WO2024012439A1 - 一种用于低铁损取向硅钢板的激光刻痕方法及取向硅钢板 - Google Patents

一种用于低铁损取向硅钢板的激光刻痕方法及取向硅钢板 Download PDF

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WO2024012439A1
WO2024012439A1 PCT/CN2023/106738 CN2023106738W WO2024012439A1 WO 2024012439 A1 WO2024012439 A1 WO 2024012439A1 CN 2023106738 W CN2023106738 W CN 2023106738W WO 2024012439 A1 WO2024012439 A1 WO 2024012439A1
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silicon steel
oriented silicon
steel plate
laser
focused
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PCT/CN2023/106738
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English (en)
French (fr)
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赵自鹏
李国保
向邦林
马长松
孙焕德
吴美洪
吉亚明
凌晨
刘海
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宝山钢铁股份有限公司
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Publication of WO2024012439A1 publication Critical patent/WO2024012439A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/067—Dividing the beam into multiple beams, e.g. multifocusing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/073—Shaping the laser spot
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/073—Shaping the laser spot
    • B23K26/0736—Shaping the laser spot into an oval shape, e.g. elliptic shape
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/362—Laser etching
    • 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

Definitions

  • the invention relates to a manufacturing process of oriented silicon steel, and in particular to a laser scoring method for oriented silicon steel plates.
  • the transformer loss accounts for about 40% of the total loss.
  • the iron core made of oriented silicon steel material is the core component of the transformer, and its loss accounts for about 20% of the total loss.
  • This loss caused by the transformer core is often referred to as iron loss. Therefore, reducing the iron loss of the oriented silicon steel used to prepare the transformer core has huge economic and social benefits.
  • oriented silicon steel is named because its internal grain arrangement direction is roughly the same as the rolling direction of the steel plate.
  • grain-oriented silicon steel sheets since the grains are arranged in the direction of easy magnetic conduction, the higher the grain orientation, the better the magnetic properties of the silicon steel sheets. Specifically, the higher the magnetic induction, the lower the iron loss.
  • Inside the grains of oriented silicon steel there is a magnetic domain structure produced by the spontaneous magnetization of ferromagnets. The magnetic moments of the atoms inside each magnetic domain are spontaneously arranged in parallel to form a 180° magnetic domain, which is parallel to the easy magnetization direction of the grains ⁇ 110 ⁇ 001>.
  • Adjacent magnetic domains are opposite 180° magnetic domains, and there are magnetic domain walls with dozens to hundreds of atomic layers between them. During the magnetization process, the magnetic moments in adjacent magnetic domains move in the same direction through the magnetic domain walls, thereby achieving the magnetic permeability function. Therefore, the magnetic domain structure is the result of the principle of minimum energy action and is the basic element affecting the loss, magnetic induction and magnetostrictive properties of oriented silicon steel.
  • the magnetic permeability function of the silicon steel sheet is specifically represented by magnetic induction, which is generally characterized by B 8 , that is, the magnetic flux density of the silicon steel sheet under an excitation magnetic field of 800A/m, and its unit is T; iron loss is generally represented by P 17/50 represents the ineffective electric energy consumed by the magnetization of the silicon steel sheet when the magnetic flux density in the strip reaches 1.7T under an AC excitation field of 50Hz. Its unit is W/kg.
  • the iron loss of oriented silicon steel sheets specifically includes three parts: hysteresis loss, eddy current loss and abnormal eddy current loss. Among them, hysteresis loss occurs during the magnetization and demagnetization process of magnetic materials.
  • Energy loss is caused by factors such as inclusions, crystal defects, internal stress, and crystal orientation in the material that hinder domain wall movement, causing the change of magnetic flux to be blocked, resulting in a hysteresis phenomenon in which the magnetic induction intensity lags behind the change in magnetic field intensity; eddy current loss is caused by oriented silicon steel During the alternating magnetization process of the oriented silicon steel sheet, the change in magnetic flux induces local electromotive force and causes energy loss caused by eddy current, which is related to the conductivity and thickness of the oriented silicon steel sheet. Correspondingly, the abnormal eddy current loss is caused by the eddy current loss when the oriented silicon steel sheet is magnetized. The energy loss caused by different magnetic domain structures is mainly affected by the magnetic domain width.
  • the above-mentioned method (3) has received the most attention and is one of the current research hotspots in this field.
  • the following is a brief description of the principle of scoring and refining magnetic domains to reduce iron loss in the above method (3):
  • the magnetic moment is driven by an external field to rotate, and the magnetic domain wall migration causes adjacent magnetic domains to engulf each other, thereby achieving the magnetic permeability function.
  • the differences in magnetic domain structures in different regions during the migration of magnetic domain walls cause micro-eddy currents to be generated in micro-regions, thus producing eddy current losses. This part of the loss is called abnormal eddy current loss Pa in grain-oriented silicon steel.
  • the abnormal eddy current loss Pa is directly related to the inherent magnetic domain structure of oriented silicon steel, which is further directly related to the magnetic domain width. Therefore, reducing the magnetic domain width can effectively reduce the abnormal eddy current loss Pa.
  • the abnormal eddy current loss Pa accounts for a large proportion of the overall loss of oriented silicon steel, especially for thin gauge oriented silicon steel with a thickness of 0.23mm and below, the abnormal eddy current loss Pa accounts for more than 40%. Therefore, the use of scoring to refine the magnetic domains of grain-oriented silicon steel, that is, to reduce the width of the magnetic domains, can effectively reduce abnormal eddy current losses, thereby reducing the overall iron loss of grain-oriented silicon steel.
  • stress-relieving annealing scoring which uses laser, plasma beam, electron beam, etc. to form linear thermal stress zones at a certain distance on the surface, thereby reducing the width of the main magnetic domain and reducing iron loss. Since linear thermal stress will disappear due to stress relief annealing, this type of product is generally used in manufacturing without stress relief. Annealed laminated core transformer. The other type is resistant to stress relief annealing scoring.
  • the basic technical solution is to use mechanical gear rollers, electrochemical etching and other means to form linear strain areas or grooves on the surface of oriented silicon steel to reduce the 180° magnetic domain width, thereby reducing Iron loss. Since the strain zone does not change after stress relief annealing, this type of product can be used to manufacture wound core transformers that require stress relief annealing.
  • the publication number is CN1216072A
  • the publication date is May 5, 1999
  • the Chinese patent document titled "Grain-oriented electrical steel sheet with excellent magnetic properties and its production process and equipment” discloses a non-damaging
  • the method of laser heat-resistant scoring of oriented silicon steel on the surface film realizes a stress zone with a large depth closed domain area by controlling the spot size, energy density and other parameters of the incident laser to reduce the iron loss and magnetostriction of the oriented silicon steel.
  • the publication number is CN101528951A
  • the publication date is September 9, 2009
  • the Chinese patent document titled "Unidirectional Electromagnetic Steel Plate with Excellent Iron Loss Characteristics” discloses a unidirectional electromagnetic steel plate with excellent iron loss characteristics.
  • the steel plate further takes into account the stress distribution state formed by laser notching, and performs fine control by controlling the integral value of the compressive residual stress generated by laser irradiation of the steel plate, thereby improving the iron loss improvement rate of laser notching.
  • the measurement of residual stress relies on offline detection methods such as X-ray diffraction, the detection cycle is long, so its application in actual large-scale production still faces certain difficulties.
  • the publication number is CN102477484A
  • the publication date is May 30, 2012
  • the Chinese patent document titled "A rapid laser scoring method” discloses a rapid laser scoring method, which passes through the upper and lower strips. The surface is scored at the same time in a staggered manner at equal intervals to ensure the uniformity of the iron loss improvement effect of the scoring.
  • the notches on the upper and lower surfaces require high-precision control of the vibration of the strip, and the spatial layout is relatively complex, making the implementation of this technical solution difficult.
  • the inventor found through extensive research that when laser marking is performed and laser irradiation is used to form local stress, local areas on the surface of the steel plate will cause the temperature to rise due to heat absorption. Since the thermal conductivity of silicon steel is isotropic, it is extremely difficult to obtain a thermal stress area that is deep in the thickness direction of the steel plate and narrow in the rolling width.
  • the present invention proposes a new temperature rise-controllable laser scoring method to ensure that the surface coating of the steel plate is not lost while effectively improving and reducing the orientation. Iron loss of silicon steel.
