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Heraeus resistance-heated vacuum furnaces
VA C U UM
NEWS
Technical and Industrial Developments Efco modify 200kVA vacuum brazing furnace A report of a new, short-cycle cold retort furnace manufactured by Efco Furnaces Ltd. of Surrey appeared in the February issue of Vacuum News. In the report, Efco stated that they had reduced overall treatment-cycles by as much as 200 per cent, principally by reducing the cooling of the charges by the forced convection of an inert gas. Efco have now announced that they have applied this forcedconvection principle to what is reputed to be one of the largest vacuum brazing furnaces in Europe, increasing its output by 50 per cent. The furnace is installed in the Metallurgy Department of Delaney Gallay Ltd., and is rated at 200kVA and has a working space of 2 ft. in diameter by 3 ft. high. Brazing is performed at temperatures up to 1,250°C and the brazed components are cooled to 200°C if they are of stainless steel and to 150°C if of mild steel. Before modification, they were cooled in a vacuum to 800°C, then cooled further by the convection of hydrogen. The modifications carried out are similar to those described in the February issue, which contained a section drawing of the new design. They have consisted in providing an inlet for the inert gas at the bottom of the furnace, and in fitting a gas-circulation fan, heat-exchanger, and pneumatically-operated system for displacing radiation screens so as to give a flow-path for the gas through the chamber. It is stated that, for example, a charge consisting of 56 stainlesssteel stator blades weighing 220 lb., which used to take two hours to cool from 1,120°C to ambient temperature, now takes 50 minutes. Another advantage claimed is in brazing alloys like Nimonic 80A; when cooled slowly from 1,100°C subsequent heat-treatment was necessary, but now is not. Delaney Gallay Ltd. is a member of the Lindustries Group of companies and for many years has been making aircraft-engine heat-exchangers. The furnace described is used not only for assembling the Company's own products, but also for providing a high-temperature brazing service to industry. Calls on this service are made by aircraft and motor-car manufacturers, chemical, electronic and nuclear engineering firms, and from manufacturers of dairy and medical equipment.
SEPTEMBER, 1964
Page Technical and Industrial Developments .... Modified vacuum brazing furnace--resistanceheated vacuum furnaces--larger electron-beam furnace--electron-gun control--substrate changer --cleaning thin-film sources--high-purity metals for deposition--gold-dipping c o m p o n e n t s - reactor control oven--helium refrigeration for space simulation---cryogenic equipment with low evaporation rates--gauge with new alpha source --liquid nitrogen solenoid valves
361
Vacuum Commercial News US firm exploits Japanese'thin-fil'm development --large German vacuum arc furnaces for British firms--new Ferranti contract--large US firms' financial report--sensitive British mass spectrometer for German research institute
365
British Scientific Instrument Research Association .. Description of organisation--details of thin-film research
366
Vacuum Study Group . . . . . . . . 1964/65 programme of meetings
369
Vacuum Personalities .. Prof. Dr. Kurt Diels--Mrl "L. Hol'land--'Mr. @] Steckelmacher--Mr. T. W. G. Rowe
369
• Manufacturers and others are invited to submit information for inclusion in this feature, addressed to the Vacuum News Editor, Vacuum, Pergamon Press, 4 & 5 Fitzroy Square, London W.1. • For further information on any matter mentioned in " Vacuum News ", tear out and post one of the R E A D E R E N Q U I R Y SERVICE CARDS. Readers in the U.S.A. should use the cards addressed to New York ; all other readers are requested to use the cards addressed to London.
