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By John Gillie

PRioR to the year 1902 electricity was used in the Butte district only for lighting, for the tramming of ores on the surface, and for the electrolytic refining of copper. In that year the Canyon Ferry hydro-electric plant on the Missouri river, with a transmission line to Butte and Anaconda, was completed, and enabled the mining operators to purchase electric current in large quantities at reasonable rates, and its application and use in the various mining operations and reduction works proceeded rapidly. The principal applications of electric current in metal mining may be listed as follows: Compressing air for hoisting. Compreeaing air for rock drills and pneumatic tools. Pumping. Ventilating. Lighting. Tramming. Compressing air for blast furnaces and converters Running shop and miscellaneous motors. Compressed Air for Hoisting. The Anaconda Copper Mining Co. operates 22 mine shafts and plants at Butte. Of these, 15 are large plants and hoists, through which most of its ores are hoisted. In 1912 this company commenced using compressed air in place of steam, in operating a number of its large hoists, and at this date has 10 main hoisting engines and 10 auxiliary hoists driven by compressed air. The compressed air is furnished from a central plant containing six compressors, each having a capacity of 7,500 cu. ft. of free air per minute compressed to 90 lb. pressure in large receivers, and conducted by suitable pipe lines to the various hoists, the air being reheated before passing to the engines. Each of these compressors is driven by a 1,200-h.p. synchronous motor, directly attached to the drive shaft, and takes electric current at 2,200 volts. Two additional compressors are being installed,

Jan 1, 1914

By H. W. Hitzrot

THE new 4800-ton fine-grinding plant at the Hollinger Consolidated Gold Mines property at Timmins, in the Porcupine district of northern Ontario, went into operation in November 1937, and represents the culmination of an experimental program. The plant is a moderately low rectangular building of hollow tile on a steel frame, large enough to house four 7 by 15-ft. ball mills, with a 12 by 27-ft. classifier beside each mill. At one end is space for the addi-tion of another mill and classifier or a mill and classifier for the regrinding of table concentrates. This regrinding is now done in the old grinding department of the main mill building. Also within the new building are the four 6-in. sand pumps for lifting the product from the low-dis-charge ball mills up to the classifier feed launders and the containers and appurtenances of a complete dust-collecting system. Together with the usual overhead crane, these constitute the major units of equipment within the new plant. The location is at the lower end of the main mill buildings toward the old tailings pond, now so neatly leveled off and sodded to rival the very best of our own W.P.A. projects. Close by the new grinding plant is a large dome-shaped structure-the new fine-ore bin designed and built by Mr. Longmore and the Hollinger milling and engineering staffs. There are four separate automatically loaded inclined belt conveyors leading up from the bottom of the bin to the grinding plant. Each belt is equipped with a recording weightometer, in the grinding building. The whole structure and the machinery within it give the impression of permanence and a carefully integrated design with close attention to details, giving the operators every advantage for consistently good work.

Jan 1, 1939

"The Southern Cross mining district was discovered during the early rush of gold seekers over Montana following the discovery of gold in 1861. Placers were worked near the Atlantic Cable mine in 1866, and soon attention was turned to quartz lode mining. High grade ores were discovered in the North Atlantic claim, adjoining the present Southern Cross group. The early metallurgical treat¬ment of these ores was by means of arrastres, a crude form of amalgamating mill, illustrated on the page opposite. This old arrastre located by the roadside on Warm Springs creek, was built by Barker Bros. in 1879. Further discoveries overtaxed the capacity of this plant, and in 1875 Thomas' Stuart employed a contractor named Jeptha J. Corner to convert the old Wilson & Fifer sawmill located at the Big Spring into an up-to-date gold quartz mill. 'For this trans¬formation Corner received the sum of $1,400.00. The illustrations give a good idea of the nature of its construction. Practically no iron was used in the mill, excepting for the stamps, dies and cams and cam shafts. Whether or not the saving attained reached the limits of present day perfection is not known. There being no steam boilers available, the early prospectors believed in the principle of conservation of fire wood, water power was therefore used, generated by a ""direct-connected"" over-shot wheel. Water for power purposes was supplied by the nearby spring. History fails to record the tonnage treated in this relic of early Montana milling practice.The ores of the Southern Cross district have not proved readily amenable to mill treatment, but being largely composed of iron oxides, they are most desirable fluxing ores for smelter operations. The B. A. & P. Ry. extends into the district. Electric power is furnished by the Flint Creek 'station, three miles distant."

