Laser heat-resistant nicking oriented silicon steel and nicking method thereof

Abstract

The invention discloses oriented silicon steel with laser heat-resistant nicks, the surface of the oriented silicon steel is provided with parallel linear grooves formed by laser nicks, the depth of each groove is 15-45 [mu] m, and the width of each groove is 5-15 [mu] m. The invention also discloses a nicking method of the laser heat-resistant nicking oriented silicon steel, which comprises the following steps of: outputting pulse laser in a pulse string mode, and forming the parallel linear grooves on the surface of an oriented silicon steel plate through single scanning. According to the laser heat-resistant nicking oriented silicon steel and the nicking method thereof, narrow and deep grooves can be formed in the surface of a steel plate through one-time scanning, the obtained oriented silicon steel has the advantages of being low in iron loss and high in magnetic induction, the iron loss P17 / 50 of the oriented silicon steel is smaller than 0.78 W / kg, the magnetic induction B8 of the oriented silicon steel is larger than 1.92 T, and the lamination coefficient of the oriented silicon steel is larger than or equal to 95.5%.

Description

Technical Field

[0001] This invention relates to a type of steel and a method for manufacturing the same, and more particularly to a high-strength steel and a method for manufacturing the same. Background Technology

[0002] The technique of refining magnetic domains and reducing iron loss by scoring the surface of grain-oriented silicon steel can be divided into two main categories based on the scoring effect: One type is non-stress-relief annealing scoring, which uses lasers, plasma beams, electron beams, etc., to form linear thermal stress zones at certain intervals on the surface, thereby reducing the width of the main magnetic domains and lowering iron loss. Since the linear thermal stress disappears due to stress-relief annealing, this type of product is generally used to manufacture laminated core transformers that do not require stress-relief annealing. The other type is stress-relief annealing scoring, whose basic technical solution is to use mechanical toothed rollers, electrochemical corrosion, etc., to form linear strain zones or grooves on the surface of grain-oriented silicon steel, reducing the 180° magnetic domain width and thus lowering iron loss.

[0003] Due to the high surface hardness of grain-oriented silicon steel sheets, the above-mentioned methods of mechanical pressure and electrolytic corrosion are inefficient and environmentally unfriendly for manufacturing heat-resistant grooved grain-oriented silicon steel products, hindering large-scale mass production. To overcome this challenge, the industry has recently focused on laser heat-resistant groove marking as a research direction. For example:

[0004] Chinese patent document CN1090242C, published on May 14, 2000, entitled "Oriented Silicon Steel Sheet with Excellent Magnetic Properties and its Production Method", discloses an oriented silicon steel sheet with excellent magnetic properties and its production method. The method uses a high-density energy pulse-modulated laser beam to simultaneously score the upper and lower surfaces of the steel sheet to form grooves or heat-affected layers. The depth of the grooves or heat-affected layers formed is not greater than 5% of the thickness. Summary of the Invention

[0005] One of the objectives of this invention is to provide a laser-etched heat-resistant silicon steel that reduces iron loss while also reducing the adverse effects of laser-etched grooves on magnetic induction. The resulting silicon steel has the characteristics of low iron loss and high magnetic induction.

[0006] One of the objectives of this invention is to provide a laser-etched heat-resistant oriented silicon steel with parallel linear grooves formed by laser etching on its surface. The grooves have a depth of 15-45 μm and a width of 5-15 μm.

[0007] Through research, the inventors discovered that there is a coupling effect between the two walls of the groove. The larger the groove width and the greater the distance between the two walls, the weaker the coupling effect and the more significant the decrease in magnetic induction. Simultaneously, the inventors determined the range of groove parameters for obtaining the oriented silicon steel described in this invention through a series of experiments: the groove width is between 5-15 μm, and the groove depth is between 15-45 μm.

[0008] In this invention, to minimize the impact of leakage flux at the groove on the magnetic induction of the grain-oriented silicon steel sheet, the groove width should be controlled within 15 μm. When the width exceeds 15 μm, the leakage flux at the groove is large, and the coupling effect of the free magnetic poles on both sides of the groove is small, thus reducing the magnetic induction of the finished grain-oriented silicon steel sheet. Although a smaller groove width results in a higher magnetic induction of the finished grain-oriented silicon steel sheet, the groove width still needs to be controlled above 5 μm. This is because a smaller groove width results in a smaller laser focusing spot diameter used for marking the steel sheet surface. Consequently, the laser focusing focal length and depth of focus are also smaller, significantly increasing the complexity of the overall laser optical path system and the difficulty of marking control. Therefore, considering the above factors, this invention controls the groove width within the range of 5-15 μm.

