Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/82—After-treatment
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1216—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the working steps
  • C21D8/1238—Flattening; Dressing; Flexing
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties characterised by the heat treatment
  • C21D8/1272—Final recrystallisation annealing
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1277—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a particular surface treatment
  • C21D8/1283—Application of a separating or insulating coating
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
• • 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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
  • C23C22/08—Orthophosphates
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
  • C23C22/08—Orthophosphates
  • C23C22/20—Orthophosphates containing aluminium cations
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
  • C23C22/08—Orthophosphates
  • C23C22/22—Orthophosphates containing alkaline earth metal cations
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/24—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds
  • C23C22/33—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds containing also phosphates
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
  • C23C22/74—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process for obtaining burned-in conversion coatings
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/78—Pretreatment of the material to be coated
• • 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
  • C21D2201/00—Treatment for obtaining particular effects
  • C21D2201/05—Grain orientation
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1294—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a localised treatment

Definitions

• the present invention relates to a grain-oriented electrical steel sheet and a method for forming an insulating coating.
• a grain-oriented electrical steel sheet is mainly used for a transformer.
• the transformer is continuously magnetized for a long period of time from installation to disposal and continues to generate energy loss. Therefore, energy loss when the transformer is magnetized by alternating current, that is, iron loss is a main index for determining performance of the transformer.
• applying tension to the steel sheet is effective for reducing iron loss. It is an effective means for reducing iron loss to form a coating made of a material having a thermal expansion coefficient smaller than that of the steel sheet on a sheet surface at a high temperature.
• a forsterite film (inorganic coating) having exceptional coating adhesion, generated by a reaction between an oxide on a sheet surface and an annealing separator in a finishing annealing step of an electrical steel sheet is a coating capable of applying tension to the steel sheet.
• a method for forming an insulating coating by baking a coating liquid mainly containing colloidal silica and a phosphate on a sheet surface is an effective method for reducing iron loss because the method has a large effect of applying tension to the steel sheet. Therefore, a general method for manufacturing a grain-oriented electrical steel sheet is to leave the forsterite film generated in the finishing annealing step and to form an insulating coating mainly containing a phosphate on the forsterite film.
• a grain-oriented electrical steel sheet is required to have exceptional high magnetic field iron loss such that iron loss is favorable even when magnetic flux density is high.
• the forsterite film hinders movement of a magnetic domain wall and adversely affects iron loss.
• a magnetic domain changes by movement of a magnetic domain wall under an alternating magnetic field.
• the smooth and rapid movement of the magnetic domain wall is effective for reducing iron loss, but the forsterite film itself is a non-magnetic body and has an uneven structure at the interface between the steel sheet and the coating, and it is considered that this uneven structure hinders the movement of the magnetic domain wall and thus adversely affects iron loss.
• a technique for manufacturing a grain-oriented electrical steel sheet having no forsterite film (inorganic coating), or a technique for bringing a sheet surface into a mirror surface state have been studied by: removing a forsterite film by using a mechanical means such as polishing or a chemical means such as pickling; or preventing generation of a forsterite film in high-temperature finishing annealing.
• Patent Document 2 discloses a technique in which a surface-formed product is removed through pickling after normal finishing annealing and then a sheet surface is brought into a mirror surface state through chemical polishing or electrolytic polishing. It has been found that a better iron loss improving effect can be obtained by forming a tension-applying insulating coating on the surface of a grain-oriented electrical steel sheet having no forsterite film, obtained by using such a known method.
• the tension-applying insulating coating can impart various characteristics such as corrosion resistance, heat resistance, and slippage in addition to improvement of iron loss.
• the forsterite film has an effect of exhibiting an insulation property and an effect as an intermediate layer for securing adhesion when a tension coating (tension-applying insulating coating) is formed. That is, since the forsterite film is formed in a state of deeply entering the steel sheet, the forsterite film is exceptional in adhesion to the steel sheet which is metal. Therefore, when a tension applying type coating (tension coating) mainly containing colloidal silica, phosphate, or the like as a main component is formed on the surface of the forsterite film, the coating adhesion is exceptional. On the other hand, since it is generally difficult to bond a metal and an oxide, it is difficult to ensure sufficient adhesion between a tension coating and a sheet surface when a forsterite film is not present.
• tension coating tension-applying insulating coating
• Patent Document 3 discloses a technique in which a grain-oriented electrical steel sheet having no forsterite film (inorganic film) is annealed in a weakly reducing atmosphere, and silicon inevitably contained in a silicon steel sheet is thermally oxidized selectively to form a SiO 2 layer on the sheet surface, and then a tension-applying type insulating coating is formed.
• Patent Document 4 discloses a technique in which a grain-oriented electrical steel sheet having no forsterite film (inorganic film) is subjected to an anodic electrolytic treatment in a silicate aqueous solution to form an SiO 2 layer on the sheet surface, and then a tension-applying type insulating coating is formed.
• Patent Document 3 it is necessary to prepare an annealing facility capable of controlling an atmosphere in order to perform annealing in a weakly reducing atmosphere, and there is a problem in treatment cost.
