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By H. Van F. Furman

As the cyanide-method for the extraction of gold from ores is extensively used in the United States and elsewhere, and appears destined to prove a factor of increasing importance in the metallurgy of gold, a description of the latest laboratorymethods may prove of interest. The history of the development of the process in the United States has been analogous to that of all new processes. Many failures are to be recorded and a few successes. It is the opinion of the writer that, had the following simple tests been better understood, many of the failures would not have occurred, and we should probably have a larger number of successful plants in operation. While the process is not simple, but requires a high degree of chemical and engineering skill, the determination of the adaptability of an ore to the method is generally not difficult. While the laboratory-results will not always coincide with the actual results obtained in the mill, they will serve as a guide and control on the working of the mill, and mill generally suffice to determine if the ore can be

Jan 1, 1897

By J. D. Meakin, H. G. F. Wilsdorf

An etching technique.has been used to investigate the dislocation structure of deformed @-brass single crystals. Isolated single ended pileups have been observed, and it is shown that, in certain cases, the configurations of such pileups agree with theoretical predictions. Many discrete pileups within heavily deformed regions have also been detected and the influence of surrounding dislocations on these groups are reported and discussed. Divergences between the experimental and theoretical spacings in the isolated pileups and the origin of the stress maintaining the pileups are discussed. THE spatial configuration of a linear array of identical dislocations has been evaluated theoretically by Eshelby, Frank, and Nabarro.' Of particular interest is the equilibrium spacing of a series of dislocations under a uniform shear sti-ess when the leading dislocation is held fixed in the lattice; such an array is termed a single ended pileup. Eshelby, Frank, and Nabarro' found that an explicit analytical solution to the problem of n dislocations in a pileup is not possible, but they were able to derive approximate formulae applicable under various limiting conditions. An alternative method of determining the equilibrium configuration was proposed by Leibfried and Leibfried and Haasen in which the discrete dislocations are replaced by a continuous dislocation density. This technique was used by Head and Louat to solve in first approximation, a number of problems of particular interest, eg., single and double ended pileups. Head has also solved numerically a number of specific configurations involving up to six dislocations. Recently Kuhlmann-Wilsdorf has obtained numerical solutions for single-ended pileups containing between three and seventy dislocations, thus making possible a comparison between appropriate experimental results and accurate theoretical values. The considerable use of the pileup concept in theories of plastic flow has stimulated a number of attempts to observe such arrays experimentally. There is of course considerable intrinsic value in revealing an isolated pileup because a direct check on the elastic theory of dislocations then becomes possible. The only technique generally applicable for studying pileups in bulk metal specimens is selective etching of the point of emergence of individual dislocations. Confining our attention to etching studies which have revealed pileups, the earliest reported work

Jan 1, 1961

By A. Eiders

THE year 1874 marks a decided advance in the metallurgy of the West, in two directions. On the one hand, the technical management has been very materially improved, and on the other, the production has been largely increased over that of the previous year. The technical improvements of greatest importance are the introduction of condensation-chambers, or flues, at several works, and the further treatment of the lead matte produced in the ore smelting. These two are of general importance, and although by no means introduced at the majority of works, their adoption at the few where their great importance has begun to be understood will no doubt bring about their universal introduction. To these may be added a third step. forward, which for some localities is vital enough, though for others it must still remain doubtful whether it is to be regarded as an improvement or not. This is the introduction, at several

Jan 1, 1875

By A. Eilers

The year 1874 marks a decided advance in the metallurgy of the West, in two directions. On the one hand, the technical management has been very materially improved, and on the other, the production has been largely increased over that of the previous year. The technical improvements of greatest importance are the introduction of condensation-chambers, or flues, at several works, and the further treatment of the lead matte produced in the ore smelting. These two are of general importance, and although by no means introduced at the majority of works, their adoption at the few where their great importance has begun to be understood will no doubt bring about their universal introduction. To these may be added a third step forward, which for some localities is vital enough, though for others it must still remain doubtful whether it is to be regarded as an improvement or not. This is the introduction, at several

By Jonathan S. Jackson, Bruce P. Ream

Leach water management is one of the few areas in dump leaching subject to operator control. As such, it is of considerable importance. Theoretical considerations indicate that high leach solution application rates are inefficient in washing solubilized copper from dumps. The high rates cause unnecessary dilution of copper values, raising unit recovery costs. Use of excessive amounts of leach solution also cools dumps, resulting in reduced leaching rates. This paper reviews leach solution application methods and details the results of field tests run to determine the benefits and feasibility of low versus high application rate techniques of applying water to dump surfaces.

