CN113584279B - Stress relief annealing notch resistant oriented silicon steel and manufacturing method thereof - Google Patents

Stress relief annealing notch resistant oriented silicon steel and manufacturing method thereof Download PDF

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CN113584279B
CN113584279B CN202010366049.4A CN202010366049A CN113584279B CN 113584279 B CN113584279 B CN 113584279B CN 202010366049 A CN202010366049 A CN 202010366049A CN 113584279 B CN113584279 B CN 113584279B
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silicon steel
oriented silicon
laser
notch
scoring
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CN113584279A (en
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赵自鹏
储双杰
杨勇杰
李国保
刘宝军
沈侃毅
向邦林
马长松
谢伟勇
周琳
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Baoshan Iron and Steel Co Ltd
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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
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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Abstract

A stress relief annealing notch resistant oriented silicon steel and a manufacturing method thereof are provided, wherein a composite superposition notch is formed on one side or both sides of the oriented silicon steel by front and rear laser scanning, namely a front notch and a rear notch which are superposed up and down, wherein the front notch forms a groove with the width of 10-300 mu m and the depth of 0.5-5 mu m; the post-notch forms a groove with the width of 300 μm or less and the depth of 5-60 μm in the groove of the pre-notch. The invention forms the composite superposition groove on the surface of the oriented silicon steel plate, further refines the magnetic domain, reduces the iron loss, has better adhesiveness of the surface coating, has simple manufacturing process, can realize batch production, has no disappearance of the scoring effect of the finished product in the stress relief annealing process, and is particularly suitable for manufacturing the winding iron core transformer.

Description

Stress relief annealing notch resistant oriented silicon steel and manufacturing method thereof
Technical Field
The invention relates to oriented silicon steel and a manufacturing method thereof, in particular to stress relief annealing notch resistant oriented silicon steel and a manufacturing method thereof, which can be applied to manufacturing of winding iron core transformers.
Background
In recent years, the global energy and environment problems are increasingly prominent, the energy saving and consumption reduction requirements are continuously increased worldwide, the corresponding energy consumption equipment standards are generally improved in various countries, and the reactive power consumption of various equipment on energy sources is reduced. Currently, transformers are used as an essential component in power transmission systems, and their losses account for about 40% of the losses in the power transmission systems. Wherein, the reactive loss of the iron core made of laminated or wound oriented silicon steel in the working state is about 20% of the total loss. The core loss is generally referred to simply as core loss. Therefore, the reduction of the iron loss of the oriented silicon steel has great significance for national economy and social environment protection.
Oriented silicon steel is a ferromagnetic material, named after its internal grain {110} <001> orientation substantially aligned with the rolling orientation of the steel sheet. Since oriented silicon steel {110} <001> has the best magnetic permeability, it is widely used for manufacturing transformers for power transmission. Due to the combined action of spontaneous magnetization and demagnetizing field, magnetic domain structures are formed inside the oriented silicon steel grains, and the atomic magnetic moments inside single magnetic domains are arranged in the same direction, so that the macroscopic crystal shows ferromagnetic properties. The oriented silicon steel magnetic domains are mainly 180 DEG magnetic domains which are arranged in antiparallel under the condition of no external magnetic field, and the width of a single magnetic domain can reach tens of micrometers or even several millimeters. There are several tens to hundreds of atomic layer transition layers between the adjacent oppositely arranged magnetic domains, called domain walls. In the magnetizing process, magnetic moment is driven by an external field to rotate, and magnetic domain walls migrate to enable adjacent magnetic domains to be swallowed mutually, so that finally 180-degree magnetic domains which are arranged in an antiparallel mode are combined into a single magnetic domain parallel to the external field direction, and therefore the magnetic conduction function is achieved. The magnetic permeability of the oriented silicon steel is generally characterized by B8, namely the magnetic flux density of the silicon steel plate under an excitation magnetic field of 800A/m is expressed as T; the core loss is generally characterized by P17/50, namely, the ineffective electric energy consumed by magnetization when the magnetic flux density in the silicon steel plate reaches 1.7T under the alternating current excitation field of 50Hz is expressed as W/kg., and B8 and P17/50 are used for representing the basic performance of the oriented silicon steel.
Research shows that the iron loss of the oriented silicon steel consists of three parts of hysteresis loss, eddy current loss and abnormal eddy current loss. Hysteresis loss is energy loss caused by hysteresis phenomenon that magnetic induction intensity lags behind magnetic field intensity change due to the fact that factors such as inclusion, crystal defect, internal stress and the like in materials block magnetic domain wall movement in the magnetization and reverse magnetization processes; eddy current loss is energy loss caused by eddy current due to the fact that magnetic flux changes induce local electromotive force in the magnetizing process, and is related to conductivity and thickness of the silicon steel plate; abnormal eddy current loss is energy loss caused by different magnetic domain structures when a silicon steel plate is magnetized, and is mainly influenced by the width of the magnetic domain. The magnetic domain is thinned, namely the width of the magnetic domain is reduced, so that abnormal eddy current loss can be effectively reduced, the method is an important method for reducing the iron loss of the silicon steel plate, and the method is one of the main directions of the progress of oriented silicon steel technology.
The technique of refining the magnetic domain and reducing the iron loss by scoring the surface of the oriented silicon steel can be divided into two main categories according to the scoring effect: the thermolabile nick refines the magnetic domain, forms the linear thermal stress area on the surface with certain interval by means of laser, plasma beam, electron beam, etc., makes the sub-magnetic domain appear around the area, thus reduce 180 degree magnetic domain width, achieve the goal of reducing iron loss. The magnetic domain refining effect of the method disappears along with the thermal stress elimination at the notch after the stress elimination annealing, and the iron loss returns to the original level, so that the method can only be used for manufacturing the laminated iron core transformer without the stress elimination annealing; the other is a heat-resistant nick refined magnetic domain, the technical means reported at present comprise mechanical, electrochemical corrosion, laser beams and the like, the technical principle is that a linear strain area is formed on the surface of the oriented silicon steel, and the existence of the strain area introduces additional surface energy and net magnetic energy, so that the energy in the crystal is redistributed, the 180-degree magnetic domain width is reduced, the iron loss is reduced, and the oriented silicon steel manufactured by the method is not recovered after stress relief annealing, so that the method can be applied to manufacturing of a winding iron core transformer needing the stress relief annealing. The winding direction and the rolling direction of the winding iron core transformer are completely the same when the oriented silicon steel plate is used, so that the superiority of the oriented silicon steel in the rolling direction is fully utilized, and the winding iron core transformer has obvious advantages in the aspects of energy conservation, consumption reduction and transformer noise, and is favored by downstream users. The heat-resistant magnetic domain refined oriented silicon steel is particularly suitable for manufacturing the transformer of the type and is the direction of technical progress.
