Preparation method of high-magnetic-induction low-iron-loss non-oriented silicon steel for new energy driven motor

Abstract

This invention discloses a method for preparing high-magnetic-induction, low-iron-loss non-oriented silicon steel for new energy drive motors, comprising: 1) smelting and continuous casting; 2) slab heating; 3) hot rolling process; 4) normalizing treatment; 5) pickling and cold rolling; 6) continuous recrystallization annealing; the chemical composition by mass percentage includes: C≤0.0025%, Si 3.2~3.6%, Als 0.8~1.1%, Mn 0.3~0.6%, Sb 0.02~0.05%, Sn 0.01~0.03%, P≤0.012%, S≤0.001%, N≤0.002%, Ti≤0.001%, O≤0.0015%, C+S+N+Ti≤50ppm, with the balance being Fe and impurities. The purpose of this invention is to solve the problems of insufficient magnetic induction, high iron loss, weak texture control, and poor process stability of existing non-oriented silicon steel.

Description

Technical Field

[0001] This invention belongs to the field of electrical steel materials technology, specifically relating to a technology for improving the magnetic properties of non-oriented silicon steel for drive motors and high-efficiency variable frequency motors in new energy vehicles. In particular, it relates to a non-oriented silicon steel and its industrial preparation method that significantly improves magnetic induction intensity and reduces iron loss through precise control of composition, synergy of hot / cold rolling processes throughout the entire process and optimization of recrystallization annealing texture. Background Technology

[0002] New energy vehicles and high-efficiency motors place stringent requirements on core iron core materials, demanding high magnetic induction, low iron loss, and high-frequency stability. Non-oriented silicon steel, as a key material for motor cores, directly determines motor efficiency, power density, and range. Existing technologies generally suffer from problems such as difficulty in simultaneously improving magnetic induction and reducing iron loss, insufficient texture control, harmful inclusions and fine micro-alloy phases hindering grain growth, and poor process stability, thus restricting the domestic production of high-end silicon steel and the upgrading of motor energy efficiency.

[0003] Reference 1 (patent application number CN202210848889.3) discloses a high-strength non-oriented silicon steel strip with excellent magnetic properties for automotive drive motors and its manufacturing method. This patent achieves precipitation strengthening by adding 0.8~1.7wt% Cu, and improves strength by secondary warm rolling and aging, resulting in excellent high-frequency iron loss and mechanical properties. However, it has significant shortcomings: high Cu content easily leads to hot rolling brittleness and cold rolling strip breakage, resulting in large fluctuations in yield; the recrystallization annealing temperature window is narrow and the cycle is long; the magnetic induction B5000 is only 1.67~1.72T, which is difficult to meet the requirement of ≥1.75T high magnetic induction for 800V high-voltage platform motors; and the magnetic flux density is limited because the {100} / {110} favorable texture is not directionally strengthened.

[0004] Reference 2 (application number CN202110332150.2) discloses a non-oriented electrical steel for wide-frequency, low-iron-loss variable frequency motors and its manufacturing method. This patent improves wide-frequency iron-loss performance through Si / Al / Mn ratio optimization and low-temperature normalizing, and controls C+S+N+Ti≤0.009% to reduce harmful inclusions. However, it has significant drawbacks: the normalizing temperature is too low (850~950℃), resulting in insufficient homogenization of the hot-rolled structure; the total reduction rate of cold rolling is fixed, and a synergistic mechanism of "reduction rate-annealing temperature-texture" has not been established; the improvement in magnetic induction is limited, and texture control elements such as Sb / Sn are not introduced, resulting in a high proportion of unfavorable {111} textures, leading to low high-field permeability.

[0005] Reference 3 (application number CN201080059853.2) discloses a non-oriented electrical steel sheet with excellent magnetic properties and its preparation method. This patent promotes the formation of coarse inclusions by adjusting the Al / Mn / N / S ratio, thereby reducing the pinning effect on grain growth and improving magnetic properties. However, it has limitations: the upper limit of Si content is 3.5wt%, the resistivity improvement is insufficient, and the high-frequency iron loss is relatively high; it only focuses on inclusion coarsening and does not systematically design the texture of the entire process; the annealing temperature range is wide (750~1100℃), the process repeatability is poor, and it is difficult to stably achieve a combination of high magnetic induction and low iron loss.

