Article of interest: 1946 War Dept. analysis of gunto

[Randy McCall]

Some of our members may be interested in my latest blog article:

 

Metallurgical analysis of Japanese gunto by US War Department, 1946

http://www.tameshigiri.ca/2014/04/03/me ... ment-1946/

 

This is taken from a declassified War Department report; a link to the source article is included in the posting. Unfortunately, this is a digital copy of a mimeographed copy (possibly microfilmed) of the report, so many of the actual photographs are unreadable... which is unfortunate, as they included a picture of "writing on the tang".

[zentsuji2]

Interesting article,

I wonder if they wanted the metallurgical tests for weaponry, or for future ventures where steel like this would come in useful for advanced projects.

Great find, it's nice to see that after creating the world's most destructive weapon,they had time to test the properties of the world's greatest sword.

Thanks for sharing.

Best regards. Ian bellis

[ROKUJURO]

An interesting find, thank you for sharing!

 

I would have liked to know what kind of blade that was; probably not a traditionally made one. The results of the hardness tests are nevertheless surprising, and I wonder how they found out that:

 

5) Temper: Tests showed the blade had been air quenched from a temperature of approximately 1600 degrees F. .

 

There are a number of ways to quench a blade and I think it is very difficult if not impossible to differentiate between a blade quenched in a warm liquid medium and another blade having been cooled in cold air (depending on the travel speed of the air).

[Randy McCall]

An interesting find, thank you for sharing!

 

I would have liked to know what kind of blade that was; probably not a traditionally made one. The results of the hardness tests are nevertheless surprising, and I wonder how they found out that:

 

5) Temper: Tests showed the blade had been air quenched from a temperature of approximately 1600 degrees F. .

 

 

Only too happy to share

 

On how they determined quenching methods: On page four of the report, it describes how they took small sections of the blade, heated them to 1600 F, quenched them in air, water and oil, and then compared the hardness to the original blade. The air quenched section had a hardness of 35-38 Rockwell; both water and oil quenched came in around 64 R. This compares to the original blade hardness of 41 R.

 

From this it would appear that quenching the steel of this sword in any medium other than air greatly increased hardness beyond the blade's original level, suggesting those had not originally been used. Additionally, by examining the blade's microstructure -- and knowing what structures would form at what temperatures during quenching -- they were able to draw their conclusion.

 

At least, this is what I understand from the report. Not that this is a speciality of mine...