DE102012106273A1 - Producing vacuum-tight connection between materials such as metal or ceramic and glass or glass ceramic comprises coating material with oxide layer, and enameling connection portion of material glass winding - Google Patents

Abstract

The method comprises coating a material with an oxide layer, enameling a connection portion of a material glass winding, and applying a coating made of slurry, paste, suspension of glass powder and alcohol, water and binder on the connection portion of the material. The material connection has a ring or cap shape. A grain size of the glass powder is 20-40 mu m. The glass includes transition glasses, glass solder or glass ceramic, and has a concentration of 3-4 x 10 -> 6> K -> 1>. The method further comprises heating the material by an oven, by lasers or flame. The method comprises coating a material with an oxide layer, enameling a connection portion of a material glass winding, and applying a coating made of slurry, paste, suspension of glass powder and alcohol, water and binder on the connection portion of the material. The material connection has a ring or cap shape. A grain size of the glass powder is 20-40 mu m. The glass includes transition glasses, glass solder or glass ceramic, and has a concentration of 3-4x 10 -> 6> K -> 1>. The method further comprises heating the material by an oven, by lasers or flame, cooling the material by supplying hydrogen, nitrogen, nitrogen-hydrogen mixture, protective gas, noble gas or a gaseous mixture. An enamel layer has a thickness of 0.1-0.2 mm. The thermal coefficient of the material is 18x 10 -> 4> k -> 1> at a temperature of 500[deg] C.

Description

The invention relates to a method for producing a high-vacuum-tight connection between a material, in particular metal or ceramic, and glass or glass ceramic, in particular of an element with a closed vacuum chamber.

State of the art

Particularly in thermal solar technology, the highest longevity and thermal shock resistance (TWB) of the products are being met with ever-higher and more extreme demands on high vacuum-compatible glass-metal joints. In addition, techniques are required that are both easy to automate and, on the other hand, reproducible and manageable even under difficult conditions in so-called emerging countries.

The production of parabolic trough receivers (CSP, "power from the desert") is a technology that has already been awarded the German Future Prize in recent years.

The two key technologies in addition to high-temperature-resistant absorber layers are the production of suitable high-vacuum-tight glass-metal compounds.

It is known to close the end of the glass tube with a ring-shaped or cap-shaped glass-metal connection vacuum-tight. So far, the glass is applied directly to the smelting metal (stainless steel, copper or Einschmelzlegierungen, such as Kovar). Kovar is today the most widely used metallic material for technical "tempered glass" blends. (The pretreatment steps required by the prior art, mechanical processing, degreasing, pickling, electrolytic polishing, decarbonization, degassing, coating, oxidation of fused metals, will not be discussed here.)

To bridge the expansion differences between glass and metal, a method known from X-ray tube technology of so-called adapted glass-metal compounds is used. Here, a metal with a low thermal expansion coefficient (AK) is first melted into a glass with the same or similar AK. At this a number of intermediate glasses with each decreasing AKen can be melted.

For example, Schott 8250, 8245, 8447 or: 8448, 8449, 8447, 8330 or comparable glasses from other manufacturers are used as melting, transition and intermediate glasses with graduated expansion behavior. In addition to the poor hydrolytic, corrosion and acid resistance of intermediate glasses, a high, costly manufacturing effort is required to produce such multistage transitions to a durable borosilicate glass tube (e.g., Schott 8330). In addition, such intermediate glasses are very expensive and are not offered / manufactured in dimensions greater than 100mm outer diameter.

All these factors stand in the way of both industrial automation and deployment in emerging markets.

Known from the DE 10 2004 008559 B9 (respectively. US 2005/0181925 A1 ) is a modified glass-metal compound process involving the use of a customized, largely barium and iron oxide-free special glass. Here, a metal with a low AK, preferably Kovar without cutting edge molding, ie, without material reduction in the glazing directly into a special glass (eg Schott 8800) with the same or approximately the same coefficient of expansion melted, whose thermal expansion was raised in the region of the metal or is adjusted ".