US patent 4770720 uses mechanical pressure to form micro-strain region on silicon steel surface, and forms small grains under the strain region after stress relief annealing, and the magnetic domain refinement effect is generated due to the different orientation of the small grains and the substrate. US patent 7063780 utilizes electrolytic corrosion to create a heat resistant scoring effect. Firstly, linear processing is carried out on an oriented silicon steel plate with a bottom layer by utilizing laser, the bottom layer is peeled off to expose a metal matrix in the area, then the area is soaked in electrolyte, an electrode pair is formed by the silicon steel plate and a platinum electrode, and the area is formed into a linear groove which is nearly rectangular by electrolytic corrosion of a substrate by alternately controlling the positive and negative changes of the electrode potential. However, the problems of low production efficiency and limited productivity exist in the scheme. In order to overcome the difficulty, researchers introduce laser and other modes to micromachine the surface of oriented silicon steel, such as U.S. Pat. No. 5, 7045025, wherein laser beams are utilized to locally heat the surface of a silicon steel plate before or after hot stretching flattening annealing to form a remelting area, the coating substance and part of the metal matrix are melted and then cooled and solidified to form a remelting area, and the iron loss of the silicon steel plate is reduced by controlling the width and depth of the remelting area. Chinese patent CN102941413A adopts a mode of multiple laser grooving to realize accurate control of grooving depth and width, and the protrusion formed at the edge of the groove due to laser thermal melting is controlled within 5 mu m, so that the manufactured oriented silicon steel plate has good lamination property and iron loss property. Japanese patent JP2012102395 controls the inclination angle of the side walls of the formed grooves, and realizes the performance optimization of the manufactured transformer under the condition that the third harmonic occupies a relatively large area in use.
The heat-resistant notch technology of oriented silicon steel is to form a series of grooves or strains on the surface of a steel plate by a certain means, so that magnetic domains are thinned, and the iron loss is reduced. The groove or strain is not changed due to annealing, so that the iron loss reducing effect is not lost in the stress relief annealing process, and the method is particularly suitable for manufacturing the winding iron core transformer.
How to efficiently produce heat-resistant oriented silicon steel with low cost is a common problem facing steel manufacturing enterprises, and the key difficulty is the incorporability of microscopic characteristics and macroscopic batch manufacturing of the notch groove.
The prior technical proposal of forming grooves by mechanical pressure has extremely high requirements on the toothed roller, and the high hardness of the magnesium silicate bottom layer on the surface of the oriented silicon steel leads to rapid abrasion of the toothed roller, and the mass production cost is high; the heat-resistant scoring technology realized by an electrochemical mode has complex working procedures, chemical pollution to a certain extent, poor controllability of the shape and depth of the formed groove, and difficulty in obtaining an oriented silicon steel sheet with stable and uniform magnetic performance; the grooving is formed by adopting a laser multi-scanning mode, the repeated positioning precision requirement is high, and the production line is difficult; the laser thermal melting mode is adopted to form a groove or a remelting area, so that crater-shaped bulges and splashes are easy to generate at the edge of the groove and nearby, the lamination coefficient of the silicon steel sheet is reduced, and the manufactured transformer has the risk of conducting between sheets in the service process.
Disclosure of Invention
The invention aims to provide stress relief annealing notch resistant oriented silicon steel and a manufacturing method thereof, wherein a composite superposition groove is formed on the surface of an oriented silicon steel plate, so that magnetic domains are further refined, iron loss is reduced, the adhesiveness of a surface coating is better, the manufacturing process is simple, batch production can be realized, the notch effect of a finished product is not lost in the stress relief annealing process, and the stress relief annealing notch resistant oriented silicon steel is particularly suitable for manufacturing a winding iron core transformer.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
the notch oriented silicon steel resistant to stress relief annealing is characterized in that front and back laser scanning is adopted on one side or two sides of the oriented silicon steel to form a composite superposition notch, namely a front notch and a rear notch which are superposed up and down, wherein the front notch forms a groove with the width of 10-300 mu m and the depth of 0.5-5 mu m; the post-notch forms a groove with the width of 300 μm or less and the depth of 5-60 μm in the groove of the pre-notch.
Preferably, the ratio K of the width of the groove formed by the pre-notch and the post-notch is between 1 and 60.
The invention relates to a manufacturing method of notch oriented silicon steel resistant to stress relief annealing, which comprises the following steps: smelting, continuous casting, hot rolling, cold rolling for one time or two times with intermediate annealing, rolling to the final thickness, decarburizing annealing, coating MgO separating agent on the surface, annealing at high temperature to form complete secondary recrystallization, final annealing and coating insulating coating to form the finished oriented silicon steel plate, and laser scoring, wherein after decarburizing annealing, before final annealing or after final annealing, the composite superposition scoring is formed on one side or both sides of the oriented silicon steel plate by adopting front and rear laser scanning,
the prepositive nick adopts continuous or pulse laser, and the diameter of the light spot a along the scanning direction 1 A spot diameter b perpendicular to the scanning direction of between 0.05 and 20mm 1 Between 0.01 and 0.3 mm;
the post-scoring adopts high instantaneous pulse energy laser, and the spot diameter a along the scanning direction 2 A spot diameter b perpendicular to the scanning direction of between 0.005 and 5mm 2 Between 0.005 and 0.3 mm.
Preferably, the laser energy density of the pre-notch is 0.16-10.2J/mm 2 Between them.
Preferably, the high instantaneous pulse energy laser used for post-scoring scans the surface of the steel plate in a singular or plural beam splitting mode to form the score, and the average single pulse peak instantaneous power density of the beam splitting is not less than 1.2×10 5 ～1.2×10 13 W/mm 2 Between them, the total energy density is 1-42J/mm 2 The total energy density is the sum of the energy densities of the beam-splitting laser scanning.
