HU210093B - Molybdenum material, particularly for producing lamps and process for producing same - 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

The term "molybdenum material" shall be understood in the following as a basic material which can be used for many purposes in lamp structures. In the production of molybdenum, it first appears in the form of its colored bars, which are then further processed mechanically so that its chemical composition is no longer changed. Rolling, forging and drawing can produce pins and wires. From now on the pins and wires are made into semi-finished tubes or tapes for film production. Molybdenum films are important auxiliaries for vacuum sealing the lamp current supply in the pass-through region.

The addition of molybdenum material with iron and / or cobalt is known from patent application DD 49 592. These measures served to achieve greater elongation and greater resistance to fracture. In the meantime, however, cobalt has been shown to have health hazards and very strict workplace requirements (MAKs). It was also shown that the desired values of elongation and rigidity could only be achieved with a high standard deviation and therefore had to be considered with great waste.

JP 60194043 and US 3,676,083 disclose molybdenum materials in which aluminum, potassium and / or silicon are used as additives. A process for the addition of additives to molybdenum dioxide is also described.

The object of the present invention is to solve the problem of improving the quality of the molybdenum feedstock used especially in lamp production and reducing the waste material.

It was also our task to produce molybdenum material exclusively using materials that are not hazardous to health.

This problem can be solved by using aluminum as an additive and a small amount of 5-50 ppm potassium relative to aluminum, with an aluminum content of 150-800 ppm by weight and a potassium content of less than the total amount of (Al + K) additive. 10% by weight and aluminum is added to the powdered molybdenum trioxide, more than 99.97% pure The trioxide is reduced to molybdenum in two steps, the doped molybdenum is extruded into a rod, sintered and the doped molybdenum sintered is processed. Particularly preferred embodiments of the invention are set forth in the dependent claims.

Requirements for the thermal and mechanical load-bearing capacity of molybdenum materials have been steadily increasing in recent years, particularly in connection with the development of PAR lamps and halogen filament lamps. These first led to the production of special molybdenum materials adapted to different applications. For example, different grades of molybdenum have been made for core wires, gas-tight soldering pins, holding wires and sealing foils. Loop support wires developed between power conductors were particularly expected to have high and constant extensibility, which was considered to be the most important feature. But this still required high fracture toughness and high recrystallization temperature. (U. S. Patent DE-OS 2,746,850).

In addition, the problem of long dispersion in these properties has long been a seemingly unresolved problem and has required constant re-control of the production line parameters if large debris were to be avoided.

By properly adding aluminum instead of iron and / or cobalt, the difficulties outlined have now been overcome. In addition, very small amounts (550 ppm) of potassium are added. However, the prerequisite for this is a very pure molybdenum starting material: the purity must be at least 99.97% by weight in total and at least 99.999% by weight in relation to potassium.

Unlike potassium, aluminum does not evaporate during the manufacturing process. The addition of aluminum thus prevents the dispersion of material properties.

This positive property can be achieved by the addition of aluminum, 150-800 ppm by weight; particularly good results are obtained with the addition of 400600 ppm aluminum. In addition, for processing reasons, very small amounts of 5-50 ppm potassium additives are used to control the particle size.

This type of molybdenum material is very suitable for the production of wires used in lamp production, especially for certain types of lamps (PAR lamp, halogen lamp), which are subject to high thermal and mechanical stress. An example is a 300 W PAR light bulb. The element holding the bulb is approx. Made of 125 pm molybdenum wire. Molybdenum was added with 500 ppm aluminum and 15 ppm potassium.

This molybdenum wire has a slightly greater extensibility (Δ 1/1) than the corresponding molybdenum wire fed with 500 ppm cobalt (approximately 20.8%). This is illustrated in the attached figure. Of particular note is the fact that the standard deviation of the wire extensibility constant of aluminum additives is lower than that of cobalt: about 2% compared to the conventional 5% (see figure). Other properties are also preferred over those known in the art. Thus, for example, the recrystallization temperature is approx. 1700 ° C as opposed to 1100 ° C known in the art.

For smaller requirements, other, particularly smaller, dosages may be used. An example of σσε is molybdenum wire fed with 250 ppm aluminum and 15 ppm potassium. Its extensibility constant is approx. 3.5%.

Molybdenum material can be prepared according to the principle of the Coolidge process (cf. Agte / J. Vacek, Wolfram und

HU 210 093 Β

Molybdán, Akademie Verlag, Berlin, 1959, especially Chapter 6).

The starting material used for the production of molybdenum material is 99.97% by weight of MoO ₃ . Aluminum and a small amount of potassium are added to this powdered oxide. The aluminum is preferably introduced in the form Al (NO ₃ ) ₃ . Other unstable aluminum compounds may be considered, e.g. also the application of AIC1 ₃ . In contrast, it is a very stable aluminum compound, e.g. aluminum oxide is inadequate as aluminum cannot be released during further heat treatment.

Potassium is added in the form of its salt, in particular an aqueous solution of potassium silicate.

Subsequent two-stage reduction of molybdenum trioxide is carried out in a known manner in a H ₂ / N ₂ mixture or in H ₂ gas. Preferably, a rotary tube furnace is used instead of a sliding furnace with a boat. MoO _{3 is} reduced through MoO ₂ to Mo at 500-600 ° C (step 1) and 1000-1100 ° C (step 2).

The metal is pressed into a steel die by a hydraulic press to produce the desired ductile material. Sintered in a sliding furnace at low temperature (1700 'C). The sintered bar formed during this process is processed into molybdenum wire by rolling, forging and drawing. For example, this wire can be made into a holding wire or a core wire.

Claims (4)

1. Molybdenum material, in particular for lamp production, characterized in that it contains aluminum and a small amount of 5-50 ppm potassium relative to aluminum, with an aluminum content of 150-800 ppm by weight and a potassium content of (Al + K). less than 10% of the total. Molybdenum material according to claim 1, characterized in that it contains 400-600 ppm aluminum. 3. A process for the production of molybdenum material according to claim 1, characterized in that aluminum is added to the powdered molybdenum trioxide having a purity above 99.97% by weight as an unstable compound, in particular nitrate, and potassium, in particular potassium silicate, as an aqueous salt solution. the molybdenum trioxide is reduced to molybdenum in two steps, the doped molybdenum is pressed into a rod, sintered and the doped molybdenum sintered rod is processed. A method according to claim 3, characterized in that, without direct current supply, about 5 to 10 minutes. It is sintered at a temperature of 1700 C. 5. The method of claim 3, wherein the rod of doped molybdenum is processed into tubes, core wire or holding wire.