HU192912B - Method for making gas-catching and gas-composition controlling metal strips /getter strips/ - Google Patents

Abstract

The invention relates to a method for the production of metal strips which bind gas or control the composition of a gas (getter strips), in which the metal(s) employed is (are) melted and the molten metal assumes the form of a metal strip. The method according to the invention can be characterized in that the molten metal(s) is made to flow, under a vacuum or blanketing gas, via one or more nozzles onto a metal surface which is moved at high speed underneath the nozzles and is cooled relative to the melting point of the molten metals, and in that the molten metal solidifies on the metal surface to form a metal strip of a desired thickness and width. The moving metal surface can be the outer surface of a rotating metal cylinder or a metal strip rotating with the outer surface of the metal cylinder.

Description

FIELD OF THE INVENTION The present invention relates to a method for producing gas binding or gas composition controlling metal tapes (getters).

Geters, as it is known, are substances that are capable of absorbing gases. It is commonly used in gas tubes, other vacuum devices, gas discharge tubes, discharge lamps as gas absorbing material. Getters include, in addition to tightly-received getter materials, materials which are capable of releasing components such as getters. mercury, hydrogen, etc., which can be used to control the composition of the gas field.

Getter has a huge literature. Reference is made to U.S. Patent Nos. 3,203,901 and 3,722,976, which are incorporated herein by reference. The former refers to a non-volatile getter and the latter to a mercury delivery getter.

Getters - gas binders - can be divided into two groups: evaporators and so-called mirrorless getters. From now on, we will also deal with metal getters. Whatever the group, it is an important requirement that the getter must be airborne and, for most applications (cathode ray tubes - light sources), be able to withstand high heat demand, often in a reactive gas atmosphere (soldering). In some light sources, the getter must trap unwanted polluting gases in the presence of the desired fill gas, not necessarily noble gas. Occasionally, gas or gas is added to the gas tube. steam components, eg. mercury, hydrogen, halogen.

The getters are air- and air-tight. their soldering resistance is due to their oxide or nitride structure, similarly to stainless noble metals. The condition is that the oxide (nitride, oxide nitride) must have a slightly higher specific volume than the metal from which it is formed. If the volume of the corrosion product is smaller or much larger than that of the metal, the layer will crack, not close. This lock should only occur below a certain temperature for getter, hence the getter cannot be activated. Easy activation and solder resistance are contrary requirements. Therefore, there is no ideal getter. Different users require different layers of protection. From the above point of view a special case is the gettering of hydrogen. Hydrogen can diffuse through a thin barrier layer, especially at elevated temperatures. Hydrogen uptake in most cases results in volumetric growth, fracturing the layer, so hydrogen gettering can be an “autocatalytic process”.

Most of the protective layer is Al, Zr, or ' Ye oxide, therefore, alloys are used in which the structure of the oxide (etc.), despite the alloying, meets the above conditions.

The range of getler materials that can be produced by conventional alloying is limited because it is difficult to prevent the hydrogen-bonding ability from deteriorating. Hydrogen is reversibly absorbed by conventional metal getters. It is known that at a given temperature, the equilibrium pressure H1 formed is proportional to the square of the amount already drawn (the one-atom hydrogen in the metal, the two-atom law outside the metal, the law of mass effect) and the temperature curve shifts steeply to higher values. The equilibrium constants of currently used materials are such that the Ih-gettering ability is lost at best above 400-500 ° C, except in the special case of Y in nib or tantalum.

The available getter materials are usually brittle, and this is a good idea to do with standard technology, since most cases require powder. These powders are either smeared and sintered (which is not always possible) or pressed into coarse powders or pastes. rings. In this compression, sometimes two layers of a material of different properties, e.g. an evaporator (eg Zr-Al) and an evaporator (eg Ba-Al).

Getter materials are expensive compared to starting materials. The reason for this is that in addition to the difficulties in the metallurgy of highly reactive metals, these delicate materials also need to be milled, which requires operations under vacuum or very pure noble gas to avoid an increase in gaseous content, and these dust technology operations are very cumbersome.

Pure metals such as zirconium, tantalum, and titanium that are mechanically machined, dragged, rolled, gettered, are rarely suitable for gettering tasks. Alloys are used in most cases. Alloys suitable for gettering, such as the well-known zirconium-aluminum alloy, are so brittle that they cannot be formed by rolling, drawing. These getter alloys are produced by vacuum metallurgy. The molds are crushed to a powder, preferably in a protective gas, or possibly under a solvent that does not react with the getter material. Where it is not advisable to use material as a powder for gettering tasks, this powder is powder metallurgy! Rings, pastilles, usually by the use of a carrier metal strip, are produced by methods such as extrusion or by simple pressing. Where the web is important to the user, the getter material is applied to the carrier web, generally to the metal edges of the iron group, by rolling or batch pressing.

