Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/20—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by extruding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
  • F26B21/004—Nozzle assemblies; Air knives; Air distributors; Blow boxes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
  • F26B21/006—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects the gas supply or exhaust being effected through hollow spaces or cores in the materials or objects, e.g. tubes, pipes, bottles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2201/00—Treatment under specific atmosphere
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F3/1017—Multiple heating or additional steps
  • B22F3/1021—Removal of binder or filler
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F3/1039—Sintering only by reaction

Definitions

• the present invention relates to a method of manufacturing a powder- metallurgical component having at least one longitudinally extending channel.
• a method of manufacturing a powder- metallurgical component having at least one longitudinally extending channel In particular it relates to a method wherein the green body is dried by guiding a flow of gas along the channel before sintering or oxidizing of the green body.
• the at least one longitudinally extending channel may be closed along all side walls thereof. It may also be open along one of the sides in which case it may be necessary to close off the open side to obtain the necessary guiding of the flow of gas that is to provide the drying.
• the processing equipment may e.g. be an extruder, such as a piston extruder.
• the powder mixture may be in the form of a paste.
• paste is meant a thick, soft, sticky substance made by mixing a liquid with a powder.
• pastes typically consist of a suspension of granular material in a background fluid.
• the viscosity of the paste should be so that it allows for the necessary handling of the paste during the transfer from the device used for the mixing and to the processing equipment. It should also allow for the subsequent process steps; i.e. it should be low enough to allow for the forming and high enough to ensure that the green body keeps the desired geometry.
• the viscosity of a given paste can be determined by equipment and methods designed therefore, such as by use of a capillary rheometer which is typically used to measure shear viscosity and other rheological properties. However, since the viscosity is correlated to the hardness of the material, it will also be possible to use this parameter in the determination of whether a given paste is suitable for the manufacturing method or not.
• a possible related measure to use is the Shore Hardness which can be determined in accordance with ISO 868/ ASTM D2240. Another option is to use a special tool designed for clays; this has been used during the development of the present invention.
• This tool is similar to a Shore tester but has been adapted for the characterization of clays; such an instrument can also be referred to as a durometer for clays.
• the operating principle is based on the force exerted by the sample material on the penetration of the calibrated spring of the instrument, when a pin of the tool is pressed into the material being tested until the pin reaches a support. In this way, a steady force at a steady stroke is always applied to the instrument. It has a scale from 0 to 20 to use as a relative hardness reference parameter, and gram scale of applied force.
• the metal may be any metal that is available as powder.
• a non-exhaustive list of possible metals include: 316L, FeCrAI, Inconel 625, Hastalloy X, 17-4PH, 430L, and 304L.
• a binder or a binding agent is any material or substance that holds or draws other materials together to form a cohesive unit mechanically, chemically, by adhesion or cohesion.
• the binder is preferably organic, such as cellulose ethers, agarose or polyoxymethylene.
• binders are: methylcellulose, 25 poly(ethylene oxide), poly(vinyl alcohol), sodium carboxymethylcellulose (cellulose gum), alginates, ethyl cellulose and pitch.
• the powder mixture may also comprise other constituents, such as ceramic powder or lubricant.
• ceramic powder or lubricant include: AIO, SiO, ZiO, Alumina, Zirconia, Boron Nitride, Cordierite, and Silicon Nitride.
• the step of drying further comprises guiding a flow of gas along outer surfaces of the green body so that the drying also takes place from the outside due to this flow of gas.
• the step of drying further comprises covering outer surfaces of the green body, e.g. with plates, so that the drying takes place due to the flow of gas being through the at least one longitudinally extending channel only.
• the drying process e.g. to avoid undesired deformation or cracking. This may e.g. depend on the geometry of the component being manufactured, including the thickness of the walls surrounding the longitudinally extending channel.
• plates or other elements used for the covering of the outer surfaces can provide structural support to the green body during drying. Hereby the supporting effect can be used to ensure that the green body keeps the desired shape during drying.
