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By H. V. Churchill

There are two distinct methods of combating corrosive conditions. The first and most popular method is to choose a surface or material which will give adequate service under the specific and general conditions which are present. The second is a control or modification of the corrosive conditions to the end that metals and materials which would be attacked and corroded without such control or modification may be used. Under the first method of attack of the corrosion problem may be grouped such devices as the selection of metals or alloys which offer great resistance or the use of protective coatings such as paints, lacquers or metallic coatings. Such procedures are exceedingly useful. It is undoubtedly true that most of the problems of corrosion will be solved by recourse to this first method of attack. However, it must be remembered that there are many conditions in which metals are used where the choice of the particular metal to be used must depend upon other factors than corrosion behavior. Some of the factors which may govern the selection of metals for specific use are the physical and mechanical properties of the metals. But there is another factor which is of prime importance and that is relative price. It is the pressure of these factors of mechanical properties, physical characteristics, and relative price that has acted as the stimulus for the second methhod of combating corrosion. The producer and user of various metals is confronted with the fact that because of mechanical properties, physical characteristics, or price, the use of a particular metal is desirable even though the corrosion conditions are adverse to the use of the metal. In many cases, the successful use of the metal may be made even though it is impossible to protect the metal by coatings. This is rendered possible by control or modification of the corrosive media. Use of Sodium Silicate to Prevent Attack by Alkali Solutions This idea of controlling or modifying corrosive media is well illustrated by some recent experiences with aluminum. For a number of years collapsible tubes have been made of aluminum. Due to the ease with which aluminum is attacked by even mild alkalies, the use of such tubes

Jan 1, 1929

By H. V. Churchill

There are two distinct methods of combating corrosive conditions. The first and most popular method is to choose a surface or material which will give adequate service under the specific and general conditions which are present. The second is a control or modification of the corrosive conditions to the end that metals and materials which would be attacked and corroded without such control or modification may be used. Under the first method of attack of the corrosion problem may be grouped such devices as the selection of metals or alloys which offer great resistance or the use of protective coatings such as paints, lacquers or metallic coatings. Such procedures are exceedingly useful. It is undoubtedly true that most of the problems of corrosion will be solved by recourse to this first method of attack. However, it must be remembered that there are many conditions in which metals are used where the choice of the particular metal to be used must depend upon other factors than corrosion behavior. Some of the factors which may govern the selection of metals for specific use are the physical and mechanical properties of the metals. But there is another factor which is of prime importance and that is relative price. It is the pressure of these factors of mechanical properties, physical characteristics, and relative price that has acted as the stimulus for the second methhod of combating corrosion. The producer and user of various metals is confronted with the fact that because of mechanical properties, physical characteristics, or price, the use of a particular metal is desirable even though the corrosion conditions are adverse to the use of the metal. In many cases, the successful use of the metal may be made even though it is impossible to protect the metal by coatings. This is rendered possible by control or modification of the corrosive media. Use of Sodium Silicate to Prevent Attack by Alkali Solutions This idea of controlling or modifying corrosive media is well illustrated by some recent experiences with aluminum. For a number of years collapsible tubes have been made of aluminum. Due to the ease with which aluminum is attacked by even mild alkalies, the use of such tubes

Jan 1, 1929

By Shun-ichi Satoh

The electric arc welding of cast iron has been studied by Braune Lamberton, Schimpke, Kenyon, Gale Manufacturing Co., Wedemeyer Candy, Neese, Miller, Carter, American Welding Society, Namack Lebrun, Achenbach, Jansson, Xochendorffer and others.' The write of this paper has been able to obtain a series of cast irons, from gray tc white, without using cast-iron electrodes but by coating on wrought-iron bars mixtures of carborundum (Sic) and graphite (C). In this work, he found the curious phenomenon of barium carbonate.

