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US3589695A - Device for the absorption of the expansion of a charge in a retort used in a nitriding process - Google Patents

Device for the absorption of the expansion of a charge in a retort used in a nitriding process Download PDF

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Publication number
US3589695A
US3589695A US755219A US3589695DA US3589695A US 3589695 A US3589695 A US 3589695A US 755219 A US755219 A US 755219A US 3589695D A US3589695D A US 3589695DA US 3589695 A US3589695 A US 3589695A
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US
United States
Prior art keywords
retort
discs
stand
retort according
expansion
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
Application number
US755219A
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English (en)
Inventor
Arne Ivar Backstrom
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.)
Outokumpu Stainless AB
Original Assignee
Avesta Jernverks 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 Avesta Jernverks AB filed Critical Avesta Jernverks AB
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0053—Details of the reactor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0053—Details of the reactor
    • B01J19/006—Baffles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00389—Controlling the temperature using electric heating or cooling elements
    • B01J2208/00407—Controlling the temperature using electric heating or cooling elements outside the reactor bed

Definitions

  • Nitriding the metal is carried out in the solid phase, nor mally at 900 to 1,000 C.
  • the nitrogen supply source is generally nitrogen gas. Since the nitrogen diffuses into the metal extremely slowly, the latter must present a large surface area if the time the treatment takesis not to be unreasonably long.
  • the metal is therefore treated in the shape of flakes of a thickness of about I to 2 mm., for instance manganese metal produced electrolytically or in the shape of a crushed product produced with a grain size less than mm., for instance crushed ferrochromium, manganese or ferromanganese produced pyrometallurgically.
  • Suitable equipment for the nitriding operation is a retort of heat-resistant steel which during the treatment is placed vertically in an electric pit furnace.
  • the retort should preferably have a circular cross section, and it should be somewhat coneshaped, in order to facilitate the discharging of the material.
  • the volume of the charge increases by about 5 to percent, the charge will thus exert a considerable pressure on the wall of the retort. Since the strength of the retort material is rather poor at 900 to 1,000 C. the
  • the deformation appears as a bulge which is often largest at about half the height of the retort and which may be so extensive that the retort has to be discarded after a comparatively short time of operation.
  • the risk of cracking increases in proportion to the heating cycles performed, the welds are especially delicate areas.
  • the object of the present invention is to prevent the charge in the course of the volume increase in connection with the nitriding from exerting such a pressure on the wall of the retort that the retort is deformed or that cracks appear in it.
  • the present invention is characterized in that the retort is provided with a number of discs preferably orientated centrally, horizontally and in a vertical pile.
  • the discs When the retort is charged vacant spaces develop under the discs. In the nitriding process these vacant spaces are entirely or partly filled by the expanding material.
  • the discs may suitably be arranged at a distance from each other by means of spacer members.
  • the spacer members consist of centrally arranged sleeves, preferably welded onto one disc each, the discs being provided with holes so that the discs and sleeves may be threaded on a central removable stand attached to the retort.
  • FIG. 1 shows a vertical cross section of a retort with an expansion absorber according to the present invention
  • FIG. 2a schematically shows the above absorber during charging of the retort
  • FIG. 2b schematically shows part of the retort after the charging.
  • FIG. 20 schematically shows part of the retort during heat treatment
  • FIG. 2d schematically shows part of the retort after completed heat treatment
  • FIG. 3 shows a disc with an attached spacer member, partly in section
  • FIG. 4 shows a view from above of the disc in FIG. 3,
  • FIG. 5 shows another embodiment of the disc, partly in section.
  • FIG. 1 shows retort l with a circular section.
  • the retort has a circular-cylindrical body 2, a cone-shaped lower part 3 and a rounded bottom part 4.
  • the retort is covered by lid 5 which, via flanges 6 on body 2, may be fastened to the re tort body.
  • An expansion absorber 7 has been placed centrally in the retort.
  • the absorber consists of a vertical metal stand 8 provided with a number of rounded metal discs 9 horizontally placed and with their centers coinciding with the vertical stand.
  • a device should be provided with one or several supporting devices which maintain expansion absorber 7 in its vertical, central position.
  • the stand ends in a loop for hoisting expansion absorber 7 and the nitrated cake after the final reaction.
  • FIG. 2a The way in which metal material 10 which is to be nitrided is fed into the retort is illustrated in FIG. 2a.
  • the material flows into the retort down vertically, then it is symmetrically distributed in the retort.
  • vacant space 11 is formed in the shape of an inverted cone or a frustum of a cone whose top rake angle is minus twice the angle of repose a of the metal material, FIG. 2b.
  • FIGS. 3, 4 and 5 show examples of the way in which a disc and a spacer member may be designed in practice.
  • circular disc 12 is plane but provided with edge bevelling on the upper surface.
  • the expansion absorber consists of a number of such disc threaded onto central stand 16, which may, for instance, consist of a pipe or a round bar.
  • the wall of the retort is marked 17.
  • FIG. 5 shows a construction where disc I8 has been shaped into an obtuse-angled cone with a top rake angle chosen so that an assumed line drawn from central stand 19 and in the plane of the disc towards wall 20 of the retort forms a right angle to the latter in the vertical plane.
  • this embodiment corresponds with the one shown in FIGS. 3 and 4.
  • the discs need not necessarily be of a circular shape.
  • Square, pentagon or hexagon discs, etc. may very well be used even if stereometrically the circle is the logical shape.
  • a retort for nitriding metal particles at elevated temperatures comprising a vertically elongate container for retaining the metal particles therein in a substantially stationary mass during nitriding, means for reducing forces to the container by accommodating expansion of the mass of metal particles therein, the force reducing means including a plurality of means for forming pockets within the mass of particles to permit inward expansion of the mass, the pocket forming means including a plurality of members spaced-apart, positioned to interrupt the flow of particles into the container during filling to produce said pockets beneath each of the members, and supported throughout the fill depth to form an axially extending series of pockets throughout the particulate mass.
  • the spaced members are a plurality of discs supported on a shaft, the shaft extends axially and supports the disc throughout the fill depth of the retort, and the shaft and discs are removable from within the retort following nitriding to facilitate removal of the nitrided mass of particles.
  • discs and sleeves may be positioned on the stand by means of threads cut into the exterior surface of the stand and corresponding threads cut into the interior surface of the sleeves and the interior surface of the holes provided in the discs.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
US755219A 1967-09-11 1968-08-26 Device for the absorption of the expansion of a charge in a retort used in a nitriding process Expired - Lifetime US3589695A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE12495/67A SE320655B (de) 1967-09-11 1967-09-11

