WO2019132420A1 - Tôle d'acier électrique mince et non orientée présentant d'excellentes propriétés magnétiques et procédé pour la fabriquer - Google Patents

Tôle d'acier électrique mince et non orientée présentant d'excellentes propriétés magnétiques et procédé pour la fabriquer Download PDF

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WO2019132420A1
WO2019132420A1 PCT/KR2018/016350 KR2018016350W WO2019132420A1 WO 2019132420 A1 WO2019132420 A1 WO 2019132420A1 KR 2018016350 W KR2018016350 W KR 2018016350W WO 2019132420 A1 WO2019132420 A1 WO 2019132420A1
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steel sheet
rolling
thickness
hot
relation
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PCT/KR2018/016350
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Korean (ko)
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공종판
정제숙
이세일
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주식회사 포스코
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    • 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
    • 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
    • C21D8/1233—Cold 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
    • C21D8/1272—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 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
    • C21D8/1277—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties involving a particular surface treatment
    • 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
    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/004—Dispersions; Precipitations
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

Definitions

  • the present invention relates to a non-oriented electrical steel sheet having excellent magnetic properties and shapes and a method for producing the same.
  • nonoriented electrical steel sheets are used for iron core materials in rotating equipment such as motors, generators, etc. that convert electrical energy into mechanical energy and stationary equipment such as small transformers.
  • the magnetic properties of the non-oriented electrical steel sheet have iron loss and magnetic flux density.
  • the iron loss is the loss energy, so the lower the better, the higher the magnetic flux density, the more magnetic field can be induced with the same energy. In order to obtain the same magnetic flux density, Since the current can be applied, it is possible to reduce the driving force.
  • Patent Document 1 the range of Si, Al, and Mn that can be rolled while sufficiently increasing the resistivity of the electrical steel sheet is limited, and an appropriate range of amounts of P, Sn, Sb, Mo, C, S, N, Ti,
  • the present invention provides a non-oriented electrical steel sheet excellent in high-frequency magnetic properties and a method of manufacturing the same.
  • Patent Document 2 the relationship between aluminum (Al) and sulfur (S) Directional electric steel sheet having improved magnetic properties and a manufacturing method thereof.
  • Patent Document 2 there is a limitation in manufacturing a hot rolled steel sheet as a manufacturing method in a conventional hot melt mill process.
  • Patent Document 1 Korean Patent Laid-Open Publication No. 2014-0062225
  • Patent Document 2 Korean Published Patent Application No. 2015-0149426
  • One aspect of the present invention is to provide a natural oriented non-oriented electrical steel sheet excellent in magnetic characteristics and shape and a method of manufacturing the same.
  • An embodiment of the present invention is a steel sheet comprising, by weight%, 0.0005 to 0.01% of C, 0.5 to 2.5% of Si, 0.03 to 1.0% of Al, 0.03 to 1.0% of Mn, 0.0005 to 0.01% 0.01 to 0.01%, balance Fe and other unavoidable impurities, wherein C, Si, Al, Mn, Ti and N satisfy the following relational formulas 1 to 3, the average grain size of ferrite is 25 to 80 ⁇ , Directional thickness deviation? T CR satisfies the following relational expression (4).
  • ⁇ t CR is the width direction thickness deviation ( ⁇ m) of the strip
  • S the thickness of the predetermined distance away from the point from the strip width direction edge (Mm)
  • t is the thickness (mm) of the strip.
  • a method of manufacturing a semiconductor device comprising: 0.0005 to 0.01% of C, 0.5 to 2.5% of Si, 0.03 to 1.0% of Al, 0.03 to 1.0% of Mn, 0.0005 to 0.01% Continuously casting molten steel containing C, Si, Al, Mn, Ti, and N satisfying the following relational expressions 1 to 3 to obtain a thin slab; Subjecting the thin slab to rough rolling to obtain a bar; Heating the bar to satisfy the condition of the following expression (6); Hot rolling the heated bar to obtain a hot rolled steel sheet; And winding the hot-rolled steel sheet, wherein each of the steps is carried out continuously, cold-rolling the rolled hot-rolled steel sheet to obtain a cold-rolled steel sheet; And a step of recrystallization annealing the cold-rolled steel sheet.