Jan 1, 1929

By C. H. Herty

The reactions that occur in the basic open-hearth process are complicated and are subject to many different factors such as temperature, slag composition and rate of boiling of the bath. It is difficult, therefore, to present an extended theoretical discussion of open-hearth operations without confusing the theory of the process with the application of the theory. This paper attempts to present some of the theory of the open-hearth process without mentioning theory at any point, simply giving some of the practical applications of results founded both on theory and practice and on experimental work both in small and large furnaces. It is hoped that an answer to a number of questions commonly asked by the open-hearth operator may be found in this paper. Discussion of the subject matter is taken up more or less in the order in which a heat ie worked, beginning with the oxidation of the scrap charged, sulfur absorption by the scrap, calcination of the limestone, and extending into the pig iron for the charge, the slags formed during the process, and some of the phenomena occurring in deoxidation of the steel and in its action in the molds. Oxidation of Scbap When scrap is charged into a furnace it immediately begins to oxidize, Oxidation is carried out by.three reactions: Fe + H20 + FeO + Hz (absorbs heat) (1) Fe + C02 + FeO + CO (absorbs heat) (2: Fe+ ½O2 + FeO (gives off heat) (3: The product of oxidation contains some Fe3O4, but FeO usually predominates on account of the iron present in close contact with the scale formed For a given type of scrap the amount of oxidation is controlled by thc fuel and by the excess air being carried in the furnace, the temperature 01 the furnace, and the length of time that the scrap is in contact with the furnace gases. In general, less oxidation occurs when the furnace is rur hot so that the scrap melts rapidly. More important in operation thar the two variables atmosphere and temperature, is the type of scrap being

Jan 1, 1929

An informal discussion on the application of physical chemistry to steelmaking was held during the Annual Meeting of the Institute in February, 1929. Alexander L. Feild presided. In opening the session, Mr. Feild said: We are all familiar with the cooperative mining and metallurgical studies that were begun in 1920 by the U. S. Bureau of Mines, the Carnegie Institute of Technology, and the Mining and Metallurgical Advisory Boards, and in particular with the work on the physical chemistry of steelmaking which was launched under the technical direction of Dr. C. H. Herty, Jr., in May, 1926. It was this work at Pittsburgh more than anything else that was the immediate cause of the formation within the Institute of a committee on the physical chemistry of steelmaking. During the latter part of 1927 a small group of Institute members interested in. the general subject of the physical chemistry of steelmaking undertook the organization of a subcommittee within the Iron and Steel Committee, to foster an active interest in this comparatively new field among the Institute membership and to obtain papers for publication in the Transactions, covering the various phases of the general subject. This plan was conceived by C. E. Meissner, to whose active efforts at the outset as well as during the past year is largely due whatever measure of success the plan has thus far attained. The subcommittee, now a committee of the Iron and Steel Division, was recognized and formally made a part of the Institute's organization at the February, 1928, meeting. As originally organized and as const,it,uted during the past year the committee has been made up as follows: C. H. Herty, Jr., C. D. King, A. B. Kinzel, John Johnston, C. E. Meissner, L. F. Reinartz, R. B. Sosman, and A. L. Feild, Chairman. Dr. C. H. Herty, Jr. has just been elected chairman for the coming year and C. E. Meissner has been reelected as secretary. From the outset it has been the settled policy of the committee to make membership an annual rather than a permanent matter and to reconstitute in part the membership of the committee each year by dropping a certain number of members and adding new members. In view of the fact that the work of the committee is still in a

