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By Thomas Darlington

THE obligation of an employer to the State requires certain things of him as matters of good citizenship: for instance, that his workmen shall have a living wage, that child labor shall not be employed, that injuries from accidents shall not- make workmen a charge upon the State, and that the laborer's children shall have opportunity for education and to become good and useful citizens. Affairs of this kind are not taken up as philanthropy, for the officials of a corporation or a large manufacturing concern may not feel at liberty to spend the funds of their company as prompted simply by motives of kindliness; but they may spend company money on such matters because it is good business. For years, the poisonous effects of lead, phosphorus and dust have been emphasized in books on industrial hygiene and their elimination has been urged; but the more important and everyday physiology of the workman himself has been neglected. Part of my object in writing this paper is to show how our knowledge of physiology may be applied to working conditions in everyday life. In the interest of industrial laborers, accident compensation laws have been enacted in 33 States. This has been carried forward rapidly, because it has been shown that it pays both employer and employee. A further step is the recognition of sickness and disablement independent of accidents, not only because of their immediate cost to the worker and to the employer, but because continued efficiency in work and business depends largely upon health. Some measure of the importance of health in industry can be gained by the knowledge that records kept by some companies which now make this the subject of careful inquiry show that the time lost by employees, through illness; is several times as much as that lost as the result of industrial accidents. It is true that accidents frequently result in permanent disability or death, but it is equally true that illness is also a cause of permanent disablement or death. Thus the chief difference is that the loss to the employee through accidents occurring in the course of his employment is now generally recognized as a cost

Jan 2, 1918

By R. S. French, W. R. Hibbard

FOR tensile deformation, if the stress value is defined by the ratio of the load to the actual area, and the strain value by the natural logarithm of the ratio of the immediate length to the original gauge length of the sample, the resulting data when plotted with logarithmic coordinates result in a linear relation extending from the initial plastic yielding through the maximum load and in some cases, such as for copper and brass, to fracture'.'. The normal form of the curve, therefore, is a parabola, satisfying the following equation: S = Kem [1] where S and e represent true stress and strain, K is a constant, and m is a coefficient evaluating the slope of the curve and designated therefore as the strain hardening coefficient. Hollomon² has reported that this coefficient is a function of the yield strength as effected by grain size in alpha brass, and the carbon content and heat treatment of steel. In the case of steel, the value of the proportionality constant is a function of the carbon content. It was further shown in that paper2 and also by Low and Prater -hat, if the power relation between stress and strain remains valid, the strain hardening coefficient m, is equal to the strain at the maximum or necking load. Thus, an added significant feature is that this coefficient may serve as an index of the capacity for deformation prior to localized necking and subsequent fracture, e.g. drawability. The constant K may be defined as the strength of the material at unit strain. Together the K constant and the m coefficient describe an alloy's physical properties as far as strength and ductility are concerned for a particular yield strength and, in the case of steel, a particular carbon content. The work of Lacy and Gensamer4 gives data on alloy ferrites from which very close estimates of the strength of ternary and higher iron alloys have been made. It was the purpose of this investigation to develop similar data for commercial copper base alpha solid solution alloys. Preparation of Specimens Commercial binary alloys of copper with aluminum, beryllium, cadmium, nickel, silicon, tin and zinc were investigated. In addition, laboratory castings were made of a 1 pct silicon alloy and a 2 pct aluminum alloy to complete these particular series. Two types of copper were used, oxygen free OFHC and tough pitch FC. The analyses of these alloys are shown in table I. Standard ASTM sheet tensile specimens were used to determine the usual physical properties of each alloy and to obtain stress data at strains from 0.0005 to 0.01. Small (1/4 in. x 3 in. x tk.) samples

Jan 1, 1951

By AIME AIME

THE 139th meeting of the Institute will be held Feb. 17-20, in the Engineering Societies Building, New York. The annual business meeting will be held on Feb. 18 at 10 a. m., and no technical sessions will be scheduled at that time, so that all members may participate in the election of officers, hear the presentation of the annual reports of officers and committees and discuss any matter which they may care to bring up at that time. The annual dinner will be held at the Conlmodore Hotel on the evening of Feb. 20, and the usual good time is promised. Arrangements for this and other social features of the meeting are, as usual, in hands of the New York Sec- tion, of which the chairman this year, Ralph M. Roosevelt, has a well-established reputation earned as president of the Zinc Institute, as host.

