The Bottineau courant. (Bottineau, Bottineau County, N.D.) 1895-1929, 1913-09-05
BATTLES SCIENCE.
Why Hot Steel Is Tempered by
a Sudden Cooling.
SLOW COOLING KEEPS IT SOFT

S1Vv OOO6Sv0 MEET y ~ 0OVt
Vet the Busy Brain Of Man Cannot
Succeed In Reasoning Out Why This
10 so-Ths Mysterious Properties
Exhibited by Water, Tin and Glass.
Here Is a fact, known to everybody.
which Is as mysterious az would be
the actual appearance of a ghost. by
which mean that the fundamental ex-
PLANTATION Of the phenomenon il about
az far beyond our reach In the one
case as in the other.
The fact to which I refer IL the pro-
duction Of tempered steel by quenching
In cold water. II hot steel is cooled
very slowly 1t becomes soft and cannot
take a cutting edge. but IL 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? II
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 OF q head at q blow. or to
open a swift passage for the soul of
the victim Of the harakiri mania, to
the temperature Of boiling water 1t
gradually softens and loses the keen
ness that once made it 80 formidable.
It IL the same steel. but 1t, too. seems
to have lost its soul. At q tempera-
ture Of $50 degrees centigrade the
hardened steel commits harakiri in o
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 II you put
the water In q vase and carefully pro
tect it 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 a bit of Ice. and the
water Immediately solidiies! I,
Owe the collection of these facts to
a paper by Professor James II. Wal
ton, Jr.. of Wisconsin university. The
explanation which he gives is that sub
stances like the hardened steel and the
~unfreezing water are in a state of
suspended change" That accounts
for the phenomena. but in q certain
sense they remain mysterious. just as
life is mysterious.
Many substances possess the same
curious characteristics. Professor Val
ton says that If a 1ask containing So
dunn acetate. which has been cooled
below its natural freezing point with
out solidifying. is opened in a room
containing dust of the solid acetate the
ane particles Of the latter dropping into
the fask will the whole. contents
to solidify.
Tin is a very strange metal with re-
gard to this state of suspended change
or 'metastability." A severe winter cold
will sometimes cause It to lose its
hardness and crumble.
Objects made Of tin sometimes I'm
dergo such change and are then said
to be suffering from 1.-The tin disease
The contact Of diseased" tin with
bright. hard tin Ia capable Of setting
up the transformation.
Glass. Professor Walton informs Us.
is IAN undercooled substance that ia.
it is In q nletastab BILE condition if old
glass tubes through which water has
frequently passed are heated the glass
.crysta llizes and loses its ira sT,a rency
All substa noes in this state are liz bic
to change. and the change. under prop
er conditions. may he sudden. Hard
ened steel ~ In a similar category lf
1t were as p%prishable "a tin II could not
be safely used for many purposes for
which It IL ha bituaiiy employed. For
~tunately steel e exhibits great resistance
to change OF state after It has been
tempered. Transformation IL retarded
or arrested.
Does steel slowly return to the sta
BILE form and thus grow softer" asks
Professor Walton. and then answers:
THAT we do not know: We ran only
say that IL such Il change does take
place. hundreds Of Years are necessary
to bring It about"
The same ancient Japanese swords.
which. when heated. an before desrrflr
ed. become soft. retain all their hard
lei II carefully preserved.
It is evidently Of the highest I'm
p0rtance q the practical world that
science is Investigating these things
and discovering the way and the cir
cumstances In which the changea come
about. even II II hax nOt unveiled the
underlying mystery Of, their cause.
Garrett r serviss 10 New York Jour
nal
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