EP0130674A2 - Procédé pour la fabrication d'acier électromagnétique au silicium à grains orientés cube-sur-arête - Google Patents

Procédé pour la fabrication d'acier électromagnétique au silicium à grains orientés cube-sur-arête Download PDF

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Publication number
EP0130674A2
EP0130674A2 EP84302946A EP84302946A EP0130674A2 EP 0130674 A2 EP0130674 A2 EP 0130674A2 EP 84302946 A EP84302946 A EP 84302946A EP 84302946 A EP84302946 A EP 84302946A EP 0130674 A2 EP0130674 A2 EP 0130674A2
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EP
European Patent Office
Prior art keywords
steel
heating
temperature
hour
recrystallization
Prior art date
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Application number
EP84302946A
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German (de)
English (en)
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EP0130674A3 (fr
Inventor
Frank Angelo Malagari, Jr.
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.)
Allegheny Ludlum Corp
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Allegheny Ludlum Corp
Allegheny Ludlum Steel Corp
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Application filed by Allegheny Ludlum Corp, Allegheny Ludlum Steel Corp filed Critical Allegheny Ludlum Corp
Publication of EP0130674A2 publication Critical patent/EP0130674A2/fr
Publication of EP0130674A3 publication Critical patent/EP0130674A3/fr
Withdrawn legal-status Critical Current

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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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing

Definitions

  • This invention relates to a process for producing electromagnetic silicon steel having a cube-on-edge orientation and particularly to a final texture annealing cycle to promote improved secondary recrystallization. Particularly, the invention relates to a substantially isothermal anneal at a selected recrystallization temperature.
  • the Goss texture (110) [001] in accordance with Miller's indices, refers to the body-centered cubes making up the grains or crystals being oriented in the cube-on-edge position.
  • the texture or grain orientations of this type refers to the cube edges being parallel to the rolling direction and in the plane of rolling, and the cube face diagonals being perpendicular to the rolling direction and in the rolling plane.
  • steel having this orientation is characterized by a relatively high permeability in the rolling direction and a relatively low permeability in a direction at right angles thereto.
  • a steel that has not obtained optimum texture development may have a substantially uniform but inadequate grain size and structure and resulting poor magnetic properties or may exhibit a "banding" of inferior grain structure.
  • banding means areas or bands of inferior grain structure extending across the width of the coil surrounded by areas of well-textured steel.
  • initial phases of secondary recrystallization occur at about 1550°F (843°C), however, secondary grain growth proceeds much faster and more efficiently at temperatures of about 1600°F (871°C) or more.
  • final texture annealing The operation through which the secondary grains are preferentially grown and consume the primary grains is known as final texture annealing.
  • the typical steps include subjecting the melt of 2.5-4% silicon steel through a casting operation, such as a continous casting process, hot rolling the steel, cold rolling the steel to final gauge with an intermediate annealing when two or more cold rollings are used, decarburizing the steel, applying a refractory oxide base coating to the steel, and final texture annealing the steel, such as in a hydrogen atmosphere, to produce the desired secondary recrystallization, and purification treatment to remove impurities, such as nitrogen and sulfur.
  • the final texture annealing is typically performed at a temperature in excess of 2000°F (1093°) and held for an extended time period of at least 4 hours and generally longer to remove impurities.
  • a typical thermal cycle of the final texture annealing practice may include a reasonably continuous heating rate of approximately 50°F/hour (27.8 C/hour) from the charge temperature of the coated strip to a temperature high enough to effect purification.
  • the charge temperature in mill practice typically, is of the order of room temperature of 80°F (26.7°C) or more and the purification temperature may range from 2000°F (1093°C) up to a maximum of about 2300°F (1260°C) and preferably up to 2250°F (1232°C).
  • the steel is generally subjected to a soaking at the purification temperature to remove the impurities for a long time, typically of the order of about 20 hours at or higher than 2100°F (1150°C).
  • U.S. Patent 2,534,141 - Morrill et al discloses a two-stage final texture anneal to improve the orientation.
  • First, the cold-rolled decarburized sheet is held for 4-24 hours at 850-900°C (1560-1650°F), and preferably at 875°C (1605°F), in a reducing or non oxidizing atmosphere to encourage and permit nucleation of well-oriented crystals and their growth.
  • Second, the steel is then held at a temperature of 900 to 1200°C (1650-2192°F), and preferably 1175°C (2147 0 F), in a reducing atmosphere to permit completion of the growth of the well-oriented crystals and to relieve mechanical strain.
  • U.S. Patent 4,157,925 - Malagari et al discloses a process for producing a cube-on-edge orientation in a boron-inhibited silicon steel.
  • the process includes heating the steel from a temperature of 1700 to 1900°F (926 to 1038°C) at an average rate of less than 30°F/hour (16.7°C/hour) so as to provide a minimum time period for the selective grain-growth process to occur and to final texture anneal the steel by heating to a temperature in excess of 2000°F (1093°C) and to a maximum temperature of 2300 o F (1260°C) for purification of the steel.
  • U.S. Patent 4,318,758 - Kuroki et al discloses in Example 3 a method for producing grain-oriented silicon steel containing aluminium wherein the decarburized and coated sheet is heated u p to 900°C (1650 o F ) in a 75% H 2 and 25% N 2 atmosphere with a heating rate of 20° C/ hour (36°F/hour), then heating between 900 to 1050°C (1650-1922 F) in the same atmosphere at a heating rate of 5°C/hour (9°F/hour), between 1050 and 1200°C (1922 -2192°F) in 100% H 2 atmosphere at a heating ratio of 20 C/hour (36°F/hour) where the steel is maintained at 1200°C (2192°F) for 20 hours in the 100% H 2 atmosphere.
  • a process for producing electromagnetic silicon steel having cube-on-edge orientation wherein the process includes the conventional steps of preparing a steel melt containing 2.5-4% silicon, casting the steel, hot rolling the steel, cold rolling the steel to final gauge, decarburizing the steel, applying a refractory oxide base coating to the steel, and final texture annealing the steel by heating to and maintaining at a temperature in excess of 2000°F (1093 0 C).
  • the improvement comprises heating the steel during the final texture annealing to a selected recrystallization temperature within the range of 1600 to 1700 0 F (871 to 926 0 C), isothermally heating the steel at that temperature for 6 to 20 hours to substantially complete secondary recrystallization, and heating the steel from that isothermal hold temperature to a temperature in excess of 2000 u F (1093 C) to effect purification.
  • the final texture annealing process of the present invention includes a controlled heating cycle wherein the steel is substantially isothermally annealed at selected temperatures for particular periods of time to effect substantially complete secondary recrystallization.
  • isothermal heating or annealing during recrystallization means heating at a very low heating rate.
  • the heating rate need not be zero, but preferably should be less than 10°F/hour (5.5 C/hour), and more preferably less than 5°F/hour (2.8°C/hour).
  • Specific processing of the steel up to final texture annealing may be conventional and is not critical to the present invention.
  • the specific processing may include a number of conventional steps which include preparing a melt of the steel, casting the steel, hot rolling the steel, cold rolling the steel to final gauge with intermediate annealing steps, decarburizing the steel, applying a refractory oxide base coating, and then final texture annealing the steel in excess of 2000°F (1093°C).
  • Sample Groups of Table I were obtained from various heats of nominally 11-mil (0.279mm) gauge silicon steel having the above-identified typical composition. The samples were all coated with MgO slurry and heated from a charge temperature at a relatively constant heating rate of about 50°F/hour (27.7°C/hour) or greater. Groups D-G and I-M and O-DD were all heated from charge temperature up to the specified hold temperature. Sample Groups A, B, C, H and N were not isothermally annealed and so were not held at any temperature, but were heated from the charge temperature up to a purification soak temperature. All the Sample Groups were texture annealed in a hydrogen atmosphere at a soak temperature of 2150°F (1177°C). Groups A-Z were held at 2150°F for 20 hours, and Groups AA-DD for 10 hours.
  • the magnetic properties listed in Table I represent an average value for core loss and permeability for the number of samples for that group.
  • the distrubution of 60 Hz core losses at 17 KG (1.7 Telsa) and permeability at 10 Oersteds for those samples are shown in Figures la and lb.
  • the data show that generally the samples which were held for time at a temperature within the recrystalization range of 1600 to 1700°F (871 to 726° C ) have improved properties over those samples not held at temperature (Samples A, B, C, H and N).
  • the data demonstrate that annealed samples demonstrate incomplete recrystallization if the hold temperature is 1550°F (843°C). All samples were completely recrystallized at about 1650°F (900°C) hold temperature.
  • the data also suggest that within the 1600-1700°F (871 to 926°C) range, there may be a range of temperatures within which substantial recrystallization occurs so as to result in improved magnetic properties. The range of about 1600-1650°F (871-900°C) is preferred.
  • the hold time for the isothermal anneal is also critical. Insufficient time results in incomplete recrystallization. Too much time will generally result in some deterioration of magnetic properties, as shown by Groups S and T at 50 hours hold time. Results of tests have shown that the hold times of 6 to 20 hours provide good properties with a practical preferred time being about 12 hours.
  • All the Sample Groups of Table II were obtained from various heats of nominally 9-mil (0.229mm) gauge silicon steel having the same nominal composition as for the 11-mil samples of Table I.
  • the samples were all coated with MgO slurry and heated from a charge temperature at a relatively constant heating rate of about 50°F/hour (27.7°C/hour) or greater.
  • All of the Sample Groups, except Group E were heated from charge temperature up to the specified hold temperature. Sample Group E was not isothermally annealed and so was not held at temperature, but was heated from the charge temperature up to a purification soak temperature. All the Sample Groups were texture annealed in a hydrogen atmosphere at a soak temperature of 2150°F (1177°C) and held for 10 hours.
  • the magnetic properties listed in Table II represent an average value for core loss and permeability for the number of samples for that group.
  • the distribution of 60 Hz core losses at 17 KG (1.7 Tesla) and permeability at 10 Oersteds for those samples are shown in Figures 2a and 2b.
  • the data also confirm that the hold times for the isothermal anneal are critical.
  • the 9-mil samples demonstrate some deterioration of magnetic properties at 50 hours hold time, as shown by Groups H, I and J. Groups H and J show such poor properties that they are not plotted in figures 2a and 2b. It appears that the thin guage 9-mil material is even more sensitive to hold times than the 11-mil material. Results of tests have shown that hold times up to 20 hours provide good results, preferably 6 to 20 hours, and a practical preferred time of about 12 hours.
  • the method of the present invention relates to an improved final texture annealing process wherein the steel is heated to a recrystallization temperature within the range of 1600 to 1700°F (871 to 926°C).
  • the heating rate may be of the order of a conventional 50°F per hour (27.7°C/hour) and the selected isothermal hold temperature be about 1650°F (900°C).
  • the steel is then isothermally heated by holding the steel at that temperature for about 6 to 20 hours, preferably about 12 hours, to substantially complete secondary recrystallization.
  • the steel is heated from that temperature to a purification temperature in excess of 2000°F (1093°C), preferably about 2000°F (1204°C), at a heating rate such as 50°F per hour (27.7°C/hour) and held at that temperature to effect purification.
  • a purification temperature in excess of 2000°F (1093°C), preferably about 2000°F (1204°C), at a heating rate such as 50°F per hour (27.7°C/hour) and held at that temperature to effect purification.
  • the heating rate up to the hold temperature and up to the purification temperature are relatively constant heating rates.
  • the heating rate does not appear to be critical to significantly affect the properties.
  • An advantage of the method of the present invention is that secondary recrystallization is essentially completed during the isothermal portion of the heat treatment, rather than being completed in accordance with conventional practice during heating to the higher purification temperature.
  • the effect of the present invention is to improve both magnetic permeability and core loss values.
  • the method of the present invention is able to improve the magnetic properties in a manner not heretofore recognized in the art.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Electromagnetism (AREA)
  • Manufacturing Of Steel Electrode Plates (AREA)
  • Soft Magnetic Materials (AREA)
EP84302946A 1983-07-05 1984-05-02 Procédé pour la fabrication d'acier électromagnétique au silicium à grains orientés cube-sur-arête Withdrawn EP0130674A3 (fr)