Jan 1, 1930

By David W. Brunton

The list of our past-Presidents comprises the names of many who, in their official addresses, have sketched the current progress of the arts and professions with which they were familiar. Such addresses are, in my judgment, highly useful, setting forth the results of our own work as a society, and recalling to our minds the particular lines in which discussion would prove most fruitful. Following this course with some hesitation, I venture to offer an outline of the recent improvements and the present situation in mining and metallurgy in the Western United States. The wonderful advances in mechanics, chemistry, and electricity have all combined to aid these arts to such an extent that progress during the last decade has undeniably been more rapid than ever before in the history of the profession. In all mining countries improved transportation-facilities, in many instances called into existence by the traffic created by the mines themselves, have done much to enlarge the field of operations by the reduction of freight-, operating- and living-expenses, thereby bringing lower-grade properties into the producing class. Under normal conditions, as the age of a district increases, all these different factors should combine to off-set the augmented costs attendant on deep mining, and greatly tend to prolong the profitable life of the mines. The more recent and important improvements in our Western mining-practice which have contributed most towards the advancement of the art may be briefly summarized as follows; but, before beginning this portion of my address, I wish to thank most heartily the many engineering friends who have so

Jan 1, 1910

By E. N. Pennebaker

A PRESENT, a comprehensive account of the geology and ore deposits of the Robinson mining district, in eastern Nevada, is not warranted. Though several years' work has been done, the district is so large that it will be some time before the investigation nears completion. In this paper I purpose merely to discuss methods of study and the application of geologic data to the search for ore. In the first place, the purpose of a geological depart¬ment in a mining organization is to collect and correlate all geologic and engineering data likely to be useful. In an extensive and well developed mining camp this involves a detailed study of the structure and stratigraphy of the district as a whole, as well as careful analysis of the orebodies exposed. The problem then is to find continuations or similar ore environments in other parts of the district in which like phenomena have been active, and to explore these for new orebodies. Experience gained in other similar mining districts is useful but one must always remember that a great many mining districts are unique and that exploration rules and procedure applying to one cannot always be transferred to another of apparently similar character and be made to work. One also has to be careful in moving from one to another part of the same district. The geologist must first examine the region critically to determine its individual characteristics. .

Jan 1, 1932

By Helmut Thielsch

MeTallographic specimens whose surfaces are to be investigated are too thick to allow either light or electrons to pass through them for microexamination by transmission. This difficulty is overcome with optical microscopes by illuminating the surface through the objective lens. For electron microscopes best results are obtained by preparing thin replicas of the surface of the specimen, placing them in the microscope and passing the electron beam through them. Since electron microscopes represent a rather recent invention, they have found little application as compared with optical microscopes. This is true because, aside from the cost of new equipment and development of new techniques, some of the older replica methods necessitated the destruction of the surface from which a thin transparent replica was obtained. In other processes in which the surface is preserved, either too tedious a procedure is required, unsuited to "mass-production" requirements of industrial laboratories, or replicas of insufficient contrast and sharpness are produced. In general, investigations with the electron microscope involve five steps: (I) polishing the surface of the metal specimen, (2) proper etching of the surface, (3) preparing the suitable replica from the surface, (4) examination and phorography in electron microscope and (5) interpretation. Preparation of Metal Surfaces Usual metallographic polishing is generclly satisfactory. It is important though that the final polish be applied very carefully, since otherwise evidence of a small amount of deformation might show up even on relatively deeply etched surfaces. A high-power microscope should be used to determine the suitability of the polish and etch. This, of course, is not different from optical examinations, but in these, if a deep etch is used, the problem is less serious. It is frequently difficult to detect with optical microscopes poor polishing aside fiom superficial scratches before etching. Figs. I and 2 show micrographs of "well" and "poorly" polished nickel etched by immersing the sample for 20 min. in a solution containing 8 grams cupric sulphate in 40 C.C. of concentrated HCl and 40 C.C. of Hz0 (Marble's reagent). The sample shown in Fig. I was polished in its final stages for 5 min. on a carborundum wheel followed by ro min. on a rouge wheel, whereas the sample shown in Fig. 2 was polished only I min. on the rouge wheel. Generally, this procedure does not guarantee that the surface of the specimen will be either undistorted or deformed. It was applied here merely to show the effects Of good and poor polishing. To the experienced investigator, plastic deformation is

