2
TERMINOLOGY RELATING TO NONMETALLIC ELEMENTS IN METALS
The report as accepted by the Executive Committee in Detroit, Oct. 5,
1933, slightly modified, is as follows:
Through gradual development and evolution the term "gases in
metals" as now employed usually comprises the following three types of
nonmetallic elements or substances:
1. Gases in blowholes or seams (CO, COz, HZ,H20, Nz, CH4).
2. Hydrogen, oxygen, nitrogen combined with metals in the form of
hydrides, oxides and nitrides.
3. Hydrogen, oxygen and nitrogen in solution in solid metals.
Among these three the substances of the first and the third types meet
the definition of a gas-a fluid having neither definite shape nor volumewhile those of the second type do not. They are solids with definite shape
and volume in the temperature range with which we are usually concerned.
The term "gases in metals," therefore, is not now confined to elements
or substances existing in the metal in the gaseous state, but rather to the
three elements, oxygen, hydrogen and nitrogen, either in the atomic or
molecular state or combined with other elements.
The question therefore arises: Do these three elements, oxygen,
hydrogen and nitrogen, possess characteristics that entitle them to be
placed in a class by themselves as far as metals are concerned? This
does not appear to be the case, because other elements like carbon, sulfur
and phosphorus occur in the metals in very much the same way and cause
very much the same kind of phenomena as do oxygen, nitrogen and
hydrogen. In the metals oxygen occurs as atomic oxygen and as oxides,
hydrogen as atomic hydrogen and as hydrides, nitrogen as atomic nitrogen
and as nitrides; but, quite similarly, carbon occurs as atomic carbon and
as carbides, sulfur as atomic sulfur and as sulfides, and phosphorus as
atomic phosphorus and-if present in large amount-as phosphides. All
of these elements-and probably others less common-form the same
type of structures in metals. Why should they be separated into different classes because of their characteristics outside the metals'? I t is their
actions and reactions with the metals with which metallurgists are chiefly
concerned and not whether one element is a gas under ordinary atmospheric conditions while another is a solid. T o go a step further: oxygen
is important to the formation of blowholes in base metals, but oxygen
by itself will not form a blowhole; carbon is just as important. Again,
while oxygen, nitrogen and hydrogen have determining effects on the
physical properties of metals, so do carbon, sulfur and phosphorus.
Looked at from any angle or point of view, there appears to be no
logical reason for the term "gases in metals" as it is being used today, and
the sooner we decide to limit it to its proper sphere, the more confusion we
shall save ourselves in the future. I t is well enough to say that those who
3
T. D. YENSEN AND C. H. HERTY, JR.
are in intimate contact with the subject understand what is being talked
about, when the term "gases in metalsJJ is being used. But these are
relatively few, and among students and among metallurgists and engineers, outside the ranks of the few, the term as now used is causing needless confusion. At the symposium on gases in metals in New York a year
ago, for example, the discussion as applied to ferrous metallurgy did not,
. . .. ... ..
. . . .. . . .
.. .. .. .
'
INTERCRYSTALLINE
PRECIPITATE
(SOLIW INCLUSIONS)
INTRACRYSTALLINE
,
PRECIPITATE.
SOLID
(INCLUSION).
'
.
.
.
'
•
ADJACENT
GRAIN
.. .. .. .. ......... .. .. .. .. .............................be.. ...
.. .. ..... ...='.
- . .....
. . . . . .. .. .. ..... .. .. .
..
... ... ... .................... ... ... ... .. .. ... ... ... ............
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ........
........
. . . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .
...........................................
/ .............
. . . . . . . . . . * .+. .. .. .. ..... .
....
-
-
-
e . . . . . . . . . . . .
0
e . . . . . . . . . . . .
-GASEOUS
O.........~NCLIJSION
0
.O..
8)
='.
