EP0875586A1 - Process for producing non-oriented electrical steel sheet having high magnetic flux density and low iron loss - Google Patents

Process for producing non-oriented electrical steel sheet having high magnetic flux density and low iron loss Download PDF

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Publication number
EP0875586A1
EP0875586A1 EP96941184A EP96941184A EP0875586A1 EP 0875586 A1 EP0875586 A1 EP 0875586A1 EP 96941184 A EP96941184 A EP 96941184A EP 96941184 A EP96941184 A EP 96941184A EP 0875586 A1 EP0875586 A1 EP 0875586A1
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EP
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Prior art keywords
steel sheet
hot rolling
rolling
flux density
magnetic flux
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EP96941184A
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German (de)
English (en)
French (fr)
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EP0875586A4 (zh
Inventor
Ryutaro Nippon Steel Corporation KAWAMATA
Takeshi Nippon Steel Corporation KUBOTA
Takahide Nippon Steel Corporation SHIMAZU
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Nippon Steel Corp
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Nippon Steel Corp
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Priority claimed from JP21809696A external-priority patent/JP4191806B2/ja
Priority claimed from JP8321886A external-priority patent/JPH10102147A/ja
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Publication of EP0875586A1 publication Critical patent/EP0875586A1/en
Publication of EP0875586A4 publication Critical patent/EP0875586A4/xx
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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
    • C21D8/1261—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 following hot rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B1/24—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process
    • B21B1/26—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length in a continuous or semi-continuous process by hot-rolling, e.g. Steckel hot mill
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C21D8/1222—Hot 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
    • 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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B15/00—Arrangements for performing additional metal-working operations specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
    • B21B15/0085—Joining ends of material to continuous strip, bar or sheet
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
    • B21B2001/228—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length skin pass rolling or temper rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2265/00—Forming parameters
    • B21B2265/20—Slip
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
    • B21B27/06—Lubricating, cooling or heating rolls
    • B21B27/10—Lubricating, cooling or heating rolls externally
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B21B3/02—Rolling special iron alloys, e.g. stainless steel

