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By R. H. Brown, F. Keller

Because of the extensive use of Alclad 24s alloy sheet in aircraft construction, there is much interest in the metallurgical changes caused by heat-treatment of this product.1, 2 One of these changes is the result of the diffusion of soluble elements from the core into the coating during treatment. This paper deals with the thermal treatments that may influence diffusion and with the practical effects of diffusion on the serviceability of the product. As is well known, Alclad 24s-T sheet has a core of high-strength alloy combined with surface layers of relatively pure aluminum. The microstructure of a cross section of this product is shown by Fig. I. Not only does the relatively high-purity coating have a high resistance to corrosion, and hence serves as a mechanical barrier between the core metal and the corroding environment, but in addition this coating exerts electrochemical protection over areas where the core may be exposed, such as cut edges. In addition, the coating affords electrochemical protection to projecting heads of A17s-T, 17s-T and 24s-T rivets, or attached members made from these alloys. Under some conditions of heat-treatment, however, diffusion of copper into the coating will alter the electrochemical relationship between the coating and the core to the extent that only partial protection will be obtained under some corrosive conditions. The reason for the electrochemical protection lies in the fact that the coating layers of pure aluminum are anodic to the alloy core. The addition of copper to aluminum produces alloys in which the potential is lower than that of the pure metal. Moreover, as the amount of copper in solid solution in 24s alloy is increased, the potential of the alloy becomes more cathodic. When heat-treated at 920°F. and quenched in cold water, 24s-T is about 0.16 volt cathodic to pure aluminum. However, copper will diffuse from the core into the coating, and if it reaches the surface the potential will be altered in a cathodic direction. Thus the potential difference between the core and coating may be less than 0.16 volt, depending uponIthe thickness of the coating, and the time and temperature of heat-treatment. Of the methods available for determining the extent of diffusion of copper from the core into the coating of Alclad 24s-T, two are generally used; namely, the metallo-graphic and the solution potential methods.3 Metallographic Methods Metallographic methods will reveal the progress of diffusion of copper into the coating. For instance, the diffusion zone in the coating intermediate between the coating surface and the core is shown in Fig. I. This photomicrograph is of a polished and etched cross section of 0.040-in. Alclad 24s-T sheet. Diffusion proceeds into the coating more rapidly along the grain boundaries than through the body of the grains. Consequently, the diffusion zone is not of uniform width

Jan 1, 1944

By F. Keller, R. H. Brown

Because of the extensive use of Alclad 24s alloy sheet in aircraft construction, there is much interest in the metallurgical changes caused by heat-treatment of this product.1, 2 One of these changes is the result of the diffusion of soluble elements from the core into the coating during treatment. This paper deals with the thermal treatments that may influence diffusion and with the practical effects of diffusion on the serviceability of the product. As is well known, Alclad 24s-T sheet has a core of high-strength alloy combined with surface layers of relatively pure aluminum. The microstructure of a cross section of this product is shown by Fig. I. Not only does the relatively high-purity coating have a high resistance to corrosion, and hence serves as a mechanical barrier between the core metal and the corroding environment, but in addition this coating exerts electrochemical protection over areas where the core may be exposed, such as cut edges. In addition, the coating affords electrochemical protection to projecting heads of A17s-T, 17s-T and 24s-T rivets, or attached members made from these alloys. Under some conditions of heat-treatment, however, diffusion of copper into the coating will alter the electrochemical relationship between the coating and the core to the extent that only partial protection will be obtained under some corrosive conditions. The reason for the electrochemical protection lies in the fact that the coating layers of pure aluminum are anodic to the alloy core. The addition of copper to aluminum produces alloys in which the potential is lower than that of the pure metal. Moreover, as the amount of copper in solid solution in 24s alloy is increased, the potential of the alloy becomes more cathodic. When heat-treated at 920°F. and quenched in cold water, 24s-T is about 0.16 volt cathodic to pure aluminum. However, copper will diffuse from the core into the coating, and if it reaches the surface the potential will be altered in a cathodic direction. Thus the potential difference between the core and coating may be less than 0.16 volt, depending uponIthe thickness of the coating, and the time and temperature of heat-treatment. Of the methods available for determining the extent of diffusion of copper from the core into the coating of Alclad 24s-T, two are generally used; namely, the metallo-graphic and the solution potential methods.3 Metallographic Methods Metallographic methods will reveal the progress of diffusion of copper into the coating. For instance, the diffusion zone in the coating intermediate between the coating surface and the core is shown in Fig. I. This photomicrograph is of a polished and etched cross section of 0.040-in. Alclad 24s-T sheet. Diffusion proceeds into the coating more rapidly along the grain boundaries than through the body of the grains. Consequently, the diffusion zone is not of uniform width

