EP0482220A1 - Procédé de préparation de pièces de forme compliquée à partir de poudre métallique ou céramique - Google Patents

Procédé de préparation de pièces de forme compliquée à partir de poudre métallique ou céramique Download PDF

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Publication number
EP0482220A1
EP0482220A1 EP90120136A EP90120136A EP0482220A1 EP 0482220 A1 EP0482220 A1 EP 0482220A1 EP 90120136 A EP90120136 A EP 90120136A EP 90120136 A EP90120136 A EP 90120136A EP 0482220 A1 EP0482220 A1 EP 0482220A1
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EP
European Patent Office
Prior art keywords
film
powder
negative mold
interior
negative
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.)
Withdrawn
Application number
EP90120136A
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German (de)
English (en)
Inventor
Heinrich Prof. Dr. Feichtinger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ABB Asea Brown Boveri Ltd
ABB AB
Original Assignee
ABB Asea Brown Boveri Ltd
Asea Brown Boveri AB
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by ABB Asea Brown Boveri Ltd, Asea Brown Boveri AB filed Critical ABB Asea Brown Boveri Ltd
Priority to EP90120136A priority Critical patent/EP0482220A1/fr
Publication of EP0482220A1 publication Critical patent/EP0482220A1/fr
Withdrawn legal-status Critical Current

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    • 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
    • B22F3/12—Both compacting and sintering
    • B22F3/1208—Containers or coating used therefor
    • B22F3/1216—Container composition
    • B22F3/1233—Organic material
    • 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
    • B22F3/02—Compacting only
    • B22F3/04—Compacting only by applying fluid pressure, e.g. by cold isostatic pressing [CIP]

