[ I asked Richard to write about the steel from which
 [ piano strings are made.  -- Robbie

I can't address the matter of comparing old steel to the modern
product, since I know nothing of the history of when the things
I mention were first introduced.  But I do know that steel metallurgy
is a surprisingly old science, well developed as far back as the 19th
century, so one would have to go back pretty far to find piano wire
that is 'worse' in some way when compared to today's product.

I am not a metallurgist, so anything I say is only what I have picked
up hanging around steel mills.  The thing that makes steel metallurgy
so fiendishly complex, compared to most other metals, is that molten
iron (and only a very few other metals) is a true electrolytic solvent
like water.  It supports all the complex ionic reactions and solution
phenomena just like water does.

Comparing the chemistry of iron to, say, copper, is like comparing
water to kerosene.  Steel is even worse, because steel is not just a
mixture, but is also a complex linkage of iron, iron carbide in several
species, oxygen, carbon, and up to 10 or more other elements in
significant amounts.

All this stuff influences the 'shape' of the steel.  In the steel
business, shapes mean steel beams or other rolled profiles, but 'shape'
means the way the various molecules in steel are piled up and linked in
the crystalline form of the metal, which profoundly influences the
strength, elasticity, and hardness of the metal.

The thing that struck me, while reading the catalogs of piano string
makers, is that piano wire is made from cast steel.  The significance
of this will be explained further on.

This is woefully simplistic, but there are three fundamental things
that can go wrong with steel:

First, it could have the incorrect composition, or include the
wrong 'other' elements.  Suffice it to say, that careful selection
of the raw materials and additives, and constant testing with the
mass spectrometer, has gotten this problem pretty much licked.

Second, gas easily dissolves in iron, and such dissolved gas must
be carefully controlled or eliminated.  O2 and CO percent must be not
zero, but just right.  H2 and N2 are no-no's, but are easily absorbed
from atmospheric N2 or water vapor that breaks down into H2 and O2 on
the hot surface.

It may surprise you to learn that molten steel is not allowed to touch
air once it is made.  Any ladle, tundish*, or mold is provided with a
layer of slag on top,  but some unwanted gas gets in along with the raw
materials or additives.

(Another 'term of the art': in iron making, slag is the layer of oxide
and other crap that floats to the top, as everybody thinks of it.  But
in steel making, slag is an artificial material, essentially powdered
glass, which is sprinkled on the liquid surface, where it melts and
forms an air impregnable layer.)

All good steels are finally degassed at the ladle met station, which is
the last stage where a ladle of molten steel is prepared for casting.
Aluminum is added which 'gets' (links to) the excess O2, which floats
off as light aluminum oxide.  H2, N2, and excess CO are then sucked off
under very high vacuum.

The third 'problem', of particular interest when discussing piano wire,
is inclusions; that is, either voids or tiny bits of insoluble matter
that end up in the finished metal.  One can see how these could spoil
a piano wire.

Of course all steel must be cast, to make it into a solid product.
Most steel is now continuously cast by pouring it into a narrow mold
as a liquid at the top, and pulling it out the bottom of the mold as
a partially hardened strip of essentially infinite length, analogous to
the traditional way of making sheets of organ metal.  However carefully
they try to eliminate them, continuously cast steel still contains a
few inclusions.

But when steel is advertised as cast steel, as for piano wire, this
usually means that the steel is solidified the old fashioned way, by
pouring it into individual ingot molds, and then rolling, drawing or
machining the resultant billets individually.

The Timken Steel company in Canton, Ohio, has the only modern mill
that I know of which still casts much of its production as ingots.
Many people don't know that Timken makes steel not only for its own
bearings, but they also sell a large quantity of super-high quality
steel to tool makers, knife smiths, and any anybody else who needs
steel that is virtually free of inclusions.

Timken's procedure is as follows:  The steel is made, adjusted in
composition, and degassed just like in any other mill.  But then the
ladle of molten steel is poured into a row of ingot molds instead of
into the tundish (distributor box) of a caster.  The molds are bottom
poured; that is, they are filled from the bottom up, through a
refractory tube.

The full molds are allowed to cool very slowly.  This is important.
Any voids settle out or rise to the top.  Inclusions either migrate
to the walls of the mold and stick there, sink to the bottom, or float
to the top.  Then the cooled billets are cropped -- the bottom foot and
the top two or three feet are sawn off and discarded.  Finally the
billets are scarfed; an inch or so is planed off the four sides.

What is left is the ultra-pure center part, free from any inclusion.
This process is wasteful and labor intensive, like eating soft-shell
crabs from Chesapeake Bay.  No wonder Timken steel is very expensive,
and used only by those who need its special properties.  But I wouldn't
be surprised to learn that Mapes Piano String Co. buys its billets for
piano wire from Timken or someone like them.

Richard Vance

 [ * Editor's note:
 [
 [ My 7 kg 1927 dictionary says, in the fine print:
 [   tundish: a funnel (obsolete)
 [
 [ In Shakespeare's "Measure for Measure", Act 3, Scene 2,
 [ Lucio is asked why Claudio will be executed.  Lucio replies,
 [ "Why?  For filling a bottle with a tundish."
 [ Richard notes that "the steel industry, with its ancient roots,
 [ is full of similar argot."
 [
 [ Chemical compound abbreviations: O2 oxygen, N2 nitrogen,
 [ H2 hydrogen, CO carbon monoxide.
 [
 [ Frank Himpsl adds, "The research efforts that 19th century wire
 [ makers did to come up with piano wire of appropriate strength is
 [ just incredible.  Some of this is documented in Alfred Dolge's
 [ book, 'Pianos and Their Makers,' which is available as a reprint
 [ by Dover Books."
 [
 [ -- Robbie