the space containing the heating element is evacuated, relieving the wall of the chamber of pressure and thus permitting it to be made thinner. With steel receivers, temperatures up to 1,050°C may be reached. In the third design, the receiver is heated by the direct passage of electrical current. The temperatures that can be reached are similar to those in the first two designs, but since the wall of the vessel receives the current directly, temperature changes can be effected very rapidly. This principle is used mainly in ultra-high vacuum installations. In the fourth design, the heat source is placed inside the high vacuum vessel and is insulated from the cooled wall by radiation screens (the " cold wall " furnace). The temperatures this design can achieve is limited only by composition of the heating elements themselves : the maximum temperatures which can be reached are about 2,500°C for tantalum heating elements and about 2,800°C for tungsten elements. The firm also builds a large range of special furnaces for research and production. Effective capacities range from a few cc. to several cubic metres, and temperatures up to 3,000°C can be r e a c h e d . . I n the firm's straight-through furnaces, the heated section remains under vacuum throughout, and charges are
Efco Furnaces Ltd., Queens Road, Weybridge, Surrey, Great Britain. Heraeus resistance-heated vacuum furnaces Fleischmann (London) Ltd., the British agents for Heraeus G m b H of Hanau, West Germany, have sent us the firm's latest brochure on its range of resistance-heated vacuum furnaces. The 24 pp. brochure is illustrated and contains comprehensive descriptions of furnaces with indirect resistance-heating produced either externally (the W A series) or internally (the WI series), special furnaces (straight-through vacuum furnaces), furnaces with direct resistance-heating (sintering plant), and metal distillation plant. About two-thirds of the brochure is concerned with indirectresistance heated furnaces, of which there are four basic designs. In the first, a heating muffle is placed over the receiver to heat the container wall (the " hot wall " furnace). For the steel receivers normally used, the maximum temperature that can be reached is about 900°C, for quartz or quartz materials, about 1,050°C, and for aluminium oxide tubes, about 1,500°C. In the second design, 361
362
Vacuum News
introduced and removed through special locks which are removed from the furnace for charging and discharging. Cooling times are shortened by the forced circulation of an inert gas. These furnaces are said to have proved themselves especially suitable for bright-annealing steel, in carburization-free annealing and the subsequent hardening of large components made of tool-steel, and in the age-hardening of workpieces made from Ni base alloys and for soldering high-temperature materials. The sintering plant is suitable for sintering rods compressed from powder and for annealing metals with a high melting point in rod and sheet form. The process takes place under high vacuum or an inert gas, and heating is produced by direct resistance. The temperatures that can be reached are stated to be limited only by the melting point of the materials and the electrical power available. These installations are described as being particularly suitable for sintering and annealing niobium and tantalum and also molybdenum, rhenium, tungsten and their alloys. No standard models of metal distillation plant are built since requirements for them differ so widely. However, the brochure describes a process used for the distillation of magnesium from titanium sponge. The furnace is divided into separate heating zones, each independently controlled by thermocouples. Hydrochloric acid is first removed from the titanium sponge under rough vacuum at 400°C, and is drawn off by a backing pump. A high vacuum pumping unit with a separate backing pump is then switched on and, as the temperature rises, magnesium and magnesium chloride are evaporated and collected in a condenser adjoining the furnace. To obtain magnesium in the purest possible form, the condenser is oil-heated so that no further highly volatile impurities are precipitated. A specially designed oil-circulation system maintains the double-walled condenser at a constant temperature.
Heraeus GmbH, 6450, Hanau, West Germany. British agents : Fleischmann (London) Ltd., Chancery House, Chancery Lane, London W.C.2., Great Britain.
TRANSVERSEFIELD ELECTROMAGNET
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Diagram A, above, illustrates the principle of the transverse field electron gun system used in the 250 kW electron-beam furnace recently installed by Murex Ltd., a leading British producer of refractory metals. Diagram B, below, illustrates the general layout of the furnace. Manufactured by Messrs. Degussa Wolfgang of Hanau, it is the secondlargest such furnace known to exist in Great Britain.
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I British firm instals 250kW electron-beam furnace Murex Ltd., a leading British producer of refractory metals, has recentlyYcommissioned a 250kW electron-beam melting furnace supplied by Messrs. Degussa Wolfgang A G of Hanau, West Germany. It is among the largest of its kind outside the U.S. and is probably the second-largest in Britain : the only other furnace of comparable size known to exist in Britain is IMI's, which, commissioned about 18 months ago, has a rating of 260kW and was then claimed to be the largest of its kind in the country. (It was built by W. C. Heraeus G.m.b.H. of Hanau). The Murex furnace is described as the first of the " third generation " designs, and is equipped with transverse electron guns, automatic feed mechanisms, closed-circuit television systems and certain refinements in its controls. At present, it is producing ingots of tantalum and niobium, both pure and alloyed, and should soon be available for the custom-melting of other metals and alloys. The size of the ingots ranges from 3 in. diameter for tungsten (melting point 3,400°C) to 8 in. diameter for metals and alloys whose melting points are lower. It is stated that a melting rate of 60 kilos an hour has been achieved for a 2 in. diameter ingot of tantalum alloy, but that slower rates are normally used when a high degree of purity is required. Dagrams A and B illustrate, respectively, the principle of the transverse field electron-gun system and the general layout of the furnace itself. It will be seen that the guns are placed below and away from the molten metal, to avoid contamination, and that their beams are turned through approximately 180 °, vertically, by the horizontal field of an electro-magnet above each filament, so that they strike down into the mould. They are also distributed evenly about the pool of melt and each can, if necessary, be withdrawn into separate chambers for maintenance.
