Laser-scribed grain-oriented silicon steel resistant to stress-relief annealing and manufacturing method therefor

Abstract

A laser-scribed grain-oriented silicon steel resistant to stress-relief annealing and a manufacturing method therefor. Parallel linear grooves (20) are formed on one or both sides of grain-oriented silicon steel (10) by laser etching. The linear grooves (20) are perpendicular to, or at an angle to, the rolling direction of the steel plate. A maximum height of edge protrusions of the linear grooves (20) does not exceed 5 μm, and a maximum height of spatters in etch-free regions between adjacent linear grooves (20) does not exceed 5 μm, and the proportion of an area occupied by spatters in the vicinity of the linear grooves (20) does not exceed 5%. The steel has low manufacturing costs, and the etching effect of the finished steel is retained during a stress-relief annealing process. The steel is suitable for manufacturing of wound iron core transformers.

Claims

1. A laser-scribed grain-oriented silicon steel resistant to stress-relief annealing, wherein parallel linear grooves are formed on one or both sides of grain-oriented silicon steel by laser etching, wherein the linear grooves are perpendicular to, or at an angle to, the direction of rolling the silicon steel into a steel plate; a maximum height of edge protrusions of the linear grooves does not exceed 5 μm, and a maximum height of spatters in etch-free regions between adjacent linear grooves does not exceed 5 μm, and the proportion of spatters per unit area in the etch-free regions between adjacent linear grooves does not exceed 5%, wherein the line roughness R.sub.a of a center line in the bottom of the linear grooves is not more than 2.1 μm.

2. The laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 1, wherein the heights of the spatters do not exceed 2 μm, and the proportion of spatters per unit area in the etch-free regions between adjacent linear grooves does not exceed 2.5%.

3. The laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 1, wherein the line roughness Ra of a center line in the bottom of the linear grooves is not more than 0.52 μm.

4. The laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 1, wherein the linear grooves are approximately triangular, trapezoidal, semi-circular or elliptical.

5. The laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 1, wherein an angle between the linear grooves and the direction of rolling the silicon steel into a steel plate is 0 to 30°.

6. The laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 1, wherein the linear grooves have a width of 5 to 300 μm and a depth of 5 to 60 μm, and a space between adjacent linear grooves is 1 to 10 mm.

7. A method for manufacturing the laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 1, comprising steps of smelting, continuous casting, hot rolling, single cold rolling, or double cold rolling with intermediate annealing, decarburization annealing including applying MgO separator on a surface of the silicon steel, high-temperature annealing, and forming a finished grain-oriented silicon steel by hot stretching, temper rolling and annealing, wherein the method further comprises laser-etching, which is performed before the decarburization annealing, or before or after the hot stretching, temper rolling and annealing; the laser-etching comprises the following steps: 1) forming a protective film on a surface of the grain-oriented silicon steel; 2) laser-etching a surface of the grain-oriented silicon steel to form a series of linear grooves perpendicular to or at an angle to the direction of rolling the silicon steel into a steel plate; 3) brushing the surface of the grain-oriented silicon steel to remove the protective film, and drying, thereby producing the laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 1.

8. The method for manufacturing the laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 7, wherein the protective film is formed by a metal oxide powder, and has a moisture content of between 0.3 wt % and 5.5 wt %.

9. The method for manufacturing the laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 7, wherein the protective film has a thickness of between 1.0 μm and 13.0 μm.

10. The method for manufacturing the laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 8, wherein the metal oxide powder is water-insoluble, and is a single powder or a combination of several powders, and the proportion of particles having a particle diameter of 500 μm or more in the powder(s) is 10% by volume or less.

11. The method for manufacturing the laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 8, wherein the metal oxide powder is one or more of an alkaline earth metal oxide, Al.sub.2O.sub.3, ZnO or ZrO.

