Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
  • B22D17/007—Semi-solid pressure die casting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
  • B22D17/20—Accessories: Details
  • B22D17/30—Accessories for supplying molten metal, e.g. in rations
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S164/00—Metal founding
  • Y10S164/90—Rheo-casting

Definitions

• the invention relates to a device for producing semifinished products and molded parts from metallic material with an extruder for generating a metal stream and devices downstream of the extruder for molding the semifinished products and molded parts.
• a device of this type for die casting molded parts is known from EP 0 080 787, in which a metallic material with dendritic properties, for example a magnesium alloy, is brought into a thixotropic state in an extruder. In this state, the metallic material has a slurry-like or pulp-like consistency and can be processed into metallic molded parts in the shaping devices downstream of the extruder.
• a metallic material with dendritic properties for example a magnesium alloy
• the magnesium alloy) in the extruder to a thixotropic mass takes place in the manner described in EP 0 080 787 in that the material in granulate form is introduced into a preheated filling funnel, the granulate particles being sized are adjusted so that they can be processed well by the screw of the extruder.
• the granules are heated to a temperature close to or above the solidus temperature, and the heating can take place before and / or in the extruder.
• the metallic material is further heated in the extruder by heating devices acting from the outside via the screw cylinder and by frictional heat (shear stress).
• the heating in the extruder is metered so that the temperature of the metallic material remains below its liquidus temperature.
• a conveying channel between the screw flanks from the beginning of the screw to the end of the screw consists of a continuous helical channel.
• the principle of conveyance of an extruder consists essentially in the fact that the material to be conveyed experiences friction on the cylinder wall of the extruder and slides on the so-called screw base.
• a melt film builds up on the cylinder wall, which is very low viscosity and which considerably reduces the friction of the material to be conveyed on the cylinder wall, which is reflected in a drastic reduction in the delivery rate.
• the mixing capacity also suffers considerably, as a result of which a temperature gradient that builds up cannot be effectively reduced from outside to inside over the cross section in the interior of the extruder barrel.
• the invention has for its object to improve a device of the type mentioned constructively and functionally so that reproducible component qualities can always be produced.
• the processing of the metallic material for example starting from the granulate to the thixotropic solid-liquid or to the liquid material, based on the axial length of the extruder, is carried out largely in constant process steps and with constant conveyance.
• the negative consequences of temperature fluctuations and the associated irregularities in the viscosity and the proportionate composition of the liquid material components are thus reduced to a negligible level.
• the problem previously described for the single-screw extruder can be eliminated by an extruder with a screw system with two or more intermeshing screws, although the problems described above can also be expected with this type of extruder.
• a mechanism has a counteracting effect of a surprisingly large extent, by means of which the material to be conveyed is transferred from one screw to the neighboring, meshing screw.
• a sufficiently large mixing and transport effect is obviously achieved when processing metallic material, which, in addition to reducing the temperature gradient, also ensures a constant conveyance of the metallic material to be conveyed.
• a stable intake of fresh material is observed in the feed zone of the extruder.
• Heating tapes or inductively operating heating devices are conventionally used in the processing of metallic melts for introducing heat.
• inductive heaters are very expensive.
• Classic heating tapes are mounted on the circumference of the extruder cylinder and, at the high temperatures that prevail in the processing of metallic melts, tend to oxidize and scale the cylinder surface, thereby reducing the heat transfer between the radiator and the cylinder.
• precautions must be taken with heating tapes in order to keep them in permanent contact with the cylinder surface in order to achieve sufficient heat transfer.
• heating tapes Another disadvantage of heating tapes is the large distance between the heating tapes mounted on the outside of the extruder cylinder and the melt present inside the cylinder with the required high heat flux densities and temperature gradients of up to 200 ° C and more during operation.
• heating cartridges which comprise resistance heating elements arranged in a usually cylindrical housing.
• the heating cartridges can be arranged in transverse bores in the extruder cylinder jacket very close to the inner wall of the cylinder, for example above and below the double-cylindrical cavity of the twin-screw extruder.
• the cross holes themselves can be hermetically sealed with an airtight and heat-resistant material so that they are protected against scaling.
• the outer surface of the extruder barrel can also be insulated much better against heat radiation when using the heating cartridges arranged in the barrel wall.
• the extruders equipped with the heating cartridges can be manufactured in such a way that their tie rods are arranged outside the insulation and thus in a considerably cooler area. As a result, much cheaper materials can be used for this.