The disadvantage here is the relatively high coefficient of thermal expansion of the glass in the range 5.5 × 10 ^-6 K ^-1 and its compared to borosilicate 3.3 higher sensitivity to thermal cycling, which are known to be extreme in the solar thermal range. Also disadvantageous is the availability of the glass, which is not given for market tactical reasons. Another disadvantage is the use of unnecessarily strong metal rings or large and relatively expensive Kovar material quantities, as well as the improved heat conduction, which is adversely affected by the higher material cross-section, into the glass, which is relatively sensitive to temperature changes. Another disadvantage is that in conventional thermal manufacturing processes a metal ring side (usually inside) is time-delayed wetted with the glass, which can lead to different inhomogeneous oxide layer thicknesses. A disadvantage of this method is further that a pre-oxidized or still unoxidized unprotected Kovarring is exposed in advance of general pollution and, in the course of melting, a difficult to control oxidation, if necessary, by an uneven, possibly highly contaminating flame atmosphere. This can lead to a negative influence on the oxide layer and thus to the reduction of the actual sealing surface and thus make the reliability of this connection in question.

Known in the prior art are also methods of unmatched glass Metal compounds, according to which a metal with a higher elongation of about 15 to 18 × 10 ^-6 K ^-1 (copper, preferably stainless steel ...) is provided with a very thin sharpened glazing edge. This metal cutting edge is then melted into a temperature change resistant glass with considerably lower thermal expansion of eg 3 to 4 × 10 ^-6 K ^-1 .

The expected during operation thermal and mechanical loads are intercepted by elastic and plastic deformation of the expansion zone (metal cutting edge). The metal used preferably has a low thermal conductivity. A disadvantage of this connection is the mech. Sensitivity of the very thin cutting edges, the difficult industrial automation or the high demands that make the production of this compound (oxidation, coating, Vorbewicklung) both on the glass technical expertise, as well as the craftsmanship. The disadvantage here is that in conventional thermal manufacturing processes a cutting side (meisst inside) is only time-delayed wetted with the glass, which can lead to different, inhomogeneous and defective oxide film thicknesses. It is also disadvantageous that the thermal stresses that occur primarily during production, as well as the mechanical loads occurring during later operation of solar thermal receivers and vacuum tube collectors, can lead to a failure of these very thin and sensitive connections. Such unmatched compounds are for example in the US 1,294,466 or the US 6,324,870 B described.

task

When producing glass-metal compounds for the solar thermal range, the type of refractory metal used is preferably the unrestricted glass type borosilicate glass (3.3). Kovar is particularly well suited to the curved expansion characteristics of these glasses. The object and purpose of the present invention is to find in a preferred embodiment, based on the proven, safe oxide compound of Kovar and 3.3 Borosilicate glass commercially available, high vacuum-tight, unmatched glass-metal joining technology, based on a robust method, the production high vacuum-sealed glass-metal connections for the production of solar receivers, vacuum tube collectors and many other products.

The task here is to keep the thermal expansion coefficients of the connection as low as possible with regard to the subsequent thermal stress.

The aim of the invention is also to find an unconventional method that allows the use of such a technique in emerging countries with lower glass technology training level and with conventional production technology.

In addition, and on the other hand, it was also a goal to find a technology that allows the leading companies in high-tech industrialized countries, in turn, the products mentioned with innovative advanced materials and joining techniques (laser, HF, microwave ....) free from contaminating, outdated Flame processes, qualitatively high-quality, without separate evacuation process, fully automatable and without a necessary for evacuation pump nozzle, for example, in a vacuum chamber system or under protective gas or inert gas atmosphere eg to produce an "element with a hermetically sealed vacuum chamber" or a vacuum insulating glass ( DE 101 38 277 ). Another goal is the use of material combinations with the lowest possible thermal expansion coefficient.

Solution of the task

To achieve the described object leads that a connection region of the material is cut enclosing both sides enamelled / glassed.

