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
  • 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
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
• • 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 invention relates to grain-oriented electrical steel sheets and manufacturing methods thereof, and in particular to grain-oriented electrical steel sheets with high manufacturing stability and manufacturing methods thereof.
• Patent Document 1 discloses a method using AlN
• Patent Document 2 discloses a method using MnS and MnSe, both of which have been put into industrial use.
• Patent Document 3 discloses a method using Pb, Sb, Nb, and Te
• Patent Document 4 discloses a method using Zr, Ti, B, Nb, Ta, V, Cr, and Mo.
• Patent Document 5 proposes the development of a technology (inhibitor-less method) that allows secondary recrystallization to occur without the inclusion of inhibitor components.
• the inhibitor-less method uses highly purified steel to induce secondary recrystallization through texture (control of the texture).
• Patent Document 6 proposes a technology that achieves stable magnetic properties by reducing oxides containing Ca and/or Mg with diameters of 1 to 3 ⁇ m. Furthermore, Patent Document 7 proposes a technology that achieves stable magnetic properties throughout the entire length of the coil by appropriately controlling the form of trace amounts of Ti.
• the inhibitor-less method induces secondary recrystallization by controlling the texture, so uniformity of the texture during secondary recrystallization annealing is extremely important.
• the precipitation of trace elements can often pose a major problem depending on their state.
• an appropriate amount of Al is added as a deoxidizer, or to mitigate the effects of the annealing atmosphere during secondary recrystallization annealing.
• Al is known to be a raw material for AlN, which has an effect on inhibiting grain growth.
• N is also sufficiently reduced, the amount of precipitation is extremely small, and it is thought to be difficult to make it function fully as a so-called inhibitor during secondary recrystallization annealing.
• N may affect grain growth during primary recrystallization annealing, which is carried out at a relatively low temperature for a short period of time. Because the amounts of these elements added are also extremely small, they are prone to uneven precipitation, which is expected to be one of the factors that destabilize the magnetic properties within the coil.
• the present invention advantageously solves the above problems and aims to provide grain-oriented electrical steel sheets that have stable, excellent magnetic properties throughout the entire length of the coil when manufactured using an inhibitor-less process.
• the inventors evaluated the characteristics of materials that actually exhibited large fluctuations in magnetic properties within coils, which occur with a certain frequency. As a result, it became clear that one of the factors behind the fluctuations in magnetic properties within coils was that the Al contained in the steel precipitated unevenly within the steel, promoting a non-uniform structure and destabilizing the behavior of secondary recrystallization.
• MnS precipitate that is actively used in grain-oriented electrical steel sheets. It is known that adding Se, an element in the same group as S in the periodic table, results in good magnetic properties. This takes advantage of the fact that MnS and MnSe are precipitates that can take the same form (crystal structure), and that each element affects the other's precipitation.
• the inventors therefore decided to investigate controlling the amount of Ga depending on the amount of Al. Because Al is used as a deoxidizer during steelmaking, there is both acid-soluble Al and insoluble Al in the form of an oxide. Here, they focused their investigation on acid-soluble Al, which is thought to function as a precipitate. As a result, they found that mixing Ga at an atomic weight ratio of 3% to 100% of the Al amount tends to reduce variation in magnetic properties within the coil.
• the inventors discovered that by adding an appropriate amount of Ga depending on the amount of Al added to the steel sheet, it is possible to suppress uneven precipitation of Al and obtain a grain-oriented electrical steel sheet with stable, excellent magnetic properties throughout the entire length of the coil, leading to the completion of the present invention.
• the gist of the present invention is as follows.
• the component composition further includes, in mass%, 1.