Jan 1, 1929

By H. E. Searle, Robert J. McKay, O. B. J. Fraser

The practical study of corrosion requires consideration of its economic aspects. It must be based on sound scientific principles, but it should be borne in mind that probably the most important object of a corrosion test is to determine what metal in corrosion-resisting construction will produce the greatest operating profit. Thus the corrosion test must be directly connected with money values or it is not a practical corrosion test. This, perhaps unusual, connection between corrosion and economics is partially due to the fact that corrosion deals only with the time factor or duration of equipment, and it is almost the only test which deals with this feature. In these statements a departure is made from the academic definition of the word corrosion and it is done deliberately. The use of the term corrosion is unusual. It is as though we spoke of a tensile test as a "breaking" test. We are not interested primarily in the break but in the strength of the metal. There is no English word which expresses our main interest in corrosion-testing, but let us have clearly in mind that we make corrosion tests to prevent corrosion. Our real interest is in this corrosion-prevention, not in the corrosion. Previous to 1922, it was common comment that "it is impossible to determine the course of corrosion by laboratory testing.'' This statement was true at that time in that the technique of laboratory testing for corrosion resistance was so vague that tests in the laboratory gave untrue results almost as often as true ones. This was so, even in the simple case of determining which one of two metals better resists a given solution. While this is no longer true the number of misleading "corrosion tests" still being ground out by laboratories is too large in the light of our present knowledge. There are two important features of corrosion testing whose neglect is a large contributing factor to misleading results: (1) The economic relations of the corrosion tests to other tests; (2) testing technique. Regarding economic relations J. F. Thompson l has said: "The use of any particular metal is rarely based upon the sole property of resistance to corrosion. In fact, I should like to venture the assertion

Jan 1, 1929

By Robert J. McKay, O. B. J. Fraser, H. E. Searle

The practical study of corrosion requires consideration of its economic aspects. It must be based on sound scientific principles, but it should be borne in mind that probably the most important object of a corrosion test is to determine what metal in corrosion-resisting construction will produce the greatest operating profit. Thus the corrosion test must be directly connected with money values or it is not a practical corrosion test. This, perhaps unusual, connection between corrosion and economics is partially due to the fact that corrosion deals only with the time factor or duration of equipment, and it is almost the only test which deals with this feature. In these statements a departure is made from the academic definition of the word corrosion and it is done deliberately. The use of the term corrosion is unusual. It is as though we spoke of a tensile test as a "breaking" test. We are not interested primarily in the break but in the strength of the metal. There is no English word which expresses our main interest in corrosion-testing, but let us have clearly in mind that we make corrosion tests to prevent corrosion. Our real interest is in this corrosion-prevention, not in the corrosion. Previous to 1922, it was common comment that "it is impossible to determine the course of corrosion by laboratory testing.'' This statement was true at that time in that the technique of laboratory testing for corrosion resistance was so vague that tests in the laboratory gave untrue results almost as often as true ones. This was so, even in the simple case of determining which one of two metals better resists a given solution. While this is no longer true the number of misleading "corrosion tests" still being ground out by laboratories is too large in the light of our present knowledge. There are two important features of corrosion testing whose neglect is a large contributing factor to misleading results: (1) The economic relations of the corrosion tests to other tests; (2) testing technique. Regarding economic relations J. F. Thompson l has said: "The use of any particular metal is rarely based upon the sole property of resistance to corrosion. In fact, I should like to venture the assertion

Jan 1, 1929

By J. M. Stuart, G. D. Bengough, A. R. Lee

Corrosion tests should be designed so as to facilitate as far as possible the interpretation of results, consequently factors which may affect the rate of corrosion should be controlled as far as practicable, and very full data should be given regarding the conditions of the test. Among the most important factors affecting the rate of corrosion is often the rate of supply of oxygen to the metal surface. It is essential therefore to understand the mechanism by which oxygen is transferred from the liquid surface to the surface of the metal. The work of Adeney and his coworkers has thrown much light on this mechanism. They have shown1 that the aeration of deaerated water and salt solutions proceeds much more rapidly than can be accounted for by mere diffusion, and have suggested that downward "streaming" takes place from the surface of the water, due mainly to an increase of density brought about by evaporation. The evaporation reduces the temperature of the surface layer, and also increases the concentration in the case of salt solutions. The effect of evaporation in facilitating the transfer of oxygen to a metal and increasing the corrosion of the metal was shown in some experiments due to Friend.2 He tested the corrosion of mild steel plates immersed in water in glass jars, a steady stream of air being drawn over the surface of the water in the jars. The air passing through half the number of jars was saturated with moisture, that passing through the others was dried with calcium chloride. He found that "in every case the water exposed to dry air was approximately twice as corrosive as that exposed to air saturated with water vapor." Conditions for Quantitative Corrosion Tests These results show that we must either control or prevent evaporation at the liquid surface, if we wish to avoid effects on the rate of cor-