Definitions

  • the present invention relates to a process for production of non-oriented electrical steel sheet having a high magnetic flux density, low iron loss, and superior magnetic properties which can be used as a core material of electrical appliances.
  • Japanese Unexamined Patent Publication (Kokai) No. 59-745 discloses the technique of not only defining the impurities in one cold rolling to limit them to S ⁇ 15 ppm, O ⁇ 20 ppm, and N ⁇ 25 ppm, but also defining the conditions of the annealing of the hot rolled sheet and defining the cold rolling reduction rate as not less than 65%, while Japanese Unexamined Patent Publication (Kokai) No.
  • 59-74225 discloses the technique of not only defining the impurities in two steps cold rollings to S ⁇ 15 ppm, O ⁇ 20 ppm, and N ⁇ 25 ppm, but also defining the conditions of process annealing and defining the second cold rolling reduction rate as not less than 70%.
  • Japanese Unexamined Patent Publication (Kokai) No. 54-76422 discloses, as a technique for inexpensively enlarging the crystal structure before cold rolling a non-oriented electrical steel sheet to raise the magnetic flux density, a self annealing method where the hot rolled steel sheet after the finish hot rolling is coiled at a high temperature of 700°C to 1000°C and is annealed by the retained heat by the coil.
  • Japanese Examined Patent Publication (Kokoku) No. 62-61644 discloses a method for controlling temperature after the hot rolling a high temperature of not less than 1000°C, setting the non-water injection time, and promoting the recrystallization and grain growth of the hot rolled structure before coiling on a run-out table.
  • Japanese Unexamined Patent Publication (Kokai) No. 59-74222 discloses a technique of controlling the reduction of the final stand in the finish hot rolling not less than 20% and also controlling the coiling temperature of the hot rolled sheet not less than 700°C.
  • the aim is to raise the reduction ratio at the final stand and raise the coiling temperature so as to promote recrystallization and grain growth of the hot rolled structure after the hot rolling and as a result improve the magnetic properties.
  • the Si content in the steel sheet is high, however, the subsequent grain growth is insufficient and therefore again the problem inherent to high Si type non-oriented electrical steel sheet of an insufficient improvement in the magnetic flux density is not solved.
  • the present invention differs in concept from that of the prior art and is based on the technical concept of reducing the average friction coefficient at the time of controlled rolling so as to deliberately cause the formation of a recovery structure and of suitably controlling the work deformation rate (strain rate) at the time of hot rolling so as to improve the aggregate structure near the surface of the steel sheet and as a result cause enlargement of the actual grain size of the hot rolled crystal structure and improve the aggregate structure before cold rolling.
  • the object of this is to provide a process for production of a high Si content high grade non-oriented electrical steel sheet with a high magnetic flux density and a low iron loss, which had been difficult in the prior art.
  • the gist of the present invention is as follows:
  • Figure 1 is a view of the relationship between the Si content and the magnetic flux density.
  • Figure 2 is a view of the relationship between the average coefficient of friction at the finish hot rolling and the magnetic flux density of the product.
  • Figure 3 is a view of the relationship between the strain rate of the final stand at the finish hot rolling and the magnetic flux density of the product.
  • Figure 4 is a view of the relationship between the average coefficient of friction and maximum strain rate of all of the stands at the finish hot rolling and the magnetic flux density of the product.
  • Figure 5 is a view of the relationship between the average coefficient of friction at the finish hot rolling and the magnetic flux density of the product after annealing of the hot rolled steel sheet.
  • Figure 6 is a view of the relationship between the average coefficient of friction and maximum strain rate of all of the stands at the finish hot rolling in the annealing process of the hot rolled sheet by continuous annealing and the magnetic flux density of the product.
  • Figure 7 is a view of the relationship between the annealing a hot rolled steel sheet by continuous annealing and the magnetic flux density of the product.
  • Figure 8 is a view of the relationship between the temperature of annealing a hot rolled steel sheet by continuous annealing and the magnetic flux density of the product.
  • Figure 9 is a view of the relationship between the average coefficient of friction at the hot rolling and the magnetic flux density of the product which has been self annealed.
  • Figure 10 is a view of the relationship between the average coefficient of friction at the hot rolling and the magnetic flux density of the product which has not been subjected to strip coolant application for a certain period of time after hot rolling.
  • Figure 11 shows electron micrographs of the changes in the crystal structure of the hot rolled steel sheet due to differences in the coefficient of friction, wherein Figs. 11A and 11C show the present invention and Figs. 11B and 11D show comparative examples.
  • Figure 12 shows electron micrographs of the changes in the crystal structure after annealing of the hot rolled steel sheet due to differences in the coefficient of friction, wherein Fig. 12A shows the present invention and Fig. 12B shows a comparative example.
  • the present inventors engaged in intensive studies to overcome the limit of controlled rolling of such a high Si content non-oriented electrical steel sheet and as a result discovered that by either hot rolling a steel containing more than 1.0% to 7.0% of Si, 0.1% to 1.5% of Mn, and, if necessary, 0.10% to 2.0% of Al by an average coefficient of friction between the hot rolling roll and steel sheet at the finish hot rolling of not more than 0.25 or by further suitably controlling the work deformation rate at the hot rolling (strain rate) in addition to the average coefficient of friction in the hot rolling, the formation of a fine grain structure caused by the recrystallization of the surface of the hot rolled steel sheet is suppressed and a rough recovered structure is obtained over the entire thickness of the steel sheet.
  • this recovered structure is a structure rougher than even the recovered structure seen in the center layer of the hot rolled steel sheet obtained by a conventional high coefficient of friction rolling method and as a result that a rough crystal structure can be substantially obtained over the entire thickness of the sheet.
  • the inventors made the completely novel discovery that even in a process predicated on various types of annealing of hot rolled steel sheets, a process of self annealing by high temperature coiling, and a process of high temperature finishing setting a non-water coolant period, by hot rolling at an average coefficient of friction between the hot rolling roll and the steel sheet at the finish hot rolling of not more than 0.25 or further suitably controlling the work deformation rate at the time of hot rolling (strain rate) in addition to the average coefficient of friction in the hot rolling, crystal grain growth at the time of the annealing of the hot rolled sheet, at the time of the self annealing with the objective of replacing annealing of the hot rolled sheet, or at the time of the high temperature finishing setting a non-water coolant application period, is promoted.
  • the technical concept of the present invention is a completely different technical concept from the conventional reduction of the coefficient of friction at the time of finish hot rolling to positively promote the formation of a recovered structure and at the same time maintain the strain rate at the finish hot rolling at a certain level or more so as to further promote this effect.
  • the inventors discovered that as a means for lubricant rolling as in the present invention, it is effective to mix a certain amount or more of lubricant oil in the coolant (cooling water) for the rolling roll and apply it on the work roll.
  • the inventors discovered that to stably perform the finish hot rolling at a low friction rate, as in the present invention, it is effective to weld the sheet bar after rough rolling with the preceding sheet bar and continuously perform the finish hot rolling.
  • Si is added to increase the inherent resistance of the steel sheet, reduce the eddy current loss, and improve the iron loss value. If the Si content is less than 1.0%, even if the coefficient of friction at the finish hot rolling is reduced and the strain rate is controlled, the effect of improvement of the magnetic flux density is small. Further, the inherent resistance required for the low iron loss non-oriented electrical steel sheet aimed at by the present invention cannot be sufficiently obtained, so it is necessary to add an amount of over 1.0%. On the other hand, if the Si content is over 7.0%, the edge cracking at the not rolling remarkably increases and rolling operation becomes difficult, so it is necessary to contain it not more than 7.0%.
  • the following experiment was performed to investigate the dependency of the effect of improvement of the magnetic properties of the present invention on the Si content.
  • the steel composition of non-oriented electrical steel sheets with different Si contents were melted and subjected to finish rolling.
  • Mn As the amount of other components other than Si, Mn was controlled to 0.1 to 0.2%, the sol-Al to not more than 20 ppm, and the C, N, and S to 10 to 20 ppm each.
  • the steel compositions were adjusted to clarify the relationship between the effect of the present invention and the Si content.
  • the average coefficient of friction at the finish hot rolling was made 0.21 by adjusting the content of the lubricant oil in the coolant to 2.5% by percent volume.
  • the average coefficient of friction was found by calculating the coefficients from the actually measured forward slip ratio of the stands and finding the average of the same. Further, the strain rate of the final stand in the finishing mill was made 280 s -1 .
