Search Documents

By T. F. Witherbee

IN a paper read at the Lake Superior meeting, August, 1880, an account was given of the successful use of Rendrock and Monaky powder upon a scaffoldn and salamander in the furnace. On April 5th, 1881, the same trouble called for like treatment, which, though not so immediately. successful, was on the whole more instructive than the first trial, and points, I trust, to a reasonably sure remedy for all such difficulties. Up to December 4th, 1880, foundry and mill iron were made from Old Bed and New Bed magnetite, and Kearneyy red hematite, when a return was made to Bessemer iron, from an inferior quality of New Bed ore as compared with that used during first blast. January 18th, 1881, New Bed, Chateangay, and East-shaft, a newly-opened Bessemer deposit of Messrs. Witherbee, Sherman & Co., were first used, and continued up to February 13th, on a fuel charge of 80 per cent. anthracite and 20 per cent. coke, the product on the three ores being about 10 tons more per day than on New Bed alone. From this time until March 11th all coal was used, and New Bed, Chateangay, and East-shaft ores, up to February 22d, and from that date Chateangay and New Bed, the product falling off 9 6/10 tons per day as a result of not using coke. It is fair, however, to state that the furnace was not in good condition during' this period, being over-burdened, and the New Bed ore was, temporarily, uncommonly poor, for reasons of no particular interest here.. It required to properly flux it at least 140 per cent. of limestone; and 101 per cent was actually used. March 11th, all Chateangay ore and 80

Jan 1, 1882

By Philip D. Wilson

FEAST and famine-or, chronologically, famine and feast-have characterized the aluminum supply program during 1943. Fortunately for the war effort the famine phase is over and aluminum production is now in the happy position of being abundantly able to supply all the requirements of the armed services plus a monthly surplus which is building up a substantial stock pile as a reserve against any contingencies. But the present condition of oversupply cannot be attributed to the super-efficiency of the aluminum production program which was designed to take care of the over-all requirements of the war with little or no margin of safety. The present more than comfortable situation is due primarily to the fact that the armed services generally have not consumed anything approaching the amount of aluminum which their requirement estimates indicated.

Jan 1, 1944

By L. N. Brown

The use of sheet and strip metal has increascd rapidly during the last few years and manufacturers have been called upon for an ever-increasing tonnage, better drawing quality, and better surface. The automobile industry is probably the most insistent in striving for a better product and a desire to reduce costs. Confronted by these demands, the mills have directed their efforts toward the delivery of material. Their personnel has been occupied largely with the problems incident to production, as any increase forced the use of new sources of raw material with their problems. These problems, combined with those met in the daily routine, have demanded immediate attention, with the result that the standardizing of heat treatments, quality, or temper, etc., have been neglected. Considerable work in standardizing has been done by many companies, but no acceptable method has been developed. The following method, therefore, is given with the hope that some method that can be accepted by the manufacturers and users may be developed. The problem of selecting a material with such properties that the losses in processing are a minimum is interesting and difficult. A description of the properties required is likewise difficult, largely because of loose terms. Another handicap is the number of methods of testing which have not been standardized and concerning which little information is available. In the selection of drawing or forming stock, it is advisable to eliminate as many variables as possible; consequently the method of testing the material is of the utmost importance. The method should be rapid and comparatively easy of application, as it is more important that a large percentage of the stock be tested with reasonable accuracy than that

Jan 1, 1923

By L. N. Brown

The use of sheet and strip metal has increascd rapidly during the last few years and manufacturers have been called upon for an ever-increasing tonnage, better drawing quality, and better surface. The automobile industry is probably the most insistent in striving for a better product and a desire to reduce costs. Confronted by these demands, the mills have directed their efforts toward the delivery of material. Their personnel has been occupied largely with the problems incident to production, as any increase forced the use of new sources of raw material with their problems. These problems, combined with those met in the daily routine, have demanded immediate attention, with the result that the standardizing of heat treatments, quality, or temper, etc., have been neglected. Considerable work in standardizing has been done by many companies, but no acceptable method has been developed. The following method, therefore, is given with the hope that some method that can be accepted by the manufacturers and users may be developed. The problem of selecting a material with such properties that the losses in processing are a minimum is interesting and difficult. A description of the properties required is likewise difficult, largely because of loose terms. Another handicap is the number of methods of testing which have not been standardized and concerning which little information is available. In the selection of drawing or forming stock, it is advisable to eliminate as many variables as possible; consequently the method of testing the material is of the utmost importance. The method should be rapid and comparatively easy of application, as it is more important that a large percentage of the stock be tested with reasonable accuracy than that

