JPH02263923A - Production of grain-oriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet having superior magnetic properties by specifying hot rolling finishing temp. and cumulative rolling reduction, respectively, at the time of producing a grain-oriented silicon steel sheet from a silicon steel slab. CONSTITUTION:A silicon steel having a composition consisting of, by weight, 0.021-0.100% C, 2.5-4.5% Si, usual inhibitor components, and the balance Fe with inevitable impurities is hot-rolled and successively subjected, without hot rolled plate annealing, to cold rolling at >=80% rolling reduction, to decarburizing annealing, and to final finish annealing, by which a grain-oriented silicon steel sheet is produced. At this time, hot rolling finishing temp. and cumulative rolling reduction in the final three passes are regulated to 750-1150 deg.C and >=40%, respectively. By this method, the grain-oriented silicon steel sheet excellent in magnetic properties can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a unidirectional electrical steel sheet with excellent magnetic properties used as an iron core of a transformer or the like.

[Conventional technology]

Unidirectional electrical steel sheets are mainly used as core materials for transformers and other electrical equipment, and are required to have excellent magnetic properties such as excitation properties and iron loss properties. As a numerical value representing the excitation characteristic, a magnetic flux density B8 at a magnetic field strength of 800 A/m is usually used. In addition, as a numerical value representing iron loss characteristics, iron loss Wlff/S per 1 kg when magnetized to 1.7 Tesla (T) at a frequency of 50 Hz. are using.

Magnetic flux density is the most dominant factor in iron loss characteristics, and generally speaking, the higher the magnetic flux density, the better the iron loss characteristics. In general, when the magnetic flux density is increased, secondary recrystallized grains become larger, which may result in poor iron loss characteristics. On the other hand, by magnetic domain control, the iron loss characteristics can be improved regardless of the grain size of the secondary recrystallized grains.

This unidirectional electrical steel sheet undergoes secondary recrystallization in the final finish annealing process, resulting in (110) on the steel sheet surface and <000 in the rolling direction.
1> Manufactured by developing a so-called Goss structure with an axis. In order to obtain good magnetic properties,
It is necessary to align the easy magnetization axis <001> to a high degree in the rolling direction. The orientation of secondary recrystallized grains is MnS
, jVN, etc. as an inhibitor and a final heavy reduction rolling method can significantly improve the iron loss properties, and accordingly, the iron loss characteristics can also be significantly improved.

[Problem to be solved by the invention]

By the way, in the production of unidirectional electrical steel sheets, hot rolled sheets are usually annealed for the purpose of making the structure non-uniform, precipitation treatment, etc. after hot rolling. For example, in a manufacturing method using A7N as the main inhibitor, as shown in Japanese Patent Publication No. 46-23820, a method is used in which the inhibitor is controlled by performing a precipitation treatment of AZN during hot-rolled sheet annealing.

Normally, unidirectional electrical steel sheets are manufactured through the following main processes: casting, hot rolling, annealing, cold rolling, charcoal annealing, and final annealing, which requires a large amount of energy, and in addition, compared to ordinary steel manufacturing processes, etc. The manufacturing cost is also high.

In recent years, such manufacturing processes that consume large amounts of energy have been reviewed, and there has been a growing demand for simplification of processes and energy. In order to respond to such requests,
In the manufacturing method using AZN as the main inhibitor, 8! A method (Japanese Patent Publication No. 59-45730) has been proposed in which N precipitation treatment is replaced by high-temperature coiling after hot rolling. It is true that magnetic properties can be maintained to a certain extent even if hot-rolled sheet annealing is omitted using this method, but
In the normal method of winding into a 20-ton coil, differences in thermal history occur locally within the coil during the cooling process.
Inevitably, the precipitation of AIN becomes non-uniform, and the final magnetic properties vary depending on the location within the coil, resulting in a decrease in yield.

Therefore, the present inventors focused on the recrystallization phenomenon after the final pass of finish hot rolling, which had not received much attention in the past, and utilized this phenomenon to develop a manufacturing method using one cold rolling under a strong reduction of 80% or more. We considered omitting hot-rolled sheet annealing.

