US3278301A - Method for the manufacture of dense sintered articles - Google Patents

Method for the manufacture of dense sintered articles Download PDF

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Publication number
US3278301A
US3278301A US355029A US35502964A US3278301A US 3278301 A US3278301 A US 3278301A US 355029 A US355029 A US 355029A US 35502964 A US35502964 A US 35502964A US 3278301 A US3278301 A US 3278301A
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United States
Prior art keywords
compacts
vacuum
aluminum
sintered
chamber
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.)
Expired - Lifetime
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US355029A
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English (en)
Inventor
Solomir John George
Akeret Rudolf
Douady Paul
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.)
Rio Tinto Switzerland AG
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Alusuisse Holdings AG
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.)
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Publication date
Application filed by Alusuisse Holdings AG filed Critical Alusuisse Holdings AG
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Publication of US3278301A publication Critical patent/US3278301A/en
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    • 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
    • C04B33/00—Clay-wares
    • C04B33/32—Burning methods
    • C04B33/326—Burning methods under pressure
    • 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
    • B22F3/003—Apparatus, e.g. furnaces
    • 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
    • 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
    • C04B33/00—Clay-wares
    • C04B33/32—Burning methods
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
    • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
    • C22C32/0036—Matrix based on Al, Mg, Be or alloys thereof
    • 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
    • Y10S425/00—Plastic article or earthenware shaping or treating: apparatus
    • Y10S425/20—Molding plants