  • One of the purposes of the present invention is to provide a laser scoring method for oriented silicon steel plates.
  • This laser scoring method optimizes the design of its own process. It adopts a split-beam laser focusing scanning method, which can achieve the purpose of marking the oriented silicon steel plate without losing the surface of the oriented silicon steel plate. Coating conditions further improve magnetic domain refinement to reduce iron losses.
  • the oriented silicon steel plate made by this laser scoring method has the characteristics of low iron loss and coating resistance to breakdown. It can be used to manufacture energy-saving ultra-high voltage transmission network transformers and has broad application prospects.
  • the present invention provides a laser scoring method for oriented silicon steel plates, which corresponds to each length along the rolling direction of the oriented silicon steel plates when performing surface laser scoring on the oriented silicon steel plates.
  • laser beam splitting is used to form multiple focused spots on the surface of the oriented silicon steel plate.
  • the multiple focused spots are arranged along the width direction of the oriented silicon steel plate, and have energy gap areas between them; each focused spot is along the
  • the dimension b in the width direction of the oriented silicon steel plate is larger than the dimension a along the length direction of the oriented silicon steel plate.
  • corresponding to the length position along the rolling direction of the oriented silicon steel plate means that relative to the rolling direction of the steel plate, the laser focused spot is elongated in the width direction of the steel plate, and the long spot shape is scanned to form a score line s position.
  • the inventor innovatively designed a new composite laser marking method to achieve the conflict between the damage improvement effect of oriented silicon steel and the laser energy required to prevent damage to the surface coating of oriented silicon steel. While coating, its iron loss reduction effect is further improved.
  • the inventor studied in detail the temperature rise phenomenon caused by the irradiation of the steel plate surface during the laser marking process, and found that because the local micro-area on the steel plate surface continuously receives laser irradiation, the temperature of this area continues to rise. When the temperature in this area rises to the damage threshold of the surface coating, the surface coating of the steel plate will also crack due to excessive temperature.
  • the heat irradiated by the laser in the local micro area of the silicon steel surface is still continuous.
  • the residence time is It is on the microsecond level, so there is still a problem that excessive temperature rise can easily cause damage to the surface insulating film.
  • the inventor used beam splitting to divide the incident beam into several beams when designing the laser marking method of the present invention, and strictly controlled the spacing of the formed focused spots in the laser scanning direction. and the energy distribution of each spot, so as to realize the temperature rise of the steel plate surface produced by laser irradiation Control, forming a larger thermal stress zone in the thickness range of the steel plate, which can not only increase the iron loss improvement rate of the oriented silicon steel plate before relative notching to 15% or even higher, but also avoid the effects of excessive temperature rise. Damage to the film on the surface of the steel plate.
  • the focused spot is elliptical or rectangular.
  • the focused spot formed by the laser can be specifically realized by one or more combinations of diffractive beam splitters, polarizing beam splitters, etc., and the shape of the focused spot formed can be specifically: Oval or rectangular.
  • a plurality of focused light spots are formed in the width direction of the oriented silicon steel plate.
  • the total extended length D ⁇ 80mm.
  • the total length of the multiple focused light spots formed needs to be controlled within a certain range so that the total residence time is limited to a certain range.
  • the inventor determined after repeated experiments that the total extended length of multiple focused light spots arranged along the width direction of the oriented silicon steel plate can be preferably controlled to ⁇ 80 mm. When the total length exceeds 80mm, hysteresis loss will increase, resulting in an increase in total loss and a decrease in magnetic induction B8 .
  • the dimension a along the length direction of the oriented silicon steel plates is 10-100 ⁇ m.
  • the dimension b along the width direction of the oriented silicon steel plate is ⁇ 8 mm. If it exceeds 8mm, the total spot length will be difficult to control, and a longer residence time will accumulate heat and destroy the surface coating.
  • the distance between the forward focused light spot and the backward focused light spot is The ratio of the length of the energy gap area ds to the forward focused light spot in the scanning direction is between 0.5-2.
  • the size of the energy gap area between the focused light spots also has a direct impact on the temperature reduction formed during scanning.
  • the ratio of the energy gap area between each focused spot to the next focused spot and the length of the focused spot should be controlled between 0.5-2.
  • the length ratio is lower than 0.5, it is difficult to form an effective temperature reduction, and the surface coating of oriented silicon steel will crack; when the length ratio is high At 2 o'clock, the temperature drops too much, and it is difficult for the backward focused light spot to maintain the surface temperature of the steel plate in a range that generates sufficient thermal stress, and the effect of magnetic domain refinement and iron loss reduction cannot be achieved.
  • the power density p of each focused spot is 1000-3000W/mm 2 .
  • the present invention in order to achieve the purpose of reducing iron loss without damaging the surface coating, can further control the range of the power density p of the laser focus spot.
  • the power density exceeds 3000W/ mm2 , excessive laser energy will cause damage to the surface coating of the oriented silicon steel plate; when the power density is lower than 1000W/ mm2 , the laser energy is too low, and it will be difficult to damage the surface coating of the oriented silicon steel plate.
  • An effective thermal stress zone is formed on the surface, which is not enough to form a magnetic domain refinement effect, and the iron loss improvement rate is low.
  • the power density ratio of the backward focused light spot and the forward focused light spot is 0.75-0.95.
  • the ratio is lower than 0.75, the energy carried by the subsequent focused spot is too little.
  • the surface temperature of the steel plate begins to gradually decrease after the initial laser spot scan, making it difficult to form an effective thermal stress zone.
  • the effect of magnetic domain refinement on reducing iron loss is limited. ;
  • the ratio is higher than 0.95, the energy carried by the backward focusing spot is too large, the surface temperature of the steel plate gradually increases, and the damage threshold of the surface coating will still be reached.
  • the plurality of focused light spots are formed through at least one of a diffraction beam splitter and a polarization beam splitter.
  • another object of the present invention is to provide a oriented silicon steel plate, which has the characteristics of low iron loss and a coating that is resistant to breakdown. It can be used to manufacture energy-saving ultra-high voltage transmission network transformers and has Very broad application prospects.
  • the present invention provides a oriented silicon steel plate, which is produced by the above-mentioned laser scoring method of the present invention.
  • the steel with a certain Si content can be first subjected to iron making, steel making, continuous casting, and then hot rolling, and then cold rolling once or twice including intermediate annealing. , rolling steel into silicon steel sheets with target thickness.
  • the prepared silicon steel sheet is controlled to undergo decarburization annealing to form a primary recrystallized steel sheet with an oxide film on the surface; after being coated with a magnesium oxide release agent, the silicon steel sheet is further annealed at high temperature to form a Gaussian texture through secondary recrystallization.
  • the surface oxide film reacts with the release agent to form a magnesium silicate bottom layer.
  • the silicon steel sheet undergoes hot drawing, flat annealing, coating and baking processes, and then the surface of the steel sheet is The laser marking of the present invention is applied to the surface to produce a finished oriented silicon steel sheet.
  • the improvement rate of the iron loss before scoring is increased to more than 15%.
  • the laser scoring method for low iron loss oriented silicon steel plate and the oriented silicon steel plate of the present invention have the following beneficial effects:
  • the inventor designed a new laser scoring method.
  • This optimized laser scoring method is used to form a thermal stress zone, which can realize the temperature rise control of the steel plate, thereby reducing the iron loss of the oriented silicon steel plate. , without damaging the surface coating of the scored area.
  • the laser marking method of the present invention When specifically implementing the laser marking method of the present invention, it can form multiple focused spots on the surface of the steel plate by using laser beam splitting, and the power density of each focused spot can be controlled between 1000-3000W/ mm2 ; correspondingly At each length position along the rolling direction of the oriented silicon steel plate, the length ratio of the energy gap area and the corresponding focused spot in the scanning direction can be controlled between 0.5-2; at the same time, along the direction of laser scanning, the length ratio The power density ratio of the row focused light spot and the forward focused light spot can be controlled between 0.75-0.95.
  • the laser marking method designed in the present invention due to the existence of energy gap areas between the focused spots of the laser beams, it can effectively avoid the continuous heating of the surface caused by the continuous accumulation of laser thermal irradiation, thus ensuring that the surface is engraved
  • the coating in the traced micro-region is complete and improves the effect of magnetic domain refinement and iron loss reduction, and its iron loss improvement rate is increased to more than 15% compared with that before scoring.
