US3201293A - Coated silicon iron sheet stock - Google Patents

Coated silicon iron sheet stock Download PDF

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Publication number
US3201293A
US3201293A US261270A US26127063A US3201293A US 3201293 A US3201293 A US 3201293A US 261270 A US261270 A US 261270A US 26127063 A US26127063 A US 26127063A US 3201293 A US3201293 A US 3201293A
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Prior art keywords
decarburizing
final
silicon iron
silicon
anneal
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Expired - Lifetime
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US261270A
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English (en)
Inventor
Victor W Carpenter
John M Jackson
Robert W Squibb
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Armco Inc
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Armco Inc
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Priority to US261270A priority Critical patent/US3201293A/en
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/68—Temporary coatings or embedding materials applied before or during heat treatment
    • C21D1/70—Temporary coatings or embedding materials applied before or during heat treatment while heating or quenching
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
    • C21D3/02—Extraction of non-metals
    • C21D3/04—Decarburising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the heat treatment
    • C21D8/1272—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1216—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the working steps

Definitions

  • the invention pertains to magnetic materials which can be made by strip annealing methods. Much of this type of product is of a non-oriented nature, but aspects of this invention can also be used in the manufacture of oriented products where the particular qualities imparted by the essential sequence of steps taught herein are of importance. The invention will, however, be described in connection with the production of non-oriented silicon iron, without limitation.
  • non-oriented silicon iron is meant a product devoid of such a degree of preferred orientation of the crystals as would produce marked differences in magnetic permeability of the product as measured in the rolling direction and in a direction at right angles thereto.
  • Nonoriented silicon irons are of utility in the manufacture not only of rotating electrical machinery, but also in the manufacture of transformers the cores of which are made up of E-shaped, I-shaped, or L-shaped laminations. In such uses rotating elements such as motor armature laminae and transformer laminations are formed from the steel sheet stock by means of dies and the importance of a good die life is obvious.
  • a primary object of the invention is the provision of a silicon-iron stock of either type which will be nonaging and at the same time characterized by a high die life.
  • FIG. 1 is a photornicrograph at 1000 magnification of a piece of silicon iron sheet stock which has been processed in a typical fashion as hitherto known in the art.
  • FIG. 2 is a photomicrograph at l000 magnification of silicon iron stock which has been processed in accord ance with this invention, and showing a novel surface condition as compared with the product of FIG. 1.
  • the figures are micro sections made in the standard way, the lower layer being the silicon iron, and the upper layer being a layer of copper or the like. Between the two layers is an indication of the surface condition on the silicon iron produced by the process steps hereinafter discussed.
  • Thin bar is usually a material about .1 in. in gauge, although the exact thickness is not critical.
  • the thin bar after decarburizing, was reduced to final gauge, usually by hot rolling; and if originally produced in the form of sheets, the sheets were welded end to end to form a coil suitable for continuous annealing.
  • Various temper rolling and pickling steps might be employed intermediate the rolling of the ice material to final gauge and the welding step, all preliminary to a final anneal at a relatively high temperature, namely, a temperature of about 2050" F. It is generally understood that, in order to produce the opti mum magnetic characteristics which the product is capable of acquiring, a high temperature final anneal is necessary.
  • Products made as above indicated have many desirable characteristics; but they may have erratic core loss behavior generally known as aging, in which the product in instances suffers a change in core loss with the passage of time, a phenomenon believed to be due to an instability which gives rise to a tendency to precipitate carbon compounds.
  • the material is reduced to gauge in any suitable way.
  • the reduction may be accomplished either by hot rolling or by cold rolling, or by combinations of the two, which is a distinct advantage in processing.
  • the product may be hot rolled to thin bar, and then further hot rolled to gauge, giving a product in sheet form which will require welding to form it into a coil of indefinite length.
  • the principles of this invention are equally applicable to a material which is hot rolled from slabs into long coils, and thereafter pickled and cold rolled to final gauge while still in coil form.
  • the final thickness of the material may be substantially in the range of 24 to 29 gauge.
  • Silicon iron suitable for the practice of the invention, particularly in the manufacture of non-oriented stock, may be defined as a material containing substantially 0.5% to about 3.8% silicon.
  • Aluminum may be present in quantities up to about 0.5%.
  • the carbon content initially is not a limitation on the invention but usually varies from about 0.02% to about 0.08% in accordance with the manner in which the steel has been made.
  • the alloy may contain such amounts of other elements, e.g. manganese, phosphorus, sulfur, and the like as are usual in silicon irons as produced commercially. The balance of the alloy will be substantially all iron.
  • the analysis given above relates to the material after processing has started, i.e. it is not a ladle analysis; but it may be the analysis of the silicon iron immediately before or immediately after the hot rolling.
  • the material is hot rolled, or hot rolled and cold rolled to final gauge as stated above.
  • the material has been hot rolled to final gauge, it will be usual to temper roll it, pickle it, and then again temper roll it prior to welding the individual sheets end to end to form a coil. If the material has been cold rolled to final gauge in sheet form, the temper rolling and pickling steps may be omitted, but the individual sheets will then be welded end to end to form a coil. If the material has been produced in coil form by cold rolling to gauge, the welding step will, of course, be unnecessary. It will be noted that the material is not subjected to a decarburizing treatment at an intermediate gauge.
