Volume 15 - Casting Part 7 potx

Vertical Feeding of Ingots. Refractory and reactive metal ingots of high purity, homogeneity, and smooth surface are remelted by vertical feeding (Fig. 35d). The molten metal droplets run down the conical, rotating electrode tip, are refined, and then drop into the pool center. The crucible pool is normally of the same diameter as the electrode but is sometimes smaller or larger. It is kept in the liquid state to allow final refining and to guarantee ingot homogeneity. Because two or more electron guns are used, the entire pool can be equally bombarded; thus, shadow effects of the electrode can be eliminated. Simultaneous melting of horizontally and vertically fed electrodes (Fig. 35e) can be used for the production of critical alloys. In this case, the feedstock should be of the desired purity. Horizontally Fed Ingots. Drip melting of horizontally fed material with a single electron gun (Fig. 36) is used for refining some steel alloys in East Germany and other Soviet bloc countries. In this process, the feedstock size is smaller than the pool diameter to minimize the shadow effect of the horizontally fed bar. In production units, feeding can be carried out from two opposite sides. Fig. 36 Drip melting of 330 mm (13 in.) square steel billet in a 1100 kW single- gun furnace. Melt rate: 1000 kg/h (2200 lb/h). Courtesy of VEB-Edelstahlwerk, East Germany. Other Process Considerations. To ensure the production of clean, homogeneous metals and alloys in electron beam drip melting furnaces, various aspects of material processing and handling must be controlled. Key considerations include: • Dimensions and quality of the feedstock, and the feeding system used • Ingot cooling and unloading during melting of another ingot • Passivation and removal of condensates from the melt chamber • Planning of melt sequences to minimize the number of furnace cleanings required • Routine preventive furnace maintenance to ensure reliability • Operator skill in operation of the furnace • Material yield and energy consumption Equipment for Drip Melting The essential equipment groups required for drip melting melting furnaces, control systems, and power supply units are all important for achieving optimum productivity. The melting furnace (Fig. 37) includes the electron beam gun as the heat source, material feeding and ingot withdrawal systems, a crucible for material solidification, and a vacuum system to maintain the low pressure. Process observation, both visually and with video systems, is possible through viewports. The melt chamber flanges are equipped with x-ray absorbing steel boards, and interlocking systems prevent operation failures and accidents. Fig. 37 Single-gun 1200 kW fur nace for horizontal drip melting of steels. Melting rates of up to 1100 kg/h (2425 lb/h) are possible. The control system allows the adjustment and control of such operating process parameters as electron beam power, operating vacuum level, material feed rate, and ingot withdraw speed. The control system also records and logs the process data. Power Supply Units. One or more high-voltage power supply units are needed to supply the electron beam guns with the required continuous voltage (30 to 40 kV). The beam power of each gun can be adjusted between zero and maximum power with an accuracy of ±2%. Other Equipment. Large production furnaces are equipped with lock-valve systems to allow simultaneous melting and unloading of ingots without breaking the vacuum in the melt chamber. Production is thus limited only when the condensate remaining in the melt chamber requires cleaning or when a different alloy is to be melted. Characteristics of Electron Beam Drip Melted Metals Electron beam melted and refined material is of the highest quality. The amount of interstitials present is very low, and trace elements of specific high vapor