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By Fred H. Poettmann

An equation has been derived for use in calculating the sandface pressure of flowing gas wells in which the variation of the compressibility factor of the gas with pressure is taken into consideration. This variation due to compressibility has been put into both graphical and tabular form. Comparison of calculated results with field measured results were made on 20 dry gas wells from a given field and 11 distillate wells from different fields. The agreement between calculated and observed results is good. In addition to their use in the calculation of sandface pressures of flowing wells, the factors can be used in the direct calculation of the static bottom hole pressure of gas wells, the capacity of gas transmission lines, and in the calculation of the theoretical isothermal horsepower necessary to compress a natural gas. Examples demonstrating the use of various equations are given. INTRODUCTION Many of the equations used to calculate the sandface pressures of flowing gas wells from well head data do not take into consideration rigorously the deviation of the natural gas from ideal gas behavior. For low pressure wells this error is not serious. For high pressure wells flowing at high rates this error call be serious. Sandface pressures are used to determine the producing capacity of gas wells as shown in the U. S. Bureau of Mines' Monograph 7.' An equation has been derived for use in calculating the sandface pressure of flowing gas wells in which the variation of compressibility of the gas with pressure is taken into consideration. This variation due to compressibility has been put into both graphical and tabular form. In addition to their use in the calculation of sandface pressures, these "factors" can also be used to give a direct solution in the calculation of the static bottom hole pressure of gas wells, the calculation of the capacity of gas transmission lines, and the calculation of the isothermal horsepower necessary to compress a gas. CALCULATION OF SANDFACE PRESSURE OF FLOWING GAS WELLS The starting point in the derivation of any specific flow equation is an energy balance on the fluid flowing between any two points in the system. This energy balance based on one pound of flowing fluid is expressed by the well known general flow equation: jp~- vdP+ Ah + -— + wt + r. = o . . (i) P, 2 g. where V = specific volume of flowing fluid in cu ft/lb P = pressure in Ib per sq ft ah = difference in height above datum plane in, ft ------ = kinetic energy change of one lb of flowing fluid, v equals velocity in ft/sec and g. = 32.174 Ws = Work done by fluid while in flow (similar to shaft work in driving a turbine) W, = Znergy losses due to the irreversibilities of the flowing fluid This equation contains no limiting assumptions and can be made the basis of any fluid flow relationship by limitations or substitutions. The energy units are usually expressed in term* of foot-pounds of energy per pound of mass. Considering the vertical flow of gas through tubing or annu-lus, the external work W, done by the gas is zero. Let us also assume that the value of the kinetic energy function is small and can be neglected. Equation (1) is reduced to: /P: VdP + Ah+Wt = 0 .......(2) Pi The energy loszes PI can be expressed in terms of the well known Fanning equatinn: 4/Lf: rf = —— ............(3) 2g,D where L = the integrated average velocity in ft/sec of vertical flow in a uniform flow string -~h = L v = the integrated average velocity in ft/sec / = dimensionless correlating function

Jan 1, 1951

By Fred H. Poettmann

An equation has been derived for use in calculating the sandface pressure of flowing gas wells in which the variation of the compressibility factor of the gas with pressure is taken into consideration. This variation due to compressibility has been put into both graphical and tabular form. Comparison of calculated results with field measured results were made on 20 dry gas wells from a given field and 11 distillate wells from different fields. The agreement between calculated and observed results is good. In addition to their use in the calculation of sandface pressures of flowing wells, the factors can be used in the direct calculation of the static bottom hole pressure of gas wells, the capacity of gas transmission lines, and in the calculation of the theoretical isothermal horsepower necessary to compress a natural gas. Examples demonstrating the use of various equations are given. INTRODUCTION Many of the equations used to calculate the sandface pressures of flowing gas wells from well head data do not take into consideration rigorously the deviation of the natural gas from ideal gas behavior. For low pressure wells this error is not serious. For high pressure wells flowing at high rates this error call be serious. Sandface pressures are used to determine the producing capacity of gas wells as shown in the U. S. Bureau of Mines' Monograph 7.' An equation has been derived for use in calculating the sandface pressure of flowing gas wells in which the variation of compressibility of the gas with pressure is taken into consideration. This variation due to compressibility has been put into both graphical and tabular form. In addition to their use in the calculation of sandface pressures, these "factors" can also be used to give a direct solution in the calculation of the static bottom hole pressure of gas wells, the calculation of the capacity of gas transmission lines, and the calculation of the isothermal horsepower necessary to compress a gas. CALCULATION OF SANDFACE PRESSURE OF FLOWING GAS WELLS The starting point in the derivation of any specific flow equation is an energy balance on the fluid flowing between any two points in the system. This energy balance based on one pound of flowing fluid is expressed by the well known general flow equation: jp~- vdP+ Ah + -— + wt + r. = o . . (i) P, 2 g. where V = specific volume of flowing fluid in cu ft/lb P = pressure in Ib per sq ft ah = difference in height above datum plane in, ft ------ = kinetic energy change of one lb of flowing fluid, v equals velocity in ft/sec and g. = 32.174 Ws = Work done by fluid while in flow (similar to shaft work in driving a turbine) W, = Znergy losses due to the irreversibilities of the flowing fluid This equation contains no limiting assumptions and can be made the basis of any fluid flow relationship by limitations or substitutions. The energy units are usually expressed in term* of foot-pounds of energy per pound of mass. Considering the vertical flow of gas through tubing or annu-lus, the external work W, done by the gas is zero. Let us also assume that the value of the kinetic energy function is small and can be neglected. Equation (1) is reduced to: /P: VdP + Ah+Wt = 0 .......(2) Pi The energy loszes PI can be expressed in terms of the well known Fanning equatinn: 4/Lf: rf = —— ............(3) 2g,D where L = the integrated average velocity in ft/sec of vertical flow in a uniform flow string -~h = L v = the integrated average velocity in ft/sec / = dimensionless correlating function

Jan 1, 1951

By M. P. Tixier, A. Poupon, M. E. Loy

Simple qualitative methods are explained for identifying those shaly sands in a well that are most likely to contain oil. A need for more precise measurement of the variables that enter shaly sand analysis is indicated. Field examples are given to illustrate the methods. A theoretical discussion of the quantitative interpretation of shaly sands is given as a basis for discussion and as a guide for the future. While not generally capable of practical application at the present time because of the lack of sufficient accuracy of the electric log data, these methods may become more feasible in the future as the result of the improved logging methods now being introduced. INTRODUCTION Experience has shown that for porous formations containing only a negligible amount of clayey material, reliable information on the fluid saturation and porosity of the reservoir rocks can usually be derived from the electrical logs. The interpretation is based on empirical formulae relating the true resistivity of a porous formation to its lithologic character, to the resistivity of the interstitial water, and to the proportions of water and hydrocarbons in the pores.' If the resistivity of the interstitial water is not known, its approximate value can be derived from the SP curve.2,3 The porosity can usually be determined to a good approximation from a MicroLog, or a MicroLaterolog.4,5 When the reservoir rocks contain an appreciable percentage of clayey material, an additional factor is introduced into the analysis. In a clean formation, the matrix is an electrical insulator, so that the ability of the formation to conduct current is due only to the conductivity of the electrolytes in the pores; in a shaly formation, the shale constitutes a part of the rock matrix able to conduct current, and influences the resistivity of the formation. On the other hand, the spontaneous emf's and the circulation of the SP currents are also responsive to the presence of the shaly material. All other factors being the same, the deflection of the SP curve opposite a shaly permeable formation is smaller than the deflection which would be observed if the formation were clean. The effects of the presence of shale on the resistivity and on the SP curves in a shaly formation are functions of the amount, of the specific resistivity, and of the geometrical distribution of the shaly material within the formation. The presence of shale therefore constitutes an important complication in electrical log interpretation. It is easy to realize, for example, that the presence of a large amount of clayey material in a sand may have such a predominant effect that the resistivity of the sand will not change very much, whether the pores are entirely filled with connate water, or contain a high saturation of hydrocarbons. Important research projects have been undertaken to investigate the influence of shales and to find a way to allow for this influence in the interpretation of a log. The problem of the SP in shaly sands was analyzed mathematically by H. G. Doll"' for the case of sands with shale laminations. Formulae expressing the resistivity of shaly formations were proposed by Patnode and Wyllie8 and de Witte.9 Other quite interesting theoretical and experimental results have been published by various authors.l0,ll,12,l3,14 The purpose of the present paper is to discuss an approach to electrical log interpretation in shaly sands. This approach is based partly on some of the theoretical and experimental data available in the literature and partly on observations made on actual field logs. Comparatively simple methods for qualitative and semi-quantitative analysis are described. These methods depend principally upon information provided by the electrical logs.

