US3764295A - Method of manufacturing low alloy steel powder having a low content of oxidic constituents - Google Patents

Method of manufacturing low alloy steel powder having a low content of oxidic constituents Download PDF

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Publication number
US3764295A
US3764295A US00250056A US3764295DA US3764295A US 3764295 A US3764295 A US 3764295A US 00250056 A US00250056 A US 00250056A US 3764295D A US3764295D A US 3764295DA US 3764295 A US3764295 A US 3764295A
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powder
particles
steel
oxide
acid
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US00250056A
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P Lindskog
A Bengtsson
S Grek
L Lagerholm
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Hoganas AB
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Hoganas AB
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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
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0235—Starting from compounds, e.g. oxides

Definitions

  • Low-alloy steel powder is usually manufuactured by atomizing molten steel. This is generally done by spraying a liquid, usually water, or a gas, for example air or steam, under high pressure against a stream of the molten steel. The stream is thus split into drops which rapidly cool and form solid particles of steel powder. It is often advisable to collect the particles formed in this 'way in water. The powder is then separated from most of the water, for example by filtering, and is finally dried by being heated. If the powder is to be used for manufacturing machine components by the powder metalliurgical method, it must be softened by annealing in a reducing atmosphere, for example hydrogen.
  • a reducing atmosphere for example hydrogen.
  • the steel only contains alloying elements whose oxides have lower or only negligibly higher free energy of formation than iron oxide, the oxide formation before and during the atomization is no great problem, since it is then possible to completely reduce the oxide layer to metal during annealing in reducing atmospher, for example hydrogen gas.
  • alloying elements which are extremely suit able and desirable from other points of view, form oxides having considerably higher free energy of fromation than iron oxide. Examples of such alloying elements are manganese, chromium, vanadium, titanium, boron, silicon, niobium, tantalum, beryllium and aluminium.
  • the oxide crust formed on the particles when steel containing such alloying materials is atomized, is enriched with respect to the oxides of these alloying elements and Will not be completely reduced during the annealing. Oxides of the alloying elements (MnO, Cr O etc.) will, therefore, remain on and near the surface of the particles after the annealing. When the powder is then used in the manufacture of solid steel, for example by hot pressing porous preforms, these oxides form a substantially coherent network in the structure. This has a considerable detrimental influence on the strength of the material.
  • the first alternative is possible, for example by atomizing the steel using a pressure medium without oxidizing properties, for example nitrogen or argon, and also protecting the steel particles from oxidation until they have cooled.
  • a pressure medium without oxidizing properties, for example nitrogen or argon
  • Such a method is expensive, however, and is also impractical since most of the particles acquire a spherical shape which is generally not suitable for compaction.
  • the invention comprises a method which is described and characterized in the claims. According to this method molten steel is atomized in the manner described in the first paragraph.
  • the steel powder thus produced is treated with at least one inorganic or organic acid so that the oxide crust is removed from the metallic part of the particles.
  • Most of the acid is then separated from the powder, for example by means of some form of decanting, after which the rest is removed by washing with water.
  • the oxide residue can now be separated from the powder either while this is still wet or when it has been dried.
  • the oxides are nonmagnetic and the steel powder magnetic, this can be done by means of wet or dry magnetic separation. Otherwise satisfactory separation can be achieved while the powder is being washed since the oxide residue, which has relatively low density and high specific surface, has a greater tendency to be carried along by the flowing water than the heavier and more compact steel particles. In certain cases it is advisable to separate the oxide resdue by air classification after the powder has dried.
  • the powder particles are subjected to mechanical treatment before, after or both before and after the acid treatment. If the treatment is performed prior to the acid treatment, cracks are formed in the oxide crust which make it easier for the acid to penetrate to the boundary surface between the oxide layer and the metallic part of the particles and the surface layer is easily dislodged from the particles. It the powder is subjected to mechanical treatment even those oxide residues which have only been partially loosened by the acid will be removed.
  • Aqueous solutions of both inorganic and organic acids and mixtures thereof can be used for the treatment.
  • Sulphuric acid, hydrochloric acid and nitric acid in concentrations of 5-10 percent of weight or mixtures of these are particularly suitable.
  • organic acids oxalic acid, acetic acid and formic acid may be mentioned. It is advantageous to carry out the acid treatment in a rotating drum allowing good contact between each particle and the acid.