Jan 1, 1946

By Helmut Thielsch

MeTallographic specimens whose surfaces are to be investigated are too thick to allow either light or electrons to pass through them for microexamination by transmission. This difficulty is overcome with optical microscopes by illuminating the surface through the objective lens. For electron microscopes best results are obtained by preparing thin replicas of the surface of the specimen, placing them in the microscope and passing the electron beam through them. Since electron microscopes represent a rather recent invention, they have found little application as compared with optical microscopes. This is true because, aside from the cost of new equipment and development of new techniques, some of the older replica methods necessitated the destruction of the surface from which a thin transparent replica was obtained. In other processes in which the surface is preserved, either too tedious a procedure is required, unsuited to "mass-production" requirements of industrial laboratories, or replicas of insufficient contrast and sharpness are produced. In general, investigations with the electron microscope involve five steps: (I) polishing the surface of the metal specimen, (2) proper etching of the surface, (3) preparing the suitable replica from the surface, (4) examination and phorography in electron microscope and (5) interpretation. Preparation of Metal Surfaces Usual metallographic polishing is generclly satisfactory. It is important though that the final polish be applied very carefully, since otherwise evidence of a small amount of deformation might show up even on relatively deeply etched surfaces. A high-power microscope should be used to determine the suitability of the polish and etch. This, of course, is not different from optical examinations, but in these, if a deep etch is used, the problem is less serious. It is frequently difficult to detect with optical microscopes poor polishing aside fiom superficial scratches before etching. Figs. I and 2 show micrographs of "well" and "poorly" polished nickel etched by immersing the sample for 20 min. in a solution containing 8 grams cupric sulphate in 40 C.C. of concentrated HCl and 40 C.C. of Hz0 (Marble's reagent). The sample shown in Fig. I was polished in its final stages for 5 min. on a carborundum wheel followed by ro min. on a rouge wheel, whereas the sample shown in Fig. 2 was polished only I min. on the rouge wheel. Generally, this procedure does not guarantee that the surface of the specimen will be either undistorted or deformed. It was applied here merely to show the effects Of good and poor polishing. To the experienced investigator, plastic deformation is

Jan 1, 1946

By J. B. Gayle

PRESENT flotation processes depend almost entirely on the buoyant properties of air bubbles to effect separations of mineral and gangue, but there is no convenient method for measuring aeration in flotation cells. Consequently the relation between aeration and cell performance has not been definitely established. In connection with a comparative study of kerosene and froth flotation processes, a modification of the displacement method' was developed in which air escaping from the cell surface is measured with a wet-test meter. The arrangement shown in Fig. 1 is satisfactory for use with a number of cells and is not critical, except that care must be taken to use connections and tubing large enough to avoid excessive back pressures. Attempts to use smaller tubing resulted in back pressures that caused displacement of the liquid level in the receiver, so that some air was lost around the sides, an occurrence readily visible when measurements were taken with only water passing through the cell. With the arrangement shown, the manometer indicated an average reading of about 1/2-in. water pressure. No loss of air was evident. Fig. 2 presents typical data for a standard Denver sub-A 24x24-in. unit cell operated at impeller speeds from 0 to 710 rpm. Each plotted point represents the average for five readings distributed over the entire cell surface. Readings were taken with only water passing through the cell. Results of this type have been used in a study of the influence of operating variables on cell performance and in detecting inherent differences in the operating characteristics of cells of various kinds. Although the information presented in Fig. 2 resulted only with water passing through the cell, the apparatus is suitable for use during flotation of coal when various reagents are present. Possible modi- fications that might prove convenient under special circumstances include varying the size and shape of the receiver and substituting a calibrated, inverted, water-filled carboy or other gas-measuring device for the wet-test meter. If such modifications result in excessive back pressures, some form of draft should be applied at the discharge end of the measuring system.