Jan 1, 1955

By N. L. Carwile, G. W. Geil

A metallographic study was made of deformation twinning (Neumann lamellae) in ingot iron slowly deformed in tension at —196O and —150°C. The results showed that twinning is initiated mainly during the initial stages of plastic deformation. However, the breadth of the twins generally increases with increase in strain up to fracture of the specimen. HE results of an investigation of the effect of low I temperatures on the flow, fracture, strain hardening, and strain aging characteristics, and the true stress-strain relationship for specimens of ingot iron deformed in tension were reported recently.1,2 In that study specimens of ingot iron, in different initial conditions, were slowly deformed in tension at various temperatures between —196" and +100°C. A phenomenon observed, but only briefly reported, was the formation of deformation twins (Neumann lamellae) in the specimens deformed at the lower temperatures. Preliminary metallographic examination of these specimens indicated that there was apparently some correlation between the deformation twinning and the strain of the specimen and that this factor merited further investigation. Some recent investigations have indicated a direct association of Neumann lamellae and the fracture of the metal. Bruckner".' * postulated that the twinning immediately precedes the fracture and the latter is initiated by the stopping of the propagation of twins, either at subgrain boundaries or at other structural features. Tipper and Sullivan5 postulated that Neumann lamellae are initiated by the shock or a shock wave set up at fracture in the still highly stressed unbroken metal, and that a high rate of deformation is a necessary condition for their formation. An extensive metallographic examination, therefore, was made of many of the specimens used in the study of ingot iron at this Bureau and of additional specimens deformed to selected strains under various conditions. The present paper summarizes the effects of deformation under these conditions upon the breadth and scope of the deformation twins. Other features of twinning will be discussed in another paper. Material and Testing Procedure All of the specimens were prepared from one lot of ingot iron, as hot-rolled, of chemical composition other than iron as follows: C, 0.02 pct; Mn, 0.02; P, 0.005; S, 0.018; Si, 0.002; Cu, 0.10; 0, 0.058; and N, 0.002. Cylindrical tensile specimens with a 2 in. gage length were used. The reduced section was slightly tapered from each end; the diameter (0.438 in.) at the midsection of the gage length was about 0.003 in. less than at the ends. The specimens were finished to the final dimensions by grinding and polishing in the axial direction. The ends of the specimens were machined with 3/4 in. x 10 threads and the shoulder fillets were machined to a radius of 0.75 in. The specimens were extended slowly in tension (deformation rate less than 0.5 pct reduction in area per minute) while immersed in an appropriate cryogenic liquid maintained at the desired temperature. The minimum diameter of the specimen was measured during the test by means of a specially designed reduction of area gage accurate to 0.0001 in." A detailed description of the testing equipment and the method of maintaining the desired temperature is given in a previous paper.' Each specimen, after deformation to a specified strain at a selected temperature, was sectioned longitudinally and examined metallographically. The preparation of specimens for metallographic examination was carried out in the usual manner by mechanical polishing and etching. Results and Discussion Deformation twins in specimens of ingot iron extended slowly in tension at —196" and —150°C are shown by the representative micrographs of Figs. 1

Jan 1, 1954

By R. M. Fowler, H. L. Hamner

DURING the last 25 years, there appeared in the literature a number of papers describing equipment and operating techniques for the determination of total oxygen in iron and steel. In the early papers, comparatively little attention was paid to side reactions that occur when iron is saturated with carbon at a high temperature in a high vacuum. As more experience was gained with the new method, the limitations appeared. Metals, with a boiling point lower than iron, distilled out of the crucible, condensed in the cooler part of the furnace, and subsequently reacted with carbon monoxide to form oxides and carbon. Aluminum, manganese, and the alkaline earth metals proved troublesome in this respect. Modifications have been devised to overcome the difficulties due to aluminum and manganese, while the alkaline earth metals are not of too much concern as yet to the steel chemist. The reactions of sulphur have received less attention, although it is generally recognized that some carbon disulphide is probably formed. Liquid air traps have been used in some cases to prevent any carbon disulphide from entering the analytical train. Sulphur was not a particular problem at the Union Carbide and Carbon Research Laboratories until the analysis of the irons of higher than usual sulphur contents became necessary. In order to describe the procedure developed for such irons, it will be necessary to first describe the type of vacuum-fusion equipment employed because the operation of vacuum-fusion equipment is an art to a considerable extent. At the Laboratories, vacuum-fusion equipment has been in daily operation since about 1930. Over the years, the evolution of this apparatus has been governed by the versatility required to analyze a wide variety of materials. Since all types of materials from high purity metals to slags are analyzed and, since seldom more than a few samples of one type are analyzed in succession, the apparatus was designed for accuracy and flexibility rather than for speed. A general view of the equipment is shown in Fig. 1, while Fig. 2 shows the relationship of the various parts. In Fig. 2, A is a vertical double-glazed 24X27/8 in. OD silica tube heated with a 20 kva mercury-arc high frequency generator. The tube is closed with a water-cooled brass head attached with de Khotinsky cement. A turret cap fits on this head and is sealed with a 1/8x3 in. "0" ring. The head contains a sight glass and two 8 in. horizontal glass tubes, for sample storage, cemented in with de Khotinsky cement. B is a four-stage Gaede mercury diffusion pump connected to the water-cooled head with a 11/2 in. copper tube through a flange with an "0" ring. The output of the vacuum pump feeds into an automatic Toepler F pump which compresses the gas sample over mercury in the measuring burettes, G and H. There are bypasses in this line for a McLeod gage C and a Piranni gage D, a manometer E, and for initial pumping out of the system with a Cenco Megavac backing-up pump. The reduction crucible shown in Fig. 3 is machined of Tungar Bulb quality (A.G.K.T.E.-2) graphite. The sample is guided into the crucible with the graphite funnel depicted on this figure. The arrangement of the crucible, radiation screens, etc. in the furnace is as follows: A 1 15/16x61/2 in. Alundum thimble, porosity RA-84, with two 1/8 in. holes near the top and opposite each other which take a pair of special tongs used for lowering it in place, is prepared. A 3/4 in. layer of powdered graphite is placed in this Alundum thimble, and the graphite crucible containing 20 g of ingot iron and 0.5 g of carbon is carefully centered on this bed of graphite powder and graphite powder is packed around it to the top of the graphite cru-

