DE1303257B - - Google Patents

Description

Int. Cl.

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

C 22c, 27/00

German class: 40 b, 27/00 Interpretation document 1 303 257

File number: P 13 03 257.0-24 (N 24173) Filing date: December 17, 1963

Open date: - Open date: July 8, 1971

Exhibition priority: - Union priority

Date:

Country:

File number:

17th December 1962 V. St. v. America 244955

Description: Use of a tantalum-yttrium alloy for wires or sheets

Addition to: Elimination from: Applicant:

Norton Co., Worcester, Mass. (V. St. A.)

Representative:

Sommerfeld, E., Dr.-Ing .; Bezold, D. v., Dr .; Patent Attorneys, 8000 Munich

Named inventor: Torti Jr., Maurice Leo, Boston, Mass. (V. St. A.)

eo O CO

Publications considered for the assessment of patentability: Nuclear Science and Engineering, Journal of Metals, 13 (1961), issue 7,

Vol. 14 (1962), No. 2, October, p. 109, pp. 487 to 489 to 122 Metal Progress, 80 (1961), No. 4,

Pp. 92 to 96

Q7A

© 6.71 109 528/156

The present invention relates to a tantalum-yttrium alloy as a material for wires or Sheets that, after annealing at 2040 ° C for one hour, have a fine-grain structure with a grain size of about 0.1 to 0.026 mm.

For many technical and industrial purposes there is a need for tantalum alloys with higher Recrystallization temperatures, resistance to grain coarsening at temperatures the same or above the recrystallization temperature, uniform grain size and better ductility. Wires or sheets that not only have high strength at elevated temperatures, but also sufficient ductile are particularly needed. Especially with filaments and electrode connection lines Small diameter for electrotechnical purposes represents the grain growth and the resulting Embrittlement of the wires in a manufacture using temperatures above the recrystallization temperature, pose a serious problem. Grain growth occurs in fine wires and electrode leads large grains that take up the entire cross-section of the wire can. Such large grains or crystallites tend to slide on the grain boundaries and thereby the usability of the wire or the electrode connection is reduced or completely eliminated. Coarse-grained structures also tend to become brittle and crack.

In practice, it has proven difficult to simultaneously use a high recrystallization temperature with tantalum alloys, a suppression of grain growth or coarsening, a uniform one To achieve grain size and at the same time sufficient ductility.

It is known from "Nuclear Science and Engineering", Vol. 14 (1962), pp. 109 to 122, tantalum alloys with traces of yttrium that are below the detection limit of 40 or 10 ppm (0.004 to 0.001 percent by weight) are considered for use as corrosion-resistant plutonium containers in reactors to pull. The addition of yttrium leads to a fine-grain structure and higher recrystallization temperatures.

The object of the invention is to create a material for wires and metal sheets, which after 1 hour Annealing at 2040 ° C still has a fine-grain structure with a grain size that corresponds to a grain size ASTM from 4 to 8 (about 0.1 to 0.026 mm).

This task is accomplished through the use of a tantalum-yttrium alloy consisting of 0.001 to 1.0 percent by weight yttrium, the remainder tantalum, dissolved. The alloy can optionally also contain 8 percent by weight Contain tungsten and 2 percent by weight hafnium or 10 percent by weight tungsten.

The alloys can be made in a known manner by melting, casting and other metallurgical processes Process are produced. One can, for example, weighed amounts of the individual metallic Melt the ingredients together, allow to solidify and melt again until the desired homogeneity is reached. In powder metallurgical processes, the individual metallic components powdered in weighed amounts uniformly mixed and then into a uniform Mass sintered together. A number of known ones can be used to produce the alloys

Use melting equipment. For example, one can use a vacuum arc or electron beam oven work. In the case of vacuum arc melting furnaces, consumable and / or non-consumable Electrodes are used. If a consumable electrode is used, the yttrium metal can be used in the electrode to be melted may be added or the yttrium may be in the form of particles, e.g. B. chips or powder of the enamel, can be added from which the electrode is made. The yttrium can also be used in the melt are added separately. The molten metals must be regardless of the type of furnace used be protected against pollution from the ordinary atmosphere, so they should do not come into contact with oxygen, nitrogen, etc. The melting should therefore take place in an inert Atmosphere, such as a vacuum or a protective gas, can be carried out.

so Since yttrium has a relatively high vapor pressure, the initial yttrium addition required to make a certain percentage in the finished alloy depends on a number of circumstances, for example the substances to be melted, the melting rate and the temperature of the molten one Metal. So initially so much yttrium is added that the cast metal finally still has an yttrium content of about 0.001 to 1.0 percent by weight.

The invention will now be explained in more detail with reference to the following examples.

example 1

In this example, small pieces of tantalum metal in the form of turnings are mixed with enough yttrium metal turnings to give a total concentration of 0.05 percent by weight yttrium. The mixture of tantalum and yttrium was then hydraulically pressed into a consumable arc electrode. The electrode was then melted in a conventional electric arc furnace under high vacuum. The power was generated by a welding generator group capable of delivering 5600 amperes. The crucible had an inside diameter of about 10 cm. The tantalum-yttrium electrode was melted at 30 volts, 5000 amperes under a pressure of IO ^-4 to IO ^-3 Torr, measured in the furnace housing. The melted ingot contained 0.005 percent by weight yttrium, the remainder tantalum. The ingot from the alloy was then rolled to a degree of rolling of over 90% into a 0.5 mm thick sheet. Sections of the rolled sheet were then annealed at temperatures between about 1040 to 2210 ° C for about 1 hour.

