Annealing treatment method for ultra-thin strip of non-oriented silicon steel

Abstract

The present invention relates to a method for annealing an ultra-thin strip of non-oriented silicon steel, belonging to the field of heat treatment of metal materials, and solves the problems that the existing annealing method for the ultra-thin strip of silicon steel by planar flow casting has a relatively complicated process, high cost, and at least one problem such as high iron loss, bending, oxidation, insufficient magnetic induction, etc. after annealing. A method for annealing an ultra-thin strip of non-oriented silicon steel: S1. Perform vacuum treatment on a vacuum tube furnace, introduce an inert gas, and raise the temperature; S2. When the annealing temperature is reached, place the sample in the cooling zone of the vacuum tube furnace, close the furnace door, and introduce a reducing gas; the sample is an ultra-thin strip of non-oriented silicon steel obtained by the planar flow casting method; S3. Push the sample to the heat preservation zone for annealing; S4. Push the sample to the cooling zone, stop introducing the reducing gas, and only introduce the inert gas. After the reducing gas is exhausted, take out the sample. The present invention provides an annealing method with a simple process and low cost, and improves the comprehensive performance of the ultra-thin strip of non-oriented silicon steel: P 1.0 / 1000Hz ≤40 W / kg, B 5000 ≥1.66 T, with good flatness and quality.

Description

Technical Field

[0001] The present invention relates to the technical field of heat treatment of metal materials, and particularly to an annealing treatment method for an non-oriented silicon steel ultra-thin strip. Background Art

[0002] The planar flow casting method is an advanced manufacturing technology, which can be used to prepare non-oriented silicon steel ultra-thin strips. Non-oriented silicon steel is an important soft magnetic material, which is widely used in the manufacture of iron cores of motors and transformers. The planar flow casting method has the characteristics of short process and high efficiency. By rapidly solidifying molten metal on a high-speed rotating cooling roll, silicon steel ultra-thin strips can be directly produced, and the final product can be obtained through subsequent processing.

[0003] According to the existing literature reports, the post-treatment steps for preparing non-oriented silicon steel ultra-thin strips by the planar flow casting method mainly include two key links: tempering and annealing. The existing problems and difficulties include: (1) Easy to bend and deform during annealing treatment: During the annealing treatment of silicon steel ultra-thin strips, due to their very thin thickness and low strength, they are extremely prone to bending, deforming or sagging during annealing, resulting in damage to the surface quality of the product and reduction of dimensional accuracy; (2) Easy to oxidize during annealing treatment: In the prior art, some people have tried to first perform a rolling tempering treatment on the silicon steel ultra-thin strip obtained by the planar flow casting method, then coat an insulating layer and wind it into a coil, and anneal the silicon steel ultra-thin strip in a protective atmosphere. However, this method not only has cumbersome processes (including tempering + coating insulating layer + annealing), but also because there is no reducing gas or the proportion of reducing gas in the protective atmosphere is relatively small, it is impossible to effectively avoid the oxidation of the silicon steel ultra-thin strip. Although some rare elements other than silicon and iron are added, the comprehensive performance of the finally obtained product (especially in terms of high-frequency iron loss, magnetic induction, etc.) is still not ideal; (3) Improper setting of process parameters during annealing treatment affects the comprehensive performance of the annealed sample: In the prior art, for the relatively simple composition of silicon steel ultra-thin strips obtained by the planar flow casting method, the annealing process parameters with the best synergistic effect (including annealing temperature, time, cooling time, rate) are not given, because the optimal ratio of these parameters is not easily obtained. In the actual annealing process, there are interactive effects between these parameters, and the influence on the annealing treatment result is often complex and non-linear. During the annealing process, if the annealing temperature, time and parameters during the cooling process are set improperly, it is very easy to cause uneven temperature in different parts of the silicon steel ultra-thin strip, thereby causing stress concentration and unevenness of the organizational structure, and further affecting the plate shape and surface quality of the silicon steel ultra-thin strip, as well as iron loss, magnetic induction, etc.

[0004] Therefore, for the non-oriented silicon steel ultra-thin strips prepared by the planar flow casting technology, it is necessary to research and develop an annealing treatment method with relatively simple process, low cost and excellent comprehensive performance suitable for non-oriented silicon steel ultra-thin strips without addition. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a method for annealing an ultra-thin strip of non-oriented silicon steel, so as to solve at least one of the problems existing in the existing annealing methods for ultra-thin silicon steel strips prepared by the planar flow casting method, such as cumbersome process, high cost, high iron loss (especially high-frequency iron loss), surface defects such as bending and oxidation, and insufficient magnetic induction after annealing.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] The present invention provides a method for annealing an ultra-thin strip of non-oriented silicon steel, comprising the following steps:

[0008] S1. Perform vacuum treatment on the vacuum tube furnace, introduce an inert gas, and then heat up the heat preservation zone in the vacuum tube furnace.

[0009] S2. When the heat preservation zone reaches the preset annealing temperature, place the sample from the furnace door of the vacuum tube furnace into the cooling zone in the vacuum tube furnace, close the furnace door, and introduce a reducing gas.

[0010] Wherein, the sample is an ultra-thin strip of non-oriented silicon steel obtained by the planar flow casting method;

[0011] S3. When the volume ratio K of the reducing gas in the vacuum tube furnace to the annealing atmosphere is ≥ 30%, push the sample to the heat preservation zone and perform annealing treatment at the annealing temperature;

[0012] Wherein, the annealing atmosphere is set as a mixed gas of a reducing gas and an inert gas;

[0013] S4. After the annealing is completed, push the sample to the cooling zone for cooling. During the cooling process, stop introducing the reducing gas and only introduce the inert gas. After the reducing gas is exhausted from the vacuum tube furnace, open the furnace door and take out the sample.

[0014] Further, during the whole process of steps S2 to S4, the sample is clamped from above and below by a porous ceramic plate.

[0015] Further, the thickness of the ceramic plate is 8 mm to 20 mm, the pore size of the ceramic plate is 80 μm to 150 μm, and the porosity of the ceramic plate is 16% to 22%.

[0016] Further, in S3, the volume ratio K of the reducing gas in the vacuum tube furnace to the annealing atmosphere is ≥ 50%.

[0017] Further, in S2 and S3, the annealing temperature is 950 °C to 1050 °C.

