Automatic column for the chemical purification of mercury

Classified abstracts 496---504 E C Nelson and R Houston, Trans 6 Vac Metall Conf, American

H S Philbrick, Jr, Trans 6 Vac Metall Conf, American Vacuum

Vacuum Society, 1964, 345-353.

Society, 1964, 297-327.

37 496. De-oxidation of molten steel by Dortmund Horder vacuum degassing process. (USA) This paper describes theoretical considerations with some assumptions for de-oxidation in the D H vacuum degassing process; they are compared with the results of experiments carried out with 30 ton and 70 ton degassing equipment. The authors found that it is possible to calculate and estimate the progress of de-oxidation in the vacuum vessel from the carbon and oxygen content, the amount of melt per cycle, diameter of vessel, number of cycles per minute and pressure in vessel. The calculations involve many assumptions and the figures can only be regarded as approximate. In order to follow the process of degassing more exactly, the surface area and motion of the melt should be known at any instant. T Kato and K Matsuda, Trans 6 Vac Metall Conf, American

37 : 41 500. The stability of molten uranium and refractory carbides in high vacuum. (USA) Conclusions based upon results of this study are: (1) An electron beam furnace technique which was devised can be used satisfactorily for the semi-quantitative study of materials at high temperatures. (2) Carbides of uranium, tungsten, tantalum, vanadium, zirconium, and niobium can be melted in the electron beam furnace. Allowances, however, must be made for vaporization losses. (3) Molten carbides of tungsten, zirconium, vanadium, titanium, tantalum, uranium (with 6.9 and 9.0 wt per cent carbon), and niobium all lose carbon atoms preferentially to metal atoms. Uranium atoms are lost preferentially to carbonatoms in uranium monocarbide (5.02 wt per cent carbon). (4) Carbides at temperatures of approximately their melting points ranked in order of increasing rates of evaporation are: W2C, WC, NbC, UC, ZrC, TaC, UC2, VC, and TiC. (5) Larger carbon partial vapour pressures than metal vapour pressures were noted for W2C, WC, and ZrC. For all other carbides, metal partial vapour pressures were larger than carbon vapour pressures. (USA) S G Nelson et al, Trans 6 Vac Metall Conf, American Vacuum

Vacuum Society, 1964, 328--344. 37 497. Vacuum sampler. (USSR) A metallic vacuum sampler for collecting samples of liquid metal from a mould is described. The sampler is connected to a vacuum installation comprising of a pump of VN-461 type, vacuum flask with gauge and a three-way tap, serving to connect sampler with the pump or acting as air inlet when the pump is disconnected. Prior to operation, the sampler is heated to about 100°C. The negative pressure during sampling should not exceed 3 torr. V I Dorokhov et al, Machines and Instruments for testing of metals

and plastics, Collection of Papers Moscow, 1965, (in Russian). 37 498. Vacuum mould degassing. (USA) The Gero vacuum mould degassing process is described in some detail and some preliminary results noted. The process is essentially a vacuum degassing process in which ingot moulds are equipped with a hood through which the vacuum is applied. Vacuum casting is carried out at pressures of 300 to 500 microns. The preliminary evaluation of the process indicates that it is at least as effective as other more elaborate systems in removing hydrogen and in lowering oxygen. Thus it is capable of the same quality improvements as those attainable with other processes.

