High-magnetic-induction low-iron-loss non-oriented silicon steel continuous annealing process and grain boundary characteristic regulation and control method

Abstract

The invention discloses a high-magnetic-induction low-iron-loss non-oriented silicon steel continuous annealing process and a grain boundary characteristic regulation and control method, and belongs to the technical field of metal material processing. The specific optimization parameter combination is as follows: the preheating temperature is 300 DEG C, and the time is 3 minutes; the heating temperature is 900 DEG C, and the heating time is 5 minutes; the soaking temperature is 870 DEG C, and the soaking time is 5 minutes; the cooling speed is 30 DEG C / second; annealing atmosphere: the volume ratio of nitrogen to hydrogen is 3: 1; the grain size is 100 microns; the trace element is Sb, and the addition amount is 0.03%. By means of the continuous annealing process and the grain boundary characteristic regulation and control method, the magnetic induction intensity of the non-oriented silicon steel can be remarkably improved, and meanwhile iron loss is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material processing, and in particular relates to a continuous annealing process for high magnetic induction and low iron loss non-oriented silicon steel and a method for controlling grain boundary characteristics. Background Art

[0002] Non-oriented silicon steel is widely used in the manufacture of motors and transformers, and its magnetic properties directly impact the efficiency and energy consumption of these devices. During the production process, conventional non-oriented silicon steel often suffers from low magnetic induction intensity and high iron loss due to imperfect grain boundary properties. While existing technologies can improve the magnetic properties of silicon steel to a certain extent through adjustments to chemical composition and heat treatment processes, the conflict between magnetic induction intensity and iron loss persists, making it difficult to simultaneously achieve both high magnetic induction and low iron loss. Summary of the Invention

[0003] The purpose of the present invention is to provide a continuous annealing process for non-oriented silicon steel with high magnetic induction and low iron loss and a method for controlling grain boundary properties, so as to significantly improve the magnetic properties of silicon steel by optimizing annealing process parameters and controlling grain boundary properties.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a continuous annealing process for high magnetic induction and low iron loss non-oriented silicon steel and a method for controlling grain boundary properties. The continuous annealing process includes four stages: a preheating stage, a heating stage, a soaking stage, and a cooling stage; wherein:

[0006] (1) Preheating stage

[0007] Temperature range: 200-400℃;

[0008] Time range: 1-5 minutes;

[0009] Function: The heating stage is the key stage for grain recrystallization and growth. By controlling the heating temperature and time, the grain size and grain boundary distribution can be regulated. Too high a temperature may lead to excessive grain growth, while too low a temperature may lead to insufficient recrystallization.

[0010] (2) Heating stage

[0011] Temperature range: 800-950℃;

[0012] Time range: 2-10 minutes;

[0013] Function: The heating stage is the key stage for grain recrystallization and growth. By controlling the heating temperature and time, the grain size and grain boundary distribution can be regulated. Too high a temperature may lead to excessive grain growth, while too low a temperature may lead to insufficient recrystallization.

[0014] (3) Soaking stage

[0015] Temperature range: 850-900℃;

[0016] Time range: 3-8 minutes;

[0017] Function: The main purpose of the soaking stage is to further homogenize the grains, eliminate microstructural inhomogeneities, and optimize grain boundary properties. The choice of soaking temperature and time has a significant impact on grain boundary cleanliness and chemical stability.

[0018] (4) Cooling stage

[0019] Cooling method: rapid cooling;

[0020] Cooling rate: 10-50℃ / second;

[0021] Function: Rapid cooling can inhibit the secondary growth of grains and fix the optimized grain boundary structure formed during high temperature annealing. Too slow cooling may cause excessive grain growth, while too fast cooling may introduce internal stress.