Jan 1, 1913

By W. E. STOKES

SOME extension of flying service to the mining industry occurred in 1938, particularly in Canada, where freighting activity radiated from Edmonton into the new northern mining districts. Again the airplane demonstrated its usefulness in getting new equipment rapidly into the field and in decreasing shutdown time while waiting for repairs. An 18-ton Caterpillar tractor with shovel attachment was disassembled, brought in by plane, and placed in operation at Berens River, Ont., within seven days after its de- livery at Winnipeg. At Central Patricia a mill breakdown required the replacement of a full mill head and trunnion with ball bearings, weighing 2700 lb. The Canadian Airways Junkers, termed the "flying boxcar," was called in from Yellowknife, 1300 mi. away, and the new installation was completed three days later.

Jan 1, 1939

By Frank Firmstone

In 1871, two furnaces at the Glendon Iron Works, which had been blown out on account of the "coal strike," were altered from the open-top plan with side flues for collecting the gas, to closed tops with cup and cone. In one furnace the suppression of the side flues permitted a considerable alteration in the profile, but in the other (No. 5) no change in this respect was made; the side flues were simply bricked up and new ones cut through the sides close to the top. This furnace was in blast over four years, and we can, therefore, form a pretty good idea of the effect of the alterations on the furnace process. The principal dimensions are; Height 72'; greatest diameter, 18'; diameter at tuyeres, 8'; diameter of top, 10'; diameter at stock line (point at which the top of the materials is kept), 11'; cubic contents, 11,900 cubic feet. The table below shows the average results for periods of twentysix weeks each. 1st, of the open-topped furnace; 2d, of the furnace with the first charger used, which was an ordinary cup and cone (diameter of cone 5' 2") 3d, with the charger used ever since, a " double " cone 7' 5" diameter outside, having a central opening 3' in diameter. The diagram (Plate 11) shows the daily variations, in the grade of the irons for the same periods.*

By D. R. Mitchell

FOR the second consecutive year, attendance at the Coal Division sessions far exceeded exoectations. Those in charge were continually faced with problems of finding seats and space for attending members. 115 seats were set - II~ for the annual luncheon meeting of the Division and approximately 175 members showed un. Since the hotel management would not serve more than the 115 it meant that 60 members were forced to eat elsewhere. This created hard feelings with some members. How- ever, officials of the Division were not able to obtain in advance any indication of this overflow crowd, but are suggesting to the New York Office that some means other than ticket sales be adopted to obtain an estimate of Division luncheon and dinner attendance. Members could be circularized prior to he meeting or they could be checked when registering as to the events they expect to attend. Under the inspiring leadership of Cadwallader Evans, Jr., Chairman, the Coal Division had a phenomenal growth during the year. Reporting at the luncheon meeting, Newel1 Alford stated that approximately 190 new members had been obtained. A few more years of continuing increase at this rate will make the Coal Division one of the largest Divisions in the Institute.

Jan 1, 1944

By MORTON WEBB

Discussion of the paper of Max Boehmer, presented at the Pittsburg meeting, March, 1910, and printed in Bulletin. No. 38, February, 1910, pp. 119 to 122. W. MORTON WEBB, Germiston, Transvaal, South Africa (communication to the Secretary*):-The experience of Mr. Boehmer in the Leadville district and his reputation as an engineer assure the interest of anything he may write on the ore-bodies of that district; and all engineers who have operated in Leadville will agree that the theory of the origin of the Leadville deposits, as given by Mr. Emmons in his famous monograph, does not adequately explain the genesis of all the deposits. The solution of the problem does not, however, appear to be quite so simple as Mr. Boehmer would make it; and the advance pamphlet issued by the U. S. Geological Survey, pending the completion of the main report, shows that there is still much ground for controversy. No doubt the later eruptives had a greater influence on the deposition of the ore-bodies than was thought at the time of the first investigation by the Survey; but it has always appeared to me that the influence exerted by these dikes was more in the nature of a physical than a chemical one. The weight of evidence in recent years is mostly in the direction of ascension rather than lateral secretion; and one of the strongest evidences is the fact that most of the ore-bodies lie under one of the comparatively impervious layers which help to make up the structure of these hills. On Iron hill I have found a very persistent white porphyry sheet, split off from the overlying porphyry and lying from 30 to 60 ft. below the main white porphyry and blue limestone contact. This sheet varies from a few to 50 ft. in thickness, and where found adds another "contact" to that region ; some of the largest ore-bodies on Iron hill lie immediately under this sheet. Above this is the main white porphyry and * Received Mar. 3, 1910.

