JPH04233125A - Getter-strip - Google Patents

Abstract

PURPOSE: To provide a getter strip structure with increased getter capacity by increasing the filling amount of getter powder per unit surface area. CONSTITUTION: A getter strip structure contains pressed getter powder in and on an open net structure carrier strip. The getter powder particles form a coagulated material having strength caused by the intertwinement of the getter particles and the support of the coagulated material by net structure. The getter strip structure is manufactured by continuously rolling the getter powder in and on the net structure carrier strip by gravity powder supply and with a cylindrical rolling machine.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION The present invention relates to the structure of a strip-shaped getter and its manufacturing technology. Getta strip is
It is widely used to remove residual gas from various vacuum tubes or inert gas filling devices, such as high-intensity lamps. This getter is, for example, H2, O2
, H2O, CO, CO2, etc., and thus remove them from the atmosphere where they are gettered.

Most practical strip getters consist of depositing active metal powders on the surface of an inert carrier strip in such a way as to provide a correspondingly high surface area for good getter speed and capacity. ing. The active powder is typically composed of an alloy of Zr, Ti, Cr, Ba, Ca, rare earth elements, U or Th, with alloys with Zr being predominant.

The method utilized to manufacture most commercial getter strips in use today is described in US Pat.
, No. 620,645, No. 3,652,317, No. 3,
No. 856,709 and No. 3,957,304. These patents describe a mechanical pressing technique according to which, by using an intermediate having a hardness between hard getter particles and a soft substrate, relatively hard getter particles are pressed into a softer substrate. It is pressed onto a carrier. In the production of continuous double-sided getter strips, this pressing operation is carried out using a pair of moving rolls that exert a force on a pair of intermediate strips, which in turn press two layers of getter powder together.
Two layers will be pressed onto the surface of a single substrate strip. After rolling, the intermediate strip is removed and discarded, leaving a substrate strip with hard getter particles embedded on both sides thereof.

Getter strip products obtained by the commercially established manufacturing methods described above have certain undesirable characteristics. First and foremost, the resulting strip product has only a thin layer of active getter on each surface, typically only a few grain sizes thick. . This is due to the need for direct physical cold bonding of large numbers of particles to the substrate. This getter layer exhibits an almost two-dimensional nature. It is advantageous to maximize getter capacity by increasing the getter loading per unit length or surface area to produce a more three-dimensional getter structure. Second, the aforementioned manufacturing method requires, for processing,
It relies on a critical chain of relative substrate-getter-intermediate hardness. These chains combine materials with available additives, sometimes requiring a blend of soft and hard getter powders to achieve a higher specific surface area and increase getter capacity. It is a restriction. Third, the relative positioning of the getter powder band, ie, the substrate strip and the intermediate strip, must be done with precise control before the composite feed passes through the rolls or the product is not homogeneous. Fourthly, the intermediate strip used in the above-described method is apparently used only once and is uneconomically disposed of.

[0005]

OBJECTS OF THE INVENTION The present invention obviates many of the aforementioned drawbacks. An improved getter strip is provided, which is manufactured by pressing getter powder into the openings of a preformed strip with an open network, said network comprising: ,
itself and supported by a mesh strip,
This results in three-dimensional agglomeration of the pressed getter powder.

[0006] Therefore, the object of the present invention is to prepare getter powder by
It is an object of the present invention to provide a getter strip that achieves a higher getter loading than is achievable by cold pressing onto the surface of a monolithic substrate.

Another object of the present invention is to provide a getter with greater adhesion of the pressed getter powder resulting from the bonding and entanglement of the getter particles with the soft substrate alone, rather than from the bonding and entanglement of the getter particles with each other.・
It is to provide strips.

Yet another object of the present invention is to obtain a getter powder by directly and vertically rolling said getter powder into and onto a preformed network strip using gravity feeding of the getter powder and step rolls. It is an object of the present invention to provide a convenient method of manufacturing strips.

For a more complete understanding of these and other features and advantages of the present invention, reference is made to the following detailed description and accompanying drawings, as well as the examples.

In the accompanying drawings, the same reference numerals refer to corresponding parts and/or systems throughout the several figures.