• Patent Document 4 it is necessary to prepare a new electrolysis treatment facility in order to obtain a SiO 2 layer that maintains sufficient adhesion to a tension-applying type insulating coating on a sheet surface by performing an anodic electrolytic treatment in a silicate aqueous solution, and there is a problem in treatment cost.
• Patent Document 5 discloses a grain-oriented electrical steel sheet including a base steel sheet and an insulating coating formed on a surface of the base steel sheet, in which the insulating coating is formed on the base steel sheet side and includes an intermediate layer containing a crystalline metal phosphate and a tension coating layer formed on a surface side of the insulating coating.
• the intermediate layer can be formed through a chemical conversion treatment.
• the intermediate layer made of a crystalline metal phosphate is provided between the base steel sheet and the tension coating, so that coating adhesion, coating tension, and magnetic characteristics can be improved.
• the intermediate layer can be formed by chemical conversion treatment, no special facility is required. Therefore, this is a useful technique.
• an object of the present invention is to provide a grain-oriented electrical steel sheet in which a layer containing a metal phosphate is formed on a surface of a steel sheet through chemical conversion treatment, the grain-oriented electrical steel sheet being exceptional in adhesion of a tension coating and magnetic characteristics and not reducing a space factor of a transformer (core).
• core a transformer
• the present inventors have found that when a layer containing a metal phosphate is provided as an intermediate layer for enhancing adhesion between a base steel sheet and a tension coating layer, coarsening of metal phosphate crystals can be curbed by containing a substance for curbing crystallization of phosphate in a chemical treatment liquid.
• the present invention has been made in view of the above findings.
• the gist of the present invention is as follows.
• FIG. 1 An example of a cross-sectional view of a grain-oriented electrical steel sheet according to the present embodiment.
• a grain-oriented electrical steel sheet according to an embodiment of the present invention (grain-oriented electrical steel sheet according to the present embodiment) and a method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment, including a method for forming an insulating coating included in the grain-oriented electrical steel sheet according to the present embodiment, will be described.
• a grain-oriented electrical steel sheet 100 has a base steel sheet 1 and an insulating coating 2 formed on a surface of the base steel sheet 1.
• a forsterite film is not intentionally formed on the surface of the base steel sheet 1, and a forsterite film is not present in many cases.
• the presence of the forsterite film is acceptable as long as the coating mass is 1.0 g/m 2 or less (in that case, the forsterite film is present between the base steel sheet 1 and the insulating coating 2).
• the insulating coating 2 has a tension coating layer 22 formed on a surface side of the insulating coating 2 (that is, a surface side of the grain-oriented electrical steel sheet 100), and an intermediate layer 21 formed on the base steel sheet 1 side and containing a crystalline metal phosphate.
• the intermediate layer 21 contains a crystalline metal phosphate and one or more of amorphous silica, an inorganic filler, and a metal oxide, having an average particle diameter of 10 to 500 nm.
• the grain-oriented electrical steel sheet 100 has a major feature in the structure of the insulating coating 2 formed on the surface of the base steel sheet 1, and the base steel sheet 1 included in the grain-oriented electrical steel sheet 100 is not limited in terms of its chemical composition. However, in order to obtain characteristics generally required for a grain-oriented electrical steel sheet, it is preferable to include the following components as chemical components. In the present embodiment, % relating to the chemical composition is mass% unless otherwise specified.
• the C content is an element effective in controlling the microstructure of the steel sheet in steps up to completion of the decarburization annealing step in the manufacturing process.
• the C content is preferably 0.010% or less.
• the C content is more preferably 0.005% or less.
• the C content is preferably as low as possible, but even when the C content is reduced to less than 0.0001%, a microstructure control effect is saturated, and manufacturing cost is merely increased. Therefore, the C content may be 0.0001% or more.
• Si is an element that increases the electric resistance of a grain-oriented electrical steel sheet and improves iron loss characteristics.
• the Si content is preferably 2.50% or more.
• the Si content is more preferably 2.70% or more, and still more preferably 3.00% or more.
• the Si content is preferably set to 4.00% or less.
• the Si content is more preferably 3.80% or less, and still more preferably 3.70% or less.
• Mn manganese
• MnS manganese
• This precipitate functions as an inhibitor (inhibitor of normal grain growth) and causes secondary recrystallization in steel.
• Mn is also an element that enhances hot workability of steel.
• the Mn content is preferably 0.01% or more.
• the Mn content is more preferably 0.02% or more.
• the Mn content is preferably 0.50% or less.
• the Mn content is more preferably 0.20% or less, and still more preferably 0.10% or less.
• N nitrogen
• the N content is preferably 0.010% or less.
• the N content is more preferably 0.008% or less.
• the lower limit value of the N content is not particularly limited, but even when the N content is reduced to less than 0.001%, manufacturing cost is merely increased. Therefore, the N content may be 0.001% or more.
• Sol. Al (acid-soluble aluminum) is an element that is bonded to N in the manufacturing process of the grain-oriented electrical steel sheet to form AlN that functions as an inhibitor.