The above difficulties, especially due to the brittleness, do not make metal strips directly from getter alloys, although they are in great demand. The multistage powder metallurgy methods described above are very cumbersome and costly, precisely because the gas-binding capacity of the getter materials must be maintained during processing. This practically means that all operations must be carried out in a high purity shielding gas or under a suitable solvent.

Our aim is, despite the above difficulties, to produce metal strips of suitable metals, alloys for direct use in as few steps as possible. In order to accomplish this object, we have adapted a known process for processing magnetic materials.

In U.S. Patent No. 905,758, Strange and Pim described in 1908 the principle that a metal strip may be produced by dripping a molten metal jet onto the surface of a rapidly rotating cold metal cylinder. The metal solidifies on the cylinder to a ribbon. However, due to the lack of technical conditions at the time, this procedure was not feasible. It was only decades later that this method began to be used mainly for the production of magnetic materials, not least because the conditions for its realization were understood. (See the corresponding article by Liebermann and Graham, IEEE Transactions on Magnetics, Vol. MAG-12, No.6, Nov. 1976, p. 921-923.)

SUMMARY OF THE INVENTION It has now been found that the metal which may be usefully used for the getter purposes is necessarily highly reactive in the vacuum chamber or in the above process. can be transformed into a metal strip by its use in shielding gas. In addition, unexpected additional advantages have been gained in developing the process, which will be explained in detail in the present invention.

According to the present invention there is provided a process for producing gas binding or gas composition controlling metal strips by melting the metal (s) to be used and converting the molten metal (s) to a metal strip. The process of the present invention is characterized in that the molten metal (s) are flushed under vacuum or shielding gas through one or more nozzles to a metal surface which is moved at high speed under the nozzles to a cold metal surface relative to the melting point of the molten metal.

In the manner we have suggested, it is possible to reduce the difficulties of the conventional process and to produce multilayer materials having properties which cannot be produced by the alloying process. The process involves the use of amorphous metals, so called modifying the process for making metal bottles in accordance with our goals; of course not trying to keep the getter metals from crystallizing. The metal, alloy for the purpose of the getter, is melted, either in a crucible, preferably by induction method, with or without a float, and then poured through the bottom of the crucible, or through a separate nozzle, onto the periphery of a rapidly comes in the form of a belt at a speed corresponding to the circumferential velocity of the cylinder shell. In order to make a multilayer material, several nozzles are used one after the other. In most cases, the bonding of the layers requires that the solidified layer is still warm enough. Therefore, in some cases, it is advisable to use a material with a lower thermal conductivity instead of the copper commonly used in amorphous technology as the material of the rotating cylinder. The temperature of the roller can also be controlled, but in the case of a roller operating at high temperatures, the bearing arrangement may become uncomfortable. The temperature of the layer at the outlet of the second layer also influences the speed of rotation and the distance between the two nozzles. Since the latter is difficult to obtain very small, it is advisable to reduce the speed compared to the amorphous metal technology. Since the materials to be melted are necessarily highly reactive, the melting, casting, solidifying system, and winder, il. the cutting device is housed in a closed, aspirated chamber and is in a vacuum or inert gas during operation. The latter is used when working at a melting temperature with an easily volatile component. In fact, gas filling greatly reduces the evaporation rate. If you get the getter with some gas, eg. hydrogen or nitrogen, these gases or a mixture of noble gas and saturation gas are used instead of noble gas. We will return to this case.

The multi-jet technique can be saved or saved. one layer less can be cast by placing a tape under the nozzle (s). So we start with a single layer. In this way, material or geometry that cannot be produced as described may be used.

The melting chamber is a quartz tube, which is largely covered by eBet, with a die hole (nozzle) in the center. The space is surrounded by an induction coil. It can be used permanently up to 1200 ° C with a shorter life up to 1400-1500 ° C. Aluminum and high aluminum materials attack quartz, in which case carbon black is used. No significant amount of Al-carbide is formed in the short melting time. In the case of rare earth metals, tantalum is preferable, and rare earth metals do not react with tantalum.

In the case of alloys containing a rare earth metal and a tantalum reactive component, floating melting may also be used. A nozzle is needed in this case, either cold copper or warm BN. In the case of cold copper, Al or. high Al content alloys tend to stick.