  • the temperature at the end of the finish hot rolling was made a constant 860°C in all cases and the hot rolled sheets in all cases were finished to a thickness of 2.5 mm.
  • the above hot rolled strip were then pickled and cold rolled to a thickness of 0.50 mm, then annealed in a continuous annealing furnace, and then Epstein specimens were cut out and the magnetic properties were measured.
  • the dependency of the magnetic flux density of the products, obtained as a result of the experiments, on the Si content is shown in Fig. 1. Even in the low Si region, a slight effect of improvement of the magnetic properties was observed, but it was learned that as the Si content became higher, the effect of improvement of the magnetic properties of the present invention became greater and that the increase was remarkable when the Si content was over 1%.
  • the range of the Si content defined in the present invention was made at least 1.0% not only for securing the above-mentioned inherent resistance of the steel sheet, but also because this was the Si content effectively giving the hot rolling conditions of the present invention.
  • Al also, like Si, has the effect of increasing the inherent resistance of the steel sheet and reducing the eddy current loss.
  • at least 0.1% must be added.
  • the Al content is over 2.0%, the magnetic flux density falls and the cost rises, so the Al content limit not more than 2.0%.
  • the effect of the present invention is not impaired in any way.
  • Mn like Al and Si has the effect of increasing the inherent resistance of the steel sheet and reducing the eddy current loss.
  • the Mn content must be limited to at least 0.10%.
  • the present invention it is possible to provide high magnetic flux density and low iron loss non-oriented electrical steel sheet even better than the prior art, therefore for applications where a certain level of magnetic properties and electrical resistivity are required, normally the Mn content of 0.1% to 1.0% is sufficient.
  • the Mn content is over 1.5%, the deformation resistance at the time of hot rolling increases and hot rolling becomes difficult. Also, the crystal structure after the hot rolling easily becomes fine and the magnetic properties of the product deteriorate, so the Mn content must be limited to less than 1.5%.
  • the amount of Mn added is extremely important from the viewpoint of ensuring the strength of the welded parts of the sheet bars at a high temperature before the finish hot rolling.
  • the reason is that to prevent hot shortness of the welded parts of the sheet bars due to the presence of low melting point sulfides at the crystal grain boundaries, it is necessary to make the ratio of the concentration by weight of the Mn and S, that is, the Mn/S value, at least 20.
  • the Mn content is not less than 0.1% and the S content is not more than 0.005%, so the Mn/S value is held at 20 or more. There is no problem from this viewpoint.
  • the magnetic aging during use causes the iron loss to deteriorate and increases the energy loss at the time of use, so it is necessary to control it to not more than 0.0050%.
  • the value of the coefficient of friction between the rolling roll and steel sheet at the hot rolling should be not more than 0.25 in terms of the average value for all stands in the finish hot rolling. If the coefficient of friction over 0.25, the effect is insufficient and the magnetic flux density of the product decreases.
  • the lower limit of the coefficient of friction is not particularly decided, but if the value is excessively small, slip occurs during the rolling and stable rolling no longer becomes possible, so it is preferably set to not less than 0.05.
  • the amount of the lubricant oil mixed with the coolant for rolling roll at the finish hot rolling is made 0.5% to 20% by percent volume.
  • the oil is mixed in an emulsion state. If the amount of the lubricant oil in the coolant is less than 0.5%, the effect is not obtained, while if over 20%, the effect becomes saturated and becomes uneconomical, so the upper limit is made 20%.
  • a surfactant may be added to prevent separation of the lubricant oil and cooling water.
  • the emulsion mixed state may be created by feeding the lubricant oil and cooling water by separate systems of piping and simultaneously spraying the rolling roll with the lubricant oil and cooling water from the same spray nozzles.
  • a known hot rolling oil for finishing mills should be used.
  • the hot rolling oil for finishing mills Kyudoru 5149®, Kyudoru 0B068®, and Kyudoru 4B313® all brand names of Kyodo Yushi Co. may be mentioned.
  • a method for bonding the preceding sheet bar and the succeeding sheet bar there are the method of aligning the rear end of the preceding sheet bar and the front end of the succeeding sheet bar and applying a pressing force to the aligned portion to join them, the method of applying a pressing force to the aligned portion and laser welding it, the method of induction heating the aligned portion to bond it, etc.
  • the strain rate of at least one pass in the finish hot rolling at least 150 s -1 it is possible to improve the magnetic properties more.
  • the strain rate is inherently determined from the capabilities of the rolling mill and the controllability of the shape of the hot rolled steel sheet. That is, the strain rate is determined by the rolling speed, the hot rolling roll diameter, and the amount of the reduction ratio. If the rolling speed and the amount of the reduction ratio are made larger, the strain rate increases, but control of the shape of the hot rolled sheet becomes difficult. Since a non-oriented electrical steel sheet is supplied for use stacked with other sheets, strict control of its shape is required. Therefore, there are inherent limits to the increase of the strain rate. From this viewpoint, there is a limit of about 600 s -1 on the strain rate.
  • the pickled hot rolled sheet may be annealed by continuous annealing or box annealing. Further, the hot rolled strip may be coiled at a temperature of 750°C to 1000°C and self-annealed by the heat which the coil itself retains for 5 minutes to 5 hours. Alternatively, the strip may be coiled without coolant for a period of time defined by a specific equation after the end of the hot rolling.
  • the hot rolled sheet obtained in this way may be subjected to one cold rolling process and then finishing annealing or may be subjected to two or more cold rolling processes including a process annealing step and then finishing annealing. Further, rolling for finishing the sheet to the final thickness may be performed by the known cold rolling technique, but in the case of a high Si composition system, to prevent breakage or edge cracking during rolling, it is also possible to raise the temperature of the steel sheet in accordance with the Si content and immerse the coil in warm water or perform warm rolling at 100 to 400°C.
  • a steel slab comprised of the above composition is produced by melting by a converter and continuous casting or ingot-making and slabbing.
  • the steel slab is re-heated by a known method. This slab is then hot rolled to a predetermined thickness.
  • lubricant oil is mixed into the coolant to reduce the coefficient of friction between the work roll of the finish hot rolling mill and the steel sheet.
  • a surfactant is added in accordance with need to prevent the lubricant oil and the cooling water from separating.
  • the amount of the lubricant oil mixed into the cooling water is made 0.5% to 20% by percent volume. If the amount of the lubricant oil in the cooling water is less than 0.5%, an effect is not obtained, while if it is over 20%, the effect becomes saturated so the result is uneconomical, therefore the amount is made more than 0.5% and less than 20%.
  • the average coefficient of friction at the finish hot rolling was changed from 0.1 or so to over 0.3 by changing the content of the lubricant oil in the cooling water.
  • the average coefficient of friction was found by calculating the coefficients from the actually measured forward slip ratio of the mill stands and finding the average of the same.
  • the temperature at the end of the finish hot rolling was maintained at a temperature of 860°C and the sheet finished to a thickness of 2.0 mm.
  • the hot rolled strip was then pickled and cold rolled to a thickness of 0.35 mm, then annealed for 30 seconds at 900°C in the case of the steel A and 980°C in the case of the steel B, then Epstein specimens were cut out and measured for magnetic properties.
  • the inventors succeeded in developing a means for improving the magnetic properties of high Si type non-oriented electrical steel sheet, in particular the magnetic flux density, by a technical concept completely different from the promotion of recrystallization and grain growth by raising the temperature at the final hot rolling in the prior art, that is, by suppressing the hot rolled crystal structure by the means of reducing the average coefficient of friction between the steel sheet and work roll at the finish hot rolling.
  • the value of the average coefficient of friction between the rolling roll and steel sheet at the finish hot rolling should be no more than 0.25 in terms of the average for all stands in the finish hot rolling. If the average coefficient of friction value is above 0.25, as explained above, the occurrence of recrystallized grains causes the crystal structure near the surface layer of the hot rolled steel sheet to become particularly finer and the magnetic flux density of the product to decline. There is no particular lower limit set on the coefficient of friction, but if the value becomes excessively small, slip occurs during rolling and stable hot rolling no longer becomes possible, so at least 0.05 is preferable.
  • the hot rolled sheet obtained in this way is then subject to one cold rolling process and then finishing annealing or two or more cold rolling processes including annealing, then finishing annealing.
  • the rolling speed and pass schedule were changed for tests to change the strain rate at the finish hot rolling.
  • the pass schedule was adjusted so that the maximum strain rate was obtained in the final stand.
