An annealing process for an extremely thin oriented electrical steel laminated core

Abstract

The application discloses an annealing process for an extremely thin oriented electrical steel strip core, and belongs to the technical field of extremely thin oriented electrical steel. The application is aimed at the extremely thin oriented electrical steel strip core with different steel belt thicknesses, eliminates the damage of stress to the texture and grains of the oriented electrical steel thin strip by synergistically regulating the heating speed, annealing temperature, annealing time and cooling speed, restores the Goss texture and grain size of the oriented electrical steel thin strip, obtains the strip core with excellent magnetic properties, and is beneficial to realizing the excellent magnetic properties of the oriented electrical steel extremely thin strip core with different steel belt thicknesses.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of extremely thin oriented electrical steel, and particularly relates to an annealing process for an extremely thin oriented electrical steel coil core. BACKGROUND

[0002] The extremely thin oriented electrical steel with a thickness of less than or equal to 0.1 mm is mainly applied to the cores of medium and high frequency electrical appliances, and the medium and high frequency magnetic elements are the key to realizing large capacity and compactness of high-power power electronic equipment. Therefore, it is an important development direction of the core to use the extremely thin oriented electrical steel strip with a thickness of less than or equal to 0.1 mm to make a coil core and apply it to the core of a medium and high frequency electrical appliance.

[0003] During the manufacturing process of the coil core, stress will be generated in the transportation, shearing and winding links of the electrical steel strip, and the loss will increase sharply. Therefore, after the winding of the core is completed, stress relief annealing treatment is generally required to restore the inherent electromagnetic properties of the electrical steel strip, so that there is no high magnetic resistance in each part of the magnetic circuit, so as to reduce the no-load loss and excitation current.

[0004] The patent with the patent publication number CN116042972A discloses a coil core annealing process, which uses a vacuum horizontal annealing furnace for stress relief annealing. The vacuum degree is controlled at -0.1 - 0.5 MPa, the resistance strip is heated to 600 ℃ at a speed of 150-200 ℃ / h, and the temperature is maintained for 30-60 min; the temperature is raised to 800 ℃ at a speed of 30-50 ℃ / h, and the temperature is maintained for 60-90 min, and then the furnace is cooled from 800 ℃ to 400 ℃ and discharged. The process is for the coil core of the conventional thickness of the steel strip, and is not applicable to the coil core with a thickness of less than or equal to 0.1 mm.

[0005] The patent with the patent publication number CN101599358A discloses a processing method for a silicon steel thin strip core of a direct current transmission and transformation high frequency reactor. The silicon steel strip with a thickness of less than or equal to 0.08 mm is wound into a core, and then the core is vacuum annealed. The vacuum degree is -2 MPa, the heating temperature is 820 ± 5 ℃, the temperature rising speed is 150 ℃ / h, the constant temperature time is 5-8 hours, the temperature decreasing speed of the thin strip core during annealing is controlled at 60 ℃ / h, and the furnace is discharged when cooled to 300 ℃.

[0006] However, the extremely thin oriented electrical steel has a thickness of less than or equal to 0.1 mm, and the thinner the thickness, the greater the influence of stress on the texture and grain structure of the steel strip, and the greater the influence of the stress relief annealing process on the organizational structure and magnetic properties of the extremely thin oriented electrical steel. Therefore, different stress relief annealing process systems need to be developed for the coil cores of the extremely thin oriented electrical steel with different thicknesses, so as to ensure the excellent magnetic properties of the core. SUMMARY

[0007] The application aims to provide an annealing process for an extremely thin oriented electrical steel coil core, and realize excellent magnetic properties of the oriented electrical steel coil core with different steel strip thicknesses.

[0008] To solve the above technical problems, the application provides the following technical solutions.

[0009] The application provides an annealing process for an extremely thin oriented electrical steel coil core, which comprises the following steps.

[0010] The extremely thin oriented electrical steel coil core with a steel strip thickness of x to be stress annealed is placed into an annealing furnace for stress relief annealing; pure nitrogen atmosphere is adopted for annealing, and the furnace is heated at a heating speed V 加 The temperature is raised to a stress relief annealing temperature T, and the holding time is t; finally, the temperature is cooled at a cooling speed V 冷 The temperature is cooled to 200-300 DEG C and discharged from the furnace, and air cooling is performed to room temperature; wherein:

[0011] The heating speed V 加 The following relationship exists between the heating speed V

[0012] 100 / e 2x + 1.1 / x ≤ V 加 ≤ 100 / e x + 1.2 / x (1)

[0013] The heating speed should not be too fast, and the inner and outer coils of the coil core should be uniformly heated. The thinner the steel strip, the faster the heating speed can be, and the efficiency can be improved; the thicker the steel strip, the slower the heating speed can be, and the inner and outer coils of the coil core can be uniformly heated. The thinner the steel strip, the faster the heat transfer speed of the steel strip, and the higher the sensitivity of the steel strip to the heating speed, so the control precision of the heating speed is also higher.