Jan 1, 1944

By E. R. Smith

ANALYSIS of the requirements for gun perforation equipment suitable for penetrating casing and cement showed that these points would be involved: (1) Powder charges electrically detonated under high fluid lieads and at remote distances. (2) Selective firing of sliots in sequence. (3) Sufficient velocity for the bullet to penetrate at least two strings of seamless casing and all cement beyond the strings. (4) Heat-treatment of steels to withstand great pressures and penetration. (5) Esclusiorl of fluid under extremely high hydrostatic pressure. (6) Stranded steel wire line acting as weight - suspending and current - carrying medium. (7) Firing controls operated above the surface. (8) Determining gun depth and suspended weight by means of the wire line. (9) Portability for field use.

Jan 1, 1936

By L. E. Young

MUCH has been said and written on this subject and probably little new can be said. However, the point of view of the operating company changes from time to time, and more stress may be laid upon a subject today than was done some years ago, and it is with this changing point of view that the following observations are presented: The writer wishes to limit the discussion to views of a company mining bituminous coal, particularly to what the production department expects of the college grad¬uate. In an editorial in MINING AND METALLURGY for February, 1929, entitled "Is. Mining Engineering Passing?" it is stated that: It is not by accident that mining engineering courses have been general rather than special and form even today the only general engineering courses widely offered and followed by engineering students.'* * * even in this age of specialization, the mining engineers remain a body characterized particularly by broad knowledge.

Jan 1, 1929

By JOHN R. SUMAN

COMMENCEMENT exercises this year have a peculiar significance because the graduating students are entering upon their life's work at the most critical time in the history of the United States. We are engaged in a great struggle the outcome of which is none too clear even to the best informed students of international affairs. We are starting late in a vicious world conflict where it is generally recognized that our adversaries have distinct superiority over us in armament on the land, on the sea, and in the air. We have the gigantic task of building up our armed forces and armament and at the same time supplying our allies with equipment which they must have. We can do this job if we are given sufficient time, but there is a possibility that the war will be over before we are ready. Few realize the seriousness of this situation. If this fight is to be won-and we dare not try to visualize the future of this country if it is lost-all dissension and bickering between Congress, capital, labor, and agriculture must cease. When and where voluntary co-operation proves inadequate for the successful conduct of the war effort, laws must be enacted or strengthened to achieve our purpose.

Jan 1, 1942

By Simon D. Strauss

What are future prospects for U.S. mining? In many quarters the assumption is made that this country has passed its zenith as a mineral producer -- that it is in a period of decline and that it is becoming a have-not nation like Japan and much of Western Europe. These industrial rivals of ours must depend almost entirely on others for their mineral supplies. In trying to answer this question one must of course distinguish between resources and productive capacity. In today's volatile and competitive markets, the definition of what are reserves and what are merely identified resources becomes ever more difficult. Many large deposits have been found that are unlikely to be viable in the marketplace under normal conditions but that can be of significance to the nation's military and industrial security in times of emergency. I should like to draw on personal experience from World War I1 for illustration. 4fter Pearl Harbor great concern developed over the availability of a long 1ist of strategic materials for which this country was largely dependent on imports. Included were a number of minerals of which domestic deposits had been identified. Among these were chromite, manganese ore, mercury, mica and tungsten.

Jan 1, 1982

By W. B. Clark

IN OPERATING the Alpha mine of the Consolidated Coppermines Corp., Kimberly, Nev., it was necessary to pump out approximately 1200 gallons of waiter per minute to prevent the mine being flooded. There were three levels in the mine at which water accumulated and from which it was pumped, the 1200, 1400 and the 1800- ft. levels. At each, the pumping equipment was installed in duplicate so that if for any reason one unit was out of commission the other would be available to prevent flooding. The two centrifugal pumps at the 1200-ft. level were 600 hp. each; at the 1400-ft. level, 100 hp. each; and at the 1800-ft. level, 300 hp. each.