• the sol. Al content in the base steel sheet exceeds 0.020%, the inhibitor excessively remains in the base steel sheet, so that magnetic characteristics deteriorate. Therefore, in the base steel sheet of the grain-oriented electrical steel sheet according to the embodiment, the sol. Al content is preferably 0.020% or less.
• the sol. Al content is more preferably 0.010% or less, and still more preferably less than 0.001%.
• the lower limit value of the sol. Al content is not particularly limited, but even when the content is reduced to less than 0.0001%, manufacturing cost is merely increased. Therefore, the sol. Al content may be 0.0001% or more.
• the S content is preferably 0.010% or less.
• the S content in the grain-oriented electrical steel sheet is more preferably as low as possible. For example, the S content is less than 0.001%.
• the S content in the base steel sheet of the grain-oriented electrical steel sheet may be 0.0001 % or more.
• the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment may contain the above-described elements, with the remainder of Fe and impurities.
• the base steel sheet may further contain Sn, Cu, Se, and Sb in the following ranges for the purpose of improving magnetic characteristics and the like.
• the base steel sheet contains any one or more selected from W, Nb, Ti, Ni, Co, V, Cr, and Mo in a total amount of 1.0% or less as elements other than these elements, the effect of the grain-oriented electrical steel sheet according to the present embodiment is not impaired.
• the impurity is an element that is a contaminant derived from ore or scrap as a raw material, a manufacturing environment, or the like when the base steel sheet is industrially manufactured and means an element that is allowed to be included in a content that does not adversely affect the effect of the grain-oriented electrical steel sheet according to the embodiment.
• Sn (tin) is an element that contributes to improvement in magnetic characteristics through primary recrystallization structure control.
• the Sn content is preferably 0.01% or more.
• the Sn content is more preferably 0.02% or more, and still more preferably 0.03% or more.
• the Sn content is preferably 0.50% or less.
• the Sn content is more preferably 0.30% or less, and still more preferably 0.10% or less.
• Cu is an element that contributes to an increase in Goss orientation occupancy in a secondary recrystallization structure.
• the Cu content is preferably 0.01% or more.
• the Cu content is more preferably 0.02% or more, and still more preferably 0.03% or more.
• the Cu content is preferably 0.50% or less.
• the Cu content is more preferably 0.30% or less, and still more preferably 0.10% or less.
• Se is an element having an effect of improving magnetic characteristics.
• the Se content is preferably 0.001% or more such that Se favorably exhibits the effect of improving magnetic characteristics.
• the Se content is more preferably 0.003% or more, and still more preferably 0.006% or more.
• the Se content is preferably s 0.020% or less.
• the Se content is more preferably 0.015% or less, and still more preferably 0.010% or less.
• Sb antimony
• Sb is an element having an effect of improving magnetic characteristics.
• the Sb content is preferably 0.005% or more such that Sb favorably exhibits the effect of improving magnetic characteristics.
• the Sb content is more preferably 0.01% or more, and still more preferably 0.02% or more.
• the Sb content is preferably 0.50% or less.
• the Sb content is more preferably 0.30% or less, and still more preferably 0.10% or less.
• the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment contains the above-described elements, with the remainder of Fe and impurities.
• the chemical composition of the base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment can be measured by using a known ICP emission spectrometry. Note that, at the time of measurement, in a case where an insulating coating is formed on a surface, the measurement is performed after the insulating coating is peeled off. As a peeling method, it is possible to peel off the insulating coating by immersing the base steel sheet with the insulating coating in a high-concentration alkaline solution (for example, a 30% sodium hydroxide solution heated to 85°C) for 20 minutes or more. It is possible to visually determine whether or not the insulating coating has been peeled off. In a case of a small sample, the insulating coating may be peeled off through surface grinding.
• a high-concentration alkaline solution for example, a 30% sodium hydroxide solution heated to 85°C
• the insulating coating 2 is formed on the surface of the base steel sheet 1.
• the insulating coating 2 includes the intermediate layer 21 and the tension coating layer 22 in this order from the base steel sheet 1 side.
• a grain-oriented electrical steel sheet has a forsterite film generated in a finishing annealing step and an insulating coating (tension insulating coating) formed thereon.
• an insulating coating tension insulating coating
• the intermediate layer 21 containing a crystalline metal phosphate is formed between the base steel sheet 1 and the tension coating to improve adhesion between the base steel sheet 1 and the tension coating layer 22 via the intermediate layer 21.
• the intermediate layer 21 contains a crystalline metal phosphate
• adhesion between the intermediate layer and the tension coating layer is exceptional because the tension coating (which becomes the tension coating layer 22 after formation) formed on the intermediate layer 21 also contains a metal phosphate and affinity is high.
• the intermediate layer when the intermediate layer is formed by immersion in a treatment liquid containing a metal phosphate, the intermediate layer can be formed on a surface of the base steel sheet 1 using a chemical reaction, and adhesion between the intermediate layer 21 and the base steel sheet 1 can also be ensured.
• the proportion of the crystalline metal phosphate in the intermediate layer is preferably 80 mass% or more, preferably 90 mass% or more, and may be 99 mass% or more.