The sheet metal sections were then examined with regard to their recrystallization temperature and grain size. The recrystallization temperature is understood here to be the approximate minimum value of the temperature, in which a complete recrystallization of the cold-worked metal within one hour enters into new equiaxed grains. Grain size is understood here to mean the number of grains by comparison with a standard ASTM grain size map at a magnification of one hundred was determined. The recrystallization temperature in this example was about 2040 ° C, and the grain size was ASTM 4 (according to "Dictionary of Metallurgy" by A. D. Merriman, 1958,

Claims (3)

S. 114/115, this corresponds to a grain size of 0.101 mm). Example 2 In this example, powdered tantalum 5 was mixed with so much yttrium metal chips that the total concentration of yttrium was 0.2%. As in Example 1, a consumable arc electrode was made from this mixture and melted. Another electrode was then made from the ingot and melted again. The resulting twice-melted alloy ingot contained 0.005% yttrium with the balance tantalum. Recrystallization temperature and grain size were determined as in Example 1 and were found to be about 2200 ° C and ASTM 5 (about 0.07 mm). Example 3 In this example, a melt containing 0.02% yttrium was prepared by melting a mixture of yttrium and tantalum, which was solidified and remelted three to five times to produce a uniform ingot. The initial yttrium content of the mixture was 0.1 weight percent. The melting device was a dry welding box with a permanent tungsten electrode and a water-cooled copper crucible. The melting was carried out under argon. The alloy was then cold worked, and the recrystallization temperature and grain size were determined as in Example 1. At around 2040 ° C, this alloy only recrystallized to 75%. B e i s ρ i e 1 4 • 30 An alloy with the following composition was produced using the method described in Example 3: 0.003% yttrium, the remainder tantalum. The initial yttrium content of the melt was 0.2 percent by weight. Recrystallization temperature and grain size of this alloy were about 2040 ° C and ASTM 6 (about 0.05 mm). Example 5 An alloy of the following composition was produced according to the procedure of Example 3: 0.005% yttrium, the remainder tantalum. The melt initially contained 0.5 percent by weight yttrium. This alloy did not show any recrystallization at the test temperatures, so that the recrystallization temperature is above about 2040 ° C. Example 6 An alloy of the following composition was produced according to the procedure of Example 3: 0.1% yttrium, remainder tantalum. The initial yttrium content of the melt was 1.0 percent by weight. The recrystallization temperature and grain size of this alloy were about 1870 ° C and ASTM 8 (about 0.026 mm), respectively. After heating the alloy to about 2040 ° C. for 1 hour, the grain size was ASTM 6 (about 0.05 mm). The progress achieved by adding yttrium metal to tantalum is shown directly by a comparison of the recrystallization temperatures and grain sizes of the alloys described in Example 1 with 5 with the values for tantalum without the addition of yttrium. Pure tantalum metal has a recrystallization temperature of 1177 ° C and a grain size of ASTM 6 (approx. 0.05 mm). If pure tantalum metal in the form of a 0.5 mm thick sheet or wire is heated to around 2040 ° C, grains are formed that take up the entire thickness of the wire or sheet. After heating to 2040 ° C, the grain size of pure tantalum is considerably larger than ASTM 0 (larger than 0.28 mm). Example 7 An alloy of the following composition was produced according to the method described in Example 3: 8% tungsten, 2% hafnium, 0.02% yttrium, the remainder tantalum. The melt initially contained 0.05 percent by weight yttrium. The recrystallization temperature of this alloy is between about 1780 and 2040 ° C. When heated to 2050 ° C., the alloy had a grain size of ASTM 7 to 8 (about 0.036 to 0.026 mm). In contrast to this, the recrystallization of a tantalum alloy containing 8% tungsten and 2% hafnium without the addition of yttrium is approximately 1790 ° C. with an ASTM grain size of 7 to 8 (approximately 0.036 to 0.026 mm). After heating to about 2060 ° C. for 1 hour, this alloy had a grain size ASTM 5 to 8 (about 0.07 to 0.026 mm). Example 8 An alloy of the following composition was produced according to the method of Example 3: 10% tungsten, 0.01% yttrium, the remainder tantalum. The initial yttrium addition to the melt was 0.2%. The recrystallization temperature of this alloy was 1790 ° C, the grain size was ASTM 7 to 8 (about 0.036 to 0.026 mm). When heated to about 2050 ° C. for 1 hour, the grain size of this alloy was still ASTM 4 to 8 (about 0.1 to 0.026 mm). In contrast, the recrystallization temperature and grain size of a 10% tungsten-containing tantalum alloy without the addition of yttrium are approximately 1540 to 1590 ° C. and ASTM 5 to 8 (approximately 0.07 to 0.026 mm), respectively. The grain size of a 10% tungsten-containing tantalum alloy without the addition of yttrium was ASTM 1 to 2 (about 0.28 to 0.2 mm) after heating at about 2050 ° C. for 1 hour. Patent claims: 1. Use of a tantalum-yttrium alloy, consisting of 0.001 to 1.0 percent by weight Yttrium, the remainder tantalum, as a material for wires or sheets that are annealed for one hour at 2040 ° C have a fine-grain structure with a grain size of about 0.1 to 0.026 mm. 2. Use of a tantalum alloy according to claim 1, characterized in that it still Contains 8 percent by weight tungsten and 2 percent by weight hafnium. 3. Use of a tantalum alloy according to claim 1, characterized in that it still Contains 10 percent by weight tungsten.