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
  • B22F3/10—Sintering only
  • B22F3/1003—Use of special medium during sintering, e.g. sintering aid
  • B22F3/1007—Atmosphere
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B21/00—Open or uncovered sintering apparatus; Other heat-treatment apparatus of like construction
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/02—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity of multiple-track type; of multiple-chamber type; Combinations of furnaces
  • F27B9/029—Multicellular type furnaces constructed with add-on modules
• • 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
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps
• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/06—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated
  • F27B9/10—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity heated without contact between combustion gases and charge; electrically heated heated by hot air or gas

Definitions

• the invention relates to a method for sintering aluminum-based sintered parts, in which the following steps are carried out in separate atmospheres in spatially separated areas:
• the sintered parts are brought to the sintering temperature and held there for a certain time;
• pure aluminum powder is not processed; rather, powder mixtures or alloy powders, which contain silicon as an additive, are preferably used. All powders that contain aluminum as an important component are collectively called "aluminum-based" and are at risk of forming oxides during sintering. Aluminum sintered parts with a relatively high silicon content are particularly desirable. However, as the silicon content increases, the sintering process becomes more difficult. Another difficulty with the sintering of aluminum-based powders is that they require a higher binder content during the pressing process.
• binding aids which simultaneously serve as a lubricant for the pressing tool, make up a content of about 0.7 to 1.0 percent by weight, about 1.0 to 1.5 percent by weight of binding aids must be added for sintering aluminum , These binding aids must be complete again before the sintering process be removed. All in all, all requirements for accuracy, reproducibility and the homogeneity of the temperature distribution when sintering aluminum-based powder are much more critical than when sintering other powders, especially iron. For this reason, aluminum sintered parts have not yet been used wherever this would be desirable in and of itself.
• the object of the present invention is to provide a method of the type mentioned at the outset with which high-quality aluminum-based sintered parts can be produced.
• process step b) an inert gas is used as the atmosphere, the oxygen content of which corresponds to a dew point of at most -40 ° C., and in that the sintered parts are circulated to a sintering temperature of 560 - by circulating the correspondingly heated inert G Gaassess. 620 C can be heated
• the invention is based on a double insight: The fact that a maximum limit is set for the oxygen content of the inert atmosphere ensures that there are no undesired oxides in the sintering process can form, which adversely affect the sintering product. Characterized in that, unlike the subject of DE-PS 197 19 203 mentioned above, the sintered parts are not heated by radiant heat but by convection heat, for which purpose the highly pure inert mentioned
• the sintered parts are heated with a homogeneity that would otherwise not be possible. It is only in the sum of these characteristics that the high quality of the sintered products is achieved.
• Nitrogen is preferably used as the inert gas. This can be obtained commercially with the required purity and is much cheaper than noble gases, which in principle are also possible.
• Another object of the present invention is to design a device of the type mentioned at the outset in such a way that it is suitable for producing high-quality aluminum-based sintered parts.
• the atmosphere in the sintering area is formed by an inert gas, the oxygen content of which
• the sintered area has at least one heating device for the sintered parts, which comprises indirectly heated heat exchange surfaces, a blower and an air guiding device such that a circulating flow of the inert gas flowing around the sintered parts can be set.
• the sintering area of a sintering device must have a length that corresponds to the time required for sintering at the selected transport speed. In general, it is advisable if a longer sintering area has a plurality of zones delimited by partitions, each of which has a heating device with heat exchange surfaces, blowers and air devices. As a result, defined flow conditions can be set anywhere, even with longer sintering areas.
• the temperature of the inert gas differs from zones of the sintered area located one behind the other in the direction of movement.
• the embodiment of the invention leads to particularly good sintering results due to the high homogeneity of the temperature profile, in which the flow around the sintered parts is different in zones of the sintered region lying one behind the other in the direction of movement.
• the sintered parts can be washed from bottom to top, the other from top to bottom, once by a flow rotating clockwise, the other by a flow rotating counterclockwise.
• Figure 1 schematically shows a sintering furnace for sintering aluminum-based sintered parts
• Figure 2 shows a section on an enlarged scale through the sintering furnace of Figure 1 in the region of the sintering zone.
• FIG. 1b shows a sintering furnace in vertical section, which is intended for sintering aluminum-based sintered parts.
• the entire sintering furnace is divided into different zones or areas, which are shown schematically in FIG.
• the sintered parts 23 (cf. FIG. 2) are conveyed through the sintering furnace from left to right in a continuous pass in the drawing with the aid of a transport system T.
• the sintering furnace contains, seen in the conveying direction, one after the other an inlet area 8, a debinding area 3, a sintering area 2, a cooling area 4 and an outlet area 9.
• Each of these areas 2, 3, 4, 8, 9 of the sintering oven is a separately drivable and controllable Assigned conveyor T2 to T9, which together form the above-mentioned conveyor system T.