STRANGERATOM
NON-MET*LLI=
ELEMENT I N SOLID
SOLUTION
METAL~IC ALLOYING ELEMENT
IN SOLID SOLUTION
(JU~JTITUTION
ELEMENT)
F I ~ .~ . ~ C H E M A T I CDIAGRAM
.
LATTICE USTORTION ALONG
BOUNDARIES AND IN NEIGHBORHOOD OF INCLUSIONS AND
STRANGER ATOMS
O F METALLIC CRYSTAL GRAIN WITH
ELEMENTB.
NONMETALLIC
except to the select few, concern itself with gases in metals at all, but
rather with carbon, oxides and their reactions. Very few in the audience
understood why the term "gases in metals" was used.
In order to clarify the situation still further, a schematic diagram is
submitted showing various forms in which foreign elements of the type
with which we are here concerned may occur in metals (Fig. I), and charts
showing how and a t what stage t h e various inclusions and precipitates
are formed during the cooling of metals from the liquid state (Figs. 2 and
3), using steel in Fig. 3 as an illustration of the general subject.
Figs. 2 and 3 diagrammatically represent the separation of both
dissolved and suspended substances during solidification and cooling to
4
TERMINOLOGY RELATING TO NONMETALLIC ELEMENTS IN METALS
room temperature. Liquid metal entering the mold contains dissolved
and suspended substances. Some of the dissolved substances are precipitated during cooling prior to solidification, some during solidification,
and others remain in solution in the metal after solidification. Of those
precipitated during solidification, some are precipitated so as to coalesce
with certain other precipitates and result in large inclusions that are
visible under the microscope a t some arbitrary magnification. Others
are precipitated too late to coalesce and these would be classed as fine
fine
S
~
N
I
M
fine
El~rntmtedbv
Y ~ ~ ~ I ~ J i(sl~taOon
I M
WuYe ~n'sdklmet&
F I G . 2.-DIAGRAMMATIC
REPRESENTATION OF ACTION OF NONMETALLIC ELEMENTS I N
SOLIDIFICATION OF METALS.
suspensions, the size of the individual particles varying from those just
too small to be seen at the stated magnification to those that might be
molecularly dispersed. The suspended materials in the ladle may be
divided into large inclusions, which would be eliminated by flotation,
and fine suspensions. Some of the fine suspensions may coalesce or
grow during solidification and form large globules or crystals visible a t
the stated magnification. Other fine suspensions may remain as such
during solidification.3 I t is thus possible that there may be present in
the solid metal, at the solidus temperature, materials in molecular or
colloidal suspension and a wide range of particles of varying composition
and size.
Referring to Fig. 3, as the metal cools from the solidus t o room temperature, precipitation of dissolved substances may take place: (1) when
the solid solubility of any substance decreases from the solidus to the
upper critical temperature; (2) when there is a lowering in solubility
The substances precipitated during solidification of steel consist largely of
sulfides. The suspended materiala in the liquid steel would be low in sulfur, and the
large globules resulting from the fluxing of these two types would contain an intermediate amount of sulfur.
T. D. YENSEN AND C. H. HERTY, JR.
-
5
during an allotropic transformation; and (3) when the solid solubility
of a substance decreases with falling temperature below the lower critical
temperature. Changes in any one substance in solution may well affect
the solid solubility of another s01ute.~
Gases may be formed in liquid or solid metal by three methods: (1) by
reaction (such as the formation of CO from C and FeO) ; (2) by dissociation of compounds containing gaseous
1
elements; (3) by change in solubility
ffater~alssduble/n sd/d
of any dissolved gaseous element.
These gases are either eliminated from
the metal or trapped therein. Those
trapped may appear as visible blowholes or may be submicroscopic in size.
I
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I
)
RECOMMENDATION
On the basis of these considerafi
tions, we propose the general title,
"Nonmetallic elements in metals," as
the name of the general subject dealing with :
1. Nonmetallic elements introduced
s ~ s p e n ~ ~
into metals unintentionally or for variat mom temperature
definite purposes (O- N 1 H 1 C1
Flo.3.-DIAGRAMMATICREPRESENTATION OF ACTION OF MATERIALS IN
P, etc.).
