TWI817398B - Electrical steel sheet and method for producing the same - Google Patents

Abstract

The present invention relates to an electrical steel sheet and a method for producing the same. A hot-rolling process and a hot-rolled annealing process are performed to produce a hot-rolled annealed steel plate having a high ratio of specific textures, such that the electrical steel sheet having high magnetic flux and low iron loss can be produced. After the aforementioned hot-rolling process is performed, the hot-rolled annealing process is performed by heating a hot-rolling steel plate to an annealing temperature with a specific heating rate, thereby increasing amounts of the specific textures in the annealed steel plate.

Description

Electromagnetic steel sheet and production method thereof

The present invention relates to an electromagnetic steel sheet, and in particular provides an electromagnetic steel sheet with high magnetic flux, low iron loss, and good strength performance and a manufacturing method thereof.

Due to the depletion dilemma faced by fossil fuels, electric vehicles are booming. Among them, the electromagnetic steel sheets required for the drive motors mounted on electric vehicles must have the characteristics of low iron loss, high magnetic flux and high strength. However, in general metallurgical processes, in order to reduce iron loss and increase strength, the magnetic flux value will be reduced accordingly. For example, alloying elements such as silicon and aluminum are generally added to reduce iron loss and increase strength, but the magnetic flux value is reduced.

Furthermore, the general method of increasing the magnetic flux value may include cold rolling using a warm rolling process and secondary rolling combined with a secondary annealing process. Among them, cold rolling adopts a warm rolling process, which is cold rolling at a higher temperature (such as 200°C to 500°C), and the content of alloying elements (such as carbon and nitrogen) is adjusted so that during rolling, the alloying elements and The interaction of differential rows optimizes the collective organization of the product, thus increasing the magnetic flux value. However, the content of alloying elements in this method is difficult to control, and it is easy to transform into carbides or nitrides during the heating process, thereby reducing iron loss. The secondary rolling and secondary annealing process is performed after the hot rolling process. By combining multiple annealing processes and cold rolling processes to adjust the collective structure, and finally performing the final annealing process, the collective structure of the product can be optimized. . However, the process cost of this method is significantly increased.

In view of this, there is an urgent need to provide an electromagnetic steel sheet and its manufacturing method to solve the shortcomings of conventional electromagnetic steel sheets and their manufacturing methods that cannot achieve high magnetic flux, low iron loss and high strength at the same time.

Therefore, one aspect of the present invention is to provide a method for manufacturing electromagnetic steel sheets, which can make the hot-rolled annealed steel sheets after annealing have a specific collective structure by adjusting the temperature rise rate of the hot-rolling annealing process, thereby improving the The electromagnetic properties of the subsequently produced electromagnetic steel sheets.

Another aspect of the present invention is to provide an electromagnetic steel sheet, which is manufactured by the aforementioned manufacturing method.

According to an aspect of the present invention, a method for manufacturing electromagnetic steel sheets is proposed. In this production method, a steel blank is first provided, and the steel blank is subjected to a hot rolling process to form a hot-rolled steel plate. Among them, the steel blank contains 0.001 to 0.1 weight percent of carbon, 2 to 4 weight percent of silicon, 0.1 to 3 weight percent of aluminum, 0.1 to 2 weight percent of manganese, and no more than 0.1 weight percent. of phosphorus, no more than 0.01 weight percent of sulfur and a balance of iron, and the steel blank does not contain nickel and/or nitrogen. The completion temperature of the hot rolling process is 800°C to 1000°C. Then, the hot-rolled steel plate is subjected to a hot-rolling annealing process to form a hot-rolled annealed steel plate. Among them, the heating rate of the hot rolling annealing process is not greater than 15°C/s, and the annealing temperature of the hot rolling annealing process is 900°C to 1100°C. Next, the hot-rolled annealed steel plate is subjected to a cold rolling process to form a cold-rolled steel sheet. After the cold rolling process, the cold rolled steel sheet is subjected to a final annealing process to obtain the electromagnetic steel sheet.

According to some embodiments of the present invention, before performing the aforementioned hot rolling process, the steel blank is heated to 1000°C to 1200°C.

According to some embodiments of the present invention, after performing the aforementioned hot rolling process, the manufacturing method can selectively perform a coiling process on the hot-rolled steel plate, wherein the temperature of the coiling process is 500°C to 750°C.

According to some embodiments of the present invention, the temperature holding time of the aforementioned hot rolling annealing process is 30 seconds to 240 seconds.

According to some embodiments of the present invention, the aforementioned hot-rolled annealed steel plate has a collective structure of Rotated cube{001}<110> and/or ND//<001>.

