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By William Phillips

This paper was prepared at the request of Capt. A. F. Lucas, Chairman of the Institute's Committee on Petroleum and Gas, as a preliminary discussion of the fuel oils which are used-in the Southwest, giving their composition, uses, prices, etc. Should it afterward be found desirable, these observations may be extended over a larger area. In this connection, J suggest that samples of all kinds of fuel oils, including various tars, from all over the country, be collected and sent to some testing laboratory for examination. We would be glad to extend the facilities of the laboratory of the Bureau of Economic Geology and Technology, at the University of Texas, for this purpose, and to do the work free of all expenses. After such examinations are made and the results classified and studied, it would be possible to suggest specifications under which fuel oils should be purchased, and to arrive at some conclusions respecting the uniformity of such specifications, with due allowance for climatic and other more or less local conditions. While such specifications do not now depart from a common standard anything like as much as specifications for illuminating oils do, yet there are discrepancies which should not exist. Some of these discrepancies are of lessening importance, due to the pronounced tendency to distill every crude oil that can be distilled with profit, and to send residues into the market for fuel oil. Residues from the refineries are of a more uniform chemical composition and physical nature than many of the crude oils that go direct into the fuel market. The lower flash-point oils are disappearing from the fuel trade and in place of them we are getting oils that do not flash below 220° F., nor burn under 320° F. In the Southwest, it has not been long since we had fuel oils that flashed at as low as 110° F., and the average flash point over a considerable period was 151° F. Now we are using oil that flashes at about 30° lower than the former burning point, which was 256° F. In other words, the flash point has risen, on the average, 100°; and the burning point about 75°.

Jan 6, 1914

mean to say that these explosions are mechanical, but that the ejectment of the stock, throwing out of tops, etc., are mechanical. I see no reason at present, although I have had almost no experience in the use of large quantities of Mesabi ore, to change my ideas on the subject. That these explosions should follow irregular working or slipping in the furnace, I think can be explained. I have noticed that immediately following slips there is little or no settling of the stock on top, although there is no lessening of the volume of gas passing into the stoves and boilers. Supposing that, after a slip of 3 or 4 feet, the filling continues, but for some distance from the 'top the stock fails to move: there would be a much better chance for the deposited carbon to clog interstices in the stock, and for the additional effect in the same direction of the fine ore in the charge, than if the stock were properly settling. Under such conditions it is easily supposable that the openings would be entirely closed, or closed so tightly that the pressure below the obstruction would be raised to a point approaching the blast-pressure, or to a point high enough to force a passage or an enlargement of the small passages which may remain. When this occurs, gas from below under pressure carries with it large quantities of deposited carbon and fine ore; if the case is aggravated, coke, stone, bell, etc. As soon as the red-hot deposited carbon meets the air there are perfect conditions for a dust explosion, which naturally follows, the same as in a coal-mine or flour-mill.

Jan 1, 1899

By Robert Glass Cleland

FROM the time of its organization down to 1917, a period of more than eighty years, Phelps, Dodge & Co. was seldom involved in what could be called a major labor difficulty. Behind this remarkable record lay both a philosophy and its practical application. The philosophy was an attitude toward society called the Golden Rule. That philosophy had been a living principle in the lives of the founders of the company, Anson Phelps, Daniel James, and William E. Dodge. Their successors, William E. Dodge, Jr., and Daniel Willis James, accepted the same philosophy. Dr. James Douglas governed his life by it. All of these men and their families had given tangible expression to that conviction in benefactions of great magnitude and variety-churches, hospitals, educational institutions, libraries, missionary undertakings, and other organizations for human betterment, such as the Young Men's and Young Women's Christian Associations, and the development of model communities about their mills and factories. According to the best standards of their generation, they had sought to improve the condition of labor,