Definitions

  • the invention relates to the further development, perfection and simplification of powder metallurgical manufacturing methods for the production of workpieces with comparatively complicated shapes, where the problems of shrinkage during sintering play an important role.
  • the main area of application is in the area of components for turbine construction.
  • the invention relates to a method for producing a complicated workpiece starting from metal and / or ceramic powders using a sintering process, a powder or a powder mixture being filled into a mold and precompacted.
  • metal injection molding In metal injection molding ("metal injection molding”; MIM), a mixture of the metal powder to be compacted is injected into a mold together with a suitable thermoplastic in accordance with the injection molding technique. A summary of the methods of "metal injection molding” is given in a chapter of the Metals Handbook.
  • the vacuum molding process is known from foundry technology and is used to produce casting molds from refractory granular molding material, usually quartz sand.
  • refractory granular molding material usually quartz sand.
  • a negative pressure is created in the sand, which exerts a compression pressure of the external gas atmosphere on the sand bed via the film.
  • the resulting compressive stresses between the grains prevent their mutual mobility, which means that a loose body creates a mechanically resistant body with a defined shape.
  • the invention has for its object to provide a method with which, starting from metal or ceramic powders, a comparatively complicated shaped workpiece of any cross-section and unlimited wall thickness can be produced.
  • the process is intended to provide a reproducible finished product that no longer has to be processed, or at most only slightly. Bubbles and unwanted harmful residues should be avoided during powder processing.
  • the process is intended to ensure the greatest possible freedom of movement and universality.
  • FIG. 1 A flow diagram (block diagram) of the method is shown in FIG.
  • the individual process steps correspond exactly to those of claim 1 and require no further explanation.
  • the powder solidified by external pressure thanks to the frictional forces between the powder particles has sufficient "green strength" to be processed further (green body).
  • 2 shows a schematic elevation / section of a negative mold with a container.
  • 1 is a tubular, one-sided closed thin film made of a gas-tight organic or inorganic material which, when the method is carried out, conforms completely and without folds to the inner walls of the mold.
  • 2 represents an at least simply divided negative mold from a solid, the shape of the workpiece is clearly defined 3 is a container that can be placed under pressure or vacuum via the feed line 4.
  • FIG. 3 shows a schematic elevation / section of a negative mold including the device for carrying out the method in the state before the powder filling.
  • the reference numerals 1 to 4 correspond exactly to those in FIG. 2.
  • 5 is the powder intended for the production of the workpiece, which can be found in FIG a storage container 6, which can be closed gas-tight with a lid and is provided with a feed line 7.
  • 8 represents a blocking element for the powder in the form of a slide.
  • 9 is an intermediate chamber for gas supply and discharge, which can be acted upon via the supply line 10 with a gaseous medium (e.g. air) of any pressure (also negative pressure). The pressure conditions are indicated by arrows.
  • a gaseous medium e.g. air
  • FIG. 4 shows a schematic elevation / section of a negative mold including the device for carrying out the method in the state after the powder filling. All the reference numerals correspond to those in FIG. 3.
  • the slide 8 is in the open position, the powder 5 fills the film 1 completely, so that it is pressed against the inner walls of the negative mold 2, the container 3 is under pressure and the intermediate chamber 9 is under Vacuum.
  • the pressure conditions are again indicated by arrows.
  • FIG. 5 shows a schematic elevation / section of the green body at the moment the negative form is removed.
  • the reference numerals 2, 8, 9 and 10 correspond exactly to those in FIG. 4.
  • the intermediate chamber 9 is under negative pressure, which is indicated by the arrow.
  • the green compact formed by the powder 5 compressed in the film 1 under the external pressure (see arrows!) And thus solidified by frictional forces has sufficient inherent strength so that it can be handled as such.
  • Fig. 6 relates to a schematic elevation / section of the blank including support mass when sintering in an oven.
  • 1 is the film which holds the powder 5 together to form the "blank” thanks to the negative pressure acting as a closed vessel in its interior.
  • the “blank” is also mechanically stabilized by the ceramic support compound (backfill compound) 11 used to embed it.
  • 12 is a furnace chamber with supply line 13, in which the heating element (electrical resistance element, induction coil, etc.) is located.
  • a steam turbine blade was produced from a corrosion-resistant chrome steel powder with an average grain size of 50 ⁇ m.
  • the steel with the designation DIN X20CrMo 12 1 according to the German standard had the following composition:
  • the blade of the footed blade had the following dimensions: A tube-like film 1, closed on one side, in the form of a latex rubber sack with a diameter of 12 mm and a length of 90 mm, was inserted into the top fill opening of a two-part negative mold 2, which in turn was located in a vacuum-tight container 3, with the exception of this fill opening. The container 3 was then placed under reduced pressure.
  • the arrangement essentially corresponded to FIG. 2.
  • the film 1 Under the effect of the air inside the film 1 and the negative pressure acting over the dividing line of the negative mold 2, the film 1 was pressed firmly against the inner walls of the mold 1, whereby it was a true positive image of the Form 1 formed.
  • the above-mentioned powder 5 was now filled in with a funnel and compacted by means of a vibrator, the filling height of the powder going up to the center of the cylindrical filling opening. Now a pierced cylindrical metal plug was inserted into the upper part of the film 1 until its end face came into direct contact with the powder. In this way, an excellent seal was achieved between the film 1 and the outer surface of the stopper.
  • a negative pressure being set below 30 mbar.
  • the film 1 remained statically under vacuum and could now be removed from the mold after releasing the negative pressure in the container 3 and after removing the two-part negative mold 2.
  • a molded body of compacted powder 5 which exactly corresponds to the mold cavity was left, which under the influence of the air pressure showed an astonishing dimensional stability. This stability was so high that, with appropriate caution, the body can easily be placed in a backing mass could.
  • the powder molding was further processed by sealing sintering at 1350 ° C with a subsequent hot isostatic pressing process.
  • a turbine blade of the same dimensions and composition as in Example 1 was produced.
  • the molded article was produced using the same powder material as in Example 1, but the two-part negative mold 2 located in the container 3 with the film 1 (latex sack) (FIG. 2) sucked against the inner surfaces under the action of the negative pressure was pressed against an end face (Flange) of the intermediate chamber 9 is pressed with a lateral feed line 10.
  • Above the intermediate chamber 9 was a slide 8, which separated the powder 5 located in the reservoir 6 and under 2 bar nitrogen from the mold cavity. Via the feed line 10, the interior of the film 1 was now evacuated to approximately 50 mbar and then the slide 8 was suddenly opened, as a result of which the precisely measured amount of powder suddenly entered the film and filled it up to half the height of the filler neck.
  • this molding was backfilled with quartz sand, which was cured with a water glass-carbonic acid mixture in accordance with the method customary in foundry technology to form a stable molded body.
  • quartz sand which was cured with a water glass-carbonic acid mixture in accordance with the method customary in foundry technology to form a stable molded body.
  • sufficient green strength of the metal powder was achieved as a result of the sintering process, while the consistency of the ceramic support mass 11 under the influence of the vacuum heating became so low that it also cooled after cooling could be removed from the molding with little mechanical effort. In this case, too, there was perfect dimensional accuracy with a first-class surface structure.
