DE1078294B - Glass for fusion purposes - Google Patents

Description

The invention relates to a glass which is particularly suitable for fusing with iron-cobalt-nickel alloys suitable is.

Such glasses for fusions with iron-cobalt-nickel alloys with 28% Ni, 18% Co, the remainder% Fe have been known for a long time. she are increasingly used in the field of electron tube construction, because compared to others known melting metals, such as tungsten and molybdenum, such iron-cobalt-nickel alloys are less sensitive to oxidation and are therefore preferred to other metals.

A fusing glass should meet three conditions:

1. Merger adaptation to the
Iron-cobalt-nickel alloy

It is well known that the quality of a glass-metal fusion depends on the maximum stresses, which exist in it at the service temperature of the fusion and the cohesion of the Jeopardize merger partners more or less depending on their size. These tensions are through Differences in the thermal expansion of both merging partners caused. You can basically can be reduced to a minimum by using the mean linear coefficient of thermal expansion both fusing partners between room temperature and the temperature at which the last of the both merging partners solidified, equalized if possible. This means that both expansion curves in the solidification area of the lowest softening Partners should cut. When adapting a glass to molybdenum or tungsten, for example, whose expansion curves have a steady, almost linear course, can be the above Achieve the condition by varying the coefficient of expansion of the glass alone. The adaptation a glass to the iron-cobalt-nickel alloy cited above is more difficult because the Thermal expansion does not show a steady course, but a sudden change of direction at around 400 ° C learns. In order to meet the requirement here that both expansion curves intersect in the solidification or transformation area of the glass In addition to thermal expansion, the transformation point of the glass is also important.

When adjusting the glass, care must also be taken to ensure that both expansion curves are aligned Do not move too far apart between the freezing point and room temperature, otherwise there is a risk exists that the fusion cracks during the cooling process. The between freezing point and room temperature occurring stresses are to be kept small.

Fusing glass

Applicant:

JENAer Glaswerk Schott & Gen.,
Mainz, Hattenbergstr. 10

Dr. Werner Sack, Mainz,
has been named as the inventor

2. Low electrical conductivity
For use in electron tube construction, the lowest possible electrical conductivity is required, which ensures adequate insulation of the electrodes even at the operating temperatures of high-performance tubes. The conductivity of glasses is characterized by the temperature at which the glass has a specific electrical resistance of 10 ⁸ ohm-cm; this temperature is referred to as T ^ ₁₀₀ point. As the T ^ ₁₀₀ value increases, the electrical conductivity of a glass decreases. _{Good sealing glasses} for iron-cobalt-nickel alloys should have T Kl00 values of at least 340 ° C.

3. Good chemical resistance

The chemical composition of the glass must not contain any reducible components, such as Contain lead oxide, arsenic oxide and antimony oxide, which cause discoloration when processed in the flame or lead to the precipitation of a metallic coating on the glass surface. the Chemical resistance must continue to ensure proper cleaning of the glass bulb and the melted Iron-cobalt-nickel electrodes through diluted Allow acids without impairing usability. Likewise, through a longer storage the usability of the glass will not suffer any damage. Such a sealing jar must therefore have a sufficient one hydrolytic resistance and acid resistance exhibit.

+5 If one considers the melting jars that have become known in relation to the above statements examined, one arrives at the result that the older glass compositions correspond to the first two Partly meet the points, but do not meet the third requirement for good chemical resistance. In recent times, glass compositions have become known that compared to the previous glasses have a significantly better chemical resistance. As in German patent specification 1 003 925

909 767/169

is explained in detail, is the inadequate chemical resistance of the previous fusion glasses for iron-cobalt-nickel alloys on the fact that they are without exception to the pronounced alkali borosilicate glasses belong to which more or less strongly experience the phenomenon of phase separation when they are heated for a long time between the transformation area and the softening point. A comprehensive Representation of the phase separation of the alkali borosilicate glasses can be found in German patent specification 645 128. In this document, the unstable composition ranges, which lead to phase separation, listed. One recognizes from this as essential Feature that the area of phase separation is increasingly reduced when lithium oxide passes through Sodium oxide or potassium oxide is replaced. From the same document it can also be seen that for a silica content between 60 and 70% for the purpose of good phase stability of the boric acid content Should not exceed 20%. An addition of so over 2.5% aluminum oxide to one for phase separation According to the same writing, inclined glass does not eliminate this instability, it merely reduces it the leach rate.

An improved phase stability of the glasses is achieved according to the German patent 1 003 925 a higher potassium oxide content than previously achieved. The resulting difficult meltability such a mixture is compensated for by reducing the aluminum oxide content to 1 up to 4% with simultaneous introduction of up to 2% sodium oxide and 0.2 to 1.5% lithium oxide. These However, glasses still belong to the alkali borosilicate glasses that tend to phase separate.

