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Executive.. CHARLES F. RAND, Chairman. JAMES F. KEMP, JOSEPH W. RICHARDS. ALBERT R. LEDOUX, BENJAMIN B. THAYER. Membership. BENJAMIN B. THAYER, Chairman. WALTER R. INGALLS, JOHN H. JANEWAY, Jr., JOHN D. IRVING, HERMAN A. PROSSER. Finance. EDWARD L, YOUNG, Chairman. KARL EILERS, JAMES GAYLEY. Library. JAMES F. KEMP, Chairman. JOHN HAYS HAMMOND,3 E. GYBBON SPILSBURY,2 ALES. C. HUMPHREYS 4 BRADLEY STOUGHTON.

Jan 7, 1913

By R. B. Muter, W. C. Grady, T. D. Wheelock, D. G. Chedgy

INTRODUCTION Topics of special interest, such as preparation plant flowsheets and noise pollution, are described in this chapter along with a discussion of non- state-of-the-art processes such as chemical cleaning, high intensity magnetic separation, and bacterial oxidation. PREPARATION PLANT FLOWSHEETS by RICHARD B. Muter In determining the layout or combination of unit operations to be utilized in a modern preparation plant several factors must be taken into account.

Jan 1, 1979

By J. C. Swartz

Measurements of the effect of precipitation stresses on the solubility of cementite (Fe3C) precipitates in a iron are reported. Solubilities were determined from measurements of the Snoek relaxation due to interstitial carbon after quenching from various equilibrium treatments. Stress-free precipitates were obtained by a spheroidizing treatment of vacuum-melted Fe 0.06 wt pet C. Subsequent equilibration treatments were designed to suppress nucleation of other precipitates. The results for stress-free cementite give a heat of solution of 14.8 i 0.2 keal per mole and an entropy change of 1.1 i 0.2 eu in the temperature range 400" to 715°C. Comparison with previous data indicates that the heat of solution increases about 6 keal per mole as temperature increases from 700" to 1000°C. Data on self-stressed cementite in quench-aged specimens of Fe 0.013 wt pet C indicate 1) an apparent heat of solution of 12.1 i 0.4 keal per mole in the range 280" to 690°C, 2) a strain energy of- 1.1 keal per mole Fe3C accompanying precipitation at 280°C, and 3') a gradual decrease in the strain energy of precipitation with increasing equilibration temperature. In com-parison with 2 and 3 the strain energy calculated for an isotropic model is 1.7 keal per mole Fe3C. The lower values obtained from the experiment indicated substantial stress velaxation by dislocation motion. WHEN a supersaturated solution of carbon in a iron is aged at temperatures in the range 200o to 700oC, the carbon clusters by interstitial diffusion and forms cementite (Fe3C) precipitate particles. Unstressed cementite has a volume per iron atom 9 pet higher than that of a iron;' hence, cementite precipitate particles are usually under pressure from the iron matrix. The pressure would tend to increase the solubility of cementite in iron.' This report describes anelastic measurements of the solubilities of self-stressed and stress-free cementite in a iron. Previous determinations of the cementite solubility are summarized in Table I. The method of cementite formation for each reference was studied to ascertain the state of stress of the cementite. The results judged to be for stress-free and stressed cementite are distinguished in the table. In the next section an estimate of the stress effect is obtained which is clearly too small to account for the large difference between the previous results in parts A and B of the table. THEORETICAL Let AGO be the standard free-energy change of the reaction Fe3C (eem.) = 3Fe (a) + C (in a) [1] in the absence of stresses. Since cementite precipitates appear to be rather pure10 and the carbon is so dilute in the iron,8 the cementite and iron of Eq. [ I] for the stress-free case have essentially unit activities and the activity of carbon equals its atom fraction xoC Then the stress-free equilibrium is expressed by RT In XoC = -?GO 121 To first approximation the change in the chemical potential of carbon due to the precipitation stresses equals the elastic strain energy W accompanying precipitation of a mole of cementite.2 Hence, in the presence of the precipitation stresses the equilibrium is described by RT In x sq = -?G° + W [3] where xsC is the mole fraction of dissolved carbon in the stressed case. An approximate value of W can be obtained from analysis of the inclusion problem in elasticity theory. The inclusion is a small portion of the matrix phase which has suffered a transformation while still imbedded in the matrix. In the absence of the constraint of the matrix the transformation would be equivalent to a uniform dilational strain eT. Both the matrix (a) phase and inclusion (0) phase are assumed to be homogeneous, isotropic materials. When the a and 0 phases have the same elastic moduli, which is approximately true for iron and cementite,11 the total strain energy per mole ß is12 2µVß(eT)2(3 +4 µx)-I [4]