[0014] The atmosphere is pure nitrogen atmosphere, and the nitrogen atmosphere is adopted for annealing, which is beneficial to keeping the temperature of the inner and outer coils of the coil core consistent through the movement of the nitrogen atmosphere in the furnace, and beneficial to improving the magnetic properties of the coil core.

[0015] The stress relief annealing temperature T and the steel strip thickness x, the holding time t satisfy the following relationship:

[0016] 750 + 1 / x + 10000 / t ≤ T ≤ 760 + 1.5 / x + 10000 / t (2)

[0017] The thinner the steel strip, the more sensitive it is to stress of punching and shearing processing, the greater the change of texture direction caused by crystal slip, and the higher the stress relief annealing temperature should be to eliminate the influence of stress on grain and structure. The thinner the steel strip, the shorter the holding time, and the higher the stress relief annealing temperature should be. However, the stress relief annealing temperature should not be too high, otherwise it may cause the growth of non-Goss texture grains, reduce the proportion of Goss texture in the ultra-thin oriented electrical steel, and reduce the magnetic properties of the core.

[0018] The holding time t and the thickness x of the steel strip have the following relationship:

[0019] 120 + 2000 x ≤ t ≤ 120 + 2200 x (3)

[0020] The thinner the steel strip, the shorter the holding time. The thinner the steel strip, the faster the heat transfer from the surface to the center of the wound core, and the shorter holding time is beneficial to improve the production efficiency and reduce the energy consumption. The holding time cannot be too short, because the thinner the steel strip, the more obvious the grain affected by stress relief, the greater the dislocation caused by crystal slip, and the greater the change of texture direction, so enough time is needed to promote grain recovery. The holding time cannot be too long, otherwise it will lead to the growth of non-Goss texture grains, affect the proportion of Goss texture in the ultra-thin oriented electrical steel, and reduce the magnetic properties of the core.

[0021] After the stress relief annealing is completed, the core needs to be cooled and discharged, and the cooling speed of the wound core needs to be controlled properly during the cooling process to avoid too large temperature difference between the inside and outside of the wound core. At the same time, the grain size of the steel strip in the outer ring is maintained during annealing, and the grain in the inner ring will not continue to grow due to slow cooling speed, which will reduce the magnetic properties of the core.

[0022] The cooling speed V of the core 冷 and the thickness x of the steel strip and the annealing temperature T have the following relationship:

[0023] 200 / e x + 21 - 10 x lnT ≤ V 冷 ≤ 235 / e x - 10 x lnT (4)

[0024] The cooling speed of the core is related to the annealing temperature and the thickness of the steel strip. The higher the annealing temperature, the slower the cooling speed, which prevents the temperature of the outer ring from decreasing too fast while the temperature of the inner ring cannot decrease quickly enough, resulting in too large difference in grain size between the inside and outside of the wound core, and reduces the magnetic properties. The thinner the steel strip, the faster the cooling speed, because the heat transfer is faster, so the cooling speed can be appropriately increased to improve the efficiency.

[0025] The different thicknesses of the very thin strip oriented electrical steel are not consistent in the influence of shearing force, the thinner the steel strip, the greater the dislocation of the crystal slip caused by the stress, the greater the influence on the texture, and the thinner the steel strip, the greater the range of the shearing edge affected by the stress, and the more obvious the performance reduction. In the stress relief annealing process of the wound iron core, for the wound iron cores of different thicknesses of the very thin oriented electrical steel, by synergistically regulating the heating speed, annealing temperature, annealing time and cooling speed, it is beneficial to make the grains and textures of the electrical steel strips of different thicknesses return to the state before being affected by the stress, so as to restore the magnetic properties. The thinner the steel strip, the more accurate the control of the heating speed, annealing temperature, annealing time and cooling speed, the more conducive to promoting the recovery of the grains and textures of the shearing edge of the steel strip affected by the stress.

[0026] In the above relationships (1)-(4), V 加 , T, t, x and V 冷 are unitless and represent specific numerical values, where x is in units of mm, V 加 , V 冷 is in units of °C / h, T is in units of °C, and t is in units of min.

[0027] According to the above scheme, the thickness x of the steel strip is 0.03-0.1 mm.

