart different properties to parts of the sword by putting different kinds of steel/iron exactly where you want them. The construction method does not define the performance characteristics of the blade by itself. It needs the next process to give the blade 'life'.



Heat treatment

This is the process used to harden a blade by heating to an appropriate temperature for the type of steel and then cooling it off fast in oil or water. It also encompasses any post hardening processes such as tempering.

You can harden the entire blade and temper it to make it softer and tougher. You could just harden the edges and leave the center softer. You could harden the entire blade and temper back the center more than the edges (differential tempering). Perhaps make the area near the guard softer and tougher than the area near the tip or the edges. There are many variations a smith can use. Again these various heat treatments can be done to modern and traditional steel.



The big picture - understanding historical swords and technique

There is no one steel type (traditional or modern) or heat treatment or construction method that will always be the best or strongest for all situations. As you can see there are numerous ways a smith can chose to construct and heat treat a sword. Our ancestors used traditional steels because this is what they had. If they had the technology level, chemical, and production infrastructure to make modern steels they had better stop making swords and make tanks and rpgs or their neighbor with the same technology level will eat their lunch in no time. These 'simple' steel swords were used to create and destroy kingdoms and empires. The swords of the day worked and worked well. They were concerned with making swords that would bend before breaking. They developed techniques and armor with these types of sword capabilities in mind. To truly understand the sword that was used in the past it needs to be made like the ones in the past. Just because a modern steel tempered to a spring can withstand a certain technique and not take a set could its historical counter part? If the historical blade couldnt stand up to a certain technique perhaps we are misinterpreting the technique or perhaps we have different expectations than our ancestors who grew up with swords as a military weapon of their day.



Also keep this in mind -swords do most of their work by cutting, not using the flat. In this direction even a differentially heat treated blade that will take a set with a poor cut, can still cut into hard material and suffer no bending in the cutting direction.



I hope that this caused you to have more questions instead of fewer... I know its caused me a couple of decades worth of intense study, many many experiments, a lot of test cutting, sword disections, and much enjoyment.

B.Ko
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Post by B.Ko » Mon Jun 18, 2007 11:44 pm

I have referred back to this thread many times as I examine my antiques and modern blades.

One question I have for experts like Paul, Philip, and Laoshi.

What are the edge hardnesses of the modern replicas...let's say Huanuo as a standard, Zhengwu is also another good company...specifically the edge hardnesses of the mono spring temper vs. mono differential, as well as the sanmai swords.

Now I did inquire at Zhengwu and they described that the sanmai can be through heat treated or differentially treated and regardless of the technique the different composite steels end up with different hardness with the differential treated one having a slightly harder edge.

Any observations on this???

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Post by Peter Dekker » Wed Sep 19, 2007 8:11 am

I only know the numbers for Huanuo swords:

Their sanmei swords typically have a harder edge than spine, between 40-50 for the spine and 58-62 HRC for the edge. The monosteel versions are generally around 55 HRC all over.*

Huanuo does not have differential heat treated monosteel swords, but I believe they do differentially heat treat their sanmei swords.

*There are differences per sword as they are hand made.
Now I did inquire at Zhengwu and they described that the sanmai can be through heat treated or differentially treated and regardless of the technique the different composite steels end up with different hardness with the differential treated one having a slightly harder edge.

Any observations on this???
This is due to the fact that some steels have more potential for hardening than others, depending on the amounts of contamination in the steel by substances such as manganese, sulphur, and carbon.


What I find odd myself is that I am always told that high carbon steel can be hardened to a higher degree as is the case lower carbon steels. Carbon is also the substance that makes a steel more vulnerable for rust, which is why we need to take good care of our swords by oiling them and keeping them free from moist and such.

However, in antique examples I've encountered yet the opposite on a number of occasions: the edge is sometimes significantly less corroded than the softer body. Can anybody comment on this?

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hmm....

Post by Chris Fields » Wed Sep 19, 2007 11:57 am

For the Huanuo swords, I was under the impression that they stacked their monosteel swords for heat treating, therefore the edges get hotter than the spines, so differential heat treatment occurs. This is how I heat treat my swords, and it seems to work well. It also keeps the blade deflection and warpage due to the quench to a minimum. I thought Scott did a file test on the Huanuo monosteel dao, and get a higher hardness at the edge. I have not done this myself, but I may tonight.

As for the edges, I would say that what you found is a possible result of more attention and care paid to the edges of the sword by it's past owners compared to the attention and care paid to the spine.
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Peter Dekker
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Re: hmm....

Post by Peter Dekker » Tue Sep 25, 2007 7:21 pm

Chris Fields wrote:For the Huanuo swords, I was under the impression that they stacked their monosteel swords for heat treating, therefore the edges get hotter than the spines, so differential heat treatment occurs.
It sounds pretty logical that it does exactly as you say when superficially heated but when done right the whole sword gets to the same temperature.

When Lance Chan from Realistic Sparring Weapons tested edge and spine some time ago he came with identical hardnesses for all parts of the monosteel blade. Also, when I visited the factory the oven they used didn't seem that large. They are not the incredibly large sword producing factory that many assume they are.
Chris Fields wrote:As for the edges, I would say that what you found is a possible result of more attention and care paid to the edges of the sword by it's past owners compared to the attention and care paid to the spine.
Your reasoning is very logical but on the examples on which I've seen this the patina follows the wavy line of what the Japanese call "hada", where the harder steel comes out the softer steel. The throwing knife I posted here has a similar clear but natural demarcation between edge and body.

See: viewtopic.php?t=594

Other examples are antique Chinese chisels, where often the entire hard steel insert clearly stands out rather than only the part which is sharpened.

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Post by Chris Fields » Wed Sep 26, 2007 10:07 am

I guess huanuo's vary too much still to say if their mono steel swords are through tempered or not. My Huanuo dao appears to have a slightly softer back edge. I depends on who is heat treating it I guess. If they only do one or two at a time, I would think the heat treater would be watching the sword to see when the edge heats up to a bright reddish yellow while the center still remains a very dark red. Once that is reached, they would yank it out and quench it, resulting in a differential temper. As you can imagine, there can be alot of variability in that process.

Were you able to watch their processes? I would love to make it out there some day.
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Post by Peter Dekker » Wed Sep 26, 2007 3:39 pm

Metalworks is not my area of expertise so I would not know if that would result in radically different hardnesses like found on Japanese katana. I'd figure they didn't use the clay for nothing if something similar can also be reached as you describe.

I can imagine that not all Huanuo swords are alike, but as their European agent for over 2 years the pool I've seen is larger than most people and I found that their temper felt pretty similar over that time. I must admit that I don't have edge hardness testing files here so I didn't get the numerical data on all.

A difference are the lengths and weights that changed over time. Most notably their jians got heavier.

What are the respective hardnesses of your edge and backedge?

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Post by Chris Fields » Wed Sep 26, 2007 10:15 pm

About 55 to 58 on edge, and about 45 to 50 on the back. I should double check that though, not much of a spread, but enough to count. If it was 56 to 58 through out, I would expect it to snap due to it being too brittle.

The use of clays makes the temper line much more predominant sharp line. Clays really create a barrier for heat transfer, therefore the temperature difference across that small line where the clay starts to thicken is very high. It's not that it heats up hotter faster in the forge, but during the quench, it cools much faster. With out the clay, the temperture drop is far less drastic, and it is not necessarily a pronounced "line". However, differential heat treating can still take place with out clay. Almost all historical swords I have seen, mostly european, are differentially tempered, though there is no pronounced temper line.
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