Search Documents

By H. Margolin, E. Ence

Two versions of the Ti-Mn binary diagram have been published recently.' , -0th diagrams show two compounds in the region between 40 and 70 wt pct Mn, but disagree as to the reaction in which these compounds are involved. The investigation of the manganese-rich portion of the Ti-Mn binary diagram was undertaken at New York University as part of an investigation of ternary systems with titanium and manganese in order to determine which of the proposed diagrams is correct. A number of alloys between 31 and 70 pct Mn were prepared in a manner similar to that described by Cadoff and Nielsen; except that low currents (110 amp in argon atmosphere) and long melting times (up to 20 min) were used to prepare the alloys. Compositions were determined from weight-loss data, assuming all loss as due to manganese. Heat treatments were carried out with relatively large pieces, since there was a tendency for manganese to be lost during heat treatment. When X-ray diffraction data was to be obtained, the central parts of heat-treated specimens were used to make filings or powders which were not heat treated. Specimens were heat treated from the as-cast state. Heat-treatment times were as follows: 1150°C, 1 day; ll00°C, 2 days; 1000°C, 5 days; and 900°C, 15 days. It should be noted that equilibrium was not attained at 900°, 1000°, and in one case, at 1150°C. Metallographic specimens were electrolytically polished and strain etched by a technique described elsewhere.' At least four, and possibly six, phases were found in the region investigated. On the basis of information available at this time, a completely self-consistent diagram cannot be constructed, and therefore data are presented only for those phases which have been identified by both X-ray and microstruc-ture. Of the compounds detected, the one highest in manganese is the Laves phase, TiMn,, which is hexagonal with a MgZn, type of structure.V he diffraction data for TiMn2 from a 70 pct Mn alloy annealed at 1150°C are shown in Table I. The c/a ratio and parameters of TiMn2 agree well with those of Wall-baum hnd Rostoker et al. The values obtained here are c/a = 1.641, a = 4.825A. Another compound is the y-phase which is estimated to contain about 60 pct Mn. The y-phase has a structure which is identical to that of TiMn, with c/a = 1.639, a = 4.906Å. The fact that y has a Laves-type lattice would suggest that TiMn, has a range of solubility which extends from the composition of TiMn2 (69.6 Mn) to that of y (60 pct Mn). However, this could not account for microstructures which, in the 60 to 70 pct Mn region, show several phases in both the as-cast state and after annealing at 1150°C. Fig. 1 shows a two-phase structure of a 60 pct Mn alloy annealed at 1150°C. The phases present are y (white) and e (dark). If y were TiMn, then, according to Rostoker et al.,' the second phase of Fig. 1 should be P-Ti. The diffraction data for the 60 pct Mn alloy of Fig. 1 are shown in Table I. The starred d-values are from the e-phase and these lines do not correspond to those of &Ti. Comparison of as-cast and 1150°C microstructures of the 60 pct Mn alloy indicates that e precipitated from y. Since y has a

Jan 1, 1955

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members.) Experienced mining. engineer, Columbia School of Mines graduate, practical experience in drifting, shaft sinking and development work, also in mining, operating and equipping iron, copper, and zinc properties. Married, age 32, available at once. Open for position as superintendent or assistant. No. 462. Member, age 33, married, desires position as mining engineer or engineering executive.- Twelve years experience as mining engineer, geologist, and chief engineer of iron and copper properties. Experience in United States, Mexico and South America. Fluent Spanish. Technical graduate. Minimum salary $3000. No. 466. Member, technical, general superintendent and mill superintendent: Well experienced in latest methods of ore reduction, especially on copper and complex ores. Draft exempt. Not less than $250 per month considered. No. 469. Consulting mining geologist, member of Geological Society of America and A. I. M. E., Professor of Geology and Mineralogy, Lawrence College, desires temporary position during summer in mine surveying, mining methods, expert mine valuation or any exploration work or mine development. Applicant has had nearly three years' experience in gold mining in Mexico and many years professional mine examination work in all regions of Western U. S. Terms reasonable. No. 470. Member, mining engineer, age 46, desires engagement as manager of mining properties, coal or metal mines. Education and 25 years experience in all branches of mining. Have been successful with labor in the management of large properties. No. 471.