Jan 1, 1923

Human engineering was the keynote of the thirty-ninth annual meeting of the American Society of Mechanical Engineers, which was held in New York, December 3-6. This note was sounded by President Charles T. Main in his address at the opening session and was carried through by all the speakers. In his survey of the year's work, he said that more than 6000 names of engineers were furnished the Government for filling a wide variety of positions. In addition to the 1400 members in service, two members of the council of the society are in uniform in France and one, as a distinct war service, is in charge of one of the largest shipyards. After giving other ways in which the Society has helped the Government, President Main called attention to the necessity for thoroughgoing efforts to increase production and the settlement of questions involving industrial relationships. At the following meeting, President Adams of the American Institute of Electrical Engineers called attention to the necessity of meeting labor in a progressive way, facing labor questions fairly and squarely, as the real interests of labor cannot be separated from those of the engineer. Charles E. Knoeppel, discussing "Industrial Organization as It Affects Executives and Workers," said the problem of the cost of living might be settled in two ways: 1, there must be more producers, and 2, there must be a greater amount supplied by those now producing. The first solution is practicable, he said, if labor is allowed shorter hours, better conditions, and a remuneration that will attract workers. The second can be employed by eliminating waste, standardizing conditions, setting fair tasks, and allowing men to earn an amount that will compensate them for' their skill and cooperation. Dudley R. Kennedy of Philadelphia, employment manager of the American International Shipbuilding Corporation, said the human-engineering phase of the country's industrial development had generally been overlooked. "We hardly yet know what competition means; we will learn it within a few years. Permit me to prophesy that the executive of the next decade will be the man who best knows men. He will be an originator, a handler of men as individuals, a handler of men in the mass, a leader not a driver, a very human man. The science of human engineering is here to stay. The study of human characteristics is the most enduring, as well as the most fascinating in the world, and still the most complex."

Jan 1, 1919

By Warden A. Moller

(Pittsburg Meeting, March, 1910.) THE Fushun coal-field, now being opened up by the South Manchurian Railway Co., is connected with the main line by a branch, 30 miles long, from Sui Chia Tun, 10 miles south of Mukden, the capital of Manchuria. The coal-field, which lies on the southern bank of the Hun river, 25 miles east of Mukden, consists of a long narrow valley,. running east and west between hills composed of granitic and volcanic rocks. At the foot of the northern hills, the Hun river flows westward towards the Liao river, which drains the greater part of South Manchuria. At the foot of the southern hills, resting immediately upon volcanic rocks, and overlain by 20 ft. of alluvial, is a thick layer of Tertiary shales, carrying near the base two coal-seams. In many places the lower of these two seams is in immediate contact with volcanic lauds and basalts, the flows of which were evidently both prior and subsequent to the formation of the coal-seams. This contact has practically destroyed the lower seam for commercial purposes. The value of the field lies in the upper seam, which, for a length of nearly 8 miles, varies from 100 to 130 ft. thick. Of this seam, 85 per cent is good coal. The seam dips to the north conformably with the shales, at angles of from 25° to 30°, and appears to have an uninterrupted dip for about 1.5 miles before being possibly cut o$' by the northern hills. The coal-bearing shales extend east and west for a length of about 20 miles, but towards the east the continuity of the seams is broken by intrusive rocks. The coal is of the sub-bituminous variety, low in ash, bright in appearance, and breaks with a conchoidal fracture. It has the usual qualities of Tertiary coal-quick steam-raising and poor stacking-qualities. Pieces of resin, varying in size from