  • the present invention also provides a method for manufacturing a non-oriented steel sheet having excellent magnetic properties and shape.
  • the cold rolling reduction rate can be reduced compared to the conventional hot rolling mill process.
  • the magnetic flux density is higher than that of the conventional steel sheet,
  • the non-oriented electrical steel sheet of high efficiency can be produced.
  • FIG. 1 is a schematic view of a facility for a performance-rolling direct process that can be applied to the present invention.
  • FIG. 2 is another schematic diagram of a facility for a performance-rolling direct process that can be applied to the present invention.
  • FIG 3 is a schematic view showing a thickness measurement position and a widthwise thickness deviation at a position a certain distance from the edge in the strip width direction.
  • FIG. 4 is a schematic view for explaining the thickness variation in the width direction of the strip.
  • Fig. 6 is a result of examining the correlation between the S / t and the thickness deviation in the width direction of the final product strip for Inventive Examples 17 to 21 and Comparative Examples 16 to 19 according to an embodiment of the present invention.
  • the inventors of the present invention have found that there is a problem that the magnetic flux density of the electric steel sheet decreases and the iron loss increases when the reduction rate is increased during cold rolling. In order to cope with such a problem, it is conceivable to reduce the thickness of the thermal expansion layer and reduce the cold reduction rate in the cold rolling, thereby improving the magnetic flux density and the iron loss at the same time.
  • slabs having a thickness of 200 mm or more are produced through low-speed casting in a normal rolling process, and the produced slabs are reheated in a heating furnace and then hot-rolled in batches in units of one sheet, .
  • this type of batch rolling since the top portion is drawn into the rolling mill for each slab and the tail portion must escape from the rolling mill, frequent operating accidents occur frequently, .
  • the inventors of the present invention have pointed out that the problem of manufacturing such an electric steel sheet can be solved when a manufacturing process (mini-mill process) using a so-called thin slab, particularly a continuous casting (performance) Leading to the present invention.
  • the process of direct rolling of the steel to the rolling process is excellent in the material deviation because the width of the strip and the temperature deviation in the longitudinal direction are small due to the process characteristic of constant velocity isotherm.
  • unlike conventional processes in which the slabs or bars are finely rolled in batches only the first slab or the top portion of the bar is drawn between rolls and rolls of the rolling mill, It is possible to drastically reduce the possibility of a problem of accident involving the introduction of a slab or a bar.
  • it since it produces products through constant velocity isothermal rolling, it is considered to be a suitable process for manufacturing hot-rolled steel sheets because it has the advantages of excellent dimensional accuracy of thickness and width compared with existing batch materials and low crown crowns .
  • the electric steel sheet produced by the direct rolling process from the performance to the rolling has excellent performance in terms of the inner material as compared with the electric steel sheet produced by the conventional batch rolling method.
  • alloy composition of the electric steel sheet of the present invention will be described.
  • the alloy composition described below is based on weight percent unless otherwise specified.
  • the carbon (C) deteriorates the iron loss, so the smaller the carbon loss, the better.
  • C exceeds 0.01%, it is preferable that C is in a range of 0.01% or less from the standpoint that the iron loss increase is considerably increased. Since C is preferably as small as possible, C is not particularly limited, but it is preferable to control the lower limit to 0.0005% in consideration of decarburization cost. Therefore, the C content is preferably 0.0005 to 0.01%.
  • the content of C is more preferably 0.0007 to 0.0050%, and still more preferably 0.0010 to 0.0040%.