Jan 1, 1952

By Basil Prescott

Resume.—The district of Santa Eulalia lies 12 miles to the southeast of the city of Chihuahua, Mexico. The ore deposits occur in a Cretaceous limestone of unknown thickness, overlain by a series of rhyolitic tuffs and flows. The limestone is very gently folded and is cut by several systems of fissures, of which only those with a general north-south strike are pre-mineral and control the deposition. The deposits are of two main types; the earlier silver-bearing iron sulphide type occurs as high-grade tabular bodies resembling veins and as large masses of relatively low-grade ore, The gangue of this type is composed of lime-iron silicates that point toward a close association with an igneous rock mass which has not yet been encountered. In the later silver-lead-zinc type the ore occurs in vertical chimneys and horizontal mantas, principally as oxides, though at a depth of 1,500 ft. some sulphides have been encountered. During oxidation the ore chambers have increased in size owing to the solution of the walls by the sulphuric acid generated in the process, and a substitution has taken place of nearly one-half part by weight of the original constituents of the ore, by newly introduced elements and radicals. Both types are believed to have come from greater depths than those yet reached by mining, and their ultimate source, from a consideration of similar deposits, is believed to be an igneous rock in contact with the limestone at some horizon below. The deposits are believed to have been formed at unusually great depths, as indicated by the proved great vertical range of the silicate minerals coupled with the absence of the igneous rock, and by the practically unchanged character of the silver-lead-zinc ores as far as developed. The volcanic capping is believed to be distinctly later than the economically important ore deposition. Introduction The Santa Eulalia district is situated in the State of Chihuahua, Mexico, and lies about 12 miles southeast of the capital, the city of Chihuahua. (See map, Fig. 1.) The district embraces the Sierra de La

Jan 1, 1915

By Harry K. Ihrig

Jan 1, 1947

By Harry K. Ihrig

Jan 1, 1947

By C. H. G. Bushell, James E. Lawver, William Barbarowicz

Proper use of automatic controls in the process industries is a combination of art and science. Although many phases of automatic control theory can be expressed by precise mathematical relationships, the final control arrangement usually requires considerable effort by trial and error before the optimum control circuit is found. The failure of flotation operators to recognize that control circuits require study and plant experimentation before satisfactory operation occurs has led to a popular misconception that flotation plants simply do not lend themselves to automation. This widespread belief has been overcome to some degree in recent years by the numerous installations of automatic controls that have paid their way by increasing profits in terms of increased recoveries, lowered costs, or higher grade concentrates. WHY CONTROL ? Any form of automation must be justified in terms of ultimate return on in- vestment by improving quality, by increasing plant throughput, or by reducing the total operating costs. Generally speaking, automatic controls rarely re- place a mill operator. They assist the operator in holding important variables within predetermined limits. Large tonnage operations usually can justify a great deal of automation because an increase in one or two units of recovery results in enormous savings compared to the capital and operating costs of controls. DETERMINATION OF CONTROL The first questions in considering plant automation are: 1) What variables must be controlled? 2) What are the optimum levels of the variables? The optimum operating conditions for any process are those which maximize profits. Many of the variables active in flotation processing can be determined by experimentation in the laboratory or pilot plant 10. Although laboratory experiments can pinpoint variables, the true optimum conditions existing at plant level usually must be determined by plant scale experiments. In recent years, the concepts of detailed experimental designs in the laboratory, followed by plant experiments, have reached the stage of maturity where

Jan 1, 1962

By J. M. Pilcher

The application of oil to coal for-the reduction of dust has greatly increased the consumers' satisfaction with solid fuels, especially those for domestic use. The combination of oil-treated coal and automatic firing by a small stoker has made possible clean, automatic heating with bituminous coal. This, with the added pressure of competition by other fuels, has caused a rapid development of oil treating practice. A variety of materials derived" from petroleum oils is available from which one may choose for treating a par-ticular coal. Until recently, however, little information had been published to guide the choice. It is most im-portant that the proper type and amount of oil be used in order that all coals marketed as "dustless" will be reason-ably dustless, and thereby maintain a good reputation for oil-treatment. During the past two and one-half years, an investigation of a number of the problems related to the treatment of coal with oil has been conducted at Battelle Memorial Institute. This project was jointly sponsored by Bituminous Coal Research. Inc., Standard Oil Company of New Jersey, Sun Oil Company, and Viking Manufacturing Company. A progress report giving the principal results of the work of the first year was presented before the American Society of Mechanical Engineers in December 1937.1 The present paper is a summary of the entire inves-tigation.

