Low iron loss non-oriented silicon steel and method for manufacturing the same

Abstract

The application discloses a low-iron-loss non-oriented silicon steel and a preparation method thereof, and belongs to the technical field of non-oriented silicon steel production. The chemical components of the low-iron-loss non-oriented silicon steel are controlled according to the following mass percentage: 0.0015%<=C<=0.0035%, 3.5%<=Si<=3.8%, 0.8%<=Al<=1.5%, 0.05%<=Mn<=0.15%, P<=0.015%, S<=0.0010%, N<=0.0015%, 0.04%<=Sb<=0.08%, 0.05%<=Cr<=0.15%, and the balance is Fe and inevitable impurities. The application adopts a hot-rolled coil normalizing and direct trimming process, and continuous production can be completed in one process, so that the production efficiency is high, and the cost is low. Compared with a conventional process, the iron loss can be reduced by about 5%.

Description

Technical Field

[0001] This invention belongs to the field of non-oriented silicon steel production technology, specifically relating to a low-iron-loss non-oriented silicon steel and its preparation method. Background Technology

[0002] Non-oriented silicon steel, as an important functional metallic material, is mainly used in the manufacture of motor and transformer cores. In recent years, with the rapid development of the national power industry and the continuous improvement of manufacturing level, the single-unit capacity of power generation equipment has been developing towards larger size and higher efficiency. For example, the single-unit capacity of pumped storage generator sets can reach up to 400,000 kilowatts, and their stator cores require the use of low-iron-loss non-oriented silicon steel for manufacturing.

[0003] To reduce iron loss, the common practice is to continuously increase the silicon and aluminum alloy content in non-oriented silicon steel. However, with a significant increase in silicon and aluminum alloy content, especially aluminum, the surface of the finished steel sheet is significantly affected by the annealing atmosphere, making it highly susceptible to oxidation and leading to a deterioration in surface quality and magnetic properties. Furthermore, high silicon and aluminum content makes the product both hard and brittle, making it prone to strip breakage during cold rolling, thus affecting production efficiency and yield.

[0004] To address surface oxidation, a high-hydrogen-ratio atmosphere is typically used for annealing. However, during production, the bottom rollers of the annealing furnace are prone to nodule formation, leading to surface quality issues such as roller bulges and scratches. To improve cold working performance, a heating system is usually added before rolling to increase the temperature of the rolled piece and enhance its plasticity. However, this method involves significant investment and has high energy consumption and costs.

[0005] In the existing technology, Chinese invention patent CN114045433A adopts a process of first trimming the hot-rolled coil and then normalizing it. This process needs to be carried out between two processes, which is cumbersome, has low production efficiency, and increases production costs. Summary of the Invention

[0006] To address the aforementioned technical problems in the prior art, this invention provides a low-iron-loss non-oriented silicon steel and its preparation method.

[0007] In a first aspect of the invention, a low-iron-loss non-oriented silicon steel is provided, the chemical composition of which is controlled by mass percentage as follows: 0.0015%≤C≤0.0035%, 3.5%≤Si≤3.8%, 0.8%≤Al≤1.5%, 0.05%≤Mn≤0.15%, P≤0.015%, S≤0.0010%, N≤0.0015%, 0.04%≤Sb≤0.08%, 0.05%≤Cr≤0.15%, with the balance being Fe and unavoidable impurities.

[0008] Furthermore, the chemical composition of the aforementioned low-iron-loss non-oriented silicon steel is controlled by mass percentage as follows: 0.0020%≤C≤0.0025%, 3.57%≤Si≤3.72%, 1.23%≤Al≤1.42%, 0.10%≤Mn≤0.13%, 0.010%≤P≤0.013%, 0.0006%≤S≤0.001%, 0.0010%≤N≤0.0013%, 0.06%≤Sb≤0.07%, 0.07%≤Cr≤0.12%, with the balance being Fe and unavoidable impurities.

[0009] Furthermore, when the thickness of the aforementioned low-iron-loss non-oriented silicon steel finished product is 0.35–0.65 mm, the iron loss P 1.5 / 50 It ranges from 2.03 to 2.65 W / kg.