SOLID STEEL WITH CHANGES IN TEM2. Phenomena occurring in metals PERATURE.
caused by nonmetallic elements.
I n this title carbon is included in the term "nonmetallic element " and
the title obviously includes. elements present in metals in the gas.
.
eous state.6
Under the heading recommended the following classification is
proposed for the various states in which nonmetallic elements may occur
in metals, and for the various reactions in which they may be involved.
o"ry$z
A. State of aggregation
1. Suspensions
a. Gaseous (nonmetallic elements in the form of gases or vapors in blowholes,
seams or bubbles = "gases in metals'1B)
4 Inclusions may also be formed by reaction of the metal with its surroundings;
for example, (1) diflusion of oxygen into the metal during heating and (2) absorption
of hydrogen during pickling.
6 At the meetings of the Advisory Council other titles were proposed, such as (1)
LLInclusion-and precipitate-forming elements"; (2) "Gases and othernonmetallic
substances"; (3) "Nonsoluble ingredients"; and (4) "Carbon, oxygen, hydrogen,
nitrogen, phosphorus and their compounds." All of these were rejected for various
reasons.
"8
a special case, blowholes may be caused by metallic vapors.
~
b. Liquid (nonmetallic elements in the liquid state suspended in liquid or solid
metal)
c. Solid (nonmetallic elements in the solid state suspended in liquid or solid
metal]
2. Solutions
a. Liquid (nonmetallic elements dissolved in liquid metal)
b. Solid (nonmetallic elements dissolved in solid metal)
B. Reactions due to nonmetallic elements
1. Gaseous (involving gases) FeO
CO Fe
COX
2. Liquid (involving nonmetallic liquids) 2Fe0 SiOn 5 Fe2SiOc
3. Solid (involving nonmetallic solids) 3Fe0
2A1* 3Fe A1108
+ * +
+
+
l
i
+
This classification has been kept as simple and general as possible.
I t may be desirable, therefore, to amplify the terms with a few explanatory remarks.
In the term "suspensions" both "inclusions" and "precipitates" are
included, whether found inside the crystal grains or in the grain boundaries. "Gaseous suspensions" may be gases or vapors in bubbles in
liquid metal, in blowholes or in seams7 in solid metal, and this i s the only
part o j the subject that should be included i n the term "gases i n metals."
Nonmetallic elements dissolved in liquid metal and in atomic state
(interstitial) in solid metal should be excluded from this term.
It should be emphasized that gases in blowholes are inclusions or
precipitates just as much, and in the same sense, as carbides, nitrides, etc.
"Liquid suspensions" may occur: (1) in liquid metal when liquid
foreign matter is immiscible in the metal, or (2) in solid metals a t a
temperature above the melting point of certain compounds of nonmetallic
elements, such as FeS in iron at a temperaturk of 1200' C. "Solid
suspensions" include slag inclusions and all other solid precipitates.
A "solution" is a state of aggregation in which two or more components are present in a single phase. The microscope is the instrument
mostly used for distinguishing separate phases in solid metals, but this
necessarily introduces uncertainties, because of the magnification used.
Particles or precipitates that may be invisible at 100 dia. may be seen a t
1000 dia. Results of microscopic examination, therefore, should not be
accepted as conclusive evidence of solid solubility. At present it is
assumed, and there is fairly good evidence for this assumption, that nonmetallic elements are slightly soluble in metals a t room temperature
and that this solubility changes with temperature and phase changes.
A "liquid solution" in the case under consideration is molten metal
holding nonmetallic elements in solution. "Solid solutions" are solid
metals in which atoms of nonmetallic elements have entered the space
lattice of the metal. It is assumed a t present that the nonmetallic atoms
occupy interstitial spaces in the lattice. It is also assumed that a compound is a separate phase and consequently should be regarded as a
In certain types of worked metals shrinkage cavities may sometimes be confused with blowholes.
r,
L
T. D. Y E N S E N AND C. H. HERTY, JR.
1
precipitate or inclusion, no matter how small the particle. On this basis,
therefore, it is meaningless to talk about compounds dissolved in a
solid metal.
