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Vol. 17, No. 1
GRASSELLI MEDAL A W A R D Fundamentalism in Ferrous Metallurgy By B. D. Saklatwalla
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HE average human mind displays a tendency towards veneration of the complex and unwittingly ties up the advance-
ments of the world should condition one another for the world to be a unity, and such conditioning cannot but follow the prinment and progress of a science or art with the degree of its ciple of equilibrium. The constant reduction of his observacomplexity. On the contrary, complexity may be indicative of tions to this principle will undoubtedly help the metallurgist lack of progress, especially of the lack of clear understanding of the to arrive at a clarified explanation of his phenomena. This basic fundamentals of the art or science. The science of ferrous principle should furnish him the keystone of his scientific strucmetallurgy seems to be more or less in this category. hToless an ture as it has done in other branches of human endeavor. We authority than Dr. Rosenhain all-realize the importance of has stated that in ferrous metequilibrium, or balance, or A t the meeting of the Society of Chemical Industry allurgy we are attempting to harmony, as we may call it, a t the Chemists’ Club, New York City, on December run before we have learned to not only in the sciences and in 5, 1924, the Grasselli Medal was presented to Dr. B. D. engineering, but also in the crawl. There is no doubt in Saklatwalla, general superintendent of the Vanadium Corarts and metaphysics. The the mind of any conscientious poration of America, Bridgeville, Pa., in recognition of his works of the great masters scientist or technologist workpaper on “Ferrous Alloys Resistant to Corrosion.” could not have been produced ing in the field of ferrous metThis medal is awarded annually by the American Secwithout homage to this prinallurgy that he is hampered tion of the Society of Chemical Industry for the paper ciple, applying it to composiby the lack of explanation and presented before that section which offers the most usetion, color, etc. The metad a t a r e g a r d i n g the fundaful suggestion in applied chemistry. Dr. Saklatwalla physics of human relations mentals of his subject. The is the third recipient of this honor, the first award having undoubtedly is founded on ferrous industry seemed for a been made to Dr. Allen Rogers, professor of industrial equilibrium, and it would not long time to have adopted the chemistry at Pratt Institute, Brooklyn, N. Y., for his be an undue claim to class attitude of considering science paper on “Industrial Uses for the Shark and Porpoise,’’ the Golden Rule, “DO unto as the merely abstract. Sciand the second to Mr. Walter H. Fulweiler, Gas Improveothers as you would that they ence is not the abstract, but ment Co., Philadelphia, Pa., in recognition of his paper should do unto you,” as an a correlation of the abstract entitled, “Chemical Problems in the Gas Industry.” admonition to remember the to actual exDerience. tenet of equilibrium. We, as The progress of that comchemists, can perhaps discern in this great rule the principles plex of existing conditions which we term “modern civilization” of our reversible equation, mass action, and phase rule. If has proved itself to depend more and more on the progress of metallurgy and especially on that of ferrous metallurgy. This has you do not want the reaction to reverse, keep the concentration brought to our attention the importance of visualizing metallurgy of your deeds constant. The importance of the doctrine of equilibrium from a metafrom a broad scientific viewpoint, and the necessity of establishing its procedure on a systematic basis comparable with other physical standpoint seems to have been recognized early in human history. The Chinese author, Chung Yung, in his “DOCbranches of engineering. It has frequently been suggested that the metallurgist view his subject from the standpoint of the nat- trine of Equilibrium and Harmony” states: ural philosopher, rather than that of the specialized technician. When anger, sorrow, joy, pleasure are in being but are not The merit of this suggestion is apparent when we consider all manifested, the mind may be said to be in a state of equilibrium; the various sciences that find a common meeting ground in when the feelings are stirred and codperate in due degree, the mind may be said to be in a state of harmony. Equilibrium is metallurgy. Not only the older sciences of chemistry, physics, the great principle. and mechanics enter into its field, but the newer forms of physAn elaboration of the principle of equilibrium as applied to ical sciences, such as “ultra-microscopy” and “atomistics,” play important parts in understanding the phenomena of met- mathematics and physics would be redundant. Lewis and als. The metallurgist can with profit extend his experience to Randall, in their “Thermodynamics,” under the heading of a wider field than that of the physical sciences by even entering Equilibrium state : “In all thermodynamics there is no concept the field of metaphysics-in other words, by surveying the laws more fundamental than this.” Can the metallurgist, then, lightly treat-much less, ignoregoverning the existing nature around him and drawing his corollaries therefrom. Nature is no better understandable than a factor as fundamental as this? On the other hand, by fundamentally deducing his phenomena to this great principle, he can from nature. inject greater clarity in his technic and