[0010] Furthermore, when the thickness of the aforementioned low-iron-loss non-oriented silicon steel product is 0.35–0.65 mm, the magnetic induction B 5000 It ranges from 1.65 to 1.67 T.

[0011] In a second aspect of the present invention, the method for preparing low-iron-loss non-oriented silicon steel includes the following steps: (1) Slab smelting: Smelting raw materials to obtain slabs; (2) Heating and hot rolling: The billet is heated to 1030℃~1080℃, held for 3~4 hours and then hot rolled to form a hot rolled plate with a thickness of 2.1mm~2.45mm; (3) Hot-rolled plate pretreatment: The hot-rolled plate is subjected to normalizing treatment, pickling treatment and edge trimming treatment in sequence. During the edge trimming process, the strip steel is sheared into waste edge area and mother body area by the upper and lower shear blades. The side of the mother body area that abuts the upper shear blade is the shearing area. The corresponding fracture surfaces of the mother body area and the waste edge area are the fracture areas. By adjusting the side gap and overlap between the upper and lower shear blades, the ratio of the shearing area to the fracture area is controlled to be 1: (4~8). (4) Warm cold rolling: The steel coil after edge trimming is immediately fed into the 20-roll mill while still warm. It is rolled to the target finished thickness using a multi-pass, one-time cold rolling process. Before rolling, the edges of the strip are heated by open flame at the mill entrance to keep the temperature of the strip edges at 60℃~100℃ when they enter the mill. During the rolling process, a rolling emulsion with a temperature of 70℃~75℃ and a flow rate of 1000L / min~1500L / min is used for lubrication and cooling. (5) Two-stage protective annealing: The cold-rolled strip is continuously annealed in a mixed protective atmosphere of hydrogen and nitrogen. The volume fraction of hydrogen in the mixed protective atmosphere is 8%~12%, and the remainder is nitrogen. The annealing adopts a two-stage process. The first stage annealing temperature is 1040℃~1080℃, the second stage annealing temperature is 980℃~1020℃, and the strip annealing running speed is 90m / min~120m / min. (6) Gradient cooling: After annealing, the strip steel is first cooled to 700°C at a cooling rate of no more than 10°C / s, then cooled to 400°C at a cooling rate of no more than 15°C / s, and then cooled to below 60°C. (7) Coating and drying: Apply an insulating coating to the surface of the cooled strip steel and dry it to obtain the finished non-oriented silicon steel product.

[0012] Furthermore, in the above-mentioned method for preparing low-iron-loss non-oriented silicon steel, in step (3), the ratio of the shearing zone to the fracture zone of the strip cutting surface is controlled to be 1:(4~6).

[0013] Furthermore, in the above-mentioned method for preparing low-iron-loss non-oriented silicon steel, in step (4), the temperature of the strip edge when entering the rolling mill is maintained at 80℃~95℃.

[0014] The low-iron-loss non-oriented silicon steel and its preparation method of the present invention have the following advantages and beneficial effects: This invention employs a direct edge-trimming process after normalizing hot-rolled coils, enabling continuous production in a single step, resulting in high efficiency and low cost. By controlling edge quality after trimming, edge heating, and adjusting the temperature and flow rate of the rolling emulsion, this invention improves the cold-working properties of the material, eliminating the need for complex heating systems and saving significant equipment investment. Adding a small amount of oxidation-inhibiting elements significantly reduces the proportion of H2 in the annealing protective atmosphere, achieving a bright surface while reducing surface defects such as bumps and scratches caused by furnace roll nodules. Compared to conventional processes, iron loss can be reduced by approximately 5%. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application 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 for further understanding of the embodiments of this application and constitute a part of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the shear cross-section of low-iron-loss non-oriented silicon steel prepared according to an embodiment of this application; Figure 2The surface color of the low-iron-loss non-oriented silicon steel product prepared according to the embodiments of this application; Figure 3 The surface color of the low-iron-loss non-oriented silicon steel product prepared as a comparative example of this application.

[0016] Explanation of reference numerals in the attached figures: 1. Upper shear blade; 2. Shearing zone; 3. Fracture zone; 4. Mother body zone; 5. Lower shear blade; 6. Waste edge zone. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0018] In a first aspect of the present invention, a low-iron-loss non-oriented silicon steel is provided, which improves cold working performance by improving the edge quality of the strip and the plasticity of the rolled piece during cold rolling.

