September, 1923
I,VDcS‘l’RI-SL A S D EXGINEERI:1’G CHEMISTRY
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T h e Trend of Research in t h e Nonferrous Industry By Paul D. Merica THEINTERNATIOXAL KICKEL C o . , NEWYORK, N. Y.
0 ASYOKE familiar with the nonferrous industries the title of this article \vi11 probably appear a highly idealized one. In the first place, the components of this industry-the aluminium, the copper, the zinc, the white metals, the nickel and cobalt, the brass rolling mill, the brass foundry, the die-casting industries-are, many of them a t least, widely separated in interests, in uses, and in production methods, and it appears by courtesy only that we thus speak of a nonferrous industry. It may also seem difficult a t first thought to conceive of this composite group, each one of which is actually day by day wrestling with its o ~ v npeculiar problems, as exhibiting any definite “trend of research” activities whatever. The term seems to infer a greater degree of group consciousness than actually exists. However, curiously enough, some major problems do appear to be common to most members of the industry and with which each is vitally concerned, and in this sense such a trend may be discerned; it is perhaps a statistical and not a conscious one. It is pleasant to be able to record the fact that research is very definitely establishing itself to-day in practically all the nonferrous groups as a major element of industrial organizations. This realization may well be regarded as the consummation of a development which has taken place within the past twenty to twenty-five years-namely, the gradual assumption of administrative authority by men of engineering and technical training. Twenty-five years ago, for example, the greater part of the copper refining in this country was done on the Atlantic seaboard, where coal and coke were to be had. The operating personnel was drawn from practical Welsh refiners, who a t that time were coilsidered to know everything which was worth knowing about the art. Copper they could produce, but it remained for the young technical graduates, entirely ignorant of it at the time, actually to advance the art of copper refining. The influence of these men and of later ones like them is being felt in ever increasing strength; their word to-day even penetrates to boards of directors, and, if I hear it correctly it is this: You cannot continue to produce your (metal) products to-day, and-what is more importaiityou cannot continue to sell them in competition, except you have more and still more accurate information concerning them. It is in the clearly e\yident response to this call throughout the nonferrous metal industries that the most clearly defined trend within them is seen. Research activity is here to stay; it is not a luxury, it is recognized to be a necessity. Individual companies are equipping themselves in every way to learn, both in physical and in human equipment. The amount of engineering and scientific thought now applied to these industries is probably fifty times as great as in 1900 and tell times as great as in 1912. A recent suwey revealed the fact that over sixty manufacturers within the nonferrous industries maintained research departments and laboratories in 1920, in addition to the numerous control aiid operating technical personnel attached to many more smaller companies, principally foundries. Parallel with the increased use of atcurate thought and knowledge in these industries is developing also the increased use of new and better tools for aiding and testing production,
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a few gears ago hardly known in the metal trades, The use of pyrometers is increasing rapidly in all branches, as well as that of testing instruments of all sorts-particularly, however, the microscope, which is, after all, responsible for some of the impetus which has been given to the research spirit of these industries in the past twentyfive years. Well-defined standards for products are also rapidly making headway, stimulated by the splendid work of the American Society for Testing Materials1 and other technical organizations, as well as standards for the testing of those products, such, for example, as the well-known standard of chemically analyzed samples of nonferrous (and other) metals provided by the U. S. Bureau of Standards. The industry refuses to work longer in the old darkness; the light is being let in. Finally, still another indication of the new research spirit in the industry is the increasing willingness and even desire on the part of individual companies t o exchange information with others and even to undertake cooperative research work such as that of the Copper and Brass Research Association and of the American Society for Testing Materials. Granted now the remarkable meiital growth within the industry and its new activity in research, what are some of its features?