Jan 8, 1918

By N. J. Themelis, A. W. Last

Autogenous grinding, broadly defined as the self-comminution of ore in a cylindrical tumbling mill without using auxiliary grinding media, was first applied in the early 1930s in the so-called Hadsel mills (Hardinge, 1955) as seen in [Fig. 1], mainly used in gold mines on the US West Coast. A number of these mills were built in sizes of 6.1 to 7.3 m (20 to 24 ft) in diameter and 1.5 to 1.8 m (5 to 6 ft) in length but were later abandoned because of operating and maintenance problems. Further development of autogenous grinding led to the Hardinge wet grinding mill, the Aerofall dry grinding mill, and others. A tabulation of all known autogenous and semiautogenous installations around the world was sent recently to the authors by G. J. Kushner of Koppers Metal Processing Division. In the size range of 7.3 to 9.8 m (24 to 32 ft) in diameter, it lists a total of thirty mills used in the processing of copper ores. An additional 120 units are listed in the same size range for the processing of iron ores and other minerals. The largest mills in existence are 11.1-m-diam X 4.6-m-long (36-ft-diam X 15-ft-long) mills in Minnesota, powered by 8950 kW (12,000 hp) motors and used in taconite beneficiation. It is indicative of the phenomenal growth of this technology that none of the above 150 mills was in operation prior to 1964. Grinding rates in autogenous mills are very sensitive to variations in ore breakage characteristics and even with fairly constant ore type can exhibit large fluctuations in throughput. Autogenous grinding also depends on availability of a fraction of the ore to be ground in the form of "competent" rock which can withstand to a certain degree the tumbling and impact action within the mill. If the ore is uniformly "soft", it will soon be crushed into small size particles and further grinding, which depends on the existence of large size rocks in the mill, becomes impossible. This apparently is the case with most copper ores, as discussed by Bachman, Last and Nabbs (1970) who described pilot testing of a large number of ore samples from Kennecott 's Chino Mines. Under circumstances where autogenous grinding is impractical, it is possible to realize most of its benefits by utilizing large grinding balls in place of the "competent" rock and practice what has become known in the mining industry as semiautogenous grinding. In semiautogenous grinding (SAG), a grate discharge tumbling mill is fed the product of a primary crusher or run-of-mine rock. Forged steel or alloy grinding balls, in proportions ranging from 3.10% of the total volume in the mill, are used to complement the self-grinding ability of the ore. Semiautogenous circuits can be either designed for single-stage closed-circuit grinding which produces a final product for recovery processes, or for two-stage operation in which the SAG mill product is fed to a second stage of grinding in a conventional ball mill.

Jan 1, 1981

By Hiland G. Batcheller

HISTORY shows that the nation which makes the most steel is the most likely to win wars. Today the course of war shows that the nations which get there first with the most steel of the right kind will be the ones to win. Not only the most steel, mind you, but the right kind. Adequate production, which was enough for victory before the days of totally mechanized warfare of 1943, must now be accompanied by still better quality as well as more effective distribution. Further, both production and distribution must be flexible enough to permit rapid shifts from one weapon to another for use in varying elements in varying geographical areas. Thus the problem of making enough steel of the right kind at the right time in the face of changing requirements dictated by experience has been and will remain highly complex. This does riot permit us to ease our restrictions on nonessential use. War is a complex business, like the job of making steel for war. Each time we solve one problem, another pops its head up. Yet we are making some progress.