Applications Claiming Priority (2)

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US51084483A 1983-07-05 1983-07-05
US510844 1983-07-05

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EP0130674A2 true EP0130674A2 (fr) 1985-01-09
EP0130674A3 EP0130674A3 (fr) 1985-05-15

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EP (1) EP0130674A3 (fr)
JP (1) JPS6036619A (fr)
CA (1) CA1240592A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0211486A1 (fr) * 1985-08-13 1987-02-25 Allegheny Ludlum Steel Corporation Procédé pour modifier la formation du revêtement de base appliqué sur de l'acier silicone par le contrôle de la tension d'enroulement

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2534141A (en) * 1948-01-14 1950-12-12 Gen Electric Heat-treatment of cold rolled silicon steel strip
FR2262703A1 (fr) * 1974-02-28 1975-09-26 Kawasaki Steel Co
FR2357660A1 (fr) * 1976-07-05 1978-02-03 Kawasaki Steel Co Pellicule isolante de forsterite formee sur la surface d'une tole d'acier au silicium a grains orientes avec une induction magnetique elevee et procede de formation de cette pellicule
FR2388383A1 (fr) * 1977-04-18 1978-11-17 Nippon Steel Corp Tole magnetique a grains orientes ayant de bonnes proprietes magnetiques
US4157925A (en) * 1978-04-12 1979-06-12 Allegheny Ludlum Industries, Inc. Texture annealing silicon steel

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4213804A (en) * 1979-03-19 1980-07-22 Allegheny Ludlum Industries, Inc. Processing for cube-on-edge oriented silicon steel

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2534141A (en) * 1948-01-14 1950-12-12 Gen Electric Heat-treatment of cold rolled silicon steel strip
FR2262703A1 (fr) * 1974-02-28 1975-09-26 Kawasaki Steel Co
FR2357660A1 (fr) * 1976-07-05 1978-02-03 Kawasaki Steel Co Pellicule isolante de forsterite formee sur la surface d'une tole d'acier au silicium a grains orientes avec une induction magnetique elevee et procede de formation de cette pellicule
FR2388383A1 (fr) * 1977-04-18 1978-11-17 Nippon Steel Corp Tole magnetique a grains orientes ayant de bonnes proprietes magnetiques
US4157925A (en) * 1978-04-12 1979-06-12 Allegheny Ludlum Industries, Inc. Texture annealing silicon steel

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0211486A1 (fr) * 1985-08-13 1987-02-25 Allegheny Ludlum Steel Corporation Procédé pour modifier la formation du revêtement de base appliqué sur de l'acier silicone par le contrôle de la tension d'enroulement

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Publication number Publication date
JPS6036619A (ja) 1985-02-25
JPH0447010B2 (fr) 1992-07-31
CA1240592A (fr) 1988-08-16
EP0130674A3 (fr) 1985-05-15

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