Jan 1, 1980

By J. W. Snavely

WITH all the advantages of handling bulk materials by means of belt conveyor also go some problems, one of the most persistent being that of cleaning. When sticky materials are being carried; the build-up of material on the return idler rolls results in difficulty of belt training. Much attention has been given to the problem of cleaning conveyor belts, and a great variety of cleaning devices have been developed. Even the best involve troublesome maintenance, and none can completely remove the fine particles imbedded in the belt cover, which cause rapid wear of the return idler rolls, and at the same time, of the belt cover as well. One of the major rubber companies has been promoting a two-way belt system, in which the conveyor belt is given two successive 90" twists at each end to enable it to carry material in both directions simultaneously. For many years the flat belt transmission industry has installed quarter-turn and half-turn twists in countless numbers of instances. While quarter-turn and half-turn twists in transmission belts is a familiar application, the 180" twist apparently has never been previously attempted with a conveyor belt. About a year ago, two officials of the National Iron Co. of Duluth, Lester and Lewis Erickson, proposed twisting the return run of a conveyor belt on an installation that they were designing for one of the major iron ore producers. Since then the soundness of the idea has been demonstrated, both in theory and by practical test, with the result that the installation of two conveyor belts involving the twisting of the return run is now under way. These two installations are designed to have the return run of the conveyor belt twisted 180" as it leaves the snub pulley at the head drive. The clean underside of the belt is thus placed against the idlers on the return run as well as on the carrying run. Just before it enters the tail pulley, the belt will be twisted an additional 180°, restoring it to its normal position. Because this twisting of the return run of a conveyor belt is a radical departure from accepted practice, an elaborate and extensive test was conducted early in 1950 to demonstrate that this twisting of the return run could be done successfully, also to establish application data for accomplishing this twisting, and to determine if any special equipment would be required. In studying this concept of twisting the return run of a conveyor belt, a number of problems need to be solved, primarily the ones brought about by deliberately introducing an unequal distribution of stress across the conveyor belt and controlling that maldistribution of stress, while confining it to the return run portion. The tension conditions existing in the return run of a conveyor belt are clear to all designers. First, the return run carries the initial or slack side tension of the conveyor belt, the tension that must be supplied to the return run to provide proper frictional contact between the belt and the driving pulley so that the necessary power can be transmitted from the driving pulley to the belt without slippage. This slack side tension is supplied to the belt by means of takeups, either of the gravity type, which can be vertical or horizontal, or by means of the screw type. With inclined or declined belt conveyors the slope tension also must be considered, which is the tension imposed by the weight of the belt hanging from the top pulley. This slope tension frequently can furnish part or even all of the initial tension required. The maximum value of the slope tension will be at the top pulley, and it decreases in direct proportion to the length. In addition to the foregoing, it frequently is desirable to impose arbitrarily additional slack side tension to provide sufficient tension at the loading point at the tail, so that the belt will adequately support its load between the carrying idlers. Design Conditions for Twisting A number of design conditions exist, which must be satisfied successfully to accomplish the twisting of the return run without exceeding normal working limits in any portion of the conveyor belt. It is obvious that the belt edge, in its relation to the center of the belt, must stretch in making a twist, because as the twist is accomplished, the belt edge travels through a longer path than does the center of the belt. It is further obvious that if the edge of the belt is stretched, a redistribution of stress in the belt is required to allow this edge stretching. Moreover, this stress will be unequal across the width of the belt, having a maximum value at the edges, with a minimum value at the- center of the belt. With correct initial tension in the return run of a conveyor belt, the existing slack side tension will be unequally distributed when a twist is introduced. A condition then exists in which the edge stresses,