  • the temperature at the end of the finish hot rolling was 860°C.
  • the steel sheet was finished to a thickness of 2.5 mm, water cooled, then coiled at 650°C.
  • the average coefficient of friction at the finish hot rolling was controlled to 0.20 by changing the content of the lubricant oil in the cooling water.
  • the average coefficient of friction was found by calculating the coefficients from the actually measured forward slip ratio in the mill stands and taking the average value of the same.
  • hot rolled steel sheet was pickled, cold rolled to a thickness of 0.50 mm, then annealed at 950°C for 30 seconds. Epstein specimens were cut off and the magnetic properties measured.
  • Fig. 3 The dependency of the magnetic flux density of the product on the strain rate of the final pass at the finish hot rolling is shown in Fig. 3. According to Fig. 3, it is learned that the magnetic flux density of the product rises with a strain rate of not less than 150 s -1 .
  • strain rate was calculated by the following formula.
  • r is the reduction ratio in %/100
  • n is the rotational speed of the roll (rpm)
  • R is the radius of the rolling roll (mm)
  • H 0 is the sheet thickness before rolling (mm).
  • Strain rate (2 ⁇ n/(60r 0.5 ))(R/H 0 ) 0.5 ln(1/(1-r))
  • the strain rate in at least one pass in the finish hot rolling should be at least 150s -1 .
  • No upper limit is set on the strain rate.
  • the strain rate is determined by the rolling speed, the hot rolling roll diameter, and the reduction ratio. If the rolling speed and the reduction ratio are made larger, the strain rate increases, but control of the shape of the hot rolled steel sheet becomes difficult. Since non-oriented electrical steel sheet is supplied for use stacked with other sheets, strict control of its shape is required. Therefore, there are inherent limits to the increase of the strain rite. From this viewpoint, there is a limit of about 600 s -1 on the strain rate.
  • the hot rolled steel sheet obtained in this way may be subjected to one cold rolling process and then final annealing and then further a skin pass rolling process.
  • the stable finish hot rolling at a high strain rate and a low friction rate as in the present invention it is particularly effective to weld the sheet bar after rough rolling to the preceding sheet bar and continuously supply the sheet bars to the finish hot rolling.
  • a method for welding the preceding sheet bar and the succeeding sheet bar there are the method of aligning the rear end of the preceding sheet bar and the front end of the succeeding sheet bar and applying a pressing force to the aligned portion to join them, the method of applying a pressing force to the aligned portion and laser welding it, the method of induction heating the aligned portion to join it, etc.
  • the rolling rate and pass schedule were changed for tests to change the strain rate at the finish hot rolling.
  • the pass schedule was adjusted so that the maximum strain rate was obtained in the final stand.
  • the strain rate was calculated by the following formula.
  • r is the reduction ratio in %/100
  • n is the rotational speed of the roll (rpm)
  • R is the radius of the rolling roll (mm)
  • H 0 is the sheet thickness before rolling (mm).
  • Strain rate (2 ⁇ n/(60r 0.5 ))(R/H 0 ) 0.5 ln(1/(1-r))
  • the average coefficient of friction at the time of finish hot rolling was controlled by changing the content of the lubricant oil in the cooling water.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio for the stands and finding the average value.
  • the temperature at the end of the finish hot rolling was 860°C.
  • the sheet was finished to a thickness of 2.5 mm, water cooled, then coiled at 650°C.
  • Figure 4 shows the relationship between the average coefficient of friction and strain rate at the time of finish hot rolling at the time of hot rolling and the magnetic flux density of the product.
  • a high magnetic flux density of at least 1.68T is obtained in the region of the range defined by the present invention, that is, an average coefficient of friction of not more than 0.25 and a maximum strain rate of not less than 150s -1 .
  • the coefficient of friction at the finish hot rolling was changed from 0.1 or so to at least 0.3 by changing the content of the lubricant oil in the cooling water.
  • the average coefficient of friction was found by calculating the coefficients from the actually measured forward slip ratio of the stands and finding the average of the same.
  • the temperature at the end of the finish hot rolling was maintained a constant 900°C and the steel sheet finished to a thickness of 2.0 mm. After the hot rolling was finished, it was quenched and coiled at 500°C.
  • This hot rolled coil was annealed in a continuous annealing furnace for 90 seconds at 950°C in the case of the steel C and at 980°C in the case of the steel D. This was then pickled and cold rolled to a thickness of 0.35 mm, then annealed for 30 seconds at 900°C in the case of the steel C and 980°C in the case of the steel D, then Epstein specimens were cut out and measured in magnetic properties.
  • the value of the coefficient of friction between the rolling roll of the finish hot rolling and the steel sheet should be not more than 0.25 in terms of the average value for all of the stands at the finish hot rolling. If above 0.25, the effect is not sufficient and the magnetic flux density of the product falls.
  • Composition of Material Used C Si Mn S sol-Al N Steel C 0.0018 2.10 0.19 0.0019 0.30 0.0015 Steel D 0.0015 3.00 0.10 0.0015 0.70 0.0017
  • the sheet bar is hot rolled by the finishing mill, rolling defects of the sheet bar occur, slip occurs between the roll and the steel sheet during the finish hot rolling, the lifetime of the rolling roll is remarkably shortened, and deep rolling defects are caused in the surface layer of the steel sheet.
  • it is particularly effective to weld the sheet bar after rough rolling to the preceding sheet bar before the finish hot rolling and continuously supply the sheet bars to the finish hot rolling.
  • the average coefficient of friction at the finish hot rolling was made 0.21 by making the content of the lubricant oil in the cooling water 2% by percent volume and the maximum strain rate was made 270 s -1 in the final stand.
  • the average coefficient of friction at the finish hot rolling was adjusted to 0.35 by making the content of the lubricant oil in the cooling water 0.3% and the maximum strain rate was made 120 s -1 in the final stand.
  • the average coefficient of friction was found by calculating the coefficients from the actually measured forward slip ratio in the stands and taking the average value of the same.
  • the temperature at the end of the finish hot rolling was kept a constant 860°C in both cases and the steel sheet finished to a thickness of 2.3 mm.
  • the hot rolled steel sheet was annealed in a continuous annealing furnace at 950°C for 90 seconds. Specimens were cut out from the resultant hot rolled steel sheet and the metal structure of the hot rolled steel sheet observed by an electron microscope. The results are shown in Fig. 12. As shown in Fig. 12A, in the present invention, where the average coefficient of friction is low and the strain rate is high, the metal structure after annealing of the hot rolled steel sheet becomes coarser than the comparative example shown in Fig. 12B. As a result, it was observed that the magnetic properties of the product after annealing were improved.
  • the rolling speed rate and pass schedule were changed for tests to change the strain rate at the finish hot rolling.
  • the pass schedule was adjusted so that the maximum strain rate was obtained in the final stand.
  • the strain rate was calculated by the following formula.
  • r is the reduction ratio in %/100
  • n is the rotational speed of the roll (rpm)
  • R is the radius of the rolling roll (mm)
  • H 0 is the thickness of the steel sheet before rolling (mm).
  • Strain rate (2 ⁇ n/(60r 0.5 ))(R/H 0 ) 0.5 ln(1/(1-r))
  • the average coefficient of friction at the finish hot rolling was controlled by changing the content of the lubricant oil in the cooling water.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio for the stands and finding the average value.
  • the temperature at the end of the finish hot rolling was 900°C.
  • the sheet was finished to a thickness of 2.5 mm, water cooled, then coiled at 650°C.
  • the hot rolled steel sheet was then annealed in a continuous annealing furnace at 930°C for 2 minutes.
  • the obtained hot rolled steal sheet was pickled and cold rolled to a thickness of 0.50 mm, then annealed for 30 seconds at 900°C. Epstein specimens were cut out and measured in magnetic properties.
  • Figure 6 shows the relationship between the average coefficient of friction and strain rate at the finish hot rolling and the magnetic flux density of the product.
  • a high magnetic flux density of at least 1.72T is obtained in the region of the range defined by the present invention, that is, an average coefficient of friction of not more than 0.25 and a maximum strain rate of not less than 150s -1 .
  • the content of the lubricant oil in the cooling water at the finish hot rolling was adjusted to make the average coefficient of friction 0.21.
  • the temperature at the end of the finish hot rolling was kept a constant 900°C and the steel sheet finished to a thickness of 2.0 mm. After the end of the hot rolling, the steel sheet was quenched and then coiled at 500°C.
  • the average coefficient of friction was found by calculating the coefficients from the actually measured forward slip ratio of the stands and finding the average of the same. Further, the strain rate of the final stand was made 290 s -1 .
  • the hot rolled coil was annealed in a continuous annealing furnace at an annealing temperature of a constant 950°C and different annealing times.
  • the hot rolled steel sheet was annealed by continuous annealing for 90 seconds and different annealing temperatures.
  • the steel sheet was pickled, cold rolled to a thickness of 0.35 mm, then annealed at 900°C for 30 seconds. Epstein specimens were cut off and measured in magnetic properties.