[0019] Specifically, the chemical composition of the low-iron-loss non-oriented silicon steel of the present invention is controlled by mass percentage as follows: 0.0015%≤C≤0.0035%, 3.5%≤Si≤3.8%, 0.8%≤Al≤1.5%, 0.05%≤Mn≤0.15%, P≤0.015%, S≤0.0010%, N≤0.0015%, 0.04%≤Sb≤0.08%, 0.05%≤Cr≤0.15%, with the balance being Fe and unavoidable impurities.

[0020] Preferably, the chemical composition of the low-iron-loss non-oriented silicon steel of the present invention is controlled by mass percentage as follows: 0.0020%≤C≤0.0025%, 3.57%≤Si≤3.72%, 1.23%≤Al≤1.42%, 0.10%≤Mn≤0.13%, 0.010%≤P≤0.013%, 0.0006%≤S≤0.001%, 0.0010%≤N≤0.0013%, 0.06%≤Sb≤0.07%, 0.07%≤Cr≤0.12%, with the balance being Fe and unavoidable impurities.

[0021] Specifically, when the thickness of the low-iron-loss non-oriented silicon steel product of the present invention is 0.35–0.65 mm, the iron loss P 1.5 / 50 It ranges from 2.03 to 2.65 W / kg.

[0022] Specifically, when the thickness of the low-iron-loss non-oriented silicon steel product of the present invention is 0.35–0.65 mm, the magnetic induction B 5000 It ranges from 1.65 to 1.67 T.

[0023] The function of the required element and content control range for the low-iron-loss non-oriented silicon steel of this invention is described below: During the annealing of finished cold-rolled silicon steel sheets, an outer oxide layer and an inner oxide layer are formed on the surface. Metal ions diffuse outward to form the outer oxide layer, while oxygen diffuses inward to form the inner oxide layer. Currently, the most common method to obtain extremely low iron loss is to significantly increase the (Si+Al) content of the substrate and the annealing temperature. In this invention, the Si and Al content in the silicon steel is controlled at 3.5%≤Si≤3.8% and 0.8%≤Al≤1.5% by mass percentage. Experiments have shown that increasing the (Si+Al) content and annealing temperature, and reducing the content of oxidizing elements in the annealing protective atmosphere, makes it easier to form an outer oxide layer. Especially when the aluminum content in the steel is high, high-temperature annealing accelerates the oxidation rate, resulting in severe oxidation, easy blackening of the surface, and a significant adverse effect on magnetic properties. The basic idea of ​​this invention is to add a small amount of oxidation-inhibiting elements to the steel to form a dense oxide film on the substrate surface and hinder the diffusion rate of oxygen in the substrate, thereby reducing oxidation. The specific method involves adding a certain amount of chromium to the steel. Utilizing chromium's selective oxidation properties at high temperatures, a dense chromium oxide protective film is formed, hindering further oxidation. Simultaneously, 0.04-0.08 wt% Sb is added to the steel. Its segregation along grain boundaries hinders oxygen diffusion, slowing the formation of the inner oxide layer, resulting in a thinner inner oxide layer. Sulfur is a harmful element to magnetic properties; iron loss increases significantly with increasing sulfur content. Furthermore, sulfur competes with antimony for space at grain boundaries. To fully utilize the role of antimony, the sulfur content in the steel is controlled below 0.0010% by mass.