  • the material, produced as indicated, is first subjected to a-continuous decarburizing anneal at about 1475 F. in a decarburizing atmosphere.
  • the material is treated to a continuous high temperature anneal at about 2050" F. in a dry, non-decarburizing atmosphere. It will be found not only that the material is devoid of aging characteristics, but also that it has an excellent die life, as will be hereinafter more fully set forth.
  • a decarburizing atmosphere is meant an atmosphere of hydrogen, hydrogen-nitrogen mixtures containing Water vapor as the decarburizing agent, or cracked gases such as DX, which, in addition to nitrogen, hydrogen, and carbon monoxide, contain carbon dioxide and Water vapor as decarburizing agents.
  • a dew point about 125 F.i25 is maintained by adding water.
  • cracked gases are used, the dew point is somewhat lower, since CO is available as an additional decarburizing agent.
  • the annealing treatment can normally be accomplished in 1 to 3 minutes at a temperature substantially within a range of 1350 to 1650 F.
  • a dry non-decarburizing atmosphere is meant atmosphere that is substantially non-oxidizing to carbon but is also not carburizing.
  • Such an atmosphere can be hydrogen, nitrogen, or mixtures thereof having a dew point less than +50 F.
  • the temperature for the final continuous anneal should be within the range of substantially 1800 to 2200 F. Higher temperatures may be employed if desired but are generally found uneconomical.
  • FIG. 1 is a photomicrograph of a material rolled from decarburized bars, pickled, welded, and strip annealed at 2050 F. in dissociated ammonia.
  • the dark line in the photomicrograph shows a layer of silica particles coalesced by the high temperature anneal. These silica particles adversely affect die life; and the material of FIG. 1 gave a die life of only about 20,000 strokes. The die life would not have been improved had the final anneal been carried on in a decarburizing atmosphere, although under these circumstances, a diminution of the aging tendency might have been achieved.
  • a decarburizing treatment oxidizes silicon, producing at and near the surfaces of the stock a distinct layer comprising a very substantial quantity of silica.
  • an annealing separator must be used; and the result is the finished product is characterized by a glassy coating which, while it may under some circumstances have utility as an interlamination insulator, is destructive of die life.
  • H6. 2 which shows, as 1000 magnification, the surface of a silicon iron which has been hot rolled to gauge, pickled, welded, treated at 1475 F. in a decarburizing atmosphere, and then continuously annealed at 2050 F. in a dry non-decarburizing atmosphere.
  • the surface of such material exhibits a very thin band of dark oxide at about the mid-thickness of the surface skin.
  • this band or line represents the original location of the interface between the base metal and the skin formed during the decarburizing operation.
  • some slight oxidation of silicon and aluminum took place below this band, raising the band to about the mid-thickness of the final surface skin.
  • a continuous thin band of silica been formed at the interface with the base metal during the final high temperature anneal, it is likely that the surface skin would have been subject to peeling.
  • the appearance of the sheet surface of silicon iron stock, made by the prior art procedure and having the characteristics illustrated in FIG. 1, is dark, while the stock of this invention has a lighter silvery visual appearance.
  • the product of this invention will blue very readily when heated in an open flame, indicating an iron surface, while the prior art material blues much less readily.
  • the surface skin on the material of this invention is not loosened by repeated bending of the stock.
  • the furnace should consist of a first section for decarburizing with a ccuntercurrent flow of the dccarburizing gas, a middle transition section wherein the stock can be maintained under a neutral atmosphere and which serves to isolate the decarburizing section from the high temperature section of the furnace, and a final high temperature section characterized by concurrent fiow of a dry nondecarburizing atmosphere, as herein defined. Precautions should be taken against mixing of the atmospheres in the composite furnace except in the transition section, from which the mixed gases can be exhausted.
  • Example A silicon iron stock containing 3.0% silicon was hot rolled to final gauge in sheet form. It was then temper rolled, pickled, and again temper rolled,'after which the sheets were welded together so as to form a coil for continuous annealing.
  • the coil was treated at 1475 F. in a dccarburizing atmosphere, as herein defined, for about three minutes at temperature. It was then subjected to a strip anneal at 2050 F. in a dry non-decarburizing atmosphere as above defined, the atmosphere also consisting of dissociated ammonia. The duration of the high temperature heat treatment was about two minutes.
  • the material so treated was non-aging and had a die life of 135,000 strokes as compared with a die life of 20,000 strokes for a material of the same composition processed in accordance with the prior practice set forth herein.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Electromagnetism (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacturing Of Steel Electrode Plates (AREA)
US261270A 1958-11-12 1963-02-27 Coated silicon iron sheet stock Expired - Lifetime US3201293A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0730039A1 (fr) * 1995-02-28 1996-09-04 Armco Inc. Revêtement d'oxyde de magnésium et un procédé de fabrication de tÔles en acier électrique à grains orientés ayant une bonne aptitude à l'estampage

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS54160514A (en) * 1978-06-09 1979-12-19 Nippon Steel Corp Decarburization and annealing method for directional electromagnetic steel plate
US4244757A (en) * 1979-05-21 1981-01-13 Allegheny Ludlum Steel Corporation Processing for cube-on-edge oriented silicon steel

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2992951A (en) * 1960-04-21 1961-07-18 Westinghouse Electric Corp Iron-silicon magnetic sheets
US3021237A (en) * 1958-08-05 1962-02-13 Allegheny Ludlum Steel Processing of metal

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3021237A (en) * 1958-08-05 1962-02-13 Allegheny Ludlum Steel Processing of metal
US2992951A (en) * 1960-04-21 1961-07-18 Westinghouse Electric Corp Iron-silicon magnetic sheets

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0730039A1 (fr) * 1995-02-28 1996-09-04 Armco Inc. Revêtement d'oxyde de magnésium et un procédé de fabrication de tÔles en acier électrique à grains orientés ayant une bonne aptitude à l'estampage

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FR86292E (fr) 1966-01-07
BE584172A (fr) 1960-02-15
FR84573E (fr) 1965-03-05
FR1240806A (fr) 1960-12-16

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