Non-oriented electrical steel for large electric machines and method for producing the same

Abstract

The application provides a non-oriented electrical steel for large motors and a production method thereof, and the composition comprises the following components: [C] is less than or equal to 0.0020%, [S] is less than or equal to 0.0025%, [N] is less than or equal to 0.0025%, [Sn] is 0.040-0.070%, [P] is less than or equal to 0.0035%, [Mn]+[Si]+[Als] is equal to 4.0-5.0%, and the rest is Fe and inevitable impurities. Compared with the prior art, the application adjusts the alloying amount of Mn, Si and Als, controls the ratio of alloy [AlS] / [Si] to be 1 / 8-1 / 6 and the ratio of [Mn] / [Si] to be 1 / 5-1 / 3, and adds Sn elements, so that the magnetic induction of the material itself is improved, and the production process is matched to improve the magnetic performance of the finished product and improve the mechanical properties of the material.

Description

Technical Field

[0001] This invention belongs to the field of high-grade cold-rolled non-oriented electrical steel production, specifically relating to a non-oriented electrical steel for large motors and its production method. Background Technology

[0002] The non-oriented electrical steel for large motors is produced by segmented stamping, i.e. fan-shaped stamping. The size of the stamped pieces varies between different units. Due to the influence of stamping process and production efficiency, the iron core stacking for large motors adopts a thickness of 0.490-0.510mm.

[0003] Non-oriented electrical steel for large motors requires minimal wear on silicon steel sheets to improve unit operating efficiency. Cold-rolled non-oriented electrical steel strips for large motors are laminated using high-speed punching machines, resulting in a large number of laminations with a height of several meters or even tens of meters, leading to high strength requirements for the material itself.

[0004] Patent CN116121653A, published on May 16, 2023, discloses a low-noise non-oriented silicon steel, its production method, and its applications. The composition is: C≤0.0025%, 2.15%≤Si≤2.90%, 0.25%≤Mn≤0.65%, P≤0.25%, 0.3%≤Als≤0.6%, S≤0.0030%, N≤0.0030%, Ti≤0.0030%, with the remainder being Fe and unavoidable impurities. The alloy composition design clearly defines the optimal composition system for obtaining lower-noise non-oriented silicon steel. This method requires controlling the thickness of the insulating coating to control the surface tension of the silicon steel, thereby further controlling magnetostriction and reducing noise. The manufactured low-noise arc suppression coil has an operating noise ≤55dB. While it primarily addresses the noise problem, it does not disclose how to solve the problems related to the magnetic and mechanical properties of non-oriented electrical steel used in large motors. Summary of the Invention

[0005] This invention provides a non-oriented electrical steel for large motors and its production method. By designing the composition, this invention optimizes the ratio of [Als] / [Si] and [Mn] / [Si], and adds Sn element to improve the magnetic induction of the material itself. Combined with the production process of this application, it improves the magnetic properties of the finished product and enhances the mechanical properties of the material.

[0006] The specific technical solution of this invention is as follows:

[0007] A non-oriented electrical steel for large motors comprises the following components by weight percentage:

[0008] [C]≤0.0020%, [S]≤0.0025%, [N]≤0.0025%, [Sn]0.040-0.070%, [P]≤0.0035%, [Mn]+[Si]+[Als]=4.0-5.0%, the remainder being Fe and unavoidable impurities.

[0009] The composition of the non-oriented electrical steel for large motors also satisfies: [Als] / [Si] = 1 / 8-1 / 6;

[0010] The composition of the non-oriented electrical steel for large motors also satisfies: [Mn] / [Si]=1 / 5-1 / 3;

[0011] The thickness of the non-oriented electrical steel for large motors is 0.490-0.510 mm.

[0012] The non-oriented electrical steel for large motors has a grain size of 90-130μm after annealing.

[0013] The annealed non-oriented electrical steel for large motors contains {114} <481> The proportion of textures that are beneficial to electromagnetic properties is above 25%, while the proportion of {111} textures that are detrimental to electromagnetic properties is reduced to less than 10%.

