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By C. B. Foster, S. I. Freedman, E. M. Jamgochian

Coal-oil mixture (COM) combustion technology is regarded by the US Department of Energy (DOE) as near term and Potentially applicable to existing utility and industrial steam generators and for injection into blast furnaces. From work done previously, it has been established that COM can be burned in existing boilers and blast furnaces. Therefore, the issues being addressed by the current DOE program are: (1) determination of best available technology to achieve environmentally acceptable long-term reliable operation and (2) determination of applications for which COM can be utilized economically. Some of the technological options have begun to be determined by projects already under way. However, many projects are still in the early stages of development.

Jan 1, 1980

By Edward Martinez

Although the copper segregation process has been known as a method for treating oxide copper ores since the 1920's, the reactions involved in this process are still a matter of conjecture. However, the evidence turned up in a recent series of experiments at Asarco's Central Research Laboratories strongly indicates that some of the proposed reactions may not be occurring. Experimental work on oxide copper ores from the Sagasca mines in Chile led to the discovery of the copper segregation process in 1923. It was found that the reduction of the copper with coal at about 700°C occurred on the surface of the coal instead of remaining disseminated in the ore. The unusual behavior of the copper, which caused it to migrate from the ore particles to the coal, was traced to the presence of a small quantity of sodium chloride occurring in the ore. Further experiments with oxide copper ores proved that the presence of a halide, either occurring naturally or admixed with the ore, caused the copper to migrate from the ore particles and to segregate in the charge.

Jan 8, 1966

By M. Kaufman, D. Rosenthal

IT would be of great importance to our understanding of the phenomena of fracture in metals if a unique relationship could be established between stress and some easily measurable parameter of deformation up to the fracture. It is known that no such relationshir, has been found when the parameter was the mechanically measured strain,' the major part of which is plastic. The present investigation was initiated to determine, among other things, if the X-ray or lattice strain" might be a • For the definition of lattice strain see ref. 2. more suitable parameter. To this end, annealed stress free*' specimens of 61s aluminum alloy were ** Freedom of stress in this particular case means absence of those stresses which can be checked by the technique employed. tested at room temperature and liquid nitrogen temperature (—195OC), by first maintaining the same temperature from the beginning until the end of the test, and then with crossovers from one temperature to the other. Three major factors had to be taken into consideration in designing the specimens and testing equipment. The test setup must allow X-ray pictures to be taken while the specimen is under load (for as much as 2 hr at a given load). Provision must be made for maintaining the test specimen at the temperature of liquid nitrogen as well as at room temperature. In addition, the specimen must be able to rotate to allow the X,ray beam to take in as large a sample of grains as possible, to maintain centering, and to correct for effects of large grains. The final design of the specimen and equipment is shown in Figs. 1 and 2. The specimen and grips are hollow, enabling liquid nitrogen to be poured in through a funnel-container arrangement while the specimen is rotating. The diameter of the specimens at the 2 in. gage section is 5/16 in. with a 3/16 in. diameter hole through the center. A small pilot valve in the lower grip allows a very small stream of liquid nitrogen to escape, thus assuring circulation of the liquid at all times. A low temperature silicone grease-tissue paper packing is used to seal all joints. The specimen is held in the grips by a pin. Spherical socket joints at top and bottom are used to allow for proper alignment. The grips are connected to the thrust bearings by means of plastic couplings to decrease the heat flow. Rotation is accomplished by means of a motor which drives a plastic gear (integral with the lower coupling) through a semiuniversal joint to allow for deforma- tion of the specimen. The torque applied to the specimen is very small. The maximum stress caused by this torque at the highest loads reached was found to be less than 200 psi, The whole unit was mounted in a 10,000 Ib testing machine. An insulation cage was placed around the specimen to cut down air circulation, and consequent frosting of the specimen, and also to reduce radiation and convection heat losses. A narrow window, covered on both sides with a thin plastic materiai allows the X-ray beam to reach the specimen. Thermocouples placed just outside the pilot hole at the lower grip, in the bottom of the funnel container and near the top of the funnel container permitted checks of the