12. The method for manufacturing the laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 7, wherein the laser in the laser-etching step has a power density I of not less than 1.0×10.sup.6 W/cm.sup.2, and an average energy density e.sub.0 of between 0.8 J/mm.sup.2 and 8.0 J/mm.sup.2, and a ratio of the average energy density to the thickness of the protective film of between 0.6 and 7.0.

13. A method for producing the laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 1, comprising steps of smelting, continuous casting, hot rolling, single cold rolling, or double cold rolling with intermediate annealing, decarburization annealing, applying MgO separator on a surface of a steel plate produced above, high-temperature annealing, forming a finished oriented silicon steel by hot stretching, temper rolling, annealing and applying an insulating coating, wherein laser-etching is performed after the decarburization annealing to form a series of linear grooves perpendicular to or at an angle to the direction of rolling the silicon steel into a steel plate, on a surface of the grain-oriented silicon steel.

14. The method for manufacturing the laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 13, wherein a laser-generating pump source used in the laser-etching step is one or more of a CO.sub.2 laser, a solid laser, and a fiber-optic laser, and laser is continuous or pulsed.

15. The method for manufacturing the laser-scribed grain-oriented silicon steel resistant to stress-relief annealing of claim 7, wherein a laser-generating pump source used in the laser-etching step is one or more of a CO.sub.2 laser, a solid laser, and a fiber-optic laser, and laser is continuous or pulsed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a macroscopic view of linear grooves formed on the surface of grain-oriented silicon steel by laser-etching in the present invention.

(2) FIG. 2 shows the scope of the maximum height of the protrusions on the edge of the grooves required by the present invention.

(3) FIG. 3 shows the proportion of the surface area occupied by the spatters and the range of the maximum height of the spatters required by the present invention.

(4) FIG. 4 shows the range of the roughness of the center line in the bottom of the grooves required by the present invention.

(5) FIG. 5 shows the range of power density of the laser required by the present invention.

(6) FIG. 6 shows the range of the ratio between the energy density of the laser and the thickness of the film required by the present invention.

(7) FIG. 7 is a view showing the surface morphology of a steel plate subjected to laser-etching after applying the protective film in the present invention.

(8) FIG. 8 is a view showing the morphology of the grooves after cleaning the protective film in the present invention.

DETAILED DESCRIPTION

(9) The embodiments and effects of the present invention are exemplified below, but the present invention is not limited to the specific embodiments described in the examples.

(10) FIG. 1 shows the laser-scribed grain-oriented silicon steel 10 resistant to stress-relief annealing in the present invention, wherein parallel linear grooves 20 are formed on one or both sides of grain-oriented silicon steel by laser etching, the linear grooves are perpendicular to, or at an angle to, the direction of rolling the silicon steel into a steel plate; a maximum height of edge protrusions of the linear grooves does not exceed 5 μm, and a maximum height of spatters in etch-free regions between adjacent linear grooves does not exceed 5 μm, and the proportion of an area occupied by spatters in the vicinity of the linear grooves does not exceed 5%.

(11) Preferably, the line roughness R.sub.a of the center line in the bottom of the linear grooves is not more than 2.1 μm.

(12) Preferably, the linear grooves are approximately triangular, trapezoidal, semi-circular or elliptical.

(13) Preferably, the angle between the linear grooves and the rolling direction of the steel plate is 0˜30°.

(14) Preferably, the linear grooves have a width of 5 to 300 μm and a depth of 5 to 60 μm, and the space between adjacent linear grooves is 1 to 30 mm.