  • the powder When the powder has thus been freed from oxidic constituents, it is annealed in reducing atmosphere in order to acquire the desired ductility.
  • EXAMPLE 1 A steel melt consisting of 1.42% Cr, 0.94% Mn, 0.04% Si, 0.025% S, 0.014% P, 0.03% Al, 0.63% C and the remainder Fe was atomized with water in a chamber filled with nitrogen gas. During the atomizing water vapour was produced which reacted with the hot steel particles to form an oxide layer on them. The powder was collected in water, whereupon it became rapidly cooled. A small quantity (A) was taken out and dried separately. This sample proved to have an oxygen content of 0.87%. The
  • the acid-treated steel powder (B) the quantity of which was 83% of the quantity of molten steel, had the following composition: 1.04% Cr, 0.71% Mn, 0.02% Si, 0.022% S, 0.015% P, 0.02% Al, 0.60% C, 0.26% O.
  • the powders A and B were annealed at 1050 C. for 30 minutes in a gas consisting of 75% hydrogen and 25% nitrogen, after which the powder cakes, somewhat sintered, were ground down to a maximum particle size of 0.15 mm. After the annealing powder A had an oxygen content of 0.67% and powder B 0.12%.
  • the powder was pressed to test bodies having a density of 6.5 g./cm. which were hot forged to full density.
  • the forged test bodies were cut up and the exposed surface ground and polished with diamond paste.
  • the volume percentage of oxide inclusions was determined microscopically by means of linear analysis in the section surface The results can be seen from the following table:
  • EXAMPLE 2 A steel melt consisting of 2.28% Mn, 0.03% Si, 0.021% S, 0.011% P, 0.02% A1, 0.42% C and the remainder Fe was atomized with water in a chamber filled with air. During the atomizing air and water vapour reacted with the hot particles and formed a layer of oxide on them. The powder was collected in water so that it was rapidly cooled. It was then dried and a sample (C) was taken out. It was found to have an oxygen content of 1.58%.
  • the powder was then allowed to pass a hammer mill and afterwards treated with hydrochloric acid with 0.05% pickling inhibitor added, for 5 minutes at 25 C., after which the acid was decanted and the powder transferred to a vertical cylindrical vessel provided with an overflow at the top. Water was pumped in at the bottom and a mixture of water, acid residue and solid oxide particles flowed over the overflow. The rinsed powder was collected and dried.
  • a sample of this powder (D) the quantity of which was 80% of the quantity of molten steel, had the following composition: 1.64% Mn, 0.02% Si, 0.018% S, 0.010% P, 0.02% Al, 0.40% C, 0.63% O.
  • the powders C and D were annealed at 850 C.
  • EXAMPLE 3 A steel melt consisting of 2.1% Cr, 2.0% Al, 0.82% Mn, 0.31% Mo, 0.07% Si, 0.030% S, 0.025% P, 0.55% C and the remainder Fe was atomized with water vapour. During the atomization the water vapour reacted with the hot steel particles and formed a layer of oxide on them. The powder was collected in water, where it cooled rapidly. It was then dried and a sample (B) was taken out. This proved to have an oxygen content of 1.38%. The powder was then allowed to pass a desintegrator, whereupon cracks were produced in the oxide layer on the steel particles. It was then treated with a solution of oxalic acid in water with a concentration of g./l. at 50 C.
  • the powder (F) treated in this way had the following composition: 1.68% Cr, 1.05% Al, 0.59% Mn, 0.31% Mo, 0.04% Si, 0.025% S, 0.025% P, 0.54% C, 0.51% O.
  • the powders E and F were annealed at 950 C. for 15 minutes under vacuum, after which the slightly sintered powder cakes were ground to powder having a maximum particle size of 0.175 mm. After the annealing the powder E had an oxygen content of 1.08% and the powder F 0.35%.
  • the quantity of inclusions was determined on the forged test bodies as in Examples 1 and 2. The results are shown in the following table:
  • the quantity of inclusions was thus reduced to between one quarter and one fifth of the quantity of obtained with methods known hitherto.
  • the powder is perfectly satisfactory for manufacturing sinter-forged material.
  • a method of manufacturing low alloy steel powder comprising creating a stream of molten steel, creating a jet of an atomizing fluid, directing said jet in an oxidizing environment towards said stream to atomize the molten steel into particles consisting of a metallic core and an oxide skin, allowing the particles to solidify and cool, treating the powder thus produced with an aqueous solution of an acid to remove the oxide skin from the metallic core, rinsing, collecting and drying the metallic powder thus produced, and annealing the dry metallic powder to produce a substantially oxide-free steel powder having ductile particles.
  • a method as claimed in claim 1, comprising exposing the powder, before the treatment with the acid, to a mechanical treatment to produce cracks in the oxide skin of the particles thus facilitating the penetration of the acid through the oxide skin.
  • a method as claimed in claim 1, comprising exposing the powder, after the treatment with the acid, to a mechanical treatment to detach any remaining oxide skin residues adhering to the metallic core.
  • a method as claimed in claim 1, comprising treating the powder with an aqueous solution containing an acid and a pickling inhibitor, to reduce the attack of the c d on he m ta l c co e 3,764,295 5 6 5.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Soft Magnetic Materials (AREA)
US00250056A 1971-05-14 1972-05-03 Method of manufacturing low alloy steel powder having a low content of oxidic constituents Expired - Lifetime US3764295A (en)