Jan 1, 1968

By W. C. Phalen

SALT-MAKING PROCESSES THE production of salt in the United States divides itself at the outset into two distinct classes: (1) The mining of rock salt and its purification and separation into marketable sizes, and (2) the production of salt by evaporation from brines, bitterns, and other solutions. The processes employed at the present time in the manufacture of salt by evaporation may be outlined as follows: 1. Solar evaporation. 2. Direct-heat evaporation (a) in open kettles; (b) in open pans. 3. Steam evaporation, (a) in jacketed kettles, (b) in grainers. 4. Vacuum-pan evaporation. In this paper only the solar-evaporation processes practised in different parts of the United States will be described. SOLAR EVAPORATION Localities In the Eastern States the solar-evaporation process is not generally employed for climatic reasons. In the Western States, particularly in California and Utah, the great bulk of the salt produced originates in the solar-evaporation process. Of the Eastern States producing salt, this process, so far as the writer is aware, is employed in New York State only.

Jan 9, 1914

By J. V. Emmons

It has long been known that the outside skin of tool steel frequently exhibits properties widely different from the interior of the mass.

Jan 1, 1915

By Taylor Lyman, E. P. Klier

The structures formed when austenite is quenched to subcritical temperatures and allowed to transform isothermally have been the subject of intensive study since the work of Davcnport and Bain.' Isothermal transformation diagrams summarizing the results of many of these studies have become widely familiar to metallurgists. Of particular interest to metallographers are the dark-etchingl acicular products of transformation formed by isothermal reaction below the temperature of maximum velocity of the austenite to pearlite reaction. These products, the bainite structures, can he formed in a wide variety of steels. However, the constitution of bainite is not well understood and divergent views have been expressed as to its mode of formation. In this investigation a combination of dilatometric, microscopic and X-ray methods has been brought to bear upon the problem in the hope of some elucidation of the bainite reaction as it occurs in hypo-eutectoid steels. Mechanism OF Bainite Formation Davenport and Bainl considered the mechanism of bainite formation to consist of two steps—an allotropic transformation followed by precipitation of carbide. The separation in time of the two processes was considered to be very slight in the upper temperature range and very marked at temperatures just above the martensite range. This concept has been restated by Vilella, Guellich and Bain2 in the form of a definition of the acicular mode of transformation as: The successive, abrupt formation of flat plates of supersaturated ferrite along certain crystallographic planes of the austenite grains; this supersaturated ferrite begins at once to reject carbide palticles, (not lamellae), at a rate depending upon temperature In effect, this is the acicular mode of transformation, even though the temperature be such as to limit the actual life of the quasi-martensite to millionths of a second. The investigation of isothermal decomposition of austenite in certain alloy steels (notably those containing chromium or molybdenum) has revealed that there may be a range of temperatures between the pearlite and bainite reactions in which the austenite decomposes at a relatively low rate.3-6 Further, it is characteristic that in the second region of fast reaction the decomposition of the austenite is incomplete by one reaction but goes to completion by a second reaction. These observations led Wever7 to a description of the bainite reaction as follows: I. The reaction takes place by initial precipi. tation of a martensitic intermediate structure. 2. In the upper temperature range this structure readily decomposes into ferrite and cementite. In the lower range carbon separates in an unknown form. 3. In the upper temperature range the precipitated carbide nucleates the precipitation

