Non-oriented electrical steel and method for producing the same

Abstract

This invention discloses a non-oriented electrical steel and its production method. The chemical composition of the non-oriented electrical steel, by mass percentage, includes: C ≤0.002%, Si 1.2%~1.6%, Al 0.3%~0.8%, Mn 0.4%~0.6%, Sn 0.03%~0.05%, Sb 0.08%~0.12%, with the balance being Fe and unavoidable impurities. This non-oriented electrical steel is produced through smelting, hot rolling, cold rolling, and continuous annealing. Through synergistic optimization of composition and process, this invention yields an electrical steel that not only achieves a magnetic induction strength of B... 50 ≥1.70T, iron loss P 1.5 / 50 With a purity of ≤2.7 W / kg, and without the need for normalization processes or special production equipment, it has significant industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of non-oriented electrical steel manufacturing technology, specifically relating to a non-oriented electrical steel and its production method. Background Technology

[0002] Non-oriented electrical steel is a core magnetic material in home appliances, process motors, and new energy fields. Its magnetic properties and production costs directly determine the energy efficiency and market competitiveness of end-use equipment. Although existing low-silicon electrical steel (Si≤1.5%) has excellent processing performance, it lacks effective microstructure control methods, resulting in iron losses generally exceeding 3.5W / kg and magnetic induction intensity below 1.65T. Consequently, it cannot simultaneously meet the comprehensive requirements of low cost, high magnetic properties, and ease of processing.

[0003] Since silicon is a non-magnetic element, it can increase the resistivity of ferrite and suppress eddy current losses. In existing technologies, increasing the silicon content is often used to reduce iron losses. However, excessively high silicon content (≥2.0%) will lead to a significant increase in the hardness and strength of electrical steel, making it prone to edge cracks and strip breaks during cold rolling. This requires increasing the number of rolling passes or using special rolling mills, increasing processing costs by more than 15%.

[0004] In addition, the existing production process for non-oriented electrical steel requires a separate normalizing process (e.g., 850℃×2h) to eliminate work hardening of hot-rolled plates and refine grains, which not only increases energy consumption (about 120kWh / ton) but also extends the production cycle. Summary of the Invention

[0005] The purpose of this invention is to provide a non-oriented electrical steel and its production method, which achieves a balance between magnetic properties, processing performance and cost through synergistic optimization of composition and simplification of process.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A non-oriented electrical steel, wherein the chemical composition of the non-oriented electrical steel, by mass percentage, comprises: C ≤0.002%, Si 1.2%~1.6%, Als 0.3%~0.8%, Mn 0.4%~0.6%, Sn 0.03%~0.05%, Sb 0.08%~0.12%, with the balance being Fe and unavoidable impurities.

[0007] As a further aspect of the present invention, the ratio of the mass percentage of Als to the mass percentage of Si is 0.2 to 0.4, preferably 0.25 to 0.3.

[0008] In a preferred embodiment of the present invention, Als and Si can synergistically improve resistivity, and the deoxidizing effect of aluminum can purify the matrix. By controlling the ratio of the mass percentage of Als to the mass percentage of Si, the decrease in magnetic induction caused by excessive aluminum content can be avoided.

[0009] As a further aspect of the present invention, the ratio of the mass percentage of Mn element to the mass percentage of Si element is 0.3 to 0.5, preferably 0.4 to 0.5.

[0010] In a preferred embodiment of the invention, Mn can improve hot working performance and suppress the formation of iron oxide scale during hot rolling. Eddy current losses can be further reduced by optimizing the ratio of Mn mass percentage to Si mass percentage.

[0011] As a further aspect of the present invention, the mass percentage of the C element is ≤0.0015%, preferably 0.001%~0.0015%.

[0012] In a preferred embodiment of the present invention, the precipitation of cementite during annealing can be avoided by strictly controlling the carbon content, thereby reducing hysteresis loss.

[0013] As a further aspect of the present invention, the mass percentage of the Si element is 1.3% to 1.5%.

[0014] In a preferred embodiment of the present invention, the resistivity and processing performance are balanced by a low-silicon design, which ensures that eddy current losses do not increase significantly and reduces the hardness of electrical steel to avoid cold rolling cracking.

