Grain-oriented electrical steel with heat-resistant laser-scribing and scribing method therefor

Abstract

A scribing method for grain-oriented electrical steel with heat-resistant laser-scribing, comprising: outputting a pulsed laser in burst mode, and forming parallel line-shaped grooves (2) on a surface of a grain-oriented electrical steel sheet (1) by means of a single scan, the grooves (2) having a depth of 15-45 μm and a width of 5-15 μm. The method allows for narrow and deep grooves (2) to be formed on a surface of a steel sheet by means of a single scan, so as to obtain grain-oriented electrical steel having a low core loss and a high magnetic flux density, wherein the core loss P17 / 50 of the grain-oriented electrical steel is less than 0.780 W / kg, the magnetic flux density B8 of the grain-oriented electrical steel is greater than 1.920 T, and a stacking factor of the grain-oriented electrical steel is greater than or equal to 95.5%. The present invention also relates to grain-oriented electrical steel with heat-resistant laser-scribing.

Description

Laser heat-resistant notch oriented silicon steel and notch method thereof TECHNICAL FIELD

[0001] The present application relates to a steel and a method for manufacturing the same, in particular to a high-strength steel and a method for manufacturing the same. BACKGROUND

[0002] The technology of implementing notch on the surface of oriented silicon steel to refine magnetic domain and reduce iron loss can be divided into two categories according to the effect of notch: one category is not resistant to stress relief annealing notch technology, which forms linear thermal stress zone on the surface by laser, plasma beam, electron beam and other means, so as to reduce the width of main magnetic domain and reduce iron loss. Since the linear thermal stress will disappear due to stress relief annealing, the products of this category are generally used to manufacture laminated core transformers which do not need stress relief annealing. The other category is resistant to stress relief annealing notch technology, which forms linear strain zone or groove on the surface of oriented silicon steel by mechanical tooth roller, electrochemical corrosion and other means, so as to reduce the width of 180° magnetic domain and reduce iron loss.

[0003] Due to the characteristics of high surface hardness of oriented silicon steel plate, the above-mentioned mechanical pressure and electrolytic corrosion method has low processing efficiency and is not environmentally friendly when manufacturing heat-resistant notch oriented silicon steel products, and cannot be mass-produced. In order to overcome this difficulty, laser heat-resistant notch has been taken as a research direction in the industry in recent years. For example:

[0004] The Chinese patent document with publication number CN1090242C and publication date May 14, 2000, entitled "Oriented silicon steel sheet with excellent magnetic properties and method for producing the same" discloses an oriented silicon steel sheet with excellent magnetic properties and a method for producing the same, which forms grooves or heat affected layers on the upper and lower surfaces of the steel plate by using high-density energy pulse modulated laser beams, and the depth of the formed grooves or heat affected layers is not greater than 5% of the thickness. SUMMARY

[0005] One of the purposes of the present application is to provide a laser heat-resistant notch oriented silicon steel which can reduce the adverse effects of laser notch grooves on magnetic induction while reducing iron loss, and the obtained oriented silicon steel has the characteristics of low iron loss and high magnetic induction.

[0006] One of the purposes of the present application is to provide an oriented silicon steel which has a plurality of parallel linear grooves on the surface, and the depth of the grooves is 15-45 μm and the width is 5-15 μm.

[0007] The inventors find that there is a coupling effect between the two sidewalls of the notch groove, the wider the groove, the farther the distance between the two sidewalls, the weaker the coupling effect, and the more obvious the decrease in magnetic induction. Meanwhile, the inventors determine the notch groove parameter range of the oriented silicon steel through a series of experiments, i.e. the notch groove width is between 5-15 μm, and the groove depth is between 15-45 μm.

[0008] In the present application, in order to minimize the influence of the leakage magnetic flux at the groove on the magnetic induction of the oriented silicon steel sheet, the groove width should be controlled within 15 μm. When the width is greater than 15 μm, the leakage magnetic flux at the groove is large, and the coupling effect of the free magnetic poles on both sides of the groove is small, resulting in a decrease in the magnetic induction of the finished oriented silicon steel sheet. Although the smaller the groove width, the higher the magnetic induction of the finished oriented silicon steel sheet, the groove width should still be controlled to be greater than 5 μm. This is because the smaller the groove width, the smaller the laser focusing spot diameter used when notching the surface of the steel sheet, at this time, the laser focusing focal length is also smaller, and the laser focal depth is also smaller, which results in a significant increase in the complexity of the overall laser optical system and the difficulty of notch control. Therefore, considering the above factors, the range of the groove width is controlled to be between 5-15 μm.