• the metal phosphate is preferably one or two or more of zinc phosphate, manganese phosphate, iron phosphate, and zinc calcium phosphate from the viewpoint of adhesion.
• the intermediate layer may contain, as the remainder other than the metal phosphate, an oxide or an element diffused from the base steel sheet, such as Fe or Si.
• the space factor decreases when an actual transformer is manufactured, so that the magnetic flux density per unit volume decreases and the transformer iron loss increases.
• the grain-oriented electrical steel sheet in order to curb the crystal coarsening by curbing the crystallization of the crystalline metal phosphate, one or more of colloidal silica, an inorganic filler, and a metal oxide having an average particle diameter of 10 to 500 nm are contained as an additive in the treatment liquid for forming an intermediate layer.
• the average grain diameter of the crystalline metal phosphate is, for example, 1.0 to 12.0 ⁇ m.
• one or more of the colloidal silica, the inorganic filler, and the metal oxide having an average particle diameter of 10 to 500 nm are not localized in the intermediate layer and are uniformly dispersed.
• aggregates having a size of several ⁇ m or less are formed even when secondary aggregation occurs.
• the amorphous silica is preferable from the viewpoint of availability.
• the amorphous silica is different in form and effect from crystalline silica generated through thermal oxidation annealing or the like.
• the inorganic filler preferably contains 90 mass% or more of one or two or more of alumina, BN, AlN, and kaolin (those having a purity of 90 mass% or more are used).
• BN preferably has a hexagonal crystal in consideration of ease of dispersion.
• the metal oxide is preferably one or two or more of titanium oxide, zinc oxide, and calcium oxide from the viewpoint of stability of a treatment liquid.
• a carbonate may be used as an additive, but the carbonate does not remain in the intermediate layer under normal baking conditions, and specific baking conditions are required to obtain an intermediate layer containing a carbonate, which is not preferable.
• the content of one or more of the amorphous silica, the inorganic filler, and the metal oxide is preferably 0.01 to 1.00 mass%.
• the content is less than 0.01 mass%, the effect of curbing crystal coarsening of the metal phosphate may be poor, and when the content is more than 1.00 mass%, the adhesion of an intermediate layer may be poor.
• the intermediate layer 21 is formed at a timing different from that of the tension coating formed thereon, but both the intermediate layer 21 and the tension coating layer 22 exhibit an effect as the insulating coating 2.
• the thickness of the intermediate layer is preferably 1.0 to 9.0 ⁇ m.
• the average thickness of the intermediate layer 21 is less than 1.0 ⁇ m, the effect of improving the adhesion between the base steel sheet and the insulating coating via the intermediate layer may not be sufficiently obtained.
• the average thickness of the intermediate layer is more than 9.0 ⁇ m, magnetic characteristics may deteriorate.
• the mass proportion of the crystalline metal phosphate for the metal phosphate and the type of the metal phosphate in the intermediate layer can be obtained by measuring a cross section of the intermediate layer in the thickness direction by using a scanning electron microscope and an energy dispersive elemental analyzer. Whether the metal phosphate of the intermediate layer 21 is a crystalline metal phosphate can be determined according to X-ray crystallography.
• the base steel sheet and the insulating coating can be discriminated on the basis of the concentration of P (phosphorus) (when the P content is 1.0 mass% or more, the insulating coating is determined, and when the P content is less than 1.0 mass%, the steel sheet is determined).
• the intermediate layer 21 and the tension coating layer 22 can be discriminated on the basis of the concentration difference of Si (when the Si content is 10 mass% or more, the tension coating layer is determined, and when the Si content is less than 10 mass%, the intermediate layer is determined).
• the average grain diameter of the crystalline metal phosphate can be determined by using the following method.
• the steel sheet is cut into a few mm square, which is easy to observe, and subjected to ion milling (CP processing) to remove micro shape defects such as shear droop and cracks, and then a cross section parallel to the rolling direction and the sheet thickness direction of the steel sheet and a cross section perpendicular to the rolling direction and parallel to the sheet thickness direction of the steel sheet are observed with a scanning electron microscope.
• CP processing ion milling
• the crystal form of the metal phosphate observed in the cross section is observed, and an average value of the major axis and minor axis of each crystal is measured for five or more of the cross sections, and the measured value is taken as a grain diameter.
• the electron microscope magnification at the time of observation is 1000 times.
• the contents of the amorphous silica, the inorganic filler, and the metal oxide, and the average particle diameter can be determined according to the following method.
• the steel sheet is cut into a few mm square, which is easy to observe, and subjected to ion milling (CP processing) to remove micro shape defects such as shear droop and cracks, and then a cross section parallel to the rolling direction and the sheet thickness direction of the steel sheet and a cross section perpendicular to the rolling direction and parallel to the sheet thickness direction of the steel sheet are observed with a scanning electron microscope at a magnification of 5000 times.
• the measurement is performed by analyzing a portion of the intermediate layer by using an energy dispersive elemental analyzer at five or more cross sections.