Feb 1, 1911

By William H. Spice

No devclopment of major importance has been made in the south central fault-line district of Texas during 1939. Four new fields have been discovcred, all of which appear to be of minor importance, with small wells in the Navarro sand, the Taylor marl or the Austin chalk. Drilling along the fault line has not developed any new prospects in the Edwards lime, the most prolific producing horizon of the district. At the close of the year, a few deep tests for lower producing horizons have been projected and should prove to be of interest, and plans are under way for further development of the Pearsall field, which has been under the control of a single company until recently. Production from the 46 producing fields was maintained at 8,460,000 bbl. for the year, a decrease of approximately 400,000 bbl. under 1938. This decrease is due in part to natural decline of production and in part to decreased allowed production. Approximately 55 producing wells were completed on proven acreage in the Darst Creek and Salt Flat fields. No new lease plays were made during the year, although approximately the same amount of land, 600,000 acres, remained under lease during the year. Some geophysical operations of various types were carried on along the fault-line area itself and also in the Edwards plateau and in the area south and southeast of the main fault line.

Jan 1, 1940

By William H. Spice

No devclopment of major importance has been made in the south central fault-line district of Texas during 1939. Four new fields have been discovcred, all of which appear to be of minor importance, with small wells in the Navarro sand, the Taylor marl or the Austin chalk. Drilling along the fault line has not developed any new prospects in the Edwards lime, the most prolific producing horizon of the district. At the close of the year, a few deep tests for lower producing horizons have been projected and should prove to be of interest, and plans are under way for further development of the Pearsall field, which has been under the control of a single company until recently. Production from the 46 producing fields was maintained at 8,460,000 bbl. for the year, a decrease of approximately 400,000 bbl. under 1938. This decrease is due in part to natural decline of production and in part to decreased allowed production. Approximately 55 producing wells were completed on proven acreage in the Darst Creek and Salt Flat fields. No new lease plays were made during the year, although approximately the same amount of land, 600,000 acres, remained under lease during the year. Some geophysical operations of various types were carried on along the fault-line area itself and also in the Edwards plateau and in the area south and southeast of the main fault line.

Jan 1, 1940

By John J. Collins

The plight of the Japanese mining business is pitiful. Coal mines were given the highest priority for all materials they needed, yet between the end of the war and June 1948, the government was obliged to subsidize them to the extent of 22 billion yen, this being the difference between the consumer's price and the producer's price. Most of the metal mining companies have been operating at only one fifth to one third of war-time production rates, and financial losses have been terrific. The chief difficulties have been a plethora of office workers and a dearth of equipment, supplies, and miners. The principal material needs at metal mines are steel rails. cars, plates, nails, rubber hoses, and belting, to say nothing of modern core drills which are totally lacking. Until recently the great shortage was in coal; for lack of fuel the smelters and factories failed to produce the very metals and equipment now needed to operate the mines. Nation-wide shortages have created a monstrous inflation of prices throughout all the economy, currently amounting to 200 times the prewar figures. For example, the price of copper ranged from 500 to 900 yen per metric ton for many years until 1937, but in mid-1948 producers were

Jan 1, 1949

EVERY English-speaking mining, engineer or geologist knows that some terms used by his profession are not rigid but vary regionally; for example: what is called a vein by some, is called a lode by others and is known as a reef to their Australian colleagues. There are parallels in, the German language. Since, in addition, the meaning of some words may change considerably in 450 years-and other words may disappear completely-and not only the terminology but the concepts of a science are subject to drastic changes over such a long period of time, translating the Bergbüchlein posed some interesting problems. Old German texts and glossaries such as C. T. Delius' Anleitung zu der Bergbaukunst (1773), Minerophilus' Neues and Curieuses Bergwercks-Lexicon (1730), and H. Veith's Deutsches Bergwörterbuch (1871) proved useful sources of information when defini¬tions of obscure terms were needed. The task of translating was made even more challenging by the author's personality. As Ulrich Rülein von Kalbe was primarily a physician, his information must have been mostly secondhand. Since the nomenclature of the miners of Saxony, where he gathered his material on silver ores, undoubtedly varied from that of the German miners in Hungary, for instance, who probably supplied him with data on gold ores, it is not astonishing that he is not consistent in his use of some expressions. To give an example: there is every indication that Flöz and schwebender Gang (see footnote p. 21) are used interchangeably in spite of his occasional disapproval of such usage. It is obvious that he was an educated man with a questing and active mind and, although he apologizes-not wholly sincerely, one might suspect-for the simple

