JPH0742504B2 - Method for producing unidirectional electrical steel sheet with excellent magnetic properties - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, which is used as an iron core of a transformer or the like.

[Conventional technology]

The unidirectional electrical steel sheet is mainly used as a core material for transformers and other electric devices, and is required to have excellent magnetic characteristics such as excitation characteristics and iron loss characteristics. The magnetic flux density at a magnetic field strength of 800 A / m is used to express the excitation characteristics.
B ₈ is usually used. As the numerical value showing the iron loss characteristic, the iron loss W _17/50 per kg when magnetized to 1.7 Tesler (T) at a frequency of 50 Hz is used. The magnetic flux density is
It is the most dominant factor of iron loss characteristics, and generally speaking, the higher the magnetic flux density, the better the iron loss characteristics. Generally, when the magnetic flux density is increased, the secondary recrystallized grains become large, which may result in poor iron loss characteristics. On the other hand, by controlling the magnetic domains, the iron loss characteristics can be improved regardless of the grain size of the secondary recrystallized grains.

This unidirectional electrical steel sheet is manufactured by causing secondary recrystallization in the final finishing annealing step and developing a so-called Goss structure having {110} on the steel sheet surface and <001> axis in the rolling direction. There is. In order to obtain good magnetic properties, it is necessary to highly align <001>, which is the easy axis of magnetization, in the rolling direction. The directionality of the secondary recrystallized grains is significantly improved by the method of using MnS, AlN, etc. as inhibitors and performing the final strong reduction rolling, and accordingly the iron loss characteristics are also significantly improved.

[Problems to be Solved by the Invention]

By the way, in the production of unidirectional electrical steel sheets, hot-rolled sheet annealing is usually performed after the hot-rolling for the purpose of homogenizing the structure, precipitating treatment and the like. For example, in a production method using AlN as a main inhibitor, a method of controlling the inhibitor by performing precipitation treatment of AlN in hot-rolled sheet annealing is adopted as shown in JP-B-46-23820.

Normally unidirectional electrical steel sheet is manufactured through the main processes such as manufacturing-hot rolling-annealing-cold rolling-decarburizing annealing-finishing annealing and requires a large amount of energy. And the manufacturing cost is also high.

In recent years, a review of manufacturing processes that consume a large amount of energy has been promoted, and there has been an increasing demand for simplifying the processes. In order to meet such demands, in a production method using AlN as a main inhibitor, a method of substituting the precipitation treatment of AlN in hot-rolled sheet annealing with high-temperature winding after hot-rolling (Japanese Patent Publication 59).
No. -45730) was proposed. Certainly, even if the hot-rolled sheet annealing is omitted by this method, the magnetic characteristics can be secured to some extent, but in the additional method of winding in a coil shape of 5 to 20 tons, the inside of the coil is cooled during the cooling process. There is a difference in the thermal history at different locations, which inevitably causes non-uniform deposition of AlN, and the final magnetic properties vary depending on the location within the coil, resulting in reduced yield.

Therefore, the present inventors paid attention to the recrystallization phenomenon after the final pass of finish hot rolling, which has hardly received attention in the past, and utilizing this phenomenon, the hot rolling was performed in the manufacturing method by single cold rolling under a high pressure of 80% or more. It was considered to omit the sheet annealing.

For hot rolling of unidirectional electrical steel sheet, prevent secondary recrystallization failure (generation of fine linear grains in the rolling direction) due to coarse growth of slab crystal grains during high temperature slab heating (eg 1300 ° C or higher) In order to achieve this, a method has been proposed in which coarse crystal grains are divided by performing recrystallization high-pressure rolling at a reduction rate of 30% or more per pass at a temperature of 960 to 1190 ° C during hot rolling (Japanese Patent Publication No. 60- 37172 publication). Although this method certainly reduces the generation of linear fine grains, it is premised on the manufacturing process of hot-rolled sheet annealing.