[0009] In the present application, when the depth of the groove is lower than the lower limit of 15 μm, the effect of refining magnetic domains and reducing iron loss of the groove is limited, and the iron loss of the finished oriented silicon steel sheet is high. When the depth of the groove is higher than the upper limit of 45 μm, the leakage magnetic flux at the groove is large, and the magnetic induction of the finished oriented silicon steel sheet is reduced. Therefore, the range of the groove depth is controlled to be between 15-45 μm.

[0010] Preferably, in the laser heat-resistant notched oriented silicon steel, the distance between adjacent grooves is 2-8 mm.

[0011] In the present application, the parallel linear grooves refer to linear grooves parallel to the transverse direction of the silicon steel, and the distance between adjacent grooves refers to the distance between adjacent grooves along the rolling direction of the silicon steel.

[0012] When the distance between adjacent grooves is lower than the lower limit of 2 mm, the magnetic induction of the finished oriented silicon steel sheet is low. When the distance between adjacent grooves is higher than 8 mm, the effect of refining magnetic domains and reducing iron loss is limited, and the iron loss of the finished oriented silicon steel sheet is high. Therefore, the distance between adjacent grooves is controlled to be between 2-8 mm.

[0013] Preferably, the iron loss P 17 / 50 Below 0.780 W / kg, the magnetic induction B8 is above 1.920 T, preferably above 1.924 T.

[0014] Preferably, the lamination factor of the laser heat-resistant notched oriented silicon steel is ≥95.5%.

[0015] Preferably, the thickness of the oriented silicon steel plate used in the present application is 0.15-0.25 mm, for example, 0.18-0.23 mm, 0.22-0.23 mm.

[0016] Another object of the present application is to provide a method for laser heat-resistant marking of oriented silicon steel, which can form narrow and deep grooves on the surface of the steel plate through one scan, and the obtained oriented silicon steel has the characteristics of low iron loss and high magnetic induction.

[0017] To achieve the above-mentioned objects, the present application provides a marking method, which comprises: outputting pulsed laser in pulse train mode, and forming parallel linear grooves on the surface of the oriented silicon steel plate through single scan, the depth of the grooves is 15-45 μm, and the width is 5-15 μm. In the present application, single scan refers to scanning the surface of the oriented silicon steel plate only once by using pulsed laser. The operation is repeated on the entire surface of the steel plate to form multiple parallel linear grooves.

[0018] Preferably, in the marking method of the present application, the number of single pulses in the pulse train is ≥200, and the energy density of single pulse is 0.09-0.45 J / cm 2 .

[0019] In the present application, in order to form the narrow and deep marking grooves required by the present application, the number of pulse trains needs to be kept above 200. When the number of single pulses in the pulse train is less than 200, the width of the marking groove increases and the depth decreases, and the groove required by the present application cannot be formed. The upper limit of the number of pulse trains in the present application is not particularly limited (usually below 2000, for example, below 1500, below 1000 or below 800), but it needs to meet the requirement of the energy density of single pulse in the present application, that is, the energy density ps of single pulse is in the range of 0.09-0.45 J / cm 2 . This is because when laser marks and peels atoms on the surface of the silicon steel to form a groove, the time of laser interaction with the atoms on the surface of the silicon steel in the micro time domain is kept within the time of single pulse. If the energy density in this time period is too large, exceeding 0.45 J / cm 2 , the depth of the groove formed by laser marking will exceed the designed 45 μm in the present application, and the magnetic induction of the finished product will decrease significantly; if the energy density in this time period is too small, less than 0.09 J / cm 2 , the depth of the groove formed by laser marking cannot reach the lower limit of refining magnetic domains and reducing iron loss, that is, 15 μm, and the effect of marking on refining magnetic domains and reducing iron loss is limited, and the iron loss of the finished product is high.