Jan 1, 1955

By Eric J. Jette, Frank Foote

The unusual physical, electrical and magnetic properties of the iron-nickel alloys has given rise to a voluminous literature. This work will be reviewed critically in "The Alloys of Iron and Nickel," a monograph of the Alloys of Iron Research Series, soon to be published. In what follows we shall therefore confine ourselves to those of the earlier investigations that involved the use of X-ray crystal-structure methods. The earliest X-ray work on the iron-nickel system was by Miss Andrewsl. Using the powder method of X-ray analysis purely as a means of identifying the phases present, she located a region between 20 and 30 weight per cent nickel in which body-centered and face-centered phases coexisted. No lattice constants nor details of heat-treatment were reported. Bain2 also reported some qualitative observations. McKeehan3 made a systematic investigation over the whole of the system, giving many of his alloys four and some five different heat-treatments. In alloys furnace-cooled from 900' to 950' C. he found two coexisting phases between 0.15 and 30 per cent nickel. The precision of the lattice-constant measurements was low in comparison with what can be obtained today. Even for alloys of the same heat-treatment, differences in the constants were often between two and ten parts per thousand. In regions where no change of lattice constant with heat-treatment should occur, differences of the same order of magnitude were found. Since the maximum change in the lattice constant of nickel with change of composition is only about 2 per cent of the constant for pure nickel, these variations in the constants for a given alloy cause the points to "scatter" badly about any curve that may be drawn to represent them and it is difficult to interpret such results. In spite of this, McKeehan shows that the lattice constant of nickel increased as the iron content increased. His results for the alpha-iron phase are less conclusive. Osawa4 also investigated the entire system. For alloys slowly cooled from 1150' C. and then filed into samples for X-ray analysis, he found

Jan 1, 1936

By Frank Foote, Eric J. Jette

The unusual physical, electrical and magnetic properties of the iron-nickel alloys has given rise to a voluminous literature. This work will be reviewed critically in "The Alloys of Iron and Nickel," a monograph of the Alloys of Iron Research Series, soon to be published. In what follows we shall therefore confine ourselves to those of the earlier investigations that involved the use of X-ray crystal-structure methods. The earliest X-ray work on the iron-nickel system was by Miss Andrewsl. Using the powder method of X-ray analysis purely as a means of identifying the phases present, she located a region between 20 and 30 weight per cent nickel in which body-centered and face-centered phases coexisted. No lattice constants nor details of heat-treatment were reported. Bain2 also reported some qualitative observations. McKeehan3 made a systematic investigation over the whole of the system, giving many of his alloys four and some five different heat-treatments. In alloys furnace-cooled from 900' to 950' C. he found two coexisting phases between 0.15 and 30 per cent nickel. The precision of the lattice-constant measurements was low in comparison with what can be obtained today. Even for alloys of the same heat-treatment, differences in the constants were often between two and ten parts per thousand. In regions where no change of lattice constant with heat-treatment should occur, differences of the same order of magnitude were found. Since the maximum change in the lattice constant of nickel with change of composition is only about 2 per cent of the constant for pure nickel, these variations in the constants for a given alloy cause the points to "scatter" badly about any curve that may be drawn to represent them and it is difficult to interpret such results. In spite of this, McKeehan shows that the lattice constant of nickel increased as the iron content increased. His results for the alpha-iron phase are less conclusive. Osawa4 also investigated the entire system. For alloys slowly cooled from 1150' C. and then filed into samples for X-ray analysis, he found

Jan 1, 1936

The surface area that mining requires is a minuscule fraction of the total land mass of the United States, according to the US Bureau of Mines' latest report "Land Utilization and Reclamation in the Mining Industry, 1930-71." During the 42-year period from 1930 to 1971, the mining industry utilized 3.65 million acres-only 0.16% of a total 2.27 billion acres of land-and reclaimed 1.46 mil- lion acres, or 40% of what it used. Which leaves, as still unreclaimed, 0.096% of the nation's total land mass.

Jan 10, 1974

By L. E. Shiffman

W. J. Parton—Those operators faced with the problem of treating fine coal whether in bituminous or anthracite will find this paper most timely. I would like to take this opportunity of discussing Mr. Schiffman's paper and at the same time express certain views relating to our Tamaqua plant. I would like to ask the author what type of impeller and diffuser is used in the Denver cells? Screen analysis of products from individual cells indicate that coarser material resists flotation and only floats after greater retention time in the last few cells. Also, the need for a scavenger screen to reclaim non-floated coal particles further stresses this point. I have always felt that more efficient means of cleaning coal between 10-mesh and 28-mesh existed than flotation. Reagent and power costs are high for the flotation process. When floating +28-mesh particles, cell capacity is lowered and some of the particles are lost with the refuse. The Tamaqua plant of the Lehigh Navigation Coal Co. floats —28-mesh coal and capacity of recoverable coal is 40 tph for 1800 cu ft of Denver cells; or 0.05 tons per cu ft of cell. At Kimberly 7.75 tph for 600 cu ft of cell gives 0.013 ton per cu ft of cell. At Bessie 14 tph for 800 cu ft of cell gives 0.017 tons per cu ft of cell. It would be appreciated if the author would comment on what he feels is the upper size limit of particle to attain most efficient utilization of the flotation process. The dewatering screw is a very interesting development since it offers a simple way to prepare coal sludge for more complete clewatering by drainage or mechanical dewatering on screen or filters. In other words it could be used to accomplish the same thing as a thickener tank. I would appreciate having the author's comment on how he thinks such a screw dewaterer would work on a froth.* The process as used in floating coal at the Bessie and Kimberly plants may be referred to as more of a bulk oil float in contrast to a froth flotation process. Experiments on increasing capacity of cells is most interesting since we are going through such an experi- mental period at the present time. Recently a double overflow was installed on our No. 30 Denver cells. So far results are not conclusive. In reviewing this paper the following comments are made pertaining to investigation of methods for increasing capacity: Supercharging: Supercharged air in matte flotation or for that matter the use of the normal amount of air drawn in by the impeller would in all probability cause such an aeration in the cell as to destroy the buoyant effect given to the coal particles by the excessive amount of kerosine used. In other words, air creates an agitation zone throughout the cell, creating a boiling and thereby giving a lower recovery in the cell. It would be interesting to know whether the 7 pct increase in recovery was with no air being admitted to the stand pipe. Changing Impeller Speed: The speed of a receded disc impeller for a No. 30 cell as recommended by the Denver Equipment Co. is, I believe, approximately 250 rpm. At this speed and using supercharged air in excess of 8-oz pressure, we have observed a boiling action in the cells. In our flotation we endeavor to obtain some degree of froth flotation using pine oil as a frother. The boiling action as caused by increasing the amount of air added to the cells is detrimental to recovery in froth flotation. It is our belief that to obtain increased recovery from a cell in froth flotation, additional air must be introduced but at the same time this air must be dispersed throughout the pulp in the form of small bubbles and this can only be done by increasing the speed of the impeller. Therefore, if Mr. Schiffman decreased the speed of the No. 30 impellers and at the same time continued to use supercharged air, the boiling action may have been increased because larger bubbles developed. The lower recovery as reported could be due to this factor. Decreasing the impeller speed will definitely decrease the power consumed but may have other disadvantages. First, we believe it will permit "sanding" in the cell and this in our opinion will increase the wear on the impeller and diffuser, especially so, if there is pyrite and/or sand present in the feed. "Sanding" in the cell when air is used, as in froth flotation, will effect the dispersion of this air and cause boiling.