• [3] A method for producing the grain-oriented electrical steel sheet according to [1] or [2], In mass%, C: 0.08% or less, Si: 2.0% or more and 4.5% or less, Mn: 0.01% or more and 0.5% or less, in ppm by mass, Se, Te and O: each less than 50 ppm, acid-soluble Al: 20 ppm or more and less than 100 ppm, S: less than 50 ppm, N: 80 ppm or less, Ga: the concentration of acid-soluble Al satisfies the following formula (2), i.e., 0.030 ⁇ Al ⁇ 2.58 ⁇ Ga ⁇ 1.000 ⁇ Al ⁇ 2.58 (2) and the remainder being Fe and unavoidable impurities, the steel slab is hot-rolled to form a hot-rolled sheet, which is then annealed and rolled to form a cold-rolled sheet of a final thickness, which is then subjected to primary recrystallization annealing, further subjected to secondary recrystallization annealing, and then an
• the component composition further includes, in mass%, 4.
• grain-oriented electrical steel sheets can be manufactured using an inhibitorless process to provide grain-oriented electrical steel sheets that have stable, excellent magnetic properties throughout the entire length of the coil.
• FIG. 1 is a diagram showing the relationship between the atomic ratio of Ga to Al and the average value of B8 .
• the starting material is a steel slab for grain-oriented electrical steel plate (hereinafter sometimes simply referred to as a steel slab) cast from molten steel having the following chemical composition.
• % stands for “mass %”
• ppm stands for “mass ppm” unless otherwise specified.
• C 0.08% or less C suppresses grain coarsening during hot rolling and improves the structure before cold rolling. It also improves the texture after primary recrystallization during cold rolling by interacting with dislocations. However, if C remains in the final product sheet, it can cause magnetic aging and lead to magnetic deterioration. If the C content exceeds 0.08%, the load in the decarburization process becomes too high and cannot be sufficiently reduced. Therefore, the C content is limited to 0.08% or less. Furthermore, to obtain the above-mentioned structure improvement effect, the C content is preferably 0.01% or more.
• Si 2.0% or more and 4.5% or less Si is a useful element that increases the electrical resistance of steel and improves iron loss. If the Si content is less than 2.0%, a sufficient iron loss reduction effect cannot be expected. On the other hand, if the Si content exceeds 4.5%, cold rolling becomes significantly difficult. Therefore, the Si content is limited to the range of 2.0% or more and 4.5% or less.
• Mn 0.01% or more and 0.5% or less Mn is a useful element for improving hot workability. If the Mn content exceeds 0.5%, the primary recrystallization texture deteriorates, making it difficult to obtain secondary recrystallized grains highly concentrated in the Goss orientation. Therefore, the Mn content is limited to a range of 0.5% or less. Furthermore, in order to improve hot workability, the Mn content must be 0.01% or more. The Mn content is preferably 0.02% or more and 0.3% or less.
• Se, Te, and O Less than 50 ppm each. Excessive Se and Te form selenides and tellurides, making secondary recrystallization difficult. This is because coarsened precipitates caused by slab heating cause the primary recrystallization structure to become non-uniform. Therefore, to prevent them from acting as inhibitors, the Se and Te contents are each limited to less than 50 ppm. The Se and Te contents are preferably 30 ppm or less. On the other hand, O forms oxides and remains as inclusions in the final product, degrading magnetic properties. Therefore, the O content must be limited to less than 50 ppm. The Se, Te, and O contents may be 0%.
• Acid-soluble Al 20 ppm or more but less than 100 ppm, S: less than 50 ppm, N: 80 ppm or less.
• these precipitate-forming elements are not necessarily required when considering secondary recrystallization alone.
• Al is effective as a deoxidizer in the smelting process to reduce problematic inclusions.
• the content of acid-soluble Al is preferably in the range of 20 ppm or more but less than 100 ppm.
• the S content and N content are 50 ppm or more and exceed 80 ppm, respectively, the precipitates formed during slab heating will coarsen, similar to Se and Te, and deteriorate the primary recrystallization structure. Therefore, the S content and N content are limited to less than 50 ppm and 80 ppm or less, respectively.
• the S content and N content are each 0%, but these elements are difficult to completely remove, and in fact, setting the S content to less than 10 ppm and the N content to less than 20 ppm leads to a significant increase in production costs. Therefore, it is preferable that the S content and the N content are 10 ppm or more and 20 ppm or more, respectively. This can reduce the burden when producing grain-oriented electrical steel sheets using the inhibitor-less method, which aims to produce high-quality grain-oriented electrical steel sheets at low cost.