pressure can also be reduced to very low values (Ref 37, 38). Reactive and Refractory Metals Tantalum and niobium ingots have smooth surfaces and are of sufficient ductility that they can be cold worked, and sheets and wires can be produced. Tungsten and molybdenum ingots are also of the highest possible purity, but the ingots are brittle because of the very large grain size and the concentration of impurities at grain boundaries. Hafnium. Electron beam melted hafnium is of higher ductility than the vacuum arc remelted metal (Ref 39). The main application of electron beam melted hafnium is as control elements for submarine nuclear reactors. Vanadium is refined by electron beam drip melting. The aluminothermically produced feedstock is drip melted in several steps. During this procedure, the ingot diameter is reduced at each step by approximately 30 to 40 mm (1.2 to 1.6 in.) to obtain an ingot 30 to 40 mm (1.2 to 1.6 in.) in diameter, regardless of the initial ingot diameter. The clean vanadium ingots are primarily used in nuclear reactor applications (Ref 40). Applications for electron beam melted refractory and reactive metals are listed in Table 6. Table 6 Principal applications for vacuum arc remelted (VAR), electron beam melted (EB), and powder metallurgy (P/M) reactive and refractory metal ingots Metal Applications Reactive metals, VAR and EB melting Hafnium Flash bulbs and glow discharge tubes for the electronics industry; control rods and breakoff elements in submarine nuclear reactors Vanadium Targets for high deposition rate sputtering processes in the electronics industry; breakoff elements, fixtures, and fasteners in nuclear reactors; standards for basic research; alloying element for certain high-purity alloys Zirconium Getter material in tubes in the electronics industry; stripes for flash bulbs; fuel claddings, fasteners, and fixtures for nuclear reactors Titanium Components for bleaching equipment and desalination plants in the chemical industry; superconductive wires; turbine engine disks, blades and housings, rain erosion boards, landing legs, wing frames, missile cladding, and fuel containers in the aircraft and aerospace industries shape memory alloys; biomedical fixtures and implants; corrosion resistant claddings Refractory metals, EB melting and P/M Tungsten Heating elements, punches and dies, and nonconsummable electrodes for arc melting and gas tungsten arc welding for metal processing equipment; targets for x-ray equipment and high sputtering rate devices such as very large-scale integrated circuits, cathodes and anodes for electronic vacuum tubes in the electronics industry; radiation shields in the nuclear industry; cladding and fasteners for missile and reentry vehicles Tantalum Condensers, autoclaves, heat exchangers, armatures, and fittings for the chemical industry; electrolytic capacitors for the electronics industry; surgical implants; fasteners for aerospace applications Molybdenum Dies for conventional and isothermal forging equipment; electrodes for glass melting; targets for x-ray equipment; cladding and fasteners for missile and reentry vehicles Niobium Superconductive wire for energy transmission and large magnets for the electrical and electronics industries; heavy ion accelerators and radio frequency cavities for nuclear applications; components for aircraft and aerospace applications Steels The purity and properties of electron beam melted steels are in some respects better than those of vacuum arc and electroslag remelted steels, but the processing costs are higher. The electron beam melting of steel is primarily used in East Germany and other Soviet bloc countries. The resulting ingots are up to 1000 mm (40 in.) in diameter and weigh up to 18 Mg (20 tons). The furnaces used have been in operation since 1965, and have beam powers of up to 1200 kW. Larger furnaces for