For hot rolling of unidirectional electrical steel sheets, high-temperature slab heating (
For example, in order to prevent secondary recrystallization failure (generation of linear fine grains connected in the rolling direction) caused by coarse growth of slab crystal grains at temperatures of 960 to 1190 during hot rolling,
A method has been proposed in which coarse crystal grains are divided by performing recrystallization high-reduction rolling at a temperature of 30% or more per pass at a temperature of .degree. C. (Japanese Patent Publication No. 60-37172). This method certainly reduces the generation of linear fine grains, but it is based on the manufacturing process of hot-rolled sheet annealing.

In addition, in a manufacturing method using MnS, MnSe, or Sb as an inhibitor, the temperature at 950 to 1200°C during hot rolling is
A method has been proposed in which MnS and MnSe are uniformly and finely precipitated by continuously hot rolling at a temperature of 10% or more with a reduction rate of 10% or more and then cooling at a cooling rate of 3°C/sec or more to improve magnetic properties. (Japanese Unexamined Patent Publication No. 51207
Publication No. 16). In addition, a method has been proposed to improve magnetic properties by performing hot rolling at a low temperature to suppress the progress of recrystallization and to prevent the (110) <001> oriented grains formed by shear deformation from being reduced by subsequent recrystallization. (Japanese Patent Publication No. 59-32526.

Special Publication No. 59m-35415). Even in these methods, production by a one-time cold rolling method without hot-rolled sheet annealing has not even been considered. In addition, when hot-rolling silicon steel slabs containing ultra-low carbon, we perform low-temperature, large-reduction hot rolling that accumulates strain in the hot-rolled plate, and then recrystallize in the subsequent hot-rolled plate annealing to create the coarse crystals characteristic of ultra-low carbon materials. A method of dividing grains has been proposed (Japanese Patent Publication No. 5934212). However, even in this method, production by a one-time cold rolling method without hot-rolled sheet annealing has not even been considered.

Therefore, the present inventors focused on the recrystallization phenomenon after the final pass of finishing hot rolling, which had not received much attention in the past, and utilized this phenomenon to develop a method for manufacturing by cold rolling in one pass under a strong reduction of 80% or more. Research was conducted with the aim of obtaining unidirectional electrical steel sheets with excellent magnetic properties by omitting the hot-rolled sheet annealing process.

[Means to solve the problem]

In the present invention, in order to achieve the objective, the hot rolling finish temperature is set at 75% for silicon steel slabs made of ordinary components.
0 to 1150°C, and the cumulative reduction rate of the final three passes was 40
% or more, followed by cold rolling with a rolling reduction of 80% or more, decarburization annealing, and final finish annealing without hot-rolled sheet annealing.

Furthermore, in addition to this feature, by setting the rolling reduction ratio in the final pass of finish hot rolling to 20% or more, a unidirectional electrical steel sheet with excellent -layer magnetic properties can be obtained.

[For production]

The unidirectional electrical steel sheet to which the present invention is directed is produced by casting molten steel obtained by a conventional steel manufacturing method using a continuous casting method or an ingot forming method, and forming a slab through a blooming process as necessary. Subsequently, hot rolling is performed to obtain a hot rolled sheet, followed by cold rolling with a rolling reduction of 80% or more without annealing the hot rolled sheet, decarburization annealing,
Manufactured by sequential final annealing.

The present inventors focused on the recrystallization phenomenon after the final pass of finish hot rolling and conducted extensive research from various viewpoints, and as a result, confirmed that this phenomenon and magnetic properties are closely related. A detailed explanation will be given below based on experimental results.

FIG. 1 is a graph showing the influence of the hot rolling end temperature and the cumulative reduction rate of the final three passes of hot rolling on the magnetic flux density of the product. Here, C: 0.054% by weight.

Si: 3.25% by weight, acid-soluble Af: 0.027% by weight, N: 0.0080% by weight, S: 0.007% by weight.

