阅读说明：本技术 一种磁性能优良的无取向电工钢板及其制造方法 (Non-oriented electrical steel plate with excellent magnetic property and manufacturing method thereof ) 是由 张峰 吕学钧 陈晓 宗震宇 谢世殊 孙业中 阎朝红 周琳 于 2018-06-26 设计创作，主要内容包括：本发明公开了一种磁性能优良的无取向电工钢板,其化学元素质量百分比为：0＜C≤0.005％、Si：0.1～1.2％、Mn：0.1～1.0％、S：0.008～0.020％、Al：0.1～0.4％、Cu：0.01～0.05％、0＜N≤0.003％、Ti≤0.002％,余量为Fe及其他不可避免的杂质。本发明还公开了一种上述磁性能优良的无取向电工钢板的制造方法,包括步骤：(1)制得连铸坯；(2)热轧；(3)酸洗和连轧；(4)连续退火；(5)涂覆绝缘涂层。本发明所述的磁性能优良的无取向电工钢板成本低廉,具有优良的磁性能。(The invention discloses a non-oriented electrical steel plate with excellent magnetic property, which comprises the following chemical elements in percentage by mass: c is more than 0 and less than or equal to 0.005 percent, Si: 0.1-1.2%, Mn: 0.1-1.0%, S: 0.008-0.020%, Al: 0.1 to 0.4%, Cu: 0.01-0.05%, more than 0 and less than or equal to 0.003% of N, less than or equal to 0.002% of Ti, and the balance of Fe and other inevitable impurities. The present invention also discloses a method for manufacturing the non-oriented electrical steel sheet having excellent magnetic properties, comprising the steps of: (1) preparing a continuous casting billet; (2) hot rolling; (3) acid washing and continuous rolling; (4) continuous annealing; (5) and (4) coating an insulating coating. The non-oriented electrical steel plate with excellent magnetic property has low cost and excellent magnetic property.)

1. A non-oriented electrical steel sheet with excellent magnetic property is characterized in that the non-oriented electrical steel sheet comprises the following chemical elements by mass percent:

c is more than 0 and less than or equal to 0.005 percent, Si: 0.1-1.2%, Mn: 0.1-1.0%, S: 0.008-0.020%, Al: 0.1 to 0.4%, Cu: 0.01-0.05%, more than 0 and less than or equal to 0.003% of N, less than or equal to 0.002% of Ti, and the balance of Fe and other inevitable impurities.

2. A non-oriented electrical steel sheet excellent in magnetic characteristics as claimed in claim 1, which has inclusions mainly of spherical or spheroidal MnS.

3. The non-oriented electrical steel sheet having excellent magnetic properties as claimed in claim 2, which further has a very small amount of Cu₂S inclusions, very small amount of Cu₂The S inclusions are precipitated with the MnS inclusions as a core and are aggregated around the MnS inclusions.

4. The non-oriented electrical steel sheet having excellent magnetic properties as claimed in claim 1, wherein the number of grains of 10 μm or more accounts for 65 to 85% of the total number of grains, and the number of grains of 10 to 30 μm accounts for 50 to 70% of the total number of grains.

5. The non-oriented electrical steel sheet having excellent magnetic properties as claimed in claim 1, wherein the Mn and Cu elements satisfy: [ Mn ]]/[Cu]²300-1500, wherein Mn and Cu both represent the values of the two elements without percentage numbers.

6. The non-oriented electrical steel sheet having excellent magnetic properties as claimed in claim 1, wherein the core loss P is_15/50Less than or equal to 4.5W/kg, and magnetic induction B₅₀≥1.745T。

7. The method of manufacturing a non-oriented electrical steel sheet having excellent magnetic properties as claimed in any one of claims 1 to 6, comprising the steps of:

(1) preparing a continuous casting billet;

(2) hot rolling;

(3) acid washing and continuous rolling;

(4) continuous annealing;

(5) and (4) coating an insulating coating.