Double-sided enamelled Kovar cutting edge treatment:

The solution is a direct transition and inter-glass free bonding process for unmatched glass-to-metal joints. These are the production of a robust component based on a controllable intermediate step with a double-sided thin embossing in a tapered, precoated / pre-oxidized connection region. This does not require fine tuning of the expansion coefficients of glass and metal. It does without the traditional glass pre-lapping of the metal cutting edge and also allows manufacturers in emerging countries with inferior glass tube quality to greatly differing glass tube tolerances solar parabolic trough receivers, solar vacuum tube collectors, vacuum flat plate collectors, vacuum insulated glass, X-ray air collectors and to manufacture all forms of vacuum tubes (advantageously as direct Kovar-3.3 borosilicate glass compounds) in the highest possible quality and highest thermal capacity.

All known in the solar thermal field conventional connection systems especially for the production of the above solar receivers and vacuum tube collectors use combinations of materials higher elongation and are therefore in In view of their thermal shock resistance more vulnerable, which can have a fatal effect for the above-mentioned products under high thermal cycling.

In contrast to unmatched stainless steel or copper compounds according to the prior art, in a tapered, enamelled Kovarschneide the strain zone of the cutting area because of their compared to other Einschmelzlegierungen significantly lower thermal expansion coefficient - also in comparison to enamel and cladding glass - much stronger and thus more robust, ie mechanically stable, produced.

A kovar cutting edge can also be made with a different pitch and need not be as thin, sharp and tightly tolerated as e.g. Copper or stainless steel cutting.

In addition, the oxide layer of the kovar compound, which is protected on both sides by the embossing / enamelling, ensures the best possible vacuum tightness.

In contrast to Housekeepertechnik ( US 1,294,466 ) and related, non-adapted techniques, the transition of the wacky / crushed expansion zone to the normal material thickness of the band, ring or cap-shaped material is preferably formed not sharp as an angle, but as a rounding with radius. In contrast to known forms of housekeeping technology, the pre-oxidized and enamelled cutting edge is not pre-wound with a glass.

The difference to adapted glass-metal connection forms (eg Schott, Narva ...) consists in the material rejuvenation / the Schneidanformung, as well as the possibility of preserving the by a previous furnace process precisely controllable and reproducible oxidation of the Kovars (metal), resulting in a Consistent quality of the oxide layer leads - and the intermediate step of enameling.

By "enameling" is meant glazing / tempering preferably by means of a glass powder on the joining partner metal or ceramic, which preferably consists of the same glass as the cladding glass tube to be clipped.

Likewise, and sometimes in an advantageous manner (especially in connection partners with particularly widely spaced expansion coefficients), for this purpose, a glass, Glaspulver-, glass powder mixture, a transition or intermediate glass, a glass solder or a coordinated sequence of such glazings can be used with respect to their thermal expansion coefficient between the connection partners glass jacket tube and the material metal (or the ceramic) are.

Thus, the process according to the invention is by no means bound to Kovar and 3.3 borosilicate glass, but opens up a wide variety of possible variations with regard to other glasses, transition glasses, intermediate glasses, glass solders and other metals, alloys and ceramics.

The application of the glass powder coating required for emplacement (enamelling) takes place, for example. in that a slurry / emulsion / suspension of glass powder and e.g. Alcohol, water, binder ... and this is applied to the pre-oxidized connection area of the cutting edge. This can be done by brushing, dipping, spraying (if necessary with mask) or a sequence of these process techniques)

Other application methods such as dispensing, plasma and forming processes are also possible. The viscosity of the glass or the suspension depends on the application method.

The material (eg metal ring) with the dried glass powder coating applied in the pre-oxidized connection region is heated and melted down (enameled) after any binder burnout in the atmosphere (advantageously under H ₂ , N ₂ or under protective gas) over the transformation region of the relevant glass.

The glaze "enamel" ensures the adhesion between metal and glass. The metal oxide dissolved in the glass acts like an intermediate glass in which the oxide content decreases. The sealing function takes over the oxide layer. The enamel protects the oxide layer / adhesive layer from contamination and difficult-to-control actions such as harmful flame gases. The thus preserved oxide layer can not change adversely before, during and after further processing.