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SE06285/71A SE350770B (it) 1971-05-14 1971-05-14

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US (1) US3764295A (it)
JP (1) JPS551324B1 (it)
CA (1) CA1001375A (it)
DE (1) DE2222854C3 (it)
FR (1) FR2137862B1 (it)
GB (1) GB1340805A (it)
IT (1) IT960627B (it)
SE (1) SE350770B (it)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3900309A (en) * 1973-08-16 1975-08-19 United States Steel Corp Process for the production of high apparent density water atomized steel powders
US3909239A (en) * 1972-06-29 1975-09-30 Mannesmann Ag Method of controlling bulk density of ferrous powder
US3915690A (en) * 1973-12-28 1975-10-28 Hoeganaes Ab Composition and method of making alloy steel powder
US4049436A (en) * 1974-06-24 1977-09-20 Hoganas Ab Boron alloyed iron powder for filler metals
DE2827694A1 (de) * 1977-06-27 1979-01-11 American Can Co Sinterprodukt aus metallpulver und verfahren zu dessen herstellung
US4209326A (en) * 1977-06-27 1980-06-24 American Can Company Method for producing metal powder having rapid sintering characteristics
US4385929A (en) * 1981-06-19 1983-05-31 Sumitomo Metal Industries Limited Method and apparatus for production of metal powder
US4469313A (en) * 1981-06-19 1984-09-04 Sumitomo Metal Industries Apparatus for production of metal powder
US4613362A (en) * 1981-12-03 1986-09-23 Kernforschungsanlage Julich Method of making magnesium-containing metal granulate for the storage of hydrogen
US4615736A (en) * 1985-05-01 1986-10-07 Allied Corporation Preparation of metal powders
US4723994A (en) * 1986-10-17 1988-02-09 Ovonic Synthetic Materials Company, Inc. Method of preparing a magnetic material
US4960459A (en) * 1987-07-09 1990-10-02 Inco Alloys International, Inc. Method for surface activation of water atomized powders by pickling
US5044613A (en) * 1990-02-12 1991-09-03 The Charles Stark Draper Laboratory, Inc. Uniform and homogeneous permanent magnet powders and permanent magnets
DE19535444A1 (de) * 1995-01-20 1996-07-25 Scholz Paul Friedrich Dr Ing Verfahren zum Herstellen von Metallpulvern und zum pulvermetallurgischen Herstellen von Gegenständen sowie auf diese Weise hergestellte Gegenstände
US6749662B2 (en) 1999-01-29 2004-06-15 Olin Corporation Steel ballistic shot and production method
US20040211292A1 (en) * 1999-06-10 2004-10-28 Olin Corporation, A Company Of The State Of Illinois. Steel ballistic shot and production method
CN116174732A (zh) * 2023-04-26 2023-05-30 河南省远洋粉体科技股份有限公司 一种铝基合金粉的多喷嘴雾化装置