[0011]

General Description of the Invention A novel feature of the present invention is a strip with a substantially three-dimensional distribution of active getters. This strip is obtained by rolling or pressing getter powder into and onto a preformed network strip. The resulting structure is shown in cross section in FIG. The main requirement is that the mesh strip 1 be provided with a large number of holes or openings 2. During the production of getter strips, getter powder 3
a, 3b and 3c are the pores of the reticular strip (
3b) and the outside of the central part (3c) are forced into the holes (3a) of the mesh strip. The resulting structure is an agglomerate of porous getter powder 3,
This is substantially retained both by the carrier network 1 and also by the mechanical entanglement of the getter powder itself. This type of getter strip arrangement has a higher getter loading than traditional strip getters prepared by pressing a getter layer onto the surface of a monolithic (non-perforated) substrate. This is to achieve the required amount. Additionally, the entanglement of getter particles through the pores of the network getter strips, in contrast to conventional surface-attached strips, is highly susceptible to getter particle fragmentation during bending, vibration, handling, etc.
This results in a structure with significantly greater resistance. actually,
The getter condensate is mechanically fixed or attached to the network carrier.

For most practical purposes, the manufacture of getter strips in the structure disclosed herein involves applying the powder into and onto the network strip, particularly through the rolling or gradual rolling procedure discussed herein below. dice(
This can be practically achieved by using progressive dies and pressing at room temperature. Although this type of aggregate has good strength for most practical purposes, the strength of getter aggregates derives mostly from mechanical particle entanglement and therefore cold-pressed structures It should be specifically mentioned that , should not be considered completely resistant to crushing and atomization. If greater strength and atomization resistance are desired, as will be appreciated by those skilled in the art, sintering the cold pressed strip at high temperatures creates a true metallurgical bond between the grains. It is also possible to promote this. To minimize damage to the getter condensate, this type of sintering should be performed under vacuum or an inert gas atmosphere. Sintering time and temperature depend on the composition and particle size of the getter powder to be sintered. Typically, times of up to 1 hour and temperatures in the range of 800-1300°C are sufficient for sintering the getter powder.

The preformed open network carrier strip 1 can be constructed in many forms, such as a perforated metal strip, an expanded metal strip or a wire mesh screen, cut into long strips. This type of network strip is immune to the atmosphere to be gettered and to the getter alloy to be pressed into and onto it, either inherently or during any subsequent sintering procedure employed. It can be constructed from any convenient metallurgically compatible metal. For example, the network carrier strip can be formed from stainless steel, copper, iron, plated iron, and the like. This network strip itself should be suitably malleable, allowing it to be slightly elongated during rolling of the getter powder and making it flexible in the final composite getter strip form. . The holes or openings disposed within the network strip to form the open network can be formed by punching, etching, perforating, cutting or weaving. The shape of the holes may be circular, oval, square, rectangular, hexagonal, or any other convenient shape, but the preferred embodiment is circular. The preferred distribution of pores is a hexagonally arranged arrangement, although direct and other arrangements can also be used. Generally, the smaller and more numerous the pores, the better the getter adhesion in the final composite aggregate, but the higher the cost of forming the pores. Preferably, the holes range in diameter from about 0.35 to about 1.0 mm. The area occupied by the pores preferably ranges from about 15 to 60% of the area to be covered by the getter material. The allowable pore packing density decreases as the pore size increases. Preferably, the pore packing density is 0.0.
For 35mm, 150 to 62 per cm2
5 range and for a hole size of 1.0 mm, 1c
It ranges from 20 to 80 per m2. Preferred carrier strip thicknesses are from about 0.05 to about 0.25
ranges from mm to mm. Reticulated strips with high electrical resistance (eg, stainless steel) can activate getters by direct electrical resistance heating.

The preformed mesh strip embodiments described above constitute a single mesh layer, as exemplified by a single perforated strip or a screen cut into a single strip. do. As will be readily appreciated by those skilled in the art, the network strips can be stacked prior to deposition of getter powder and form thicker getter composite strips (to form a multilayer base). In this case, compression can be used. Variations of this type should be considered within the scope of the invention.

The most preferred embodiment of the mesh strip is sheet metal perforated with a large number of holes distributed in a hexagonal array. This arrangement, combined with the powder rolling technique disclosed herein below, results in useful changes in the resulting getter strip. Besides the numerous possibilities, two examples of embodiments for the mesh getter strip manufacture are shown in the plan views of FIGS. 2 and 3. For both of these embodiments, some getter layer 3 is typically present.
is shown removed from the mesh strip 1 to show the number of hexagonally arranged perforations contained therein. In Figure 2, all holes are intended to be filled and covered by getter, and a narrow getter-free margin 4 on both sides is provided by the user to the structure within the volume to which the strip is to be gettered. ,
What remains to be fused, fitted or otherwise attached is shown. FIG. 3 shows a strip in which the two outer rows of holes are not filled with getter, and which can be passed to and through a machine used in an automated manufacturing operation. Continuous getter
It is designed to function as a sprocket to ensure the reliable supply of strips.