Jan 1, 1943

By Clyde E. Williams

THROUGHOUT its history the American iron and steel industry has constantly striven to improve the quality and reduce the cost of its products. No one needs to be told how well it has succeeded. Its success in making steel products at such a low cost has been achieved mainly through large-scale production. While costs have gone down as the rate of production and the degree of mechanization increased, quality of product has been actually improved. Thus high-tonnage records are important only in the light of high quality of the steel. Quality is the watchword! Continual improvement in quality has come as a result of research, not only in the laboratory but in the large commercial units in the plant. In fact, so many operations of the industry are on such a huge scale that experimental work must be done under commercial operating conditions so every progressive steel plant is a research laboratory.

Jan 1, 1938

A plan which has just been approved by President Wilson, by, the Secretary of the Navy, and the Naval Consulting Board, provides for the active cooperation of the Associated Advertising Clubs of the World with the 30,000 engineers who will soon undertake the task of making a card index survey of American industry, so that it may be prepared for national defense, if need comes. Herbert S. Houston, President of the Associated Clubs of the World comments on the plan. "Through the great power of advertising we expect-to arouse manufacturers, workingmen, businessmen, in fact the whole country, to the vital need of making industry the basic line of defense so that, if necessity arises, it can supply munitions quickly and abundantly. "This is not a war measure, but a peace measure. The militarist will support it and so will the pacifist, as well as the great body of Americans in between. So the slogan `national defense and international peace, has been adopted believing that the two causes will be best served by linking them together. "While the primary thing, of course, is service to the country, it is manifest that this work of the engineers will be of the greatest service to industry in times of peace. If industry is mobilized for defense, it will be placed on a basis of efficiency to meet the keen competition that will surely follow the present war." Howard E. Coffin, one of the leaders of the American automobile industry, in outlining the far-reaching plans of his committee, the Committee of Industrial Preparedness of the Naval Consulting Board, said: "At the outset I wish to emphasize the absolutely non-partisan nature of this work. I am not even familiar with the political affiliations of the great majority of the members of the Board or of my committee. In setting out to, mobilize the industrial resources of the United States, we are concerned only with the benefit to the nation, and to that end we have called into being an organization made up of the best technical and business brains of the country, and that organization will work along business lines with strictly business methods. I think it reasonable to say that this is a movement perhaps unique in the history of national governments, and one geared up to the highest standards of twentieth century efficiency. "It is vitally necessary that American industry be made aware of the part it must play in the national defense. Our whole conception of warfare has been changed almost overnight. Our military heads at Washington are largely, of course, graduates of the very best technical schools, have been taught the profession of fighting, and are masters of that profession. As members of the Naval Consulting Board, we are unable to tell these men how to do their work. But while these departmental heads have lived with military problems all their adult years, we on the other hand have slept and eaten and lived with the industrial problems of the country. The two questions are wholly distinct, and the masters of one cannot possibly be the masters of the other. We are confronted then with the necessity of interlocking these two vast elements of our national life into a great working organization for the national defense. It is that which we are about to do.

Jan 5, 1916

By James Douglas

THOUGH liberality is not supposed to be a prominent trait of the Scottish character, Canada owes to a Scotchman, Sir Wm. Macdonald, more than to any other of its people, not only wise ideas, but pecuniary help towards extending education: and another Scotchman, in New York, has sumptuously housed under one roof three branches of the engineering fraternity, of which we are one. Having thus created us members of the same family-for the metaphorical meaning of house and kinship is identical-Mr. Carnegie expresses more emphatically than even he could in words, that, by affording facilities for closest intercourse, he in¬vites the mechanical, electrical and mining engineers to par¬ticipate in the freest interchange of idea and experience, and to correlate and combine the results of their studies and activi¬ties; and, being members of the same household, to banish re¬serve and secrecy. And now we, the members of the - American Institute of Mining Engineers, meet as though we were at home in a neighboring country. For whether we meet in Canada, in England, or elsewhere, the Institute is always received as though no political or geographical divisions separated its members from those of congenial associations in the land of its host. In truth, the title which we have assumed claims for the sphere of our activities the whole American continent, regardless of such trifling details as boundary-lines. The fact that we meet to communicate each other's experience, to discuss our difficulties, and to seek each other's aid in solving the intricate problems that so often present themselves in the course of our profes¬sional life, is an acknowledgment of our individual helpless¬ness; and therefore an argument for united effort. But no effort can be of any value if there is an underlying suspicion