• Such a drying tool will be particularly advantageous for the drying of a green body having a plurality of longitudinally extending channels as such a geometry might otherwise be more difficult to dry uniformly.
• the method may comprise using a drying tool as just described, but the step of arranging the drying tool in relation to the green body is performed so that nozzles of the drying tool extend into an end region of at least some, such as a majority, of the plurality of longitudinally extending channels of the green body.
• a majority is preferably meant more than 50%, such as more than 70%, such as more than 90%.
• the nozzles By using a drying tool as described and letting the nozzles extend into each or a majority of the longitudinally extending channels, a uniform drying throughout the volume can be ensured.
• the nozzles may be shaped and dimensioned so that they provide structural support to the part of the walls of the at least one longitudinally extending channel that is in contact with the tool and thereby prevent deformation thereof. The advantage thereof is both that the green body remains undeformed and that the gas flow is not hindered as it could be by deformed, such as collapsed, longitudinally extending channels.
• the plurality of nozzles of the drying tool are arranged over the whole cross section of the green body to be dried. Hereby a uniform drying throughout the component may be ensured.
• the nozzles may be shaped and dimensioned so that they provide structural support to the part of the walls of the at least one longitudinally extending channel that is in contact with the tool and thereby prevent deformation thereof.
• drying tool having a connecting end for guiding the gas flow into the at least one longitudinally extending channel.
• a drying tool should preferably have at least one sealing or gasket to be placed in engagement with the green body or an opening end of the at least one longitudinally extending channel so that the gas is thereby guided into the channel.
• any suitable method of providing the guiding of the gas through the at least one longitudinally extending channel is covered by the scope of the claims. It may be provided by a blowing or a sucking action.
• the flow generating device may be any type of device which is adapted to provide a gas flow. It may e.g.
• the gas flow generating device may be an integrated part of the drying tool, or it may be an external device connected thereto.
• An auxiliary tool may be arranged at an opposite end of the green body as the one where the drying tool is arranged, the auxiliary tool being adapted to support the at least one longitudinally extending channel during drying and thereby prevent undesired deformation of the green body.
• support is preferably meant that the auxiliary tool supports part of the inner surfaces of the at least one channel and thereby prevents it from deforming, such as collapsing. This should preferably be done without significantly restricting the gas flow.
• the step of drying may have a length being a predetermined time period or being determined by measurements of the humidity of the gas that has flown through the green body. It will depend on parameters including the material, the geometry, and the dimensions of the green body. Which measures to use may be determined experimentally, possibly assisted by computer simulations.
• the component being manufactured has a plurality of longitudinally extending internal channels, such as having a honeycomb structure.
• the gas used for the drying may have a higher or a lower temperature than the surrounding air, and/or the gas may have a higher or a lower humidity than the surrounding air.
• the gas may e.g. be air.
• the drying may also be controlled by varying the speed of the flow of gas.
• a step of debinding may precede the step of sintering or oxidizing, the debinding step typically comprising heating the green body to a temperature at which at least some, such as all, of the binder burns off.
• This debinding step is typically performed after the step of drying.
• Debinding is the process in which the binder is removed from the green body to ensure that no leftover carbon is present in the component during sintering. This debinding is typically done by heating the green body to a temperature between 200 to 750 degrees Celsius and allowing the binder to burn off. Different binders require different debinding temperatures.
• the debinding is typically done in an oxidizing atmosphere, typically air, but it can also be done partially in the same atmosphere as the sintering atmosphere, if the final component is not ruined by the extra content of carbon. In order to ensure that the debound green body can still be handled, it may be necessary to oxidize the powder slightly together; these oxides will be removed in the sintering process.