• Ga 0.030 ⁇ Al ⁇ 2.58 ⁇ Ga ⁇ 1.000 ⁇ Al ⁇ 2.58 with respect to the concentration of acid-soluble Al
• Ga has a high boiling point but a low melting point, making it difficult to add it as metallic Ga.
• various Ga concentrations can be achieved by adding metallic Ga.
• there are technical challenges in adding high concentrations of Ga Using an electric furnace process using low-temperature scrap or an iron source as a raw material is relatively easy to use compared to the general blast furnace-converter process.
• the amount of Ga added is determined based on the amount of acid-soluble Al added.
• the magnetic property stabilization effect was observed when the amount added was 3.0% or more, calculated as atomic number, relative to the amount of acid-soluble Al added. Because the atomic weights of Al and Ga differ by approximately 2.58 times, the target mass percentage is added by multiplying this by mass. While the mechanism behind the optimum range of Ga addition is unclear, a relationship with the amount of Al added has been confirmed, making it highly likely that complex precipitation with Al is the cause. It is believed that the effect is insufficient at less than 3.0% relative to the Al content. On the other hand, with regard to the upper limit, the degree of effect saturates from a performance perspective, but increasing the amount does not necessarily result in deterioration.
• the Ga content, calculated as atomic number, relative to the amount of Al added is preferably 100.0% or less, more preferably 50.0% or less, and even more preferably 30.0% or less.
• Ni 1.50% or less Ni improves the magnetic properties by increasing the uniformity of the hot-rolled sheet structure.
• the Ni content is 0.005% or more, the effect of adding Ni is manifested.
• the Ni content exceeds 1.50%, secondary recrystallization becomes unstable, and the magnetic properties deteriorate. Therefore, it is preferable that the Ni content be within the above range.
• Sn 0.50% or less
• Sb 0.50% or less
• Cu 0.50% or less
• Sn, Sb, and Cu are elements that are sometimes considered auxiliary inhibitors through grain boundary segregation, and may be useful in inhibitor-less processes that do not actively utilize inhibitors due to precipitates.
• the effects of adding Sn, Sb, and Cu are manifested by setting the contents of Sn, Sb, and Cu to 0.01% or more, 0.005% or more, and 0.01% or more, respectively.
• exceeding the upper limit increases the possibility of secondary recrystallization defects. Therefore, it is preferable that the contents of Sn, Sb, and Cu be within the above ranges.
• P and Cr have the effect of improving the reaction during the formation of the forsterite film.
• the effects of adding these elements are manifested when the P content and Cr content are 0.0050% or more and 0.01% or more, respectively.
• the P content and Cr content exceed 0.50% and 1.50%, respectively, the formation of the forsterite film is excessively promoted, resulting in problems such as peeling of the film. Therefore, it is preferable to set the P content and Cr content within the above ranges.
• Mo 0.50% or less
• B 0.0050% or less
• Nb 0.0100% or less
• Mo, B, and Nb all contribute to suppressing grain growth and have the effects of improving texture and stabilizing secondary recrystallization. Therefore, the effects of adding Mo, B, and Nb are manifested by setting the Mo content, B content, and Nb content to 0.01% or more, 0.0001% or more, and 0.0005% or more, respectively.
• Mo, B, and Nb are added in excess, they precipitate and function as strong inhibitors. Therefore, in the inhibitorless process, it is preferable to set the Mo content, B content, and Nb content to the above-mentioned upper limits or less.
• a steel slab adjusted to the above chemical composition range is cast. Since there is a concern that steel with added Ga may become slightly embrittled when hot, when casting a slab thickness exceeding the usual 200 mm, it is preferable to use a casting machine that minimizes excessive re-bending. Furthermore, if the bending of the casting machine is so great that breakouts occur, a medium-thickness slab with a thickness of 30 mm to 180 mm can also be used.
• the cast steel slab is hot-rolled to produce hot-rolled sheet, either without reheating or after reheating. If the steel slab is reheated, the reheating temperature is preferably between 1100°C and 1300°C. Heating the slab to above 1300°C is meaningless in the present invention, where the steel contains almost no inhibitors at the steel slab stage, and is unnecessary as it increases costs.