Jan 1, 1929

By A. R. Lee, G. D. Bengough, J. M. Stuart

Corrosion tests should be designed so as to facilitate as far as possible the interpretation of results, consequently factors which may affect the rate of corrosion should be controlled as far as practicable, and very full data should be given regarding the conditions of the test. Among the most important factors affecting the rate of corrosion is often the rate of supply of oxygen to the metal surface. It is essential therefore to understand the mechanism by which oxygen is transferred from the liquid surface to the surface of the metal. The work of Adeney and his coworkers has thrown much light on this mechanism. They have shown1 that the aeration of deaerated water and salt solutions proceeds much more rapidly than can be accounted for by mere diffusion, and have suggested that downward "streaming" takes place from the surface of the water, due mainly to an increase of density brought about by evaporation. The evaporation reduces the temperature of the surface layer, and also increases the concentration in the case of salt solutions. The effect of evaporation in facilitating the transfer of oxygen to a metal and increasing the corrosion of the metal was shown in some experiments due to Friend.2 He tested the corrosion of mild steel plates immersed in water in glass jars, a steady stream of air being drawn over the surface of the water in the jars. The air passing through half the number of jars was saturated with moisture, that passing through the others was dried with calcium chloride. He found that "in every case the water exposed to dry air was approximately twice as corrosive as that exposed to air saturated with water vapor." Conditions for Quantitative Corrosion Tests These results show that we must either control or prevent evaporation at the liquid surface, if we wish to avoid effects on the rate of cor-

Jan 1, 1929

By R. O. Day, R. S. Dean

In constructing a theory of the flow and hardening of metals, v necessarily make use of such phenomena as seem to be universal1 observed in metals. It is, therefore, a matter of concern to the con structors of such mnemonic systems if one or two of the group classific as metals show anomalous behavior. Such egregious phenomena observed in pure or nearly pure iron in the reaction of its mechanic properties to low-temperature annealing after cold work and to increase temperature of testing. In short it has been generally observcd tha iron, as an outstanding exception among metals, increases its hardnes and strength by low-temperature annealing after cold work,' and alt by increase of testing temperature to the range of 150" to 300" C. The investigation here recorded was made then with the object ( ascertaining if similar phenomena were observed in high-purity iro and, if not, to the presence of which impurities these phenomena coul be traced. Experimental Procedure Three kinds of iron were taken for a study of hardening by rehcatin after cold work: 1. Vacuum-melted electrolytic iron; melted in an Arsem furnace in a magnesia crucible. That this iron was of high purity is indicated b a magnetic permeability above 20,000. 2. Electrolytic iron melted in air in a small laboratory furnace. 3. Armco iron, commercial material. These materials in the form of forged bars, annealed at 980" C. in vacuum, were reduced 30 per cent. in thickness by cold rolling and the reheated to temperatures varying from 100' to 500' C. The Rockwe hardness number was measured after each treatment. The results and shown in Fig. 1, curves 1, 2 and 3.