[0018] Further, in S3, the annealing treatment time is 1.0 h to 1.8 h.

[0019] Further, in S4, the cooling time T ≥ 6 min.

[0020] Further, in S4, the cooling rate is 1.8 °C / s to 3 °C / s.

[0021] Further, the flow rate of the inert gas is 0 L / min to 7 L / min, and the flow rate of the reducing gas is 1.5 L / min to 5 L / min; by controlling the flow rates of the inert gas and the reducing gas, the annealing atmosphere ratio inside the vacuum tube furnace is regulated to maintain a positive pressure inside the vacuum tube furnace.

[0022] Further, the chemical composition of the non-oriented silicon steel ultra-thin strip is, by mass percentage, Si: 2.8% to 4.0%, and the rest is Fe and inevitable impurities; and / or,

[0023] In S1, the main steps of the vacuum treatment include evacuating the vacuum tube furnace to make the vacuum degree Pa ≤ 150 Pa inside the furnace.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] (1) The present invention provides an annealing treatment method for non-oriented silicon steel ultra-thin strips with relatively simple process (without rolling and leveling / coating an insulating layer, directly annealing), low cost (without adding expensive trace elements and with simplified steps). By using an annealing atmosphere with a reducing gas ratio of at least 30% and cooperating with a preferred annealing device (vacuum tube furnace) and operation sequence (steps S1 - S4), the safety and operation feasibility when the reducing gas ratio is relatively high are ensured, thereby effectively improving the comprehensive performance of the non-oriented silicon steel ultra-thin strip, including: reducing iron loss, increasing magnetic induction (B 5000 ≥ 1.66 T), excellent surface quality, etc. In particular, the high-frequency iron loss (P 1.0 / 1000Hz ≤ 40 W / kg) is effectively reduced, which has important practical value for silicon steel ultra-thin strips in high-frequency applications (such as high-frequency motors, radio equipment, radar systems). Reducing the high-frequency iron loss can better meet the strict requirements of high-frequency applications. Compared with the silicon steel ultra-thin strips in the prior art (P 1.0 / 1000Hz is difficult to be controlled below 50 W / kg. Even if it is below 50 W / kg, the annealing process is often more complicated, or expensive trace elements need to be added, resulting in higher costs), the annealing treatment method of the present invention has a simpler process, lower cost, and better comprehensive performance of the obtained silicon steel ultra-thin strip.

[0026] (2) In the present invention, by sandwiching the ultra-thin silicon steel strip with porous ceramic plates on both the upper and lower sides and performing annealing treatment, it is simple and easy to operate, and can further effectively improve the comprehensive performance of the non-oriented ultra-thin silicon steel strip, including: improving flatness (for example: reducing deformation and stress), reducing iron loss, increasing magnetic induction, etc.; sandwiching the sample with ceramic plates of appropriate thickness, pore diameter and porosity for annealing treatment is conducive to obtaining the best annealing effect.

[0027] (3) By using an annealing atmosphere with a relatively high proportion of reducing gas (K≥50%), the comprehensive performance of the non-oriented ultra-thin silicon steel strip can be further effectively improved, including: reducing iron loss, increasing magnetic induction, improving surface quality, flatness, etc.

[0028] (4) By selecting preferred process conditions / parameters with synergistic effects, including annealing temperature, annealing time, cooling time, cooling rate, etc., the comprehensive performance of the non-oriented ultra-thin silicon steel strip can be further effectively improved. For example, the examples using the preferred process parameters shown in Table 1 have lower iron loss and higher magnetic induction.

[0029] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combination schemes. Other features and advantages of the present invention will be described in the subsequent specification, and some advantages can be made obvious from the specification, or understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained from the content specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are only for the purpose of showing specific embodiments, and are not considered as a limitation to the present invention. Throughout the drawings, the same reference signs represent the same components.

[0031] Figure 1 It is a grain structure diagram of the non-oriented ultra-thin silicon steel strip provided by an embodiment of the present invention, where (a) is before annealing treatment and (b) is after annealing treatment;

[0032] Figure 2 It is a photograph of the non-oriented ultra-thin silicon steel strip provided by an embodiment of the present invention, where (a) is before annealing treatment and (b) is after annealing treatment;

[0033] Figure 3 It is a photograph of the non-oriented ultra-thin silicon steel strip after annealing treatment in Comparative Example 1 (without using ceramic plates);

[0034] Figure 4 It is a photograph of the non-oriented ultra-thin silicon steel strip after annealing treatment in Comparative Example 2 (only using nitrogen). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. The accompanying drawings form a part of this application and are used together with the embodiments of the present invention to explain the principles of the present invention, rather than to limit the scope of the present invention.

[0036] The present invention provides a method for annealing an non-oriented silicon steel ultra-thin strip, comprising the following steps:

[0037] S1. Perform vacuum treatment on a vacuum tube furnace, introduce an inert gas, and then heat up the heat preservation zone in the vacuum tube furnace;

[0038] S2. When the heat preservation zone reaches the preset annealing temperature, place the sample in the cooling zone of the vacuum tube furnace through the furnace door of the vacuum tube furnace, close the furnace door, and introduce a reducing gas;

[0039] Wherein, the sample is an non-oriented silicon steel ultra-thin strip obtained by a planar flow casting method;

[0040] S3. When the volume ratio K of the reducing gas in the vacuum tube furnace to the annealing atmosphere ≥ 30%, push the sample to the heat preservation zone and perform annealing treatment at the annealing temperature;

[0041] Wherein, the annealing atmosphere is set as a mixed gas of a reducing gas and an inert gas;

[0042] S4. After annealing, push the sample to the cooling zone for cooling. During the cooling process, stop introducing the reducing gas and only introduce the inert gas. After the reducing gas is completely discharged from the vacuum tube furnace, open the furnace door and take out the sample.