[0024] In a second aspect of the present invention, a method for preparing low-iron-loss non-oriented silicon steel is provided, comprising the following steps: (1) Slab smelting: Smelting raw materials to obtain slabs; (2) Heating and hot rolling: The billet is heated to 1030℃~1080℃, held for 3~4 hours and then hot rolled to form a hot rolled plate with a thickness of 2.1mm~2.45mm; (3) Hot-rolled plate pretreatment: The hot-rolled plate is subjected to normalizing treatment, pickling treatment and edge trimming treatment in sequence. During the edge trimming process, the strip steel is sheared into waste edge area 6 and mother body area 4 by the upper shear blade 1 and the lower shear blade 5. The side of the mother body area 4 that abuts against the upper shear blade 1 is the shearing area 2. The corresponding fracture surface of the mother body area 4 and the waste edge area 6 is the fracture area 3. By adjusting the side gap and overlap between the upper shear blade 1 and the lower shear blade 5, the ratio of shearing area 2 to fracture area 3 is controlled to be 1: (4~8), and the shearing surface and fracture surface are ensured to be smooth and free of cracks and burrs. (4) Warm cold rolling: The steel coil after edge trimming is immediately fed into the 20-roll mill while still warm. It is rolled to the target finished thickness using a multi-pass, one-time cold rolling process. Before rolling, the two sides of the strip are heated by open flame at the mill entrance to keep the temperature of the strip edge at 60℃~100℃ when it enters the mill, so as to improve the plasticity of the strip edge. The temperature of the rolling emulsion is increased and its flow rate is reduced to increase the temperature of the roll system and the rolled piece. During the rolling process, a rolling emulsion with a temperature of 70℃~75℃ and a flow rate of 1000L / min~1500L / min is used for lubrication and cooling. (5) Two-stage protective annealing: The cold-rolled strip is continuously annealed in a mixed protective atmosphere of hydrogen and nitrogen. The volume fraction of hydrogen in the mixed protective atmosphere is 8%~12%, and the remainder is nitrogen. The annealing adopts a two-stage process. The first stage annealing temperature is 1040℃~1080℃, the second stage annealing temperature is 980℃~1020℃, and the strip annealing running speed is 90m / min~120m / min. (6) Gradient cooling: After annealing, the strip steel is first cooled to 700°C at a cooling rate of no more than 10°C / s, then cooled to 400°C at a cooling rate of no more than 15°C / s, and then rapidly cooled to below 60°C. (7) Coating and drying: Apply an insulating coating to the surface of the cooled strip steel and dry it to obtain the finished non-oriented silicon steel product.

[0025] Preferably, in the method for preparing low-iron-loss non-oriented silicon steel of the present invention, in step (3), the ratio of the shearing zone 2 to the fracture zone 3 of the strip cutting surface is controlled to be 1:(4~6).

[0026] Preferably, in the method for preparing low-iron-loss non-oriented silicon steel of the present invention, in step (4), the temperature of the strip edge when entering the rolling mill is maintained at 80°C to 95°C.

[0027] The following detailed description of the low-iron-loss non-oriented silicon steel and its preparation method of the present invention, with reference to embodiments and comparative examples, is provided in detail.

[0028] Example 1 The chemical composition of the low-iron-loss non-oriented silicon steel in Example 1, by mass percentage, is as follows: C: 0.0025%, Si: 3.57%, Al: 1.42%, Mn: 0.13%, S: 0.001%, P: 0.012%, N: 0.0012%, Sb: 0.07%, Cr: 0.12%, with the remainder being Fe and unavoidable impurities.

[0029] (1) Smelting of billet: Smelting according to the above composition to obtain billet.

[0030] (2) Heating and hot rolling: The billet is heated to 1080℃ and held for 3 hours before hot rolling to form a hot-rolled plate with a thickness of 2.3mm.

[0031] (3) Hot-rolled plate pretreatment: The hot-rolled plate is subjected to normalizing treatment, pickling treatment and edge trimming treatment in sequence; during the edge trimming process, the side gap and overlap of the upper shear blade 1 and the lower shear blade 5 are adjusted to control the ratio of the shearing zone 2 to the fracture zone 3 to be 1:5.

[0032] (4) Warm Cold Rolling: After edge trimming, the steel coil is immediately fed into a 20-roll mill while still warm, and is rolled to the target thickness using a multi-pass, one-time cold rolling process. Before rolling, the edges of the strip are heated with an open flame at the mill entrance to maintain the temperature of the strip edges at 80°C when entering the mill. During the rolling process, a rolling emulsion with a temperature of 70°C and a flow rate of 1500 L / min is used for lubrication and cooling, and finally cold-rolled to a thickness of 0.50 mm. In this embodiment, the average number of strip breaks per coil during cold rolling is about 0.2, which increases the production efficiency by about 50% and the yield by 12% compared to the conventional process.