considerably enhance Application of Equilibrium to Metallurgy his progress. It is no doubt in a great measure true that the We can follow our reasoning along this line with more clarity metallurgist has studied the chemical equilibria of his furnace if we select as an example some universal principle and survey its reactions and has applied the principles of physical chemistry application to metallurgical phenomena. For this purpose to his slag reactions. In the case of steel metallurgy, however, this has been only a very small part of his art. The attainwe can do no better than take the great principle of ppuilibrium. ment of right chemistry in the ladle has merely furnished him I t is no exaggeration to say that there is no phenomenon, physical or otherwise, that does not follow this great concept. In the basis for the further application of metallurgical science. The function of the engineer is to control the progress of fact, a digression from it is inconceivable, as the different ele-
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is established. On this principle are based such phenomena as natural reactions constituting his process by controlling the grain refinement, dispersion and solution of carbides, spheroidconditions influencing such reactions. We may then say that izing, etc. rather meager engineering is applied to the phenomenon of The equilibrium changes are not restricted to microscopic solidification of steel. During this procedure the inherent and grains, but apply also t o the ultra-microscopic regions, as in the prime qualities of the steel, which the writer in some of his previous publications has termed “prenatal” qualities, are estab- formation of solid solution by substitution or addition of a foreign atom in the iron space lattice through the application lished and their influence persists through all later working of the metal. It is during this stage that the condition of harm- of extraneous energy. Diffusion phenomena may be of this class. The verv nature of the procedure of heat treatment operations, fulness or innocuousness of the nonmetallic constituents, absorbed gases, etc., is established. During the solidification such as annealing, quenching, drawing, etc., suggests that they are based on energy equilibria and that the segregation of the various elements and their physical results are obtained by fixing or combination to definite chemical compounds holding a certain equilibrium condition, and or otherwise take place. These are all by making this condition persist a t the ordiphenomena subject to the law of equilibrium, nary temperature a t which the steel is to both chemical and physical. It is true that perform its particular useful function. It the phenomena are studied from a thermowould, therefore, have been more rational dynamic standpoint, and as a result we have and scientific to have based the nomenclathe iron-carbon equilibrium diagram of ture of the constituents produced by heat Rozeboom. However, we have not made treatment in steel on the condition of equiany engineering progress and applied this librium established rather than on an emknowledge towards attainment of control pirical basis such, for example, as their tenover the equilibrium factors which establish dency of behavior towards etching agents, the inherent qualities of steel. As such facas a t present. tors may be mentioned size and distribution of crystals, dispersion or coagulation of nonI m p o r t a n c e of Surface Tension metallics, elimination of gases, etc. Some In connection with heat treatment may time ago the writer suggested, as a trial, the be mentioned another phenomenon that has expediency of allowing a steel ingot to soreceived little study from the metallurgist lidify under the influence of a controllable and is of paramount importance. This electrostatic or electromagnetic field, for the phenomenon is surface tension. It can purpose of controlling all these factors. If readily be seen that, since the interaction of the equilibrium conditions during solidificaB. D. SAKLATWALLA the microscopic, and probably also of the tion could be controlled to eliminate, a t submicroscopic, grains of the steel on one least partially, the so-called cast structure, the subsequent manufacturing operations would be simplified another produces the desired engineering properties, surface and the engineering qualities of the finished product considerably tension is the determining factor in the attainment of these improved. properties, At first it may seem an exaggeration t o suggest that the force of surface tension is a more universally The steel metallurgist has undoubtedly manifested some realization of the equilibrium conditions in a solidifying ingot, but pervading and a more important force, from the engineering standpoint, than the force of gravity. However, very little only from the standpoint of its thermal equilibrium or rate of deliberation will convince us that matter is inconceivable withcooling. The results achieved, however, although of importance from an economical standpoint, can hardly be called justifiably out being shbjected to this force. In fact, all characteristic a control over the grain structure or quality of the material. and fundamental properties of matter, manifested to us, are The general ingot structure, aside from segregation of shrinkage surface tension properties. We are not concerned with the intercavities and blowholes, is not appreciably altered by different molecular or interatomic properties, but are interested in the mold practices. external energy