Preferably, the high instantaneous pulse energy laser used for post-scoring forms the score on the surface of the oriented silicon steel plate in a singular or plural beam splitting mode, the total length of a focusing beam splitting spot formed on the surface of the oriented silicon steel plate in the scanning direction by beam splitting is not more than 20mm, and the number of repeated scanning on the surface of the steel plate is not more than 5.
Preferably, the post-scoring laser is no more than 1000mm from the pre-scoring laser in the direction of travel of the oriented silicon steel sheet.
Preferably, the running speed fluctuation of the oriented silicon steel plate is controlled within +/-0.5 m/s in the laser scoring process.
The oriented silicon steel is named as an electrical steel sheet having a certain silicon content and having an easy magnetization direction substantially the same as the rolling direction in the manufacturing process because the internal crystal grains have substantially the same direction. 180-degree magnetic domains with the same or opposite direction as the easy magnetization direction of the crystal grains exist in the steel plate, and the magnetic poles in the steel plate move through the magnetic domain walls between the adjacent magnetic domains to realize rapid rotation in the alternating current magnetization process, so that the transformer has good magnetic conductivity, and the manufactured transformer has high magnetic conductivity and low iron loss.
The method comprises the steps of (1) carrying out iron making, steel making and continuous casting on steel with certain silicon content, carrying out hot rolling, carrying out cold rolling once or twice including intermediate annealing, rolling the steel to a target thickness, and carrying out decarburization annealing to form a primary recrystallized steel plate with an oxide film on the surface; then coating a spacer agent which is mainly MgO on the surface of the steel plate, carrying out high-temperature annealing of more than 20Hr to form an oriented silicon steel plate with a secondary recrystallization structure, then carrying out hot stretching leveling annealing, and carrying out coating and baking processes to prepare the finished oriented silicon steel plate. The oriented silicon steel plate has the characteristics of high magnetic induction and low iron loss, and is particularly suitable for manufacturing transformer cores.
The continuous reduction of the iron loss of silicon steel materials is the development direction of silicon steel technology, and at present, three technical directions can be realized:
the secondary recrystallization structure is controlled by a metallurgical method, so that the grain orientation degree is improved, and the grain size is reduced moderately to refine the magnetic domains and reduce the iron loss.
And (3) applying a high-tension coating on the surface of the silicon steel plate, refining magnetic domains by the tension effect of the coating, and reducing iron loss.
The surface nicks apply linear stress or strain on the surface of the silicon steel plate in a laser, electron beam and other modes, so that magnetic domains are refined, and iron loss is reduced.
In recent years, the technical level of the metallurgical industry is continuously improved, and the control of the secondary recrystallization structure by a metallurgical method is already close to the theoretical maximum value. Therefore, the refinement of magnetic domains by means of surface tension and scoring is a main technical progress point of oriented silicon steel.
Refining the magnetic domains can reduce abnormal eddy current loss of the oriented silicon steel. Such as those disclosed in US7442260B2 and US5241151a, in which a miniature linear thermal stress region is applied to the surface of the finished oriented silicon steel by means of laser or electron beam, the stress generates a 90 ° magnetic domain perpendicular to the rolling direction in the vicinity thereof, and the 180 ° magnetic domain width is reduced, thereby reducing the iron loss of the oriented silicon steel, the product has been widely used in the manufacture of various laminated core transformers.
With the increasing demand of energy conservation and environmental protection, wound core transformers are increasingly favored in the market. Because the silicon steel plate of the coiled iron core is rolled along the rolling direction of the steel plate, the superiority of the magnetic property of the oriented silicon steel is fully utilized, and therefore, compared with the laminated iron core, the coiled iron core has the advantages of low loss, low noise, no shearing waste and the like, and is particularly suitable for manufacturing small and medium-sized energy-saving transformers. However, since the iron core generates internal stress during rolling, the iron loss performance of the silicon steel sheet is deteriorated, and thus the iron core must be subjected to stress relief annealing. The stress relief annealing process is usually carried out in a protective atmosphere at 800 ℃ or above for not less than 2hr, and at this time, the dislocation inside the material is completely recovered, the internal stress is completely relieved, and the magnetic performance of the silicon steel sheet reaches the optimal state. The oriented silicon steel sheet in which the linear stress region refined magnetic domains are generated by the conventional laser or electron beam is used, and the effect of refining the magnetic domains disappears with the disappearance of the stress after the stress relief annealing, so that the oriented silicon steel sheet cannot be used for manufacturing the wound core transformer.
In order to maintain the effect of refining magnetic domains after stress relief annealing, stress relief annealing resistant refining magnetic domain technology has been developed, that is, chemical erosion, mechanical pressure and other modes are adopted to form grooves with a certain shape on the surface of a silicon steel plate, and free magnetic poles are generated at the grooves to redistribute material energy, reduce magnetic domain width and iron loss. Because the grooves do not change in the stress relief annealing process, the oriented silicon steel sheet produced by the technology can be applied to manufacturing of wound core transformers, and is commonly called a heat-resistant scoring technology.
The heat resistant scoring techniques currently in commercial use are chemical attack and mechanical scoring, respectively. The chemical erosion method is adopted, and the production process belongs to chemical reaction, so that the time is long, the uniformity of the groove and the process controllability are poor, and the environment is polluted to a certain extent; by adopting the technical scheme of forming the strain area by mechanical pressure, the silicon steel material has high hardness and the groove has small size, so that the requirements on the hardness and the machining precision of the mechanical device are high. The defects of the scheme are that the production efficiency is low, the productivity of the heat-resistant notch oriented silicon steel product is limited, and the increasingly expanded market demand of the coiled iron core is difficult to meet. In order to improve the production efficiency, research has been focused on the development of laser heat-resistant scoring technology in recent years. As described in US7045025, a high-energy laser is used to ablate material instantaneously to a melting temperature on the surface of a steel sheet, thereby forming a hot melt zone for the purpose of refining magnetic domains. Because the metal has high melting point and quick heat conduction, a crater-shaped bulge formed by metal melting can be formed at the edge of the groove during laser ablation, an adhesion accumulation formed by cooling and recondensing after metal gasification can be generated nearby, the lamination coefficient of the silicon steel sheet is reduced, and meanwhile, the inter-sheet conduction risk in the service process of the transformer is increased; further, a solution to overcome the problem of protrusion of the edges of the score groove caused by laser thermal melting, such as chinese patent CN102941413a, uses relatively low energy laser to scan repeatedly, so as to achieve the effect of controlling protrusion of the edges of the groove to be no more than 5 μm. However, the width of the notch line is in the micron-scale range, so that the repositioning difficulty on the surface of the strip steel in the production process is extremely high, and the repeated notch mode is difficult to realize the mass production of an industrial assembly line.
