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By Walter H. Ortel, George B. Wallace

INTRODUCTION A greater understanding is required about the factors which control tunneling operations if we are to meet the expected demand for tunnels. Much of the needed information can best be achieved by the proper use of instrumentation and advanced engineering concepts. Tunnel measurements and their analysis may prove to be the key which will give the insight necessary to understand the relationship of rock, tunnel supports, and linings. There are three main areas which can be improved through the use of tunnel instrumentation. First, and of prime importance, is safety for men and the project. When unstable conditions occur, sets become distorted. Even without measurements, it is sometimes possible to tell when trouble is approaching. In effect, the set acts as a load cell. Distortions in the set indicate reinforcements may be required to maintain stability. Additional sets or rock bolts, if they are placed soon enough, may provide this stability. However, when large rock displacements occur in short periods of time, it could be too late. Figure 1 is an example of the difficulties encountered in stopping moving rock. To stop the movement and possible failure, large props were placed above the spring line and the massive concrete gravity buttress was constructed along the legs. Rock bolts from the buttress deep into the rock were also used in an attempt to stabilize the rock mass. However, this work is for a highway tunnel and eventually these props and buttresses must be removed.

Jan 1, 1971

By John K. Hammes, Stanley D. Michaelson

The material presented in this chapter is supplemental information on those significant aspects of open-pit copper mining that are to an extent unique and therefore not detailed in previous sections covering the fundamentals of open-pit mine planning, operations and maintenance. In addition, tabulated cost and operating data are presented for a variety of open-pit copper mines. 13.3-1 History. The history of the civilized use of copper began at the end of the Stone Age when man discovered that the red metal, in the form of native copper, could be readily worked into a variety of weapons and tools which simplified the primitive requirements for survival. Almost concurrently, the high value of these early copper products became so widely known that they soon assumed major importance as trading commodities. Copper and copper-alloyed artifacts, even though produced in very limited quantities by ancient miners and metalworkers in a few parts of the Near East and the Western Hemisphere, were so valuable that early warriors and traders carried them into nearly all the world's known areas of importance. As far as copper is concerned, the Bronze Age, at sometime around 8000 BC to 6000 BC, marked the vague, little-known beginning of metallurgy. Man learned to alloy the valuable red metal to make it harder and tougher; its use multiplied as did the variety of weapons and tools made with the gradually increasing metallurgical and fabricating skills. By 3000 BC bronze alloy products became relatively widespread ; copper mining activities assumed tremendous importance and the mines on the Isle of Cyprus developed into prized possessions of each Mediterranean empire from the times of Egyptian supremacy to well beyond the decline of the Roman Empire.

Jan 1, 1968

By P. T. Gallagher, W. A. Oates

THE partial excess entropy of interstitial solutes in metals, SXS , has usually been interpreted as being principally vibrational ever since the initial statistical treatment of hydrogen in metals by Fowler and Smith-ells. The vibrational entropy is considered being due to the optical modes of the light interstitial atom. Little attention has been given to the magnitudes of the values of SXS'. Leiser and Witte2 and Ebisuzaki and O'Keeffe3 have noted that for hydrogen in metals Si is approximately constant for different metals. On the other hand if it is assumed that the interstitial solute is an isotopic defect then, as shown by McLellan, SXS should vary from metal to metal as follows: where S is the standard entropy of the solvent and Mi, M, are the masses of the interstitial and solvent atoms. respectively. Fair agreement with this equation was found for oxygen in silver and nitrogen in iron4 and for carbon in iron.= Ln a subsequent analysis of metal- hdrogen systems McLellan' found a variation of $' from metal to metal but not in a manner expected from the isotopic impurity equation. However, a possible correlation between the energy of solution, Ei, and sf was noted. Similar correlations have been noted for certain dilute substitutional solid Solutions 7, 8 and recently Kubaschewski 9 has demonstrated a correlation between integral heats and ex-