[0009] In this invention, when the trench depth is below the lower limit of 15 μm, the effect of trench refinement in reducing magnetic domains and lowering iron loss is limited, resulting in high iron loss in the finished grain-oriented silicon steel sheet. When the trench depth is above the upper limit of 45 μm, the leakage magnetic flux through the trench is large, leading to a decrease in the magnetic induction of the finished grain-oriented silicon steel sheet. Therefore, this invention controls the trench depth within the range of 15-45 μm.

[0010] Furthermore, in the laser heat-resistant etched oriented silicon steel described in this invention, the spacing between adjacent grooves is 2-8 mm.

[0011] In this invention, when the spacing between adjacent grooves is less than the lower limit of 2mm, the magnetic induction of the finished grain-oriented silicon steel sheet is low; when the spacing between adjacent grooves is greater than 8mm, the effect of refining the magnetic domains and reducing iron loss is limited, resulting in high iron loss of the finished grain-oriented silicon steel sheet. Therefore, this invention controls the spacing between adjacent grooves to be between 2-8mm.

[0012] Furthermore, in the laser heat-resistant etched grain-oriented silicon steel described in this invention, the iron loss P... 17 / 50 At a value below 0.78 W / kg, the magnetic induction B8 is above 1.92 T.

[0013] Furthermore, the stacking factor of the laser heat-resistant etched oriented silicon steel described in this invention is ≥95.5%.

[0014] Another objective of this invention is to provide a laser heat-resistant etched graining method for grained silicon steel. This method can form narrow and deep grooves on the surface of a steel plate in a single scan, resulting in grained silicon steel with low iron loss and high magnetic induction.

[0015] To achieve the above objectives, the present invention provides a laser heat-resistant etching method for grain-oriented silicon steel, comprising: outputting pulsed laser in a pulse train manner to form the parallel linear grooves on the surface of the grain-oriented silicon steel plate by a single scan.

[0016] Furthermore, in the scoring method described in this invention, the number of individual pulses within the pulse train is ≥200, and the energy density of a single pulse is 0.09-0.45 J / cm². 2 .

[0017] In this invention, to form the narrow and deep grooves described herein, the number of pulse trains needs to be maintained at 200 or more (including 200). When the number of individual pulses within a pulse train is less than 200, the width of the groove increases while the depth decreases, making it impossible to form the grooves required by this invention. Furthermore, although there is no specific upper limit on the number of pulse trains, its value should meet the requirements of this invention for single-pulse energy density, i.e., the single-pulse energy density ps should be between 0.09 and 0.45 J / cm². 2 Within this range. This is because when the laser scribing and ablates atoms to form grooves on the surface, the interaction time between the laser and the atoms on the silicon steel surface is limited to a single pulse. During this time period, the energy density is excessively high, exceeding 0.45 J / cm². 2 This will cause the depth of the grooves formed by laser etching to exceed the 45μm designed in this invention, resulting in a significant decrease in the magnetic induction of the finished product; the energy density is too low during this period, below 0.09J / cm². 2 The depth of the grooves formed by laser engraving cannot reach the lower limit of refining magnetic domains to reduce iron loss, namely 15μm. Therefore, the effect of engraving in refining magnetic domains to reduce iron loss is limited, and the iron loss of the finished product is too high.

[0018] Furthermore, in the scribe method described in this invention, the time interval between individual pulses within a pulse train is 0.5 to 1.25 ns.

[0019] In this invention, when the time interval between individual pulses within a pulse train is greater than 1.25 ns, the coupling between pulses is poor, which may result in a wide groove, making it difficult to form the narrow and deep sharp grooves designed in this invention. When the time interval between individual pulses within a pulse train is less than 0.5 ns, the coupling between consecutive pulses is too strong, causing the laser etching process to degenerate into thermal processing, resulting in poor groove quality. Therefore, in this invention, the time interval between individual pulses within a pulse train is controlled between 0.5 and 1.25 ns.

[0020] Furthermore, in the scribe method described in this invention, the pulse width of the pulse train is ≤40ps.

[0021] In this invention, to achieve the desired laser processing effect, the pulse width of the control laser needs to be controlled within 40 ps, ​​and the smaller the better. This pulse width is determined by the lattice thermal conduction time of silicon steel. When the pulse width is above 40 ps, ​​increasing the laser output power will degrade the quality of the groove, producing a lot of molten material and spatter. However, reducing the laser output power can reduce the production of molten material and spatter, but it is difficult to form grooves. Therefore, when the pulse width is above 40 ps, ​​it is difficult to form the grooves required by this invention.

