Copper hearth

The melt is heated by passing a large elecuical cunent between two electrodes, one of which is tire metal rod to be refined, and the otlrer is the liquid metal pool standing in a water-cooled copper hearth, which collects the metal drops as tlrey fall tluough the molten electrolyte. This pool tlrerefore freezes at the bottom, forming the ingot. Under optimum chcumstances tire product billet takes the form of a cylindrical solid separated from the molten salt by... 

In a crystal-pulling procedure using a tri-arc furnace (Fig. 2), a resistor box, a d.c. power supply (300 A, 80/40 V) and a set of water-cooled power cables are used to bring power and water to the electrodes. The upper part of the furnace is equipped with three equally spaced copper cathodes, to which are fixed W-Rh electrodes. The upper part (cathode) is separated from the lower part (anode) by a transparent quartz glass tube. In the bottom of the furnace there is a tapered opening for a water-cooled copper hearth containing the boride melt. All parts of the furnace are also water... 

Figure 2 3.5 KW electron beam furnace components (a) Water-cooled furnace block (b) Copper hearth (c) Cooling pipes (d) Top plate of furnace (earth potential) (e) Filament (f) Focus lid (g) Lid (h) High-tension supply (i) Low-tension supply (j) Ceramic insulators (k) Cooling pipes for top plate (1) locating stud for hearth adjustment and (m) Water conduit.

For the synthesis of materials, the reactants are placed in the copper crucible. An arc is struck by allowing the cathode to touch the anode. The current is raised slowly while the cathode is simultaneously withdrawn so as to maintain the arc. The arc is then positioned so that it bathes the sample in the crucible. The current is increased until the reactants melt When the arc is turned off, the product solidifies in the form of a button. Because of the enormous temperature gradient between the melt and the water-cooled crucible, a thin solid layer of the sample usually separates the melt from the copper hearth in this sense, the sample forms its own crucible and hence contamination with copper does not take place. Contamination of the sample by tungsten vaporizing from the cathode can be avoided by using water-cooled cathodes. The arc method has been successfully used for the synthesis of various oxides of Ti, V and Nb. A number of lower-valence rare-earth oxides, LnO, 5 have been prepared by arc fusion of LnjOj... 

Alloys were prepared from metals of 99.9% purity by arc melting on a water-cooled copper hearth under an argon atmosphere. The alloys were homogenized at 800° C. Diffraction patterns of cast material were equally as sharp as those of homogenized alloys. X-ray diffraction patterns were taken with filtered FeKa radiation. Computer programs verified x-ray pattern indexes. 

Figure 6. Graphite crucible for lining water-cooled copper hearths of reverse polarity electron beam furnaces.

Phase equilibria have been established in the ternary Nd-Ag-Ge system over the whole concentration region for the isothermal sections at 870 K and 1070 K by Salamakha et al. (1996f) and Zaplatynsky et al. (1996) (figs. 67a,b). The existence of four and five ternary compounds respectively have been observed. Samples were melted from pieces of high purity components (Nd 99.85 mass%, Ag 99.99 mass%, Ge 99.99 mass%) under argon atmosphere in an arc furnace with water-cooled copper hearth. The ingots were subsequently annealed at 870 K (1070 K) and quenched in cold water. The isothermal sections were constructed using X-ray powder diflraction film data obtained by the Debye-Scherrer technique with non-filtered CrK radiation. 

Levitation samples were produced using two different methods involving laser fusing of powders on a copper hearth. 

Pocket (e-beam evaporation) The cavity in the water-cooled copper hearth that holds the material to be evaporated in electron beam evaporation. See also Liner. 

The skull may be due to cooling (for example, a molten material in contact with a water-cooled copper hearth) or the formation of a reaction layer (such as molten titanium in contact with a carbon liner, giving a TiC skull). 

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