A preferred method of manufacturing the network getter strip described above is carried out by rolling the getter powder directly into and onto the open network carrier strip. The inventors successfully modified and implemented this manufacturing method by utilizing the apparatus and method shown in FIG. The network strip 1 is fed via a slit 5 to a powder hopper 6 which is divided into two chambers and which accommodates the getter powder 3 . Both chambers of this hopper are provided with carefully dimensioned slots 7,
This causes the getter powder 3 to flow downward by gravity with a flow having a constant velocity and a well-defined width. The hopper is mounted vertically above the pair of rolls 8. In this roll, getter powder 3 is
From slot 7 to carrier strip 1 and roll surface 8, 8a
As it flows between it, it rotates in the direction shown because it is continuously compressed. The dimensions of the slot 7, the roll speed and the roll spacing are such that there is a continuous compression of the getter powder within the open network carrier strip and a constant getter powder in terms of mass per unit length or unit area. Arrangements are made for charging to take place. The result is an automated, continuous and economical powder rolling method that produces a set getter strip having the structure shown in FIGS. It constitutes.

The rolls 8, 8a used for compacting the getter powder may be conventional cold rolls widely used in rolling metal sheets or strips. To minimize wear, the roll surface should be significantly harder than the getter powder to be compacted. Surface-hardened steel rolls or rolls coated with hardfacing alloys, titanium nitride, boron nitride, etc. can all be used advantageously. It is very useful to control the width of the compressed band by using step rolls as shown in the partial cross-sectional view of FIG. The preferred embodiment uses rolls 8, 8a, which have small steps or lands.
s) 10, which are equal in width to the getter band 3 to be deposited on the reticular network strip 1. In operation, only the getter powder falling between the lands of the two opposing compaction rolls will be compacted into and onto the network strip, resulting in a strictly uniform getter deposition layer. is brought about. Powder that falls outside the land is not compacted and is collected below the rolls for recirculation into the feed hopper.

The present invention is easy to handle for producing condensed getter strips from essentially any getter raw material that can be prepared in powder form. These raw materials include, but are not limited to, the following elements, such as Zr, Ti, Cr, Ba, T, among many other possibilities.
h, V, Nb, Ta, Ca and rare earth elements. In addition to elemental getters, it is also clearly within the intended scope of the invention to include getter powders or alloys, with or without elemental powders mixed therein, intermetallic compounds, and mixtures of the two. It is in. Examples of getter alloys include, but are not limited to, the common and commonly used U.S. Application No. 126,7
Getter Zr-Al or Zr-V disclosed in No. 50
-Fe-Ni-Mn-Al alloy. Examples of getter intermetallic compounds include, but are not limited to:
BaA disclosed in U.S. Patent No. 4,668,424
l4, ZrMna and rare earth element doped ZrNi and Zr2Ni. Examples of mixtures of alloys and elemental powders include, among other possibilities, U.S. Pat.
There is a Zr-Al alloy mixed with Ti disclosed in No. 832. Among other possibilities, examples of mixtures of intermetallic compounds with elemental powders include BaAl4 mixed with Ni.
There are vaporizable getter complexes widely used in the electronic vacuum tube industry.

By adopting the reticular network strip concept inherent in the present invention, the inventors have determined the specific getter loading (speci?
c getter loadings) 40 to 70m
A condensed network strip with g/cm2 was produced. Those skilled in the art will know that such getter charges are commercially available and produced by rolling on monolithic (non-reticulated) carrier strips and as described in U.S. Pat. No. 3,62
No. 0,645, No. 3,652,317, No. 3,856
, 709 and 3,975,304.

The general description of the invention set forth above together with the preferred embodiments precisely described above shall now be presented in a modified form in the following examples.

[0021]

