CA2070841A1 - Loading device for supporting workpieces inside an oven - Google Patents
Loading device for supporting workpieces inside an ovenInfo
- Publication number
- CA2070841A1 CA2070841A1 CA 2070841 CA2070841A CA2070841A1 CA 2070841 A1 CA2070841 A1 CA 2070841A1 CA 2070841 CA2070841 CA 2070841 CA 2070841 A CA2070841 A CA 2070841A CA 2070841 A1 CA2070841 A1 CA 2070841A1
- Authority
- CA
- Canada
- Prior art keywords
- bed
- oven
- beds
- pyrocarbon
- loading device
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000002131 composite material Substances 0.000 claims abstract description 25
- 239000002296 pyrolytic carbon Substances 0.000 claims abstract description 4
- 125000006850 spacer group Chemical group 0.000 claims description 26
- 239000002184 metal Substances 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 5
- 230000001590 oxidative effect Effects 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 description 9
- 238000000576 coating method Methods 0.000 description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 8
- 239000000835 fiber Substances 0.000 description 7
- 239000011159 matrix material Substances 0.000 description 7
- 238000005219 brazing Methods 0.000 description 6
- 230000002787 reinforcement Effects 0.000 description 6
- 239000011153 ceramic matrix composite Substances 0.000 description 5
- 229910002804 graphite Inorganic materials 0.000 description 5
- 239000010439 graphite Substances 0.000 description 5
- 238000005229 chemical vapour deposition Methods 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000000919 ceramic Substances 0.000 description 3
- 238000000280 densification Methods 0.000 description 3
- 238000001764 infiltration Methods 0.000 description 3
- 230000008595 infiltration Effects 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- 230000000875 corresponding effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 239000007833 carbon precursor Substances 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 239000003870 refractory metal Substances 0.000 description 1
- 239000012783 reinforcing fiber Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
Classifications
-
- 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
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
- C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
- C04B41/5001—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials with carbon or carbonisable materials
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D5/00—Supports, screens, or the like for the charge within the furnace
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D5/00—Supports, screens, or the like for the charge within the furnace
- F27D5/0006—Composite supporting structures
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Inorganic Chemistry (AREA)
- Furnace Charging Or Discharging (AREA)
- Chemical Vapour Deposition (AREA)
- Furnace Details (AREA)
- Heat Treatments In General, Especially Conveying And Cooling (AREA)
- Carbon And Carbon Compounds (AREA)
- Fluid-Damping Devices (AREA)
- Electric Ovens (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The loading device comprises beds of thermostructural composite material and coated with respective layers of pyrolytic carbon or "pyrocarbon", at least on those surfaces thereof that are to come into contact with workpieces.
The beds are made up of a plurality of juxtaposed portions or sectors and they are disposed at different levels, being spaced apart from one another by spacersmade up of components placed end-to-end.
The loading device comprises beds of thermostructural composite material and coated with respective layers of pyrolytic carbon or "pyrocarbon", at least on those surfaces thereof that are to come into contact with workpieces.
The beds are made up of a plurality of juxtaposed portions or sectors and they are disposed at different levels, being spaced apart from one another by spacersmade up of components placed end-to-end.
Description
2~8~1 A LOADING DEVICE FOR SUPPOR IING WORKPIECES INSIDE AN
OVEN
The present invention relates to a loading device for supporting workpieces inside an oven.
BACK5~ROUND OF THE INVENTION
The field of the invention is more particularly that of ovens or furnaces ~or processing metal workpieces in a vacuum or in a non-oxidizing atmosphere at temperatures that are relatively high, possibly reaching 1300-C
Such ovens may be used for performing the following operations on workpieces: carbonization, chemical vapor deposition, heat treatment, or brazing.
Ovens of this type are mainly constituted by an insulated structure, heating means, and a loading device. The loading device is generally in the form of a plurality of support beds, i.e. bed plates or trays, that are held spaced apart from one another by spacers and that stand on the bottom structure of the oven. The workpieces to be treated or brazed are placed on the beds, possibly together with tooling for holding them.
The beds are conventionally rnade of graphite or of metal.
Graphite beds are very thick, very fragile, and very heavy. They occupy a major fraction of the inside volume of an oven, thereby limiting the amount of room available for workpieces.
Metal beds, generally made of refractory steel, are also very thick and very heavy. Thus, apart from being less fragile, they suffer from the same drawbacks as graphite beds. In addition, metal beds have high thermal inertia 2s and are subject to deformation which means that they require regular surfacing or rectifying operations to be performed on them.