Example 1

(15) The grain-oriented silicon steel was subjected to iron making, steel making, continuous casting, and hot rolling process. Next, single cold rolling was performed to roll the steel to a final thickness of 0.23 mm. Then, decarburization annealing was performed to form a surface oxide layer. Then, the steel was coated with MgO separator on the surface, and subjected to high-temperature annealing at 1250° C. for 20 hours. Then, unreacted residual MgO was washed away. Thereafter, the surface of the steel was roll coated and dried to form a protective film. Next, a YAG laser was used to etch linear grooves at equal intervals along the rolling direction of the steel plate. The laser has an output power of 2000 W and an average pulse width of 800 ns. The spot formed by the laser focusing on the surface of the steel plate was elliptical with a short axis of 0.016 mm and a long axis of 0.5 mm. The scanning speed is 50 m/s. The calculated laser power density was 3.2×10.sup.7 W/cm.sup.2, and the laser energy density was 3.2 J/mm.sup.2. The formed scoring lines are perpendicular to the rolling direction of the steel plate. The space between adjacent scoring lines is 4 mm. Then, a brushing process was performed to remove the surface protective film and the scored spatter residue. Finally, an insulating coating was applied to the surface of the steel and final annealing was performed to obtain a finished silicon steel sheet.

(16) The magnetic properties were measured according to “GB/T 3655-2008 Methods of Measuring Magnetic Properties of Electrical Steel Sheet and Strip by Epstein Frame”. The lamination factor was determined according to “GB/T 19289-2003 Methods of Measuring Density, Resistivity and Lamination Factor of Electrical Steel Sheet and Strip”. The measurement results of Examples and Comparative Examples are shown in Table 1.

(17) As can be seen from Table 1, Examples 1-10 have better iron loss, magnetic induction and lamination factor. However, the magnetic properties or lamination factor of Comparative Examples 1-10, which are not within the scope of the present invention, are relatively inferior.

Example 2. Influence of the Roughness R.SUB.a .of the Center Line on Magnetic Properties

(18) The grain-oriented silicon steel was subjected to iron making, steel making, continuous casting, and hot rolling process. Next, single cold rolling was performed to roll the steel to a final thickness of 0.225 mm. Then, decarburization annealing was performed to form a surface oxide layer. Then, the steel was coated with MgO separator on the surface, and subjected to high-temperature annealing at 1200° C. for 20 hours. Then, unreacted residual MgO was washed away. Thereafter, the surface of the steel was roll coated and dried to form a ZnO protective film with a thickness controlled to 2.5 μm. Next, a continuous CO.sub.2 laser was used to etch linear grooves at equal intervals along the rolling direction of the steel plate. The formed scoring lines are perpendicular to the rolling direction of the steel plate. The space between adjacent scoring lines is 4.5 mm. Then, a brushing process was performed to remove the surface protective film and the etching spatter residue. Finally, an insulating coating was applied to the surface of the steel and final annealing was performed to obtain a finished silicon steel sheet.

(19) The magnetic properties were measured according to the SST 60 mm×300 mm method. The measurement results of the Examples and Comparative Examples are shown in Table 2.

(20) As can be seen from Table 2, the laser parameters within the scope of the present invention enable the silicon steel sheet to obtain uniform and stable magnetic properties. However, in Comparative Examples beyond the scope of the present invention, the fluctuation of the magnetic properties is increased due to the overlarge R.sub.a of the center line in the bottom of the grooves.

Example 3

(21) The grain-oriented silicon steel was subjected to iron making, steel making, continuous casting, and hot rolling process. Next, single cold rolling was performed to roll the steel to a final thickness of 0.225 mm. An Al.sub.2O.sub.3 protective film was applied by spraying on the surface of the steel. The proportion of Al.sub.2O.sub.3 particles having a particle diameter of 500 μm or more in the protective film is about 5%. Then, a YAG laser having a pulse width of 300 ns was used to etch linear grooves. Approximate triangular grooves were formed by adjusting the size of the focused spot, the scanning speed, and the laser scoring energy. The angle between scoring lines and the transverse direction of the steel plate is 8°, and the space between scoring lines in the rolling direction is 4 mm. Then, a brushing process was performed to remove the surface protective film. Then, decarburization annealing was performed to form a surface oxide layer. Then, the steel was coated with MgO separator on the surface, and subjected to high-temperature annealing at 1250° C. for 20 hours after winding into a coil. Finally, the residual MgO was washed away, an insulating coating was applied to the surface of the steel, and final annealing was performed to obtain a finished silicon steel sheet.