manifestations of the molecules or particles In the subsequent fabrication of the solidified ingot to rolled or forming the aggregate body. forged products, the equilibrium conditions and their control Alloy Steels are of even greater importance. The constituents of steelThe importance of fundamental deduction appears all the namely, iron and iron carbide-enter into physical interaction a t temperatures considerably below the melting point of the more potently in the study of alloy steels. It is being more and constituents and reach a state of equilibrium depending on the more conceded that the progress of our mechanistic civilization conditions of temperature, time, external physical deformation, is closely linked with the advancement of alloy steel metallurgy. etc. Inasmuch as we are concerned with the ultimate engineer- This recognition has stimulated the exploitation of alloys on a ing properties of the finished steel, and as such properties are more ur less purely experimental and empirical basis, with disdetermined by the equilibrium established between the grains regard to fundamental study. We have probably unwittingly of the steel copstituents, we can readily see the paramount im- adopted the tactics of the “pill doctor,” and if we persist in the portance of the most exact study of such equilibrium. The purely experimental channel of making steels with different eleengineering properties are established by such factors as grain ments and different percentages of these elements with the varisize, physical nature of the pearlitic constituent, state of defor- ations of the other accompanying elements, and then trying mation or strain of the grains, and these factors are nothing else out their properties, our task becomes not only endless but also but results of stable or metastable condition of equilibrium and thankless. Inasmuch as the study of steel is more or less a study of the are produced by transformation of one form of equilibrium to another. The same reasoning applies, even in a greater degree, equilibrium conditions of its constituents, both in the liquid and to the phenomena of heat treatment of the finished steel. The the solid state, it stands to reason that the introduction of another achievement of remarkably different properties by heat treat- metal, which chemically enters into these constituents, alters ment is brought about by changes in the equilibrated free energy these conditions. For instance, in the liquid state the presence conditions of the grains. Their surface energy content is al- of another metal in solution in iron F a y change the viscosity, tered by application of external energy and a new equilibrium heat conductivity, capability of crystal growth, diffusion through
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the liquid or the solidified grain, facility or retardation to passage of nonmetallics, which would all strongly influence the “prenatal” qualities of the steel formed. Moreover, we can readily see that the surface energy qualities of the solidified grains will be altered, thus changing the conditions of heat treatment and producing altered engineering properties in the finished material. From the standpoint of equilibrium we can summarize the effect of alloys in general by recalling the iron-carbon equilibrium diagram. By introducing another alloying element we have disturbed the equilibrium conditions. Hence the position of the lines in the diagram representing the equilibria is altered. We can, therefore, shift in any direction the position of the entire diagram in the picture field. By proper selection of the alloying element the direction of shifting can be controlled. The transformations depicted by the diagram, therefore, take place a t different temperatures, or for the same temperature different thermal changes are presented. We can thus readily see the possibility of producing similar physical properties by the use of different elements and of the necessity of different heat treatments for different alloy steels. This naturally suggests some equivalence among alloying elements, not from the chemical equivalent standpoint, but from that of equivalence in final engineering properties. A fundamental study of the effect of alloying elements will undoubtedly reveal the key to the secret of equivalence. “Stainless” Steels Recently another class of steel alloys has gained preeminence. These are the alloy steels commonly known as of the “stainless” or “rustless” type. These steeis contain amounts of alloying elements in very much larger percentages than do the usual structural alloy steels. Our fundamental knowledge as t o the effect of such percentages in resisting corrosion is even more l i t e d than in the case of the structural steels. Empirism seems to have flourished more rampantly. This is not strange when we consider that our fundamental knowledge as to the cause of various forms of corrosion is extremely meager, and therefore progress temporarily must lie in the course of experimentation. The principle that has heretofore stimulated experimentation in this field seems to be that of equivalence. I n the case of highchromium rustless steels some of the chromium content has been successfully replaced by such elemeqts as copper, nickel, silicon, etc. In such substitution there seems to be the additional advantage, as in the case of copper, of imparting to the steel acidresisting properties as well as resistance to oxidation. Reverting to our principle of equilibrium, undoubtedly the phenomena of noncorrosiveness can be traced back to it after we