The enamel thus shuts off unfavorable dangers, such as contamination, (H ₂ O incorporation) and uncontrolled oxidation, even before the actual attachment / melting to the enveloping glass tube.

In addition to the danger of harmful flame gases, the enameling also eliminates the risk of uneven oxidation between the inside and the outside of the double-sided glass fusion.

With the solution mentioned and in each case suitable oxide layers, adhesive layers and cutting geometries, the use of a variety of Metals and glass melts, such as borated copper, stainless steel, etc., possible. Even material pairings of higher elongation, such as Dilaton 51 with AR, soda-lime or float glass in the expansion range 8-10 × 10 ^-6 K ^-1 , are possible.

With ceramic and glass-ceramic material combinations (e.g., sintered glass ceramics and glass-ceramic composites), compounds with extremely low AK can be produced.

The possibly very thin cutting edge, depending on the particular material selection and connection geometry, is protected both mechanically and in particular in flame processes under the atmosphere from overheating (burning), from uncontrolled non-uniform oxidation and, in particular, from overoxidation in the thinnest cutting region through the enamel. Due to this protection, the susceptibility to interference during the subsequent attachment of the enveloping glass tube is significantly lower than without the enamel protective coating. The joining process to the cladding tube is thus significantly simplified, the quality of the product is better and more reproducible.

The intermediate step of controlled oxidation and enameling also allows quality control of the intermediate product of the finished glass-metal compound prior to the actual addition / melting of the cladding tube, which significantly reduces rejects and losses.

The controlled pre-oxidation (in the oven) allows a simple and uniform homogeneous oxide layer structure with regard to its subsequent sealing function.

The following on this oxide layer 0.01mm to 1mm thick (advantageously 0.1mm to 0.2mm thick) enamelling allows the required simple, straightforward, double-sided, Schneidbereichsumfassende Beglaung.

Enamelling permanently preserves the oxide layer under the enamel, which is crucial for the vacuum-tightness, thus guaranteeing the safe presence and effectiveness of two (!) Effective sealing surfaces with exactly the same, identical and controlled-optimized degree of oxidation.

The enamelling allows a variable shape and width of Glasanschmelzung between the inside and outside of the material, whereby tensile and compressive stresses can be absorbed by the glass in an advantageous manner.

The produced by the enamelling, glassed Kovar or metal rings can be stored for any length of time and are suitable for mass production, even under different, both manufacturing demanding and simplest production conditions.

The further processing in Glaszugeprozess the actual connection with the glass tube can then be completely uncomplicated and uncritical, using all joining methods and under vacuum or under protective or inert gas as a simple glass-glass compound, running.

So far there is no glass-metal compound combination in the solar thermal field with comparably advantageous-low thermal expansion coefficients and with a comparably robust, high thermal shock resistance. An elaborate subsequent annealing is no longer absolutely necessary.

In addition, the cutting-related material reduction of the material advantageously also has an effect on the already insensitive 3.3 borosilicate glass with regard to the resulting reduced heat conduction.

The somewhat increased effort for the described production of the component (cutting edge shaping, controlled pre-oxidation and double-sided enamelling) is justified by the given inventive advantages for high-quality products.

How thin the cutting edge must be depends on the material geometry as well as the choice of material (type of metal as well as the type of glass of the enamel or the cladding tube to be attached). Vorteihafterweise should be the enamelled cutting edge thickness in 1mm distance from the cutting edge between 0.01mm and 0.49mm.

For cutting thicknesses greater than 0.2 mm, the tapered edge of the material wrapped around the glass should have a radius of 0.1 mm to avoid tensions.

Materials to be protected (metals, alloys and ceramics) preferably have a thermal elongation of less than 18 × 10 ^-6 K ^-1 , preferably in the range of 4 to 6 × 10 ^-6 K ^-1 (Kovar 5.5), but also in addition to the known melt-in alloys Stainless steel and copper.