  • Silicon (Si) is generally added as a deoxidizing agent for steel, but an electric steel sheet is an important element because it has an effect of increasing the electrical resistance and reducing iron loss at high frequencies. In order to obtain such effect, addition of 0.5% or more is required . However, if it is more than 2.5%, cracks are generated during cold rolling, resulting in a reduction in the composition of the steel and a decrease in the magnetic flux density. Therefore, the upper limit is set to 2.5%. Therefore, the Si content is preferably 0.5 to 2.5%, more preferably 0.6 to 2.0%, still more preferably 0.8 to 1.6%.
  • Aluminum (Al) is generally used as a deoxidizing agent of steel in the same manner as Si, and is an element having a large effect of reducing iron loss by increasing electrical resistance. However, if it exceeds 1.0%, the casting may be interrupted because the physical properties of the mold flux are picked up in the mold flux during continuous casting and the lubrication is not achieved.
  • the Al content is preferably 0.03 to 1.0%, more preferably 0.05 to 0.8%, and even more preferably 0.1 to 0.6%.
  • Mn manganese
  • the Mn is preferably in the range of 0.03 to 1.0%, more preferably 0.05 to 0.8%, and most preferably 0.1 to 0.6%.
  • Titanium (Ti) is picked up from molten steel slag or picked up from alloy steel to be included in the steels of the present invention. It is preferable that the Ti is controlled to 0.01% or less since it forms carbides or nitrides to cause grain growth to deteriorate iron loss and promote undesired ⁇ 111 ⁇ texture development in magnetism.
  • the lower limit of the above-mentioned Ti is preferably as small as possible, and therefore the lower limit is not particularly limited, but is preferably limited to 0.0005% considering the level inevitably contained in the process. Therefore, the Ti content is preferably in the range of 0.0005 to 0.01%, more preferably 0.0008 to 0.06%, and even more preferably 0.01 to 0.03%.
  • the nitrogen (N) has a range of 0.01% or less.
  • the number of N is preferably as small as possible, and is not particularly limited. However, considering the denitrification cost, it is preferable to control the lower limit to 0.001%. Therefore, the content of N is preferably 0.001 to 0.010%, more preferably 0.0012 to 0.008%, and even more preferably 0.0014 to 0.006%.
  • C, Si, Al, Mn, Ti, and N satisfy the following relational expressions 1 to 3.
  • C, Si, Al, Mn, Ti and N in the following relational expression 1 means the content (weight%) of the corresponding element, respectively.
  • the value is preferably 1.2 to 3.0, more preferably 1.4 to 2.8, and even more preferably 1.6 to 2.6.
  • (C] + [N]) is more than 0.009 in the relational expression (2), carbon / nitride is generated, crystal grain growth does not occur well, and iron loss may become large. It is preferable that the above ([C] + [N]) is as low as possible, but it is preferably controlled to 0.003 or more in consideration of the cost of decarburization / denitrification. Therefore, in the above-mentioned formula 2, the value is preferably 0.003 to 0.009, more preferably 0.004 to 0.008, and still more preferably 0.005 to 0.007.
  • the value is preferably 0.15-0.85, more preferably 0.16-0.80, and even more preferably 0.17-0.75.
  • the remainder of the present invention is iron (Fe).
  • impurities which are not intended from the raw material or the surrounding environment may be inevitably incorporated, so that it can not be excluded. These impurities are not specifically mentioned in this specification, as they are known to any person skilled in the art of manufacturing.
  • the electrical steel sheet according to the present invention may further comprise a metal selected from the group consisting of Nb, V, Ti, Mo, Cu, Cr, Ni, Zn, Se, Sb, Zr, W, Ga, One or more of which may be contained in an amount of 0.2 wt% or less.
  • the tramp element is an impurity element derived from scrap used as a raw material in the steelmaking process, ladle, tundish refractory or the like. When the total amount exceeds 0.2%, the tramp element is liquefied at a high temperature to deteriorate performance , And precipitates may be formed to deteriorate magnetism.