Jan 1, 1929

By H.A. Bedworth

AlloTs of copper and silicon have been known for one hundred years or more but the commercial development of this type of alloy has taken place during the past few years. In 1905, Sperry l proposed the use of copper-silicon alloys for springs and other purposes for which copper-tin bronzes were used. Some attention was given to this proposal at the time but no one succeeded in producing a practical alloy containing more than a fraction of a per cent. of silicon. The equilibrium relations of the copper-silicon system were studied first by Rudolfi2 and later by Sanfourche 3 and Corson. 4 The constitution of the system has also been recently investigated by Matuyama, 5 and in the laboratories of the American Brass Co. by Smith. 6 Some of the physical properties of the copper-silicon alloys have been investigated by Norbury7 and by Geiss and Van Liempt.8 Summarizing the results of various investigators of the constitution of copper-silicon alloys, the solubility reaches its maximium value, 6.7 per cent. silicon, between 721" and '782" C. At 852" (1. the solubility is 5.25 per cent., while at 400" C. it is only 4.1 per cent. silicon. The copper-silicon alloy begins to get so hard at about 3 per cent, silicon that it is difficult to manage. It was found by Jacobs that the addition of manganese to this alloy considerably improved the working

Jan 1, 1929

By H. A. Bedworth

AlloTs of copper and silicon have been known for one hundred years or more but the commercial development of this type of alloy has taken place during the past few years. In 1905, Sperry l proposed the use of copper-silicon alloys for springs and other purposes for which copper-tin bronzes were used. Some attention was given to this proposal at the time but no one succeeded in producing a practical alloy containing more than a fraction of a per cent. of silicon. The equilibrium relations of the copper-silicon system were studied first by Rudolfi2 and later by Sanfourche 3 and Corson. 4 The constitution of the system has also been recently investigated by Matuyama, 5 and in the laboratories of the American Brass Co. by Smith. 6 Some of the physical properties of the copper-silicon alloys have been investigated by Norbury7 and by Geiss and Van Liempt.8 Summarizing the results of various investigators of the constitution of copper-silicon alloys, the solubility reaches its maximium value, 6.7 per cent. silicon, between 721" and '782" C. At 852" (1. the solubility is 5.25 per cent., while at 400" C. it is only 4.1 per cent. silicon. The copper-silicon alloy begins to get so hard at about 3 per cent, silicon that it is difficult to manage. It was found by Jacobs that the addition of manganese to this alloy considerably improved the working

Jan 1, 1929

By Donald E. Ackerman, Norman B. Pilling

The solubilities of a series of experimental alloys covering the range 0 to 100 per cent. Ni, 0 to 30 per cent. Cr have been studied under conditions of complete submersion in several fully aerated acid solutions, and in solutions containing sulfurous acid. In nonoxidizing, hydrogen-discharging acids, if the nickel content is below a certain critical amount, chromium increases the rate of solution and nickel decreases this rate; this critical content of nickel is about 13 per cent. Alloys containing more than this corrode at a constant minimum rate independent of iron, nickel or chromium contents. Austenitic chrome-nickel steels may thus have a resistance to these acids equal to that of nickel-chromium alloys. In nitric acid and in unaerated sulfurous acid rather sharp limits of attack occur which are principally dependent on chromium content. In the former the limit of attack is not related to a particular chromium content but varies continuously with acid concentration. The action of sulfurous acid on these alloys is highly dependent on the presence of small amounts of other substances in solution, and many sulfurous acid mixtures rapidly attack alloys to which the pure acid is wholly inert. The observed effects are not compatible with Tammann's theory relating corrosion resistance to lattice structure but are believed to be concordant with current views of the electrochemical nature of corrosion. Introduction The discovery, development and engineering application of iron alloys resistant to corrosion may well claim a place among the important developments in metallurgy of the past two decades. The varied demands of industry coupled with the skill of the metallurgist have resulted in the production of an extensive group of steels and alloys ranging from the now familiar "stainless " chromium steels of the kitchen to special alloys of great chemical complexity for particular, exacting needs. Any adequate description of the important properties of these-— physical, chemical and economic—would be a formidable undertaking.

