JPS5813606B2 - It's hard to tell what's going on. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a unidirectional silicon steel strip comprising crystal grains with (110) (001) orientation.

Unidirectional silicon steel sheets are soft magnetic materials that are mainly used as iron core materials for transformers and generators, and have low iron loss (Wl7
It is required to have good magnetic properties such as a low magnetic flux density (represented by B8) and a high magnetic flux density (represented by B8).

Using electrical steel sheets with excellent magnetic properties not only allows transformers to be made smaller and saves power resources, but also reduces magnetostriction, which is the cause of transformer noise, which has recently become a particular problem. It is also effective in reducing

What is the unidirectional silicon steel sheet that meets these requirements? (11)
0) (001) orientation has an extremely high degree of accumulation,
In order to industrially manufacture such products, it is necessary to suppress the normal grain growth of primary recrystallization up to a certain temperature, and to
01) To promote the growth of oriented secondary recrystallized grains,
It is an essential condition that a suitable precipitated dispersed phase (inhibitor) exists in the steel in a favorable state during the final annealing.

It is generally said that the grain boundary restraining force due to different phase fine particles is inversely proportional to the size and average spacing of precipitated particles, and the more uniform and fine the distribution of these particles, the stronger the normal grain growth of primary grains until the start of secondary recrystallization. suppress, resulting in (110) [0
01] A secondary recrystallized structure with a high degree of orientation integration is obtained.

The heterogeneous precipitated phase that acts as an inhibitor is MnS and MnS.
e has traditionally been the most common.

The dispersed precipitation state of these heterogeneous precipitated phases is substantially determined by the thermal history up to the hot rolling process.

Therefore, in order to make the dispersion of the heterogeneous precipitated phases uniform, first of all, the S and Se contained in the steel must be prepared before the start of hot rolling.
When making a hot rolled sheet directly from a slab or a steel ingot, the temperature of the steel ingot must be set to a temperature that allows all of S and Se to become a solid solution, and the steel ingot must be heated sufficiently.

Second, it is necessary to satisfy appropriate cooling conditions in the process of hot rolling a slab or steel ingot heated to a temperature that satisfies these conditions into a hot-rolled steel strip. Even if either of the conditions 1 and 2 are lacking, a sufficient suppressing effect by the different-phase precipitated particles cannot be expected.

From this point of view, the present invention controls the rolling conditions and cooling conditions during hot rolling to make the inhibitor dispersion state particularly uniform and fine, thereby producing a unidirectional silicon steel strip (sheet) with extremely excellent magnetic properties. ) provides a new method for manufacturing.

In other words, the feature of the present invention is that prior to hot rolling, the raw material slab is heated to a temperature of 1230°C or higher to completely dissolve S and Se, which are inhibitors, and then MnS and MnS are dissolved during hot rolling. In order to uniformly and finely disperse the precipitated phases such as e, the steel plate temperature is 950 to 1200°C while hot rolling at a hot rolling reduction rate of 10 or more.
The hot-rolled steel strip thus obtained having a preferable distribution of inhibitors is cooled at a rate of at least 1 sec, and the hot-rolled steel strip thus obtained is cold-rolled one or more times (in the case of two or more times, an appropriate intermediate annealing is performed). The steel is finished to the final thickness by decarburization annealing to reduce the amount of C in the steel to 0.004% or less, and then subjected to secondary recrystallization and high-temperature finishing annealing for purification. Unidirectional silicon steel strips can be produced.

Another feature of the present invention is that during the final finishing annealing of the hot-rolled steel strip with a preferred distribution of inhibitors according to the method described above, the secondary recrystallization is completed at a temperature of 800-900'C. 0.5~5℃/h
The effect of the present invention can be further improved by slow heating at a heating rate of r or by holding at an appropriate temperature during this time for 5 hours or more, and then performing purification annealing at 1000° C. or higher.

Generally, when the above-mentioned inhibitor elements precipitate and grow as MnS or MnSe during the cooling process after solid solution treatment, it is known that the faster the cooling rate, the smaller the size of the precipitated particles and the narrower the average interval. For example, U.S. Patent No.
As seen in No. 069, No. 299, a method has been proposed for improving the magnetic properties of grain-oriented silicon steel strip by regulating the cooling rate of the steel ingot.