In addition, in the production method using MnS, MnSe, and Sb as inhibitors, hot rolling is continuously performed at a reduction rate of 10% or more at a temperature of 950 to 1200 ° C during hot rolling, and subsequently cooled at a cooling rate of 3 ° C / sec or more. Therefore, a method of uniformly and finely depositing MnS and MnSe to improve the magnetic properties has been proposed (JP-A-51-
20716 publication). Also proposed is a method to improve the magnetic properties by performing hot rolling at low temperature to suppress the progress of recrystallization and prevent the {110} <001> oriented grains formed by shear deformation from being reduced by subsequent recrystallization. It has been done (Japanese Patent Sho 59-
No. 32526, Japanese Patent Publication No. 59-35415). Even in these methods, production by the single cold rolling method without hot-rolled sheet annealing has not been studied. In the hot rolling of silicon steel slabs containing ultra-low carbon, hot rolling at low temperature and large pressure that causes strain to accumulate in the hot-rolled sheet is performed, and the coarse crystals peculiar to the ultra-low carbon material are obtained by recrystallization during subsequent hot-rolled sheet annealing. A method of dividing grains has been proposed (Japanese Patent Publication No. 59-34212). However, even in this method, production by the single cold rolling method without hot-rolled sheet annealing has not been studied.

Therefore, the present inventors have paid attention to the recrystallization phenomenon after the final pass of finish hot rolling, which has received little attention in the past, and by utilizing this phenomenon, the heat treatment in the manufacturing method by single cold rolling under high pressure of 80% or more A study was carried out for the purpose of obtaining a grain-oriented electrical steel sheet with excellent magnetic properties by omitting the annealing of rolled sheet.

[Means for Solving the Problems]

In the present invention, in order to achieve the object, a hot rolling end temperature is set to 750 with respect to a silicon steel slab composed of ordinary components.
~ 1150 ℃, hot rolling to make the final 3 passes cumulative rolling reduction of 40% or more, and then rolling reduction without subsequent hot-rolled sheet annealing.
It is characterized by 80% or more cold rolling, decarburization annealing, and final finishing annealing.

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

[Work]

The unidirectional electrical steel sheet that is the subject of the present invention is a molten steel obtained by a conventional steelmaking method, is cast by a continuous casting method or an ingot making method, and is a slab by sandwiching the agglomeration step, if necessary. Successively, hot rolling is performed to form a hot rolled sheet, and then cold rolling with a reduction of 80% or more, decarburization annealing, and final finishing annealing are sequentially performed without annealing the hot rolled sheet.

The present inventors have focused on the recrystallization phenomenon after the final pass of finish hot rolling and have conducted extensive research from various viewpoints, and have confirmed that this phenomenon and magnetic properties are closely related. The details will be described below based on the experimental results.

FIG. 1 is a graph showing the influence of the hot rolling finish temperature and the cumulative rolling reduction in the final three passes of hot rolling on the magnetic flux density of the product. Here, C: 0.054 wt%, Si: 3.25 wt%, acid-soluble Al: 0.027 wt%, N: 0.0080 wt%, S: 0.007 wt%, Mn:
A slab with a thickness of 0.14% by weight and a balance of Fe and unavoidable impurities with a thickness of 20 to 60 mm is heated to 1150 to 1400 ° C, hot-rolled with a 6-pass to a hot-rolled sheet with a thickness of 2.3 mm, and water-cooled after about 1 second. 550 ℃
After cooling down to 550 ° C for 1 hour, the furnace is cooled to simulate coiling. Without hot-rolled sheet annealing, about 85% strong reduction rolling is performed to obtain a final rolled sheet with a thickness of 0.335mm. 830
Decarburization annealing was performed at a temperature of up to 1000 ° C, and then an annealing separator containing MgO as a main component was applied to perform final finishing annealing.

As is apparent from Fig. 1, B ₈ ≧ 1.88 when the hot rolling end temperature is 750 to 1150 ° C and the cumulative rolling reduction of the final three passes is 40% or more.
A high magnetic flux density of T is obtained. The present inventors also examined this new finding in more detail.

Fig. 2 shows the hot rolling finish temperature of 750 to 1150 ° C, which had good magnetic flux density in Fig. 1, and the final rolling reduction of the final three baths of hot rolling of 40%.
It is a graph showing the relationship between the rolling reduction and magnetic flux density of the final pass of hot rolling in the above case.