A slab with a thickness of 20 to 60 inches containing Mn: 0.14% by weight and the remainder Fe and unavoidable impurities was
Heating to 50-1400°C, hot-rolling into a 2.3M thick hot-rolled plate in 6 passes, cooling with water after about 1 second, cooling to 550"C, holding at 550°C for 1 hour, and cooling in the furnace. The final plate J!!0.335mm cold-rolled plate was subjected to a winding simulation and subjected to strong reduction rolling of about 85% without hot-rolled plate annealing, and decarburized annealed at a temperature of 830 to 1000°C. Then, an annealing separator containing MgO as a main component was applied and final annealing was performed.

As is clear from Figure 1, the hot rolling finish temperature is 750 to 115.
A high magnetic flux density of B8≧1.8 B T is obtained when the temperature is 0° C. and the cumulative reduction rate of the final three passes is 40% or more. The present inventors also investigated this new finding in more detail.

Figure 2 shows the rolling reduction ratio of the final pass of hot rolling when the magnetic flux density was good in Figure 1, at a hot rolling end temperature of 750 to 1150°C, and when the cumulative rolling reduction ratio of the final three passes of hot rolling was 40% or more. It is a graph showing the relationship with magnetic flux density.

As is clear from FIG. 2, a high magnetic flux density of B≧1.90 T is obtained when the rolling reduction ratio in the final pass is 20% or more.

Although it is not necessarily clear why the relationships shown in Figures 1 and 2 hold between the hot rolling end temperature, the cumulative rolling reduction rate of the final three passes, the rolling reduction rate of the final pass, and the magnetic flux density of the product. , the present inventors speculate as follows.

Figures 3 and 4 show the metal structures of hot-rolled sheets under different hot-rolling conditions, respectively.
An example of set m (plate thickness 1/4 point) after decarburization annealing (decarburization plate) is shown. In this case, a slab of 33.2 mm and 26n+a+ thickness with the same composition as that explained in Fig. 1 was
After heating at °C, start hot rolling at 1050 °C, ■33゜2
→18.6→11.9→8.6→5.1→3.2→2.
3 (mm), ■26→11.8→6.7→3.5→
A hot-rolled sheet with a thickness of 2,3+n+n was prepared using a pass schedule of 3.0→2.6→2.3 (mm), and cooling was performed under the same conditions as described in FIG. 1. At this time, the hot-rolling end temperature was 935°C and 912"C, respectively.The hot-rolled sheet was then subjected to heavy reduction rolling of about 85% without hot-rolled sheet annealing, and the final thickness was A cold-rolled sheet of 0.335 mm was then decarburized by holding it at 830°C for 150 seconds in an atmosphere of 25% N, 75% Hz, and 60°C at the n point.

As is clear from FIG. 3, in the case of (1) which satisfies the conditions of the present invention, the recrystallization rate of the hot rolled sheet is extremely high and the crystal grain size is small compared to (2). Moreover, as is clear from FIG. 4, in the case of (1) which satisfies the conditions of the present invention, compared to (2), the decarburization plate (11
1) Many oriented grains, few (100) oriented grains, (110
) There is no difference in orientation grains. The recrystallization rate of the hot-rolled sheet (at the 1/4th point of the sheet thickness) is determined by E CP (E
electron channeling patte
rn) to measure crystal strain by image analysis (Summary of the Autumn Conference of the Japan Institute of Metals (1988, November) P289
), and the area ratio of grains (
The area ratio of low strain grains) is called the recrystallization rate. This method is much more accurate than the conventional method of visually determining the metal structure and measuring the recrystallization rate.

As is clear from FIGS. 3 and 4, in the case of the present invention (2), the recrystallization rate of the hot-rolled sheet is extremely high (with little strain () and the crystal grain size is small). When recrystallized by extension, the 1111 crystals do not affect the (110) oriented grains.
) A texture with many oriented grains and few (100) oriented grains can be obtained.