To avoid these drawbacks, proposals havs been made to use beds made of a thermostructural composite material, and in particular of a carbonlcarbon (C/C) composite material.
Thermostructural composite materials, such as C/C composites or ceramic matrix composites (CMC) are characterized by excellent mechanical properties and by the ability to retain these mechanical properties and their shape at high temperatures. Thus, beds made of C/C composite matcrial can be much thinner than beds made of graphite. They are therefore lighter and they 3s occupy a srnaller fraction of the inside volume of an oven. In addition, C/C
207~8~1 composite material beds present thermal behavior that is similar to that of graphite beds. As a result, and in particular in comparison with metal beds, oven utilization cycles are improved.
However, known loading devices that use C/C composite material s beds still suffer from drawbacks. It has thus been observed that steel worl~pieces (tooling, or workpieces for treatment, or for brazing) are subjectedto a carbiding phenomenon on contact witll the C/C compvsite bed. In addition, when workpieces are being brazed, the brazing can ovexflow and the workpieces may adhere to the C/C composite bed, and the adhesion may be 10 substantially equivalent to the workpieces being brazed to the bed.
An object of the invention is to provide a loading device that does not have the above-mentioned drawbacks of prior art devices.
A particular object of the invention is to provide a loading device that includes at least one bed of thermo structural composite material wllile 15 avoiding problems of carbiding or of brazing adhesion that are encountered using known beds made of C/C composite.
SUMMARY OF THE INYENTION
According to the invention, this object is achieved by a loading device in which tlle bed of thermostructural composite material is coated, at 20 least on its surface that is to come into contact with workpieces, with a layer of pyrolytic carbon or "pyrocarbon".
Unexpectedly, it has been discovered that the phenomena of carbiding and of brazing adhesion observed with C/C composite material beds does not happen when beds of thermostructural composite material are coated ~5 with a ply of pyrocarbon.
The pyrocarbon is formed on the bed by chemical vapor deposition after the surface of the bed has been machined. The thickness of the layer of pyrocarbon is preferably not less than 2S microns.
The bed(s) constituting the loading device may be made up of a 30 plurality of juxtaposed portions or sectors. The pyrocarbon coating is preferably performed on the sectors prior to assembly thereof.
The loading device includes at least one bottom bed which stands on the bottom structure of the oven via legs which are interconnected by bars for the purpose of constituting a rigid support stmcture.
2 ~ 4 ~
When the loading device comprises a plurality of beds placed at dif-ferent levels, then they are spaced apart from one another by spacer means.
The spacers are advantageously made of a thermostructural composite material and they are coated with a pyrocarbon layer.
BRIEF DESCRIPTION OF TEIE DRAWINGS
An embodiment of the invention is described by way of example with reference to the accompanying drawings, in which:
Figure 1 is a highly diagrammatic view ir~ elevation and in section through an oven provided with a loading device of the invention;
Figure 2 is a -fragmentary perspective view of the loading device of Figure 1 comprising a bottom bed and a plurality of intermediate beds;
Figure 3 is a view seen from below of the device for supporting the bottom bed in the oven of Figure 1;
Figure 4 is a section view on an enlarged scale showing details of one of the ways of connecting the bottom bed to a leg of its support structure, and also to a spacer; and Figure 5 is a section view on a larger scale showing details of another way of connecting the bottom bed to a leg of its support structure.
DETAILED DESCRIPTION
Figure 1 is highly diagrammatic and shows a bottom-loading oven that is suitable, for example, for performing heat treatment operations on metalworkpieces in a vacuum.
The oven comprises an insulating enclosure 2 having a vertically movable bottom structure 4. The inside of the oven is accessible via its base 6 for loading the oven with work pieces to be treated disposed on a loading device 10 which is supported by the bottom structure of the oven via a support structure 20.
The loading device 10 comprises a plurality of bPds 12a, 12b, 12c, ... disposed at different levels and spaced apart from one another by spacers.
30 The bottom or base bed 12a stands on the bottom structure of the oven via a support structure 20.
Figure 2 shows a portion of the loading device, namely its bottom bed 12a and the beds 12b and 12c which are situated immediately above it. The spacing between the beds is adjusted by means of spacers 16 which are 35 advantageously made up of identical spacer elements placed end-to-end.
~7D8~1 In order to achieve optimum loading of the oven, the spacing between the beds is adjusted by making spacers using the desired number of elements 17, as a function of the height of the workpieces to be treated. When the workpieces disposed on a given bed are of dif~erent heights, partial s intermediate beds may be installed above the shorter workpieces. For example, as shown in Figure 2, for a bottom bed 12a that is circular, the bed 12b is in the form of a semicircle, and the bed 12c is in the form of one-fourth o~ a circle.