[0022] Furthermore, in the marking method described in this invention, the repetition frequency of the pulsed laser is 300-5000KHz.

[0023] In this invention, when the repetition frequency of the pulsed laser is below 300 kHz, the interval between pulse trains is too large, and the energy density of a single pulse is too high, resulting in a significant thermal melting effect. This may lead to poor trench quality, and forming the extremely sharp trenches designed in this invention is relatively difficult. When the repetition frequency of the pulsed laser exceeds 5000 kHz, the laser pulse train also interacts with the next pulse train, resulting in poor trench quality. Therefore, in this invention, the repetition frequency of the pulsed laser is controlled between 300 and 5000 kHz.

[0024] Furthermore, in the scoring method described in this invention, the focused spot formed by the pulsed laser on the surface of the oriented silicon steel plate is circular, elliptical, or rectangular.

[0025] In this invention, the shape of the focused spot can be a circular spot, an elliptical spot, or a shaped rectangular spot.

[0026] The laser heat-resistant marking process can be performed before decarburization annealing, before hot stretching and flattening annealing, or after hot stretching and flattening annealing. As long as the size, quality, and spacing of adjacent marking lines are within the scope of the invention, the effect of the invention can be achieved.

[0027] The laser heat-resistant etched grained silicon steel and its etching method described in this invention have the following advantages and beneficial effects compared with the prior art:

[0028] The laser heat-resistant etched grained silicon steel and its etching method described in this invention can form narrow and deep grooves on the surface of a steel plate in a single scan, resulting in grained silicon steel with low iron loss and high magnetic induction.

[0029] In some embodiments, the iron loss P of the laser heat-resistant etched grain-oriented silicon steel described in this invention... 17 / 50 For values ​​below 0.78 W / kg, with a magnetic induction B8 above 1.92 T, the lamination factor is ≥95.5%. Attached Figure Description

[0030] Figure 1 The diagram schematically illustrates a parallel linear groove formed by laser etching in one embodiment of the laser heat-resistant etched oriented silicon steel according to the present invention.

[0031] Figure 2 The diagram schematically illustrates a laser output in a pulse train mode in one embodiment of the scoring method described in this invention.

[0032] Figure 3 The diagram illustrates the relationship between pulse width and time interval within a pulse train.

[0033] Figure 4 The diagram schematically illustrates the relationship between the groove depth and iron loss of the laser-etched heat-resistant oriented silicon steel described in this invention. Detailed Implementation

[0034] The laser heat-resistant etched oriented silicon steel and its etching method described in this invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. However, this explanation and description do not constitute an improper limitation on the technical solution of this invention.

[0035] The quality of the grooves affects the service safety of the laser heat-resistant oriented silicon steel sheets after they are manufactured into transformers. In particular, the spatter may fall off during the transformer's service life due to vibrations such as magnetostriction. If the detached particles enter the transformer oil, the transformer may be at risk of breakdown.

[0036] To solve this technical problem, the present invention provides a method for etching the surface of oriented silicon steel plates using ultrashort pulse train lasers with low energy density. This method can achieve narrow and deep etched grooves, enhance the coupling effect between the two walls of the groove, and reduce iron loss by refining the magnetic domains while ensuring that the magnetic induction does not decrease significantly.

[0037] Figure 1 The diagram schematically shows a surface marking line of the laser heat-resistant etched oriented silicon steel according to one embodiment of the present invention.

[0038] like Figure 1 As shown, the laser-etched heat-resistant oriented silicon steel plate 1 of the present invention has parallel linear grooves 2 formed by laser etching.

[0039] The inventors discovered through research that when a laser ablates the surface of a steel plate in a pulse train manner, the repetition frequency R f The time interval t between single pulses b The coupling effect between laser pulses is determined by the energy density of a single pulse. The formula for calculating the energy density of a single pulse is as follows:

[0040]

[0041] Where, p s This represents the energy density of a single pulse, expressed in J / cm². 2 P represents the total laser output power, in watts (W); N represents the number of single pulses contained in the pulse train; R F S is the repetition frequency of the pulsed laser, in Hz; S is the focused spot area, in cm². 2 .

[0042] Figure 2 The diagram schematically illustrates a laser output in a pulse train mode in one embodiment of the scoring method described in this invention.

