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1234. A vacuum sealing grease
Classified abstracts 1230--1238 longest streams during fall. The rate of hydrogen removal increases as the stream temperature is reduced. S J Hellier and G H J Bennett, J Vac Sci Technol, 7 (6), Nov~Dec 1970, S154-S157. 37 1230. Removal of hydrogen by pouring molten steel in vacuum. (USA)* An investigation was made into the removal of hydrogen from the melt of medium carbon steel on 10 heat practices of vacuum, pouring under a pressure of 8-12 mmHg. The degassing process can be divided into three steps according to observation from high-speed photography. By vacuum degassing, hydrogen, nitrogen, and oxygen are reduced from an average of 3.5 to 1.7 ppm, from 70 to 60 ppm, and from 60 to 35 ppm, respectively. With the composition and the volume of purge gas which comes out of the steel in the vacuum tank, hydrogen, nitrogen, and oxygen in the melt should decrease by about 2, 9, and 15 ppm, respectively. The removal of hydrogen depends upon the formation and the growth of gas bubbles. In this case, the amount of oxygen has a large affect upon the removal of hydrogen. In other practices, it is recognized that a lower pressure such as 1-3 m m H g is more favourable for the removal of hydrogen than 8-12 m m H g from the view point of growth and formation of gas bubbles. M Fukumoto and K Taniguchi, J Vac Sci Technol, 7 (6), Nov~Dec 1970, S158-S161. 37 1231. Design and operation of a one-chamber vacuum furnace for dewax, presinter, and sinter of cemented carbide. (USA)* Cemented carbide production is via normal powder metallurgy processes. Cobalt is the most common "cement" and commercial paraffin is the most common pressing lubricant. Production furnaces for processing cemented carbide have evolved from simple hydrogen atmosphere furnaces to complex, specialized, multi-chamber vacuum furnaces. A single chamber design inherently more simple, with good flexibility, and lower incremental investment is described. W M McCain, J Vac Sci Technol, 7 (6), Nov~Dec 1970, S162-S167.
IV. Materials and techniques used in vacuum technology 42. GLASS, CERAMICS AND REFRACTORY OXIDES 42 1232. Rheologieal properties of eleetro-vacuum glass S 88-1. (USSR) The high-temperature viscosity and thermo-meehanical properties of electro-vacuum glass type S 88-1 are investigated. Conditions of manufacture and annealing were found to exert a considerable influence on the deformation properties. G D Abrosimova and A I Kolbasnikova, Elektron Tekh Materialy, 6, 1970, 3-12 (in Russian). 42 1233. Glass stable with respect to caesium vapour at temperatures up to 650°C. (USSR) A glass, type TSM 901, has been developed which will withstand temperatures up to 650°C in a caesium vapour ambient for long periods of time with a decrease in light transmission smaller than 20 per cent. This glass is characterized by an enhanced crystallization capability as compared to industrial electro-vacuum glasses and for this reason it can be only worked by casting and pressing. Gas-tight seals to niobium are obtained by diffusion welding in vacuum. Using the same sealing technique, windows were manufactured which remained hermetic after prolonged operation in caesium vapour at 650°C. L F Shumitskaya et al, Elektron Tekh Materialy, 4, 1970, 66-70 (in
Russian). 44. WAXES, LUBRICANTS, CEMENTS, LACQUERS, PAINTS, OILS 44 1234. A vacuum sealing grease. (USSR) Methods of imparting a low vapour tension and a high oxidation resistance to vacuum greases so as to increase the vacuum-tightness