In case our application requires a powdered getter, we prefer to use a brittle alloy and work with a nozzle. The casting speed and speed are preferably selected so that the strip thickness is in the order of the desired particle size. The tape produced in this way is incomparably easier to grind than a die-casting die. The ribbon can be broken into pieces immediately after it has been cut, facilitated by the transverse periodic scratching of the roll. If this is not enough, the cage placed in the reel-in position will cut it. Grinding can be carried out in a continuous operation with a direct grid connection, for example with a coffee grinder 5-10 thousand rpm. The cylindrical part of the mill is preferably made of titanium sheet by spot welding, the milling rod is also titanium or titanium coated. In this case, it is expedient to operate the system in noble gas, whereby the apertures on the lid carry the desired particle size according to their location, and the system acts as a wind separator. The powder fractions are captured in small cyclones.

The procedure described above can be simplified for most materials. In the case of a very fast rotating cylinder, the material is discharged in the form of a powder jet instead of a belt. However, the particle size is very difficult to influence, and the resulting powder is generally fine, with a few pm average.

More often, when the material is not intended to be used in powder form, it is not bound to the brittle or chilled composition. The tape is used directly or welded to a ring. For higher temperature (or evaporative) geters, which are a large part of the application area, the larger surface area of the powder-pressed body is not an advantage. Multilayer technology, as we will see in the application examples, gives a great deal of design freedom.

In order to facilitate the understanding of the process of the invention, a description is attached to the description which illustrates an exemplary embodiment of the process. The drawing attachment shows

Figure 1 is a schematic diagram of an apparatus for carrying out the process of the invention, a

Fig. 2 is a schematic cross-sectional view of a three-layer gettable tape obtainable by the process of the present invention.

In Fig. 1, 1 - the rotating cooling cylinder, 2 the vibration-free electric motor, 3 - the drive belt, 4,5,6 - the melting crucible, 7,8,9 - the gas line, 10 - the shielding gas connection, 11 - the pipe, 12 the working chamber, 13 - the baffle, 14 - cage reel, 15,16,17 - high frequency coil.

The following describes how, by way of example, a three-layer gettable tape can be produced by the process of the invention.

Into the melting pot 4 was added an alloy of the composition 48Fe-48Ni-4B, to the melting pot 5 there was added mischmetal (a mixture of rare earth containing predominantly Y) and in the melting pot 6 the alloy 15Al-12Y-73Zr. The system is pumped to high vacuum through line 11. A short flush of Ar gas is used through the 7,8,9 gas lines. The system is then pumped again. The system is rotated. The melting crucibles 4,5,6 together with the metals contained in them are ca. Heat to 600-700 ° C. The system is rotated and heated for approx. It is pumped for a further 20 minutes, after which it is flushed through the gas lines 7,8,9 and the shielding gas jet 10 with ca. it is charged at atmospheric pressure to reduce evaporation. With the high-frequency annealing device, the metals in the melting crucibles are melted and then approx. 20-30 ° C above the melting point. Then, by positioning the nozzle of the melting pot 4 and adjusting the pressure of the gas applied to the gas line 7, the blasted metal jets are adjusted so that a 5 mm wide, 0.05 mm thick belt is drawn on the rotating cooling roller 1. Once the metal strip so produced is carried by the cage reel 14, the metal jet is started from the nozzle of the melting crucible 5 so that about 50% of the mischmetal is applied to said strip. 2-2.5 mm wide approx. A 0.005 mm thick strip is deposited. Then, the nozzle of the melting pot 6 is started with the gas line 9 and it is ensured that the outgoing metal layer necessarily covers the mischmetal and is as wide as possible with the base layer.

As an example of implementation, the following options are provided:

a) Casting of self-supporting active layer, eg Zi-Al rare earth layer.

b) Thicker, broader layers can be applied under or over the active layer to provide suitable mechanical properties (bendable, impact-resistant, weldable) and thus to be used for electrode or other plate components (lead-in strips, springs).

c) Two different getter (s) (eg one containing Ba on one side and one without mirror) on the other side can be applied to the substrate or to one side. to produce a combined getter.

d) It is possible to apply an exotherm to the evaporator under the getter or to cover at least part of the drive with heat (eg Ba-Al nickel), possibly with a melting point additive, or with a separate carrier.

e) Can be applied to magnetic material or contacting material with a gas-binding layer, e.g. for hermetically sealed switching devices.

f) The usability limit of a lower-temperature hydrogen bonding getter can be shifted upwards by placing a rare-earth or non-soldering rare-earth metal between the hydrogen (also) gettering layer and the passive or individual gettering carrier.

g) Getter on the substrate side by side or on both sides and additive necessary for the device to be bonded, e.g. a layer of mercury can be applied. In the case of Hg, a strip of mercury alloy is applied to the substrate, the alloy component of which reacts with the substrate or additional coating to prevent absorption. Recovery can be partially destructive, resulting in controlled lower Hg vapor pressures of amalgam systems in saturated vapor systems.