Jan 1, 1953

By George W. Crawford, W. P. Aycock, E. W. Hough

Forty oilfield brines have been examined so far by a polarographic technique new in petroleum engineering called the "tensatnmetric method" by the team of biochemists who perfected its use in their field. Samples of brine were obtained from various oil fields in which the wells were known to be producing fluid from oil productive zones in well-known geologic formations. Most of the reservoirs from which the samples were obtained are believed to have an active water drive under the prevailing conditions of operation. The 40 samples represent brines produced front 16 different formations of various geologic ages. Graphs have been prepared of the data obtained in the testing of each sample, and the distinctive waife-like curves so obtained are characterized by reproducible profiles, called "response curves." Careful comparison of the response curves of salt water coming from different fields producing from the same geologic formation reveals that the curves are similar. The response curves of salt water coming from productive zones of different geologic formations are characteristically different. Preliminary work offers the further hope that response curves of an oilfield brine indigenous to a particular oil-bearing formation and hence representative of a particular geologic environment, such as deposit-ional and all subsequent morphological conditions, may be of value in reservoir engineering in the interpretation of surface and interfacial phenomena. For example, the wettability of the rock matrix and more specifically, the classification of productive oil-bearing strata as hydrophyllic or hydrophobic may be determinable. However, many more brines must be examined and the resulting response curves analyzed in comparison to known causal phenornena before this objective is achieved. INTRODUCTION One of the perennial moot questions in the literature of petroleum engineering is whether the reservoir rock is oil- or water-wet. Possibly an answer to this question could come from a careful examination of oilfield brines. None of the conventional methods of examining brines (chemical analysis, pH and electrical conductivity measurements, and the like) answer the question. Careful analysis of reservoir behavior observed in the exploitation of oil fields, particularly in the application of fluid injection, has been fruitful to the extent that a few reservoirs are believed to be properly classified. Physical chemistry suggests the behavior of reservoir brine and rock may be due to something in the brine in small amount. The ever increasing development and modification of theory in the general field of surface and interfacial chemistry has, and is, contributing to a better understanding of the problem, particularly as theory is verified by data. The work herein reported was begun in 1953 by Hough and Roebuck 1,2 who employed a new form of alternating current polarography, i.e., tensammetry, developed by Breyer, et a13,4 and who studied eight oilfield brines in adapting tensammetry to petroleum engineering needs. THEORY AND DEFINITIONS Tensammetry is a new technique of inquiry into surface phenomena. Specifically, a weak alternating current voltage is superimposed upon the direct current voltage applied to a dropping mercury electrode in contact with an electrolyte containing a small amount of a surfactant. The resultant alternating current can be measured and provides the experimental data for this new area of research. Under the influence of the direct current voltage, polar molecules arrange themselves in a double layer at the electrode. This double layer may be compared to a variable condenser, the capacitance of which is a function of the imposed direct current voltage. The direct current voltage determines the degree of adsorption of the surface active molecule on the electrode. Whenever the molecules are strongly adsorbed on the electrode, the capacitance of the double layer is low and the alternating current through the cell is low. Desorption occurs at some values of the direct current voltage, and at these voltages the capacitance of the double layer is high, resulting in an increase in the alternating current through the cell. The direct current

Jan 1, 1958

By W. H. Yarroll

This paper presents a general discussion of the utility of the statistical technique known as multiple correlation, and gives three specific examples of its application. The first demonstrates the most simple form, or straight-line, multiple correlation. The other two demonstrate multiple correlation analysis in best-fitting third-degree parabolas. With the increasing availability of digital computers, the method becomes entirely feasible where heretofore its use was impractical. The advantages of the method are discussed, and curves are presented which were developed by computerizing the regression equations developed in the examples. The method described in this paper is for use with complex systems, and the examples given are complex metallurgical systems. This subject falls under the general classification of cybernetics, which is defined' as "the science of control and communication, in the animal and the machine." Machine, in this case, can include chemical and physical processes which take place within machines and processing equipment of all kinds. The classical approach to scientific investigation has been the construction of simple models and the changing of variables one at a time. This method is wholly inadequate for obtaining useful information from the complex systems of modern technology including many of our flotation and hydrometallurgical processes. Cybernetics offers the method by which complex systems which have been implemented as an art in the past can now be analyzed with all the discipline of a science. Mathematical techniques for achieving multiple correlation analysis have decided advantages over some of the other statistical methods.2-4 Multiple correlation does not require a series of experiments that have been rigidly planned as do many of the other statistical methods. For this reason, it can be used effectively for interpretation of information from op- erating plants, where planned experiments are impractical, as well as for laboratory experiments. First-degree multiple correlation has been used for many years, and was useful, but limited to linear or nearly linear relationships. The technique described in this paper provides a method for analyzing systems which may be non-linear. This particular technique is multiple correlation analysis in best-fitting third-degree parabolas. It is quite possible that lack of reference to the technique has been due to the overwhelming mass of computations it requires even for relatively simple problems. With the advent of computers, however, its use has become entirely feasible. For the benefit of those who may not be familiar with the subject, it might be well to pause at this point to discuss multiple correlation analysis — what it is and what it achieves. To go back to the old familiar fitting of a set of points with a best-fitting straight line by the least squares procedure, it is conceded that this a good method where there is only one independent variable influencing the dependent variable under consideration, and providing that the relationship is linear. In most fields of investigation, however, there are usually a number of factors exerting important influence, and they frequently bear relationships with the dependent variable other than straight line. Under these conditions, it is easy to see how misleading a simple correlation study might be. Multiple correlation can be used for any number of variables. Within the experience of the writer, this technique has been used to establish regression equations for determination of carbon rate, burden permeability, and production rate on iron blast furnaces, production rate on open hearth steel furnaces, life of molds for steel ingots, rolled steel tensile strength and various defects in rolled products, the performance of ore dressing equipment, and optimization of extractive metallurgical process variables. The discovery of mathematical correlation does not prove, per se, true cause-and-effect relationship, but simply establishes a hypothesis. If the regression equation can be used to make successful predictions of what will happen with future arrays of independent variables, then one can feel reasonably assured that true cause-and-effect relationships have been discovered.

Jan 1, 1968

By D. R. Walker, M. C. Shaw

Dimitri Kececioglu (Allis-Chalmers Manufacturing Co., Milwaukee)—The idea of applying metal cutting theory to comminution and vice versa is very impressive. Among others, the demarcation of wheel-grinding data into two regions, namely Kick's and Rittinger's, draws attention here. A study of Figs. 6 to 9 shows the following: In Fig. 6, 1 point out of 8; in Fig. 7, 4 points out of 26; in Fig. 8 only 1 point out of 13; and in Fig. 9 practically none out of 13 points fall out of curve No. 2. Also when grinding particles smaller than 5x10." in. it is difficult to measure very accurately the grinding forces, chip geometry, and particle size. In view of the above it would be difficult to make a positive and distinct demarcation of the Wheel-grinding data into two regions, namely, Kick's and Rittinger's. The idea of using machine grinding to determine the comminution properties of materials is indeed unique. The following cautions come to mind, however, regarding applicability of machine grinding data to comminution: 1—Grinding gives uniform particle size, whereas comminution gives a variety of particle sizes in the same process. The fact that grinding gives uniform particle size is not necessarily an advantage because in comminution the overall energy under actual comminution is desired and comminution invariably results in the production of a variety of particle sizes. 2—In grinding, a small particle is ground off a comparatively large surface. In comminution small bodies are broken down to smaller bodies. This makes it difficult to establish a concept of reduction ratio in machine grinding. 3—The mechanics of machine grinding involve direct shearing action under very high strain and comparatively high compression at the shear zone, whereas: comminution involves direct dynamic compression and surface friction with comparatively little strain and shear. Consequently the mechanics of machine grinding appear to be different from those involved in comminution. Hence one might arrive at erroneous con- clusions when comminution characteristics are eval-uated from machine grinding results. It is noticed also that functions other 'than Eq. 16 which do not involve the concept of direct proportionality of useful energy input to new surface area created (Eq. 2 and particularly Eq. 12) may be derived to fit the, data of curve No. 2. One such relationship may be u = ct-", where c is a positive constant and n is a positive constant less than unity. This, of course, is made possible because data of a very small range. of particle size are being fitted by the curves of No. 2 and the hereby suggested relationship. A sound comminution theory should be applicable to a relatively large range of particle size. George B. Clark (Department of Mining Engineering, University of Illinois)—While the experimental work of Walker and Shawin this article is of intrinsic value in revealing certain fundamental aspects of machine grinding, milling, and related processes and in adding to the store of information concerning the comminution of solid materials by this particular process, it appears doubtful that the results of their research can be employed to verify either Kick's or Rittinger's theories. Both these laws were originally developed and proposed on the basis of very simple, idealized hypotheses. The creation of parallel idealized physical laboratory conditions which would be required for either their proof or disproof appear to be well beyond the scope of human ingenuity, at least at present. One great weakness of the imputed verification is that the spread of the points plotted on the graphs is not sufficient to permit accurate 'curve fitting. The range of particle sizes included in the belt and wheel grinding is not extensive enough to show any general trends, particularly for the horizontal portion of the curves, said to represent Kick's laws. That the milling; grinding, and turning data obtained by Walker and Shaw for both metals and minerals happen to comply with. certain interpretations of these two theories under certain specialized conditions