• the drive of the extruder screws as well as the drive of the die casting pistons is often accomplished by means of hydraulic systems.
• Electric drives are therefore preferably used for the screw, but electric drives can also be used instead of a hydraulic system for driving the die-casting piston.
• the constant conveyance reduces the range of the residence time of the materials to be conveyed in the extruder, which is reflected in a uniform grain size of the globules in the structure of the finished molded parts or semi-finished products.
• One or more die-casting molds can be arranged downstream of the extruder, which can be fed with metallic material continuously or discontinuously via multi-way switches and heated channels.
• the side feed can be done with volumetric or gravimetric dosing.
• the side feed takes place for the different materials in the temperature and functional zones suitable for the respective material.
• Pure metals e.g. B. Li, Mg, Ca, Al, Si, Zn, Mn, rare earth metals and the like combine to metal alloys, also master alloys, such as. B. AlZn, the extruder according to the invention.
• non-metallic materials such as. B. Reinforcing materials, fillers, nucleating agents, processing aids and the like, work into the solid-liquid or liquid metal stream, whereby the extruder according to the invention the function of a machine for the production of alloys or composite materials.
• Proposed units e.g. Extruders, processed, especially liquid materials are fed.
• components of constant quality can thus be produced, which can consist of pure metal, metal alloys, or of non-metallic materials homogeneously mixed with the metal or the metal alloys.
• the equipment downstream of the extruder for shaping the semi-finished products and molded parts can be selected from a large selection. To name just a few of the most important:
• die casting units equipped with a separate piston / cylinder unit, as are known, for example, from EP 0 080 787, should be mentioned.
• Piston / cylinder units which are filled in front of the piston surface, the piston remaining in the retracted position at the beginning of the filling in one variant and the filling taking place either directly in front of the piston or away from it in the direction of the cylinder outlet; in an alternative variant, filling is carried out at the cylinder outlet and the piston is retracted / pushed back during filling, and in a further variant the cylinder space in front of the piston is filled in the cylinder outlet duct and the piston from the front Dead position with the incoming metallic material moved to the retracted position.
• a variant which is fundamentally different is a so-called stepped piston which divides the cylinder space of the die-casting cylinder into a feed space connected to the extruder via a heated channel and an injection space connected to the mold cavity.
• a fluid connection is created between the feed space and the injection space, which contains a non-return valve or a check valve, which counteracts a backflow of metallic material from the injection space into the feed space.
• the stepped piston has the larger piston area on the side of the injection space and the smaller, usually annular piston area on the side of the feed space.
• this can be from the extruder in the feed area with a pressure of z. B. less than 120 bar fed thixotropic metallic material at injection pressure of z. B. 500 bar and more, in particular 1000 - 2000 bar, with leakage losses playing no role, since the leakage quantities coming from the injection space into the feed space are conveyed back into the injection space at the next injection stroke.
• stepped piston Another advantage of the stepped piston is that the material entered into the die-casting cylinder with a relatively low pressure automatically resets the stepped piston due to the pressure difference between the larger piston surface and the smaller annular piston surface, which eliminates the need to install multi-way switching valves between the extruder and the die-casting cylinder. If necessary, this can be supported hydraulically. Finally, there is the advantage that the current generated by the extruder of metal material is only conveyed in one direction up to the injection into the mold cavity, which is particularly suitable for the processing of material that has long reinforcing fibers (e.g. carbon fibers) incorporated into the extruder via a side feed.
• long reinforcing fibers e.g. carbon fibers
• the invention further relates to a method for die casting, continuous casting or extrusion of metallic materials using an extruder and downstream units for forming semi-finished products and molded parts, in particular of the type described above.
• the use of an extruder with a screw system with two or more intermeshing Screws allow a controlled conveyance of the metallic material in the direction of extrusion. This applies in particular to material in the solid-liquid thixotropic state and in the liquid state.
• the controlled conveyance or forced conveyance avoids discontinuities in the processing of the metallic material, which contributes significantly to an improved constancy of the component quality of the metallic components produced in the die casting process.
• the inventive processing of the metallic material and its controlled or forced conveyance in the extruder now allows the side feeding of further components, for example alloy components in the manufacture of alloys, reinforcement components in the manufacture of metallic composite materials or other additives for modifying the metallic material in a particularly simple and defined manner Wise.