Jan 1, 1970

By J. J. Egan, A. B. Kinzel, W. Crafts

Advances in the production of quality steel have emphasized the need for greater knowledge of the amount and distribution of oxygen in the steel. Control of inclusion content and quality is largely dependent on such knowledge. While many analytical methods have been devised for the accomplishment of this end, few are without serious limitations in accuracy, convenience, or skill required in application. Usually at least two methods are necessary to determine total oxygen and constituent oxides. Because of the great importance of this problem and the specific interest in the application of such methods of analysis, the various procedures were carefully reviewed at the Union Carbide and Carbon Research Laboratories, with the view of developing a method free from the limitations mentioned above. Intensive experimentation finally led to an improved iodine extraction analysis described by Cunningham and Price.1 After this had been thoroughly checked from the standpoint of the analytical chemist, it was rechecked from that of the metallurgist. This involved preparation of a number of small heats of varying composition with determination of total oxygen in the molten metal by the alumina method2 and an analysis of the solidified material without the aluminum addition by means of iodine extraction; the oxides of iron, manganese, silicon and aluminum also being determined by the iodine analysis. The report of this work constitutes the subject of this paper. The Iodine Method Fundamentally the iodine method is well established. It is based on the procedure first described by Eggertz3 and depends upon the fact that iron, manganese, silicon and aluminum, as well as the metallic constituents of the pertinent sulfides, carbides and nitrides of these metals

Jan 1, 1933

DESIRABLE as it is to summarize what has been set forth in preceding chapters, the task can only be approached with great hesitation. What follows represents the personal views of the author at the moment of writing, reserving the privilege to change them on more mature reflection or in the light of further evidence. With that reservation they may be stated somewhat as follows. Education for the mineral industries falls into two categories; general education and technical vocational, using the word vocational not in its usual sense but to signify preparation for specific activities, in which sense a law school is a vocational school. Even at the beginning, as indicated in the first chapter, mineral industry education was partly general and partly technical and that relationship still persists, because technical education requires a firm basis of general education. Our general American system is to provide free public general education through the twelfth grade, or completion of high-school work, though there are already many technical vocational high schools, and even in a community where nearly all the young people are preparing for entrance to college there will be some who wish to qualify for employment at the end of the high-school course, or even on completing junior high. Our educational system, therefore, has not only to provide education for those who intend to proceed beyond the twelfth grade but also for those who, for a variety of reasons, may wish or be forced to cease full-time education at any level between the first and twelfth grades. This study has been chiefly concerned with the problem of what kind and how much technical education to provide for those who have completed the twelfth grade and who wish to make their living in the mineral industries. The obvious fact that the mineral industries employ all sorts of trained persons,

Jan 1, 1941

By C. L. Pillar

TWO shafts have been completed since the spring of 1948 when underground development started, and three are now under construction. The new program provides two main ore shafts, Nos. 3A and 3B, spaced 195 ft apart and located on the south- western end of the orebody. It is planned that eventually 35,000 tons of copper ore per day will be hoisted by these identical four-compartment shafts. The third shaft of this new group is 600 ft from the present No. 1 shaft and will provide caged sup- plies for the underground mining operations. This No. 4 shaft has the largest cross-section of any shaft in Arizona.

Jan 7, 1954

By Laurence Delisle

The aim of this paper is the description of a technique to be applied to the study of sections of metal powder particles, less than 20 microns in diam. with the electron microscope, by the replica method, using for replica a material such as formvar or parlodion. This work originated with the study of particles of tungsten powders. Such particles were too small to be examined in sufficient detail with the light microscope. On the other hand, examination with the electron microscope of the powders dispersed in the supporting film was not found satisfactory because: 1. It did not permit differentiating between single particles and aggregates. 2. It did not show the true outlines of the particles but only the projection of a whole surface. 3. No details appeared. For that reason it was attempted to make replicas of sections of the particles imbedded in a mounting material suitable for polishing and etching. The method proved satisfactory for the examination of tungsten powder and was then extended to car-bonyl nickel and carbonyl iron powders. Procedure Several mounting materials commonly used in ordinary metallography were investigated. The problem consisted in finding a mounting material