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0513079A (ja) * 1991-07-03 1993-01-22 Matsushita Electric Ind Co Ltd 電池用亜鉛合金粉末の製造方法およびその亜鉛合金粉末を用いたアルカリ電池
US5112572A (en) * 1991-10-01 1992-05-12 Inco Limited Deoxidation treatment for consolidated atomized metal powder

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB628183A (en) * 1946-05-03 1949-08-24 Sk Wellman Co Improvements in or relating to metallic powders and treatment thereof
FR1154761A (fr) * 1955-07-22 1958-04-16 Mannesmann Ag Procédé permettant de diminuer la teneur en oxygène d'une poudre métallique, notamment d'une poudre de fer
US3476548A (en) * 1966-12-09 1969-11-04 Crucible Inc Method for removing oxides from alloy powder
GB1236271A (en) * 1967-09-28 1971-06-23 Smith Corp A O Method of forming steel powder

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3909239A (en) * 1972-06-29 1975-09-30 Mannesmann Ag Method of controlling bulk density of ferrous powder
US3900309A (en) * 1973-08-16 1975-08-19 United States Steel Corp Process for the production of high apparent density water atomized steel powders
US3915690A (en) * 1973-12-28 1975-10-28 Hoeganaes Ab Composition and method of making alloy steel powder
US4049436A (en) * 1974-06-24 1977-09-20 Hoganas Ab Boron alloyed iron powder for filler metals
DE2827694A1 (de) * 1977-06-27 1979-01-11 American Can Co Sinterprodukt aus metallpulver und verfahren zu dessen herstellung
US4209326A (en) * 1977-06-27 1980-06-24 American Can Company Method for producing metal powder having rapid sintering characteristics
US4385929A (en) * 1981-06-19 1983-05-31 Sumitomo Metal Industries Limited Method and apparatus for production of metal powder
US4469313A (en) * 1981-06-19 1984-09-04 Sumitomo Metal Industries Apparatus for production of metal powder
US4613362A (en) * 1981-12-03 1986-09-23 Kernforschungsanlage Julich Method of making magnesium-containing metal granulate for the storage of hydrogen
US4615736A (en) * 1985-05-01 1986-10-07 Allied Corporation Preparation of metal powders
US4723994A (en) * 1986-10-17 1988-02-09 Ovonic Synthetic Materials Company, Inc. Method of preparing a magnetic material
US4960459A (en) * 1987-07-09 1990-10-02 Inco Alloys International, Inc. Method for surface activation of water atomized powders by pickling
US5044613A (en) * 1990-02-12 1991-09-03 The Charles Stark Draper Laboratory, Inc. Uniform and homogeneous permanent magnet powders and permanent magnets
DE19535444A1 (de) * 1995-01-20 1996-07-25 Scholz Paul Friedrich Dr Ing Verfahren zum Herstellen von Metallpulvern und zum pulvermetallurgischen Herstellen von Gegenständen sowie auf diese Weise hergestellte Gegenstände
DE19535444C2 (de) * 1995-01-20 1999-07-22 Scholz Paul Friedrich Dr Ing Verfahren zum pulvermetallurgischen Herstellen von Gegenständen sowie auf diese Weise hergestellte Gegenstände
US6749662B2 (en) 1999-01-29 2004-06-15 Olin Corporation Steel ballistic shot and production method
US20040211292A1 (en) * 1999-06-10 2004-10-28 Olin Corporation, A Company Of The State Of Illinois. Steel ballistic shot and production method
CN116174732A (zh) * 2023-04-26 2023-05-30 河南省远洋粉体科技股份有限公司 一种铝基合金粉的多喷嘴雾化装置
CN116174732B (zh) * 2023-04-26 2023-11-07 河南省远洋粉体科技股份有限公司 一种铝基合金粉的多喷嘴雾化装置

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Publication number Publication date
SE350770B (it) 1972-11-06
DE2222854B2 (de) 1978-06-29
DE2222854C3 (de) 1979-03-01
DE2222854A1 (de) 1972-12-07
CA1001375A (en) 1976-12-14
FR2137862A1 (it) 1972-12-29
GB1340805A (en) 1973-12-19
IT960627B (it) 1973-11-30
JPS551324B1 (it) 1980-01-12
FR2137862B1 (it) 1974-08-30

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