Apr 1, 1910

By James F. Kemp

Jan 1, 1914

By G. P. Connell, R. E. Gilmore, J. H. H. Nicolls

The purpose of this paper is to suggest a procedure for indicating the dividing line between noncaking coals and those that have weakly caking properties. A laboratory agglomerating test as an aid in classifying weakly caking coals is outlined and its merits in comparison with the standard agglutinating method advanced by the U. S. Bureau of Mines are discussed. No attempt, however, is made to discuss in detail either the different methods for determining "caking" and "agglutinating" indices or the various systems of classification. Two methods, differing somewhat in procedure, have been employed and recognized as suitable for determining the caking or agglutinating values of coals; namely, those in which an inert material such as sand, electrode carbon, etc., has been mixed with the coal before being heated, and those in which the coal is carbonized alone. In all such methods, the coal with or without the inert material is in the finely divided state and the index or value sought is derived from the examination of the residue after heating in a closed crucible or other container. The procedure outlined by Selvig, Beattie and Clellandl is the most recent representative of the method using sand as inert material, while the agglomerating test described below is representative of the method in which the coal is carbonized alone. The standard volatile-matter determination affords a means for observing the coking properties of a coal, and this has been described by Rose2 as the simplest of all coking tests. According to him, "the resulting coke button will indicate whether the coal is noncoking, feebly coking or strongly coking," despite the fact that "almost every condition in this test is at variance with large-scale carbonizing practice." Lessing,3 the

Jan 1, 1934

By L. A. Mekler

The recirculating furnace is primarily a heating apparatus of the convection type in which the heat-absorbing surfaces are heated by a mixture of fresh products of combustion and a portion of the combustion gases that have already given off a part of their heat in their previous passage over the heat-absorbing surfaces. In its basic conception, the recirculating furnace can be considered as a closed thermal system in which the heat-absorbing surfaces are constantly swept by a fixed quantity of products of combustion at a given initial temperature with the gases being constantly returned to the furnace and reheated before they again enter the heating zone. Gases equal in amount to those produced by the fuel burned to reheat the circulating gases are constantly ejected from the system to the stack. The recirculating furnace is the most suitable apparatus for heating by convection where low furnace temperatures must be maintained and where only a small portion of the available heat is taken out of the gases, particularly where the maximum allowable furnace temperature is low and where the final temperature of the gases is only a few hundred degrees below their initial temperature. In such cases, recirculation not only provides a method of reducing the rather high combustion temperatures of the fuel when burned without a large amount of excess air, but, by returning to the furnace the heat content of the gases at their final temperature, recovers a large portion of heat that otherwise would have been lost through the stack. The convection-type oil still is particularly suitable for the application of flue-gas recirculation. In an oil still, the heating of the oil is accomplished by applying to the tube surfaces a given quantity of heat of a certain predetermined quality, usually with the initial temperature of the gases not over 1500" F. as measured by thermocouples placed above the tube bank. To obtain the full benefit of the heating surface of the coil, the final temperature of the gases, after passing over the coil, is kept 200" to 300" higher than the temperature of the incoming oil. This final temperature varies from 500" F. for a topping still with only a slight or no

Jan 1, 1928

By Oliver M. W. Sprague

THIS gold problem is full of complications and can hardly be handled adequately or comprehensively in any short period of time. Perhaps I might begin by mentioning a few aspects of the subject about which I suppose there will be no disagreement. The first of these is that we already have a stock of monetary gold in the United States far in excess of what is needed to support any desirable increase in the present volume of currency and credit. The second is that this already superabundant gold stock is certain to be considerably enlarged during the course of the war, and presumably during the months of readjustment following its conclusion. Some billions of additional gold, we may reasonably presume, will come into the country during these next few years, thus increasing the aggregate monetary gold stock from the present eighteen billions to perhaps twenty- two or even twenty-five billion dollars.