(22) The magnetic properties were measured according to “GB/T 3655-2008 Methods of Measuring Magnetic Properties of Electrical Steel Sheet and Strip by Epstein Frame”. The lamination factor was determined according to “GB/T 19289-2003 Methods of Measuring Density, Resistivity and Lamination Factor of Electrical Steel Sheet and Strip”. The measurement results of Examples and Comparative Examples are shown in Table 3.

(23) As can be seen from Table 3, the Examples in which the energy density of the laser is within the scope of the present invention have good magnetic properties. Comparative Examples beyond the scope of the present invention have magnetic properties inferior to those of the present invention.

Example 4

(24) The grain-oriented silicon steel was subjected to iron making, steel making, continuous casting, and hot rolling process. Next, single cold rolling was performed to roll the steel to a final thickness of 0.195 mm. Then, decarburization annealing was performed to form a surface oxide layer. Then, the steel was coated with MgO separator on the surface to obtain a film having a thickness of about 9.5 μm. Next, a YAG laser was used to etch linear grooves at equal intervals along the rolling direction of the steel plate. The laser has an output power of 2000 W and an average width of a single pulse of 800 ns. The spot formed by the laser focusing on the surface of the steel plate was elliptical with a short axis of 0.016 mm and a long axis of 0.5 mm. The scanning speed is 50 m/s. The calculated laser power density was 3.2×10.sup.7 W/cm.sup.2, and the laser energy density was 3.2 J/mm.sup.2. The formed scoring lines are perpendicular to the rolling direction of the steel plate. The space between adjacent scoring lines is 4 mm. Then, the steel was subjected to high-temperature annealing at 1250° C. for 20 hours. Then, unreacted residual MgO was washed away. Finally, an insulating coating was applied to the surface of the steel plate, and final annealing was performed to obtain a finished silicon steel sheet.

(25) The magnetic properties were measured according to “GB/T 3655-2008 Methods of Measuring Magnetic Properties of Electrical Steel Sheet and Strip by Epstein Frame”. The lamination factor was determined according to “GB/T 19289-2003 Methods of Measuring Density, Resistivity and Lamination Factor of Electrical Steel Sheet and Strip”. The measurement results of Examples and Comparative Examples are shown in Table 4.

(26) In Example 4, the thickness of the film formed by MgO separator was adjusted to make the ratio of the energy density to the film thickness within the range of the present invention, so that the magnesium oxide functions as both a separator and a protective film. The residual magnesium oxide was washed away together with the spatters and the like after annealing at a high temperature. As can be seen from the comparison of the above Examples and Comparative Examples, when the process parameters of the laser are within the scope of the present invention, a silicon steel sheet having refined magnetic domains and reduced iron loss can be obtained. When the process parameters of the laser are beyond the scope of the invention, the silicon steel sheet obtained either has a high iron loss or a low lamination factor.

(27) In summary, the present invention forms linear grooves on the surface of the steel plate by applying a protective film and one-time laser scanning. Since the protective film has the absorption characteristics on the laser, it is ensured that the morphology of the formed grooves is controllable, the iron loss of the obtained finished silicon steel sheet is remarkably lowered, and the lamination factor is not significantly deteriorated. The silicon steel of the present invention is particularly suitable for manufacturing of wound iron core transformers. The method of the invention has the advantages of simple process, high production efficiency, and high application value and application prospect.