Jan 1, 1944

By E. P. Klier, Taylor Lyman

The structures formed when austenite is quenched to subcritical temperatures and allowed to transform isothermally have been the subject of intensive study since the work of Davcnport and Bain.' Isothermal transformation diagrams summarizing the results of many of these studies have become widely familiar to metallurgists. Of particular interest to metallographers are the dark-etchingl acicular products of transformation formed by isothermal reaction below the temperature of maximum velocity of the austenite to pearlite reaction. These products, the bainite structures, can he formed in a wide variety of steels. However, the constitution of bainite is not well understood and divergent views have been expressed as to its mode of formation. In this investigation a combination of dilatometric, microscopic and X-ray methods has been brought to bear upon the problem in the hope of some elucidation of the bainite reaction as it occurs in hypo-eutectoid steels. Mechanism OF Bainite Formation Davenport and Bainl considered the mechanism of bainite formation to consist of two steps—an allotropic transformation followed by precipitation of carbide. The separation in time of the two processes was considered to be very slight in the upper temperature range and very marked at temperatures just above the martensite range. This concept has been restated by Vilella, Guellich and Bain2 in the form of a definition of the acicular mode of transformation as: The successive, abrupt formation of flat plates of supersaturated ferrite along certain crystallographic planes of the austenite grains; this supersaturated ferrite begins at once to reject carbide palticles, (not lamellae), at a rate depending upon temperature In effect, this is the acicular mode of transformation, even though the temperature be such as to limit the actual life of the quasi-martensite to millionths of a second. The investigation of isothermal decomposition of austenite in certain alloy steels (notably those containing chromium or molybdenum) has revealed that there may be a range of temperatures between the pearlite and bainite reactions in which the austenite decomposes at a relatively low rate.3-6 Further, it is characteristic that in the second region of fast reaction the decomposition of the austenite is incomplete by one reaction but goes to completion by a second reaction. These observations led Wever7 to a description of the bainite reaction as follows: I. The reaction takes place by initial precipi. tation of a martensitic intermediate structure. 2. In the upper temperature range this structure readily decomposes into ferrite and cementite. In the lower range carbon separates in an unknown form. 3. In the upper temperature range the precipitated carbide nucleates the precipitation

Jan 1, 1944

By M. R. Geer, H. F. Yancey, P. S. Jacobsen

Two growing problems confront the preparation engineer—still further restrictions on stream pollution and a greater proportion of fine coal as more and more continuous miners come into use. The de-watering screens, centrifuges, and settling ponds that sufficed a few years ago must often be supplemented by more effective equipment, and in some instances the finest solids are now being recovered by vacuum filtration, once considered too costly in many coal washeries. Unfortunately not all slurries can be readily filtered. Some are virtually unfilter-able, and others do not permit the high cake rates needed to hold costs within reason. Often, however, these difficult slurries can be rendered filterable by flocculation. Starch and lime have long increased settling rate in thickeners and can also aid filtration. More recently there have been other flocculants, primarily synthetic polymers or gums. Reports of their great effectiveness prompted the U. S. Bureau of Mines to test their use in filtration as part of its program on recovering and cleaning fine coal. The object of the present work was to compare some of the newer flocculants with starch and lime and to test the reaction of different types of slurries to flocculation. Three natural slurries, three synthetic coal-clay mixtures, and five flocculants were tested, all with a laboratory filter leaf. Slurries and Flocculants Tested: First of the slurries was the thickener feed from the washed coal section of the Michel colliery of Crow's Nest Pass Co. Ltd., Michel, B.C. As shown by the screen and ash analyses in Table I, practically all this slurry was finer than 28 mesh, and about half the solids were finer than 200. Substantially all material coarser than 200 mesh was clean coal, but the ash content of 20.7 pct in the finest size indicates a moderate amount of impurity. This coal is medium-volatile bituminous in rank. Slurry was also obtained from the Black Diamond washery of Palmer Coking Coal Co., King County, Wash. This underflow of a 1/2-mm vibrating slurry screen is a waste product discharged to a settling pond. As shown by the data in Table I it contained about 20 pct material finer than 200 mesh, which analyzed 77.5 pct ash, indicating a high proportion of clay. The coarser sizes were also high in ash content because of the presence of bone and shale. Black Diamond coal is on the dividing line between bituminous and subbituminous rank. The third slurry, from the washery of Roslyn-Cascade Coal Co. in Kittitas County, Wash., was the underflow of a battery of 8-in. cyclones that is wasted with the coarser refuse from the plant. In both size and ash content this slurry was similar to the Black Diamond, but since it was a cyclone-underflow product, the fraction finer than 200 mesh undoubtedly contained a much smaller proportion of finely divided clay than was present in the Black Diamond slurry. The Roslyn-Cascade coal is high-volatile A bituminous in rank. Initially the slurry samples were stored in the laboratory at a concentration of 40 pct solids. A progressive change in filtration and flocculation characteristics during storage was noted, however, presumably because of progressive disintegration of the clay. After careful testing demonstrated that the slurry solids could be dried and then repulped without changing the original filtration characteristics, this procedure was adopted. The flocculants used were Separan 2610, Kylo 27, Jaguar MD-A, Idaho potato starch, and lime. The lime was used as a slurry, the Separan 2610 as a 0.10 pct aqueous solution, and the other flocculants as 0.50 pct aqueous solutions. The starch was causti-cized with sodium hydroxide before use. As some of the flocculants are reported to deteriorate on storage, new batches of flocculants were prepared every two days. Test Procedure: Fig. 1 diagrams the filter leaf apparatus employed. This consists of a test leaf having an effective area of 0.10 sq ft., a 60°, 8 1/2-in. diam cone to hold the slurry sample, a variable-speed electric stirrer, vacuum gage, bleed line for controlling vacuum, filtrate flask, moisture trap, and vacuum pump. Two filter cloths were selected—Saran SA 603, a monofilament, coarse-weave cloth, and polyethylene PO-801 HF, a monofilament, fine-weave cloth. The Saran was selected to provide maximum cake rate without regard to clarity of filtrate and the polyethylene to provide the best quality of filtrate without regard to cake rate. The test charge for the filtering vessel consisted of 800 g of solids (previously soaked for 24 hr) and

