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 by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
• • 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
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
  • C21D8/1222—Hot rolling
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
  • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
  • C21D8/1244—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest
  • C21D8/1255—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the heat treatment(s) being of interest with diffusion of elements, e.g. decarburising, nitriding

Definitions

• the present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties used as an iron core of a transformer or the like.
• the unidirectional electromagnetic plate is mainly used as a core material for transformers and other electric devices, and is required to have excellent magnetic characteristics such as excitation characteristics and iron loss characteristics.
• magnetic flux density B 8 in the strength of 800 A / m of magnetic field is usually used.
• As the number representing the iron loss characteristics iron loss W per 1 kg when 1. magnetized to 7 Tesla one (T) at a frequency 50 Hz, 7/5.
• You are using Magnetic flux density is the largest controlling factor of iron loss characteristics. Generally, the higher the magnetic flux density, the better the iron loss characteristics. Generally, when the magnetic flux density is increased, the secondary recrystallized grains become large, and the iron loss characteristics may become poor. On the other hand, by controlling the magnetic domain, the iron loss characteristics can be improved irrespective of the grain size of the secondary recrystallized grains.
• This unidirectional electromagnetic steel plate is manufactured by causing secondary recrystallization in the final finish annealing process to develop a so-called Goss structure with ⁇ 110 ⁇ axis on the steel plate surface and ⁇ 001> axis in the rolling direction. It has been. In order to obtain good magnetic properties, the axis of easy magnetization must be 001> must be highly aligned in the rolling direction.
• a method is used in which MnS is dissolved completely and then precipitated during hot rolling.
• a temperature of about 1400 is required to completely dissolve the required amount of MnS for secondary recrystallization. This is more than 200 times higher than the ordinary slab heating temperature, and this high-temperature slab heat treatment has the following disadvantages.
• the slab heating temperature should be reduced to the ordinary level, but at the same time, the amount of MnS that is effective as an inhibitor should be reduced or smashed. Not necessarily, which inevitably leads to instability of secondary recrystallization. For this reason, in order to realize low-temperature slab heating, it is necessary to strengthen the inhibitor in some way with precipitates other than MnS to sufficiently suppress normal grain growth during finish annealing. is there.
• Such inhibitors include nitrides, oxides, and grain boundary precipitation elements in addition to sulfides. Examples of known techniques include the following.
• Japanese Patent Publication No. 54-24685 discloses a method in which a slab heating temperature is set in a range of 1050 to 1350 by including grain boundary segregation elements such as As, Bi, Sn, and Sb in a steel.
• Japanese Patent Application Laid-Open No. 52-24116 discloses that the slab heating temperature is increased from 1100 to 100% by containing nitride forming elements such as Zr, Ti, B, Nb, Ta, V, Cr, and Mo in addition to A £. 1260t: A method has been disclosed for the range of: In Japanese Patent Publication No.
• low-temperature slab heating is carried out by lowering the ⁇ content and the ratio of MnZS to 2.5 or less, and secondary recrystallization is stabilized by addition of Cu.
• the technology was disclosed.
• a technique was also disclosed that was improved from the metal organization side in combination with the reinforcement of these inhibitors. That is, in Japanese Patent Publication No. 57-89433, in addition to Mn, elements such as S, Se, Sb, Bi, Pb, Sn, and B were added, and the columnar crystal ratio of the slab and the secondary cold rolling were added thereto.
• Low temperature slab heating of 1100 to 1250 has been realized by combining the reduction ratio.
• an inhibitor is composed mainly of A ⁇ , B and nitrogen in addition to S or Se, and pulse annealing is performed during the primary recrystallization annealing after cold rolling.
• a technology to stabilize secondary recrystallization by applying it has been disclosed. As described above, great efforts have been made so far to realize low-temperature slab heating in the production of directional electromagnetic steel plates.
• hot-rolled sheet annealing is usually performed for the purpose of making the structure after hot rolling non-uniform and performing a precipitation treatment.
• the inhibitor is controlled by performing precipitation treatment of ⁇ £ N in hot-rolled sheet annealing. The method is adopted.
• unidirectional electromagnetic steel plates are manufactured through main processes such as manufacturing, hot rolling, one annealing, cold rolling, decarburizing annealing, and finishing annealing, and require a large amount of energy. Manufacturing costs are also higher than in processes and the like.
• the present invention is a method of obtaining a unidirectional electromagnetic steel plate having excellent magnetic properties by a single cold rolling method on the premise of low-temperature slab heating and omitting hot-rolled sheet annealing.
• the purpose is to provide.
• the present inventor conducted a study focusing on the winding process after hot rolling, and found that a specific range of the winding temperature has a great influence on the magnetic flux density.
• the present inventors have found that in order to stabilize the secondary recrystallization in the production method, it is necessary to perform nitriding at the stage after hot rolling to the completion of secondary recrystallization at the time of final annealing, and completed the present invention. Things.