Jan 1, 1955

By L. A. Roe, E. A. Elevatorski

Wollastonite, named after William H. Wollaston, an English chemist, is a calcium metasilicate, CaSiO3; CaO: 48.30%, SiO2: 51.70%. It has a short history as an industrial mineral. The earliest production of wollastonite is reported to be from a deposit near Code Siding, located north of Randsburg, CA. At this locality small tonnages of wollastonite were quarried during 1933-34 and 1938-41, and processed into mineral wool. This operation was largely experimental and virtually no United States production was again reported until the 1950s when a large deposit near Willsboro, NY, was developed by the Cabot Corp. A processing plant was placed onstream in 1953, with nearly continuous production to date. It is currently operated by NYCO, a division of Processed Minerals, Inc. Since 1958, wollastonite deposits in the Little and Big Maria Mountains of Riverside County, and in the Panamint Range of Inyo County, both in California, have operated intermittently for production of both ornamental and commercial wollastonite. During 1980, the United States was the major producing country, furnishing about 75% of the world's output. Current production comes from Finland, Mexico, India, and Kenya. Small amounts have been shipped intermittently from the USSR, New Zealand, Republic of the Sudan, Republic of South Africa, and Namibia (South-West Africa). The principal use of wollastonite is in the manufacture of plastics. Other uses are for paints, ceramics, adhesives, fluxes, glazes, thermal insulation board, and refractory products. Mineralogy Pure wollastonite, CaSiO3, has the composition of 48.3% CaO and 51.7% SiO2. However, it is seldom found in the pure state due to the ease with which it takes into solution the metasilicates of manganese, magnesium, iron, and strontium. Predominantly, wollastonite occurs as a contact metamorphic deposit forming between limestones and igneous rocks. Commonly associated minerals are garnet, diopside, epidote, calcite, and quartz. It has a specific gravity of 2.8 to 3.0, and hardness of 4.5 to 5 on Mohs' scale. When pure, it has a brilliant white color, but with impurities it may be grayish or brownish. Luster is vitreous to pearly. Melting point of wollastonite is about 1540ºC. Wollastonite occurs in coarse-bladed masses, rarely showing good crystal form. It is usually acicular or fibrous, even in the smallest of particles. The most unique property of crushed and ground wollastonite is its cleavage. Fragments of crushed wollastonite tend to be needle-shaped, imparting a high strength, and this property is the basis for many of its uses. The fiber lengths are commonly in the ratio of 7 or 8 to 1, length to diameter. The average diameter of wollastonite is 3.5 µm. Some crystals of wollastonite fluoresce under short-wave or longwave ultraviolet light, or both, with colors ranging from yellow-orange to pink-orange. Specimens may also show phosphorescence. The acicularity of wollastonite is a property of considerable importance to the marketplace. The plastics industry makes utilization of high aspect ratio grades of wollastonite (20:1) for reinforcing thermoplastics and thermoset polymer compounds. The naturally high pH of 9.9 (10% water slurry) is a prime property to the coatings industry. The coatings industry uses milled grades of wollastonite as a pH stabilizer in interior and exterior PVA and acrylic latex systems. Processed wollastonite can have a G.E. brightness of 90 to 93. Chemically, wollastonite is inert and this property makes it useful as a filler and reinforcing agent. There are two polymorphs of calcium silicates: wollastonite, a low temperature form, and pseudowollastonite, a high temperature

Jan 1, 1983

By John S. Brock

INTRODUCTION The Oxford Dictionary says that the word "promoter" has usually been used in an opprobrious sense since at least 1876. This popular image of mining promoters is of cigar-chomping shysters and Brooklyn-Bridge vendors, improving their standard of living with the aid of funds raised through the sale of stock to little old ladies. It is unfortunate that mining promoters are considered crooks until they can prove their integrity and honesty by finding a mine. A common rule of thumb states that for every 1,000 prospects, 100 come to be drilled, and one becomes a mine. However, it is also a statistic that there have been mining promotions, where money raised has gone elsewhere than into the ground; Junior exploration companies can be handy vehicles for unscrupulous financial activity. One must remember though that every stock exchange has had its share of sound mining promotions that, because of the one in 1,000 odds, have failed for legitimate reasons. The promoter must be able to rationalize the worth of a mineral discovery which, on an industry- average basis, probably cost more to find than the discounted value of its net return, which return is not an assured percentage of invested capital, and furthermore, is ultimately from a wasting asset. So, it is easy to understand why the promoter must constantly justify the credibility of his operation to his grubstakers during the course of the "five phases of exploration," those being (1) euphoria, (2) disillusionment, (3) search for the guilty, (4) punishment for the innocent, and (5) distinction for the uninvolved. The promoter with the exploration organization that does not have the benefit of positive cash flow, by definition for the sake of this article, works for a promotional outfit, a Junior Company, that must raise its exploration budget from a variety of sources. Promotion, as discussed here, will not entirely refer to the formation and operation of a joint- stock company but rather to the overall methods of raising risk capital for mineral exploration ventures from outside sources. THE NECESSITY OF PROMOTION In Canada, the publicly financed Junior Company has had an enviable record of mine-finding success. In the Province of British Columbia alone, the discovery of fifteen out of twenty-four mines has been as a result of the activity of the Junior Company (B. C. & Yukon Chamber of Mines, 1977). In the Province of Ontario, one research study indicated that between 1951 and 1974 the 'Juniors' spent only 28 percent of the total exploration funds but were responsible for 62 percent of all economic discoveries (Freyman, 1978). The reasons for the success of the Juniors are tied to a variety of factors, the main one being personal initiative based on incentive. In other words, the principals, or their employees have 'a piece of the action.' The smaller companies can operate faster and more efficiently than their larger counterparts. The Junior Company is also destined to take some bigger risks, the 'long shots,' many of which efforts by virtue of the Junior's perseverance coupled with a touch of 'ore is where you find it' philosophy, result in major discoveries. The individuals, syndicates, private and publicly financed Junior Companies, because of high costs of exploration and development, cannot hope to finance most mineral prospects all the way to production. Exceptions do exist, those being the lower capital cost, small, high-grade deposits. Private investors and publicly financed Junior companies, therefore, can usually afford to finance most exploration through the initial drill-testing stage. The major resource company will enter a mining deal with a Junior Company usually by way of option or joint venture agreement, and will finance to production to earn an equity in the prospect or the Junior Company or both. The conventional lending institutions, banks and government agencies, will usually only participate through loaning a portion of capital

