Classifications

• • 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
  • C21D8/1294—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a localized treatment

Definitions

• the present invention relates to a method for reducing the ohmic losses in sheets as they are used in electrical equipment.
• the invention relates to improvements in the making of sheets of silicon iron alloys or iron molybdenum or the like, whereby the improvement concerns particularly the electric power loss in equipment using such sheets, e.g. transformers.
• Sheets with secondary recrystallization are known for use in electrical equipment in which the grains are singly oriented and have (110) [001] position, which is also called Goss-position. These types of sheets have been used for about 30 years. In the past ten years interest in doubly oriented iron alloy sheets has developed, whereby the metal secondarily recrystallizes in the (100) [001] position, also called cube position. Sheets having Goss-texture are used primarily in large transformers. These sheets have a direction of easy magnetization (and thus lowest losses) in the direction of rolling. However, sheets with recrystallization in cubic position have two directions of easy magnetization, the direction of rolling and the direction transverse thereto.
• cube texture sheets recrystallize in grains or crystals which are considerably larger than in a singly oriented sheet.
• the cube texture sheets have large ferromagnetic domains so that in case of magnetization in an alternating field the Block walls obtain large speeds, which in turn results in larger eddy current losses. Consequently the overall ohmic losses are relatively high.
• the orientation of the individual crystallites in the sheet is not ideal, which is true for singly as well as in doubly oriented sheets.
• the cube edge or [001] direction of the crystals or grains along which magnetization is the easiest deviates from the ideal position.
• One component of the deviation occurs in the plane of the sheet, and there is in particular some deviation of the [001] directions from the direction of rolling. This deviation is to both sides from the direction of rolling and can be considerable.
• the (100) surface of most crystals is rotated out of the surface of the sheet by a few degrees or more.
• the deviation of the (100) surface from ideal orientation is within five degrees or less of about 80 to 90% of the grains which deviation does not materially increase the ohmic losses of such a 3,647,575 Patented Mar. 7, 1972 Ice sheet.
• disorientation of the (100) surface relative to the surface of a doubly oriented sheet and amounting to one or two degrees only already causes considerable increase in ohmic losses.
• the surface of such a sheet has compensating areas or regions in a thin surface layer, having the form of the well-known pine tree or dendrite pattern and having walls reducing stray fields caused by the grain surface disorientation.
• the groove distance should preferably be between 0.1 and 1.0 mm. It is not required to obtain deeper grooves, serrations, etc. than 40.10 depth.
• sheets of similar composition show different losses without inventive treatment, but the method in accordance with the invention tends to equalize the losses, i.e., losses are reduced to approximately the same value in different sheets, and the residual loss is essentially dependent only upon the composition, e.g., the silicon content.
• the surface treatment in accordance with the invention changes the mechanism (large Bloch walls and pine tree or dendrite pattern) which tends generally to increase losses in cube texture sheets.
• grooving changes the loss producing mechanism so that the losses are, in effect, cut.
• Grooves placed as outlined above partitions a thin surface layer underneath a large grain surface, normally available for these loss increasing mechanisms, and establishes therein many small and separate regions. The depth of the layer so affected is determined by the depth of the grooves.
• the method of the present invention differs from this known treatment of sheet metal in that presently the deformation requires very narrow grooves, provided upon already existing large grains and in a thin surface layer of sheets consisting of oriented crystals. Moreover, the invention is practiced on the finally annealed and recrystallized sheet. Subsequent stress annealing for tension elimination at recrystallization temperature may, but does not have to be, provided. Whether such annealing can take place will be seen after testing small samples.
• Practicing the invention does not require particular change or arrangement of the cube texture grains or crystals, even through grains or crystals are usually very large and may cover up to several square centimeters. Also, should the crystals accidentally have elongated shape, there are no particular requirements of the orientation of the longitudinal axis of such grain relative to any other direction, for successfully practicing the invention. Moreover, if first there was hot or cold rolling with subsequent annealing the providing of grooves should not cause recrystallization, particularly primary recrystallization, for obtaining grains or crystals, which are coarser and are particularly oriented as to their long crystallite axis.
• a method for reducing ohmic power losses of silicon or molybdenum containing iron alloy steel sheets which comprises providing a completely recrystallized, coarse grained sheet; and partially plastically deforming said completely recrystallized, coarse grained sheet by imparting grooves or serrations to the surface portion on at least .one side of said sheet whereby the domain texture in a surface region of the individual crystallites is locally modilied and surface portions adjacent to the localized deformation remain substantially undeforrned.
• the deformation step including grooving of the surface of the sheet, the grooves provided having distance from each other considerably smaller than the mean size of oriented sheet elements.
• the plastic deformation including the providing of grooves on both sides of the sheet, the grooves on one side thereof oriented parallel to the direction of rolling, the grooves on the other side of the sheet oriented transverse to the direction of rolling.
• the plastic deformation including the providing of grooves at different orientation on both sides, the grooves having distance from each other considerably smaller than the grain size the grooves having depth not deeper than about 0.04 mm.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Crystallography & Structural Chemistry (AREA)
• Thermal Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Electromagnetism (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Soft Magnetic Materials (AREA)
• Manufacturing Of Steel Electrode Plates (AREA)

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Publications (1)

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ID=5711044

Family Applications (1)

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Cited By (36)

Families Citing this family (14)

Family Cites Families (1)

• 1968
  • 1968-10-17 DE DE19681804208 patent/DE1804208B1/de not_active Withdrawn
• 1969
  • 1969-09-26 JP JP44076327A patent/JPS5035679B1/ja active Pending
  • 1969-10-16 GB GB1253115D patent/GB1253115A/en not_active Expired
  • 1969-10-17 US US867406A patent/US3647575A/en not_active Expired - Lifetime

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