Jan 1, 1940

By Jennings S. Cox

(Glen Summit Meeting, June, 1911.) THE following notes, prepared in 1908, as the result of a personal examination and extensive explorations under my direction in 1906, have been revised and greatly augmented after two subsequent visits and further explorations in 191.0. The hard iron-ores of the south coast of Oriente Province, in the island of Cuba, have been known for many years, in fact one mine has been in operation for more than 20 years ; but it is only within the past four years that the large mantle-deposits of brown ores of the north coast have attracted serious attention. A. C. Spencer 1 has described these ores in a paper, entitled Three Deposits of Iron Ore in Cuba, which refers to the Mayari, Moa, and Cubitas deposits. C. M. Weld,2 in a scholarly paper on The Residual Brown Iron-Ores of Cuba, has discussed the character and possible genesis of these deposits with particular reference to the Moa field, calling attention also to the Taco and Navas fields in addition to those described by Spencer. Descriptive articles with reference to the Mayari field, and a few words about the Moa deposit, have also appeared.3 It is the purpose of the present paper to give some account of the exploration of the Moa deposit and to call attention to its commercial importance. LOCATION. The Moa district is situated on the north coast of the . Province of Oriente, which is the most easterly province of the island of Cuba. It lies on the northern or seaward slope of 1 Bulletin No. 340, U. S. Geological Survey, pp. 318 to 329 (1908). 2 Trans., xl., 299 to 312 (1910). 3 Iron Age, vol. lxxx., No. 7, pp. 421 to 426 (Aug. 15, 1907), and vol. lxxxi., No. 15, pp. 1149 to 1157 (April 9, 1908).

Mar 1, 1911

By L. O. Howard

R. HATCH, Garfield, Utah.-The object of the meeting, I believe, is to determine the proper chemical composition to insure long wear of a ball in a mill, This might also apply to rods. I feel that there is only one way of determining accurately the wearing qualities of balls in mills, and that is by actually wearing out 400 or 500 tons of different kinds of balls. Two things add to the wearing qualities of a ball: (1) the tenacity, with which the particular particles of iron or steel are cemented together; (2) the individual hardness of each particle. My experience is that a ball that has a Brinell of 550 to 650 will give comparatively long life. There is considerable difference of opinion as to the best steel and iron alloys necessary to produce a satisfactory grinding ball. Some favor chrome, some manganese and some nickel. Personally, I believe cast iron alloyed with chrome makes the best ball for small sizes; for large sizes (3 1/2 in. and up) steel alloyed with manganese is best. L. 0. HOWARD, Pullman, Wash.-How would this method apply to lining? A. KissocK, New York, N. Y.-I do not subscribe to that exactly. As I am connected with the Climax Molybdenum Co. you would hardly expect me to. We have been much interested in trying to work out this grinding-ball problem and have spent a great deal of thought and effort on it. As we are associated with the American Metal Co. and have a number of properties of our own, we are in position to try our ideas on ourselves first. We have tried different compositions, but have not done anything very remarkable with them yet, except that we have been able to say that the combination of chrome and molybdenum has given the best wearing ball. Mr. Hatch feels that iron is the best medium for grinding, but since toughness as well as hardness is a factor in wearability we feel that a well made steel is better for this purpose. Another difficulty with cast, or chilled, iron is lack of uniformity from day to day or from heat to heat and the impossibility of producing balls free from blow or shrinkage holes which materially affect their life. If cast iron is made hard it becomes brittle and lacks stretch or toughness. This prevents its use in the larger sizes, as breakage is a serious handicap to efficiency. We have tried hard and brittle balls and softer but very tough balls and have proved that maximum hardness, with sufficient toughness to prevent breakage, is the most important factor in resistance of a steel to abrasion. It is well known that chromium is one of the best hardening agencies for either iron or steel, and molybdenum is recognized as an element capable of introducing toughness. In other words, the proper combination of chromium and molybdenum permits unusual hardness with still sufficient toughness to stand up under severest impact. It is yet too early to give any actual mill results of this new combination and though we are proving our ideas at our own properties we have to depend on others to help us make the data more general and more worth while and would like to get some tests