Jan 1, 1960

By H. R. Peiffer

Hardening of soft metals can be accomplished by dispersing finely divided hard particles in them. The dispersing of finely divided alumina in silver in the presence of oxygen yields a high strength material which is unusual in that its mechanical properties above the melting point of the continuous Ag-O alloy matrix are similar to other solids. The tensile strength is studied for two of these alloys, one of which contains 15 pct by weight alumina and the other 20 pct by weight alumina. The average fracture strengths above 960°C of these alloys were found to be 0.4 x106 dynes per sq cm and 3.8x106 dynes per sq cm respectively. The strengths appenred to be independent of temperature above 960° C. The creep behavior of the 20 pct alumina material was studied above 960°C. The initial creep rate, 6 , of this material can be represented by where s is the applied stress and E the activation energy for the process. This energy is of the order of 1.7 to 2.1 ev. HARDENING of soft metals by the addition of finely divided, hard particles has resulted in the production of materials with excellent creep resistance and with inhibited recrystallization.' It has been demonstrated that such composites have useful strength up to temperatures very near the melting point of the soft metals, but one might expect that the strengthening by the dispersed particles ceases to be of importance above the melting point of the softer phase. This, however, is not so.2 In this paper the strengthening of a liquid Ag-O solution by the presence of dispersed alumina is discussed and experimental data concerning the mechanical properties of such a material at temperatures above 960°C presented. EXPERIMENTAL PROCEDURE Specimens were prepared using powder metallurgical techniques. Finely divided silver oxide was mixed in the appropriate proportions with "Linde B" alumina. For these experiments the specimens contained 15 or 20 wt pct alumina in pure silver.* These alloys were used in these experiments since they were the ones that could be handled readily enough to yield experimental data. Silver oxide was used in preference to silver because it is readily available in a very finely divided form and because the presence of excess oxygen in the silver is important to the properties2 of the material. The powders were mixed wet, using alcohol as the medium, in an ordinary food blender until a uniform mixture was obtained. They were then dried and heated to reduce the silver oxide to silver. Only a fraction of the finely divided silver remains unoxi-dized upon removal from the oven since the finest particles of silver oxidize immediately upon contact with air. The remaining fine silver served as a binder during pressing. The mixture was then pressed at 20 tons per sq in. into shoulder-grip (reduced section 1/4 in. by l/4 in. by 1 1/4 in.) and rectangular bar specimens (l/4 in. by 1/4 in. by 2 in.). The green specimens were heated very rapidly in a globar furnace to 1000°C, held at temperature untic they had reached theoretical density and then furnace cooled. The strength of the two compositions at temperatures above 960 °C was determined by pulling shoulder grip specimens inside a furnace mounted on a tensile machine. Specimens were gripped by means of wires wrapped around the shoulders of the specimen. Temperatures were measured by means of a chro-mel-alumel thermo-couple placed in the vicinity of the specimen. Control of temperature (within ±°15C) was accomplished by means of a Weston Recorder-Controller. Before loading, specimens were held at temperature for approximately 15 min in order to insure uniform specimen temperature. The low loads were measured by a special load cell designed by Baldwin Lima Hamilton. All testing was performed on a FGT testing machine of the same com-pany. Creep studies were performed in bending utilizing rectangular specimens of the 20 pct alumina alloy. Specimens supported at both ends by knife edges of inconel were placed in a globar furnace, heated quickly to temperature, and the deflection of the beam measured optically as a function of time. The weight and size of the specimen were predetermined and the maximum stress on the beam calculated from