Jan 1, 1985

By T. M. Morris

THE rate of flotation of solid particles determines the percentage recovery of these particles which can be obtained during a given time interval. It is an established fact that the recovery is greatest in the fine sand size range and falls off on either side of this size range. It is also a fact that the history of the development of concentrating devices has been marked by a desire to recover the small particles: tables were developed to treat material too fine to recover in jigs; flotation recovers material too fine to be recovered on tables. As our ores become more complex and require finer grinding, a greater proportion is in the slow-floating size range. It is therefore of economic importance that the effect of size of particle upon rate of flotation be studied. Many studies have been made along this line. The present investigation attempts to quantify the rate of flotation by means of a rate equation, and then compares the effect of size upon the rate of flotation. It was found that the flotation rate constant increases with increase in diameter of particle in the size range smaller than the optimum size particle. The flotation rate constant decreases with an increase in diameter of particle in the size range coarser than the optimum size particle. This suggested two different actions taking place, and these are discussed. Suggestions for further work in order to improve the flotation rate of both fine and coarse particles are made. The usual method of expressing rate is to plot cumulative percent recovery vs time. If we knew the equation of this kind of curve we could replot it as a straight line, and the slope of the line would be an index of the magnitude of the flotation rate. It is easier to compare straight lines than curves. The basis used for obtaining the equation of the recovery vs time curve is the law of mass action. This law states that the "rate of a chemical reaction is proportional to the `active masses' of the reacting substances present at any given time." This, of course, implies a constant temperature. We can modify this for our use by using the term flotation reaction instead of chemical reaction and the term floatable particle instead of active masses. [ ] where C denotes concentration of particles, t denotes time, k denotes a proportionality constant. If the exponent of C is 1, then we have a first order rate reaction. If the exponent of C is 2, then we have a second order rate reaction. For a first order rate reaction, we obtain, after integration, [ ] where k is again a proportionality constant and has the dimension of the reciprocal of time. C, is the original concentration or weight or percentage of floatable particles. C, is the concentration or weight or percentage of floatable particles remaining in the flotation cell after time t. If all particles of the mineral to be floated were capable of floating we could take C, as 100 and C, would be 100 - R, where R is the cumulative percentage recovery of mineral at time t. But it is not usual for all of the particles to be capable of floating, because of surface oxidation, etc. Therefore, we must introduce a factor x which is the percentage of unfloatable mineral. Hence the first order equation is [ ] It has been proposed by various workers1-3 that this equation describes the flotation rate. More recently N. Arbiter4 states that a second order rate equation fits the recovery vs time curve more closely than does a first order rate equation. Morris' has discussed the evidence presented for this statement. It has been concluded that the first

Jan 1, 1952

By A. W. Schlechten, C. M. Hsiao

The apparent vapor pressures of a number of metal sulphides were determined by measuring their rate of weight loss when they were heated under vacuum. The calculated pressures are due in some instances to the volatility of the sulphide and in others to the decomposition pressure. FIE direct reduction of metallic sulphides, as in the precipitation method for lead or antimony, is not a widely used process today. However, it might be employed for the production of a number of metals if the operation were carried out under reduced pressures. Two general procedures are possible; the reducing agent could form a stable nonvolatile sulphide from which the valuable metal could be removed by volatilization or liquation. The other approach would be to choose a reducing agent which would form a sulphide that could be volatilized away from the valuable metal. A vacuum operation would serve to protect the sulphides and metals from oxidation and would increase the evaporation rates. A related process is the separation of metallic sulphides by selective volatilization either at atmospheric pressure or under vacuum. This procedure is already used commercially for the elimination of lead and cadmium as PbS and CdS from zinc calcines; it might well have other applications. To predict such processes it is necessary to know the relative volatilities of the metallic sulphides and to know whether they volatilize as sulphides or whether the predominant weight loss is due to decomposition. Such data would also be of value in studying problems such as the use of sulphides for refractories, as described by Brewer,] or in the evaluation of the theory of ore deposition from the vapor state, as proposed by Brown.' Qualitative statements concerning the volatility of metallic sulphides can be found frequently in the literature and are well summarized by Mellor, but accurate determinations of rates of evaporation or vapor pressures are very scarce. Kelly" lists vapor pressure data only for PbS; his reference being to the work of Schenck and Albers,4 who measured the vapor pressure of PbS by a dynamic method between 850" and 995°C. More recently Veselovskii5 has determined the vapor pressures of the sulphides of antimony, lead, cadmium, and zinc at temperatures ranging from 360" to 1000°C using Knudsen's method. A second Russian worker, Pogorelyi,6 determined the vapor pressures of CdS and ZnS at temperatures from 900" to 1250°C. The results obtained by these workers are shown in subsequent graphs in comparison with the data of this paper. Brewer and coworkers1 have studied some of the metallic sulphides to determine their suitability as refractories in vacuum. Veselovskii's determinations on PbS checked well with those of Schenck and Albers, and his determinations of CdS check almost exactly with Pogo-relyi. For the vapor pressure of ZnS the data of Veselovskii and that of Pogorelyi are in fair agreement, as shown in Fig. 1, but it should be pointed out that Lumsden7 has discovered that the equation given by Veselovskii for the vapor pressure of ZnS: - 14,200 log P9.495 is in error by a factor of ten when compared to the experimental data. In contrast with the scarcity of data on vapor pressures, the decomposition pressures of many metal sulphides have been determined and are summarized by Smithells.8 Theoretical Considerations The experiments described in this paper consisted of determinations of the rate of weight loss of certain metallic sulphides under very low pressures at different temperatures. These data plus observation and analyses of the products reveal the mechanism of the weight loss and also provide a basis for the calculation of the vapor pressure or apparent vapor pressures of the sulphides.

Jan 1, 1953

By E. A. Gulbransen, K. F. Andrew

Thermodynamic information on the solubility of hydrogen in exothermic metals is limited. Thus, the overall solubility decreased as the temperature rose, which suggests the heat of solution of hydrogen in the metal is negative; yet the terminal solubility in the metal phase increased, which suggests an endothermic reaction. A thermodynamic analysis, therefore, was made of the several equilibria involved when hydrogen dissolved in the metal. Equations were derived expressing the solubility, terminal solubility, and decomposition pressures of hydrogen in terms of the heat, entropy, and free energy of solution of hydrogen in the given phase. The relations between the thermodynamic functions for the a-zirconium and 8-hydride phase were developed. The thermodynamic quantities were determined experimentally by the measurement of the decomposition pressures over a broad composition and temperature range. Two new methods of analyzing the experimental data were developed for determination of the terminal solubility. STUDIES', ' of the impact strength of zirconium at room temperature indicated that small quantities of hydrogen, of the order of 10 parts per million, embrittles the metal. Micrographic' and X-ray diffraction' studies showed this embrittlement to result from the precipitation of a second phase upon slow cooling. These studies suggested that the terminal solubility of hydrogen in the metal phase increased with increase of temperature. This behavior appeared to contradict the effect of temperature on exothermic hydrogen occluders such as zirconium. For these metals, the solubility of hydrogen should decrease with increase of temperature. Before these facts could be understood, a thorough analysis of the several equilibria was essential. It was the purpose of this paper to consider the several equilibria involved when hydrogen was reacted with zirconium from both the theoretical and experimental points of view. Since the overall solubility of hydrogen in the metal has been considered by a number of workers, it was proposed to study the composition range 0 to 6 atomic pct H in detail. Literature Schwartz and Mallett' determined the terminal solubilities of hydrogen in the metallic phase from diffusion studies. They extrapolated concentration-penetration curves to the boundary between the solid solution phase and the hydride phase at the surface. Their results showed values of 2.6 atomic pct at 400°C and 5.2 atomic pct at 500°C. Extrapolations of the data to room temperature suggested very low values for the terminal solubilities. This study confirmed the hydrogen embrittlement results and indicated that the terminal solubilities increased as the temperature was raised. The solution of hydrogen in zirconium over the complete concentration range was studied by Hall, Martin, and Rees3 and by others. The results showed that hydrogen was absorbed up to a maximum composition of 66 atomic pct or ZrH This composition represented the t-hydride phase. The maximum amount of hydrogen absorbed increased with pressure and decreased with temperature. Due to this temperature behavior, zirconium was classed as an exothermic occluder." In 1930 Hägg studied the crystal structures of the Zr-H alloys over a broad composition range. Four hydride phases were found. However, the range of homogeneity of the several phases was not studied. Gulbransen and Andrew" recently studied the phase diagram of this system by X-ray diffraction methods and by a thermodynamic method based on decomposition pressure measurements. The results showed that only two hydride phases existed for low temperatures, the 6 and the .-phases of Hagg.' Both phases had broad regions of homogeneity. The lower limit of the two-phase region of a and d-phases suggested a terminal solubility of 4 atomic pct at 500°C. This value was in agreement with the results of Schwartz and Mallett.' To avoid hydrogen embrittlement at low temperatures, it was necessary to heat the metal in high vacuum at elevated temperatures. To choose the conditions of temperature and high vacuum, it was

