US1932306A - Electrical steels and method of making same - Google Patents

Electrical steels and method of making same Download PDF

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Publication number
US1932306A
US1932306A US593783A US59378332A US1932306A US 1932306 A US1932306 A US 1932306A US 593783 A US593783 A US 593783A US 59378332 A US59378332 A US 59378332A US 1932306 A US1932306 A US 1932306A
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United States
Prior art keywords
strip
strain
silicon
steel
electrical
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US593783A
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English (en)
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Edward M Freeland
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Individual
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Priority to BE390446D priority Critical patent/BE390446A/xx
Priority to BE398905D priority patent/BE398905A/xx
Application filed by Individual filed Critical Individual
Priority to US593783A priority patent/US1932306A/en
Priority to FR740867D priority patent/FR740867A/fr
Priority to US688410A priority patent/US1932308A/en
Priority to US688411A priority patent/US1932309A/en
Priority to FR44079D priority patent/FR44079E/fr
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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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
    • C21D8/1272—Final recrystallisation annealing
    • 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 by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
    • C21D8/1233—Cold rolling
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • 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
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/30—Foil or other thin sheet-metal making or treating
    • Y10T29/301—Method

Definitions

  • the present invention relates broadly to the art of metal working, and more especially to that branch of metal working having to do with the subjecting of a predetermined composition or alloy to a treatment of such nature that the electrical properties thereof are materially modified.
  • ferrous material usually in the form of a series of sheets or laminae characterized by a high electrical efnciency from the standpoint for example of watt loss, magnetic permeability, low magnetic hysteresis and the like.
  • sheets of iron-silicon, or iron-silicon-aluminum alloys constitute a superior material for this purpose.
  • the present invention contemplates not only a variation in the constituent alloys utilized as to their relative proportions for obtaining certain predetermined results as required for example by the apparatus in which the finished product is to be used, but also a special mechanical and heat treatment whereby with a given material the desired electrical properties are imparted thereto.
  • the present invention is preferably characterized by the step of deliberately introducing a strain by cold rolling in excess of any limits heretofore considered permissible, and thereafter subjecting the material having such excessive strain therein to a controlled treatment such that the strain in excess of the maximum limit is effectively removed, and only the desired strain for imparting the required electrical properties is retained.
  • I retain only that amount of strain which has heretofore been determined .as being decidedly beneficial, and make the process adaptable to the production in quantity of electrical steels.
  • the adaptation to the strip process also enables the production of a product having materially greater lengths than has heretofore been possible, and thereby correspondingly reducing the fabricating costs in the manufacture of electrical apparatus.
  • the present invention therefore has for one of its objects an improved method of producing electrical steel, as well as the production of a new article of manufacture comprising electrical steel in strip form having a length in excess of lengths heretofore obtainable from sheets as individually produced.
  • Figure 1 is a diagrammatic view, partly in side elevation, illustrating the various treatment steps to which strip material may be subjected in accordance with the present invention
  • Figure 2 illustrates a modified method of heat treating material produced in accordance with the present invention
  • Figure 3 is a chart illustrating one method of effecting partial strain removal prior to final heat treatment
  • Figure 4 is a diagrammatic view, partly in side elevation, illustrating a slightly modified form of treatment from that shown in Figure 1;
  • Figure 5 is a view similar to Figure 4, illustrating still another embodiment of my invention.
  • a slab 2 of desired composition suitable for use in accordance with the present invention is subjected to hot rolling, as commonly practiced in the art in a suitable series of hot rolling mills 3 of such nature as to form a hot rolled strip, herein illustrated in the form of a coil 4. It may be assumed, by way of example only, that the hot rolled strip thus pro-- quizd and which is substantially free from any cold working strains, has a thickness of .0625 inches, and any desired width. I prefer to use a minimum finishing temperature of approximately 1300 F.
  • This hot rolled strip, in accordance with the present invention is subjected to a cold rolling operation in a continuous mill 5, herein illustrated as comprising four roll stands of the four-high type arranged in tandem.
  • the setting of the cold rolling mills is such as to reduce the thickness of the hot rolleTi strip to approximately .024 inches, this being a reduction of .0385 inches, equal to approximately 61%. It will be apparent to those skilled in the art that the figures herein given are representative of thicknesses frequently produced in the cold rolling of steel for purposes other than the production of electrical steels.
  • the cold rolling operation while it is effective for reducing the hot rolled strip to the desired finished gauge, introduces in such material by reason of the reduction effected, a strain which is far in excess of the strain heretofore thought permissible in the production of steels to be used for electrical purposes.
  • the strip having these two strain components is subjected to a special heat treating operation of such nature as to retain the desirable component and eliminate the undesirable component.
  • the strip leaving the cold rolling mill 5 is formed into a coil 6 for convenience in handling.
