Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B30—PRESSES
  • B30B—PRESSES IN GENERAL
  • B30B11/00—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses
  • B30B11/001—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses using a flexible element, e.g. diaphragm, urged by fluid pressure; Isostatic presses
  • B30B11/002—Isostatic press chambers; Press stands therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
  • B23K20/02—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating by means of a press ; Diffusion bonding
  • B23K20/021—Isostatic pressure welding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
  • B23K20/02—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating by means of a press ; Diffusion bonding
  • B23K20/023—Thermo-compression bonding
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B37/00—Joining burned ceramic articles with other burned ceramic articles or other articles by heating
  • C04B37/02—Joining burned ceramic articles with other burned ceramic articles or other articles by heating with metallic articles
  • C04B37/021—Joining burned ceramic articles with other burned ceramic articles or other articles by heating with metallic articles in a direct manner, e.g. direct copper bonding [DCB]
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/02—Header boxes; End plates
  • F28F9/0219—Arrangements for sealing end plates into casing or header box; Header box sub-elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/04—Tubular or hollow articles
  • B23K2101/06—Tubes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/04—Tubular or hollow articles
  • B23K2101/14—Heat exchangers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/08—Non-ferrous metals or alloys
  • B23K2103/12—Copper or alloys thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/18—Dissimilar materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/18—Dissimilar materials
  • B23K2103/22—Ferrous alloys and copper or alloys thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
  • B23K2103/52—Ceramics
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2311/00—Metals, their alloys or their compounds
  • B32B2311/12—Copper
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
  • C04B2237/30—Composition of layers of ceramic laminates or of ceramic or metallic articles to be joined by heating, e.g. Si substrates
  • C04B2237/32—Ceramic
  • C04B2237/38—Fiber or whisker reinforced
  • C04B2237/385—Carbon or carbon composite
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
  • C04B2237/30—Composition of layers of ceramic laminates or of ceramic or metallic articles to be joined by heating, e.g. Si substrates
  • C04B2237/40—Metallic
  • C04B2237/407—Copper
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
  • F28F19/02—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings

Definitions

• the present invention relates to a device for the construction of heat exchanger elements provided with protection materials.
• it relates to a device for obtaining a junction between at least two elements to be joined; ceramic
• divertors are conduction heat exchangers apt to transfer heat from the plasma to a coolant which flows in a metallic tube internal to the divertor itself.
• the divertor of the Tokamak reactor therefore is the component under the greatest thermal stresses, with very high heat flows and specifically in the order of 20 MW/m 2 . Therefore, the aforesaid metallic tube must be protected against direct contact with plasma by means of an outer coating made of refractory ceramic material such as graphite fibre composites (CFC).
• CFC graphite fibre composites
• divertors are generally divided in two areas: in a first area, where a higher heat flow is expected, the metallic tube is protected by the Carbon Fibre Composite (CFC), whilst in a second area, in which a lower heat flow is expected, the tube is protected by blocks or single-piece blocks of tungsten (W).
• CFC Carbon Fibre Composite
• W tungsten
• junction systems used for the applications described above generally provide for the injection of a pressurised fluid, such as to increase the pressure exerted by the metallic surface on the corresponding coupling surface of the ceramic (or metallic) material, so they are intimately in contact with each other.
• junctions between metallic components also has several problems, in particular when the junction has to meet highly strict qualitative requirements.
• Other sample cases of particularly burdensome welds are represented by tungsten-copper connections in thermo-technical applications at high temperatures, as stated previously, where, in addition to the poor mutual wettability of the metals, there is also the need to obtain a junction that does not constituted a thermal barrier.
• Another example is constituted by connections between metals, such as aluminium-aluminium, aluminium-iron, aluminium-steel, which easily develop surface oxides and can make the weld less effective than required.
• metals such as aluminium-aluminium, aluminium-iron, aluminium-steel
• aluminium-aluminium finned tubes are required in numerous thermo-technical applications to exploit the high thermal conductivity of aluminium, but they have the limitation of the heat barrier between fin and tube.
• a junction system that has been used for the applications described above is the so-called Hot Isostatic Pressing (HIP) Diffusion Bonding.
• HIP Hot Isostatic Pressing
• a tubular component is fitted with fins keyed on its outer surface according to the following operating procedures: enclosing the bodies to be welded in a metallic container that keeps them in position and that has to transmit external pressure; placing the metallic container in an autoclave at high pressures and temperature (pressure in the order of 1000 bar and temperatures ranging between 500 0 C and 2000 0 C); separating the piece obtained from the metallic container, which is often deformed by isostatic pressure.
• the work processes for separating piece and container may cause the piece to be damaged and during the execution of the weld it is not possible to monitor the process parameters (pressure and temperature, local deformation), because of the barrier constituted by the autoclave.
• said procedure is generally indicated for obtaining metal/metal junctions, but it has several drawbacks when it is necessary to obtain ceramic/metal junctions where the protection material has low mechanical strength.
• the junction systems employed for this type of applications have additional and greater drawbacks when it comes to effecting mixed junctions of composite materials with part of the protection material being ceramic and part metallic, with additional difficulties when the junctions are for the construction of composite materials and with internal metallic element, having curvilinear longitudinal geometry (e.g.: a tube).