It has been conventionally believed that the matrix of (1101<001> secondary recrystallized grains) is formed by shear deformation in the surface layer during hot rolling, and (110)<001> oriented grains in hot rolled sheets are In order to enrich after crystallization, (110)<001 in hot rolled sheet
>It is considered effective to make the oriented grains coarse and have little strain. In the present invention, the grain size of the hot-rolled sheet is small, but the strain is small, and as a result,
In the state after decarburization annealing (no effect on 1101<001> oriented grains).

On the other hand, the main orientations of the decarburization plate (111)<112>, (
10(N<025> is known as the orientation that affects the grain growth of (110)<ooi> secondary recrystallized grains,
111) The more <112>, the more (100) <025>
It is thought that the smaller the number (1101<001>), the easier the grain growth of secondary recrystallized grains.In the present invention, by applying high pressure in the final three passes of hot rolling, nucleation in the recrystallization that follows after the final pass is reduced. The number of sites increases, recrystallization progresses, and the crystal grains become finer.If the hot-rolled sheet of the present invention is subsequently cold-rolled and recrystallized, since the grain size before cold rolling is small, (111) There are many <112> nuclei, and (100) <025> nuclei are relatively reduced from inside the grain.

Therefore, in the present invention, since the hot-rolled sheet has a low strain and a small grain size due to the recrystallization that continues after the final pass of hot rolling, the decarburized annealed sheet has (110)<
(110)< without affecting the 001> oriented grains
We succeeded in increasing grains with an IIN <112> orientation, which is advantageous for the grain growth of grains with a 001> orientation, and decreasing grains with a (100) <025> orientation, which hinders the growth of grains with a (110) <001> orientation. This makes it possible to obtain good magnetic properties even if hot-rolled plate annealing is omitted.

Next, each requirement of the present invention will be explained.

The slab used in the present invention has a weight C: 0.021
~0.100%, St; 2.5-4.5% and the usual inhibitor components, the remainder consisting of Fe and unavoidable impurities.

Next, the reason for limiting the above components will be described. C is 0,02
If it is less than 1%, secondary recrystallization becomes unstable, and even if secondary recrystallization is performed, it is difficult to obtain B > 1.80 (T), so it is set to 0.021% or more. Moreover, if it exceeds 0.100%, decarburization failure will occur, which is not preferable. Moreover, if Si exceeds 4.5%, cold rolling becomes difficult, which is undesirable.
If it is less than 2.5%, it becomes difficult to obtain good magnetic properties, which is not preferable.

In addition, as an inhibitor constituent element, AI
, N, Mn, S, Se, sb, B, Cu
, Bit Nb.

Cr, Sn+Ti, etc. can also be added.

The heating temperature of this slab is not particularly limited, but from the viewpoint of cost, it is preferably 1300°C or less.

The heated slab is subsequently hot-rolled into a hot-rolled sheet. The feature of the present invention lies in this hot rolling process.

That is, the hot rolling end temperature is set to 750 to 1150°C, and the cumulative reduction rate of the final three passes is set to 40% or more. In addition, it is more preferable that the rolling reduction in the final pass is 20% or more in order to obtain good magnetic properties.

The hot rolling process usually consists of rough rolling and finish rolling, each of which is performed in multiple passes after heating a slab with a thickness of 100 to 400 mm. The rough rolling method is not particularly limited and may be carried out by a conventional method.

The feature of the present invention is the finish rolling that follows the rough rolling.

Finish rolling is usually performed by high-speed continuous rolling of 4 to 10 passes. Normally, the reduction distribution in finish rolling is such that the reduction rate is high in the first stage and the reduction rate is lowered toward the latter stage to obtain a good shape.

The rolling speed is usually 100 to 3000 m/win, and the time between passes is 0.01 to 100 seconds.

What is limited in the present invention is only the end temperature of hot rolling, the cumulative rolling reduction ratio of the final three passes, and the rolling reduction ratio of the final pass, and other conditions are not particularly limited. If the interpass time is abnormally long, such as 1000 seconds or more, the strain will be released by recovery and recrystallization between passes, making it difficult to obtain the effect of accumulated strain, which is not preferable.

Regarding the rolling reduction ratio in the several passes before finishing hot rolling, it is not particularly limited because it is difficult to expect that the strain applied until the final pass remains, and it is sufficient to focus only on the final three passes.