  • the prepared low iron loss oriented silicon steel plate can be used to manufacture energy-saving ultra-high voltage transmission network transformers, which has broad application prospects.
  • Figure 1 is a schematic diagram of the laser scoring method according to the present invention using laser beam splitting to form a focused spot and scanning the surface of the steel plate.
  • Figure 2 schematically shows a schematic diagram of the focused light spot according to the present invention focusing on the surface of the steel plate.
  • Figure 3 schematically shows the relationship between the irradiation time and the temperature change of the local micro-area on the surface of the steel plate when the laser scoring method of the present invention and the laser scoring method of the prior art are used to score the steel plate.
  • Figure 4 schematically shows a system architecture diagram of an optical path system for implementing the laser marking method of the present invention.
  • Figure 1 is a schematic diagram of the laser scoring method according to the present invention using laser beam splitting to form a focused spot and scanning the surface of the steel plate.
  • Figure 2 schematically shows a schematic diagram of the focused light spot according to the present invention focusing on the surface of the steel plate.
  • Figure 1 and Figure 2 provide a schematic diagram of the laser scoring method of the present invention using laser beam splitting to form multiple focused spots on the surface of the steel plate.
  • a plurality of focused spots 1, 2, 3...n-1, n can be formed on the surface of the steel plate.
  • Each focused spot is in the laser scanning direction (i.e., the width direction of the oriented silicon steel plate).
  • the sum of the lengths of each focused spot in the width direction of the oriented silicon steel plate is the total length D of the spot.
  • forward focused light spot and “rearward focused light spot” refer to any two adjacent focused light spots along the laser scanning direction. For example, if the laser scanning direction starts from spot 1 in Figure 2, spot 1 is the “forward focused spot” and spot 2 is the “backward focused spot”. Similarly, between light spot 2 and light spot 3, light spot 2 is the “forward focused light spot”, light spot 3 is the “rearward focused light spot”, and so on.
  • the length of each focused spot in the direction perpendicular to the laser scanning direction (ie, the length direction of the oriented silicon steel plate) can be set to a uniform value a.
  • the lengths of different focused light spots in the direction perpendicular to the laser scanning direction may also be different, but they all need to meet the laser power density range required by the present invention.
  • the laser scanning speed is very fast, reaching 100m/s or even higher.
  • the full scan of a steel plate with a width of about 1m only takes 0.01s or less. Therefore, in order to simplify the space layout in production, laser scanning is usually used.
  • the direction is roughly the same as the width direction of the steel plate.
  • Figure 3 schematically shows the relationship between the irradiation time and the temperature change of the local micro-area on the surface of the steel plate when the laser scoring method of the present invention and the laser scoring method of the prior art are used to score the steel plate.
  • the laser scoring method according to the present invention corresponds to the solid line in Figure 3; the laser scoring method in the prior art corresponds to the dotted line in Figure 3.
  • control parameters directly related to the effect of the present invention include: focused spot size a and b, power density p of each focused spot, focused spot gap ds, and the total spot length directly related to the total laser residence time. D (see Figure 2). It should be noted that the single laser beam of the continuous laser or pulse laser used in the prior art is divided into multiple laser beams through laser beam splitting to form a number of energy gap regions ds between each other. The focused spot can reduce the accumulated heat in the corresponding scored area on the steel plate surface during the laser scoring process.
  • the focused spot gap ds and the total spot length D which is directly related to the total laser residence time, they can be selected within any preferred range, as long as the marks are formed during the laser marking process. At the same time, it can effectively avoid the continuous heating of the steel plate surface caused by the continuous accumulation of laser thermal radiation.
  • the focused spot designed in the present invention has a smaller size a in the rolling direction of the steel plate (i.e., the length direction of the oriented silicon steel), thereby reducing the diffusion of laser irradiation heat in the rolling direction and avoiding hysteresis loss. increase.
  • the smaller the dimension a means the better the effect of the present invention.
  • the laser scanning range needs to cover the entire plate width direction, usually 900mm or more, a longer focal length is required, and in order to prevent the defocusing phenomenon caused by the fluctuation of the strip shape, a certain amount of laser scanning is required.
  • the focal depth is enough to cover the defocus deviation caused by plate shape fluctuations and strip jitter.
  • the lower limit of the focus spot size a is limited by the optical system and cannot be less than 10 ⁇ m.
  • the complexity of the optical system increases greatly, and multiple lasers need to be arranged simultaneously in the board width direction to complete laser marking across the entire board width direction.
  • the upper limit of the rolling direction size a of the focused spot is set to 100 ⁇ m. Beyond this value, heat diffuses in the rolling direction, that is, the thermal stress zone in the rolling direction area near the score increases, the hysteresis loss increases, and the total loss If it cannot be further reduced, the magnetic induction B8 will also be reduced.
  • the incident laser after the incident laser is split by a diffraction beam splitter and a polarization beam splitter, it can form a plurality of focused spots on the surface of the steel plate.
  • the focused spots are usually elliptical, that is, in the laser scanning direction (i.e., oriented silicon steel plate
  • the spot size b in the width direction is larger than the rolling direction size a. This is to make the laser energy Be as dispersed as possible to prevent excessive power density from damaging the surface coating.
  • the power density p of the focused light spot can specifically adopt the average value, and its definition is as follows:
  • the calculation formula for the area S of the focused spot can be specifically expressed as:
  • the laser can also form a rectangular spot through the beam shaper.
  • the long side of the rectangle is b, extending along the width direction of the steel plate; the short side of the rectangle is a, along the rolling direction of the steel plate (i.e., the orientation). length direction of the silicon steel plate).
  • the focused light spot being a rectangular light spot is the same as the technical solution of the present invention, and therefore is also within the protection scope of the present invention, and will not be described again here.
  • the present invention needs to strictly control the value range of the power density p of the laser focused spot.
  • the power density p exceeds 3000W/ mm2 , excessive laser energy will cause damage to the surface coating; when the power density p is lower than 1000W/ mm2 , the laser energy is too low, and it will be difficult to form on the surface of the oriented silicon steel plate.
  • the effective thermal stress zone is not enough to form a magnetic domain refinement effect, and the iron loss improvement rate is low. Therefore, in practical applications, the power density of each focused spot needs to be controlled between 1000-3000W/ mm2 .
  • the gap between adjacent focused light spots will cause a certain temperature drop, which can avoid surface coating damage caused by excessive temperature in the scanning area. Therefore, it is necessary to control the power distribution ratio between the rear focused light spot and the forward focused light spot and the energy gap area size ds.
  • the surface temperature of the steel plate begins to gradually decrease after the initial laser spot scan, making it difficult to form an effective thermal stress zone. The effect of magnetic domain refinement on reducing iron loss is limited; and when higher than When 0.95, the energy carried by the backward focusing spot is too large, the surface temperature of the steel plate gradually increases, and the damage threshold of the surface coating will still be reached.
  • the size of the energy gap area ds between the focused light spots also has a direct impact on the temperature reduction formed during scanning.
  • the ratio of the energy gap area between each focused spot to the next focused spot and the length of the focused spot in the scanning direction should be controlled between 0.5-2, that is The range should be 0.5-2. when When it is lower than 0.5, it is difficult to form an effective temperature reduction, and the surface coating of oriented silicon steel will crack; when When it is higher than 2, the temperature decreases too much, and it is difficult for the backward focused light spot to maintain the surface temperature of the steel plate in a range that generates sufficient thermal stress, and the effect of magnetic domain refinement and reduction of iron loss cannot be achieved.
  • the heat transfer of the oriented silicon steel plate has isotropic characteristics, if the total residence time of the laser is too long, the heat will diffuse in a larger range in the rolling direction of the steel plate, forming a larger heat wave. Stress zones, which increase hysteresis losses and reduce magnetic induction.
  • the total length of the multiple focused light spots formed needs to be controlled within a certain range so that the total residence time is limited to a certain range.
  • the inventor determined after repeated experiments that the total length D of multiple focused light spots extending in the width direction of the oriented silicon steel plate can be preferably controlled to be ⁇ 80 mm. When the total length exceeds 80mm, hysteresis loss will increase, resulting in an increase in total loss and a decrease in magnetic induction B8 .