In order to overcome the defects in the technical scheme of forming the groove by laser ablation, the inventor creatively provides a composite laser scoring scheme through detailed research, so that the processing efficiency of the laser heat-resistant scoring is effectively improved, and the product has good comprehensive performance in the aspects of low iron loss, lamination coefficient and the like.
The strip steel forms a series of primary scoring linear grooves when passing through the front laser, mainly stripping coating and bottom materials, and then ablates the metal matrix on the basis of primary scoring through the rear laser to form a series of secondary scoring grooves. In order to realize accurate positioning processing of front and rear nicks, the rear nick laser and the front nick laser should keep a proper distance in the running direction of the strip steel, so that a composite linear groove with a certain depth is formed.
The basic principle of the present invention is explained below.
As described above, after the high temperature annealing process, the oriented silicon steel is formed with a bottom layer mainly containing magnesium silicate on the surface, and then is subjected to hot stretching, leveling and annealing, phosphate coating, baking and sintering to obtain the finished oriented silicon steel plate. The inventors found through research that the phosphate coating and the magnesium silicate underlayer on the surface of the oriented silicon steel plate are completely different from the physical properties of the steel matrix. The coating and the bottom layer are made of ceramic materials, the melting point is high, the heat conductivity coefficient is small, and the melting point of the steel substrate is relatively low, but the heat conductivity coefficient is large. The inventor makes full use of the difference of the physical properties of the materials by adopting a mode of compound laser scoring. Because of the high melting point of the magnesium silicate underlayer, the inventors used a high energy density continuous or pulsed laser to ablate the release coating, controlling the ablation depth to be in the range of 0.5 μm to 5 μm. When the ablation depth is less than 0.5 mu m, the front notch cannot play a notch effect, the rear laser cannot ablate on the substrate to form a secondary linear groove efficiently, a fusion mixing solidification phenomenon of a coating and substrate substances can be formed, the quality of the groove is reduced, and the lamination coefficient of the silicon steel sheet is increased; if the front laser ablation depth exceeds 5 mu m, the temperature rise effect formed by laser energy is conducted to the matrix, the substrate is melted due to the characteristic of high energy density of the front laser, the melt is piled up at the edge of the linear groove to form a bulge, the lamination coefficient of the finished oriented silicon steel plate is reduced, and meanwhile, the ablation effect of the rear laser is also influenced.
The invention uses pulse laser with high instantaneous peak power density to re-score at the same position on the basis of forming a series of primary linear grooves by pre-scoring, controls the depth of the linear grooves formed by post-scoring to be 5-60 mu m, and can lead the iron loss P of the silicon steel plate to be reduced 17/50 Obviously reduce by more than 6 percent and maintain the magnetic induction B 8 Without significant degradation. This is because the magnetic permeability of the oriented silicon steel sheet is determined by the substrate thereof, irrespective of the underlying layer and the surface insulating coating. In order to achieve the refinement of magnetic domains and reduce the iron loss, the depth of the linear groove formed on the substrate must be controlled to be 5 μm or more, the depth is not reached, the magnetic domain refinement effect formed by the nicks is limited, and the iron loss of the silicon steel sheet cannot be effectively reduced; meanwhile, since the linear groove portion leaks magnetic flux to reduce the magnetic induction of the silicon steel sheet, the groove depth needs to be controlled to be atAnd the magnetic induction B8 is obviously reduced within 60 mu m and exceeds the upper limit, and the magnetic conduction efficiency of the manufactured transformer core is seriously reduced.
The magnesium silicate bottom layer is formed through chemical reaction in the high-temperature annealing process of the steel plate, and a pinning structure exists between the magnesium silicate bottom layer and the substrate, so that the binding force between the bottom layer and the substrate is strong, and when the surface insulating coating is applied on the magnesium silicate bottom layer, the coating has good adhesiveness and is not easy to fall off. The adoption of the scoring mode to refine the magnetic domains reduces the iron loss, can lead the coating of the scoring area to be cracked and peeled off, leads the steel plate matrix to be exposed, and leads the coating adhesiveness of the scoring area to be reduced. The inventors have determined through detailed studies and trial and error that the width of the score formed in the composite score manner is not more than 300 μm at maximum, beyond which the adhesion of the silicon steel sheet coating is significantly deteriorated, and the risk of the on-chip risk of the transformer being manufactured during service is increased. Meanwhile, in order to effectively exert the advantages of the scoring mode of the present invention, the width of the groove formed by the rear score is required to be smaller than or equal to the width of the groove formed by the front score, i.e. the ratio of the front score to the rear score needs to be controlled. When the ratio is smaller than 1, the width of the rear notch is larger than that of the front notch, and the rear laser part scans on the bottom layer or the coating layer, so that the ablation efficiency of the rear laser on the substrate is reduced, the coating layer and the substrate are molten and resolidified, the coating layer and the substrate are accumulated near the linear groove, and the lamination coefficient of the silicon steel plate is reduced. When the ratio is more than 60, the width of the groove formed by the front notch is seriously more than that of the groove formed by the rear notch, the exposed quantity of the substrate is large, and the adhesiveness of the coating is obviously reduced, so that the inventor controls the ratio of the front notch width to the rear notch width to be 1-60.
Meanwhile, the width of the groove formed by the pre-notch should not be smaller than 10 μm, which is determined by the mode of the compound superposition notch. When the width of a groove formed by the front notch is smaller than 10 mu m, the rear notch is difficult to accurately position the primary notch line and ablate the notch on the basis of the primary notch line in the strip steel operation process, so that fluctuation of the quality of the groove is caused, splash and bulge are locally generated, the lamination coefficient of the silicon steel sheet is reduced, and the composite superposition notch required by the invention cannot be formed.
In summary, the width of the pre-notch is 10 μm to 300 μm, and the ratio of the width of the groove formed by the pre-notch to the post-notch is 1 to 60.
The following describes a specific laser scoring method and the scope of the claimed invention.
The invention aims to ablate and peel off the surface coating and the bottom layer of a silicon steel plate. Because of the high melting point and small thermal conductivity of the coating and underlying materials, a high energy density laser must be used.