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So far, this is said not to have proved necessary, although the filaments have been changed every 50 hours or so as a precaution. The metal is fed into the furnace in the form of a bar pressed from powder, either horizontally or vertically, and this process is automatic, although manual override is also provided. Horizontal feed is carried out from a magazine with eight chambers, which can be refilled during a melt. It will be seen that the feedstock is protruded until it interrupts the beam, and then melts and drips into the pool. The resulting ingot is normally remelted by introducing it vertically (see diagram B) until, as in the first method, it interrupts the beam, melts, and drips into the mould. In either of these two methods the ingot is continuously and automatically withdrawn into the ingot chamber (see B), and when it is complete, a new chamber can be fitted with a minimum delay in the melting process. The melting process can be viewed (see B) either directly, through a protected window, or by means of a Pye closedcircuit TV system. There are two cameras on top of the furnace sighted onto the mould area through stroboscopic windows, which reduce transmitted light by a factor of 1000. Since brightness and contrast can be adjusted, this form of indirect observation has certain advantages over direct observation, as, for example, in the focusing of the beams. Evacuation is accomplished by two 800 litres/sec Leybold vacuum diffusion pumps, backed by a Roots pump and a rotary pump. Vacuum during melting is generally kept between 10 -4 and 10 -5 torr, depending on the material. The leak rate is stated to be 10 -4 torr litres/sec.
Murex Ltd., Rainham, Essex, Great Britain.
NEWS
Technical and Industrial Developments Efco modify 200kVA vacuum brazing furnace A report of a new, short-cycle cold retort furnace manufactured by Efco Furnaces Ltd. of Surrey appeared in the February issue of Vacuum News. In the report, Efco stated that they had reduced overall treatment-cycles by as much as 200 per cent, principally by reducing the cooling of the charges by the forced convection of an inert gas. Efco have now announced that they have applied this forcedconvection principle to what is reputed to be one of the largest vacuum brazing furnaces in Europe, increasing its output by 50 per cent. The furnace is installed in the Metallurgy Department of Delaney Gallay Ltd., and is rated at 200kVA and has a working space of 2 ft. in diameter by 3 ft. high. Brazing is performed at temperatures up to 1,250°C and the brazed components are cooled to 200°C if they are of stainless steel and to 150°C if of mild steel. Before modification, they were cooled in a vacuum to 800°C, then cooled further by the convection of hydrogen. The modifications carried out are similar to those described in the February issue, which contained a section drawing of the new design. They have consisted in providing an inlet for the inert gas at the bottom of the furnace, and in fitting a gas-circulation fan, heat-exchanger, and pneumatically-operated system for displacing radiation screens so as to give a flow-path for the gas through the chamber. It is stated that, for example, a charge consisting of 56 stainlesssteel stator blades weighing 220 lb., which used to take two hours to cool from 1,120°C to ambient temperature, now takes 50 minutes. Another advantage claimed is in brazing alloys like Nimonic 80A; when cooled slowly from 1,100°C subsequent heat-treatment was necessary, but now is not. Delaney Gallay Ltd. is a member of the Lindustries Group of companies and for many years has been making aircraft-engine heat-exchangers. The furnace described is used not only for assembling the Company's own products, but also for providing a high-temperature brazing service to industry. Calls on this service are made by aircraft and motor-car manufacturers, chemical, electronic and nuclear engineering firms, and from manufacturers of dairy and medical equipment.