Example I A single piece of stainless steel strip measuring 8 mm wide x 0.1 mm thick x 23 m long is cut with a die along its entire length along a 5.5 mm wide band with a number of holes. Open reticulated network strips were obtained by punching and providing small holes. The holes have a diameter of 0.75 mm and have a density of approximately 66 holes/hole in a hexagonal array.
Punched into cm2. This arrangement corresponds to a hole area of 29.1% relative to the covered band area. This strip was carefully cleaned and fed with getter powder through a powder mill as shown in Figure 4. The getter powder used was obtained by pulverizing an alloy consisting of 16% by weight Al and the remainder Zr, and then dividing it into particles with a particle size ranging from 230 to 140 mesh (63 to 10% by weight).
6 micrometers). The powder flow from the hopper to the rolls was on the order of 0.33 g/sec for each of the two hopper sides. The roll surface was equipped with small lands of 5.5 mm width to precisely control the width of the getter band deposited. The tangential speed of the roll at the compaction (land) surface is 5.7
cm/sec. A piece with a total length of 23 m was successfully roll pressed with getter powder in a single roll pass to produce Figures 1, 2 and 5.
A composite getter strip similar to that shown in Figure 1 was obtained, which contained about 42 mg/c for the final strip length.
It had a getter charge of m. The thickness of the finished strip upon getter deposition was approximately 0.3 mm. The resulting product exhibited resistance to flaking and cracking of the getter layer while producing elasticity and limited plastic bending. CO and H2 getter properties were estimated essentially utilizing standard ASTM test methods for non-evaporable getters as outlined in ASTM Designation F 798-82. A 1 cm test length was taken from the reticular getter strip described above and 84
Activated by direct resistance heating (19 amps) for 5 minutes under vacuum at 0°C, cooled to room temperature, and applied a pressure of 3 content” curve was obtained. After the CO curve achieved near saturation as shown in Figure 6, the same sample was reactivated at 840 °C under vacuum for 5 min, cooled to room temperature, and the corresponding H2 getter curve was determined. This curve is also shown in FIG. For those skilled in the getter technology,
It will be immediately recognized that the data shown in FIG. 6 shows excellent properties for the strip getter and thus clearly demonstrates the fundamental utility of the present invention.

[0022]

Example II Another powder rolling experiment was carried out with all parameters and procedures identical to Example I except for the size of the holes and the density of the holes in the starting perforated carrier strip. In this example, the pore diameter was 0.45 mm and the density was approximately 248 pores/cm2. This arrangement corresponds to a hole area of 39.4% relative to the covered band area. After roll bounding, the resulting composite getter strip had a substantially higher getter loading than that of Example I, 70 mg/cm2. This product also appeared to have qualitatively higher atomization and crush resistance than in Example I. This example shows that the getter loading and mechanical properties of a getter strip according to the invention can be improved by varying the properties of the reticulated network carrier strip.
It shows that it can be changed to your advantage.

[0023]

Example III In this powder rolling experiment, the perforated network strip and rolling parameters were maintained as in Example I. The slight differences were in getter alloy composition and powder particle size range. The getter alloy used was 25.5V-3Fe-1.5Ni-balance Zr by weight, and the getter composition required a relatively low activation temperature and was disclosed in U.S. Patent Application No. 126,750. It was milled into powder using hydrogen milling techniques. Powder size range was 230 to 100 mesh (63 to 130 micrometers). After rolling and bonding, the getter strip had a getter loading of 51 mg/cm2. Getter testing on a 1 cm length of this product was performed in the same manner as Example I, except that the activation conditions were 450° C. for 10 minutes and separate specimens were used for the CO and H2 tests. The results of these tests are shown graphically in FIG. Good getter behavior will be apparent to those skilled in the art. Therefore, the practicality of the present invention is demonstrated when used with low activation temperature getter powders.

It is to be understood that the specific embodiments of the invention illustrated and described herein are intended to be representative only. It should be understood that certain modifications may be made to the invention described above without departing from the clear teachings of the disclosure. Reference should therefore be made to the following claims which determine the full scope of the invention.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a getter strip prepared by rolling getter powder into and onto an apertured network strip.

2 is a plan view of the getter strip shown in FIG. 1 with portions of the getter removed to show how the perforations of the mesh strip are arranged with respect to the extent of the getter; FIG. be.

FIG. 3 is a plan view of a getter strip prepared in such a way that, for certain reasons, the outer rows of perforations of the reticular strip are not filled with getter;

FIG. 4 is a side elevation cross-sectional view showing the powder supply and roll assembly for manufacturing getter strips according to the present invention.

FIG. 5 is a cross-sectional view of a getter strip according to the invention and a step roll used to manufacture it;

FIG. 6: CO at a pressure of 3×10 Torr for a getter strip prepared by using the teachings of the present invention and a getter powder consisting of an alloy of Zr and Al.
and H2 are graphs showing the getter behavior.

FIG. 7 shows a pressure of 3×10− for a getter strip prepared by using the teachings of the present invention and a getter powder consisting of an alloy of Zr, V, Fe, and Ni;
6 is a graph showing the getter behavior of CO and H2 at 6 Torr.