However, up until now, MnS and Mn precipitated during cooling have been
Since the details of Se precipitation behavior have not been clarified, it is important to increase the cooling rate at which stage in the process of finishing heated slabs or steel ingots into hot-rolled steel strips through rough rolling and finish rolling. It was not clear whether

On the other hand, in order to clarify this point, the present inventors
We conducted several experiments and found that MnS and MnS in silicon steel
e shows that the precipitate growth rate is fastest when the steel plate temperature is in the temperature range of 950 to 1200°C during the cooling process, and the cooling rate during this period is important. The present invention was completed based on the new finding that even if the cooling rate is the same, a more uniform and finer distribution of the inhibitor can be obtained than in the case where there is no inhibitor.

Figure 1 shows an example of the results of an experiment conducted by the present inventors. 1350℃
After conducting solid solution treatment for 30 minutes at a temperature, the precipitation and growth behavior of MnSe was investigated by holding each temperature for 10 minutes during cooling. This shows that growth occurs rapidly.

Such a tendency is similarly observed in the case of MnS precipitation growth.

Figure 2 shows a steel billet with a thickness of 5 to 30 mm having the above-mentioned components heated at 1300°C for 30 minutes to completely dissolve Se, and then taken out and cooled by a reversible rolling mill for 3 to 30 minutes. Mn when hot rolled in 6 passes and cooled at several constant cooling rates, and when similar cooling conditions were used without hot rolling and therefore without deformation.
It shows how the dispersion of Se differs.

In Figure 2, the cooling rate is the temperature of the steel billet from 1200℃ to 950℃.
This refers to the temperature range up to ℃, and the temperature drop during this period is approximated by a straight line.

Here, "while hot rolling" means that the steel sheet undergoes hot working continuously until the processing strain caused by rolling is almost released by self-annealing due to the steel sheet's own heat, and the steel sheet temperature is 950 to 1200. ℃ refers to a state in which the interval between each pass is within 10-odd seconds.

Further, the hot rolling reduction ratio shown in FIG. 2 is the hot rolling reduction ratio continuously applied during the period from 1200°C to 950°C after the steel sheet temperature has been solid solution treated at 1300°C.

As shown in the figure, the average radius of MnSe becomes smaller as the cooling rate increases, but even at the same cooling rate, cooling while hot rolling or deforming by hot rolling reduces the grain size. Recognize.

The electron micrograph in Figure 3 shows the steel plate temperature between 950 and 1200.
The dispersion of MnSe differs between (A) when hot rolling is performed at a cooling rate of 28°C/sec and (B) when cooling is performed at the same cooling rate without hot rolling. (A), which was cooled while hot rolling at a rolling reduction of 85%, shows that even more uniform and fine dispersion can be obtained.

Figure 4 shows the differences in cooling rate and hot rolling reduction during cooling while the billet temperature is within the above range after solid solution treatment.
This diagram illustrates the effect on the value.

In the same figure, in order to obtain an excellent product with a B8 value of 1.88wb/m^ or more, the cooling rate in the range of 950 to 1200°C must be at least 3°C/sec or more, and the hot rolling reduction rate must be 10% or more. It turns out that it is necessary.

The experimental facts represented in Figures 3 and 4 above show that during the hot rolling process of unidirectional silicon steel strip (plate), the steel plate temperature was 950°C.
This shows that the cooling conditions in the temperature range of ~1200°C and the hot rolling reduction rate during that time are important points that determine the dispersion form of inhibitors such as MnS and MnSe.

In a hot rolling process generally carried out on an industrial scale, a silicon steel slab extracted from a heating furnace is finished into a hot rolled steel strip by rough rolling and finish rolling.

As mentioned above, it is desirable to rapidly cool the steel sheet while continuously hot rolling the steel sheet at a temperature between 950 and 1200°C, but such conditions are easily achieved by continuous rolling using a tandem finishing mill, etc. This is the finish rolling stage.

A method of controlling the timing at which the temperature of the steel sheet during hot rolling reaches the above temperature range coincides with that during finish rolling is advantageous in obtaining a uniform fine precipitated dispersed phase in the hot rolled steel strip.
It was thought that this would make it possible to improve the magnetic properties of products.

FIG. 5 shows the results of an experiment conducted on an industrial scale to clarify these points.