• a second aspect of the invention relates to a drying tool for drying a green body during the manufacturing of a powder metallurgical component before sintering or oxidizing, the drying tool comprising:
• the drying tool being suitable for drying a component obtained by a method according to the first aspect of the invention.
• the plurality of nozzles may be arranged in a predetermined pattern, such as in a regular pattern of aligned rows and columns. They may e.g. be arranged to match a pattern formed by the mutual positions of longitudinally extending channels of a component being manufactured by a method according to the first aspect of the invention as described above. In some embodiments, there are at least three rows of nozzles, each row comprising at least three nozzles.
• a drying tool according to the invention may comprise a plurality of fluid channels each extending between the first end and a nozzle.
• At least some of the nozzles may comprise a closing mechanism for closing off the respective nozzle so that there is no flow of gas there-through during use of the drying tool.
• the mutual position of at least some of the nozzles may be adjustable.
• Figure 1 shows schematically a method of manufacturing a powder-metallurgical component according to the first aspect of present invention.
• Figure l.a shows the steps of preparing the powder mixture, transferring it into the processing equipment, and forming a green body.
• Figure l.b shows how a gas flow is guided through an internal channel of the green body having the outer surfaces covered by plates.
• Figure l.c shows the sintering.
• Figure 2 shows schematically an example of a component having a plurality of longitudinally extending inner channels arranged in a regular pattern.
• Figure 3 shows schematically an embodiment of a drying tool according to the second aspect of the present invention.
• Figure 3. a is a side view
• figure 3.b is three-dimensional partial view of the second end comprising nozzles.
• Figure 4 shows how the drying tool of figure 3 can be arranged with the nozzles being engaged with end sections of channels of a green body during drying.
• Figure 5 is a cross-sectional view of the drying tool in figure 4.
• Figure 6 shows schematically the drying tool in figures 3-5 having some of the nozzles closed by a plug.
• Figure 7 shows schematically a drying tool wherein the mutual positions of nozzles are adjustable.
• Figure 8 shows schematically a step of drying wherein an auxiliary tool is used to support the green body.
• Figure 9 shows experimental results of tests performed during the development of the present invention.
• Figure 1 shows schematically a method of manufacturing a powder-metallurgical component according to the first aspect of present invention.
• a powder mixture is prepared by mixing at least metal powder 11 and a binder 12.
• the powder mixture may comprise further constituents, such as ceramic powder or lubricant.
• the powder mixture is then transferred to a processing equipment 31 comprising a die 32; it may e.g. be an extruder, such as a piston extruder.
• the powder mixture is formed into a green body 20 by forcing it through the die 32. This step is done by applying a pressure P as shown schematically in the figure as an arrow.
• the die 32 is designed so that it is adapted to form the component 21 in a shape having the at least one longitudinally extending channel 22. In figure 1 the component has only one channel, but a component having a plurality of channels can be produced by a similar method by using another die.
• Figure l.b shows schematically the step of drying the green body 20 by guiding a flow of gas G through the longitudinally extending channel 22.
• the outer surfaces of the green body 20 are covered by plates 39 so that the drying takes place due to the flow of gas G being through the longitudinally extending channel 22 only.
• the gas may have a higher or a lower temperature than the surrounding air, and/or the gas may have a higher or a lower humidity than the surrounding air.
• the gas is typically air, but other gasses can also be used.
• the covering plates can also provide structural support to the green body during the drying.
• the step of drying could have a length being a predetermined time period, e.g. determined experimentally. It could also be determined during the drying process from measurements of the humidity of the gas that has flown through the green body 20.
• the final component 21 is obtained by sintering the dried green body as shown schematically in figure l.c. This may e.g. be done in a reducing atmosphere, in vacuum, or in an inert atmosphere.
• the sintering is typically performed in a furnace 34 at temperatures of 950 to 1430 degrees C.
• a step of debinding may precede the step of sintering or oxidizing, the debinding step typically comprising heating the green body 20 to a temperature at which at least some, such as all, of the binder burns off.
• Figure 2 shows schematically an example of a component 21 having a plurality of longitudinally extending inner channels 22 arranged in a regular pattern, separated by walls 23.