THECORROSIOX PROBLEM TT7ith the exception of electrical copper, the light metals and alloys, and those used for bearings and solders, metals and alloys other than those with an iron base are used in the arts to-day, as always, because of their greater resistance to corrosion. If there is any positive term with which we might properly name the nonferrous metals, it would be “corrosion-resistant” metals. B s this is their ruison d’elre, cominercially speaking, it is naturally the chief concern of most of the producers and users of nonferrous metals. The demands made upon metals in regard to their resistance to corrosion are more and more severe, particularly those of our expanding chemical and allied industries, which are demanding alloys for pipes, vessels, autoclaves, valves, etc., to withstand the action of the many chemicals with which they deal, and under severe conditions of temperature, pressure, velocity of flow, etc. The development of these industries depends in a large measure on the success yith which these demands are met, and with this in view the , ~ M E R I C A N CHENICAL SOCIETY a t its recent ISew Haven meeting held a symposium on the subject of materials for the construction of chemical equipment. Users of metals are evincing a more critical attitude toward their use; they are more willing to consider the installation, in place of iron and steel, of the more expensive, but more durable nonferrous metals, such as for roofs and plumbing, because of the rising labor costs of repairs and renewals. The Copper and Brass Research Association is doing much valuable educational work in demonstrating the economies which may result from the adoption of nonferrous materials. Consumers are, however, in many cases reverting to the cheaper steel and protecting it by various coatings. 1 The nonferrous industries working within this society have provided about forty standard specifications for its products
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I N D U S T R I A L A N D ENGINEERING CHEiMISTRY
Perhaps the noise of the exertions of the steel industry in producing “stainless” and “resist-all” steelB has created an alarm within the industry and a fear that unless something is done, their cheaper cousin, steel, will supplant the nonferrous base metals for spoons and pots and plumbing as it once did centuries ago for axes and hatchets. Certainly competition, both within and without the industry, is having a good deal to do with the recent accession of interest in this subject. Consumers ask more questions and have more exacting requirements to-day than ever before. They wish to cease guessing; they want to know. Along these lines each nonferrous group is active, but a much more striking evidence of the value the industry attributes to this problem is the existence of a number of cooperative research groups devoting their time to it. The British Institute of Metals has for a number of years maintained an active Corrosion Research Committee, which has presented six very useful reports. More recently in this country a similar committee has been organized under the auspices of the National Research Council, and will devote its energies primarily to the elucidation of the fundamental factors and the mechanism of corrosion. At the same time a committee (B-3) of the American Society for Testing Materials, and committees of the American Institute of Chemical Engineers and of the American Foundrymen’s Association, have been formed to give consideration to the proper methods for corrosion-resistance testing of nonferrous metals. It seems safe to predict that our knowledge of corrosion and our practice of studying it will in the course of five or ten years be greatly advanced, and it may be possible a t some future time for engineers to predict the course and extent of corrosion with the accuracy and confidence comparable with that with which they design structures to resist mechanical stresses. Mention might be made of the very illuminating scrutiny to which the various theories of corrosion are being subjected, particularly the electrolytic one and what may be called the chemical or oxygen theory. There are two rather positive schools of thought on this subject just now and the clarifying results of their strenuous discussions can readily be foreseen. WHATIs TO BE DONEWITH SCRAP The problem of the disposition of its alloys and scrap is an intimate one with every user and producer of metals, and each manufacturer is meeting it as best he can-there being little evidence as yet of concerted action toward general solution of the problem. Naturally, it grows worse each year instead of better, since a portion of each ton of new metal sold comes ultimately on the market as scrap and must be taken care of. No statistics are available, except during the war and post-war periods in which conditions were unsettled, but the ratio of new metal to old used in producing nonferrous mill ingots and sand castings is steadily decreasing, just as the ratio of pig iron to steel produced is decreasing year by year. The complete solution of this problem will lie in many directions. Two of its prominent aspects which will well illustrate its nature are-the steady accumulation of impurities on repeated re-melting and re-working, and the difficulty of positively identifying without chemically analyzing each piece of scrap. Considering the first item in the light of a well-known thermodynamic principle, the summation of the operations of industry in buying and selling would ultimately result in the degradation of all metals into one form of alloy containing everything (!), were it not for the scrap dealers, the ‘[Maxwell demons” in the industry who exert themselves to keep certain alloys well separated throughout their course and returned to the producer for re-melting, practically intact,
VOl. 1.5, No. 9