( USA ) A E Nehrenberg, Trans 6 Vac Metall Conf, American

Vacuum

Society, 1964, 258-272. 37 499. Ladle degassing: a report on in-plant tests with the Finkl-Mohr units. (USA) Beginning in March, 1961 a portable vacuum degassing unit (Steel, June 12, 1961) was offered to steelmakers for in-plant tests and evaluation of the Finkl vacuum degassing process. A second, 10,000 lb unit was placed in service in 1962. To date these units have operated in a total of nine melt shops, 3 making sand mold castings, the balance ingots, degassing a variety of steel from these tests makes up the bulk of the material presented by the author and contributes to our knowledge of vacuum degassing. Two years of operation have shown that floor mounted shell and tube intercondensers in place of full leg barometrics are practical for vacuum degassing service provided a regular schedule of water flushing is followed. The units were ready for steel frequently within 30 rain following start up of boiler from cold water. Low micron pressures were not required for hydrogen removal. Fifty per cent reduction was obtained at 1 to 2 m m Hg absolute. Oxygen on the other hand was dependent on steel analysis and its removal was improved by lower pressures, some tests being conducted near 100 microns. Low carbon steels showed the greatest oxygen changes, high carbon and high alloy steels the least. Lowest oxygen levels were reached with ball bearing steels. Oxygen levels on all carbon and low alloyed steels seemed to have a limit shown by the 100 mm pressure equilibrium line for carbon with oxygen in an iron solution. The drop in oxygen for several selected heats was accompanied by a loss in carbon greater than could be accounted for by a carbon monoxide reaction. Two proposals for improved degassing of steels under vacuum are made. One unit is for large tonnage open hearth and basic oxygen furnace steels. The second unit is intended for high alloy electric furnace steels. (USA)

Society, 1964, 148-166. 37 501. Kinetics of vacuum degassing of steel. (USA) The author considers the kinetics of vacuum stream degassing in some detail, paying special attention to the effect of pour rate, nozzle size, length of fall and vacuum level. In vacuum stream degassing, practically all the degassing occurs during the fall. Curves are given showing the removal of hydrogen, oxygen and nitrogen as a function of exposure time and the difference in the response of "killed" and "unkilled" steels is pointed out. Vacuum degassing significantly improves the quality of the steel and reduces many internal operating costs. In addition it will make new casting techniques a practical reality. A E Hokanson, Trans 6 Vac Metall Conf, American Vacuum

Society, 1964, 238-257.

38. Distillation, organic chemistry, isotopic gas analysis 38 502. Superpurification of metals by vacuum distillation: a theoretical study. (USA) The effect of process variables in the production of very-highpurity metals (i.e. impurity levels for metallics and gases at low ppm levels) has been explored. The most important variables for high purity are: (1) High evaporation rate, i.e. a high evaporation temperature. (2) Minimum contamination from vacuum environment, i.e. a good clean vacuum chamber and accessories. (3) Control over the condensation temperature. (4) A high-quality starting material, if necessary prepurified by vacuum melting. (5) Elimination of melt-crucibles reactions. (USA) R F Bnnshah, Trans 6 Vac Metall Conf, American Vacuum Society,

1964, 121-139. 38 : 41 503. Production of hydrocarbons on barium films. (USA) Typical features of the cracking patterns of simplest hydrocarbons obtained with an omegatron mass spectrometer are preliminarily illustrated. The well known production of hydrocarbons by the action of water vapour over barium films previously treated with carbon monoxide is re-examined, with special attention to the time evolution of the gaseous phase in an isolated system. Other possible ways for the formation of hydrocarbons are considered; in particular the direct low pressure hydrogenation of the "carbide" complexes present at the surface of barium films is studied. P della Porta and T A Giorgi, Trans 10 A VS Nat Vac Symp,

MacMillan & Co, 1963, p 491.

39. Miscellaneous applications 39

504. Automatic column for the chemical purifcation of mercury. (ussR) The purification is carried out by the simultaneous application of air scavenging and successive exposure to the chemical action of

283

Classified abstracts 505--509 a 20½ caustic soda solution, 5 per cent nitric acid and distilled water contained in three columns. Scavening and transfer is carried out with the help of a water-jet pump. The output of the installation is 75 cc of high purity mercury per hour. V G Artamanov, Zavod Lab, (2), 1965, 254, (in Russian).

model: (1) Contamination introduced by the evaporation process is so great that the mean free path of the conduction electrons is experimentally undetectable; (2) the contamination is not uniform but is greatest at the surface. I G Young and C W Lewis, Trans 10 A VS Nat Vac Symp, MacMillan

& Co, 1963, p 428.

45. Soldering, welding, brazing, solders 45

IV. Materials and techniques used in vacuum technology 40. Gases and vapours

40

Electron diffraction from thin films of solidified gas. See abstract number 473.