It should be noted that many metals dissolve Hg better at higher temperatures. Systems that can be over-saturated with metal glass technology can be produced. Similarly, alkali metal as well as non-metallic material such as phosphorus, nitrogen and, within certain limits, halogen may be added.

h) Hydrogen may be added by hydrogenation or addition of hydrogen. a hydrogen-containing layer is formed which, upon activation, releases hydrogen and, as a getter, does not absorb it upon cooling, because it undergoes a process of activation during activation. it crystallizes (amorphous Fe or Ni alloys can dissolve many Ηι) or blends with another layer to reduce their H1 uptake. (For example, a rare earth metal dripped in a HI atmosphere into which Cu, Ag, or Ni is doped from the substrate or lid.)

For specific applications above, specific implementation examples are given below:

a) to 10-20% Al, 10-15% rare earth, e.g. mischmetall, Y, La, Ce (other rare earths work similarly, but due to high commodities they are less appropriate), the remaining Zr. The brittleness of this alloy depends on the nitride content of the starting material, particularly Zr and the rare earth oxide. If the material is clean, the tape is quite flexible, but if oxidized, it can be easily ground.

b): Applying the layer of a) to a support layer consisting of Fe + 4% B alloy.

c): Similar to solution b), but with a Fe + 4% B coating on one side and a 44% Al - 56% Ba alloy (BaAU) coating on one side.

d): 48% Fe - 48% Ni - 4% B (poor thermal conductivity) alloy thin Ni 4% B alloy with a BaAl layer. For antimagnetic systems: Cu + 0.5-1% P alloy, Ni + 4%. Alloy B and then BaAl «layer over it. When activated, Ni is partially blended into Cu and partly into Al, and once activated, no ferromagnetic material remains.

e): standard amorphous (spring) magnetic metal material e.g. Fe + 4% B, or Fe +

1-3% Si or Fe + 0.5-3% P alloy with a layer of Alloy according to a). There are two difficulties here: Applying the getter cannot crystallize the substrate, so the getter must be applied to relatively cold metal, which can degrade the bond. A good trade-off can be found if the magnetic material is much thicker than the getter.

The getter cannot be heat activated. The remainder gas of the device to be getted usually contains water, by brewing or soaking. should be activated by glimming. The discharge from the water cleaves H1, which initiates activation as described in the first section.

f): This solution is illustrated in Figure 2, where 18 is the base metal, 19 is the rare earth layer, 20 is the alloy according to a). As an antimagnetic variant, see c). You can also use Ti as the base metal.

g): For Hg, the carrier may be Cu, followed by the Sn amalgam and the getter layer of a). Upon activation, Cu and Sn react with each other. Bronze practically does not absorb mercury. The% composition, activation time (incomplete alloy), and indium additive can be used to control recovery. To release phosphorus, 20% phosphorus must be incorporated into the Cu to remove phosphorus without a copper mirror.

A molten silver halide bar is used to add a halogen element, which remains well-molded, soft and amorphous. For activation, a silver-reacting parent metal, e.g. Sn and Cu can be used.

In order to judge the above, it is worth considering that the properties of suddenly cooled metals may vary greatly from equilibrium. Crystalline materials may contain a metastable phase, and even greater differences than amorphous ones are expected, such as, surprisingly, amorphous Fe (high Fe alloys, non-corrosive), iron is widely used where more expensive nickel or nickel plated materials are common.

Claims (3)

CLAIMS 1. A process for the production of gas binder or gas mixture control metal strips (getter strips), comprising melting the metal (s) to be used and converting the molten metal (s) to a metal strip, characterized in that the molten metal (s) are vacuum or, in a shielding gas, flowed through one or more nozzles at high velocity under the nozzles to a cold metal surface relative to the melting point of the molten metal and solidified to a metal strip of the desired width and thickness. A process according to claim 1, characterized in that the molten metal (s) is fed to the periphery of a metal cylinder rotating at high peripheral speed. 3. A method according to claim 2, characterized in that the high peripheral speed A metal strip is applied to the circumference of the -511 rotating metal cylinder and the molten metal (s) is fed to the surface of the high speed metal strip rotating with the metal cylinder.