508
of the joints using them are described. Thus, as the hydrocarbon thickening agent, a mixture of 76 per cent of solid hydrocarbons evaporating at over 500°C is recommended, as the high-molecular polymer, 5 per cent of polyisobutylene, and as the mineral oil an oil with a viscosity of at least 30 centistokes at 100°C, making the total up to 100 per cent. This mixture is heated to 120°C for melting and then allowed to cool to room temperature. L I Nazarova and E D Makeeva, USSR Patent, No 272,467, appl 14th Aug 1968, publd 4th Sept 1970. 46. GLASS BLOWING, GLASS-TO-METAL AND CERAMICTO-METAL SEALING TECHNIQUES 46 1235. Theoretical investigation of the relationship between size of elements of glass- and ceramic-to-metal seals and the magnitude of isothermal stresses. (USSR) The formulas for calculation of isothermal stresses in glass- and ceramic-to-metal seals are presented. L P Serebryanikov et al, Elektron Tekh Materialy, 6, 1970, 17-30 (in
Russian). 47. OUTGASSING DATA, V A P O U R PRESSURE DATA, GETTERING DATA, RESIDUAL GASES IN V A C U U M SYSTEMS, RESIDUAL GAS ANALYSIS 47 1236. Method of obtaining low and very low partial oxygen pressures. (USSR) An improved method of producing low and very low partial pressures of oxygen in an evacuated space is proposed. This is achieved by having a double-walled vessel, in which the outer cavity is filled with argon carefully freed from oxygen and moisture, the argon pressure being held above the pressure of the external atmosphere. The inner vessel is then evacuated in the normal fashion. Removal of oxygen from the original argon is achieved by passing the gas over aluminium amalgam. Some of the inert gas leaks into the vacuum chamber, and the partial oxygen pressure in the latter is thus brought to a very low level even in a comparatively rough vacuum. V F Yal'yasheako et al, USSR Patent, No 271,879, appl 8th Oct 1968, publd 21st Aug 1970. 47 1237. Investigation of the temperature dependence of the outgassing rates of molybdenum and yttrium with different degrees of cleanliness in ultrahigh vacuum. (USSR) The method of investigation of the outgassing of metals and alloys in ultrahigh vacuum conditions at 10-9 tort with measurement of the liberated gases by a mass spectrometer, is developed. The spectrum of gases evolved on heating molybdenum and yttrium with different degrees of cleanliness, is presented. E M Savitskiy et al, Elektron Tekh Materialy, 5, 1970, 122-124 (in
Russian). 47 1238. Outgassing of nuclear rocket fuel elements. (USA)* In order to predict the gaseous environment in a nuclear rocket engine before and after operation in space, an apparatus has been developed for measuring the type, quantity, and outgassing rates of gases that are released from graphite fuel elements at various temperatures in vacuum. Data readout from a quadrupole residual gas analyzer (QRGA) and nude Bayard-Alpert type ion gauges permit analysis of up to 12 gases simultaneously. The data are processed by a computer programme which first calculates the partial pressures of the various gases from a least square fit to a set of 18 simultaneous equations (one for each spectrometer peak) with 12 unknowns (12 separate gases). The coefficients of the unknowns are obtained from the cracking patterns of individual gases. The programme then calculates and tabulates the outgassing rate of each gas for each sampling time and produces plots of the outgassing as functions of time or temperature. D S Easton and R E Clausing, J Vac Sci Technol, 7 (6), Nov~Dec 1970, Sl16-S123.