  • the effect of the annealing time of the hot rolled steel sheet by the continuous annealing on the magnetic flux density of the product is shown in Fig. 7.
  • the annealing time of the hot rolled steel sheet by the continuous annealing is made 20 seconds to 5 minutes.
  • the preferred annealing time of the hot rolled sheet by the continuous annealing viewed from the effect of the annealing and of economy is 30 seconds to 3 minutes.
  • the annealing temperature of the hot rolled steel sheet by the continuous annealing is made 850°C to 1150°C.
  • the preferred annealing temperature of the hot rolled steel sheet by the continuous annealing viewed from the effect of the annealing and of economy such as the pickling ability is 850°C to 1000°C.
  • the annealing of the hot rolled sheet may also be performed by box annealing.
  • the annealing temperature of the hot rolled steel sheet is less than 750°C, the annealing time required for improving the magnetic properties of the product becomes remarkably long, which is not economical.
  • the annealing temperature is more than 850°C, a large amount of funds are required for the capital investment for the furnace and generating sticking of the coil during annealing.
  • the lower limit of the annealing temperature is made 750°C and the upper limit is made 850°C.
  • the annealing time of the hot rolled steel sheet by box annealing is less than 5 minutes, the annealing temperature required for improving the magnetic properties of the product becomes remarkably high and the capital investment for the furnace itself becomes excessive and uneconomical, therefore the lower limit of the annealing time is not less than 5 minutes. Further, if the annealing time of the hot rolled steel sheet is over 30 hours, like when the annealing temperature is excessively high, the coil sticks, so the annealing time of the hot rolled steel sheet by box annealing is made less than 30 hours.
  • the hot rolled sheet annealed in this way may then be subjected to one cold rolling process and then finishing annealing or then subjected to a skin pass rolling process to make the final product.
  • the finishing annealing is performed by continuous annealing, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 61-213320, it is possible to perform the finishing annealing by first annealing for a short period of 5 seconds to 1 minute in a temperature range of 950°C to 1100°C and then holding the sheet for 10 seconds to 2 minutes at 800°C to 950°C.
  • the coefficient of friction at the finish hot rolling was changed from 0.1 or so to at least 0.3 by changing the content of the lubricant oil in the cooling water and the composition of the lubricant oil.
  • the average coefficient of friction was found by calculating the coefficients from the actually measured forward slip ratio of the stands and finding the average of the same.
  • the temperature of the end of the finish hot rolling was made a constant 1000°C, the sheet was finished to a thickness of 2.5 mm, coiled at 900°C, then immediately carried into the heat maintaining furnace and self annealed at 860°C for 1 hour.
  • the strain rate of the final stand was made 300 s -1 .
  • the steel sheet was pickled, cold rolled to a thickness of 0.50 mm, then annealed for 45 seconds at 900°C in the case of the steel E and 980°C in the case of the steel F. Epstein specimens were cut out and measured in magnetic properties.
  • the value of the coefficient of friction between the rolling roll of the finish hot rolling and the steel sheet should be not more than 0.25 in terms of the average value for all of the stands at the finish hat rolling. If above 0.25, the effect is not sufficient and the magnetic flux density of the product falls.
  • the coiling temperature of the coil at the self annealing is less than 750°C, the improvement of the magnetic properties is insufficient, so the temperature is made at least 750°C.
  • 1000°C coiling deviations of the coil easily occur and oxidation of the surface layer of the steel sheet becomes severe.
  • the self annealing is less than 5 minutes, the improvement of the magnetic properties is insufficient, so self annealing is made at least 5 minutes. Further, if the self annealing is over 5 hours, the oxidation of the steel sheet becomes severe and pickling defects easily occur, so the self annealing is made more than 5 hours.
  • the preferred self annealing time viewed from the effect of the annealing and economy is 30 minutes to 120 minutes.
  • the self annealing may be performed in a reducing atmosphere containing hydrogen or an inert gas atmosphere of nitrogen, argon, etc. or under reduced pressure.
  • the hot rolled steel sheet subjected to self annealing in this way is subjected to one or two or more cold rolling processes including annealing, then finishing annealing or then further a skin pass rolling process to produce the final product.
  • the amount of the lubricant oil mixed in with the cooling water for cooling the roll at the finish hot rolling is 0.5% to 20% by percent volume.
  • a surfactant may be added if necessary to prevent the lubricant oil and cooling water from separating. If the amount of the lubricant oil in the cooling water is less than 0.5%, the effect is not obtained, while if over 20%, the effect becomes saturated and is uneconomical, so the amount is made less than 20%.
  • the hot rolled steel sheet obtained in this way is subjected to one cold rolling process and continuous annealing to make the product. Further, it may be subjected to an additional skin pass rolling process to make the product. If the reduction ratio at the skin pass rolling is less than 2%, the effect is not obtained, while if the reduction ratio is over 20%, the magnetic properties deteriorate, so the reduction ratio must be limit to 2% to 20%.
  • the coefficient of friction at the finish hot rolling was changed from 0.1 or so to at least 0.3 by changing the content of the lubricant oil in the cooling water and the composition of the lubricant oil.
  • the average coefficient of friction was found by calculating the coefficients from the actually measured forward slip ratio of the stands and finding the average of the same.
  • the temperature at the end of the finish hot rolling was made a constant 1050°C and, according to formula (1), the non-coolant time was made 3.5 seconds, then the steel sheet was cooled and coiled at 680°C.
  • the strain rate at the final stand in the finish rolling was made 290 s -1 .
  • the steel sheet was then pickled and cold rolled to a thickness of 0.50 mm, then annealed for 30 seconds at 900°C, then Epstein specimens were cut out and measured for magnetic properties.
  • Fig. 10 The dependency of the magnetic flux density of the product on the average coefficient of friction at the finish hot rolling is shown in Fig. 10.
  • the average coefficient of friction the average of the actually measured values of the stands of the finish hot rolling mill was used. From Fig. 10, it was learned that the magnetic flux density of the product rises if the average coefficient of friction at the finish hot rolling is less than 0.25.
  • the value of the coefficient of friction between the rolling roll and steel sheet at the finish hot rolling should be not more than 0.25 in terms of the average value of all of the stands in the finish hot rolling. If over 0.25, the effect is insufficient and the magnetic flux density of the product falls. No upper limit is particularly set for the coefficient of friction, but if the value is excessively small, slip occurs during the rolling and stable rolling operation is no longer possible, so the value is preferably at least 0.05.
  • Composition of Material Used C Si Mn S sol-Al N Steel E 0.0017 2.50 0.22 0.0016 0.28 0.0019
  • the coiling temperature of the coil is not defined, but to prevent the occurrence of an excessive oxidation layer on the surface of the steel sheet and deterioration of the pickling ability after the end of the high temperature hot rolling, the coil it preferably coiled at under 750°C.
  • the time set for non-coolant after the end of the hot rolling is determined as follows in relation to the temperature T (°C) at the end of the hot rolling.
  • the inventors studied the relationship between the temperature T (°C) at the end of the hot rolling in finish hot rolling, the time t (seconds) until the start of the coolant spray after the end of the hot rolling, and the magnetic properties in detail and as a result found that it was possible to set excellent conditions satisfying the pickling ability, rolling speed, and magnetic properties in the range determined by: 950 ⁇ T(°C) ⁇ 1150 9.6 - 8 x 10 -3 T ⁇ t (sec) ⁇ 15.6 - 8 x 10 -3 T Further, if the time until the start of coolant spray after the end of the hot rolling exceeds the time set by formula (2), the time for cooling the steel sheet becomes insufficient and it is necessary to coil at a high temperature or lower the rolling speed to enable sufficient cooling or else the productivity will deteriorate.
  • the non-coolant time was made not more than the upper limit time set by formula (2). If the non-coolant time becomes shorter than the time set by formula (2), the improvement of the magnetic properties becomes insufficient. In the same way as when the temperature T (°C) at the end of the hot rolling is lower than 950°C, the improvement of the magnetic properties is insufficient.
  • the slab heating temperature would have to be made remarkably high, precipitates re-dissolve during the slab heating precipitate finely during the hot rolling, and the magnetic properties are made to remarkably deteriorate, so the temperature at the end of the hot rolling is made not more than 1150°C.
  • the steel sheet may be subjected to one cold rolling process and then a finishing annealing process or a further skin pass rolling process to make the final product.