• the technical problem constituting the basis for the present invention is to provide a device for diffusion bonding that enables to overcome the drawbacks mentioned with reference to the prior art.
• the present invention provides some considerable advantages.
• the main advantage of the device according to the present invention is that it enables to obtain a reusable device to achieve a junction between two or more elements to be joined, even with different shapes and dimensions, which can be heated with any means and in which it is possible to exercise a controlled pressure.
• An additional advantage of the device is that it enables to construct components that entail the obtainment of junctions between material with low mechanical strength and metal, such as ceramic/metal junctions.
• FIG. 1 shows a schematic view, in longitudinal section, of the device according to the present invention
• Figure IA shows an enlarged detail of the device of Figure 1;
• FIG. 2 shows a partially sectioned perspective view of a device according to the present invention
• FIG. 3 shows an exploded perspective view of the containment means with related elements to be joined of the device according to a preferred embodiment
• Figures 3A and 3B respectively show the assembled containment means of Figure 3 and a variant of said assembled containment means relating to elements to be joined having a different geometry, according to the present invention
• FIG. 4 schematically shows a step of the method for using the device in Figure 1 ;
• FIG. 5 shows the device of Figure 1 in a step of said method.
• the embodiment example of the device described below shall be illustrated within the context of a preferred application thereof, i.e. the construction of components for a divertor of a Tokamak reactor.
• a device for obtaining a junction between at least two elements to be joined according to the present invention is globally designated by the number 1.
• a divertor requires the obtainment of a junction between an inner metallic tube 2 (generally made of copper) and an outer coating 3 comprising blocks or tiles made of ceramic or ceramic composite material
• the device 1 comprises a first main container 4, preferably made of stainless steel, with substantially tubular shape and characterised by being open at both its ends.
• Each end has a flange 41 whereon are removably fastened closing means 5 which, together with the main container 4, define an area destined to the junction of the two elements to be joined; first element 2 and second element 3.
• the main container 4 has, in central position, an opening 42 whereto it is possible to fasten a conduit through which the washing fluid can be sent, e.g. an inert gas such as argon, or to extract gases formed by the inner atmosphere to achieve a high degree of vacuum.
• a conduit through which the washing fluid can be sent e.g. an inert gas such as argon, or to extract gases formed by the inner atmosphere to achieve a high degree of vacuum.
• a second main container 10 Internal to the first main container 4 and structurally independent therefrom, is present a second main container 10.
• Said container 10 is defined by a plurality of means for the containment 6 and 7 of the two elements to be joined 2 and 3, by a spacer 8, apt to enclose the first element 2, and by the closing means 5 in collaboration with a plug 9.
• the closing means 5 comprise a counter-flange 51 Conflat ® apt to be removably fastened to the flange 41 and a closing flange 52 interposed between the spacer 8 and the inner surface of the counter-flange 51, as shown in Figure 1.
• the closing flange 52 has an opening 53 with such inner diameter that it can be fitted on the tube 2, without an appreciable inter-space, and such as to be able to receive the plug 9 when fastened to the tube 2.
• the flange 41 and the counter-flange 51 are vacuum and/or ultra- vacuum closing means and they comprise teeth, whose function is to block a first gasket 43, preferably made of copper, when flange and counter-flange are fastened by means of appropriate bolts 54.
• the closing flange 52 and the counter-flange 51 are also vacuum and/or ultra- vacuum closing means and they comprise a second gasket 43', preferably made of copper, interposed between the two when fastened by means of additional bolts 55, as shown in Figure 1.
• the plug 9 is also fastened through adequate bolts 91 to the closing flange 52 and secured to the tube 2 by means of mechanical deformation with no need for bonding.
• the plug 9 is provided with an access 11 for the introduction of a fluid under pressure, which is positioned in such a way as to induce, on a surface opposite to the coupling surface of the first element 2, such a pressure as to press the two elements to be joined (2 and 3) against each other at the contact area.
• a fluid under pressure which is positioned in such a way as to induce, on a surface opposite to the coupling surface of the first element 2, such a pressure as to press the two elements to be joined (2 and 3) against each other at the contact area.
• the access 11 is suitable to be connected to a high pressure circuit, whilst the opposite access 11 ' can be used to connect an instrumentation for measuring the pressure inside the tube 2.
• the second main container 10 comprises at its ends, in contact with the closing flange 52, a spacer 8 made of inert material, obviously not bonded on the first element 2, which in the present embodiment comprises multiple tubular elements with such an inner diameter that they can be fitted on the tube 2.
• the spacer 8 supports at least one thermal shield 12 which extends from the spacer in order to thermally shield a portion of the first main container positioned in proximity to the closing means 5.
• the second main container 10 comprises, flanking the spacer 8, the means for the containment, 6 and 7, of the two elements to be joined, 2 and 3, as shown in Figures 1 and 2.
• the containment means in a preferred embodiment, comprise first means for containment 6 apt to contain the coating of ceramic material 31 and the metallic tube
• second means for containment 7 apt to contain the coating of metallic material 32 and the metallic tube 2 to effect the metallic material/metal j unction.
