Method for micro-tension control of non-oriented electrical steel

Abstract

This invention belongs to the field of steel material technology, specifically relating to a micro-tension control method for non-oriented electrical steel, comprising the following steps: S1, obtaining a strip of non-oriented electrical steel with a thickness of 0.1~0.5mm and a width of 200~1500mm; S2, continuously annealing the non-oriented electrical steel, the continuous annealing sequentially passing through: the tension roller at the annealing furnace inlet, the bottom roller of the annealing furnace zone, and the tension roller at the annealing furnace outlet, with an annealing temperature of 750~780℃; S3, controlling the tension of the strip to 0.5~1kN; S4, rewinding to obtain annealed electrical steel; This invention significantly reduces the initial internal stress of the strip and optimizes its favorable texture, so that the comprehensive internal stress and iron loss of the electrical steel can still be kept within a low range after the stamping process, thereby eliminating the need for the traditional stress-relief annealing step in the bell-type furnace after stamping in the overall manufacturing process.

Description

Technical Field

[0001] This invention belongs to the field of steel materials technology, specifically a micro-tension control method for non-oriented electrical steel. Background Technology

[0002] Non-oriented electrical steel is mainly used as the stator and rotor of motors. The final process for non-oriented electrical steel is continuous annealing and coating. During the continuous annealing and cooling stage, the strip steel will still have internal stress when cooled from a high temperature of more than 900°C to room temperature.

[0003] After non-oriented electrical steel is made into stators and rotors, the internal stress is further increased due to the laminations, which leads to an increase in iron loss of 10% to 15% and a decrease in motor efficiency. Therefore, after the stators and rotors are made, the iron core needs to be stress-relieved and annealed as a whole, and a bell-type furnace is generally used, which has low efficiency.

[0004] Therefore, a method is needed to further reduce the internal stress of non-oriented electrical steel. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a micro-tension control method for non-oriented electrical steel, comprising the following steps: S1. Obtain non-oriented electrical steel strip with a thickness of 0.1~0.5mm and a width of 200~1500mm. Its composition, by mass percentage, is: the sum of Si, Al and Mn is 2.0wt%~6.0wt%, the sum of C, S, O, N, Nb, V, Ti, Mo and Cr is less than or equal to 0.009wt%, and the balance is iron and unavoidable impurities. S2. The non-oriented electrical steel is continuously annealed, and the continuous annealing process passes through the following rollers in sequence: the tension roller at the inlet of the annealing furnace, the bottom roller of the annealing furnace zone, and the tension roller at the outlet of the annealing furnace. The annealing temperature is 750~780℃. S3. Control the tension of the strip steel in the annealing furnace zone to be 0.5~1kN; S4, after rewinding, annealed electrical steel is obtained.

[0006] Furthermore, in step S1, the thickness of the strip is any one of 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, or a range between two of them.

[0007] Furthermore, in step S1, the width of the strip is any one of 200mm, 400mm, 600mm, 800mm, 1000mm, 1200mm, 1400mm, and 1500mm, or a range between two of them.

[0008] Furthermore, in step S2, the annealing temperature is any one of 750°C, 760°C, 770°C, and 780°C, or a range between two of them.

[0009] Furthermore, in step S3, the tension of the strip in the annealing furnace zone is controlled to be any one of 0.5kN, 0.6kN, 0.7kN, 0.8kN, 0.9kN, 1.0kN, or a range between two of them.

[0010] In step S3, the speed of the strip is 30~50m / min.

[0011] In step S3, the lead rate of the tension roller at the annealing furnace inlet is controlled at 3% to 4%, the lead rate of the bottom roller in the annealing furnace zone is controlled at 5% to 6%, and the lead rate of the tension roller at the annealing furnace outlet is controlled at 6% to 8%.

[0012] Furthermore, the speed of the strip is any one of 30m / min, 35m / min, 40m / min, 45m / min, 50m / min, or a range between two of them.