The lengths of the spacers between the beds 12a and 12c are then longer than the spacers between the beds 12a and 12b.
lo The beds are advantageously made up of standard components such as sectors 14. Each sector may occupy one-fourth of a circle, for example. The bottom bed 12a is then made up of four sectors 14, whereas the beds 12b and 12c are respectively made up of two sectors 14 and of one sector 14.
Thus, the loading device 10 comprising the beds and the spacers can 15 be built up as a function of.requirements so as to ensure that the oven is optimally filled, while using bed components and spacer components that are standard. A loading device is built up from the bottom upwards as the workpieces to be treated are installed thereon, starting with the bottom bed 12a.
The bottom structure of the oven may be vertically movable so as to be 20 displaced progressively downwards while loading is taking place, and so as subsequently to be returned to a high position once loading has been completed.
As also shown in Figure 2~ the beds of the loading device are regularly pierced by holes 1~. In an oven for performing heat treatment in a 2s vacuum, the main object of the holes is to facilitate evacuating the oven. In an oven for performing chemical vapor deposition or infiltration operations, the holes 18 are likewise required for ensuring that the gas flow used for infiltration or deposition can diffuse throughout the volume of the oven. In general, the holes 18 also serve in any event to reduce the weight of the loading device.
30 Furthermore, some of the holes 1~ are used for m~l~ing connections between the beds and the spacers and for connecting the bottom bed to the support structure 20.
In accordance with the invention, the beds of the loading device 10 are made of a thermostructural composite material and they are coated with a ~708~1 pyrolytic carbon or "pyrocarbon" layer on at least one of their surfaces that isintended to come into contact with workpieces.
The thermostructural composite material from which the beds are made may be a carbonlcarbon (UC) composite or it may be a ceramic matrix composite (CMC~.
A C/C composite is rnade up of carbon ~iber reinforcement densi~led by a matrix that is made of carbon. Ihe fiber reinforcement may be constituted by superposed two-dimensional plies, e.g. pieces of cloth. The plies may be linked together by installing threads through the plies or by needling.
0 Densification by means of the carbon matrix can be performed using a liquid or using a gas. Densificatis)n using a liquid consists in impregnating the fiber reinforcement with a carbon precursor, e.g. a resin, which is subsequently polymerized and pyrolyzed. A plurality of consecutive impregnation-polymerization-pyrolysis cycles are generally performed in order to achieve the desired degree of densification. Densification using a gas, i.e. "chemical vapor in~lltration", consists in placing the fiber reinforcement (possibly held ;n shape by tooling) in an oven into which a gas is admitted under conditions of temperature and pressure such that the matrix is formed by the gas decomposing or by the components of the gas reacting when they come into contact with the reinforcing Flbers. In general, a caibon matrix is obtained by chemical vapor infiltration by making use of a gas that contains one or more hydrocarbons.
A CMC is constituted by a reinforcement of refractory fibers (carbon fibers or ceramic fibers) densified by means of a ceramic matrix. By way of example, the ceramic material of the matrix, and optionally of the reinforcing fibers, may be silicon carbide (SiC). As before, the fiber reinforcement may be made up of superposed two-dimensional plies, and it may be densified with the ceramic matrix by using a liquid or by using a gas.
For example, a silicon carbide vapor in~lltration method is described in Document F~ 2 401 888.
The beds are coated with a layer of pyrocarbon in conventional manner by chemical vapor deposition. This method leads to a pyrocarbs)n coating being formed over the entire outside surface of each bçd. It would be possible to form the pyrocarbon coating only on those surfaces of the beds that 2~708~ ~
are intended to come into contact with the workpieces loaded into the oven, e g.by masking other surfaces.
The pyrocarbon coating should be thick enough to ensure that there is no risk of it being damaged by the workpieces. Its thickness is preferably not less than 25 microns. In practice, there appears to be no point in having a thickness of more than 250 microns. For example, a pyrocarbon coating having a thickness of about 100 microns appears to be entirely satisfactory.
In practice, plates of thermostructural composite material are initially formed and then the sector-shaped beds 14 are cut out therefrom. The o bed sectors are subjected to machining in order to correct surface defects. This rectification or surfacing operation bares fibers of the reinforcing texture at the surface of the bed. The pyrocarbon coating operation is then advantageously performed on the bed sectors prior to the sectors being assembled to~ether. The spacer components likewise have a pyrocarbon coating formed thereon under the same conditions.
After they have been used for a certain length of time, the bed sectors may be "retreaded" by rectifying their surfaces again and by depositing a new layer of pyrocarbon.
