Oriented silicon steel and method for manufacturing same

Abstract

The invention discloses an oriented silicon steel with excellent magnetic properties and a manufacturing method thereof. The present invention obtains the oriented silicon steel with excellent magnetic properties by controlling the area ratio of small crystal grains of D<5 mm in an oriented silicon steel finished product to be not more than 3%, and controlling the ratio 17/15 of the magnetic conductivity under the magnetic induction of 1.7 T and 1.5 T in the oriented silicon steel finished product to be 0.50 or more. In addition, by using a slab of the oriented silicon steel with suitable components and an optimized cold rolling step, the present invention effectively decreases the heating temperature of the slab and the production cost thereof, and simultaneously better controls the size and ratio of the crystal grains in the oriented silicon steel finished product and the magnetic conductivity in a certain range of magnetic induction, ensures that secondary recrystallization has good Goss texture orientation and finally, stably obtains the oriented silicon steel product with excellent magnetic properties.

Claims

1. A manufacturing method of an oriented silicon steel, comprising the following steps in sequence: heating a slab of the oriented silicon steel to 1100-1200 C. and then performing a hot rolling to obtain a hot rolled plate; performing, directly after hot rolling without an annealing treatment of the hot rolled plate, a cold rolling on the hot rolled plate at a cold rolling reduction ratio of 85% or more, so as to obtain a cold rolled plate having a thickness of a finished product of the oriented silicon steel; performing an annealing treatment on the cold rolled plate to obtain the finished product of the oriented silicon steel, wherein the annealing treatment comprises the following in sequence: decarbonization annealing, coating an annealing separator, high-temperature annealing, applying an insulating coating, and hot-stretching leveling annealing; and the manufacturing method further comprises: before the high-temperature annealing, performing a nitriding treatment on the cold rolled plate; wherein, the slab of the oriented silicon steel comprises the following components by weight percentage: 2.5-4.0% of Si, 0.010-0.040% of acid-soluble aluminum Al, 0.004-0.012% of N, and 0.015% or less of S; and an area ratio of small crystal grains having a grain size of less than 5 mm in the finished product of the oriented silicon steel is not more than 3%, and a ratio 17/15 of a magnetic conductivity under magnetic induction of 1.7 T and 1.5 T in the finished product of the oriented silicon steel is 0.50 or more, wherein Goss texture in the finished product is within 7 degrees.

2. The manufacturing method of the oriented silicon steel according to claim 1, wherein the area ratio of small crystal grains having a grain size of less than 5 mm in the finished product of the oriented silicon steel is not more than 2%.

3. The manufacturing method of the oriented silicon steel according to claim 1, wherein the ratio 17/15 of the magnetic conductivity under magnetic induction of 1.7 T and 1.5 T in the finished product of the oriented silicon steel is 0.55 or more.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) The invention is described in more detail below in conjunction with the examples, but the protection scope of the invention is not limited to these examples.

EXAMPLES 1-8 AND COMPARATIVE EXAMPLES 1-5

(2) A slab of an oriented silicon steel comprises the following components by weight percentage: 0.050% of C, 3.0% of Si, 0.030% of Als, 0.007% of N, 0.008% of S, 0.14% of Mn and the balance of Fe and inevitable impurities. The slab is heated in a heating furnace at the temperature of 1000-1250 C. and then hot-rolled to obtain a hot rolled plate with the thickness of 2.5 mm, cold rolling is performed on the hot rolled plate at different cold rolling reduction ratios to obtain the finished product thickness of 0.30 mm, then decarbonization annealing is performed, an annealing separator taking magnesium oxide as a main component is coated, and high-temperature annealing is performed after coiling; nitriding treatment is performed after final cold rolling and before high-temperature annealing and secondary recrystallization; and applying an insulating coating and stretching leveling annealing are performed after uncoiling to obtain an oriented silicon steel finished product. The relationship between the area ratio of small grains with D<5 mm and the magnetic conductivity ratio 17/15 in the oriented silicon steel finished product and the magnetic properties of the oriented silicon steel finished product is studied, and the results are as shown in Table 1.