[0014] The elongation A of the non-oriented electrical steel for large motors 50 ≥12%; Yield strength R eL ≥450MPa, tensile strength R m ≥560Mpa; Typical product 50XW310 iron loss P 1.5 / 50 ≤2.7W / kg, minimum magnetic polarization intensity B 5000 ≥1.65T; 50XW290 iron loss P 1.5 / 50 ≤2.6W / kg, minimum magnetic polarization intensity B 5000 ≥1.64T; 50XW270 iron loss P 1.5 / 50 ≤2.6W / kg, minimum magnetic polarization intensity B 5000 ≥1.64T.

[0015] The present invention provides a method for producing non-oriented electrical steel for large motors, comprising the following process steps: converter smelting, RH vacuum refining, continuous casting, slab heating, hot rolling, coiling, normalizing, shot blasting, pickling, bell-type annealing, cold rolling, continuous annealing, cooling, coating, and recoiling.

[0016] In the production process of this invention, the residual element content of high-grade cold-rolled non-oriented electrical steel is reduced by using a clean steel platform for high-grade cold-rolled non-oriented electrical steel. By controlling the sulfur content in the molten iron and adding high-quality scrap steel in the converter, the inclusions in the billet are reduced, thereby improving the cleanliness of the molten steel.

[0017] The converter smelting process controls the residual element S in the molten iron to within 0.010%, and after slag removal, the purity of the molten iron is increased to >90%. At the same time, the converter adopts a double slag production method to control the P content ratio to within 0.020%.

[0018] The RH vacuum smelting process involves adding alloys in the following order during RH vacuum refining: aluminum, high-purity ferrosilicon, and manganese. Based on the measured weight of the molten steel, alloys are added in proportions of 80%-85% for aluminum alloy, 94%-97% for high-purity ferrosilicon, and 97%-98% for manganese. This ensures that the [Mn]+[Si]+[Als] content in the molten steel is within the controlled range of 4.0-5.0%, [Als] / [Si] = 1 / 8-1 / 6, and [Mn] / [Si] = 1 / 5-1 / 3, while the Sn content is within the range of 0.040-0.070%. Simultaneously, a desulfurizing agent of Ca and Si alloys is added to the RH vacuum furnace to control the S content within the range of ≤0.0025%. Additionally, a top slag modifier is added to improve the activity of inclusions in the molten steel and control inclusions.

[0019] The continuous casting process specifically involves casting a 230mm thick billet with the following chemical elements: [C]≤0.0020%, [S]≤0.0025%, [N]≤0.0025%, [P]≤0.0035%, [Sn]0.040-0.070%, ensuring [Mn]+[Si]+[Als] at 4.0-5.0%, controlling [Als] / [Si] = 1 / 8-1 / 6 and [Mn] / [Si] = 1 / 5-1 / 3, and removing the remaining Fe and unavoidable impurities.

[0020] The slab is heated in a heating furnace using a four-stage heating method. The furnace gas temperature is controlled at 1080-1200℃, the heating time in the furnace is controlled at 180-260 minutes, and the soaking time is not less than 30 minutes.

[0021] In the hot rolling process, the slab is heated in a furnace, then first roughed and then finished.

[0022] In the rough rolling process, R1 is rolled in one pass and R2 is rolled in three passes. The thickness of the intermediate strip after rolling is 40-50 mm. The rolling temperature after rough rolling is controlled at 940-1000℃.

[0023] The finishing rolling is carried out by a finishing mill unit of a 7-mill, with the ratio of intermediate billet thickness to finished product thickness after hot rolling controlled at a reduction of 13 to 20. The temperature after finishing rolling reaches 840-890℃; the rolled thickness is 2.5-3.0mm, the controlled crown is required to be 20-40μm, and the controlled wedge shape is required to be within ±15μm.

[0024] After the coiling and finishing rolling, the coiling temperature is controlled by laminar flow cooling, with the coiling temperature being 550-620℃.