• C 0.021 to 0.075%
• Si 2.5 to 4.5%
• acid-soluble Ai 0.010 to 0.60%
• N 0.000% by weight.
• Mn 0.05 ⁇ 0.8%
• the rest is a slab consisting of Fe and unavoidable impurities.
• Fig. 1 is a graph showing the relationship between the coiling temperature after hot rolling and the magnetic flux density.
• the unidirectional electromagnetic steel plate to which the present invention is directed is manufactured by continuously manufacturing or agglomerating a molten metal obtained by a conventionally used manufacturing method, and performing a sizing step if necessary.
• the slab is sandwiched between the slabs, hot-rolled to form a hot-rolled sheet, and then cold-rolled at a reduction rate of 80% or more, decarburizing annealing, and final finish annealing without performing hot-rolled sheet annealing.
• the present invention is premised on low-temperature slab heating, omission of hot-rolled sheet annealing, and one-time cold rolling.
• Fig. 1 shows the relationship between the coiling temperature after hot rolling and the magnetic flux density.
• the starting materials contain C: 0.052% by weight, Si: 3.25% by weight, acid soluble A £: 0.027% by weight, N: 0.0078% by weight, S: 0.007% by weight, and Mn: 0.14% by weight.
• a 40 mm thick slab consisting of the balance of Fe and unavoidable impurities is heated to 1150 to make it 2.3 mm thick in 6 passes, and then cooled to 200 to 900 by various combinations of water cooling and air cooling.
• the effects of the present invention which are not obtained in the case of high-temperature winding at 600, which are not obtained, are that Fe 3 C tends to coarsen during cooling after high-temperature winding, or that precipitation of A ⁇ N, S13N4, etc. occurs. increases, the precipitation of Fe 16 N 4 is insufficient, or even Fe 16 N 4 was deposited, coarsened and combed on cooling, for reasons of equal, Do insufficient dissociation solid solution in subsequent cold rolling Rukoto It is thought that. Therefore, the effect of the present invention is that a relatively small amount of Fe 3 C, Fe 16 N 4, etc.
• the other feature of the present invention that the nitriding is performed at a stage from after hot rolling to completion of secondary recrystallization at the time of final finish annealing, is based on the premise that low-temperature slab heating and hot-rolled sheet annealing are omitted. This is because, in the present invention, nitridation at the above stage is necessary to stabilize the secondary recrystallization.
• the N content of the slab component is reduced, and a predetermined amount of nitrogen, for example, 0.0001% by weight or more is increased at an appropriate stage after the above-described hot rolling. I can do that.
• the plate of the present invention can extremely stabilize the secondary recrystallization, thereby obtaining a high magnetic flux density.
• Si exceeds 4.5%, cracking during cold rolling becomes remarkable, so it was set to 4.5% or less. If the content is less than 2.5%, the specific resistance of the material is too low, and the low iron loss required for the trans- fer core material cannot be obtained. Desirably it is 3.2% or more.
• a ⁇ and N are required to have an acid solubility of 0.010% or more in order to secure A £ N or (A i, S i) nitrides necessary for stabilizing the secondary recrystallization. If the acid-soluble ftA ⁇ exceeds 0.060%, A / N of the hot-rolled sheet becomes inappropriate and secondary recrystallization becomes unstable, so the content was set to 0.060% or less.
• N is difficult for N to be less than 0.0030% in normal production work, and it is not economically desirable to make N less than this value.Therefore, it is made 0.0030% or more. It is set to 0.0130% or less because of the occurrence of so-called "swelling of the plate surface".
• the lower limit of M n is 0.05%. If the content is less than 0.05%, the shape (flatness) of the hot-rolled sheet obtained by hot rolling, particularly the side portion of the strip, becomes corrugated, which causes a problem of lowering the product yield. On the other hand, if the ⁇ amount exceeds 0.8%, the magnetic flux density of the product will decrease, so it was set to 0.8% or less.
• the slab heating temperature was limited to less than 1280 for the purpose of lowering the cost of the slab. It is preferably 1200 and the following.
• the heated slab is subsequently hot rolled into a hot rolled sheet.
• the hot rolling process usually consists of rough rolling and finish rolling in which a slab having a thickness of 100 to 400 ⁇ is heated and then passed in multiple passes.
• the method of rough rolling is not particularly limited, and the rough rolling is performed by a usual method.
• Finish rolling is usually performed by high-speed continuous rolling of 4 to 10 passes. The rolling speed is usually 100 to 3000 mZmin, and the time between passes is 0.01 to 100 seconds.
• the steel plate temperature is lowered by water cooling, which is usually followed by air cooling, and it is wound into a coil of 5 to 20T0N.
• the feature of the present invention lies in this winding step. Is adjusted to below 600 for the coiling temperature after hot rolling is to obtain a product having a good magnetic flux density of ⁇ ⁇ ⁇ 1. 88 ( ⁇ ) as previously described
• the hot-rolled sheet is cold-rolled without performing hot-rolled sheet annealing.