[0033] (5) Two-stage protective annealing: The cold-rolled strip is continuously annealed in a mixed protective atmosphere with hydrogen gas as the integral of 12% and nitrogen as the balance. The annealing adopts a two-stage process, with the first stage annealing temperature at 1060℃ and the second stage annealing temperature at 1000℃. The strip annealing running speed is 100m / min.

[0034] (6) Gradient cooling: After annealing, the strip steel is first cooled to 700°C at a cooling rate of no more than 10°C / s, then cooled to 400°C at a cooling rate of no more than 15°C / s, and then rapidly cooled to below 60°C.

[0035] (7) Coating and drying: Apply an insulating coating to the surface of the cooled strip steel and dry it to obtain the finished non-oriented silicon steel product.

[0036] Iron loss P of the product in this embodiment 1.5 / 50 2.18W / kg, magnetic induction B 5000 It has a strength of 1.66T, excellent magnetic properties, and a bright, silvery-gray surface.

[0037] Example 2 The chemical composition of the low-iron-loss non-oriented silicon steel in Example 2, by mass percentage, is as follows: C: 0.0020%, Si: 3.68%, Al: 1.31%, Mn: 0.10%, S: 0.0008%, P: 0.010%, N: 0.0013%, Sb: 0.06%, Cr: 0.10%, with the remainder being Fe and unavoidable impurities.

[0038] (1) Smelting of billet: Smelting according to the above composition to obtain billet.

[0039] (2) Heating and hot rolling: The billet is heated to 1060℃ and held for 3.5 hours before hot rolling to form a hot-rolled plate with a thickness of 2.1mm.

[0040] (3) Hot-rolled plate pretreatment: The hot-rolled plate is subjected to normalizing treatment, pickling treatment and edge trimming treatment in sequence; during the edge trimming process, the side gap and overlap of the upper shear blade 1 and the lower shear blade 5 are adjusted to control the ratio of the shearing zone 2 to the fracture zone 3 to be 1:6.

[0041] (4) Warm Cold Rolling: After edge trimming, the steel coil is immediately fed into a 20-roll mill while still warm, and is rolled to the target thickness using a multi-pass, one-time cold rolling process. Before rolling, the edges of the strip are heated with an open flame at the mill entrance to maintain the temperature of the strip edges at 90°C when entering the mill. During the rolling process, a rolling emulsion with a temperature of 75°C and a flow rate of 1200 L / min is used for lubrication and cooling, and finally cold rolled to a thickness of 0.35 mm. In this embodiment, the average number of strip breaks per coil during cold rolling is approximately 0.25.

[0042] (5) Two-stage protective annealing: The cold-rolled strip is continuously annealed in a mixed protective atmosphere with hydrogen gas fraction of 10% and nitrogen gas fraction of the remainder. The annealing adopts a two-stage process, with the first stage annealing temperature at 1040℃ and the second stage annealing temperature at 980℃. The strip annealing running speed is 120m / min.

[0043] (6) Gradient cooling: After annealing, the strip steel is first cooled to 700°C at a cooling rate of no more than 10°C / s, then cooled to 400°C at a cooling rate of no more than 15°C / s, and then rapidly cooled to below 60°C.

[0044] (7) Coating and drying: Apply an insulating coating to the surface of the cooled strip steel and dry it to obtain the finished non-oriented silicon steel product.

[0045] Iron loss P of the product in this embodiment 1.5 / 50 2.03W / kg, magnetic induction B 5000 It has a strength of 1.65T, excellent magnetic properties, and a bright silver-gray surface.

[0046] Example 3 The chemical composition of the low-iron-loss non-oriented silicon steel in Example 3, by mass percentage, is as follows: C: 0.0024%, Si: 3.72%, Al: 1.23%, Mn: 0.11%, S: 0.0006%, P: 0.013%, N: 0.0012%, Sb: 0.07%, Cr: 0.07%, with the remainder being Fe and unavoidable impurities.

[0047] (1) Smelting of billet: Smelting according to the above composition to obtain billet.

[0048] (2) Heating and hot rolling: The billet is heated to 1030℃ and held for 4 hours before hot rolling to form a hot-rolled plate with a thickness of 2.45mm.