[0025] This invention first employs a double roughing mill for repeated rolling, with R1 rolled in one pass and R2 rolled in three passes. The thickness of the intermediate strip after rolling is 40-50 mm. The rolling temperature after roughing is controlled at 940-1000℃. The strip is then rolled through a seven-pass mill, and the thickness of the finished product after rolling is 2.5-3.0 mm. The intermediate billet is rolled in the finishing mill of mill 7. By reducing the ratio of intermediate billet thickness to finished product thickness after hot rolling, the reduction is controlled at 13-20, thereby changing the rolling load of each stand in the finishing mill and reducing the current during rolling. Simultaneously, due to the thicker rolled thickness, the control accuracy of the equipment thickness in the hot rolling mill is improved, ultimately stabilizing the centerline of the rolled strip. Calculations show that using a finished product thickness of 2.5-3.0 mm can reduce the current of each mill in the finishing mill: the current of finishing mills F1-F4 is reduced by 1-3%, and the current of finishing mills F5-F7 is reduced by 1-2%. The temperature after finishing rolling reaches 840-890℃, and then laminar flow cooling is used to control the coiling temperature, with a coiling temperature of 550-620℃.

[0026] The present invention controls the heating temperature, mainly to prevent the second phase from solidifying in the steel billet in the heating furnace, to prevent the precipitation of the second phase during the subsequent hot rolling process, to prevent the recrystallization of the grains, and to prevent the deterioration of electromagnetic properties.

[0027] The normalizing process involves controlling the temperature at 870-930℃ and holding it at that temperature for 30-50 seconds. The hot coil is heated in a normalizing furnace at 870-930℃, with a speed of 40-50 m / min and a holding time of 30-50 seconds. The furnace gas temperature is controlled according to the composition parameters to induce recrystallization in the hot coil, resulting in a grain size of 90-120 μm with uniform grain size and microstructure. The protective gas is N2. After normalizing {114} <481> The proportion of texture has been increased to over 25%.

[0028] The shot blasting process involves the steel coil undergoing a process where, after heating in the normalizing unit, the iron oxide scale on the surface of the coil has changed, making it difficult to directly clean with hydrochloric acid. Therefore, shot blasting is necessary. The shot used is cast iron shot with a particle size of 0.4-0.8 mm to break up the iron oxide scale on the surface of the coil, facilitating subsequent hydrochloric acid pickling. By controlling the blasting speed of each shot blasting unit at 60-100 m / s and the maximum blasting rate of each blast head at 1000 kg / min-1500 kg / min, two to three shot blasting units can be operated simultaneously to break up the iron oxide scale on the surface of the hot-rolled coil after normalizing.

[0029] The pickling process employs a four-stage acid tank, with a hydrochloric acid solution concentration of 130-280 g / L, an acid solution temperature of 70-85℃, and a pickling time of 90-150 seconds.

[0030] After pickling, the furnace is first cooled to ≤560℃ by a water jacket, and then cooled to ≤80℃ by water mist before being air-cooled.

[0031] The bell-type annealing process involves heating the steel coil to 150-200℃ and holding it at that temperature for 4-6 hours. After exiting the furnace, the coil temperature is controlled at 150-200℃, and the protective atmosphere is 99.99% H2 by volume. Raising the coil temperature to 150-200℃ avoids the brittle-ductile temperature point of high-grade silicon steel, which is beneficial for increasing the edge temperature of high-grade non-oriented electrical steel. This also helps control small cracks at the edges of the rolled strip, reducing strip breakage caused by cracks.

[0032] The cold rolling process employs a 20-roll mill with work rolls of 60-80mm diameter, using a four-pass rolling method. Each pass utilizes a high reduction rate, with the reduction rate controlled above 30% in the first three passes and between 20-25% in the fourth pass, resulting in a total reduction of 80-84%. The reduced reduction rate in the final pass helps improve the sheet shape of the rolled electrical steel. The finished product thickness is 0.490-0.510mm. Using a 20-roll mill facilitates rolling stability; the small-diameter 20-roll mill allows for control of the rolled thickness accuracy within ±4μm, while also controlling the transverse thickness difference within 7μm. Increasing the temperature of the steel coil and using a small-diameter 20-roll mill, along with a small reduction rate in the final rolling pass, facilitates the rolling of high-grade non-oriented electrical steel. This reduces strip breakage during rolling, helps control the strip shape after rolling, and makes subsequent lamination easier, resulting in uniform lamination height.