• the presence of amorphous silica, an inorganic filler, and a metal oxide is confirmed at ten or more points in the intermediate layer through elemental analysis by using a transmission-type electron microscope for a cross-sectional sample subjected to ion milling in the same manner, and then an average value of the major axis and the minor axis of the particle observed at a magnification of 20,000 times is calculated as a particle diameter.
• the thickness of the intermediate layer can be obtained according to the following method.
• the total average thickness of the intermediate layer and the tension coating layer can be measured by observing the cross section of the sample with a scanning electron microscope and measuring the thickness at five or more points.
• the intermediate layer and the tension coating layer can be discriminated from each other on the basis of a concentration difference of silicon (Si) derived from silica. Therefore, the thickness of the intermediate layer can be calculated by subtracting the thickness of the tension coating layer from the total average thickness at each measurement point.
• the grain-oriented electrical steel sheet 100 has the tension coating layer 22 on a surface side of the insulating coating 2 by forming a tension coating on a surface of the intermediate layer 21.
• the tension coating layer 22 is not particularly limited as long as it is used as an insulating coating of the grain-oriented electrical steel sheet, but from the viewpoint of adhesion to the intermediate layer 21 (adhesion to the base steel sheet 1 via the intermediate layer 21), it is preferable that the tension coating layer 22 has a composition containing a metal phosphate and silica as main components. It is more preferable to substantially contain a metal phosphate and silica.
• the tension coating layer 22 preferably contains a metal phosphate and silica (derived from colloidal silica of the coating liquid) such that the content of silica is 20.0 mass% or more.
• a metal phosphate and silica derived from colloidal silica of the coating liquid
• the silica content of the tension coating layer 22 is more than 60.0 mass%, it causes powdering, and thus it is preferable that the silica content is 60.0 mass% or less.
• it is preferable to contain the metal phosphate and silica are 70 mass% or more in total.
• the metal phosphate and silica may be 100 mass% in total.
• alumina or ceramic fine particles such as silicon nitride may be contained.
• the metal phosphate is preferably an aluminum phosphate from the viewpoint of heat resistance.
• the thickness of the tension coating layer 22 is not limited, but the average thickness of the insulating coating 2 (the intermediate layer 21 + the tension coating layer 22) is preferably set to 1.0 to 20.0 ⁇ m when the average thickness of the intermediate layer 21 is in the above range.
• the average thickness of the insulating coating 2 is less than 1.0 ⁇ m, a sufficient coating tension cannot be obtained.
• dissolution of phosphoric acid increases. In this case, this may cause stickiness and corrosion resistance deterioration and may cause coating peeling.
• the thickness of the insulating coating 2 is more than 20.0 ⁇ m, a space factor decreases, so that magnetic characteristics deteriorate, or adhesion decreases due to cracks or the like, or corrosion resistance decreases.
• the mass ratio of the metal phosphate and the type of the metal phosphate can be determined in the same manner as in the intermediate layer in the cross section in the thickness direction.
• the tension coating layer and the intermediate layer can be discriminated on the basis of the content of Si.
• the thickness of the tension coating layer can be determined on the basis of in the same manner as in the intermediate layer.
• the sum of the thickness of the tension coating layer and the thickness of the intermediate layer is the thickness of the insulating coating.
• the grain-oriented electrical steel sheet according to the present embodiment can be suitably manufactured.
• the grain-oriented electrical steel sheet according to the present embodiment is not particularly limited in its manufacturing method. That is, a grain-oriented electrical steel sheet having the above-described configuration is regarded as the grain-oriented electrical steel sheet according to the present embodiment regardless of manufacturing conditions therefor.
• the grain-oriented electrical steel sheet according to the present embodiment can be manufactured by using a manufacturing method including the following steps.
• the method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment may further include one or both of
• the manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment is characterized by the steps of (V) finishing annealing step to (X) tension coating layer forming step (collectively referred to as an insulating coating forming method) mainly related to formation of the insulating coating, and other steps or conditions not described can adopt known conditions.
• a steel piece having a predetermined chemical composition such as a slab is heated and then hot-rolled to obtain a hot rolled sheet.
• the heating temperature of the steel piece is preferably in a range of 1100 to 1450°C.
• the heating temperature is more preferably 1300 to 1400°C.
• the chemical composition of the steel piece may to be changed according to a chemical composition of a base steel sheet of a grain-oriented electrical steel sheet to be finally obtained, but examples thereof include a chemical composition containing, in mass%, C: 0.01 to 0.20%, Si: 2.50 to 4.00%, sol. Al: 0.01 to 0.040%, Mn: 0.01 to 0.50%, N: 0.020% or less, S: 0.005 to 0.040%, Cu: 0 to 0.50%, Sn: 0 to 0.50%, Se: 0 to 0.020%, and Sb: 0 to 0.50%, with the remainder of Fe and impurities.
• the hot rolling conditions are not particularly limited, and is appropriately set according to required characteristics.
• the sheet thickness of the hot rolled sheet is preferably within a range of 2.0 to 3.0 mm, for example.
• the hot-rolled sheet annealing step is a step of annealing the hot rolled sheet manufactured through the hot rolling step. By performing such an annealing treatment, recrystallization occurs in the metallographic structure, and favorable magnetic characteristics can be preferably achieved.