Jan 1, 1949

"In 1899 the American Refining and Smelting Company obtained control of the East Helena Smelter, and have added improvements from time to time.The plant is four miles east of Helena, on the Northern Pacific and Great Northern railroads, with hourly street car service from Helena.Electric power is obtained from Canyon Ferry dam, twelve miles east on the Missouri river, and about 800 h-p. is used in the blowing engines, crushing machinery, cranes and locomotives.Besides the Montana ores convenient to the above railroads, a large part of the ore supply comes from the Coeur d'Alene district, Idaho, and is mainly lead ore and concentrates.A modern automatic sampling mill, with Vezin samplers and a capacity of 50 tons per hour, was completed in 1912.Three blast furnaces, each 48 inches by 136 inches, are now in continuous operation, and the monthly production of silver-lead bullion is six thousand tons.A part of the ore roasting is done in Godfrey furnaces, in connection with the Huntington-Heberlein process, 12 pots being in use, with a capacity of 300 tons per day.Four Dwight-Lloyd sintering furnaces, each 42 inches by 264 inches, and a smaller experimental machine, with a combined capacity of 440 tons per day, are in steady operation, and are successfully roasting ore as well as sintering flue dust. These machines are in great favor and results are being carefully watched.Three bag houses are used in connection with the 1,800 brick flue chamber, and each bag house contains 1,260 cotton bags, each 18 inches in diameter by 30 feet long, suspended on vertical roads. The product saved by the bags contains about 50 per cent lead and is retreated in the blast furnace after sintering.About 450 men are employed."

Jan 1, 1913

"The pumping of the underground water of the Butte mines is largely done from two central plants of the Anaconda Copper Mining Co. The mines of one part of the mining district are served by a modern and mechanically efficient underground plant at the High Ore mine, and the remaining part by a similar one at the Leonard mine. Properties not affiliated with the A. C. M. Co. have separate pumping plants, although in several instances that company handles the water of outside companies, under which arrangement costly single plants are dispensed with. An extensive system of underground crosscuts and drifts connects these mines to both the main pumping plants, so that either may receive the water from all the mines in case there should be a failure in the other to perform its designed service.Quintuple) vertical electric pumps, 7 inches by 12 inches each, of a capacity of 600 gals. per minute under a head of 1,203 feet, are installed at both the plants. Each pump is direct connected to two 150 h-p. motors using 2,300 volts, the motors being on top of the pumps.At the High Ore plant the power cable of 400,000 c. m. is placed in a nearby shaft, the cable at present being hung from the surface to the 2,200 level. From this cable feeders of 300,000 c. m. are laid in connecting crosscuts to the pumping station at the High Ore shaft.The Leonard motors use 440 volts. The practice of building the pumps with the motors on top requires stations with high roofs, but permits the operation of the pumps if they should be submerged by an unusual flow of water."

Jan 1, 1913

By C. M. EYE

IN the spring of 1905 I was employed by Messrs. Bradley and Requa, under our fellow member, Thomas Cox, on the mill plans for the Nevada Consolidated, when an opportunity came to go to the Philippines to erect a small mill on the property of the Benguet Consolidated. This I accepted, expecting to be away eight months or so, but it was seven years before I got back. .I sailed in May, on the Coptic, having as room-mate as far as Kobe, A. E. Drucker, who was going out to Korea for the Oriental Consolidated. It was the first trans-ocean trip for either of us, and we had some rather unusual experiences. This was toward the close of the Russo-Japanese war and the Russian fleet was known to be on the way from Suez to Asiatic waters, but it was a matter of doubt whether they would risk a passage between Japan and the mainland, or take the longer but obviously safer route outside of Japan. The Coptic carried much contraband of war for Japan, so naturally did not care to meet this fleet. No definite word being available at Honolulu, we went to the Midway Islands, but the cable station there had very little information to offer, so we proceeded cautiously toward Japan. On the last afternoon out, we steamed due north at half speed for several hours, and finally sneaked into Yokohama at night, to learn that ' the Russian fleet had met the Japanese the day before and had been annihilated. We sailed over the spot in the Sea of Japan a week later, and when we got to Manila we found three of the Russian boats interned and being guarded by the monitor Monadnock and a cruiser. This was only a matter of form, as the Russians were only too glad to be there for the rest of the war, and the boats could not have gone far anyway, for they were literally shot to pieces. The Admiral's flagship had a hole within 3 ft. of the water line, for ward, through which a man could enter by stooping.