Next, the reasons for limiting the hot rolling conditions described in 1 will be described.

The reason why we set the hot rolling end temperature to 750 to 1150°C2 and the cumulative reduction rate in the final three passes to 40% or more is because, as is clear from Figure 1, we have a good magnetic flux density of 88≧1.88 (T) in this range. This is because a product with B8 can be obtained. Although there is no particular limitation on the upper limit of the cumulative rolling reduction of the final three passes, it is industrially difficult to apply a cumulative rolling reduction of 99.9% or more. More preferably, the rolling reduction ratio in the final pass is set to 20% or more, as is clear from FIG. This is because it can be obtained. Note that the upper limit of the rolling reduction rate in the final pass is not particularly limited;
Industrially, it is difficult to apply a reduction of 90% or more.

After the final pass of hot rolling, it is usually air cooled for about 01 to 100 seconds, then water cooled, wound up at a temperature of 300 to 700'C, and slowly cooled. Although this cooling process is not particularly limited, air cooling for 1 second or more after hot rolling is preferable in order to advance recrystallization.

This hot-rolled sheet is cold-rolled at a rolling reduction of 80% or more without performing hot-rolled sheet annealing. The reason why the rolling reduction rate is set to 80% or more is that by setting the rolling reduction rate to the above range, sharp (1101 <001> oriented grains and corresponding oriented grains ((111) <112> This is because an appropriate amount of oriented grains, etc.) can be obtained, which is preferable for increasing magnetic flux density.

After cold rolling, the steel plate is decarburized and annealed in the usual way, coated with an annealing separator,
After finishing annealing, it becomes a re-Hiragi product. Note that if the inhibitor strength required for secondary recrystallization is insufficient in the state after decarburization annealing, a treatment to strengthen the inhibitor such as finish annealing is required. As an example of an inhibitor strengthening method, a method is known in which the nitrogen partial pressure of the final annealing atmosphere gas is set to be high in steel containing A2.

[Example〕 Examples will be described below.

Example 1-C: 0.054% by weight, Si; 3.25% by weight, Mn
: 0.16% by weight, S: 0.005% by weight, acid soluble A
/: Contains 0.026% by weight, N: 0.0078% by weight, and the balance consists of Fe and inevitable impurities.
After heating the slab at a temperature of 1150°C, 1050°C
Hot rolling was started at °C and hot rolled in 6 passes to obtain a hot rolled sheet with a gloss of 2.3. At this time, the reduction distribution is ■40 → 15 → 7 → 3.5 →
3→2.6→2.3 (mm), ■40→30→20
→10→5→2.8→2.3 (mm), ■40
→30-20 →10 →5 →3 →2.3 (mm
). After hot rolling, air cool for 1 second and then 550°
A winding simulation was performed in which the hot-rolled sheet was water-cooled to C, held at 550"C for 1 hour, and then cooled in a furnace. This hot-rolled sheet was pickled to form a cold-rolled sheet of 0.335 mm at a rolling reduction of 85%.
Decarburization annealing was performed at 30°C for 150 seconds.

The obtained decarburized annealed plate was coated with an annealing separator mainly composed of MgO, heated to 1200°C at a rate of 10"C/hour in an atmosphere gas of 225% N and 8275%, and then heated to 1200°C with HzlOO. Final annealing was performed at 1200° C. for 20 hours in an atmosphere gas.

Table 1 shows the hot rolling conditions, hot rolling end temperature, and magnetic properties of the product.

Example 2 - C: 0.055% by weight, St: 3.28% by weight, Mn
: 0.15% by weight, S: 0.007% by weight, acid soluble/
V: o, 028% by weight, N: 0.0080% by weight
26o, with the remainder consisting of Fe and unavoidable impurities.
After heating the slab with a thickness of 100° C. to 1150° C., it was hot-rolled in 6 passes to obtain a 2.3 mm hot-rolled plate. At this time, the reduction distribution is 26 → 15 → 10 → 7 → 5 → 2.8 → 2.3 (n
un), and the hot rolling start temperature is ■1000°C1■900
Four conditions were used: °C1, 800'C, and 0700°C. The cooling conditions after hot rolling and the process conditions up to the final final annealing were the same as in Example 1.