• the hot rolled sheet manufactured through the hot rolling step may be annealed according to a known method.
• the means for heating the hot rolled sheet at the time of annealing is not particularly limited, and a known heating method can be adopted.
• the annealing conditions are not particularly limited.
• the hot rolled sheet can be annealed in a temperature range of 900 to 1200°C for 10 seconds to 5 minutes.
• the hot rolled sheet after the hot-rolled sheet annealing step is subjected to cold rolling to obtain a steel sheet (cold rolled sheet).
• the cold rolling may be performed one time (continuously performed without intervening intermediate annealing(s)).
• intermediate annealing may be performed at least one time or two or more times by interrupting cold rolling, that is, cold rolling may be performed several times with intervening intermediate annealing(s).
• the intermediate annealing When the intermediate annealing is performed, it is preferable to hold the hot rolled sheet at a temperature of 1000 to 1200°C for 5 to 180 seconds.
• the annealing atmosphere is not particularly limited.
• the number of times of intermediate annealing is preferably 3 or less in consideration of manufacturing cost.
• the surface of the hot rolled sheet may be subjected to pickling.
• the hot rolled sheet after the hot-rolled sheet annealing step is cold-rolled according to a known method to form a steel sheet.
• the final rolling reduction can be in a range of 80 to 95%.
• the final rolling reduction is 80% or more, a Goss nucleus in which the ⁇ 110 ⁇ 001> orientation has a high development degree in a rolling direction can be obtained, which is preferable.
• the final rolling reduction exceeds 95%, there is a high possibility that secondary recrystallization is unstable in the subsequent finishing annealing step, which is not preferable.
• the final rolling reduction is a cumulative rolling reduction of cold rolling, and when intermediate annealing is performed, the final rolling reduction is a cumulative rolling reduction of cold rolling after the final intermediate annealing.
• the obtained steel sheet is subjected to decarburization annealing.
• decarburization annealing conditions are not limited as long as the steel sheet can be primarily recrystallized and C that adversely affects magnetic characteristics can be removed from the steel sheet, but for example, the steel sheet is held at an annealing temperature of 800 to 900°C for 10 to 600 seconds with a degree of oxidation (PH 2 O/PH 2 ) of 0.3 to 0.6 in an annealing atmosphere (furnace atmosphere).
• a nitriding treatment may be performed between the decarburization annealing step and the finishing annealing step that will be described later.
• the steel sheet after the decarburization annealing step is maintained at about 700 to 850°C in a nitriding treatment atmosphere (atmosphere containing a gas having nitriding ability, such as hydrogen, nitrogen, or ammonia) to perform the nitriding treatment.
• a nitriding treatment atmosphere atmosphere containing a gas having nitriding ability, such as hydrogen, nitrogen, or ammonia
• the N content of the steel sheet after the nitriding treatment step is preferably 40 ppm or more by the nitriding treatment.
• the N content of the steel sheet after the nitriding treatment step exceeds 1000 ppm, AlN is excessively present in the steel sheet even after completion of secondary recrystallization in the finishing annealing. Such AlN causes iron loss deterioration. Therefore, the N content of the steel sheet after the nitriding treatment step is preferably 1000 ppm or less.
• an annealing separator containing 10 to 100 mass% of Al 2 O 3 is applied to the steel sheet that is after the decarburization annealing step or has been further subjected to the nitriding treatment (after the nitriding treatment step), and dried, and then finishing annealing is performed.
• a forsterite film is formed on the surface of a steel sheet (cold rolled sheet) by applying an annealing separator mainly containing MgO and performing finishing annealing.
• an annealing separator containing Al 2 O 3 is used so that a forsterite film is hardly formed.
• the percentage of Al 2 O 3 may be 100 mass% but, in the method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment, the annealing separator preferably contains MgO from the viewpoint of preventing Al 2 O 3 from burning into a sheet surface.
• MgO may be 0%, but the percentage of MgO is preferably set to 5 mass% or more when the above effect is to be obtained.
• the percentage of MgO is 90 mass% or less in order to secure 10 mass% or more of Al 2 O 3 .
• the percentage of MgO is preferably 50 mass% or less.
• Al 2 O 3 and MgO may be more than 50 mass% in total in terms of solid content with respect to the annealing separator.
• the annealing separator may further contain a chloride.
• a chloride an effect that a forsterite film is more hardly formed can be obtained.
• the content of the chloride is not particularly limited, and may be 0%, but is preferably 0.5 to 10 mass% when the above effect is to be obtained.
• the chloride for example, bismuth chloride, calcium chloride, cobalt chloride, iron chloride, and nickel chloride are effective.
• Finishing annealing conditions are not limited, but for example, a condition of holding the steel sheet at a temperature of 1150 to 1250°C for 10 to 60 hours can be adopted.
• an excess of the annealing separator is removed from the steel sheet after the finishing annealing step.
• the excess of the annealing separator can be removed by performing water washing.