Jan 1, 1959

By Wolfgang Pitsch

INVESTIGATIONS on the above topic have recently been published by Shapiro and Kraussl and Jana and wayman in this journal and by Kessler and Pitsch.- Parts of the results in these papers are in good agreement with each other but there are also some results which are substantially different. The main points of these differences shall be briefly discussed in this communication. Shapiro and Krauss' measured single-surface traces of the habit planes of reversed austenite plates formed within the martensite crystals and deduced from these measurements two distinct habit planes A = (0.174; 0.309; 0.935) and B = (0.375; 0.545; 0.749) within 3 deg. Kessler and pitsch4 found instead by two-surface analysis7 one habit plane n = {0.23; 0.62: 0.75) with a real scatter of 6 deg. The latter observation of a single habit plane apart from a certain scatter is in agreement with most of the investigations of martensite transformations. The differences between these two results are so great that they cannot be explained by experimental error. The purpose of this communication is to show that the A- and B-poles of Shapiro and Krauss are due to an erroneous interpretation of a single-surface trace analysis. The difficulties in the interpretation of such single-surface trace analyses are due to the high symmetry of cubic lattices, from which it follows that there are in general twenty-four equivalent possibilities of plotting a single-surface trace in a pole figure. All these possibilities must be taken into account, when putting different traces from different plates together in order to construct the habit plane. Alternatively the poles of all the traces may be plotted in a unit triangle. This is done in Fig. 1 with twenty-nine traces of different reversed austenite plates, all of this were measured by Shapiro and Krauss in the same plane of a single martensite ther traces taken from Fig. 13 in the Shapiro and Krauss paper' which were determined by electron diffraction. The traces in Figs. 1 and 2 have to be compared with the habits A, B, and n which are under discussion. Therefore the great circles of the poles A, B, and n are plotted in Figs. 3, 4, and 5 together with a 3-deg scatter region for poles A, B and a 6-deg scatter region for pole n. Comparing Figs. 1 and 2 with Figs. 3, 4, and 5 one finds the statements which

Jan 1, 1969

By Thomas Darlington

The obligation of an employer to the State requires certain things of him as matters of good citizenship: for instance, that his workmen shall have a living wage, that child labor shall not be employed, that injuries from accidents shall not make workmen a charge upon the State, and that the laborer's children shall have opportunity for education and to become good and useful citizens. Affairs of this kind are not taken up as philanthropy, for the officials of a corporation or a large manufacturing concern may not feel at liberty to spend the funds of their company as prompted simply by motives of kindliness; but they may spend company money on such matters because it is good business. For years, the poisonous effects of lead, phosphorus, and dust have been emphasized in books on industrial hygiene and their elimination has been urged; but the more important and everyday physiology of the workman himself has been neglected. Part of my object in writing this paper is to show how our knowledge of physiology may be applied to working conditions in everyday life. In the interest of industrial laborers, accident compensation laws have been enacted in 33 States. This has been carried forward rapidly, because it has been shown that it pays both employer and employee. A further step is the recognition of sickness and disablement independent of accidents, not only because of their immediate cost to the worker and to the employer, but because continued efficiency in work and business depends largely upon health. Some measure of the importance of health in industry can be gained by the knowledge that records kept by some companies which now make this the subject of careful inquiry show that the time lost by employees, through illness, is several times as much as that lost as the result of industrial accidents. It is true that accidents frequently result in permanent disability or death, but it is equally true that illness is also a cause of permanent disablement or death. Thus the chief difference is that the loss to the employee through accidents occurring in the course of his employment is now generally recognized as a cost