the production of ingots weighing up to 30 to 100 Mg (33 to 110 tons) are under construction (Ref 41). The essential advantage of the electron beam melting of steel is the drastic reduction of metallic and nonmetallic impurities and interstitial elements (Ref 42, 43). The principal applications for electron beam melted steels are in the machinery industry for parts for which high wear resistance and long service life are required. The extended service lives of the parts and the reduced manufacturing time (for example, less surface polishing is required for electron beam melted steel) can justify the higher material costs. The electron beam melting of steel and superalloys can become much more economical when melting and refining are done by continuous flow melting or cold hearth refining. These melting and refining methods reduce energy costs and minimize material losses. References cited in this section 37. R.E. Lüders, Tantalum Melting in a 800 kW EB Furnace, in Proceedings of the Bakish Conference on Electron Beam Melting and Refining (Reno, NV), R. Bakish, Ed., 1983, p 230-244 38. J.A. Pierret and J.B. Lambert, Operation of Electron Beam Furnace for Melting Refractory Metals, in Proceedings of the Bakish Conference on Electron Beam Melting and Refining (Reno, NV), R. Bakish, Ed., 1984, p 208-218 39. H. Sperner, Hafnium, Metallwis. Technik., Vol 7 (No. 16), 1962, p 679-682 40. R. Hähn and J. Krüger, Refining of Vanadium Aluminium Alloys to Vanadium 99.9% by EB Melting, in Proceedings of the Bakish Conference on Electron Beam Melting and Refining (Reno, NV), R. Bakish, Ed., 1986, p 53-67 41. J. Lambrecht, D. Rumberg, and K.H. Werner, Stand der Technologie der Stahlerzeugung im Elektronenstrahlofen mit Blockmassen bis 100 t, Neue Hütte, Vol 10, Oct 1984 42. C.E. Shamblen, S.L. Culp, and R.W. Lober, Superalloy Cleanliness Evaluation Using the EB Button Melt Test, in Proceedings of the Bakish Conference on Electron Beam Melting and Refining (Reno, NV), R. Bakish, Ed., 1983 43. F. Hauner, H. Stephan, and H. Stumpp, Ergebnisse bei Elektronenstrahl- Schmelzen von gerichtet erstarrten Knopfproben zur Identifizierung von nichtmetallischen Einschlüssen in hochreinen Superlegierungen, Metall., Vol 2 (No. 40), 1986, p 2-7 Continuous Flow Melting The continuous flow melting process (cold hearth refining process) (Fig. 38) was developed approximately 10 years after drip melting (Ref 44). Continuous flow melting is mainly used for refining specialty steels and superalloys and for refining and recycling reactive metal scrap, especially Ti-6Al-4V from high-density tungsten carbide tool tips (Ref 45). Fig. 38 Schematic of the continuous flow melting process. Principles of Continuous Flow Melting Continuous flow melting (Fig. 39) is the most flexible vacuum metallurgical melting process. It is a two-stage process in which the first step (material feeding, melting, and refining) takes place in a water-cooled copper trough, ladle, or hearth. In the second step, solidification occurs in one of several round, rectangular, or specially shaped water-cooled continuous copper crucibles. Both process steps are nearly independent from each other; they are linked only by the continuous flow of the liquid metal stream. The major refining actions are carried out in the hearth, but some postrefining takes place in the pool of the continuous casting crucible, similar to the drip melting of horizontally fed billets. Refinement in continuous flow melting occurs by vacuum distillation in the hearth pool, superheating, and stirring of the molten metal pool. Fig. 39 Four-gun 1200 kW combined electron beam drip melting and continuous flow melting furnace. Removal of Impurities. Most impurities with densities lower than that of the melt (for example, metalloids in steels and superalloys) can be segregated by flotation and formed into a slag raft. The