Definitions

  • This invention relates to the manufacture of dense articles made from metal powder and sintered in a vacuum, particularly of objects pressed from aluminum powder or aluminum alloy powder, having, when heated up to several hundred degrees centigrade or after this heating, a higher tensile strength and a higher temper than objects made from the same material but not by powder metallurgy.
  • Such sintered aluminum objects of a considerable high-temperature stability have become known about years ago by the investigations of Swiss Aluminium Ltd.
  • the aluminum powder utilized for the purpose is usually manufactured from comminuted aluminum by several hours dry grinding in a ball mill with addition of a small amount of stearic acid, in an atmosphere with a measured content of oxygen.
  • the metallic surface is coated with a layer of brittle oxide which is broken again during the further milling or deformation of the metal particles; at the same time the particles are welded to each other wherever the metallic surface is laid bare by the oxide layer being shorn off.
  • alternate comminution and welding particles are thus formed which contain oxide as a fine dispersion and which are further coated with an oxide skin to which in turn a layer of grease adheres.
  • Such a powder therefore contains, according to the type, 6 to 15% of oxide which is not pure A1 0 but is in a more or less hydrated state, and some tenths of percent of grease consisting of stearic acid as well as aluminum stearate.
  • this powder is usually first cold-compacted into cylindrical shape in a vertical press with a compacting pressure of l-2 t./cm. these cold-compacts having a porosity of about to Subsequently several compacts are, for the sintering process, packed together in a sheet of pure aluminum, heated up to 550 to 600 C. in the course of several hours and kept at this temperature for a further several hours.
  • This heat-treatment starts certain processes which cause the generation of gases:
  • the air enclosed in the pores is partially expelled due to dilation, the greasy remnants are volatilized; the water chemically bonded in the hydrated oxide is liberated at this temperature forming steam, parts of which react exothermically with the metallic aluminum, forming further oxide and hydrogen, the latter either escaping as a gas or being dissolved in the aluminum.
  • the heating of the still porous cold-compacts has to be done slowly in order to avoid their destruction through overheating.
  • the transformation of the hydrate of aluminum oxide requires a relatively long period to be completed.
  • the sintered aluminum manufactured in the described way at normal atmospheric pressure necessarily still contains a certain amount of gas or of material generating gas at high temperature.
  • the sintered aluminum is exposed to high temperatures for days or even for months, the gases diffuse out of the sintered material and thus may cause the formation of minute pores or fissures. This phenomenon may cause serious trouble, particularly in the case of nuclear reactors where absolute density and undisturbed heat transfer are of necessity and only material of the highest possible structural stability may be incorporated.
  • the heat-treatment, subsequently called vaccumsintering, of a cold-pressed, porous compact of aluminum powder in a vacuum may be performed in several ways.
  • the porosity of the cold-compact made of aluminum powder is substantially retained and therefore the compact is extremely sensitive to subsequent oxidation when exposed to air at elevated temperatures. Consequently it is very useful if the compact sintered in a vacuum and still porous undergoes a hot-upsetting operation, called sinter-pressing, while still under vacuum.
  • the purpose of the present invention is to eliminate the drawbacksof the known methods of vacuum-treatment and to allow an economical industrial production of vacuum sintered compacts.
  • the particles of aluminum oxide have a hardening effect even at elevated temperature, being insoluble in the matrix.
  • the present invention relating first of all to the manufacture of sintered aluminum compacts, may also be applied to metallic as well as nonmetallic, e.g. ceramic, material.
  • the method of manufacturing in a vacuum dense sintered bodies with a low content of gas is characterized by the facts that cold-compacts are made from powder, that a number of these compacts, without being wrapped, are heated and sintered in a vacuum inside the heated portion of a gastight chamber, that the compacts are then, one after the other, while still under vacuum, transported to another portion of the chamber and, one at a time, submitted to a hot-upsetting operation inside the container of a compacting press.
  • the vacuum may be applied from the beginning of the heat-treatment; it is however advisable to start with an average vacuum and to apply the high vacuum only after the sintering temperature (above 550 C.) has been attained.
  • the apparatus for the manufacture of dense sintered compacts in a vacuum may consist substantially of a gastight chamber connected to a vacuum-pump unit, a portion of which chamber, being developed into a sintering chamber, is provided with a heating device as Well as a device to receive a number of cold-compacts, in which sintering chamber these compacts are submitted to heating and vacuum-sintering; and a further portion of which gastight chamber is developed into a pressing room, wherein at least the tooling of a compacting press is accommodated and where the sintered compacts are subsequently hot-upset, one at a time, the vacuum chamber being equipped with a transport device for the moving of the individual compacts from the heated portion of the chamber to the container of the press.
  • the device inside the sintering furnace receiving the compacts to be sintered may have the form of, eg a conveyer belt or a drumshaped receptacle.
  • the supporting members of the receiving device are preferably formed of slats or grids.
  • FIG. 1 presenting a longitudinal section and FIG. 2 presenting a cross section following the line AA of FIG. 1.
  • the apparatus chiefly comprises a heatable sintering chamber 1 containing a device 2 for simultaneously receiving a number of cold-compacts 3 to be degasified and sintered, a pressing room 4 wherein the compacting tools, i.e. the container 5 and the plunger of the press 6, are situated respectively are reaching in to leave sufficient room for the reception of the hot-upset compacts 7 of one charge, whereby these members are enclosed in a vacuumtight metal casing 8 connected to a vacuumpump unit 9.
  • the heatable sintering chamber 1 has cylindrical shape and is closed at one end by a cover 10,
  • the sintering chamber 1 is heated from outside by an electrical f-urnace 11 open at both ends, which advantageously can be displaced longitudinally and may be removed for control or repair purposes. It is however possible as well to provide for a complementary heating inside the sintering chamber or even to accommodate the complete heating device inside this sintering chamber.