That is, C: 0.040, Si: 3.02%, Mn: 0.
A 140 mm thick silicon steel slab containing 0.06% and 0.014% Se was heated at 1300°C for 2 hours and then rough rolled to form a 35 mm thick sheet bar (rough rolling completion temperature approx.
250°C), and then in the process of producing a 3.0 mm thick hot rolled steel strip by continuous finishing rolling using six tandem finishing mills, the finishing rolling start temperature was set at 120°C.
Those that are finished rolled immediately to a temperature of 0°C or higher, those whose finish rolling start temperature is in the range of 1050 to 1100°C, and those whose finish rolling start temperature is in the range of 1050 to 1100°C
℃ or less on the table in front of the finishing rolling mill.
The specimens were held for 200 seconds, the cooling conditions varied during that time, and then finished rolled.

The hot rolled steel strip thus obtained was cold rolled twice including intermediate annealing to achieve a zero. After finishing to 35 mm and decarburizing,
Products were manufactured by a known method of final high-temperature annealing, and the relationship between their B8 value and cooling rate during hot rolling is shown in FIG. 5 using the finish rolling start temperature as a parameter.

As is clear from the figure, the conditions of the present invention are completely satisfied, that is, the finishing rolling start temperature is 1200°C or higher, and the temperature range of 950 to 1200°C is continuously hot rolled at 3°C/sec. The product cooled in the above manner is B8 of the product.
It can be seen that it has excellent magnetic properties with a value exceeding 1.88 wb/m^.

When the finishing rolling start temperature is 1030 to 1070°C or 95°C
When the temperature is 0° C. or lower, even if the cooling rate is 3° C./sea or higher, MnSe precipitate growth progresses considerably until the start of finish rolling, so the B8 value is lower than in the above case.

In order to achieve the same effect as the present invention, it is necessary to increase the cooling rate, but there is a limit to the industrially possible cooling capacity, and products with a B8 value exceeding 1.88wb/m^ It is difficult to produce it stably.

It has already been mentioned that the steel strip hot-rolled by the method of the present invention has a particularly uniform and fine distribution of inhibitors, and such a steel strip undergoes secondary recrystallization at 800 to 900°C in the final annealing step. Adding a strengthening treatment is advantageous in further enhancing the magnetic properties of the product.

Regarding this process, if secondary recrystallization is performed at as low a temperature as possible, it becomes possible to preferentially grow only secondary recrystallized grains with less deviation from the (110) [001,1 orientation; It was found that the more uniform and fine the inhibitor dispersion, the more pronounced it is.

FIG. 6 shows this, and the conditions of the present invention, namely 13
During the cooling of the steel billet treated with solid solution treatment at 00°C for 30 minutes, the steel billet was cooled at a cooling rate of 18°C/sec while hot rolling at a hot rolling reduction rate of 85% while the steel billet temperature was between 950 and 1200°C. A hot-rolled sheet with a thickness of .0 mm was heated to 18℃/Se without deformation until the billet temperature reached 950℃ after solid solution treatment.
Two types of hot-rolled sheets were cooled at a cooling rate of C and then hot-rolled to a thickness of 3.0 mm, and the final thickness was obtained by a known method of cold rolling twice, followed by final finish annealing after decarburization. The secondary recrystallization treatment temperature was changed several times and the B8 characteristics were compared when each temperature was held for 50 hours.

It can be seen that by adopting the hot rolling conditions of the present invention, the temperature at which secondary recrystallization can be completed in 50 hours is lowered by about 20°C, and as a result, the B8 value is further increased.

The method of the present invention, in which the steel sheet is cooled at a cooling rate of 3°C/sec or more while hot rolling at a hot rolling reduction rate of 10% or more while the steel sheet temperature drops from 1200°C to 950°C, achieves particularly uniform and fine inhibitor dispersion. Although the mechanism by which this occurs has not been fully elucidated, according to the inventors' opinion, various lattice defects introduced during hot rolling cause MnS and Mn
It is thought that by acting on the precipitation nuclei of Se and adding deformation before the precipitation growth occurs or during the progress of the precipitation growth, the number of precipitation nuclei increases and at the same time inhibits their coarse growth.

A method of controlling the cooling conditions during hot rolling and dispersing the precipitated dispersed phase, which acts as an inhibitor, in a preferable state has already been proposed in JP-A-47-20010 and JP-A-48.
-51852.

However, all of these methods attempt to obtain a preferable precipitated dispersed phase of AlN by accelerating the cooling conditions after slab extraction.