Jan 1, 1950

By Campbell M. Hunter

Petroleum is found in almost every province in Persia. On the northern frontier, along the southern shore of the Caspian Sea, it is found near Enzelli and Shakhtesar and gas at Khoremabad. Oil is also found at Gumish Tepe, northwest of Astrabad, on the southeastern shore of the Caspian Sea. Further inland, to the south of Astrabad, oil is found at Dehahkuh-i-balae, also on the margin of the Khorasan desert at Semnan, 115 mi. (35 m.) east of Teheran. Along the western frontier, from northwest to southeast, oil is encountered at Ouschachi, north of Lake Urumieh; in the province of Azerbaijan, at Zohab, Khanikin, and other places in. the district of Kormanshah in the province of Ardelan. Further south, in the province of Luristan, oil is found east of Mendeli and in the Pusht-i-kuh districts. Considerable quantities of oil are also obtained from Schuster, Maidan-i-Naphtun, Ram-Hormuz, Beheban, which are almost on a straight line, running northwest and southeast along the foothills of the Bakhtiari Mountains. At Ahwaz, in the province of Arabistan, oil has been found along another range of hills whose axis also lies in a northwest-southeast direction. In the Fars province, boring for oil has taken place at Daliki, and indications of oil are found at Kheri, Fasa, Darab, and other places. A gas show is also recorded at Kuhi-Sung-Atush in this province, 30 mi. (48 km.) east of Darab. In the south of Persia, oil is encountered on Qishm Island, also at Ahmedi and other places north of Bunder Abbas. On the southeastern frontier, oil is found on the Sarhad range of hills. Thus, oil indications have been noted over a distance of approximately 1100 mi. along the western and 700 mi. along the northern frontiers of Persia. History The first working of oil in Persia of which there is any record took place at Kir-ab-US, Susiana, now known as Kiab, about 57 mi. northwest of Schuster. Herodotus (about B. C. 450) reported a well near Ardericca that produced three different substances; namely, asphalt, salt, and oil. The oil, which was black and had a strong smell, was called Rhadamance by the Persians.

Jan 1, 1921

By John C. Branner

Inquiries are frequently made concerning the chalk- and clay-beds of Arkansas, usually with a view to the manufacture of Portland cement. The chalk-deposits were first described by Professor R. T. Hill in the annual report of the Geological Survey of Arkansas for 1888, vol. ii., pp. 153-162. Since the publication of that report I have visited localities then unknown, and have accumulated considerable additional information concerning these deposits, dl of which is brought together in the present paper. My report upon the clays of the State has never been published; only a few of the more conveniently available deposits are mentioned in the present paper. The Chalk-Deposits. Stratigraphic Position of the Chalk.—The chalk-deposits of Arkansas belong to rocks of Cretaceous age. The Cretaceous rocks are confined to a single definite area in Southwest Arkansas. Beginning on the Ouachita river, a little northeast of Arkadelphia, its southern or upper margin follows a line about five miles southeast of, and approximately parallel to, the St. Louis, Iron Mountain and Southern Railway from Arkadelphia

Jan 1, 1898

By J. Versluys

WHEN a well strikes an oil-bearing layer, the oil has a pressure which is generally sufficient to enable it to rise to near the surface (sometimes above the surface). As soon as a well begins to produce, however, the liquid moves through the pores of the reservoir bed and the pressure in the well becomes much lower than the pressure originally prevailing there. At some distance from the well, however, the pressure in the reservoir bed remains unaltered; thus the pressure of the oil has not only to lift the oil, but also to overcome the friction resistance in the pores. The fact that so many oil wells are gushers is a consequence of the energy accumulated in the gas. In gushing the well acts as a gas-lift. A mixture of liquid and gas (the latter partly dissolved in the former) rises vertically from the oil¬bearing layer through a cylindrical casing to the surface. In time conditions alter and the well ceases to gush regularly, then the gushing can be further promoted by inserting a narrower tube in the well and connecting the top of the oil string to the tubing. If the action in time becomes irregular, the gushing can be kept up for a further period by forcing gas between the two tubes. In the oil fields the term "gas-lift" is used actually only where extraneous gas is applied, as in the last of the stages mentioned. The action, however, is just the same whether the gas exclusively originates from the formation, or is partly applied artificially. Thus by gas-lift we simply mean a vertical tube in which the energy of gas under pressure, and of dissolved gas, is utilized for raising a liquid. In gushing oil wells the pressure is frequently very high and the absorption coefficient 0.4 (expressed in vol. ratio) of the coexisting gas is not particularly high, so that in reality it should be assumed that a considerable portion of the gas, at any rate at the bottom of the gas-lift, is dissolved in the oil. For water-producing wells this is not usually of such importance.