Jan 9, 1907

By C. P. Proctor

WESTERN Pennsylvania, eastern Ohio, and Illinois are carrying out experiments wherein much more slate and other impurities are loaded with the coal in the mine and hauled to the surface preparation plant for removal. In general everything is sent to the cleaning plant although there may be some gobbing in the mine. No conclusions have been announced as to the effect of such a mining system on clean coal costs. Such factors as ability of the surface plant to handle the impurities, land and facilities for disposing of the impurities, and the transportation facilities underground should be considered.

Jan 1, 1942

By J. C. Bokros

At temperatures above 950°F, zirconium which has been strained a critical amount will experience critical recrystalli-zation. The large grain size thus formed can result in a reduction in the fatigue life by a factor of 2 to a factor of 9 at both high and low temperatures. The critical strains for zirconium vary from 15 pct at 900°F to about 2 pct at 1125°F, while those for zircaloy III vary from 15 pct at 1050°F to 5 pct at 1200°F. Zircaloy II ,experiences no critical recrystallization up to 1200°F. ZIRCONIUM has become increasingly important for nuclear applications and is being employed in reactors at temperatures where recrystallization can occur. Recent work' on the fatigue properties of zirconium has shown that coarse-grained structures developed in zirconium during recrystallization have much lower fatigue lives than fine-grained material. The development of these large grain sizes under such conditions is well known to be the result of critical recrystallization.2-4 Briefly, critical recrystallization occurs when a metal is strained a critical amount and annealed in the recrystallization range. The critical strain is defined as that minimum strain necessary to promote nucleation in the time unit and temperature considered. The maximum grain size occurs at the critical strain, since at this strain the fewest stable nuclei per unit volume grow into new grains. Recrystallization is not evident below this; strain since the nucleation rate is vanishingly lolw, and metal strained more than the critical amount has a higher nucleation rate per unit volume which results in a finer grained structure. This paper describes the critical recrystallization observed in reactor-grade zirconium, zircaloy 11, and zircaloy I11 as a function of annealing temperature and temperature of strain. EXPERIMENTAL The zirconium used was hafnium-free, double arc-melted sponge obtained from the Bureau of Mines. The ingots were forged and hot reduced to 0.08 to 0.10-in. sheet and subsequently cold reduced to 0.035-in. sheet with intermediate and final anneals at 1200 OF for 15 min. The zircaloy II and zircaloy III used were 0.035-in. sheets in the annealed condition. Compositions of these materials as tested are given in Table I. To determine the critical strain at a given temperature, tensile specimens having a0.065-in. taper in a 2-in. gage length were machined from the sheets parallel to the rolling direction. The specimens were polished, etched, and examined metallographically to ensure that all of them were strain-free, initially. Tukon indentations were made every half millimeter along the gage length of each specimen. These served as fiducial marks enabling the plastic strain to be measured with a microscope and micrometer stage. The specimens were pulled to failure at a rate of 0.002 in. per min in an Instron tensile-testing machine. Three temperatures were used for straining: room temperature, 500 ºF, and 900 ºF. The 500º and 900 ºF tests were run in an argon atmosphere. Since the rate of work hardening changes with temperature, a different critical strain was obtained for each temperature of strain. Specimens, prepared in the manner described, were annealed in vacuunl at various temperatures ranging from 900" to 1200 F for up to 1000 hr, after which they were examined metallographically. The critical strain and the recrystallized grain size as a function of strain were determined for each specimen. Results for the same temperature and time indicated that the critical strain measured was reproducible to within 5 pct of each other. RESULTS AND DISCUSSION Since increasing the time of anneal increases the probability of the nucleation of a new grain, the critical strain decreases with time at a decreasing