Jan 1, 1952

By R. W. Prouty, R. T. Green

The object of this paper is to describe, as concisely as possible, the methods of sampling and ore estimating used at the Copper Queen Branch, Phelps Dodge Corpn., as applied to the Copper Queen mines at Bisbee, Ariz. Because of the difference in occurrence, manner of prospecting, and methods of mining, the sampling and estimating practice falls into two divisions: That for the underground operations, and that for the Sacramento Hill steam-shovel operations. The orebodies of the Warren district may be divided into three main classes: Replacements of limestone, replacements of porphyry, and replacements of contact breccia. The first class is more or less intimately related to porphyry intrusions, although in badly fractured country this relationship may not be well shown. These orebodies are mainly oxide and carbonate ore and very irregular, both in size and outline, although usually roughly lenticular and following the bedding of the limestones. There is usually quite a sharp boundary between the ore and waste in the carbonate and oxide orebodies and sampling is not necessary to determine the limits of commercial ore. In the sulfide orebodies, it is exceedingly difficult, without sampling, to determine the boundary between commercial ore and the surrounding low-grade or barren pyrite. Calculations made a few years ago showed that these orebodies had an average thickness of 35 ft, As some of the orebodies are from 100 to 300 ft. thick, it can be seen that the smaller ones form a difficult prospecting and estimating problem. In the replacements in porphyry, both underground and in Sacramento Hill, the boundary usually cannot be determined without sampling. There is a gradual decrease in value until barren material is reached; this gradation may occur within a short distance or it may extend for several yards.

Jan 1, 1925

By Edwin A. Sperry

The use of steam-stamps in the crushing of ore for the purpose of amalgamation has been very limited, and little has been written on the subject. As the writer has been operating a mill of this kind during the past year, it is possible that he may be able to present a few points in regard to mill-practice in this line which will be of interest. The mill herein referred to contains two Tremain steamstamps, a more detailed description of which will be given below. A bond and lease had been taken on a property on Cross mountain, Gunnison county, Colo., and the parties operating wished to prospect it thoroughly and did not wish to ship out the ore, owing to high freight-rates. They looked around to find some mill that would answer the purpose and not be too expensive. The steam-stamp in question was finally decided on, and the writer was employed to erect and operate it. The economy of construction was demonstrated at the outset. The stamps were dropping within ten days from the time that the machinery was unloaded on the ground. A large portion of this period was consumed in waiting for supplies and fittings which should have been on the ground at the Hame time with the machinery. Ore.—The ore to be treated was a mixture of white, porous quartz, with the decomposed and undecomposed oxides of iron and manganese in varying proportions, from the pure white quartz to solid pieces of the oxides. It appeared to be the product of replacement in a soft dolomite at or near the line of contact with a dike of porphyry. On careful examination with the aid of a microscope it was found that the gold was in the form of an extremely thin film over the surfaces of the quartz, making only a bronzy-yellow coating, quite readily distinguished from the film of iron oxide, which was also present. Mill.—The mill was constructed on the usual plan, with the ore-bin above and against the hill, which was cut into for the

Jan 1, 1897

By Hallan N. Marsh, Bruce H. Robinson

It is now generally recognized that to secure the greatest ultimate recovery of petroleum from a field it is necessary to maintain at all times the lowest possible ratio of gas to oil production. The numerous ways of securing low ratios are not so generally understood or practiced. To many operators, reduction of gas-oil ratio simply means "beaning back" wells, with resultant reduced production rate. This postponement of production is often considered and spoken of as "lost" production, with the result that control of gas-oil ratio is in disfavor with some operators. Various methods are herein discussed by which gas-oil ratio may be reduced, some of which invoLve no curtailment of current production, while others are accompanied by an actual increase of daily production. It is further shown that in cases where rate of production is reduced to conserve gas, the indicated ultimate recovery is generally increased. Principles involved are discussed, and conclusions are illustrated by data from the operation of wells. General Principles The rate and ratio in which oil and gas enter a well are solely dependent, so far as the operation of that well is concerned, upon the pressures maintained in the well opposite the producing strata at various times and at various depths. The method of getting the oil out of the hole, whether by natural flow, gas-lift, or pumping, has no effect upon either rate of production or ultimate recovery except through its effect upon pressures. Oil apparently enters wells according to some such equation as the following: R = KC(Pf - Pw)n Where R = rate of production. K = well coefficient, depending upon thickness of sand, and size and number of pores in the sand. C = fluid coefficient, depending upon viscosity, surface tension, etc.