[Explanation of symbols]

1. Network tissue carrier strip 2 holes 3 Porous getter powder 4 Margin 5 Slit 6 Powder hopper 7 Slot 8 roll

Claims (20)

[Claims] 1. The getter powder particles form an aggregate having a strength derived from both the entanglement of the getter particles and the support of the getter aggregate by the network structure.
A composite strip getter structure having getter powder pressed into and onto an open network network carrier strip. 2. A method for manufacturing a getter strip structure according to claim 1, by continuously rolling the getter powder into and onto the open network carrier strip by means of a gravity powder feed and a cylindrical rolling mill. 3. A strip getter structure according to claim 1, wherein the carrier strip is comprised of a porous metal strip. 4. A strip getter structure according to claim 1, wherein the carrier strip is comprised of a wire mesh screen. 5. The strip getter structure of claim 1, sintered at 800-1300°C. 6. A strip getter structure according to claim 3, wherein the carrier strip is prepared from stainless steel mesh. 7. The method of claim 2, wherein the roll includes raised lands having a width equal to the desired width of the getter band deposited on the carrier strip. 8. The strip getter structure of claim 1, which is activatable by electrical resistance heating. 9. The getter powder contains one or more of Ti, Zr, Cr, V, Nb, Ta, Ba, Th, C
The strip getter structure of claim 1, comprising a getter composition selected from the group consisting of a, Al, Ni, Mn, Fe, and one or more rare earth elements. 10. The strip getter structure of claim 9 with an elemental getter composition. 11. The strip getter structure of claim 9 with a getter composition in an alloyed state. 12. The strip getter structure of claim 9 with a getter composition in an intermetallic state. 13. The strip getter structure of claim 9 with a getter composition that is a physical mixture of elemental and alloyed metals. 14. The strip getter structure of claim 9 with a getter composition that is a physical mixture of elemental and intermetallic metals. 15. The getter powder particles are arranged in an open network carrier strip such that the getter powder particles form an agglomerate with strength derived from both the entanglement of the getter particles and the support of the getter agglomerates by the network structure. It has a getter powder pressed thereon, the getter powder being one or more of Ti, Zr, Cr, V, Nb, Ta,
Ba, Th, Ca, Al, Ni, Mn, Fe, and 1
or more rare earth elements, and the getter powder composition is a physical mixture of metals in the form of alloys and intermetallic compounds. 16. The getter powder particles are arranged in an open network carrier strip such that the getter powder particles form an agglomerate with strength derived both from the entanglement of the getter particles and from the support of the getter agglomerates by the network structure. It has a getter powder pressed thereon, the getter powder containing one or more of Ti, Zr, Cr, V, Nb, Ta, B
a, Th, Ca, Al, Ni, Mn, Fe, and one or more rare earth elements, the getter powder composition is a physical mixture of elemental, alloyed, and intermetallic metals. A composite strip getter structure that is 17. One or more of Ti, Zr,
Cr, V, Nb, Ta, Ba, Th, Ca, Al, N
selecting a getter powder from the group consisting of i, Mn, Fe, and one or more rare earth elements; passing the carrier strip continuously through a rolling mill; and as the carrier strip passes through the rolling mill. , using a gravity feeder to deliver the getter powder onto a carrier strip, and sintering the composite structure at a temperature ranging from 800°C to 1300°C, whereby the getter powder is
A composite structure comprising getter powder in and on an open network carrier strip characterized by forming an aggregate with strength derived from both entanglement of the getter particles and support by the carrier strip. manufacturing method. 18. A rolling mill comprising a pair of opposing cylindrical rollers and at least one roller with raised lands spaced apart from each other by a distance equal to the desired width of the band of getter powder. 18. The method according to claim 17, characterized in that: 19. Getter powder particles are disposed within and within an open network network carrier strip such that the getter powder particles form an aggregate with strength derived from both the entanglement of the getter particles and the support of the getter aggregates by the network structure. comprising getter powder pressed thereon, the getter powder comprising: 1
or more Ti, Zr, Cr, V, Nb, T
A composite strip getter structure wherein the getter powder composition is elemental selected from the group consisting of a, Ba, Th, Ca, Al, Ni, Mn, Fe, and one or more rare earth elements. 20. Getter powder particles are disposed within and within an open network network carrier strip such that the getter powder particles form an aggregate with strength derived from both the entanglement of the getter particles and the support of the getter aggregates by the network structure. comprising getter powder pressed thereon, the getter powder comprising: 1
or more Ti, Zr, Cr, V, Nb, T
A composite strip getter structure wherein the getter powder composition is selected from the group consisting of a, Ba, Th, Ca, Al, Ni, Mn, Fe, and one or more rare earth elements and is in the form of an alloy.