and the secondary metal refiners who separate other scrap alloys into their constituents and thus tend to maintain the “entropy” of the industrial alloy system within bounds. The refining of scrap into secondary metal of value is probably still in its infancy. It requires a different technic than that of the separation of metals from ores, and although there are now being carried out a number of operations of this sort, the volume of this secondary metal business must constantly increase and its character change and increase in complexity and refinement. At present only the principal metal values are often obtained, such as in the recovery of pig copper from brass, with considerable loss of minor but valuable metals. Or small amounts of the secondary elements are left which depreciate in value of the base metal, such as is generally the case in the brass foundry, secondary metal industry-for example, secondary yellow brass ingot may contain small amounts of aluminium. This indicates another line of partiaI solution of the secondary metal problem, and one to which active effort is being given just now in many plants-that is, the acquisition of more exact knowledge of the maximum amounts of impurities Firhich may practically be harmless in different alloys and metals. Although in many cases the evil reputation which certain impurities enjoy-such, for example, as aluminium in red brass, antimony in copper, tin in aluminiumis well justified and often structurally understood, in many others it rests partly on tradition. For example, in the early days of aluminium bronze it was considered absolutely necessary to keep iron out of the metal; subsequently, it was shown that iron in even greater amounts actually benefited it and is used generally for t,hat purpose to-day. Considerable research is being carried out by individual companies as R-ell as by cooperative groups in an effort to establish more accurate and fundamental understanding of the effects of usual impurities in metals and alloys, with the idea both of real protection to the users of such materials in the case of actually harmful impurities and of eliminating unnecessary restrictions of chemical composition in specifications for elements which are demonstrated to have little or no harmful effects within wider limits than are now accepted. Although many are thinking and working along these lines, the work of the Naval Gun Factory of the Washington Kavy Yard on manganese bronze deserves special mention. The scrap metal itself, particularly around foundries, before remelting into secondary ingot metal could be handled much more efficiently were there quick methods available for identifying the individual pieces. Thus, if the amount of iron or of aluminium in brass scrap could be determined in a few seconds, pieces having excess amounts could be separated and the quality of the secondary metal produced greatly enhanced. A start has been made along this line in studies of the availability of the magnetic method (for iron) and the spectroscopic method for the identification of small amounts of different impurities. The Bureau of Standards and the American Brass Company have done some pioneer work in this direction. It is interesting to consider what will be the aspects of the metallurgical industries when the source of all metals and alloys is the scrap pile. Certainly, a new metallurgy of metal refining must be born. CHEMISTRY OF METALS AT HIGHTEMPERATURE Unfortunately, practically all we know about the chemistry of metals is valid only within narrow and lorn temperature ranges; what happens a t temperatures a t which metals are melted and cast, at-temperatures at which they are hotworked, and at temperatures to which they are often subjected in service, is known only in barest outline. All metals
September, 1923
INDUSTRIAL A,VD ENGINEERING CHEMISTRY
normally contain small amounts of oxides, sulfides, and gases--particularly hydrogen, carbon monoxide, sulfur dioxide-as well as in many cases, arsenides, nitrides, carbides, etc., in addition to their metallic impurities. The former are either present in the original metals or, oftener, absorbed from the refractories or slags in the melting furnace or from the fuel gases or furnace atmosphere. All these impurities may exercise a profound effect on the course of manufacture of the metals and on their properties in the finished form, and many are known to do so, but unfortunately that knowledge is very meager. It can generally be expressed in some such manner as this: “The bronze was brittle because it was oxidized,” or “Aluminium is very sensitive to the absorption of gases during melting.” Many individuals are beginning to realize the necessity of obtaining precise knowledge along these lines of it and are trying to attack the problem as best they can. More has been said and done on the gas absorption problem than on any of the other features of this subject, since the production of sound and dense castings and ingots is almost a s i n e qua non of the manufacturing nonferrous industry. The whole subject is, however, a difficult one and will require the development of a new investigative technic, but it is nevertheless extremely important. Exact knowledge of the chemical relations between the metals and the impurities to which they are subjected during manufacturing and refbing must be the basis for economical operation of mill and foundry; rejections of off-heats and defective castings will be eliminated when these matters are better understood. Furthermore, such knowledge must be the basis for the broad development of the secondary metal industry which was forecast above. Pure metals may be dealt with in some ignorance, but impure ones require knowledge and care both in their preparation and in their use. Complete knowledge of slag and gas reactions with metals at high temperatures will permit of their refinement and separation from undesirable impurities.