[0006] In summary, existing technologies cannot simultaneously meet the following requirements: B5000 ≥ 1.75T, P1.5 / 50 ≤ 3.0W / kg, high frequency and low loss, stable cold rolling forming, and continuous industrial production. This invention addresses these shortcomings by controlling component purity, regulating microalloy texture, precisely matching hot / cold rolling parameters, and optimizing the annealing atmosphere / rate in a closed-loop manner, achieving a significant improvement in magnetic properties. Summary of the Invention

[0007] To address the problems of insufficient magnetic induction, high iron loss, weak texture control, and poor process stability in existing non-oriented silicon steel, the purpose of this invention is to provide a method for preparing high-magnetic-induction, low-iron-loss non-oriented silicon steel for new energy drive motors, achieving the following objectives:

[0008] 1. Magnetic induction intensity B5000≥1.75T, iron loss P1.5 / 50≤2.8W / kg, iron loss is significantly reduced at high frequency (400Hz);

[0009] 2. Enhance the favorable textures of {100} and {110}, suppress the unfavorable texture of {111}, and improve the permeability and magnetization response speed;

[0010] 3. Strictly control harmful elements such as C, S, N, Ti, and O, as well as fine inclusions, to promote uniform and coarse grain growth;

[0011] 4. Eliminate the cold rolling brittleness caused by high Si / high Al, improve yield and production stability, and adapt to continuous large-scale manufacturing.

[0012] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0013] This invention discloses a method for preparing high magnetic induction, low iron loss, non-oriented silicon steel for new energy drive motors, comprising:

[0014] 1). Smelting and continuous casting

[0015] The process employs RH vacuum refining and calcium treatment to control O to ≤15ppm and S to ≤10ppm. Continuous casting uses fully protected casting and electromagnetic stirring, with a slab thickness of 220~250mm and an equiaxed crystal ratio of ≥70%, eliminating central segregation and subcutaneous bubbles.

[0016] 2) Slab heating

[0017] Walking beam furnace, temperature 1120~1180℃, holding time 2.5~3.5h; ensures full solution dissolution of the alloy and avoids overheating leading to coarse grains; furnace exit temperature fluctuation ≤±20℃;

[0018] 3) Hot rolling process

[0019] Rough rolling 5 passes, intermediate slab thickness 35~45mm; finish rolling 7 passes, final rolling temperature 820~860℃, coiling temperature 580~620℃; hot rolled plate thickness 2.0~2.5mm; laminar flow cooling segmented control to avoid banded structure and internal stress;

[0020] 4) Normalization treatment

[0021] The protective atmosphere is N2+H2, where the volume fraction of H2 is 5~10%, the normalization temperature is 980~1030℃, the time is 3~6min, and the rapid cooling to room temperature is used to homogenize the hot-rolled structure and spheroidize the precipitated phase, providing a homogeneous structure basis for cold rolling and recrystallization.

[0022] 5). Pickling and cold rolling

[0023] Turbulent hydrochloric acid pickling is used to remove iron oxide scale; a one-time cold rolling method is adopted, with a total reduction rate of 85~88% and a finished product thickness of 0.25~0.30mm; the rolling speed is 150~220m / min, the tension is stable, and edge cracks and poor plate shape are avoided;

[0024] 6) Continuous recrystallization annealing

[0025] Atmosphere: H2 volume fraction 50~70%, the remainder is N2, dew point ≤ -40℃;

[0026] Heating range: 350~650℃, rate 15~20℃ / s;

[0027] Incubation section: 920~960℃, hold for 4~8 minutes to complete recrystallization;

[0028] Cooling section: rapidly cools to below 200℃ at 30~50℃ / s to lock in favorable texture and coarse grains;

[0029] The chemical composition of the high magnetic induction, low iron loss non-oriented silicon steel by mass percentage includes: C≤0.0025%, Si 3.2~3.6%, Als 0.8~1.1%, Mn 0.3~0.6%, Sb 0.02~0.05%, Sn 0.01~0.03%, P≤0.012%, S≤0.001%, N≤0.002%, Ti≤0.001%, O≤0.0015%, C+S+N+Ti≤50ppm, with the balance being Fe and unavoidable impurities.

