Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties 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
  • 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
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/147—Alloys characterised by their composition

Definitions

• the present inventors have investigated the effect of stress relief annealing on the coating adhesion of an insulating coating. As a result, they found that by forming a phosphate coating by chemical conversion treatment on the surface of grain-oriented electrical steel sheet that does not have a forsterite-based coating, fusing the phosphate coating with the insulating coating during stress relief annealing, and controlling the aggregation of silica microparticles, it is possible to suppress a decrease in the coating adhesion of the insulating coating layer without degrading the magnetic properties or other coating properties.
• Si 2.50-4.00%
• Silicon (Si) is an element that increases the electrical resistance of grain-oriented electrical steel sheets and improves their iron loss characteristics. If the Si content is less than 2.50%, a sufficient eddy current loss reduction effect cannot be obtained. Therefore, the Si content is preferably 2.50% or more. The Si content is more preferably 2.70% or more, and even more preferably 3.00% or more. On the other hand, if the Si content exceeds 4.00%, the grain-oriented electrical steel sheet becomes embrittled and the threading property deteriorates significantly. Furthermore, the workability of the grain-oriented electrical steel sheet deteriorates, and the steel sheet may break during rolling. Therefore, the Si content is preferably 4.00% or less. The Si content is more preferably 3.80% or less, and even more preferably 3.70% or less.
• the nitrogen concentration of the steel sheet exceeds 1000 ppm, excess AlN remains in the steel sheet even after the completion of secondary recrystallization in the finish annealing. Such AlN causes iron loss degradation. For this reason, it is preferable to set the nitrogen concentration of the steel sheet after the nitriding process to 1000 ppm or less.
• an annealing separator containing 10 to 100 mass% of Al 2 O 3 is applied to the steel sheet after the decarburization annealing step (or nitriding treatment step), the steel sheet is dried, and then final annealing is performed.
• a forsterite-based coating is formed on the surface of the steel sheet (cold-rolled sheet) by applying an annealing separator mainly composed of MgO and performing final annealing.
• an annealing separator containing Al 2 O 3 is used so as not to form a forsterite-based coating.
• the proportion of Al2O3 may be 100% by mass, but from the viewpoint of preventing Al2O3 from seizing onto the steel sheet surface, in the method for producing a grain-oriented electrical steel sheet according to this embodiment, it is preferable that the annealing separator contains MgO. While the MgO content may be 0%, to obtain the above effect, the proportion of MgO is preferably 5% by mass or more. When MgO is contained, the proportion of MgO is 90% by mass or less to ensure 10% by mass or more of Al2O3 . The proportion of MgO is preferably 50% by mass or less. It is sufficient that the total of Al2O3 and MgO exceeds 50% by mass in terms of solid content relative to the annealing separator.
• the annealing separator may further contain chloride.
• the inclusion of chloride in the annealing separator provides the effect of making it more difficult for a forsterite-based coating to form.
• the chloride content is not particularly limited and may be 0%, but to obtain the above effect, a content of 0.5 to 10.0 mass% is preferred.
• Examples of effective chlorides include bismuth chloride, calcium chloride, cobalt chloride, iron chloride, and nickel chloride.
• the conditions for the finish annealing are not limited, but for example, conditions in which the steel is held at a temperature of 1150 to 1250° C. for 10 to 60 hours can be adopted.
• annealing separator removal process In the annealing separator removing step, excess annealing separator is removed from the steel sheet after the finish annealing step. For example, excess annealing separator can be removed by washing with water.
• the steel sheet after the annealing separator removal step is pickled with 0.1 to 5.0 mass % of an inorganic acid for 10 to 60 seconds. If the conditions for light pickling are not favorable, excess annealing separator may remain on the surface of the steel sheet, increasing the surface roughness and reducing the space factor, while if the acid is too strong, the surface of the steel sheet may be etched, resulting in reduced magnetic properties.
• First insulation film forming step In the first insulating coating formation process, the steel sheet after the water-rinsing process is immersed for 5 to 150 seconds in a treatment solution having a liquid temperature of 30 to 85°C and a metal phosphate concentration of 1.0 to 20.0 mass %, and after the treatment solution is washed away with water, the steel sheet is dried, thereby forming a first insulating coating on the surface of the steel sheet.
• the concentration of the metal phosphate is less than 1.0 mass %, it will take too long to form the first insulating coating, which is disadvantageous in terms of cost, whereas if the concentration of the metal phosphate is more than 10.0 mass %, the first insulating coating will be thick in some places, ultimately resulting in an uneven insulating coating.
• the immersion time is less than 5 seconds, the amount of the first insulating coating formed will be too small, resulting in partial deterioration of the adhesiveness of the insulating coating, whereas if the immersion time is more than 150 seconds, the time taken will be too long, which will be disadvantageous in terms of cost.