Jan 1, 1961

By A. CHESTER BEATTY

MAGNESIUM oxide is by far the most refractory of the common oxides, since it has a melting point of 5072 deg. F. as compared with 3110 deg. F., the melting point of silica (crystobalite) ; 3722 deg. F., the melting point of alumina (corundum) ; and 4127 deg. F., the melting point of chromite (Cr2O33FeO). Its large-scale use in the lining of metallurgical furnaces dates back to the latter part of the nineteenth century, when extensive deposits of magnesium carbonate were discovered in southern Austria in the province of Styria. Before the development of Austrian magnesite, calcined dolomite, a mixture of lime and magnesia, was used in basic steel-making furnaces. The lime in the dolomite was quite objectionable, since it slaked on exposure to the atmosphere, and dolomite therefore could not be made' .into permanent furnace bottoms or into brick. The Austrian magnesite, with its very low lime content, was free from these objections and soon displaced much of the dolomite. With the extensive development of basic steel-melting, the rise of the copper industry, and other metallurgical and chemical processes which dealt with chemically basic substances, the use of magnesite grain and magnesite brick increased rapidly.

Jan 1, 1931

By Hugh H. Waesche

OF all the military services, the Signal Corps is the most concerned with piezoelectric minerals because of its function as a supply service to the strategic and tactical military forces. Consequently this paper is written from the point of view of one associated with that organization. The Signal Corps is responsible for the research, development, and supply of communications, radar, and components to the using services of the Department of the Army and to some extent the other branches of the National Defense Department. Their work therefore includes the study of the sources, characteristics, and application of quartz and other piezoelectric materials. These materials have become a vital consideration in strategic planning and are essential for efficient tactical operation by all the Armed Forces. The Signal Corps at the beginning of World War II was responsible for both Army Ground and Air Force electronic equipment. Since that time this Army service organization has probably done more in the development of frequency control devices using piezoelectric materials than any other group.

Jan 1, 1949

By W. J. Helfrich, C. L. Sollenberger

Many present direct reduction processes utilize iron ore concentrates for the production of sponge iron and the sponge iron is usually preferred as an agglomerate. Pelletizing a high grade iron oxide concentrate prior to reduction is a simple approach to the high capacity production of a uniform and agglomerated sponge iron product. The present paper describes the effect of different atmospheres and physical characteristics on the reduction of pelletized iron oxide concentrates. The kinetics of iron oxide reduction have been I studied by numerous investigators1-4 and a rate equation for the hydrogen reduction of hematite and magnetite has been proposed. Mc Kewan' obtained kinetic data for the reduction of hematite spheres sintered at 13'70°C (2498'F'). The kinetics of magnetite reduction was studied by Quets. He compacted the oxide at a pressure of 1 ton per sq cm and sintered the specimens to densities of 95 to 96 pct of theoretical. These studies demonstrated that the reduction of iron oxide is a topochemical process and that the rate of reduction is proportional to the receding surface area of remaining iron oxide. Thus, the measurement of the kinetics of iron oxide reduction depends upon the development of a measurable and well defined interface between metal and reacting oxide. It is evident that the reduction rate will be constant only when the rate of formation of the reaction product layer is constant. It was recognized by Joseph' and Edstrom' that the physical character of the oxide will determine the configuration of the interface between oxide and metal. The reduction of oxides which exhibit few pores or no interconnected pores should proceed by topochemical processes. However, if a massive or dense crystalline ore cracks during the reduction of the oxide, thus allowing the reduction to Proceed away from a well defined oxide/metal interface, then the observed reduction rate will vary or change during reduction. From a process standpoint, it would be difficult to apply absolute reduction rates determined for crystalline or nonporous iron oxide to the direct reduction of a porous pellet of iron ore concentrate. Most present direct reduction processes are attempts to utilize iron ore concentraates in the production of sponge iron. The sponge iron is usually preferred in an agglomerated form for subsequent melting practices. Pelletizing a high grade iron oxide concentrate prior to reduction is a simple approach to the high capacity production of a uniform and agglomerated sponge iron product. One process for preparing such a product has already been de-scribed. This paper describes the effect of different atmospheres and physical characteristics on the reduction of pelletized iron oxide concentrates. ORE CONCENTRATES STUDIED A magnetite concentrate from Reserve Mining Co. and a hematite concentrate from U.S. Steel Corp. were used in preparing pellets for these experiments. A head analysis of these concentrates is given in Table I. To compare the reduction rates of pelletized concentrates, it was necessary that each pellet contain equal amounts of oxygen which could be removed by reduction, regardless of the oxidation state, i.e., Fez% or Fe304. Also, because of the difficulty in preparing spherical pellets of uniform size, weight, density, and porosity for experimental purposes, pellets of a cylindrical shape were formed in a press.