[0030] Furthermore, it also includes: 7). Insulating coating and curing

[0031] Apply a coating with a thickness of 0.8~1.2μm; cure at 380~450℃ for 25~45s; ensure interlayer resistance ≥200Ω·mm. 2 This reduces additional losses in the iron core.

[0032] Furthermore, the coating is an organic-inorganic composite coating.

[0033] Furthermore, the chemical composition of the high magnetic induction, low iron loss, non-oriented silicon steel by mass percentage includes: C: 0.0020%, Si: 3.45%, Als: 0.95%, Mn: 0.45%, Sb: 0.035%, Sn: 0.020%, P: 0.010%, S: 0.0008%, N: 0.0015%, Ti: 0.0008%, O: 0.0012%, with the balance being Fe and unavoidable impurities.

[0034] Furthermore, the chemical composition of the high magnetic induction, low iron loss, non-oriented silicon steel by mass percentage includes: C: 0.0022%, Si: 3.30%, Als: 0.85%, Mn: 0.50%, Sb: 0.040%, Sn: 0.015%, P: 0.009%, S: 0.0007%, N: 0.0013%, Ti: 0.0007%, O: 0.0010%, with the balance being Fe and unavoidable impurities.

[0035] Furthermore, the chemical composition of the high magnetic induction, low iron loss, non-oriented silicon steel by mass percentage includes: C: 0.0018%, Si: 3.60%, Als: 1.05%, Mn: 0.35%, Sb: 0.030%, Sn: 0.025%, P: 0.011%, S: 0.0006%, N: 0.0012%, Ti: 0.0006%, O: 0.0008%, with the balance being Fe and unavoidable impurities.

[0036] Furthermore, the magnetic properties of the prepared high magnetic induction and low iron loss non-oriented silicon steel are significantly improved: B50≥1.75T, up to 1.78T; P1.5 / 50≤2.8W / kg, down to 2.5W / kg; and the 400Hz high-frequency iron loss is reduced by 15~20% compared with conventional products.

[0037] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0038] 1. Significantly improved magnetic properties: B50 ≥ 1.75T, up to 1.78T; P1.5 / 50 ≤ 2.8W / kg, down to 2.5W / kg; 400Hz high-frequency iron loss is reduced by 15-20% compared to conventional products;

[0039] 2. Optimal texture and structure: Favorable texture accounts for ≥65%, with large and uniform grains, small magnetic anisotropy, and more stable motor output;

[0040] 3. Stable process and high yield: Eliminates the risks of high Si brittleness and thermal brittleness, with a continuous production yield of ≥95%, and costs reduced by 8~12% compared to similar products;

[0041] 4. Suitable for high-end scenarios: Meets the requirements of 800V drive motors, high-efficiency variable frequency motors, energy storage converters, etc. in new energy vehicles, supporting motor efficiency ≥97%;

[0042] 5. Excellent processing performance: moderate hardness, good punching ability, stacking coefficient ≥97%, and low core manufacturing loss. Detailed Implementation

[0043] Example 1

[0044] Chemical composition (wt%)

[0045] C: 0.0020%, Si: 3.45%, Als: 0.95%, Mn: 0.45%, Sb: 0.035%, Sn: 0.020%, P: 0.010%, S: 0.0008%, N: 0.0015%, Ti: 0.0008%, O: 0.0012%, with the balance being Fe, which is an unavoidable impurity.

[0046] Preparation process

[0047] 1. Smelting and continuous casting: RH refining, calcium treatment, slab thickness 230mm;

[0048] 2. Slab heating: Hold at 1150℃ for 3 hours;

[0049] 3. Hot rolling: Final rolling at 840℃, coiling at 600℃, hot-rolled thickness 2.2mm;

[0050] 4. Normalization: Hold at 1000℃ for 4 minutes, then rapidly cool in a protective atmosphere;

[0051] 5. Cold rolling: Total reduction rate 86.4%, finished product thickness 0.30mm;

[0052] 6. Annealing: H2 volume fraction 60% (the remainder is N2), dew point -45℃; hold at 940℃ for 6 min; cooling rate 40℃ / s;

[0053] 7. Coating curing: 400℃, 30s.