8. The manufacturing method according to claim 7, wherein in the step (1), the cooling rate of the continuously cast slab is controlled to be 10 ℃/min or less at a temperature range of 1100 ℃ to 1300 ℃ and to be 20 ℃/min to 40 ℃/min at a temperature range of 600 ℃ to 800 ℃ during the continuous casting and solidification.

9. The manufacturing method according to claim 7 or 8, wherein in the step (2), the size of the recrystallized structure of the core portion of the obtained hot-rolled steel strip accounts for 60% to 75% of the total size of the hot-rolled steel strip in the thickness direction; wherein the average grain size of the recrystallized structure is between 90 and 140 mu m; the long axis of the crystal grains of the recrystallized structure is consistent with the rolling direction of the strip steel, and the length ratio of the long axis to the short axis is 1.0-1.6.

10. The production method according to claim 7 or 8, wherein in the step (2), the cooling rate of the surface of the strip is controlled to be 20 ℃/s or less during the finish rolling, and water cooling is performed after the finish rolling to cool the strip to a coiling temperature, wherein the time from the finish rolling to the start of the water cooling is 5 to 20 seconds, and the coiling temperature is 750 to 900 ℃.

Technical Field

The present invention relates to an electrical steel sheet and a method for manufacturing the same, and more particularly, to a non-oriented electrical steel sheet and a method for manufacturing the same.

Background

With the increasing market demand of users and the increasing demands for high efficiency, energy saving and environmental protection, non-oriented electrical steel products are required to have lower iron loss values and higher magnetic induction values, and the premise is that sufficiently high price competitive advantages are still maintained. In particular, in recent years, the strength of domestic and foreign electrical steel product production enterprises is continuously improved, and the quality of the same variety of real objects of different manufacturers is obviously improved and gradually tends to be consistent. Under the condition, the optimization of the production process is effectively carried out, so that the effective reduction of the manufacturing cost of the product and the stability of the product quality are ensured, and the method has very important practical significance.

Disclosure of Invention

An object of the present invention is to provide a non-oriented electrical steel sheet having excellent magnetic properties, which is inexpensive and has excellent magnetic properties.

In order to achieve the above object, the present invention provides a non-oriented electrical steel sheet with excellent magnetic properties, which comprises the following chemical elements by mass percent:

c is more than 0 and less than or equal to 0.005 percent, Si: 0.1-1.2%, Mn: 0.1-1.0%, S: 0.008-0.020%, Al: 0.1 to 0.4%, Cu: 0.01-0.05%, more than 0 and less than or equal to 0.003% of N, less than or equal to 0.002% of Ti, and the balance of Fe and other inevitable impurities.

The design principle of each chemical element in the non-oriented electrical steel plate with excellent magnetic property provided by the invention is as follows:

c: c strongly hinders the growth of finished product crystal grains and is easy to combine with Nb, V and Ti to form fine precipitates, thereby causing the increase of iron loss and the generation of magnetic aging, so the mass percentage of C element in the non-oriented electrical steel plate with excellent magnetic property is limited to be more than 0 and less than or equal to 0.005 percent.

Si: si can improve the resistivity of the matrix and effectively reduce the iron loss of the steel. When the Si content is higher than 1.2%, the magnetic induction of the steel can be obviously reduced; and when the content is less than 0.1%, the effect of effectively reducing the iron loss cannot be achieved. Therefore, the present invention limits the mass percentage of the Si element in the non-oriented electrical steel sheet having excellent magnetic properties to 0.1 to 1.2%.

Mn: mn and S are combined to generate MnS, so that the damage to magnetism can be effectively reduced, the surface state of the electrical steel plate is improved, and hot brittleness is reduced. However, if the Mn content is more than 1.0%, the recrystallized texture is easily broken, and the production cost of steel is greatly increased. Therefore, the present invention limits the mass percentage of Mn element in the non-oriented electrical steel sheet having excellent magnetic properties to 0.1 to 1.0%.

