TWI580795B - Method for manufacturing electrical steel - Google Patents

Description

Method for manufacturing electromagnetic steel sheet

The present invention relates to a method of manufacturing a steel sheet, and more particularly to a method of manufacturing an electromagnetic steel sheet.

For electromagnetic steel sheets of the same composition, the magnetic flux density is mainly affected by the aggregate structure of the electromagnetic steel sheets. If the full-scale magnetic properties are considered, the strength of the organization with <100>//ND and <111>//ND is the most critical. On the other hand, if only the magnetic properties in the rolling direction are considered, the Gaussian aggregate structure of {011} <100> is the most important.

In general, during the production of electromagnetic steel sheets, at least two rolling (ie, hot rolling and cold rolling) and at least two annealing (ie, hot rolling coil and cold rolling annealing) are performed. The rotation of the crystal plane caused by the displacement movement will form a very strong rolling and collecting structure, and even affect the development of the recrystallized aggregate structure after annealing. Early studies have proved that the high-angle grain boundary formed by the cold rolling process is re The nucleation sites produced by crystallization. In recent years, studies have further proved that the shear band composed of specific aggregated tissues is the nucleation point in the early stage of recrystallization. The areas of these shear bands include cold rolling. {111}//The ND set organization's shear band, or multiple combination set organization Shear band at the place. These regions meet both recrystallization kinetics and thermodynamic requirements for potential early recrystallization nucleation.

The general anisothermal annealing process continuously heats the process temperature to a high temperature at a fixed heating rate, and the steel sheet undergoes three processes of recovery, recrystallization and grain growth in sequence. At present, the process of the electromagnetic steel sheet is subjected to a single-stage temperature-raising annealing treatment after cold rolling, so that the steel can only conform to the development of the assembly structure of the deformed structure after the cold rolling in the heating process.

The magnetic flux density of electromagnetic steel sheets is a key factor affecting motor efficiency. According to statistics, the motor efficiency can be increased by 0.3% to 0.4% for every 0.01 tesla of the magnetic flux density of the electromagnetic steel sheet. Since the power consumed by various motors accounts for about 45% of the total power generation, the increase in the aforementioned motor efficiency can reduce the total power generation by about 1.5%. In view of this, the steel industry does not want to develop electromagnetic steel sheets with high-pass density.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method of manufacturing an electromagnetic steel sheet which, in combination with metallurgical principles and the development of aggregated structures in steel, replaces the conventional single-stage direct temperature annealing process with a two-stage or multi-stage annealing process. Thereby, the grain orientation which is favorable for the magnetic development, such as the Gaussian orientation, can be retained, and the crystal grains grow in this direction in the subsequent grain growth stage, thereby improving the magnetic properties of the electromagnetic steel sheet.

Another object of the present invention is to provide a method for manufacturing an electromagnetic steel sheet which can effectively improve the magnetic properties of the electromagnetic steel sheet, thereby achieving the effect of energy saving and carbon reduction.

According to the above object of the present invention, a method of manufacturing an electromagnetic steel sheet is proposed. In this method, a steel blank is provided, wherein the steel embryo comprises greater than 0 and equal to or less than 2 wt% of rhodium, equal to or less than 0.5 wt% of aluminum, greater than 0 and equal to or less than 0.005 wt% of carbon, 0.1 wt% to 0.2 wt% manganese, 0.01 wt% to 0.05 wt% phosphorus, and a balanced amount of iron. The steel blank is subjected to a hot rolling step to form a steel sheet. The steel sheet is subjected to a cold rolling step to form a steel sheet. Performing a first-stage annealing step on the steel sheet, increasing the processing temperature to the first temperature at the first heating rate, and holding the steel sheet at the first temperature for the first time, wherein the first temperature is 540 ° C to 700 ° C. Performing a second-stage annealing step on the steel sheet, and heating the process temperature to a second temperature at a second heating rate, and holding the steel sheet at the second temperature for a second time, wherein the second temperature is 800 ° C to 900 ° C.

According to an embodiment of the invention, the first temperature increase rate is from 3 ° C / s to 10 ° C / s.

According to another embodiment of the invention, the first time is 50 seconds to 300 seconds.

According to still another embodiment of the present invention, the second temperature increase rate is from 3 ° C / s to 10 ° C / s.

According to still another embodiment of the present invention, the second time is 50 seconds to 100 seconds.