  • the receiving device 2 consists of a drumshaped cage rotatable round its axle 12. Both ends of this axle are embedded in the bearings 13 fixed to the casing of the sintering chamber 1 by supporting members not shown in this drawing.
  • the rotation of the receiving device 2 is performed through a worm gear drive 1415 the spindle 14 of which is reaching out through the casing of the vacuum chamber and is operated from the outside.
  • a worm gear drive a bevel gear or any other form may be adopted.
  • the actual supporting members are made of slats arranged in the longitudinal direction of the cage in a way to form two concentric circles, whereby the slats of the inner circle are designated by the number 16 and those of the outer circle by the number 17.
  • These slats 16 and 17 may be fix'ed at both of their ends to discs fixed for their part to the axle 12 and forming the front ends of the cage 2.
  • the discs For the feeding and removing of the cold-compacts respectively into and out of the cage the discs have perforations in the extension of the rows of cold-compacts.
  • the front end discs of the cage preferably do not have massive center portions but are developed into wheels with spokes 18 in order to facilitate the degasification through these front ends.
  • the cage has a certain length it may be necessary to support the slats 16 and 17 by further wheels with spokes arranged between the ends of the cage.
  • the cold-compacts are set within the single rows at short distances in order not to obstruct the degasification in any direction.
  • FIG. 1 only the top and the bottom row of coldcompacts with their corresponding supporting slats are shown, in order not to overcharge the drawing. There are however arranged in the cage such rows of cold-compacts and such supporting slats round about, as is to be seen in the cross section FIG. 2.
  • the removing of the sintered compacts from the cage is done by means of a sliding carriage 21.
  • This carriage travels on a rail 22 fixed in longitudinal direction to the inside, preferably the bottom, of the sintering chamber 1 and reaching out into the adjacent pressing room, which sliding carriage is displaced by an endless wire rope 24, arranged between two return pulleys 23 and being moved to and fro from outside the vacuum chamber by a suitable gear 25.
  • the sliding carriage has a hinged tappet 26 held in upright position, e.g. by a spring not shown in this drawing.
  • This tappet 26 is able to stretch in between two of the outer slats 17 supporting the compacts of one file.
  • the sliding carriage 21 has a fixed security pin 27 which too stretches in between the outer slats 17 of the cage and protects the hinged tappet 26 from being damaged through unintended turning of the cage 2 during the removing of the compacts 3.
  • the sliding carriage has its place outside the range of the cage in the unheated pressing room of the vacuum chamber.
  • the drum cage is first brought into a position which places one row of compacts exactly above the sliding carriage and in which position the discharging can proceed. Then the sliding carriage is moved into the sintering chamber so far that the hinged tappet 26, being pressed down when passing by the first compact, gets back in its upright position behind this first compact and into the interstice between the latter and the second compact. Then the sliding carriage is pulled out of the sintering chamber whereby the first compact is removed out of the cage.
  • the sliding carriage is drawn back into the sintering chamber so far that the hinged tappet is set up again into the interstice between the second and the third compact and then pulled out again from the sintering chamber. This proceeding is repeated until all the compacts of one file are removed from the cage.
  • the heated container 5 of a compacting press propped and fixed in any suitable manner to the bottom of the vacuum chamber.
  • the bottom of this container is formed by a blind die 28 laterally movable from the outside. It is however possible too to provide for another hydraulic punch entering through the bottom of the pressing chamber, in stead of a blind die.
  • a pair of bellows securing the vacuum tight closure between the casing of the chamber and the punch.
  • the driving means for the press are situated outside the vacuum chamber.
  • a tipping trough 30 taking over the compacts removed from the cage and setting them into the container of the press.
  • two juxtaposed and permanent sliding bars are fixed, between which the tappet 26 of the sliding carriage 21 may travel to push the compacts into the tipping trough 30.
  • the vacuum chamber is connected, whenever possible without reduction of the cross-sectional area, to the diffusion pump 31 of the pumpstand 9.
  • a pre-vacuum pump there serves e.g. the rotary oil pump 32.
  • the pre-vacuum pump 32 may be connected directly to the vacuum chamber through the by-pass valve 33.
  • the accompanying drawing shows the vacuum-pumpstand 9 following the pressing room 4. It would however be possible to place the pumpstand at the other end of the entire apparatus, i.e. in front of the sintering chamber, instead of the cover 10, which latter would then have to close the pressing room. The feeding of the cage would in this case have to be done across the pressing room.
  • the punch is pressed upon the compact set in the container in such a way that the specific pressure is 2 to 20 t./cm. preferably 6 to 12 t./cm.
  • the pun-ch has borne upon the compact during a certain time, preferably to 30 seconds with this pressure, the blank die 28 at the bottom of the container is removed and the compact pushed down by the punch into the lower portion of the pressing room which has such a capacity as to receive all the compacts of one charge of the cage after the hot-upsetting.
  • a press of a power of 200 t. is sufficient to apply a specific pressure of 10 t./cm. over the cross-section of the container 5.
  • the length of the cold-compact may be about 120 mm., that of the hot-upset compact about 80 mm. corresponding to a weight of about 400 grams.
  • 120 compacts may be heated and sintered at once. According to experience a good degasification requires a vacuum-treatment of 12 to 20 hours at 600 to 630 C.
  • Sintered aluminum compacts produced by this method are a useful starting material for the manufacture of small thin walled smooth or finned of tubes to be manufactured by extrusion. Such tubes are used as canning tubes for nuclear fuel elements, e.g. in organically cooled reactors.
  • Method according to claim 2 wherein the heating for said 12 to 25 hours is at a temperature of 600 to 630 C.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Organic Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Structural Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Metallurgy (AREA)
  • Powder Metallurgy (AREA)
US355029A 1963-03-27 1964-03-26 Method for the manufacture of dense sintered articles Expired - Lifetime US3278301A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH389463A CH434586A (de) 1963-03-27 1963-03-27 Verfahren und Anlage zur Herstellung von dichten Sinterkörpern, insbesondere von gasarmen Aluminiumsinterkörpern, unter Vakuum