Table 2 shows the hot rolling conditions, hot rolling end temperature, and magnetic properties of the product.

-Example 3- C: 0.058% by weight, Si: 3.30% by weight, Mn
: 0.15% by weight, S: 0.006% by weight, acid soluble 7
A 40 mm thick slab containing V: 0.030% by weight, N: 0,0081% by weight, and the balance consisting of Fe and unavoidable impurities was heated at a temperature of 1250°C, and then hot rolled in 6 passes. It was made into a hot rolled sheet of .0 rMl. At this time, the reduction distribution is 40 → 30 → 20 → 10 → 5 → 3 → 2 (n + m)
The binding hot rolling start temperature is ■1250°C2■tioo'c■
Three conditions were used: 1000°C. After the hot rolling was completed, cooling was performed under the same conditions as in Example 1. This hot-rolled plate is pickled and the rolling reduction is approximately 86.
Cold-rolled plate with a thickness of 0.285 mm at 830°C
Decarburization annealing was performed by holding at 910°C for 0 seconds and then holding at 910°C for 20 seconds. An annealing separator containing MgO as the main component was applied to the obtained decarburized annealed plate, and the temperature was raised to 880°C at a rate of 10°C/hour in an atmospheric gas containing 25% N and 75% H.
Continued to 15' in N275%, H225% cloud surrounding gas.
The temperature was raised to 1200°C at a rate of C/hour, and then H,
A final finish annealing was performed at 1200'C in 100% atmospheric gas for 20 hours.

Table 3 shows the hot rolling conditions, hot rolling end temperature, and magnetic properties of the product.

Example 4-C: 0.052% by weight, Si: 3.21% by weight, Mn
: 0.14% by weight, S: 0.006% by weight Acid soluble A
! : 0.031% by weight, N: 0.0079% by weight, and the remainder was Fe and unavoidable impurities after heating a 40mm thick slab at a temperature of 1150°C.
Hot rolling was started at °C and hot rolled in 6 passes to obtain a hot rolled sheet of 1.8 mm. At this time, the pressure distribution is ■40 → 16 → 7 → 2
．． 9 → 2.5-2.1 → 1.8 (mm), ■40 → 30
→20→10→5→2.5→1.8 (mm), ■4
0→30→22→12→6→3.5→1.8 (mm)
,■40→30→22→16→8→4→1.8 (m
The four conditions were set as m). Cooling after hot rolling was performed under the same conditions as in Example 1. This hot-rolled sheet is pickled and the rolling reduction is approximately 86%.
．． A 260-gate cold-rolled plate was prepared, and the process conditions up to final annealing were the same as in Example 1.

Table 4 shows the hot rolling conditions, hot rolling end temperature, and magnetic properties of the VA product.

Example 5 - C: 0.033% by weight, St: 3.25% by weight, Mn
: 0.14% by weight, S: 0.006% by weight, acid soluble I
After heating a 26cm thick slab containing V: 0.027% by weight, N: 0.0078% by weight, and the balance consisting of Fe and unavoidable impurities at a temperature of 1150°C, it was heated to 1050°C.
Hot rolling was started in 6 passes to obtain a 2.3 mm hot rolled sheet. At this time, the pressure distribution is ■26 → lO → 5 → 3.5
→3→2.6→2.3 (mm), ■26→15→1
Two conditions were set: 0→7→5→3→2.3 (mm). The cooling conditions after hot rolling and the process conditions up to the subsequent decarburization annealing were the same as in Example 1. The resulting decarburized annealed plate was coated with an annealing separator containing MgO as a main component, and then treated with 25% N.
,H! 8 at a rate of 10 °C/h in 75% atmospheric gas
Raise the temperature to 80″C, then continue to heat up to 1200°C with N, 7
5%.