Jan 1, 1956

By J. L. Lytton, T. E. Tietz

The recovery of flour stress of recrylstallized are-cast molyhdenum after 10 pet prestrain at 150°C was studied for recovery temperatures of 725o 801o and 901oC. The yield phenomenon observed after recovery was such that the yield drop diminished and disappeared as recovery proceeded. A fractional flow-stress recovery parameter fr, was developed and it was shown that, independent of recovery ternperatzwe, equal f, values of about 0.16 produced superposition of stress-strain curves except for the initial yield phenomenon. The activation energy for low degrees oj recovery was found to he 32,600 cal per mole, in close agreement with a reported valzie for difjzdsion of carbon in molybdenum. For values of fr greater than about 0.15 where recovery was thought to predominate over strain aging, the activation energy varied from 43,600 to 82,500 cal per mole and increased with increasing recovery and recovery temperature. A 10 pet pre-strain shifted the ductile-brittle transition temperature, as indicated by tensile elongation, from 10°C. to about -22"C. A 100-hr recovery anneal at 801oC was shown to shift the transition temperature to about —5oC, the major shift occurring during the first hour of recovery. ThE recovery of cold-worked metals is accompanied by changes in the arrangement of the dislocations generated during cold work. In recent years, the use of transmission electron microscopy has allowed direct observation of some of the dislocation configurations formed, such as "tangles", networks, cells, subboundaries, and loops. These observations have recently been reviewed by Keh and Weissmann.' Accordingly, some understanding has been gained concerning the nature of the dislocation rearrangements involved. The relationship between recovery and the decrease of mechanical strength, however, has only recently been explored. Previous efforts of the authors were directed toward investigating the decrease of tensile flow stress of aluminum and Al-1 pet Mg during recovery2 and the effects of concurrent elastic and plastic strain on the flow-stress recovery of aluminum.3 In addition, an investigation of the effect of four different solute additions on the tensile flow-stress recovery of aluminum has been made.4 Many important metals, however, have the bee crystal structure, e.g., iron, molybdenum, tungsten, vanadium, columbium, tantalum, and chromium. These metals might be expected to behave differently during recovery from those with other crystal structures for two reasons. First, the previous and present investigations of aluminum and its alloys have shown that tensile flow-stress recovery is strongly affected by foreign atoms in the lattice. In the bee metals, interstitial impurities are usually present and might be expected to have various effects upon both flow behavior and recovery. For example, heterogeneous yielding might occur during prestraining. The diffusion of these interstitials can also relock dislocations during recovery so that a yield point might be obtained upon restraining (strain aging). Second, some of the bee metals (e.g., iron, molybdenum, and tungsten) undergo the familiar structure-sensitive ductility transition and exhibit brittle fracture at suitably low temperatures. It is of considerable interest to determine the effects of recovery on the transition temperature of such metals. The purpose of the present investigation was to extend our knowledge of flow-stress recovery to the bee metals and to study the effects of recovery on the ductile-brittle transition temperature. Unalloyed recrystallized are-cast molybdenum was chosen as a test material, since it exhibits a well-defined ductility transition near room temperature. As in the previous studies, the degree of recovery was measured in terms of the decrease of tensile flow stress. Prestraining and restraining were carried out at 150°C to avoid the possibility of brittle fracture. EXPERIMENTAL PROCEDURE The are-cast molybdenum sheet used in this investigation was obtained from the Climax Molybdenum Co. of Michigan. It was 0.060 in. thick by 10

Jan 1, 1964

By L. S. Darken, H. A. Wriedt

An investigation has been made of nitrogen absorption by the lattice defects in a low-carbon steel afte~ Plastic deformation. Specimens in which defects were distributed by various combinations of cold rolling and vacuum heat treatment were equilibrated with controlled ammonia + hydrogen mixtures at 300° to 450°C to study the relation between the solubility and the thermodynamic activity of nitrogen. The results are interpreted in terms of nitrogen being absorbed upon two different types of defect sites, called A sites and B sites. The concentrations of these sites are calculated for specimens with various histories of straining and annealing; and the thermodynamic relations descrihing the equilibrium distribution of nitrogen among the A, B, and ordinary interstitial sites in ferrite are evaluated as follows: THE generalization that the solute atoms in a solid solution interact with imperfections in the solvent lattice is now universally recognized and the subject of an extensive literature. All types of imperfections—point, line, or surface—exhibit these interactions, but the relative importance of each type depends upon its concentration, the strength of its interaction with the particular solute atom, and whether the interaction is attractive or repulsive. The strength and sign of the interaction vary with the vectorial displacement of the solute atom from the imperfection in the crystal. The concentration of lattice defects increases during plastic deformation and the effect of the imperfections upon the solute atoms is usually perceived only after cold work or irradiation. Two experimental methods have previously been used to observe the effects of interaction between nitrogen atoms and lattice imperfections in a iron. Internal friction, which was first used for this purpose by Dijkstra,1 has been applied more often than the electrical-resistivity method of Cottrell and Churchman.2 The method of the present investigation has not been used before.* Uniform specimens of steel with a metastable defect structure are produced by cold rolling and subsequent heat treatment below the recrystallization temperature. Variations in the defect structure are obtained by varying the amount of strain and the heat-treatment conditions. The specimens are then saturated with nitrogen at moderately elevated temperatures in ammonia + hydrogen mixtures having various thermodynamic activities of nitrogen below saturation with Fe4N. From the nitrogen contents of analyzed samples, the metastable equilibria of interactions between the defects and nitrogen can be established and the concentration of sites for nitrogen atoms in the lattice defects calculated. A steel was used in the present experiments instead of purified iron or iron alloys because the amount of nitrogen absorbed at defects is larger in the steel over a much wider range of experimental conditions and could therefore be measured more accurately. The effect of alloy composition is discussed in Part II of this paper; it is sufficient to say here that impurities and phase heterogeneity in ferritic alloys favor the generation and/or retention of larger defect concentrations during plastic deformation and annealing at 300° to 500°C. MATERIALS AND EXPERIMENTAL PROCEDURE The experimental specimens were prepared from stock of a low-carbon steel, which will be called "X steel" here, with the composition: C, 0.12 pct; Mn, 0.43 pct; P, 0.010 pct; S, 0.034 pct; Si, 0.007 pct; As, 0.086 pct; Cu, 0.022 pct; Ni, 0.009 pct; Cr, 0.003 pct. The stock was all from a single ingot made by the basic open-hearth process, which was hot-rolled to strip 0.080 in. thick.. This hot-rolled strip, given the code designation "XH", was the starting material for preparing a series of cold-rolled sheets. The latter are designated "XC27",