Jan 1, 1929

By P. M. Robinson, J. S. LI. Leach

The heats of solution oj' indiurrr, tin, lend, nrzd tellurium have been calculated from the measured heat effects when mechanical mixtres of indium and telLuium tin and tellurium, and lead and tellurium were added to liquid bismuth. The results are in good agreement xith publislzed values.s for the separate sollction of each eleltzent in bismuth. The heats oj solution of cadmium and tellurium calculated from the rneasuved heat effects on adding trechanical mixtures of these elements do not ugree zc,itl the published values jbv the separate solution of each element. It is shown that at 623°K Ile interaction between cadmium and tellurium dissolved in liquid bismuth is strong enough to led lo preciPitation of solid CdTc. The heats oj- jor-mation of CdTe at 273" nd 623°K (1)-c crilculated fi-or the measured heat ejlfecls. The calcnlaled az'erage deviation from the Kopp-l\'ez?,zunrz rule fov solid CdTe is less than 0.06 cat per g-atom- C over this lertzperalure range. Tlze importance 0.f these oDserl.ations to the determination of heals of formation hy metal solution calorimetry is considered. LIQUID metal solution calorimetry is a convenient method for determining the heats of formation of solid compounds. In this technique the heat of formation is the difference between the measured heat effects on dissolution of the compounds and of mechanical mixtures of the components in the liquid metal.' The heat of solution of the mechanical mixture may be calculated from the measured heat effect. At infinite dilution of the solutes, this heat of solution is equal to the sum of the heats of solution of the separate components. If the heat of solution of one of the components is known, the value for the other can be derived; if both are known, they may be used to check the accuracy of the calorimetric technique. The heats of formation of the tellurides of cadmium, indium, tin, and lead have recently been measured by metal solution alorimetr. The heats of solution of indium, tin, lead, and tellurium at infinite dilution in liquid bismuth at 623"K, calculated from the measured heat effects on solution of the mechanical mixtures, are in good agreement with the published values. The heats of solution of cadmium and of tellurium calculated from the measured heat effect on solution in bismuth at 623'K of mechanical mixtures of cadmium and tellurium, however, do not agree with values estimated from the literature. 1) EXPERIMENTAL PROCEDURE AND RESULTS The Heats of Solution of Indium, Tin, Lead, and Tellurium in Bismuth. The heat effects were measured when mechanical mixtures corresponding to the compounds In,Te, InTe, In2Te3, In2Te5, SnTe, and PbTe were dissolved in bismuth. The calorimetric procedure and the method of calculation have been described elsewhere.' The heats of solution of the mechanical mixtures were obtained by subtracting the change in heat content per gram-atom of the sample between the addition temperature (273°K) and the bath temperature (623"K), (H623°K - H273°K)S, from the measured heat effects. The calorimeter was calibrated with pure bismuth. The reported values of the measured heat effects are based on (HGoK - ^273oK)Bi = 4.96 kcal per g-atom.3 The measured heat effects are found to be linear functions of the solute concentrations of the bath in the dilute solution range. The values, extrapolated to infinite dilution, are listed in Table I, together with the heats of solution of the mechanical mixtures calculated using the published values of (H 623°K - H273°k)s for indium, tin, lead,3 and tellrium. All the error limits quoted in this work represent the spread of values obtained. The heats of solution in liquid bismuth at 623°K of mechanical mixtures of indium and tellurium in four different proportions were determined. Values of the heats of solution of the two components were then calculated from the resulting four simultaneous equations: The heats of solution at infinite dilution of tin and lead in liquid bismuth at 623°K were calculated from the heats of solution of the mechanical mixtures of tin and tellurium and of lead and tellurium using the heat of solution of tellurium calculated above. These values of the heats of solution are listed in Table I1 together with some published values for comparison.

Jan 1, 1967

W. P. WHITE,* Washington, D. C. (written discussion?).-The authors seem to have proved that for a phenomenon as irregular as the one they were investigating there was no perceptible conduction effect in the platinum wire. It should be mentioned, however, that the conduction of heat to and from small wires is not proportional to their surface and might give unexpected value, varying largely with the medium in which the wire was situated. Attempts to eliminate a conduction effect in the wire by extrapolating the curve obtained by using different sizes have in some cases given incorrect results, so that the authors' result should be applied with great care as a guide in other cases. The difference in size of wire employed by them is really rather small. If the desire had been to find out how great the effect was instead of merely to demonstrate its absence, a greater difference of diameter would, of course, have been selected. The sharp gradient immediately in front of the burning portion of the cigar is quite surprising at first sight. The weight of air coming from a flame is considerably greater than the weight of material burned, and it would be thought that this stream of heated air would heat very con-siderably the material not yet reached by the zone of combustion. Pos-sibly the heat is exhausted in evaporating moisture from the material. In that case the cigar is really a sort of regenerative furnace, except that it is not air but the, material which is preheated, and the pre-heating produces dryness rather than increase of temperature. Whether or not this is the case would be shown by finding how hot a thoroughly dry cigar would get.

