JPH04297543A - Molybdenum material, and its manufacture - Google Patents

Abstract

(A) A novel Mo material, esp. for lamp mfr., consists of at least 99.97 wt. % purity Mo contg., as sole dopant, Al pref. in amt. 150-800 (esp. 400-600) wt. ppm. (B) Prodn. of the Mo material involves addn. of the Al as an unstable cpd. (esp. the nitrate) to a pulverised Mo cpd. (pref. MoO3 of more than 99.97 wt. % purity) and then redn.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to molybdenum materials having a purity of at least 99.97%, especially for the manufacture of lamps.

0002

BACKGROUND OF THE INVENTION Molybdenum material is to be understood in the following as a preliminary material which is applied in lamp construction for various purposes. The end product of molybdenum production, which initially exists as a fired bar, is subsequently reprocessed only purely mechanically, so that the chemical composition no longer changes. The desired preliminary material is produced by rolling, hammering and drawing. More precisely, this process first produces pins or wires. The tube or strip material for film production is then produced again as a semi-finished product from wire or pins.

The doping of molybdenum materials with iron and/or cobalt is known from East German Patent No. 49,592. The method is used to achieve high elongation and high breaking strength. However, it has recently become clear that cobalt is a substance that poses a health hazard, and strict regulations have been applied for the time being in workplaces (MAK value). Furthermore, it has been found that the desired properties of elongation and strength can only be achieved with large scattering widths, so that a high rate of waste must be disposed of during production.

0004

SUMMARY OF THE INVENTION The object of the invention was to achieve an improvement in the material properties of molybdenum semi-finished products, especially for the lamp industry, and to reduce waste.

Another challenge was to use only substances without health concerns when producing molybdenum materials.

[0006]

This object is achieved in that the molybdenum material contains aluminum as the only doping material. Particularly advantageous developments of the invention are described in the subclaims.

In recent years, the demands on the thermal and mechanical load capacity of molybdenum materials have constantly increased, especially in connection with the development of PAR lamps and halogen incandescent lamps. This has led, first of all, to a sufficient specialization of molybdenum materials for various fields of use. For example, various molybdenum materials have been produced for core rods, gas-tight melting pins, supporting wires and filler films. In particular, in the case of support wires that support filaments stretched between lead wires (
(see, for example, DE 27 46 850), high modulus and constant elongation are the most important properties. Furthermore, high breaking strength and high recrystallization temperature are important.

Furthermore, there has long been an apparently insoluble problem at high scattering widths of these characteristics, which forces constant post-adjustment of machine parameters in order to avoid high rates of waste.

It has now been possible to overcome this difficulty by moderate doping of aluminum instead of iron and/or cobalt. Furthermore, it has been found to be particularly advantageous to add very small amounts of potassium. However, this prerequisites extremely high purity of the molybdenum starting material. This purity is generally at least 99.9
7% by weight and at least 99.99 for potassium
Must be 9% by weight.

[0010] Aluminum, contrary to potassium, does not evaporate during the manufacturing process. The addition of aluminum therefore suppresses the scattering of material properties.

This advantageous property can be obtained only by the addition of aluminum, in particular from 150 to 800 ppm by weight of aluminum.
Particularly good results are obtained when using 400 to 600 ppm. For reasons of manufacturing technology, it may be advantageous to additionally use very small amounts of potassium, in particular 5 to 50 ppm, as doping substance in order to adjust the particle size.

Such molybdenum materials are particularly suitable as supporting wires in the lamp industry. Fields of use are in particular those with extremely high thermal and chemical loads, e.g.
This is the case with loads generated on AR lamps, halogen lamps).

[0013]

[Example] As an example, a PAR with an output of 300W
Name an incandescent light bulb. The support for the luminescent body is manufactured from a molybdenum wire with a diameter of approximately 125 μm. The molybdenum contains 500 ppm (by weight) of Al and K15.
ppm (by weight) doped.

[0014] Elongation rate of this molybdenum wire (△1/1)
is shown in FIG. 1, which is somewhat higher (approximately 21.5%) than the elongation of the corresponding molybdenum wire doped with 500 ppm (by weight) cobalt (approximately 20.8%). However, of particular importance is the situation in which the scattering width of the elongation when doped with aluminum is significantly reduced compared to when doped with cobalt. The scattering width is about 2% compared to about 5% when doped with cobalt (see Figure 1).
. Other properties are also improved compared to known dopings. Therefore, for example, the recrystallization temperature is 1 at the prior art level.
Compared to only 100°C, it is now about 1700°C.

[0015] Due to reduced requirements, other, particularly slight dopings can be used. An example is a molybdenum wire doped with 250 ppm aluminum and 15 ppm K. The elongation constant of the wire is approximately 3.5
%.

The method for producing molybdenum materials basically proceeds based on the principle of the Coolidge method (this is described in C. Agte/J. Vacek, W.
Olfram und Molybdaen, Akad
emily-Verlag, Berlin, 1959, especially chapter 6). The starting material for producing molybdenum products is, for example, MoO3 with a purity of 99.97% by weight. To this oxide, which is present as a powder, aluminum and optionally small amounts of potassium are added as doping substances. Aluminum is added as a nitrate (Al(NO3)3). Other unstable aluminum compounds, such as AlCl
3 may also be used. Highly stable compounds, such as Al2O3, on the other hand, are unsuitable, since the aluminum is not liberated during the subsequent heat treatment.

[0017] Subsequently, the reduction of molybdenum oxide was carried out in two steps.
It is carried out in a manner known per se using H2/N2 mixtures and pure H2 gas. Advantageously, a rotary tube furnace is used instead of a feed furnace which should be equipped with a boat. MoO in 2 steps
3 at about 500~600℃ (first stage) and 1000~
It is reduced to Mo via MoO2 at a temperature of 1100°C (second stage).

[0018] In order to be able to produce a material of the desired ductility, the metal is pressed in a steel mold with a hydraulic press. Firing is carried out at a low temperature (sliding-bat kiln).
1700°C). The fired rod formed at that time,
It is then processed into molybdenum wire by rolling, hammer forging and drawing. This wire can now be processed, for example, into a supporting wire or also into a core rod.

[Brief explanation of the drawing]

FIG. 1 is a graph showing a comparison of the elongation rates of a molybdenum wire rod doped with cobalt and a molybdenum wire rod doped with aluminum.

Claims (9)

[Claims] 1. A molybdenum material, characterized in that the molybdenum has a purity of at least 99.97% by weight and contains aluminum as the only doping substance. [Claim 2] Aluminum content is 15% by weight.
The molybdenum material according to claim 1, which has a content of 0 to 800 ppm. [Claim 3] Aluminum content is 400 to 600p
The molybdenum material according to claim 2, which is pm. 4. Molybdenum material according to claim 1, wherein the molybdenum material is additionally doped with a small amount of potassium. 5. Molybdenum material according to claim 4, having a potassium content of 5 to 50 ppm. 6. A method for producing a molybdenum material according to claim 1, characterized in that aluminum is added as an unstable compound to a powdered molybdenum compound, and the compound is subsequently reduced. . Claim 7: The molybdenum compound has a purity of >99.97.
7. The method according to claim 6, wherein MoO3 has a weight percent of MoO3. [Claim 8] Press reduced molybdenum into a rod,
7. A method as claimed in claim 6, characterized in that subsequent closed firing is carried out at a temperature of about 1700 DEG C. without direct current application. 9. A method as claimed in claim 8, characterized in that the fired bar of doped molybdenum is subsequently reprocessed into tubes, core rods or support wires.