Jan 1, 1929

By G. Sandoz, C. A. Siebert

Oil quenching of steel, in good commercial practice, is carried out using a great deal of agitation in the quenching bath. Many of the tests reported in the literature represent the results obtained on steels quenched into still oil. Scott1 describes three stages of cooling in liquid quenching baths, namely: "State 'A'— Vapor Blanket Cooling—In this, the first stage, a thin stable vapor film surrounds the hot metal. Cooling is by conduction and radiation through the gaseous film and is therefore relatively slow. "Stage 'B'—Vapor Transport Cooling— Termination of the 'A' stage is marked by wetting of the metal surface. Vapor forms copiously in bubbles and is carried away by gravity and convection currents to condense in cooler surrounding liquid. This is the fastest stage of cooling. "Stage 'C'—Liquid Cooling—The 'B' stage ends as the surface temperature of the metal approaches the boiling point of the quenching liquid. Vapor no longer forms, so cooling is by conduction and convection and the temperature difference is greatly decreased. This mode of cooling is slower than that of the 'B' stage." Mechanical agitation of the quenching medium will accelerate all three stages of cooling. The greatest effect, however, will be noted on stage ' B' because the removal of the bubbles from the surface of the steel will not be entirely dependent upon gravity and natural convection currents. The method employed in this investigation for evaluating the oils was the end quench test. The various oils were substituted for water as the quenching liquid and hardness determinations were made at various distances from the quenched end. Most of the tests were run using a 3/8-in. orifice with a 21/2-in. stream height. However, to check the effect of other velocities two additional conditions were used, namely: (I) A 3/8-in. orifice and I-in. stream height, and (2) a 1/2-in. orifice and a 31/2-in. stream height. In all cases the samples were suspended so that the quenched end was 1/2-in. above the orifice. Some tests were run on an NE 8740, .3,312, and a 4340 steel. The results obtained on these steels confirmed those obtained on the NE 9450 and have therefore been Omitted from this paper. The test bars were machined from 1/8-in. stock to I-in. diam by 4 in. long.

Jan 1, 1949

By E. W. Shilling Harwick Johnson

The separation of hematite by hysteretic repulsion was first brought to the attention of the public in 1922, by W. M. Mordeyl. Three years later another paper2 was published and after another four years a third paper3 appeared in the South African publications. Certain data were lacking in these papers. In order to continue the work intelligently a knowledge of the shapes of the hysteresis curves for certain minerals was very necessary. This information was not available until the present year4. It was known that reduction of certain ores rendered them amenable to this process of separation but definite data in the form of curves showing exactly the effect of such treatment were lacking. Probably our best source of information on the separation of minerals by the use of alternating-current magnetic fields today is the reports from the U. S. Bureau of Mines5"7. It is not the purpose of this paper to tell the reader in detail how to make a commercial separator. Experimental models have recently been made? and the results obtained have been so good that it is the opinion of the authors that the public will soon take an active interest in the subject and its development. The writers have constructed a separator that is considerably different in construction and operation from the two types described by Mr. Davis. This will be described, but the real purpose of this paper is to outline certain experiments and give curves showing data that have a fundamental bearing upon the practical construction of a separator of this type. Specular hematite is usually considered nonmagnetic; that is, it is very feebly magnetic as compared to some other minerals. If specular hematite is placed in a steady magnetic field there is no apparent attraction. At the moment of closing the switch, however, some particles may be seen to move. If the field is alternating, the particles are con-

Jan 1, 1936

By Ellis Clark

Within the last ten years the progressive party of China, headed by Li Hung Chang, the Viceroy of Chi-Li, has been making great efforts to develop the mining resources of that country, and particularly those that are within reasonable distances of the sea-board. Attention was first paid to the coal-deposits, especially those at KaiPing, which have been placed on a profitable basis with an output of 1500 tons per day, under the energetic management of Mr. Claude Kinder, M.I.C.E., and the successful financiering of Tong King Sing. These coal-mines were described in a report by Kwong Yung Kwang, edited as a paper for the Institute (Duns., xvi., 95.) The attention of the leaders of the progressive party has for the past five years been turned also toward the development of the precious and related metals—gold, silver, copper and lead. De-