Jan 1, 1928

By O. J. C. Runnalls, L. M. Pidgeon

Some observations on the kinetics of the iodide process are reported. The deposition rate is geometry-sensitive in a system containing a finely divided titanium charge. Further, results indicate that the iodine diffusion rate influences the velocity of the process. The nonvolatile iodide, Til,, forms in the hot filament zone, thus removing iodine from the cycle. TITANIUM metal of 99.9 pct purity may be prepared using a refining technique originated by Van Arkel and de Boer.' The purity of this metal, commonly called iodide titanium, exceeds that produced by any known process. In a recent application, the method was employed by Gonser et al.² to prepare titanium rods up to 2 to 3 cm in diam. In the Van Arkel-de Boer system, the relative influence of the fundamental mechanisms: l—production of titanium iodides, 2—gaseous countercurrent diffusion, and 3—decomposition, on the deposition rate have not been clearly established. Blocher and Campbell" have indicated that the controlling step in the process under practical conditions of operation may be the reaction rate of iodine with the crude metal. Fast' reported that crude titanium metal reacted with iodine rapidly, even at room temperature, in his apparatus. Little has been reported on the effect of gaseous diffusion or decomposition on the deposition rate. It is these aspects of the process about which this investigation is centered. An attempt has been made to separate these latter effects from those due to the formation of the iodides at the crude metal surface by a division of the experimental program. Reaction of Iodine with Titanium Apparatus: In the investigation of gas-metal reactions of this type, the chemical reactivity of the halogen and halide vapors dictates the use of all-glass apparatus. In such a system standard techniques for measuring reaction rates are difficult to employ. Here, a simple apparatus was devised (Fig. 1) so that some indication of the reactivity of titanium powder with iodine vapor could be obtained. A stream of iodine gas was evolved from a bulb of controlled temperature and passed over a sample of titanium powder heated in a horizontal tube furnace. The product of the reaction, TiI4, volatilized and was condensed outside the furnace in a series of four glass bulbs, each cooled to room temperature in turn. Preliminary experiments indicated that distillation was retarded in a sealed evacuated system due to a pressure build-up in the condensing end of the apparatus. Hence, the system was pumped continuously using a mechanical pump and two oil diffusion pumps in series, through a liquid air trap. The iodine bulb was made large and a capillary restriction was inserted between the titanium bulb and the condensers so that the iodine pressure over the metal would approach the equilibrium pressure over solid iodine crystals. The effect of this restriction on the evaporation rate of TiI4, was determined separately. The iodine bulb was heated in an oil bath controlled to ±2°C. The titanium bulb temperature was automatically controlled to ±5°C. Procedure: About 200 mg of —30 mesh titanium powder, weighed to 0.1 mg, was placed in the reaction bulb after part B had been joined to part A. The powder was tapped into a long (5 cm) shallow mass along the bottom of the tube. Two chromel-alumel thermocouples were inserted into the magnesium radiator which was clamped to the reaction

Jan 1, 1953

By HENRY M. HOWEL

1. Introduction.-The first part of this papers treats of the causes and the restraining of piping in steel ingots; the second& considers the causes and the restraining of -segregation; and the third proposes certain precautions in engineering specifications concerning these two defects. Into their causes I have looked carefully, with the purpose of arriving at rational methods of restraining them, and at efficient ways of detecting. and measuring the harm which they cause, so as to benefit the public by reducing this harm at once effectively and with the least expense to the manufacturer, and therefore in the end with the least expense to the consumer. In Part I., I infer that the pipe is chiefly due to what I, call the virtual expansion of the outer walls of the ingot in the early part of the freezing. I find that the upper and smooth-faced part of the pipe probably forms while the interior is still molten, but that the lower, steep, and crystal-faced part probably forms in metal which is already firm. Of the five causes which may co-operate to limit the depth of the pipe, I find that three-blow-holes, sagging, and the progress of freezing from below upwards-are usually effective. I find that the pipe may be lessened by casting (1) in wide ingots,; (2) in sand molds, especially if these are pre-heated (this is rarely expedient); (3) at the tops instead of at the bottom; (4) slowly; (5) and with the large end up; (6) by the use of a sinking-head or other means of retarding the cooling of the top; (7) by permitting blow-holes to form; and (8) by liquid compression.) Most of these I consider in some detail, and in particular I dwell on the advantages of casting with the large end up, and I propose certain administrative arrangements to permit this.