[0049] (3) Hot-rolled plate pretreatment: The hot-rolled plate is subjected to normalizing treatment, pickling treatment and edge trimming treatment in sequence; during the edge trimming process, the side gap and overlap of the upper shear blade 1 and the lower shear blade 5 are adjusted to control the ratio of the shearing zone 2 to the fracture zone 3 to be 1:4.

[0050] (4) Warm Cold Rolling: After edge trimming, the steel coil is immediately fed into a 20-roll mill while still warm, and is rolled to the target thickness using a multi-pass, one-time cold rolling process. Before rolling, the edges of the strip are heated with an open flame at the mill entrance to maintain the temperature of the strip edges at 95°C when entering the mill. During the rolling process, a rolling emulsion with a temperature of 75°C and a flow rate of 1000 L / min is used for lubrication and cooling, and finally cold rolled to a thickness of 0.65 mm. In this embodiment, the average number of strip breaks per coil during cold rolling is approximately 0.1.

[0051] (5) Two-stage protective annealing: The cold-rolled strip is continuously annealed in a mixed protective atmosphere with hydrogen gas component of 8% and nitrogen gas component of the remainder. The annealing adopts a two-stage process, with the first stage annealing temperature at 1080℃ and the second stage annealing temperature at 1020℃. The strip annealing running speed is 90m / min.

[0052] (6) Gradient cooling: After annealing, the strip steel is first cooled to 700°C at a cooling rate of no more than 10°C / s, then cooled to 400°C at a cooling rate of no more than 15°C / s, and then rapidly cooled to below 60°C.

[0053] (7) Coating and drying: Apply an insulating coating to the surface of the cooled strip steel and dry it to obtain the finished non-oriented silicon steel product.

[0054] Iron loss P of the product in this embodiment 1.5 / 50 2.65W / kg, magnetic induction B 5000 It has a strength of 1.67T, excellent magnetic properties, and a bright, silvery-gray surface.

[0055] Comparative Example 1 The chemical composition of the non-oriented silicon steel in Comparative Example 1, by mass percentage, is as follows: C: 0.0023%, Si: 3.28%, Al: 1.08%, Mn: 0.23%, S: 0.0012%, P: 0.009%, N: 0.0014%, with the remainder being Fe and unavoidable impurities.

[0056] After obtaining the billet by smelting according to the above composition, the billet is heated to 1080℃ and held for 3 hours, and then hot-rolled to a 2.3mm thick hot-rolled plate. The hot-rolled plate is subjected to conventional normalizing, pickling and trimming treatment. The ratio of shear zone 2 to fracture zone 3 is not specifically controlled during the trimming process.

[0057] The trimmed steel coils are processed using conventional cold rolling technology: they are fed directly into a 20-roll mill without being preheated, and the edges of the strip are not heated by open flame before rolling. A rolling emulsion with a temperature of 55℃ and a flow rate of 2500L / min is used, and the strip is cold rolled to a thickness of 0.50mm in one pass. In this comparative example, the average number of strip breaks per coil during cold rolling is approximately 1.2.

[0058] Annealing is performed using a single-stage process: the cold-rolled strip is passed through a mixed protective atmosphere in which hydrogen gas accounts for 45% and the remainder is nitrogen gas, and continuous annealing is carried out at 1000℃. The annealing speed of the strip is 100m / min.

[0059] After annealing, a rapid cooling process is adopted: the temperature is directly cooled to below 60°C at a cooling rate of more than 30°C / s, followed by coating and drying to obtain the finished non-oriented silicon steel product.

[0060] Iron loss P of the comparative product 1.5 / 50 2.35W / kg, magnetic induction B 5000 It has a strength of 1.66T, average magnetic properties, and poor surface color, appearing bluish-black.

[0061] Comparative Example 2 The chemical composition of the non-oriented silicon steel in Comparative Example 2, by mass percentage, is as follows: C: 0.0026%, Si: 3.32%, Al: 1.05%, Mn: 0.27%, S: 0.0010%, P: 0.011%, N: 0.0021%, with the remainder being Fe and unavoidable impurities.

[0062] After obtaining the billet by smelting according to the above composition, the billet is heated to 1060℃ and held for 3.5 hours, and then hot-rolled to a 2.1mm thick hot-rolled plate. The hot-rolled plate is subjected to conventional normalizing, pickling and trimming treatment. The ratio of shear zone 2 to fracture zone 3 is not specifically controlled during the trimming process.