Jan 1, 1951

By L. E. Shiffman

W. J. Parton—Those operators faced with the problem of treating fine coal whether in bituminous or anthracite will find this paper most timely. I would like to take this opportunity of discussing Mr. Schiffman's paper and at the same time express certain views relating to our Tamaqua plant. I would like to ask the author what type of impeller and diffuser is used in the Denver cells? Screen analysis of products from individual cells indicate that coarser material resists flotation and only floats after greater retention time in the last few cells. Also, the need for a scavenger screen to reclaim non-floated coal particles further stresses this point. I have always felt that more efficient means of cleaning coal between 10-mesh and 28-mesh existed than flotation. Reagent and power costs are high for the flotation process. When floating +28-mesh particles, cell capacity is lowered and some of the particles are lost with the refuse. The Tamaqua plant of the Lehigh Navigation Coal Co. floats —28-mesh coal and capacity of recoverable coal is 40 tph for 1800 cu ft of Denver cells; or 0.05 tons per cu ft of cell. At Kimberly 7.75 tph for 600 cu ft of cell gives 0.013 ton per cu ft of cell. At Bessie 14 tph for 800 cu ft of cell gives 0.017 tons per cu ft of cell. It would be appreciated if the author would comment on what he feels is the upper size limit of particle to attain most efficient utilization of the flotation process. The dewatering screw is a very interesting development since it offers a simple way to prepare coal sludge for more complete clewatering by drainage or mechanical dewatering on screen or filters. In other words it could be used to accomplish the same thing as a thickener tank. I would appreciate having the author's comment on how he thinks such a screw dewaterer would work on a froth.* The process as used in floating coal at the Bessie and Kimberly plants may be referred to as more of a bulk oil float in contrast to a froth flotation process. Experiments on increasing capacity of cells is most interesting since we are going through such an experi- mental period at the present time. Recently a double overflow was installed on our No. 30 Denver cells. So far results are not conclusive. In reviewing this paper the following comments are made pertaining to investigation of methods for increasing capacity: Supercharging: Supercharged air in matte flotation or for that matter the use of the normal amount of air drawn in by the impeller would in all probability cause such an aeration in the cell as to destroy the buoyant effect given to the coal particles by the excessive amount of kerosine used. In other words, air creates an agitation zone throughout the cell, creating a boiling and thereby giving a lower recovery in the cell. It would be interesting to know whether the 7 pct increase in recovery was with no air being admitted to the stand pipe. Changing Impeller Speed: The speed of a receded disc impeller for a No. 30 cell as recommended by the Denver Equipment Co. is, I believe, approximately 250 rpm. At this speed and using supercharged air in excess of 8-oz pressure, we have observed a boiling action in the cells. In our flotation we endeavor to obtain some degree of froth flotation using pine oil as a frother. The boiling action as caused by increasing the amount of air added to the cells is detrimental to recovery in froth flotation. It is our belief that to obtain increased recovery from a cell in froth flotation, additional air must be introduced but at the same time this air must be dispersed throughout the pulp in the form of small bubbles and this can only be done by increasing the speed of the impeller. Therefore, if Mr. Schiffman decreased the speed of the No. 30 impellers and at the same time continued to use supercharged air, the boiling action may have been increased because larger bubbles developed. The lower recovery as reported could be due to this factor. Decreasing the impeller speed will definitely decrease the power consumed but may have other disadvantages. First, we believe it will permit "sanding" in the cell and this in our opinion will increase the wear on the impeller and diffuser, especially so, if there is pyrite and/or sand present in the feed. "Sanding" in the cell when air is used, as in froth flotation, will effect the dispersion of this air and cause boiling.