According to some embodiments of the present invention, the annealing temperature of the aforementioned final annealing process is 750°C to 1100°C.

According to some embodiments of the present invention, the temperature holding time of the final annealing process is 30 seconds to 120 seconds.

According to some embodiments of the present invention, after performing the aforementioned final annealing process, the temperature is lowered to room temperature at a rate of 2°C/s to 30°C/s to form an electromagnetic steel sheet.

According to another aspect of the present invention, an electromagnetic steel sheet is proposed, which is made by the aforementioned manufacturing method, and the electromagnetic steel sheet has Cube{001}<100> and/or Goss{110}<100> collective organization.

By applying the electromagnetic steel sheet and its manufacturing method of the present invention, by adjusting the temperature rise rate of the hot rolling annealing process, the steel sheet after hot rolling and annealing can have a high content of Rotated cube{001}<110> and/or ND// Specific aggregate structures such as <001> can then form specific aggregate structures such as Cube and/or Goss in the produced electromagnetic steel sheet, so the magnetic flux of the electromagnetic steel sheet can be increased and its iron loss can be reduced. In addition, through the specific annealing temperature of the final annealing process, the grains in the steel sheet can grow stably and are less likely to form a collective structure that is not conducive to magnetism, so the electromagnetic properties and mechanical strength of the electromagnetic steel sheet can be improved. Therefore, the manufacturing method of the present invention can effectively make the electromagnetic steel sheet have both good electromagnetic properties and strength by simply adjusting the process parameters. Therefore, there is no need to significantly adjust the manufacturing process of the electromagnetic steel sheet, and it can still have good electromagnetic properties. Production efficiency.

The making and using of embodiments of the invention are discussed in detail below. It is to be appreciated, however, that the embodiments provide many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are illustrative only and are not intended to limit the scope of the invention.

Please refer to FIG. 1 , which is a flow chart illustrating a method for manufacturing an electromagnetic steel sheet according to some embodiments of the present invention. Method 100 is to first provide a steel blank, and perform a hot rolling process on the steel blank to form a hot rolled steel plate, as shown in operation 110 . This steel blank contains 0.001 to 0.1 weight percent of carbon, 2 to 4 weight percent of silicon, 0.1 to 3 weight percent of aluminum, 0.1 to 2 weight percent of manganese, and no more than 0.1 weight percent of Phosphorus, no more than 0.01 weight percent sulfur and a balance of iron, wherein the steel blank does not contain nickel and/or nitrogen. If the steel blank contains nickel, the resulting electromagnetic steel sheet will have higher production costs. If nitrogen is included, it will form nitrides with impurity elements inside the steel, which will hinder the movement of the magnetic domain wall, thereby increasing the iron loss of the electromagnetic steel sheet and failing to meet application requirements. The steel blank of the present invention can be prepared by processes (such as steelmaking and continuous casting) and equipment that are well known to those with ordinary knowledge, so they will not be described again here.

The completion temperature of the hot rolling process is 800°C to 1000°C. If the completion temperature of the hot rolling process is not the aforementioned temperature, the grains in the steel plate will not be able to grow into an appropriate collective structure (such as Rotated cube {001 }<110> and/or ND//<001> (λ-fiber) collective organization), which is difficult to meet the needs of the application. In some embodiments, the reduction rate of the hot rolling process may be 80% to 98%. When the reduction rate of the hot rolling process is within the aforementioned range, the rolling stress applied at high temperature helps to nucleate the grains in the steel plate, and can grow into the specific set mentioned above in the subsequent hot rolling and annealing process. organization. Preferably, the reduction rate of the hot rolling process can be 90% to 95%.

In some embodiments, before performing the hot rolling process, the steel blank can be heated to 1000°C to 1200°C to reduce the resistance of the steel blank during hot rolling and help to reduce the stress exerted by the hot rolling process. Form crystal nuclei. In some embodiments, after performing the hot rolling process, the method 100 may selectively perform a coiling process on the hot rolled steel plate. Among them, the temperature of the coiling process can be 500°C to 750°C to help form the nucleation structure in the hot-rolled steel plate into Rotated cube {001}<110> and/or ND/ in the hot-rolling annealing process described later. /<001> (λ-fiber) specific collective organization. In some embodiments, the temperature of the coiling process may preferably be 600°C to 700°C.