[0063] The trimmed steel coils are processed using conventional cold rolling technology: they are fed directly into a 20-roll mill without being preheated, and the edges of the strip are not heated by open flame before rolling. A rolling emulsion with a temperature of 60℃ and a flow rate of 2000L / min is used, and the strip is cold rolled to a thickness of 0.35mm in one pass. In this comparative example, the average number of strip breaks per coil during cold rolling is approximately 1.6.

[0064] Annealing is performed using a single-stage process: the cold-rolled strip is passed through a mixed protective atmosphere in which hydrogen gas accounts for 35% and the remainder is nitrogen gas, and continuous annealing is carried out at 980℃. The annealing speed of the strip is 120m / min.

[0065] After annealing, a rapid cooling process is adopted: the temperature is directly cooled to below 60°C at a cooling rate of more than 30°C / s, followed by coating and drying to obtain the finished non-oriented silicon steel product.

[0066] Iron loss P of the comparative product 1.5 / 50 2.12W / kg, magnetic induction B 5000 It has a strength of 1.65T, average magnetic properties, and poor surface color, appearing bluish-black.

[0067] Comparative Example 3 The chemical composition of the non-oriented silicon steel in Comparative Example 3, by mass percentage, is as follows: C: 0.0030%, Si: 3.35%, Al: 1.07%, Mn: 0.25%, S: 0.0014%, P: 0.011%, N: 0.0018%, with the remainder being Fe and unavoidable impurities.

[0068] After obtaining the billet by smelting according to the above composition, the billet is heated to 1030℃ and held for 4 hours, and then hot-rolled to a 2.45mm thick hot-rolled plate. The hot-rolled plate is subjected to conventional normalizing, pickling and trimming treatment. The ratio of shear zone 2 to fracture zone 3 is not specifically controlled during the trimming process.

[0069] The trimmed steel coils are processed using a conventional cold rolling process: they are fed directly into a 20-roll mill without being preheated, and the edges of the strip are not heated by open flame before rolling. A rolling emulsion with a temperature of 65℃ and a flow rate of 2200L / min is used, and the strip is cold rolled to a thickness of 0.65mm in one pass. The average number of strip breaks per coil during cold rolling in this comparative example is approximately 0.8.

[0070] Annealing is performed using a single-stage process: the cold-rolled strip is passed through a mixed protective atmosphere in which hydrogen gas accounts for 25% and the remainder is nitrogen gas, and continuous annealing is carried out at 1020℃. The annealing speed of the strip is 90m / min.

[0071] After annealing, a rapid cooling process is adopted: the temperature is directly cooled to below 60°C at a cooling rate of more than 30°C / s, followed by coating and drying to obtain the finished non-oriented silicon steel product.

[0072] Iron loss P of the comparative product 1.5 / 50 2.87W / kg, magnetic induction B 5000 It has a strength of 1.67T, average magnetic properties, and poor surface color, appearing bluish-black.

[0073] In summary, compared with the prior art, the low-iron-loss non-oriented silicon steel and its preparation method of the present invention have the following advantages and positive effects: This invention employs a direct edge-trimming process after normalizing hot-rolled coils, enabling continuous production in a single step, resulting in high efficiency and low cost. By controlling edge quality after trimming, edge heating, and adjusting the temperature and flow rate of the rolling emulsion, this invention improves the cold-working properties of the material, eliminating the need for complex heating systems and saving significant equipment investment. Adding a small amount of oxidation-inhibiting elements significantly reduces the proportion of H2 in the annealing protective atmosphere, achieving a bright surface while reducing surface defects such as bumps and scratches caused by furnace roll nodules. Compared to conventional processes, iron loss can be reduced by approximately 5%.

[0074] In the description of this specification, the term "embodiment" means a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The illustrative expressions of the above terms in this specification do not necessarily refer to the same embodiment. Furthermore, those skilled in the art can combine or combine the different embodiments and features described in this specification without creating contradiction.