[0054] Performance Results

[0055] B50=1.76T, P1.5 / 50=2.65W / kg, grain size 82μm, favorable texture accounts for 68%.

[0056] Example 2

[0057] Chemical composition (wt%)

[0058] C: 0.0022%, Si: 3.30%, Als: 0.85%, Mn: 0.50%, Sb: 0.040%, Sn: 0.015%, P: 0.009%, S: 0.0007%, N: 0.0013%, Ti: 0.0007%, O: 0.0010%, with the balance being Fe, which is an unavoidable impurity.

[0059] Preparation process

[0060] 1. Continuous casting: Fully protected casting + electromagnetic stirring;

[0061] 2. Slab heating: Hold at 1130℃ for 3.5 hours;

[0062] 3. Hot rolling: Final rolling at 830℃, coiling at 590℃, hot-rolled thickness 2.0mm;

[0063] 4. Normalization: Hold at 990℃ for 5 minutes;

[0064] 5. Cold rolling: Total reduction rate 87.5%, finished product thickness 0.25mm;

[0065] 6. Annealing: H2 volume fraction 65% (the remainder is N2), hold at 930℃ for 5 min, cooling rate 45℃ / s;

[0066] 7. Coating: 1.0μm thickness, cured at 420℃.

[0067] Performance Results

[0068] B50=1.77T, P1.5 / 50=2.55W / kg, high-frequency iron loss P1.0 / 400=18.2W / kg, stacking factor 97.2%.

[0069] Example 3

[0070] Chemical composition (wt%)

[0071] C: 0.0018%, Si: 3.60%, Als: 1.05%, Mn: 0.35%, Sb: 0.030%, Sn: 0.025%, P: 0.011%, S: 0.0006%, N: 0.0012%, Ti: 0.0006%, O: 0.0008%, with the balance being Fe, which is an unavoidable impurity.

[0072] Preparation process

[0073] 1. Smelting: Deep degassing of RH, C+S+N+Ti=42ppm;

[0074] 2. Slab heating: Hold at 1170℃ for 2.5 hours;

[0075] 3. Hot rolling: Final rolling at 850℃, coiling at 610℃, hot-rolled thickness 2.5mm;

[0076] 4. Normalization: Hold at 1020℃ for 3 minutes;

[0077] 5. Cold rolling: Total reduction rate 88.0%, finished product thickness 0.30mm;

[0078] 6. Annealing: H2 volume fraction 55% (the remainder is N2), hold at 950℃ for 7 min, cooling rate 35℃ / s;

[0079] 7. Coating curing: 440℃, 40s.

[0080] Performance Results

[0081] B50=1.78T, P1.5 / 50=2.50W / kg, grain size 88μm, favorable texture accounts for 70%, and yield is 96.5%.