IV. Materials and techniques used in vacuum technology 42. GLASS, CERAMICS AND REFRACTORY OXIDES 42 1232. Rheologieal properties of eleetro-vacuum glass S 88-1. (USSR) The high-temperature viscosity and thermo-meehanical properties of electro-vacuum glass type S 88-1 are investigated. Conditions of manufacture and annealing were found to exert a considerable influence on the deformation properties. G D Abrosimova and A I Kolbasnikova, Elektron Tekh Materialy, 6, 1970, 3-12 (in Russian). 42 1233. Glass stable with respect to caesium vapour at temperatures up to 650°C. (USSR) A glass, type TSM 901, has been developed which will withstand temperatures up to 650°C in a caesium vapour ambient for long periods of time with a decrease in light transmission smaller than 20 per cent. This glass is characterized by an enhanced crystallization capability as compared to industrial electro-vacuum glasses and for this reason it can be only worked by casting and pressing. Gas-tight seals to niobium are obtained by diffusion welding in vacuum. Using the same sealing technique, windows were manufactured which remained hermetic after prolonged operation in caesium vapour at 650°C. L F Shumitskaya et al, Elektron Tekh Materialy, 4, 1970, 66-70 (in
Russian). 44. WAXES, LUBRICANTS, CEMENTS, LACQUERS, PAINTS, OILS 44 1234. A vacuum sealing grease. (USSR) Methods of imparting a low vapour tension and a high oxidation resistance to vacuum greases so as to increase the vacuum-tightness
508
of the joints using them are described. Thus, as the hydrocarbon thickening agent, a mixture of 76 per cent of solid hydrocarbons evaporating at over 500°C is recommended, as the high-molecular polymer, 5 per cent of polyisobutylene, and as the mineral oil an oil with a viscosity of at least 30 centistokes at 100°C, making the total up to 100 per cent. This mixture is heated to 120°C for melting and then allowed to cool to room temperature. L I Nazarova and E D Makeeva, USSR Patent, No 272,467, appl 14th Aug 1968, publd 4th Sept 1970. 46. GLASS BLOWING, GLASS-TO-METAL AND CERAMICTO-METAL SEALING TECHNIQUES 46 1235. Theoretical investigation of the relationship between size of elements of glass- and ceramic-to-metal seals and the magnitude of isothermal stresses. (USSR) The formulas for calculation of isothermal stresses in glass- and ceramic-to-metal seals are presented. L P Serebryanikov et al, Elektron Tekh Materialy, 6, 1970, 17-30 (in
Russian). 47. OUTGASSING DATA, V A P O U R PRESSURE DATA, GETTERING DATA, RESIDUAL GASES IN V A C U U M SYSTEMS, RESIDUAL GAS ANALYSIS 47 1236. Method of obtaining low and very low partial oxygen pressures. (USSR) An improved method of producing low and very low partial pressures of oxygen in an evacuated space is proposed. This is achieved by having a double-walled vessel, in which the outer cavity is filled with argon carefully freed from oxygen and moisture, the argon pressure being held above the pressure of the external atmosphere. The inner vessel is then evacuated in the normal fashion. Removal of oxygen from the original argon is achieved by passing the gas over aluminium amalgam. Some of the inert gas leaks into the vacuum chamber, and the partial oxygen pressure in the latter is thus brought to a very low level even in a comparatively rough vacuum. V F Yal'yasheako et al, USSR Patent, No 271,879, appl 8th Oct 1968, publd 21st Aug 1970. 47 1237. Investigation of the temperature dependence of the outgassing rates of molybdenum and yttrium with different degrees of cleanliness in ultrahigh vacuum. (USSR) The method of investigation of the outgassing of metals and alloys in ultrahigh vacuum conditions at 10-9 tort with measurement of the liberated gases by a mass spectrometer, is developed. The spectrum of gases evolved on heating molybdenum and yttrium with different degrees of cleanliness, is presented. E M Savitskiy et al, Elektron Tekh Materialy, 5, 1970, 122-124 (in
Russian). 47 1238. Outgassing of nuclear rocket fuel elements. (USA)* In order to predict the gaseous environment in a nuclear rocket engine before and after operation in space, an apparatus has been developed for measuring the type, quantity, and outgassing rates of gases that are released from graphite fuel elements at various temperatures in vacuum. Data readout from a quadrupole residual gas analyzer (QRGA) and nude Bayard-Alpert type ion gauges permit analysis of up to 12 gases simultaneously. The data are processed by a computer programme which first calculates the partial pressures of the various gases from a least square fit to a set of 18 simultaneous equations (one for each spectrometer peak) with 12 unknowns (12 separate gases). The coefficients of the unknowns are obtained from the cracking patterns of individual gases. The programme then calculates and tabulates the outgassing rate of each gas for each sampling time and produces plots of the outgassing as functions of time or temperature. D S Easton and R E Clausing, J Vac Sci Technol, 7 (6), Nov~Dec 1970, Sl16-S123.