Jan 1, 1929

By Donald E. Ackerman, Norman B. Pilling

The solubilities of a series of experimental alloys covering the range 0 to 100 per cent. Ni, 0 to 30 per cent. Cr have been studied under conditions of complete submersion in several fully aerated acid solutions, and in solutions containing sulfurous acid. In nonoxidizing, hydrogen-discharging acids, if the nickel content is below a certain critical amount, chromium increases the rate of solution and nickel decreases this rate; this critical content of nickel is about 13 per cent. Alloys containing more than this corrode at a constant minimum rate independent of iron, nickel or chromium contents. Austenitic chrome-nickel steels may thus have a resistance to these acids equal to that of nickel-chromium alloys. In nitric acid and in unaerated sulfurous acid rather sharp limits of attack occur which are principally dependent on chromium content. In the former the limit of attack is not related to a particular chromium content but varies continuously with acid concentration. The action of sulfurous acid on these alloys is highly dependent on the presence of small amounts of other substances in solution, and many sulfurous acid mixtures rapidly attack alloys to which the pure acid is wholly inert. The observed effects are not compatible with Tammann's theory relating corrosion resistance to lattice structure but are believed to be concordant with current views of the electrochemical nature of corrosion. Introduction The discovery, development and engineering application of iron alloys resistant to corrosion may well claim a place among the important developments in metallurgy of the past two decades. The varied demands of industry coupled with the skill of the metallurgist have resulted in the production of an extensive group of steels and alloys ranging from the now familiar "stainless " chromium steels of the kitchen to special alloys of great chemical complexity for particular, exacting needs. Any adequate description of the important properties of these-— physical, chemical and economic—would be a formidable undertaking.

Jan 1, 1929

By T. S. Fuller

The work of D. J. McAdam, Jr.1,2 at the U. S. Naval Engineering Experiment Station, Annapolis, Md., on what has been called by him "corrosion-fatigue" has focussed the attention of the engineering profession in general, and of those interested especially in the study of corrosion in particular, on the importance of making tests which will indicate as nearly as possible what can be expected from a given material in service. Pitting is unquestionably the chief agent operating so tremendously to reduce fatigue limits, but in the light of previous work3, 4, 5, 6, 7, 8 it is fair to assume that absorbed hydrogen resulting from the action of the corroding medium upon steel may, under certain conditions, have a perceptible influence. The experiments described in this paper deal more precisely with stressless corrosion, or "prior-corrosion fatigue,"9 and have been carried out to test such an assumption, to segregate, if possible, the effect of pitting from that of absorbed hydrogen, and although very preliminary in nature they indicate results which are striking.

Jan 1, 1929

By T. S. Fuller

The work of D. J. McAdam, Jr.1,2 at the U. S. Naval Engineering Experiment Station, Annapolis, Md., on what has been called by him "corrosion-fatigue" has focussed the attention of the engineering profession in general, and of those interested especially in the study of corrosion in particular, on the importance of making tests which will indicate as nearly as possible what can be expected from a given material in service. Pitting is unquestionably the chief agent operating so tremendously to reduce fatigue limits, but in the light of previous work3, 4, 5, 6, 7, 8 it is fair to assume that absorbed hydrogen resulting from the action of the corroding medium upon steel may, under certain conditions, have a perceptible influence. The experiments described in this paper deal more precisely with stressless corrosion, or "prior-corrosion fatigue,"9 and have been carried out to test such an assumption, to segregate, if possible, the effect of pitting from that of absorbed hydrogen, and although very preliminary in nature they indicate results which are striking.