Jan 1, 1939

By L. F. Bishop

The ore bodies of the Butte district1 are found in many different vein systems having many different structural characteristics; some are narrow with self-supporting ore but with weak walls; some are wide with weak or strong ore and weak walls; some of the veins dip steeply and others do not; some have well defined walls, and others, in the "horsetail" area, are mined to sample limits. Consequently, many types of stoping methods are used in mining these ores. The stoping methods used in the Anaconda Copper Mining Company's properties are the square-set and cut-and-fill. The square-set method is the principal stoping method used because, generally speaking, the ore and walls are weak, the ore is high grade, and good extraction is required. These square-set stopes may be classified as conventional, vertical slice, slot, timber rill, and Mitchell slice types. The conventional type square sets are those of various shapes and sizes, mined by horizontal slicing to the boundaries of the stopes. The rock is slid to the chute and the filling is moved by gravity. The ore and waste may be handled with a scraper when local conditions require it. The vertical-slice square-set system is the type used in narrow veins that are mined in vertical panels. The slot stopes are stopes in wide veins that employ a slot across the vein instead of a con- ventional chute to handle the ore. The timber rill is a type of square set in which the ore is mined as in inclined cut and fill but the square-set timber is used. The Mitchell slice is the type used for some broken or heavy ore blocks, or for pillar extraction between two converging slot stopes. The cut-and-fill method is used where the ore will stand without much support although the walls may be weak. The principal type of this method is the horizontal cut-and-fill, with mechanical scraping. The inclined cut-and-fill, or rill, stopes are used in some veins too narrow for scraping. The production from the various methods in use for the second six months of 1944 are shown in Table I. This paper deals mainly with the vertical slice and slot types of square-set stoping, because of their effect on production locally and their potential possibilities here and in other districts, with sufficient reference to conventional square-setting for comparison.

Jan 1, 1946

By B., Hoyaux

A first requirement for assessing the safety of a rock slope, either artificial or natural, particularly if the rock behaves in an elastic-brittle manner, is a proper knowledge of the distribution of stresses within the slope and their development with time and advancement of workings.

Jan 1, 1972

By JOSEPH MACDONALD

STRIPPED of its romantic possibilities, mining is a commercial business, carried on for the profit there is in it, and the business of the manager, in its ultimate analysis, is to make the profit as large as possible. The general manager of a mining company should keep himself personally familiar with all the details of its operations. If be fails to do so, chaos results, labor becomes inefficient, costs go up, and profits go down. Nowhere is this emphasized more than in Mexico. If the mining operations are extensive and complex, involving, besides the work of mining the ore, its transportation and treatment by various milling operations, and the marketing of the products, the business, to be carried on properly, must be divided into a number of main departments, which are subdivided into minor departments. Each main department should be under the immediate charge of a superintendent, or a foreman, and each minor department under a shift-boss. Organized in this way, and with all the principal centers of activity connected by telephone, the manager can keep in touch at all times with the details of every branch of the business, and be in a position to perform effectively the full duty of manager. The ?total cost of mining operations may be broadly divided under the heads of Labor, Supplies, and Marketing. Of these, it will be found, on averaging a number of cases, that the cost of labor will be about two-thirds of the total cost. The importance, therefore, of an efficient labor-department will be apparent. This department must be sub-divided and organized differently, according to the peculiar conditions at each mine, and no one system, however well suited for one particu-

