US3772009A - Method for manufacturing an object from iron-based alloy by isostatic compression - Google Patents

Method for manufacturing an object from iron-based alloy by isostatic compression Download PDF

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Publication number
US3772009A
US3772009A US00298579A US3772009DA US3772009A US 3772009 A US3772009 A US 3772009A US 00298579 A US00298579 A US 00298579A US 3772009D A US3772009D A US 3772009DA US 3772009 A US3772009 A US 3772009A
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United States
Prior art keywords
phase
iron
temperature
based alloy
hot pressing
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Expired - Lifetime
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US00298579A
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English (en)
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S Isaksson
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ABB Norden Holding AB
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ASEA AB
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B11/00—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses
    • B30B11/001—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses using a flexible element, e.g. diaphragm, urged by fluid pressure; Isostatic presses
    • B30B11/002—Isostatic press chambers; Press stands therefor
    • 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
    • B22F3/14—Both compacting and sintering simultaneously
    • B22F3/15—Hot isostatic pressing
    • 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
    • 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

Definitions

  • ABSTRACT In a procedure in which a body formed of an ironbased alloy is manufactured from powder by isostatic compression, the powder is placed in a flexible container and subjected to isostatic pressure and heat. The isostatic hot pressing is carried out at two temperatures, at one of which the iron-based alloy is at least 25 percent in a-phase and at the other of which the iron-based alloy is in y-phase. If the treatment at the temperature for y-phase is carried out first, the body is cooled below the temperature level at which it is at least 25 percent in a-phase to prevent retention of the 'y-phase and then raised to the temperature at which it is at least 25 percent in a-phase.
  • the invention relates to the manufacture of objects from iron-based alloys using isotatic hot pressing.
  • the method described can be used when manufacturing objects from different materials, among other things from iron-based alloys such as steel of different kinds. It is known to use the method when manufacturing billets from iron-based alloys for further machining to the desired shape,by means of rolling or forging.
  • the isotatic hot pressing is carried out at temperatures when the iron alloy is in y-PhtlSC, generally at a temperature of about l,lC. A frequently used pressure is 1,000 bar. Under these conditions a 100 percent compactness in the hot pressing process is not obtained. Such a compactnessis not obtained until the hot pressed object has been subjected to further machining by means of forging or rolling.
  • the present invention it has proved possible to obtain a 100 percent compactness in objects of iron-based alloys directly during the isotatic hot pressing process, and therefore the forging or rolling operations can be eliminated as working steps to increase the compactness in the goods.
  • the possibility of avoiding these working steps mentioned makes the present invention particularly suitable for forming objects with complicated shape, for example gear cutters, cylinders, dies, and for forming objects having such a shape that machining by means of forging or rolling is impractical, for example tubular parts.
  • the present invention relates to a method for manufacturing objects from iron-based alloys, a powder of the iron-based alloy being placed in a flexible container and subjected to isostatic hot pressing with formation of the object in the form of a sintered powder body, characterised in that the isostatic hot pressing is carried out at two temperature levels with the iron-based alloy at least up to 25 percent in a-phase at the one temperature level and in 'y-phase at the other temperature level.
  • the hot pressing at the temperature level with the iron-based alloy at least up to 25 percent in az-phase is preferably carried out before the hot pressing at the temperature level with the iron-based alloy in 'y-phase, but can also be carried out after the last-mentioned hot pressing.
  • iron-based alloy an alloy which contains at least 50 percent by weight of iron.
  • iron-based alloys are ordinary steel, high-speed steel, tool steel, toughened steel and stainless steel.
  • the temperature level at which at least 25 percent of the ironbased alloy is in a-phase and the temperature level when the iron-based alloy is in -y-phase varies with the composition of the iron-based alloy. 1n the following, examples are given of iron-based alloys with different compositions in percentages by weight (the names within brackets are Swedish designations):
  • High-speed steel (SIS 2722) 0.85 C, 0.2 Si, 0.3 Mn, 4.2 Cr, 5.0 M0, 6.4 W, 1.9 V, rest Fe.
  • High-speed steel (S 30 ISTORAI) 1.2 C, 0.2 Si, 0.3 Mn, 4.2 Cr, 5.0 M0, 6.4 W, 10.3 Co, 3.4 V, rest Fe.
  • Toughened steel (SIS 2541) 0.35 C, 0.25 Si, 0.65 Mn, 1.4 Cr, 1.4 Ni, 0.20 Mo, rest Fe.
  • the lower temperature limit during the hot pressing, when at least part of the iron-based alloy is in a-phase is kept, according to the invention, preferably at 700 C also for other alloys than those noted above.