Energy density E of front laser 1 The definition is as follows:
wherein P is 1 The unit of the output power of the front laser is W; s is S 1 Is the spot area of the front laser with the unit of mm 2 ；t d1 The dwell time of the front laser is in ms.
Dwell time t of laser scanning d The definition is as follows:
wherein V is s The laser scanning speed is m/s; a is the length of the light spot in the laser scanning direction, and the unit is mm. Here equation 2 is equally applicable to the calculation of post laser scan dwell time.
E 1 The laser irradiation energy received by the unit area on the score line in unit time is characterized, and the ablation temperature which can be locally reached by the surface of the steel plate during scanning is determined. The inventor confirms through detailed study and trial and error that E 1 Exceeding 10.2J/mm 2 When the energy injected by the front laser on the surface of the steel plate is too large, the depth of the formed groove is too large to reach the steel plate substrate, thereby melting the substrate and carrying out large-area thermal diffusion, causing the phenomena of thermal deformation and thermal melting of the steel plate and the silicon steel plate lamination coefficient to be obviousA significant decrease; e (E) 1 Too small, less than 0.16J/mm 2 When the energy of the front laser injected into the surface of the steel plate is too small, the requirement of the groove depth of 0.5 μm cannot be met. At the same time, the diameter a of the light spot formed on the surface of the steel plate by the laser along the scanning direction 1 Between 0.05 and 20mm, diameter b perpendicular to the scanning direction 1 Between 0.01 and 0.3 mm. a, a 1 When the thickness is less than 0.05mm, the residence time is too short during laser scanning, so that molten splashes generated by the surface coating are accumulated near the groove, and the lamination coefficient of the silicon steel plate is reduced; when the length of the laser beam is more than 20mm, the scanning residence time is too long, the heat generated by laser injection is accumulated, and the phenomenon of melting splashing can also occur. b 1 When the thickness is smaller than 0.01mm, the stripping width of the front laser nick is very small and smaller than 10 mu m, the rear laser nick is difficult to realize accurate positioning on the basis, the remelting phenomenon of a coating and a matrix substance is generated by the rear laser ablation coating, the quality of a groove is deteriorated, and the stacking coefficient of a silicon steel plate is reduced; when b 1 When the thickness of the coating is more than 0.3mm, the stripping amount of the front laser nick coating is too wide and exceeds 300 mu m, the adhesiveness of the silicon steel coating is reduced, and the manufactured transformer iron core has the risk of conducting among sheets.
The front laser utilizes the heat fusion and evaporation effect generated by the high-energy irradiation of the laser, so the laser pumping source and the pulse width and wavelength thereof are not particularly limited. Using solids, CO 2 The beneficial effects of the invention can be produced by continuous or pulsed laser generated by gas, semiconductor, optical fiber and other pump sources.
The post-scoring method is described below.
As described above, the post-scoring ablates the exposed part of the substrate formed on the basis of the pre-scoring, thereby forming linear grooves, reducing the magnetic domain width and lowering the iron loss of the silicon steel plate. According to the characteristics of relatively low melting point and large heat conductivity coefficient of the steel substrate, the inventor creatively invents a mode of using short pulse laser ablation with high single pulse instantaneous peak power density, namely increasing pulse energy and reducing pulse width, thereby controlling the thermal diffusion of the substrate and preventing thermal deformation. This is because the rate of thermal diffusion between atoms of the silicon steel plate matrix is in picoseconds (10 -15 s) the magnitude of the force,therefore, the shorter the laser and the substrate are, the smaller the phenomenon of thermal diffusion occurs; and meanwhile, the energy of the laser pulse is controlled in a higher range, so that the steel plate can be melted or even evaporated after being irradiated by the laser of the energy, and the steel plate is peeled to form a groove. The inventor also found that if the instantaneous laser pulse energy is too high, the thermal diffusion phenomenon can occur due to the too high heat injection energy in a short time, so that deposits and splashed substances are formed near the grooves, the lamination coefficient of the finished product is reduced, and in order to solve the problem, the inventor creatively adopts a mode of combining laser beam splitting and repeated scanning to realize the control of the phenomena of thermal deformation, melting splashing and the like caused by the thermal diffusion, and simultaneously improves the processing efficiency.
Fig. 4 is a schematic representation of laser beam splitting according to the present invention. Before scanning, one beam of laser is divided into N beams of beam splitting through a beam splitter, the average energy value of each beam of laser is reduced to 1/N of the original energy, and the beam splitting beam moves on the surface of the steel plate in an integral mode, so that the problem of repeated positioning of the beam does not exist, and the quality of a groove formed by a notch is obviously improved.
The invention relates to a single pulse instantaneous peak power density p 0 The definition is as follows:
wherein p is the power of the split beam after the beam splitting of the rear laser, and the unit is W; f (f) r The unit is Hz for the repetition frequency of the rear laser; s is(s) 2 The unit is mm for the beam splitting light spot area after the rear laser beam splitting 2 ；t p2 The pulse width of the post-scoring laser is s.
The present inventors have determined, through detailed studies, that p required for scoring a linear groove can be effectively achieved with good quality 0 Is controlled by the control range of (a). When p is 0 Higher than 1.2X10 13 W/mm 2 In this case, although the linear grooves can be formed due to the excessively high energy of the laser beam injected to the surface of the steel sheet in a short period of time, excessive heat is scattered near the grooves, and on the other hand, hot-melt protrusions are formedThe control of the groove type is not facilitated, and the magnetic domain width is effectively reduced; when p is 0 Below 1.2X10) 5 W/mm 2 In this case, the laser energy injected in a short time is too small to reach the melting point of the substrate, and thus the linear grooves cannot be formed efficiently. Thus, the single pulse peak instantaneous power density p of the present invention 0 Limited to 1.2X10 5 ～1.2×10 13 W/mm 2 Between them.
In order to achieve the scoring effect of thinning magnetic domains to reduce iron loss without obviously reducing the magnetic induction of the silicon steel plate, the scheme of the invention controls the total laser current density to be 1-42J/mm 2 Within the range. The total fluence of the laser is defined as:
wherein p is i,j 、s i,j The laser power and the focused spot area of the ith scanning beam and the jth beam splitting beam are respectively W, mm 2 ；t p2 The pulse width of the laser is s.