  • Figure 4 schematically shows a system architecture diagram of an optical path system for implementing the laser marking method of the present invention.
  • FIG. 4 illustrates a system architecture diagram of an optical path system for implementing the laser marking method of the present invention.
  • Other ways to achieve the spectral focusing effect of the present invention are also within the scope of the present invention.
  • the optical path designed in Figure 4 after the laser beam 8 is emitted from the laser 1, it passes through the reflector 2 and the reflector 3, and then passes through the beam shaping system 4 to form a light with an elliptical energy distribution.
  • the beam then passes through the diffraction spectroscopic element 5 to form a plurality of beams, which pass through the scanning focusing mirror 6 and rapidly scan on the surface of the oriented silicon steel plate 7 to form a notch stress area 9.
  • the present invention has no special limitations.
  • the commonly used continuous laser in this field is a continuous laser with a wavelength of 1066 nm.
  • Other laser forms can also achieve the purpose of the present invention and are within the scope of the present invention, so they will not be described again here. .
  • the oriented silicon steel plates of Examples 1-7 and Comparative Examples 1-2 are produced using the following steps:
  • Grain-oriented silicon steel undergoes iron-making, steel-making, continuous casting, hot-rolling processes, and then is cold-rolled to a final thickness of 0.22mm. After a decarburization annealing process at 850°C, a surface oxide layer is formed and then coated on the surface. MgO isolation agent is rolled into steel coils and kept under high temperature annealing conditions of 1200°C for 20 hours. Afterwards, the unreacted residual MgO on the surface is cleaned and dried, and then an insulating coating is applied to the surface of the steel plate.
  • multiple focused spots are formed on the surface of the oriented silicon steel plate by laser beam splitting corresponding to each length position along the rolling direction of the oriented silicon steel plate.
  • the focused light spots are arranged along the width direction of the oriented silicon steel plate, and have energy gap areas between each other; wherein the size b of each focused light spot along the width direction of the oriented silicon steel plate is larger than the size a along the length direction of the oriented silicon steel plate;
  • the control size a is 10-100 ⁇ m; corresponding to each length position along the rolling direction of the oriented silicon steel plate, control the extension of multiple focused spots arranged along the width direction of the oriented silicon steel plate.
  • the total length D ⁇ 80mm; the ratio ds/b of the energy gap area length ds and the corresponding focused spot length b in the scanning direction is controlled to be between 0.5-2; the power density of each focused spot is controlled to be 1000-3000W/mm 2 ;
  • the power density ratio of the backward focused light spot and the forward focused light spot is controlled to be 0.75-0.95.
  • the lasers in Examples 1-7 and Comparative Examples 1-2 all use continuous single-mode fiber lasers with a wavelength of 1066 nm, which use customized diffractive optical elements to divide the beam into sub-sections with different parameters.
  • the beam is scanned on the surface of the steel plate to form a notched stress zone.
  • the comparative example does not use diffractive optical elements for light splitting, and adjusts the power density by adjusting the laser output power.