Jan 12, 1919

By L. O. Howard

L. D. RICKETTS, New York, N. Y.-The advance which has been made in Smelting has been in the line of cheaper cost of handling, due to larger units and decrease in losses. At the International smelter, Mr. McGregor designed everything to handle the ore under cover. But we do find an unaccounted for loss of 0.7 per cent. of our copper, which is serious. Mr. Wallace has made a suggestion that I think metallurgists ought to know of and think about. He made it years ago-and that is that one of the chief losses is undoubtedly in the charging and discharging of the calcine cars. His idea is that possibly the dryers and heaters might be put immediately over the reverberatories So that they could discharge in conveyors. They could feed on both sides, and thereby the dust raised by discharging in the cars from the hoppers could be overcome. E. P. MATHEWSON, Anaconda, Mont.-I might Say a few words on the plants we have visited So far. I was particularly struck with the cleanliness of the plants, which is next to Godliness. I noticed also that the skull-cracker arrangement they have for handling their converter slag is very good. And they have paid considerable attention to ventilation, and are taking steps to take care of the health of the men. "Safety first" has been well looked after in all the plants we have visited so far. The steel structures are right up to date, and the buildings are of the most modern type, and everything is conveniently arranged. I think the designers of the plants in the Southwest are to be congratulated on what they have done.

Jan 12, 1916

By K. T. Aust

It is proposed that the intergranular corrosion of austenitic stainless steels is associated with the presence of continuous grain houndary paths of either second phase, or solute segregate resulting from solute-vacancy interactions. Experimental observations of structural changes and crrosion behavior of different types of austenitic stainless steel provide support for this poposal. On the basis of this model, it is shown that the intergranular -corrosion susceptibility of austenitic stainless steels in nitric-dic hromate solution may be substantially reduced either by suitable heat treatments or by impurity control. AUSTENITIC stainless steels, such as Type 304, generally have excellent corrosion resistant properties when properly solution heat-treated and used at temperatures where carbide precipitation is slow. However, several corrosion environments have been found which produce intergranular corrosion of solu-tion-treated stainless steels, that is, those steels with no detectable carbide precipitation.''2 Of the various corrosion environments, the most widely used test solution has been the boiling nitric-dichromate solution. In these acid solutions, stainless steels have been found to be susceptible to intergranular attack despite the addition of carbide-forming elements such as titanium or columbium, or despite lowering of the carbon content or use of high-temperature solution treatments. Studies of the electrochemical mechanism of corrosion attack have been made by several worke1s3'4 who found that oxidizing ions such as crt6 depolarize the cathodic reactions and consequently raise the open-circuit potential of stainless steel immersed in nitric acids. As a result of this, the anodic reaction is accelerated. The reason for the localization of anodic activity at the grain boundaries, and resulting intergranular corrosion, has not been conclusively determined. Several workers, e.g., Streicher,3 and Coriou et al.,4 have suggested that the strain energy associated with grain boundaries provides the driving force for the accelerated intergranular corrosion. This argument would predict that alloys of high purity would still be susceptible to intergranular attack. However, work by chaudron5 and by ArmijO,6 has shown that high-purity alloys are immune to attack, in disagreement with this argument. An alternative suggestion is that chemical concentration differences exist between grains and grain boundaries, that is, impurity segregation at boundaries, and that these chemical differences provide the driving force for localized attack. It is this impurity segregation which can lead to accelerated dissolution of grain boundaries when the alloy is exposed to a suitable corrodant. This mechanism would predict the immunity of high-purity alloys to inter-granular attack, which is in agreement with experi-mental observations. In the present paper, some recent studies on inter-granular corrosion of austenitic stainless steels which were conducted by coworkers and myself will be re-tibility A simple model will be described in which it is proposed that the intergranular corrosion of aus-tenitic stainless steel is associated with the presence of continuous grain boundary paths of either second phase or solute-segregated regions.* On the basis of this model, it is suggested that the intergranular corrosion rate can be markedly reduced by the formation of a discontinuous second phase at the grain boundaries if the discontinuous second phase incorporates the major part of the segregating solute, drained from the grain boundary region. Results are presented of corrosion tests and electron microscopic studies of different types of austenitic stainless steel after various heat treatments which provide experimental support for this model. Finally, a solute clustering mechanism, based on a solute-vacancy interaction, is shown to be consistent with the results obtained for inter-granular corrosion of solution-treated austenitic stainless steels. EXPERIMENTAL Corrosion tests using weight loss measurements were made on sheet specimens, which were lightly electropolished, washed, and immersed in boiling (115°C) 5 N HN03 containing 4 g crt+6 per liter added as potassium dichromate. Studies in which the inter-granular penetration depth was measured both by electrical resistance and metallographic methods have shown an empirical correlation between the rate of intergranular penetration and the weight loss per unit time for identically treated specimens of stainless steel." As a result, although all the corrosion data reported here are in terms of simple weight loss measurements, these data are considered to reflect primarily the rate of intergranular dissolution. Fig. 1 shows a typical result of intergranular attack of a solution-treated Type 304 stainless steel after 4 hr in a boiling nitric-dichromate solution. The wide grain boundary grooving at the surface, and the attack at incoherent twin boundaries, are evident; very little corrosion attack is seen at the coherent twin boundaries. INTERGRANULAR CORROSION MODEL