As can be seen from equation 4, the total fluence of the laser characterizes the total fluence received over the surface area of the substrate during the pulse time, and is a determining factor in determining the trench depth. When the total current density is less than 1J/mm 2 When the depth of the groove is smaller than 5 mu m, the effect of thinning magnetic domains and reducing the iron loss of the silicon steel plate can not be achieved; when the total current density is higher than 42J/mm 2 When the depth of the groove is more than 60 mu m, the magnetic leakage effect caused by the groove is serious, and the magnetic induction of the silicon steel plate is obviously reduced.
In addition, the diameter of a light spot or a beam splitting light spot formed on the surface of the steel plate by the post-notch laser is not more than 300 mu m in the direction perpendicular to the scanning direction, after the diameter is exceeded, the post-notch laser is difficult to accurately compound with a notch area formed by the pre-notch, so that phenomena such as splashing and melting of bottom materials can be caused, the lamination coefficient is reduced, and meanwhile, the adhesiveness of a silicon steel plate coating is obviously reduced due to the fact that the width of a formed notch groove is overlarge.
In order to realize composite superposition nicks, the invention accurately positions the front nicks and the rear nicks:
1. the number of times N of repeated scanning of the rear nick is limited to 5 times or less, because when the number of times of scanning exceeds 5 times, repeated positioning is difficult when the oriented silicon steel plate runs, and the composite superposition effect of the front nick and the rear nick cannot be ensured;
2. the total light spot length formed by beam splitting should not exceed 20mm, if the total light spot length exceeds 20mm, the residence time of the rear laser at a certain position is increased, so that the width of the rear nick is increased, the accurate matching of the rear nick and the front nick position is very difficult, and the industrial production practical value is not achieved;
3. the running speed precision of the oriented silicon steel plate is controlled within the range of 0.5m/s, and exceeds 0.5m/s, and the effect of the invention cannot be achieved because the effective superposition of the rear notch in the front notch area cannot be realized;
4. the distance between the front notch laser and the rear notch laser in the running direction of the oriented silicon steel plate should not exceed 1000mm, and beyond the range, the superposition of the rear notch in the front notch forming area can not be realized, the effective matrix groove depth refined magnetic domain can not be formed, the iron loss is reduced, and meanwhile, the processing efficiency is also obviously reduced.
The invention has the beneficial effects that:
the invention adopts the mode of front and back laser compound nicks to form the compound superposition groove on the surface of the oriented silicon steel plate, which can further refine magnetic domains, reduce iron loss and has better surface coating adhesiveness. The invention fully utilizes the two laser characteristics and the physical characteristics of the oriented silicon steel plate coating and the substrate, furthest controls the thermal diffusion and melting phenomena generated in the laser scoring process, has good lamination coefficient of the finished product and the adhesiveness of the surface coating, does not deteriorate the iron loss after stress relief annealing, and is particularly suitable for manufacturing the high-energy-efficiency winding iron core transformer.
Drawings
FIG. 1 is a schematic illustration of the formation of a composite superimposed score in accordance with the present invention;
FIG. 2 is a schematic cross-sectional view of a composite superimposed score in the thickness direction of a steel sheet;
FIG. 3 is a schematic diagram of the beam splitting of a post scoring laser (7: incident beam, 8: beam splitter, 9: beam splitting cluster);
fig. 4 is a schematic diagram of front-back scoring laser beam splitting light spots.
Detailed Description
The present invention will be further described with reference to examples and drawings, but the aspects of the present invention are not limited to the aspects described in the examples.
Referring to fig. 1 and 2, the oriented silicon steel sheet 1 forms a series of primary score line grooves 3, mainly comprising a release coating 6 and a primer, when passing through the front laser 2, and then ablates the metal substrate of the oriented silicon steel sheet 1 on the basis of the primary score line grooves 3 by passing through the rear laser 4 to form a series of secondary score grooves 5. In order to realize accurate positioning processing of the front and rear scores, the rear score laser and the front score laser should keep a proper distance in the running direction of the oriented silicon steel plate 1, so as to form a composite linear groove with a certain depth.
Referring to fig. 3, the high instantaneous pulse energy laser used for the post-scoring is that the incident beam 7 forms a score on the surface of the oriented silicon steel plate 1 in a singular or plural spectroscopic mode through the beam splitter 8, the total length of the focused sub-light spot formed on the surface of the oriented silicon steel plate 1 in the scanning direction by the spectroscopic is not more than 20mm, and the number of repeated scanning times on the surface of the oriented silicon steel plate is not more than 5.
Referring to fig. 2, the notch oriented silicon steel resistant to stress relief annealing of the invention forms composite superimposed notches, namely front notches and rear notches which are superimposed up and down on one side or both sides of an oriented silicon steel plate 1 by front and rear laser scanning, wherein the front notches form grooves (primary notch linear grooves 3) with the width of 10-300 μm and the depth of 0.5-5 μm; the post-scoring forms a groove (secondary scoring groove 5) with a width of 300 μm or less and a depth of 5 to 60 μm in the groove (primary scoring linear groove 3) of the pre-scoring.
Preferably, the ratio K of the width of the groove formed by the pre-notch and the post-notch is between 1 and 60.
Example 1
The oriented silicon steel is processed by iron making, steel making, continuous casting and hot rolling,and then cold rolling to a final thickness of 0.22mm, forming a surface oxide layer through a decarburization annealing process at 850 ℃, coating an MgO isolating agent on the surface of the surface oxide layer, rolling into a steel coil, keeping the steel coil for 20 hours under a high-temperature annealing condition at 1200 ℃, cleaning residual MgO unreacted on the surface, drying, and then forming a composite superposition notch on one side of the oriented silicon steel plate through laser scanning before and after the transverse direction of the oriented silicon steel plate. Namely, after the steel plate is subjected to the first nick formation by the nick laser scanning as shown in the table 1, the composite nick is formed by the post nick laser scanning, the distance between the composite nick lines along the rolling direction of the steel plate is 5mm, and the distance between the front nick laser and the post nick laser in the running direction of the oriented silicon steel plate is 300mm. CO is adopted for the pre-scoring laser 2 Continuous laser with the wavelength of 10.6 mu m, post-positioned scoring laser output power of 1000W, repetition frequency of 800KHz, pulse width of 1 nanosecond, laser beam splitting of 100 beams, forming light spots on the surface of the oriented silicon steel plate by the split beams into circles, and calculating to obtain the single-pulse instantaneous peak power density p of the pre-positioned laser beam splitting by the laser beam splitting, wherein the light spot diameter of the split beams is 8 mu m in the scanning direction and the scanning direction perpendicular to the scanning direction, and the scanning speed is 10m/s 0 Is 2.5X10 8 W/mm 2 Total energy flow density J F 15.9J/mm 2 The average depth of the linear grooves formed by the secondary scoring is 12 μm, and the average width is about 9 μm. Then, an insulating coating is coated on the surface of the steel sheet and final annealing is performed to form a silicon steel sheet. Measuring the surface coating adhesion of a silicon steel plate by using GBT2522-2017 ' method for testing the surface insulation resistance and the coating adhesion of an electrical steel plate (belt) ', and measuring the P of the silicon steel plate by using GBT3655-2008 ' method for measuring the magnetic performance of the electrical steel plate (belt) by using an Epstein square ring 17/50 And B 8 Values. The effect of the examples and comparative examples is shown in Table 1.