Jan 1, 1951

(The following list contains the names of those members of the Institute of whose connection with military service. we have only recently become acquainted; it also includes the names of a few who have recently been promoted or transferred. A complete list was published in the Year Book, issued as a supplement of the Bulletin for March, 1918.) ADAMS, HENRY, Major, Assistant to Department Engineer, North-eastern Dept. ALINE, P. A., Co. C, 316th Supply Trains. * Low-cost cottage construction in America; a study based on the housing collection in the Harvard Social Museum, by Winthrop A. Hamlin. Cambridge, Mass., Harvard University, 1917. (Publications of the Department of Social Ethics, No. 7.) 30 pp., 4 charts. Illus.

Jan 5, 1918

By T. A. Dungan

THE thermal processes for the production of metallic magnesium can be divided into two general classifications, the direct reduction of magnesia with carbon and the indirect reduction of compounds of magnesium by reducing agents that are themselves products of carbon reduction. The latter are so chosen as to cause reduction of magnesium compounds wherein only the magnesium is liberated in the vapor phase. Reducing agents used are: calcium carbide, silicon carbide, silicon, aluminum, various silicides or combinations of calcium, aluminum, silicon in iron. All of these are products of highly endothermic reactions and, with the exception of scrap aluminum, can be produced in an open, submerged arc furnace; that is, the arc is covered only by the charge itself. The more investment in energy required to prepare such a reducing agent, the less is the energy required in the subsequent step to reduce the magnesium compound to the metal. It is impossible, however, to avoid the laws of thermodynamics, no matter how much circumambulation is resorted to in the preparation of successively more powerful reducing agents. Since each such step carries forward its own inefficiencies, it appears evident that the ultimate status of such processes is dependent upon the development of by-products. EARLY EXPERIMENTS IN DIRECT REDUCTION The direct reduction of magnesium oxide by carbon has a decided appeal to both the scientist and the industrialist. The successful production of the carbothermic plant at Permanente is a significant fact in the substantiation of this concept. Like most developments, however, the history of carbon reduction of magnesia is not one of triumph after triumph, or immediate heady success to the investigators. It is understood that one of the early investigators conducted an experiment wherein he placed carbon and magnesia in one end of an evacuated tube and managed to heat this end to a temperature high enough that magnesia and carbon deposited at the other end of the tube. The charge, unreduced, appeared to have been completely transported from the hot to the cold end of the tube. This raised doubt for some time as to whether magnesia could be reduced at all with carbon. It was correctly suspected, however, that the magnesia was in fact reduced and the resultant magnesium vapor and carbon monoxide reacted upon one another upon reduction in temperature to reform the starting ingredients. Attempts were then made to dilute the two vapors by passing a considerable stream of hydrogen through an arc furnace charged with magnesia and carbon. Thus by dilution of the products it was expected to obtain metallic magnesium. The results were positive and metallic magnesium was