• the steel sheet after the annealing separator removal step is subjected to pickling with 0.1 to 10.0 mass% of one inorganic acid selected from sulfuric acid, chloric acid, nitric acid, and phosphoric acid at a liquid temperature of 30 to 85°C for 1 to 20 seconds.
• the inorganic acid is preferably one selected from sulfuric acid, nitric acid, and phosphoric acid.
• the steel sheet after the light pickling step is immersed in the treatment liquid for 5 to 150 seconds, and in the drying step, the steel sheet after the immersion step is pulled up from the treatment liquid, the excess of the treatment liquid is removed, and then the steel sheet is dried. As a result, an intermediate layer is formed on the surface of the base steel sheet.
• the treatment liquid is adjusted to contain 0.3 to 10 mass% of a metal phosphate at a liquid temperature of 30 to 85°C, and 0.01 to 10.0 g/l of one or more of colloidal silica, an inorganic filler, and a metal oxide having an average particle diameter of 10 to 500 nm.
• the content of the additive in the treatment liquid is less than 0.01 g/l, a sufficient effect cannot be obtained.
• the content is more than 10.0 g/l, the treatment liquid becomes unstable.
• the average particle diameter of the additive is less than 10 nm, aggregation occurs and the treatment liquid becomes unstable.
• the average particle diameter is more than 500 nm, the particles are precipitated and the dispersibility in the treatment liquid becomes poor.
• the liquid temperature of the treatment liquid is lower than 30°C or the treatment time is less than 5 seconds, the adhesion is poor.
• the liquid temperature is higher than 85°C or the treatment time is longer than 150 seconds, the average grain diameter of the crystalline metal phosphate becomes too large.
• the average grain diameter of the metal phosphate may be coarsened to cause a decrease in adhesion.
• the metal phosphate contained in the treatment liquid may be one or two or more selected from zinc phosphate, manganese phosphate, and zinc calcium phosphate.
• the metal phosphate in the treatment liquid is less than 0.3 mass%, formation of the intermediate layer is slow and cost is industrially high.
• the metal phosphate is preferably 1.0 mass% or more.
• the temperature at the time of drying is high, voids may be generated and adhesion may be poor, and thus the temperature at the time of drying is preferably 300°C or lower.
• the temperature is preferably 200°C or lower.
• the temperature at the time of drying is preferably 100°C or higher.
• a coating liquid containing a metal phosphate and colloidal silica and having a total concentration of the metal phosphate and the colloidal silica of 10 to 40 mass% is applied to the steel sheet after the drying step, dried, and then heated and held for 10 to 50 seconds at a sheet temperature of 700 to 950°C to form a tension coating layer on the surface of the intermediate layer.
• the sheet temperature at the time of holding is lower than 700°C, the tension is low and the magnetic characteristics are poor. Therefore, the sheet temperature is preferably set to 700°C or higher.
• the sheet temperature is higher than 950°C, rigidity of the steel sheet decreases and the steel sheet is easily deformed. In this case, the steel sheet may be distorted due to transfer or the like, resulting in poor magnetic characteristics. Therefore, the sheet temperature is preferably set to 950°C or lower.
• the holding time is set to 10 seconds or more.
• the holding time is preferably 50 seconds or less.
• the coating liquid (insulating coating solution) contains 10 to 40 mass% of a metal phosphate and colloidal silica.
• the applied treatment liquid When the total concentration of the metal phosphate and the colloidal silica is less than 10 mass%, the applied treatment liquid easily flows, which causes an uneven application amount. On the other hand, when the content is more than 40 mass%, the viscosity becomes too high, which causes a pattern or coating unevenness.
• metal phosphate for example, one or a mixture of two or more selected from aluminum phosphate, zinc phosphate, magnesium phosphate, nickel phosphate, copper phosphate, lithium phosphate, and cobalt phosphate may be used.
• An aluminum phosphate is preferable from the viewpoint of stability of the treatment liquid.
• the coating liquid may contain vanadium, tungsten, molybdenum, zirconium, and the like as additional elements. When these elements are contained, the elements may be added to the coating liquid, for example, as an oxygen acid.
• colloidal silica S-type or C-type colloidal silica may be used.
• the S-type colloidal silica means colloidal silica in which a silica solution is alkaline
• the C-type colloidal silica means colloidal silica in which a silica particle surface is subjected to an aluminum treatment, and a silica solution is alkaline to neutral.
• the S-type colloidal silica is widely and generally used, and is relatively inexpensive in price, but it is necessary to be careful because the S-type colloidal silica may aggregate and precipitate when being mixed with an acidic metal phosphate solution.
• the C-type colloidal silica is stable even when being mixed with a metal phosphate solution, and there is no possibility of precipitation, but the C-type colloidal silica is relatively expensive because the number of treatment steps is large. It is preferable to select and use them according to the stability of a coating liquid to be prepared.
• the method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment may further include a magnetic domain refinement step of performing magnetic domain refinement on the steel sheet after the tension coating layer forming step.