  • the laser scoring process used in the present invention is performed after the final annealing of the oriented silicon steel. Therefore, the present invention has no special limitations on the oriented silicon steel plate. In actual implementation, it is not limited to the oriented silicon steel made by the above process. plate.
  • Table 1 lists the specific process parameters of the oriented silicon steel plates of Examples 1-7 and Comparative Examples 1-2 in the above process.
  • the oriented silicon steel plates of Examples 1-7 have good iron loss and magnetic permeability after laser marking; The surface coating of the steel plate is not damaged, and the iron loss decreases significantly after the magnetic domain is refined. Compared with before notching, the iron loss improvement rate can reach more than 15%.

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Abstract

本发明公开了一种用于取向硅钢板的激光刻痕方法，采用该激光刻痕方法在对取向硅钢板进行表面激光刻痕时，对应于沿取向硅钢板的轧制方向上的每一个长度位置，均采用激光分束的方式在取向硅钢板表面形成多个聚焦光斑，该多个聚焦光斑沿取向硅钢板的宽度方向排布，并且彼此之间具有能量间隙区；其中每一个聚焦光斑沿取向硅钢板宽度方向的尺寸b均大于沿取向硅钢板长度方向的尺寸a。相应地，本发明还公开了一种取向硅钢板，其采用本发明上述的激光刻痕方法进行制得，且可以在降低取向硅钢铁损的同时，不损失表面涂层。

Description

一种用于低铁损取向硅钢板的激光刻痕方法及取向硅钢板 技术领域
本发明涉及一种取向硅钢的制造工艺，尤其涉及一种取向硅钢板的激光刻痕方法。
背景技术
近年来，随着全球能源环境问题日益突出，世界各国均普遍提高了相应能耗设备的能耗标准，以降低各类设备对能源的无功消耗。其中，在电力传输系统中，变压器损耗约占总损耗的40％，由取向硅钢材料制造而成的铁芯是变压器的核心部件，其损耗约占总损耗的20％左右。
这种由变压器铁芯所造成的损耗通常简称为铁损，由此，降低用于制备变压器铁芯的取向硅钢的铁损具有巨大的经济和社会效益。
众所周知，取向硅钢因其内部晶粒排列方向与钢板轧制方向大致相同而得名。在取向硅钢板中，由于晶粒排布方向为易导磁方向，因而晶粒取向度越高，硅钢片的磁性能越好，其具体表现为磁感越高，铁损越低。在取向硅钢的晶粒内部，存在由于铁磁体自发磁化而产生的磁畴结构，每个磁畴内部各原子磁矩自发平行排列，以形成180°磁畴，其平行于晶粒易磁化方向{110}<001>。相邻磁畴为反向180°磁畴，二者之间存在着由几十到数百个原子层的磁畴壁。在磁化过程中，相邻磁畴内的磁矩通过磁畴壁移动而排列方向相同，进而能够实现导磁功能。因此，磁畴结构是最小能量作用原理的结果，是影响取向硅钢铁损、磁感和磁致伸缩性能的基本要素。
需要说明的是，硅钢片的导磁功能具体表现为磁感，其一般用B8表征，即在800A/m的激励磁场下的硅钢片的磁通密度，其单位为T；铁损一般用P17/50表征，即在50Hz的交流励磁场下，带钢中磁通密度达到1.7T时硅钢片磁化所消耗的无效电能，其单位为W/kg。
在当前现有技术中，取向硅钢片的铁损具体包括：磁滞损耗、涡流损耗和反常涡流损耗三部分。其中，磁滞损耗是在磁性材料在磁化和反磁化过程中， 由于材料中夹杂物、晶体缺陷、内应力和晶体位向等因素阻碍畴壁运动，导致磁通变化受阻，造成磁感应强度落后磁场强度变化的磁滞现象而引起的能量损耗；涡流损耗是取向硅钢片在交变磁化过程中，磁通改变感生出局部电动势而引起涡电流所造成的能量损耗，其与取向硅钢片的电导率和厚度有关；相应地，反常涡流损耗是取向硅钢片在磁化时由于磁畴结构不同而引起的能量损耗，其主要受磁畴宽度影响。
目前，公认的提高取向硅钢性能的方法主要有三种：(1)通过冶金学手段控制成品二次再结晶组织，从而提高取向度，并降低取向硅钢的铁损；(2)在取向硅钢表面形成张力涂层，以细化磁畴，降低铁损；(3)通过激光、电子束、机械、电化学等手段在取向硅钢表面刻痕，以形成线状应力或应变，从而细化磁畴，降低铁损。
在这三种方法中，上述方法(3)受关注程度最高，是目前该领域的研究热点之一。以下是对上述方法(3)的刻痕细化磁畴降低铁损的原理进行简述：取向硅钢晶粒内部存在磁畴结构，在无外场条件作用下，取向硅钢内部磁畴主要为反向平行排列的180°磁畴，单一磁畴宽度通常可以达到几十微米甚至数毫米。相邻磁畴间存在着几十到数百个原子层的过渡层，称为磁畴壁。在磁化过程中，外场驱动下磁矩转动，磁畴壁迁移使相邻磁畴相互吞并，从而实现导磁功能。同时，磁畴壁迁移过程中不同区域磁畴结构的不同使得微区域产生微涡流，因而产生涡流损耗，这部分损耗在取向硅钢中被称为反常涡流损耗Pa。
由此可见，反常涡流损耗Pa与取向硅钢的固有磁畴结构直接相关，其进一步地与磁畴宽度直接相关，因此减小磁畴宽度可以有效降低反常涡流损耗Pa。反常涡流损耗Pa在取向硅钢的整体损耗中所占比重较大，特别是厚度为0.23mm及以下的薄规格取向硅钢，其反常涡流损耗Pa占比可达到40％以上。因此，利用刻痕手段细化取向硅钢的磁畴，即减小磁畴宽度，可有效降低反常涡流损耗，从而降低取向硅钢整体铁损。
当前，在取向硅钢表面实施刻痕使磁畴细化而降低取向硅钢铁损的技术，根据刻痕的效果可分为两大类：
一类是不耐消除应力退火刻痕，其通过激光、等离子束、电子束等方式在表面以一定间距形成线状热应力区，从而减小主磁畴宽度，降低铁损。由于线状热应力会因消除应力退火而消失，因此该类产品一般用于制造无需消除应力 退火的叠片铁芯变压器。另一类是耐消除应力退火刻痕，其基本技术方案是采用机械齿辊、电化学腐蚀等手段在取向硅钢表面形成线状应变区或沟槽，以减小180°磁畴宽度，从而降低铁损。由于消除应力退火后应变区不发生变化，因此该类产品可用于制造需要消除应力退火的卷绕铁芯变压器。
例如：公开号为CN1216072A，公开日为1999年5月5日，名称为“具有优良磁性能的晶粒取向性电工钢薄板及其生产工艺和设备”的中国专利文献，公开了一种不损伤表面薄膜的激光耐热刻痕取向硅钢方法，其通过控制入射激光的光斑尺寸、能量密度等参数，实现具有较大深度闭合畴区域的应力区，以降低取向硅钢的铁损和磁致伸缩。
又例如：公开号为CN101528951A，公开日为2009年9月9日，名称为“铁损特性优异的单向性电磁钢板”的中国专利文献，公开了一种铁损特性优异的单向性电磁钢板，其进一步地考虑了激光刻痕所形成的应力分布状态，并通过控制钢板经激光照射所产生压缩残余应力积分值进行精细控制，从而提高激光刻痕的铁损改善率。然而，在该技术方案中，由于残余应力的测定依赖于X射线衍射等离线检测方法，其检测周期较长，因此在实际大生产中应用仍然面临着一定的困难。
再例如：公开号为CN102477484A，公开日为2012年5月30日，名称为“一种快速激光刻痕方法”的中国专利文献，公开了一种快速激光刻痕方法，其通过在带钢上下表面以等间距交错方式同时刻痕，以保证刻痕铁损改善效果的均匀性。但需要注意的是，上下表面刻痕需要对带钢震动以高精度方式控制，且空间布局较为复杂，该技术方案的实现难度较大。
然而，发明人通过大量的研究发现，在进行激光刻痕，利用激光照射形成局部应力的时候，钢板表面的局部区域因吸热会导致温度升高。由于硅钢热传导系数具有各向同性，因此，获得钢板厚度方向上较深、同时轧向宽度上较窄的热应力区域极为困难。