raft is then held in place by either mechanical or electrothermal means. Impurities denser than the melt, such as tungsten carbide tool tips in titanium, are removed by sedimentation. Inclusions with densities such that efficient flotation or sedimentation does not occur can be partially removed by adhesion to the slag raft. Hearth dimensions are based on the type and amount of refining required. For example, hearths for vacuum distillation should be nearly square and relatively deep to allow sufficient melt stirring. For flotation refining, the hearth should be long and narrow (for superalloys, approximately 10 mm, or 0.4 in., of hearth length for each 100 kg/h, or 220 lb/h, of melt rate is recommended). Hearths for titanium alloy scrap recycling can be relatively short if all the materials can be transported to the pool of the hearth rather than to the ingot pool. Feeding. Material feeding criteria include 100% homogenous material transportation to avoid uncontrolled evaporation of alloying elements and correct feeding into or above the hearth pool. Horizontal feeding of compacted, premelted, or cast material is most often used. Loose scrap and raw material are used only when compaction is too expensive. Feeding of liquid metal was used in one of the first continuous flow melting furnaces to produce a ferritic steel in a vacuum induction furnace (Ref 46). Postrefining was carried out in a cascade of five hearths 1.5 m (60 in.) long and 1 m (40 in.) wide. Casting and Solidification. The criteria for material casting and solidification include the shape of the final product and the solidification rate required to avoid ingot tears or other defects and to ensure a homogeneous ingot structure. The multiple casting of small ingots is sometimes used, especially when forging is impossible because of the brittleness of the solidified material (for example MCrAly wear-resistant coating alloys). The casting of round and rectangular ingots and slabs is common practice, and the continuous casting of hollow ingots is also being used (Ref 47). The casting of segregation-free ingots and ingots with a fine grain size is under development to improve the workability of superalloys (Ref 48, 49). Continuous Flow Versus Drip Melting Table 7 compares the essential features of drip melting and continuous flow melting. Generally, continuous flow melting is used for all refractory metals, superalloys, and specialty steels, especially when flotation or sedimentation of inclusions is required. Drip melting is used for refractory metals because of their high melting points and the resulting high heat losses to the water-cooled copper crucible. Depending on production quantity, double or triple drip melting may require less energy than a single continuous flow melt of some materials, such as niobium. Table 7 Comparison of the characteristics of drip melting and continuous flow melting Characteristic Refractory metals Reactive metals, superalloys, and specialty steels Power density High Soft; smoothly distributed Inclusions Irrelevant Must be removed Ingot shape and structure Round; coarse grain Round or flat; fine grain, segregation-free Mass production Low High Competitive economical processes Vacuum arc remelting Vacuum arc remelting; electroslag remelting Preferred method Drip melting Continuous flow melting Refining and Production Data Data on continuous flow electron beam melting and refining in laboratory and pilot production furnaces are given in Table 8. The data demonstrate the effectiveness of the process in reducing impurities and interstitial elements. It can also be seen that the selective evaporation of chromium from superalloys can be controlled by the distribution of beam power at the trough pool and by controlling trough pool area and melt rate. The selective evaporation of aluminum from Ti-6Al- 4V alloy is much more difficult to control; additional aluminum must be used to compensate for the aluminum evaporated. Table 8 Refining and production data for the continuous flow melting of reactive and refractory metals and stainless steels in laboratory and pilot production furnaces Composition of feedstock and product Metal Feedstock size, mm (in.) Trough size, mm (in.) Ingot size, mm (in.) Ingot weight, kg (lb) Melt rate, kg/h (lb/h) Electron beam power, kW Operating pressure, Pa (torr) Specific melting energy, kW · h/kg C, ppm O, ppm N, ppm H, ppm Al, % V, % Cr, % . . . 