Jan 1, 1970

By F. I. Grace, L. E. Murr

The mechanical responses and residual defect structures in 70/30 brass and type 304 stainless steel following explosive shock loading and cold reduction by rolling have been studied. A distinct relationship was observed to exist between the residual mechanical properties and micro structures observed by transmission electron microscopy. Shock-loaded brass deformed primarily by the formation of coplanar arrays of dislocations and stacking faults at lower pressures, and twin-faults (deformation twins and €-martensite bundles) at higher pressures (> 200 kbar). The micro -structures of cold-rolled brass were characterized by dense dislocation fields elongated in the rolling direction. Stainless steel was observed to deform by the formation of dense arrays of stacking faults at lower shock pressures and twin-faults at high shock pressures (>200 kbar). Lightly cold-rolled stainless steel deformed similar to low Pressure shock-loaded stainless steel, but transformed to a' martensite in heavily cold-rolled stainless steel. Discontinuous yielding was observed for the heavily cold-rolled stainless steel, and stress reluxution in the weyield region for cold-rolled and shock -loaded stainless steel was interpreted as an indication of the ability of twin-faults and stacking faults to act as effective barriers to dislocation motion. A simple model for the formation of the planar defects and a' martetnsite is presented based on the propagating of Shochley partial and half-partial dislocations. A considerable effort has been expended over the past decade in an attempt to elucidate the response of metallic-crystalline solids to the passage of a high velocity shock wave (e.g., smith,' Dieter,2 and zukas3). While it has been possible to obtain relevant information pertaining to the residual defect structures and mechanical properties, there have been few rigorous attempts to draw a direct comparison between these structures and properties. In addition, numerous investigators have recently observed the occurrence of deformation twinning in shock deformed fcc metals (e.g., Nolder and Thomas,4 and Johari and Thomas5), but little attempt has been made to elucidate the mechanisms of formation of these defects. Comparative data for metals deformed by shock-loading and the same metals deformed by more conventional modes of deformation such as cold-reduction by rolling is also generally lacking. The present investigation therefore has the following objectives: 1) to examine the mechanical properties of some explosively shock loaded and cold-rolled fcc metals of low stacking-fault energy as a function of their residual substructures; 2) to present a simple model for the formation twin-faults and related defect structures in the low stack-ing-fault energy materials of interest (70/30 brass, ySFg= 14 ergs per sq cm; and 304 stainless steel, ySF = 21 ergs per sq cm); 3) to make some deductions with regard to the residual characteristics of dislocation and planar defect substructures in cold rolled and shock loaded 70/30 brass and type 304 stainless steel. In particular, it was desirable to characterize the residual hardening effects of particular deformation substructures. I) EXPERIMENTAL PROCEDURE Sheet samples of 70/30 brass (0.005 and 0.15 in. thick; annealed at 659°C for 2 hr) and type 304 stainless steel (0.007 in. thick; annealed 0.25 hr at 1060°C) of nominal compositions shown in Table I were cold-rolled in one direction only to produce reductions in thickness of 15, 30, 45, 60, and 75 pct in the brass; and 5, 15, 25, 35, and 45 pct in the stainless steel. Identical sheet samples in the annealed (unrolled) state were subjected to plane compressive shock waves to various peak pressures ranging from 0 to 400 kbar in the brass and 0 to 425 kbar in the stainless steel; and with a constant peak pressure duration of approximately 2 microseconds. A detailed description of the shock loading technique has been given previously.6 Tensile specimens 1.0 in. in length and 0.125 in. in width were cut from the cold-rolled sheets (tensile axis parallel to the rolling direction), and the shock-loaded sheet specimens. Stress (load)-strain (elongation) measurements on the tensile specimens were made on a Tinius-Olsen load-compensating tensile tester using a strain rate of 2.7 x 10-3 sec-1. Tensile tests were repeated at least twice, giving essentially the same results. Stress relaxation measurements in the preyield region were also made using an initial strain rate of 5.4 x 10-4 sec-1. In addition to tensile and stress relaxation measurements, Vickers microhardness measurements were made on all samples. A total of 100 microhard-ness readings were obtained for each specimen following a light electropolish to ensure uniform surface conditions for all tests. The hardness averages ob-