The original report as resented to, and accepted by, the Executive
Committee of the Iron and Steel Division was sent to the following 15
representatives of American and foreign societies, with the request that
the representative either send in his own discussion or refer the report to
someone well qualified to discuss the subject in an impartial manner.
The list gives the representative to whom the report was sent and also
the man to whom it was referred:
I
1
Ir
RDPRE~DNTATIV~
I
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11
1
7
i
John Johnston, Chairman,
Iron and Gteel Division, A.I.M.E.
T. 8. Fuller, Chairman,
Institute of Metals Division, A.I.M.E.
W. H. Eisenman, Secretary,
American Society for Metals.
George C. Lloyd,
Secretary Iron and Steel Institute.
G. Shaw Scott,
Secretary Institute of Metals.
E. H. 0. Peterson,
Verein deutscher Eisenhuttenleute.
Friederich Korber, Editor,
Kaiser Wilhelm Institut fur Eisenforschung.
Georg Masing,
Deutsche gesellschaft fur Metalk1 nde.
e.h.W. Eilender,
Institut fur Eisenhiittenkunde.
L. ~ u i i l e t ,
President, ComitB de RBdaction,
Revue de M@tallurgie.
Louis Delville, Editor in Chief,
Aciers Sphciaux m6taux et Alliages.
K. Honda,
Tohoku Imperial University.
C. Benedicks,
Metall~~rafiska
Instituet.
H. S. Rawdon, Metallurgist,
Bureau of Standards, Washington, D. C.
C. H. Desch,
Supt. Chem. and Met. Dept.,
National Physical Laboratories.
H. W. Gillett, Director,
Battelle Memorial Institute.
REFERRED
TO
John P. Freeman, Jr.,
American Brass Co., Waterbury, Conn.
E , E. Thum, Editor Metal Progress
Cleveland, Ohio.
W. H. Hatfield, Director,
Brown-Firth Research Labs.,
Sheffield, England.
D. Hanson,
Birmingham University, England
No reply.
No reply.
A. M. Portevin, Paris;
R. J. Caatro, Ugine, France.
No reply.
No reply.
G. Thompson and Louis Jordan,
Bureau of Standards.
No reply.
.
The authors take this opportunity to express their appreciation to all
those who have contributed to the discussion of this paper and to urge
those who for one reason or another have not yet been able to do so to
set forth their views in letters to the Secretary of the Institute.
In the report as given above a few minor changes have been incorporated, which were suggested by Eilender, Gillett, Portevin and Freeman.
Of greater importance than these minor changes, however, are the
opinions of these representatives in regard to the recommendations
as to nomenclature and classification. Pertinent quotations and
abstracts from their communications are given below, together with
our comments.
PROF.DR. ING.e.h.W. EILENDER,
Institut fur Eisenhuttenkunde der
technische Hochschule, Aachen, Germany: "The report on Nonmetallic
Elements in Metals . . . has my complete approval. I am glad that it
will be possible to give a unified nomenclature on this subject for laymen."*
Dr. Eilender states that methane (CHr) should be included among
gases enclosed in blowholes, and also calls attention to some other points
where minor corrections might be made to advantage. He particularly
suggests that the term "impurity" be avoided, as it represents an expression of opinion. Dr. Eilender further suggests that the second and third
methods of gas formation (page 5) be combined, as follows: "Gases can
be formed by the decomposition of chemical compounds at temperatures
at which they are unstable, and therefore dissociate." This statement
leaves no place for evolution of gas by change in solubility unless dissociation of a compound occurs. This is such a controversial subject, with
little direct experimental evidence, that the committee has left the
manuscript unchanged on this point.