[0033] The continuous annealing process employs a continuous annealing technique, controlling the annealing temperature in the RTF section at 800-1000℃, with the strip heating rate controlled at 15℃ / s or higher, and the furnace heating time at 70-100s. The protective atmosphere contains 5%-20% H2 and 80%-95% N2 by volume, with a dew point of (-20℃)-(+20℃). The SF section annealing temperature is controlled at 980-1030℃, with the protective atmosphere containing 5%-20% H2 and 80%-95% N2 by volume, and a dew point of (-30℃)-(+30℃). The furnace holding time is 30-50s, with N2 and H2 protection during furnace heating. Decarburization is performed using wet hydrogen in the front section of the furnace. Rapid heating in the RTF section ensures sufficient grain growth in the finished product, reduces the precipitation of the second phase, and improves {114} <481> The volume fraction of favorable texture is above 25%, while the {111} texture, which is detrimental to electromagnetic performance, is reduced to less than 10%. At the same time, the grain size of the product is ensured to be 90-130μm, which helps to reduce iron loss and improve the electromagnetic performance of the finished product.

[0034] The cooling process after annealing employs a staged cooling method, using in-furnace N2 protection. The strip is cooled in the tube cooling section (where nitrogen flows through a U-shaped pipe in the furnace to remove heat), with the cooling rate controlled at ≥35℃ / s and the strip exiting the tube cooling section at 500-550℃. In the spray pipe cooling section (where nitrogen is directly sprayed onto the strip for cooling), the cooling rate is controlled at ≤15℃ / s and the strip exiting the spray pipe at 150-190℃. In the final cooling section, the cooling rate is controlled at ≤18℃ / s, and the strip is cooled to room temperature.

[0035] Compared to traditional stacked motors, the non-oriented electrical steel used in large motors adopts a composition of [Mn]+[Si]+[Als]=4.0-5.0%, [Als] / [Si]=1 / 8-1 / 6, and [Mn] / [Si]=1 / 5-1 / 3. This control is primarily aimed at increasing the Mn and Si content in the alloy, which helps improve the material's strength. While increasing the Mn and Si content, it also ensures the material's low iron loss and high magnetic induction electromagnetic properties, reducing no-load current loss and preventing breakage during use.

[0036] Because the material itself has a high Si content, it is not conducive to cold rolling. Strip breakage often occurs during the rolling process, which is not conducive to the smooth progress of production. The steel coil needs to be heated to 150-200℃ in a bell-type annealing furnace to change the brittle-ductile point of the material itself.

[0037] Hot rolling with a thickness of 2.5-3.0 mm facilitates the control of plate shape and temperature during hot rolling, making it easier to control the plate shape, crown and wedge shape of the hot roll, and helps to reduce the current consumed during rolling.

[0038] Finally, the strip steel is coated to form finished steel strips, which are then rewound, slit, and packaged.

[0039] Compared with existing technologies, controlling the total content of Si, Mn, and AlS within the range of 4.0-5.0% is mainly to facilitate subsequent cold rolling. Controlling the [Mn] / [Si] ratio to 1 / 5-1 / 3 and the [AlS] / [Si] ratio to 1 / 8-1 / 6 increases the content of Mn and Si in the steel while decreasing the AlS content. AlS does not significantly improve the strength of the steel as much as Mn and Si, ensuring that while improving the strength and toughness of the steel, it also increases the resistivity of the strip, reducing core loss. Sn has a pinning effect on grain boundaries, which is beneficial for improving the magnetic induction of electromagnetic properties. By rationally adjusting Si, Mn, and AlS, the goal of reducing core loss can be achieved while meeting the requirements of magnetic induction. Constructing a steel cleanliness platform improves the purity of the molten steel, reducing residual C, N, and S elements, which helps to reduce the aging reaction of the product. High-Si electrical steel exhibits a brittle-ductile transition temperature during cold rolling. Heating in a bell-type annealing furnace avoids this transition temperature, reducing strip breakage. The introduction of 99.99% H2 further improves the surface cleanliness of the steel coil. Controlling the Si, Mn, and Al alloy composition and residual elements from steelmaking achieves advantages such as low iron loss, high magnetic induction, and high strength. Attached Figure Description