  • the effect is not obtained if the skin pass rolling rate is less than 2%. If over 20%, the magnetic properties deteriorate, so the rate is made 2% to 20%.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 7 was heated by an ordinary method, was finished to a sheet bar of a thickness of 35 mm by a roughing mill, then was finished to 1.8 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill. The amount mixed was changed to 0.2% to 10% by percent volume to adjust the coefficient of friction. The average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the hot rolling finishing temperature was made 860°C.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 9 was heated by an ordinary method, was finished to a sheet bar of a thickness of 36 mm by a roughing mill, then was finished to 2.3 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill. The amount mixed was changed to 0.2% to 7% by percent volume to adjust the coefficient of friction. The average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the temperature at the end of the finish hot rolling was made 950°C.
  • the sheet was then immediately quenched and coiled at 600°C.
  • the obtained hot rolled sheet was annealed by a continuous annealing furnace at 930°C for 2 minutes.
  • a slab for non-oriented electrical sheet having the composition shown in Table 11 was heated by an ordinary method, was finished to a sheet bar of a thickness of 30 mm by a roughing mill, then was finished to 1.0 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill. The amount mixed was changed to adjust the coefficient of friction.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the hot rolling finishing temperature was made 860°C.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 13 was heated by an ordinary method, was finished to a sheet bar of a thickness of 35 mm by a roughing mill, then was finished to 2.5 mm by a finish hot rolling mill.
  • 5% by percent volume of lubricant oil was mixed with the cooling water of the finish hot rolling mill to adjust the average coefficient of friction of the stands to 0.19.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same. Further, to prevent the occurrence of slip between the steel sheet and the work roll during the finish hot rolling and the formation of defects on the surface of the steel sheet, the rough rolled sheet bar was welded to the preceding sheet bar and the finish hot rolling continuously performed.
  • the hot rolling finishing temperature was made 860°C.
  • the sheet was immediately water cooled and coiled at 650°C.
  • the pass schedule was adjusted so that the maximum strain rate was obtained at the final stand.
  • the strain rate of the final stand wag changed in the range between 131 s -1 to 322 s -1 .
  • a slab for non-oriented electrical sheet having the composition shown in Table 15 was heated by an ordinary method, was finished to a sheet bar of a thickness of 40 mm by a roughing mill, then was finished to 2.0 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill in an emulsion state. The amount mixed was changed to adjust the average coefficient of friction.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the strain rate of the final stand was made 305 s -1 .
  • the hot rolling finishing temperature was made 860°C.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 17 was heated by an ordinary method, was finished to a sheet bar of a thickness of 50 mm by a roughing mill, then was finished to 2.5 mm by a finish hot rolling mill. 2% to 11% by percent volume of lubricant oil was mixed with the cooling water of the finish hot rolling mill in accordance with the change of the strain rate to adjust the average coefficient of friction of the stands to 0.20. The average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the rear end of the preceding sheet bar was aligned with the front end of the succeeding sheet bar, a force was applied pressing the aligned portion, and the aligned portion was joined by laser welding and the finish hot rolling continuously performed.
  • the hot rolling finishing temperature was made 860°C.
  • the steel sheet was immediately water cooled and coiled at 650°C.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 19 was heated by an ordinary method, was finished to a sheet rough bar of a thickness of 40 mm by a roughing mill, then wan finished to 2.0 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill. The amount mixed was changed to adjust the average coefficient of friction.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the temperature at the end of the finish hot rolling was made 900°C.
  • the strain rate of the final stand was made 320 s -1 .
  • the obtained hot rolled steel sheet was then annealed in a continuous annealing furnace at 900°C for 2 minutes.
  • the steel sheet was pickled and finished to a thickness of 0.50 mm by cold rolling. This was then annealed in a continuous annealing furnace at 900°C for 30 seconds. Next, Epstein specimens were cut out and measured for magnetic properties.
  • the material shown in Table 19 was processed under the same conditions up to the pickling, then was cold rolled to a finished sheet thickness of 0.55 mm. This was then annealed in a continuous annealing furnace at 900°C for 30 seconds. Next, this was subjected to skin pass rolling to finish it to 0.50 mm. Epstein specimens were cut out, annealed at 750°C for 2 hours to relieve the stress, and measured for magnetic properties.
  • Table 20 shows the results of measurement of the magnetic properties for the present invention and comparative examples together.
  • the strain rate is made at least 150 s -1 at least at one pass, and the annealing conditions of the hot rolled steel sheet suitably controlled, it is possible to obtain a non-oriented electrical steel sheet with a high value of magnetic flux density, a low iron loss, and superior magnetic properties.
  • a slab for non-oriented electrical sheet having the composition shown in Table 21 was heated by an ordinary method, was finished to a sheet bar of a thickness of 40 mm by a roughing mill, then was finished to 1.8 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill in an emulsion state. The amount mixed was changed to adjust the average coefficient of friction.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the strain rate of the final stand was made 315 s -1 .
  • the rough rolled sheet bar was welded to the preceding sheet bar and the finish hot rolling continuously performed.
  • the hot rolling finishing temperature was made 900°C.
  • the steel sheet was immediately cooled and coiled at 500°C.
  • the obtained hot rolled steel sheet was then annealed in a continuous annealing furnace at 950°C for 2 minutes.
  • the sheet was pickled and finished to a thickness of 0.35 mm by cold rolling. This was then held in a continuous annealing furnace at 1050°C for 10 seconds in a front stage and was held at 900°C for 30 seconds in a rear stage. Next, Epstein specimens were cut out and measured for magnetic properties. Table 22 shows the results of measurement of the magnetic properties for the present invention and comparative examples together.
  • the strain rate is made at least 150 s -1 at least at one pass, and the annealing conditions of the hot rolled sheet suitably controlled, it is possible to obtain a non-oriented electrical steel sheet with a high value of magnetic flux density, a low iron loss, and superior magnetic properties.
  • Composition of Material Used C Si Mn S sol-Al N 0.0011 3.01 0.12 0.0011 0.50 0.0014 Results of Measurement of Magnetism Average coefficient of friction at finish rolling Magnetic flux density B50 (T) Iron loss W15/50 (W/kg) Invention 0.11 1.691 2.31 Invention 0.16 1.690 2.33 Invention 0.20 1.690 2.34 Comp. Ex. 0.27 1.671 2.51 Comp. Ex. 0.34 1.670 2.53
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 23 was heated by an ordinary method, was finished to a sheet bar of a thickness of 40 mm by a roughing mill, then was finished to 1.8 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill in an emulsion state. The amount mixed was adjusted to 4% by percent volume to make the average coefficient of friction 0.20. The average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the strain rate of the final stand was made 310 s -1 .
  • the hot rolling finishing temperature was made 900°C. After the end of the rolling, the sheet was immediately cooled and coiled at 500°C. The obtained hot rolled steel sheet was then annealed in a continuous annealing furnace at different annealing temperatures and annealing times.
  • the sheet was pickled and finished to a thickness of 0.35 mm by cold rolling. This was then annealed in a continuous annealing furnace at 900°C for 30 seconds. Next, Epstein specimens were cut out and measured for magnetic properties. Table 22 shows the annealing conditions of the hot rolled steel sheet and the results of measurement of the magnetic properties together.
  • the annealing temperature of the hot rolled steel sheet is 850°C to 1150°C, it is possible to obtain a non-oriented electrical steel sheet with superior properties. If the annealing temperature of the hot rolled steel sheet is less than 850°C, the improvement of the magnetic properties is insufficient, while if it is over 1150°C, pickling defects occur, the surface properties of the product deteriorate, and the iron loss deteriorates.
  • the annealing time of the hot rolling sheet by the continuous annealing is from 20 seconds to 5 minutes, superior magnetic properties are obtained.
  • the annealing time of the hot rolled steel sheet by the continuous annealing is more than 5 minutes, pickling defects occur and the iron loss conversely deteriorates.
  • the strain rate is made at least 150 s -1 at least at one pass, and the annealing conditions of the hot rolled steel sheet suitably controlled, it is possible to obtain a non-oriented electrical steel sheet with a high value of magnetic flux density, a low iron loss, and superior magnetic properties.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 25 was heated to 1200°C by an ordinary method, was finished to a sheet bar of a thickness of 30 mm by a roughing mill, then was finished to 1.8 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill in an emulsion state. The amount mixed was adjusted to change the average coefficient of friction. The average coefficient of friction was calculated by calculating the coefficients from the actually measured forwarding rates in the stands and then taking the average of the same.
  • the maximum strain rate of the final stand was made 175 s -1 .
  • the hot rolling finishing temperature was made 1000°C. After the end of the rolling, the steel sheet was immediately cooled and coiled at 650°C.