S: the content of S element is designed and Cu is added in the technical scheme₂The formation of S inclusions. If the S content is more than 0.0When 20%, MnS and Cu will be added₂The S inclusion precipitation is greatly increased, the grain growth is strongly hindered, and the magnetism of the steel is deteriorated. Therefore, the present invention limits the mass percentage of the S element in the non-oriented electrical steel sheet having excellent magnetic properties to 0.008 to 0.020%.

Al: when the Al content is less than 0.1%, a good deoxidation effect cannot be obtained, but when the Al content is more than 0.4%, AlN inclusions are greatly precipitated, the growth of crystal grains is strongly inhibited, and the magnetism of the steel is deteriorated. Therefore, the present invention limits the mass percentage of Al element in the non-oriented electrical steel sheet having excellent magnetic properties to 0.1 to 0.4%.

Cu: the design of Cu element content and Cu in the technical scheme₂The formation of S inclusions. When the Cu content exceeds 0.05%, a precipitation phase of Cu is generated to strongly inhibit the growth of crystal grains and deteriorate the magnetic properties of the steel, and when the Cu content is less than 0.01%, a specific sulfur fixation effect is not exhibited in the hot rolling and heat treatment processes. Therefore, the present invention limits the mass percentage of the Cu element in the non-oriented electrical steel sheet having excellent magnetic properties to 0.01 to 0.05%.

N: when the N content exceeds 0.003%, the precipitates of Nb, V, Ti and Al of N are greatly increased, the growth of crystal grains is strongly inhibited, and the magnetic properties of the steel are deteriorated. Therefore, the present invention limits the mass percent of N element in the non-oriented electrical steel sheet with excellent magnetic property to 0 < N < 0.003%.

Ti: when the Ti content exceeds 0.002%, the Ti C, N inclusion is greatly increased, which strongly hinders the growth of crystal grains and deteriorates the magnetic properties of the steel. Therefore, the present invention limits the mass percentage of Ti element in the non-oriented electrical steel sheet with excellent magnetic property to Ti less than or equal to 0.002%.

In the technical scheme of the invention, other inevitable impurities mainly comprise P, and when the content of P exceeds 0.2%, the cold brittleness phenomenon is easily caused, and the cold rolling manufacturability is reduced. Therefore, the present invention limits the mass percentage of the P element in the non-oriented electrical steel sheet with excellent magnetic property to P less than or equal to 0.2%.

It should be noted that, compared with the prior art, the difference of the technical solution is as follows: in the invention, the content of the S element is adjusted consciously in the design process of each element component. In the prior art, it is common to reduce the S content as much as possible in order to reduce the content of harmful inclusions as much as possible. According to the technical scheme, a certain amount of S element is intentionally added, the production process is adjusted, and the harmless treatment of the content of the S element is realized to the maximum extent by controlling the size, the quantity, the type and the morphology of the S compound. Thus, chemical component collocation and combination beneficial to obtaining excellent magnetic performance and reasonable inclusion species control prerequisites are realized, so that the shape, the size and the quantity of the inclusions can be controlled simply, conveniently and efficiently by limiting the cooling rates of different cooling temperature sections in the continuous casting process, and the inclusions are developed towards the direction beneficial to obtaining excellent magnetic performance.

Particularly, when the S content is more than 0.008 percent, the saturation of Mn and S elements is increased and the precipitation time of MnS inclusions is advanced in the continuous casting process, so that the MnS inclusions are easy to polymerize and grow, and the magnetic hazard of the MnS inclusions to finished strip steel is greatly reduced. In addition, in order to further promote the continuous stability of the process, the invention dynamically adjusts the adding amount of Mn according to the S content and ensures that the Mn content is ensured to be in a proper control range so as to ensure that MnS inclusion is precipitated as early as possible in the initial solidification stage of molten steel, so that convenience in temperature and time is provided for the sufficient growth of the subsequent MnS inclusion, and the influence of the MnS inclusion growing to be 0.5 mu m or more on the electromagnetic property of a finished product material is obviously weakened. In addition, when the S content is more than 0.02%, the amount of MnS inclusions is greatly increased and the Cu-S bonding is delayed, i.e., Cu₂The precipitation time of S is delayed, and the precipitation size is small and the amount is increased, thereby deteriorating the magnetic performance of the finished strip steel. Therefore, the S content is controlled within the range of 0.008% -0.02%, and the type, the quantity, the size and the appearance of the S compounds in the steel are controlled by matching with the adjustment of the casting process.