[0013] Preferably, in step S1, the thickness of the strip is 0.3~0.4mm and the width is 500~1000mm.

[0014] Preferably, in step S2, the annealing temperature is 760°C.

[0015] Preferably, in step S3, the tension of the strip in the annealing furnace zone is controlled to be 0.7~0.9kN.

[0016] In this step, the iron loss of the annealed electrical steel obtained in step S4 is reduced by 15% to 25% compared to the iron loss of the non-oriented electrical steel obtained in step S1.

[0017] In this step, the coercivity of the annealed electrical steel obtained in step S4 is reduced by 15% to 20% compared to the coercivity of the non-oriented electrical steel obtained in step S1.

[0018] This invention significantly reduces the initial internal stress of the strip steel and optimizes its favorable texture, so that the overall internal stress and iron loss of electrical steel can still be kept within a low range after the stamping process, thereby eliminating the need for the traditional stress-relief annealing step in the stamping furnace in the overall manufacturing process. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 The hysteresis loop of the non-oriented electrical steel in Embodiment 1 of the present invention; Figure 2 This refers to the hysteresis loop of the annealed electrical steel in Embodiment 1 of the present invention.

[0021] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention provides a method for micro-tension control of non-oriented electrical steel, comprising the following steps: S1. Obtain non-oriented electrical steel strip with a thickness of 0.1~0.5mm and a width of 200~1500mm. Its composition, by mass percentage, is: the sum of Si, Al and Mn is 2.0wt%~6.0wt%, the sum of C, S, O, N, Nb, V, Ti, Mo and Cr is less than or equal to 0.009wt%, and the balance is iron and unavoidable impurities. S2. The non-oriented electrical steel is continuously annealed, and the continuous annealing process passes through the following rollers in sequence: the tension roller at the inlet of the annealing furnace, the bottom roller of the annealing furnace zone, and the tension roller at the outlet of the annealing furnace. The annealing temperature is 750~780℃. S3. Control the tension of the strip steel in the annealing furnace zone to be 0.5~1kN; S4, after rewinding, annealed electrical steel is obtained.

[0024] After stress-relief annealing, the strip shape of non-oriented electrical steel must be maintained. Poor strip shape can lead to defects such as wavy edges or wrinkles, affecting the quality of subsequent sheeting and the stacking coefficient. Strip shape control is mainly achieved by establishing micro-tension through the tension rollers at the annealing furnace inlet, the bottom rollers of the annealing furnace, and the tension rollers at the annealing furnace outlet. By properly matching the lead rate of each roller section, ensuring the tension is stable within a suitable range, strip shape problems caused by uneven tension can be effectively avoided, guaranteeing the straightness and surface quality of the strip after stress-relief annealing. Excessive lead rate results in excessive strip tension, leading to defects such as narrowing and wavy edges; insufficient lead rate results in insufficient micro-tension, making the strip prone to wrinkles and other shape defects.

[0025] Furthermore, micro-tension annealing can promote grain growth and optimize favorable texture, thereby reducing iron loss. If the micro-tension is too low, it has little effect on magnetic properties and may even worsen the strip shape, causing defects such as wrinkles. Conversely, if the micro-tension is too high, it will inhibit grain growth, increase unfavorable textures, worsen magnetic properties, and cause strip shape defects such as narrowing. For non-oriented electrical steel annealing, higher temperatures are more beneficial for reducing magnetic properties. However, higher temperatures can lead to stress re-induction during strip cooling and lower strip strength, resulting in less tensile strength. Therefore, temperature and micro-tension need to be strictly matched to prevent defects such as narrowing at high temperatures. Thus, only through coordinated control of micro-tension, temperature, and strip thickness and width during continuous annealing of non-oriented electrical steel can low iron loss and a good strip shape be achieved.

[0026] The flatness test method used in this embodiment of the invention is ASTM A568 / A568M-25.

