DE1202990B - Process for the production of ductile, compact titanium or a titanium alloy by fused-salt electrolysis - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

Number:
File number:
Registration date:
Display day:

C22d

German KL: 40 c- 3/14

1202990
T19305VI a / 40c
November 21, 1960
October 14, 1965

The invention relates to a method for producing ductile, compact titanium or a Titanium alloy with a degree of purity over 99% by fused-salt electrolysis, whereby the molten Electrolyte made from a mixture of alkali and alkaline earth halides, especially barium bromide, Magnesium bromide and sodium bromide, and of di- and trivalent titanium halides consists.

In the known processes, the cathodic deposition of titanium takes place in the form of dendrites, granular agglomerates, spongy metal, etc. Due to the easy oxidizability of the Titans at elevated temperatures has made processing such titanium metal, especially in spongy ones Form led to difficulties.

The invention is now based on the object to overcome the disadvantages associated with the known methods and in particular To create an economical process for the electrolytic production of ductile titanium is one thing Has a degree of purity of over 99% and in compact form, e.g. B. in the form of a plate or one Cake.

It has now been found that the object according to the invention can be achieved by a method which is characterized in that a molten electrolyte is used which contains 3 moles of sodium bromide, at least 2 moles of barium bromide, 2 to 4 moles of magnesium bromide and calcium chloride in an amount corresponding to 0.2 to 0.6 times the total amount of sodium bromide, barium bromide and magnesium bromide, as well as titanium (II) bromide and titanium (III) bromide in a molar ratio in an amount of more than 0.66 times the amount of titanium (III) -bromids that the bottom of the electrolyte is kept at a temperature of at least 500 ° C and the composition of the electrolyte in the vicinity of the cathode by introducing an inert gas on the bath surface and at a temperature of 400 to 500 ⁰ C and that with an intermittent current with a frequency of 1500 to 8000 oscillations per minute, a voltage greater than 1.0 V and a current density at the cathode of greater than a ls 6 A / dm ^{2 is} worked.

According to a further characteristic feature of the method, the procedure is such that a molten electrolyte is used which has at least 90 mol percent of all constituents around the cathode, and the higher temperature of the molten electrolyte at the bottom of the electrolytic cell compared to the temperature at the upper process for production from ductile,
compact titanium or a titanium alloy
by fusible electrolysis

Applicant:

Shin-ichi Tokumoto, Tokyo

Representative:

Dipl.-Ing. Ph. Eyer, patent attorney,

Frankfurt / M. 1, Emil-Claar-Str. 30th

Named as inventor:
Shin-ichi Tokumoto, Tokyo

Claimed priority:

Japan 23 November 1959 (36 663)

surface is achieved by using two independently working heating devices.

According to the invention one proceeds in such a way that the titanium (II) bromide in the electrolyte by reacting titanium with the present titanium (III) bromide at at least 500 ° C.

It is absolutely necessary that the working steps characteristic of the method according to the invention and working conditions are strictly observed.

To achieve a compact, ductile titanium with a purity level above 99% it is necessary that no foreign matter is deposited on the cathode on which the titanium is built up. It is therefore important to ensure that no solid particles are suspended in the vicinity of the cathode the bathroom. These particles can be, for. B. to metal powder, metal oxides and undissolved act trivalent titanium salt, which is present in excess. Avoidance caused by this Difficulties can arise by adjusting the temperature within the specified temperature values can be achieved.

The addition of the specified amount of calcium chloride is necessary, as otherwise a strong hold-up of the bath is necessary, which also creates difficulties regarding the presence of suspended solid particles in the vicinity of the cathode.

509 717/355

The invention is described below, for example, with reference to FIGS. 1 and 2 explained:

F i g. 1 is a cross-sectional view of the method in use for carrying out the method of the present invention coming device that is heated with gas.

F i g. FIG. 2 is a sectional view of a modified embodiment of the device of FIG. 1. which is electrically heated.

The in the F i g. 1 and 2 reproduced devices are each constructed so that the melt flow electrolysis is carried out in the upper part of the device at a relatively low temperature, however, the lower part is kept at a relatively high temperature.