Jan 1, 1918

After the explosion in the Black Heath pit, that company sent to England for some experienced miners to reopen the mine. The results of their work in this vicinity are mentioned in an advertisement for pit hands by the Mid-Lothian Co., as follows: "PIT HANDS WANTED.-In consequence of reports having been circulated of the insecurity of hirelings in the Mid-Lothian Mines, the Company deem it proper to make known, that the mines have recently been opened, and that not the slightest explosion from gas has occurred; the workings were laid out and are now progressing, ° under a plan furnished by Messieurs Foster & Hall, .two distinguished English Colliers, sent over from England to reclaim the Pits of the Black Heath Company after the recent explosion of gas-and the present under ground operations are now conducted under the management of one of the English foremen left here by these gentlemen, and supervised by Mr. Wm. Hall, who has under his superintendence the Black Heath Company's Works at present. The skill and capacity of those gentlemen, is fully evinced in their skilful reclamation of the Black Heath Mines, and their present successful working of said Pits; and their confidence in the safety of the hands in the Mid-Lothian Mines, will be seen, by reference to the annexed extract from the Plan left by Messrs. Foster & Hall for laying out and working the Mid-Lothian Mines, and from the Certificate of Mr. William Hall, as to the manner in which that plan is carried into effect. This publication has been deemed proper, as the Company are now in want of some ten or fifteen additional able-bodied, active Pit-hands, on hire by the year, for which they will give the most liberal hire. The Company have not hitherto spared any labor or expense, deemed necessary to secure the absolute safety and comfort of the hands in their mines; nor is it designed in future to omit any thing that can add to the security of their own hands, or the hired laborers of other persons-indeed they can, with great propriety, say, as far as they have progressed, that no mines in this country exhibit stronger, if as strong, evidence of general safety. The Company will receive on hire, no hands who do not voluntarily enter their service -and they request of those having hands to hire out, to remember that they will want upon hire, successively, at intervals of every ninety days, some additional four or five hirelings during the year, or to purchase, progressively, that number of healthy, able-bodied young men. "Owners of slaves at a distance from the Coal Mines, would do well to give some attention to the subject. There is no place in this country where slave labor commands as much, where their general health is better, and where the treatment and contentment of the slaves are surpassed. It is true that within the last few years several disastrous accidents have occurred, but from the scientific and practical skill attracted to the mines, these accidents will be of rare occurrence, it is to be hoped. A. S. WOOLDRIDGE, President, at the Mines in Chesterfield County.

Jan 1, 1942

A record $18.7 billion worth of metals, non- metals and fuels was produced in the U.S. during 1962, according to a year-end estimate from the USBM. The 1962 total value, based on preliminary statistics compiled by the Bureau, was nearly $600 million more than in 1961. Most minerals gained both in value and volume of production during 1962 according to information collected by the Bureau. All mineral fuels except anthracite showed increases. Among nonmetallic minerals- other than fuels-gains exceeded losses by two to one. Metal production held steady as gains and losses balanced.