900 . . . . . . . . . . . . . . . Hafnium 60 (2.4) square 120 × 250 (5 × 10) 100 (4) diam 83.0 (183) 40 (88) 180 4 × 10 -2 (3 × 10 -4 ) 4.5 . . . 600 . . . . . . . . . . . . . . . . . . 950 95 30 . . . . . . . . . Zirconium 100 (4) square 120 × 300 (5 × 12) 150 (6) 90.5 (200) 42 (92.5) 185 3.5 × 10 -2 (2.6 × 10 - 4 ) 4.4 . . . 540 30 3 . . . . . . . . . . . . 4000 800 10 . . . . . . . . . Zirconium 80 (3.2) square 120 × 300 (5 × 12) 100 (4) 40.2 (89) 80 (176) 140 3.5 × 10 -2 (2.6 × 10 - 4 ) 1.75 . . . 1520 210 3 . . . . . . . . . . . . 1045 210 10 . . . 99 . . . Vanadium 50 (2) square 120 × 300 (5 × 12) 100 (4) . . . 20 (44) 130 1.5 × 10 -2 (1.1 × 10 - 4 ) 6.5 . . . 277 50 3 . . . 99 . . . 400 2600 110 84 6.0 4.0 . . . Ti-6Al-4V Swarf 120 × 300 (5 × 12) 150 (6) 62.6 (138) 40 (88) 122 2 × 10 -2 (1.5 × 10 - 4 ) 3.0 200 2700 110 22 4.4 4.2 . . . Ti-6Al-4V Solid scrap 120 × 300 (5 × 12) 150 (6) 62.6 (138) 70 (154) 140 7 × 10 -2 (5.3 × 10 - 4 ) 2.0 1520 1520 75 15 6.0 4.0 . . . (5 × 12) 4 ) . . . 1320 76 8 4.8 4.1 . . . . . . . . . . . . . . . 6.0 4.0 . . . Ti-6Al-4V 125 (5) diam 150 × 400 (6 × 16) 2 × 75 (3) diam 2 × 32 (70.5) 91 (200) 147 6 × 10 -2 (4.5 × 10 - 4 ) 1.61 . . . . . . . . . . . . 3.6 4.3 . . . . . . . . . . . . . . . . . . . . . . . . Commercially pure titanium 160 (6.3) 150 × 250 (6 × 10) 100 × 400 (4 × 16) 96.4 (213) 86.3 (190) 148 6 × 10 -2 (4.5 × 10 - 4 ) 1.71 . . . . . . . . . . . . . . . . . . . . . Commercially pure titanium Sponge 150 × 500 (6 × 20) 100 × 400 (4 × 16) 103.0 (227) 41.2 (91) 226 8 × 10 -2 (6 × 10 -4 ) 5.5 . . . . . . . . . . . . . . . . . . . . . 701 97 155 . . . . . . . . . 18.25 Stainless steel 150 (6) diam 150 × 400 (6 × 16) 2 × 75 (3) diam 2 × 55 (121) 136 (300) 144 6 × 10 -2 (4.5 × 10 - 4 ) 1.06 536 33 68 . . . . . . . . . 18.11 417 14 52 . . . . . . . . . 19.11 Alloy 718 133 (5.2) diam 150 × 400 (6 × 16) 2 × 75 (3) diam 2 × 57 (126) 136 (300) 156 6 × 10 -2 (4.5 × 10 - 4 ) 1.15 363 17 34 . . . 0.72 . . . 18.73 AISI type 316 stainless steel 150 (6) diam 150 × 400 (6 × 16) 3 × 65 (2.6) diam 3 × 41.5 (91.5) 136 (300) 156 6 × 10 -2 (4.5 × 10 - 4 ) 1.15 . . . . . . . . . . . . . . . . . . . . . Source: Ref 50 References cited in this section 44. C.d'A. Hunt and H.R. Smith, Electron Beam Processing of Molten Steel in Cold Hearth Furnace, J. Met., Vol 18, 1966, p 570-577 45. H.R. Harker, Electron Beam Melting of Titanium Scrap, in Proceedings of the Bakish Conference on Electron Beam Melting and Refining (Reno, NV), R. Bakish, Ed., 1983, p 187-190 46. C.d'A. Hunt, H.R. Smith, and B.C. Coad, The Combined Induction and Electron Beam Furnace for Steel Refining and Casting, in Proceedings of the Vacuum Metallurgy Conference (Pittsburgh, PA), June 1969, p 1-22 47. H.R. Harker, The Present Status of Electron Beam Melting Technology, in Proceedings of the Bakish Conference on Electron Beam Melting and Refining (Reno, NV), R. Bakish, Ed., 1986, p 3-7 48. C.d'A. Hunt, J.C. Lowe, and T.H. Harrington, Electron Beam, Cold Hearth Refining for the Production of Nickel and Cobalt Base Superalloys, in Proceedings of the Bakish Conference on Electron Beam Melting and Refining (Reno, NV), R. Bakish, Ed., 1984, p 295-304 49. H. Stephan, R. Schumann, and H.J. Stumpp, Production of Superclean Fine- Grained Superalloys for Improvement of the Workability