On the other hand, the present invention is applied to silicon steel containing S, Se, and if necessary sb.
This is intended for uniform dispersion of precipitated particles such as e.

Furthermore, the present invention is characterized in that even more preferable inhibitor dispersion can be brought about by cooling while hot rolling in the temperature range of 950 to 1200°C where these precipitate and grow at a hot rolling reduction ratio of 50% or more. It is based on new technical ideas that did not exist before.

Next, the present invention will be explained based on embodiments. Materials suitable for use in the present invention include C0.01 to 0.06%, Si
2. O~4.5% and Mn 0.0 1~0. 2
0 coefficient, and either one or two of S or Se as an inhibitor forming element is 0.005 to 0.1 in total
00%, and sometimes further contains sb at 0.20% or less, and the remainder is essentially composed of iron, meaning a steel ingot when using the ordinary ingot-forming method, and a slab when using the continuous casting method. .

As the melting method, any known method can be used.

The necessity of such components is based on the following reasons.

Regarding C, in order to make the crystal structure uniform in the hot rolling process and the cold rolling process, an amount that produces a γ phase is required in some parts, and the amount of C required for this varies depending on the amount of Si, but there is a lower limit. is approximately 0.010% or more.

The upper limit is set at 0.06% mainly due to the limit of decarburization ability.

The lower limit of Si is set as an amount that does not impair directionality due to γ deformation when promoting purification in final finish annealing, and the upper limit is set as an amount that can prevent plate cracking during cold rolling.

The lower limit of Mn is set at 0.20% because if it falls below 0.01%, the amount of MnS and MnSe necessary as inhibitors cannot be secured, and the upper limit is set at 0.20%.
This is because the slab heating temperature or steel ingot soaking temperature required to dissociate and dissolve all n S e becomes too high.

The lower limit of S or Se is determined as the minimum amount necessary as an inhibitor, and the upper limit is set because hot cracking will occur for S if the amount exceeds this, and for Se, it is mainly based on economic reasons.

sb is added because it brings about a stronger grain boundary suppressing effect when coexisting with MnS and Mnce, and the upper limit of its required amount is 0.20%, and it is meaningless to add more than that. The upper limit is regulated.

However, the effects of the present invention are not necessarily limited to the case where sb is included, and therefore no lower limit is set for sb.

In the case of the ordinary ingot making method, a steel ingot having the above-mentioned components is soaked and then finished into a slab of a predetermined thickness by blooming rolling according to a known method, and then heated in a heating furnace.

At this time, it is important to select the heating temperature so that all the S and Se contained in the steel dissolve into solid solution, and by heating to 1230°C or higher, the intended purpose can be achieved regardless of the component composition. be able to.

Further, in the direct rolling method that does not include the step of heating the slab, it is necessary to determine the soaking temperature and soaking time of the steel ingot so that all the S and Se in the steel ingot are dissolved.

Regarding solid solution conditions for S, it is generally known from the relationship between the dissolution product of MnS and the heating temperature that it is necessary to select the heating temperature according to the amount of S and Mn, and the same applies to the case of Se. Consideration is required.

FIG. 7 shows the relationship between the melting product of MnSe and temperature, which was determined by the present inventors.

In order to dissolve all Se contained in the steel by soaking the steel ingot or heating the slab, the temperature at the time of extraction must be in the solid solution region shown in the figure.

A slab or steel ingot heated under such conditions is finished into a hot-rolled steel strip by rough rolling and finish rolling, but the present invention focuses on hot rolling conditions in this case, particularly when the steel plate temperature is 950 to 1200.
℃ cooling rate and hot rolling reduction ratio are the issues.

That is, the most important point of the present invention is to cool the product at a cooling rate of 3° C./SeC or more while hot rolling at a hot rolling reduction of 10% or more during this period.

One means that should be specifically adopted when carrying out the present invention in a continuous hot rolling process is to set the finishing rolling start temperature to 1200° C. in order to cool at the above-mentioned cooling rate while continuously hot rolling.
℃ or higher, and for this purpose, the amount of descaling water and roll cooling water during rough rolling is reduced.
It is preferable to reduce the number of passes and increase the temperature before starting finish rolling.

Subsequently, the above conditions can be achieved by increasing the amount of cooling water during finish rolling and adjusting the rolling schedule in order to increase the cooling rate during finish rolling.