[0043] It should be noted that the present invention provides a method for annealing an non-oriented silicon steel ultra-thin strip with relatively simple process (no leveling / coating insulation layer is required, direct annealing), low cost (no expensive trace elements need to be added, and the steps are simplified). By using an annealing atmosphere with a reducing gas content of at least 30% and cooperating with a preferred annealing device (vacuum tube furnace) and operation sequence (steps S1 - S4), the safety and operation feasibility when the reducing gas content is relatively high are ensured, thereby effectively improving the comprehensive performance of the non-oriented silicon steel ultra-thin strip, including: reducing iron loss, increasing magnetic induction (B 5000 ≥ 1.66T), excellent surface quality, etc. In particular, the high-frequency iron loss (P 1.0 / 1000Hz ≤ 40W / kg) is effectively reduced, which has important practical value for silicon steel ultra-thin strips in high-frequency applications (such as high-frequency motors, radio equipment, radar systems). Reducing the high-frequency iron loss can better meet the strict requirements of high-frequency applications. Compared with the silicon steel ultra-thin strips in the prior art (P 1.0 / 1000HzIt is difficult to control it below 50 W / kg. Even if it is below 50 W / kg, the annealing process is often cumbersome, or expensive trace elements need to be added, resulting in high costs. The annealing treatment method of the present invention has a simpler process, lower cost, and better comprehensive performance of the silicon steel ultra-thin strip.

[0044] Preferably, throughout the process of steps S2 to S4, a porous ceramic plate is used to clamp the sample from above and below.

[0045] In some preferred embodiments, the porous ceramic plate is a ceramic plate with micro-leakage sintered micropores. The ceramic plate with micro-leakage sintered micropores is a porous ceramic material with micron or sub-micron pore diameters.

[0046] It should be noted that by using a porous ceramic plate to clamp the silicon steel ultra-thin strip from above and below for annealing treatment, the comprehensive performance of the non-oriented silicon steel ultra-thin strip can be further effectively improved, including: improving flatness (for example: reducing deformation and stress), reducing iron loss, and increasing magnetic induction, etc. Specifically, a) Improving flatness: Clamping the silicon steel strip can prevent it from bending due to stress during annealing, effectively reducing deformation during annealing, maintaining the flatness and dimensional accuracy of the material, and improving the sheet shape of the silicon steel strip. The ceramic plate has excellent heat insulation performance, which can ensure that the silicon steel ultra-thin strip is heated evenly during annealing, helping to evenly release the internal stress of the silicon steel ultra-thin strip and reducing the residual stress after annealing; b) Preventing oxidation: The porous design on the ceramic plate allows the annealing atmosphere to fully contact the sample, preventing oxidation and improving the surface quality; c) Reducing iron loss and increasing magnetic induction: The ceramic plate can make the silicon steel ultra-thin strip be heated evenly during annealing treatment, helping to reduce iron loss and increase magnetic induction; (d) Simple and easy to operate: Directly using the ceramic plate to clamp the sample, the clamping and unloading processes of the sample are very simple and convenient, and excellent annealing effects can be obtained without additional tooling fixtures.

[0047] In some preferred embodiments, a porous ceramic plate is used to clamp the sample from above and below, and then the sample together with the ceramic plate is placed in a container with an open top. During annealing treatment, the container is moved through a transfer device in a vacuum tube furnace, and the sample can be conveniently moved between the heat preservation zone and the cooling zone while ensuring the positions of the ceramic plate and the sample are fixed. Exemplarily, the container with an open top includes but is not limited to a tray. Exemplarily, the transfer device includes but is not limited to a conveyor belt and a push rod.

[0048] In some preferred embodiments, using a ceramic plate with appropriate thickness, pore diameter, and porosity to clamp the sample from above and below for annealing treatment is beneficial to obtaining the best annealing treatment effect.

[0049] Preferably, the thickness of the ceramic plate is 8 mm to 20 mm, the pore diameter size of the ceramic plate is 80 μm to 150 μm, and the porosity of the ceramic plate is 16% to 22%.

[0050] More preferably, the thickness of the ceramic plate is 10 mm to 20 mm, the pore size of the ceramic plate is 90 μm to 120 μm, and the porosity of the ceramic plate is 18% to 20%.

[0051] Exemplarily, the thickness of the ceramic plate is 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, the pore size of the ceramic plate is 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, and the porosity of the ceramic plate is 18.0%, 18.4%, 18.6%, 18.8%, 19.0%, 19.4%, 19.6%, 20.0%.

[0052] Using the ceramic plates with the above-preferred thickness, pore size, and porosity to sandwich the sample for annealing treatment is beneficial to obtaining the best annealing treatment effect and ensuring sufficient contact between the annealing atmosphere and the sample; specifically, (a) the thickness of the ceramic plate: a ceramic plate with a suitable thickness can effectively conduct heat, ensure uniform heating of the ultra-thin silicon steel strip during annealing, reduce thermal stress and the risk of potential cracks, and a suitable thickness can provide sufficient downward pressure and upward support for the ultra-thin silicon steel strip to prevent it from deforming, bending, or wrinkling at high temperatures; (b) the pore size of the ceramic plate: if the pores are too small, the annealing atmosphere cannot fully contact the ultra-thin silicon steel strip, and if the pores are too large, the stress is uneven; a suitable pore size can ensure full contact between the annealing atmosphere and the surface of the ultra-thin silicon steel strip, effectively prevent oxidation and other unwanted chemical reactions, and at the same time make the stress on the surface of the ultra-thin silicon steel strip uniform, reducing the risk of stress concentration and deformation; (c) the porosity of the ceramic plate: if the porosity is too low, the annealing atmosphere cannot fully contact the ultra-thin silicon steel strip; if the porosity is too high, the stress is uneven, and the ceramic plate may not provide sufficient downward pressure and upward support for the ultra-thin silicon steel strip to control deformation; a suitable porosity can ensure the flow of the annealing atmosphere in the pores of the ceramic plate, timely replenish the fresh annealing atmosphere, help the annealing atmosphere to evenly cover the ultra-thin silicon steel strip, and reduce the risk of oxidation and other surface defects; a suitable porosity can accelerate the heating and cooling processes, shorten the annealing cycle, and improve production efficiency.

[0053] Optionally, in step S1, the inert gas includes one or a combination of nitrogen and argon. Preferably, the inert gas is nitrogen.

[0054] Preferably, in step S1, the main steps of the vacuum treatment include evacuating the vacuum tube furnace to make the vacuum degree in the furnace Pa ≤ 150 Pa.

[0055] Preferably, in step S2, the thickness of the non-oriented ultra-thin silicon steel strip is 50 μm to 70 μm. Exemplarily, the thickness of the non-oriented ultra-thin silicon steel strip is 50 μm, 55 μm, 60 μm, 65 μm, 70 μm.