  • This coil is then placed in a suitable coil b x '7 located in the de sired relationship to the charging end of a heat treating furnace 8 provided with suitable burners or resistors 9 effective for maintaining the desired temperature conditions therein.
  • the coil 6 is progressively unwound from the coil box 7 and passed in single thickness through the furnace 8 at a speed which is determined not only upon the temperature conditions existing within the furnace, but also upon the composition of the material undergoing treatment, the thickness of such material and the amount of strain introduced therein by the cold rolling operation.
  • the strip material may again be formed into a coil 10, which will be characterized, as will be hereinafter more fully explained, by the elimination of the undesirable strain component and will have only the desirable strain component remaining therein.
  • This coil may then be subjected to a final heat treating operation as by subjecting it to a box annealing operation in coil form in an annealing box 11.
  • the strip material in coil form may be sold as an article of manufacture for use in the fabricating of electrical equipment, or may be cut into individual sheets and so sold for fabrication.
  • the coil 10 as formed at the delivery end of the heat treating furnace 8 may be sheared into individual sheets 12, which sheets when placed in superimposed relationship as illustrated in Figure 2, may be subjected to a box annealing operation in a suitable annealing box 14. After the desired annealing operation, the sheets 12 as such may then be sold for use.
  • the undesirable strain component will likewise vary with changes in the reduction effected by the cold rolling operation, the strain increasing with increased reductions and decreasing with decreased reductions. While the actual strain introduced under varying reductions is not a straight line function, it is a function which is readily deter minable.
  • Figure 3 I have illustrated diagrammatically by the point A on the curve the particular heat treatment above described.
  • the curve of Figure 3 is obtained by plotting the thickness of the material against the heating time in seconds. It is generally assumed that the rate of heat penetration varies directly with the thickness of the material; and hence if the strip being treated were only half as thick, that is to say, .0125 inches, then only 15 seconds would be required to bring it up to the desired minimum temperature. Adding to this the continued heating time of 90 seconds, the total time for treating such strip would be 105 seconds. This condition is indicated by the point B on the curve.
  • the curve for determining the length of time for treating strips of different thicknesses will be a straight line connecting the points A and B.
  • the points C, D, E and F have been marked on this line in Figure 3 to show the time required for heat treating strips having thicknesses, respectively, of .014, .016, .018 and .020 inches.
  • the above described curve is for steel having a silicon content of approximately 1% and which has been reduced approximately 61% by cold rolling. It sets forth the general principle of treatment to be followed in the continuous heat treatment of such strip for the elemination of the undesirable strain component, but it will be understood that the curve is by way of example only; that modifications in the heat treatment may be made; that the customary tolerances in mill practice are allowable, and that the percentage of reduction by cold rolling may be varied according to the particular circumstances encountered and the results desired.
  • the undesirable strain component is eliminated as involving two factors, these being respectively, time and temperature. If it is desired to decrease the time of treatment, it is necessary to eifect an increase in the temperature, while if it is desired to increase the time interval, this may be accomplished by effecting a reduction in the temperature conditions.
  • the examples given therefore are by way of illustration of actual times required for a given temperature condition, it being possible in accordance with the invention to vary either the time or temperature by making a corresponding change as indicated in the other heat treating factor.
  • the present invention will thus be found to be applicable commercially to the cold rolling of silicon steel in strip form in direct accordance with the past commercial practices determined for cold rolling operations generally as applicable to products other than ferrous materials for elec- 'trical purposes, thus enabling commercial installations to be utilized for carrying out the present invention.
  • the silicon content may be varied through appreciable limits.
  • a silicon content of approximately 1% is desirable for example in the production of that grade of material known generally as electrical sheets; that a silicon content of approximately 2 5% is desirable for the production at that grade of material commonly referred to as special motor sheets; that a silicon content of approximately 3% is desirable for the production of that grade of material commonly referred to as special dynamo sheets, and that a silicon content of approximately 3 5% produces the desired properties for use in so-called transformer sheets.
  • All of the material produced in accordance with the present invention will be characterized by having a relatively low watt loss at a given flux density.
  • a table containing seven difierent grades of electrical steel, each with an identifying title together with the watt loss per lb. at frequencies of both and cycles at the assumed specific gravities indicated, the maximum watt losses in the case of some of the grades being shown for a plurality of different gauges, these ranges covering the gauges ordinarily manufactured.
  • the watt loss is figured at a flux density of 10,000-B and determined in accordance with specification A-3428 of the American Society for Testing Materials. In each instance I have also indicated one permissible range of silicon variation for each grade:
  • my improved electrical strip has 9. watt loss not exceeding 2.8 per pound in 22 gauge strip containing .3 to .'7% silicon and that the watt loss decreases progressively as the silicon content increases, within the range herein disclosed, and also decrease with a decrease in thickness of the strip.
  • the coil material as delivered by the annealing box 11 for example will have a coil set which will be reflected in the individual pieces formed therefrom. Inasmuch slight curvature reflected in the individual lamina may be objectionable.