Jan 1, 1929

By S. Y. Ezz

The quality and extent of fluidization of fine iron ore beds with gases were investigated. Factors affecting the rate of reduction with H, and the sintering of the partially reduced material were studied. Trials to retard sintering by covering the particles' surface with nonsintering materials were successful. THE gaseous reduction of iron ores is a gas-solid reaction. Hence the fluidization technique seems ideally suited to it. However, a serious drawback

Jan 1, 1961

By Harry H. Nowlan

A heavy development campaign progressed during the year 1936 in South Texas1, following up important discoveries made in 1935. Oil and gas wells completed during the year were 1473 against 704 in 1935. The drilling program reached its peak of operations in June in consequence of offset requirements made necessary principally in Duval County in the Seven Sisters, Loma Novio, Lopez and Cole fields. There were six new fields discovered during 1936 as follows: Rhode in McMullen County; Peters, El Mesquite and North Kohler in Duval County; Wood in Starr County and Colorado in Jim Hogg County. No discovery of unusual consequence was made during the year. The pools mentioned above are simply in the primary stages of development. The most intensive exploratory work during the year was in Duval, Webb and Zapata Counties. Considerable activity also prevailed in Starr and Brooks Counties. Much significance is attached to the California Company's discovery in the Alta Mesa field in Brooks County, which is considered to be a deep-seated salt dome. The Comitas field, in Zapata County, developed some surprisingly good production in a shallow sand at 900 ft. and is being followed by a heavy wildcat campaign throughout that area in search of like production. In Starr County an active wildcat campaign is in progress in a continued effort to find new fields northwest of the Sam Fordyce field, in Hidalgo County. This play continues in a northerly direction through Starr and Jim Hogg Counties. New Fields Rhode.—The Rhode field, in southeastern McMullen County, was opened in May by the Magnolia Petroleum Co. with a gas well in the Whitsett (Upper Jackson) sand at a depth of 1810 to 1822 ft., this test is located in the southeast corner of sec. 86 on the Rhode ranch. Four gas wells have been completed, proving up a gas area of 1000 acres, more or less. Development will be slow because of lack of market for the gas.

Jan 1, 1937

By Theodore B. Comstock

Prior to 1885, the College of Engineering in the State University was under the care of such professors and instructors as were required for efficient work in the Schools of Mechanical Engineering, Civil Engineering and Architecture. The development of the coal and other important mineral resources of the commonwealth led gradually to a considerable demand for instruction in the branches more closely related to mining engineering, and a very creditable effort was made to meet this want by arranging special work in the field and in the laboratory for students of mining and metallurgy. This plan, while it gave much added labor to several already heavily taxed professors, caused such students to become something like undesirable excrescences upon the regular courses. But its partial success gave abundant proof of the real necessity for a complete course in Mining Engineering. The famous Braidwood disaster emphasized anew the importance of thorough training on the part of those to whom the responsible duties of mining must be confided. As is well known, a very excellent beginning was made some years ago by the Legislature in the matters of inspection and regulation by the enactment of a reasonably effective law, which was afterward much improved.* About the date of the last Acts, it was deemed wise to enlarge the facilities at the University arid to furnish adequate training for the increasing number of applicants. Accordingly, in August, 1885, the writer was requested to assume the duties of the professorship, it being the expressed desire of the Board of Trustees and the Regent of the University that a School of Mining Engineering should be founded which might eventually come to rank with the other engineering schools already flourishing here. It is the main object of this paper to state plainly the steps thus