• the controlled or forced delivery in the extruder ensures a high degree of homogeneity of the metallic material produced.
• Figure 1 is a schematic, partially broken illustration of a twin-screw extruder according to the invention
• FIG. 2 shows a schematic representation of various embodiments of the die casting units to be arranged after the extruder from FIG. 1;
• FIG. 3 shows a sectional view through the extruder of FIG. 1 along line 3 - 3.
• FIG. 1 shows in FIG. 1 a schematic representation of an extruder 1 of the type of a twin-screw extruder, in the extruder barrel 2 of which two screws are mounted, of which only the front screw 3 can be seen in the area shown broken away.
• the profile of the screw 3 engages in the profile of the neighboring screw behind it.
• the top surface 4 of the screw flights of the one screw 3 adjoins the core surface 5 of the (not visible) neighboring screw.
• the distance from the head diameter K j of one screw to the core diameter K 2 of the neighboring screw and the distance of the screw flanks from one another are to be selected so that a metallic material to be processed with dendritic properties Shafts on the one hand a desired shear stress can be generated, but on the other hand the liquefied phase of the metallic material due to its lower viscosity is not uncontrolled by the gaps between the screw flanks, the head surfaces 4 and the core surfaces 5 and the head surfaces 4 and the inner wall 6 of the extruder barrel 2 can flow.
• the intermeshing screws form, in the event that they are driven in opposite directions, progressively closed chambers in which the material is forcibly transported.
• the shearing process converts the dendritic structures of the solidifying phase into globulitic particles, and on the other hand it releases frictional heat.
• the drive unit 8 for the screws 3 is located after the area of the filling funnel 7 for feeding the extruder 1 with metallic material, for example in granulate, chip or powder form.
• Heat decouplings (not shown) are arranged between the drive unit and the cylinder and the screw.
• feed devices 9 to 12 Following the filling funnel 7 there are a number of feed devices 9 to 12 through which additional materials can be input into the extruder 1 at the process and temperature stages, which are suitable for the respective input material. Thermal energy is introduced into the extruder 1 from the outside via heating sleeves 13 each shown in half section.
• the feed devices 9 to 12 can optionally be insertion funnels, metering screws, stuffing devices, belt or roving feeders, extruders (including the twin screw extruders according to the invention) or injection units for liquids.
• the feed devices 9 to 12 are preferably supplied with an inert gas as a protective gas.
• the screw 3 is shown purely schematically and of course can have a varying configuration over its length. Opposite to the feed devices 9 to 12 in particular, the corresponding screw sections will be adapted to the respective function of the screw.
• the solid-liquid, metallic, thixotropic material produced in the extruder 1, which can be mixed with a wide variety of additional materials, is passed via a first heated channel 14 into the feed space 15 of a die casting cylinder 16.
• a stepped piston 17 is reversibly arranged in the die-casting cylinder 16 and divides the cylinder space of the cylinder 16 into the feed space 15 and into the injection space 18.
• the piston area 19 delimiting the injection space 18 is larger than the annular piston area 20 delimiting the injection space 15.
• a non-return valve 21 of the type, e.g. a check valve.
• the non-return valve 21 blocks the fluid connection in the form of a passage passage (not shown) in the stepped piston 17 from the injection space 18 to the feed space 15 and switches the passage passage freely in the opposite direction.
• the injection chamber 18 is followed by a second heated channel 22 leading to the form cavity (not shown), which can be closed with an actively controllable closure nozzle 23.
• the stepped piston 17 can be displaced in a reversible manner in the injection piston 16 via a hydraulic piston-cylinder unit 24 of a hydraulic system 25.
• the thixotropic or else liquid metallic material produced in the extruder 1 which can be mixed with the various additional materials, is passed via the first heated channel 14 into the feed chamber 15 and passes through the passage in the stepped piston 17 into the injection chamber 18, the outlet of which is shut off by the closure nozzle 23. Because of the area ratio of the larger piston surface 19 to the smaller annular piston surface 20, the stepped piston acts
• the hydraulic piston / cylinder unit 24 is controlled for the filling process of the die-casting cylinder 16 in such a way that the stepped piston 17 can be pushed back in a controlled manner and is stopped when the required filling quantity is reached.
• the filling process takes place at the low pressure level generated by the extruder 1 (for example 5 to 120 bar).
• the stepped piston 17 is advanced by the hydraulic piston-cylinder unit 24, the non-return valve 21 closing and in the injection chamber
• the injection pressure e.g. 1500 - 2000 bar.
