Abstract
LONDON. The Institute of Metals (Autumn Meeting), September 9.—R. J. Anderson and E. G. Fahlman: A method for measuring internal stress in brass tubes. The method for measuring longitudinal internal stress is called the strip method, and is carried out by slitting a narrow strip longitudinally in a piece of tubing; for example, a strip 2-75 inches long and 0-10 inch wide in a 3.25 inch tube length; and then releasing one end of such a slit strip by cutting. Stress is indicated by the springing out of the freed end, and can be calculated from the modulus of elasticity of the material and the distance in movement of the freed end.—D. H. Andrews and J. Johnston: The application of the ideal solubility curve to the interpretation of equilibrium diagrams in metal systems. The method of plotting here discussed has not been applied previously to metal systems. In many systems the simple theory fits the observations better than had been anticipated, and may at least be used as a guide in criticising and simplifying experimental work.—Guy D. Bengough and R. May: Seventh report to the corrosion research committee of the Institute of Metals. The problem of corrosion is considered largely from the point of view of the “scale “of corrosion products which forms on the surfaces of such metals as copper, zinc, and brass immersed in sea-water. A large proportion of tube failures in modern condensers is due to local impingement of aerated sea-water; the rapid corrosion is due to the local removal of protective scale by the impinging stream. Certain types of preformed scales may be very resistant to this type of action. The occurrence of “dezincification “is due, not to bad mixing of copper and zinc in the manufacture of brass, but to the absence of arsenic from tubes. The electrolytic method of protection of condenser tubes generally gives negative results, but occasionally good results have been reported; these seem to be due to chance secondary effects particularly of the anode products. Corrosion of brass may be due to metal-ion concentration cells or oxygen-distribution cells. With high-speed water streams the metal-ion concentration cell may become the more powerful and render the metal anodic and severely corroded; deposits of sand, porous masses of corrosion products, etc., may cause oxygen distribution cells to become active and set up local corrosion, but the most rapid cases of corrosion seem to belong mainly to the former type. Sometimes the two types of action reinforce one another.—E. H. Dix, Jr., and A. J. Lyon: Comparative results on copper-silicon-aluminium and other aluminium alloys as obtainecL on separately cast specimens and specimens cut from a crankcase casting. Copper-silicon-aluminium alloy is particularly well adapted for complicated castings which do not require a large amount of machining. The casting properties of Alpax are similar, but it has a very low proportional limit and is inferior in this respect. Lynite 195 has uniform and desirable physical pro-perties. The proportional limit is considerably above any of the alloys tested. The foundry practice, however, is more difficult for this type of an alloy. 8 per cent, copper-aluminium alloy is suitable for the general run of castings and can be cast in sections V in. or more in thickness without much difficulty.—R. Genders: The extrusion of brass rod by the inverted process. Precautions are necessary to secure good surface, the method adopted for the present being the avoidance of entrance of the skin of the billet into the region of flow. The structure of the extruded rod does not show the concentric zones of material varying in crystal size and physical properties often produced by the peculiar nature of the flow which obtains in the ordinary process. The rear portion of the rod is variable in structure and hardness from centre to outside, but in a continuous gradient. All possibility of “core” defect is ex-claded, and, if defects are allowed to arise, they will be visible on the surface of the rod.—D. Hanson and Grace W. Ford: Investigation of the effects of impurities on copper. Part II.—The effect of iron on copper. Solid copper will dissolve about 4 per cent, of iron at 11000 C., but the solubility at lower tem-peratures is much less. Within the limits of solid solubility, the electrical resistivity increases rapidly as the iron content is raised: hence iron is extremely deleterious in copper for electrical purposes. The tensile strength is raised by 2 per cent, of iron from 14-5 tons per sq. in. to about 20 tons per sq. in. The effect of heat-treatment is relatively small. Iron has no great embrittling effect.—Sir Thomas K. Rose and J. H. Watson: Experiments on the working of nickel for coinage. The experiments were made in order to determine the conditions in which nickel for coinage could be cold-rolled in the existing rolls at the Royal Mint. It was found impossible to prepare coins containing 99 per cent, nickel with 1 per cent, of manganese, magnesium, carbon, iron, silicon, etc., such as are manufactured with the aid of hot-rolling. By the addition of 2 per cent, manganese, however, castings can be prepared suitable for cold-rolling and conversion into coin. The coins consist of a solid solution, and accordingly resist tarnishing and corrosion equally well with those containing 99 per cent, or more of nickel, such as are in circulation abroad.
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Societies and Academies. Nature 114, 487–488 (1924). https://doi.org/10.1038/114487b0
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DOI: https://doi.org/10.1038/114487b0