[0040] Figure 1 The metallographic structure of the finished product in Example 1;

[0041] Figure 2 The metallographic structure of the finished product is shown in Comparative Example 1;

[0042] Figure 3 Example 3 shows the texture of the non-oriented electrical steel finished product for large motors. Detailed Implementation

[0043] Examples 1-10

[0044] A non-oriented electrical steel for large motors comprises the following mass percentage components as shown in the table. The balance not shown in Table 1 is Fe and unavoidable impurities.

[0045] Comparative Examples 1-10

[0046] A non-oriented electrical steel for large motors comprises the following mass percentage components as shown in the table. The balance not shown in Table 1 is Fe and unavoidable impurities.

[0047] Table 1. List of chemical composition values ​​(mass percentage) for each embodiment and comparative example of the present invention.

[0048]

[0049]

[0050] The specific production methods of the above embodiments and comparative examples of non-oriented electrical steel for large motors are as follows:

[0051] 1) By utilizing a clean steel platform for high-grade cold-rolled non-oriented electrical steel, the residual element content of high-grade cold-rolled non-oriented electrical steel is reduced. This is achieved by controlling sulfur (S) in the molten iron and adding high-quality scrap steel to the converter to reduce inclusions in the billet and improve the cleanliness of the molten steel. In converter smelting, the residual sulfur content in the molten iron is controlled to be below 0.010%, and after slag removal, the purity of the molten iron is increased to >90%. Simultaneously, the converter employs a double-slag method to control the phosphorus (P) content to be below 0.020%. RH vacuum refining involves adding aluminum, high-purity ferrosilicon, and manganese (tin) in a specific order, based on the weight of the molten steel. The aluminum alloy yield is 80%-85%, the high-purity ferrosilicon yield is 94-97%, and the manganese yield is 97%-98%. This ensures that the [Mn]+[Si]+[Als] content in the molten steel is within the controlled range of 4.0-5.0%, [Als] / [Si] = 1 / 8-1 / 6, and [Mn] / [Si] = 1 / 5-1 / 3, while the Sn content is within the range of 0.040-0.070%. Simultaneously, a desulfurizing agent containing Ca and Si alloys is added to the RH vacuum furnace to control the S content within the range of ≤0.0025%. A top slag modifier is also added to improve the activity of inclusions in the molten steel and control inclusions. This ensures both electromagnetic properties and improved steel strength. Si, Mn, and Al alloys have similar effects, significantly increasing resistivity. However, Al's impact on steel strength and hardness is less pronounced than that of Mn and Si. Adding Al to steel slightly increases brittleness, but its hardness increase is approximately one-third that of Si. Al can increase the {100} composition and decrease the {111} composition, correspondingly increasing magnetic induction. By controlling the settling time, inclusions can be floated to the surface, reducing the amount of inclusions in the steel molten metal. The slab is continuously cast to a thickness of 230 mm. Its chemical composition should meet the following requirements: [C]≤0.0020%, [S]≤0.0025%, [N]≤0.0025%, [Sn]0.040-0.070%, [P]≤0.0035%. Ensure that the [Mn]+[Si]+[Als] alloy content is 4.0-5.0%, control the ratio of [Als] / [Si]=1 / 8-1 / 6 and [Mn] / [Si]=1 / 5-1 / 3, and the remainder is Fe and unavoidable impurities.