Jan 1, 1944

By Victor deWolfe

INTRODUCTION The Henderson Mine, located near Empire, Colorado, utilizes a continuous panel caving system to extract ore as one of the world's major producers of molybdenum. Any mine using a caving-by-gravity technique of mining must rely on closely controlled draw of the caved ore. This control is essential to insure proper caving action, to avoid damaging load concentrations of weight and to minimize the dilution of ore with waste material. Henderson is no exception. Draw control is a major factor in all production planning, from long- range plans to short-range and day-to-day ore scheduling. Draw control is reviewed constantly and administered daily in an effort to optimize production efficiency, ore recovery, and cave management. MINING METHOD The cave at Henderson is massive, moving slowly through large panels that are 244 m (800 ft.) wide by 610 m (2,000 ft.) long. Generally two cave areas are drawn at one time. The areas under active draw vary in size but can be as large as 244 m (800 ft.) by 244 m (800 ft. ) containing 400 draw points. Each draw point contains 45,360 mt (50,000 st) on the average and takes about two and one half years to exhaust. A complete panel is worked for seven to ten years. No pillar exists between panels, but rather a buffer zone of broken ore, or "static face," is left in each panel to be drawn with the adjacent, yet-to-be-caved panel in efforts of minimizing dilution of a working area from an exhausted one. (Figure 1) Production drifts are driven on 24.4 m (80 ft.) centers through the ore body. Between the production drifts are funnel-shaped draw bells on 12.2 m (40 ft.) x 24.4 m (80 ft.) centers to receive ore from the cave. Each bell is accessed by two draw points, one from the production drift on either side, thus forming a 12.2 m (40 ft.) x 12.2 m (40 ft.) draw pattern. Extraction of the ore is by rubber-tired, 3.8 m3 (5 yd3) load-haul-dump equipment. The LHDs then tram the ore a maximum of 49 m (160 ft.) to ore passes. Cave initiation and bell development are done from the undercut drifts which are parallel to and 17 m (55 ft.) directly above the production drifts. Longhole rings are drilled and blasted from the undercut drifts to define the bells and establish the undercut for caving. (Figure 2) DRAW CONTROL Since the cave line at Henderson is constantly advancing, it is necessary to be continually initiating new cave at one end while exhausting it at the opposite end. There must exist, therefore, an angle on the ore-waste contact in the broken rock from initiation to exhaustion. The basic concept of draw control is to keep this angle as smooth and even as possible, particularly at the time of exhaustion. If this is achieved, draw points are exhausted more or less in a line, avoiding pockets of remaining ore surrounded by exhausted areas. These pockets would cause spotty ore extraction at the time of exhaustion, increasing the amount of dilution occurring while introducing the potential for significant weight problems in the production area. To arrive at the desired angle on the ore- waste contact, maximum tonnage percentages are assigned to each row of draw points increasing at 10% or 15% increments (depending on cave size and velocity of draw) working away from the cave line. The available tonnage indicated by these percentages is the maximum allowable tonnage to be extracted from each draw point until the available tonnage percent- age is increased. As the cave moves, these percentages increase for each draw point regularly. However, in general the tonnage drawn from each draw point is kept at about 50% of this allowable maximum in order to maintain adequate available tonnage in the cave to sustain production for seven months if cave initiation were to cease. This available tonnage cushion is a safeguard built into the draw control program at Henderson to accommodate fluctuations in the rate of cave advance. When draw points move past the row of 100% tonnage availability, they are drawn past the desired 50% at the same increments per row until exhausted. (Figure 3) To achieve proper draw control, the number of LHD buckets to be taken from each draw point is assigned daily. The actual buckets taken, which may at times deviate from the

Jan 1, 1981

ZAY JEFFRIES (written discussion*).-I have read with much interest Mr. Ruder's discussion of Professor Howe's paper, "The Supposed Reversal of Inheritance of Ferrite Grain Size from that of Austenite." I am yet of the opinion that my first explanation' of Mr. Ruder's samples is substantially correct. In that explanation I did not intend, however, to convey the impression that "reversed inheritance" was the general rule nor even of common occurrence but rather that." Non-inheritance" was the general rule. Mr. Ruder suggests that a " perfectly formed" grain is an indication of inheritance. The grains in my Fig. 52 are perfectly formed and in fact more nearly equiaxed than those in Mr. Ruder's Fig: C,3 yet the grains in the former are known not to be inherited but to have been formed by the partitioning of larger austenite grains. On close examination of Mr. Ruder's Fig. C the very shapes of the grain suggest partitioning. Again, the grain size (25 to 30 grains per square millimeter) is at least 10 or- more likely 20 times smaller than might be expected of the austenite from which these grains were .formed under the given time and temperature conditions. Mr. Ruder's newer results on electrolytic and Armco iron are most interesting and instructive. His results fit in. nicely with my conclusions 5, 6 and 10.4 His photographs, however, indicate that the thickness of the pieces of sheet metal are such that abnormal grain growth is promoted. He indicates that equilibrium grain size after heating to 950° C., with furnace cooling, is about the same as his Fig. 1, above. I estimate this to be approximately one-half -grain per square millimeter, or 40 times as large as I have obtained with the same material (Armco iron) after heating Y4-in. bars to 1300° C. for 2 hr. and cooling in the furnace. The effect of thickness of sample on grain size is one which needs more attention.

Jan 3, 1918

By L. G. Evans, C. Rampacek, G. A. Freeman

A large aggregate tonnage of oxidized and mixed oxide-sulfide copper ore of the southwestern U.S. is not amenable to conventional flotation concentration or sulfuric acid leach treatment. Most of the ores contain chrysocolla as the principal oxide copper mineral, for which no successful commercial flotation method has yet been developed. Acid leaching some ores is not feasible since they contain substantial quantities of calcite and other acid-consuming constituents. Other ores decrepitate during leaching or contain excessive slime and clay minerals which cause plugging of the ore beds.

Jan 10, 1961

By E. A. Holbrook

MINING Metallurgy, and Petroleum Engineering department in our colleges are facing a crisis; indeed, conditions that threaten their very existence. Unless the Army, Navy, and War Manpower Commission change their present policy, within two years mineral industries education as now carried on will die, because no ablebodied students will be left in the course. If this is the decision of our responsible governmental agencies we of the mining schools must perhaps accept it as a war measure. It might be well however, for the executive of our mining metallurgical, and oil companies to look ahead a, to where they are to recruit a supply of young technically trained engineers. You can no more operate a mine, a steel plant or an oil company without trained engineers than you can operate a battleship without mechanical and electrical engineers.