FABRICATION OF METALS ~
897 N ALLOYS D
Few, perhaps, realize the study and effort necessary to produce a new product and to fit it for industrial utilization. It is not enough to discover and market a new alloy of useful properties; if it is to enjoy any general use, methods must be developed by which it may be fabricated into the various forms desired. This often requires more time and effort than the discovery of the product itself-and, conversely, a new product is valuable somewhat in proportion as the methods of its fabrication are generally known and understood. The details of various developments along these linesmachining, welding, forging, drawing, spinning, casting, etc.would be of little interest here. Two developments of this sort, however, seem to be increasing in favor and usefulness. One is the development of the centrifugal casting of metals, particularly of tube and ring forms, which seems to offer much promise both in economy of cost and increase of quality. The other is not very new-the increased use of chill molds in the production of castings which have to be duplicated a large number of times, and in particular the increased use of pressure die castings. Chill castings are now being produced in brass and bronze and pressure die castings of intricate form in lead, tin, zinc, and aluminium base alloys. Only the lack of a satisfactory mold material prevents the possibility of producing pressure die castings in brass and bronze which could thus be cast to size and require little or no machining.
CONCLUSIOSS
Out of the mass of research work now in progress in the nonferrous industries have been selected those features which appear to be the most fundamental and to have the greatest permanent significance for the industry. Extremely valuable and interesting work along more special lines, such as fundamental studies of the structure of metals and alloys by microscope and X-ray, the production of corrosion-resistant coatings by new and old methods, the study and diagnoNEW ISDUSTRIAL USESFOR SOKFERROUS sis of the many curious so-called “diseases” to which some METALSAND , ~ L L O Y B alloys are subject, the development of the use of the electric The business depressions following the war have stimulated furnace in both the rolling mill and the brass foundry, the development work in each group to an unusual degree look- cooperative research initiated by the Engineering Division ing toward the increased commercial application of its prod- of the National Research Council, and the American ucts, arid many coiicerns have actually organized products- Foundrymen’s Association on the use and reclamation of development departments with engineering and scientific foundry sands, have necessarily been neglected. personnel. The copper producers have gone still farther What has been said will a t least illustrate the direction and have initiated cooperative development work through of research in the nonferrous industries, as far as its objects the instrumentality of the Copper and Brass Research Associa- and purposes are concerned. As to its method, which is of tion. vastly greater ultimate importance, enough has been said Most of this work is intimately connected with, and indeed to demonstrate: that within these industries, as elsewhere, based upon, research work, of which the results are contin- not only is increasing effort being put on the solution of ually yielding information as to new products with valuable the daily engineering problems, but the volume of fundaproperties and new applications of newly discovered valuable mental research is growing also; research activity is growing, properties of old materials. Much of this material is in not only in volume, but in depth and self-consciousness. direct response to the more and more diversified and severe requirements of the metal users, each requiring a material for a special purpose and to meet new and exacting conNew M o t o r Fuel ditions. I t is going on in all the nonferrous groups, but The Australian commonwealth government is manifesting perhaps it is most active in the aluminium, magnesium, great interest in experiments with eucalyptus oil as a motor nickel, and zinc groups; the producers of some of the rare fuel. C. M. Dyer is said to have demonstrated that it can metals have also been active-for example, metallic tantalum be used in petrol engines, with efficient means of vaporization. The only difficulty he has encountered is that it will has recently been the subject of development. not start an engine from cold without priming, but its calorific This development and research activity represents acommon value is high. Tests made with cheap cars showed 24 miles purpose but hardly a trend, unless we realize with sajisfaction to the gallon with gasoline; 28 miles with half gasoline and half the general value to all industries of the mass of practical eucalyptus oil; and 36 miles on eucalyptus oil alone. Eucalyptus oil mixes with gasoline, benzene, and alcohol, and acts as a deand useful information which is daily being secured in the carbonizing agent. The main difficulty of manufacture on an effort. extensive scale would be in securing laborers to gather the leaves.