Jan 1, 1909

By William Rawles

THIS report is the first of a series planned by The Mineral Inquiry, organized by the American Institute of Mining and Metallurgical Engineers to make factual studies of the world's mineral resources in their political and international relations. The efforts of The Inquiry are directed toward filling certain notable gaps in available information, without duplication of many other investigations touching this field which are being conducted by other organizations, public and private. Much of its work is indirect-suggesting topics for study by other individuals and organizations and aiding in their planning and correlation. The present report is designed to show the nationality of the commercial control of mineral resources, in addition to the geographic distribution of production by nation-in other words, the overlapping of political and commercial control. Detailed accuracy cannot be claimed for the figures presented. For some companies division of ownership by nationality has been very difficult to ascertain, as many companies are reluctant to dis-close the extent of their holdings in other corporations, and the impossi-bility of tracing all stock ownership is obvious. Also there are frequent changes in the distribution of stock control. The percentages given rep-resent only the participation that has been identified definitely, even though it is known in some cases with fair certainty that larger interests exist, as, for instance, American participation in foreign chromite companies. In bringing together these figures we have had the cordial co-operation of the United States Bureau of Mines, the United States Geologi-cal Survey, the Mineral Division of the Bureau of Foreign and Domestic Commerce, the Brookings Institution, and of many specialists connected with the mineral industries covered. The report does not cover the entire list of minerals. Coal, although it is one of the most important minerals, was omitted because, not more than one or two per cent of the world's production comes from mines that are owned by companies foreign to the countries where the coal is produced. Others, such as gold, are omitted because sufficient data have not yet been accumulated. It is hoped that some of these may be covered in subsequent reports. It is not our purpose here to discuss the significance of the figures sub-mitted, but only to point out the general nature of the problems on which they have a bearing.

Jan 1, 1933

By Pol Duwez, H. E. Martens

The high temperatures encountered in the operation of jet engines have imposed most drastic requirements upon the materials used in their construction. There are two different approaches to the materials problem connected with the design of parts in contact with high temperature gases. The first approach is to use a material which will perform satisfactorily at a temperature comparable to that of the gas. The second approach is to use a cooling system so that the material is maintained at a temperature appreciably lower than that of the gas. Besides the conventional method of cooling by means of a liquid in contact with the material exposed to a high rate of heat transfer, a less orthodox method consists of making the part to bc cooled of a porous material', so that the cooling fluid can be forced through the pores, In this scheme, the temperature of the coolant moving in a direction opposite to that of the heat flow increases gradually while passing through the porous material, and the coolant forms a protective layer on the surface exposed to heat, This method, referred to as ((sweat cooling," was pro- posed at the Jet Propulsion Laboratory in September 1944, and the experimental work on the preparation of porous metals was started early in 1945. The sweat cooling method opens new lines of research in powder metallurgy by extending the field of application of porous metals. The porous metals available at the present time are used mostly as bearings or filters, and a rather limited number of alloys are made for these applications. In addition, the fabrication of bearings or filters does not require a very close control of the permeability, while in the case of sweat cooling such a control is of primary importance. In designing a sweat cooled part it is imperative to assure a given rate of flow of coolant under certain conditions of Pressure drop. Generally, the Proper pressure drop and the rate of flow of coolant are deduced from heat transfer and design considerations, and consequelltl~ the Permeability of the Porous metal to be used is also determined. It is therefore necessary for the designer to have available a continuous series of porous metals covering a range of permeability as wide as possible. Contrary to the requirements established in the fabrication of filters, the actual pore size of a porous metal intended for sweat cooling is of little consequence, except for its effect on permeability. The tensile strength is likely to be of great importance for some applications. Since the tensile strength of a porous alloy decreases with increasing porosity, an important problem is to develop porous alloys having the maximum permeability with minimum porosity.

