Grain oriented electrical steel sheet, forming method for insulation coating of grain oriented electrical steel sheet, and producing method for grain oriented electrical steel sheet

A grain oriented electrical steel sheet without a forsterite film characterized in that the grain oriented electrical steel sheet comprises:

• a base steel sheet;
• an oxide layer arranged in contact with the base steel sheet;
• and
• a tension-insulation coating arranged in contact with the oxide layer,
• wherein the base steel sheet includes, as a chemical composition, by mass %,
• 2.5 to 4.0% of Si,
• 0.05 to 1.00% of Mn,
• 0 to 0.01% of C,
• 0 to 0.005% of S+Se,
• 0 to 0.01% of sol.Al,
• 0 to 0.005% of N,
• 0 to 0.03% of Bi,
• 0 to 0.03% of Te,
• 0 to 0.03% of Pb,
• 0 to 0.50% of Sb,
• 0 to 0.50% of Sn,
• 0 to 0.50% of Cr,
• 0 to 1.0% of Cu, and
• a balance consisting of Fe and impurities,
• the oxide layer is an iron oxide layer,
• when the iron oxide layer is analyzed by a fourier transform infrared spectroscopy, when A650 is an absorbance of an absorption peak detected at 650 cm′ in an infrared absorption spectrum, and when A1250 is an absorbance of an absorption peak detected at 1250 cm−1 in the infrared absorption spectrum,
• the A650 and the A1250 satisfy 0.2≤A650/A1250≤5.0, and
• a magnetic flux density B8 in a rolling direction of the grain oriented electrical steel sheet is 1.90 T or more.

A forming method for an insulation coating of a grain oriented electrical steel sheet without a forsterite film characterized in that

• the forming method for the insulation coating includes an insulation coating forming process of forming a tension-insulation coating on a steel substrate,
• wherein, in the insulation coating forming process,
• a solution for forming the tension-insulation coating is applied to an oxide layer of the steel substrate and the solution is baked,
• wherein the steel substrate includes a base steel sheet and the oxide layer arranged in contact with the base steel sheet,
• the base steel sheet includes, as a chemical composition, by mass %,
• 2.5 to 4.0% of Si,
• 0.05 to 1.00% of Mn,
• 0 to 0.01% of C,
• 0 to 0.005% of S+Se,
• 0 to 0.01% of sol.Al,
• 0 to 0.005% of N,
• 0 to 0.03% of Bi,
• 0 to 0.03% of Te,
• 0 to 0.03% of Pb,
• 0 to 0.50% of Sb,
• 0 to 0.50% of Sn,
• 0 to 0.50% of Cr,
• 0 to 1.0% of Cu, and
• a balance consisting of Fe and impurities,
• the oxide layer is an iron oxide layer, and
• when the iron oxide layer is analyzed by a fourier transform infrared spectroscopy, when A650 is an absorbance of an absorption peak detected at 650 cm−1 in an infrared absorption spectrum, and when A1250 is an absorbance of an absorption peak detected at 1250 cm−1 in the infrared absorption spectrum,
• the A650 and the A1250 satisfy 0.2≤A650/A1250≤5.0.

A producing method for a grain oriented electrical steel sheet without a forsterite film characterized in that

• the producing method includes
• a hot rolling process of heating and thereafter hot-rolling a steel piece to obtain a hot rolled steel sheet,
• a hot band annealing process of optionally annealing the hot rolled steel sheet to obtain a hot band annealed steel sheet,
• a cold rolling process of cold-rolling the hot rolled steel sheet or the hot band annealed steel sheet by cold-rolling once or by cold-rolling plural times with an intermediate annealing to obtain a cold rolled steel sheet,
• a decarburization annealing process of decarburization-annealing the cold rolled steel sheet to obtain a decarburization annealed steel sheet,
• a final annealing process of applying an annealing separator to the decarburization annealed steel sheet and thereafter final-annealing the decarburization annealed steel sheet to obtain a final annealed steel sheet,
• an oxidizing process of conducting a washing treatment, a pickling treatment, and a heat treatment in turn for the final annealed steel sheet to obtain an oxidized steel sheet,
• an insulation coating forming process of applying a solution for forming a tension-insulation coating to a surface of the oxidized steel sheet and of baking the solution,
• wherein, in the hot rolling process,
• the steel piece includes, as a chemical composition, by mass %,
• 2.5 to 4.0% of Si,
• 0.05 to 1.00% of Mn,
• 0.02 to 0.10% of C,
• 0.005 to 0.080% of S+Se,
• 0.010 to 0.07% of sol.Al,
• 0.005 to 0.020% of N,
• 0 to 0.03% of Bi,
• 0 to 0.03% of Te,
• 0 to 0.03% of Pb,
• 0 to 0.50% of Sb,
• 0 to 0.50% of Sn,
• 0 to 0.50% of Cr,
• 0 to 1.0% of Cu, and
• a balance consisting of Fe and impurities, and
• wherein, in the oxidizing process,
• as the washing treatment, a surface of the final annealed steel sheet is washed,
• as the pickling treatment, the final annealed steel sheet is pickled using a sulfuric acid of 5 to 20 mass %, and
• as the heat treatment, the final annealed steel sheet is held in a temperature range of 700 to 850° C. for 10 to 50 seconds in an atmosphere where an oxygen concentration is 5 to 21 volume % and a dew point is −10 to 30° C.