In addition, in order to reduce the repeated solid solution and precipitation of MnS precipitates in the hot rolling and heat treatment processes and inhibit the growth of crystal grains, the invention also considers that the lower the content of Mn element is, the MnS and the Cu are under the chemical composition system of the technical scheme₂S composite precipitationThe higher the ratio. Therefore, the technical scheme adopts a mode of adding a proper amount of Cu into the steel so as to reduce the Mn content in the steel as much as possible. Thereby reducing MnS inclusion precipitation and ensuring the subsequent Cu generation₂The S inclusion and the MnS inclusion are compounded and grown, thereby reducing the pinning effect on the crystal grains. Further, Cu produced in this part₂The melting point of S precipitates is lower than 600 ℃, the S precipitates can be completely dissolved in a steel matrix under high-temperature annealing, and the Cu precipitates again after the high-temperature annealing and the grain growth₂The S precipitate does not have adverse effect on the electromagnetic performance of the finished strip steel.

Further, the non-oriented electrical steel sheet having excellent magnetic properties according to the present invention has inclusions mainly comprising spherical or spheroidal MnS.

Further, the non-oriented electrical steel sheet having excellent magnetic properties according to the present invention has a very small amount of Cu₂S inclusions, very small amount of Cu₂The S inclusions are precipitated with the MnS inclusions as a core and are aggregated around the MnS inclusions.

Further, in the non-oriented electrical steel sheet having excellent magnetic properties according to the present invention, the number of grains of 10 μm or more accounts for 65% to 85% of the total number of grains, and the number of grains of 10 μm to 30 μm accounts for 50% to 70% of the total number of grains.

In the technical scheme of the invention, in order to ensure that a good iron loss value is obtained, the number of the crystal grains with the diameter of more than 10 microns in the non-oriented electrical steel sheet with excellent magnetic performance is controlled to be 65-85% of the total number of the crystal grains, so that the hysteresis loss in the iron loss value is reduced as much as possible. In order to ensure that a good magnetic induction value is obtained, the number of the grains of 10-30 μm in the non-oriented electrical steel sheet with excellent magnetic performance is controlled to be 50-70% of the total number of the grains, so that a texture proportion favorable for magnetic induction is obtained as much as possible.

Further, in the non-oriented electrical steel sheet having excellent magnetic properties according to the present invention, Mn and Cu elements satisfy: [ Mn ]]/[Cu]²300-1500, wherein Mn and Cu both represent the values of the two elements without percentage numbers.

Further, the non-oriented electrical steel sheet having excellent magnetic properties according to the present invention has an iron loss P_15/50Less than or equal to 4.5W/kg, and magnetic induction B₅₀≥1.745T。

Accordingly, another object of the present invention is to provide a method for manufacturing the above-mentioned non-oriented electrical steel sheet having excellent magnetic properties, which is inexpensive, simple and easy to handle, does not require a normalizing process or a bell type furnace intermediate annealing, and has excellent magnetic properties.

In order to achieve the above object, the present invention provides a method for manufacturing the non-oriented electrical steel sheet having excellent magnetic properties, comprising the steps of:

(1) preparing a continuous casting billet;

(2) hot rolling;

(3) acid washing and continuous rolling;

(4) continuous annealing;

(5) and (4) coating an insulating coating.

In the above manufacturing method, in the step (1), in some embodiments, a continuous cast slab is manufactured after molten iron pretreatment, converter smelting, molten steel vacuum circulation degassing (RH) refining, and continuous casting.