[0056] Optionally, the chemical composition of the non-oriented silicon steel ultra-thin strip is, by mass percentage, Si: 2.8% - 4.0%, and the rest is Fe and unavoidable impurities. In some preferred embodiments, the Si content is 3.0%, 3.2%, 3.4%, 3.6%, 3.8%.

[0057] It can be understood that in step S2, the main steps of the planar flow casting method include: melting the alloy raw materials into molten steel, and the molten steel flows through a flat slit onto a rapidly rotating copper roll for rapid cooling and ejection to obtain an alloy thin strip.

[0058] Preferably, the reducing gas is hydrogen.

[0059] It should be noted that in steps S2 and S3, the annealing temperature is 950°C - 1050°C. Exemplarily, the annealing temperature is 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C. Preferably, the annealing temperature is 1000°C - 1050°C.

[0060] It can be understood that in step S3, during the annealing process of the silicon steel ultra-thin strip, using a mixed gas of inert gas and reducing gas can bring the following benefits: (1) Prevent oxidation: Inert gases such as nitrogen or argon have good chemical inertness, and they will not chemically react with silicon steel, and can be used as a protective atmosphere to prevent silicon steel from oxidizing at high temperatures; (2) Improve magnetic properties: The reducing property of reducing gases such as hydrogen can reduce the scale on the surface of the silicon steel ultra-thin strip, ensuring the surface quality. At the same time, compared with inert gases such as nitrogen, reducing gases such as hydrogen are more conducive to reducing the proportion of harmful {111} oriented grains in the silicon steel ultra-thin strip, reducing iron loss, and increasing magnetic induction. Especially in high-frequency applications, reducing iron loss and increasing magnetic induction intensity are beneficial to energy conservation and consumption reduction, and improving equipment performance; (3) Improve production efficiency and yield: Using a mixed gas can accelerate the annealing speed, shorten the production cycle, and improve production efficiency; by precisely controlling the proportion of the annealing atmosphere, material defects caused by oxidation or other chemical reactions can be reduced, and the yield can be improved.

[0061] Optionally, in step S3, the proportion of the mixed gas can be adjusted as needed to control the oxidation-reduction property of the annealing atmosphere, optimize the annealing conditions, and improve the performance of the silicon steel ultra-thin strip.

[0062] Preferably, in step S3, the volume ratio K of the reducing gas in the vacuum tube furnace to the annealing atmosphere is ≥ 50%.

[0063] It should be noted that by using an annealing atmosphere with a relatively high proportion of reducing gas (K≥50%), the comprehensive properties of the ultra-thin strip of non-oriented electrical steel can be further effectively improved, including: reducing iron loss, increasing magnetic induction, improving surface quality, flatness, etc. Specifically, a) Reducing iron loss: Using an annealing atmosphere with a relatively high proportion of reducing gas can effectively reduce the oxidation phenomenon, thereby reducing the iron loss of the ultra-thin strip of silicon steel. Especially in high-frequency applications, reducing oxidation can reduce eddy current loss, and thus reduce the iron loss; b) Improving comprehensive magnetic properties: Using an annealing atmosphere with a relatively high proportion of reducing gas helps to improve the comprehensive magnetic properties of the ultra-thin strip of silicon steel. By reducing the negative impact of oxidation on grain orientation and microstructure, the magnetic permeability is increased and the hysteresis loss is reduced; c) Improving surface quality and preventing oxidation: A higher proportion of reducing gas can prevent the surface of the ultra-thin strip of silicon steel from oxidizing during annealing, thereby improving the surface quality and reducing the scale and decarburization phenomenon; d) Improving flatness and reducing stress: The annealing treatment under a higher proportion of reducing atmosphere can reduce the internal stress of the material, and reducing oxidation can reduce the surface non-uniformity, which helps to improve the flatness of the ultra-thin strip of silicon steel.

[0064] The higher the ratio of reducing gas (such as hydrogen) to inert gas (such as nitrogen), the greater the positive impact on the comprehensive properties (such as iron loss, magnetic induction, flatness and surface quality) of the ultra-thin strip of silicon steel during annealing, which helps to produce ultra-thin strips of silicon steel with better performance.

[0065] It should be noted that considering the safety issues when the proportion of reducing gas (such as hydrogen) is relatively high (for example, K≥50%), the present invention can ensure safety and operability while improving the magnetic induction of the ultra-thin strip of silicon steel, reducing iron loss, improving flatness and surface quality by adopting a preferred annealing device (vacuum tube furnace) and combining with a preferred operation sequence (the operation sequence and steps described in S1-S4), which has important industrial application value for the production of high-quality ultra-thin strips of silicon steel.

[0066] A. Using a vacuum tube furnace can bring the following beneficial effects: a) The vacuum tube furnace has an over-temperature protection function and can precisely control the pressure inside the furnace, thus avoiding safety problems caused by high temperature and high pressure. The vacuum tube furnace is equipped with a gas leakage detection (such as a hydrogen detection device) and a flame detection and alarm system, which can timely detect and handle potential safety problems; b) Due to the good sealing performance of the vacuum tube furnace, the mixing ratio of reducing gas and inert gas in the annealing atmosphere can be precisely controlled, optimizing the annealing process while ensuring safety.

[0067] B. Adopting the preferred operation sequence (the specific steps described in S1-S4) can ensure safety and operation feasibility, improve the magnetic induction of the ultra-thin strip of silicon steel, reduce iron loss, improve surface quality and flatness; specifically:

[0068] a) In steps S1 and S2, first introduce an inert gas to ensure that the pressure inside the furnace is always positive. After opening the furnace door to place the sample and then closing the furnace door, introduce a reducing gas (such as hydrogen). This can prevent the danger brought by the reducing gas (such as hydrogen) because there is a potential safety hazard of explosion if the furnace door is opened when introducing the reducing gas (such as hydrogen).

[0069] b) In steps S2 and S3, first place the sample in the cooling zone and introduce a reducing gas (such as hydrogen) for a period of time to effectively ensure that when the sample enters the insulation zone, the ratio of the reducing gas to the inert gas inside the furnace has reached stability. This avoids directly placing the sample in the insulation zone where the ratio of the reducing gas is insufficient, which may cause the sample to oxidize at a relatively high temperature, thereby improving the surface quality.