and Engine Efficiency by EB Melting and Refining Methods, in Proceedings of the Eighth International Conference on Vacuum Metallurgy (Linz), 1985, p 1219-1309 50. H. Stephan, Production of Ingots and Cast Parts From Reactive Metals by Electron Beam Melting and Casting, in Proceedings of the Third Electron Beam Processing Seminar (Stratford, UK), 1974, p 1b1-1b69 Equipment for Continuous Flow Electron Beam Melting The equipment required for continuous flow melting is different from that used in drip melting mainly because of the trough and the somewhat larger melting chamber. In addition, because of the materials often melted in the continuous flow process (superalloys and titanium alloys), additional instrumentation is often provided. This may include an ingot pool level control system, metal vapor and partial pressure analyzers, a two-color temperature control system, and a data logging system. Accurate beam power distribution is achieved in two- or three-gun furnaces by microprocessor control, which allows the splitting of a single beam to 64 locations and the adjustment of dwell time at each location between 0.01 and 1000 s. The beam spot at each of the 64 locations can be scanned over an elliptical or rectangular area. With such systems, the required refining can be achieved without unnecessary power consumption and evaporation of alloying elements (Ref 51). Process observation is accomplished with a video monitoring system. Samples can be obtained from both the trough pool and the ingot pool for nearly continuous control of material quality. Feeding systems for continuous flow furnaces must maintain homogeneity along the length of the feed material. The trough and crucible should be easily accessible for convenient maintenance, especially when different alloys are to be melted in the same furnace. Reference cited in this section 51. H. Ranke, V. Bauer, W. D ietrich, J. Heimerl, and H. Stephan, Melting and Evaporation With the Newly Developed Leybold-Heraeus 600 kW EB Gun at Different Pressure Levels, in Proceedings of the Bakish Conference on Electron Beam Melting and Refining (Reno, NV), R. Bakish, Ed., 1985 Characteristics of Continuous Flow Melted Materials Titanium ingots and slabs can be produced from titanium scrap contaminated with tungsten carbide tool tips. The electron beam melted product contains tungsten carbide particles no larger than 0.7 mm (0.028 in.) in diameter. Oxygen content can be reduced by fitting titanium sponge compacts around a forged ingot or slab. Continuous flow melted titanium ingots can be directly remelted in a VAR furnace. Superalloys. Continuous flow electron beam melted superalloy ingots 150 to 200 mm (6 to 8 in.) in diameter are often used in VIM investment casting furnaces. Such ingots are nearly free of nonmetallic inclusions and trace elements (Ref 52). The simultaneous continuous casting of twin, triple, or multiple ingots is under development in a 200 kW pilot [...]... long 5 0 -7 0 (11 0155 ) 2. 0-2 .5 ≥ Atmospheric Probably tungsten tip; 500 kW 58 Soviet type II Specialty steels, heatresistant alloys Ingot 150 -2 00 ( 6-8 ) diam, 1200 ( 47) long; slabs 70 × 300 × 1200 (2.8 × 12 × 47) 9 0-1 35 (200300) 1. 5-2 ≥ Atmospheric Probably tungsten tip; 50 0-1 000 kW 58 Soviet "large scale" Specialty steels, heatresistant alloys Ingots 650 (25.5) diam, 150 0-2 300 (6 0-9 0) long 40 0-9 00 (8801985)... CRR(b), ppm/min Temperature °C °F 1200 151 0 275 0 65 830 170 0 3100 0. 47 45 430 170 0 3100 0. 17 30 133 173 0 3150 O2 N2 Ar Ar N2 CO 3. 