Imperial Valley press., 1923-08-11

sticks broom corn splint into the !
loaf to sec now 1t is progressing.
The candy maker frequently drops |
sample of his syrup into a cup
Of cold water to find out if it is |
gummy, hard or brittle. Both are /
testing the effects of heat treat
ments.
The cook takes three potatoes
that grew in the same hill, bakes /
Cne, boils another and fries the |
ether. Put cross section of the |
potatoes prepared by The three pro- |
cesses under microscope and q |
great difference in texture win be |
found. This is called the micro |
scopic test. Now apply the chem |
ical test to each Of the three sam
pies, determining what has happen !
Cd to the chemical composition. The |
baked potato is found TO have |
lost some of its starch. Next, |
squeeze the three samples between
the fingers. There will be notice
able difference in the resistance to
pressure. This is the physical test.
Heat has been applied to each
If the samples, but in a different
way in each case Yet the effects
Of the three kinds of treatment are
so widely different that three kinds
of tests disclose changes in the
position, and physical properties.
Heat Works Changes
And so it is with the steel used
in automobiles. Heat treatment |
works remarkable changes in the
properties of steel. Various meth
DDS of application cause various
changes.
Abort the most interesting skill
cd cooks and among the most sci
tntific kitchens in the world viii bc
found at the big motor ear shops
at Lansing, Michigan.
Here 1t is that engineers work
seeming miracles in their heat
treating department analyzing steels
and determining exactly what
treatment will make them most
enduring in the various duties they
are called upon to perform in actual
road work.
Then, in order to make sure
that every cad viii carry TO its own
or the full benefit of such exhaus-
aineers are charged with Gevising
and installing in factory production
practice exacting tests to tell quick
ly and accurately the iEnermost
secrets of heat treated stcels pass
ing through. in, regular production. |
Applied In Several Ways
Tests are applied several ways
to the raw steel that goes into |
products after being treated. For
high standards must apply in ev-
cry step of the process of manu-
facture. The purchasing depart |
ments and engineering organiza- |
tions work hand in hand in the
selection of materials.
Experience and long research, |
based on hundreds OF experiments, |
have taught engineers w h |
strengths various steeis mast have |
to insure fhithful performance. |
Some must have great elasticity, |
combined with strength. Others !,
must present extremely smooth, |
hard surfaces. Still others must |
combine these two, or have addi- |
tional wear-resisting qualities.
Once having established their
formulas for raw steels, these en- |
gineers turn their skill TO the test |
ing of steels after heat treat
ment
For one thing they must deter
mine what happened during heat
treatment. The photomicrograph |
tells them this. Cross. sections of
the steel are filed smooth, then
brought to polish on special
buffing machines, and are placed
IN the device which enlarges an
exact image of the cross section
100 times, 400 times or even as
much MS 1000 times if necessary.
This image is thrown against a
screen or a sensitized Photographic
plate as desired.
Shows What Happened
just what happened 10 every
particle of the steel is disclosed
graphically by this analytical test.
For example, in ease hardened steel
the particles forming the surface
exposed to heat are shown to be
drawn so closely together for
depth of perhaps a full sixteenth
of an inch that they present a sur
face capable of defying ordinary
cutting tools. The PARTICLES form
ing the steel inside this glass-hard
girdle are Shown to be much more
loosely related.
Flaws in texture of steel or i'm
purities so fine as to have escaped
notice in other tests are brought TO
light in full detail by The photo
mierographic test.
Yet even this type of test does
not tell engineers what physi-
cal properties of hardness, elastici-