• the cold-rolled sheet is then subjected to primary recrystallization annealing.
• the purpose of this primary recrystallization annealing is to cause primary recrystallization of the cold-rolled sheet with a rolled texture and adjust the primary recrystallized grain size to an optimal size for secondary recrystallization.
• Another purpose is to use a wet hydrogen-nitrogen or wet hydrogen-argon annealing atmosphere to decarburize the carbon contained in the steel and simultaneously form an oxide film on the surface.
• the annealing temperature (holding temperature) for primary recrystallization annealing is preferably set to a temperature of approximately 800°C or higher and lower than 950°C.
• secondary recrystallization annealing (finish annealing) is performed to form a secondary recrystallization and forsterite film.
• the secondary recrystallization annealing is preferably performed in a N atmosphere, Ar atmosphere, or a mixed atmosphere of N and Ar without H during the temperature rise process, with a residence time of 35 hours or more in a temperature range of 800°C to 900°C, and further in an atmosphere containing 5% or more by volume of H at a maximum temperature exceeding 1150°C for 3 hours or more, and further in a cooling process with a residence time of 10 hours or more in a temperature range of 1100°C to 900°C.
• the Al in the steel is in a state of complex precipitation with Ga, which makes it more difficult to remove from the steel than usual, and if excessive residual content remains, it can cause deterioration in hysteresis loss in the finished steel sheet.
• MgO is used as an annealing separator, oxidation of the steel sheet progresses during annealing, and during this process, some of the Al in the steel is removed from the steel by forming Al2O3 in the surface layer.
• the steel sheet substrate preferably contains 50 ppm or less of C, more preferably 30 ppm or less, and even more preferably 20 ppm or less of C.
• the steel sheet substrate also preferably contains 50 ppm or less of N, more preferably 30 ppm or less, and even more preferably 20 ppm or less of N.
• Ni 1.50% or less
• Sn 0.50% or less
• Sb 0.50% or less
• Cu 0.50% or less
• P 0.50% or less
• Cr 1.50% or less
• Mo 0.50% or less
• B 0.0050% or less
• Nb 0.
• Example 1 When steel containing 0.05% C, 3.3% Si, 0.05% Mn, 0.03% Cr, 0.02% P, 20 ppm S, 30 ppm N, and 40 ppm acid-soluble Al was melted, metallic Ga was added in a laboratory, and vacuum steel ingots with various Ga contents shown in Table 1 were melted. Each steel ingot was then heated to 1200°C and hot-rolled to a thickness of 2 mm. Subsequently, 50 hot-rolled sheets measuring 100 mm in width and 300 mm in length were used as test materials and subjected to hot-rolled sheet annealing at 1000°C for 50 seconds.
• test materials were cold-rolled to a final thickness of 0.27 mm and subjected to annealing for decarburization and primary recrystallization.
• an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, and annealing including a secondary recrystallization process and a purification process was performed.
• This annealing involved soaking at 850°C for 40 hours in a N2 atmosphere during the temperature rise process, followed by soaking at 1200°C for 5 hours in a H2 : N2 mixed gas atmosphere of 25:75, and then cooling at a cooling rate of 10°C/h in the temperature range from 1100°C to 900°C, resulting in a residence time of 20 hours.
• An insulating coating consisting of 60% colloidal silica and aluminum phosphate was applied to the surface of the obtained steel sheet and baked at 800°C.
• the C and N contents of the product sheets were 30 ppm or less at all levels.
• Epstein test specimens were cut from the 50 test pieces obtained from the hot-rolled sheets, and the magnetic flux density ( B8 ) and hysteresis loss ( Whys ) at a magnetic flux density of 1.7 T were measured.
• the standard deviation of B8 (50 measurement points) obtained from each test piece was evaluated as the amount of variation.
• the results are shown in Table 1. After magnetic measurement, the test pieces were pickled to remove the coating, and then the steel composition was analyzed. As is clear from the results, when Ga is added at an atomic ratio of 3.0% or more to Al (hereinafter also referred to as the "Al:Ga atomic ratio"), the amount of variation in B8 decreases.
• test pieces with an Al:Ga atomic ratio of 48.4% one was broken during the manufacturing process, making it impossible to evaluate the product characteristics.
• 50 test pieces with an Al:Ga atomic ratio of 96.9% two were broken during the manufacturing process, making it impossible to evaluate the product characteristics.