[0043] like Figure 2 As shown, the pulsed laser has a repetition frequency R f A series of sequential laser pulses is emitted, called a pulse train. A pulse train consists of a series of laser pulses with very short time intervals. The time interval between pulse trains is... For example, the repetition frequency R f =1MHz, then the time interval between the pulse train and the next pulse train is 1μs.

[0044] Figure 3 The diagram illustrates the relationship between pulse width and time interval within a pulse train.

[0045] like Figure 3 As shown, the pulse width is t p The pulse interval is t b In this invention, when a laser performs micro-area processing on the surface of a steel plate in a pulse train mode, the single pulse width is very small, meaning the interaction time between the single pulse and the material is very short, reaching the picosecond level, which is comparable to or even shorter than the heat conduction time of the material's internal lattice. The laser pulse interacts with individual atoms to strip them away, and only a small amount of energy is transferred from the stripped atom to its neighboring atoms. Therefore, the thermal melting phenomenon during the entire laser etching process of forming grooves can be effectively controlled. Because the time interval between individual pulses within the pulse train is very short, and the atoms adjacent to the atoms stripped by the previous laser are also stripped away, since these atoms already possess a certain amount of energy, a coupling effect can be formed, reducing the energy threshold for atom stripping. This effectively controls the diffusion of heat to both sides, thus enabling the creation of extremely sharp grooves with very small widths and very deep depths.

[0046] Figure 4 The diagram schematically illustrates the relationship between the groove depth and iron loss of the laser-etched heat-resistant oriented silicon steel described in this invention.

[0047] like Figure 4As shown in the diagram, taking a 0.23mm oriented silicon steel sheet as an example, the groove depth is between 15-45μm, which can simultaneously maintain low iron loss and high magnetic induction.

[0048] The laser heat-resistant etched grained silicon steel and its etching method described in this invention are further illustrated below using Examples 1-15 and Comparative Examples 1-3.

[0049] Examples 1-9 and Comparative Examples 1-2

[0050] The grain-oriented silicon steels of Examples 1-9 and the comparative steels of Comparative Examples 1-2 described in this invention were prepared using the following steps:

[0051] After undergoing ironmaking, steelmaking, continuous casting, and hot rolling processes, followed by a cold rolling process to a final thickness of 0.22mm, the steel strip is degreased and then pulsed laser light is output in a pulse train manner to form several parallel linear grooves on the surface of the grain-oriented silicon steel sheet through a single scan. Figure 1 As shown, each groove is perpendicular to the rolling direction of the steel plate, and the spacing between adjacent grooves is controlled at 5 mm. After the scoring is completed, the steel plate undergoes decarburization annealing, is coated with MgO release agent and dried, then undergoes high-temperature annealing at 1250℃ for 20 hours, and after cleaning off the residual MgO on the surface, it undergoes hot stretching and leveling annealing to form the final finished product, grain-oriented silicon steel. Table 1 lists the specific process parameters for laser scoring in Examples 1-9 and Comparative Examples 1-2.

[0052] Table 1.

[0053]

[0054]

[0055] Subsequently, the groove dimensions of the oriented silicon steels of Examples 1-9 and the comparative steels of Comparative Examples 1-2 were measured and their magnetic properties were tested. The test results are listed in Table 2. Wherein:

[0056] Iron loss P 17 / 50 Test method for B8: Refer to GB / T 3655-2022 "Method for measuring the magnetic properties of electrical steel strips (sheets) using Epstein squares".

[0057] The test method for the lamination factor is in accordance with GB / T 19289-2019 Measurement Methods for Resistivity, Density and Lamination Factor of Electrical Steel Strips (Sheets).

[0058] Table 2.

[0059]

[0060]

[0061] Note: In the table above, ◎ represents excellent groove quality with no obvious protrusions or spatter on both sides of the groove; ◎ represents good groove quality with protrusions on the edge of the groove and very little spatter formed by the condensation of liquid or gas phases during laser ablation in the vicinity of the groove.

[0062] As can be seen from Table 2 above, the iron loss P of the oriented silicon steel in Examples 1-9 of the present invention is... 17 / 50 All values ​​are less than 0.78 W / kg, and the magnetic induction B8 is greater than 1.92 T. The obtained grooves are of good quality, and their stacking factor is greater than 95.5%.

[0063] However, the single-pulse energy of Comparative Example 1 is lower than the lower limit of the present invention, and cannot reach the lower limit of the trench depth required by the present invention, resulting in high iron loss in the finished product.