• the first containment means 6 comprise an outer armour 61, with preferably cylindrical shape, made of material with low heat expansion coefficient, e.g. a molybdenum alloy, and a plurality of elements 62 with greater coefficient of thermal expansion than the material composing the outer armour 61.
• the elements 62 can be inserted inside the armour 61 in order to define an inner space 63, suitable shaped to contain the elements 2 and 31 to be joined. Said elements 62 have in proximity to their contact surface and matching the edges of the parallelepiped constituted by the ceramic material 31, grooves 64.
• the elements 62 are in contact with the ceramic material 31 in such a way as to exercise, during the process for effecting the junction between the tube 2 and the material 3, an opposite pressure to the one exercised by the pressurised fluid inserted in the second main container 10.
• the second containment means 7 comprises an outer armour, preferably made of steel, with inner space formed on the basis of the measurements and geometry of the coating metallic material 32 and closed by means of appropriate bolts 71, Figure 2.
• the method is executed thanks to a furnace F that has a heated compartment 13, which is advantageously shaped to measure on the first main container, containing the area of the junction of the first and second element to be joined.
• the device 1, as described above, and the elements to be joined, i.e. tube 2 and tiles 3, are assembled.
• the tiles are pre-brazed and subjected to an appropriate preparation process.
• the elements to be joined are initially arranged in the first containment means 6, as shown for example in Figure 3.
• the first containment means 6 are aligned by means of a dowel pin 65 passing through a hole 66 drilled in one of the elements 62, Figures 1 and 3B. Said dowel pin 65 is then removably fastened to the second containment means 7 once the latter has been assembled with the respective metallic tiles 32 and the tube 2, as shown in Figure 1.
• thermocouple or other equivalent measuring instrument to monitor the temperature of the contact area.
• the degree of vacuum will preferably be between 10 "3 and 10 " Pa.
• the interior of the tube 2 is subjected to gaseous washing with argon before the complete closure of the device, with the connection to the plug 9 of a circuit under pressure 14 and of a pressure gauge 15 ( Figure 5).
• the device is placed with the first main container 4 in said heated compartment 13.
• the activation of the furnace F allows a first slow heating up to a temperature of 350°C-400°C. Once equilibrium is reached, the heating continues to a predetermined temperatures, which enables to favour the atomic inter-diffusion between the materials to be joined.
• Said inter-diffusion temperature depends on the materials involved and it may generally vary between 500°C and 2000 0 C.
• the initial melting temperature of the first main container 4, made of stainless steel in the present example, is an upper limit to the maximum operating temperature, because the heating of the container is effected from the exterior and hence the armour 4 is at a higher temperature than the one measurable at said contact area.
• the elements to be joined are appropriately pressed against each other increasing the pressure inside the second main container 10 of the device, i.e. within the copper tube 2.
• a fluid under pressure preferably an inert gas
• said pressure shall be between 50 and 100 MPa.
• Said pressure and temperature status must be controlled through appropriate temperature and pressure up and down ramps.
• the elements 62 of the first containment means 6 can compensate, through their heat expansion coefficient, and hence the related volume increase as temperature rises, the pressure exerted on the inner contact surface of the ceramic tiles 31 by the metallic tube 2, as a result of the pressurised fluid injected into it.
• the purpose of this system is to avoid that in a material with low mechanical strength like the ceramic one, the inner pressure exerted by a system like the one described above may cause it to be damaged. Said risk of damaging the ceramic tiles is present both in the step of increasing temperature and pressure and in the step in which temperature and pressure are returned to ambient values. Therefore, in both cases, the pressure and temperature up and down ramps must be controlled.
• the duration of the entire process will be a function of pressure and temperature and of their up and down ramps. From the above description, it is readily apparent that the heating can be obtained in very simple fashion, e.g. by an non-pressurised resistance furnace without controlled atmosphere, hence at highly reduced costs.
• the device can be varied in dimensions and shape to be adapted to the shapes and dimensions of more complex pieces to be joined, even with hollow bodies of any shape which require a complete or partial external covering, made of a different material. It is not necessary to destroy the device to free the bonded pieces. Therefore, the device can be reused.
• dimensionally stable materials with high heat resistance are suitable: AISI 316L, Nickel or Tungsten based alloys or otherwise appropriate ceramic materials.
• materials with rather high coefficient of thermal expansion are preferred, such as: Stainless Steel and Inconel®.
• the first containment means 6 can comprise a plurality of elements 62 of different material in order to compensate, through the specific heat expansion coefficient, any pressure imbalances, present during the execution of the junction, due to the anisotropy present in the materials or ceramic compounds.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Ceramic Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Thermal Sciences (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Fluid Mechanics (AREA)
• Pressure Welding/Diffusion-Bonding (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

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• 2005
  • 2005-08-05 IT IT000105U patent/ITRM20050105U1/it unknown
• 2006
  • 2006-08-01 EP EP06780270A patent/EP1919650A2/de not_active Withdrawn
  • 2006-08-01 WO PCT/IB2006/052631 patent/WO2007017798A2/en active Application Filing

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