[0028] According to the above scheme, the wound iron core to be stress annealed is a wound iron core made by shearing the very thin oriented electrical steel into strips according to the width requirement of the iron core, and then winding the strips; or a finished product wound iron core purchased directly; or an iron core obtained by shearing and processing a finished product wound iron core and then winding it.

[0029] According to the above scheme, before stress relief annealing, the magnetic induction B 800 of the wound iron core is 1.60-1.57T; and the iron loss P 1.5 / 400 is 16.3-18.5w / kg.

[0030] According to the above scheme, after stress relief annealing, the magnetic induction B 800 of the wound iron core of different steel strip thicknesses changes by 0.03T; and the iron loss P 1.5 / 400 changes by 0.8w / kg.

[0031] Preferably, after stress relief annealing, the magnetic induction B 800 of the wound iron core is 1.85-1.87T; and the iron loss P 1.5 / 400 is 9.5-10.3w / kg.

[0032] The beneficial effects of the present application are as follows:

[0033] The application provides an annealing process for an extremely thin oriented electrical steel strip core, and the extremely thin oriented electrical steel strip core with different strip thicknesses is subjected to coordinated regulation of the heating speed, annealing temperature, annealing time and cooling speed, so that the damage of stress to the texture and grain of the oriented electrical steel strip is eliminated, the Goss texture and grain size of the oriented electrical steel strip are restored, the electrical steel strip core with excellent magnetic properties is obtained, and the excellent magnetic properties of the oriented electrical steel extremely thin strip core with different strip thicknesses are realized. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0035] Embodiments 1-8

[0036] The application provides an annealing process for an extremely thin oriented electrical steel strip core, and the extremely thin oriented electrical steel strip core with different strip thicknesses is subjected to coordinated regulation of the heating speed, annealing temperature, annealing time and cooling speed, so that the damage of stress to the texture and grain of the oriented electrical steel strip is eliminated, the Goss texture and grain size of the oriented electrical steel strip are restored, the electrical steel strip core with excellent magnetic properties is obtained, and the excellent magnetic properties of the oriented electrical steel extremely thin strip core with different strip thicknesses are realized.

[0037] The extremely thin oriented electrical steel strip with a strip thickness of 0.03-0.10 mm is cut into a strip according to the core width requirement, and then the strip is wound into an electrical steel winding core; the electrical steel winding core is placed into an annealing furnace for stress relief annealing, and pure nitrogen atmosphere protection annealing is adopted; the furnace is heated at a heating speed V 加 to a stress relief annealing temperature T, and the holding time is t; finally, the temperature is cooled to 200 DEG C and discharged from the furnace, and air cooling is performed to room temperature; the specific process of the stress relief annealing is shown in Table 1, wherein: 冷

[0038] The heating speed V 加 and the strip thickness x satisfy the following relationship:

[0039] 100 / e 2x + 1.1 / x ≤ V 加 ≤ 100 / e x + 1.2 / x (1)

[0040] The heating speed V 加 in each embodiment is shown in Table 1.

[0041] The stress relief annealing temperature T and the strip thickness x and the holding time t satisfy the following relationship:

[0042] 750 + 1 / x + 10000 / t ≤ T ≤ 760 + 1.5 / x + 10000 / t (2)

[0043] The stress relief annealing temperature T in each embodiment is shown in Table 1. ​

[0044] The holding time t at the stress relief annealing temperature and the steel strip thickness x have the following relationship:

[0045] 120 + 2000 x ≤ t ≤ 120 + 2200 x (3)

[0046] The holding time t in each example is shown in Table 1.

[0047] The cooling speed V of the wound core 冷 The relationship between the cooling speed V, the steel strip thickness x and the annealing temperature T is as follows:

[0048] 200 / e x + 21 - 10 x lnT ≤ V 冷 ≤ 235 / e x - 10 x lnT (4)

[0049] The cooling speed V in each example is shown in Table 1. 冷

[0050] Cooling to 200°C and air cooling to room temperature.

[0051] The magnetic properties of the wound cores of the electrical steel before and after stress relief annealing in each example are shown in Table 2.

[0052] Comparative Example 1-2:

[0053] The wound core of the very thin oriented electrical steel after stress relief annealing was prepared according to the specific steps of the reference example, wherein the heating speed V 加 , the stress relief annealing temperature T, the holding time t at the stress relief annealing temperature and the cooling speed V 冷 of the wound core are shown in Table 1; the magnetic properties of the wound core before and after stress relief annealing in each comparative example are shown in Table 2.