Jan 1, 1970

By W. G. Pfann

In zone-melting, a small molten zone or zones traverse a long charge of alloy or impure metal. Consequences of this manner of freezing are examined with impurerespect to solute distribution in the ingot, with particular reference to purification and to prevention of segregation. Results are expressed in terms of the number, size, and direction of travel of the zones, the initial intermsofsolute distribution, and the distribution coefficient. IF a charge of binary solid-solution alloy is melted and then frozen slowly from one end, as for example in the Bridgman method of making single crystals,' coring usually occurs, with a resulting end-to-end variation in concentration. Such coring, or normal segregation, is undesirable where uniformity is an object. On the other hand, for certain systems, it can be utilized to refine a material by concentrating impurities at one end of the ingot.'. ' In the present paper a different manner of freezing will be examined with respect to the distribution of solute in the ingot. A number of procedures will be indicated which have in common the traversal of a relatively long charge of solid alloy by a small molten zone. Such methods will be denoted by the general term zone-,melting, while the process described in the preceding paragraph will be called normal freezing. It will be shown that, in contrast to normal freezing, zone-melting affords wide latitude in possible distributions of solute. Segregation can either be almost entirely eliminated or it can be enhanced so as to provide a high degree of sttparation of solute and solvent. A number of simplifying assumptions will be invoked which, while not entirely realizable in practice, nevertheless provide a suitable point of departure for more refined treatments. Moreover, our own experience with zone-melting has shown that, for certain systems at least, the analysis holds quite well. The present paper will be confined to a discussion of principles and a general description of procedures. Comparison with experiment is planned for later publication. Normal Freezing Before considering zone-melting, segregation during normal freezing will be reviewed briefly. If a cylinder of molten binary alloy is made to freeze from one end as in Fig. 1, there usually will be a segregating action which will concentrate the solute in one or the other end of the ingot. If the constitutional diagram for the system is like that of Fig. 2, then the distribution coefficient k, defined as the ratio of the concentration in the solid to that in the liquid at equilibrium, will be less than one and the solute will be concentrated in the last regions to freeze. If the solute raises the freezing point, then k will be greater than one and the solute will be concentrated in the first regions to freeze. The concentration in the solid as a function of g, the fraction which has solidified, can be expressed by the relation: C = kC0 (1-g)k-1 [I] where C, is the initial solute concentration in the melt. Eq 1 is based on the following assumptions: 1—Diffusion in the solid is negligible. 2—Diffusion in the liquid is complete (i.e., concentration in the liquid is uniform). 3—k is constant. Concentration curves representing eq 1 for k's from 0.01 to 5.0 are plotted in Fig. 3. This equation, in one form or another, has been treated by Gulliver,³ Scheuer,4 Hayes and Chipman5 for alloys and by McFee2 for NaCl crystals. It is derived in Appendix I. It should be pointed out that the k which is calculated from the phase diagram will be valid only in the ideal case for which the stated assumptions are correct. In all actual cases, the effective k will be larger than this value for solutes which lower the melting point, smaller for solutes which raise the melting point, and will probably vary during the beginning of the freezing process. For simplification it will be assumed that the ideal k is valid. Zone-Leveling Processes The processes of this part are designed to produce a uniform, or level, distribution of solute in the ingot. Single Pass: Consider a rod or charge of alloy whose cross-section is constant and whose composition, C2, is constant, although permissibly varying on a microscopic scale." Such a charge might be a rapidly frozen casting or a mixture of crushed or powdered constituents. Cause a molten zone of

Jan 1, 1953