[0015] As a further aspect of the present invention, the mass percentage of Als is 0.4% to 0.6%.

[0016] As a further aspect of the present invention, the mass percentage of the Sn element is 0.04% to 0.05%.

[0017] As a further aspect of the present invention, the mass percentage of the Sb element is 0.09% to 0.11%.

[0018] In the preferred embodiment of the present invention, by adding composite microalloys, Sn and Sb composite microalloys synergistically segregate at the grain boundaries, inhibiting abnormal grain growth, purifying matrix impurities, and optimizing recrystallization texture, the effect is far superior to adding a single microalloy.

[0019] As a further aspect of the present invention, the magnetic induction intensity B of the non-oriented electrical steel is... 50 It is 1.70~1.75T.

[0020] As a further aspect of the present invention, the iron loss of the non-oriented electrical steel is P. 1.5 / 50 It is 2.5~2.7W / kg.

[0021] As a further aspect of the present invention, the yield strength of the non-oriented electrical steel is 260~280MPa.

[0022] As a further aspect of the present invention, the tensile strength of the non-oriented electrical steel is 390~410MPa.

[0023] A method for producing non-oriented electrical steel as described in any of the above, comprising a smelting process, a hot rolling process, a cold rolling process, and a continuous annealing process.

[0024] As a further aspect of the present invention, the smelting process includes: using converter smelting and RH vacuum refining processes to control the oxygen content of molten steel to ≤30ppm, and continuously casting to obtain a billet with a thickness of 210~230mm.

[0025] As a further aspect of the present invention, the smelting process includes controlling the oxygen content in the molten steel to be 20-35 ppm.

[0026] As a further aspect of the present invention, the hot rolling process includes: heating the billet to 1180℃~1220℃, holding it at that temperature for 2~3 hours, and then hot rolling it.

[0027] As a further aspect of the present invention, the heating temperature of the billet is 1200℃~1210℃.

[0028] As a further aspect of the present invention, the holding time of the billet is 2.4~2.5h.

[0029] As a further aspect of the present invention, the hot rolling process includes: a hot rolling final temperature of 880℃~920℃, preferably 890℃~910℃.

[0030] As a further aspect of the present invention, the hot rolling process includes: a coiling temperature of 650°C to 700°C, preferably 670°C to 690°C.

[0031] As a further embodiment of the present invention, the hot rolling process includes: heating the billet to 1180℃~1220℃, holding it at that temperature for 2~3 hours, and then rough rolling and finish rolling to a thickness of 1.5~2.5mm, with a hot rolling final temperature of 880℃~920℃ and a coiling temperature of 650℃~700℃ to obtain a hot-rolled plate.

[0032] As a further aspect of the present invention, the cold rolling process includes a total reduction rate of 77% to 84%.

[0033] As a further aspect of the present invention, the cold rolling process includes: performing single-pass or multi-pass cold rolling on the hot-rolled plate, with a total reduction rate of 75% to 85%, to obtain a cold-rolled plate with a thickness of 0.3 to 0.5 mm.

[0034] As a further aspect of the present invention, the continuous annealing process includes: holding at 900℃~920℃ for 3~4 minutes.

[0035] As a further aspect of the present invention, the continuous annealing process includes a cooling rate of 20°C / s to 25°C / s.

[0036] As a further aspect of the present invention, the continuous annealing process includes: placing the cold-rolled plate in a continuous annealing furnace, heating it to 900℃~920℃, holding it at that temperature for 3~4 minutes, and cooling it at a cooling rate of 20℃ / s~25℃ / s.

[0037] As a further aspect of the present invention, the production method does not include a normalizing process.

[0038] In a preferred embodiment of the present invention, by optimizing the hot rolling final temperature (e.g., 880°C~920°C) and the coiling temperature (e.g., 650°C~700°C), the hot-rolled plate can directly obtain uniform initial grains, and can meet the cold rolling requirements without additional normalization treatment.

[0039] In a preferred embodiment of the invention, a high cold rolling reduction rate (e.g., 75%~85%) can accumulate sufficient processing energy to provide power for complete recrystallization during continuous annealing and promote the formation of favorable texture.