  • the coil set may be eliminated, but in this case it is not possible to furnish to a customer a material in coil form .with its consequent advantages.
  • I may practice a method as illustrated diagrammatically in Figure 4.
  • a furnace 15 indicated as being a bell type electric furnace characterized by the ability to closely control temperature conditions. I may place within such furnace a coil produced in any desired manner, such for example as the product of the cold roll- .ing mill 5 of Figure 1 and subject the coil to such accurately controlled heat treating conditions as to efiect removal only of the undesirable strain component;
  • tlriis coil may be placed in a suitable coil box 16 and passed through a heat treating furnace 17 corresponding to the furnace 8 of Figure l and effective for giving the final heat treatment to the material.
  • a heat treating furnace 17 corresponding to the furnace 8 of Figure l and effective for giving the final heat treatment to the material.
  • I may carry it to a point ap-.
  • the location of the coil 18 relatively to the furnace 17 will be such that the material will have cooled to such an extent that it will not have a tendency even when coiled to take a coil set, but will always tend to return to its substantially fiat condition.
  • FIG 5 I have also illustrated one method of practicing the invention means of which the desired results may be obtained.
  • the material with this strain representing only the desirable strain compo nent, may be passed through a furnace 23 corresponding to the furnaces 8 and 1'7, and then at a suitably remote point coiled into a coil 24.
  • this coil 24 the material will possess the same attributes as the material in coil 18 of Figure 4.
  • the annealing box temperatures will be such as to effect final removal of the strain. I have found that this temperature may vary within the range of from 1500 to 1700" F., although the lower temperature ranges of from 1550 to 1650 arepreferable. The same will of course be tru of the heat treating furnaces 17 and 23.
  • electrical steel in sheet-like form containing .3-6% silicon and having electrical properties characteristic of those obtained when a steel of substantially the same silicon content, within such range is formed by hot roll'ng to strip form substantially free of cold working strains having a thickness of approximately .0625 inches, cold rolling to approximately .024 inches or 61%, passed through a furnace having a temperature of approximately 1900 F., the total heating time being such as to remove the undes?rable strain component in the steel, that is to say, about two minutes in the case of a steel whose silicon content is approximately l%, and increasing as the silicon content increases, then cooling and then annealing, the steel being in the form of a strip as that term is used in the metal rolling art.
  • electrical steel in the form of strip containing from .3% to silicon and having electrical properties characteristic of those obtained when a steel of substantially the same silicon content, within such range, is subjected to heavy reduction by cold work followed by heating to remove part but not all of the strain thus imparted, cooling, and then annealing, the watt loss property of such strip being not more than about 2.8 watts per pound in 22 gauge thickness and decreasing as the silicon content increases, and also decreasing as the thickness of the strip decreases.
  • electrical steel in the form of strip containing from .3 to .7% silicon and having electrical properties characteristic of those obtained when a steel of substantially the same silicon content, within such range, is subjected to heavy reduction by cold work followed by heating to remove part but not all of the strain thus imparted, cooling, and then annealing, the watt loss property of such strip being not more than about 2.8 watts per pound in 22 gauge thickness, and decreasing as the thickness of the strip decreases.
  • electrical steel inthe form of strip containing from 375% to 1.5% silicon and having electrical properties characteristic of those obtained when a steel of substantially the same silicon content, within such range, is subjected to heavy reduction by cold work followed by heating to remove part but not all of the strain thus imparted, cooling, and then annealing, the watt loss property of such strip being not more than about 2.3 watts per pound in 22 gauge thickness, and decreasing as the thickness of the strip decreases.
  • electrical steel in the form of strip containing from 2% to 3% silicon and having electrical properties characteristic of those obta ned when a steel of substantially the same silicon content, within such range, is subjected to heavy reduction by cold work followed by heating to remove part but not all of the strain thus imparted, cooling, and then annealing, the watt loss property of such strip being not more than about 1.3 watts per pound in 24 gauge thickness, and decreasing as the thickness of the strip decreases.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Manufacturing & Machinery (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
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US593783A 1932-02-18 1932-02-18 Electrical steels and method of making same Expired - Lifetime US1932306A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
BE390446D BE390446A (enrdf_load_html_response) 1932-02-18
BE398905D BE398905A (enrdf_load_html_response) 1932-02-18
US593783A US1932306A (en) 1932-02-18 1932-02-18 Electrical steels and method of making same
FR740867D FR740867A (fr) 1932-02-18 1932-08-04 Perfectionnements apportés aux aciers électriques et procédé de fabrication des dits aciers
US688410A US1932308A (en) 1932-02-18 1933-09-06 Electrical steel
US688411A US1932309A (en) 1932-02-18 1933-09-06 Electrical steel
FR44079D FR44079E (fr) 1932-02-18 1933-09-29 Perfectionnements apportés aux aciers électriques et procédé de fabrication desdits aciers

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US593783A US1932306A (en) 1932-02-18 1932-02-18 Electrical steels and method of making same

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3224909A (en) * 1961-11-29 1965-12-21 Licentia Gmbh Siliconizing of electrical sheet steel by diffusion

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3224909A (en) * 1961-11-29 1965-12-21 Licentia Gmbh Siliconizing of electrical sheet steel by diffusion

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FR740867A (fr) 1933-02-02
FR44079E (fr) 1934-10-11
BE398905A (enrdf_load_html_response)
BE390446A (enrdf_load_html_response)

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