  • the upper temperature limit during the hot pressing with the ironbased alloy in y-phase is correspondingly kept preferably at 1,225C for other alloys also.
  • the time for the hot pressing with a-phase present is at least 1 hour, preferably 1-10 hours, and the time for the hot pressing in 'y-phase at least one-half hour, preferably r'z--l0 hours.
  • a possible explanation of the favourable result obtained according to the present invention is that the diffusion of the different substances in the powder at the grain boundaries will be considerably greater if part of the sintering is carried out in a-phase or with a-phase present than if it is carried out completely in 'y-phase. This results in the product aquiring a more homogeneous structure. Because of the higher temperature level, the sintering in 'y phase results in an efficient plastic compression of the powder so that a complete compactness in the product is obtained.
  • the isostatic hot pressing in a-phase or with a-phase present and the isostatic hot pressing in 'y-phase are preferably carried out in immediate connection with each other.
  • the temperature is increased after the treatment in a-phase is finished directly to the temperature required for -y-phase. If the hot pressing in y-phase is carried out first, the temperature is first lowered to a value below that at which the treatment with a-phase present is carried out, in order to prevent retention of -y-phase, before it is increased to the temperature required for the treatment with a-phase present.
  • the pressure during the isostatic hot pressing according to the present invention reaches preferably 7003,000 bar.
  • the particle size of the powder is below 1,000 microns, preferably between 50 microns and 800 microns.
  • the oxygen content of the powder should be low, 200 ppm at most.
  • the powder is then enclosed in a flexible container which is preferably the same as is used later during the isostatic hot pressing and which has the same shape as the object to be manufactured. After evacuation and sealing the container is inserted for the isostatic cold pressing into a pressure chamber where it is subjected to a high, all-sided pressure, preferably at least 1000 bar. The powder is then compresseduniformly in all directions so that the powder body formed becomes a somewhat smaller copy of the container.
  • FIG. 1 shows schematically an for manufacturing objects by means of the method according to the present invention
  • FIG. 2 the upper part of a powder-filled flexible container
  • FIGS. 3 and 4 a press for isostatic cold pressing of powder to a coherent powder body
  • FIG. 5 a furnace for isostatic hot pressing of the powder body mentioned to a finished object
  • FIGS. 6 and 7 curves showing the temperatures as a function of the time during the isostatic hot pressing according to the present invention.
  • l designates a storage container for powder of a high-speed steel consisting of S 30 (STORA), the composition of which has been indicated above, and 2 designates a rotatable table which can be turned stepwise. Close to the table is a store of flexible containers 3, for example for ordinary steel consisting of SIS 1240 (composition given above). On the table an empty container 3a has been placed which by turning the table 2 in steps is moved between a number of different stations. Opposite the storage container 1 is a container 3b in a filling station where it is filled with powder from the storage container 1 through a hose or pipe 64.
  • a container 3c filled with powder 9 if provided with a lid 4 which is welded to the wall 7 of the container 3 by means of a welding seam 8, as shown in FIG. 2.
  • the container 3d is shown at a transfer station from which it is transferred to a testing station where the tightness of the container is checked.
  • the checking equipment is designated 10.
  • the equipment 1 which is further described in connection with FIGS. 3 and 4, consists of a high pressure cylinder 12 supported by a stand 13 and a movable press stand 14 which runs on rails 15.
  • the press stand 14 is of the type having two yokes and two spacers, held together by a pre-stressed strip sheath. It is carried by two pairs of brackets 16 in which the shafts 18 of the transport wheels 17 are journalled. An electric motor 19 drives the shaft 18 of one of the wheel pairs by way of a a gear drive in one of the brackets 16.
  • the transport wheels run on the rails 15.
  • the cylinder 12 is provided with two end closures 20 and 21 projecting into the cylinder, the lower one being suspended and vertically movable to a limited extent in the cylinder 12, whereas the upper one can easily be lifted for charging and emptying the container.
  • the container 12 is provided at its ends with flanges 22 and the stand 13 with brackets 23 having holes through which a rod 24 passes.
  • the stand is moved with the help of the motor 19 above the cylinder 12 so that their centre lines coincide, after which pressure medium in the form of oil is introduced into the pressure chamber.
  • the axial pressure operating on the end closure is taken up by the press stand.
  • FIG. 1 shows a group of pre-heating furnaces 25.
  • the powder bodies in the furnaces are connected to a vacuum pump 27 by way of pipe connections 5 and a conduit 26 which passes through the lids or roofs of the furnaces 25.
  • the opening in pipe connection 5 in the lid 4 of the container is closed and the powder body is transferred to a second pre-heating furnace.
  • the furnaces may be of conventional type, for example electric resistance furnaces.
  • the auxiliary equipment of the furnaces is designated 31.