Jan 1, 1943

By T. L. Joseph

A study is made of the amount of solution loss necessary to maintain the reducing power of the gas stream in the blast furnace. Curves are presented to show the effect of solution loss, moisture in the blast, and carbon dioxide from the flux on the nitrogen in the THE blast furnace process is based upon the counter flow of gases and solids. As CO, N, and H, flow upward from the combustion zones, oxygen is acquired from the descending charge. In the reduction of iron ore, a portion of CO is converted to CO, and similarly a portion of H, is converted to water vapor. The inert N,, from the air used in combustion, passes through the furnace with little change. Its concentration is, however, decreased by reactions such as direct reduction and solution loss which increase the volume of CO in the gas stream; Similarly the evolution of C02 from the limestone also dilutes the nitrogen. he purpose of this paper is to illustrate an idealized and simplified method of studying furnace processes by following changes in the gas phase between the tuyeres and the stock line. A more specific objective is to evaluate the effect of solution loss upon the CO/CO, ratio in that region of the furnace in which FeO is reduced to metallic iron. This last stage of reduction requires relatively high CO/CO, ratios to exceed the equilibrium requirements. Solution loss or the reaction of COZ with C to produce CO has a pronounced effect upon the ratio of the carbon gases and is necessary to maintain the reducing power of the gas stream if the consumption of coke is low. It will be explained later that indirect reduction followed by solution loss is stoichiometri-cally equivalent to direct reduction. Calculations will be made to show how the composition of the gas in the region of the mantle varies with coke consumption and with different amounts of solution loss. Such calculations show the condi- tions under which gasification of C with oxygen in the charge is needed to maintain the reducing power of the gas. Equilibrium conditions for FeO and the carbon gases will be used to establish a minimum CO/CO, ratio below which reduction will not proceed. The manner in which carbon is gasified in the furnace, at the tuyeres with oxygen in the air or above the tuyeres with oxygen from the charge, will be a basic feature of all calculations. It is hoped that greater interest in the use of top gas as a means of following furnace reactions will be aroused by the calculations and generalized curves which are presented. Bosh Gas Equations Subject to some alteration by the amount of moisture in the blast and by direct reduction, the gas leaving the combustion zones of a blast furnace has a definite composition. Because a relatively small amount of oxygen is acquired from the charge in the bosh and in the crucible, the products of combustion undergo little change until they enter the shaft. Bosh gas is, therefore, essentially the products of combustion of carbon in a deep fuel bed with air. The relative weights and volumes of reacting materials are expressed by the equation: 2~ + 0? + 3.76N, = 2C0 $ 3.76NZ [I] Air Bosh Gas -air = 79% N? = 3.76) 21% 02 Starting with a known mass of C consumed largely by air, Eq 1, but partly by water vapor, Eq 2, the volume and C + H2O = CO $ H? [21 composition of the bosh gas can be calculated and subsequent changes followed as reactions take place at various elevations in the furnace. As shown in