It has now been found that the chemical resistance and the electrical insulation properties of the glasses known from German patent specification 1003 925 can be improved quite considerably if, contrary to the provisions of this patent specification (column 4, lines 5 to 13), part of the potassium oxide content is increased by 1 to 4% barium oxide is replaced with the complete omission of lithium oxide and the introduction of 0.3 to 1.5% fluorine. The transition from the previous pure alkali-borosilicate glasses to alkaline-earth-alkali-borosilicate glasses through the introduction of barium oxide thus brings a further advantageous improvement in the phase stability and thus the chemical resistance of this type of fusion glasses, whereby the simultaneous introduction of fluorine in the form of potassium bifluoride (KHF ₂ ) or in the form of sodium silicofluoride _{(Na 2 SiF 6} ) the adaptation to the iron-cobalt-nickel alloy is guaranteed. According to the passage cited above in German patent specification 1003 925, it has so far not been possible to achieve a good fusion voltage adjustment to the iron-cobalt-nickel alloy with such alkaline-earth-alkali-borosilicate glasses. The improved stability of the glasses according to the invention makes it possible to reduce the aluminum oxide content to 0.8 to 1.8%, which has an advantageous effect on the meltability of the mixture and the homogeneity of the gas flow. In this practically pure glass containing potassium oxide, the flux effect of the fluorine is not only surprisingly effective. With the help of the fluorine content, the transformation point of the glasses according to the invention can be changed at the same time, namely the transformation point is shifted to lower temperatures with increasing fluorine content. This is very important for a perfect fusion of these glasses with the iron-cobalt-nickel alloy. With regard to a desirable maximum possible phase stability or chemical resistance and an increased electrical insulation value, the flux lithium oxide can thus also be dispensed with while reducing the sodium oxide content to 0.4 to 0.8% at the same time. The advance compared to the known glasses of German patent specification 1 003 925 is therefore particularly due to the simultaneous introduction of barium oxide and fluorine. This advantageously creates the basis for dispensing with the introduction of lithium oxide and reducing the sodium and aluminum oxide content. The melting and refining temperatures of these glasses are between 1430 and 1460 ° C. These are not unusual temperatures for a pan melt; the glass can still be manufactured in port melts. A particularly effective refining agent is an addition of 0.5 to 2.0% potassium chloride.

The glasses according to the invention are thus characterized by the following composition in percent by weight :

SiO ₂ 64.0 to 69.0%

B ₂ O ₃ 18.0 to 20.0%

AIoO ₃ 0.8 to 1.8%

Na ₂ O 0.4 to 0.8%

K ₂ O 7.0 to 9.5%

BaO 1.0 to 3.5%

F 0.2 to 1.5%

KCl 0.5 to 2.0%

According to the German test method DIN 12 111, the glasses according to the invention belong to the fourth hydrolytic class, the class of the softer apparatus glasses. The glasses in use up to now were outside the five existing hydrolytic classes. The acid resistance of the glasses has been improved by 50 to 80 times at the same time. The T _Kl00 values are between 400 and 430 ° C. If one determines the specific electrical resistance at 350 ° C. analogously to German patent specification 1003 925 (column 4, lines 43 to 45), values between 830 and 2000 megohms are obtained. cm. The progress of the glasses according to the invention over the known glasses is particularly impressive. The electrical resistances of these known glasses are between 30 and 500 megohms * cm.

The following are examples of compositions for sealing glasses according to the invention specified:

Components

Silica (Si O ₂ )

Boric acid (B ₂ O ₃ )

Aluminum oxide (Al ₂ O ₃
Sodium Oxide (Na ₂ O) ..

Potassium oxide (K ₂ O)

Barium Oxide (BaO) ....

Fluorine (F)

Potassium Chloride (KCl) ..

composition
in percent by weight
II II I ΙΠ

69.0
18.1
0.8
0.4
7.1
1.1
1.5
2.0

64.0
20.0
1.8
0.7
9.4
3.4
0.2
0.5

65.5
19.5
1.2
0.5
7.5
3.5
0.8
1.5

The manufacture of fusion glasses according to the invention can be carried out, for example, as follows will:

Claims (1)

5 6 To melt 100 kg of calculated glass, characterized by the following composition: 6.6 kg of potassium feldspar, 61.2 kg of quartz flour, 34.6 kg of mixture in percent by weight: boric acid containing water of crystallization 0.82 kg of soda 8.5 kg of silica 64 , 0 to 69.0% potash, 4.4 kg barium carbonate, 1.5 kg potassium boric acid 18 0 to 20 0% chloride and 1.7 kg potassium bifluoride as usual intimately 5 aluminum oxide ". '.'. '.'. 0 ^ 8 to 1-8% mixed The mixture is melted at temperatures of 0.4 to 0.8% sodium oxide about 1440 ° C and the melt is refined with potassium oxide 70 to 95% 1460 ° C. The processing of the melt with barium oxide '.'. '.'. '.'. '.'. '.'. '. 1 ^ 0 to 4 / Where the glassmaker's pipe is at temperatures between fluorine 0 2 to 1 5% 1190 and 1220 ° C. The specified potassium chloride Υ. '.'. '.'. '.'. '. Θ', 5 to 2 ', 0 "/ above production example gives a fusing glass which has a composition according to the second fusing glass according to claim 1, marked example III be sits. characterized by the following composition: 65.5% silica, 19.5% boric acid, 1.2% aluminum patent claims: lg Qxydj O5o / o sodium oxide) 7; 5o / o potassium oxide, 1. Fusion glass, particularly suitable for 3.5% barium oxide, 0.8% fluorine, 1.5% potassium Fusion with iron-cobalt-nickel alloy monochloride. ® 909 767/169 3.60