Method of direct assembly of a portion of glass structure to a metal element
The method of heating glass and metal above 400°C and differentially cooling them addresses the issue of thermal expansion mismatch, ensuring robust glass-metal bonds without chemical baths, enhancing adhesion and preventing embrittlement.
Patent Information
- Application Number
- FR2023006264
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-06-19
- Publication Date
- 2025-09-26
- Estimated Expiration
- 2043-06-19
AI Technical Summary
Existing glass-metal assembly methods require chemical baths for surface preparation, imposing legal and safety constraints, and do not effectively manage the differing thermal expansion coefficients of glass and metal, leading to weakened adhesion and embrittlement at the junction.
A method involving heating the glass and metal to above 400°C, followed by differentiated cooling, where the metal is cooled faster than the glass, using gas projection or thermal conduction to control thermal contraction and maintain adhesion, without the need for chemical baths.
Ensures strong adhesion and prevents embrittlement by managing thermal contraction, maintaining material interaction and adhesion quality, while eliminating the need for chemical baths.
Smart Images
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Abstract
Description
Title of the invention: Method for direct assembly of a portion of glass structure to a metal element
[0001] The present invention relates to the field of methods for assembling a portion of a glass structure with a metallic element and more particularly to assembly methods which involve different expansion coefficients.
[0002] The assembly of a glass structure with a metal element, in particular by melting one end of the glass onto the metal element, is a conventional, and sometimes even necessary, bonding technique to avoid the presence of a binder as an intermediary between the glass and the metal. This direct assembly also makes it possible to obtain an effective bond of glass to the metal which corresponds to a mechanically resistant seal capable of ensuring perfect sealing at the junction between the two materials. This type of assembly is thus particularly popular for the construction of electrical connectors or vacuum-tight elements required in electronics, in computer systems or even for the production of solar tubes.
[0003] The principle of glass-metal assembly involves in particular heating the end of the glass structure to a temperature higher than its melting point and bringing it into contact with the end of the metal element before it cools. However, the implementation of this technology imposes certain prerequisites such as cleaning the surfaces brought into contact, or decarburizing the metal end intended to participate in the bonding so as to avoid the appearance of bubbles at the glass-metal interface. Similarly, a step of oxidation of the ends intended to be brought into contact so as to improve their adhesion.
[0004] Publication US 6,324,870 proposes a detailed solution involving this principle of glass-metal assembly. One of the necessary, if not essential, steps in the proposed method for producing an effective glass-metal bond is based on an electrolytic polishing operation of the metal end so as to reduce its thickness to a value of the order of 0.01 mm, this operation being carried out in particular in a sulfo-phosphoric solution. However, this solution for producing a glass-metal assembly requires the use of a chemical bath in the preparation of the metal portion of the bond to be made and therefore imposes constraints, both legal and safety-related, for the effective implementation of the proposed method.
[0005] The present invention aims to overcome this drawback by proposing a solution which makes it possible, on the one hand, to avoid a step requiring the use of a chemical bath and, on the other hand, to preserve the qualities of the glass-metal bonds obtained by assembly methods known from the prior art.
[0006] The invention relates to a method for direct assembly of a portion of glass structure to a metallic element comprising different respective expansion coefficients, characterized in that the method comprises: a step of heating the glass portion and the metal element to a temperature above at least 400°C, a step of bringing the glass and the metal element into contact, a step of differentiated cooling of the parts in contact consisting in particular of faster cooling of the metal element compared to the glass portion.
[0007] The invention also relates to a product comprising a junction between a glass structure and a metal element, characterized in that the junction is obtained by an assembly method according to the invention.
[0008] The invention also relates to a device for implementing an assembly method according to the invention, characterized in that the device comprises: a support interface of a glass structure in contact with a metallic element, a cooling mechanism by projecting gas against at least part of the metal element.
[0009] The invention will be better understood from the following description, which relates to the preferred embodiments, given as non-limiting examples, and explained with reference to the appended schematic drawing, in which:
[0010] [Fig-1] represents a schematic illustration of an example of construction of a device for implementing a direct assembly method according to the invention.
[0011] The invention relates to a method for direct assembly of a portion of glass structure 1 to a metallic element 2 comprising different respective expansion coefficients, characterized in that the method comprises: a step of heating the glass portion 1 and the metal element 2 at a temperature above at least 400°C, a step of bringing the glass 1 and the metal element 2 into contact, a step of differentiated cooling of the parts 1, 2 in contact consisting in particular of faster cooling of the metal element 2 compared to the glass portion 1.