Jan 2, 1963

By Wayne Loel

The application of aerial photographs to all phases of geologic mapping is set forth, indicating the advantages to be gained in different types of country and undcr varying climatic conditions. Methods of field and office procedure are given from a geological point of view, as well as suggestions regarding the best methods of aerial mapping for different uses and under varying field conditions, including the study of submarinc geology. Aerial photographs with accompanying geologic maps are shown to illustrate the appearance from the air of different geologic features under varying climatic and topographic conditions. Introduction The following paper is in no sense a contribution to knowledge; it is merely an attempt to indicate some of the benefits that may be expected from the use of aerial photographs in geologic mapping and to mention some inherent limitations. The writer has used aerial photographs in his own work for the past 13 years and has had ample opportunity to observe their use in the hands of others. From this experience certain conclusions have been drawn, which may be helpful to those using aerial photographs for the first time. It must he remembered that a photograph of the earth's surface can delineate only that which the eye can see; therefore the geologist should not expect more from an aerial photograph than he would be able to observe were he in the photographer's airplane looking at the area to be photographed. Theoretically, if the geologist had sufficient artistic ability, he could draw as good a geologic map from his position in the plane as he could from observation of the photograph. Practically this cannot be done because the airplane moves at a high rate of speed, which in itself prohibits detailed observation and, no matter how great the geologist's artistic ability, he could not reproduce the detail that can be recorded by a camera. An aerial photograph is a picture map of an area. The picture may be studied in the office until the geologist is thoroughly familiar with every minute detail of the surface of the ground he is about to geologize. If it is an area, underlain by sedimentary rocks, much may be learned

Jan 1, 1941

By Wayne Loel

The application of aerial photographs to all phases of geologic mapping is set forth, indicating the advantages to be gained in different types of country and undcr varying climatic conditions. Methods of field and office procedure are given from a geological point of view, as well as suggestions regarding the best methods of aerial mapping for different uses and under varying field conditions, including the study of submarinc geology. Aerial photographs with accompanying geologic maps are shown to illustrate the appearance from the air of different geologic features under varying climatic and topographic conditions. Introduction The following paper is in no sense a contribution to knowledge; it is merely an attempt to indicate some of the benefits that may be expected from the use of aerial photographs in geologic mapping and to mention some inherent limitations. The writer has used aerial photographs in his own work for the past 13 years and has had ample opportunity to observe their use in the hands of others. From this experience certain conclusions have been drawn, which may be helpful to those using aerial photographs for the first time. It must he remembered that a photograph of the earth's surface can delineate only that which the eye can see; therefore the geologist should not expect more from an aerial photograph than he would be able to observe were he in the photographer's airplane looking at the area to be photographed. Theoretically, if the geologist had sufficient artistic ability, he could draw as good a geologic map from his position in the plane as he could from observation of the photograph. Practically this cannot be done because the airplane moves at a high rate of speed, which in itself prohibits detailed observation and, no matter how great the geologist's artistic ability, he could not reproduce the detail that can be recorded by a camera. An aerial photograph is a picture map of an area. The picture may be studied in the office until the geologist is thoroughly familiar with every minute detail of the surface of the ground he is about to geologize. If it is an area, underlain by sedimentary rocks, much may be learned

Jan 1, 1941

By Henry M. Howe

in Cast-Iron. It has been generally accepted that the presence of silicon in cast-iron leads to the formation of graphite; and this has been explained by saying that the silicon lowers the solvent power of iron for carbon at and somewhat below the freezing-point, so that, in the presence of silicon, the iron is unable to retain in solution or combination the whole of the carbon with which it has united while molten, and therefore expels the excess of carbon in the form of graphite, during and immediately after solidification. Probably the best way to study this question would be to examine pure cast-irons, i.e., those containing nothing but iron, carbon and silicon, which at the same time should have been saturated with carbon when molten. But the data for such a study are not at hand; so we must turn to commercial pig-irons as they are made in the blast-furnace, and before their composition has been changed by remelting. Much evidence has been offered of late, tending to oppose the theory of the action of silicon above set forth. Some of this evidence will be examined here. 1. Mr. Bachman's Results. In particular, Mr. F. E. Bachman† has published a collection of analyses of cast-iron, in which the proportion of graphite at first appears to be nearly independent of the proportion of silicon present. Thus, in his Table LI., we find that with pro-

Jan 1, 1901

By T. Fraser, R. L. Sutherland

Under a cooperative agreement between United States Bureau of Mines and the Truax-Traer Coal Company, some operating-scale experiments have been made with the cyclone thickener in the preparation plant of the Shamrock No. 1 mine at Kayford, West Virginia. These tests were made with a 14-in. cyclone of the type developed by the Dutch State Mines in Limburg. It was applied experimentally to the thickening of solids in washery water to obtain performance data to show the range of sizes that may be recovered and other operating characteristics that would indicate the field of usefulness of this device in coal preparation practice. This is a progress report only. It covers results obtained in a series of 17 tests of the operation of what has been considered a unit of commercial size operating on suspensions of fine coal mixed with a relatively small amount of freeimpurities. The underflow material, after further dewatering in centrifuges, is a marketable grade of coal.