Thus, in a loading system rnade up of beds and spacers, the workpieces come into contact only with surfaces that are coated in pyrocarbon.
With workpieces or tooling made of steel, it has been verified that the presenceof pyrocarbon ensures that no carbiding phenomenon takes place. In addition, if a workpiece is being brazed, it has been observed that any brazing which may flow onto the bed does not adhere to the pyrocarbon coating, or adheres very 2s poorly thereto.
An embodiment of the support structure 20 that supports the bottorn bed 12a is described below with reference to Figures 3 and 4.
The bottom ends of tubular legs 22 made of thermo structural composite material are fitted over studs 24 (e.g. made of metal) which are fixedto the bottom structure of the oven. The top ends of the legs 22 are closed by caps 26 which are glued to the legs. The bottom bed 12a stands on the caps 26 via thickness pieces 28 placed on the legs, and via blocks 30. For each leg 22, a screw 32 passes through the corres ponding block 30 and thickness piece 28 and is screwed into the cap 26. The head of the screw 32 bears against the top face of the bed via a washer 34. The caps 26, the thickness pieces 28, the 21~ r7 ~
blocks 30, and the washers 34 are made of thermostructural composite material, while the screws 32 are made of refractory metal. Reference 13a designates the layer of pyrocarbon formed on the bottom bed 12a.
The blocks 30 are provided with horizontal blind holes which are s force fits on the ends of connecting bars 36. These bars interconnect the blocks so as to form a stiffening lattice that provides the mechanical strength required for the support structure. The bars 36 are rnade of thermostructural eomposite materials.
Each washer 34 has a projecting central portion making it suitable for engaging in the bottom spacer component 17 of a spacer that establishes the spacing between the bottom bed and a bed above it. Each spacer component 17 has an upwardly projecting central portion and a central recess in its bottom face. As a result, a spacer of desired length is formed merely by stacking the desired number of spacer components.
The support structure 20 enables a loading system of the invention to be installed without difficulty in an existing oven. Using the thickness pieces 28, it is possible to compensate for possible geometrical defects and thus ensure that the bottom bed is plane and horizontal.
When the axes of the studs 24 that are fixed to the bottom structure of the oven are not accurately vertical, it is possible to use support structurecomponents such as those shown in Figure 5 (where components that are common bet~,veen the structures of Figures 4 and 5 are given the same references).
The support structure shown in Figure S differs from that of Figure 2s 4 in that the caps 26' glued to the top ends of the legs 22 have respective top faces that are in the form of spherical caps and that co-operate with the correspondingly shaped bottom faces of the blocks 30' so as to form ball--and-socket type joints. Thus, if the axis of a stud 24 should be out of alignment with the vertical, than that is automatically compensated by the leg 22 tilting. In addition, the screws 32' are no longer screwed into the caps 26', but into the blocks 3~)'. Otherwise, the structure of Figure S is identical to the structure of Figure 4.
From the above, it can be seen that the invention is remarkable not only because of a pyrocarbon coating which makes it pvssible to bene~lt from 3s the advantages of thermostructural composite materials (weight, compactness~
8 2~ 4~
mechanical strength), but also because of the modular structure of the component parts of the loading device wh;ch make it possible to manufacture only a small number of different kinds of component with the corresponding advantages in manufacture and storage, and also because of the architecture of s the support structure which makes it easy to adapt the loading device to ovensthat are already in existence.
OVEN
The present invention relates to a loading device for supporting workpieces inside an oven.
BACK5~ROUND OF THE INVENTION
The field of the invention is more particularly that of ovens or furnaces ~or processing metal workpieces in a vacuum or in a non-oxidizing atmosphere at temperatures that are relatively high, possibly reaching 1300-C
Such ovens may be used for performing the following operations on workpieces: carbonization, chemical vapor deposition, heat treatment, or brazing.
Ovens of this type are mainly constituted by an insulated structure, heating means, and a loading device. The loading device is generally in the form of a plurality of support beds, i.e. bed plates or trays, that are held spaced apart from one another by spacers and that stand on the bottom structure of the oven. The workpieces to be treated or brazed are placed on the beds, possibly together with tooling for holding them.
The beds are conventionally rnade of graphite or of metal.
Graphite beds are very thick, very fragile, and very heavy. They occupy a major fraction of the inside volume of an oven, thereby limiting the amount of room available for workpieces.
Metal beds, generally made of refractory steel, are also very thick and very heavy. Thus, apart from being less fragile, they suffer from the same drawbacks as graphite beds. In addition, metal beds have high thermal inertia 2s and are subject to deformation which means that they require regular surfacing or rectifying operations to be performed on them.