Mar 1, 1907

By Geoffrey Purcell

For anyone contemplating flotation research with only a very limited amount of mineral available for testing, the choice of suitable experimental equipment is by no means obvious. Hallimond's original and delightfully simple cell1 has been modified by subsequent investigators2to give quantitative and reproducible results on small samples. However, the modifications have necessarily compromised its simplicity, and the services of a skilled glass blower are required to duplicate the cell. Vacuum flotation tests3 at best qualitative and may, under certain conditions4, be quite impracticable. A hundred years ago, Thoreau observed that "our life is frittered away by detail," and his advice was to "simplify, simplify," The success of the simple cell described below, which was developed by the author and differs somewhat from Hallimond's original, suggests that Thoreau's advice still has merit a century later. CELL CONSTRUCTION The cell [Fig. 1 (a) and 1 (b)] consists essentially of a 25-ml pipet from which has been cut the con- stricted top. The length cut off is not critical since this merely determines the final volume of the cell. Cell volume may be varied in this way from 20 to 50 cc. A pyrex extension tube, equal in diameter and approximately half the length of the cut pipet, is attached to the top of the pipet by means of 2 ½ in. of close-fitting tygon tubing. When assembled, the two pyrex tubes should be spaced about ½ in. apart. Another length of tygon tubing is added to the extension piece for sealing purposes. A ¾ -in. disc of porous material (teflon cloth is ideal), secured in place over the pipet tip with another piece of shaped tygon tubing, completes the cell assembly. Tygon tubing may be shaped by pushing it over the pipet tip or some similar form and heating carefully over a low flame. For flotation [Fig. 1 (c) 1, the pyrex extension tube is rotated approximately 70º from the vertical and held in position by a wire hook and eye. Floated material, after reaching the free surface, falls and rests on this inclined plane. The barrier formed by the bent tygon tubing ensures that floated material does not slide back and return to the vertical portion of the cell.

Jan 11, 1965

By H. H. Klepfer, M. E. Snyder

UNTIL very recently, the commercial availability of the rare earths as metals has been very limited. Fabrication of mill products from these metals has not been studied in most cases. This note reports the results of the development of fabrication techniques for thulium. Thulium has a melting point of about 1550°C and a hexagonal close-packed crystal structure. It oxidizes in air to give a black oxide (TmzO,). The procedures for producing thin thulium foil were developed on one ingot weighing about 220 g and were subsequently applied in processing about a pound of metal to foil. Several alternates for the various fabrication steps were investigated and will be discussed. The metal fabricated was in the form of commercial chill-cast ingots 1 in. in diam and 2 in. long weighing approximately 220 g. Impurities in the ingots were reported by the vendor to be 4000 ppni tantalum, 2000 ppm calcium, 200 ppm nickel, 100 to 200 ppm iron, 100 ppm europium, and less than 100 ppm copper, lutetium, and ytterbium. In addition to these impurities, several salt-like inclusions as large as l/8 in. in diam were revealed along the center line of the one ingot sectioned. Preliminary tests indicated that small wafers cut from the as-cast ingot would not fabricate readily by rolling. Forging of copper-jacketed wafers was therefore attempted. At 1550"F forging was satisfactory but an apparent reaction of copper with thulium demanded investigation of lower temperatures. Therefore, the remainder of the test ingot was forged at 1450°F—with only minor cracking. All ingots forged were inserted into copper tubes of 1 in. 1D and 0.125-in. wall thickness. The jackets were sealed by flattening the ends of the tubes and welding under helium. Heating time at 1450°F was 30 min. Press forgings of 1/8 in. per pass were used, followed by 10 min reheats. When the ingots had been squared and reduced to 0.250 in. in thickness, the original copper jacket was stripped off and replaced by a new jacket in preparation for hot rolling. Hot rolling at 1450" F without edge cracking was readily accomplished after forging. Excellent results were obtained with 10 pct reductions of thickness followed by 5 to 10 min reheats. After reduction of thickness from 0.250 to 0.100 in. the copper jacket was removed. It was found, in fact, that hot rolling in air was possible. A tenacious black oxide similar to that seen on zirconium was formed during 3 min reheats at 1450°F. Reduction in air to 0.010 in. foil was possible taking 10 pct reductions per pass. The oxide coat formed during hot rolling in air could best be removed by sand blasting and pickling. Common pickling solutions containing polar solvents were found to attack the metal too rapidly and a concentrated nitric-hydrofluoric acid mixture attacked neither the oxide nor the metal. The most satisfactory pickling solution was 52 vol pct concentrated nitric acid-48 vol pct glacial acetic acid. After forging to 0.250 in., vacuum annealing and cold rolling was found to be another satisfactory alternate to hot rolling in copper jackets. After forging. a hardness of Rockwell B76 was found. Annealing in vacuum (2 X l0-5 mm of Hg) for 1 hr at 1200"F did not alter this value. Annealing at 1470"F for 1 hr brought the hardness down to R;]63. With cold rolling (5 pct per pass) the hardness returned to about R,1:76 after 20 pct reduction and edge cracking became noticeable. However, cold rolling to a total of 40 pct reduction in thickness (RI,,83) was possible before edge crack propagation became serious. Good surface finish was obtained, and the metal loss due to oxidation was minimized by cold rolling and vacuum annealing. Using this procedure the yield of 1.25 in. wide by 0.010 in. thick foil from a 1-in. diam ingot was about 40 pct.