  • the microstructure of the non-oriented electrical steel sheet according to the present invention is composed of 95% or more ferrite in an area fraction; And at least one selected from the group consisting of pearlite, precipitate, and inclusions in a total amount of 5% or less. If the ferrite area fraction is less than 95%, the percentage of pearlite, precipitate, and inclusions becomes relatively high, and even if annealing is performed after cold rolling, magnetic properties may be deteriorated.
  • the fraction of the ferrite is more preferably 97% or more, and still more preferably 98% or more.
  • the precipitate may be a single or composite carbonitride composed of Ti, Nb, V, Mo, C, and N, and may include a single or complex sulfide such as CaS, MnS, CuS, and MgS.
  • the individual materials may include a single or complex inclusion such as Al, Si, Ca, Nb, V, Ti, Mo, Cu, Cr, Ni, Zn, Se, Sb, Zr, W, Ga, .
  • the mean grain size of the ferrite is preferably 25 to 80 ⁇ ⁇ in terms of circle equivalent diameter.
  • the average size of the ferrite grains is less than 25 mu m, the grains do not grow sufficiently and magnetic properties deteriorate.
  • the average size of the ferrite grains exceeds 80 mu m, the magnetic flux density may be lowered.
  • Mu m more preferably 20 mu m to 70 mu m, still more preferably 25 mu m to 60 mu m.
  • the thickness variation ⁇ t CR in the width direction of the strip satisfies the following relational expression (4).
  • the following relational expression (4) it is possible to secure a superior appearance shape quality.
  • ⁇ t CR is the width direction thickness deviation ( ⁇ m) of the strip
  • S is a distance position (mm) the thickness measurement of the position apart from the strip width direction edges
  • t means a thickness (mm) of the strip.
  • the sum of the molar fraction (%) of TiC and Ti (C, N) preferably satisfies the following relational expression (5).
  • the sum of the mole fractions of TiC and Ti (C, N) precipitates exceeds 15 ⁇ 10 -5 (%) in the following formula 5, precipitates of TiC and Ti (C, N) (Martix), it may interfere with grain growth and increase iron loss.
  • the thickness of the non-oriented electrical steel sheet provided by the present invention is preferably 0.15 to 0.50 mm. When the thickness is less than 0.15 mm, the productivity is lowered. When the thickness is more than 0.5 mm, the iron loss reducing effect may be small.
  • the electric steel sheet of the present invention provided as described above has a magnetic flux density (B50) of 1.70 to 1.74 T and an iron loss (W15 / 50) of 4.0 to 5.3 W / kg.
  • the magnetic flux density (B50, T) is the magnetic flux density induced in the magnetic field of 5000 A / m and the iron loss (W15 / 50) is the average of the rolling direction and magnetic flux density perpendicular to the rolling direction when magnetic flux density of 1.5 Tesla is induced at 50 Hz frequency Loss (W / kg).
  • an expensive segregation element must be additionally added to increase the manufacturing cost.
  • the magnetic flux density is less than 1.70, sufficient magnetic properties can not be secured.
  • FIG. 1 is a schematic view of a facility for a performance-to-rolling direct process that can be applied to the present invention, and is a schematic diagram of a performance-to-rolling direct process facility applicable to the manufacture of hot rolled steel sheets for obtaining a final electrical steel sheet.
  • the steel slabs of excellent shape quality according to one embodiment of the present invention can be manufactured from the hot-rolled steel sheets produced by applying the direct rolling-to-rolling direct connection equipment as shown in Fig.
  • the performance-to-rolling direct connection facility consists largely of a continuous casting machine 100, a roughing mill 400, and a finishing mill 600.
  • the performance-to-rolling direct connection plant comprises a high-speed continuous casting machine (100) producing a thin slab (a) of a first thickness and a rolling bar (b) of a second thickness thinner than the first thickness
  • a roughing scale breaker 300 and a finishing mill scale breaker 500 are placed in front of the roughing mill 400 and before the finishing mill 600, FSB '), and it is possible to produce an electrical steel sheet having excellent surface quality in the post-process because of easy removal of the surface scale.