[0022] The grain boundary characteristics control method:

[0023] (1) Control of heating rate and cooling rate

[0024] Heating rate: controlled at 5-15°C / min;

[0025] Function: Appropriate heating rate can promote uniform recrystallization of grains and avoid abnormal grain growth caused by local overheating;

[0026] Cooling rate: controlled at 10-50℃ / second;

[0027] Function: Rapid cooling can inhibit the secondary growth of grains and fix the optimized grain boundary structure;

[0028] (2) Control of annealing atmosphere

[0029] Atmosphere composition: A mixed gas of nitrogen N2 and hydrogen H2, wherein the volume ratio of nitrogen to hydrogen is 2:1-4:1;

[0030] Function: Nitrogen can prevent oxidation of the silicon steel surface, while hydrogen has a reducing effect, which can remove impurities at the grain boundaries and improve the cleanliness and chemical stability of the grain boundaries;

[0031] (3) Optimization of grain size and grain boundary distribution

[0032] By controlling the heating temperature, soaking time and cooling rate, the grain size is controlled within the range of 50-150μm; the grain boundaries are evenly distributed, and the grain boundary angles are mainly concentrated between 15°-45°, thereby reducing the resistance to the movement of the magnetic domain wall and lowering the iron loss;

[0033] (4) Trace element addition

[0034] Add trace alloy elements to silicon steel composition, the addition amount is 0.01%-0.05%;

[0035] Function: The addition of trace elements can further optimize the grain boundary characteristics, increase the strength and stability of the grain boundary, and thus improve the magnetic properties.

[0036] Furthermore, the preheating temperature is 300°C and the time is 3 minutes to achieve uniform recrystallization and moderate growth of grains.

[0037] Furthermore, the heating temperature is 900° C. and the time is 5 minutes to achieve uniform recrystallization and moderate growth of the grains.

[0038] Furthermore, the soaking temperature is 870° C. and the time is 5 minutes to achieve sufficient homogenization of the grains and optimization of the grain boundary characteristics.

[0039] Furthermore, the cooling rate was 30°C / s to cool to room temperature to achieve stabilization of the grain boundary structure and minimization of internal stress.

[0040] Furthermore, the alloy element includes at least one of Sb and Sn.

[0041] Furthermore, the specific optimization parameter combinations are as follows:

[0042] Preheating temperature: 300℃, time: 3 minutes;

[0043] Heating temperature: 900°C, time: 5 minutes;

[0044] Soaking temperature: 870℃, time: 5 minutes;

[0045] Cooling rate: 30℃ / s;

[0046] Annealing atmosphere: nitrogen to hydrogen volume ratio 3:1;

[0047] Grain size: 100 μm;

[0048] Trace element addition: Sb, addition amount 0.03%.

[0049] Compared with the prior art, the present invention has the following beneficial technical effects:

[0050] Through the above technical solution, the present invention can significantly improve the magnetic induction intensity of non-oriented silicon steel, while effectively reducing iron loss, meeting the application requirements of high-efficiency motors and transformers.

[0051] The present invention, through the continuous annealing process and grain boundary property control method, can significantly improve the magnetic flux density of non-oriented silicon steel while effectively reducing iron loss. Specific effects include: (1) a 10-20% increase in magnetic flux density; (2) a 15-30% reduction in iron loss; and (3) uniform grain size and high grain boundary cleanliness, improving the overall performance of the material. DETAILED DESCRIPTION

[0052] Example 1

[0053] Specific composition and mass percentage content: Si: 2.5%; Al: 0.5%; Mn: 0.3%; C: ≤ 0.003%; P: ≤ 0.01%; S: ≤ 0.005%; the remainder is Fe and impurities.

[0054] (1) Process parameters

[0055] Preheating stage: preheating temperature 300℃, time 3 minutes.

[0056] Heating stage: heating temperature 900℃, time 5 minutes.

[0057] Soaking stage: Soaking temperature 870℃, time 5 minutes.

[0058] Cooling stage: cooling rate 30℃ / s, cooling to room temperature.

[0059] Annealing atmosphere: nitrogen to hydrogen volume ratio 3:1.

[0060] Grain size: 100μm.

[0061] Trace element addition: Sb, addition amount 0.03%.