[0027] Example 1 A method for micro-tension control of non-oriented electrical steel includes the following steps: S1. Obtain non-oriented electrical steel strip with a thickness of 0.1 mm and a width of 200 mm. Its composition, by mass percentage, is: Si, Al, and Mn totaling 2.0 wt%, C, S, O, N, Nb, V, Ti, Mo, and Cr totaling 0.009 wt%, with the balance being iron and unavoidable impurities. S2. The non-oriented electrical steel is continuously annealed, and the continuous annealing process passes through the following rollers in sequence: the tension roller at the inlet of the annealing furnace, the bottom roller in the furnace zone of the annealing furnace, and the tension roller at the outlet of the annealing furnace. The annealing temperature is 750℃. S3. Control the speed of the strip steel to 30m / min, control the lead rate of the tension roller at the annealing furnace inlet to 3%, control the lead rate of the bottom roller in the annealing furnace zone to 5%, and control the lead rate of the tension roller at the annealing furnace outlet to 6%, thereby controlling the tension of the strip steel to 0.5kN. S4, after rewinding, annealed electrical steel is obtained.

[0028] The annealed electrical steel was tested and found to have good plate shape. The iron loss of the annealed electrical steel obtained in step S4 was reduced by 15% compared with the iron loss of the non-oriented electrical steel in step S1, and the flatness was 3I-unit. Please see Figure 1 , Figure 1 For the hysteresis loop of the non-oriented electrical steel in Embodiment 1 of this invention, please refer to further details. Figure 2 , Figure 2 The hysteresis loop of the annealed electrical steel in Embodiment 1 of the present invention; As can be seen from the figure, its coercivity decreased from 103.4 A / m to 85.4 A / m, a reduction of 17.4%.

[0029] Example 2 A method for micro-tension control of non-oriented electrical steel includes the following steps: S1. Obtain non-oriented electrical steel strip with a thickness of 0.5 mm and a width of 1500 mm. Its composition, by mass percentage, is: Si, Al, and Mn totaling 6.0 wt%, C, S, O, N, Nb, V, Ti, Mo, and Cr totaling 0.0085 wt%, with the balance being iron and unavoidable impurities. S2. The non-oriented electrical steel is continuously annealed, and the continuous annealing process passes through the following rollers in sequence: the tension roller at the inlet of the annealing furnace, the bottom roller of the annealing furnace zone, and the tension roller at the outlet of the annealing furnace. The annealing temperature is 780℃. S3. Control the speed of the strip steel to 50m / min, control the lead rate of the tension roller at the annealing furnace inlet to 4%, control the lead rate of the bottom roller in the annealing furnace zone to 6%, and control the lead rate of the tension roller at the annealing furnace outlet to 8%, thereby controlling the tension of the strip steel to 1kN. S4, after rewinding, annealed electrical steel is obtained.

[0030] The annealed electrical steel was tested and found to have good plate shape. The iron loss of the annealed electrical steel obtained in step S4 was reduced by 25% and the coercivity was reduced by 20% compared with the non-oriented electrical steel in step S1. The flatness was 4I-unit.

[0031] Comparative Example 1 Unlike Example 1, in step S3, the speed of the strip is controlled to be 40 m / min, the lead rate of the tension roller at the annealing furnace inlet is controlled to be 5%, the lead rate of the bottom roller in the annealing furnace zone is controlled to be 8%, and the lead rate of the tension roller at the annealing furnace outlet is controlled to be 10%, thereby controlling the tension of the strip to be 2 kN.

[0032] The annealed electrical steel was tested and found to have a narrowing defect. The iron loss of the annealed electrical steel obtained in step S4 was reduced by 5% and the coercivity was reduced by 4% compared with the non-oriented electrical steel in step S1. The flatness was 71-unit.

