[TheForge] Samurai program

[David E. Smucker]

Jim, It is more than just thermal expansion differences that makes the 
blades curve -- it also includes the volume increase as the transformation 
takes place on cooling. (Both effects are important.)  This is one of the 
problems that makes heat-treating of large items very difficult.

Also on the run out table / cooling table of some steel hot strip mills you 
can actually see the strip hump up as it goes through the transformation and 
gets longer as it cools.

And yes the blades are curved this way.

Dave Smucker
----- Original Message ----- 
From: "James Binnion" <jbin at well.com>
To: "Sponsored by ABANA" <theforge at mailman.qth.net>
Sent: Sunday, October 07, 2007 4:44 PM
Subject: Re: [TheForge] Samurai program


>
>
>
> On Oct 7, 2007, at 12:15 PM, schade at acegroup.cc wrote:
>
>>
>> If you go to the Nova site there is an interactive slide show
>> showing some of the highlights of the show. In one segment they
>> say that the curve in the finished blade is made by quenching
>> (clipped/pasted below). I am not a knifemaker or student of
>> damascus/samurai swords/patternwelding/etc but I have never
>> heard this before.
>>
>> Is it true?
>
> Yes, there is a difference in thermal expansion between low carbon  steel 
> and high carbon steel that will make the low carbon steel  contract more 
> than the high carbon steel on cooling. Result a curved  blade.
>
> Jim
>
> James Binnion
> jbin at well.com
>
>
>
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