According to still another embodiment of the present invention, between the first-stage annealing step and the second-stage annealing step, the manufacturing method of the electromagnetic steel sheet further comprises performing a third-stage annealing step on the steel sheet, and the processing is performed at a cooling rate. temperature The degree is lowered from the first temperature to the third temperature, and the steel sheet is held at the third temperature for a third time.

According to still another embodiment of the present invention, the temperature drop rate is from 3 ° C/s to 10 ° C/s, and the third temperature is less than the first temperature and equal to or greater than 400 ° C.

According to still another embodiment of the present invention, the third time is 30 seconds to 300 seconds.

According to still another embodiment of the present invention, between the first-stage annealing step and the second-stage annealing step, the method for manufacturing the electromagnetic steel sheet further comprises performing a plurality of third-stage annealing steps on the steel sheet, wherein each third The stage annealing step includes holding the steel sheet at a third temperature for a third time, wherein the third temperatures are both lower than the first temperature and equal to or greater than 400 ° C, and each third time is from 30 seconds to 300 seconds.

According to still another embodiment of the present invention, the third temperature is different.

100‧‧‧ steps

102‧‧‧Steps

104‧‧‧Steps

106‧‧‧Steps

108‧‧‧Steps

The above and other objects, features, advantages and embodiments of the present invention will become more <RTIgt; <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; A flow chart of a manufacturing method; [Fig. 2A] is a diagram showing a crystal orientation distribution function (ODF) of a conventional electromagnetic steel sheet; 2B is a graph showing a crystal orientation distribution function of an electromagnetic steel sheet according to an embodiment of the present invention.

In view of the close relationship between the magnetic flux density of the electromagnetic steel sheet and its aggregate structure, the present invention proposes a method for manufacturing an electromagnetic steel sheet, which is subjected to a two-stage or multi-stage annealing process for steel after cold rolling of the steel material. Annealing, which will favor the development of magnetic nucleation, such as Gaussian grain nucleation, remains during recrystallization and coarsens during subsequent grain growth. Thereby, the magnetic properties of the electromagnetic steel sheet can be improved.

Please refer to FIG. 1 , which is a flow chart showing a method of manufacturing an electromagnetic steel sheet according to an embodiment of the present invention. In some examples, when manufacturing an electromagnetic steel sheet, step 100 may be performed to perform a steel making process to produce and provide a steel blank. The method for producing an electromagnetic steel sheet according to the present embodiment can be used to produce an electromagnetic steel sheet having a Si-Al-C chemical composition. In some exemplary examples, the steel blast comprises greater than 0 and equal to or less than 2 wt% bismuth, equal to or less than 0.5 wt% aluminum, greater than 0 and equal to or less than 0.005 wt% carbon, and 0.1 wt% to 0.2 wt% manganese. , 0.01 wt% to 0.05 wt% phosphorus, and a balanced amount of iron. In addition, steel embryos usually contain unavoidable impurities.

Next, step 102 may be performed to hot-roll the steel blank into a steel sheet by performing a hot rolling step on the steel blank. In some examples, after hot rolling of the steel preform, the steel sheet formed by hot rolling may be selectively annealed. After the hot rolling of the steel sheet is completed, the steel sheet can be coiled into a steel coil.

Next, step 104 may be performed to cold-roll the steel sheet into a steel sheet by subjecting the steel sheet to a cold rolling step. In general, the cold rolling step of the steel sheet may include multiple rough rolling treatments and finish rolling treatments.

After the cold rolling is completed, the steel sheet may be subjected to a two-stage annealing process or a multi-stage annealing process. In some examples, the steel sheet is subjected to a two-stage annealing process. Referring again to FIG. 1, in the two-stage annealing process, step 106 may be performed first to perform a first-stage annealing step on the steel sheet. In this first stage annealing step, the process temperature is raised to a first temperature at a first ramp rate and the steel sheet is held at the first temperature for a first time. In some exemplary examples, the first rate of temperature increase may range from about 3 ° C/s to about 10 ° C/s, the first temperature may range from about 540 ° C to about 700 ° C, and the first time may range from about 50 seconds to about 300 seconds. .

Next, step 108 may be performed to further perform a second-stage annealing step of the two-stage annealing process on the steel sheet. In the second-stage annealing step, the process temperature is raised from the first temperature to the second temperature at a second temperature increase rate, and the steel sheet is held at the second temperature for a second time. That is, the second temperature of the second-stage annealing step is higher than the first temperature of the first-stage annealing step. In some exemplary examples, the second rate of temperature increase may range from about 3 ° C/s to about 10 ° C/s, the second temperature may range from about 800 ° C to about 900 ° C, and the second time may range from about 50 seconds to about 100 seconds. .