After operation 110 is performed, the hot-rolled steel plate is subjected to a hot-rolling annealing process to form a hot-rolled annealed steel plate, as shown in operation 120 . During the hot-rolling annealing process, the hot-rolled steel plate is heated to an annealing temperature of 900°C to 1100°C at a rate of no more than 15°C/s, so that the crystal nuclei in the hot-rolled steel plate can grow into a Rotated cube{001}< 110> and/or ND//<001> specific collective organization. If the heating rate of the hot rolling annealing process is greater than 15℃/s, the too fast heating rate will cause the crystal nuclei in the steel plate to fail to grow into the aforementioned specific collective structure (such as Rotated cube{001}<110> and/or ND// <001>), which cannot meet the application requirements. In some embodiments, the temperature rise rate of the hot rolling annealing process may be 1°C/s to 15°C/s. Preferably, the heating rate of the hot rolling annealing process can be 1°C/s to 5°C/s. When the annealing temperature is greater than 1100°C, although the excessively high temperature will help the growth of crystal nuclei in the steel plate, the crystal grains formed will be too coarse, thereby reducing the electromagnetic properties of the produced electromagnetic steel sheet and easily forming the aforementioned special characteristics. Collective organizations other than collective organizations. When the annealing temperature is less than 900°C, the too low temperature will not allow the crystal nuclei in the steel plate to further grow into a specific collective structure, so the electromagnetic steel sheet produced cannot meet the needs of the application. In some embodiments, the annealing temperature may preferably range from 900°C to 1050°C. The hot-rolled annealing process uses a specific heating rate and annealing temperature to form a hot-rolled annealed steel plate with the collective structure of Rotated cube{001}<110> and/or ND//<001>, which can effectively improve the obtained The electromagnetic properties and strength of electromagnetic steel sheets.

After performing the hot rolling annealing process, the hot rolled steel plate is subjected to a cold rolling process to form a cold rolled steel sheet, as shown in operation 130 . During the cold rolling process, the rolling device applies stress to the steel plate to make it thinner to meet the dimensional requirements of the application. Since the cold rolling process is carried out at low temperatures (such as 20°C to 200°C), the applied stress will not easily cause the continuous growth and change of the collective structure in the steel plate. There are no special restrictions on the reduction rate and rolling passes of the cold rolling process. They only need to make the size of the formed cold-rolled steel sheet meet the application requirements. In some embodiments, the cold rolling process can roll a hot-rolled annealed steel plate of 2.0 mm to 2.5 mm into a cold-rolled steel sheet of 0.20 mm to 0.50 mm.

Next, a final annealing process is performed on the cold-rolled steel sheet to produce the electromagnetic steel sheet of the present invention, as shown in operations 140 and 150 . In some embodiments, the annealing temperature of the final annealing process may be 750°C to 1100°C, and the temperature holding time may be 30 seconds to 120 seconds. When the final annealing process is carried out at the above-mentioned annealing temperature and holding time, the continuous application of heat energy helps to stably grow the grains in the steel sheet to have appropriate grain sizes, and helps to make the obtained Electromagnetic steel sheets have specific collective structures such as Cube{001}<100> and/or Goss{110}<100> that can effectively increase magnetic flux and reduce iron loss. Preferably, the annealing temperature of the final annealing process may be 850°C to 1050°C, and the temperature holding time of the final annealing process may be 50 seconds to 80 seconds.

In some embodiments, after the final annealing process, the formed electromagnetic steel sheet can be cooled to room temperature at a rate of 2°C/s to 30°C/s. Among them, when the electromagnetic steel sheet is cooled at this rate, this cooling rate can effectively release the residual stress in the steel sheet, thereby reducing the iron loss value of the electromagnetic steel sheet. Preferably, the electromagnetic steel sheet formed by the final annealing process can be cooled to room temperature at a rate of 3°C/s to 10°C/s.

In some application examples, the present invention can be produced by making the hot-rolled annealed steel plate have a high proportion (such as not less than 30%) of Rotated cube{001}<110> and/or ND//<001>. Electromagnetic steel sheets with collective structures such as Cube and/or Goss are obtained. In these application examples, the electromagnetic steel sheet of the present invention can have a magnetic flux value of no less than 1.68 Tesla and an iron loss value of no more than 20 W/Kg.

The following examples are used to illustrate the application of the present invention, but they are not intended to limit the present invention. Anyone familiar with this art can make various changes and modifications without departing from the spirit and scope of the present invention.