Jan 1, 1952

By P. M. Kelly, E. P. Butler

Four Mn-CLL alloys, containing 60, 70, 80, and 90 pct Mn, respectively, have been examined in the quenched and the quenched and aged conditions using electron microscopy and electron, neutron, and X-ray diffraction. After certain heat treatments the alloys transform from fee to fct and in the tetraom1 condition show a domain structure parallel to {101} planes. Neutron diffraction indicates that the domains are antiferrornagnetically ordered. The domain boundary contrast has been examined using bright- and dark-field microscopy, and the contrast effects observed under favorable conditions have been used to deduce the c axis orientation in each domain. The domains are extremely mobile and can be nucleated at precipitate particles and screw dislocations. The domain mobility is responsible for the high damping capacity. In the aged material a Mn precipitates in the Kurdjumov-Sachs orientation and results of both electron microscopy and neutron diffraction indicate that the matrix separates into two components—one rich in manganese and the other rich in copper. ALLOYS of manganese and copper have the unusual combination of a high damping capacity and good mechanical properties and have been the subject of a number of investigations as part of a general interest in high damping capacity alloys for engineering purposes.&apos;,&apos; SO far, however, there has been no reported electron metallographic study of these alloys. The Mn-Cu system has an extensive range of solid solubility at high temperatures, and the equilibrium phases are expected to be y (fee) and a Mn. The high damping capacity is associated with a metastable tetragonal structure of variable c/a ratio, which forms from the high-temperature y phase. This latter phase becomes more difficult to retain as the manganese content increases, and alloys containing more than 82 wt pct Mn undergo a reversible martensitic fcc — fct transformation on quenching. The X-ray work of Basinski and christian3 showed that the Ms temperature for the transformation was below room temperature for alloys in the range 70 to 82 pct Mn and increased linearly with manganese content. When quenched from the y region, alloys in the range 50 to 82 pct Mn are cubic at room temperature, but become tetragonal if aged at temperatures between 400" and 600°C. The martensite transformation occurs on cooling from the aging temperature. Tetragonal alloys have a banded microstructure and the bands analyze to be traces of (110) planes. Similar microstructures have been observed in In-Tl4 and in other manganese-base systems, such as Mn-Au5 and Mn-Ni.6 The mobility of the bands in Mn-Cu alloys can be demonstrated by optical examination of a polished specimen surface subjected to a cyclic stress.7 The bands appear and disappear as the stress is varied, and X-ray measurements of the (200,020) and (002) peak intensities confirm that a reversible reorientation of the tetragonal structure occurs. Meneghetti and sidhu8 investigated the magnetic structure of Mn-Cu alloys and found antiferromagnetic ordering in furnace-cooled alloys of composition >69 at. pct Mn. Magnetic super lattice reflections occurred at the (110) and (201) positions and the proposed structure was fct with the spins along the c axis. A more complete investigation by Bacon et al.9 confirmed this structure. The magnetic ordering temperature Tn was found to increase linearly with manganese content in the same way as the Ms temperature, and at any composition, Tn > Ms. This relationship suggested that the magnetic ordering was responsible for the cubic — tetragonal transformation in the manganese-rich alloys. The purpose of this investigation was to study the mechanism of high damping and the structural changes that occur on aging. The main technique used was transmission electron microscopy, but X-ray and neutron diffraction experiments were also carried out. EXPERIMENTAL Materials and Heat Treatment. The four alloys, provided by the Admiralty Materials Laboratory. were of nominai composition 60, 70, 80, and 90 Mn and all had low impurity levels, <0.05 pct C, <0.2 pct Fe. This material was cold-rolled to 200-µ strip with intermediate annealing and then given a final heat treatment of 24 hr in the range 800° to 900°C followed by water quenching. An identical heat treatment was given a length of 3/4-in.-diam bar of the 70/30 alloy from which the neutron diffraction specimens were machined. It was suspected that the tetragonal structures would be metastable at room temperature, and so the alloys were not aged until required for experiments. After aging in a salt bath the alloys were water-quenched. Thin Foil Preparation. Initial thinning to 50 to 75 µ was possible in a solution consisting of: 50 ml nitric acid 25 ml acetic acid 25 ml water The surface deposit and grain boundary etching was removed by a final electropolish at around 20 V in an electrolyte consisting of:

Jan 1, 1969

By Leo F. Reinartz

Part II of a four-part series on the history of steelmaking in the US, points out the inadequate safety and living conditions that existed in steel mills at the turn of the Century. Also defined are furnace and process developments. OPERATIONS in steel plants today are highly mechanized. Men work in light, clean, orderly melting shops, making it difficult for old timers to convince young men that primitive, hazardous conditions existed in steel plants at the turn of the century. Working conditions then were very poor as compared to present day standards. In small plants especially, sanitary, locker, and washroom facilities, first-aid practices and stations were un- known Accidents were frequent and severe. Workers had a fatalistic attitude toward getting hurt. He who had an accident was looked upon as a hero. A dirty bandanna often served as a bandage. Infections were frequent. Electric cranes were in their infancy and broke down often Cables had not as yet replaced chains. Pig iron and scrap iron were loaded by hand in the stockyard, and stockyard locomotives were un- known; mules served as the usual motive power. It was not unusual to see recorded a delay of ½ hr in charging a furnace because of a balky mule. Furnace operations A few plants had primitive charging machines, but most furnaces were charged by placing scrap or pig iron on the paddle of a long peel, which rested on a bar across the furnace door opening. Laborers at the handle end of the peel, using the bar as a fulcrum, would heave the material into the furnace by a down and sideward motion of the peel handle. In time they became expert in placing these materials in the furnace, but it was hard, hot work, and a long time was required for charging. Cold charges of 25 tons required more than 12 hr for melting and re- fining the steel. Ports, doors, and frames were not water cooled. The charging and working area in front of the furnace was covered with steel plates. They were hot and often warped by the intense heat of the un- insulated checker chambers directly below. In the summer, working conditions on the charging floor were almost unbearable. Silica refractories were of poor quality. Because of this, and the inadequate training of furnace men in fuel control and furnace operations, roofs, front and back walls, and ends burned out rapidly. Dolomite machines were unknown; consequently, furnace banks and hearths were fettled with dolomite by the use of hand shovels. The round system required six or more men. Each man took a shovelful of dolomite and, in his turn, deposited it on the back wall and bank by a dexterous forward swing and twist of the shovel. The upward swing of the shovel partially protected his face from the searing heat of the furnace coming out through the wide-open door. Considerable skill and stamina were required to do this job properly. Reverse valves, usually of the cast-iron butterfly type, were located below the charging floor. They were operated by long levers on the charging floor level men they became warped, because of heat and abuse, great strength and skill were required to reverse them. Furnace operations were difficult. The quality and quantity of producer gas coming from irregularly stoked, hand-operated gas producers was uncertain and unreliable. Furnace Linings and ports were quickly burned out. Poor bottom and side-wall refractories, indifferent and inexperienced crews, as well as irregular re-