[0020] Preferably, in the marking method of the present application, the time interval between single pulses in the pulse train is 0.5-1.25 ns.

[0021] In the present application, when the time interval between the single pulses in the pulse train is greater than 1.25 ns, the coupling effect between the pulses is poor, which may result in the increase of the groove width and the difficulty in forming the narrow and deep sharp groove designed in the present application; when the time interval between the single pulses in the pulse train is less than 0.5 ns, the coupling effect between the front and rear pulses is too strong, which will turn the laser marking process to thermal processing, resulting in poor groove quality. Therefore, in the present application, the time interval between the single pulses in the pulse train is controlled to be between 0.5-1.25 ns.

[0022] Preferably, in the marking method of the present application, the pulse width of the pulse train is ≤40 ps. The present application does not limit the lower limit of the pulse width, which is usually above 0.4 ps, for example, above 0.8 ps, above 1 ps, above 6 ps or above 20 ps.

[0023] In the present application, in order to further realize the effect of laser processing, the pulse width of the pulsed laser is preferably controlled to be within 40 ps, and the smaller the better. The pulse width is determined by the lattice heat conduction time of silicon steel. When the pulse width is greater than 40 ps, increasing the laser output power will result in poor quality of the marking groove, producing a lot of molten and splashed materials, and reducing the laser output power can reduce the production of molten and splashed materials, but it is difficult to form the marking groove. Therefore, when the pulse width exceeds 40 ps, it is relatively difficult to form the marking groove required in the present application.

[0024] Preferably, in the marking method of the present application, the repetition frequency of the pulsed laser is 300-5000 KHz.

[0025] In the present application, when the repetition frequency of the pulsed laser is lower than 300 KHz, the interval between the pulse trains is too large, and the energy density of the single pulse is too high, the thermal melting effect is obvious, which may result in poor groove quality and relatively difficult to form the extremely sharp groove designed in the present application; when the repetition frequency of the pulsed laser exceeds 5000 KHz, the interaction between the laser pulse train and the next pulse train is formed, and the obtained groove quality is poor. Therefore, in the present application, the repetition frequency of the pulsed laser is preferably controlled to be 300-5000 KHz, for example, 500 KHz-3300 KHz.

[0026] The present application does not have specific limitations on the laser power and the scanning speed, for example, the laser power can be 20-220 W, and the scanning speed can be 1-10 m / s.

[0027] Preferably, in the marking method of the present application, the focused light spot formed by the pulsed laser on the surface of the oriented silicon steel plate is circular, elliptical or rectangular. In the present application, the shape of the focused light spot can be a circular spot, an elliptical spot or a long rectangular spot after shaping.

[0028] The laser heat-resistant notch forming process can be performed before decarburization annealing of the silicon steel plate, or before hot stretch leveling annealing, or after hot stretch leveling annealing, as long as the notch groove size, quality and adjacent notch line spacing are within the scope of the application, the effect of the application can be achieved.

[0029] The laser heat-resistant notch oriented silicon steel and the notch forming method thereof have the following advantages and beneficial effects compared with the prior art:

[0030] The laser heat-resistant notch oriented silicon steel and the notch forming method thereof can form narrow and deep grooves on the surface of the steel plate through one scan, and the obtained oriented silicon steel has the characteristics of low iron loss and high magnetic induction.

[0031] In some embodiments, the iron loss P 17 / 50 At 0.780 W / kg or less, the magnetic induction B8 is 1.920 T or more, preferably 1.924 T or more, and the lamination coefficient is ≥ 95.5%. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a schematic diagram of parallel line-shaped grooves formed on the surface of an oriented silicon steel by laser notching according to an embodiment of the application.

[0033] Figure 2 is a schematic diagram of a laser output in a pulse train mode according to an embodiment of the application.

[0034] Figure 3 is a schematic diagram of the pulse width t p and the time interval t b in a pulse train according to the notch forming method of the application.

[0035] Figure 4 shows the relationship between the groove depth d and the iron loss P 17 / 50 and the magnetic induction B8 of the oriented silicon steel in an embodiment of the application.