在以往的现有技术中，在激光刻痕时，通常采用具有椭圆形特征的激光光斑，并控制这种椭圆形光斑的长轴与扫描方向一致，且近似与钢板轧向垂直方向一致，以此方式来获得较长的停留时间，使钢板局部区域温升到足以产生磁畴细化效果的范围。然而，无论是采用连续式激光或是脉冲式激光，激光照射所产生的热量总是会快速累积，如果停留时间过长，虽然可以获得更好的铁损 降低效果，但不可避免的会存在温度过高而损伤涂层的问题，其会增加变压器在服役过程中短路击穿风险；如果停留时间过短，虽不至于损伤涂层，但激光刻痕所实现的降低铁损的效果也将受到限制。
为此，针对解决现有技术所存在的这种问题，本发明提出一种新的温升可控的激光刻痕方法，以保证在不损失钢板的表面涂层的同时，有效改善并降低取向硅钢的铁损。
发明内容
本发明的目的之一在于提供一种用于取向硅钢板的激光刻痕方法，该激光刻痕方法对自身工艺进行了优化设计，其采用分束激光聚焦扫描方式，能够在不损失取向硅钢表面涂层的条件下，进一步改善磁畴细化，以降低铁损。采用该激光刻痕方法所制成的取向硅钢板具有铁损低、涂层耐击穿的特点，其能够用于制造节能型的特高压输电网用变压器，具有广阔的应用前景。
为了实现上述目的，本发明提供了一种用于取向硅钢板的激光刻痕方法，其在对取向硅钢板进行表面激光刻痕时，对应于沿取向硅钢板的轧制方向上的每一个长度位置，均采用激光分束的方式在取向硅钢板表面形成多个聚焦光斑，该多个聚焦光斑沿取向硅钢板的宽度方向排布，并且彼此之间具有能量间隙区；其中每一个聚焦光斑沿取向硅钢板宽度方向的尺寸b均大于沿取向硅钢板长度方向的尺寸a。
本文中，“对应于沿取向硅钢板的轧制方向上的长度位置”是指相对于钢板轧制方向，激光聚焦光斑在钢板宽度方向上延伸拉长，以此长光斑形态扫描形成刻痕线的位置。
在当前现有技术中，本领域降低取向硅钢片铁损及振动噪音水平的主要方法主要有如下三种：1.冶金学方法：通过成分体系及工艺参数的优化，获得完善的二次再结晶组织，并提高取向度；2.张力控制：改善基板表面涂层的张力，细化磁畴，降低铁损和磁致伸缩；3.表面刻痕：通过激光、电子束、等离子等手段在硅钢表面沿轧向施加一定间距的连续或间断的刻痕线，施加应力或应变以细化磁畴，降低铁损。
近年来，利用冶金学方法已将取向度提高到很高水平，Hi-B钢中晶粒的取向偏离角平均水平低于5°，张力涂层及表面刻痕技术也得到成熟化商业应用， 获得了磁性能良好的取向硅钢片。
然而，随着世界经济发展及人口增长，人们对生活环境的要求越来越高。这就要求进一步提高能源效率，以减少不必要损耗。对于制造输电网节能变压器铁芯材料的取向硅钢而言，即需要进一步降低其铁损。以往采用的激光刻痕技术，通过激光辐照形成局部热应力，从而减小磁畴宽度以降低铁损。在实际使用过程中，激光能量高导入的热量多，相应的对细化磁畴降低铁损的效果更好，即高铁损改善效果需要导入较高的激光能量。然而，过高的激光能量可能导致取向硅钢表面硅酸盐和磷酸盐涂层的损伤，增加服役过程中片间导通的风险，即取向硅钢表面涂层不受损伤需要较低的激光能量。当前商业化应用的激光刻痕技术中，为了不损伤取向硅钢表面涂层，激光导入热量受到限制，铁损降低效果一般在10％～15％左右，要想进一步降低铁损十分困难。
为此，本发明人针对取向硅钢铁损改善效果与其表面涂层不受损伤所需激光能量所存在的矛盾，创新地设计了一种新型复合的激光刻痕方式，以在不损伤取向硅钢表面涂层的同时，进一步改善其铁损降低效果。
在本发明中，发明人详细研究了激光刻痕过程中钢板表面受到辐照所产生的温升现象，发现由于钢板表面局部微区域连续接受激光辐照，该区域的温度是持续上升的。当该区域温度上升到表面涂层的损伤阈值时，则钢板的表面涂层也将因为温度过高而破裂。
近年来，本领域工作者提出了采用光束整形方式，将聚焦在钢板表面的光斑整形成为椭圆形或矩形，即在激光扫描方向上具有较长长度，这一方案有效分散了激光能量，避免了能量过于集中造成的局部区域温升过快，同时由于扫描方向光斑尺寸的延长增加了局部微区域的激光辐照时间，即停留时间，可以使辐照产生的热量有效向周围扩散，可形成轧向宽度较大、厚度方向较深的热应力区，有利于磁畴细化，取得了明显效果。然而，该方案中硅钢表面局部微区域接受激光辐照的热量仍为连续的，同时由于产线运行速度快、匹配的激光扫描速度很快，通常为100m/s甚至200m/s以上，停留时间为微秒级，因此仍然存在温升过快易导致表面绝缘膜易产生损伤的问题。
为了解决这一难题，发明人在设计本发明的这种激光刻痕方法时，采用分束的方式将入射光束分成若干个分束，并严格控制所形成的聚焦光斑在激光扫描方向上的间距及各光斑能量分布，从而实现激光辐照所产生的钢板表面温升 控制，形成了在钢板厚度范围上较大的热应力区，其不仅能够使取向硅钢板相对刻痕前的铁损改善率提高至15％甚至更高，还能够避免过高的温升所导致的钢板表面薄膜损伤。
优选地，在本发明所述的用于取向硅钢板的激光刻痕方法中，所述聚焦光斑为椭圆形或矩形。
在本发明上述技术方案中，激光所形成的聚焦光斑可以具体由衍射分束器、偏振分束器等一种或多种方式的组合方式实现，且其所形成的聚焦光斑的外形可以具体为椭圆形或矩形。
优选地，在本发明所述的用于取向硅钢板的激光刻痕方法中，对应于沿取向硅钢板的轧制方向上的每一个长度位置，多个聚焦光斑在取向硅钢板的宽度方向上延伸的总长度D≤80mm。
在本发明上述技术方案中，由于取向硅钢板的传热具有各向同性的特点，因此，若激光总的停留时间过长将会使热量在钢板轧向形成较大范围的扩散，从而形成更大的热应力区，其不仅会增加磁滞损耗，还会降低磁感。因此，所形成的多个聚焦光斑的延伸的总长度需要控制在一定范围，以使总停留时间限制在一定范围内。发明人经反复实验后确定，可以优选地控制沿取向硅钢板的宽度方向排布的多个聚焦光斑的延伸的总长度≤80mm。当总长度超过80mm时，则会致使磁滞损耗增加，导致总损耗增加，磁感B8也下降。
优选地，在本发明所述的用于取向硅钢板的激光刻痕方法中，沿取向硅钢板长度方向的尺寸a为10-100μm。
优选地，在本发明所述的用于取向硅钢板的激光刻痕方法中，沿取向硅钢板宽度方向的尺寸b≤8mm。若超过8mm会使得总光斑长度难以控制，且较长的停留时间会发生热量累计，破坏表面涂层。
优选地，在本发明所述的用于取向硅钢板的激光刻痕方法中，对应于沿取向硅钢板的轧制方向上的每一个长度位置，前行聚焦光斑与后行聚焦光斑之间的能量间隙区ds与前行聚焦光斑在扫描方向上的长度比值在0.5-2之间。
在本发明上述技术方案中，聚焦光斑之间的能量间隙区大小对扫描时形成的温度降低同样有直接影响。每个聚焦光斑至下一个聚焦光斑之间的能量间隙区与该聚焦光斑的长度比例均应在控制0.5-2之间。当长度比值低于0.5时，则难以形成有效的温度降低，取向硅钢的表面涂层会产生破裂；当长度比值高 于2时，则温度降低过大，后行聚焦光斑难以将钢板表面温度维持在产生足够热应力的范围，无法实现磁畴细化降低铁损的效果。
优选地，在本发明所述的用于取向硅钢板的激光刻痕方法中，每一个聚焦光斑的功率密度p为1000-3000W/mm2。
在本发明上述技术方案中，为了达到本发明降低铁损同时不损伤表面涂层的目的，本发明可进一步控制激光聚焦光斑的功率密度p取值范围。当功率密度超过3000W/mm2时，过高的激光能量较导致取向硅钢板的表面涂层产生损伤；当功率密度低于1000W/mm2时，激光能量过低，则难以在取向硅钢板的表面形成有效的热应力区，其不足以形成磁畴细化效果，铁损改善率低。
优选地，在本发明所述的用于取向硅钢板的激光刻痕方法中，沿着激光扫描的方向，后行聚焦光斑与前行聚焦光斑的功率密度比值为0.75-0.95。
本发明人通过反复实验，确定了后行聚焦光斑与前行聚焦光斑的功率密度比值为0.75-0.95。当比值低于0.75，则后行聚焦光斑携带的能量过少，钢板表面经过初次激光光斑扫描后表面温度即开始逐步下降，难以形成有效的热应力区，磁畴细化降低铁损的效果有限；而当比值高于0.95时，则后行聚焦光斑携带能量过大，钢板表面温度逐步升高，仍然会达到表面涂层的损伤阈值。
优选地，在本发明所述的用于取向硅钢板的激光刻痕方法中，所述多个聚焦光斑经由衍射分束器、偏振分束器中的至少其中之一形成。
相应地，本发明的另一目的在于提供一种取向硅钢板，该取向硅钢板具有铁损低、涂层耐击穿的特点，其能够用于制造节能型的特高压输电网用变压器，具有十分广阔的应用前景。
为了实现上述目的，本发明提供了一种取向硅钢板，其采用本发明上述的激光刻痕方式制得。