Jan 1, 1949

By D. G. Westlake

Levine has concluded that prismatic slip in titanium is controlled by two distinct thermally activated processes in the temperature ranges O° to 220°K and 220" to 300°K. We feel that his evidence is not convincing. He has drawn a curve through the plot of activation volume u* vs temperature T with a break at 22WK, Fig. 2. We believe that considering the possible experimental error apd the fact that there are only four points between 4° and 196°K, one could be justified to represent these points by the smooth curve we show as a solid line in Fig. 12. Levine believes that (8rf/aT)+ is discontinuous at 220°K, but he hints that he recognizes the possible doubt. We doubt seriously that the results shown in Fig. 1 indicate a discontinuity at 220°K. Certainly if he were justified in drawing a straight line through only four points on Fig. 2, we are even more justified in drawing straight lines through the seven points between 77" and 297°K on Figs. 1 and 3, because a straight line touches all seven of his circles. If his measurements of t were so precise that his decision to draw two curves in Fig. 3 is valid, then the experimental technique is deserving of further mention. We have drawn a smooth curve through the results in Fig. 3 and used this and the curve in Fig. 12 to obtain the values of shown in Fig. 13. Finding continuous is a contradiction of Fig. 4, which deserves comment itself. Levine obtained the solid circles in Fig. 4 using Fig. 2 and a smooth curve through the points shown in Fig. 3. We have replotted these solid circles in Fig. 14. We submit that there is no basis for his two straight lines (dashed in Fig. 14), and therefore have superimposed the curve that we believe is indicated. Certainly, there is reasonable doubt that a discontinuity in dH/dT exists at 220°K, even when one accepts Fig, 2. Furthermore, if one draws the straight lines indicated by least-squares treatments of the results presented as open circles in Fig. 4, their intersection is at about 196°K, not at 220°K as shown. Thus the alleged agreement between Figs. 3 and 4 with respect to "break" temperatures is not apparent. In Fig. 9, Levine has drawn a straight line very much different from the one indicated by a least-squares treatment. Obviously, he has done this because he recognized that H = 0 when T = 0. He is consistent in drawing the low-temperature curves in

Jan 1, 1968

By I. C. Edwards, G. E. Agar

INTRODUCTION Many research efforts over the past years have been devoted to the study of energy consumption in comminution and the characteristics of the broken material. The old "laws" have been superseded by more general methods of analysis1,2,3 but these methods have not received much attention outside the laboratory. The work to be described here was done in order to obtain scale-up information on wet rod milling of sylvinite. EXPERIMENTAL A 30 x 51 in. Denver rod mill with a scoop feeder was used for these tests. Ore was fed from a variable speed screw conveyor into the feed box along with saturated brine. The mill was filled to approximately 45% of its volume with 2400 lbs of a mixed rod charge. The minimum possible feed rate was 2.5 tph and the practical maximum for this mill was 8 tph. Individual tests were run by setting the solid feed rate, then adjusting the brine flow rate to give the desired pulp density. After steady state, as evidenced by constant discharge pulp density, had been reached, samples of the discharge were taken at 15-minute intervals. These samples were filtered, washed with alcohol, dried, then screened on Tyler screens using a Ro-tap shaker. The sylvinite feed was regular plant feed that had been scalped at 20 mesh and was tapped from the coarse ore bins. It had been previously passed through a roll crusher set at 3 inches and after scalping was essentially minus 1 in. plus 20 mesh. RESULTS The screen analysis of samples from each series of tests was plotted on double logarithmic scale paper to determine the reliability of the series. In some cases, a faulty sample or screening procedure dictated that the results of one test be discarded. The criterion is a simple one — if the slope of one plot was noticeably different from the others in the series, it was discarded. The only cases that caused difficulty were those in which the brine was not thoroughly displaced from the solids. When this occurred agglomerates were easily identified on the screens and the whole of the sample was retained on 3 or 4 screens. There were no border line cases. The number N given in Table 1 is the number of size analyses that were pooled to form the data shown in Fig. 1. While examining the reliability of the sizing and sampling by plotting the data, it became apparent that there was no significant difference between grinds made at 50 and 60% solids. For the analysis given here, these tests were regarded