As can be seen from the effects of Table 1, the silicon steel sheet has no thermal deformation, good adhesion, C-grade or higher, lamination coefficient of 95% or higher, and core loss P 17/50 Lower, B 8 Higher; the comparative examples outside the scope of the present invention have problems of thermal deformation of the steel sheet, poor adhesion, or reduced lamination factor.
Example 2
The oriented silicon steel is subjected to iron making, steelmaking, continuous casting and heatingThe rolling process comprises the steps of cold rolling again to a final thickness of 0.22mm, forming a surface oxide layer, coating an MgO isolating agent on the surface of the surface oxide layer after a decarburization annealing process at 850 ℃, keeping the surface oxide layer for 20 hours under a high-temperature annealing condition at 1200 ℃ after coiling a steel coil, cleaning residual MgO unreacted on the surface, drying, applying an insulating coating on the surface of an oriented silicon steel plate, and carrying out composite superposition scoring on one side of the steel plate along the transverse direction of the steel plate. The front-end notch laser adopts pulse fiber laser with wavelength of 533nm, output power of 6000W and diameter a of focusing light spot in scanning direction 1 10mm, perpendicular to the scanning direction b 1 The diameter is 0.3mm, the scanning speed is 10m/s, and the laser energy density E is obtained by calculation 1 2.5J/mm 2 The score width formed by the peeling of the coating was 300. Mu.m, and the depth was 3. Mu.m. Then, the surface of the oriented silicon steel plate is scored again by pulse laser as shown in the table 2, and finally, composite superposition scores with rolling direction intervals of 4mm are formed on the surface of the oriented silicon steel plate; the distance between the front and rear scoring lasers in the running direction of the oriented silicon steel plate is 800mm. Finally, coating the insulating coating again and carrying out final annealing to form the finished silicon steel plate. Measuring the surface coating adhesion of a silicon steel plate by using GBT2522-2017 ' method for testing the surface insulation resistance and the coating adhesion of an electrical steel plate (belt) ', and measuring the P of the silicon steel plate by using GBT3655-2008 ' method for measuring the magnetic performance of the electrical steel plate (belt) by using an Epstein square ring 17/50 And B 8 Values. The effect of the examples and comparative examples is shown in Table 3.
As can be seen from the above effects, the silicon steel sheet lamination factor is 95% or more and the core loss P is within the scope of the present invention 17/50 Lower, B 8 Higher; comparative examples 7 to 12, which are outside the scope of the present invention, have the problem that the lamination factor is lowered due to the hot melting of the steel sheet, and comparative example 13, which is outside the scope of the present invention, cannot form effective scores due to the excessively small energy flow density, and the score depth is smaller than the scope of the present invention, thereby failing to achieve the effect of refining magnetic domains and reducing the iron loss.
Example 3
The oriented silicon steel is subjected to iron making, steelmaking, continuous casting and hot rolling processes, cold rolling and rolling for the second time until the final thickness is 0.26mm, decarburization annealing process at 870 ℃ is carried out, mgO isolating agent is coated on the surface of the surface oxide layer after the surface oxide layer is formed, and the coil is rolledAfter the steel coil is manufactured, the steel coil is kept for 20 hours under the high-temperature annealing condition of 1250 ℃, then the unreacted residual MgO on the surface is cleaned and dried, and then the composite superimposed nicks are formed on one surface of the oriented silicon steel plate through front and rear laser scanning along the transverse direction of the steel plate. The front laser adopts continuous solid laser, and specific parameters are shown in table 4; the post laser adopts pulse solid laser, the output power is 800W, the repetition frequency is 100KHz, the pulse width is 1 nanosecond, the beam is split into 80 beams after passing through a beam splitter, the total length of a focusing light spot is 5mm, the scanning times are 1 time, and other laser parameters are regulated to enable the laser parameters to meet the requirement range of the invention; the rolling direction distance of the composite superimposed nicks is 6mm, and the distance between the front nick laser and the rear nick laser in the running direction of the oriented silicon steel plate is 600mm; then, an insulating coating is coated on the surface of the steel sheet and final annealing is performed to form a silicon steel sheet. The surface coating adhesion of the oriented silicon steel plate is measured by GBT2522-2017 'method for testing surface insulation resistance and coating adhesion of electrical steel sheet (band)', and the P of the silicon steel plate is measured by GBT3655-2008 'method for measuring magnetic properties of electrical steel sheet (band) by Epstein square ring' 17/50 And B 8 Values. The effect of the examples and comparative examples is shown in Table 5.
From the above effects, it can be seen that the coating adhesion of the oriented silicon steel sheet is good, the C-grade or higher, the lamination coefficient is 95% or higher, and the iron loss P is 17/50 Lower, B 8 Higher; comparative examples 14, 15 and 17, 18 outside the scope of the present invention exhibited reduced lamination factor due to the occurrence of hot melting during laser scoring; comparative examples 16 and 19 outside the range of the present invention are because the pre-score width or the ratio K of the pre-score width to the post-score width exceeds the range of the present invention, and the coating adhesion is deteriorated.