• the reduction rate was set to 80% or more because the reduction rate was within the above range, and the sharp ⁇ 110 ⁇ ⁇ 001> -oriented grains in the decarburized plate and the corresponding orientations that were easily eaten by silkworms This is because it is possible to obtain an appropriate amount of grains ( ⁇ 111 ⁇ and 112> orientation grains, etc.), which is preferable for increasing the magnetic flux density.
• the steel sheet After cold rolling, the steel sheet is subjected to decarburization annealing, application of an annealing separator, and finish annealing in the usual manner to become the final product.
• nitriding is performed at a stage after hot rolling to completion of secondary recrystallization at the time of final finish annealing, but the nitriding step, method, and the like are not particularly limited.
• any method such as a method of nitriding the steel plate and a method of nitriding by increasing the nitrogen partial pressure of the final annealing atmosphere gas may be used.
• the resulting 40 mm thick slab was heated at a temperature of 1150, then hot rolled at 1040 :, and hot rolled in 6 passes to form a 2.3 mm thick hot rolled sheet.
• the hot rolling end temperature was 905.
• the hot-rolled sheet was rolled at a rolling rate of about 85% without performing hot-rolled sheet annealing to obtain a 0.335-mm-thick cold-rolled sheet.
• the cold-rolled sheet to 830 * C x 150 seconds de charcoal blunt (soaking) subjected then, 750: x30 seconds by mixing the NH 3 gas during the annealing at atmosphere (soaking), ⁇ Was nitrided.
• the N content of the steel sheet after this annealing was 0.0195 to 0.0211 weight.
• an annealing separator containing MgO as a main component is applied to the plate after nitriding, and then the temperature is increased to 1200 at the speed of Z at 15 in an atmosphere gas of 25% S and 75% H 2. And then continue in H 2 100% : Final annealing was performed for 20 hours.
• Table 1 shows the process conditions and the magnetic properties of the products.
• the cold rolled sheet was subjected to decarburizing annealing at 830: for 120 seconds and then at 850 for 20 seconds, and then (a) 700 at X30 seconds.
• NH 3 gas was mixed into the atmosphere gas during annealing (soaking) to nitride ⁇ ⁇ (N content after nitriding: 0.0215 to 0.0240% by weight), and (b) two treatments without nitriding treatment were performed. Thereafter, an annealing separator containing MgO as a main component is applied, and then an atmosphere of N 2 15% and H 2 85% In a gaseous gas, the temperature was increased to 1200 at a speed of 15: Z, and then a final finish annealing was performed in a 100% H 2 atmosphere gas at 1200 for 20 hours.
• Table 2 shows the process conditions and the magnetic properties of the product.
• the N content after nitriding was 0.0185 to 0.0215% by weight.
• the MgO was coated with an annealing separator composed mainly of the ⁇ after nitriding, then, N 2 25%, in H 2 75% of the atmospheric gas, 20: at a rate of at Z was raised to 1200. Subsequently, final finish annealing was performed in which the atmosphere was kept at 1200: for 20 hours in a 100% H 2 atmosphere gas.
• Table 3 shows the process conditions and the magnetic properties of the product.
• the hot-rolled sheet was rolled at a rolling reduction of about 85% without performing hot-rolled sheet annealing to obtain a 0.335 mm thick cold-rolled sheet.
• the cold rolled sheet was held at 830 for 120 seconds, followed by decarburizing annealing at 890: for 20 seconds.
• An annealing separator composed mainly of thereafter MgO was coated, and then, N 2 25%, the temperature was raised to 880 at a rate of at 10 "CZ in H 2 75% of the atmospheric gas, then, N 2 75 %, H 2 in an atmosphere gas of 25%, at a rate of lO t Z up to 1200, and then a final finish annealing was performed in a 100% H 2 atmosphere gas at 1200 for 20 hours.
• Table 4 shows the process conditions and the magnetic properties of the products.
• the low-temperature slab heating is performed by controlling the winding temperature after hot rolling and performing nitriding at the stage until the completion of secondary recrystallization at the time of final finishing annealing after hot rolling.
• good magnetic properties can be obtained by one-time cold rolling without annealing.

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• 1990
  • 1990-04-13 JP JP2098267A patent/JPH0730397B2/ja not_active Expired - Fee Related
• 1991
  • 1991-04-15 KR KR1019910701850A patent/KR940008934B1/ko not_active IP Right Cessation
  • 1991-04-15 WO PCT/JP1991/000493 patent/WO1991016462A1/ja not_active Application Discontinuation
  • 1991-04-15 EP EP91906970A patent/EP0477384A1/en not_active Ceased
• 1995
  • 1995-07-13 US US08/502,238 patent/US5597424A/en not_active Expired - Fee Related

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