However, the present invention is not limited to such a method, and similar effects can be obtained by controlling the reduction schedule and cooling rate during rough rolling.

The thus obtained hot-rolled steel strip with a thickness of 2 to 4 mm has a uniform and fine distribution of the inhibitor, and is rolled by a known method one or more times (in the case of two or more times, an appropriate rolling process is performed as necessary). After that, decarburization annealing is performed in wet hydrogen at a temperature of 750 to 900°C to reduce C to 0.005% or less, and then annealing separation of MgO, etc. A coating agent is applied and the material is subjected to final annealing.

The purpose of the final first finish annealing is secondary recrystallization and purification, but in order to complete the secondary recrystallization in the temperature range of 800 to 90oC, this temperature range is
The effects of the present invention can be further enhanced by slow heating at a heating rate of 5 to 5 °C/hr, or by holding the above temperature range for 5 hours or more, and then annealing at a high temperature of 1000 °C or higher for purification. Desirable in that it makes it salient.

The magnetic properties of the unidirectional silicon steel strip product obtained through such a series of steps are extremely excellent.

Next, examples will be given.

Example I C0.035%, Si3.01%, Mn0.06%, S
e0.030%, S0.006%, SbO. A silicon steel ingot containing 0.020% was heated in a soaking furnace for 5 hours, then bloomed into a slab with a thickness of 170 mm.
It was heated at 320°C for 2 hours.

In the subsequent hot rolling step, hot rolling was carried out under the conditions shown in Table 1 to obtain a 3.0 mm hot rolled steel strip.

The cooling rate in this table is the cooling rate in the temperature range of 950 to 1200°C, which has the most significant effect on the precipitation growth of MnS and MnSe. ) was determined from the readings of thermometers placed on the front and rear surfaces of the rolling stock and between the stands, and the rolling time during that time.

Further, the hot rolling reduction rate is the hot rolling reduction rate during finish rolling in which the steel plate is continuously rolled, and represents the total reduction rate applied until the steel plate temperature reaches 950°C.

These hot-rolled sheets undergo intermediate annealing at 900°C for 5 minutes.
The final product plate thickness was made to 0.30 mm by two-time cold rolling method (secondary cold rolling rate 60%), then decarburized at 800°C for 3 minutes in a wet hydrogen atmosphere, coated with an annealing separator, and finally rolled at 1200°C. ℃1
Finish annealing was performed in dry hydrogen for 0 hours.

The magnetic properties of the thus obtained product in the rolling direction are shown in Table 1, and it can be seen that the magnetic properties of the product hot rolled by the method of the present invention are excellent.

Example 2 CO. 04 1%, Si 3.08%, MnO. 0
A 140 mm thick silicon steel slab containing 7% S and 0.018% S was heated in a heating furnace at 1330°C for 3 hours and then hot rolled under the conditions shown in Table 2 in the hot rolling process. A hot rolled sheet with a thickness of .5 mm was obtained.

These hot-rolled sheets are subjected to intermediate annealing at 900°C for 5 minutes2.
The final product plate thickness was made to 0.30 mm by the double cold rolling method (secondary cold rolling rate 55%), then decarburized at 800°C for 3 minutes in a wet hydrogen atmosphere, and after applying an annealing separator, the final product was heated to 1200°C for 10 minutes. Final annealing was performed in time-dry hydrogen.

The magnetic properties of the thus obtained product in the rolling direction are shown in Table 2, and it can be seen that the magnetic properties of the product hot rolled by the method of the present invention are excellent.

Example 3 C0.034%, Si3.04%, Mn0.04%, S
e0.022%, SO. 1 containing 0 0 4%
Heat a 70mm thick silicon steel slab to 1320℃2 in a heating furnace.
In the hot rolling step after Hr heating, hot rolling was carried out under the conditions shown in Table 3 to obtain a hot rolled steel strip with a thickness of 3.0 mm.

These hot-rolled sheets were subjected to intermediate annealing at 900°C for 5 minutes.
The final product was made to have a thickness of 0.30 mm by a double cold rolling method (secondary cold rolling reduction rate of 60%), and then decarburized at 800° C. for 3 minutes in a wet hydrogen atmosphere and coated with an annealing separator.

The subsequent final annealing was carried out under the conditions shown in Table 3.