0-0 .7 4 1 0.14 0.86 80 1-0 .25 3 1 0.20 0.80 0.2 5-0 .12 1 1 0.53 0.1 2-0 .04 1 3 0.83 (a) CRE, carbon removal efficiency (b) CRR, carbon removal rate Carbon and Low-Alloy Steels The refining of carbon and low-alloy steels involves a two-step practice: a carbon removal step,... Carbon in Liquid Iron- Chromium-Carbon Metals, J Iron Steel Inst., Nov 1953, p 25 7- 2 63 2 R.J Choulet, F.S Death, and R.N Dokken, Argon-Oxygen Refining of Stainless Steel, Can Metall Q., Vol 10 (No 2), 1 971 , p 12 9-1 36 3 R.B Aucott, D.W Gray, and C.G Holland, The Theory and Practice of the Argon-Oxygen Decarburizing Process, J W Scot Iron Steel Inst., Vol 79 (No 5), 1 97 1-1 972 , p 9 8-1 27 Equipment The processing... Conference on Vacuum Metallurgy (San Diego), 1 979 , p 78 5 -7 94 A Choudhury, R Jauch, H Löwenkamp, and F Tince, Application of the Electroslag Remelting Process for the Production of Heavy Turbine Rotors from 12 %-Cr-Steel, Stahl Eisen, Vol 97, 1 977 , p 85 7- 8 68 Ch Kubisch, Druckstickstoffstähle eine neue Gruppe von Edelstählen Berg und Hüttenmännische Monatshefte, 1 971 , p 8 4-8 8 A Choudhury, "Vacuum Electroslag Remelting... and sponge Ingot 35 5-4 30 (1 4-1 7) diam, 3000 (120) long; density >90% 25 0-2 60 (550 570 ) 1. 4-1 .6 Argon ≥ Atmospheric Tungsten tip with external ignition bar; 6 × 90 kW 56 Retech furnace at OREMET, United States Titanium scrap and sponge Ingot 70 0 ( 27. 5) diam, 3800 (150 ) long; density 98% 25 0-6 70 (5501480) 0.8 9-2 .4 Argon ≥ Atmospheric Hollow copper electrode with graphite liner; 600 kW 57 Plasma arc remelting... Institute of Japan, 1982, p 93 3-9 40 6 A Choudhury et al., World Steel and Metalworking Manual, Vol 9, 198 7- 1 988, p 1-6 7 P Hupfer, Fachberichte Hüttenpraxis Metallverarbeitung, 1986, p 77 3 -7 81 8 O Kamado et al., Method of Producing Electrical Conductor, European Patent 012 1152 , 1986 9 J.G Krüger, Proceedings of the Fifth International Vacuum Metallurgy Conference (Munich), 1 976 , p 7 5-8 0 Electroslag Remelting... changing alloys or part weight, can also be accomplished without venting the melt chamber More than 50% of the evaporating and splattering material can be condensed and collected at the condensate plate This plate can be replaced through a lock-valve system Vacuum pressure during melting and pouring is in the range of 0.001 to 0.0001 Pa (1 0-5 to 1 0-6 mbar, or 7. 5 × 1 0-6 to 7. 5 × 1 0 -7 torr) Leak and wall... 27 W.A Tiller and J.W Rutter, Can J Phys., Vol 311, 1956, p 96 28 W.H Sutton, in Proceedings of the Seventh International Vacuum Metallurgy Conference (Tokyo), The Iron and Steel Institute of Japan, 1982, p 90 4- 915 29 J Preston, in Transactions of the Vacuum Metallurgy Conference, American Vacuum Society, 1965, p 36 6-3 79 30 A.S Ballentyne and A Mitchell, Iron-making Steelmaking, Vol 4, 1 977 , p 22 2-2 38... Ergebnisse einer 10 t ESU-Anlage, Radex-Rundsch., Vol 2, 1 970 , p 9 9-1 11 17 G.H Klingelhöfer, A Choudhury, and E Königer, Etude comparée des caractéristique des aciers e aborés à l'air et 18 19 20 21 22 23 24 25 26 des aciers refondus selon le procédé sous laiter electroconducteur (ESR) pour les cylindres de laminage à froid et les cylindres calandreurs, Rev Metall., Vol 67, 1 970 , p 51 2-5 22 H.J Klingëlhofer,... Processing, J Feinman, Ed., Iron and Steel Society, 19 87, p 2 7- 4 7 56 T Yagima et al., Development of the Plasma Progressive Casting Process and Its Application for Titanium Melting, in Titanium 1986: Products and Applications, Vol II, Proceedings of the Technical Program from the 1986 International Conference, Titanium Development Association, 19 87, p 98 5-9 93 57 S Stocks and D Hialt, Plasma Consolidation of . . . Ti-6Al-4V Solid scrap 120 × 300 (5 × 12) 150 (6) 62.6 (138) 70 (154 ) 140 7 × 10 -2 (5.3 × 10 - 4 ) 2.0 152 0 152 0 75 15 6.0 4.0 . . . (5 × 12) 4 ) . . . 1320 76 8 4.8. long 5 0 -7 0 (11 0- 155 ) 2. 0-2 .5 . . . ≥ Atmospheric Probably tungsten tip; 500 kW 58 Soviet type II Specialty steels, heat- resistant alloys Ingot 150 -2 00 ( 6-8 ) diam, 1200 ( 47) long;. (2 27) 41.2 (91) 226 8 × 10 -2 (6 × 10 -4 ) 5.5 . . . . . . . . . . . . . . . . . . . . . 70 1 97 155 . . . . . . . . . 18.25 Stainless steel 150 (6) diam 150 × 400 (6 × 16) 2 × 75