在实际制备本发明所述的取向硅钢板时，可以先将具有一定Si含量的钢材经过炼铁、炼钢、连铸，而后经过热轧工序，再经过一次或含中间退火的两次冷轧，将钢材轧制成具有目标厚度的硅钢片。
然后，控制所制备的硅钢片经过脱碳退火，以形成表面具有氧化膜的初次再结晶钢板；在涂布氧化镁隔离剂后，硅钢片再经过高温退火，通过二次再结晶形成具有高斯织构的硅钢片，表面氧化膜与隔离剂反应形成硅酸镁底层。之后，硅钢片经过热拉伸平整退火，并施以涂层涂覆及烘烤工艺，然后在钢板表 面施加本发明所述激光刻痕，从而制成成品取向硅钢片。
优选地，在本发明所述的制造方法中，其相对刻痕前的铁损改善率提高至15％以上。
相较于现有技术，本发明所述的用于低铁损取向硅钢板的激光刻痕方法及取向硅钢板与现有技术相比具有如下有益效果：
在本发明中，发明人设计了一种新的激光刻痕方法，利用这种优化的激光刻痕方法形成热应力区，可以实现钢板的升温控制，从而能够在降低取向硅钢板铁损的同时，不损伤刻痕区域的表面涂层。
在具体实施本发明的激光刻痕方法时，其通过采用激光分束方式能够在钢板表面形成多个聚焦光斑，且每一个聚焦光斑的功率密度可以控制在1000-3000W/mm2之间；对应于沿取向硅钢板的轧制方向上的每一个长度位置，能量间隙区与对应的聚焦光斑在扫描方向上的长度比值可以控制在0.5-2之间；同时，沿着激光扫描的方向，后行聚焦光斑与前行聚焦光斑的功率密度比值可以控制在0.75-0.95之间。
采用本发明所设计的这种激光刻痕方法，由于激光分束的聚焦光斑间存在能量间隙区的存在，其可以有效避免激光热辐照连续累积所造成的表面持续升温，因此在保证表面刻痕微区域涂层完整的同时提高了磁畴细化降低铁损效果，其相对刻痕前的铁损改善率提高至15％以上。所制备的低铁损取向硅钢板能够用于制造节能型的特高压输电网用变压器，其具有广阔的应用前景。
附图说明
图1为本发明所述的激光刻痕方法采用激光分束的方式形成聚焦光斑并对钢板的表面进行扫描的示意图。
图2示意性地显示了本发明所述的聚焦光斑聚焦在钢板表面的示意图。
图3示意性地显示了本发明所述的激光刻痕方法与现有技术的激光刻痕方法在对钢板进行刻痕时的辐照时间与钢板表面局部微区域温度变化的关系图。
图4示意性地显示了一种用于实施本发明所述激光刻痕方法的光路系统的系统架构图。
具体实施方式
下面将结合说明书附图和具体的实施例对本发明所述的用于低铁损取向硅钢板的激光刻痕方法及取向硅钢板做进一步的解释和说明，然而该解释和说明并不对本发明的技术方案构成不当限定。
图1为本发明所述的激光刻痕方法采用激光分束的方式形成聚焦光斑并对钢板的表面进行扫描的示意图。
图2示意性地显示了本发明所述的聚焦光斑聚焦在钢板表面的示意图。
结合图1和图2可以看出，图1和图2给出了本发明所述的激光刻痕方法采用激光分束的方式在钢板表面形成多个聚焦光斑的示意图。
在本发明中，入射激光分束后，能够在钢板表面形成复数形式的若干个聚焦光斑1、2、3……n-1、n，各聚焦光斑在激光扫描方向(即取向硅钢板宽度方向)上的长度分别为b1、b2、b3……bn-、bn；该多个聚焦光斑沿取向硅钢板的宽度方向排布，并且彼此之间具有能量间隙区，长度分别为ds1、ds2、ds2……dsn-1。每个聚焦光斑在取向硅钢板的宽度方向上的长度之和即为光斑总长度D。
本文中，“前行聚焦光斑”和“后行聚焦光斑”指沿激光扫描方向的任意两个相邻的聚焦光斑。例如，若激光扫描方向起始于图2的光斑1，则光斑1为“前行聚焦光斑”，光斑2为“后行聚焦光斑”。类似地，在光斑2和光斑3之间，光斑2为“前行聚焦光斑”，光斑3为“后行聚焦光斑”，以此类推。
在该实施方式中，各聚焦光斑在与激光扫描方向垂直的方向(即取向硅钢板长度方向)长度可以设定为统一值a。当然，在某些其他的实施方式中，不同的聚焦光斑在与激光扫描方向垂直的方向长度也可不同，但均需满足本发明所要求的激光功率密度范围。在通常的生产条件下，激光扫描速度很快，达到100m/s甚至更高，宽度为1m左右的钢板全幅扫描仅需0.01s或更短，因此生产上为了空间布置简洁，通常会使激光扫描方向与钢板宽度方向大致相同。
需要说明的是，本发明人还详细研究了激光刻痕过程中硅钢表面的温度升高过程，如图3所示。图3示意性地显示了本发明所述的激光刻痕方法与现有技术的激光刻痕方法在对钢板进行刻痕时的辐照时间与钢板表面局部微区域温度变化的关系图。
在图3所列出的关系图中，本发明所述的激光刻痕方法对应的是图3中的实线；现有技术中的激光刻痕方法对应的是图3之中的虚线。
参阅图3可以看出，在采用现有技术的激光刻痕方法时，由于钢板表面局 部微区域连续接受激光辐照，其区域温度连续升高，并在激光辐照停留时间范围内达到峰值，之后区域温度方才逐渐降低。而在采用本发明所设计的这种激光刻痕方法时，由于彼此相邻的聚焦光斑间存在一定间隔，其聚焦光斑间形成一定能量间隙区，因此钢板表面局部微区域的温度在一定程度上会有所降低，且后行聚焦光斑能量低于前行聚焦光斑，辐照区域温度始终控制在表面涂层的损伤阈值之下，同时总停留时间延长，热扩散在较大范围内进行，因此可以在较大区域内形成热应力，进而提高铁损改善效果。
基于上述原理，可确定与本发明效果直接相关的控制参数包括：聚焦光斑尺寸a和b、每一个聚焦光斑的功率密度p、聚焦光斑间隙ds，以及与总激光停留时间直接相关的光斑总长度D(参阅图2)。需要说明的是，将现有技术中采用的连续式激光或是脉冲式激光的单束激光通过激光分束的方式将单束激光分为多束激光，形成若干彼此之间具有能量间隙区ds的聚焦光斑，即可降低激光刻痕过程中在钢板表面相应刻痕区域的累积热量。至于每一个聚焦光斑的功率密度p、聚焦光斑间隙ds，以及与总激光停留时间直接相关的光斑总长度D，它们可在任意优选范围内选择，只需在激光刻痕过程中形成刻痕的同时有效避免激光热辐照连续累积所造成的钢板表面持续升温即可。
相比于现有技术，本发明所设计的聚焦光斑在钢板轧向(即取向硅钢长度方向)具有较小的尺寸a，以此减小激光辐照热量在轧向方向扩散，避免磁滞损耗增大。理论上，该尺寸a越小意味着本发明效果更好。然而，在实际的工业化生产中，由于激光扫描范围需覆盖到整个板宽方向，通常为900mm甚至更大，需要较长的焦距，且为了防止带钢板形波动造成的离焦现象，因此需要一定的焦深，足以覆盖板形波动及带钢抖动等产生的离焦偏差，因此聚焦光斑尺寸a下限受到光学系统限制，不能低于10μm。当聚焦光斑尺寸a低于该值，则光学系统的复杂性大大增加，板宽方向上需要同时布置多台激光器才能完成全板宽方向的激光刻痕。根据本发明人的研究，聚焦光斑轧向尺寸a的上限值定为100μm，超过该值，热量在轧向扩散，即刻痕附近轧向区域的热应力区增加，磁滞损耗增加，总损耗得不到进一步下降，还会使磁感B8下降。
在本发明中，入射激光经过衍射分束器和偏振分束器分光后，能够在钢板表面上形成复数个的聚焦光斑，聚焦光斑通常为椭圆形，即激光扫描方向上的(即取向硅钢板宽度方向)光斑尺寸b大于轧向尺寸a，这是为了使激光能量 尽可能较为分散，防止形成过高的功率密度，破坏表面涂层。
需要注意的是，在本发明中，聚焦光斑的功率密度p可以具体采用平均值，其定义式如下：
其中，P0为激光器总输出功率，单位为W；n为聚焦光斑的数量，S为聚焦光斑的面积，单位以mm2表示。当所形成的聚焦光斑为椭圆形光斑时，则聚焦光斑的面积S的计算式可以具体表示为：
需要说明的是，在某些其他的实施方式中，激光经过光束整形器也可形成矩形光斑，矩形长边为b，沿钢板宽度方向延伸；矩形短边为a，沿钢板轧向(即取向硅钢板长度方向)延伸。聚焦光斑为矩形光斑与本发明技术方案相同，因此也在本发明保护范围内，此处不再赘述。
为了达到本发明降低铁损同时不损伤表面涂层的目的，本发明需要严格控制激光聚焦光斑的功率密度p取值范围。当功率密度p超过3000W/mm2时，过高的激光能量较导致表面涂层产生损伤；当功率密度p低于1000W/mm2时，激光能量过低，则难以在取向硅钢板的表面形成有效的热应力区，其不足以形成磁畴细化效果，且铁损改善率低。因此，在实际应用时，需要将每一个聚焦光斑的功率密度控制在1000-3000W/mm2之间。
在本发明中，激光经过分光后，相邻聚焦光斑的间隙会形成一定的温度降低，这可避免扫描区域温度过高使表面涂层损伤。因此，需要控制后行聚焦光斑与前行聚焦光斑的功率分配比例及能量间隙区大小ds。
本发明人通过反复实验，确定了后行聚焦光斑与前行聚焦光斑的功率密度比值为0.75-0.95，即范围应为0.75-0.95。当低于0.75，则后行聚焦光斑携带的能量过少，钢板表面经过初次激光光斑扫描后表面温度即开始逐步下降，难以形成有效的热应力区，磁畴细化降低铁损的效果有限；而当高于 0.95时，则后行聚焦光斑携带能量过大，钢板表面温度逐步升高，仍然会达到表面涂层的损伤阈值。