have gained a little more insight into the mechanism of corrosion. Solubility or chemical activity is without doubt a function of the free energy of matter, especially the surface energy. I n aqueous solutions, the size of grains of the solute is known to alter the solubility. We may therefore find in the study of free energy an explanation of the relation of noncorrosiveness of such steels to their structure and also of the effect of heat treatment on noncorrosiveness. The fundamentals of noncorrosive steels may lead us into equilibrium phenomenq, not only of the micro constituents, but into the ultra field. The atomic arrangement or introduction of the alloying atoms into the iron lattice may have the effect of changing the surface energy content and equilibrium conditions of the resulting physical grains. We may then consider noncorrosiveness as a function of what we may term “atomic architecture.” On account of the immense economic importance of corrosion in steel metallurgy, as so ably shown by Sir Robert Hadfield, the metallurgist has been stirred t o develop processes fundamentally different from the usual steel-making practices, whereby noncorrosive steels can be produced a t such cost as t o make their application possible for general purposes. This has been accomplished by reducing the alloying element content directly from the raw ore into the finished steel. In this manner large
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percentages of the alloying metal can be introduced from a very cheap source. Besides the factor of cheapness, by such processes the alloying element is introduced in its nascent and pure state uniformly into the steel, avoiding all tendency t o segregation. Manufacturing Problems
In connection with the development of direct reduction of ores into steel, or in the manufacture of ferro-alloys for subsequent introduction into steel of such refractory metals as vanadium, chromium, tungsten, etc., the metallurgist has been obliged t o study his manufacturing problems from a fundamental standpoint. The processes and apparatus of ordinary ferrous and nonferrous metallurgy present limitations to the solution of the ferro-alloy problems. The fundamentals of electric smelting, of regulation of electric current and temperature, had to be studied and high-temperature processes suitable for each reduction operation evolved. There seems to be a lack of attempt, in ordinary ferrous metallurgy, to make the process adaptable to the product desired. Undoubtedly, ferrous products, such as pig iron and cast iron, are not just what they are desired to be, but are accepted more or less as mere results of an economical and easily operated process. This has led to the condition that the art of making ordinary steel has for its object the elimination of undesirable impurities, which have been unavoidably acquired in the blast furnace. This condition has led t o efforts to smelt iron ore directly into refined steel, either by way of sponge iron or otherwise. Such direct process portends not only t o effect revolutionizing economies but also t o produce ferrous metals of unexpected quality. The unknown factors of oxides, nitrides, and the like, and their effects on the other constitutents of steel could thus be made controllable or entirely eliminated, and probably at some future time we will understand why the ultimate chemical analysis of the various elements in steel has failed to afford a criterion of its quality. The veil of caprice and mysticism shrouding chemical analysis in relation to structural qualities will be lifted, to the joy of the construction engineer. Need for I n s t i t u t e f o r Metallurgical Research We have realized the importance of fundamental research and establishment of fundamental data in connection with the metallurgy of as important a metal as steel. Naturally, the question arises as t o how, where, or by whom such data are to be obtained and assimilated. It is in the domain of pure science, and neither the producer nor the consumer of steels seems to be immediately concerned in the accomplishment of such research. We can find the answer to this dilemma by looking around us a little. Institutions that can carry out such work have sprung up in the last few years in other countries and are amassing information of such nature, among which may be mentioned the National Physical Laboratory, a t Teddington, England, The Kaiser Wilhelm Eisen-Forschungs Institut, the Reichsanstalt, and Materialpriifungsamt in Germany, the Swedish Institute for Steel Research under the able leadership of Benedicks, and the similar institution under Honda’s guidance in Japan. It is therefore apparent that other civilized countries have recognized this question t o be of national importance and have established facilities and means for the progress of fundamental metallurgical work. I n our own country we have the unparalleled example of the Rockefeller Institute for Medical Research and the furtherance of medical science by the fundamental and purely scientific work accomplished by that institution. The peculiar conditions of the complex of our country make it desirable that an institution for metallurgical research be established by an endowment along the lines of the Rockefeller Institute, to make it untrammeled from the instincts of commercialism or governmental politics, with the one object in view-namely, to further the progress of civilization and t o make us independent in exploitation of our natural resources and unhampered in our world commerce in times of peace or of war.