[0070] c) In step S4, after annealing, first stop introducing the reducing gas (such as hydrogen) and only introduce the inert gas. Wait until the reducing gas is completely exhausted before opening the furnace door. This can prevent the danger brought by the reducing gas (such as hydrogen) because there is a potential safety hazard of explosion if the furnace door is opened when the reducing gas (such as hydrogen) inside the furnace has not been completely exhausted. Introducing the inert gas during the cooling process can prevent oxidation during cooling. At the same time, by controlling the flow rate of the inert gas, the cooling rate can be precisely controlled to reduce the thermal stress and residual stress caused by too fast cooling rate of the ultra-thin silicon steel strip, avoiding cracks or deformation, and thus improving the flatness and surface quality.

[0071] It should be noted that in step S3, the annealing treatment time is 1.0 h to 1.8 h. Exemplarily, the annealing treatment time is 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h. Preferably, the annealing treatment time is 1.2 h to 1.8 h. More preferably, the annealing treatment time is 1.4 h to 1.6 h.

[0072] It should be noted that in steps S2 and S3, by adopting the above-mentioned preferred annealing temperature and annealing treatment time with synergistic effects, the comprehensive performance of the ultra-thin silicon steel strip can be significantly improved. For example, the iron loss can be reduced, the magnetic induction can be increased, the deformation and stress can be reduced, and the flatness and surface quality can be improved. Specifically, (a) Reducing iron loss: By adopting the above-mentioned preferred annealing temperature and time, an ideal grain size can be obtained, which helps to reduce iron loss (especially high-frequency iron loss); if the annealing temperature is too low or the annealing time is too short, incomplete recrystallization may occur, resulting in an increase in iron loss; while if the annealing temperature is too high or the annealing time is too long, the grains may become coarse, increasing the iron loss. (b) Increasing magnetic induction: By adopting the above-mentioned preferred annealing temperature and time, the proportion of favorable {100}-oriented grains in the ultra-thin silicon steel strip can be increased, and the proportion of harmful {111}-oriented grains can be reduced, thereby increasing the magnetic induction. (c) Reducing deformation and stress and improving flatness / shape: By adopting the above-mentioned preferred annealing temperature and time, the internal stress generated during the processing (such as the process of manufacturing ultra-thin silicon steel strip by the planar flow casting method) can be effectively reduced or eliminated, thereby preventing the deformation of the material; adopting an appropriate annealing temperature and time helps to promote the recrystallization process inside the material, restore the microstructure of the material, thereby reducing stress and maintaining the flatness of the material, and obtaining an ideal shape. (d) Improving surface quality: By adopting the above-mentioned preferred annealing temperature and time, it helps to obtain a uniformly grown grain structure, reduce defects in the material such as cracks and pores, and further improve the surface quality and material uniformity.

[0073] Preferably, in step S4, the cooling time T≥6 min. More preferably, the cooling time T≥8 min. By adopting the above-mentioned preferred cooling time, it can ensure that the sample sandwiched between the ceramic plates is fully cooled, avoiding oxidation after the sample is taken out.

[0074] If the cooling time in the furnace is too short and the ultra-thin silicon steel strip fails to reach room temperature in time, it will react with the air when taken out, forming an oxide film on the surface, resulting in a decline in its magnetic properties, especially an increase in iron loss.

[0075] Preferably, in step S4, the cooling rate is 1.8 °C / s to 3 °C / s. More preferably, the cooling rate is 2.0 °C / s to 2.5 °C / s.

[0076] By adopting the above-mentioned preferred cooling rate, the comprehensive properties of the ultra-thin silicon steel strip can be significantly improved. For example, the iron loss can be reduced, the magnetic induction can be increased, the deformation and stress can be decreased, and the flatness and surface quality can be enhanced. Specifically, (a) reducing the iron loss: By adopting the above-mentioned preferred cooling rate, it helps to ensure the formation of a uniform microstructure during the cooling process of the ultra-thin silicon steel strip, reduce the hindrance to the movement of magnetic domain walls, thereby reducing the iron loss, and avoiding internal stress and tissue defects caused by too fast or too slow cooling rates. These defects may increase the hysteresis loss and eddy current loss, resulting in an increase in iron loss; (b) increasing the magnetic induction: By adopting the above-mentioned preferred cooling rate, it can ensure the formation of the desired microstructure and texture during the cooling process of the ultra-thin silicon steel strip, thereby increasing the magnetic induction; (c) improving the flatness / shape and surface quality: By adopting the above-mentioned preferred cooling rate, it can ensure that the temperature of the material drops uniformly at a relatively appropriate speed during the cooling process, reduce the internal stress caused by the temperature difference, thereby reducing the risk of deformation, help maintain the uniformity of the material microstructure, avoid stress concentration in local areas due to too fast cooling, and also help the uniform progress of the recrystallization process inside the material, reduce the internal stress difference caused by uneven recrystallization, be conducive to maintaining the flatness of the ultra-thin silicon steel strip, obtaining an ideal shape, reducing defects such as microcracks, and improving the surface quality.

[0077] Preferably, in steps S1 - S4, the flow rate of the inert gas is 0 L / min to 7 L / min, and the flow rate of the reducing gas is 1.5 L / min to 5 L / min. By controlling the flow rates of the inert gas and the reducing gas, the proportion of the annealing atmosphere inside the vacuum tube furnace is regulated, so that the sample is in a stable annealing atmosphere, effectively protecting the sample from oxidation and contamination during the annealing process, and maintaining a positive pressure inside the vacuum tube furnace. Specifically, in S2 and S3, by controlling the flow rates of the inert gas and the reducing gas, it is ensured that the volume ratio of the reducing gas in the annealing atmosphere (the mixed gas of the reducing gas and the inert gas) meets the set value K.