Jan 1, 1949

By G. A. Moore, D. W. Williams, C. E. Sims

During the past several years, the steel casting industry has made studies of heavy castings in which the test bar has been taken from heavy sections rather than from attached or separately cast coupons. It has been noted that the ductility properties of these heavy sections are often lower than those normally expected. Such lowered ductility is usually accompanied by a spotty test bar fracture, and the ductility values can often be greatly improved if a low-temperature aging treatment is given to the casting. A loss of ductility of this type is considered "abnormal," since it is not accompanied by an increase of tensile strength or hardness, and "temporary" when the ductility can be restored by aging. The cure of such an abnormal condition represents a real improvement in the quality of the steel. Several types of abnormal loss of duetility can be distinguished, of which those caused by excessive amounts of inclusions of undesirable type and those caused by unsuitable grain size and inget structure are well known. The particular type of abnormal lowered ductility currently under consideration may be distinguished by the fact that the low-temperature aging treatment necessary for its relief is insufficient to cause any visible change in the micro-structure as ordinarily observed. As this aging will in fact eventually occur at room temperature, the phenomenon of present interest may be given the symptomatic definition, ''Temporary Abnormal Low Ductility." Some hundreds of previous investigations, largely qualitative in nature, have established, beyond reasonable doubt, that hydrogen is normally present in newly manufactured steel and that this gas, in small amounts, can cause a temporary abnormal loss of ductility. The commonly observed association of high gas content and low ductility has given strong evidence for the presumption that hydrogen, possibly assisted by other gases, is the primary cause of the low ductility observed. Accordingly, The Steel Founders' Society of America has, since Nov. 1, 1944, sponsored investigations at Battelle Memorial Institute whose primary objective is to obtain quantitative information on the relation of the amount of hydrogen and nitrogen in steel, together with associated methods of steelmaking and treatment, to low-duetility effects and porosity. The interest of this investigation thus extends to permanent abnormal losses of ductility, such as are caused by the inclusions which sometimes result from special deoxidizing practices and possibly from metallic nitrides, but as these can he distinguished from the temporary effect of hydrogen, they have been excluded from the work reported here except when they

Jan 1, 1949

By C. E. Sims, G. A. Moore, D. W. Williams

During the past several years, the steel casting industry has made studies of heavy castings in which the test bar has been taken from heavy sections rather than from attached or separately cast coupons. It has been noted that the ductility properties of these heavy sections are often lower than those normally expected. Such lowered ductility is usually accompanied by a spotty test bar fracture, and the ductility values can often be greatly improved if a low-temperature aging treatment is given to the casting. A loss of ductility of this type is considered "abnormal," since it is not accompanied by an increase of tensile strength or hardness, and "temporary" when the ductility can be restored by aging. The cure of such an abnormal condition represents a real improvement in the quality of the steel. Several types of abnormal loss of duetility can be distinguished, of which those caused by excessive amounts of inclusions of undesirable type and those caused by unsuitable grain size and inget structure are well known. The particular type of abnormal lowered ductility currently under consideration may be distinguished by the fact that the low-temperature aging treatment necessary for its relief is insufficient to cause any visible change in the micro-structure as ordinarily observed. As this aging will in fact eventually occur at room temperature, the phenomenon of present interest may be given the symptomatic definition, ''Temporary Abnormal Low Ductility." Some hundreds of previous investigations, largely qualitative in nature, have established, beyond reasonable doubt, that hydrogen is normally present in newly manufactured steel and that this gas, in small amounts, can cause a temporary abnormal loss of ductility. The commonly observed association of high gas content and low ductility has given strong evidence for the presumption that hydrogen, possibly assisted by other gases, is the primary cause of the low ductility observed. Accordingly, The Steel Founders' Society of America has, since Nov. 1, 1944, sponsored investigations at Battelle Memorial Institute whose primary objective is to obtain quantitative information on the relation of the amount of hydrogen and nitrogen in steel, together with associated methods of steelmaking and treatment, to low-duetility effects and porosity. The interest of this investigation thus extends to permanent abnormal losses of ductility, such as are caused by the inclusions which sometimes result from special deoxidizing practices and possibly from metallic nitrides, but as these can he distinguished from the temporary effect of hydrogen, they have been excluded from the work reported here except when they

