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October. 1925
practical application, here given, of the theoretical
principles considered.
It is demonstrated that the rate of graphitization
is determined by the rate at which carbon can migrate
in iron. The progress of graphite formation with time
is shown to be an expression of the changing migratory
distances, and concentration gradients produced
by the reaction.
This demonstration, also, is believed to lie new.
The procedure by which the mathematical characteristics
of the observed graphitization curve are used to
determine the character of the physico-chemical processes
occurring is also, perhaps, sufficiently unusual,
to possess interest for the theoretical metallurgist. The
writer does not recall any other similar problem which
has been solved by this method of attack.
Reference is made to the range through which the
graphitizing rate varies in commercial material. The
effect of silicon on this constant is discussed. For a
variety of reasons, none of the other variables which
affect this constant have been considered, and the
reader is cautioned against any belief that the cumulative
effect of the many variables involved can be
summed up from assumptions as to their effect separately.
Partly on account of these theoretical perplexities,
and also because it was desired to focus the
attention upon metallurgical principles only, nothing
in the nature of operating data has been included.
The malleable metallurgist may, perhaps, find here an
explanation of some of the fundamentals of his process.
but no suggestions as to desirable or objectionable
practices.
•Manager of Research, National Malleable & Steel Castings
Company, Cleveland, Ohio.
A Study of Dendritic Structure and Crystal
Formation
By Bradley Stoughton* and F. J. G. Duckf
The authors of this paper discuss the formation of
dendritic crystals in over-heated high carbon steel and
present a study of such crystallization. Comparison
is made, both in structure and hardness, with a normal
file steel of approximately the same composition.
Evidence is offered, through the inter-crystalline
rupture of the over-heated steel, that the amorphous
metal hypothesis does not hold when the crystals are
large and there are correspondingly large surfaces of
cement. Following the same reasoning, it is thought
possible that the inter-crystalline rupture of metals at
high temperatures is due to the large size of the crystals
at those temperatures, as contrasted with their
small size at normal temperatures.
It is assumed that the smaller crystals, as well as
the inter-lamellar crystals, that occur throughout the
eutectoid areas, were formed as a result of the tremendous
pressure brought about by the expansion of
the material in its change from austenite to pearlite.
Several photo-micrographs are presented in support
of these conclusions.
It is also stated that the Brinell hardness numbers
of any steel vary inversely as the size of its constituent
crystals, although no attempt is made to show any
relation between them.
Forging- Stamping - Heat Treating
•Professor of Metallurgy, Lehigh University, Bethlehem.
Pa
tlnstructor in Metallurgy, Lehigh University, Bethlehem,
Pa.'
359
The Carbon Content of Pearlite in Iron-Carbon
Alloys Containing One Per Cent Silicon
By Anson Hayes* and H. U. Wakefieldt
The authors review a modification of the diagram
for pure iron-carbon alloys, which was constructed to
conform to experimental data. The carbon concentration
of point C had not previously been determined.
The authors have obtained a value for the
carbon content of this point and the principal object
of this paper is to report the findings of the investigation.
•Professor of Physical Chemistry and Metallography, Iowa
State College, Ames, Iowa.
tAssociated with Dr. Haves.
The Dilatometric Method of Heat Treatment
By O. E. Harder*. R. L. Dowdellf and A. C. Forsyth:
In the present paper the writers are reporting the
progress in the use of the dilatometric method of heat
treatment and the application of that method to the
study of dimensional changes in such materials as graycast
iron. Two slightly different pieces of apparatus
have been constructed and used. The details of construction
and the results obtained are given.
•Professor of Metallography, School of Mines, University
of Minnesota, Minneapolis. Minn.
tlnstructor in Metallography, School of Mines, University
of Minnesota, Minneapolis, Minn.
|Foundry Department, Bethlehem Steel Companv, Bethlehem,
Pa.
On the Nature of Some Low Tungsten
Tool Steels
By M. A. Grossmann* and E. C. Bainf
This paper is one of a series on the constitution
certain steels which have wide commercial application.
The authors have considered in this paper lowtungsten
tool steels which contain 3.00 per cent tungsten
and somewhat over 1.00 per cent carbon. The
steels investigated were of two types—oil and water
hardening. The hardness, toughness, shrinkage, and
microscopic properties of these steels were studied,
and the results plotted.
•Metallurgist, United Alloy Steel Company. Canton. Ohio.
fMetallurgist, Union Carbide and Carbon Research Laboratories,
Long Island City, N. Y.
Why Metal Warps and Cracks
By J. F. Keller*
The author of this paper has presented and has discussed
in simple terms, the various factors which come
into play in causing iron and steel bodies to warp or
crack when subjected to heat.
He illustrates by means of diagrams and experiments
the manner in which these factors cause the failure
of metallic bodies. Several photographs are included
which show the effect of external strains.
•In charge of university extension work, Purdue University,
Lafayette, Ind.