Jan 1, 1933

Jan 1, 1944

By Paul M. Tyler

OF THE 92 elements generally accepted by chemists as constituting the primary building blocks of matter, all but the very rarest have been investigated with a view to employing them in steel manufacture. The surprising thing is that so few have been found commercially acceptable. Despite the relatively small number of elements involved, the use of alloys in steel making is one of the most complicated and probably one of the least well understood of modern industrial enterprises. The action of individual elements in steel making has been described often and a profuse and somewhat acrimonious literature covers pretty much the whole field of ferroalloy ore supplies. In the middle ground between the miner and the -steel maker developments are less carefully watched by most observers and except for an occasional description of the technique of some conversion process or the tariff hearings in Congress, little is said about them. The present paper has been submitted in the hope that it will stimulate broader constructive economic thinking. It undertakes to describe in' relatively nontechnical terms this great and growing though highly complex industry and to study its relations to national progress.

Jan 1, 1932

Jan 1, 1948

Jan 1, 1922

Jan 1, 1938

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Jan 1, 1910

Jan 1, 1938

By AIME AIME

To accompanying photograph of the plant of the Beattie Gold Miner Limited, at Duparquet,. Quebec, is taken from the east and shows the open-pit from which the ore is taken during the summer. The buildings on the level ground above the open-pit are the change rooms, steel shop hoist building, compressor building, machine shop, warehouse, carpenter shop, and oil house. The main five-compartment shaft is shown west of the hoist building. The crusher plant adjoins the headframe and a long conveyor transports the fine ore

Jan 1, 1936

By H. E. McKinstry

LIKE nearly everything else, mining geology has been reconverting. Many geologists had been in military and other government service. Many more, with mining companies, had been working primarily toward increasing production from known reserves. All of these are turning now toward their normal peacetime endeavor-the search for new ore; for most mining companies, finding themselves with accumulated deficits in development work, are more than ready to go ahead with their postwar plans made a year or more ago but still stalled at the close of 1945 for lack of man power. These plans include not merely development in the old home camp but also wide exploration for new prospects both domestic and foreign. Most of the large concerns have geologists and engineers in the field in the United States, despite the outlook for higher mining costs here, and at least half a dozen strong American companies are already investigating opportunities abroad, notwithstanding past unhappy experiences in certain Latin-American nations which have welcomed capital but later found means of preventing investors from reaping the reward of their enterprise. A few of these new foreign expeditions are following well-planned programs, but too many, in their haste to get any sort of footing, are proceeding without well-considered policy. with the result that their geologists can do little more than desultory scouting.

Jan 1, 1946

Jan 1, 1879

By Lord Marley

ACTIVE participation by the United States in the war acted as a stimulant on the Annual Institute Meeting in New York rather than a retardant as feared. Attendance was about 10 per cent under the all-time high reached last year, but considering the number of men who could not possibly come because of active military service and the additional number who are devoting their whole time and effort to turning out vital war materials, the registration was really greater than might have been expected. But all in all the Institute put on a show that taxed the capacity of the Engineering Societies Building as well as the capacity of the visitors to find time to attend everything that promised to be of interest.

Jan 1, 1942

Jan 1, 1934

By R. W. Diamond

Low-grade ores can be designated by two main classifications: (1) simple low-grade ores, and (2) complex low-grade ores. As a rule the first type has a relatively small metal content, although low- grade iron ores contain a rather high percentage of metal. As the simple type is the one that is ordinarily in mind when the term "low-grade ore" is used, the paper will be devoted mainly to ores in this general category. Cheap treatment is the prime requirement in utilizing low-grade ores of the simple type, although in some cases the value of nonmetallic by-products, such as limestone for fer- tilizer and silica for flux, allows a little more lati- tude than in the usual situation. When the costs are divided under the three headings-mining, milling, and smelting-it is apparent that the last group will not constitute an important factor as a rule because the high concentrating ratio makes the smelting cost per ton of ore fairly low.

Jan 1, 1949