As is clear from FIG. 2, a high magnetic flux density of B ₈ ≧ 1.90T is obtained when the rolling reduction of the final pass is 20% or more.

The reason why the relationships shown in FIGS. 1 and 2 are established between the hot rolling end temperature, the cumulative reduction rate of the final three passes, the reduction rate of the final pass and the magnetic flux density of the product is not necessarily clear. The present inventors presume as follows.

Figures 3 and 4 show the metallographic structures of hot-rolled sheets under different hot-rolling conditions.
An example of the texture (sheet thickness 1/4 point) after decarburization annealing (decarburized plate) is shown. In this case, 3 of the same components as described in FIG.
3.2mm and 26mm thick slabs are heated at 1150 ℃ and then hot rolled at 1050 ℃, 33.2 → 18.6 → 11.9 → 8.6 → 5.1 → 3.2 → 2.3 (m
m), 26->11.8->6.7->3.5->3.0->2.6-> 2.3 (mm) pass schedule, 2.3mm thick hot-rolled sheet was used, and cooling was performed under the same conditions as described in FIG. At this time, the hot rolling finish temperatures were: 935 ℃ and: 912 ℃, respectively. Thereafter, this hot-rolled sheet was subjected to strong reduction rolling of about 85% without annealing the hot-rolled sheet to obtain a cold-rolled sheet having a final sheet thickness of 0.335 mm, followed by N ₂ 25%,
Decarburization annealing was carried out by holding at 830 ° C for 150 seconds in an atmosphere of H ₂ 75% and dew point of 60 ° C.

As is clear from FIG. 3, the recrystallization rate of the hot-rolled sheet is extremely high and the crystal grain size is small as compared with the case where the conditions of the present invention are satisfied. In addition, as is clear from FIG. 4, when the conditions of the present invention are satisfied, compared with the case of {11
There are many 1} oriented grains, few {100} oriented grains, and there is no difference in {110} oriented grains. The recrystallization rate of the hot-rolled sheet (sheet thickness 1/4 point) was determined by the ECP (Electron channell) developed by the present inventors.
ing pattern) to measure crystal strain by image analysis (Abstracts of Autumn Meeting of the Japan Institute of Metals (1988.11) P289)
The area ratio of grains (area ratio of low strain grains) that is higher than the sharpness of ECP when cold-rolled to a standard sample annealed sheet by 1.5% is called recrystallization rate. This method is significantly 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, the recrystallization rate of the hot-rolled sheet is extremely high (the strain is small) and the crystal grain size is small. When crystallized, it is possible to obtain a texture with many {111} oriented grains and few {100} oriented grains without affecting the {110} oriented grains.

It has been traditionally believed that the matrix of {110} <001> secondary recrystallized grains is formed by shear deformation in the surface layer during hot rolling, and {110} <001> oriented grains in the hot rolled sheet are cold rolled. In order to enrich after recrystallization, it is considered effective to make {110} <001> oriented grains in the hot-rolled sheet coarse and have less strain.
In the present invention, the crystal grain size of the hot rolled sheet is small, but the strain is small, and as a result, the {110} <001> oriented grains are not affected in the state after decarburization annealing.

On the other hand, the main orientation of the decarburizing plate is {111} <112>, {100}
<025> is known as an orientation that influences the grain growth of {110} <001> secondary recrystallized grains. The more {111} <112>, the less {100} <025> the less {110}. It is considered that the grain growth of <001> secondary recrystallized grains becomes easy. In the present invention, by applying high pressure in the final three passes of hot rolling, the number of nucleation sites in the subsequent recrystallization after the final pass is increased, the recrystallization proceeds, and the crystal grains are refined. When the hot-rolled sheet according to the present invention is continuously cold-rolled and recrystallized, the grain size before cold rolling is small, so that {111} <112> nucleates a lot in the vicinity of grain boundaries and nucleates from within grains {100}. <025> decreases relatively.