In the two-stage annealing process, in the first-stage annealing step, the process temperature is first raised to a temperature at which partial recovery and partial recrystallization of the steel sheet occurs, that is, a temperature at which initial recrystallization occurs, and the temperature is maintained for a while. Thereby, the orientation of the steel sheet which is favorable for the development of magnetism, for example, the Gaussian orientation and the cube orientation of {011}<100>, and the Gaussian of these nucleation points can be nucleated. Azimuth and cubic orientation are preserved. On the other hand, in the second-stage annealing step, the Gaussian and cubic equi-directional recrystallized grains which have been formed in the first annealing stage have a size advantage in the second-stage recrystallization process, and become the preferred orientation for growth. It grows up in this annealing stage, so that the magnetic properties of the steel sheet can be improved.

In some examples, between the first-stage annealing step and the second-stage annealing step, a third stage annealing step of the steel sheet may be further included. In the third-stage annealing step, the process temperature is lowered from the first temperature in the first-stage annealing step to the third temperature at a cooling rate, and the steel sheet is held at the third temperature for a third time. That is, the third temperature at the third stage annealing is lower than the first temperature at the first stage annealing. In some exemplary examples, the rate of cooling may be from about 3 ° C/s to about 10 ° C/s, the third temperature is less than the first temperature and may be equal to or greater than about 400 ° C, and the second time may be from about 30 seconds to about 300 seconds.

In other examples, between the first-stage annealing step and the second-stage annealing step, the steel sheet may be subjected to multiple third-stage annealing steps. Each third stage annealing step includes holding the steel sheet at a third temperature for a third time. In some exemplary examples, the third temperature of the third stage annealing step is lower than the first temperature and equal to or greater than 400 ° C, and the third time of the third stage annealing step is 30 seconds to 300 seconds. In such an example, the third temperatures of the third stage annealing steps may all be different, may be the same, or may be partially identical and partially different. For example, the temperature holding temperature of the third-stage annealing step of the first pass is lower than the holding temperature of the third-stage annealing step of the second pass, and the holding temperature of the third-stage third-stage annealing step is lower than the second pass. The holding temperature of the third-stage annealing step is high, and the holding temperature of the third-stage third-stage annealing step may be the same as or different from the holding temperature of the third-stage annealing step of the first pass.

The effect of the present invention is illustrated by a comparative example and three examples as follows:

The parameters relating to the annealing process after cold rolling in the comparative example and the examples, and the magnetic flux density and iron loss value of the steel sheets produced by these processes are shown in Table 1 below.

Please refer to FIG. 2A and FIG. 2B , which are respectively a graph showing a crystal orientation distribution function of a conventional electromagnetic steel sheet, and a crystal orientation distribution function diagram of an electromagnetic steel sheet according to an embodiment of the present invention. Manufacture this traditional electromagnetic In the case of a steel sheet, after the steel sheet is cold-rolled, the process temperature is directly raised to a high temperature of about 850 ° C to perform a single-stage annealing treatment of the steel sheet. As can be seen from Fig. 2A, in the crystal orientation distribution of the conventional electromagnetic steel sheet, the orientation with the highest azimuth density is {111}<112>, the intensity is 8.3, and the intensity of the Gaussian orientation is rather weak. On the other hand, as can be seen from FIG. 2B, the embodiment of the present invention can improve the orientation density of the Gaussian orientation of the electromagnetic steel sheet produced by the two-stage annealing process, for example, in the third embodiment of Table 1, above, and {111 The intensity of the }<112> orientation is reduced to 6.82.

Further, the electromagnetic steel sheets of Comparative Example 1 and the electromagnetic steel sheets of Examples 1 to 3 were subjected to magnetic measurement. The measurement results show that the magnetic flux density (B50) of the electromagnetic steel sheet produced by the conventional process is 1.736 tesla, and the iron loss value (W15/50) is 3.8 W/kg. The magnetic flux density (B50) of the electromagnetic steel sheet of Example 1 was 1.738 tesla, and the iron loss value (W15/50) was 3.75 W/kg; the magnetic flux density (B50) of the electromagnetic steel sheet of Example 2 was 1.741. Tesla, and the iron loss value (W15/50) was 3.69 W/kg; and the magnetic flux density (B50) of the electromagnetic steel sheet of Example 3 was 1.743 tesla, and the iron loss value (W15/50) was 3.72 W/kg. . It can be seen from the measurement results that the magnetic characteristics of the electromagnetic steel sheet manufactured by the present embodiment are superior to those of the electromagnetic steel sheets manufactured by the conventional process. Therefore, the present invention can obtain an electromagnetic steel sheet with better magnetic properties by changing the annealing process, thereby achieving the effect of energy saving and carbon reduction.