DR. KOTARO
HONDA,
Director, The Research Institute for Iron, Steel
and Other Metals, Imperial University, Sendai, Japan: " . . . Upon
conference with my colleagues about your proposed title, 'Nonmetallic
Elements in Metals,' this has also been approved by them. The expression is, I believe, the most suitable one ever proposed."
PROF.DR. F. K ~ ~ R B EDirector,
R,
Kaiser Wilhelm Institut fur Eisenforschung, Dusseldorf, Germany: "The objections raised in the report
against the term 'gases in metals' are justified. Furthermore, no objection can be raised against the proposed expression 'Nonmetallic elements
' in metals.'
Neither can any objection be raised against the proposed
classification in regard to the reaction phenomena . . . as it gives the
correct designation for the observed phenomena."
Dr. Korber, however, objects to the arguments used as a basis for an
explanation of the classification. He thinks ideas and notions have been
8 We do not know just why Dr. Eilender uses the word "laymen," but as he
writes in English we cannot change it. He may, however, have meant "general
metallurgists."
T. D. YENGEN AND C. H. HERTY, JR.
I
I
9
included that, as yet, have not been definitely established by experiments,
and that we should use only terms given in the classical works (of Roozeboom and Tammann). We should patiently wait with the formulation
of a comprehensive classification until we know much more about metals
than we do at present. He says: "From this point of view the proposed
term 'Nonmetallic elements in metals' is of no particular importance in the
present stage of our research" and continues, "By collecting experimental facts regarding the separate elements the foundation can in time
safely be laid for a choice of nomenclature, free from objections and of
single meaning, for the phenomena and processes in which, as a matter of
fact, there exists such an intimate relationship that an all-inclusive
conception is justified or even required."
The committee agrees with Professor Korber that our knowledge
in regard to metals is still imperfect. However, our terminology
should keep pace with our knowledge as far as possible and it should
be modified whenever there is adequate reason for doing so. It seems
that this is a good time for making a correction in a terminology that
95 per cent of the critics, including Professor Korber, admit to be faulty
and misleading.
Ugine, France:
PROF.S. A. M. PORTEVIN,
Paris,; PROF.R. J. CASTRO,
. . We are complimenting them (the committee) in their efforts in
classifying ideas relating to such complicated questions as those pertain(' to nonmetallic elements in steel. Such a classification will greatly
ing
help the clear presentation of ideas and will help to avoid lengthy explanations and preliminary introductions.''
Professors Portevin and Castro, in referring to Fig. 2, call attention to
the fact that large inclusions are not always eliminated by lavitation, but
often are trapped by rapidly growing dendrites, and also suggest that
large inclusions are sometimes formed by growth as well as by coalescing.
The committee thinks that in solid metal the two terms "growth" and
LC
coalescing" are synonymous, because solid solution and diffusion are
involved in either case. Professors Portevin and Castro object to the
term "slag inclusion" and prefer Benedicks' term, "foreign nonmetallic
inclusion, " in contradistinction to "native nonmetallic inclusion, " this
latter referring to precipitates formed from the metal itself.
The committee wishes to point out that in the classification the term
"solid suspensions" has been used to cover both these terms and only in
the explanatory remarks are these divided into "slag inclusion" and "all
other precipitates." This is a matter of detail of no great importance.
DR. W. H. HATFIELD,Director, Brown-Firth Research Laboratories,
Sheffield, England: "The action of the Executive Committee of the Iron
and Steel Division of the A.I.M.E. in attempting to clear up misunderstandings in the nomenclature concerning 'gases in metals' is one that will
be appreciated throughout the metallurgical world."
.