To avoid these drawbacks, proposals havs been made to use beds made of a thermostructural composite material, and in particular of a carbonlcarbon (C/C) composite material.
Thermostructural composite materials, such as C/C composites or ceramic matrix composites (CMC) are characterized by excellent mechanical properties and by the ability to retain these mechanical properties and their shape at high temperatures. Thus, beds made of C/C composite matcrial can be much thinner than beds made of graphite. They are therefore lighter and they 3s occupy a srnaller fraction of the inside volume of an oven. In addition, C/C
207~8~1 composite material beds present thermal behavior that is similar to that of graphite beds. As a result, and in particular in comparison with metal beds, oven utilization cycles are improved.
However, known loading devices that use C/C composite material s beds still suffer from drawbacks. It has thus been observed that steel worl~pieces (tooling, or workpieces for treatment, or for brazing) are subjectedto a carbiding phenomenon on contact witll the C/C compvsite bed. In addition, when workpieces are being brazed, the brazing can ovexflow and the workpieces may adhere to the C/C composite bed, and the adhesion may be 10 substantially equivalent to the workpieces being brazed to the bed.
An object of the invention is to provide a loading device that does not have the above-mentioned drawbacks of prior art devices.
A particular object of the invention is to provide a loading device that includes at least one bed of thermo structural composite material wllile 15 avoiding problems of carbiding or of brazing adhesion that are encountered using known beds made of C/C composite.
SUMMARY OF THE INYENTION
According to the invention, this object is achieved by a loading device in which tlle bed of thermostructural composite material is coated, at 20 least on its surface that is to come into contact with workpieces, with a layer of pyrolytic carbon or "pyrocarbon".
Unexpectedly, it has been discovered that the phenomena of carbiding and of brazing adhesion observed with C/C composite material beds does not happen when beds of thermostructural composite material are coated ~5 with a ply of pyrocarbon.
The pyrocarbon is formed on the bed by chemical vapor deposition after the surface of the bed has been machined. The thickness of the layer of pyrocarbon is preferably not less than 2S microns.
The bed(s) constituting the loading device may be made up of a 30 plurality of juxtaposed portions or sectors. The pyrocarbon coating is preferably performed on the sectors prior to assembly thereof.
The loading device includes at least one bottom bed which stands on the bottom structure of the oven via legs which are interconnected by bars for the purpose of constituting a rigid support stmcture.
2 ~ 4 ~
When the loading device comprises a plurality of beds placed at dif-ferent levels, then they are spaced apart from one another by spacer means.
The spacers are advantageously made of a thermostructural composite material and they are coated with a pyrocarbon layer.
BRIEF DESCRIPTION OF TEIE DRAWINGS
An embodiment of the invention is described by way of example with reference to the accompanying drawings, in which:
Figure 1 is a highly diagrammatic view ir~ elevation and in section through an oven provided with a loading device of the invention;
Figure 2 is a -fragmentary perspective view of the loading device of Figure 1 comprising a bottom bed and a plurality of intermediate beds;
Figure 3 is a view seen from below of the device for supporting the bottom bed in the oven of Figure 1;
Figure 4 is a section view on an enlarged scale showing details of one of the ways of connecting the bottom bed to a leg of its support structure, and also to a spacer; and Figure 5 is a section view on a larger scale showing details of another way of connecting the bottom bed to a leg of its support structure.
DETAILED DESCRIPTION
Figure 1 is highly diagrammatic and shows a bottom-loading oven that is suitable, for example, for performing heat treatment operations on metalworkpieces in a vacuum.
The oven comprises an insulating enclosure 2 having a vertically movable bottom structure 4. The inside of the oven is accessible via its base 6 for loading the oven with work pieces to be treated disposed on a loading device 10 which is supported by the bottom structure of the oven via a support structure 20.
The loading device 10 comprises a plurality of bPds 12a, 12b, 12c, ... disposed at different levels and spaced apart from one another by spacers.
30 The bottom or base bed 12a stands on the bottom structure of the oven via a support structure 20.
Figure 2 shows a portion of the loading device, namely its bottom bed 12a and the beds 12b and 12c which are situated immediately above it. The spacing between the beds is adjusted by means of spacers 16 which are 35 advantageously made up of identical spacer elements placed end-to-end.
~7D8~1 In order to achieve optimum loading of the oven, the spacing between the beds is adjusted by making spacers using the desired number of elements 17, as a function of the height of the workpieces to be treated. When the workpieces disposed on a given bed are of dif~erent heights, partial s intermediate beds may be installed above the shorter workpieces. For example, as shown in Figure 2, for a bottom bed 12a that is circular, the bed 12b is in the form of a semicircle, and the bed 12c is in the form of one-fourth o~ a circle.