Jan 1, 1962

By J. M. Avasthi

The DOE-funded (Contract No. DE-ACO3-77ET13108) Gulf Research & Development Co. (GR&DC) field tests of underground coal gasification in steeply dipping beds (UCG/SDB) were conducted in the North Knobs area, located 12.8 km (8 miles) west of Rawlins, WY. The site has a gently rolling, sparsely vegetated, semidesert terrain on the transition zone between a broad, flat basin (Great Divide Basin) to the west and the subdued mountains of the Rawlins uplift to the east. A comprehensive geotechnical program (Ahner et al., 1980) was essential to successfully complete the test program. Emphasis of the program was the subsurface characterization of the site and consisted of mapping, drilling and logging, core analyses, and hydrologic tests. The samples of lithologic units over- and underlying the G coal seam were tested in the laboratory for their modulus and strength. This program provided the required data necessary for designing surface facilities, input for permits, and ensuring correct placement of the process modules. The two UCG tests at the Rawlins site were conducted in the nominally 6.7 m (22 ft) thick G coal seam (rank-subbituminous B), dipping at 63°.

Jan 1, 1984

By H. P. Wheeler

WHEN Germany invaded Poland in September, 1939, the only operating helium plant in the United States was that near Amarillo. Texas, supplied with helium-bearing natural gas from the near-by Cliffside gas field. Today the Bureau of Mines has five plants capable of producing more than 25 times the prewar helium output of the Amarillo plant. Two of the plants have received Army-Navy "E" flags for their part in the faraway "Battle of the Atlantic," where heliumfilled Navy blimps chased Adolf Hitler's submarines away from American shores. Meteorologists, watching balloons carried high into the stratosphere by helium, determined weather conditions that influenced the selection of D-day and dates for other military operation. Demand for helium doubled overnight when the Navy decided to expand its lighter-than-air activities; and as the blimp patrol proved effective, the helium demand became ever greater. A tribute to the success of the Bureau of Mines in meeting the demand for helium was paid by the late Secretary of the Navy, Frank Knox, in a letter to the Secretary of the Interior on April 10, 1944. Secretary Knox wrote, in part,

Jan 1, 1945

The visitors to the October meeting will be given opportunity to visit the coal fields in Illinois, adjacent to St. Louis, the steam-shovel operations near Pittsburgh, Kan., and the Oklahoma oil fields. The coal mines of Illinois, Missouri, Kansas, Oklahoma and Arkansas furnish fuel over all of the central region of the country. Especially at this time, this district is of importance because of the necessity of producing enormous quantities to meet the country's demand. Some of the mines produce as much as 5,500 tons in 8 hr., and. the total output of Illinois, alone, in 1916, was 63,000,000 tons. Visitors may see elaborate underground electric tram systems, large underground machine repair shops, surface plants equipped for rapid loading, and some of the most modern coal-washing installations. The conditions for mining here are somewhat simpler than in the east.