10
TERMINOLOGY RELATING TO NONMETALLIC ELEMENT0 I N METAL0
Dr. Hatfield suggests a modification of Fig. 2, the "diagrammatic
representation of the action of nonmetallic elements in the solidification
of metal," in order more clearly to differentiate between the gaseous and
solid states, and the committee has carefully considered this in drafting
the final paper for publication. When Dr. Hatfield states that "the
question of the possible solubility of carbon monoxide in solid steel has
been evaded" he is mistaken, as we say, on page 6 : I t is also assumed that
a compound is a separate phase and consequently should be regarded as a
precipitate or inclusion, no matter how small the particle. On this
basis, therefore, it is meaningless to talk about compounds dissolved
in a solid metal." CO being a compound it will be present as a precipitate
(a blowhole). Dr. Hatfield concludes by stating that, "It is to be hoped
that this is but a preliminary to a more advanced program . . ,,
PROF. D. HANBON,
Birmingham University, Birmingham, England:
Professor Hanson objects to the bringing together of terms such as
"blowholes, shrinkage cavities, blisters," under the headings "gaseous
suspensions." It appears that this is exactly where these terms belong, if
the purpose of this paper is to make a general classification of which each
subdivision should be expanded to take in such terms as Professor Hanson
submits. He further states, "It seems to me illogical to exclude from
our consideration under the heading 'gases in metals' those equilibria and
reactions in the liquid metal which lead to the formation of gas."
These phenomena are not excluded but are found under section B-1
of the classification (page 5) of the manuscript and in Fig. 2, where it is
shown that gases may be formed by reaction in the liquid steel. Again
the manuscript has been altered somewhat to clarify this situation. The
most important part in Professor Hanson's discussion is that the terminology for one metal may not be satisfactory for another metal. He
gives as an example the action of oxygen in copper and in silver. Oxygen
in copper will not of itself cause gas formation but it will in silver, the
difference being due to the vapor pressure of oxygen in the two metals.
Professor Hanson rightly states that, "when we consider the nonmetallic
elements from the above point of view we find that they cannot be classified according to the nature of the elements alone but that the solvent
metals must also be considered."
This is a perfectly logical line of thought and shows the advisability
of applying to our classification suitable subdivisions for each metal
involved. Section A-1-a of the classification covers the case of oxygen and
silver, because the vapor pressure of oxygen is great enough to allow gas
formation. On the other hand, oxygen and copper would be placed
under the headings A-1-c or A-2-b.
Director, Battelle Memorial Institute, Columbus,
DR. H. W. GILLETT,
Ohio, and Editor, Metuls & Alloys: Dr. Gillett and his associates suggest
.
.
T. D. YENSEN AND C. H. HERTY, JR.
11
"nonmetallics in metals" as preferable to "nonmetallic elements
in metals."
After suggesting a few minor but relevant changes, Dr. Gillett concludes by stating: "On the whole, the argument is so convincing that one
wonders if it could not be considerably condensed and still be
thoroughly convincing. The report should help materially in clarifying the situation."
DR. JOHNJOHNSTON,
Director, Research Laboratory, United States
Steel Corporation, Kearny, N. J.: Dr. Johnston and some of his associates
suggest that for publication the paper might to advantage be separated
into two parts, the report proper and the comments, aside from a few
minor changes that have been made in the final draft. Dr. Johnston
concludes: "I would expect that the term proposed would find general acceptance."
JOHNR. FREEMAN,
JR., American Brass Co., Waterbury, Conn.:
. . "This title, 'Nonmetallic Elements in Metals,' the meaning of which
constitutes the discussion of the paper, is well chosen. I t is fundamental
and descriptive and yet sufficiently general to include metals in both the
solid and liquid states."
Mr. Freeman suggests the addition of a note explaining why gases in
solution in molten metal is not included in the term "gases in metals."
In line with this suggestion the explanatory remark regarding gaseous
suspensions on page 6 has been changed to read as follows: "Gaseous
suspensions may be gases or vapors contained in bubbles in liquid metals,
in blowholes or in seams in solid metals, and this is the only part of the
subject that should be included in the term 'gases in metals.' Nonmetallic
elements dissolved in liquid metal and in the atomic state (interstitial)
in solid metal are therefore excluded from this term." They are included
under "Solutions." 'It should be recognized that after entering a metal
(going into solution) a gas loses its gaseous properties.