Preparation of electromagnetic steel sheets

Example 1

The electromagnetic steel sheet of Example 1 is prepared by first subjecting the steel blank to a hot rolling process to form a hot-rolled steel plate. The steel blank contains 0.008 weight percent carbon, 3.2 weight percent silicon, 0.6 weight percent aluminum, and 0.2 weight percent. of manganese, 0.05 weight percent phosphorus and 0.005 weight percent sulfur. Before the hot rolling process, the steel blank is heated to 1100°C. After the hot rolling process, the completion temperature of the hot-rolled steel plate is 900°C, and the hot-rolled steel plate is further coiled, with the coiling temperature being 650°C. Then, the hot-rolled steel plate is subjected to a hot-rolling annealing process to form a hot-rolled annealed steel plate. The annealing temperature of the hot-rolling annealing process is 950°C, and the heating rate is 5°C/s. After hot rolling and annealing for 200 seconds, the temperature is cooled to 25°C at a rate of 10°C/s, and the cold rolling process is continued to form cold rolled steel sheets. The hot-rolled annealed steel plate formed in Example 1 was observed with an optical microscope, and its crystal orientation distribution function (ODF) diagram (φ2=0 degrees) was measured with an X-ray diffractometer (XRD). As shown in Figure 2A and Figure 3A respectively. As shown in Figure 2A and Figure 3A respectively, the grain size of the hot-rolled annealed steel plate is about 150 μm, and the hot-rolled annealed steel plate has a high content (about not less than 40%) of the Rotated cube{001}<110> collective structure. (The area indicated in Figure 3A).

During the cold rolling process, the hot-rolled annealed steel plate is rolled from 2.3 mm to 0.2 mm at a reduction rate of 91.3%. Then, the cold-rolled steel sheet is subjected to a final annealing process to obtain the electromagnetic steel sheet of Example 1. During the final annealing process, the annealing temperature is 800°C to 1000°C, and the magnetic flux (B50) of the electromagnetic steel sheet produced at each annealing temperature of the final annealing process is measured using methods and instruments well known to those with ordinary knowledge. ) value and iron loss (W10/400) value, the results are shown in the data labels "●" in Figure 4A and Figure 4B respectively.

Example 2

Example 2 uses the same preparation process as the electromagnetic steel sheet of Example 1, except that the steel blank of Example 2 contains 0.007 weight percent carbon, 2.9 weight percent silicon, 0.9 weight percent aluminum, and 0.3 weight percent. of manganese, 0.04 weight percent phosphorus and 0.004 weight percent sulfur. Before the hot rolling process, the steel blank is first heated to 1120°C, and the completion temperature of the hot-rolled steel plate is 880°C, and is coiled at a temperature of 680°C. The formed hot-rolled steel plate is heated to 1050°C at a rate of 15°C/s. A hot rolling annealing process is carried out for 60 seconds, and the temperature is cooled to 25°C at a rate of 15°C/s, and then the cold rolling process is continued to form a cold rolled steel sheet. The grain size of the hot-rolled annealed steel plate in Example 2 is approximately 155 μm. Then, the same cold rolling process and final annealing process as in Example 1 are carried out to prepare the electromagnetic steel sheet of Example 2, and the magnetic flux (B50) value and iron loss of the electromagnetic steel sheet prepared at each annealing temperature are (W10/400) value, the results are shown in the data labeled "■" in Figure 4A and Figure 4B respectively.

Comparative example

The comparative example uses the same preparation process as the electromagnetic steel sheet of Example 1, except that the steel blank of the comparative example contains 0.008 weight percent carbon, 3.0 weight percent silicon, 0.8 weight percent aluminum, and 0.2 weight percent manganese. , 0.05 weight percent phosphorus and 0.005 weight percent sulfur. Before the hot rolling process, the steel blank is first heated to 1100°C, and the completion temperature of the hot-rolled steel plate is 900°C, and is coiled at a temperature of 650°C. The formed hot-rolled steel plate is heated to 1000°C at a rate of 25°C/s. A hot rolling annealing process is carried out for 120 seconds, and the temperature is cooled to 25°C at a rate of 10°C/s, and the cold rolling process is continued to form a cold rolled steel sheet. The grain size of the hot-rolled annealed steel plate in the comparative example is about 160 μm (as shown in Figure 2B), and the ODF diagram of the hot-rolled annealed steel plate in the comparative example (as shown in Figure 3B, φ2=0 degrees) shows that it does not have The collective organization of Rotated cube{001}<110>, and under different φ2, the content of Rotated cube is less. Then, the same cold rolling process and final annealing process as in Example 1 are carried out to prepare the electromagnetic steel sheet of the comparative example, and the magnetic flux (B50) value and iron loss ( W10/400) value, the results are shown in the data mark "○" in Figure 4A and Figure 4B respectively.

As shown in Figures 4A and 4B, the electromagnetic steel sheets prepared in Examples 1 and 2 have higher magnetic flux values and lower magnetic loss values, so they have good electromagnetic properties. nature. Among them, although the grain size of the comparative example is similar to that of Example 1, the hot-rolled annealed steel sheet of the comparative example lacks the specific collective structure of Rotated cube{001}<110>, so the electromagnetic steel sheet of the comparative example has poor electromagnetic properties.