[0052] 2) Hot rolling is performed, controlling the furnace gas temperature of the billet in the heating furnace to 1080-1200℃, the time in the heating furnace to be controlled to 180-260min, and the soaking time to be not less than 30min. This invention first uses a double roughing mill for reciprocating rolling, with R1 using one pass and R2 using three reciprocating passes. The thickness of the intermediate strip after rolling is 40-50mm. The rolling temperature after roughing is controlled to 940-1000℃. The strip is then rolled through a 7-pass mill, and the thickness of the finished product after rolling is 2.5-3.0mm. The crown is controlled to be 20-40μm, and the wedge shape is controlled to be within ±15μm. The intermediate billet is rolled in the finishing mill of mill 7. By reducing the ratio of intermediate billet thickness to finished product thickness after hot rolling, the reduction is controlled at 13-20, thereby changing the rolling load of each stand in the finishing mill and reducing the current during rolling. Simultaneously, due to the thicker rolled thickness, the control accuracy of the equipment thickness in the hot rolling mill is improved, ultimately stabilizing the centerline of the rolled strip. Calculations show that using a finished product thickness of 2.5-3.0 mm can reduce the current of each mill in the finishing mill: the current of finishing mills F1-F4 is reduced by 1-3%, and the current of finishing mills F5-F7 is reduced by 1-2%. The temperature after finishing rolling reaches 840-890℃, and then laminar flow cooling is used to control the coiling temperature, which is 550-620℃.

[0053] 3) Perform normalizing pickling at a heating temperature of 870-930℃. The hot coil speed in the normalizing furnace is 40-50 m / min, and the soaking time is 30-50 s. Control the furnace gas temperature according to the composition parameters to induce recrystallization in the hot coil, achieving a grain size of 90-120 μm with uniform grain size and microstructure. The protective gas is N2. After normalizing {114} <481> The texture ratio is increased to over 25%. After the steel coil is heated by the normalizing unit, the structure of the iron oxide scale on the surface of the steel coil has changed, making it difficult to clean directly by hydrochloric acid pickling. Therefore, shot blasting is necessary. The shot material is cast iron steel shot with a particle size of 0.4-0.8mm to break up the iron oxide scale on the surface of the steel coil, facilitating subsequent hydrochloric acid pickling. By controlling the blasting speed of each shot blasting unit at 60-100m / s and the maximum blasting rate of each blasting head at 1000kg / min-1500kg / min, two to three shot blasting units are operated simultaneously to break up the iron oxide scale on the surface of the hot-rolled coil after normalizing. A four-stage acid bath pickling is used, with a hydrochloric acid solution HCl concentration of 130-280g / l, an acid solution temperature of 70-85℃, and a pickling time of 90-150s. After pickling, the coil is first cooled to ≤560℃ by a water jacket, and then cooled to ≤80℃ by water mist before being air-cooled.

[0054] 4) Perform bell-type annealing furnace. Place the normalized steel coil into the bell-type furnace and heat it at 150-200℃. Hold it at that temperature for 4-6 hours. After exiting the furnace, control the temperature of the steel coil at 150-200℃. The protective atmosphere is H2 with a volume concentration of 99.99%.

[0055] 5) Control the temperature rolling of cold-rolled steel coils and strips. The coils are heated in a bell-type annealing furnace, maintaining the surface temperature at 100℃-150℃. A 20-roll mill is used to roll the coils to a thickness of 0.490-0.510mm. The work roll diameter is 60-80mm. Four passes are used, each with a high reduction rate. The reduction rate for the first three passes is controlled above 30%, and the reduction rate for the fourth pass is controlled between 20-25%, for a total reduction of 80-84%. Using a 20-roll mill facilitates rolling stability. A small-diameter 20-roll mill can control the thickness accuracy within ±4μm, and also control the transverse thickness difference after rolling, within 7μm.