Jan 1, 1967

By J. Gordon Parr, D. H. Polonis

IN a previous study of hypereutectoid Ti-Ni alloys' a substructure was observed in quenched powder specimens when the constitution was 100 pet retained ß body-centered-cubic phase. The alloy powders were quenched from 1000°C by a blast of helium gas and precautions already described were observed throughout the work, to minimize contamination. Ogden et al.2 have previously observed subboundaries in the ß phase of a Ti-Mn-N alloy; but this structure was attributed to nitrogen-rich a precipitation. The nitrogen content of the Ti-Ni alloys does not exceed 0.02 pet and the quenching rate was sufficiently rapid to suppress precipitation reactions. Since X-ray diffraction results have confirmed the absence of any second phase which might account for this phenomenon, it seems unlikely that this substructure is explicable in terms of nitrogen content. Fig. 1 shows the substructure in adjacent grains of 100 pet ß phase in a quenched 6 atomic pet Ni alloy. Fig. 2 shows adjacent ß grains in a similarly treated alloy; one grain contains marked intracrys-talline boundaries and the other is completely free from any substructure. The suberystals appear to have fairly regular shapes, suggesting a regular orientation relationship among them. Tempering the retained ß structure at temperatures below the eutectoid eliminates the substructure at an early stage of ß decomposition. At the present time it is possible only to guess at an explanation for this subboundary phenomenon, since very little work has been reported on substructures resulting from phase changes. It is believed that the present phenomenon is due to poly-gonization resulting from unrelieved stresses set up

Jan 1, 1957

By R. W. Moore, A. B. Kinzel

Although the iron-carbon diagram has undergone many changes in the last 20 years, the region below the eutectoid line and up to approximately 1.7 per cent carbon has been little affected. This region is generally considered to consist of cenlentite and ferrite. Graphite has been noted occasionally in the hypereutectoid steel region, and the ready formation of graphite nodules in malleable cast iron is a phenomenon difficult to interpret in the light of cementite, supposedly stable at sub-eutectoid temperatures. In this case the graphite formation has been partly explained by the presence of silicon, and many have believed that silicon acts to change the stable state rather than to accelerate reactions so as to arrive at the stable state in a briefer period of time. Consideration of this phenomenon indicates that cementite is not the stable phase in the temperature composition zone referred to. In the course of examining a low-carbon steel tube taken from a petroleum cracking still, which had been in service for approximately three years at temperatures somewhat below the eutectoid temperature, observations were made that shed light on this entire subject. The tube in question analyzed:' C, 0.15 per cent; Mn, 0.49; Si, 0.02; S, 0.023; P, 0.015. The microstructure of the tube after service is shown In Figs. 1 and 2. From these it is evident that cementite as such is absent, and that in its place nodular graphite has been formed. In order to check this observation further, samples taken from the tube were heated at 850" C. for varying periods of time. The small samples were put into a large hot furnace, and the total time is recorded. The structure of the sample after 5 min. at 850" C. is shown in Figs. 3 and 4, and the nest of pearlite surrounding the graphite nodules is most satisfactory evidence of the character of the nodules. As the length of time of heating at this temperature increases, the pearlitic zone increases, with final restoration

Jan 1, 1935