[0062] (2) Implementation steps

[0063] 1. Feed the non-oriented silicon steel strip into a continuous annealing furnace, set the preheating temperature to 300°C, and the preheating time to 3 minutes.

[0064] 2. After preheating, heat the silicon steel strip to 900℃ and maintain for 5 minutes.

[0065] 3. After heating, soak at 870℃ for 5 minutes.

[0066] 4. After soaking, cool rapidly to room temperature at a rate of 30°C / second.

[0067] 5. During the annealing process, a mixture of nitrogen and hydrogen (volume ratio 3:1) is introduced.

[0068] 6. Add 0.03% Sb to the silicon steel composition.

[0069] (3) Results

[0070] Magnetic induction intensity: 1.75T.

[0071] Iron loss: 2.1W / kg.

[0072] Grain size: 100μm, evenly distributed.

[0073] Grain boundary characteristics: The grain boundary is highly clean, and the grain boundary angle is concentrated between 15° and 45°.

[0074] Example 2

[0075] Specific composition and mass percentage content: Si: 2.8%; Al: 0.6%; Mn: 0.4%; C: ≤ 0.003%; P: ≤ 0.01%; S: ≤ 0.005%; the balance is Fe and impurities;

[0076] (1) Process parameters

[0077] Preheating stage: preheating temperature 250℃, time 4 minutes.

[0078] Heating stage: heating temperature 850℃, time 8 minutes.

[0079] Soaking stage: Soaking temperature 880℃, time 6 minutes.

[0080] Cooling stage: cooling rate 20℃ / s, cooling to room temperature.

[0081] Annealing atmosphere: nitrogen to hydrogen volume ratio 2:1.

[0082] Grain size: 80μm.

[0083] Trace element addition: Sn, addition amount 0.02%.

[0084] (2) Implementation steps

[0085] 1. Feed the non-oriented silicon steel strip into a continuous annealing furnace, set the preheating temperature to 250°C, and the preheating time to 4 minutes.

[0086] 2. After preheating, heat the silicon steel strip to 850℃ and maintain for 8 minutes.

[0087] 3. After heating, soak at 880℃ for 6 minutes.

[0088] 4. After soaking, cool rapidly to room temperature at a rate of 20°C / second.

[0089] 5. During the annealing process, a mixture of nitrogen and hydrogen (volume ratio 2:1) is introduced.

[0090] 6. Add 0.02% Sn to the silicon steel composition.

[0091] (3) Results

[0092] Magnetic induction intensity: 1.72T.

[0093] Iron loss: 2.3W / kg.

[0094] Grain size: 80μm, evenly distributed.

[0095] Grain boundary characteristics: The grain boundary cleanliness is relatively high, and the grain boundary angle is concentrated in the range of 20°-40°.

[0096] Example 3

[0097] Specific composition and mass percentage content: Si: 3.0%; Al: 0.7%; Mn: 0.5%; C: ≤ 0.003%; P: ≤ 0.01%; S: ≤ 0.005%; the balance is Fe and impurities;

[0098] (1) Process parameters

[0099] Preheating stage: preheating temperature 350℃, time 2 minutes.

[0100] Heating stage: heating temperature 920℃, time 3 minutes.

[0101] Soaking stage: Soaking temperature 860℃, time 4 minutes.

[0102] Cooling stage: cooling rate 40℃ / s, cooling to room temperature.

[0103] Annealing atmosphere: nitrogen to hydrogen volume ratio 4:1.

[0104] Grain size: 120μm.

[0105] Trace element addition: Sb, addition amount 0.04%.

[0106] (2) Implementation steps

[0107] 1. Feed the non-oriented silicon steel strip into a continuous annealing furnace, set the preheating temperature to 350°C, and the preheating time to 2 minutes.

[0108] 2. After preheating, heat the silicon steel strip to 920℃ and maintain for 3 minutes.

[0109] 3. After heating, soak at 860℃ for 4 minutes.