Jan 1, 1887

By Harry A. Roe

The power drag scrapers and the slackline cableway excavator have been called "long-range excavators." Broadly, their field of usefulness is restricted to work in which their long range of action permits them to operate economically, and which other, possibly more conventional, excavating units cannot do. Both of these machines dig or lift material and transport it to a remote dumping point. They combine these two functions in a single machine, nearly always in a single straight-line motion. The purpose of this paper is to examine the important features that distinguish the machines in this group from each other, as well as from other groups. The Machines The "power drag scraper" is a long-range excavating machine that employs a bottomless drag scraper operated back and forth between digging and dumping points by two haulage cables. The typical arrangement is that of Fig. 1. This is the "slusher" of the underground mine, as well as the "dragline scraper" of the sand and gravel industry, and other open-pit mining operations.

Jan 1, 1938

By W. F. Pruden

On June 30, 1960, ground was broken for the construction of the facilities to mine, concentrate, and agglomerate the iron ores of the Atlantic City, Wyo., area which has become known as the "Atlantic City Project." This was a historic occasion for Columbia-Geneva Steel Division of United States Steel Corp. When completed, the installation will be the first integrated iron ore beneficiation plant west of the Mississippi River producing an agglomerated product. This Project, named for a nearby ghost mining town, is located in central Wyoming on the south-east flank of the Wind River Mountains. It is 16 miles north of the South Pass, where the early pioneers who followed the Mormon and Oregon Trails crossed the Continental Divide. White men first penetrated into this area in October, 1812, when Robert Stuart Party brought the returning Astorians through South Pass on route to St. Louis from the Columbia River area. Further interest in the area developed when gold was discovered in the sands of Rock Creek and the towns of Atlantic City and South Pass City were founded.

Jan 5, 1961

By Harry A. Roe

The power drag scrapers and the slackline cableway excavator have been called "long-range excavators." Broadly, their field of usefulness is restricted to work in which their long range of action permits them to operate economically, and which other, possibly more conventional, excavating units cannot do. Both of these machines dig or lift material and transport it to a remote dumping point. They combine these two functions in a single machine, nearly always in a single straight-line motion. The purpose of this paper is to examine the important features that distinguish the machines in this group from each other, as well as from other groups. The Machines The "power drag scraper" is a long-range excavating machine that employs a bottomless drag scraper operated back and forth between digging and dumping points by two haulage cables. The typical arrangement is that of Fig. 1. This is the "slusher" of the underground mine, as well as the "dragline scraper" of the sand and gravel industry, and other open-pit mining operations.

Jan 1, 1938

By Bryon W. Cheever

The greatest objection to be brought against the present methods for estimating phosphorus in iron and steel, is the time consumed in the operation. The following method, originated and perfected by Mr. E. D. Campbell, assistant in the chemical laboratory of the University of Michigan, will, 1 think, if carefully followed out, give results that are sufficiently accurate for technical purposes, and will give them in less time than they can be obtained by any other process. The process consists in comparing the color obtained by the action of stannous chloride upon a solution of the phospho-molybdate precipitate obtained from the solution of iron or steel, with that obtained from a standard solution of molybdie acid which represents a given amount of phosphorus. The operation is as follows : Take of ordinary steel 1 grm. and treat as in any of the wellknown processes until the phosphorus is precipitated as ammoniumphospho-molybdate. When precipitated, the phospho-molybdate precipitate is filtered out, thoroughly washed with an acid solution of ammonium nitrate, and, finally, twice with water, to remove most of the ammonium nitrate. The precipitate is then dissolved in about 1 c. c. of 10 per cent. potassium hydrate, which is let fall drop by drop on the filter till the precipitate is dissolved ; the filter is now washed with about 25 or 30 c. c. of water, and the potassium hydrate solution, which now consists of 25-32 c. c. of solution, is boiled until the peculiar frothy appearance, which first appears on boiling, is entirely gone. The solution is then cooled until perfectly cold, and about 10 or 15 c. c. of strong hydrochloric acid added ; if the solution is kept cold this will form no precipitate, but a light yellow or colorless solution. The solution is now ready for the addition of stannous chloride, and the subsequent comparison of color produced with that obtained from the standard molybdie acid. The comparison is made in tubes that are calibrated like carbon-tubes, but which are larger, about 5/8-inch bore, and graduated to 100 c. c.; this makes them about 18 inches long. To make the comparison of color, first transfer the now acid solu

