Subject: Re: movie metalsmithing

From: [email-masked] (Erik Halberstadt)
Date: 26 Dec 1994 14:13:21 -0800

John O. Kopf ([email-masked]) wrote:
: >The steel doesn't _gain_ carbon during the forging process, it _loses_
: >it.  The smith starts with a non-homogenous steel which is roughly
: >1.1-1.5% carbon.  It winds up being somewhere in the 0.7% range.  The
: >first step, welding many individual pieces together causes a loss of
: >about 0.3%, and each fold thereafter causes a loss of about 0.03%

: ...if the steel is initially covered with iron on both sides, then the loss
: of carbon due to oxidation is going to be much less because oxygen can't get
: at the steel except at the edges.  carbon loss from the steel will probably be
: due to diffusion into the iron.

: If, however, a single block of steel is welded to a SINGLE block of iron,
: then one face the steel will be exposed to oxygen;  after folding, there will
: still be one steel face exposed.

: Since the forge-welding range for steel overlaps that of iron only by about 40
: degrees, "cladding" the steel on both sides also makes the surface "uniformly
: iron" and thus easier to weld sucessive joints.

: JK

The Japanese swordsmith I watched started with a pig iron billet. As it 
was forged, it was rolled in rice straw. I believe that this is where 
_carbon was added_ to create steel from iron. The billet was also rolled 
in straw just prior to folding, and as result, carbon was added between 
the folds. There was no sandwich of steel cladded in iron in this smith's 
process, and hardness of the finished sword was controlled by the 
thickness of the clay and temperature control during the final heat.

BTW this smith was in line to become a living treasure at the time. I 
believ that his method of forging blades is historically accurate.

Erik

---

From: [email-masked] (Will Fischer)
Date: 30 Dec 1994 15:41:07 GMT

Erik Halberstadt ([email-masked]) wrote:
: The Japanese swordsmith I watched started with a pig iron billet. As it 
: was forged, it was rolled in rice straw. I believe that this is where 
: _carbon was added_ to create steel from iron. The billet was also rolled 
: in straw just prior to folding, and as result, carbon was added between 
: the folds. There was no sandwich of steel cladded in iron in this smith's 
: process, and hardness of the finished sword was controlled by the 
: thickness of the clay and temperature control during the final heat.

The initial "pig iron" billet has a high carbon content ( >1.5%); the
straw covering helps reduce the loss of carbon, however the result of
the folding/welding/drawing-out is a NET reduction in carbon content
(typically to around 0.7-0.9%, I think).  Most traditional smiths WILL
use different grades of steel (i.e. made from different folded/welded
billets) for different portions of the blade -- so hardness of different
parts of the blade is controlled both by composition and
heat-treatment.

-- Will

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Will Fischer				[email-masked]

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