Mr. Freeman's other suggestions in regard to definitions and solubility
have received the committee's careful consideration.
E. E. THUM,Editor, Metal Progress, Cleveland, Ohio: "No one can
uphold the loose usage of the term 'gas in metals' and fail to hope that the
Committee's suggestions (that it be confined to true gases in blowholes
and seams) will be heeded by writers and editors."
Mr. Thum then points out the possible dilemma of defining a nonmetal, and also that an element may sometimes behave like a metal,
sometimes like a nonmetal. He therefore suggests, with Professor
Korber, that "we would perhaps best refrain from setting up a new
generalized- classification which may later have to be torn down
and re-erected."
The Committee's reaction is contained in the following query: For
fear of not being able t o build a house now that will be regarded as perfect
.
12
TERMINOLOGY RELATING TO NONMETALLIC ELEMENT0 I N METALS
10 or 100 years from now, do we refrain from building? Perhaps some
do, but most of us build our houses today as best we can, tear down and
rebuild when it seems desirable or sell to somebody who is less particular..
Lours JORDAN
and G. THOMPBON,
U. S. Bureau of Standards, Washington, D. C. :Messrs. Jordan and Thompson admit that the term "gases
in metalsJ' is not entirely adequate and state: "The general term suggested by the authors of the paper under discussion ('Nonmetallic
Elements in Metals') is, they admit, far more comprehensive than the
expression they wish to replace. The use of the suggested new designation would, therefore, be a t the cost of a considerable sacrifice
of convenience."
Rather than "admitting," the authors state that the proposed term is
more comprehensive than the term "gases in metalsJJand feel that "gases
in metals" has its proper place under the more general title "Nonmetallic
elements in metals." The question of convenience is a matter of
opinion and momentary convenience often leads to general confusion
and inconvenience.
Messrs. Jordan and Thompson state that: "The elements oxygen,
nitrogen and hydrogen naturally fall into a single group distinct from the
other elements commonly encountered in metallurgy. In the free state
these elements are gases; many of their compounds are gaseous; they are
introduced in metals chiefly from the gas phase; for purposes of identification and estimation they are usually converted again into gases. In all
these respects the elements oxygen, nitrogen and hydrogen, as a group,
differ from the ordinary nonmetallic elements such as sulfur, carbon,
and phosphorus."
To designate any material by the general analytical methods involved
in this determination or by its mode of entrance into the metal would
seem quite illogical. Were this procedure followed, carbon in a carburized
part should be called a gas. Similarly, inasmuch as considerable
quantities of sulfur are introduced into liquid steel from the gas phase it
would be necessary to classify this element under gases. Oxygen enters
the metal primarily through the diffusion of FeO from slag to metal,
granted that it originates from the atmosphere. Oxygen by the Ledebur
method is evolved a8 a gas and weighed as a liquid or a hydrate. Sulfur is
generally run by the evolution method with the formation of HzS. It is
thus apparent that analytical methods or modes of entrance would lead to
endless confusion. The major point in the proposed classification is that
"gases in metals" be given its proper place rather than being used as a
general title.
From the above discussion, it is seen that these representatives almost
unanimously agree as to the present' confusion and believe that classifica-
T. D. YENBEN AND C. H. HERTY, JR.
13
tion a t the present time is highly desirable. The first reaction on reading
the report may be a question as to where such and such a substance or
reaction may fit in, or why such and such a substance was left out. In all
such cases the reader will probably find, as the authors have found in
studying the discussions, that there is a place for everything, and they
will welcome a test as to this statement. If the test fails, they will be
glad to modify the classification so as to make it more perfect.
It was not the intent of the committee to unravel the details for all
metals but to present a general classificationunder which any phenomenon
relating to the general subject could be placed.