  • FIG. 2 is another schematic diagram of a facility for a performance-rolling direct process that can be applied to the present invention.
  • the apparatus for direct rolling-to-rolling process disclosed in FIG. 2 is substantially identical in construction to the apparatus disclosed in FIG. 1, but includes a heater 200 'for further heating a slab in front of the rough rolling mill 400, It is possible to lower the occurrence of edge defects and is advantageous in securing the surface quality. In addition, a space of at least one slab length is secured before the roughing mill, and batch rolling is possible.
  • the hot rolled steel sheet having excellent magnetic properties and shapes of the present invention can be produced in all of the performance-rolling direct connection facilities disclosed in Figs. 1 and 2.
  • the continuous casting is preferably performed at a casting speed of 4.0 to 8.0 mpm (m / min).
  • the reason why the casting speed is set to 4.0 mpm or more is that a high speed casting and rolling process are connected and a casting speed higher than a certain level is required to secure the target rolling temperature.
  • the casting speed is less than 4.0 mpm, the amount of pick-up in the mold flux is increased to change the physical properties of the mold flux, so that the lubricating action may be reduced and casting may be interrupted. If it exceeds 8.0 mpm, the operation success rate may be reduced due to instability of the molten steel bath surface. Therefore, the casting speed is preferably in the range of 4.0 to 8.0 mpm, more preferably in the range of 4.2 to 7.6 mpm , And more preferably 4.5 to 7.2 mpm.
  • the thickness of the thin slab is preferably 60 to 120 mm.
  • the thickness of the thin slab is more than 120 mm, high-speed casting is difficult, and the rolling load during rough rolling is increased.
  • the thickness is less than 60 mm, the temperature of the cast steel is rapidly decreased and uniform texture is hardly formed.
  • the thickness of the thin slab is preferably controlled to 60 to 120 mm, more preferably 80 to 120 mm, and even more preferably 90 to 110 mm.
  • the inlet side temperature during the rough rolling may be 1000 to 1200 ° C. If the rough rolling inlet temperature is less than 1000 ⁇ , an increase in the rough rolling load and cracks may occur in the edges of the bars. On the other hand, if it is higher than 1200 ° C, the hot-rolled scale remains and the quality of the hot-rolled surface may deteriorate. Therefore, the inlet temperature during rough rolling is preferably 1000 to 1200 ° C, more preferably 1020 to 1180 ° C, and even more preferably 1040 to 1160 ° C.
  • the temperature at the time of rough rolling may be 900 ° C or higher. If it is less than 900 ° C, it is difficult to secure the finishing rolling temperature.
  • the rolling speed in the rough rolling may be 20 to 50 mpm. If the rolling speed is more than 50mpm during rough rolling, the performance is lowered because the performance-rolling is directly connected and problems occur in the performance process. On the other hand, in the case of less than 20 mpm, it is difficult to secure the temperature during finish rolling, and it is difficult to obtain rolling load and uniform structure. Accordingly, the rolling speed in rough rolling is preferably 20 to 50 mpm, more preferably 25 to 45 mpm, and even more preferably 30 to 40 mpm.
  • the bar is heated so as to satisfy the condition of the following expression (6).
  • the reason why the heating temperature of the bar is precisely controlled is to control precipitates such as TiC and Ti (C, N) which adversely affect the iron loss, and the heating temperature of the bar is 106.2 x ([Ti] / N))) + 1294.7 ( ⁇ ⁇ ), the precipitates of TiC and Ti (C, N) are reused and finely re-precipitated at the finish rolling to prevent the grain growth during final annealing due to the pinning effect which can adversely affect iron loss.
  • the heating temperature of the bar is less than 950 ° C, the finish rolling-out temperature becomes low, so that the rolling load increases sharply and plate breakage may occur due to poor ductility.
  • the heated bar is hot-finished and rolled to obtain a hot-rolled steel sheet.
  • the finish rolling can be performed in a finishing mill having 3 to 6 stands.