Further, in the manufacturing method of the invention, in the step (1), in the continuous casting and solidification process, the cooling rate of the continuous casting blank is controlled to be less than or equal to 10 ℃/min within the temperature range of 1100-1300 ℃, and the cooling rate of the continuous casting blank is controlled to be 20-40 ℃/min within the temperature range of 600-800 ℃.

In the manufacturing method, in the step (1), in the continuous casting billet cooling process, the cooling rate of the continuous casting billet is controlled to be less than or equal to 10 ℃/min within the temperature range of 1100-1300 ℃ in the continuous casting and solidification process, and the reason that MnS is preferentially precipitated in the cooling rate is mainly considered, so that the relatively low cooling rate is limited, and the purpose is to generate MnS inclusions with coarse sizes as fully as possible, so that the subsequent sulfides with low melting points and small sizes are prevented from being fully precipitated, and the MnS inclusions are easier to coarsen and grow and keep good spherical shapes or spheroidal shapes under the slow cooling condition. The spherical or spheroidal inclusion is not easy to form more harmful wedge-shaped domains, so that the magnetization is easier and the magnetic property is more excellent.

In addition, in the step (1), in the continuous casting and solidification process, the cooling rate of the continuous casting slab is limited to 20-40 ℃/min within the temperature range of 600-800 ℃. That is, strong cooling and rapid cooling are required during this period, and the main purpose is to make low melting point Cu₂S inclusions not coming to precipitate sufficiently, Cu₂The small amount of S inclusion precipitation is advantageous for the control of magnetic properties, and the small amount of Cu capable of precipitation₂And S inclusions are precipitated by taking MnS as a core, so that the size of the MnS inclusions is larger and the harm is smaller.

Further, in the manufacturing method of the present invention, in the step (2), the size of the recrystallized structure of the core portion of the obtained hot-rolled strip steel accounts for 60% to 75% of the total size of the hot-rolled strip steel in the thickness direction; wherein the average grain size of the recrystallized structure is between 90 and 140 mu m; the long axis of the crystal grains of the recrystallized structure is consistent with the rolling direction of the strip steel, and the length ratio of the long axis to the short axis is 1.0-1.6.

In the manufacturing method of the present invention, in the step (2), the size of the recrystallized structure of the core portion of the obtained hot rolled strip is controlled to be 60% to 75% of the total size of the hot rolled strip in the thickness direction, wherein the average grain size of the recrystallized structure is between 90 μm and 140 μm, the major axis of the grain of the recrystallized structure is aligned with the rolling direction of the strip, and the length ratio of the major axis to the minor axis is 1.0 to 1.6, so as to reduce the adverse effect on the anisotropy index of the magnetic properties of the non-oriented electrical steel sheet excellent in magnetic properties according to the present invention. The reason why the recrystallization effect of the hot rolled steel sheet is controlled by the present invention is that the quality of the recrystallization effect of the hot rolled structure is inherited. The inventors of the present invention found through studies that the more sufficient the recrystallization effect is in the recrystallized structure of the hot rolled sheet, the larger the crystal grain size is, and the higher the magnetic induction of the finished strip steel is, whereas if the recrystallization effect is worse, the larger the proportion of fine grains or fibrous structures is, and the smaller the crystal grain size is, the lower the magnetic induction of the finished strip steel is, in the recrystallized structure of the hot rolled sheet. In addition, the lower the proportion of fine grains or fibrous structures in the recrystallized structure of the hot rolled plate is, the lower the energy storage in the strip steel is in the cold rolling process, and the growth of crystal grains is not facilitated in the subsequent continuous annealing process, so that the lower iron loss is not easy to obtain.

Further, in the manufacturing method of the invention, in the step (2), the cooling rate of the surface of the strip steel is controlled to be less than or equal to 20 ℃/s in the finish rolling process, and water cooling is performed after the finish rolling is finished to cool the strip steel to the coiling temperature, wherein the time between the finish rolling and the start of the water cooling is 5-20 s, and the coiling temperature is 750-900 ℃.