Jan 1, 1886

By Bernard Rachlin

IN the mineral industry measurement of density or specific gravity of slurries is often necessary or highly desirable. To date the most successful method of measuring the specific gravity of various media is to hand weigh a constant volume sample of the slurry. This method is time-consuming, however, and is intermittent rather than continuous. Most density measuring instruments in use today are variations of three basic systems: air bubble tube systems, radioactive methods, and displacer systems. The high cost of the radioactive cell, combined with the precision electronic measuring that is required, limits the practical utility of this procedure to a small percentage of critical processes. In the air bubble systems clogging of the bubble tubes with solids has rendered this type of measurement completely ineffectual for many applications. Continuous or intermittent purging of the bubble tubes with air or water to prevent tube clogging has been tried but has not been very successful, especially in the heavy media process. The displacer system, which presents the fewest complications of all the density measuring systems, consists only of a metal immersion unit and a means of weighing it. In the past, settling of the solid in the slurry has caused untrue samples and clogging of the media at the bottom of the chamber. It is also important to dampen excessive flow surges such as those caused by reciprocating pumps. The system described here successfully overcomes these difficulties. Description of the Process System: The process equipment, on which the field tests were run, was a

Jan 1, 1957

By Alex Boozenny

The results of potential measurements between 1) a titaniurn electrode in NaCl-TiCl, melts and a graphite-cizlorine reference electrode and 2) a titanium electrode in NaC1-Nu "melts and a graphite-chlorine reference electrode show that the following relationship expresses the equilibrium relationship between the TiCl, and the dissolved metallic sodium concentrations, expressed in mole fraction units, in dilute NaCl welts at 850°C. The results of potential measurenments between a graphite electrode in NaCl-TiCl, melts that were saturated with TiCl, and a graphite-chlorine reference electrode, when combined with the standard free energy data given in literature, gave the following expression for the equilibrium relationship between the TiCl, and TiCl, concentrations, expressed in mole fraction units, in dilute NaCl melts at 850°C. These relationships are for melts in equilibrium with pure titanium. In impure systems, less sodiurn and more TiCI, can be copresent with a given concentration of TiCl,. AFTER 10 years of existence, the titanium metal industry still relies on the original Kroll and the sodium reduction processes for the only important means of converting titanium-bearing ores to titanium metal via production of titanium tetrachloride as an intermediate. Through years of modification and development these two processes have evolved to a point where any further major economic advances in the field of titanium metal production must be achieved through implementation of processes which are distinct departures from simple magnesium or sodium reduction of titanium tetrachloride. Concurrently with the refinement of the Kroll and sodium reduction processes, industries and government have sponsored research and development in the field of producing titanium by electrolysis of oxides,' carbides,' and halides3'4 in fused salt media. However, the incomplete understanding of the physical chemistry of fused salt systems has in many cases hindered the development of promising new titanium production processes to the point where they will have a clear advantage over the processes presently employed. Fortunately the volume of information on fused salt physical and electrochemistry is increasing at an accelerating pace. The first approaches tbward investigating the electrochemical behavior of fused salt systems have been the measurements of equilibrium potentials of metals immersed in melts containing their halides.' Some work on the kinetics of fused salt electrochemical processes has been reported.'09" Some descriptions of the structural composition of fused salt systems are also available. The work described herein is a continuation of the study of metal electrode potentials in fused salts. Specifically, this contribution to the growing store of fused salt chemistry information presents a description of the equilibrium relationships between the concentrations of titanium dichloride, titanium trichloride, and metallic sodium in fused sodium chloride. The investigation of the titanium dichloride-titanium trichloride equilibrium relationships is not completely new. Kellog and Krye and Melgren and opie15 have presented the results of chemical analysis of salts containing titanium chlorides. Flengas and lngrahaml' have published the results of an investigation of these equilibrium relationships obtained by measurement of electrode potentials in a fused NaCl-KC1 mixture. The investigation described herein differed from that of Flengas and Ingraham principally in the use of straight NaCl as the solvent in place of the more costly and more difficult to purify mixture. This investigation was conducted in three parts. First, the equilibrium potentials of titanium in sodium chloride containing known concentrations of titanium dichloride were measured. A graphite-chlorine electrode was employed as reference. Second, the equilibrium potentials of titanium immersed in sodium chloride containing known concentrations of elemental sodium were measured. Third, the equilibrium potentials of graphite immersed in titanium tetrachloride-saturated sodium chloride containing known concentrations of titanium trichloride were measured. The results of these three related investigations are presented in the above order. The results are combined with the thermodynamic properties of titanium chlorides and sodium chloride, obtained from literature, to give the titanium dichloride-titanium trichloride-elemental sodium equilibrium concentration relationships. In the test, whenever a melt contains titanium chlorides in predominantly divalent form, the melt