  • the finish rolling is preferably performed at 650 to 900 ° C. If the finish rolling temperature exceeds 900 ° C, austenite and ferrite transformation occur at the same time, so that the pressure load fluctuation is significant, and plate breakage may occur due to poor ductility. On the other hand, when the temperature is lower than 650 ° C, the strength of the steel increases rapidly during rolling, which may lead to plate breakage due to poor ductility due to an increase in the rolling load.
  • finishing rolling is precisely controlled at a temperature of 650 ° C to 900 ° C, and furthermore, finishing rolling is carried out at a temperature having a single-phase ferrite structure.
  • the finishing rolling temperature is more preferably 670 to 880 ⁇ , and still more preferably 700 to 850 ⁇ .
  • the average passing speed during the final rolling at the time of the hot rolling is 250 to 750 mpm.
  • the passing speed in the last rolling mill can be directly connected to the casting speed and the thickness of the hot rolled product. If the rolling speed in the last rolling mill is more than 750 mPm, it is possible to cause an accident such as a plate rupture, and since a uniform temperature is not secured due to difficulty in isothermal constant rolling, a material and thickness variation may occur . On the other hand, in the case of less than 250 mpm, the final rolling speed is too slow, which may cause problems in mass balance and heat balance, and it may be difficult to carry out continuous continuous rolling. Accordingly, the average passing speed during the final rolling at the time of the hot rolling is preferably 250 to 750 mpm, more preferably 270 to 730 mpm, and still more preferably 300 to 700 mpm.
  • the speed deviation it is preferable to control the speed deviation to 50 mpm or less during the production of one strip in the final rolling in the hot rolling. If the difference in speed of the last rolling mill exceeds 50 mpm, the temperature and rolling load become uneven, resulting in material and thickness variations of the hot rolled steel sheet, and uneven rolling during cold rolling can increase the thickness variation of the final product.
  • the speed deviation is preferably 50 mpm or less, more preferably 45 mpm or less, and even more preferably 40 mpm or less.
  • lubricating oil is applied to the surface of the bar to decrease the friction coefficient between the bar and the rolling roll, thereby reducing the rolling load, thereby reducing the thickness deviation.
  • the lubricating oil is applied in the first rolling mill having a very high rolling load during the hot finishing rolling.
  • the lubricating oil is preferably applied to the surface of the bar at a rate of 5 to 30 L / min per 1 m2. When the application of the lubricating oil is less than 5 L / min, the above-mentioned effect is insignificant.
  • the lubricating oil is more than 30 L / min per 1 m < 2 > Therefore, it is preferable that the lubricant is applied to the surface of the bar at a rate of 5 to 30 L / min per 1 m 2, more preferably 7 to 28 L / min per 1 m 2, and more preferably 10 to 30 L / desirable.
  • the coiling temperature is preferably 500 to 650 ° C.
  • the coiling temperature is less than 500 ⁇ , the crystal grain size becomes too small and crystal grains do not sufficiently grow even after the annealing. Hysteresis loss may increase as hysteresis loss increases.
  • the coiling temperature exceeds 650 ⁇ , fine precipitates increase, Can be lowered. Therefore, the coiling temperature is preferably 500 to 650 ° C, more preferably 520 to 630 ° C, and still more preferably 540 to 610 ° C.
  • the hot-rolled steel sheet preferably has a thickness of 1.6 mm or less. As the thickness of the hot-rolled steel sheet decreases, the recrystallized texture increases, thereby ensuring a uniform structure after the annealing. It is possible to improve the magnetic properties by decreasing the cold rolling reduction rate. It may not be enough. Therefore, the thickness of the hot-rolled steel sheet is preferably 1.6 mm or less. The thickness of the hot-rolled electrical steel sheet is more preferably 1.4 mm or less.
  • the thickness deviation? T HR in the width direction of the strip satisfies the following relational expression (7).