Accordingly, the electromagnetic steel sheet of the present invention can effectively improve the collective structure of Rotated cube{001}<110> and/or ND//<001> in the hot-rolled annealed steel sheet by adjusting the heating rate of the hot-rolled annealing process. The content in the electromagnetic steel sheet allows the produced electromagnetic steel sheet to contain specific aggregate structures such as Cube and/or Goss that can effectively increase magnetic flux and reduce iron loss. Among them, although the hot-rolled annealed steel sheet is further subjected to a cold rolling process and a final annealing process, the specific annealing temperature of the final annealing process of the present invention is used to stabilize the grain growth and improve the electromagnetic properties and strength of the produced electromagnetic steel sheet. , thereby meeting application requirements.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended patent application scope.

100:Method 110,120,130,140,150: Operation

In order to have a more complete understanding of the embodiments of the present invention and its advantages, please refer to the following description together with the corresponding drawings. It must be emphasized that various features are not drawn to scale and are for illustration purposes only. The relevant diagram content is explained below. FIG. 1 is a flow chart illustrating a method for manufacturing an electromagnetic steel sheet according to some embodiments of the present invention. 2A and 2B respectively show optical micrographs of hot-rolled annealed steel sheets formed according to Example 1 and Comparative Example of the present invention. 3A and 3B respectively show crystal orientation distribution function diagrams of hot-rolled annealed steel sheets formed according to Example 1 and Comparative Example of the present invention. FIG. 4A shows the magnetic flux of the electromagnetic steel sheets produced at various annealing temperatures in the final annealing processes of Example 1, Example 2 and Comparative Example of the present invention. Figure 4B shows the iron loss values of electromagnetic steel sheets produced at various annealing temperatures in the final annealing processes of Example 1, Example 2 and Comparative Example of the present invention.

Domestic storage information (please note in order of storage institution, date and number) without Overseas storage information (please note in order of storage country, institution, date, and number) without

100:Method 110,120,130,140,150: Operation

Claims (8)

A method for making electromagnetic steel sheets, including: providing a steel blank, wherein the steel blank contains: 0.001 to 0.1 weight percent of carbon; 2 to 4 weight percent of silicon; 0.1 to 3 weight percent of aluminum ; 0.1 to 2 weight percent of manganese; not more than 0.1 weight percent of phosphorus; not more than 0.01 weight percent of sulfur; and a balance of iron, and the steel blank does not contain nickel and nitrogen; the steel blank is subjected to a A hot rolling process to form a hot rolled steel plate, wherein one of the completion temperatures of the hot rolling process is 800°C to 1000°C; a hot rolling annealing process is performed on the hot rolled steel plate to form a hot rolled annealed steel plate, wherein the One of the heating rates of the hot-rolling annealing process is not greater than 15°C/s, one of the annealing temperatures of the hot-rolling annealing process is 900°C to 1100°C, and the hot-rolled annealed steel plate has Rotated cube{001}<110> and/or ND//<001> is a collective organization; performs a cold rolling process on the hot-rolled annealed steel plate to form a cold-rolled steel sheet; and performs a final annealing process on the cold-rolled steel sheet to obtain the electromagnetic steel sheet. The manufacturing method of electromagnetic steel sheet as described in claim 1, wherein Before performing the hot rolling process, the steel blank is heated to 1000°C to 1200°C. The manufacturing method of electromagnetic steel sheet as described in claim 1, wherein after performing the hot rolling process, the manufacturing method further includes: performing a coiling process on the hot rolled steel sheet, wherein a temperature of the coiling process is 500 ℃ to 750℃. The manufacturing method of electromagnetic steel sheet as described in claim 1, wherein one of the temperature holding times of the hot rolling annealing process is 30 seconds to 240 seconds. The manufacturing method of electromagnetic steel sheets as described in claim 1, wherein one of the annealing temperatures in the final annealing process is 750°C to 1100°C. The manufacturing method of electromagnetic steel sheet as described in claim 1, wherein one of the temperature holding times of the final annealing process is 30 seconds to 120 seconds. The manufacturing method of the electromagnetic steel sheet as described in claim 1, wherein after the final annealing process, the temperature is cooled to room temperature at a rate of 2°C/s to 30°C/s to form the electromagnetic steel sheet. An electromagnetic steel sheet produced by the manufacturing method described in any one of claims 1 to 7, wherein the electromagnetic steel sheet includes Cube{001}<100> and/or Goss{110}<100> a collection of organization.