  • After heating the product is transferred to a furnace 32 for isostatic hot pressing.
  • a group of two furnaces 32a and 32b is shown in FIG. 1. These furnaces are further described with reference to FIG. 5.
  • the furnaces are of the type shown in Swedish Pat. No. 315,085 and are thus charged from below.
  • the furnace comprises a furnace chamber which is enclosed in a pressure chamber.
  • This pressure chamber consists of a high pressure cylinder 33 of the type constructed of a tube 34 and a surrounding pre-stressed strip sheath 35, an upper end closure 36 and a lower end closure 37.
  • the cylinder is suspended in a stand 38.
  • the upper end closure 36 is permanently held in the cylinder and is provided with a channel 39 for the supply of pressure medium in the form of argon, helium or nitrogen and a channel for an electric cable 40 to feed electric heating elements 41 and to obtain measuring values from the thermoelement.
  • Above the end closure 36 is a plate 42 with an output for the cable 40.
  • an insulating sheath 43 and an insulating lid 44 which divide the actual furnace chamber 45 from the inner wall of the tube 34 and the lower surface of the end closure 36.
  • the heating elements 41 are suspended in the upper end closure 36.
  • a ring 46 projecting permanently into the tube.
  • the lower end closure 37 is provided with a bracket 47 and a guide 48 and is arranged vertically slidable and turnable on a guide 49. Lowering and raising is done with the help of an operating cylinder 50 attached on the stand, the operating rod 51 of which is connected to the guide.
  • the furnaces unit also includes a movable press stand to take up the forces operating on the end closures.
  • This press stand is also of the type having two yokes 53 and 54, two spacers 55 and a strip sheath 56 holding them together.
  • the stand is provided with brackets 57 to journal wheels 58 running on rails 59.
  • a cylinder 60 of insulating material On the lower end closure is a cylinder 60 of insulating material. On this stands a billet 61. During the isostatic hot pressing the stand 52 is moved in over the high pressure chamber, during emptying and charging the stand is a little distance away from the high pressure chamber so that the lower end closure can be lowered and turned, as can be seen in FIGS. 1 and 5.
  • the furnace 32 the powder body with the enclosing container is first subjected to a temperature at which the high-speed steel to at least 25 percent is in a-phase and then to a temperature at which the highspeed steel is in 'y-phase, as illustrated in FIG. 6, or first to a temperature at which the high-speed steel is in -yphase and then to a temperature at which the high-speed steel to at least 25 percent is in a-phase, as illustrated in FIG. 7.
  • the powder body is pre-heated during the period t in the furnaces 25 and 30 to the temperature T n1 at atmospheric pressure.
  • T a is a temperature at which at least 25 per cent of the iron alloy is in a-phase.
  • the isostatic hot pressing is carried out in the furnace 32 at the temperature T 24 and a pressure of 700-3,000 bar during the period t a
  • the temperature is then raised during the period t t to the temperature T a which is the temperature at which the iron alloy is in 'y-phase, and the isostatic hot pressing is carried on at the temperature T during the period t a
  • T a a pressure of 700-3,000 bar is maintained.
  • T a may be 750 950C, T a 1,000
  • a suitable pressure during the isostatic hot pressing is 1,000 bar.
  • the powder body is pre-heated during the period t to the temperature Ta at atmospheric pressure.
  • the isostatic hot pressing is carried out at the temperature T a and a pressure of 700-3,000 bar during the period t a.
  • the temperature is first lowered to the temperature T ,l in order to prevent retention of the y-phase during the continuing isostatic hot pressing at the temperature T a which takes place during srqtips (a te smwsrbor rare this has been heated from the temperature T t to T a
  • the time for lowering the temperature from T 24 to T H- and for raising the temperature from T M- to T a is designated t,,,.
  • T may be 750-950C, T 4 1,000-1,200C, 2,, 1- 5 hours, t a l- 5 hours, T 650C, t, 3 hours and r 2 hours.
  • Method for manufacturing objects from iron-based alloys in which a powder of the iron-based alloy is placed in a flexible container and subjected to isostatic hot pressing under formation of the object in the form of a sintered powder body, which comprises carrying out the isostatic hot pressing at two temperature levels, one level in which the iron-based alloy is at least up to 25 percent in a-phase, and the other level at which the iron-based alloy is in 'y-phase.
  • Method according to claim; 1, which comprises carrying out the isostatic hot pressing first at the temperature level in which the iron-based alloy is at least up to 25 percent in a-phase and then at the temperature level in which the iron-based alloy is in y-phase.
  • Method according to claim 1 which comprises carrying out the isostatic hot pressing first at the temperature level in which the iron-based alloy is in 'y-phase and then at the temperature level in which the iron-based alloy is at least up to 25 percent in a-phase, and which includes lowering the temperature after the treatment at the first-mentioned temperature level to a value below the last-mentioned temperature level and thereafter raising it to the last-mentioned temperature level.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Powder Metallurgy (AREA)
US00298579A 1971-10-18 1972-10-18 Method for manufacturing an object from iron-based alloy by isostatic compression Expired - Lifetime US3772009A (en)