[0036] Reference signs: 1 - oriented silicon steel plate, 2 - groove. DETAILED DESCRIPTION

[0037] The laser heat-resistant notch oriented silicon steel and the notch forming method thereof will be further explained and described below in conjunction with the drawings and specific examples in the specification, but this explanation and description does not constitute an undue limitation on the technical solution of the application.

[0038] The groove quality affects the service safety of the obtained laser heat-resistant notch oriented silicon steel plate after being made into a transformer, especially the spatter, which has the risk of falling off during the service process of the transformer due to vibration caused by magnetostriction, etc. The particles that fall off will enter the transformer oil, which will cause the risk of breakdown of the transformer.

[0039] In order to solve this technical problem, the present application provides a method for laser marking on the surface of oriented silicon steel sheet with a low energy density ultrashort pulse train, which can realize a narrow and deep marking groove, and the coupling effect of the groove sidewalls is enhanced, thereby refining the magnetic domain, reducing the iron loss, and maximizing the guarantee of the magnetic induction without obvious decrease.

[0040] The various properties of the present application are determined as follows:

[0041] The groove depth and width of the oriented silicon steel surface are determined by a laser confocal microscope, the magnification is kept above 200 times, and the measurement accuracy is kept above ±0.5 μm. The groove spacing is determined by using a conventional ruler or meter ruler, and the measurement accuracy is above ±0.2 mm.

[0042] Iron loss P of oriented silicon steel 17 / 50 , magnetic induction B8: determined according to "GB / T 3655-2022 Method for measuring the magnetic properties of electrical steel strip (sheet) with Epstein square";

[0043] The oriented silicon steel sheet coefficient is determined according to "GB / T 19289-2019 Measurement method of resistivity, density and sheet coefficient of electrical steel strip (sheet)".

[0044] Fig. 1 is a schematic view of the marking linear groove on the surface of the oriented silicon steel according to an embodiment of the present application.

[0045] As shown in Fig. 1, the laser heat-resistant marked oriented silicon steel sheet 1 according to the present application has parallel linear grooves 2 formed by laser marking. Among them, the groove 2 extends along the transverse direction of the oriented silicon steel sheet 1.

[0046] The inventors found through research that when the laser ablates the surface of the steel sheet in the form of pulse train, the repetition frequency R f , the time interval t b between single pulses, and the energy density of single pulse all have an effect on the coupling effect between laser pulses. Among them: the calculation formula of the energy density of single pulse is as follows:

[0047] Among them, p s represents the energy density of single pulse, the unit is J / cm 2 ; P is the total power of laser output, the unit is W; N is the number of single pulses contained in the pulse train, dimensionless; R f is the repetition frequency of pulse laser, the unit is Hz; S is the focused spot area, the unit is cm 2 .

[0048] Fig. 2 is a schematic view of the laser output in the form of pulse train according to an embodiment of the present application.

[0049] As shown in Fig. 2, the pulsed laser is operated at a repetition frequency R f A series of laser pulses, referred to as a pulse train, are emitted. The pulse train is composed of a series of pulsed laser with very short time interval. The time interval between the pulse train and the next pulse train is For example, if the repetition frequency R f = 1 MHz, the time interval between the pulse train and the next pulse train is 1 μs.

[0050] Fig. 3 is a schematic diagram of the pulse width t p and the time interval t b .

[0051] As shown in Fig. 3, the pulse width is t p and the pulse interval is t b . In the present application, when the laser is operated in the pulse train mode to perform micro-region processing on the surface of the steel plate, since the single pulse width is very small and the single pulse interacts with the material for a very short time, which is in the order of picoseconds, it is comparable to or less than the heat conduction time of the internal lattice of the material. Therefore, when the laser pulse acts on a single atom to strip it, only a small amount of energy is transferred to the adjacent atom, so that the heat melting phenomenon during the formation of the groove by the laser marking can be effectively controlled. Since the time interval between the single pulses in the pulse train is very short, it acts on the atom adjacent to the atom stripped by the previous laser, and strips it. Since these atoms already have a certain amount of energy, a coupling effect is formed, which reduces the energy threshold required for the stripping of these subsequent atoms, thereby effectively controlling the heat diffusion to the two sides of the groove, so that a very sharp groove with very small width and very deep depth can be achieved.