Jan 1, 1961

By W. C. Clarke

An empirical study of the nature of the embrittle-ment which occurs in martensitic and semiaustenitic precipitation hardening stainless steels upon exposure at temperatures of from about 550" to 875°F has been undertaken. This work was aimed at determining cazusation and means of controlling this phenomenon. A commercial copper bearing precipitation hardening alloy was used as a basic material for study. The effect of heat treatment variables was studied as was the effect of variations in analysis. It is concluded from the evidence that martensitic and semiaustenitic precipitation hardening stainless steels are subject to 885°F ernbrittlement similar to that observed in the straight chromium stainless steels. A characteristic of precipitation hardening stainless steels which has limited their use in certain applications is that they embrittle when held at temperatures in the range of from about 550" to 900°F. This is true to a more or less degree in all currently available alloys, either the basically martensitic type or the semiaustenitic type. The rate of embrittlement varies markedly with exposure temperature, being low at 550" to 600°F and in-creasing as the temperature increases. In spite of this embrittlement, these alloys with their unique combination of high mechanical strength, reasonable toughness, and good corrosion resistance are used in many hundreds of applications. Nevertheless, there are potential applications where the embrittle-ment described is a limiting factor. The purpose of this investigation was to study the embrittlement of these alloys and to find a way to control or eliminate it. GUIDELINES USED IN PRESENT WORK The work reported in this paper is based on a study of 17-4 PH*, a very widely used alloy. It has been used *Trademark of Armco Steel Corp., licensor. in pressurized water and boiling water atomic reactors operating at about 550°F for a number of years. As the life of such equipment is extended or operating temperatures are raised, the possibility of embrit-tlement becomes of increasing concern to materials engineers. Much investigation work was done with respect to the use of 17-4 PH at 550°F. K. C. Antony' states "Such estimation" (of an activation energy for the diffusion of chromium in iron) "would indicate W. C. CLARKE, Jr. is Senior Research Engineer, Advanced Materials Division, Armco Steel Corp., Baltimore. Md. This manuscript is based on a talk presented at the symposium on New Developments in Stainless Steel, sponsored by the IMD Corrosion Resistant Metals Committee, Detroit, Mich., October 14-15, 1968. significant secondary aging is improbable at temperatures less than 700°F within normal component service life". This statement is modified however by the recognition of the accelerating tendencies of applied stress and internal stress as well as the possible effect of irradiation. In this investigation of 17-4 PH, the H 1100 (1900°F-1 hr oil quench or air cool + 1100°F-4 hr-air cool) condition was used, partly because this condition is normally used in atomic reactors. As shown later, the precipitation hardening temperature has no real bearing on the rate of embrittlement. An exposure temperature of 800°F was selected since embrittlement at 800°F is rapid, permitting development of relative data in time periods of 400 to 500 hr. For those not familiar, a nominal present day analysis of 17-4 PH is: C Mn P S SiCrNiCuCbN 0.04 0.30 0.015 0.015 0.60 16.00 4.30 3.25 0.23 0.030 TYPICAL BEHAVIOR OF 17-4 PH Figs. 1 and 2 show the behavior of a commercial heat of 17-4 PH under the conditions defined. Characteristically, 800°F exposure causes a rapid drop in Charpy V-notch impact strength. Tensile and yield strengths gradually increase and a gradual loss of elongation and reduction of area occur, accompanied by an increase in hardness. Notched tensile strength increases to 125 hr exposure and then sharply decreases after exposure for 500 hr. The notched vs un-notched tensile ratio remains virtually constant to exposure for 125 hr (1.67 to 1.56) but drops to 1.15 after 500 hr. Tensile ductility is not alarmingly affected even after much longer exposure times than these. For example, samples aged at 1100°F for 1 hr exposed at 800°F for 4000 hr showed a drop in elonga-tion of from 13 to 11 pct and in reduction of area of from 58 to 37 pct. Notched impact is the property SmIgth KSI 3JJ[/__________^UTS-Nrteh 260 ;/- 240 —^ 200 UTS-Smooth________._, o ioo mo Sob" m Too Hours Exposure Fig. 1—Effect of exposure at 800°F for various times on notched tensile strength and smooth tensile and 0.2 pct yield strength of 17-4 PH in the H 1100 condition.