• a component 21 can be manufactured by a method as described in relation to figures 1 provided that a suitably designed die 32 is used.
• Figure 3 shows schematically an embodiment of a drying tool 40 for drying a green body 20 before sintering or oxidizing.
• Figure 3. a is a side view illustrating that the drying tool 40 has a first end 41 comprising or being connectable to a gas flow generating device 43, and an opposite second end 42 comprising a plurality of nozzles 44.
• the nozzles 44 are in fluid communication with the first end 41 so that gas can flow through each of the nozzles 44 under the action of the gas flow generating device 43 during use of the drying tool 40.
• Figure 3.b is three- dimensional partial view of the second end 42 comprising nozzles 44.
• the nozzles 44 are arranged in a regular pattern of aligned rows and columns.
• the nozzles 44 have two different shapes, but the nozzles may all be identical, or there may be more different shapes and sizes of nozzles.
• Figure 4 shows how the drying tool 40 of figure 3 can be arranged with the nozzles 44 being engaged with, such as extending into, end sections of the longitudinally extending channels 22 of a green body 20 during drying.
• arrangement of the nozzles 44 of the drying tool 40 of figure 3 matches the arrangement of the inner channels 22 of the component in figure 2.
• the gas flow generating device 43 is activated so that gas flows into each of the longitudinally extending channels 22.
• the fact that the nozzles 44 extend into each of the inner channels 22 means that the nozzles both provide for a uniform drying and support the walls 23. Both measures lead to a minimization of possible deformation and damage of the green body 20.
• Figure 5 is a cross-sectional view of the drying tool 40 in figure 4. It illustrates the drying tool 40 comprising a plurality of fluid channels 45 each extending between the first end 41 and a nozzle 44.
• the middle section of the drying tool 40 is one open space or a lower number of fluid channels 45.
• such an embodiment would also be covered by the scope of protection.
• Some of the nozzles 44 may comprise a closing mechanism 46 for closing off the respective nozzle 44 so that there is no flow of gas there-through during use of the tool.
• a closing mechanism 46 for closing off the respective nozzle 44 so that there is no flow of gas there-through during use of the tool.
• FIG 6 An example of such an embodiment is shown schematically in figure 6, wherein the nozzles 44 in the upper and lower rows of the drying tool 40 are shown as being closed with a closing mechanism 46, such as a removable plug. This may e.g. be relevant if the drying tool 40 is to be used for the drying of a green body 20 having a smaller cross-section or a green body 20 having outer regions without inner channels.
• Figure 7 shows schematically a drying tool 40 wherein the nozzles 44 are in the form of flexible tubes so that the mutual positions of nozzles 44 is adjustable.
• the drying tool 40 may be used for different geometries of green bodies 20.
• at least some of the nozzles 44 may comprise stiff end sections (not shown) adapted to support the walls 23 of the longitudinally extending channels 22 and thereby prevent them from deforming during the drying as described above.
• Figure 8 shows schematically how an auxiliary tool 47 can be arranged at an opposite end of the green body 20 as the one where the drying tool 40 is arranged.
• the auxiliary tool 47 is used to support the longitudinally extending channel 22 during drying.
• this is shown schematically as small pins 48 protruding from an end surface of the auxiliary tool 47 so that they can extend into the longitudinally extending channels 22 of the green body 20 being dried.
• Figure 9 shows results of some tests made to study the effect of using a drying tool according to the present invention. All the six components were made from the same materials and extruded to have a plurality of inner channels as shown in figure 2. The experiments were repeated three times as shown in figures 9. a, 9.b and 9.c, respectively. The lower components in the figures were left to dry without any forced flow of air, and the upper component were dried by guiding air through the inner channels by use of a drying tool according to the invention. The results clearly show how the use of a drying tool and method according to the present invention can be used to stabilize the component during drying and thereby prevent undesired deformation thereof.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Devices For Post-Treatments, Processing, Supply, Discharge, And Other Processes (AREA)
• Drying Of Solid Materials (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=68771508

Family Applications (1)

Country Status (3)

Family Cites Families (10)

• 2020
  • 2020-12-03 CN CN202080083993.7A patent/CN114761156A/zh active Pending
  • 2020-12-03 WO PCT/EP2020/084453 patent/WO2021110830A1/en unknown
  • 2020-12-03 EP EP20816479.8A patent/EP4069451A1/de active Pending

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