Jan 1, 1929

By L. Russell, van Wert

During an investigation in which the solubility relations of the phases in Muntz metal (60 per cent. copper, 40 per cent. zinc) were under study, certain phenomena that had no immediate connection with the main problem were observed, which were thought sufficiently interesting to study further. Because of lack of time, only a preliminary survey was made of two of these; namely, the cleavage structure developed under certain conditions in a 60:40 brass and abnormal grain growth in this alloy. Cleavage Structure in Heat-treated Muntz Metal Carpenter noted many years ago that cold-working a brass of the Muntz metal type, which had been quenched previously from within the beta field, results in a partial breakdown of the supersaturated beta solution and the precipitation of the solute (the alpha solution) in the cleavage planes of the beta grains. This manner of rejection of a solute from a metastable solid solution is not peculiar to this particular alloy, for among others, it occurs in the cold-working of certain austenitic steels; for example, the austenitic nickel steels. In these ferrous alloys, cold deformation produces a partial decornposition of the austenite, with the formation of martensitic "needles" and zigzags in the austenitic poly-hedra. It is interesting to note that while the two solid solutions— austenite and quenched Muntz metal— are metastable and in their mode of decomposition behave quite alike when deformed in the cold, the metastability of each results from a different cause; viz., that of the austenite from the fact that it is a supercooled solution (its solvent. gamma iron, at ordinary temperatures is below its normal stable range whereas the metastability of the quenched Muntz metal is the result of supersaturation. When a 60:40 brass is quenched from above 800" C.—that is, from within the field where the beta phase alone is stable—this solution is retained practically intact and the alloy so cooled is found to consist almost entirely of polyhedra of this solution with only a little alpha present ordinarily at the boundaries of the beta grains—the result of a slight

Jan 1, 1929

By van Wert, L. Russell

During an investigation in which the solubility relations of the phases in Muntz metal (60 per cent. copper, 40 per cent. zinc) were under study, certain phenomena that had no immediate connection with the main problem were observed, which were thought sufficiently interesting to study further. Because of lack of time, only a preliminary survey was made of two of these; namely, the cleavage structure developed under certain conditions in a 60:40 brass and abnormal grain growth in this alloy. Cleavage Structure in Heat-treated Muntz Metal Carpenter noted many years ago that cold-working a brass of the Muntz metal type, which had been quenched previously from within the beta field, results in a partial breakdown of the supersaturated beta solution and the precipitation of the solute (the alpha solution) in the cleavage planes of the beta grains. This manner of rejection of a solute from a metastable solid solution is not peculiar to this particular alloy, for among others, it occurs in the cold-working of certain austenitic steels; for example, the austenitic nickel steels. In these ferrous alloys, cold deformation produces a partial decornposition of the austenite, with the formation of martensitic "needles" and zigzags in the austenitic poly-hedra. It is interesting to note that while the two solid solutions— austenite and quenched Muntz metal— are metastable and in their mode of decomposition behave quite alike when deformed in the cold, the metastability of each results from a different cause; viz., that of the austenite from the fact that it is a supercooled solution (its solvent. gamma iron, at ordinary temperatures is below its normal stable range whereas the metastability of the quenched Muntz metal is the result of supersaturation. When a 60:40 brass is quenched from above 800" C.—that is, from within the field where the beta phase alone is stable—this solution is retained practically intact and the alloy so cooled is found to consist almost entirely of polyhedra of this solution with only a little alpha present ordinarily at the boundaries of the beta grains—the result of a slight

Jan 1, 1929

By E. A. Anderson, W. M. Peirce

Deflection in a corrugated roofing sheet under load may be considered to take place in two stages; an initial bending of the sheet under the load and a slow, permanent flow or creep under continued application of the load. Stresses great enough to produce permanent set when prolonged may produce apparent elastic deformation when applied for only a brief interval. It is impossible to set a time limit on the duration of stress in actual roof installations. Roofs in industrial locations where dust accumulations are heavy, as in cement plants, are often loaded continuously with

Jan 1, 1929

By W. M. Peirce, E. A. Anderson

Deflection in a corrugated roofing sheet under load may be considered to take place in two stages; an initial bending of the sheet under the load and a slow, permanent flow or creep under continued application of the load. Stresses great enough to produce permanent set when prolonged may produce apparent elastic deformation when applied for only a brief interval. It is impossible to set a time limit on the duration of stress in actual roof installations. Roofs in industrial locations where dust accumulations are heavy, as in cement plants, are often loaded continuously with

Jan 1, 1929