The invention preferably relates to glasses in the glass elongation range of less than 10 × 10 ^-6 K ^-1 , advantageously in the range of commercially available borosilicate glasses between 3 × 4 × 10 ^-6 K ^-1 (3.3). However, it also refers to the aforementioned use of intermediate glasses, transition glasses, glass solders and glass ceramics (possibly also in the form of glass powder or enamel), in particular and advantageously on such intermediate glasses, transition glasses, glass solders, glass ceramics and glass powder mixtures whose thermal coefficient of linear expansion lies between that of the metal and that of the glass tube to be joined.

Apart from the protective effect of Emaills is the addition / melting of a pre-glazed enameled cutting edge to a glass tube in addition to the classic flame method of atmosphere also by laser, HF or microwave under protective or inert gas or in a vacuum possible, which in terms of DE 101 38 277 opens up innovative possibilities for the production of receivers and vacuum tubes (without the weak point of a pumping gel). Various, sometimes complex manufacturing processes, such as joining / fusing, heating and evacuation can be carried out in a single operation.

Advantages of the mentioned technique:

• - Maximum independence of the type of glass used and quality (monopoly to glass 8800R);
• - Maximum independence with regard to the types of metal and alloy used and ceramics;
• - Facilitating various new glass technology "high-tech joining processes" in vacuum under protective and inert gas (laser, HF, microwave);
• By the "enamel" an uncontrolled oxidation e.g. the kovar or metal prevented;
• - Already "enameled" metal or Kovar rings are as a component completely insensitive to contamination and unlimited storage. (conventional unembellished ones are highly sensitive here);
• The protective enamelling prevents over- or under-oxidation or corrosion even during further processing as described, for example, in US Pat. occurs in conventional flame atmospheres;
• - The enamel ensures the adhesion between metal and glass. The metal oxide dissolved in the glass acts like an intermediate glass in which the oxide content decreases;
• - Also copper, stainless steel, iron, and Einschmelzlegierungen are possible, each with a suitable oxide layer structure;
• - The compound is characterized by the highest vacuum tightness and can be processed in a robust manner as a glass-glass compound;
• - The compound is particularly stable (especially when using materials with lowest thermal expansion coefficients such as Kovar and borosilicate glass 3.3) because of their outstanding thermal shock resistance TWB, so they do not have to be post-annealed;
• All known, conventional connection systems, in particular for the production of solar receivers and vacuum tube collectors, use material combinations of higher elongation and are therefore more susceptible to their TWB, which can have a fatal effect for solar parabolic trough receivers, vacuum tube collectors, thermal solar collectors etc. under high thermal load ;
• - With the above-mentioned high-vacuum-tight connection, temperature changes beyond 500 ° C are easily possible.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102004008559 B9 [0009]
• US 2005/0181925 A1 [0009]
• US 1294466 [0012, 0023]
• US 6324870 B [0012]
• DE 10138277 [0016, 0051]

Claims (31)