相应地，聚焦光斑之间的能量间隙区ds大小对扫描时形成的温度降低同样有直接影响。每个聚焦光斑至下一个聚焦光斑之间的能量间隙区与该聚焦光斑在扫描方向上的长度比例均应在控制0.5-2之间，即的范围应为0.5-2。当低于0.5时，则难以形成有效的温度降低，取向硅钢的表面涂层会产生破裂；当高于2时，则温度降低过大，后行聚焦光斑难以将钢板表面温度维持在产生足够热应力的范围，无法实现磁畴细化降低铁损的效果。
此外，需要注意的是，由于取向硅钢板的传热具有各向同性的特点，因此，激光总的停留时间过长将会使热量在钢板轧向形成较大范围的扩散，形成更大的热应力区，其会增加磁滞损耗，并会降低磁感。所形成的多个聚焦光斑的延伸的总长度需要控制在一定范围，以使总停留时间限制在一定范围内。发明人经反复实验后确定，可以优选地控制多个聚焦光斑在取向硅钢板的宽度方向上延伸的总长度D≤80mm。当总长度超过80mm时，则会致使磁滞损耗增加，导致总损耗增加，磁感B8也下降。
在本发明中，多个聚焦光斑的延伸的总长度D的计算式如下所示：
图4示意性地显示了一种用于实施本发明所述激光刻痕方法的光路系统的系统架构图。
如图4所示，图4举例说明一种实施本发明所述的激光刻痕方法的光路系统的系统架构图，其他方式达到本发明所述的分光聚焦效果也在本发明范围内。在图4所设计的这种光路下同中，激光光束8从激光器1发出后，经过反射镜2、反射镜3，再经过光束整形系统4，可以形成具有椭圆形能量分布的光 束，再经由衍射分光原件5，形成复数光束，经过扫描聚焦镜6，在取向硅钢板7表面快速扫描形成刻痕应力区9。
在激光源使用方面，本发明并无特殊限定，常用的本领域使用的波长为1066nm的连续式激光，其他激光形式也可达到本发明目的，亦在本发明范围内，此处便不再赘述。
下面，本技术方案将采用具体的实施例数据进一步描述本案的技术方案并证明本发明所设计的这种激光刻痕方法所带来的有益效果：
实施例1-7及对比例1-2
在本发明中，实施例1-7和对比例1-2的取向硅钢板采用以下步骤制得：
(1)取向硅钢经过炼铁、炼钢、连铸、热轧工艺，再经过一次冷轧轧至最终厚度0.22mm，经过850℃的脱碳退火工艺，形成表面氧化层后在其表面涂覆MgO隔离剂，卷制成钢卷后在1200℃高温退火条件下保持20小时，之后清洗表面未反应的残余MgO并烘干，然后在钢板表面施加绝缘涂层。
(2)在涂覆好绝缘涂层后，对取向硅钢进行激光刻痕，并具体在钢板单面沿其横向实施激光刻痕：
在对取向硅钢板进行表面激光刻痕时，对应于沿取向硅钢板的轧制方向上的每一个长度位置，均采用激光分束的方式在取向硅钢板表面形成多个聚焦光斑，该若干个聚焦光斑沿取向硅钢板的宽度方向排布，并且彼此之间具有能量间隙区；其中每一个聚焦光斑沿取向硅钢板宽度方向的尺寸b均大于沿取向硅钢板长度方向的尺寸a；
在激光刻痕过程中，控制尺寸a为10-100μm；对应于沿取向硅钢板的轧制方向上的每一个长度位置，控制沿取向硅钢板的宽度方向排布的多个聚焦光斑的延伸的总长度D≤80mm；控制能量间隙区长度ds与对应的聚焦光斑长度b在扫描方向上的比值ds/b在0.5-2之间；控制每一个聚焦光斑的功率密度为1000-3000W/mm2；并且沿着激光扫描的方向，控制后行聚焦光斑与前行聚焦光斑的功率密度比值为0.75-0.95。
需要说明的是，在本发明中，实施例1-7和对比例1-2的激光均采用连续式单模光纤激光，波长1066nm，其采用定制化的衍射光学元件将光束分成不同参数的子光束，并在钢板表面扫描形成刻痕应力区。其中，对比例不使用衍射光学元件分光，通过调整激光器输出功率调整功率密度。
本发明所采用这种激光刻痕工艺是在取向硅钢最终退火之后所进行的，因此本发明对取向硅钢板并无特殊限定，在实际实施时，并不局限于上述工艺所制成的取向硅钢板。
表1列出了实施例1-7和对比例1-2的取向硅钢板的在上述工艺中的具体工艺参数。
表1.
对实施例1-7和对比例1-2的取向硅钢板在激光刻痕前、后进行导磁性能(B8)和铁损(P17/50)测试，具体是采用GB/T 13789-2008所述方法进行测试，并控制制备的实施例和对比例试样的轧向和横向长度均为500mm，从而测得取向硅钢在800A/m的激励磁场下的磁通密度B8值，以及在50Hz的交流励磁场下的磁通密度达到1.7T时磁化所消耗的无效电能P17/50值。相应地，还对实施例1-7和对比例1-2的取向硅钢板的刻痕区域涂层损坏程度进行检测，相关检测结果列于下述表2之中。
表2.

由上述表2可以看出，实施例1-7的取向硅钢板在激光刻痕后，均有较好的铁损、导磁性能；实施例1-7的取向硅钢板在激光刻痕后，其钢板表面涂层均未被破坏，且磁畴细化铁损下降明显，相比刻痕前，其铁损改善率均可达到15％以上。
而对比例1的取向硅钢板在激光刻痕后，虽然通过调整激光功率达到了较高的铁损改善效果，但热累积导致涂层受损；相应地，对比例2的取向硅钢板在激光刻痕时，调低了激光功率，其刻痕后的钢板表面涂层虽然完整，但铁损改善效果差。
需要说明的是，本发明的保护范围中现有技术部分并不局限于本申请文件所给出的实施例，所有不与本发明的方案相矛盾的现有技术，包括但不局限于在先专利文献、在先公开出版物，在先公开使用等等，都可纳入本发明的保护范围。
此外，本案中各技术特征的组合方式并不限本案权利要求中所记载的组合方式或是具体实施例所记载的组合方式，本案记载的所有技术特征可以以任何方式进行自由组合或结合，除非相互之间产生矛盾。
还需要注意的是，以上所列举的实施例仅为本发明的具体实施例。显然本发明不局限于以上实施例，随之做出的类似变化或变形是本领域技术人员能从本发明公开的内容直接得出或者很容易便联想到的，均应属于本发明的保护范围。

Claims (12)

  1. 一种用于取向硅钢板的激光刻痕方法，其特征在于，所述方法包括：在对取向硅钢板进行表面激光刻痕时，对应于沿取向硅钢板的轧制方向上的每一个长度位置，均采用激光分束的方式在取向硅钢板表面形成多个聚焦光斑，所述多个聚焦光斑沿取向硅钢板的宽度方向排布，并且所述聚焦光斑彼此之间具有能量间隙区ds；其中每一个聚焦光斑沿取向硅钢板宽度方向的尺寸b均大于沿取向硅钢板长度方向的尺寸a。
  2. 如权利要求1所述的用于取向硅钢板的激光刻痕方法，其特征在于，所述聚焦光斑为椭圆形或矩形。
  3. 如权利要求1所述的用于取向硅钢板的激光刻痕方法，其特征在于，对应于沿取向硅钢板的轧制方向上的每一个长度位置，所述多个聚焦光斑在取向硅钢板的宽度方向上延伸的总长度D满足18mm≤D≤80mm，优选38mm≤D≤60mm。
  4. 如权利要求1所述的用于取向硅钢板的激光刻痕方法，其特征在于，聚焦光斑沿取向硅钢板长度方向的尺寸a为10-100μm，优选为40-80μm。
  5. 如权利要求1所述的用于取向硅钢板的激光刻痕方法，其特征在于，聚焦光斑沿取向硅钢板宽度方向的尺寸b为3-8mm，优选为4-6mm。
  6. 如权利要求1所述的用于取向硅钢板的激光刻痕方法，其特征在于，对应于沿取向硅钢板的轧制方向上的每一个长度位置，前行聚焦光斑与后行聚焦光斑之间的能量间隙区ds与所述前行聚焦光斑在激光扫描方向上的长度的比值在0.5-2之间，优选为0.7-1.3之间。
  7. 如权利要求1所述的用于取向硅钢板的激光刻痕方法，其特征在于，每一个聚焦光斑的功率密度p为1000-3000W/mm2。
  8. 如权利要求1所述的用于取向硅钢板的激光刻痕方法，其特征在于，沿着激光扫描的方向，后行聚焦光斑与前行聚焦光斑的功率密度比值为0.75-0.95。
  9. 如权利要求1所述的用于取向硅钢板的激光刻痕方法，其特征在于，所述多个聚焦光斑经由衍射分束器、偏振分束器中的至少其中之一形成。
  10. 如权利要求2所述的用于取向硅钢板的激光刻痕方法，其特征在于，所述 椭圆形或矩形的聚焦光斑由光束整形器形成。
  11. 一种取向硅钢板，其特征在于，所述取向硅钢板具有采用如权利要求1-9中任意一项所述的激光刻痕方式制得的刻痕。
  12. 如权利要求11所述的取向硅钢板，其特征在于，所述取向硅钢板相对刻痕前的铁损改善率提高至15％以上。
PCT/CN2023/106738 2022-07-11 2023-07-11 一种用于低铁损取向硅钢板的激光刻痕方法及取向硅钢板 WO2024012439A1 (zh)

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