(28) TABLE-US-00001 TABLE 1 Proportion Ratio a of Maximum Protec- Proportion of energy height of Maximum tive of Particles density to Groove Groove edge height Area Lami- film Moisture ≥500 μm film depth width protrusions of spatters proportion P17/50 nation Illustration powder % % thickness (μm) (μm) (μm) (μm) of spatters % (W/kg) B8 (T) factor % Example 1 MgO 0.3 10 0.6 16.2 41.0 0.8 4.3 4.6 0.813 1.920 95.1 Example 2 MgO 0.3 10 7.0 43.3 48.2 1.3 4.8 4.9 0.778 1.901 95.2 Example 3 MgO 5.5 10 0.6 13.1 38.0 0   0.2 0.4 0.811 1.919 96.5 Example 4 MgO 5.5 10 7.0 45.2 43.2 0.3 0   0   0.785 1.902 97.2 Example 5 MgO 2.1  5 3.6 24.3 36.5 0   0   0   0.792 1.913 96.9 Comparative MgO 0.2  5 3.6 23.6 38.3 1.1 5.3 5   0.793 1.905 94.6 Example 1 Comparative MgO 5.7  5 3.6 23.2 37.5 0   0.3 0.2 0.865 1.889 96.4 Example 2 Comparative MgO 2.1 12 3.6 12.1 34.3 1.3 5.2 4.6 0.815 1.921 94.7 Example 3 Comparative MgO 2.1  5 0.5 10.1 35.0 0.3 0.4 0.4 0.882 1.926 96.3 Example 4 Comparative MgO 2.1  5 7.2 53.5 55.6 1.2 0.4  0.46 0.779 1.897 96.3 Example 5 Example 6 Al.sub.2O.sub.3 0.3 10 0.6 15.3 38.9 0.6 3.8 3.8 0.815 1.922 95.8 Example 7 Al.sub.2O.sub.3 0.3 10 7.0 46.1 49.1 1.4 4.9 5   0.780 1.9 95.1 Example 8 Al.sub.2O.sub.3 5.5 10 0.6 15.2 36.2 0   0   0   0.810 1.921 97.5 Example 9 Al.sub.2O.sub.3 5.5 10 7.0 48.3 48.8 0.6 0   0   0.788 1.901 96.8 Example 10 Al.sub.2O.sub.3 2.1  5 3.6 21.2 35.3 0   0.6 0.4 0.794 1.908 95.9 Comparative Al.sub.2O.sub.3 0.2  5 3.6 21.5 46.7 5.1 5.7 6.1 0.796 1.904 93.2 Example 6 Comparative Al.sub.2O.sub.3 5.7  5 3.6 20.3 28.2 0   0   0   0.873 1.876 96.6 Example 7 Comparative Al.sub.2O.sub.3 2.1 12 3.6 11.5 25.6 0.8 3.6 5.2 0.818 1.919 94.9 Example 8 Comparative Al.sub.2O.sub.3 2.1  5 0.5 9.8 23.6 0.2 0.9 1.1 0.879 1.922 95.9 Example 9 Comparative Al.sub.2O.sub.3 2.1  5 7.2 56.6 58.2 2.1 1.0 0.9 0.775 1.885 96.3 Example 10

(29) TABLE-US-00002 TABLE 2 Ratio a of Spot Spot energy Standard Laser long short Scanning density to Power Energy Mean of deviation Mean Standard power axis axis speed film density density P17/50 of P17/50 of B8 deviation Illustration (W) (mm) (mm) (m/s) thickness (W/cm.sup.2) (J/mm.sup.2) R.sub.a (μm) (W/kg) (W/kg) (T) of B8 (T) Example 1 5000 0.030 0.5 90 0.94 4.2 × 10.sup.7 2.36 0.3 0.795 0.010 1.901 0.013 Example 2 1500 0.016 0.5 60 0.80 2.4 × 10.sup.7 1.99 0.4 0.799 0.011 1.903 0.012 Example 3 2000 0.020 1.0 60 0.85 1.3 × 10.sup.7 2.12 0.5 0.794 0.013 1.901 0.011 Example 4 1200 0.015 1.2 50 0.81 8.5 × 10.sup.6 2.04 0.8 0.8 0.016 1.902 0.015 Example 5 1000 0.014 1.2 50 0.73 7.6 × 10.sup.6 1.82 1.1 0.801 0.018 1.902 0.016 Example 6 2500 0.016 5.0 80 0.99 4.0 × 10.sup.6 2.49 1.6 0.795 0.021 1.904 0.018 Example 7 1000 0.012 10.0 50 0.85 1.1 × 10.sup.6 2.12 2.1 0.802 0.033 1.906 0.023 Comparative 1000 0.012 11.0 50 0.85 9.6 × 10.sup.5 2.12 2.2 0.821 0.035 1.901 0.031 Example 1 Comparative 2000 0.020 16.0 60 0.85 8.0 × 10.sup.5 2.12 2.8 0.828 0.040 1.901 0.035 Example 2