It can be seen from the above embodiments that one of the advantages of the present invention is that the manufacturing method of the electromagnetic steel sheet of the present invention is combined with the metallurgical principle and the development of the aggregate structure in the steel, and the two-stage or multi-stage annealing process is substituted for the traditional single-stage direct Heating and annealing process. In this way, it can be retained to facilitate the development of magnetism. The grain orientation, such as the Gaussian orientation, causes the grain to grow in this direction during the subsequent grain growth phase, thereby enhancing the magnetic properties of the electromagnetic steel sheet.

It can be seen from the above embodiments that another advantage of the present invention is that the manufacturing method of the electromagnetic steel sheet of the present invention can effectively improve the magnetic properties of the electromagnetic steel sheet, thereby achieving the effect of energy saving and carbon reduction.

While the present invention has been described above by way of example, it is not intended to be construed as a limitation of the scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100‧‧‧ steps

102‧‧‧Steps

104‧‧‧Steps

106‧‧‧Steps

108‧‧‧Steps

Claims (3)

A method of manufacturing an electromagnetic steel sheet, comprising: providing a steel embryo, wherein the steel embryo comprises greater than 0 and equal to or less than 2 wt% of rhodium, equal to or less than 0.5 wt% of aluminum, greater than 0, and equal to or less than 0.005 wt% Carbon, 0.1 wt% to 0.2 wt% of manganese, 0.01 wt% to 0.05 wt% of phosphorus, and a balance of iron; a hot rolling step of the steel blank to form a steel sheet; a cold rolling of the steel sheet a step of forming a steel sheet; performing a first-stage annealing step on the steel sheet, raising a process temperature to a first temperature at a first heating rate, and holding the steel sheet at the first temperature The first time of the first temperature, wherein the first heating rate is 3 ° C / s to 10 ° C / s, the first temperature is 540 ° C to 700 ° C, the first time is 50 seconds to 300 seconds; a second-stage annealing step, wherein the process temperature is raised to a second temperature at a second heating rate, and the steel sheet is held at the second temperature for a second time, wherein the second heating rate is 3 ° C / s to 10 ° C / s, the second temperature is 800 ° C to 900 ° C, the second time is 50 seconds to 100 seconds; and in the first stage Between the segment annealing step and the second-stage annealing step, the steel sheet is subjected to a third-stage annealing step, and the process temperature is lowered from the first temperature to a third temperature at a cooling rate, and the steel is Holding the sheet at the third temperature for a third time, wherein the temperature drop rate is from 3 ° C / s to 10 ° C / s, the third temperature is less than the first temperature and equal to or greater than 400 ° C, the third time is 30 seconds to 300 seconds. A method of manufacturing an electromagnetic steel sheet, comprising: providing a steel embryo, wherein the steel embryo comprises greater than 0 and equal to or less than 2 wt% of rhodium, equal to or less than 0.5 wt% of aluminum, greater than 0, and equal to or less than 0.005 wt% Carbon, 0.1 wt% to 0.2 wt% of manganese, 0.01 wt% to 0.05 wt% of phosphorus, and a balance of iron; a hot rolling step of the steel blank to form a steel sheet; a cold rolling of the steel sheet a step of forming a steel sheet; performing a first-stage annealing step on the steel sheet, raising a process temperature to a first temperature at a first heating rate, and holding the steel sheet at the first temperature The first time of the first temperature, wherein the first heating rate is 3 ° C / s to 10 ° C / s, the first temperature is 540 ° C to 700 ° C, the first time is 50 seconds to 300 seconds; a second-stage annealing step, wherein the process temperature is raised to a second temperature at a second heating rate, and the steel sheet is held at the second temperature for a second time, wherein the second heating rate is 3 ° C / s to 10 ° C / s, the second temperature is 800 ° C to 900 ° C, the second time is 50 seconds to 100 seconds; and in the first stage Between the segment annealing step and the second-stage annealing step, the steel sheet is subjected to a plurality of third-stage annealing steps, wherein each of the third-stage annealing steps comprises holding the steel sheet at a third temperature. The third time, wherein the third temperatures are both lower than the first temperature and equal to or greater than 400 ° C, and each of the third times is 30 seconds to 300 seconds. The method for manufacturing an electromagnetic steel sheet according to claim 2, wherein the third temperatures are different.