The lengths of the spacers between the beds 12a and 12c are then longer than the spacers between the beds 12a and 12b.
lo The beds are advantageously made up of standard components such as sectors 14. Each sector may occupy one-fourth of a circle, for example. The bottom bed 12a is then made up of four sectors 14, whereas the beds 12b and 12c are respectively made up of two sectors 14 and of one sector 14.
Thus, the loading device 10 comprising the beds and the spacers can 15 be built up as a function of.requirements so as to ensure that the oven is optimally filled, while using bed components and spacer components that are standard. A loading device is built up from the bottom upwards as the workpieces to be treated are installed thereon, starting with the bottom bed 12a.
The bottom structure of the oven may be vertically movable so as to be 20 displaced progressively downwards while loading is taking place, and so as subsequently to be returned to a high position once loading has been completed.
As also shown in Figure 2~ the beds of the loading device are regularly pierced by holes 1~. In an oven for performing heat treatment in a 2s vacuum, the main object of the holes is to facilitate evacuating the oven. In an oven for performing chemical vapor deposition or infiltration operations, the holes 18 are likewise required for ensuring that the gas flow used for infiltration or deposition can diffuse throughout the volume of the oven. In general, the holes 18 also serve in any event to reduce the weight of the loading device.
30 Furthermore, some of the holes 1~ are used for m~l~ing connections between the beds and the spacers and for connecting the bottom bed to the support structure 20.
In accordance with the invention, the beds of the loading device 10 are made of a thermostructural composite material and they are coated with a ~708~1 pyrolytic carbon or "pyrocarbon" layer on at least one of their surfaces that isintended to come into contact with workpieces.
The thermostructural composite material from which the beds are made may be a carbonlcarbon (UC) composite or it may be a ceramic matrix composite (CMC~.
A C/C composite is rnade up of carbon ~iber reinforcement densi~led by a matrix that is made of carbon. Ihe fiber reinforcement may be constituted by superposed two-dimensional plies, e.g. pieces of cloth. The plies may be linked together by installing threads through the plies or by needling.
0 Densification by means of the carbon matrix can be performed using a liquid or using a gas. Densificatis)n using a liquid consists in impregnating the fiber reinforcement with a carbon precursor, e.g. a resin, which is subsequently polymerized and pyrolyzed. A plurality of consecutive impregnation-polymerization-pyrolysis cycles are generally performed in order to achieve the desired degree of densification. Densification using a gas, i.e. "chemical vapor in~lltration", consists in placing the fiber reinforcement (possibly held ;n shape by tooling) in an oven into which a gas is admitted under conditions of temperature and pressure such that the matrix is formed by the gas decomposing or by the components of the gas reacting when they come into contact with the reinforcing Flbers. In general, a caibon matrix is obtained by chemical vapor infiltration by making use of a gas that contains one or more hydrocarbons.
A CMC is constituted by a reinforcement of refractory fibers (carbon fibers or ceramic fibers) densified by means of a ceramic matrix. By way of example, the ceramic material of the matrix, and optionally of the reinforcing fibers, may be silicon carbide (SiC). As before, the fiber reinforcement may be made up of superposed two-dimensional plies, and it may be densified with the ceramic matrix by using a liquid or by using a gas.
For example, a silicon carbide vapor in~lltration method is described in Document F~ 2 401 888.
The beds are coated with a layer of pyrocarbon in conventional manner by chemical vapor deposition. This method leads to a pyrocarbs)n coating being formed over the entire outside surface of each bçd. It would be possible to form the pyrocarbon coating only on those surfaces of the beds that 2~708~ ~
are intended to come into contact with the workpieces loaded into the oven, e g.by masking other surfaces.
The pyrocarbon coating should be thick enough to ensure that there is no risk of it being damaged by the workpieces. Its thickness is preferably not less than 25 microns. In practice, there appears to be no point in having a thickness of more than 250 microns. For example, a pyrocarbon coating having a thickness of about 100 microns appears to be entirely satisfactory.
In practice, plates of thermostructural composite material are initially formed and then the sector-shaped beds 14 are cut out therefrom. The o bed sectors are subjected to machining in order to correct surface defects. This rectification or surfacing operation bares fibers of the reinforcing texture at the surface of the bed. The pyrocarbon coating operation is then advantageously performed on the bed sectors prior to the sectors being assembled to~ether. The spacer components likewise have a pyrocarbon coating formed thereon under the same conditions.