• the method of the magnetic domain refinement treatment include: a method for narrowing the width of a 180° magnetic domain (performing refinement of a 180° magnetic domain) by forming linear or dotted groove parts extending in a direction intersecting a rolling direction at predetermined intervals in the rolling direction; and a method for narrowing the width of a 180° magnetic domain (performing refinement of a 180° magnetic domain) by forming linear or dotted stress-strain parts or groove parts extending in a direction intersecting a rolling direction at predetermined intervals in the rolling direction.
• a stress-strain part In a case where a stress-strain part is formed, laser beam irradiation, electron beam irradiation, and the like can be applied.
• a groove part In a case where a groove part is formed, a mechanical groove forming method using a blade-like or the like, a chemical groove forming method by electrolytic etching, a thermal groove forming method by laser irradiation, and the like can be applied.
• the insulating coating may be formed again to repair the damage.
• the slab was heated to 1350°C and then hot-rolled to obtain a hot rolled sheet having a sheet thickness of 2.2 mm.
• the hot rolled sheet was annealed under the condition of being held at 1100°C for 10 seconds. (Hot Rolled sheet Annealing)
• the hot rolled sheet was cold-rolled to obtain a cold rolled sheet having a sheet thickness of 0.22 mm.
• the cold rolled sheet was subjected to decarburization annealing under the condition of being held at 830°C for 90 seconds.
• an annealing separator containing 45 mass% of MgO, 50 mass% of Al 2 O 3 , and 5 mass% of BiCl 3 as a bismuth chloride was applied and dried, and then finishing annealing was performed at 1200°C for 20 hours.
• the steel sheet was washed with water to remove an excess of the annealing separator, and as a result, a forsterite film was not formed on the sheet surface.
• the steel sheet was subjected to light pickling under the conditions in Table 2-1.
• an intermediate layer was formed by using a treatment liquid in which a phosphate and an additive shown in Table 1 were mixed.
• the drying temperature was 200°C.
• the obtained intermediate layer was as shown in Table 2-2.
• the proportion of the crystalline metal phosphate in the intermediate layer was 80 mass% or more.
• an insulating coating treatment liquid containing a metal phosphate and colloidal silica shown in Table 2-3 as main components was applied, and dried at 850°C for 20 seconds after the application to form a tension coating layer on the sheet surface.
• the thickness of the insulating coating (the intermediate layer and the tension coating layer) were as shown in Table 2-3.
• the tension coating layer was substantially composed of a metal phosphate and silica.
• the obtained steel sheet (grain-oriented electrical steel sheet) was irradiated with a laser beam under the conditions that UA (irradiation energy density) was 2.0 J and an irradiation interval was 5.0 mm pitch to perform a magnetic domain refinement treatment.
• UA irradiation energy density
• the iron loss W17/50 (iron loss at 50 Hz at 1.7 T) of the steel sheet after the magnetic domain refinement treatment was measured by using a single sheet tester (SST) according to JIS C2556 (2015).
• the space factor was measured by using a method in accordance with JIS C 2550-5 (2020). 30 test pieces having a width of 30 mm and a length of 320 mm were used. The total mass of the sample was measured, and then the total mass of the sample was calculated by measuring between the upper and lower contact sheets sandwiching the laminated body in a state of being pressurized at 1 MPa.
• Adhesion of a coating was evaluated by the degree of peeling (area ratio) of the coating after a bending adhesion test was performed in which a sample having a width of 30 mm and a length of 300 mm was collected from a steel sheet, the sample was subjected to stress relief annealing at 800°C for two hours in a nitrogen stream, and then wound around a 10 mm ⁇ cylinder and unwound.
• the coating tension was calculated by back calculation from the curved state when one surface of the insulating coating was peeled off. When the obtained coating tension was 4.0 MPa or more, it was determined that the coating had a sufficient coating tension.
• a 5%NaCl aqueous solution was naturally dropped to a sample for 7 hours in an atmosphere at 35°C according to a salt spray test (JIS Z2371:2015) of JIS method.
• a rusting area was evaluated at 10 points.
• the evaluation criteria were as follows. A score of 5 or more (5 to 10) was determined to be exceptional in corrosion resistance.
• the dissolution resistance was evaluated by whether or not the dissolution of phosphoric acid from the sample could be curbed.
• the dissolution amount was measured by boiling the sample in boiled pure water for 10 minutes, measuring the amount of phosphoric acid eluted in the pure water, and dividing the amount of phosphoric acid by the area of the insulating coating of the boiled grain-oriented electrical steel sheet.
• the amount of phosphoric acid eluted in the pure water was calculated by cooling the pure water (solution) in which phosphoric acid was eluted, diluting the cooled solution with pure water, and measuring the phosphoric acid concentration of the sample by using ICP-AES.
• the coating main characteristics including adhesion are extremely exceptional, and the iron loss and the space factor are improved.
• the insulating coating did not have a preferable composition, and the tension coating was poor in one or more of adhesion, magnetic characteristics, corrosion resistance, phosphoric acid dissolution resistance, and a space factor of a transformer (core).
• the present invention it is possible to provide a grain-oriented electrical steel sheet which is exceptional in adhesion and magnetic characteristics of a tension coating and does not decrease a space factor of a transformer (core). Therefore, industrial applicability is high.

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