The Democratic banner. (Mt. Vernon, Ohio) 1898-192?, 1913-08-12
BATTLES SCIENCE.
Why Hot Steel Is Tempered by
a Sudden Cooling.
SLOW COOLING KEEPS 1T SOFT

TOT tUo busy DTdlH " We" Santoe
Succeed In Reasoning Out Why This
lie so--The Mysterious Properties
Exhibited by Water, Tin and Glass.
Here is a fact, known to everybody,
which is as mysterious as would be
the actual appearance Of a ghost, by
which mean that the fundamental ex-
planation of the phenomenon is about
as far beyond our reach in the one
case as in the other.
The fact to which | refer Is the pro-
duction of tempered steel by Quenching
In cold water. If hot steel is cooled
very slowly 1t becomes soft and cannot
take a cutting edge, but If 1t is cooled
suddenly 1t becomes very hard and can
| be ground into keen swords, knives
and cutting tools.
Now, why the difference? Have you
ever thought about that question? If
you have not, many a man of science
has, and has been puzzled over it.
Here is another related mystery. If
you heat an old Japanese sword, which
for centuries has retained its capacity
to slice off head at a blow, or to
| open swift passage for the soul of
| the victim Of the harakiri mania, tO
the temperature of boiling water II
| gradually softens and loses the keen.
ness that once made it so formidable
| 1t is the same steel, but 1t, too. seems
to have lost its soul. At tempera.
ture of 150 degrees centigrade the
hardened steel commits harakiri in 0
few minutes. Surely there Is some
thing strange in that,
Then consider this: At zero tempera
ture water changes from a liquid and
suddenly becomes solid. But If you put
the water In vase and carefully pro
tect 1t from dust you may cool it as
much as 20 degrees below zero and YET
1t will not freeze! But now shake the
vase or drop In bit of Ice, and the
water Immediately solidifies!
owe the collection Of these facts to
paper by Professor James Fl. Wal
ton, Jr., of Wisconsin university. The
explanation which he gives is that sub
stances like the hardened steel and the
unfreezlng water are in a state OF
suspended change" That accounts
for the phenomena, but In a certain
sense they remain mysterious. just as
life Is mysterious.
Many substances possess the same
curious characteristics. Professor Wal
ton says that If flask containing so
dium acetate, which has been cooled
below its natural freezing point with
out solidifying, Is opened in room
containing dust Of the solid acetate the
fine particles of the latter dropping int
the flask will cause the whole content.
to solidify.
Tin Is very strange metal with re
gard to this state of suspended chang,
or ''metastabillty." A severe winter COLI
will sometimes cause 1t to lose it,
hardness and crumble.
Objects made of tin sometimes un
dergo such change and are then sait
to be suffering from ''the tin disease
The contact of diseased" tin will
bright hard tin is capable of settin,
up the transformation.
Glass. Professor Walton informs us
is "an undercooled substance"-t is
it is In a metastabe condition. If oil
glass tubes through which water ha
frequently passed are heated the glas
crystallizes and loses its transparency
All substances in this state are liabl
to change. and the change, under prop
er conditions. may be sudden Hard
ened steel Is In n similar category.
| n nc. F,api-h ho ln II, IL could M
be safely used for many purposes 70
which 1t is b1hitually employed. For
tunately steel exhibits great Resistance
to change Of state after it has beel
tempered. Transformation is retarde
or arrested
Does steel slowly return to the sta
BILE form and thus grow softer?" ask
Professor Walton. and then answers
THAT we do not know; we can onl
say that If such a change does TAX
place, hundreds of years are necessar
TO bring it about"
The same ancient Japanese swords
which, when heated, as before descril
ed. become soft. retain all their hare
ness IL carefully preserved.
1t Is evidently of the highest In
portance to the practical world tina
science Is investigating these thing
and discovering the way and the Gil
cumstances in which the changes com
about, even II 1t has not unveiled th
} underlying mystery of their cause
: Garrett P. Serviss In New York Joul
( nal.