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June, 1925
Microscopic Examination of Sand
By A. Traeger
The quality of a casting naturally depends upon
the condition of the moulding sand. While there are
plenty of sand pits in which an entirely satisfactory
grade of moulding sand is deposited, many foundries.
clue to economic reasons, cannot avail themselves of
same, and are compelled to utilize the less satisfactory
grade of sand found in pits within their vicinity. In
many cases one resorts to mixing of sand of different
quality and endeavors in this manner to empirically
create a moulding material of as good a quality as
existing conditions permit.
Recently a number of papers have been published
dwelling upon scientific methods of testing the moulding
sand in order to eliminate those less dependable
means employed by the moulder in selecting sand,
which more or less is a matter of guess work.
Microscope for examining moulding sand.
Fbrging-Stamping- Heat Treating
The testing methods employed during recent years
were based, aside from determining the fire-durability
as well as the porosity and permeability of gases, upon
chemical analysis. Total analysis, however, was of
minor importance and the principal point involved is
to establish the ratio of quartz and clay percent within
the moulding sand, which can be accomplished by
means of a rational analysis. The two principal constituents
of moulding sand, of which quarts represents
the body-substance and clay the agglutinant, are distinguished
from each other through a definite size of
grain and their quantitative relation. For the determinaton
of these two factors several methods have
been suggested from time to time. According to
"Schoene-Wabnschaffe',, the size of grain is determined
by means of levigation-process, which method
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has recently been materially improved through suggestions
made by "Treuheit". According to the latter,
the individual grain-fraction can be determined in
a reliable and quick manner.
Aside of this somewhat troublesome and at the
same time yet procedure, the microscope, at relatively
low power, renders a very satisfactory image of the
distribution of the sharply outlined quartz grains in
conjunction with the finely powdered clay. As an instrument
which is particularly suited for these examinations,
the Binocular Ore-Dressing Microscope
after Schneiderhoehn* is recommended. Prof. Piwowarsky
of the Institute of Technology at Aachen
(Germany), refers to this apparatus in the journal
"Giesserei", vol. 44, page 721, as rendering most reliable
results for the purpose described. With the
aid of the binocular ore-dressing microscope the predominant
grain sizes of new moulding sand and sand
already used, as well as of the intermediate products
can be determined within a few minutes.
The circular glass plate, ruled in square cm, fitted
within the metal stage of the microscope, facilitates
the counting of the individual grains and the determination
of their relative quantities. The size of the
grains is measured by the aid of net-micrometers of
varying values, corresponding to the mesh of sieves
as are utilized in dressing. The micrometers referred
to are inserted into the ocular tubes. As another eminent
advantage should be mentioned that the binocular
ore-dressing microscope yields an image of highlystereoscopic
character and that the instrument permits
prolonged use without the least eyestrain.
•Manufactured by Ernst Lcitz, Wetzlar (Germany).
Aims of American Refractories Institute
Hon. William C. Sproul, former governor of the
state of Pennsylvania, has recently accepted the presidency
of the American Refractories Institute. This is
a new organization that was formed for the purpose
of promoting the common interests of the manufacturers
and consumers of refractory materials, the first
meeting having been held on April 7 at the Mellon Institute
of Industrial Research of the University of
Pittsburgh, Pittsburgh, Pa.
Refractories, or heat-resisting materials, are of
vital importance in many key industries. In their
manufacture such raw materials as fire-clay, silica
rock, magnesite, chromite and diaspor are used, the
state of Pennsylvania being the largest producer, although
manufacturing plants are located in no less
than 24 states. The annual production of all types
of refractories has a value of approximately $75,000,-
000, those made of fire clay representing about 75 per
cent of this total.
Such industries as those producing iron, steel and
many other metals, Portland cement, steam and electrical
power, porcelain, enameled ware, glass and
manufactured gas are dependent upon refractory products
for the economical operation of their plants, as
refractories form the lining for their furnaces and cannot
be replaced satisfactorily with an}- other type of
material. Refractories are also used to a considerable
extent in the chemical industries, in baking ovens, oil
refineries, and in the production of man}- other commodities
in common use. In nearly all of these manufacturing
processes, the furnace output and the cost