Jan 1, 1961

By Alfred Boyles

THE experiments described below are a continuation of work on the graphitization of cast iron conducted as part of the program of funda-mental research at Battelle Memorial Institute. In previous work it was found that melting in hydrogen increased the amount of eutectic and in others i produced al marked changes in the size of the graphite flakes. These effects seemed to be III sulphur and manganese present in the material studied. Iron-carbon- respond silicon alloys did same manner as mg cast iron and there was no evidence to show that hydrogen was able to stabilize the carbide in such alloys unless additions of sulphur were made. The two alloys examined contained about 2 per cent of FIG. 1.-APPARATUS FOR MELTING UNDER PRESSURE. silicon. The present paper is con- A, inlet for gas. cerned with alloys of lower silicon B, outlet for evacuation. content and describes the structural C, power lead. D thermocouple changes produced by melting in E, plug for access to furnace. various atmospheres at pressures F, crucible. ranging from a partial vacuum up to 300 lb. per sq. inch.

Jan 1, 1939

The following Nominating Committee having been already appointed and approved by the Executive Committee in accordance with authority vested in the Executive Committee by the Board of Directors, was approved by the Directors: John V. N. Dorr, Chairman, Percy G. Beckett, J. W. Hutchinson, Julian Kennedy, William H. Linney, Charles W. Merrill, and E. Gybbon Spilsbury. The question of the purchase of Liberty Bonds, as well as that of bringing to the attention of the members the advisability of the purchase of these bonds, was referred to the Finance Committee. Sixty Members, four Associates, and thirty-six Junior Members were elected. Two Members were reinstated. Eight resignations were accepted.

Jan 7, 1917

By R. I. Jaffee, F. C. Holden, H. R. Ogden

The properties of quenched Ti-Fe alloys have been correlated with their microstruc-tures. For specimens quenched from equilibrium in the a-ß field, the dominant micro-structural variable is the a-ß ratio. A comparison of specimens having equiaxed a-ß structures with those having acicular a-ß structures shows that the equiaxed specimens have better tensile ductility, but lower impact resistance. There is evidence to show that specimens with acicular structures reach equilibrium in the a-ß field more rapidly than specimens with equiaxed structures. Both strength and ductility are lowered by heat treatments below 700°C. IN previous work,1, 2 certain principles of the physical metallurgy of a-ß titanium alloys have been evolved. Most of these principles have been based on data obtained on alloy systems which undergo no eutectoid reaction, or in which the eutec-toid reaction is so sluggish as to be inoperative. The alloy systems previously studied included the Ti-Mn alloys, with and without a-stabilizing additions, and the binary Ti-Mo alloys. The most important of these principles are: I) The compositional factors which affect mechanical properties are solid solution strengthening, the martensite transformation, and instability of