Jan 8, 1917

By B. M. Larsen

NEVER having actually tried to engage in the systematic education of anyone, and having little direct knowledge of the practical problems and limitations in the field of education, I can pose only as a "nonexpert" in this field, one whose ideas are to be regarded as personal opinions. The necessity for compromise between educational ideals and the practical limitations of time, money, and mental capacities of both student and teacher is evident in the preparation of an end product that we may regard with a reasonable degree of conviction as a professional engineer. We need to do so many things. The engineering student must have a clear understanding of the basic sciences; he should develop manual skills and co-ordination; he should speak and write the language with simple clarity and directness; he should gather knowledge of a special field; and, he should be educated for living in a broad ..

Jan 1, 1948

By Frederic Becket

IN a recent article,1 which described the softening effect of columbium in plain high-chromium steels, the authors stated that their investi-gations had shown columbium to be also a particularly valuable inhibitor of intergranular corrosion in steels of the 18 per cent chromium, 8 per cent nickel type. It is the purpose of the present paper to record some of the results obtained through the introduction of columbium to the austenitic chromium-nickel steels. The damaging effects of this type of corrosion have become so widely known as to restrict considerably the applications of the steels under consideration, and therefore there is little question of the importance of the goal to be attained. Numerous contributions concerning the susceptibility of the aus-tenitic chromium-nickel steels to intergranular corrosion have appeared during the past few years, and among others who have dealt construc-tively with the subject are such well-known authors as Strauss and Houdremont of Germany, Hatfield of England, and Bain in the United States. Different theories have been propounded as to the cause of intergranular corrosion, and various remedial measures have been proposed, the majority of which involve the use of addition agents. Titanium is the addition agent at present most generally employed, as suggested by Houdremont and modified as described by Bain, Aborn and Rutherford.2 Little has been published on the effects of holding these steels for long periods at the relatively lower temperatures in the presence of

Jan 1, 1934

By A. C. Veatch

Jan 1, 1921

Jan 1, 1929

By Frank F. Aplan

In looking into the crystal-ball scene of minerals beneficiation for 1970 and beyond, an impartial observer becomes con- fused as to what has been done and what is possible in the way of improvements. The mining official must balance the burden which is being shouldered by the mineral industry for maintaining our environment in its pristine state on one hand, with the solid advancements made in technology and cost savings on the other hand. Then the official wonders if this is really the criterion for judging overall performance today. As a prospective engineer, Dave Bolles sees it this way: "Specialization has caused many engineers to subordinate everything to doing their job the cheapest and fastest way. In the future this won't be enough. The engineer in the mineral industry will be responsible not only for mining, concentrating and smelting, but also for the resultant wastes- the mine dumps, the tailing dams and the slag piles." (See Drift on page 63).

Jan 1, 1971

By C. M. Brinckerhoff

Safety work in mining at the Andes Copper Mining Company, Potrerillos, Chile, is divided into three parts: (1) accident prevention, (2) fire prevention and protection, and (3) silicosis prevention and control. In the company's operations a steady campaign has been waged to reduce accidents and silicosis, and to prevent fires. In the following pages the safety record for the past twelve years will be examined and the methods explained by which the accident rate was reduced. Table 1 contains yearly data pertaining to the scale of the mining operations and the accident record. Block caving is used for all ore production and the tonnage mined has averaged 30,000 short tons per day for the past seven years. Table 2 classifies 44 fatal accidents which have occurred since 1935. The leading causes of accidental death are transportation of ore and use of explosives, followed in order by persons falling, falls of ground, and by asphyxiation. In the case of serious accidents, however, the greatest cause is falls of ground, followed, in turn, by ore transportation, persons falling, explosives, and asphyxiation. Accident Prevention The improvement of the safety record was obtained by a combination of many factors. In surveying the results at Andes for the past twelve years, it is possible to select some features of the present operation which have contributed to the accident record. The most important of these are: (1) good staff planning, (2) good equipment, (3) an alert safety organization, and (4) education and selection of the workmen. GOOD STAFF PLANNING As a result of good staff planning, the mine has good working conditions, namely, good ventilation, moderate temperatures and humidity, and good lighting. These factors not only reduce accidents but also improve efficiency. In haulage work, accidents have been reduced by having traffic move in a forward direction only. The latter makes possible a one-man train crew. Trains are centrally dispatched from loading drifts which are interconnected by signal lights, so that when a train in a lateral drift is given permission to move into a main line drift, a red light signals in all other lateral drifts in that area. Good track is maintained, and safety niches are required at all switch throws. Since safety niches were provided there have been no fatal or serious accidents at such points. All main line haulage drifts are illuminated by electric lights. Haulage drifts are kept clean. Adequate clearance has been provided between cars and between cars and the sides of the haulage drifts. The 4 1/2 ton Cranby type cars are equipped with roller bearings, and the 10 ton loconlotives with trolley shoes instead of wheels. These two features are responsible for improved ore haulage conditions and contribute to greater efficiency and safety.