As shown in Fig. I, the device 1 is off a heat-insulating, fireproof masonry built, with gas burners 2 and 2i provided are. A heat-insulating plate 3 is used to separate an upper gas furnace 4 and a gas furnace lower gas furnace 5. For the upper gas furnace 4, an air inlet 6 and an outlet 7 are provided. In terms of of the lower gas furnace 5, an air inlet 8 and an outlet opening 9 are provided. The vessel 10 for the Melt electrolysis consists of mild steel; at the upper end of the device is a jacket 11 for the water cooling provided. Furthermore, an inlet pipe 12 for cooling water, a discharge pipe 13 for the cooling water and a filling 14 made of graphite powder as a buffer in the space between the cell 15 made of quartz and the vessel 10 made of mild steel. In the bath 16, a diaphragm 17 is off Alumina arranged by which the bath 16 is divided into two parts. In one part it dips Cathode 18 for the deposition of the titanium and an insoluble anode 19 in the other part. By this arrangement prevents bromination of the crude salt. There is an opening for the cathode 18 20 and for the anode 19 an opening 21 is provided for the purpose of exchanging the individual electrodes. To at To prevent such an exchange the entry of air, a locking slide 23 as well as Inlet openings or outlet openings for introducing inert gas or for pressing out air arranged as they are represented by the reference numerals 24, 25 and 26. By means of the quartz tube 27 inert gas is introduced to move the bath 16.

The required temperature gradient is maintained by setting burners 2 and 2i accordingly.

In the embodiment according to FIG. 2, the temperature gradient is set by means of a corresponding one Adjusting the resistances of the electrical heating elements.

In the embodiment according to FIG. 2, the furnace 28 is also made of heat-insulating stone material, and the vessel 29 for the melt-flow electrolysis is made of mild steel. Jackets 30 and 30i are provided for cooling water, which are fed with cooling water through lines 31 and 31i. The cooling water is discharged through lines 32 and 32i. The cell 33 is made of high purity carbon; the space between the vessel 29 and the cell 33 is filled with calcium chloride 34, which fuses together with the bath constituent diffusing out of the cell 33 and thus forms a solidified body which has a higher melting point. This prevents the bath material from flowing out of the cell. A cathode 36 for depositing the titanium and an anode 37 are arranged in the bath 35. The polarization at the cathode 36 is determined by means of a neutral electrode 38. Corresponding openings 39 and 42 are provided for exchanging the electrodes 36 and 37. In order to prevent air from entering the bath, corresponding slides 41 and 44 and corresponding inlets or outlets for inert gas or displaced air are arranged, as shown by the reference symbols 45, 46, 47 and 48. The quartz tube 49 serves to introduce the inert gas into the bath in order to keep the same in motion. A quartz tube 50 is also provided which contains the electrical heating elements 51 and 52. These are arranged and dimensioned in such a way that the relatively low temperature for the deposition of titanium in the upper part of the bath and a ^{temperature above 500 °} C. in the lower part can be maintained.

The bathroom can also be other than the one specified above Have composition; the bath can consist of 3 moles of cesium chloride and 2 moles of magnesium chloride and make up 2 moles of sodium chloride. The proportion of each component of this Ternary system can experience changes within a larger range, whereby the freezing point of the mixture does not exceed 600 ° C. Up to 2.5 mol of the cesium chloride can through a mixture of lithium chloride and potassium chloride can be substituted, which has a composition adjacent to the eutectic point.

The intermittent current used must be selected so that alternating a deposition of metallic magnesium and titanium and renewed transfer of this magnesium takes place in magnesium bromide. This creates and maintains a special polarization, which causes the development of a uniform surface of the deposited titanium will. The decomposition voltage for the magnesium bromide is 2.2 V at a bath temperature of 400 ° C. However, if a reaction in the form of bromination of the titanium at one of the Electrodes, this decomposition voltage of 2.2 V is reduced.

It turns out to be useful to counteract the polarization that occurs in the bath by that it is kept moving; the cathode on which the titanium is deposited should be convenient be kept in vibration. Furthermore, it can be rotated and a powerful stream of the bath directed against the cathode. By means of this latter method of operation, it is possible to achieve through the polarization to overcome difficulties caused by using a horizontally rotating cathode and against it directs a powerful current of the bath from below.

The invention is explained below using exemplary embodiments:

example 1

A device is used as it is in the embodiment according to FIG. 1 corresponds. The cell 15 is made of quartz with a diameter of 6.5 cm and a length of 1 m.