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Application Number Priority Date Filing Date Title
SE13138/71A SE357213B (xx) 1971-10-18 1971-10-18

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US (1) US3772009A (xx)
JP (1) JPS5030005B2 (xx)
CA (1) CA974382A (xx)
DE (1) DE2250495C3 (xx)
FR (1) FR2156788B1 (xx)
GB (1) GB1397818A (xx)
SE (1) SE357213B (xx)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4065303A (en) * 1973-12-19 1977-12-27 Messerschmitt-Bolkow-Blohm Gesellschaft Mit Beschrankter Haftung Method of producing shaped objects
US4244738A (en) * 1978-03-24 1981-01-13 Samuel Storchheim Method of and apparatus for hot pressing particulates
US4448747A (en) * 1981-09-01 1984-05-15 Kabushiki Kaisha Kobe Seiko Sho High density sintering method for powder molded products
US4492671A (en) * 1982-03-15 1985-01-08 Leland Stanford Junior University Method for consolidation of iron-based alloy powder by cyclic phase transformation under pressure
US4755119A (en) * 1987-03-26 1988-07-05 Kabushiki Kaisha Kobe Seiko Sho Multiple-container type cold isostatic press
US4820484A (en) * 1985-02-19 1989-04-11 Asea Stal Ab Method in producing a molding of an iron alloy
EP1069197A1 (en) * 1998-01-06 2001-01-17 Crucible Materials Corporation Method of compacting high alloy tool steel particles
EP1075886A3 (en) * 1999-08-13 2004-01-21 Crucible Materials Corporation Hot isostatic compacting of high alloy tool steel particles
US20050208468A1 (en) * 2003-09-15 2005-09-22 Beske Oren E Assays with primary cells

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE389812B (sv) * 1974-05-07 1976-11-22 Asea Ab Utrustning for behandling av material vid hog temperatur och vid hogt tryck

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB618293A (en) * 1946-10-14 1949-02-18 Isthmian Metals Inc Making products of powdered iron or iron alloys
CA473625A (en) * 1951-05-15 Fiske Whitney Lyman Making products of iron or iron alloys
GB752687A (en) * 1953-05-02 1956-07-11 Husqvarna Vapenfabriks Ab Improvements in the manufacture of sintered iron bodies
CA570345A (en) * 1959-02-10 G. G. Zapf Heinz Manufacture of sintered iron bodies

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA473625A (en) * 1951-05-15 Fiske Whitney Lyman Making products of iron or iron alloys
CA570345A (en) * 1959-02-10 G. G. Zapf Heinz Manufacture of sintered iron bodies
GB618293A (en) * 1946-10-14 1949-02-18 Isthmian Metals Inc Making products of powdered iron or iron alloys
GB752687A (en) * 1953-05-02 1956-07-11 Husqvarna Vapenfabriks Ab Improvements in the manufacture of sintered iron bodies

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4065303A (en) * 1973-12-19 1977-12-27 Messerschmitt-Bolkow-Blohm Gesellschaft Mit Beschrankter Haftung Method of producing shaped objects
US4244738A (en) * 1978-03-24 1981-01-13 Samuel Storchheim Method of and apparatus for hot pressing particulates
US4448747A (en) * 1981-09-01 1984-05-15 Kabushiki Kaisha Kobe Seiko Sho High density sintering method for powder molded products
US4492671A (en) * 1982-03-15 1985-01-08 Leland Stanford Junior University Method for consolidation of iron-based alloy powder by cyclic phase transformation under pressure
US4820484A (en) * 1985-02-19 1989-04-11 Asea Stal Ab Method in producing a molding of an iron alloy
US4755119A (en) * 1987-03-26 1988-07-05 Kabushiki Kaisha Kobe Seiko Sho Multiple-container type cold isostatic press
EP1069197A1 (en) * 1998-01-06 2001-01-17 Crucible Materials Corporation Method of compacting high alloy tool steel particles
EP1075886A3 (en) * 1999-08-13 2004-01-21 Crucible Materials Corporation Hot isostatic compacting of high alloy tool steel particles
US20050208468A1 (en) * 2003-09-15 2005-09-22 Beske Oren E Assays with primary cells

Also Published As

Publication number Publication date
SE357213B (xx) 1973-06-18
FR2156788B1 (xx) 1976-10-29
JPS4849609A (xx) 1973-07-13
FR2156788A1 (xx) 1973-06-01
GB1397818A (en) 1975-06-18
JPS5030005B2 (xx) 1975-09-27
DE2250495B2 (de) 1975-01-23
DE2250495A1 (de) 1973-04-26
DE2250495C3 (de) 1975-08-28
CA974382A (en) 1975-09-16

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