  • a steam turbine blade was made from corrosion-resistant chrome nickel steel.
  • the steel with the designation 316 L according to the US standard corresponding to X3CrNiMo 17.12.2 German standard had the following composition:
  • the blade of the footed scoop had the following dimensions
  • a metal powder with a maximum particle size of 40 ⁇ m was assumed.
  • a latex sack was used as film 1, which was similar to the dimensions of the later molding, but was 30% smaller than the dimensions of the molding to be achieved.
  • a positive model was made with several aluminum gas channels opening into the surface. This model was now - similar to the state of the art in the manufacture of surgical gloves - immersed in a latex mass and slowly pulled out, after which it was dried in a warm air stream. The molded latex sack could be pulled off the model by blowing compressed air through the gas channels.
  • the further processing was carried out in accordance with embodiment 1, care being taken that the film 1 in the shape of the shaped bag was positioned in the negative mold 2 during the suction process in such a way that the expanded bag was brought into exact alignment with the inner profile of the negative mold 2.
  • the advantage of this procedural variant is that the latex film 1 has a higher dimensional stability in the area of sharp corners and protruding edges, since the local restoring forces of the stretched rubber are lower (better mold filling capacity).
  • a turbine blade with the dimensions and the composition according to Example 3 was produced.
  • a turbine blade for an exhaust gas turbocharger was made from silicon carbide SiC.
  • the so-called infiltrated SiC process was used for this purpose.
  • Example 1 a tube-like film 1, closed on one side, in the form of a latex-rubber sack with a diameter of 8 mm and a length of 70 mm, was inserted into the top filling opening of a two-part negative mold 2, which in turn was located in a vacuum-tight container 3.
  • the molded body made of compacted powder 5 was then inserted into an A1 2 0 3 crucible and held in a vertical position by means of a ceramic support compound 11 (backfill compound).
  • Zr0 2 sand was used for this purpose in the present case.
  • the whole was placed in a vacuum sintering furnace and first slowly heated to 300 ° C., the latex mass of film 1 being decomposed and the decomposition products being suctioned off.
  • the temperature was then increased to 1600 ° C., and the SiC particles were presintered after a holding time of 3 hours.
  • the porous molded body was removed from the support mass 11 and sintered further under vacuum at 1800 ° C. for 1 h.
  • the still porous body was cooled under vacuum to approx. 1500 ° C. and immersed in a bath of liquid silicon at approx. 1450 ° C. and left there for 10 minutes. He was completely infiltrated with Si, which reacted with the excess C to SiC.
  • the infiltration device was flooded with argon and the whole was cooled to room temperature over a period of about 8 hours.
  • the density of the molded body reached an average of 94% of the theoretical value.
  • a round rod was made from an austenitic iron alloy containing high levels of nitrogen.
  • the powder metallurgical path was taken, since the melting of alloys with very high nitrogen contents in the high-pressure furnace is difficult and the further shaping and shaping of cast material is cumbersome and uneconomical thanks to the high heat resistance and is often linked to technological problems.
  • An alloy powder with an average grain size of 60 ⁇ m and the following composition was assumed: The finished workpiece had approximately the following dimensions:
  • a metal foil 1 of 50 .mu.m thick made of a heat-resistant Cr / Ni steel with a high chromium and nickel content, as used for the scale-free annealing of Workpieces used was formed into a tube 120 mm in diameter and 1200 mm in length.
  • the part of the surface line of the cylinder as well as that of the bottom surface was connected to the respective abutting part by folding (similar to the manufacture of a bag) and welded in a vacuum-tight manner. Since this extremely thin-walled container did not have sufficient shape stability per se, it was pushed tightly into a metal tube with a corresponding inside diameter.
  • the irregularly pleated bottom was pressed flat into a plane perpendicular to the longitudinal axis of the cylinder by means of a stamp inserted into the container and pressed against the support.
  • the metal powder 5 was filled up to 150 mm below the upper edge of the container formed from the film 1 and the support tube.
  • a thin suction tube coated on its outer surface with soft rubber was inserted centrally, so that its lower end came to be just above the powder surface.
  • the part of the film 1 protruding over the support tube was pressed flat together and fastened tightly to the jacket of the suction tube. The air was then evacuated via this suction tube, the film 1 being pressed onto the metal powder 5.
  • the workpiece consisting of film 1 and pressed powder 5 was pulled out a little from the support tube (similar to vacuum packaging of frozen goods) and the smooth film 1 was pressed together and sealed. Thanks to the evacuation, the film 1 was subjected to a slight contraction in diameter, which made it easy to remove the workpiece from the support tube.
  • the workpiece showed an amazing dimensional stability (comparison: package of vacuum-packed coffee powder). This was particularly large in the area of the edges, since the edge stiffening (rib effect) caused by the folding and wrinkling process of film 1 was added to the effect of the external pressure.
  • the workpiece was then placed in a high-temperature press and hot-isostatically pressed at a temperature of 1150 ° C. for 3 hours under a pressure of 1100 bar. The result was a round bar made of a completely dense, heat-resistant material with a high yield strength and high fracture toughness.
  • a steam turbine blade was made from a corrosion-resistant chrome steel powder.
  • the dimensions and composition of the blade corresponded exactly to the values given in example 1.
  • Example 2 The procedure was exactly the same as in Example 2.
  • the pressure-tight container 3 in the present case was additionally pressurized via the feed line 4 (cf. FIG. 4).
  • the pressure in the container 4 which was increased to 3000 bar, propagated onto the outer surface of the film 1, so that the powder 5 was cold isostatically pressed under its influence.
  • a molded body (green compact) with a density of approximately 75% of the theoretical value was formed.
  • the pre-compacted green compact was then removed from the negative mold and the procedure was exactly the same as that given in Example 2.
  • the workpiece was densely sintered at a temperature of 1350 ° C. The previous cold isostatic pressing accelerated and improved the process of the internal sealing.
  • the invention is not restricted to the exemplary embodiments.
  • the film 1 consists of metal, rubber substance (latex) or plastic (polyethylene, polypropylene, ethyl vinyl acetate, polyvinyl alcohol or polystyrene), in the latter case having a thickness of 0.01 to 0.2 mm.
  • the plastic film 1 is preferably heated before and during the pressing onto the inner walls of the negative mold 2 in order to increase its suppleness and lower its hardness.
  • a film 1 is used which, under the influence of the pressure difference directed towards the interior of the negative mold 2, supports the effect of the powder particles being compressed for their solidification by their own rigidity.
  • the pressure difference directed towards the interior of the negative mold 2 is preferably chosen so high that the mixture of the powder particles is compressed by cold isostatic pressing.
  • the workpiece is advantageously additionally hot-isostatically pressed after sintering.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Powder Metallurgy (AREA)
EP90120136A 1990-10-20 1990-10-20 Procédé de préparation de pièces de forme compliquée à partir de poudre métallique ou céramique Withdrawn EP0482220A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP90120136A EP0482220A1 (fr) 1990-10-20 1990-10-20 Procédé de préparation de pièces de forme compliquée à partir de poudre métallique ou céramique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP90120136A EP0482220A1 (fr) 1990-10-20 1990-10-20 Procédé de préparation de pièces de forme compliquée à partir de poudre métallique ou céramique