A grain oriented electrical steel sheet without a forsterite film characterized in that the grain oriented electrical steel sheet comprises:

• a base steel sheet;
• an oxide layer arranged in contact with the base steel sheet;
• and
• a tension-insulation coating arranged in contact with the oxide layer,
• wherein the base steel sheet includes, as a chemical composition, by mass %,
• 2.5 to 4.0% of Si,
• 0.05 to 1.00% of Mn,
• 0 to 0.01% of C,
• 0 to 0.005% of S+Se,
• 0 to 0.01% of sol.Al,
• 0 to 0.005% of N,
• 0 to 0.03% of Bi,
• 0 to 0.03% of Te,
• 0 to 0.03% of Pb,
• 0 to 0.50% of Sb,
• 0 to 0.50% of Sn,
• 0 to 0.50% of Cr,
• 0 to 1.0% of Cu, and
• a balance comprising Fe and impurities,
• the oxide layer is an iron oxide layer,
• when the iron oxide layer is analyzed by a fourier transform infrared spectroscopy, when A650 is an absorbance of an absorption peak detected at 650 cm−1 in an infrared absorption spectrum, and when A1250 is an absorbance of an absorption peak detected at 1250 cm−1 in the infrared absorption spectrum,
• the A650 and the A1250 satisfy 0.2≤A650/A1250≤5.0, and
• a magnetic flux density B8 in a rolling direction of the grain oriented electrical steel sheet is 1.90 T or more.

A forming method for an insulation coating of a grain oriented electrical steel sheet without a forsterite film characterized in that

• the forming method for the insulation coating includes an insulation coating forming process of forming a tension-insulation coating on a steel substrate,
• wherein, in the insulation coating forming process,
• a solution for forming the tension-insulation coating is applied to an oxide layer of the steel substrate and the solution is baked,
• wherein the steel substrate includes a base steel sheet and the oxide layer arranged in contact with the base steel sheet,
• the base steel sheet includes, as a chemical composition, by mass %,
• 2.5 to 4.0% of Si,
• 0.05 to 1.00% of Mn,
• 0 to 0.01% of C,
• 0 to 0.005% of S+Se,
• 0 to 0.01% of sol.Al,
• 0 to 0.005% of N,
• 0 to 0.03% of Bi,
• 0 to 0.03% of Te,
• 0 to 0.03% of Pb,
• 0 to 0.50% of Sb,
• 0 to 0.50% of Sn,
• 0 to 0.50% of Cr,
• 0 to 1.0% of Cu, and
• a balance comprising Fe and impurities,
• the oxide layer is an iron oxide layer, and
• when the iron oxide layer is analyzed by a fourier transform infrared spectroscopy, when A650 is an absorbance of an absorption peak detected at 650 cm−1 in an infrared absorption spectrum, and when A1250 is an absorbance of an absorption peak detected at 1250 cm−1 in the infrared absorption spectrum,
• the A650 and the A1250 satisfy 0.2≤A650/A1250≤5.0.

A producing method for a grain oriented electrical steel sheet without a forsterite film characterized in that

• the producing method includes
• a hot rolling process of heating and thereafter hot-rolling a steel piece to obtain a hot rolled steel sheet,
• a hot band annealing process of optionally annealing the hot rolled steel sheet to obtain a hot band annealed steel sheet,
• a cold rolling process of cold-rolling the hot rolled steel sheet or the hot band annealed steel sheet by cold-rolling once or by cold-rolling plural times with an intermediate annealing to obtain a cold rolled steel sheet,
• a decarburization annealing process of decarburization-annealing the cold rolled steel sheet to obtain a decarburization annealed steel sheet,
• a final annealing process of applying an annealing separator to the decarburization annealed steel sheet and thereafter final-annealing the decarburization annealed steel sheet to obtain a final annealed steel sheet,
• an oxidizing process of conducting a washing treatment, a pickling treatment, and a heat treatment in turn for the final annealed steel sheet to obtain an oxidized steel sheet,
• an insulation coating forming process of applying a solution for forming a tension-insulation coating to a surface of the oxidized steel sheet and of baking the solution,
• wherein, in the hot rolling process,
• the steel piece includes, as a chemical composition, by mass %,
• 2.5 to 4.0% of Si,
• 0.05 to 1.00% of Mn,
• 0.02 to 0.10% of C,
• 0.005 to 0.080% of S+Se,
• 0.010 to 0.07% of sol.Al,
• 0.005 to 0.020% of N,
• 0 to 0.03% of Bi,
• 0 to 0.03% of Te,
• 0 to 0.03% of Pb,
• 0 to 0.50% of Sb,
• 0 to 0.50% of Sn,
• 0 to 0.50% of Cr,
• 0 to 1.0% of Cu, and
• a balance comprising Fe and impurities, and
• wherein, in the oxidizing process,
• as the washing treatment, a surface of the final annealed steel sheet is washed,
• as the pickling treatment, the final annealed steel sheet is pickled using a sulfuric acid of 5 to 20 mass %, and
• as the heat treatment, the final annealed steel sheet is held in a temperature range of 700 to 850° C. for 10 to 50 seconds in an atmosphere where an oxygen concentration is 5 to 21 volume % and a dew point is −10 to 30° C.