[0110] 4. After soaking, cool rapidly to room temperature at a rate of 40°C / second.

[0111] 5. During the annealing process, a mixture of nitrogen and hydrogen (volume ratio 4:1) is introduced.

[0112] 6. Add 0.04% Sb to the silicon steel composition.

[0113] (3) Results

[0114] Magnetic induction intensity: 1.78T.

[0115] Iron loss: 2.0W / kg.

[0116] Grain size: 120μm, evenly distributed.

[0117] Grain boundary characteristics: The grain boundary cleanliness is extremely high, and the grain boundary angle is concentrated in 10°-35°.

[0118] It can be seen from the above three embodiments that the high magnetic induction and low iron loss non-oriented silicon steel continuous annealing process and grain boundary characteristic control method provided by the present invention can significantly improve the magnetic induction intensity of silicon steel and reduce iron loss under different process parameter combinations. Examples 1, 2, and 3 respectively demonstrate the effects of different preheating temperatures, heating temperatures, cooling rates, and trace element additions on the performance of silicon steel, demonstrating the wide applicability and excellent effects of the present invention. The embodiments described above are only a description of the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solution of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A high magnetic induction and low iron loss non-oriented silicon steel continuous annealing process and grain boundary property control method, characterized by: The continuous annealing process includes four stages: a preheating stage, a heating stage, a soaking stage, and a cooling stage; wherein: (1) Preheating stage Temperature range: 200-400℃; Time range: 1-5 minutes; (2) Heating stage Temperature range: 800-950℃; Time range: 2-10 minutes; (3) Soaking stage Temperature range: 850-900℃; Time range: 3-8 minutes; (4) Cooling stage Cooling method: rapid cooling; Cooling rate: 10-50℃ / second; The grain boundary characteristics control method: (1) Control of heating rate and cooling rate Heating rate: controlled at 5-15°C / min; Cooling rate: controlled at 10-50℃ / second; (2) Control of annealing atmosphere Atmosphere composition: A mixed gas of nitrogen N2 and hydrogen H2, wherein the volume ratio of nitrogen to hydrogen is 2:1-4:1; (3) Optimization of grain size and grain boundary distribution By controlling the heating temperature, soaking time and cooling rate, the grain size is controlled within the range of 50-150μm; (4) Trace element addition Trace alloy elements are added to the silicon steel composition, with the addition amount being 0.01%-0.05%.

2. The high magnetic induction and low iron loss non-oriented silicon steel continuous annealing process and grain boundary property control method according to claim 1, characterized in that: The preheating temperature is 300°C and the time is 3 minutes.

3. The high magnetic induction and low iron loss non-oriented silicon steel continuous annealing process and grain boundary property control method according to claim 1, characterized in that: The heating temperature was 900°C and the heating time was 5 minutes.

4. The high magnetic induction and low iron loss non-oriented silicon steel continuous annealing process and grain boundary property control method according to claim 1, characterized in that: The soaking temperature was 870°C and the soaking time was 5 minutes.

5. The high magnetic induction and low iron loss non-oriented silicon steel continuous annealing process and grain boundary characteristics control method according to claim 1, characterized in that: The cooling rate was 30°C / second, and the sample was cooled to room temperature.

6. The high magnetic induction and low iron loss non-oriented silicon steel continuous annealing process and grain boundary characteristics control method according to claim 1, characterized in that: The alloy element includes at least one of Sb and Sn.

7. The high magnetic induction and low iron loss non-oriented silicon steel continuous annealing process and grain boundary characteristics control method according to claim 1, characterized in that: The specific optimization parameter combinations are as follows: Preheating temperature: 300℃, time: 3 minutes; Heating temperature: 900°C, time: 5 minutes; Soaking temperature: 870℃, time: 5 minutes; Cooling rate: 30℃ / s; Annealing atmosphere: nitrogen to hydrogen volume ratio 3:1; Grain size: 100 μm; Trace element addition: Sb, addition amount 0.03%.