Jan 1, 1950

D EC. 20-The spirit of Christmas and good will toward men has managed a few brief appearances on the front pages, welcome relief from man's usual ill-will toward man. A couple politicos did their best to brighten the scene by well-publicized romances. There was a general exodus to Florida to patch up nervous systems, and even the UNO quieted down as Mr. Vyshinsky departed for home via Eastern Germany. Before going he opened up a preliminary bombardment for the worldwide "communist peace offensive," and it is now the duty of the 600 million (according to the Cominform) ideological converts to press home the attack. In Washington, Mr. Lilienthal resigned as Chairman of the Atomic Energy Commission and demonstrated again the difficulty of government to retain the services of capable men. The President has yet to appoint another victim- possibly someone nicely noncontroversial and timid. So might the critics be appeased, but it would bode ill for the rapid exploitation of peaceful uses of atomic energy, the relaxation of excessive secrecy, wider sharing of developmental work with friendly nations and possible revision of the Acheson-Lilienthal proposals for inter- national control of the atomic bomb.

Jan 1, 1950

By J. P. Doan, G. Ansel

The important literature concerning zirconium in magnesium-base alloys is predominantly contained in patent references. Sauerwald, Eisenreich, and Holubl-4 discovered the profound grain-refining influence of small amounts of zirconium on cast magnesium and the attendant increases in strength and ductility. They extended their work to reveal that limited amounts of certain other elements, including zinc, could be added for further improvement in strength and hardness. British Patent 5111375 relates to the parent discoveries of Sauerwald, Eisenreich, and Holub. All of these references deal primarily with casting characteristics and properties in the cast state. Minor mention is made of desirable tensile strength, ductility, and toughness of wrought Mg-Zr alloys* modified by one or more additional elements. No extensive reference in the literature5. has been found to the particular characteristics of wrought blg-Zn-Zr alloys, with which the present paper is concerned. The work to be discussed represents essentially an extrusion study of the blg-Zn-Zr alloys and indicates that this system is highly interesting in the wrought state both academically and commercially. Accordingly, an important aim of this paper is to describe the hot-workability, tension and compression properties, metallography, and toughness of these alloys. Compositional variations are limited to the ranges 0 to 7 per cent Zn and 0 to I per cent Zr. Experimental Procedure Alloying and Casting Alloying ingredients were cell magnesium, commercial zinc (intermediate grade), and a chloride salt containing approximately 50 per cent ZrCl² and 50 per cent alkali chlorides. This salt is produced by Titanium Alloy Manufacturing Company. Melting, alloying, and pouring procedure essentially followed the crucible process as described by Nelson.6 The magnesium was melted using Dow No. 310 flux, and the temperature raised to 1350° to 1400°F for the alloying operations. After alloying of the zinc, the zirconium containing salt was added in small portions with vigorous stirring. This is an adaptation of the method described in British Patent 533264.7 The alloying efficiency of zirconium was approximately 30 per cent. During the alloying of zirconium, fluorspar was added in amount required as a flux-inspissating agent. Next the melt was refined with Dow No. 310 flux and held quietly for 15 min. Finally billets were cast in a book-type permanent mold

Jan 1, 1947