• the sheet temperature is below 750°C, the tension will be low and the magnetic properties will be inferior. Therefore, it is preferable that the sheet temperature be 750°C or higher. On the other hand, if the sheet temperature is above 950°C, the rigidity of the steel sheet will decrease and it will be prone to deformation. In this case, strain may be introduced into the steel sheet due to transportation, etc., resulting in inferior magnetic properties. Therefore, it is preferable that the sheet temperature be 950°C or lower. Furthermore, if the retention time is less than 10 seconds, the elution property will be poor. Therefore, the retention time is set to 10 seconds or more. On the other hand, if the retention time is more than 120 seconds, the coating adhesion will be reduced, and if an attempt is made to avoid the reduction in coating adhesion, productivity will be poor. Therefore, the retention time is preferably 120 seconds or less.
• the coating liquid contains a metal phosphate and colloidal silica, with 30 to 150 parts by mass of colloidal silica having a particle size of 5 to 30 nm per 100 parts by mass of the metal phosphate.
• the total of the metal phosphate and colloidal silica, calculated as solid content, should be greater than 50 mass% of the coating liquid. If the colloidal silica content is less than 30 parts by mass, the space factor and core loss may deteriorate. Therefore, the colloidal silica content is preferably 30 parts by mass or more. If the colloidal silica content is more than 150 parts by mass, the adhesion, coating tension, elution, space factor, and core loss may deteriorate. Therefore, the colloidal silica content is preferably 150 parts by mass or less.
• 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, cobalt phosphate, etc. can be used.
• the coating solution may contain additional elements such as vanadium, tungsten, molybdenum, and zirconium.
• Colloidal silica can be of type S or type C.
• Type S colloidal silica refers to one in which the silica solution is alkaline
• type C colloidal silica refers to one in which the silica particle surface is aluminum-treated and the silica solution is alkaline to neutral.
• Type S colloidal silica is widely used and relatively inexpensive, but caution is required as there is a risk of aggregation and precipitation when mixed with an acidic metal phosphate solution.
• Type C colloidal silica is stable even when mixed with a metal phosphate solution and there is no risk of precipitation, but it is relatively expensive due to the large number of processing steps required. It is preferable to use the appropriate type depending on the stability of the coating liquid to be prepared.
• the surface of the insulating coating (the surface of the insulating coating provided on the grain-oriented electrical steel sheet) may be irradiated with energy rays to refine the 180° magnetic domains. By refining the magnetic domains, it is possible to further reduce the iron loss of the grain-oriented electrical steel sheet.
• the magnetic domain subdivision process can be carried out by any known method.
• one method is to narrow the width of the 180° magnetic domains (subdivide the 180° magnetic domains) by forming linear or point-like grooves that extend in a direction that intersects the rolling direction at specified intervals along the rolling direction.
• a mechanical groove forming method using gears or the like, a chemical groove forming method in which grooves are formed by electrolytic etching, and a thermal groove forming method using laser irradiation can be used. If the insulating coating is damaged by the formation of stress-strained portions or grooves, and the insulating properties and other characteristics are deteriorated, the insulating coating may be formed again to repair the damage.
• the heat treatment temperature is less than 700°C, the effect of stress relief annealing is low and magnetic properties are inferior.
• the heat treatment temperature is more than 900°C, the rigidity of the steel sheet decreases and it becomes more susceptible to deformation, which reduces the space factor, reduces coating adhesion, and deteriorates elution properties.
• the holding time is less than 30 minutes, the effect of stress relief annealing is low and the magnetic properties are inferior, whereas if the holding time exceeds 240 minutes, the annealing time becomes too long, which is not only economically disadvantageous but also deteriorates the adhesion or elution properties.
• the atmosphere during the heat treatment is preferably a hydrogen-nitrogen mixed gas, with a hydrogen content of 50% by volume or less. If the hydrogen content exceeds 50% by volume, not only will the cost increase, but the atmosphere will be too reducing, which may cause a silica layer to form on the surface and peel off the insulating coating.
• the conditions in the example are merely an example of conditions adopted to confirm the feasibility and effects of the present disclosure, and the present disclosure is not limited to this example.
• Various conditions may be adopted in the present disclosure as long as they do not deviate from the gist of the present disclosure and the objectives of the present disclosure are achieved.
• a slab containing, by mass%, 0.08% C, 3.31% Si, 0.028% sol. Al, and 0.008% N was cast, heated, and hot-rolled to produce a 2.2 mm hot-rolled sheet. This hot-rolled sheet was then annealed by holding it at 1100°C for 10 seconds.
• the steel was pickled under known conditions and then cold-rolled to 0.22 mm without intermediate annealing to obtain a steel sheet (cold-rolled sheet). This steel sheet was then subjected to decarburization annealing at 830°C for 3 minutes.
• an annealing separator containing 48 mass% MgO, 48 mass% Al2O3 , and 4 mass% BiCl3 was applied and dried, and then finish annealing was performed by heating to 1200°C and holding for 20 hours. After finish annealing, the steel sheet was washed with water to remove excess annealing separator, and it was found that no forsterite-based coating was formed on the steel sheet surface.
• a first insulating coating was formed on this steel sheet using a treatment solution containing a mixture of metal phosphate and additives shown in Table 1. Thereafter, a coating liquid containing a metal phosphate and colloidal silica in the ratio shown in Table 2 was applied and dried to form a second insulating coating.

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• 2025
  • 2025-02-07 JP JP2025575588A patent/JPWO2025170056A1/ja active Pending
  • 2025-02-07 WO PCT/JP2025/004173 patent/WO2025170056A1/ja active Pending

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