[0082] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing high magnetic induction and low iron loss non-oriented silicon steel for new energy driven motor, characterized in that: include: 1). Smelting and continuous casting The process employs RH vacuum refining and calcium treatment to control O to ≤15ppm and S to ≤10ppm. Continuous casting uses fully protected casting and electromagnetic stirring, with a slab thickness of 220~250mm and an equiaxed crystal ratio of ≥70%, eliminating central segregation and subcutaneous bubbles. 2) Slab heating Walking beam furnace, temperature 1120~1180℃, holding time 2.5~3.5h; ensures full solution dissolution of the alloy and avoids overheating leading to coarse grains; furnace exit temperature fluctuation ≤±20℃; 3) Hot rolling process Rough rolling 5 passes, intermediate slab thickness 35~45mm; finish rolling 7 passes, final rolling temperature 820~860℃, coiling temperature 580~620℃; hot rolled plate thickness 2.0~2.5mm; laminar flow cooling segmented control to avoid banded structure and internal stress; 4) Normalization treatment The protective atmosphere is N2+H2, where the volume fraction of H2 is 5~10%, the normalization temperature is 980~1030℃, the time is 3~6min, and the rapid cooling to room temperature is used to homogenize the hot-rolled structure and spheroidize the precipitated phase, providing a homogeneous structure basis for cold rolling and recrystallization. 5). Pickling and cold rolling Turbulent hydrochloric acid pickling is used to remove iron oxide scale; a one-time cold rolling method is adopted, with a total reduction rate of 85~88% and a finished product thickness of 0.25~0.30mm; the rolling speed is 150~220m / min, the tension is stable, and edge cracks and poor plate shape are avoided; 6) Continuous recrystallization annealing Atmosphere: H2 volume fraction 50~70%, dew point ≤ -40℃; Heating range: 350~650℃, rate 15~20℃ / s; Incubation section: 920~960℃, hold for 4~8 minutes to complete recrystallization; Cooling section: rapidly cools to below 200℃ at 30~50℃ / s to lock in favorable texture and coarse grains; The chemical composition of the high magnetic induction, low iron loss non-oriented silicon steel by mass percentage includes: C≤0.0025%, Si 3.2~3.6%, Als 0.8~1.1%, Mn 0.3~0.6%, Sb 0.02~0.05%, Sn 0.01~0.03%, P≤0.012%, S≤0.001%, N≤0.002%, Ti≤0.001%, O≤0.0015%, C+S+N+Ti≤50ppm, with the balance being Fe and unavoidable impurities.

2. The method for preparing high magnetic induction, low iron loss, non-oriented silicon steel for new energy drive motors according to claim 1, characterized in that: Also includes: 7) Insulating coating and curing Coating coating, thickness 0.8~1.2μm; curing temperature 380~450℃, time 25~45s; ensure interlayer resistance ≥200Ω·mm 2 , reduce the core additional loss.

3. The method for preparing high magnetic induction, low iron loss, non-oriented silicon steel for new energy drive motors according to claim 1, characterized in that: The coating is an organic-inorganic composite coating.

4. The preparation method of the high-magnetic-induction low-iron-loss non-oriented silicon steel for new energy driving motors according to claim 1, characterized in that: The chemical composition of the high magnetic induction, low iron loss, non-oriented silicon steel by weight percentage includes: C: 0.0020%, Si: 3.45%, Als: 0.95%, Mn: 0.45%, Sb: 0.035%, Sn: 0.020%, P: 0.010%, S: 0.0008%, N: 0.0015%, Ti: 0.0008%, O: 0.0012%, with the balance being Fe and unavoidable impurities.

5. The preparation method of the high-magnetic-induction low-iron-loss non-oriented silicon steel for new energy driving motors according to claim 1, characterized in that: The chemical composition of the high magnetic induction, low iron loss, non-oriented silicon steel by weight percentage includes: C: 0.0022%, Si: 3.30%, Als: 0.85%, Mn: 0.50%, Sb: 0.040%, Sn: 0.015%, P: 0.009%, S: 0.0007%, N: 0.0013%, Ti: 0.0007%, O: 0.0010%, with the balance being Fe and unavoidable impurities.

6. The preparation method of the high-magnetic-induction low-iron-loss non-oriented silicon steel for new energy driving motors according to claim 1, characterized in that: The chemical composition of the high magnetic induction, low iron loss non-oriented silicon steel by weight percentage includes: C: 0.0018%, Si: 3.60%, Als: 1.05%, Mn: 0.35%, Sb: 0.030%, Sn: 0.025%, P: 0.011%, S: 0.0006%, N: 0.0012%, Ti: 0.0006%, O: 0.0008%, with the balance being Fe and unavoidable impurities.

7. The preparation method of the high-magnetic-induction low-iron-loss non-oriented silicon steel for new energy driving motors according to claim 1, characterized in that: The magnetic properties of the prepared high magnetic induction and low iron loss non-oriented silicon steel are significantly improved: B50≥1.75T, up to 1.78T; P1.5 / 50≤2.8W / kg, down to 2.5W / kg; and the iron loss at 400Hz is reduced by 15~20% compared with conventional products.