Jan 1, 1949

By B. H. Cody

THE Morenci concentrator of the Phelps Dodge Corporation is a part of the project that was completed after five years had been spent in development of the open-pit mine, equipment and process testing in the former No. 6 concentrator, and construction of the reduction works. The reduction works, of which the concentrator is a part, is about a mile and a quarter southeast of Morenci, on the highway that leads up Morenci Canyon. The concentrator has a nominal capacity for the treatment of 45,000 tons of ore daily. The original plant, which has a rated capacity of 25,000 tons of ore daily and is now in its fifth year of operation, began production on Jan. 30, 1942. The addition, to increase the capacity 8o pct, began operation on Dec. 1, 1943. The equipment of the original plant has been described in MINING AND METALLURGY (May 1942). No changes in equipment were recommended for installation in the concentrator extension and only one major change, forced by a shortage of maintenance labor, has since been made. Metallurgical treatment has been altered in some ways as experiments progressed and as labor and economic conditions dictated. No complete description of the operation of the concentrator has been published, so this paper will record such operating and equipment changes as have been necessary, the operating methods that have been developed and the metallurgical results that have been obtained. Descriptions are given in the order of the processes with a flowsheet and an equipment list of each process for convenient reference. The questions asked by engineer visitors have guided the detail in which operation and maintenance are described. During the period Jan. 30, 1942 to Sept. 1, 1946, ore milled has totaled 43,595,253 dry tons, from which 1,643,885 tons of concentrate have been made, containing an indicated production of 783,164,809 lb of copper. The principal results obtained in operation of the concentrator during the years 1942 to 1945, inclusive, and to Sept. 1, 1946 are shown in Table 1. A graphic general flowsheet of the plant is given in Fig I. ORE The Morenci ore that is now being treated is a medium-hard monzonite porphyry in which the principal sulphide minerals are chalcocite and pyrite. A minor amount of covellite is present. Chalcopyrite and bornite have been observed under the microscope. The chalcocite occurs mainly as a coating on pyrite. Some of the coatings are so thick that the pyrite presents the appearance of being an inclusion in chalcocite. Some are less than one micron thick and are barely visible at 500 diameters magnification of a polished cross section. Some chalcocite is present as a dissemination in the gangue. Various oxidized copper minerals are present as a result of oxidation in place but they represent a minor proportion of the copper minerals of the ore body. Oxidation

Jan 1, 1947

By Norman Weiss

IF we were to measure progress this year in terms of large new mills and discoveries of fundamental significance we should certainly be disappointed. Outside of the uranium field there was little of a spectacular nature. San Manuel and Reserve completed their first year of operation; Erie approached readiness; the Toquepala project in southern Peru broke ground and gained speed. Important mill enlargements occurred at Inspiration, Anaconda, Ray, and Climax Molybdenum. A 3000-ton copper concentrator was completed at Pima, near Tucson. The Republic Mill of Marquette Iron Mining Co. started up in April. Abroad, the great developments in the African Copper Belt can be likened to the rapid growth of the porphyry coppers in this country. Fundamental research was confined nearly entirely to iron ore flotation and recovery of metal values from leach solutions, particularly uranium. The large number of review articles this year reflected a desire to take stock and consolidate past gains before taking the next bold steps. Undoubtedly a shortage of competent young engineers and technicians is stunting the natural growth of theoretical investigation in the field of minerals beneficiation, as well as the conversion of ideas into action. We find our small stock of talented young scientists concentrated in a few centers of erudition because there are not enough to diffuse through the industry. It is safe to say that among mine administrators and managers there is more interest in the education, training, and welfare of the young engineer than ever before.