• five test pieces with an atomic ratio of Al:Ga of 116.3% were similarly broken during the manufacturing process, and the final magnetic properties could not be evaluated.
• Example 2 The components were C: 0.055%, Si: 3.2%, Mn: 0.07%, Cr: 0.01%, P: 0.03%, S: 15 ppm, N: 35 ppm, and a target of 20 ppm to less than 100 ppm of acid-soluble Al.
• Scrap containing a trace amount of Ga was used as a raw material and melted in an electric furnace to obtain a cast slab having the composition shown in Table 2.
• the resulting cast slab was then heated, and hot rolling was initiated when the slab surface temperature reached 1120 ° C. to obtain a hot-rolled sheet with a thickness of 2 mm. Subsequently, the resulting hot-rolled sheet (hot-rolled coil) was subjected to hot-rolled sheet annealing at 1050 ° C.
• the steel sheets were then coated with an annealing separator primarily composed of MgO, wound into coils with a total weight of 8 t, and subjected to annealing including a secondary recrystallization process and a purification process.
• the secondary recrystallization annealing involved a single soaking treatment at 850°C during the temperature rise process. The soaking treatment at the maximum annealing temperature and the cooling conditions were controlled to the conditions shown in Table 2.
• An insulating coating composed of 60% colloidal silica and aluminum phosphate was applied to the surface of the resulting steel sheets and baked at 830°C.
• Epstein test specimens were taken from the center of the coil width every 500 m, with the point where 100 m of the end of the coil in the longitudinal direction was truncated as the origin.
• the magnetic flux density ( B8 ) and hysteresis loss ( Whys ) at a magnetic flux density of 1.7 T at each point were measured.
• the standard deviation of B8 obtained at each point on the coil was evaluated as the amount of variation.
• Table 2 After the magnetic measurements, the test pieces were subjected to pickling to remove the coating, and then the steel composition was analyzed. As shown in Table 2, it was confirmed that the steel sheets of the invention examples had good magnetic properties.
• the C and N contents of the finished sheets were 30 ppm or less at all levels.
• Example 3 A steel slab was produced having the composition shown in Table 3 as the main components, in addition to 0.06% C, 3.35% Si, and 0.03% Mn. The Al content was adjusted using an alloy containing a trace amount of Ga. The resulting steel slab was then heated at 1250°C and hot-rolled under typical conditions to produce a hot-rolled sheet (hot-rolled coil) with a thickness of 2.5 mm. The resulting hot-rolled coil was then annealed at 900°C, cold-rolled to 1.3 mm, and then subjected to intermediate annealing.
• the intermediate annealing was performed at 1050°C, and the annealed coil was cold-rolled to a final thickness of 0.23 mm and subjected to annealing for decarburization and primary recrystallization.
• An annealing separator primarily composed of MgO was then applied to the surface of the steel sheet, followed by final annealing, including a secondary recrystallization process and a purification process.
• the obtained coil was coated with a coating solution containing phosphate-chromate-colloidal silica in a weight ratio of 3:1:2, and then subjected to planarization annealing at 850°C for 30 seconds.
• test pieces were taken from the center of the coil width every 500 m, with the origin being a point where 100 m of the coil's longitudinal end was truncated, so that the total weight was 500 g or more.
• the magnetic flux density ( B8 ) and hysteresis loss ( Whys ) at a magnetic flux density of 1.7 T were measured at each point using the Epstein test specified in JIS C2550.
• the standard deviation of B8 obtained at each point on the coil was also evaluated as the amount of variation.
• the results are shown in Table 3. After magnetic measurements, the test pieces were pickled to remove the coating, and then the steel composition was analyzed. As shown in Table 3, it was confirmed that the addition of various additive elements resulted in even better properties.
• the C and N contents of the finished steel sheets were 30 ppm or less at all levels.

Landscapes

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

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

Family

ID=96991166

Family Applications (1)

Country Status (2)

Citations (3)

• 2025
  • 2025-03-06 WO PCT/JP2025/008314 patent/WO2025187797A1/ja active Pending
  • 2025-03-06 JP JP2025543355A patent/JPWO2025187797A1/ja active Pending

Patent Citations (3)

Also Published As

Similar Documents

Legal Events