[0033] Comparative Example 2 Unlike Example 2, in step S3, the speed of the strip is controlled to be 35 m / min, the lead rate of the tension roller at the annealing furnace inlet is controlled to be 1%, the lead rate of the bottom roller in the annealing furnace zone is controlled to be 2%, and the lead rate of the tension roller at the annealing furnace outlet is controlled to be 3%, thereby controlling the tension of the strip to be 0.2 kN.

[0034] The annealed electrical steel was tested and found to have wrinkle defects. The iron loss of the annealed electrical steel obtained in step S4 was reduced by 8% and the coercivity was reduced by 6% compared with the non-oriented electrical steel in step S1. The flatness was 81-unit.

[0035] Comparative Example 3 Unlike Example 2, in step S2, the annealing temperature is 700°C.

[0036] The annealed electrical steel was tested and found to have good plate shape. The iron loss of the annealed electrical steel obtained in step S4 was reduced by 6% compared with the iron loss of the non-oriented electrical steel in step S1, the coercivity was reduced by 5%, and the flatness was 4I-unit.

[0037] Comparative Example 4 Unlike Example 2, in step S2, the annealing temperature is 800°C.

[0038] The annealed electrical steel was tested and found to have obvious narrowing defects. The iron loss of the annealed electrical steel obtained in step S4 was reduced by 4% compared with the iron loss of the non-oriented electrical steel in step S1, the coercivity was reduced by 2%, and the flatness was 71-unit.

[0039] This invention significantly reduces the initial internal stress of the strip steel and optimizes its favorable texture, so that the overall internal stress and iron loss of electrical steel can still be kept within a low range after the stamping process, thereby eliminating the need for the traditional stress-relief annealing step in the stamping furnace in the overall manufacturing process.

[0040] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for micro-tension control of non-oriented electrical steel, characterized in that, Includes the following steps: S1. Obtain non-oriented electrical steel strip with a thickness of 0.1~0.5mm and a width of 200~1500mm. Its composition, by mass percentage, is: the sum of Si, Al and Mn is 2.0wt%~6.0wt%, the sum of C, S, O, N, Nb, V, Ti, Mo and Cr is less than or equal to 0.009wt%, and the balance is iron and unavoidable impurities. S2. The non-oriented electrical steel is continuously annealed, and the continuous annealing process passes through the following rollers in sequence: the tension roller at the inlet of the annealing furnace, the bottom roller of the annealing furnace zone, and the tension roller at the outlet of the annealing furnace. The annealing temperature is 750~780℃. S3. Control the tension of the strip steel in the annealing furnace zone to be 0.5~1kN; S4. After rewinding, annealed electrical steel is obtained. In step S3, the speed of the strip is 30~50m / min; In step S3, the lead rate of the tension roller at the annealing furnace inlet is controlled at 3% to 4%, the lead rate of the bottom roller in the annealing furnace zone is controlled at 5% to 6%, and the lead rate of the tension roller at the annealing furnace outlet is controlled at 6% to 8%.

2. The micro-tension control method for non-oriented electrical steel according to claim 1, characterized in that, In step S1, the thickness of the strip is 0.3~0.4mm and the width is 500~1000mm.

3. The micro-tension control method for non-oriented electrical steel according to claim 2, characterized in that, In step S2, the annealing temperature is 760°C.

4. The micro-tension control method for non-oriented electrical steel according to claim 3, characterized in that, In step S3, the tension of the strip in the annealing furnace zone is controlled to be 0.7~0.9kN.

5. The micro-tension control method for non-oriented electrical steel according to claim 1, characterized in that, The iron loss of the annealed electrical steel obtained in step S4 is reduced by 15% to 25% compared to the iron loss of the non-oriented electrical steel obtained in step S1.

6. The micro-tension control method for non-oriented electrical steel according to claim 1, characterized in that, The coercivity of the annealed electrical steel obtained in step S4 is reduced by 15% to 20% compared to the coercivity of the non-oriented electrical steel obtained in step S1.

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