Jan 1, 1957

By Irwin Roman

IN a previous paper,1 a method was suggested for determining the depth to a bed in the simple case of a uniform overlying layer of constant thickness. The main purpose of the present paper is to show how a slight modification of that method has been used to interpret specific data obtained in the upper peninsula of Michigan by the staff of the Depart- FIG. 1.-THE TECTONIC CONFIGURATION. ment of Mathematics and Physics of the Michigan College of Mining and Technology. The method of Tagg2 has also been used on the same data, thus furnishing a comparison of the e two methods, as well as a method of using the two methods jointly. The method of measuring the apparent resistivity is that suggested by Wenner,3 and illustrated in Fig. 1. A current I enters the earth at the positive pole C and leaves it at the negative pole D. The potential V of the high electrode A, with respect to the low electrode B is measured by suitable means. The separation of the collinear points in the order shown, DBAC, is 1, the same. for each interval.

Jan 1, 1934

By John Hall

THE Fremont test for measuring the energy consumed in breaking a notched bar of steel is not so well known in this country as it deserves to be. The test specimen used in this test is about 3/8 by 1/4 by about 1 1/4 in., notched with a hack saw on the lower side to cause the piece to break at a fixed point. A weight of 10 kg. falling 4 m., and provided with a knife or chisel which strikes the specimen, breaks the test piece by impact. The residual force in the falling weight after it has broken the specimen is recorded by a suitable device, and the difference between the total energy and the residual energy of the weight (in kilogrammeters) is the force consumed in breaking the specimen. An experience of several years with the Fremont testing machine has shown its great value in readily detecting brittleness not revealed by tensile testing or slow bending testing. I this paper it is proposed to discuss (1) the supersensitiveness of the test as applied to cast steel and (2) its value in revealing the effect of heat treatment under certain conditions. .

Jan 7, 1913

By Oberlin Smith

The use of cast-iron tools, with chilled cutting-edges, for lathes, planers, boring-mills, etc., is not, as Gar as I can learn, very extensive in the United States, or perhaps in England and other parts of Europe. I have, however, no data to guide me in regard to foreign

Jan 1, 1891

By John E. Sherborne, William M. Newton

THE relation between the properties of electric logs and the fluid used in drilling a well is briefly discussed in this paper, and the fact that the resistivity of the drilling mud and its filtrate can appreciably affect such logs is shown. Apparatus was designed and a procedure established to determine the effect of various factors on the resistivity of drilling mud. Five muds commonly employed in California were tested and the following observations were made: I. The effect of raising the temperature from 80°F. to 180°F. is to decrease the resistivity of the mud or filtrate approximately 50 per cent. 2. The resistivity of the mud in most cases closely approximates that of its filtrate. 3. The change in the resistivities of muds caused by the addition of chemical is not the same function of the amount of chemical added for each mud. 4. The effect produced by increased sodium chloride content is to reduce markedly the resistivity of the mud and its filtrate. 5. Weighting materials, such as Baroid and limestone, tend to increase the resistivity of drilling mud. 6. Cement and counteracting reagents reduce mud resistivity.

Jan 1, 1942

By Joseph G. Mravec

ALL manufacturers of high-quality steel are conscious of the detrimental effects of nonmetallic inclusions in steel. Entrapped refractory inclusions are particularly troublesome when encountered during machining operations. Modern cutters used for machining such parts as gears and pinions arc costly tools, which are readily nicked and damaged by hard inclusions. A single hard inclusion can so nick and damage a delicate finishing tool as to necessitate its regrinding. Frequent exposure of hard inclusions during machining, therefore, decreases cutter life, lowers production, and increases rejections of defective parts. The importance of cleanliness of the steel, therefore, is obvious and the production of the cleanest possible steel is a continual challenge to the steelmaker. Inclusions in steel may be classified in two general groups: (i) deoxidation-type inclusions, and (2) refractory-type inclusions. The latter consist of entrapped material eroded from the refractories used in melting and conveying of the steel from the melting furnace to the ingot molds. It is the purpose of this paper to dwell mainly on steel cleanliness as it is affected by various refractories used in the melting furnaces, the ladles, and the ingot molds.

Jan 1, 1947