(30) TABLE-US-00003 TABLE 3 Ratio a of Protective energy Laser Scanning Power Energy film density to power Spot long Spot short speed density density thickness film P17/50 B8 Lamination Illustration (W) axis (mm) axis (mm) (m/s) (W/cm.sup.2) (J/mm.sup.2) (μm) thickness (W/kg) (T) factor % Example 1 1100 0.012 0.1 140 8.3 × 10.sup.7 0.83 1.2 0.69 0.845 1.907 96.5 Example 2 1500 0.012 0.8 100 2.0 × 10.sup.7 1.59 2.2 0.72 0.841 1.91 96.4 Example 3 2000 0.012 1.0 90 2.1 × 10.sup.7 2.36 3.2 0.74 0.843 1.913 96.6 Example 4 3000 0.020 5.0 80 3.8 × 10.sup.6 2.39 3.0 0.80 0.839 1.908 96.3 Example 5 4000 0.020 2.0 70 1.3 × 10.sup.7 3.64 3.0 1.21 0.836 1.903 96.5 Example 6 5000 0.016 0.5 50 8.0 × 10.sup.7 7.96 6.2 1.28 0.837 1.905 95.8 Comparative 5200 0.016 0.5 50 8.3 × 10.sup.7 8.28 7.5 1.10 0.831 1.898 94.6 Example 1 Comparative 4500 0.016 0.5 35 7.2 × 10.sup.7 10.23  6.5 1.57 0.829 1.881 91.4 Example 2 Comparative 1100 0.012 0.1 150 8.3 × 10.sup.7 0.78 1.2 0.65 0.912 1.922 96.7 Example 3 Comparative 1000 0.012 0.1 150 1.1 × 10.sup.8 0.71 1.0 0.71 0.923 1.926 97.2 Example 4 Comparative 3000 0.020 5.0 80.0 3.8 × 10.sup.6 2.39 No protective film 0.853 1.901 90.1 Example 5

(31) TABLE-US-00004 TABLE 4 Ratio a of Spot long Spot Scanning Power Energy energy density Laser axis short axis speed density density to film P17/50 Lamination Illustration power (W) (mm) (mm) (m/s) (W/cm.sup.2) (J/mm.sup.2) thickness (W/kg) B8 (T) factor % Example 1 2500 0.012 1.0 40.0 2.7 × 10.sup.7 6.63 1.11 0.685 1.907 96.1 Example 2 3000 0.016 1.6 45.0 1.5 × 10.sup.7 5.31 0.88 0.681 1.91 96.2 Example 3 2500 0.012 1.0 40.0 2.7 × 10.sup.7 6.63 1.11 0.683 1.913 96.1 Example 4 3000 0.016 1.6 40.0 1.5 × 10.sup.7 5.97 0.99 0.679 1.908 96.2 Example 5 5000 0.016 0.8 80.0 5.0 × 10.sup.7 4.97 0.83 0.677 1.905 95.8 Comparative 2500 0.016 10.0 60.0 2.0 × 10.sup.6 3.32 0.55 0.753 1.916 95.9 Example 1 Comparative 3000 0.016 0.5 25.0 4.8 × 10.sup.7 9.55 1.59 0.669 1.899 91.4 Example 2