[0078] It is understandable that maintaining a positive pressure inside the vacuum tube furnace means maintaining a pressure level higher than the atmospheric pressure inside the furnace. With such a setting, for the annealing treatment of ultra-thin silicon steel strips, it has at least the following beneficial effects: (a) Improving safety: When a reducing gas (such as hydrogen) is used in the protective atmosphere, maintaining a positive pressure can prevent the reducing gas (such as hydrogen) from mixing with air and avoid the risks of explosion and fire. This is particularly important when the proportion of hydrogen is relatively high; (b) Improving magnetic induction: By maintaining a constant positive-pressure protective atmosphere, the oxidation of ultra-thin silicon steel strips during annealing can be minimized, which helps to improve their magnetic induction; (c) Reducing iron loss: The uniform atmosphere under positive pressure helps to reduce the oxidation of ultra-thin silicon steel strips, thereby reducing iron loss, especially reducing high-frequency iron loss; (d) Improving flatness: Positive pressure and an appropriate gas flow rate within a certain range help to reduce the uneven pressure of the furnace atmosphere on the ultra-thin silicon steel strip, thereby reducing deformation or stress concentration caused by uneven atmospheric pressure and helping to maintain the flatness and shape of the ultra-thin silicon steel strip; (e) Improving surface quality: The protective atmosphere under positive pressure can effectively isolate air, reduce the oxidation of ultra-thin silicon steel strips at high temperatures, and other surface defects such as cracks and pores, thereby improving the surface quality of the annealed samples.

[0079] Preferably, an inert gas (such as nitrogen) and a reducing gas (such as hydrogen) are introduced into the cylindrical furnace chamber of the vacuum tube furnace from one side, which can provide a uniform and stable atmosphere protection for the annealing treatment of ultra-thin silicon steel strips and ensure the safety and efficiency of the annealing process; specifically, it can bring at least the following beneficial effects: (a) Precise control: Introducing from one side can more easily concentrate the control of the gas flow rate and facilitate the precise control of the ratio of the two gases; (b) Simple operation: Introducing from one side can reduce equipment costs and operation complexity; (c) Improving annealing uniformity: Introducing gas from one side helps to optimize the gas flow pattern inside the furnace. Especially in a cylindrical furnace chamber, natural convection of the gas can be utilized to achieve uniform heating; (d) Improving safety: When the proportion of the reducing gas (such as hydrogen) is relatively high, introducing from one side helps to better control the distribution of hydrogen and reduce the risk of hydrogen leakage.

[0080] It should be noted that in S4, the main steps of "after the reducing gas in the vacuum tube furnace is exhausted" include: determining whether it is exhausted through a reducing gas (such as hydrogen) detection device equipped in the vacuum tube furnace.

[0081] The technical solutions of the present invention will be further described in detail below with specific examples and comparative examples.

[0082] Example 1:

[0083] This example provides a method for annealing an Fe-3% Si non-oriented ultra-thin silicon steel strip, including the following steps:

[0084] S1. Evacuate the vacuum tube furnace to make the vacuum degree in the furnace Pa < 100 Pa, introduce nitrogen with a flow rate of 6 L / min, and then heat up the insulation area in the vacuum tube furnace at a heating rate of 20 °C / min;

[0085] Among them, the manufacturer of the vacuum tube furnace is Luoyang Juxing Kiln Furnace Co., Ltd., and the model is GWL-1200GA.

[0086] S2. When the insulation area reaches the preset annealing temperature of 1000 °C, sandwich the sample with a ceramic plate with micro-leak sintered micropores up and down and place it on a tray; among them, the thickness of the ceramic plate is 10 mm, the pore size of the ceramic plate is 100 μm, and the porosity of the ceramic plate is 18.6%.

[0087] Open the furnace door of the vacuum tube furnace, place the tray containing the sample and the ceramic plate in the cooling area of the vacuum tube furnace, close the furnace door, introduce hydrogen with a flow rate of 4 L / min, and both hydrogen and nitrogen are introduced into the furnace from one side of the cylindrical furnace chamber of the vacuum tube furnace.

[0088] Among them, the sample is an non-oriented silicon steel ultra-thin strip obtained by the planar flow casting method. The thickness of the non-oriented silicon steel ultra-thin strip is 65 μm. The chemical composition of the sample is Si: 3% by mass percentage, and the rest is Fe and inevitable impurities.

[0089] S3. When the volume ratio K of hydrogen in the annealing atmosphere in the vacuum tube furnace reaches 40% and the annealing atmosphere is stable, use the push rod equipped in the vacuum tube furnace to push the tray containing the sample and the ceramic plate to the insulation area, and perform annealing treatment at 1000 °C for 1.5 h;

[0090] Among them, the annealing atmosphere is set as a mixed gas of hydrogen and nitrogen;

[0091] S4. After the annealing is completed, use the push rod equipped in the vacuum tube furnace to push the tray containing the sample and the ceramic plate to the cooling area, cool for 6 min, and the cooling rate is 2 °C / s. During the cooling process, stop introducing hydrogen and only introduce nitrogen. Detect the atmosphere in the furnace through the hydrogen detection device on the vacuum tube furnace. After confirming that the hydrogen is exhausted from the vacuum tube furnace, open the furnace door, take out the tray (together with the sample and the ceramic plate inside), open the upper ceramic plate pressing on it, and take down the sample.

[0092] Example 2

[0093] The difference between this example and Example 1 is that in S1, the flow rate of nitrogen is 7 L / min; in S2, the flow rate of hydrogen is 3 L / min; in S3, K is 30%; other steps and parameters are the same as those in Example 1.

[0094] Example 3

[0095] This embodiment is different from Embodiment 1 in that in S1, the flow rate of nitrogen is 5 L / min; in S2, the flow rate of hydrogen is 5 L / min; in S3, K is 50%; other steps and parameters are the same as those in Embodiment 1.

[0096] Embodiment 4

[0097] This embodiment is different from Embodiment 1 in that in S1, the flow rate of nitrogen is 2.8 L / min; in S2, the flow rate of hydrogen is 4.2 L / min; in S3, K is 60%; other steps and parameters are the same as those in Embodiment 1.

[0098] Embodiment 5

[0099] This embodiment is different from Embodiment 1 in that in S1, the flow rate of nitrogen is 1.8 L / min; in S2, the flow rate of hydrogen is 4.2 L / min; in S3, K is 70%; other steps and parameters are the same as those in Embodiment 1.

[0100] Embodiment 6

[0101] This embodiment is different from Embodiment 1 in that in S1, the flow rate of nitrogen is 1.2 L / min; in S2, the flow rate of hydrogen is 4.8 L / min; in S3, K is 80%; other steps and parameters are the same as those in Embodiment 1.

[0102] Embodiment 7

[0103] This embodiment is different from Embodiment 1 in that in S1, the flow rate of nitrogen is 0.5 L / min; in S2, the flow rate of hydrogen is 4.5 L / min; in S3, K is 90%; other steps and parameters are the same as those in Embodiment 1.