Therefore, in the present invention, since the hot rolled sheet has a low strain and a small crystal grain size due to the subsequent recrystallization after the hot rolling final pass, {110} <001 in the state of the decarburized annealed sheet.
> Increase the number of {111} <112> oriented grains, which is advantageous for grain growth of {110} <001> oriented grains, without affecting the oriented grains.
Interfering with grain growth of {110} <001> oriented grains {100} <025>
Succeeded in reducing the direction grain. This makes it possible to obtain good magnetic properties even if the hot-rolled sheet annealing is omitted.

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

The slab used in the present invention comprises by weight C: 0.021 to 0.100% by weight, Si: 2.5 to 4.5% and the usual inhibitor components, the balance consisting of Fe and inevitable impurities.

Next, the reasons for limiting the above components will be described. C is 0.021%
When it is less than the above value, the secondary recrystallization becomes unstable, and it is difficult to obtain B ₈ > 1.80 (T) even when the secondary recrystallization is performed, so the content was made 0.021% or more. If it exceeds 0.100%, poor decarburization occurs, which is not preferable. If Si exceeds 4.5%, cold rolling becomes difficult, which is not preferable, and if it is less than 2.5%, it is difficult to obtain good magnetic properties, which is not preferable. As an inhibitor constituent element, if necessary, Al, N, Mn, S, Se, S
It is also possible to add b, B, Cu, Bi, Nb, Cr, Sn, Ti and the like.

The heating temperature of the slab is not particularly limited, but it is preferably 1300 ° C. or lower in terms of cost.

The heated slab is subsequently hot rolled to form a hot rolled plate. 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 rolling reduction of the final 3 passes is set to 4
0% or more. In addition, the final pass reduction is 20
% Or more is more preferable in order to obtain good magnetic properties.

The hot rolling process usually consists of rough rolling and finish rolling in which a slab having a thickness of 100 to 400 mm is heated and then subjected to multiple passes.
The method of rough rolling is not particularly limited, and an ordinary method is used. The feature of the present invention is the finish rolling subsequent to the rough rolling. Finish rolling is usually performed by high speed continuous rolling with 4 to 10 passes. In the reduction distribution of normal finish rolling, the former stage has a higher reduction ratio, and the lower the rolling ratio, the better the shape. The rolling speed is usually 100 to 3000 m / min, and the time between passes is 0.01 to 100 seconds. What is limited in the present invention is only the hot rolling end temperature, the cumulative rolling reduction of the final three passes, and the rolling reduction of the final pass, and other conditions are not particularly limited. An abnormally long inter-pass time of 1000 seconds or more is not preferable because the strain is released by recovery between paths and recrystallization, which makes it difficult to obtain the effect of accumulated strain. The reduction ratio in several passes before the final hot rolling is not particularly limited because it is difficult to expect that the strain added up to the final pass remains, and it is sufficient to place importance on only the final three passes.

Next, the reasons for limiting the hot rolling conditions will be described. Hot rolling end temperature is 750 to 1150 ℃, cumulative rolling reduction of the last 3 passes is 40%
The above is within this range, as is clear from FIG.
This is because a product having a good magnetic flux density B ₈ of B ₈ ≧ 1.88 (T) can be obtained. The upper limit of the cumulative rolling reduction of the final three passes is not particularly limited, but it is industrially difficult to add a cumulative rolling reduction of 99.9% or more. Further, it is more preferable that the rolling reduction of the final pass is set to 20% or more in this range as shown in FIG. 2, B ₈ ≧ 1.90 (T)
This is because a product having a better magnetic flux density B ₈ of is obtained. The upper limit of the rolling reduction of the final pass is not particularly limited, but it is industrially difficult to apply a rolling reduction of 90% or more.

After the final pass of hot rolling, it is usually air-cooled for about 0.1 to 100 seconds and then water, for example, is wound at a temperature of 300 to 700 ° C and gradually cooled. The cooling process is not particularly limited,
Air-cooling for 1 second or more after hot rolling is preferable for promoting recrystallization.