Jan 1, 1961

By Arthur L. Hawthorne

10.1-1. Relative Position of Maintenance as Compared to the Overall Mining Costs. The basic issue regarding the importance of maintenance in the modern mining industry must be faced squarely by the top manage- ment of each company before any real progress can be made in organizing a maintenance program for optimum effectiveness. Just a few decades ago the maintenance at coal mines consisted primarily of a blacksmith for sharpening picks and shoeing mules; as a result, probably less than 5%of the total mining cost went to maintenance and some 80% was operating expenses (operating labor). With each succeeding advance in equipment design towards larger, more complex, and more productive units, the pendu- lum swings the other way. As an example, haulage trucks have progressed through various stages in the past 20 years from 15-ton units to a 240-ton truck now in the "shakedown" or experimental stage. The following com- parison between 15-ton, 50-ton, and 100-ton haulage trucks clearly illus- trates this changing cost pattern in terms of percent of overall costs for running each size unit. [Maintenance 24% 44 % 51 % Operating labor 59 % 33 % 16% Operating supplies (fuel oil) 4 %. 4% 3% Labor burden and vac. pay 6 % 4% 3% Depreciation Total] From the preceding figures it is interesting to note that, as a rule, operat- ing costs go down as the equipment gets larger and the maintenance costs increase with the larger units. This same trend in cost variation applies to nearly all mechanical equipment used in surface mining from the large

Jan 1, 1968

By Guy W. Jordan, David P. Hale

High-iRon cements have a number of advantages over cements carrying little or no iron. The presence of iron in Portland cement aids in the manufacture of the cement and also imparts certain advantageous physical properties to the finished product. In manufacture, the presence of iron lowers the fuel consumption, increases the ease of proper"burning, and lessens the destructive action of the charge on the kiln refractories. In the finished cement the presence of iron reduces the expansion and contraction, adds strength, adds increased resistance to"freezing and thawing, and increases the resistance of the cement to sea "or sulphate waters. [" During the past few years the construction of numerous dams through- "out the Southeast by the Tennessee Valley Authority has stimulated the "production of high-iron cements. At present a great number of specifica- "tions call for an iron cement, and the industry is supplying this demand "with a Portland cement carrying approximately 5 per cent iron oxide. "Several manufacturers are now making practically all of their cement "of this type and a number of others manufacture it as a special cement "over short periods to meet demands from the Tennessee Valley Authority "and other buyers. " The recent increase in the use of iron in Portland cement has created "a market for iron products that previously was nonexistent. The chief "sources of supply for the cement manufacturers at present are iron sand, "iron sinter and slag, and ocher. The Copperhill mining district, Ten- "nessee, supplies both iron sinter and slag for use in cement. The Carters- "ville district supplies iron sand, ocher, and some iron resulting from the "magnetic separation of iron from barite. The advantages of these "products vary according to the chemical properties of the raw materials "and the methods of handling used by the different manufacturers. Where "the iron is to be handled by conveying belts and in hopper cars, the iron"sand and sinter and slag are preferable. Where the silica content must "be raised, the iron sand is doubly advantageous because it supplies both

Jan 1, 1942

By David P. Hale, Guy W. Jordan

High-iRon cements have a number of advantages over cements carrying little or no iron. The presence of iron in Portland cement aids in the manufacture of the cement and also imparts certain advantageous physical properties to the finished product. In manufacture, the presence of iron lowers the fuel consumption, increases the ease of proper"burning, and lessens the destructive action of the charge on the kiln refractories. In the finished cement the presence of iron reduces the expansion and contraction, adds strength, adds increased resistance to"freezing and thawing, and increases the resistance of the cement to sea "or sulphate waters. [" During the past few years the construction of numerous dams through- "out the Southeast by the Tennessee Valley Authority has stimulated the "production of high-iron cements. At present a great number of specifica- "tions call for an iron cement, and the industry is supplying this demand "with a Portland cement carrying approximately 5 per cent iron oxide. "Several manufacturers are now making practically all of their cement "of this type and a number of others manufacture it as a special cement "over short periods to meet demands from the Tennessee Valley Authority "and other buyers. " The recent increase in the use of iron in Portland cement has created "a market for iron products that previously was nonexistent. The chief "sources of supply for the cement manufacturers at present are iron sand, "iron sinter and slag, and ocher. The Copperhill mining district, Ten- "nessee, supplies both iron sinter and slag for use in cement. The Carters- "ville district supplies iron sand, ocher, and some iron resulting from the "magnetic separation of iron from barite. The advantages of these "products vary according to the chemical properties of the raw materials "and the methods of handling used by the different manufacturers. Where "the iron is to be handled by conveying belts and in hopper cars, the iron"sand and sinter and slag are preferable. Where the silica content must "be raised, the iron sand is doubly advantageous because it supplies both

Jan 1, 1942