[0104] Embodiment 8

[0105] This embodiment is different from Embodiment 1 in that in S2, the annealing temperature is 950 °C; other steps and parameters are the same as those in Embodiment 1.

[0106] Embodiment 9

[0107] This embodiment is different from Embodiment 1 in that in S2, the annealing temperature is 980 °C; other steps and parameters are the same as those in Embodiment 1.

[0108] Embodiment 10

[0109] This embodiment is different from Embodiment 1 in that in S2, the annealing temperature is 1020 °C; other steps and parameters are the same as those in Embodiment 1.

[0110] Embodiment 11

[0111] This embodiment is different from Embodiment 1 in that in S2, the annealing temperature is 1050°C; other steps and parameters are the same as those in Embodiment 1.

[0112] Embodiment 12

[0113] This embodiment is different from Embodiment 1 in that in S3, the annealing treatment time is 1.0 h; other steps and parameters are the same as those in Embodiment 1.

[0114] Embodiment 13

[0115] This embodiment is different from Embodiment 1 in that in S3, the annealing treatment time is 1.2 h; other steps and parameters are the same as those in Embodiment 1.

[0116] Embodiment 14

[0117] This embodiment is different from Embodiment 1 in that in S3, the annealing treatment time is 1.4 h; other steps and parameters are the same as those in Embodiment 1.

[0118] Embodiment 15

[0119] This embodiment is different from Embodiment 1 in that in S3, the annealing treatment time is 1.6 h; other steps and parameters are the same as those in Embodiment 1.

[0120] Embodiment 16

[0121] This embodiment is different from Embodiment 1 in that in S3, the annealing treatment time is 1.8 h; other steps and parameters are the same as those in Embodiment 1.

[0122] Embodiment 17

[0123] This embodiment is different from Embodiment 1 in that in S4, the cooling time is 8 min; other steps and parameters are the same as those in Embodiment 1.

[0124] Embodiment 18

[0125] This embodiment is different from Embodiment 1 in that in S4, the cooling time is 10 min; other steps and parameters are the same as those in Embodiment 1.

[0126] Embodiment 19

[0127] This embodiment is different from Embodiment 1 in that in S4, the cooling rate is 1.8 °C / s; other steps and parameters are the same as those in Embodiment 1.

[0128] Embodiment 20

[0129] This embodiment is different from Embodiment 1 in that in S4, the cooling rate is 2.5 °C / s; other steps and parameters are the same as those in Embodiment 1.

[0130] Embodiment 21

[0131] This embodiment is different from Embodiment 1 in that in S4, the cooling rate is 3.0 °C / s; other steps and parameters are the same as those in Embodiment 1.

[0132] Comparative Example 1

[0133] This comparative example is different from Embodiment 1 in that in S2-S4, a ceramic plate is not used to clamp the sample; other steps and parameters are the same as those in Embodiment 1.

[0134] Comparative Example 2

[0135] This comparative example is different from Embodiment 1 in that in S3, the annealing atmosphere is only nitrogen; other steps and parameters are the same as those in Embodiment 1.

[0136] Comparative Example 3

[0137] This comparative example is different from Embodiment 1 in that in S1, the flow rate of nitrogen is 8.0 L / min; in S2, the flow rate of hydrogen is 2.0 L / min; in S3, the volume ratio K of hydrogen in the annealing atmosphere is 20%; other steps and parameters are the same as those in Embodiment 1.

[0138] Comparative Example 4

[0139] This comparative example is different from Embodiment 1 in that in S2, the preset annealing temperature is 900 °C; other steps and parameters are the same as those in Embodiment 1.

[0140] Comparative Example 5

[0141] This comparative example is different from Embodiment 1 in that in S2, the preset annealing temperature is 1100 °C; other steps and parameters are the same as those in Embodiment 1.

[0142] Comparative Example 6

[0143] This comparative example is different from Embodiment 1 in that in S3, the annealing treatment time is 0.8 h; other steps and parameters are the same as those in Embodiment 1.

[0144] Comparative Example 7

[0145] This comparative example is different from Embodiment 1 in that in S3, the annealing treatment time is 2.0 h; other steps and parameters are the same as those in Embodiment 1.

[0146] Comparative Example 8

[0147] This comparative example is different from Embodiment 1 in that in S4, the cooling time is 5 min; other steps and parameters are the same as those in Embodiment 1.

[0148] Comparative Example 9

[0149] The difference between this comparative example and Example 1 is that in S4, the cooling rate is 1.5 °C / s; other steps and parameters are the same as those in Example 1.

[0150] Comparative Example 10

[0151] The difference between this comparative example and Example 1 is that in S4, the cooling rate is 3.5 °C / s; other steps and parameters are the same as those in Example 1.

[0152] Comparative Example 11

[0153] The difference between this comparative example and Example 1 is that in S2, the thickness of the ceramic plate is 6 mm; other steps and parameters are the same as those in Example 1.

[0154] Comparative Example 12

[0155] The difference between this comparative example and Example 1 is that in S2, the pore diameter of the ceramic plate is 70 μm; other steps and parameters are the same as those in Example 1.

[0156] Comparative Example 13

[0157] The difference between this comparative example and Example 1 is that in S2, the porosity of the ceramic plate is 24%; other steps and parameters are the same as those in Example 1.

[0158] To more clearly show the parameter variables of the above examples and comparative examples, see Table 1. By performing performance tests and quality inspections on the non-oriented silicon steel ultra-thin strips obtained by annealing treatment in Examples 1-21 and Comparative Examples 1-13, the performance results shown in Table 2 are obtained.

[0159] As can be seen from Table 2, in Examples 1-21, by using the annealing treatment method provided by the present invention, the grain size can be uniformly increased to a suitable size, and the proportion of favorable {100}-oriented grains can be increased (by more than 10%), and the proportion of harmful {111}-oriented grains can be reduced (by more than 20%). The embodiments of the present invention can complete annealing at one time by using a simple "one-step" annealing process, ensuring flatness and no oxidation on the surface, and having a low cost (due to the low addition amount of silicon content and no addition of expensive trace elements). The non-oriented silicon steel ultra-thin strips obtained have excellent comprehensive performance. Especially compared with the silicon steel strips for high-frequency application fields obtained by existing annealing methods, the present invention has a higher magnetic induction (B 5000 ≥1.66 T), and a smaller high-frequency iron loss (P 1.0 / 1000Hz ≤40 W / kg), which is of great significance for energy conservation and consumption reduction and improving equipment performance. With the development of information technology and high-frequency power electronics technology, the demand for high-performance silicon steel that can work stably in a high-frequency environment is increasing day by day. The annealing treatment method provided by the present invention can obtain silicon steel ultra-thin strips with high magnetic induction and low iron loss at high frequencies, which just meets this demand and has great industrial application prospects and value.