After they have been used for a certain length of time, the bed sectors may be "retreaded" by rectifying their surfaces again and by depositing a new layer of pyrocarbon.
Thus, in a loading system rnade up of beds and spacers, the workpieces come into contact only with surfaces that are coated in pyrocarbon.
With workpieces or tooling made of steel, it has been verified that the presenceof pyrocarbon ensures that no carbiding phenomenon takes place. In addition, if a workpiece is being brazed, it has been observed that any brazing which may flow onto the bed does not adhere to the pyrocarbon coating, or adheres very 2s poorly thereto.
An embodiment of the support structure 20 that supports the bottorn bed 12a is described below with reference to Figures 3 and 4.
The bottom ends of tubular legs 22 made of thermo structural composite material are fitted over studs 24 (e.g. made of metal) which are fixedto the bottom structure of the oven. The top ends of the legs 22 are closed by caps 26 which are glued to the legs. The bottom bed 12a stands on the caps 26 via thickness pieces 28 placed on the legs, and via blocks 30. For each leg 22, a screw 32 passes through the corres ponding block 30 and thickness piece 28 and is screwed into the cap 26. The head of the screw 32 bears against the top face of the bed via a washer 34. The caps 26, the thickness pieces 28, the 21~ r7 ~
blocks 30, and the washers 34 are made of thermostructural composite material, while the screws 32 are made of refractory metal. Reference 13a designates the layer of pyrocarbon formed on the bottom bed 12a.
The blocks 30 are provided with horizontal blind holes which are s force fits on the ends of connecting bars 36. These bars interconnect the blocks so as to form a stiffening lattice that provides the mechanical strength required for the support structure. The bars 36 are rnade of thermostructural eomposite materials.
Each washer 34 has a projecting central portion making it suitable for engaging in the bottom spacer component 17 of a spacer that establishes the spacing between the bottom bed and a bed above it. Each spacer component 17 has an upwardly projecting central portion and a central recess in its bottom face. As a result, a spacer of desired length is formed merely by stacking the desired number of spacer components.
The support structure 20 enables a loading system of the invention to be installed without difficulty in an existing oven. Using the thickness pieces 28, it is possible to compensate for possible geometrical defects and thus ensure that the bottom bed is plane and horizontal.
When the axes of the studs 24 that are fixed to the bottom structure of the oven are not accurately vertical, it is possible to use support structurecomponents such as those shown in Figure 5 (where components that are common bet~,veen the structures of Figures 4 and 5 are given the same references).
The support structure shown in Figure S differs from that of Figure 2s 4 in that the caps 26' glued to the top ends of the legs 22 have respective top faces that are in the form of spherical caps and that co-operate with the correspondingly shaped bottom faces of the blocks 30' so as to form ball--and-socket type joints. Thus, if the axis of a stud 24 should be out of alignment with the vertical, than that is automatically compensated by the leg 22 tilting. In addition, the screws 32' are no longer screwed into the caps 26', but into the blocks 3~)'. Otherwise, the structure of Figure S is identical to the structure of Figure 4.
From the above, it can be seen that the invention is remarkable not only because of a pyrocarbon coating which makes it pvssible to bene~lt from 3s the advantages of thermostructural composite materials (weight, compactness~
8 2~ 4~
mechanical strength), but also because of the modular structure of the component parts of the loading device wh;ch make it possible to manufacture only a small number of different kinds of component with the corresponding advantages in manufacture and storage, and also because of the architecture of s the support structure which makes it easy to adapt the loading device to ovensthat are already in existence.
Claims (9)
1. A loading device for supporting workpieces inside an oven for the purpose of performing heat treatment on metal workpieces in a vacuum or in a non-oxidizing atmosphere, the device comprising at least one bed of thermostructural composite material, wherein the bed is coated, at least on its surface that is to come into contact with the workpieces, with a layer of pyrolytic carbon or "pyrocarbon".
2. A device according to claim 1, wherein the thickness of the pyrocarbon layer is not less than 25 microns.
3. A device according to claim 1, wherein said bed of the loading device is made up of a plurality of juxtaposed section portions.
4. A device according to claim 1, including at least one base bed bearing against the bottom structure of the oven via legs that are interconnected by bars so as to constitute a rigid support structure.
5. A device according to claim 4, wherein the legs of the support structure are designed to be fixed to studs of the bottom structure of the oven and means are provided to enable the legs to tilt so as to compensate for and misalignment between the axes of the studs and the vertical.
6. A device according to claim 1, comprising a plurality of beds disposed at different levels and spaced apart from one another by spacers.