(3) TABLE-US-00001 TABLE 1 Influences of area ratio of small grains with D <5 mm and magnetic conductivity ratio 17/15 in oriented silicon steel finished product on magnetic properties of oriented silicon steel finished product Area ratio of Magnetic small grains with induction Iron loss D <5 mm (%) 17/15 B8 (T) P17/50, (W/kg) Example 1 0.5 0.55 1.91 0.96 Example 2 1 0.56 1.92 0.95 Example 3 2 0.55 1.92 0.96 Example 4 2 0.54 1.91 0.98 Example 5 2 0.51 1.89 1.01 Example 6 3 0.54 1.90 0.99 Example 7 3 0.52 1.89 1.02 Example 8 3 0.50 1.88 1.03 Comparative 3 0.49 1.87 1.07 example 1 Comparative 3 0.43 1.85 1.16 example 2 Comparative 4 0.50 1.86 1.08 example 3 Comparative 5 0.51 1.84 1.15 example 4 Comparative 10 0.52 1.79 1.24 example 5

(4) It can be known from Table 1 that, compared with the comparative examples 1-5 in which the area ratio of the small grains with D<5 mm is more than 3% or the magnetic conductivity ratio 17/15 is less than 0.50, the examples 1-8 in which the area ratio of the small grains with D<5 mm in the oriented silicon steel finished product is not more than 3% and the ratio 17/15 of the magnetic conductivity under the magnetic induction of 1.7 T to the magnetic conductivity under the magnetic induction of 1.5 T is not less than 0.50 have higher magnetic induction and lower iron loss. Furthermore, it can be known from Table 1 that, compared with the example 6, the magnetic properties of the oriented silicon steel finished product in the example 4 in which the area ratio of the small grains with D<5 mm is 2% or less are further improved; and compared with the example 4, the magnetic properties of the oriented silicon steel finished product in the example 3 in which the magnetic conductivity ratio 17/15 is 0.55 are further improved.

EXAMPLE 9-15 AND COMPARATIVE EXAMPLES 6-14

(5) A slab of an oriented silicon steel comprises the following components by weight percentage: 0.075% of C, 3.3% of Si, 0.031% of Als, 0.009% of N, 0.012% of S, 0.08% of Mn and the balance of Fe and inevitable impurities. The slab is heated in a heating furnace at five different heating temperatures in the range of 1050-1250 C. and then hot-rolled to obtain a hot rolled plate with the thickness of 2.3 mm, cold rolling is performed on the hot rolled plate at different cold rolling reduction ratios to obtain different specification finished product thicknesses in the range of 0.20-0.40 mm, then decarbonization annealing is performed, an annealing separator taking magnesium oxide as a main component is coated, and high-temperature annealing is performed after coiling; nitriding treatment is performed after final cold rolling and before high-temperature annealing and secondary recrystallization; and applying an insulating coating and stretching leveling annealing are performed after uncoiling to obtain an oriented silicon steel finished product. The relationship among the heating temperature of the slab and the cold rolling reduction ratio and the area ratio of small grains with D<5 mm and the magnetic conductivity ratio 17/15 is studied, and the results are as shown in Table 2.

(6) TABLE-US-00002 TABLE 2 Influences of heating temperature of slab and cold rolling reduction ratio on area ratio of small grains with D <5 mm and magnetic conductivity ratio 17/15 in oriented silicon steel finished product Cold Heating rolling Area ratio of temperature reduction small grains of slab ( C.) ratio (%) with D <5 mm (%) 17/15 Example 9 1100 85 0.5 0.50 Example 1100 88 1 0.55 10 Example 1150 85 1 0.52 11 Example 1150 88 2 0.54 12 Example 1150 91 3 0.55 13 Example 1200 85 2 0.51 14 Example 1200 88 3 0.52 15 Comparative 1050 83 29 0.33 example 6 Comparative 1050 85 27 0.32 example 7 Comparative 1050 88 31 0.33 example 8 Comparative 1100 83 7 0.42 example 9 Comparative 1150 83 5 0.46 example 10 Comparative 1200 83 6 0.50 example 11 Comparative 1250 83 12 0.41 example 12 Comparative 1250 85 15 0.44 example 13 Comparative 1250 88 17 0.45 example 14

(7) It can be known from Table 2 that, in the case that the slab of the oriented silicon steel in the invention is adopted, the slab is heated in the temperature range of 1100-1200 C., then hot rolling is performed, and the cold rolling reduction ratio of 85% or more is adopted, and thus it can be ensured that in the oriented silicon steel finished product, the area ratio of the small grains with D<5 mm is not more than 3%, the ratio 17/15 of the magnetic conductivity under the magnetic induction of 1.7 T to the magnetic conductivity under the magnetic induction of 1.5 T is 0.50 or more, and thus it is ensured that the oriented silicon steel finished product with excellent magnetic properties can be obtained.