[0160] It can also be seen from Table 2 that, in contrast, the microstructures and comprehensive properties of Comparative Examples 1-13 are inferior to those of Examples 1-21;

[0161] (a) In Comparative Example 1, since the porous ceramic plate was not used to press the sample, after annealing the sample, the plate shape / flatness and surface quality were poor.

[0162] (b) In Comparative Example 2, since only nitrogen was used in the annealing process and hydrogen was not mixed, after annealing the sample, an obvious oxide film appeared on the surface, and the degree of grain growth was also lower than that of the method provided in the examples of the present invention. The magnetic induction measured in Comparative Example 2 was low.

[0163] (c) In Comparative Example 3, since the preferred proportion of reducing gas provided by the present invention was not adopted, after annealing the sample, an oxide film appeared on the surface to a certain extent. The proportion of beneficial {100}-oriented grains was lower than that of the method provided by the present invention, and the proportion of harmful {111}-oriented grains was higher than that of the method provided by the present invention. The magnetic induction measured in Comparative Example 3 was low and the iron loss was high.

[0164] (d) In Comparative Examples 4-10, since the preferred annealing temperature, annealing time, cooling time, and cooling rate with synergistic effects provided by the present invention were not adopted, after annealing the sample, the magnetic induction measured in Comparative Examples 4-10 was low and / or the iron loss was high.

[0165] (e) In Comparative Examples 11-13, since the ceramic plates with the preferred thickness, pore diameter, and porosity provided by the present invention were not adopted, after annealing the sample, the magnetic induction measured in Comparative Examples 11-13 was low and / or the iron loss was high.

[0166] Table 1: Specific process parameters in Examples 1-21 and Comparative Examples 1-13

[0167]

[0168]

[0169] Table 2: Performance results of non-oriented silicon steel ultra-thin strips obtained after annealing in Examples 1-21 and Comparative Examples 1-13

[0170]

[0171]

[0172]

[0173] As described above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any change or substitution that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An annealing treatment method for an non-oriented silicon steel ultra-thin strip, characterized in that, It includes the following steps: S1. Conduct vacuum treatment on the vacuum tube furnace, introduce inert gas, and then heat up the heat preservation zone in the vacuum tube furnace; S2. When the heat preservation zone reaches the preset annealing temperature, place the sample into the cooling zone in the vacuum tube furnace from the furnace door of the vacuum tube furnace, close the furnace door, and introduce reducing gas; Among them, the sample is an non-oriented silicon steel ultra-thin strip obtained by the planar flow casting method, which is directly annealed without temper rolling; the chemical composition of the non-oriented silicon steel ultra-thin strip is Si: 2.8% - 4.0% by mass percentage, and the rest are Fe and inevitable impurities; S3. When the volume ratio K of the reducing gas in the vacuum tube furnace to the annealing atmosphere ≥ 30%, push the sample to the heat preservation zone and conduct annealing treatment at the annealing temperature; Among them, the annealing atmosphere is set as a mixed gas of reducing gas and inert gas; In steps S2 and S3, the annealing temperature is 1000°C - 1050°C; in step S3, the annealing treatment time is 1.2 h - 1.8 h; S4. After annealing, push the sample to the cooling zone for cooling, the cooling time T ≥ 8 min, and the cooling rate is 2.0°C / s - 2.5°C / s; stop introducing reducing gas during the cooling process, only introduce inert gas, determine whether it is completely exhausted through the reducing gas detection device equipped in the vacuum tube furnace, and after the reducing gas is completely exhausted from the vacuum tube furnace, open the furnace door and take out the sample; During the whole process of steps S2 to S4, the sample is clamped up and down by a porous ceramic plate, and then the sample together with the ceramic plate is placed in a container with an open upper part. During the annealing treatment, the container is moved through the transmission device in the vacuum tube furnace, and the sample is moved between the heat preservation zone and the cooling zone while ensuring the fixed positions of the ceramic plate and the sample; the porous ceramic plate is a ceramic plate with micro-leakage sintered micropores, and the ceramic plate with micro-leakage sintered micropores is a porous ceramic material with micron or sub-micron level pore diameters; the thickness of the ceramic plate is 10 mm - 20 mm, the pore diameter size of the ceramic plate is 90 μm - 120 μm, and the porosity of the ceramic plate is 18% - 20%.

2. The annealing treatment method according to claim 1, characterized in that, The thickness of the ceramic plate is 12 mm - 18 mm, the pore diameter size of the ceramic plate is 95 μm - 110 μm, and the porosity of the ceramic plate is 18.4% - 19.6%.

3. The annealing treatment method according to claim 1, characterized in that In S3, the volume ratio K of the reducing gas in the vacuum tube furnace to the annealing atmosphere ≥ 50%.

4. The annealing treatment method according to claim 1, characterized in that, In S2 and S3, the annealing temperature is 1020°C - 1050°C.

5. The annealing treatment method according to claim 1, characterized in that, In S3, the annealing treatment time is 1.4 h - 1.6 h.

6. The annealing treatment method according to claim 1, characterized in that The flow rate of the inert gas is 0 L / min - 7 L / min, and the flow rate of the reducing gas is 1.5 L / min - 5 L / min; by controlling the flow rates of the inert gas and the reducing gas, the proportion of the annealing atmosphere inside the vacuum tube furnace is regulated to maintain positive pressure inside the vacuum tube furnace.

7. The annealing treatment method according to claim 1, characterized in that, The chemical composition of the non-oriented silicon steel ultra-thin strip is Si: 3.0% - 3.8% by mass percentage, and the rest are Fe and inevitable impurities; and / or, In S1, the main steps of the vacuum treatment include evacuating the vacuum tube furnace so that the vacuum degree in the furnace Pa ≤ 150 Pa.

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