[0040] In a preferred embodiment of the present invention, the continuous annealing parameters are optimized as follows: a heating temperature of 900℃~920℃ ensures sufficient grain growth (e.g., 80~100μm), and rapid cooling of 20℃ / s~25℃ / s avoids impurity precipitation and ensures stable magnetic properties.

[0041] This invention addresses the problems of high silicon content in existing high-grade non-oriented electrical steels, which leads to high processing difficulty and cost, limited improvement in magnetic properties due to single microalloying, and high energy consumption in existing non-oriented electrical steel production processes involving normalizing steps. It provides a non-oriented electrical steel and its production method. Through compositional design using low-silicon, medium-aluminum, Sn-Sb composite microalloying, the normalizing step is eliminated, and the process optimization ensures high magnetic properties. 50 ≥1.70T, P 1.5 / 50 Under the premise of ≤2.7W / kg, production costs are reduced by more than 10%, while ensuring that processing performance meets the requirements of industrial production.

[0042] The present invention has at least the following technical effects: By synergistically controlling grain size and texture through Sn-Sb composite microalloying and incorporating a low-silicon (1.2%~1.6%) design, the weak strengthening effect of Sn-Sb composite microalloying is balanced, resulting in a higher magnetic flux density (B) of the finished non-oriented electrical steel. 50 ≥1.70T, iron loss P 1.5 / 50With a silicon content of ≤2.7W / kg, it surpasses existing low-silicon electrical steels and reaches the level of traditional high-grade electrical steels. Furthermore, the optimized composition design ensures that the steel has no risk of cracking when cold-rolled with a reduction rate of 75%~85%, meeting the requirements for subsequent processing such as punching and stacking.

[0043] Furthermore, the production method provided by this invention does not require any new production equipment and is compatible with existing industrial production lines; the low-silicon design reduces the amount of high-cost ferrosilicon alloy used, eliminates the normalizing process, and reduces energy consumption per ton of steel by 120 kWh, resulting in a total cost reduction of more than 10%. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments.

[0045] Therefore, the following detailed description of embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0046] In the following examples / comparative examples, the amount of lime added during the converter smelting process was controlled to adjust the slag basicity to 3.3~3.7.

[0047] Example 1 A non-oriented electrical steel has the following chemical composition by mass percentage: C=0.0012%, Si=1.2%, Als=0.3%, Mn=0.4%, Sn=0.03%, Sb=0.08%, with the balance being Fe and unavoidable impurities.

[0048] Its production method includes the following steps: Smelting: According to the above chemical composition, the steel is smelted in a converter, RH vacuum refining time is 30min, the oxygen content of the molten steel is controlled at 28ppm, and a billet with a thickness of 220mm is obtained by continuous casting. Hot rolling: The billet is fed into a heating furnace, heated to 1180℃, held for 2 hours, and then rough rolled to a thickness of 30mm in 5 passes, and then fine rolled to a thickness of 2.0mm in 6 passes. The final hot rolling temperature is 880℃, and the coiling temperature is 650℃ to obtain a hot-rolled plate. Cold rolling: The hot-rolled plate is cold-rolled in 4 passes with a total reduction of 75% to obtain a cold-rolled plate with a thickness of 0.5 mm; Continuous annealing: The cold-rolled sheet is fed into a continuous annealing furnace, a protective atmosphere of N2:H2=3:1 is introduced, heated to 900℃, held for 3 minutes, and cooled to room temperature (25~30℃) at a cooling rate of 20℃ / s to obtain the finished non-oriented electrical steel.

[0049] The magnetic flux density of this non-oriented electrical steel is B50 = 1.70T, and the iron loss is P. 15 / 50 =2.65W / kg, yield strength 260MPa, tensile strength 390MPa.

[0050] Example 2 A non-oriented electrical steel has the following chemical composition by mass percentage: C=0.0010%, Si=1.4%, Als=0.5%, Mn=0.5%, Sn=0.04%, Sb=0.10%, with the balance being Fe and unavoidable impurities.