Jan 1, 1962

By Howard M. Wells

The investment worth of a mineral deposit can only be realistically evaluated in relation to specified engineering design criteria which fully detail the proposed method of exploitation. The operational design of a mine falls essentially within the technical discipline of the mining engineer, under the constraint that the technical design should be aimed at optimizing the financial attractiveness of the project. In the case of a marginally viable proposition it becomes vitally necessary to identify the best set of design parameters which together will add up to an optimum investment proposal. This paper examines some fundamental logic of optimization for a "wasting asset" type of investment such as a mine, with special reference to the rate of annual production and the strategy of selective mining.

Jan 1, 1979

By H. E. Hostetter

GROSSMANN'S method1 for calculating the hardenability of steel from the composition and grain size has gained wide acceptance, and when properly used, has been well proved in practical application, both for estimating the hardenability of known compositions and for selecting compositions to meet known hardenability requirements. The Grossmann method uses as the criterion of hardenability the "ideal critical diameter," DI, which is the size round that will just harden to a structure of 50 per cent martensite at the center when given the theoretically fastest quench, or "ideal quench." The DI can be related to actual quenching practice if the severity of quench is known; or the DI can be correlated with hardenability as determined by the Jominy end-quench method.2 The effect on hardenability of each element present in a steel can be represented by a multiplying factor, the value of which depends on the amount of the element present and the degree of effectiveness of the particular element. (The value of the factor for a given carbon content varies with the grain size.) When the factors for all elements present in a steel have been determined from charts, they are multiplied, and the resultant product is the D, of the steel. The validity of Grossmann's scheme of multiplying factors has been confirmed in a number of other investigations.3 -6 It can be appreciated that a certain desired level of hardenability can be obtained by adding chromium, molybdenum, nickel and vanadium to a base composition containing carbon, manganese, silicon and the usual impurities. Many of the ranges of hardenability used commercially can be obtained by any of the foregoing alloying elements used singly in the base composition. The same hardenability levels also can be obtained through use of any of a great number of multiple element combinations of these alloying elements. In this report a method will be presented for determining what one combination is the most efficient (based on hardenability and cost of added alloy) for a given level of hardenability. It should not be assumed from the emphasis given to hardenability, that hardenability is the only criterion for the selection of an alloy composition. Such properties as the hot-working characteristics, machinability, carburizing characteristics, amount of distortion during quenching and the retention of austenite may be considerations of importance in many applications. However, hardenability is one of the most important properties of an alloy steel and one that must be considered in almost all cases involving heat-treatment by quenching. Therefore, a method for determining the lowest-cost alloy combination should be of considerable value. DETERMINATION OF MOST EFFICIENT COMBINATIONS For comparing the alloying elements on standards of cost and hardenability, it

Jan 1, 1945