[0056] 6) Continuous annealing is adopted, with the RTF section annealing temperature controlled at 800-1000℃, the strip heating rate controlled at above 15℃ / s, the furnace heating time at 70-100s, and the protective atmosphere volume percentage of 5%-20% H2 and 80%-95% N2, with a dew point of (-20℃)-(+20℃); the SF section annealing temperature is controlled at 980-1030℃, with the protective atmosphere volume percentage of 5%-20% H2 and 80%-95% N2, and a dew point of (-30℃)-(+30℃), the furnace holding time at 30-50s, and the furnace heating using N2 and H2 protection. Wet hydrogen is used for decarburization treatment in the front section of the furnace. Rapid heating in the RTF section ensures sufficient grain growth in the finished product, reduces the precipitation of the second phase, and improves {114} <481> The proportion of favorable textures is above 25%, while the proportion of {111} textures that are detrimental to electromagnetic performance is reduced to below 10%. At the same time, the grain size of the product is ensured to be 90-130μm, which is beneficial to reducing iron loss and improving the electromagnetic performance of the finished product.

[0057] 7) After annealing, segmented cooling is adopted. After annealing, the steel strip is cooled in a protective atmosphere of N2 in the furnace. The cooling rate of the steel strip in the tube cooling section is controlled at ≥35℃ / s, and the temperature of the steel strip exiting the tube cooling section is 500-550℃; the cooling rate of the steel strip in the spray pipe cooling section is controlled at ≤15℃ / s, and the temperature of the steel strip exiting the spray pipe is 150-190℃; the cooling rate of the steel strip in the final cooling section is controlled at ≤18℃ / s, and the steel strip is cooled to room temperature.

[0058] 8) Trim the edges and separate the coils into smaller rolls for delivery on the rewinding line.

[0059] In specific implementation of the present invention, the specific process parameters of Examples 1-10 and Comparative Examples 1-10 are shown in Tables 2 and 3.

[0060] Table 2. List of main hot rolling process parameters for each embodiment and comparative example of the present invention.

[0061]

[0062]

[0063] Table 3. Process parameters for normalizing, bell-type rolling, cold rolling, annealing, etc., of each embodiment and comparative example of the present invention.

[0064]

[0065]

[0066] The main properties of the non-oriented silicon steel produced in each embodiment and comparative example are shown in Table 4.

[0067] Table 4. Main performance parameters of various embodiments and comparative examples of the present invention.

[0068]

[0069]

[0070] In Comparative Example 1, the composition [Als]+[Si]+[Mn] was not within 4.0-5.0%, while the rest were within the design requirements. This resulted in the iron loss and mechanical properties of the finished product after annealing not meeting the design requirements. In Comparative Example 2, the [Als] / [Si] ratio was not within the range of 1 / 8-1 / 6, but the Mn and Si contents were between 1 / 5-1 / 3, ensuring that the mechanical properties met the requirements. Increasing or decreasing [Als] would affect the resistivity, which is detrimental to electromagnetic performance and cost control. In Comparative Example 3, the [Mn] / [Si] ratio was not within the range of 1 / 5-1 / 3, resulting in unacceptable mechanical properties and affecting the use after stacking. In Comparative Example 4, the temperature of the hot rolling furnace was too high, causing the MnS and Als second-phase precipitates in the strip to dissolve. During the rolling process, as the plate temperature decreased, these precipitates hindered grain growth, resulting in the normalized and finished product grain size not meeting the target requirements, thus reducing {114}. <481> The texture ratio increases the proportion of unfavorable textures in the finished product {111}, ultimately affecting the electromagnetic properties of the finished product; in Comparative Example 5, the normalizing temperature and water jacket temperature are unqualified. Both high and low normalizing temperatures will affect production, performance, and favorable textures, mainly leading to grain sizes that are too large or too small, which easily affects the grain size of rolling and the finished product, reducing {114} <481> The increased texture ratio ({111}) is detrimental to the magnetic properties of the finished product. Higher water jacket temperatures can negatively impact the mechanical properties of the normalized steel coil, hindering subsequent cold rolling. In Comparative Example 6, the steel coil's heating temperature in the bell-type annealing furnace does not reach the set target temperature, making it difficult for the coil to heat evenly within the furnace. The coil's surface temperature is also low upon exiting the furnace, potentially causing strip breakage during the 20-roll mill rolling process. In Comparative Example 7, the low temperature in the soaking zone of the annealing furnace affects the recrystallization of the steel coil, impacting the size and uniformity of the grain size, and reducing the properties of {114}. <481> The increased texture ratio {111} worsened the electromagnetic properties; in Comparative Example 8, carbon and sulfur elements exceeded design requirements, and in Example 9, nitrogen and carbon elements exceeded design requirements. Other process parameters were controlled according to the present invention, affecting the finished product {114}. <481> The ratio of {111} texture resulted in substandard product performance. As the motor's operating time increased, the motor gradually heated up, and the magnetic aging became obvious. In Comparative Example 10, tin was not added as required by the design, which affected the electromagnetic performance of the finished product and failed to meet the magnetic performance requirements.