Jan 1, 1970

By L. F. Reinartz

The furnace in which rimming steel is made has an important bearing on the quality of the steel produced. Furnace.—Particularly in the manufacture of low-carbon rimming steels, it is necessary to have an efficient, easily regulated furnace, because of the relatively high finishing temperature requirements. In recent years, the most important development in design of open-hearth furnaces has been the sealing and insulation of the greater part of the furnace to prevent air infiltration and loss of heat. Efficient, straight-line valves insure proper draft. Combustion controls guarantee correct gas-air ratios. Furnaces of all sizes ranging from 20 to 200 tons have been used successfully in the manufacture of rimming steels. Metal bath is varied from 20 to 40 in. in depth without appreciable variation in quality. Charging.—A normal open-hearth charge consists of pig iron (hot or cold), scrap of miscellaneous nature, and slag-making additions, such as limestone and burnt lime. Because of local conditions, some plants find it necessary to discard the use of pig iron and use some carbonaceolis substances with varying percentages of cast iron to replace the pig iron. It is questionable whether such practice will consistently produce the quality of rimming steel required for auto stampings and other severe drawing requirements. Pig Iron.—An open-hearth furnace under proper control should melt 150 tons of low-carbon rimming steel on about 35 to 38 per cent pig-iron charge basis. In some practices, best results are obtained when the total charge contains from 0.40 to' 0.50 per cent silicon. If reasonably low-

Jan 1, 1935

By L. F. Reinartz

The furnace in which rimming steel is made has an important bearing on the quality of the steel produced. Furnace.—Particularly in the manufacture of low-carbon rimming steels, it is necessary to have an efficient, easily regulated furnace, because of the relatively high finishing temperature requirements. In recent years, the most important development in design of open-hearth furnaces has been the sealing and insulation of the greater part of the furnace to prevent air infiltration and loss of heat. Efficient, straight-line valves insure proper draft. Combustion controls guarantee correct gas-air ratios. Furnaces of all sizes ranging from 20 to 200 tons have been used successfully in the manufacture of rimming steels. Metal bath is varied from 20 to 40 in. in depth without appreciable variation in quality. Charging.—A normal open-hearth charge consists of pig iron (hot or cold), scrap of miscellaneous nature, and slag-making additions, such as limestone and burnt lime. Because of local conditions, some plants find it necessary to discard the use of pig iron and use some carbonaceolis substances with varying percentages of cast iron to replace the pig iron. It is questionable whether such practice will consistently produce the quality of rimming steel required for auto stampings and other severe drawing requirements. Pig Iron.—An open-hearth furnace under proper control should melt 150 tons of low-carbon rimming steel on about 35 to 38 per cent pig-iron charge basis. In some practices, best results are obtained when the total charge contains from 0.40 to' 0.50 per cent silicon. If reasonably low-

Jan 1, 1935

By James Lorimer

THE topography at the Stan Trg mine facilitated early exploration by adits; in consequence adit levels were developed at horizons 865, 795, and 760 meters above sea level, and the levels in the mine 'are named according to their elevation. Exploitation started from the 760-m. level . upwards while simultaneously first steps were taken with regard to mining in depth. A deep dewatering adit 2.5 km. long now gives access to the deposit at the 610-m. horizon which also is connected with the 760-m. adit level by a three-compartment main hoisting shaft. Main levels have been developed internally from

Jan 1, 1936