EXAMPLES 16-31

(8) A slab of an oriented silicon steel comprises the following components by weight percentage: 0.065% of C, 3.2% of Si, 0.025% of Als, 0.010% of N, 0.015% of S, 0.18% of Mn and the balance of Fe and inevitable impurities. The slab is heated in a heating furnace at the temperature of 1150 C. and then hot-rolled to obtain a hot rolled plate with the thickness of 3.0 mm, (A) direct cold rolling is performed on the hot rolled plate or (B) annealing is performed on the hot rolled plate at the temperature of 850-1200 C. and the cooling rate of 15-25 C./s, then cold rolling is performed at the cold rolling reduction ratio of 85%, the rolling is performed until the finished product thickness of 0.30 mm is obtained, then decarbonization annealing is performed, an annealing separator taking magnesium oxide as a main component is coated, and high-temperature annealing is performed after coiling; nitriding treatment is performed after final cold rolling and before high-temperature annealing and secondary recrystallization; and applying an insulating coating and stretching leveling annealing are performed after uncoiling to obtain an oriented silicon steel finished product. The relationship among the annealing conditions of the hot rolled plate and the area ratio of small grains with D<5 mm and the magnetic conductivity ratio 17/15 in the oriented silicon steel finished product is studied, and the results are as shown in Table 3.

(9) TABLE-US-00003 TABLE 3 Influences of annealing conditions of hot rolled plate on area ratio of small grains with D <5 mm and magnetic conductivity ratio 17/15 in oriented silicon steel finished product Whether Annealing to perform cooling Area ratio annealing Annealing rate of hot of small of hot temperature rolled grains with rolled of hot rolled plate D <5 mm plate plate ( C.) ( C./s) (%) 17/15 Example A 3 0.53 16 Example B 850 15 2 0.53 17 Example B 850 20 2 0.53 18 Example B 850 25 3 0.54 19 Example B 900 15 2 0.53 20 Example B 900 20 2 0.57 21 Example B 900 25 3 0.58 22 Example B 1000 15 2 0.54 23 Example B 1000 20 3 0.58 24 Example B 1000 25 3 0.60 25 Example B 1150 15 2 0.54 26 Example B 1150 20 3 0.59 27 Example B 1150 25 3 0.62 28 Example B 1200 15 3 0.53 29 Example B 1200 20 3 0.54 30 Example B 1200 25 3 0.54 31

(10) It can be known from Table 3 that, compared with the example 16 in which annealing of the hot rolled plate is not adopted, in the examples 17-31 in which annealing of the hot rolled plate is adopted, the area ratio of the small grains with D<5 mm in the oriented silicon steel finished product is reduced or the magnetic conductivity ratio 17/15 is increased, and thus the magnetic properties of the oriented silicon steel finished product are improved. Furthermore, it can be known from Table 3 that, performing the annealing at the temperature of 900-1150 C. and the cooling rate of 20 C./s or more on the hot rolled plate can ensure that the magnetic conductivity ratio 17/15 is 0.55 or more and thus further stably improve the magnetic properties of the oriented silicon steel finished product.

(11) Experimental results of the invention prove that, when the area ratio of the small grains with D<5 mm in the oriented silicon steel finished product is not more than 3% and the ratio 17/15 of the magnetic conductivity under the magnetic induction 1.7 T to the magnetic conductivity under the magnetic induction of 1.5 T in the oriented silicon steel finished product is 0.50 or more, the oriented silicon steel finished product with excellent magnetic properties can be obtained. According to the invention, by adopting the slab of the oriented silicon steel with suitable components and an optimized cold rolling step to control the area ratio of the small grains with D<5 mm in the oriented silicon steel finished product to be not more than 3% and control the magnetic conductivity ratio 17/15 to be 0.50 or more, the oriented silicon steel product with excellent magnetic properties can be stably obtained.

(12) The invention obtains the oriented silicon steel with excellent magnetic properties by controlling the area ratio of the small grains with D<5 mm in the oriented silicon steel finished product to be not more than 3%, and controlling the ratio 17/15 of the magnetic conductivity under the magnetic induction of 1.7 T to the magnetic conductivity under the magnetic induction of 1.5 T in the oriented silicon steel finished product to be 0.50 or more. In addition, by using the slab of the oriented silicon steel with suitable components and the optimized cold rolling step, the invention effectively reduces the heating temperature of the slab and the production cost, and simultaneously better controls the size and ratio of the grains in the oriented silicon steel finished product and the magnetic conductivity in a certain range of magnetic induction, ensures that secondary recrystallization has good Goss texture orientation and finally stably obtains the oriented silicon steel product with excellent magnetic properties.