A method for producing a high-vacuum-tight connection between a material, in particular metal or ceramic, and glass or glass ceramic, in particular an element with a closed vacuum space, characterized in that a connection region of the material is enamelled (pre-glazed). A method according to claim 1, characterized in that the material is coated before enamelling / provided with oxide layer A method according to claim 1 or 2, characterized in that a slurry / paste / suspension of glass powder and, for example, alcohol, water, binder or the like. and this is applied to the pre-oxidized (coated) connection area of the material. Method according to at least one of claims 1-3, characterized in that the material is band, ring or cap-shaped. A method according to claim 3 or 4, characterized in that the grain size of the glass powder (paste) is less than 100μm, (advantageously in the range between 20 and 40μm). Method according to at least one of claims 1-5, characterized in that it is a double-sided enamel coating without glass wadding or bead with a homogeneous oxidation degree identical on both sides. Method according to at least one of claims 1-6, characterized in that the same glass is used for the glass powder as for the glass tube to be attached. Method according to at least one of claims 1-6, characterized in that another type of glass, such as a transitional glass, intermediate glass solder glass or glass ceramic, is applied to the connection region. Method according to at least one of Claims 1-6, characterized in that a glass (glass powder mixture, Kovar glass, glass solder, transition glass, intermediate glass or the like) is used / applied with a region of expansion between the material and the enveloping glass tube to be applied. Method according to at least one of claims 1-9, characterized in that the region between the material and the cladding glass tube is provided with a gradual succession of glasses with respect to the glass expansion properties. Method according to at least one of claims 1-10, characterized in that the material (with the applied glass) is heated. A method according to claim 11, characterized in that the material (with the applied glass) is heated in the oven, by laser, high frequency or at the flame on the transformation temperature of the applied glass. Method according to at least one of the preceding claims, characterized in that the material is heated with the applied glass under H ₂ , N ₂ , forming gas, inert gas, inert gas or a gas mixture and / or cooled. Method according to at least one of the preceding claims, characterized in that the enameled material is applied after enamelling with one of the glasses mentioned in claims 3-9 glasses / wound. Method according to at least one of the preceding claims, characterized in that the coefficient of thermal expansion of the respective one of the glasses is less than 10 × 10 ^-6 K ^-1 , preferably in the range of commercially available borosilicate glasses between 3 and 4 × 10 ^-6 K ^-1 . Method according to at least one of the preceding claims, characterized in that the double-sided cross-cutting enamel layer is 0.01 to 1 mm (preferably 0.1 to 0.2 mm) thick. Method according to at least one of the preceding claims, characterized in that the enamelling takes place in several stages until the desired enamel strength or glass sequence is reached. Method according to at least one of the preceding claims, characterized in that the enamelled edge-encompassing connection region of the cutting edge, ie the width of the glass coating outside and inside is the same width. Method according to at least one of the preceding claims, characterized in that the enamelled edge-encompassing connection region of the cutting edge, ie the width of the glass coating is shorter outside than inside (preferably outside to 5 mm, inside to 7 mm). Method according to at least one of the preceding claims, characterized in that the material consists of a metal, preferably a Einschmelzlegierung NiCo 2918 metal material of the group no.1.3981 of DIN 17745 is. Composition (mass fractions in%): 28-30 Ni, 16-18 Co, up to 0.05 C (preferably up to 0.01 C), remainder Fe. Method according to at least one of the preceding claims, characterized in that the material consists of NiFe, CrFe, CrFeCo, a chromium-nickel-iron alloy, a so-called chromium nickel or stainless steel eg V2A, V4A, or US type 302, 303 , 304, 304L, 321 ... exists. Method according to at least one of the preceding claims, characterized in that the material before the enameling is vacuum-sealed connected to another material or plated with another material. Method according to at least one of the preceding claims, characterized in that the material is annealed in a furnace, degassed and preoxidized under controlled time-temperature conditions. Method according to at least one of the preceding claims, characterized in that the material is tapered and optionally formed into a cutting edge. Method according to at least one of the preceding claims, characterized in that the material towards the glass connection zone has a taper (cutting edge) whose pitch is less than 10 ° (advantageously 1 °). Method according to at least one of the preceding claims, characterized in that the gradient or expansion region, preferably of a stainless steel cutting edge, can be interrupted or set back by a further undercut. Method according to at least one of the preceding claims, characterized in that the cutting edge thickness is in the distance of 1 mm from the edge of the cutting edge between 0.01 mm and 0.49 mm. Method according to at least one of the preceding claims, characterized in that the transition between the original material thickness and the tapered expansion zone of the material (for comprehensively glazed / enamelled cutting edge out) is not sharp as an angle, but as a rounded radius formed. Method according to at least one of the preceding claims, characterized in that the thermal elongation of the material (the metals and alloys and ceramics) in the range 20-500 ° C, preferably less than 18 × 10 ^-6 K ^-1 and preferably in the range 4 to 6 × 10 ^-6 K ^-1 , lies. Method according to at least one of the preceding claims, characterized in that incorporating / using a described material, an element with a sealed vacuum chamber or a solar receiver, a vacuum tube collector, a vacuum flat collector or a vacuum insulating glass is produced. Method according to at least one of the preceding claims, characterized in that an element is produced by laser, HF or microwave under protective or inert gas or in vacuum or during evacuation (without the weak point of a filling or pumping device (a pumping gel).