The following components are introduced into the cell:

BaBr-. 12 moles

MgBr ₂ 10 moles

NaBr 15MoI

CaCl ₂ 0.5 times the total amount of the first three components

Mixture of the composition given below 0.03 times the total amount the first three components

The specified mixture consists of 15 moles of cesium chloride. 10 moles of magnesium chloride and 10 moles of sodium chloride. All components are heated ^{to 500 ° C. while stirring.} The moisture is removed from this mixture by holding it at a temperature of 500 to 520 ° C and under reduced pressure of about 5 mm Hg for 20 hours. Then argon gas is introduced and titanium (III) bromide is introduced in an amount of 0.1 times the total amount of barium bromide, magnesium bromide and sodium bromide. Then, spongy titanium in an amount 0.4 times the amount of titanium (III) bromide is added and stirred thoroughly at a bath temperature of 520 to 560.degree. After stirring, the temperature of the total bath is reduced; the upper part of the bath is maintained of the bath by means of the gas burner 2i to 460 ⁰ C by means of the gas burner 2 at 450 ° C and the lower part. You work at these temperatures for 36 hours.

Based on the analysis, the upper part of the bath contains 19.51 mol BaBr ₂ , 17.67 mol MgBr ₂ . 24.11 moles NaBr. 0.99 mol CsCl, 0.54 mol MgCl ₂ . 0.59 mol NaCl. 31.77 moles CaCl ₂ , 2.98 moles TiBr ₂ and 1.84 moles TiB3. Barium bromide is 11.8 moles when sodium bromide is 15 moles. The amount of titanium (II) bromide is more than 0.66 times that of titanium (III) bromide. Using this bath, the electrolytic deposition of titanium is carried out under the following working conditions.

Working temperature 450 ^° C. The cathode is a molybdenum sheet with the dimensions of 0.5 · 10 · 25 mm. The anode has a diameter of 10 mm and a length of 300 mm. An intermittent current is used for the deposition. Here, the intermittent ratio is 0.75 for the deposition flow and 0.25 for the opposite flow. The frequency amounts to 5000 vibrations per minute, the plating current to an average of 0.7 A. The power density on average of 14 A / dm ^"2 and the oppositely directed flow to an average of 0.15 A. The current density of the latter stream amounts to an average of 3 A / dm ² , the cell voltage of the deposition current is 4.7 V. To adjust the polarization, the cathode is vibrated. The procedure is such that the cathode is left in the rest position for 0.5 seconds and then a vibration is applied for 1.5 seconds, which has an amplitude of 1 cm and a frequency of 400 oscillations per minute.

Analysis shows that after 5 hours of electrolysis obtained titanium has a purity of 99.5%. This titanium exhibits sufficient rolling properties Ductility on. Comparatively, when electrolyzing a total of 80 hours, the amount has Barium bromide in the bath around the cathode decreased to 1.8 mol, while the amount of Sodium bromide amounts to 3 mol. When the bathroom has changed that far in its composition. the purity of titanium is not higher than 99% even when the electrolysis conditions are in any Way to be changed. The titanium obtained in this way shows cracking during rolling.

If the bath, which is present in this state, is once ^{heated to above 500 °} C., it contains a quantity of barium bromide around the cathode. which is more than 0.66 times that of sodium bromide. As soon as the bath is ^{heated to 560 °} C., it can be completely regenerated.

If, on the other hand, a comparable test is carried out while keeping the lower part of the bath at over 500 ^° C. and the upper part of the bath at 450 ^° C., no unfavorable results are obtained; the electrodeposited titanium has good mechanical properties.

When a bath of similar composition is used but containing an amount of calcium chloride 0.3 times the total amount of barium bromide. Magnesium bromide and sodium bromide equivalent, so it follows that the amount of barium over the 0,66fachen those of sodium bromide as adjacent at a temperature below 500 ⁰ C is present at the cathode in the upper part of the bath, a few hours available is even if one works under comparable working conditions; a compact titanium is obtained, but it has a degree of purity of no more than 99%.

Example 2

The same cell is used as in Example 1, and in these cells the following components for the bath are introduced:

BaBr ₂ 12MoI

MgBr ₂ 14 moles

NaBr 15 moles

CaCl ₂ 0.45 times the total amount of the first three components

Mixture of the composition given below 0.03 times the total amount the first three components

The latter mixture consists of 15 moles of cesium chloride. 10 moles of magnesium chloride and 10 moles of sodium chloride.

The melting and drying conditions of this mixture and the addition of titanium (III) bromide and the formation of the titanium (II) bromide are carried out in the same manner as described in Example 1

is. So that the bath contains iron (II) bromide, iron is immersed and dissolved in the bath.