7. A device according to claim 6, wherein the spacers are made of thermostructural composite material and are coated with a layer of pyrocarbon.
8. A device according to claim 5, wherein the spacers are made up of spacer components placed end-to-end.
9. A device according to claim 7, wherein the spacers are made up of spacer components placed end-to-end.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9107092A FR2677740B1 (en) | 1991-06-11 | 1991-06-11 | LOADING DEVICE FOR SUPPORTING PARTS INSIDE AN OVEN. |
| FR91070292 | 1991-06-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2070841A1 true CA2070841A1 (en) | 1992-12-12 |
Family
ID=9413695
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2070841 Abandoned CA2070841A1 (en) | 1991-06-11 | 1992-06-09 | Loading device for supporting workpieces inside an oven |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0518746B1 (en) |
| JP (1) | JP3215503B2 (en) |
| CA (1) | CA2070841A1 (en) |
| DE (1) | DE69209154T2 (en) |
| ES (1) | ES2086095T3 (en) |
| FR (1) | FR2677740B1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2772467B1 (en) | 1997-12-15 | 2000-03-10 | Snecma | LOADING DEVICE FOR SUPPORTING PARTS TO BE HEAT TREATED IN AN OVEN |
| FR2793311B1 (en) * | 1999-05-05 | 2001-07-27 | Snecma | DEVICE FOR LOADING WORKPIECES TO BE HEAT TREATED |
| JP2004100713A (en) * | 2002-09-04 | 2004-04-02 | National Institute Of Advanced Industrial & Technology | Simple fixing method for heating vessel |
| HU227740B1 (en) * | 2006-05-11 | 2012-02-28 | Imerys Magyarorszag Tuezalloanyaggyarto Korlatolt Feleloessegue Tarsasag | Ceramic support for kilning of ceramic bodies |
| DE102008022159B4 (en) * | 2008-05-05 | 2010-05-06 | Saint-Gobain Industriekeramik Rödental GmbH | Multi-part support element and oven shelf |
| JP6086737B2 (en) * | 2013-01-21 | 2017-03-01 | 新東株式会社 | Round corner tile firing support |
| CN112648852A (en) * | 2020-12-09 | 2021-04-13 | 航天海鹰(哈尔滨)钛业有限公司 | Tool for improving space utilization rate in hot isostatic pressing furnace and using method thereof |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2537145A (en) * | 1948-03-18 | 1951-01-09 | Lovatt William Muncaster | Support for ceramic ware during firing |
| US2871543A (en) * | 1955-05-20 | 1959-02-03 | Electro Refractories & Abrasiv | Ceramic ware support for use in kilns |
| DE1671031A1 (en) * | 1966-06-13 | 1971-09-09 | Sigri Elektrographit Gmbh | Process for the deposition of well adhering pyrocarbon layers |
| US3676179A (en) * | 1968-10-03 | 1972-07-11 | Gulf Oil Corp | Coated article and method for making same |
| FR2461690B1 (en) * | 1979-07-19 | 1985-08-16 | Europ Propulsion | HIGH TEMPERATURE THERMAL INSULATION MATERIAL AND MANUFACTURING METHOD THEREOF |
| US4487579A (en) * | 1983-12-05 | 1984-12-11 | The Potters Supply Company | Superstructure for kiln car |
| JPS6237683A (en) * | 1985-08-09 | 1987-02-18 | 東芝セラミツクス株式会社 | Tool for baking ceramic |
-
1991
- 1991-06-11 FR FR9107092A patent/FR2677740B1/en not_active Expired - Lifetime
-
1992
- 1992-06-09 CA CA 2070841 patent/CA2070841A1/en not_active Abandoned
- 1992-06-09 ES ES92401580T patent/ES2086095T3/en not_active Expired - Lifetime
- 1992-06-09 EP EP19920401580 patent/EP0518746B1/en not_active Expired - Lifetime
- 1992-06-09 DE DE1992609154 patent/DE69209154T2/en not_active Expired - Lifetime
- 1992-06-11 JP JP15207192A patent/JP3215503B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP3215503B2 (en) | 2001-10-09 |
| DE69209154D1 (en) | 1996-04-25 |
| EP0518746B1 (en) | 1996-03-20 |
| EP0518746A1 (en) | 1992-12-16 |
| DE69209154T2 (en) | 1996-08-01 |
| ES2086095T3 (en) | 1996-06-16 |
| FR2677740B1 (en) | 1998-03-13 |
| JPH05172469A (en) | 1993-07-09 |
| FR2677740A1 (en) | 1992-12-18 |
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