Example 4 illustrates other precision-related parameter ranges
The oriented silicon steel is subjected to iron making, steelmaking, continuous casting and hot rolling processes, cold rolling and rolling for the final thickness of 0.26mm, decarburization annealing processes at 870 ℃ are carried out to form a surface oxide layer, mgO isolating agent is coated on the surface of the surface oxide layer, the surface oxide layer is rolled into a steel coil, the steel coil is kept for 20 hours under the high-temperature annealing condition at 1250 ℃, unreacted residual MgO on the surface is cleaned and dried, and then the steel coil is transversely passed along the oriented silicon steel plate on one side of the oriented silicon steel plateAnd (5) scanning front and back laser to form a composite superposition notch. The front laser adopts a continuous solid laser with 4000W output power and a diameter a in the scanning direction of a focusing light spot 1 6mm diameter b perpendicular to the scanning direction 1 0.05mm, a scanning speed of 100m/s, and an energy density E thereof was calculated from the result 1 1.0J/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the The post laser adopts a pulse solid laser, the output power is 500W, the repetition frequency is 800KHz, the pulse width is 10 nanoseconds, a beam splitting 100 beam is formed after passing through a beam splitter, the diameter of a beam splitting focusing light spot in the scanning direction is circular, the light spot diameters a2 and b2 are 20 mu m, the total length of the focusing light spot is 3mm, the scanning speed is 10m/s, and the single-pulse instantaneous peak power density p of the beam splitting light spot is calculated according to the above 0 Is 2.0X10 6 W/mm 2 The total current density varies with the number of repeated scans, but remains within the scope of the invention; the rolling direction distance of the formed composite overlapped nicks is 4mm; then, an insulating coating is coated on the surface of the steel sheet and final annealing is performed to form a silicon steel sheet. Measuring the surface coating adhesion of a silicon steel plate by using GBT2522-2017 ' method for testing the surface insulation resistance and the coating adhesion of an electrical steel plate (belt) ', and measuring the P of the silicon steel plate by using GBT3655-2008 ' method for measuring the magnetic performance of the electrical steel plate (belt) by using an Epstein square ring 17/50 And B 8 Values. The effect of the examples and comparative examples is shown in Table 6.
From the above effects, it can be seen that comparative examples 21 to 23, in which the lamination factor of the silicon steel sheet was 95% or more in the range of the present invention, were reduced in lamination factor due to heat melting, splashing, etc. by laser scoring.
According to the notch oriented silicon steel resistant to stress relief annealing and the manufacturing method thereof, the purpose of refining magnetic domains and reducing iron loss is achieved by implementing composite superposition notches on the surface micro-areas. The technical scheme of the invention is easy to implement, and the produced oriented silicon steel has the characteristics of low iron loss and high lamination coefficient, does not deteriorate after stress relief annealing, and has wide application prospect in the manufacturing field of energy-saving wound core transformers.
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Claims (9)

1. The notch oriented silicon steel resistant to stress relief annealing is characterized in that front and back laser scanning is adopted on one side or two sides of an oriented silicon steel plate to form a composite superposition notch, namely a front notch and a rear notch which are superposed up and down, wherein the front notch forms a groove with the width of 10-300 mu m and the depth of 0.5-5 mu m; the rear nick forms a groove with the width of less than 300 mu m and the depth of 5-60 mu m in the groove of the front nick; the ratio K of the width of the groove formed by the pre-notch and the post-notch is 3-60.
2. The method for manufacturing a notch oriented silicon steel resistant to stress relief annealing as set forth in claim 1, comprising: smelting, continuous casting, hot rolling, cold rolling for one time or two times with intermediate annealing, rolling to the final thickness, decarburizing annealing, coating MgO separating agent on the surface, annealing at high temperature to form complete secondary recrystallization, final annealing and coating insulating coating to form the finished oriented silicon steel plate, and laser scoring, wherein after decarburizing annealing, before final annealing or after final annealing, the composite superposition scoring is formed on one side or both sides of the oriented silicon steel plate by adopting front and rear laser scanning,
the prepositive nick adopts continuous or pulse laser, and the diameter of the light spot a along the scanning direction 1 A spot diameter b perpendicular to the scanning direction of between 0.05 and 20mm 1 Between 0.01 and 0.3 mm; the prepositive nick forms a groove with the width of 10-300 mu m and the depth of 0.5-5 mu m;
the post-scoring adopts high instantaneous pulse energy laser, and the spot diameter a along the scanning direction 2 A spot diameter b perpendicular to the scanning direction of between 0.005 and 5mm 2 Between 0.005 and 0.3 mm; the post-notch forms a groove with the width of 300 μm or less and the depth of 5-60 μm in the groove of the pre-notch.
3. The method for producing a stress relief annealing resistant scored oriented silicon steel as claimed in claim 2, wherein said pre-scored laser energy density is 0.16-10.2J/mm 2 Between them.
4. The method for producing a notch oriented silicon steel resistant to stress relief annealing as set forth in claim 2, wherein a high instantaneous pulse energy laser used for post-notch is scanned in single or complex beam-splitting manner to form a notch on the surface of the oriented silicon steel sheet, and the average single pulse peak instantaneous power density of the beam-splitting is not less than 1.2x10 5 ～1.2×10 13 W/mm 2 Between them, the total energy density is 1-42J/mm 2 The total energy density is the sum of the energy densities of the beam-splitting laser scanning.
5. The method for producing a notched oriented silicon steel resistant to stress relief annealing as set forth in claim 2 or 4, wherein the high instantaneous pulse energy laser used for post-scoring forms the notch on the surface of the oriented silicon steel sheet in the form of singular or plural beam splitting, the total length of the focused beam splitting spot formed on the surface of the oriented silicon steel sheet in the scanning direction is not more than 20mm, and the number of repeated scanning on the surface of the oriented silicon steel sheet is not more than 5.
6. The method for producing a notched oriented silicon steel resistant to stress relief annealing as set forth in claim 2, wherein the running speed fluctuation of said oriented silicon steel sheet is controlled within + -0.5 m/s during laser scoring.
7. The method of producing a scored oriented silicon steel resistant to stress relief annealing as claimed in claim 2, 3, 4 or 6, wherein said post-scoring laser is spaced apart from said pre-scoring laser by not more than 1000mm in the running direction of said oriented silicon steel sheet.
8. The method of producing scored oriented silicon steel resistant to stress relief annealing as claimed in claim 5, wherein said post-scoring laser and said pre-scoring laser are spaced apart by not more than 1000mm in the running direction of said oriented silicon steel sheet.
9. The method for producing scored oriented silicon steel resistant to stress relief annealing as claimed in claim 2, wherein said finished oriented silicon steel sheet has a thickness of 0.15-0.35 mm.
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