Titanium Past, Present, and Future (1983) / Chapter Skim
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Chapter 5: Winning Titanium Metal Sponge
Chapter 5: Winning Titanium Metal Sponge
Pages 41-58
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From page 41... ...
The f inding s of the 19 74 NMAB report related to co~nmerc ial and certain other processes are summarized and up-dated in this chapter. Since the report was written, several major events have occurred: the first U e S e vacuum-distilled Kroll sponge production, since du Pant ceased production in 1962, occurred in 1980 when Teledyne Wah Chang Albany converted from zirconium to titanium production; titanium metal production by electrowinning was initiated in 1980 on a full-scale, production-module basis by the D-H Titanium Company; and construction of an advanced technology, Krol1-type plant was begun by International 41
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From page 42... ...
In the basic Kroll process, molten magnesium metal and gaseous TiC14 react in a sealed steel pot at a temperature of 800 to 900°C with formation of solid metal titanium in sponge form and molten MgC12. Theoretically, a ton of titanium metal and 7,950 lbs of MgC12 would be produced by the reaction of 2,029 lbs of magnesium with 7,921 lbs of TiC14.
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From page 43... ...
Vacuum distillation, originally used by the U.S. Bureau of Mines, and by du Pont from 1948 to 1962, is employed by Teledyne Wah Chang Albany and by ITI at Moses Lake, Washington.
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From page 44... ...
IDMET DIVISION OF TMCA The TrMET plant at Henderson, Nevada, owned by NL Industries and Allegheny International, has been producing sponge by the Kroll process since the early 1950s. It s current sponge capacity is about 15 ~ 000 tpy As a fully integrated producer, from ore to titanium ingot and finished items, TIMET makes its TiC14 by fluidized-bed chlorination of imported rutile or rutile substitutes.
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From page 45... ...
Because of a depressed market for zirconium and a shortage of titanium, idle equipment was converted in 1980 to produce titanium sponge at a rate of 1,000 to 1,500 tpy. TWCA titanium sponge is vacuum distilled and therefore has significantly lower volatiles relative to acid-leached sponge.
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From page 46... ...
Since sodium and titanium subhalides are soluble in molten sodium chloride, it is necessary to retain the reactants in the sealed pot until the reaction has been completed, the pot has been cooled, and the welded head removed. The mixture of sponge titanium and sodium chloride i s chipped from the reactor, crushed to about 3/8-inch lumps, and leached in dilute hydrochloric acid solution to dissolve the salt.
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From page 47... ...
Direct Electrowinning of Titanium Sponge Both the Kroll and Hunter sponge processes are indirect electrowinning procedures that rely on electrolytic production of magnesium or sodium for reduction of TiC14. The design and operation of test cells for direct electrowinning of titanium from TiC14 fed to a fused salt bath was reviewed in the 1974 NMAB report.
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From page 48... ...
1980~. Assessments by D-H Titanium, based on its projected capital and operating costs, are that new electrolytic plants would cost less to build than new Kroll or Hunter sponge plants and that the projected operating cost for the D-H titanium electrolytic process is equal to or below that of fully depreciated Kro11 or Hunter operations.
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From page 49... ...
Published information to date does not permit a comprehensive estimate of total energy use in the D-H process, but direct current required for electrowinning appears to be only about half that required for the Kroll and Hunter processes. If it is assumed that other D-H process steps have energy requirements roughly equivalent to analogous Kroll and Hunter process steps, total D-H process energy use would be about 250 million Btu per ton.
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From page 50... ...
used a ceramic diaphragm around the graphite anode as part of a replaceable anode assembly. A separate cathode feed tube introduced the TiC14 below the electrolyte level in the cell.
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From page 51... ...
In contrast, with titanium sponge selling for 67.22 per lb, the energy component of the price is only 6 percent for Knoll metal, 5 percent for Hunter metal, and 3 to 5 percent f or D-H metal. Appraisal of Titanium Sponge Production Technology Intricate trade-offs are involved in making a choice between using vacuum distillation, inert gas sweep with leaching, or leaching alone as a finishing operation for Kroll-process sponge.
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From page 52... ...
plants, however, may well be based on new or improved technologies such as vacuum distillation or electrolytic processes. A trend toward increasing the batch size in the Kroll process serves to improve metal quality by shrinking the ratio of pot surface to sponge weight and reduces handling costs as at OREMET.
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From page 53... ...
These traces thereby become hermetically encapsulated to the extent that neither draining, helium sweeping, leaching, or even vacuum distillation can remove them completely. These irremovable residues then cause significant problems in subsequent vacuum arc melting and in the arc welding of consolidated powder metallurgy products (as described in the direct-powder consolidation processes covered in Chapter 11~.
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From page 54... ...
~ The melting that removes essentially all volatiles f ram even high-volatile titanium sponge functions similarly when consolidated forms made from titanium sponge powder are arc welded -- the chlorides disrupt the welding arc. This adverse feature has blocked the commercialization of tonnage titanium powder metallurgy for the past two decades (see Chapter ll)
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From page 55... ...
-120 ML-120 SL-120 M1) -120 Produc Lion f eature s, reductant and finishing operation Mg reduced Mg reduced and vacuum and acid dis tilled leached or inert gas sweeping Na reduced Mg reduced and acid and vacuum leached distilled Selec ted im puri ties content Fe 0 .12 0 .10 0.0 5 0.
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From page 56... ...
As indicated by the lack of specification coverage, titanium produced by the electrolytic process is not included in either of the public specifications; indeed, there is a dearth of public experience in the matter of defining the quality and characteristics of electrolytically won titanium sponge. If the production of such material becomes sizable, the qualification testing that leads to specifications would be conducted.
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From page 57... ...
Sponge Description Ranking _ ASTM Grade ~ _ Vacuum distilled, Soviet Least difficult Vacuum distilled, Japanese Vacuum distilled, Chinese Inert gas sweep, U.S. Producer Leached sponge, British Leached sponge, U.S.
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