This hot rolling is cold-rolled at a reduction rate of 80% or more without performing hot-rolled sheet annealing. The reduction rate is set to 80% or more because the reduction rate is within the above range because the sharpened {110} <001> oriented grains in the decarburized plate and the corresponding oriented grains ({111} <112) that are easily eroded by silkworms. This is because it is possible to obtain an appropriate amount of (> orientation grains, etc.) and increase the magnetic flux density.

After cold rolling, the steel sheet is decarburized and annealed by applying the usual method,
Finished annealing is applied to obtain the final product. If the inhibitor strength required for secondary recrystallization is insufficient after decarburization annealing, a treatment for strengthening the inhibitor in finish annealing or the like is required. As an example of the inhibitor strengthening method, a method is known in which a nitrogen partial pressure of a finish annealing atmosphere gas is set to be high in a steel containing Al.

〔Example〕

 Examples will be described below.

-Example 1-C: 0.054 wt%, Si: 3.25 wt%, Mn: 0.16 wt%, S: 0.005
%, Acid-soluble Al: 0.026% by weight, N: 0.0078% by weight, and a 40 mm thick slab consisting of balance Fe and unavoidable impurities was heated at a temperature of 1150 ° C, and then hot rolling was started at 1050 ° C. It hot-rolled in 6 passes to obtain a hot-rolled sheet of 2.3 mm. At this time, the reduction distribution is 40 → 15 → 7 → 3.5 → 3 → 2.6 → 2.3 (mm), 40 → 3
0 → 20 → 10 → 5 → 2.8 → 2.3 (mm), 40 → 30 → 20 → 10 →
Three conditions of 5 → 3 → 2.3 (mm) were set. After the hot rolling was finished, a coiling simulation was conducted in which the material was air-cooled for 1 second, water-cooled to 550 ° C., held at 550 ° C. for 1 hour and then furnace-cooled. This hot-rolled sheet is pickled to make a cold-rolled sheet of 0.335 mm with a reduction rate of about 85%,
Decarburization annealing was performed for 0 seconds. The obtained decarburized annealed sheet was coated with an annealing separator containing MgO as the main component, and N ₂ 25%, H ₂
A final finishing annealing was performed in which the temperature was raised to 1200 ° C. at a rate of 10 ° C./hour in 75% atmosphere gas, and then maintained at 1200 ° C. for 20 hours in H ₂ 100% atmosphere gas.

Table 1 shows the hot rolling conditions, hot rolling finish temperature and magnetic properties of the products.

-Example 2-C: 0.055 wt%, Si: 3.28 wt%, Mn: 0.15 wt%, S: 0.007
%, Acid-soluble Al: 0.028% by weight, N: 0.0080% by weight, and a 26 mm thick slab consisting of the balance Fe and unavoidable impurities was heated at a temperature of 1150 ° C. and then hot-rolled in 6 passes to 2.3. m
It was a hot rolled sheet of m. At this time, the reduction distribution is 26 → 15 → 10 → 7 →
5 → 2.8 → 2.3 (mm), hot rolling start temperature 1000 ℃,
The four conditions were 900 ° C, 800 ° C, and 700 ° C. The cooling conditions after completion of hot rolling and the process conditions until the subsequent final annealing were the same as in Example 1.

Table 2 shows the hot rolling conditions, hot rolling finish temperature, and magnetic properties of the products.

-Example 3-C: 0.058 wt%, Si: 3.30 wt%, Mn: 0.15 wt%, S: 0.006
%, Acid-soluble Al: 0.030% by weight, N: 0.0081% by weight, and a 40 mm thick slab consisting of the balance Fe and unavoidable impurities was heated at a temperature of 1250 ° C. m
It was a hot rolled sheet of m. The reduction distribution at this time is 40 → 30 → 20 → 10 →
5 → 3 → 2 (mm) and hot rolling start temperature 1250 ℃, 1100
The conditions were 3 ° C and 1000 ° C. After the hot rolling was completed, it was cooled under the same conditions as in Example 1. This hot-rolled sheet is pickled and the rolling reduction is about 86.
% Cold-rolled sheet having a thickness of 0.285 mm and subjected to decarburization annealing at 830 ° C. for 120 seconds and then at 910 ° C. for 20 seconds. The obtained decarburized annealed plate was coated with an annealing separator containing MgO as a main component, and N ₂ 25
%, H ₂ 75% atmosphere gas at a temperature of 10 ℃ / hour to 880 ℃, then N ₂ 75%, H ₂ 25% atmosphere gas 15 ℃ /
The final annealing was carried out by raising the temperature to 1200 ° C. at an hourly rate and then holding the temperature at 1200 ° C. for 2 hours in an atmosphere gas of H ₂ 100%.