[0064] Furthermore, in Comparative Example 2, the single-pulse energy was higher than the upper limit of the present invention, the trench depth exceeded the range required by the present invention, and the magnetic induction of the finished product was lower.

[0065] Examples 10-15 and Comparative Example 3

[0066] The grain-oriented silicon steels of Examples 10-15 and the comparative steels of Comparative Examples 3-7 described in this invention were prepared using the following steps:

[0067] After undergoing ironmaking, steelmaking, continuous casting, and hot rolling processes, followed by a cold rolling process to a final thickness of 0.22mm, the steel strip is degreased and then pulsed laser light is output in a pulse train manner. The laser spot is rectangular, and several parallel linear grooves are formed on the surface of the grain-oriented silicon steel sheet through a single scan. Figure 1 As shown, each groove is perpendicular to the rolling direction of the steel plate, and the spacing between adjacent grooves is controlled at 2-8mm. After the grooves are finished, the steel plate undergoes decarburization annealing, is coated with MgO release agent and dried, then undergoes high-temperature annealing at 1250℃ for 20hr, and after cleaning off the residual MgO on the surface, it undergoes hot stretching and leveling annealing to form the final finished product, grain-oriented silicon steel.

[0068] Table 3 lists the specific process parameters for the laser marking steps in Examples 10-15 and Comparative Example 3 of the present invention.

[0069] Table 3.

[0070]

[0071]

[0072] Subsequently, the groove dimensions of the oriented silicon steels of Examples 10-15 and the comparative steel of Comparative Example 3 were measured and their magnetic properties were tested. The test results are listed in Table 4. Wherein:

[0073] Iron loss P 17 / 50 Test method for B8: Refer to GB / T 3655-2022 "Method for measuring the magnetic properties of electrical steel strips (sheets) using Epstein squares".

[0074] The test method for the lamination factor is in accordance with GB / T 19289-2019 Measurement Methods for Resistivity, Density and Lamination Factor of Electrical Steel Strips (Sheets).

[0075] Table 4.

[0076]

[0077] Note: In the table above, ◎ represents excellent groove quality with no obvious protrusions or spatter on both sides of the groove; ◎ represents good groove quality with protrusions on the edge of the groove and spatter formed by the condensation of liquid or gas phases during laser ablation near the groove.

[0078] As can be seen from Table 4 above, the iron loss P of the oriented silicon steel in Examples 1-9 of the present invention is... 17 / 50 All values ​​are less than 0.78 W / kg, and the magnetic induction B8 is greater than 1.92 T. The obtained grooves are of good quality, and their stacking factor is greater than 95.5%.

[0079] The laser pulse train used in Comparative Example 3 had fewer pulses than required by this invention, failing to achieve the required trench depth and width, resulting in a lower iron loss P in the finished product. 17 / 50 It is too high, and B8 is too low.

[0080] It should be noted that the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0081] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A laser-etched heat-resistant grain-oriented silicon steel, characterized in that, Its surface has parallel linear grooves formed by laser engraving, the grooves having a depth of 15-45μm and a width of 5-15μm.

2. The laser-etched heat-resistant grain-oriented silicon steel as described in claim 1, characterized in that, The spacing between adjacent trenches is 2-8mm.

3. The laser-etched heat-resistant grain-oriented silicon steel as described in claim 1, characterized in that, Its iron loss P 17 / 50 At a value below 0.78 W / kg, the magnetic induction B8 is above 1.92 T.

4. The laser-etched heat-resistant grain-oriented silicon steel as described in claim 1, characterized in that, Its stacking factor is ≥95.5%.

5. A laser heat-resistant etching method for grain-oriented silicon steel as described in any one of claims 1-4, characterized in that: A pulsed laser is output in a pulse train manner to form the parallel linear grooves on the surface of an oriented silicon steel plate through a single scan.

6. The scoring method as described in claim 5, characterized in that, The number of individual pulses in the pulse train is ≥200, and the energy density of a single pulse is 0.09-0.45 J / cm². 2 .

7. The scoring method as described in claim 5, characterized in that, The time interval between individual pulses within a pulse train is 0.5 to 1.25 ns.

8. The scoring method as described in claim 5, characterized in that, The pulse width of the pulse train is ≤40ps.

9. The scoring method as described in claim 5, characterized in that, The repetition frequency of pulsed lasers is 300-5000KHz.

10. The scoring method as described in claim 5, characterized in that, The focused spot formed by the pulsed laser on the surface of the oriented silicon steel sheet can be circular, elliptical, or rectangular.

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