Jan 1, 1965

By M. R. Geer, H. F. Yancey

John Grifien (Pittsburgh)—I wish to congratulate the authors on this paper, which, I am sure, will promote a clearer conception of the various criteria which have been advanced as measures of coal-cleaning performance. Their clear descriptions of the more important criteria that have been advanced and explanations of their meaning and application have been sorely needed and, if widely promulgated and followed, should remove much of the confusion which, heretofore, has been evident. I suggest that much of this confusion has also arisen from lack of common agreement as to the exact meaning of the words and terms used in our discussions of this subject. I am sure I have been equally guilty in this respect and suggest it is time that we select a committee to study vocabulary as well as criteria, so that common understanding and agreement can be had. Thus, I suggest, that the title of this paper should have used the words "coal-cleaning performance" and not "coal-washery performance." My understanding is that "washery" refers to a complete plant and it has additional functions to that of coal-cleaning, such as control of size, moisture, etc. Also, I do not agree with the authors that the formulas given in their paper, the Fraser and Yancey formulas, are necessarily the only ones that can be called efficiency formulas. When a dictionary is consulted one realizes that the words "efficiency" and "efficient" have not precise meanings but only very general ones and must be further defined for each particular use, if they are to have any precise meaning. To my mind, the first of the Fraser and Yancey formulas given should never be used as expressing "efficiency" alone but only by the fuller phrase which truly expresses the kind of efficiency it states, which is "coal recovery efficiency." For complete clarity we then need only define "coal" for the particular circumstances under which the formula is used. This would recognize the fact, fully explained by the authors, that the limits in coal qualities imposed by the market have imposed a factor—and a variable factor—which has influenced any answer obtained by this formula. Such a procedure makes it entirely practical and logical to use the values of any of the qualities of coal—ash, sulphur, phosphorus, specific gravity—or a combination of them to define what is coal for that particular use of the formula. Further, it is clear to me that the criteria to be used must be dictated by the objective in view and the use for which the data are obtained. The authors clearly point out that the Fraser and Yancey coal-recovery efficiency formula is influenced by three factors, "one is determined by the coal, one is dictated by market or use conditions, and one is an inherent characteristic of the cleaning unit itself." The formula which uses the inverse of misplaced material as a measure of efficiency is also a coal recovery efficiency formula and is influenced in like manner by these three factors. As the authors point out, both are useless in obtaining data which enables a direct and valid comparison of the performance of a given cleaning unit on two coals where the other two factors vary or of the performance of two or more cleaning units of different types unless the values of the other two factors are identical. Much of the confusion in our discussions of and literature on coal cleaning has come from failure to understand clearly this fact. Many such comparisons have been made from which erroneous conclusions have been drawn. I am, therefore, particularly glad to see the authors' emphasis on 4?-1e criteria which indicate the "sharpness of separation. I feel that these are the essential criteria

Jan 1, 1952

By P. Chiotti, J. T. Mason

Thermal, X-ray, metallographic, and resistivity data were obtained to establish the phase diagram for the Yb-Zn system. Six intermetallic compounds and five eutectics have been identified. The compounds position at 695°C. No evidence for the compound YbZn,, was observed. Whether this compound is stabilized or inhibited by small amounts of impurities is uncertain. SEVERAL aspects of the Yb-Zn system have been reported in the literature. Much of this work deals with the crystallographic identification of some of the compounds. The YbZn compound has been reported by Iandelli and palenzonal and the YbZn, structure and thermal data for the composition range between YbZn and Yb3Znll have been reported by Michel et al. A compound of uncertain stoichiometry in the range 60 to 68 wt pct Zn with a cubic structure has been reported by Kuz'ma et aL4 The YbzZn17, YbZn,,, and YbZn13 compounds have been reported by both Kuz'ma et a1 and Iandelli and Palenzona.' YbnZn17 has also been identified by Laube. This investigation was undertaken to establish the phase diagram of this system. Ytterbium in many respects behaves as an alkaline earth rather than a rare earth metal6 and it is of interest to note the resemblance between the Yb-Zn system, the Ca-Zn,' and typical rare earth-zinc systems.g'10 MATERIALS AND EXPERIMENTAL PROCEDURES The materials used in this investigation were Ames Laboratory ytterbium and Bunker-Hill slab zinc, 99.99 pct pure. Analyses of the ytterbium showed 38 ppm Ta, 82 ppm 0, and 15 ppm N with Ca, Cu, C, Mg, Al, Si, Cr, Fe, Ni, Sc, Y, Er, Tm, and Lu all less than 50 ppm. The ytterbium was dehydrogenated by heating in tantalum under vacuum for 8 hr at 900°C. The metal was kept under argon except when being cut with shears and when being weighed. Tantalum was found to be a suitable container for alloys in the composition range between ytterbium and Yb2Zn17. With higher zinc concentrations the tantalum was penetrated by the alloy and failed after several days at temperatures of 600" to 700°C. Approximately 20 g of zinc and ytterbium metal were sealed under argon in *-in.-diam tantalum cruci- bles equipped with thermocouple wells. The crucibles were in turn sealed in stainless-steel jackets. The alloys were equilibrated in an oscillating furnace and given various heat treatments in a soaking furnace. The steel jackets were removed and differential thermal analysis data were obtained under an atmosphere of argon. The thermal analysis apparatus was calibrated against the melting points of pure zinc, aluminum, silver, and copper and found to give thermal arrests within 1°C of the accepted melting temperatures for these elements. The thermal analysis apparatus has been described in an earlier paper.g Alloys were further heat-treated as necessary and subjected to metallographic examination and X-ray diffraction analysis. Most alloys were etched with Nital (0.5 to 10 pct nitric acid in alcohol). EXPERIMENTAL RESULTS The results of the thermal analysis are summarized by the points on the phase diagram, Fig. 1. Six compounds and five eutectics were observed. The eutectic temperature and compositions in weight percent zinc are 491°C and 12 pct, 645°C and 32 pct, 687°C and 54 pct, 742°C and 67 pct, and 750°C and 77 pct. The compounds YbZn, YbZn2, Yb2Zng, Yb2Zn17, and YbZnll melt congruently at 650°, 751°, 75Z°, 754", and 755"C, respectively. The compound Yb3Znll undergoes a peritectic decomposition at 695°C. The transformation and melting temperatures for the ytterbium were observed to be 797" and 817°C. re-

Jan 1, 1969

By P. B. Mee

The secondary re crystallization behavior of two vacuum-melted, nominally 3 pct Si-Fe alloys has been studied, one alloy being produced from pure electrolytic iron and semiconductor-grade silicon and the other from commercial-purity hot band. The vacuum-melted and vacuum-remelted alloys were found to develop {110}(hhl) and {lll)(hkl), respectively, on annealing in high vacuum and {100}(0kl) and {11l}(hkl), respectively on annealing in pure hydrogen of dew point, < — 60°C. H2S doping of the hydrogen or annealing in commercial argon was found to effect a reversal for the vacuum-remelted alloy from (111) to (100) secondary recrys-tallization, while prolonged vacuum annealing at 2 x 10-6 Tow resulted in a tertiary re crystallization from (111} to (110). The growth selection of the {lll}(hkl) component was found to be governed predominantly by the {111}/planar misorientation, the maximum deviation of the resulting secondaries being 5 deg. It is considered that the driving force for {111}(hkl) secondary recrystallization arises from the preferential lowering of ?111, possibly by phosphorus or nitrogen diffusion, just as oxygen and sulfur under certain conditions have been found to preferentially lower ?100. When heavily cold-rolled metals are annealed at high temperatures, primary recrystallization usually occurs rapidly and may be followed by considerable grain growth. However, in the presence of a fine dispersion of inclusions1"3 or with a strong matrix preferred orientation4&apos;&apos; the matrix may be stabilized and a secondary recrystallization may then be effected. Also, in vacuum-melted Si-Fe it has been shown possible to develop {100}(001) and {110}(001)6 surface energy driven secondary recrystallization textures. Further, it has been found that, on annealing very pure metals, grain growth normally ceases when a grain size approximately twice the strip thickness is acquired, due to the formation of V-shaped thermal grooves which result in an equilibrium being set up between surface and grain boundary stresses. If, however, a surface energy difference ??s, exists between adjacent grains (of the order of a few percent of the grain boundary energy ?b), then according to Mullins8 a secondary recrystallization may be effected, since the grains having lowest ?s would grow at the expense of their higher-energy neighbors. For clean bee metal surfaces ?110 should be lowest; however, for 3 pct Fe-Si (100) secondary structures have frequently been developed and have been attributed by Walter and Dunn9 to an alteration of the relative surface energies due to the preferential chemisorption of oxygen on (100) planes. Kohler,10 however, indicated that this reversal may be achieved by employing minute quantities of highly polar compounds in the annealing atmosphere, i.e., sulfur compounds, in par- ticular H2S being beneficial in (100) growth. This work has been verified by Kramer" using {100)/{110} bicrystals, while Mager12 demonstrated the importance of sulfur diffusion within the strip. Detert13 has intimated that carbon may be responsible for the preferential lowering of ?110 although no direct evidence has appeared yet to support this supposition. It must , be appreciated that the above-mentioned examples of surface energy driven secondary recrystallization were obtained with very pure vacuum-melted materials with oxygen contents (which is now known to be a critical factor") less than 35 ppm. During the course of a textural study on Si-Fe it has been found that under certain conditions (111) secondary recrystallization can be obtained by what is believed to be a surface energy growth selection mechanism. The purpose of the present paper is to briefly describe this result and to try and postulate the possible causes. EXPERIMENTAL Two vacuum-induction-melted, nominally 3 pct Si-Fe alloys were produced, one from pure electrolytic iron and semiconductor-grade silicon designated A and the other from commercial-purity hot band, designated B.