SEPTEMBER, 1964
Page Technical and Industrial Developments .... Modified vacuum brazing furnace--resistanceheated vacuum furnaces--larger electron-beam furnace--electron-gun control--substrate changer --cleaning thin-film sources--high-purity metals for deposition--gold-dipping c o m p o n e n t s - reactor control oven--helium refrigeration for space simulation---cryogenic equipment with low evaporation rates--gauge with new alpha source --liquid nitrogen solenoid valves
361
Vacuum Commercial News US firm exploits Japanese'thin-fil'm development --large German vacuum arc furnaces for British firms--new Ferranti contract--large US firms' financial report--sensitive British mass spectrometer for German research institute
365
British Scientific Instrument Research Association .. Description of organisation--details of thin-film research
366
Vacuum Study Group . . . . . . . . 1964/65 programme of meetings
369
Vacuum Personalities .. Prof. Dr. Kurt Diels--Mrl "L. Hol'land--'Mr. @] Steckelmacher--Mr. T. W. G. Rowe
369
• Manufacturers and others are invited to submit information for inclusion in this feature, addressed to the Vacuum News Editor, Vacuum, Pergamon Press, 4 & 5 Fitzroy Square, London W.1. • For further information on any matter mentioned in " Vacuum News ", tear out and post one of the R E A D E R E N Q U I R Y SERVICE CARDS. Readers in the U.S.A. should use the cards addressed to New York ; all other readers are requested to use the cards addressed to London.
the space containing the heating element is evacuated, relieving the wall of the chamber of pressure and thus permitting it to be made thinner. With steel receivers, temperatures up to 1,050°C may be reached. In the third design, the receiver is heated by the direct passage of electrical current. The temperatures that can be reached are similar to those in the first two designs, but since the wall of the vessel receives the current directly, temperature changes can be effected very rapidly. This principle is used mainly in ultra-high vacuum installations. In the fourth design, the heat source is placed inside the high vacuum vessel and is insulated from the cooled wall by radiation screens (the " cold wall " furnace). The temperatures this design can achieve is limited only by composition of the heating elements themselves : the maximum temperatures which can be reached are about 2,500°C for tantalum heating elements and about 2,800°C for tungsten elements. The firm also builds a large range of special furnaces for research and production. Effective capacities range from a few cc. to several cubic metres, and temperatures up to 3,000°C can be r e a c h e d . . I n the firm's straight-through furnaces, the heated section remains under vacuum throughout, and charges are
Efco Furnaces Ltd., Queens Road, Weybridge, Surrey, Great Britain. Heraeus resistance-heated vacuum furnaces Fleischmann (London) Ltd., the British agents for Heraeus G m b H of Hanau, West Germany, have sent us the firm's latest brochure on its range of resistance-heated vacuum furnaces. The 24 pp. brochure is illustrated and contains comprehensive descriptions of furnaces with indirect resistance-heating produced either externally (the W A series) or internally (the WI series), special furnaces (straight-through vacuum furnaces), furnaces with direct resistance-heating (sintering plant), and metal distillation plant. About two-thirds of the brochure is concerned with indirectresistance heated furnaces, of which there are four basic designs. In the first, a heating muffle is placed over the receiver to heat the container wall (the " hot wall " furnace). For the steel receivers normally used, the maximum temperature that can be reached is about 900°C, for quartz or quartz materials, about 1,050°C, and for aluminium oxide tubes, about 1,500°C. In the second design, 361
362
Vacuum News
introduced and removed through special locks which are removed from the furnace for charging and discharging. Cooling times are shortened by the forced circulation of an inert gas. These furnaces are said to have proved themselves especially suitable for bright-annealing steel, in carburization-free annealing and the subsequent hardening of large components made of tool-steel, and in the age-hardening of workpieces made from Ni base alloys and for soldering high-temperature materials. The sintering plant is suitable for sintering rods compressed from powder and for annealing metals with a high melting point in rod and sheet form. The process takes place under high vacuum or an inert gas, and heating is produced by direct resistance. The temperatures that can be reached are stated to be limited only by the melting point of the materials and the electrical power available. These installations are described as being particularly suitable for sintering and annealing niobium and tantalum and also molybdenum, rhenium, tungsten and their alloys. No standard models of metal distillation plant are built since requirements for them differ so widely. However, the brochure describes a process used for the distillation of magnesium from titanium sponge. The furnace is divided into separate heating zones, each independently controlled by thermocouples. Hydrochloric acid is first removed from the titanium sponge under rough vacuum at 400°C, and is drawn off by a backing pump. A high vacuum pumping unit with a separate backing pump is then switched on and, as the temperature rises, magnesium and magnesium chloride are evaporated and collected in a condenser adjoining the furnace. To obtain magnesium in the purest possible form, the condenser is oil-heated so that no further highly volatile impurities are precipitated. A specially designed oil-circulation system maintains the double-walled condenser at a constant temperature.