Jan 1, 1891

Jan 1, 1917

By Henry C. Freeman

During the early period of the construction of the Illinois and Michigan Canal, about 1838, in excavating for the canal, where the present town of Utica stands, hydraulic limestone was discovered, and its value was recognized. A kiln for calcining and a mill for grinding were erected, and the cement was used in the construction of the locks of the canal. This property was subsequently bought by the present owner, Mr. James Clark, and the work has been continued to the present time in much the same primitive manner as it was begun. The bed is exposed in the Illinois River valley by stripping off a few feet of the covering rock. It is from 4 feet to 6 feet 9 inches thick, and nearly level, dipping gently to the northeast. The Utica Cement Company's establishment, which is two miles west of Utica and two miles east of La Salle, was an outgrowth of the Illinois geological survey. The writer was in charge of the district which included La Salle county, and, in working out the details of the geology of that county, discovered, below the Utica bed, another workable hydraulic limestone, which makes its appearance in the northern bluff of the Illinois River valley, rising above the water level at the point where the company's works are established. This cement group, of which there are several thin beds, lies just below the St. Peter's sandstone, with a few feet intermediate of transition-rock, which appears to represent the Calciferous, and is exhibited in place, in concretionary form, at the top of the bluff. The hydraulic beds are very regular, and the one worked by the company is 10 feet thick; or, speaking more definitely, there are two beds, separated by 18 inches of sandstone, lying about two feet above the bottom, and the two beds are worked as one, the sandstone being first cut out and removed, to prevent mixture. In 1869 I was invited to join with a company, and to take charge

Jan 1, 1885

The opening session of the Institute was held at the rooms of the American Society of Civil Engineers, No. 4 East 23d Street, VicePresident R. W. Raymond in the chair. After a short introductory address by the chairman, the following names were presented by the Council for election as members and associates of the Institute. They were unanimously elected : MEMBERS. Abbott, James W.,.....Lake City, Col. Abbott, J. J., Jr.,...... Lake City, Col. Bartlett, J. C.,.....Cambridge, Mass. Billings, G. H.,.....Boston, Mass. Blake, Frank C.,.....Lafayette College, Easton, Pa. Dewey, Fred. P.,.....Lafayette College, Easton, Pa. Douglass, Samuel T.,. .. . Ann Arbor, Mich. Emmons, 9. F.,.....New York City. Engle, George U.,.....Philadelphia. Harrington, Dr. Bernard J.,. .. Montreal, Canada. Hayden, Wm. B.,.....Columbus, O. Hill, Leslie C.,.....Capelton, Quebec, Canada. Land, W. J.,......Atlanta, Ga. May, Wm. A.,.....Scranton, Pa. Mills, James E.,.....St. Louis, Mo. Moore, Charles W.,.... Montezuma, Ind. Page, William Byrd,.... Lexington, Ky. Putnam, Douglas, Jr.,.... Ashland, Ky. Richards, Henry,.....Dover, N. J. Boberts, Percival, Jr.,. .. . Philadelphia. Sackett, S. G.,......Brooklyn, N. Y. Schley, Wm. S.,.....Atlanta, Ga. Setz, Gustav,......Mine La Motte, Mo. Talhutt, John H.,.....Lexington, Ky. Torrey, Herbert G.,.... U. S. Assay Office, New York City. Wernlitz, Fred. W.,..., Cartersville, Bartow Co., Ga. Wiestling, Geo. B.,.....Mont Alto, Franklin Go., Pa.

By Strathmore R. B. Cooke, Emert W. Lindroos, Norman F. Schulz

DURING the course of an investigation of the effects of various starch products on hematite and quartz in regard to their separation by' flotation, it was found that whereas most starches flocculated suspensions of hematite in water, they did not flocculate similar suspensions of quartz. However, a derivative of whole corn starch containing approximately one tenth aminoethyl group (--CH2CH2NH2) per glucose unit proved to be an exception. This aminoethyl starch was a very good flocculant for both hematite and quartz, and also possessed the property of depressing both minerals in cationic flotation tests. In view of the widespread use of starch as a flocculating agent of solids in tailing water, pulps, and for coal slimes, ore and various other purposes in sulphide and nonsulphide flotation, attention is called to the effective surface activity of aminoethyl starch in flocculating suspensions of the two minerals investigated. Test Materials The starch products employed included Globe Pearl starch No. 144 and fresh aminoethyl starch, both supplied by the Corn Products Refining Co. Dr. A. L. Elder[4] has kindly furnished a description The minerals used in the various tests are listed in Table I. Their specific surfaces were determined by the air permeability method, which gave results reproducible to within plus or minus 3 pct. Surface areas obtained by krypton adsorption were greater than the air permeability values by a factor of 2.0 for quartz and 62.4 for hematite. Starch Adsorption on Mineral Surfaces Starch adsorption data were obtained by agitating for 1 hr measured volumes of neutral starch solutions of known concentrations with weighed quantities of finely divided mineral of measured specific surface. The mineral then was separated from the pulp liquor by centrifugation and the residual starch content determined by chemical analysis. The analytical procedure consisted of oxidizing the starch with an excess of dichromate in acid medium at elevated temperature and titrating the excess dichromate by the ferrous ammonium sulphate-potassium permanganate method. Analytical results were reproducible to within less than 1 pct. Adsorption data obtained in unbuffered solutions near the neutral point are plotted in Fig. 1. The adsorption on either mineral was far greater for the aminoethyl starch than for the Pearl starch. Flocculation The degree of flocculation was determined for a given pulp by measuring the time required for the supernatant liquid to reach a certain degree of clarity. This was accomplished by passing a standard light beam through the pulp, contained in a glass settling tube, and measuring the time required after agitation ceased for the intensity of the transmitted beam to reach a predetermined value. Starch reagent was added to each pulp in small uniform increments, and the settling time was determined after each such addition. Increase in pulp liquor volume due to the added starch reagent was ignored in these tests. Pulps were maintained at or near neutrality.