Jan 1, 1969

By R. F. Steigerwald

The effects of heat transfer on the corrosion behavior of type 304 stainless steel in boiling water have been studied. Heat transfer conditions increase the tendencies of the stainless steel toward stress-corrosion mucking when the water is contaminated with Cl-. Surface preparation is the most important variable in determining the severity of the stress-corrosion problem in water with a given Cl- content. Heat treatment, chemical cleaning, and degree of wet film boiling also affect the corrosion of stainless steels used as heat transfer surfaces in boiling water. An up-paratus for corrosion testing under controlled heat transfer conditions is described. THE principal objective of this investigation was to study the corrosion behavior of AISI Type 304 stainless steel in boiling high-purity water under conditions of heat transfer. The principal variables in the study were: a) boiling conditions: limited boil, agitated boil; b) metallurgical structure: annealed or sensitized; c) surface condition: rolled, pickled, or ground. The results of the study should elucidate the role of heat transfer in the corrosion of stainless steel in boiling high-purity water and provide a base line from which to assess the severity of this type of corrosion. Although there has been an investigation of the effect of heat transfer on the corrosion behavior of stainless steels in alkaline waters,&apos; work on the corrosion of stainless steels under heat transfer has been largely confined to various acid solutions.&apos;-4 Furthermore, the study of the corrosion of stainless steels in high-purity water has been generally restricted to auto-clave and instream testing in superheated (e.g., 300°C) water and steam.5&apos;6 Cooling water problems led to this study of the corrosion behavior of type 304 stainless steel in high-purity water at its atmospheric boiling point. In addition to the effects of heat transfer, this study also considered the influences of the type of boiling,7 metallurgical structure, and surface condition on the corrosion behavior of stainless steel in high-purity water. Two boiling conditions were investigated in this study: a) limiting boiling, i.e., when the heat-transfer surface had just reached the boiling point and boiling nucleated randomly over the specimen surface and b) agitated boiling, i.e., when a mild degree of superheat had been achieved on the specimen surface and boiling occurred generally over the specimen surface. Both boiling conditions are broadly classified as wet-film boiling. Originally, this program included the study of a third type of boiling, dry-film conditions. At dry-film boiling the temperature of the heat transfer surface is high enough so that it is covered with a continuous film of steam. Experimental difficulties made it impossible to study this kind of boiling with the available apparatus. Since surface condition affects heat transfer rates, three typical surfaces were chosen for study: a) as-rolled, the 2B finish received from the supplier, b) as-pickled, 30 min in 8 pct HNO3-1 pct HF, and c) as-ground on 120 grit paper. In order to evaluate the effect of improper heat treatment or welding on hot wall corrosion, both annealed and sensitized mi-crostructure were included in this study. EXPERIMENTAL Test Apparatus. The particular problems of interest in this investigation required a knowledge of the thermal gradient through the test specimen. From this gradient, the heat flux to the surface and the surface temperature could be determined. In order to satisfy this need, an apparatus similar to the boiling-disk apparatus of Fisher and whitney2 was designed. The solution is contained in a thermally-insulated, steel pipe lined with TEFLON resin. A stainless steel _______;________________________________________

Jan 1, 1970

By G. A. Vissac

The only fine coal washer with proved automatic controls, the feldspar jig is capable of good efficiencies even at low separating gravities, handles a variety of products, and treats 150 tph and over. IN continental Europe the feldspar jig is used almost exclusively for cleaning the fine sizes of coal; it operates with an artificial bed, made up generally of pieces of feldspar or of any other hard and heavy rock with good cleavages. A primitive form of this machine requiring close supervision was used in this country years ago, but output was small. The modern machines are generally air-pulsated Baum-type jigs, with capacities up to 150 tph, and treat sizes from % in. to 0, usually previously dedusted or deslimed. These jigs are equipped with very accurate and sensitive automatic controls insuring satisfactory operation even at low separating gravity and with feeds irregular in quality and quantity. This paper will deal more particularly with coal cleaning separation, but the technical studies apply equally to all minerals. Theory of the Feldspar Jig To understand fully the operation of the feldspar jig and to appreciate its potential value, it is necessary to measure and analyze the motion of small particles of various specific gravities, falling in various media, under various conditions. As no practical formulas were available for that purpose, the writer has developed new theories and established new sets of formulas, which cannot be demonstrated here. They are applicable to all minerals and to many problems of coal or mineral concentration. These formulas do not pretend to absolute accuracy, but results, tested by comparison with experimentally recorded data, are sufficient for practical purposes, as they give definite indications of trends, relative values, and order of magnitude of the many factors involved. For pulsating motions no earlier formulas are available. In the case of continuous currents or motions, such formulas as Rittinger&apos;s, Allen&apos;s, or Stokes&apos;, over a hundred years old, apply only to special shapes and sizes of particles, involve factors and coefficients difficult to measure or appreciate, and deal only with free motions. They are of little use in solving practical problems. Units used with the formulas presented here are in the CGS system. Lateral friction and suction have been taken into account according- to methods currently used in aerodynamics, and only hindered motion is dealt with. As the feldspar jig is primarily intended to create a fluid bed condition, the mixture of fluids and solids obtained is homogeneous, and the apparent specific gravity of the separating medium is calculated accordingly. For instance, if 20 pct of the volume is coal and shale, with an average of 1.60 sp gr, in a liquid of 1.10 sp gr, the actual specific gravity of the separating fluid is 0.80 x 1.1 + 0.20 X 1.6 = 1.20. The fundamental equations are as follows: The general motion of a particle falling in a medium of specific gravity equal to u, hindered motion. is dv/dt = g/Ls [ L (s-u) - u/g v2 [1] g = 981 cm per sec, acceleration of gravity, and L = thickness of the particle of specific gravity (s) and velocity (v). The initial acceleration dv/dt = g (1-u/s ) [2] is a function of the specific gravity of the particle, only for a given medium, and independent of its dimensions—an ideal separating condition. The terminal velocity Vt = gxL- (s-u)/u, [3] for a given value of u, is a function of s and L. Two particles, L, s, and L2 s2, are said to be equivalent if they have the same terminal velocity, and accordingly L1/L2=s2-u/s1-u. [4] Two such particles cannot be separated by continuous currents, in any concentrating device. Because the initial accelerated motion, which provides for efficient separation, is followed by a constant velocity, which has a limiting effect, it is essen-

Jan 1, 1956