[0012] In the context of a glass-metal assembly involving a heating step, it should be remembered that the coefficient of expansion of glass 1 is lower than that of the metal element 2. Also, after heating and bringing the two parts 1, 2 into contact, the contraction phenomenon supported by the metal element 2 is greater than that of the glass at the junction between the two parts 1, 2. This difference in contraction at equivalent temperature then leads to a reduction in the adhesion of the materials to each other and a weakening of the interaction between the materials or their adhesion at the junction of the two parts 1, 2. By involving a differentiated cooling step between the two parts 1, 2 joined together, the assembly method according to the invention makes it possible to ensure control of the contraction phenomena supported by each of the two parts 1, 2. The differentiated cooling of the respective materials of the two parts 1, 2 in contact is carried out in particular by controlling the variation in the respective temperatures of each of the two parts 1, 2.This control jointly makes it possible to manage the respective contraction phenomena supported by the respective materials of the two parts 1, 2 in contact, so that similar, or even identical, contraction phenomena of the materials are able to be obtained at their junctions. The similarity of the contraction of the materials during the differentiated cooling makes it possible to obtain a similar deformation of the materials at the level of their interaction and to limit the embrittlement phenomena at this level. Thus, during the differentiated cooling step, the end of the metal part 2 which has a higher coefficient of expansion is maintained at a lower temperature than that of the glass part 1 which has a lower coefficient of expansion.
[0013] According to an example illustrating a preferred implementation variant of the differentiated cooling step, this step is carried out, on the one hand, up to a temperature of at least 400°C of the glass and, on the other hand, up to a temperature of at least 250°C of the metal. Below these respective temperatures, in particular below a temperature of at least 400°C, the cooling glass deviates from the temperature of its vitrification point and loses the elastic properties provided by heating. Also, the material of the cooling glass is no longer able to adapt to the expansion of the metal so that the impact of differentiated cooling on the interaction and adhesion of the two materials between them is negligible, if not zero. Cooling by contact at room temperature alone is then sufficient.
[0014] It should be noted that the heating step is not limited to 400°C but is capable of being carried out at a temperature higher than the glass transition temperature of the glass, namely 450°C. Thus this heating step is capable of being carried out at a much higher temperature such as of the order of 500°, or even 600°C. Preferably, only glass 1 is heated to such temperatures, in particular when the heating is of the order of 500 or 600°C. Also, when the heating step is carried out at a temperature of the order of 400°C, the cooling differentiated is obtained, on the one hand, by maintaining the temperature of glass 1 above that of metal 2, preferably at a temperature of the order of 400°C and, on the other hand, by accentuating the cooling of metal 2.
[0015] According to an example illustrating another variant of the assembly method of the invention capable of being implemented jointly with the variants detailed above, the differentiated cooling step involves a step of projecting a targeted gas flow at at least part of the surface of the metal element 2. The projection of gas against the metal element 2 makes it possible to carry out cooling by thermal convection at the level of the environment in direct contact with the surface to be cooled. The projected gas then has a temperature lower than that of the surface of the metal element. According to a preferred implementation, the temperature of the projected gas is at most 250°C. The projected gas is likely to be oxygen, nitrogen, a rare gas such as argon or, more simply, natural air.Also preferably, this gas projection is carried out using a mechanism such as a nozzle 4 allowing very specific targeting of an area or the entire surface of the metal element 2 while avoiding a projection of gas against the surface of the glass structure 1. It should be noted that a cooling step involving a projection of gas makes it possible to target an area of the surface of the metal element 2 independently of the presence of a particular relief or specific convolutions at the surface of this metal element 2.
[0016] According to an example illustrating another variant of the assembly method of the invention capable of being implemented jointly with the variants detailed above, the differentiated cooling step involves a step of bringing the single metal element 2 into contact with a cooling element so as to effect cooling by thermal conduction of the metal element 2. This cooling element has a temperature lower than that of the surface of the metal element. According to a preferred implementation, the temperature of the cooling element is at most 250°C. According to a particular example of implementation of this variant of the method of the invention, the cooling element has at least one contact surface of a shape substantially complementary to at least a portion of the surface of the metal element 2 to be cooled.This complementarity of shape makes it possible to operate an optimized thermal interaction between the cooling element and the surface of the metallic element 2. According to another particular example, the cooling element is arranged in the form of a sleeve complementary to the metallic element 2 configured to surround it and cool it. The cooling element is likely to be produced in the form of a structure which integrates. one or more cold accumulators or eutectic blocks. These cold accumulators or eutectic blocks are thus cooled prior to bringing the cooling element into contact with the metal element 2. During the cooling operation, the cold accumulators or eutectic blocks absorb at least part of the heat from the metal element 2. The cooling element is also capable of being produced in the form of a structure which integrates a circulation circuit for a heat transfer fluid arranged to optimize its heat exchanges with the metal element 2 and absorb at least part of its heat.
[0017] According to an example illustrating another variant of the assembly method of the invention capable of being implemented jointly with the variants detailed above, the differentiated cooling step involves a separation of the respective immediate environments of the glass structure 1 and the metal element 2 so as to optimize the absorption of heat at the respective surfaces of the glass structure 1 and the metal element 2. According to an exemplary implementation, this separation of the immediate environments involves a separation means 3 such as an insulating or thermal retention capsule. This separation means is arranged to envelop, at least partially, the glass structure 1 associated with the metal element 2 and thus limit, or even ideally prevent, parasitic cooling of the glass structure 1 by a cooling element dedicated to all or part of the surface of the metal element 2.