Jan 2, 1957

By Edward O’Toole

THe Pocahontas district occupies the extreme southern end of West Virginia, principally McDowell, Mercer and Wyoming counties, and a part of Tazewell county, in southwestern Virginia. The first record of the coal field is a report by Prof. J. P. Lesley, of Pennsylvania, about 1880, in which he mentions a coal opening at the upper end of Abbs Valley, Tazewell county, Va. C. R. Boyd, a mining engineer of Wytheville, Va., published a series of articles in 1881, mentioning coal on Indian Creek, Tazewell county, and on Horse Pen creek, which coals, he stated, extended toward the Ohio River. He also mentions the Abbs Valley coal reported by Lesley. In 1881, F. J. Kimball (who became president of the Norfolk & Western R. R. in 1883)) after examining the Scott mine in Abbs Valley, went northward across Abbs Valley Mountain to the place now known as Pocahontas, where he located what has since been called No. 3 vein of Pocahontas coal. In November, 1882, Jed Hotchkiss and others prepared a cross-section of the Flat Top Mountain coal measures, some notes on which were published by Mr. Hotchkiss, between 1880 and 1892, under the title of " The Virginias.' In May, 1881, the Norfolk & Western R. R. was organized through the purchase of the Atlantic, Mississippi & Ohio R. R., an old line running from Norfolk, Va., to Bristol, Tenn., with branches from Petersburg to City Point and from Glade Springs to Saltville. At that time, charters had been granted for three railroads tributary to the New River Valley, but their proposed routes would indicate that the promoters were concerned with minerals, timber, and a connection with the Chesapeake & Ohio R. R., rather than the development of any coal in the Pocahontas district. One of them was projected to extend up Bluestone River a short distance, but not far enough to reach the coal in the Bluestone Valley, and a little grading was done for a narrow-gage road between New River Station and a point in Giles county, Virginia, near the West Virginia line. All charters and railroads in this district were acquired by the Norfolk & Western R.R.

Jan 1, 1925

By C. E. MacQuigg

In this paper it is impossible to more than touch on many of the commercial alloys of iron, chromium, and carbon, therefore the discussion is confined to the properties of some of the less well-known alloys with upwards of 20-per cent. chromium. The discussion has been based largely on the strictly engineering aspects of the alloys. Chromium has well-defined effects when added to the iron-carbon system. These effects depend on the amount of chromium added and on the composition of the iron-carbon alloy to which the addition is made, i.e. whether low- or high-carbon steel, cast iron, etc. In the case of the low-carbon steels, the chromium addition, when not in excess of several per cent., appears to exert an influence on the properties by its influence on the critical range. In the higher chromium alloys, the physical properties are influenced chiefly by the formation of new complexes, such as iron-chromium solid solutions and, with higher carbon contents, iron-chromium carbides of great hardness. Examination of the published data1 on the critical range phenomena of chromium-bearing steels up to several per cent. chromium indicates an agreement on the following points:

Jan 1, 1923

By C. E. MacQuigg

In this paper it is impossible to more than touch on many of the commercial alloys of iron, chromium, and carbon, therefore the discussion is confined to the properties of some of the less well-known alloys with upwards of 20-per cent. chromium. The discussion has been based largely on the strictly engineering aspects of the alloys. Chromium has well-defined effects when added to the iron-carbon system. These effects depend on the amount of chromium added and on the composition of the iron-carbon alloy to which the addition is made, i.e. whether low- or high-carbon steel, cast iron, etc. In the case of the low-carbon steels, the chromium addition, when not in excess of several per cent., appears to exert an influence on the properties by its influence on the critical range. In the higher chromium alloys, the physical properties are influenced chiefly by the formation of new complexes, such as iron-chromium solid solutions and, with higher carbon contents, iron-chromium carbides of great hardness. Examination of the published data1 on the critical range phenomena of chromium-bearing steels up to several per cent. chromium indicates an agreement on the following points:

Jan 1, 1923