[0051] Its production method includes the following steps: Smelting: After batching, the steel is smelted in a converter, RH vacuum refining time is 35min, oxygen content of molten steel is 25ppm, and 220mm thick billet is obtained by continuous casting. Hot rolling: The billet is heated to 1200℃, held for 2.5h, rough rolled to 32mm, finish rolled to 2.0mm, hot rolling final temperature 900℃, coiling temperature 680℃, to obtain hot rolled plate; Cold rolling: The hot-rolled plate is cold-rolled in 5 passes with a total reduction of 83% to obtain a cold-rolled plate with a thickness of 0.35 mm; Continuous annealing: The cold-rolled sheet is fed into a continuous annealing furnace, a protective atmosphere of N2:H2=3:1 is introduced, and it is heated to 910℃, held for 3.5 min, and cooled to room temperature (25~30℃) at a cooling rate of 23℃ / s to obtain the finished non-oriented electrical steel.

[0052] The magnetic induction intensity B of the non-oriented electrical steel 50 =1.71T, iron loss P 15 / 50 =2.58W / kg, yield strength 270MPa, tensile strength 400MPa.

[0053] Example 3 A non-oriented electrical steel has the following chemical composition by mass percentage: C=0.0015%, Si=1.6%, Als=0.8%, Mn=0.6%, Sn=0.05%, Sb=0.12%, with the balance being Fe and unavoidable impurities.

[0054] Its production method includes the following steps: Smelting: After batching, the steel is smelted in a converter, RH vacuum refined for 40 minutes, the oxygen content of the molten steel is 30ppm, and a 220mm thick billet is obtained by continuous casting. Hot rolling: The billet is heated to 1220℃ and held for 3 hours. The final hot rolling temperature is 920℃, the coiling temperature is 700℃, and the thickness of the hot-rolled plate is 2.0mm. Cold rolling: Total reduction rate 80%, cold rolled to 0.4mm in 5 passes; Continuous annealing: under a protective atmosphere of N2:H2=3:1, heat to 920℃, hold for 4 min, cool at a rate of 25℃ / s, and cool to room temperature (25~30℃) to obtain the finished non-oriented electrical steel.

[0055] The magnetic induction intensity B of the non-oriented electrical steel 50 =1.71T, iron loss P 15 / 50 =2.62W / kg, yield strength 280MPa, tensile strength 410MPa.

[0056] In this embodiment of the invention, by adding composite microalloying components Sn and Sb, the Sn and Sb composite segregation grain boundaries can refine the grain size to 80-100 μm, reducing the resistance to magnetic domain wall movement and lowering iron loss. The low-silicon, medium-aluminum system reduces lattice distortion, and combined with the optimization of texture by the composite microalloying, it can improve magnetic induction. The elimination of the normalization process and silicon reduction design directly reduces energy consumption and alloy costs.

[0057] Comparative Example 1 A non-oriented electrical steel has the following chemical composition by mass percentage: C=0.0015%, Si=2.3%, Als=0.7%, Mn=0.5%, with the balance being Fe and unavoidable impurities.

[0058] Production method: Smelting: After batching, the steel is smelted in a converter, RH vacuum refined for 40 minutes, the oxygen content of the molten steel is 30ppm, and a 220mm thick billet is obtained by continuous casting. Hot rolling: The billet is heated to 1200℃ and held for 2.5h. The final hot rolling temperature is 900℃, the coiling temperature is 680℃, and the thickness of the hot-rolled plate is 2.0mm. Normalizing: Heating hot-rolled plate at 850℃ for 2 hours; Cold rolling: Total reduction rate 83%, cold rolled to 0.35mm in 5 passes; Continuous annealing: under a protective atmosphere of N2:H2=3:1, heat to 880℃, hold for 5 minutes, cool at a rate of 25℃ / s, and cool to room temperature (25~30℃) to obtain the finished non-oriented electrical steel.

[0059] B of the non-oriented electrical steel 50 =1.70T, P 15 / 50 =3.3W / kg, yield strength 310MPa, tensile strength 420MPa.

[0060] In this comparative example, the production cost of non-oriented electrical steel is 12.5% ​​higher than that of Example 1, 13.2% higher than that of Example 2, and 11.8% higher than that of Example 3.

[0061] In some embodiments of the present invention, the product performance can be stabilized within the aforementioned expected range by fine-tuning parameters such as annealing temperature and microalloy content. All production steps of the present invention are based on existing industrial equipment, require no special process conditions, and are fully repeatable.