[0018] According to an example illustrating another variant of the assembly method of the invention capable of being implemented jointly with the variants detailed above, the differentiated cooling step involves cooling of a part of the glass portion 1 by thermal conduction with the metal element 2 cooled more quickly. The differentiated cooling step occurring after the step of bringing the glass 1 into contact with the metal element 2, the metal element 2 being cooled and at a temperature lower than that of the glass structure 1 is also able to participate in the cooling of this glass structure 1 by a phenomenon of thermal conduction via the interface forming the physical junction between the materials of the two parts 1, 2 in contact.Thus, from a single source of heat absorption directed towards the metal element 2, the glass structure 1 is also able to be cooled.
[0019] According to an example illustrating another variant of the assembly method of the invention capable of being implemented jointly with the previously detailed variants, the method also comprises, prior to the heating step, a step of machining the end of the metal element 2 intended to be in contact with the glass 1, so that this end has a thickness of at most 8 / 100 of a millimeter. The assembly method of the invention thus makes it possible to dispense with a chemical process in the context of a step of thinning the metal element 2 to a thickness of the order of 1 / 100 of a millimeter. Also, the method of the invention is capable of being implemented for the assembly of a thicker metal element 2 or which has not supported machining with a precision of the order of 1 / 100 of a millimeter.
[0020] According to an example illustrating another variant of the assembly method of the invention capable of being implemented jointly with the previously detailed variants, the method comprises a step of selecting at least one stainless steel whose composition comprises a carbon content of less than 0.1% for the production of at least the end of the metal element 2 intended to be in contact with the glass 1. This preliminary selection step makes it possible to carry out a glass-metal assembly which optimizes the quality of the glass-metal junction by limiting the risks of embrittlement under the effect of bubbles linked to a release of CO2 when the end of the metal element 2 is brought into contact with the glass 1. Preferably, the stainless steel selected is a low-carbon steel of type 304L or type 316L.It should be noted that, for these types of low carbon steel, the step of treating the metallic element 2 with decarburization leads to the removal of a limited quantity of carbon.
[0021] The invention also relates to a product comprising a junction between a glass structure 1 and a metal element 2, characterized in that the junction is obtained by an assembly method according to the invention.
[0022] According to an example illustrating an alternative embodiment of the product of the invention, the latter is characterized in that the junction zone between the glass structure 1 and the metal element 2 corresponds to a cylindrical arrangement with a circular section. This particular arrangement of the product certainly allows the production of an electronic connector, but also cooperation by complementarity of shape facilitated by the surface of the metal element 2 or of the glass structure 1 with, respectively, a separation means 3 or a cooling element.
[0023] The invention also relates to a device for implementing an assembly method according to the invention, characterized in that the device comprises: - a support interface for a glass structure 1 in contact with a metal element 2, - a cooling mechanism by projection of gas 4 against at least part of the metal element 2.
[0024] According to an example illustrating an alternative embodiment of the device of the invention, the latter is characterized in that it comprises a separation means 3 such as a insulating or thermal retention capsule capable of enveloping, at least partially, the glass structure 2 associated with the metal element 1. This separation means thus makes it possible to limit, or even ideally to prevent, parasitic cooling of the glass structure 1 by a cooling element dedicated to all or part of the surface of the metal element 2.
[0025] Of course, the invention is not limited to the embodiments described and shown in the attached drawing. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.
Claims
Claims
1. Method for direct assembly of a portion of glass structure (1) to a metal element (2) comprising different respective expansion coefficients, characterized in that the method comprises: - a step of heating the portion of glass (1) and the metal element (2) to a temperature greater than at least 400°C, - a step of bringing the glass (1) and the metal element (2) into contact, - a step of differentiated cooling of the parts in contact and consisting of faster cooling of the metal element (2) compared to the portion of glass (1).
2. Assembly method according to claim 1, characterized in that the differentiated cooling step involves a step of projecting a targeted gas flow at at least part of the surface of the metal element (2).
3. Assembly method according to one of the preceding claims, characterized in that the differentiated cooling step involves a step of bringing the single metal element (2) into contact with a cooling element so as to effect cooling by thermal conduction of the metal element (2).
4. Assembly method according to one of the preceding claims, characterized in that the differentiated cooling step involves cooling of a part of the glass portion (1) by thermal conduction with the metal element (2) cooled more quickly.
5. Assembly method according to one of the preceding claims, characterized in that the method also comprises, prior to the heating step, a step of machining the end of the metal element (2) intended to be in contact with the glass (1), so that this end has a thickness of at most 8 / 100 of a millimeter.
6. Assembly method according to one of the preceding claims, characterized in that the method comprises a step of selecting at least one stainless steel whose composition comprises a carbon content of less than 0.1% for the production of at least the end of the metal element (2) intended to be in contact with the glass (1).
7. Device for implementing an assembly method according to one of claims 1 to 6, characterized in that the device comprises: - a support interface for a glass structure (1) in contact with a metal element (2), - a cooling mechanism by projection of gas (4) against at least part of the metal element (2).
8. Implementation device according to claim 7, characterized in that the device comprises a separation means (3) such as an insulating or thermal retention capsule capable of enveloping, at least partially, the glass structure (1) associated with the metallic element (2).