The magnetic properties of the product thus obtained in the rolling direction are as shown in Table 3, and the steel strip hot-rolled by the method of the present invention undergoes secondary recrystallization in the temperature range of 800 to 900°C during the final annealing process. It can be seen that the product's magnetic properties are significantly improved by adding a treatment to sufficiently develop the magnetic field.

Example 4 C0.045%, Si3.12%, Mn 0.06
%, 80.023%, Se0.010%, Sb0.02
Approximately 9 tons of silicon steel ingots containing 096 were heated in a soaking furnace for 13 minutes.
After heating at 60°C for 10 hours, the steel strip was hot-rolled to 3.3 mm under the conditions shown in Table 4 in the hot rolling process of finishing it into a hot-rolled steel strip by a direct rolling method that does not involve slab heating.
A thick hot-rolled steel strip was obtained.

These hot-rolled sheets were subjected to intermediate annealing at 900°C for 5 minutes.
0.0 with double cold rolling method (secondary cold rolling reduction rate 60%). 35 m
The final product plate thickness was 1200°C after being decarburized in a wet hydrogen atmosphere for 3 minutes at SOO°C and coated with an annealing separator.
Finish annealing was performed in dry hydrogen for 0 hours.

The magnetic properties of the products thus obtained in the rolling direction are shown in Table 4, and it can be seen that the magnetic properties of the products hot-rolled by the method of the present invention are excellent.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the precipitation treatment temperature (°C) and the average radius of ■Se (A) during the cooling process of a silicon steel sheet subjected to solid solution treatment, and Figure 2 shows the relationship between the cooling rate (°C) after solid solution treatment. / se
Figure 3 shows the relationship between the average radius blow p of MnSe and the hot rolling speed (℃/sec) during the cooling process as a parameter. Electron micrographs showing the dispersion state of the inhibitor A) when cooled while hot rolling at 1/sec and B) when cooled without hot rolling. When tightening, the steel plate temperature is 9
Total reduction rate (%) applied while at 50-1200℃
Figure 5 shows the influence of the cooling rate (℃/sec) on the B8 value (Wb/m') of the final product.
The figure shows the relationship between the cooling rate (°C/sec) during hot rolling and the product B8 value (wb/m'), and Figure 6 shows the relationship between the secondary recrystallization temperature (°C) and the final finish annealing process. B8
Figure 7 shows the relationship between MnSe and the value (wb/m').
FIG. 3 is a diagram showing the relationship between the dissolution product and temperature.

Claims (1)

[Claims] lSi2.0-4.5%, C0.01-0.06%, M
nO. A silicon steel material containing 0.01 to 0.20% and a total of 0.005 to 0.10% of any one or both of S and Se is hot rolled into a hot rolled steel strip. is subjected to one cold rolling or two or more cold rolling including intermediate annealing to achieve the final plate thickness, and then subjected to decarburization annealing and final finish annealing to produce a unidirectional silicon steel strip. In a series of steps, the silicon steel material is heated to a temperature of 1230°C or higher before the hot rolling to remove the S contained in the steel.
Or, during hot rolling after all Se is dissolved in solid solution, the steel plate temperature is continuously hot rolled between 950 and 1200°C at a hot rolling reduction ratio of 10% or more, and a cooling rate of 3°C/SeC or more. A method for manufacturing a unidirectional silicon steel strip with extremely excellent magnetic properties, which is characterized by cooling with 2Si2.0-4.5%, co. oi~0.06%, M
A hot-rolled steel strip is produced by hot rolling a silicon steel material containing n 0.01 to 0.20% and a total of 0.005 to 0.10% of any one or both of S and Se. This is then subjected to one cold rolling or two or more cold rolling including intermediate annealing to achieve the final plate thickness, and then subjected to decarburization annealing and final finishing annealing to produce a unidirectional silicon steel strip. In a series of steps for manufacturing, (1) hot rolling after heating the silicon steel material to a temperature of 1230°C or higher to dissolve all the S or Se contained in the steel before the above-mentioned hot rolling; During rolling, the steel plate temperature is between 950 and 1200°C with a hot rolling reduction rate of 10
% or more while cooling at a cooling rate of 3°C/sec or more (2) During final finish annealing,
A method for producing a unidirectional silicon steel strip with extremely excellent magnetic properties, characterized by completing secondary recrystallization at a temperature of 800 to 900°C, and then performing purification annealing at a temperature of 1000°C or higher.