[0075] It should be noted that, unless otherwise specified, the terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, when a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum. Further, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Moreover, when multiple ranges are provided to describe features, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0076] It should also be noted that, in this document, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A low-iron-loss non-oriented silicon steel, characterized in that, The chemical composition of the low-iron-loss non-oriented silicon steel is controlled by mass percentage as follows: 0.0015%≤C≤0.0035%, 3.5%≤Si≤3.8%, 0.8%≤Al≤1.5%, 0.05%≤Mn≤0.15%, P≤0.015%, S≤0.0010%, N≤0.0015%, 0.04%≤Sb≤0.08%, 0.05%≤Cr≤0.15%, with the balance being Fe and unavoidable impurities.

2. The low-iron-loss non-oriented silicon steel according to claim 1, characterized in that, The chemical composition of the low-iron-loss non-oriented silicon steel is controlled by mass percentage as follows: 0.0020%≤C≤0.0025%, 3.57%≤Si≤3.72%, 1.23%≤Al≤1.42%, 0.10%≤Mn≤0.13%, 0.010%≤P≤0.013%, 0.0006%≤S≤0.001%, 0.0010%≤N≤0.0013%, 0.06%≤Sb≤0.07%, 0.07%≤Cr≤0.12%, with the balance being Fe and unavoidable impurities.

3. The low-iron-loss non-oriented silicon steel according to claim 1, characterized in that, When the finished product thickness is 0.35–0.65 mm, the iron loss P 1.5 / 50 It ranges from 2.03 to 2.65 W / kg.

4. The low-iron-loss non-oriented silicon steel according to claim 1, characterized in that, When the finished product thickness is 0.35–0.65 mm, the magnetic induction B 5000 It ranges from 1.65 to 1.67 T.

5. A method for preparing low-iron-loss non-oriented silicon steel according to claim 1, characterized in that, Includes the following steps: (1) Slab smelting: Smelting raw materials to obtain slabs; (2) Heating and hot rolling: The billet is heated to 1030℃~1080℃, held for 3~4 hours and then hot rolled to form a hot rolled plate with a thickness of 2.1mm~2.45mm; (3) Hot-rolled plate pretreatment: The hot-rolled plate is subjected to normalizing treatment, pickling treatment and edge trimming treatment in sequence. During the edge trimming process, the strip steel is sheared into waste edge area and mother body area by the upper and lower shear blades. The side of the mother body area that abuts the upper shear blade is the shearing area. The corresponding fracture surfaces of the mother body area and the waste edge area are the fracture areas. By adjusting the side gap and overlap between the upper and lower shear blades, the ratio of the shearing area to the fracture area is controlled to be 1: (4~8). (4) Warm cold rolling: The steel coil after edge trimming is immediately fed into the 20-roll mill while still warm. It is rolled to the target finished thickness using a multi-pass, one-time cold rolling process. Before rolling, the edges of the strip are heated by open flame at the mill entrance to keep the temperature of the strip edges at 60℃~100℃ when they enter the mill. During the rolling process, a rolling emulsion with a temperature of 70℃~75℃ and a flow rate of 1000L / min~1500L / min is used for lubrication and cooling. (5) Two-stage protective annealing: The cold-rolled strip is continuously annealed in a mixed protective atmosphere of hydrogen and nitrogen. The volume fraction of hydrogen in the mixed protective atmosphere is 8%~12%, and the remainder is nitrogen. The annealing adopts a two-stage process. The first stage annealing temperature is 1040℃~1080℃, the second stage annealing temperature is 980℃~1020℃, and the strip annealing running speed is 90m / min~120m / min. (6) Gradient cooling: After annealing, the strip steel is first cooled to 700°C at a cooling rate of no more than 10°C / s, then cooled to 400°C at a cooling rate of no more than 15°C / s, and then cooled to below 60°C. (7) Coating and drying: Apply an insulating coating to the surface of the cooled strip steel and dry it to obtain the finished non-oriented silicon steel product.

6. The method for preparing low-iron-loss non-oriented silicon steel according to claim 5, characterized in that, In step (3), the ratio of the shearing zone to the fracture zone of the strip cutting surface is controlled to be 1:(4~6).

7. The method for preparing low-iron-loss non-oriented silicon steel according to claim 5, characterized in that, In step (4), the temperature of the strip edge when it enters the rolling mill is maintained at 80℃~95℃.

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