41. Metals and alloys (including mercury)

41 The sticking coefficient, the optical transmission and the oxidation

of thin metallic films. See abstract number 411. 41 The detection of monolayer adsorption on silicon and germanium by low energy electron diffraction. See abstract number 420. 41 Preparation and properties of electro-luminescent ZnS:Cu, Mn, CI films. See abstract number 426. 41 The growth and structure of gold and silver deposits formed by evaporation inside an electron microscope. See abstract number 454. 41 Proton space charge in anodie oxide films. See abstract number 455. 41 Evaporation of elements from 80/20 nickel-chromium during vacuum induction melting. See abstract number 456. 41 The mierostructare and some related electrical properties Of tantalum films. See abstract number 462. 41 The preparation and properties of silicon monoxide capacitors on passivated silicon substrates. See abstract number 463. 41 Thickness and composition of nickel-chromium films. See abstract number 464. 41 A bridging phenomenon in growth of evaporated metal films. See abstract number 468. 41 Investigation of thin tantalum films. See abstract number 470. 41 Simultaneous contamination and conversion effects in germanium heated to temperatures in the evaporation range. See abstract number 471. 41 On the anisotropic dispersion in normal single axis films. See abstract number 472. 41 Hall probe using antimony-indium thin film instead of monocrystal. See abstract number 475. 41 The stability of molten uranium and refractory carbides in high vacuum. See abstract number 500. 41 Production of hydrocarbons on barium films. See abstract number 503. 41 Manufacture of Simplex ferrochrome by the vacuum process. See abstract number 509. 41 : 56 505. Residual resistivity in chromium films. (USA) The Fuchs equation accurately describes the resistivity of films of noble metals such as gold when allowance is made for imperfections. On the other hand, chromium films prepared under a wide variety of experimental conditions cannot be so characterized. Our data on these films, however, are consistent with the following

284

506. Rotary vacuum brazing furnace. (USA) The rotary furnace described by the authors employs electron bombardment heating, the transport mechanism consisting of a "lazy-susan " rotary table that allows the entrance/exit functions to be performed in a single pressure lock on the periphery of the circle. The vacuum system consists of a cryopump and a sputter ion pump, supplemented by a Roots blower for roughing the main chamber, exhausting the entrance exit lock and cleaning the cryopump. Performance of the system has been markedly efficient. The quality of the brazing has been high and the system maintenance minimal. Significant savings in production costs have resulted and interest has been stimulated in the design of other automatic metallurgical vacuum process equipment. R Zaphiropolous et al, Trans 6 Vac Metall Conf, American Vacuum

Society, 1964, 232-237. 45 507. Diffusion welding of metalloid carbides with refractory metals.

( USSR ) Experiments were carried out with technically pure cylindrical metal specimen, 6-8 mm diameter and 10-12 m m long. These were welded on to extruded samples of carbides of approximately stoichiometric composition. The welding was carried out under vacuum by the passage of an electric current through the joint, the two elements being pressed together by a force of 0.13 N / m 2. It is claimed that the method is already being used successfully on a semi-industrial scale. A L Burikina and O V Evtushenko, Powder Metallurgy, (1)

1965, 87-95, (in Russian).

47. Outgassing data, vapour pressure data, gettering data, residual gases in vacuum systems, residual gas analysis 47 Design and performance of a 50,000 l./sec pump combining cold cathode ion pumping and active film gettering. See abstract number 436.

V. Basic science and engineering 52. Physical chemistry 52 Mechano-chemical dissociation of liquids on freshly formed surfaces of solids. See abstract number 415. 52 Heterogeneous recombination of atomic gases. Interaction of hydrogen atoms with a molybdenum surface. See abstract number 452. 52 508. Effect of grain boundaries on the diffasional growth of oxides on metals. (Great Britain) The author suggests that the so-called "cubic" oxidation of thick films of titanium, zirconium and tantalum is due to a combination of diffusion along grain boundaries and normal bulk diffusion. B A Irving, Nature, 204, Dec 1964, 1082-1083.

53. Metallurgy, ceramics, inorganic chemistry 53 : 41 509. Manufacture of Simplex ferroehrome by the vacuum process.

(USA) The described vacuum process is based on the solid state reaction between the carbides of high carbon ferrochrome and oxygen bearing materials to evolve carbon monoxide. This is accom-