• locks 7 are arranged between these areas, each having two mechanical gates 6. These gates 6 are each arranged in a front shaft of the corresponding area 3, 2, 4, 9 and are preferably movable vertically, each lock 7 being assigned a conveyor which is also separately controllable and controllable (not shown in the drawing).
• the debinding area 3 preceding the sintering area 2 in the conveying direction is designed as a muffle furnace. That is, above and below the path of movement to the sintered parts there is a partition 20, which is brought to temperature by means of electric heating elements 21 or the like, essentially heats the conveyed sintered parts by radiant heat and drives out the binding aids. While in the sintering furnace described in DE-PS 197 19 203.3 and intended for sintering iron powder parts, the sintering region also works with radiant heat, the sintering region 2 of the present sintering furnace differs from this in a manner which will now be described with reference to FIG. 2.
• FIG. 2 shows a section perpendicular to the direction of movement of the sintered parts in the area of the sintering zone 2.
• the transport system T2 is shown, the exact construction of which is deliberately left open. It is characterized by good gas permeability in the vertical direction; For example, roller or link belt systems are particularly suitable.
• the sintered parts 23 are conveyed perpendicular to the drawing plane of FIG. 2, in the example shown on a carrier plate 24, which ideally should be permeable even in the vertical direction.
• the area of the interior of the housing 22 which lies above the sintered parts 23 is divided into two chambers 26 and 27 by a partition 25 which runs parallel to the direction of movement of the sintered parts 23 and essentially vertically.
• a partition 25 which runs parallel to the direction of movement of the sintered parts 23 and essentially vertically.
• the heat exchanger surfaces 28 of an indirect heater 29 which can be operated, for example, electrically.
• At the upper end of the chamber 26 there are air baffles with a central opening 30, which represents the suction opening of a blower 31.
• the blower 31 is driven by a motor 32 mounted on the top of the housing 22.
• the outlet side of the blower 31 is connected via an opening 33 to the chamber 27 on the right in FIG. 2 of the interior of the housing 22.
• This chamber 27 is closed at its lower end, just above the sintered parts 23, by a nozzle plate 34.
• the entire sintered area 2 contains, in particular
• FIG. 1b shows a plurality of identical sintered zones constructed in the manner described above, which are separated from one another by partition walls 35.
• the partitions 35 essentially only contain openings which just allow the passage of the sintered parts 23.
• the cooling area 4 is designed essentially in the same manner as described in DE-PS 197 19 203.3. The manner in which the sintered parts are tempered and cooled in this area is of no interest in the present context. Also shown in the drawing is a type of "muffle furnace" with a similar design to that used in debinding zone 3.
• the pressed sintered parts 23 are placed in the inlet area 8 on the conveyor system T8, introduced by the latter through a simple gate 6 into the debinding zone 3 and taken over by the conveyor system T3 there. With the help of the radiant heat emitted by the heated partition walls 20, the binding aids are expelled from the sintered parts 23 and essentially removed. Since all inner surfaces in the debinding zone 3 are hot, there is no risk of "sooting up" of binding agents.
• the sintered parts 23 enter individually or in small groups of sintered parts 23 lying next to and / or one above the other through the first gate of the lock 7, which lies between the debinding area 3 and the sintered area 2, into the space between the two gates of this lock 7.
• the first gate leading to the debinding zone 3 is closed and the interspace of the lock 7 is rinsed and / or pumped out.
• the sintered parts 23 are conveyed by a separate transport system T7, the speed of which can differ from the speed in the other areas of the sintering furnace in order to keep the overall system short.
• the gate of the lock 7 adjacent to the sintering area 2 opens.
• the sintered parts 23 are now transferred to the conveyor system T2 and transferred from this to a picking zone which, for example, passes through the first three zones of the Sintered area 2 extends through.
• the actual sintering takes place at a temperature between 560 and 620 ° C instead.
• the temperature of the gas present in the individual zones is monitored in each case by a temperature sensor 40 (see FIG. 4) which is arranged in the vicinity of the movement path of the sintered parts 23 and which controls the heater 29 via a control circuit.
• the sintered parts 23 pass through the lock 7, which comprises two gates and is located between the sintering area 2 and the cooling area 4, the same operations taking place as described above for the lock 7 located between the debinding area 3 and the sintering area 2 has been.
• the cooling area 4 there is then a controlled cooling of the finished sintered parts to a temperature at which the sintered parts 23 exit the cooling area 4 via a further lock 7 and are finally removed in the outlet area 9 from the conveyor system T9 there or transported to another location can.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Powder Metallurgy (AREA)
• Tunnel Furnaces (AREA)

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Publications (2)

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Cited By (1)

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• 2000
  • 2000-06-28 DE DE10066005A patent/DE10066005C2/de not_active Expired - Fee Related
• 2001
  • 2001-05-12 ES ES01956435T patent/ES2214435T3/es not_active Expired - Lifetime
  • 2001-05-12 US US10/312,652 patent/US6821478B2/en not_active Expired - Fee Related
  • 2001-05-12 EP EP01956435A patent/EP1294512B1/fr not_active Expired - Lifetime
  • 2001-05-12 AT AT01956435T patent/ATE259267T1/de not_active IP Right Cessation
  • 2001-05-12 AU AU2001278425A patent/AU2001278425A1/en not_active Abandoned
  • 2001-05-12 WO PCT/EP2001/005443 patent/WO2002000377A1/fr active IP Right Grant

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