Jan 1, 1952

By L. M. Pidgeon

The reactive metals are above manganese on the electromotive series. Their compounds are characterized by large heats of formation and they cannot be reduced from their ores by classical methods. Three general production methods have been used: a) Fused salt electrolysis, b) reduction of a halide by another metal, and c) reduction of the oxide by another metal. Method (a) is highly developed, as in the case of aluminum, (b) in the case of titanium, and (c) has been successful in the case of volatile metals such as magnesium and calcium. It is suggested that future improvements will take place in (a), and particularly in (c), but are rather less likely in the case of (b). THIS year of 1963 is the centennial of the birth of both Charles Hall and of Heroult, the founders of the aluminum industry. Aluminum is the one reactive metal which has reached massive stature in modern industry and perhaps the only such metal to have been produced in any quantity before the turn of the century. It has been joined by others, some on a very modest scale, but all of importance and all of fascinating interest. When invited to give the Fifth Extractive Metallurgy lecture, it seemed appropriate to look back upon the short history of this group to trace the developments which brought extraction methods to their present state and, at great risk, offer opinions as to future trends.

Jan 1, 1963

By Robert L. Voss, Richard D. Hagni

Sparry dolomite from all of the operating mines in the Viburnum Trend of Southeast Missouri have been found by cathodoluminescence microscopy to reveal a systematic pattern of banding resulting from a growth zoning within individual dolomite rhombs. Four principal bands have been recognized throughout the entire Trend and each of the major bands contain even finer internal banding. Minor bands a few microns in width can be correlated in specimens collected ten's of kilometers apart along the trend. The first three principal dolomite bands decrease from south to north. This feature, together with the fact that the white sparry dolomite crystals decrease in abundance from south to north in the Trend, suggests that a major source for the fluids was from the south. The application of cathodoluminescence microscopy to crystalline dolomite demonstrates a strong correlation between ore grade and the intensity of internal banding and dissolution textures.

Jan 1, 1985

By R. B. Snow

Inclusions revealed by the ultrasonic inspection of forgings, slabs, and blooms cause costly diversion or rejection of the product. Most of those inclusions are so large that they should have floated out of the liquid steel soon after teeming and been removed when the top discard was taken from the ingot. To investigate the source of the relatively large inclusions found in the body portions of ingots, a large forging ingot was examined from top to bottom along the centerline, and special studies were made of open-hearth and BOP ingots. A study of the inclusion distribution in the as-cast 134-inch-diameter forging ingot revealed only a few inclusions larger than 15 microns in the body of the ingot. Larger inclusions may be formed by entrapment of rising inclusions in large falling dendrites rather than by the precipitation and agglomeration of oxides from the liquid steel-dendrite interface during solidification. The original top crust of the ingot investigated broke away from the hot top and sank to the bottom during the solidification process, as indicated by entrapped inclusions found in a band 12-1/2 inches above the stool. A change in the hot-top insulation practice on subsequent ingots to insure the integrity of the top crust has produced clean ingots. A ZrO2 tracer was added to the hot-topping compound and to the top surface of open-hearth and BOP ingots after teeming. The tracer was found in large inclusions in slabs and blooms from these ingots. Large inclusions in the body of ingots appear to be related to disturbances of the natural freezing and shrinkage processes in the hot- top region of the ingot.

Jan 1, 1972