  • the steel sheet was rolled at a temperature of 300°C to 0.85 mm, then further process annealed at 980°C for 30 seconds, then finished to 0.25 mm by warm rolling of 200°C and pickled. This was then held and annealed in a continuous annealing furnace at 850°C for 30 seconds, then finished to 0.23 mm by 8% skin pass rolling.
  • Epstein specimens were cut out, annealed at 800°C for 2 hours to relieve the stress, then measured for magnetic properties. Table 26 shows the results of measurement of the magnetic properties for the present invention and the comparative examples together.
  • the strain rate is made at least 150 s -1 at least at one pass, and the annealing conditions of the hot rolled steel sheet suitably controlled, it is possible to obtain a non-oriented electrical steel sheet with a high value of magnetic flux density, a low iron loss, and superior magnetic properties.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 27 was heated by an ordinary method, was finished to a sheet bar of a thickness of 40 mm by a roughing mill, then was finished to 2.0 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill in an emulsion state. The amount mixed was changed to 0.2% by percent volume to adjust the average coefficient of friction. The average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the hot rolling finishing temperature was made 900°C.
  • the strain rate of the final stand was made 315 s -1 .
  • the obtained hot rolled steel sheet was annealed in a box annealing furnace at 800°C for 5 hours.
  • the sheet was then pickled and finished to 0.50 mm by cold rolling. This was annealed in a continuous annealing furnace at 900°C for 30 seconds in the case of the steel H and at 980°C for 30 seconds in the case of the steel I. Next, Epstein specimens were cut out, then measured for magnetic properties. Table 28 shows the results of measurement of the magnetic properties for the present invention and the comparative examples together.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 29 was heated by an ordinary method, was finished to a sheet bar of a thickness of 50 mm by a roughing mill, then was finished to 2.5 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill. The amount mixed was changed to 0.2% to 8% by percent volume to adjust the average coefficient of friction.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the strain rate of the final stand was made 320 s -1 .
  • the temperature at the end of the finish hot rolling was made 1000°C.
  • the steel sheet was coiled at 875°C, the coil was inserted into a heat maintaining furnace, and self annealing was performed at 850°C for 1 hour.
  • the strain rate is made at least 150 s -1 at least at one pass, and suitable self annealing conditions are set, it is possible to obtain a non-oriented electrical steel sheet with a high value of magnetic flux density, a low iron loss, and superior magnetic properties.
  • Composition of Material Used C Si Mn S sol-Al N 0.0022 2.10 0.12 0.0019 0.22 0.0021 Results of Measurement of Magnetism Average coefficient of friction at finish rolling Magnetic flux density B50 (T) Iron loss W15/50 (W/kg) Invention 0.16 1.722 3.38 Invention 0.20 1.720 3.41 Comp. Ex. 0.27 1.700 3.52 Comp. Ex. 0.35 1.699 3.55
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 31 was heated by an ordinary method, was finished to a sheet bar of a thickness of 55 mm by a roughing mill, then was finished to 2.0 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill. The amount mixed wax adjusted to change the average coefficient of friction.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the strain rate of the final stand was made 310 s -1 .
  • the rough rolled steel sheet bar was welded to the preceding sheet bar and the finish hot rolling continuously performed.
  • the hot rolling finishing temperature was made 990°C.
  • the sheet was coiled at 880°C, then the coil was immediately inserted into a heat maintaining furnace and self annealed at 850°C for 1 hour.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 33 was heated by an ordinary method, was finished to a sheet bar of a thickness of 50 mm by a roughing mill, then was finished to 2.5 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill. The amount mixed was adjusted to 2.5% by percent volume to make the average coefficient of friction 0.21.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the coil after the end of the hot rolling was self annealed at the conditions shown in Table 34.
  • the steel sheet was pickled and finished to a thickness of 0.35 mm by cold rolling. This was then annealed in a continuous annealing furnace at 980°C for 45 seconds. Next, Epstein specimens were cut out and measured for magnetic properties. Table 34 shows the self annealing conditions and the results of measurement of the magnetic properties together.
  • the self annealing temperature is from 750°C to 1000°C, it is possible to obtain a non-oriented electrical steel sheet with superior properties. In this way, if the self annealing temperature is less than 750°C, the improvement of the magnetic properties is insufficient, while if the coiling temperature of the coil is raised to over 1000°C, coiling deviations occur, therefore self annealing is impossible.
  • the self annealing time is from 5 minutes to 5 hours, superior magnetic properties are obtained. If the annealing time of the hot rolled steel sheet by the self annealing is more than 5 hours, pickling defects occur and the watt loss conversely deteriorates.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 35 was heated by an ordinary method, was finished to a sheet bar of a thickness of 50 mm by a roughing mill, then was finished to 2.5 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill. The amount mixed was changed to 0.2% to 12% by percent volume to adjust the average coefficient of friction. The average coefficient of friction was calculated by calculating the coefficients from the actually measured forwarding rates in the stands and then taking the average of the same.
  • the temperature at the end of the finish hot rolling was made 950°C and the strain rate at the final stand was made 310 s -1 .
  • the steel sheet was coiled at 850°C, then immediately inserted into a heat maintaining furnace and self annealed at 850°C for 1 hour.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 37 was heated by an ordinary method, was finished to a sheet bar of a thickness of 50 mm by a roughing mill, then was finished to 2.5 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill in an emulsion state. The amount mixed was changed to 0.2% to 4% by percent volume to adjust the average coefficient of friction. The average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the strain rate at the final stand was made 320 s -1 . At this time, the temperature at the end of the finish hot rolling was made 1020°C, the non-coolant time was made 3.5 seconds, and the sheet was coiled at 640°C.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 39 was heated by an ordinary method, was finished to a sheet bar of a thickness of 55 mm by a roughing mill, then was finished to 2.5 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill in an emulsion state. The amount mixed was adjusted to change the average coefficient of friction. The average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same. Further, to prevent the occurrence of slip between the steel sheet and the work roll during the finish hot rolling and the formation of defects on the surface of the steel sheet, the rough rolled sheet bar was welded to she preceding sheet bar and the finish hot rolling continuously performed. The strain rate of the final stand was made 305 s -1 .
  • the hot rolling finishing temperature was made 1050°C
  • the non-coolant time was made 3 seconds
  • water was then injected for cooling
  • the sheet was coiled at 680°C.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 41 was heated by an ordinary method, was finished to a sheet bar of a thickness of 50 mm by a roughing mill, then was finished to 2.5 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill. The amount mixed was adjusted to 3% by percent volume to make the average coefficient of friction 0.22.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forward slip ratio in the stands and then taking the average of the same.
  • the strain rate at the final stand was made 270 s -1 .
  • the temperature at the end of the hot rolling was made a constant 1050°C, the non-coolant time was changed, and the coiling temperature was made a constant 680°C. In this case, the non-coolant time defined by formula (2) according to the present invention was made 1.2 seconds to 7.2 seconds.
  • the steel sheet was pickled and finished to a thickness of 0.50 mm by cold rolling. This was then annealed in a continuous annealing furnace at 900°C for 30 seconds. Next, Epstein specimens were cut out and measured for magnetic properties. Table 42 shows the hot rolling conditions and the results of measurement of the magnetic properties together.
  • a slab for non-oriented electrical steel sheet having the composition shown in Table 43 was heated by an ordinary method, was finished to a sheet bar of a thickness of 35 mm by a roughing mill, then was finished to 2.0 mm by a finish hot rolling mill.
  • Lubricant oil was mixed with the cooling water of the finish hot rolling mill. The amount mixed was changed to adjust the average coefficient of friction.
  • the average coefficient of friction was calculated by calculating the coefficients from the actually measured forwarding rates in the stands and then taking the average of the same.
  • the temperature at the end of the finish hot rolling was made 900°C and the sheet was immediately quenched and coiled at 600°C.
  • the obtained hot rolled steel sheet was annealed in a continuous annealing furnace at 850°C for 2 minutes.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Organic Chemistry (AREA)
  • Metallurgy (AREA)
  • Materials Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Electromagnetism (AREA)
  • Soft Magnetic Materials (AREA)
  • Manufacturing Of Steel Electrode Plates (AREA)
EP96941184A 1995-12-05 1996-12-05 Process for producing non-oriented electrical steel sheet having high magnetic flux density and low iron loss Withdrawn EP0875586A1 (en)