[0071] The above embodiments are merely best examples and are not intended to limit the implementation of the present invention.

Claims

1. A non-oriented electrical steel for large motors, characterized in that, The non-oriented electrical steel for large motors comprises the following components by mass percentage: [C]≤0.0020%, [S]≤0.0025%, [N]≤0.0025%, [Sn]0.040-0.070%, [P]≤0.0035%, [Mn]+[Si]+[Als]=4.0-5.0%, with the remainder being Fe and unavoidable impurities; the composition of the non-oriented electrical steel for large motors also satisfies: [Als] / [Si]=1 / 8-1 / 6; [Mn] / [Si]=1 / 5-1 / 3; The non-oriented electrical steel for large motors has a grain size of 90-130 μm after annealing; The annealed non-oriented electrical steel for large motors contains {114} <481> The proportion of textures that are beneficial to electromagnetic properties is above 25%, while the proportion of {111} textures that are detrimental to electromagnetic properties is reduced to less than 10%. The thickness of the non-oriented electrical steel used in the large motor is 0.490-0.510 mm.

2. The non-oriented electrical steel for large motors according to claim 1, characterized in that, The elongation A of the non-oriented electrical steel for large motors 50 ≥12%; Yield strength R eL ≥450MPa, tensile strength R m ≥560Mpa; Typical product 50XW310 iron loss P 1.5 / 50 ≤2.7W / kg, minimum magnetic polarization intensity B 5000 ≥1.65T; 50XW290 iron loss P 1.5 / 50 ≤2.6W / kg, minimum magnetic polarization intensity B 5000 ≥1.64T; 50XW270 iron loss P 1.5 / 50 ≤2.6W / kg, minimum magnetic polarization intensity B 5000 ≥1.64T.

3. A method for producing non-oriented electrical steel for large motors as described in claim 1 or 2, characterized in that, The production method includes the following process steps: converter smelting, RH vacuum refining, continuous casting, slab heating, hot rolling, coiling, normalizing, shot blasting, pickling, bell-type annealing, cold rolling, continuous annealing, cooling, coating, and rewinding.

4. The production method according to claim 3, characterized in that, The slab is heated, and the furnace gas temperature is controlled at 1080-1200℃.

5. The production method according to claim 3, characterized in that, The hot rolling process involves rough rolling followed by finish rolling. The rough rolling temperature is controlled at 940-1000℃. The finish rolling process involves a thickness of 2.5-3.0mm, a crown of 20-40μm, and a wedge shape within ±15μm.

6. The production method according to claim 3, characterized in that, The normalization process involves controlling the temperature at 870-930℃ and holding it at that temperature for 30-50 seconds.

7. The production method according to claim 3, characterized in that, After pickling, the sample is first cooled to ≤560℃ by a water jacket.

8. The production method according to claim 3, characterized in that, The bell-type annealing process involves heating the steel coil to 150-200℃ and holding it at that temperature for 4-6 hours. After exiting the furnace, the temperature of the steel coil is controlled at 150-200℃, and the protective atmosphere is H2 with a volume concentration of 99.99%.

9. The production method according to claim 3, characterized in that, The cold rolling process involves a total reduction of 80-84%, resulting in a finished product thickness of 0.490-0.510 mm.

10. The production method according to claim 3, characterized in that, The continuous annealing process involves controlling the annealing temperature of the SF section to 980-1030℃ and holding it in the furnace for 30-50 seconds.

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