The temperature was increased at a rate of 10°C/hour in an atmosphere of 25% H2, then 1200"C in an atmosphere of 82100%.
A final finish annealing was performed for 20 hours.

Table 5 shows the hot rolling conditions, hot rolling end temperature, and magnetic properties of the product.

Example 6 - C: 0.078% by weight, Si: 3.25% by weight, Mn
Contains: 0.073% by weight, S: 0.025% by weight, acid-soluble Al 70.027% by weight, N: 0.0081% by weight, Sn: O, 0% by weight, Cu: 0.06% by weight. 4, with the remainder consisting of Fe and unavoidable impurities.
After heating a 0mm thick slab at a temperature of 1300°C1
Hot rolling was started at 050"C and hot rolled in 6 passes to obtain a 2.3M hot rolled sheet. At this time, the reduction distribution was: ■40 → 15 → 7 → 3
．． 5 → 3°-2, 6-2, 3 (in), ■40 → 3
Two conditions were set: 0 → 20 → 10 → 6 → 3.6 → 2.3 (mm). The process conditions from cooling after hot rolling to cold rolling were the same as in Example 1. This cold-rolled plate was then held at 830°C for 120 seconds and then heated to 950°C for 20 seconds.
Decarburization annealing was performed for seconds. The process conditions up to the final final annealing were the same as in Example 1.

Table 6 shows the hot rolling conditions, hot rolling end temperature, and magnetic properties of the product.

Example 7 C: 0.045% by weight, St: 3.20% by weight, Mn
: 0.065% by weight, S: 0.023% by weight, Cu
After heating a 26 nm thick slab containing 0.08 wt% Sb and 0.018 wt% Sb with the remainder Fe and unavoidable impurities at a temperature of 1300°C, hot rolling was started at 1050°C. It was hot-rolled in a pass to obtain a 2.3 wll hot-rolled plate. At this time, the reduction distribution is ■40 → 15 → 7 → 3.5 →
3→2.6→2.3 (mm), ■40→30→20
→ 12 → 8 → 4 → 2.3 (mm). The process conditions from cooling after hot rolling to cold rolling were the same as in Example 1. This cold-rolled plate was then heated at 830°C for 12
Decarburization annealing was performed by holding for 0 seconds and then holding at 910''C for 20 seconds.The process conditions up to the final finish annealing were the same as in Example 1.

Table 7 shows the hot rolling conditions, hot rolling end temperature, and magnetic properties of the product.

〔Effect of the invention〕

As explained above, in the present invention, hot-rolled sheet annealing is performed by controlling the hot-rolling end temperature, the cumulative rolling reduction rate of the final three passes of hot rolling, and more preferably the rolling reduction ratio of the final pass of hot rolling. Since good magnetic properties can be obtained in a single cold rolling process, the industrial effect is extremely large.

[Brief explanation of drawings]

Figure 1 is a graph showing the influence of the end temperature of hot rolling and the cumulative reduction rate in the final three passes of hot rolling on the magnetic flux density of the product. Fig. 3 is a graph showing the influence on density; Fig. 3 is a micrograph showing examples of hot-rolled sheet metal structures under different hot-rolling conditions;
The figure shows examples of decarburized plate textures under different hot rolling conditions. Patent distributor Nippon Steel Corporation

Claims (2)

[Claims] (1) C: 0.021-0.100%, Si: 2 by weight
．． A silicon steel slab containing 5 to 4.5% and normal inhibitor components, with the remainder consisting of Fe and unavoidable impurities, is hot-rolled and subsequently cold-rolled and de-rolled at a reduction rate of 80% or more without hot-rolled plate annealing. A method for producing a grain-oriented electrical steel sheet by subjecting it to charcoal annealing and final finish annealing, characterized in that the hot rolling end temperature is 750 to 1150°C and the cumulative reduction rate of the final three passes is 40% or more. A method for producing unidirectional electrical steel sheets with excellent properties. (2) The method for producing a unidirectional electrical steel sheet with excellent magnetic properties according to claim 1, characterized in that the rolling reduction in the final pass of finish hot rolling is 20% or more.