[0052] Fig. 4 shows the relationship between the groove depth d and the iron loss P 17 / 50 and the magnetic induction B8 of the oriented silicon steel in the embodiment of the present application.

[0053] As shown in Fig. 4, taking an oriented silicon steel plate with a thickness of 0.23 mm as an example, laser marking is performed on the surface of the oriented silicon steel plate according to the marking method of the present application. It can be seen that for an oriented silicon steel plate of the present application, when the surface groove depth d is between 15-45 μm, a balance of low iron loss and high magnetic induction can be achieved.

[0054] The laser heat-resistant marked oriented silicon steel and the marking method thereof described in the present application are further illustrated by Examples 1-15 and Comparative Examples 1-3.

[0055] Examples 1-9 and Comparative Example 1-2

[0056] The oriented silicon steel of Examples 1-9 and the comparative steel of Comparative Example 1-2 in the present application are prepared by the following steps:

[0057] The steel strip is obtained by iron smelting, steel smelting, continuous casting and hot rolling processes, and then cold rolling to a final thickness of 0.22 mm. The chemical composition of the steel strip is as follows in terms of mass percentage: C: 0.03% to 0.1%, Si: 2.5% to 4.0%, Mn: 0.06% to 0.20%, P: 0.005% to 0.012%, S: 0.005% to 0.050%, Als: 0.01% to 0.04%, N: 0.005% to 0.015%, Cr: 0.01% to 0.45%, and the balance of Fe and inevitable impurities. The same steel strip is used for subsequent processing in Examples 1-9 and Comparative Examples 1-2. After the surface of the steel strip is degreased, a pulsed laser is output in a pulse train mode according to the laser marking parameters shown in Table 1, and a plurality of parallel linear grooves are formed on the surface of the grain-oriented silicon steel sheet by single scanning, as shown in Fig. 1. Each groove extends along the transverse direction of the steel sheet and is perpendicular to the rolling direction of the steel sheet, and the spacing between adjacent grooves is controlled to be 5 mm. After the marking is completed, the steel sheet is subjected to decarburization annealing, coated with MgO separator and dried, then subjected to high temperature annealing at 1250°C for 20 hours, and then cleaned of residual MgO separator and subjected to hot stretch leveling annealing to form the final product grain-oriented silicon steel.

[0058] Table 1 lists the specific process parameters of the laser marking of Examples 1-9 and Comparative Examples 1-2.

[0059] Table 1.

[0060] Then, the groove size of the grain-oriented silicon steel of Examples 1-9 and the comparative steel of Comparative Examples 1-2 is measured and the magnetic property test is performed, and the test results are listed in Table 2.

[0061] Table 2. Note: In the above table, represents excellent groove quality, no bulges or spatters are observed on both sides of the groove; represents good groove quality, there are bulges on the groove edge, and a small amount of spatter formed by laser ablation during the marking process or condensed from liquid or gas phase is observed near the groove.

[0062] As can be seen from Table 2 above, the iron loss P 17 / 50 of the grain-oriented silicon steel of Examples 1-9 of the present application is less than 0.78 W / kg, the magnetic induction B8 is greater than 1.92 T, the quality of the marked groove is good, and the lamination factor is greater than 95.5%.

[0063] However, the energy density of a single pulse of Comparative Example 1 is lower than the lower limit specified in the present application, and cannot reach the lower limit of the groove depth required by the present application, and the finished product has high iron loss.

[0064] In addition, the energy density of the single pulse of Comparative Example 2 is higher than the upper limit of the present application, the groove depth exceeds the range required by the present application, and the finished product has a low magnetic induction.

[0065] Examples 10-15 and Comparative Example 3

[0066] The oriented silicon steel of Examples 10-15 and the comparative steel of Comparative Example 3 of the present application were prepared by the following steps:

[0067] After the iron-making, steel-making, continuous casting and hot rolling processes, the steel strip was cold-rolled to a final thickness of 0.22 mm. The chemical composition of the steel strip, in terms of mass percentage, was as follows: C: 0.03%-0.1%, Si: 2.5%-4.0%, Mn: 0.06%-0.20%, P: 0.005%-0.012%, S: 0.005%-0.050%, Als: 0.01%-0.04%, N: 0.005%-0.015%, Cr: 0.01%-0.45%, and the balance being Fe and unavoidable impurities. The same steel strip was used for subsequent processing of Examples 10-15 and Comparative Example 3. After the surface of the steel strip was degreased, a pulsed laser was output in a pulse train mode (according to the process parameters shown in Table 3), the laser spot was rectangular, and a plurality of parallel linear grooves were formed on the surface of the oriented silicon steel sheet by single scanning, as shown in FIG. 1. Each groove extended along the transverse direction of the steel sheet and was perpendicular to the rolling direction of the steel sheet, and the spacing between adjacent grooves was controlled to be 2-8 mm. After the grooving was completed, the steel sheet was subjected to decarburization annealing, MgO separator was applied to the steel sheet and dried, and then the steel sheet was subjected to high-temperature annealing at 1250°C for 20 hours. After the residual MgO separator on the surface of the steel sheet was cleaned, the steel sheet was subjected to hot stretch leveling annealing to form the final product of the oriented silicon steel.

[0068] Table 3 lists the specific process parameters of the laser grooving step of Examples 10-15 and Comparative Example 3 of the present application.

[0069] Table 3.

[0070] Subsequently, the groove size of the prepared oriented silicon steel of Examples 10-15 and the comparative steel of Comparative Example 3 was measured, and the magnetic performance test was performed, and the test results are shown in Table 4.

[0071] Table 4. Note: In the above table, represents excellent groove quality, and no bulges or spatters are observed on both sides of the groove; represents good groove quality, and there are bulges on the edge of the groove, and spatter substances formed by laser ablation during the grooving process are observed near the groove.

[0072] As can be seen from Table 4, the iron loss P17 / 50 All of them are less than 0.780 W / kg, the magnetic induction B8 is more than 1.920 T, the quality of the notch groove is good, and the lamination factor is more than 95.5%.

[0073] The number of pulses in the pulse train of the laser used in Comparative Example 3 is less than the range required by the present application, and the groove depth and width required by the present application cannot be achieved, and the finished product iron loss P 17 / 50 is high, and the B8 is low.

[0074] It should be noted that the combination of the technical features in the present case is not limited to the combination of the claims in the present case or the combination of the embodiments described in the present case. All the technical features described in the present case can be freely combined or combined in any way, unless contradictory to each other.

[0075] It should also be noted that the above examples are only specific embodiments of the present application. Obviously, the present application is not limited to the above examples, and similar changes or modifications made directly from the disclosure of the present application or easily thought of by those skilled in the art should all fall within the scope of protection of the present application.

Claims

1. An oriented silicon steel, characterized by, The surface of the oriented silicon steel has a plurality of parallel linear grooves, the depth of the grooves is 15-45 microns, and the width is 5-15 microns.

2. The oriented silicon steel of claim 1, wherein, The interval between adjacent grooves is 2-8 mm.

3. The oriented silicon steel of claim 1, wherein, The oriented silicon steel has a magnetic induction B8 of 1.920 T or more at 0.780 W / kg or less. 17 / 50 The magnetic induction B8 is 1.920 T or more at 0.780 W / kg or less.

4. The oriented silicon steel of claim 1, wherein, The lamination factor of the oriented silicon steel is greater than or equal to 95.5%.

5. A method of scoring, characterized by: The scoring method comprises outputting a pulsed laser in a pulse train mode, and forming parallel linear grooves on the surface of the oriented silicon steel plate by single scanning, the depth of the grooves is 15-45 microns, and the width is 5-15 microns.

6. The method of scoring according to claim 5 wherein, The number of individual pulses within the pulse train is > 200, wherein the individual pulses have an energy density of 0.09 - 0.45 J / cm 2 .

7. The method of scoring according to claim 5 wherein, The time interval between individual pulses in the pulse train is 0.5-1.25 ns.

8. The method of scoring according to claim 5 wherein, The pulse width of the pulse train is less than or equal to 40 ps.

9. The method of scoring according to claim 5 wherein, The repetition frequency of the pulsed laser is 300-5000 KHz.

10. The method of scoring according to claim 5 wherein, The focused spot formed by the pulsed laser on the surface of the oriented silicon steel plate is circular, elliptical or rectangular.

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