In the manufacturing method of the present invention, in the step (2), the cooling rate of the surface of the strip is controlled to be not more than 20 ℃/s in the finish rolling process, mainly because the hot rolled strip is thinner and operates at a higher speed unlike the continuous cast slab, and is thus more easily cooled, thereby affecting the recrystallization effect of the hot rolled steel sheet. Therefore, it is necessary to control the cooling rate of the surface of the strip not more than 20 ℃/s, preferably, the cooling rate of the surface of the strip not more than 15 ℃/s, and generally the cooling rate of the surface of the strip not less than 2.5 ℃/s in consideration of the productivity of the hot rolling equipment. Similarly, in order to ensure the high-temperature recrystallization effect of hot rolling, the time between the finish rolling and the start of water cooling is 5 to 20 seconds, and the coiling temperature is 750 to 900 ℃.

Compared with the prior art, the non-oriented electrical steel plate with excellent magnetic property and the manufacturing method thereof have the following beneficial effects:

(1) through reasonable component design, the non-oriented electrical steel plate with excellent magnetic property has low cost and excellent magnetic property.

(2) The method for manufacturing the non-oriented electrical steel plate with excellent magnetic property has the advantages of optimized process design, simplicity and easy operation, no need of normalizing treatment and intermediate annealing in a bell-type furnace, and ensures that the prepared non-oriented electrical steel plate with excellent magnetic property has the iron loss P_15/50Less than or equal to 4.5W/kg, and magnetic induction B₅₀≥1.745T。

Drawings

FIG. 1 is a microstructure diagram of a hot-rolled strip steel obtained by passing a non-oriented electrical steel sheet having excellent magnetic properties through step (2) of example 2.

FIG. 2 is a microstructure diagram of a hot-rolled strip obtained by the step (2) of the non-oriented electrical steel sheet having excellent magnetic properties of comparative example 6.

FIG. 3 is a microstructure view of a non-oriented electrical steel sheet having excellent magnetic properties according to example 3.

FIG. 4 is a microstructure view of a non-oriented electrical steel sheet having excellent magnetic properties according to comparative example 5.

FIG. 5 is a microstructure diagram of inclusions in a non-oriented electrical steel sheet having excellent magnetic properties in example 5.

FIG. 6 is a microstructure view of inclusions in a non-oriented electrical steel sheet having excellent magnetic properties according to comparative example 7.

FIG. 7 is a microstructure diagram of inclusions in a non-oriented electrical steel sheet having excellent magnetic properties in example 6.

FIG. 8 is a microstructure view of inclusions in a non-oriented electrical steel sheet having excellent magnetic properties according to comparative example 4.

FIG. 9 is a graph showing the relationship between the length ratio of the major axis to the minor axis of the recrystallized grains in the core of the hot-rolled steel strip obtained in step (2) of the manufacturing method according to the present invention and the core loss of the finally obtained non-oriented electrical steel sheet having excellent magnetic properties.

FIG. 10 is a graph showing the relationship between the length ratio of the major axis to the minor axis of the recrystallized grains of the core portion of the hot-rolled strip obtained in step (2) of the manufacturing method according to the present invention and the magnetic induction of the finally obtained non-oriented electrical steel sheet having excellent magnetic properties.

FIG. 11 is a graph showing the relationship between the average grain size of the recrystallized structure of the core portion of the hot-rolled steel strip obtained in step (2) of the manufacturing method according to the present invention and the core loss of the finally obtained non-oriented electrical steel sheet excellent in magnetic properties.

FIG. 12 is a graph showing the relationship between the average grain size of the recrystallized structure of the core portion of the hot-rolled steel strip obtained in step (2) of the manufacturing method according to the present invention and the magnetic induction of the finally obtained non-oriented electrical steel sheet excellent in magnetic properties.

Detailed Description

The non-oriented electrical steel sheet with excellent magnetic properties and the method for manufacturing the same according to the present invention will be further explained and illustrated with reference to the drawings and the specific examples, which, however, should not be construed to unduly limit the technical scope of the present invention.