Applications Claiming Priority (11)

Application Number Priority Date Filing Date Title
JP31687095 1995-12-05
JP316870/95 1995-12-05
JP34504495 1995-12-08
JP345044/95 1995-12-08
JP21809696A JP4191806B2 (ja) 1995-12-08 1996-08-01 無方向性電磁鋼板の製造方法
JP218096/96 1996-08-01
JP206064/96 1996-08-05
JP20606496 1996-08-05
JP321886/96 1996-12-02
JP8321886A JPH10102147A (ja) 1995-12-05 1996-12-02 磁束密度が高く、鉄損の低い無方向性電磁鋼板の製造方法
PCT/JP1996/003570 WO1997020956A1 (fr) 1995-12-05 1996-12-05 Procede de fabrication de toles d'acier electrique a grain non oriente ayant une densite de flux magnetique elevee et de faibles pertes dans le fer

Publications (2)

Publication Number Publication Date
EP0875586A1 true EP0875586A1 (en) 1998-11-04
EP0875586A4 EP0875586A4 (zh) 1998-11-04

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EP96941184A Withdrawn EP0875586A1 (en) 1995-12-05 1996-12-05 Process for producing non-oriented electrical steel sheet having high magnetic flux density and low iron loss

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EP (1) EP0875586A1 (zh)
KR (1) KR19990071916A (zh)
CN (1) CN1203635A (zh)
AU (1) AU700333B2 (zh)
WO (1) WO1997020956A1 (zh)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7922834B2 (en) 2005-07-07 2011-04-12 Sumitomo Metal Industries, Ltd. Non-oriented electrical steel sheet and production process thereof
US9666350B2 (en) 2011-11-09 2017-05-30 Jfe Steel Corporation Ultrathin electromagnetic steel sheet
EP3943203A4 (en) * 2019-04-22 2022-05-04 JFE Steel Corporation METHOD FOR PRODUCTION OF NON-ORIENTED ELECTRICAL STEEL SHEET

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CN105779728A (zh) * 2014-12-23 2016-07-20 鞍钢股份有限公司 一种无取向电工钢薄带的热轧方法
CN105779879A (zh) * 2014-12-23 2016-07-20 鞍钢股份有限公司 冷轧无取向电工钢薄带的生产方法
BR112019001581B1 (pt) * 2016-07-29 2023-03-07 Jfe Steel Corporation Chapa de aço laminada a quente e recozida para chapa de aço elétrico de grão orientado e método para produzir as ditas chapas
CN116555532B (zh) * 2023-03-31 2024-04-09 宝镁特(上海)智能工程有限公司 一种薄规格硅钢材料的高精度退火方法

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JPS6254023A (ja) * 1985-08-31 1987-03-09 Nippon Steel Corp 高級無方向性電磁鋼板用熱延板の製造方法
JPH01306524A (ja) * 1988-06-04 1989-12-11 Kobe Steel Ltd 磁束密度の高い無方向性電磁鋼板の製造方法
JPH0723509B2 (ja) * 1988-10-13 1995-03-15 新日本製鐵株式会社 優れた鉄損特性を有する無方向性電磁鋼板の製造方法
JP2790730B2 (ja) * 1990-12-26 1998-08-27 川崎製鉄株式会社 材質均一性に優れた高炭素鋼板の製造方法
JP3375998B2 (ja) * 1993-01-26 2003-02-10 川崎製鉄株式会社 無方向性電磁鋼板の製造方法

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Title
No further relevant documents disclosed *
See also references of WO9720956A1 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7922834B2 (en) 2005-07-07 2011-04-12 Sumitomo Metal Industries, Ltd. Non-oriented electrical steel sheet and production process thereof
US8157928B2 (en) 2005-07-07 2012-04-17 Sumitomo Metal Industries, Ltd. Non-oriented electrical steel sheet and production process thereof
US9666350B2 (en) 2011-11-09 2017-05-30 Jfe Steel Corporation Ultrathin electromagnetic steel sheet
EP3943203A4 (en) * 2019-04-22 2022-05-04 JFE Steel Corporation METHOD FOR PRODUCTION OF NON-ORIENTED ELECTRICAL STEEL SHEET

Also Published As

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AU1436397A (en) 1997-06-27
AU700333B2 (en) 1998-12-24
WO1997020956A1 (fr) 1997-06-12
KR19990071916A (ko) 1999-09-27
CN1203635A (zh) 1998-12-30
EP0875586A4 (zh) 1998-11-04

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