Heraeus GmbH, 6450, Hanau, West Germany. British agents : Fleischmann (London) Ltd., Chancery House, Chancery Lane, London W.C.2., Great Britain.
TRANSVERSEFIELD ELECTROMAGNET
•
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J= I
METALVAPOURHEATETC ' ' " "~
eOO,EO
_~.ECT RON GUN --re
~ t
NW IGT~OIII INGOT AWAL
Diagram A, above, illustrates the principle of the transverse field electron gun system used in the 250 kW electron-beam furnace recently installed by Murex Ltd., a leading British producer of refractory metals. Diagram B, below, illustrates the general layout of the furnace. Manufactured by Messrs. Degussa Wolfgang of Hanau, it is the secondlargest such furnace known to exist in Great Britain.
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I British firm instals 250kW electron-beam furnace Murex Ltd., a leading British producer of refractory metals, has recentlyYcommissioned a 250kW electron-beam melting furnace supplied by Messrs. Degussa Wolfgang A G of Hanau, West Germany. It is among the largest of its kind outside the U.S. and is probably the second-largest in Britain : the only other furnace of comparable size known to exist in Britain is IMI's, which, commissioned about 18 months ago, has a rating of 260kW and was then claimed to be the largest of its kind in the country. (It was built by W. C. Heraeus G.m.b.H. of Hanau). The Murex furnace is described as the first of the " third generation " designs, and is equipped with transverse electron guns, automatic feed mechanisms, closed-circuit television systems and certain refinements in its controls. At present, it is producing ingots of tantalum and niobium, both pure and alloyed, and should soon be available for the custom-melting of other metals and alloys. The size of the ingots ranges from 3 in. diameter for tungsten (melting point 3,400°C) to 8 in. diameter for metals and alloys whose melting points are lower. It is stated that a melting rate of 60 kilos an hour has been achieved for a 2 in. diameter ingot of tantalum alloy, but that slower rates are normally used when a high degree of purity is required. Dagrams A and B illustrate, respectively, the principle of the transverse field electron-gun system and the general layout of the furnace itself. It will be seen that the guns are placed below and away from the molten metal, to avoid contamination, and that their beams are turned through approximately 180 °, vertically, by the horizontal field of an electro-magnet above each filament, so that they strike down into the mould. They are also distributed evenly about the pool of melt and each can, if necessary, be withdrawn into separate chambers for maintenance.
]
IORIZONTAL EE% gO E
WATERCOOLED. RO. GON
W w' " 'wAL
So far, this is said not to have proved necessary, although the filaments have been changed every 50 hours or so as a precaution. The metal is fed into the furnace in the form of a bar pressed from powder, either horizontally or vertically, and this process is automatic, although manual override is also provided. Horizontal feed is carried out from a magazine with eight chambers, which can be refilled during a melt. It will be seen that the feedstock is protruded until it interrupts the beam, and then melts and drips into the pool. The resulting ingot is normally remelted by introducing it vertically (see diagram B) until, as in the first method, it interrupts the beam, melts, and drips into the mould. In either of these two methods the ingot is continuously and automatically withdrawn into the ingot chamber (see B), and when it is complete, a new chamber can be fitted with a minimum delay in the melting process. The melting process can be viewed (see B) either directly, through a protected window, or by means of a Pye closedcircuit TV system. There are two cameras on top of the furnace sighted onto the mould area through stroboscopic windows, which reduce transmitted light by a factor of 1000. Since brightness and contrast can be adjusted, this form of indirect observation has certain advantages over direct observation, as, for example, in the focusing of the beams. Evacuation is accomplished by two 800 litres/sec Leybold vacuum diffusion pumps, backed by a Roots pump and a rotary pump. Vacuum during melting is generally kept between 10 -4 and 10 -5 torr, depending on the material. The leak rate is stated to be 10 -4 torr litres/sec.
Murex Ltd., Rainham, Essex, Great Britain.