• the thixotropic or optionally liquid metallic material reaches the mold cavity via the opened closure valve 23 and the second heated channel 22. Leakages occurring at the high injection pressure are irrelevant, since the leakage quantities can only get into the feed space 15, from where they are fed back into the injection space 18.
• the sealing of the feed space 15 from the atmosphere or from a hydraulic space of the hydraulic piston-cylinder unit is not a problem due to the much lower pressure level.
• FIG. 2 schematically shows a die casting cylinder 30 as it can be used as an alternative to the one shown in FIG. 1 together with the twin-screw extruder 1 according to the invention as part of a shaping device.
• the die-casting cylinder 30 has a hollow cylinder 32 in which an injection piston 34 is reversibly guided.
• the die-casting cylinder 30 does not have a separate feed and injection space, but these two spaces coincide here in a space 38 in front of the piston surface 36.
• the latter has an inlet opening 40 which is arranged adjacent to the piston surface 36 in a retracted dead position of the piston 34.
• the feed / injection space fills from the piston surface 36 of the piston 34.
• the feed opening 40 ′ is arranged at the front end of the feed / injection space 38, adjacent to a heated channel 42 leading to the mold cavity.
• the space 38 can be filled as long as the piston 34 is in the retracted dead position or during the piston 34 is moved from a front dead position (dash-dotted line) to the withdrawn dead position (solid line).
• the feed opening 40 ′′ is finally provided on the heated channel 42 leading to the mold cavity, adjacent to the front end of the cylinder 32.
• FIG. 3 shows a sectional illustration of the twin-screw extruder 1 according to the invention along line 3-3 in FIG. 1, although a variant is shown here in which a different heating device is selected instead of the heating sleeves 13.
• the two screws 3 are not shown in FIG. 3. These are arranged in the double cylindrical cavity 6, which offers space for two mutually parallel, intermeshing screws 3.
• the cylinder 2 here has transverse bores 44, 45 transverse to its longitudinal direction, which are arranged adjacent to the cavity 6.
• heating cartridges 46, 47 are arranged, via which, due to their proximity to the double cylinder cavity 6, a very high heat flow to the materials to be processed in the extruder 1 can be produced.
• the transverse bores 44, 45 are closed with an airtight and temperature-insensitive material plug 48, 49, through which only electrical leads 50, 51 have to pass.
• Insulation 52 can now be attached to the outside of cylinder 1 in a very simple manner, which can be provided consistently on cylinder 2 with the same thickness, without external heating strips having to be taken into account.
• the heating cartridges 46, 47 are repeated over the length of the extruder barrel 2 and like the heating jackets 13, allow individual heating over the length of the extruder 1.
• heating cartridges can be used in the transverse bores, which protrude beyond the circumference of the extruder cylinder, so that the transition area of the heating cartridges is outside the cylinder and the heated area is inside the cylinder.
• the material plugs 48, 49 may be dispensed with. Disassembly and maintenance are simplified.
• tie rods for the extruder can be provided outside the insulation 52 and these experience far lower temperatures than with the extruders customary in the prior art. As a result, these tie rods can be made from a less expensive material because they are exposed to far less temperature loads.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)
• Forging (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)

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• 1999
  • 1999-02-19 DE DE19907118A patent/DE19907118C1/de not_active Expired - Fee Related
• 2000
  • 2000-02-21 DE DE50010397T patent/DE50010397D1/de not_active Expired - Lifetime
  • 2000-02-21 AU AU29129/00A patent/AU2912900A/en not_active Abandoned
  • 2000-02-21 EP EP00907593A patent/EP1152852B1/fr not_active Expired - Lifetime
  • 2000-02-21 AU AU32810/00A patent/AU3281000A/en not_active Abandoned
  • 2000-02-21 WO PCT/EP2000/001416 patent/WO2000049192A1/fr active Application Filing
  • 2000-02-21 WO PCT/EP2000/001417 patent/WO2000048767A1/fr active IP Right Grant
  • 2000-02-21 AT AT00907593T patent/ATE296175T1/de not_active IP Right Cessation
• 2001
  • 2001-08-16 US US09/931,289 patent/US6546991B2/en not_active Expired - Fee Related
• 2003
  • 2003-01-27 US US10/351,803 patent/US6648057B2/en not_active Expired - Fee Related

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