[0062] This invention addresses the problems of high silicon content in existing high-grade non-oriented electrical steel, which leads to difficulties in cold rolling and high production costs, and the limited improvement in magnetic properties by a single microalloying element. It employs a low-silicon, medium-aluminum, Sn-Sb composite microalloying design. The chemical composition, by mass percentage, is: C ≤ 0.002%, Si = 1.2%~1.6%, Als = 0.3%~0.8%, Mn = 0.4%~0.6%, Sn = 0.03%~0.05%, Sb = 0.08%. The content is 0.12%, with the balance being Fe and unavoidable impurities, and it satisfies (Als) / (Si)=0.2~0.3 and (Mn) / (Si)=0.3~0.5. The production method eliminates the normalizing process, and achieves a balance between the magnetic properties and cost of non-oriented electrical steel by controlling the billet heating at 1180℃~1220℃, the hot rolling final temperature at 880℃~920℃ and 75%~80%, the cold rolling reduction rate, and the continuous annealing at 900℃~920℃.

[0063] The non-oriented electrical steel product obtained by this invention has a magnetic flux density B50≥1.70T and an iron loss P1.5 / 50≤2.7W / kg. Compared with traditional high-grade products with Si=2.0%~2.5% and containing normalization process, the production cost is reduced by more than 10%, the process is simplified and no special production equipment is required. It is suitable for home appliances, industrial motors and other fields and has significant industrial application value.

[0064] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A non-oriented electrical steel, characterized in that, The chemical composition of the non-oriented electrical steel, by mass percentage, includes: C ≤ 0.002%, Si 1.2%~1.6%, Als 0.3%~0.8%, Mn 0.4%~0.6%, Sn 0.03%~0.05%, Sb 0.08%~0.12%, with the balance being Fe and unavoidable impurities.

2. The non-oriented electrical steel according to claim 1, characterized in that, The ratio of the mass percentage of Als to the mass percentage of Si is 0.2 to 0.

4. And / or, the ratio of the mass percentage of the Mn element to the mass percentage of the Si element is 0.3 to 0.

5.

3. The non-oriented electrical steel according to claim 2, characterized in that, The ratio of the mass percentage of Al to the mass percentage of Si is 0.25 to 0.

3. And / or, the ratio of the mass percentage of the Mn element to the mass percentage of the Si element is 0.4 to 0.

5.

4. The non-oriented electrical steel according to claim 1, characterized in that, The mass percentage of the C element is ≤0.0015%; And / or, the mass percentage of the C element is 0.001% to 0.0015%; And / or, the mass percentage of the Si element is 1.3% to 1.5%; And / or, the mass percentage of the Als element is 0.4% to 0.6%; And / or, the mass percentage of the Sn element is 0.04% to 0.05%; And / or, the mass percentage of the Sb element is 0.09% to 0.11%.

5. The non-oriented electrical steel according to claim 1, characterized in that, The magnetic induction intensity B of the non-oriented electrical steel 50 The value is 1.70~1.75T; And / or, the iron loss of the non-oriented electrical steel is P 1.5 / 50 It is 2.5~2.7 W / kg; And / or, the yield strength of the non-oriented electrical steel is 260~280MPa; And / or, the tensile strength of the non-oriented electrical steel is 390~410MPa.

6. A method for producing non-oriented electrical steel as described in any one of claims 1 to 5, characterized in that, It includes the smelting process, hot rolling process, cold rolling process, and continuous annealing process.

7. The production method according to claim 6, characterized in that, The smelting process includes: The oxygen content in the molten steel should be controlled at 20-35 ppm.

8. The production method according to claim 6, characterized in that, The hot rolling process includes: The billet is heated to 1180℃~1220℃ and held for 2~3 hours before hot rolling. And / or, the hot rolling final temperature is 880℃~920℃; And / or, the winding temperature is 650℃~700℃.

9. The production method according to claim 6, characterized in that, The cold rolling process includes: The total reduction rate is 77%~84%.

10. The production method according to claim 6, characterized in that, The continuous annealing process includes: Keep warm at 900℃~920℃ for 3~4 minutes; And / or, the cooling rate is 20℃ / s to 25℃ / s.