  • ⁇ t HR is a width direction thickness of a hot rolled steel sheet deviation ( ⁇ m)
  • S is a predetermined distance position (mm) the thickness measurement of the position apart from the strip width direction edges, also t means a thickness (mm) of the strip .
  • the above-described method for producing a hot-rolled steel sheet is characterized in that the above-described respective steps are performed continuously by using the continuous rolling mode in the performance-to-rolling direct connection process.
  • the reduction ratio in the cold rolling is preferably in the range of 50 to 80%. If the reduction rate is less than 50% in the cold rolling, the reduction rate is too small to recrystallize sufficiently. When the reduction rate exceeds 80%, the reduction rate is high and the crystal grains become too fine, Can be increased. Therefore, the reduction ratio in the cold rolling is preferably in the range of 50 to 80%, more preferably 52 to 78%, still more preferably 54 to 76%.
  • a step of pickling the hot-rolled steel sheet to remove the oxide layer may be further included.
  • the pickling can be carried out under ordinary conditions, and the pickling treatment that can be used in the present invention is not particularly limited as long as it is applicable to any treatment method used in the process of pickling an electrical steel sheet.
  • the cold-rolled steel sheet is subjected to final recrystallization annealing at 750 to 950 ⁇ ⁇ . If the final recrystallization annealing temperature is less than 750 ⁇ , recrystallization does not sufficiently take place. If the final annealing temperature of the recrystallization exceeds 950 ⁇ , rapid growth of crystal grains occurs, magnetic flux density becomes low and high frequency iron loss becomes high.
  • the temperature is preferably 750 to 950 ⁇ ⁇ , more preferably 770 to 930 ⁇ ⁇ , and even more preferably 790 to 900 ⁇ ⁇ .
  • the molten steel having the alloy composition shown in the following Table 1 was prepared, and the molten steel was continuously cast at a casting speed of 5.4 to 6.2 mpm by applying a direct rolling process to a rolling to a rolling to obtain a thin slab having a thickness of 90 to 100 mm,
  • the bars were subjected to heat treatment under the manufacturing conditions described in Table 2, followed by finish rolling to obtain hot rolled steel (HR) having a thickness of 1.4 mm and cold rolling at a reduction ratio of 75%
  • HR hot rolled steel
  • a cold-rolled steel sheet having a thickness of 0.35 mm was produced, followed by annealing to produce a final product.
  • Annealing conditions at the time of annealing were such that line speed (Line Speed): 170mpm, heating zone temperature: 780 ° C, and crack zone temperature: 830 ° C.
  • Table 3 shows the results of the measurement of the occurrence of plate fracture, the microstructure and the magnetic properties of the inventive and comparative examples prepared as described above.
  • the precipitation temperature / solution temperature and molar fraction of TiC and Ti were measured using thermo-Calc software (DATABASE: TCFE6) The results are shown in Table 3.
  • the ferrite fraction of the HR material was an average value of the area fraction obtained by measuring 10 field-of-view with 100 times and 500 times magnification at 1/4 point of the specimen thickness using an optical microscope
  • the size of the ferrite grain size of the final product after annealing was measured at a magnification of 200 times and a magnification of 500 times at a 1/4 point of the thickness of the specimen and the average value of all the circle equivalent diameters calculated
  • the magnetic properties of magnetic flux density and core loss were measured by cutting three or more specimens of 60mm * 60mm for each specimen, measuring the magnetic properties in the rolling direction and the vertical direction with a single sheet tester, Respectively.
  • B50 is the magnetic flux density induced in the magnetic field of 5000 A / m
  • the iron loss (W15 / 50) is the average loss (W / kg) in the rolling direction and in the direction perpendicular to the rolling direction when magnetic flux density of 1.5 Tesla is induced at 50 Hz frequency ).
  • Inventive Samples 1 to 12 satisfying all of the alloy compositions, the relational expressions 1 to 3 and the manufacturing conditions proposed in the present invention are designed to satisfy all of the target microstructure fraction, Satisfactory.