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EP0482220A1 true EP0482220A1 (fr) 1992-04-29

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9701584B2 (en) 2013-02-20 2017-07-11 Rolls-Royce Plc Method of manufacturing an article from powder material and an apparatus for manufacturing an article from powder material
CN112546870A (zh) * 2020-11-25 2021-03-26 南京工业大学 一种原位修复技术
CN112569022A (zh) * 2020-12-11 2021-03-30 四川大学华西医院 钩椎关节植骨网兜、融合部件及制作方法、植骨封装工具

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1483684A1 (de) * 1964-08-31 1969-02-20 Asea Ab Verfahren zum Herstellen von Koerpern aus pulverfoermigem Material
EP0176266A1 (fr) * 1984-09-04 1986-04-02 Nippon Kokan Kabushiki Kaisha Procédé de moulage de poudre métallique, céramique et analogues

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1483684A1 (de) * 1964-08-31 1969-02-20 Asea Ab Verfahren zum Herstellen von Koerpern aus pulverfoermigem Material
EP0176266A1 (fr) * 1984-09-04 1986-04-02 Nippon Kokan Kabushiki Kaisha Procédé de moulage de poudre métallique, céramique et analogues

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9701584B2 (en) 2013-02-20 2017-07-11 Rolls-Royce Plc Method of manufacturing an article from powder material and an apparatus for manufacturing an article from powder material
US10632536B2 (en) 2013-02-20 2020-04-28 Rolls-Royce Plc Apparatus for manufacturing an article from powder material
CN112546870A (zh) * 2020-11-25 2021-03-26 南京工业大学 一种原位修复技术
CN112569022A (zh) * 2020-12-11 2021-03-30 四川大学华西医院 钩椎关节植骨网兜、融合部件及制作方法、植骨封装工具
CN112569022B (zh) * 2020-12-11 2023-06-16 四川图灵医谷科技有限公司 钩椎关节植骨网兜、融合部件及制作方法、植骨封装工具

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