The temperature of the entire bath is adjusted so that the upper part is maintained at 430 ⁰ C and the lower part to 450 ⁰ C. After holding at this temperature for 24 hours, the upper part of the bath contains, based on the analysis: 18.40 mol BaBr ₂ , 22.10 mol MgBr ₂ . 24.57 mol NaBr, 0.91 mol CsCl, 0.56 mol MgCl ₂ . 0.60 moles NaCl, 28.22 moles CaCl ₂ , 1.91 moles TiBr ₂ , 2.37 moles TiBr ₃ and 0.33 moles FeBr ₂ . The value of barium bromide is 11.2 moles when the amount of sodium bromide is 15 moles. The amount of titanium (III) bromide is more than 0.66 times that of titanium (II) bromide. The deposition of the titanium is carried out under the following conditions.

The temperature of the bath is 430 ^° C., the electrodes are the same as in example 1.

Here, the intermittent ratio is 0.75 for the deposition flow and 0.25 for the opposite flow. The frequency amounts to 7000 oscillations per minute, the deposition current to an average of 0.5 A, the current density to 10 A / dm ² on average. The cell voltage of the deposition current is 4.5 V. To avoid polarization, the cathode is set in oscillation, namely the same 0.3 seconds in the rest position and then 0.6 seconds of vibration with an amplitude of 1 cm and a frequency of 600 oscillations each Subject to minute. Analysis of the titanium obtained after electrolyzing for 5 hours shows that the titanium has a purity of 95.4% and contains 4.3% iron.

If the electrolysis is carried out under comparable conditions for about 70 hours, it is reduced the amount of barium bromide adjacent to the cathode in the bath is 1.9 mol and that Amount of sodium bromide to 3 moles. As soon as the bath has changed to these values, a Titanium alloy purity of over 99% cannot be achieved, even if the other Electrolysis conditions can be changed in any way. The highest degree of purity of the extracted Titanium alloy in this case amounts to 98.3%.

The other results of this exemplary embodiment are analogous to Example 1.

If in Examples 1 and 2, the electrolysis using an anode made of carbon without using a diaphragm, which prevents bromination of the titanium to be deposited is to be, it follows that titanium (II) bromide is brominated in titanium (III) bromide. Among such Working conditions results in a reduction in the amount of titanium (II) bromide present and a Increase in titanium (III) bromide. This results in a reduction in the titanium (II) bromide content below an amount equal to 0.66 times that of titanium (III) bromide. and electrolysis only leads to the separation of a relatively large amount of unreduced substances. If metallic Titanium is present in the bath and the temperature is increased to above 500 ° C, the amount of Titanium (II) bromide can be brought back to more than 0.66 times that of titanium (III) bromide.

In order to be able to deposit titanium properly, the titanium (III) bromide should be used in the process according to the invention always present in a larger amount than is present in solution in the bath.

Claims (4)

Patent claims: 1. A process for the production of ductile, compact titanium or a titanium alloy with a degree of purity of more than 99% by molten electrolysis, the molten electrolyte consisting of a mixture of alkali and alkaline earth halides, in particular barium bromide, magnesium bromide and sodium bromide, and di- or trivalent titanium halides , characterized in that a molten electrolyte is used which contains 3 moles of sodium bromide, at least 2 moles of barium bromide, 2 to 4 moles of magnesium bromide and calcium chloride in an amount corresponding to 0.2 to 0.6 times the total amount of sodium bromide, barium bromide and magnesium bromide. and titanium (II) bromide and titanium (IH) bromide contains in a molar ratio in an amount of more than the 0,66fachen amount of titanium (III) bromide, that the bottom of the electrolyte at a temperature of at least 500 ⁰ C. and the composition of the electrolyte in the vicinity of the cathode by introducing an inert gas onto the bath surface and at a temperature of 400 to. 500 ⁰ C is maintained and that an intermittent current with a frequency of 1500 to 8000 oscillations per minute, a voltage greater than 1.0 V and a cathodic current density of greater than 6 A / dm ² is used. 2. The method according to claim 1, characterized in that that a molten electrolyte is used around the cathode at least 90 mole percent of all ingredients. 3. The method according to claim I, characterized in that that the higher temperature of the molten electrolyte at the bottom of the electrolytic cell compared to the temperature at the Surface by using two independently working heating devices is achieved. 4. The method according to claim 1, characterized in that the titanium (II) bromide in the electrolyte by reacting titanium with the present titanium (III) bromide is generated at least 50O ⁰ C. Considered publications:
U.S. Patent No. 2,848,395;
"Journal of inorganic and general chemistry". 298 (1959). Pp. 176/192. 1 sheet of drawings 509 717/355 10.65 © Bundesdruckerei Berlin