[0054] Table 1. Stress relief annealing process parameters in the examples and comparative examples

[0055]

[0056] Table 2. Comparison of the magnetic properties of the wound cores before and after stress relief annealing in the examples and comparative examples

[0057]

[0058] As can be seen from Table 2, when the stress relief annealing process meets the technical solution of the present application, the magnetic induction B 800 of the wound core of the very thin oriented electrical steel is higher, the iron loss P 1.5 / 400 at high frequency is lower, the wound core of the very thin oriented electrical steel with excellent magnetic properties is obtained, and the magnetic properties are well recovered. At the same time, the change range of the magnetic properties of the wound cores of different steel strip thicknesses after annealing is small, and the B​800 The change range is 0.03T, and the iron loss P 1.5 / 400 The change range is 0.8w / kg, and the stability of the magnetic property of the wound iron core after stress relief annealing is realized under the condition of different thicknesses of the steel strip.

[0059] In the comparative example 1, the temperature rising speed does not satisfy the formula (1) proposed by the present application, the stress relief annealing temperature does not satisfy the formula (2) proposed by the present application, the temperature rising speed is too slow, the temperature is too low, the stress cannot be recovered to the displacement of the grain in the steel strip, the grain of the non-gauss texture in the steel strip is easy to be too large, the orientation degree of the gauss texture in the steel strip is reduced, and finally the magnetic induction of the wound iron core of the very thin oriented electrical steel is low, and the iron loss P 1.5 / 400 is high.

[0060] In the comparative example 2, the temperature rising speed does not satisfy the formula (1) proposed by the present application, the annealing holding time does not satisfy the formula (3) proposed by the present application, and the cooling speed does not satisfy the formula (4) proposed by the present application, the temperature rising speed is too fast, the annealing time is too short, and the cooling speed is too fast, the temperature difference between the inside and outside of the wound iron core is easy to be large, and the stress cannot be recovered to the displacement of the grain in the steel strip, and finally the magnetic induction of the wound iron core of the very thin oriented electrical steel is low, and the iron loss P 1.5 / 400 is high.

[0061] It should be understood that the above description can be improved or changed by those skilled in the art, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. An ultra-thin grain-oriented electrical steel core of a coil annealing process characterized by, The method comprises the following steps: The very thin oriented electrical steel strip core with thickness x is put into an annealing furnace for stress relief annealing, pure nitrogen atmosphere is used for annealing protection, the furnace is heated at a heating rate V 加 to a stress relief annealing temperature T, and the holding time is t; finally, the furnace is cooled at a cooling rate V 冷 to 200-300℃ and discharged, and air cooled to room temperature; wherein: the temperature increase rate V 加 The following relationship exists between the steel strip thickness x: 100 / e 2x + 1.1 / x ≤ V 加 ≤ 100 / e x + 1.2 / x(1) The stress relief annealing temperature T and the steel strip thickness x and the holding time t satisfy the following relationship: 750 + 1 / x + 10000 / t ≤ T ≤ 760 + 1.5 / x + 10000 / t (2) The holding time t and the steel strip thickness x satisfy the following relationship: 120 + 2000 × x ≤ t ≤ 120 + 2200 × x (3) The cooling speed V 冷 The following relationship exists between the steel strip thickness x and the annealing temperature T: 200 / e x + 21 - 10 × lnT≤ V 冷 ≤ 235 / e x - 10 × lnT (4) In the above relational expressions (1) to (4), x takes a value in mm, V 加 , V 冷 takes a value in °C / h, T takes a value in °C, and t takes a value in min.

2. The annealing process of claim 1, wherein, The steel strip thickness x is 0.03-0.1 mm.

3. The annealing process of claim 1, wherein, The core to be stress relieved is a core wound with an extremely thin oriented electrical steel strip which is cut into a strip according to the width requirement of the core and then wound into an electrical steel core; or a finished product core wound directly; or a finished product core wound after cutting and processing.

4. The annealing process of claim 1, wherein, The magnetic induction B of the wound core before stress relief annealing 800 was 1.60-1.57 T; the iron loss P 1.5 / 400 was 16.3-18.5 w / kg.

5. The annealing process of claim 1, wherein, Magnetic induction B of the core wound with the steel strip of different thickness after stress relief annealing 800 The change range is 0.03T, and the iron loss P 1.5 / 400 The change range is 0.8w / kg.

6. The annealing process of claim 5, wherein, After stress relief annealing, the magnetic induction B of the wound core 800 was 1.85 - 1.87 T; the iron loss P 1.5 / 400 was 9.5-10.3 w / kg.

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