Publications (1)

Publication Number Publication Date
US3589695A true US3589695A (en) 1971-06-29

Family

ID=20295836

Family Applications (1)

Application Number Title Priority Date Filing Date
US755219A Expired - Lifetime US3589695A (en) 1967-09-11 1968-08-26 Device for the absorption of the expansion of a charge in a retort used in a nitriding process

Country Status (6)

Country Link
US (1) US3589695A (de)
DE (1) DE1796153B1 (de)
FR (1) FR1581305A (de)
GB (1) GB1242424A (de)
NO (1) NO122239B (de)
SE (1) SE320655B (de)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US799696A (en) * 1901-10-28 1905-09-19 Charles H Ward Treatment of sulfid and complex ores.
GB779871A (en) * 1948-12-08 1957-07-24 Zieren Chemiebau Gmbh Dr A Furnaces for treating materials in suspension, especially for use in roasting sulphide ores
DE1068021B (de) * 1959-10-29
US3116842A (en) * 1961-06-28 1964-01-07 Mohr & Sons John Gas seal structure for high top pressure operation
US3252601A (en) * 1964-07-29 1966-05-24 United States Steel Corp Blast furnace bell suspension and operating mechanism

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1068021B (de) * 1959-10-29
US799696A (en) * 1901-10-28 1905-09-19 Charles H Ward Treatment of sulfid and complex ores.
GB779871A (en) * 1948-12-08 1957-07-24 Zieren Chemiebau Gmbh Dr A Furnaces for treating materials in suspension, especially for use in roasting sulphide ores
US3116842A (en) * 1961-06-28 1964-01-07 Mohr & Sons John Gas seal structure for high top pressure operation
US3252601A (en) * 1964-07-29 1966-05-24 United States Steel Corp Blast furnace bell suspension and operating mechanism

Also Published As

Publication number Publication date
GB1242424A (en) 1971-08-11
DE1796153B1 (de) 1971-03-25
SE320655B (de) 1970-02-16
NO122239B (de) 1971-06-07
FR1581305A (de) 1969-09-12

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