  • Comparative Examples 1 to 11 do not satisfy at least one of the relational expressions 1 to 3, so that it is impossible to obtain the ferrite grain size and fraction and the molar fraction of TiC and Ti (C, N) The magnetic flux density is low, and the iron loss is high.
  • the molten steel having the alloy composition of Inventive Steel 5 (Steel E) of Example 1 was prepared, and then the molten steel was continuously cast at a casting speed of 5.8 mpm by applying a direct rolling process to obtain a thin slab having a thickness of 90 mm, The slabs were roughly rolled to prepare bars. The bars were subjected to heat treatment under the manufacturing conditions described in Table 4, followed by finish rolling to obtain hot rolled steel (HR) having a thickness of 1.4 mm and a reduction ratio of 75% To prepare a cold-rolled steel sheet having a thickness of 0.35 mm and then subjected to annealing to produce a final product.
  • HR hot rolled steel
  • Annealing conditions at the time of annealing were such that line speed (Line Speed): 170mpm, heating zone temperature: 780 ° C, and crack zone temperature: 830 ° C.
  • Line Speed Line Speed
  • the microstructure and magnetism of the fabricated inventive and comparative examples were measured, and the results are shown in Table 5, and the measurement was performed in the same manner as in Example 1.
  • the target magnet is secured by heating the bar at a temperature at which the precipitates of TiC and Ti (C, N) are not dissolved.
  • Comparative Examples 14 and 15 were lower than the heating temperature proposed in the present invention, so that the finish rolling temperature became too low, resulting in a break in the sheet due to an increase in the rolling load, resulting in a break in the plate.
  • the widthwise thickness deviation means a difference between the thickness of the center portion in the width direction (C t ) of the strip and the thickness average of both edges [(E1x t + E2x t ) / 2] This means that the appearance quality of the recorded strip is excellent. Also, the widthwise thickness deviation of the thermal laminate and the final product means the average value of the top and tail. 4 is a schematic view for explaining the thickness variation in the width direction of the strip.
  • Comparative Examples 16 and 17 do not satisfy the lubricating oil application amount proposed by the present invention
  • Comparative Examples 18 and 19 show that the rate deviation in the final rolling does not satisfy the conditions of the present invention, The load deviation was large, and it was found that the thickness deviation in the widthwise direction was severely generated in both the thermal laminate and the final product.
  • FIG. 5 shows the results of examining the correlation between the S / t and the widthwise thickness deviation of the heat-shrinkable strips for Examples 17 to 21 and Comparative Examples 16 to 19.
  • FIG. 6 shows the relationship between S / t and the final product strip And the thickness variation in the width direction of the film. As can be seen from Figs. 5 and 6, it can be seen that inventive steels (inventive examples 17 to 21) have a smaller thickness variation in the width direction than the comparative steels (comparative examples 16 to 19).

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Abstract

Un mode de réalisation de la présente invention concerne une tôle d'acier électrique mince et non orientée présentant de très bonnes formes et propriétés magnétiques, la tôle d'acier électrique comprenant : de 0,0005 à 0,01 % en poids de C ; de 0,5 à 2,5 % en poids de Si ; de 0,03 à 1,0 % en poids d'Al ; de 0,03 à 1,0 % en poids de Mn ; de 0,0005 à 0,01 % en poids de Ti ; de 0,001 à 0,01 % en poids de N ; le reste étant du Fe et d'autres impuretés inévitables et la taille moyenne des grains de ferrite allant de 25 à 80 µm.
PCT/KR2018/016350 2017-12-26 2018-12-20 Tôle d'acier électrique mince et non orientée présentant d'excellentes propriétés magnétiques et procédé pour la fabriquer WO2019132420A1 (fr)

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EP4296392A4 (fr) * 2021-02-19 2024-06-05 Nippon Steel Corporation Tôle d'acier laminé à chaud pour tôle d'acier électromagnétique non orientée ainsi que procédé de fabrication de celle-ci, et procédé de fabrication de tôle d'acier électromagnétique non orientée

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