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US527434A Expired - Lifetime US3343209A (en) 1963-03-27 1966-02-15 Apparatus for the manufacture of dense sintered articles

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3394000A (en) * 1965-03-30 1968-07-23 Euratom Process for obtaining al-al2o3 structures for nuclear applications
US3982906A (en) * 1973-11-14 1976-09-28 Nippon Telegraph And Telephone Public Corporation Production of aluminum-aluminum oxide dispersion composite conductive material and product thereof
US6547550B1 (en) 2000-06-16 2003-04-15 Ross Guenther Apparatus for hot vacuum extrusion of ceramics
US20070049487A1 (en) * 2005-08-25 2007-03-01 Ross Guenther Synthesized hybrid rock composition, method, and article formed by the method

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3521326A (en) * 1967-04-26 1970-07-21 Comstock & Wescott Powder metallurgy press apparatus
US4005956A (en) * 1973-04-11 1977-02-01 Inoue-Japax Research Incorporated Powder activation and integrated powder metallurgy system
US3832107A (en) * 1973-06-29 1974-08-27 United Aircraft Corp Apparatus for making articles from particulate matter

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2293400A (en) * 1941-01-21 1942-08-18 Isthmian Metals Inc Method for producing metal bodies
US2832583A (en) * 1952-10-07 1958-04-29 Vogt Hans Apparatus for producing porous sintered strip stock
US2933305A (en) * 1957-12-17 1960-04-19 Republic Steel Corp Apparatus for making flattened elongate metallic bodies with finished edges from powdered metal
US3122434A (en) * 1960-06-03 1964-02-25 Republic Steel Corp Continuous process of producing strips and sheets of ferrous metal directly from metal powder

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2377494A (en) * 1941-05-07 1945-06-05 Corning Glass Works Apparatus for drawing glass tubing
US2806248A (en) * 1944-06-09 1957-09-17 Burnie J Craig Apparatus for making a threadlike member
US2648759A (en) * 1950-05-11 1953-08-11 Western Electric Co Apparatus for forming parts from brittle metal strip
US3051812A (en) * 1959-12-31 1962-08-28 North American Phillips Compan Device for inductive heating of workpieces
US3156011A (en) * 1962-01-10 1964-11-10 Donald M Olson Self-contained variable-environment pressing die

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2293400A (en) * 1941-01-21 1942-08-18 Isthmian Metals Inc Method for producing metal bodies
US2832583A (en) * 1952-10-07 1958-04-29 Vogt Hans Apparatus for producing porous sintered strip stock
US2933305A (en) * 1957-12-17 1960-04-19 Republic Steel Corp Apparatus for making flattened elongate metallic bodies with finished edges from powdered metal
US3122434A (en) * 1960-06-03 1964-02-25 Republic Steel Corp Continuous process of producing strips and sheets of ferrous metal directly from metal powder

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3394000A (en) * 1965-03-30 1968-07-23 Euratom Process for obtaining al-al2o3 structures for nuclear applications
US3982906A (en) * 1973-11-14 1976-09-28 Nippon Telegraph And Telephone Public Corporation Production of aluminum-aluminum oxide dispersion composite conductive material and product thereof
US6547550B1 (en) 2000-06-16 2003-04-15 Ross Guenther Apparatus for hot vacuum extrusion of ceramics
US20070049487A1 (en) * 2005-08-25 2007-03-01 Ross Guenther Synthesized hybrid rock composition, method, and article formed by the method
US7704907B2 (en) 2005-08-25 2010-04-27 Ceramext, Llc Synthesized hybrid rock composition, method, and article formed by the method
US20100273630A1 (en) * 2005-08-25 2010-10-28 Ceramext, Llc Synthesized hybrid rock composition, method, and article formed by the method
US8216955B2 (en) 2005-08-25 2012-07-10 Ceramext Llc Synthesized hybrid rock composition, method, and article formed by the method
US8901023B2 (en) 2005-08-25 2014-12-02 Ceramext, Llc Synthesized hybrid rock composition, method, and article formed by the method

Also Published As

Publication number Publication date
DE1458258B2 (de) 1972-09-21
DE1458258A1 (de) 1968-12-19
US3343209A (en) 1967-09-26
CH434586A (de) 1967-04-30

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