Table 3 shows the hot rolling conditions, hot rolling finish temperature and magnetic properties of the products.

-Example 4-C: 0.052 wt%, Si: 3.21 wt%, Mn: 0.14 wt%, S: 0.006
%, Acid-soluble Al: 0.031% by weight, N: 0.0079% by weight, and a 40 mm thick slab consisting of balance Fe and unavoidable impurities was heated at a temperature of 1150 ° C, and then hot rolling was started at 1050 ° C. It was hot-rolled in 6 passes to obtain a hot-rolled sheet of 1.8 mm. At this time, the reduction distribution is 40 → 16 → 7 → 2.9 → 2.5 → 2.1 → 1.8 (mm),
40 → 30 → 20 → 10 → 5 → 2.5 → 1.8 (mm), 40 → 30 → 22 →
12 → 6 → 3.5 → 1.8 (mm), 40 → 30 → 22 → 16 → 8 → 4 →
There were 4 conditions of 1.8 (mm). 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 about 86%
Then, a cold-rolled sheet of 0.260 mm was obtained, and the process conditions until the final finish annealing were the same as in Example 1.

Table 4 shows the hot rolling conditions, hot rolling finish temperature, and magnetic properties of the products.

-Example 5-C: 0.033 wt%, Si: 3.25 wt%, Mn: 0.14 wt%, S: 0.006
Wt%, acid-soluble Al: 0.027 wt%, N: 0.0078 wt%, a 26 mm thick slab consisting of balance Fe and unavoidable impurities was heated at a temperature of 1150 ° C, and then hot rolling was started at 1050 ° C. It was hot-rolled for 6 passes to obtain a hot-rolled sheet of 2.3 mm. At this time, the reduction distribution is 26 → 10 → 5 → 3.5 → 3 → 2.6 → 2.3 (mm), 2
Two conditions of 6 → 15 → 10 → 7 → 5 → 3 → 2.3 (mm) were set. The cooling conditions after completion of hot rolling and the process conditions until the subsequent decarburization annealing were the same as in Example 1. For the obtained decarburized annealed plate
Applying an annealing separator containing MgO as the main component, N ₂ 25%, H ₂ 75%
In the atmosphere gas of 10 ℃ / hour, the temperature is raised to 880 ℃, and then up to 1200 ℃ in N ₂ 75%, H ₂ 25% atmosphere gas 1
A final finishing annealing was carried out by raising the temperature at a rate of 0 ° C./hour and then holding it at 1200 ° C. for 20 hours in an atmosphere gas of H ₂ 100%.

Table 5 shows the hot rolling conditions, hot rolling finish temperature and magnetic properties of the products.

-Example 6-C: 0.078 wt%, Si: 3.25 wt%, Mn: 0.073 wt%, S: 0.025
% By weight, acid-soluble Al: 0.027% by weight, N: 0.0081% by weight, Sn:
A 40 mm thick slab containing 0.10 wt% and Cu: 0.06 wt% and the balance Fe and unavoidable impurities was heated at a temperature of 1300 ° C, then hot rolling was started at 1050 ° C, and hot rolling was performed in 6 passes to 2.3. mm hot rolled sheet. The reduction distribution at this time is 40 → 15 → 7 → 3.5 →
3 → 2.6 → 2.3 (mm), 40 → 30 → 20 → 10 → 6 → 3.6 → 2.3
(Mm) as two conditions. After the hot rolling, the process conditions from cooling to cold rolling were the same as in Example 1. Next, this cold rolled sheet was held at 830 ° C. for 120 seconds, and subsequently subjected to decarburization annealing at 950 ° C. for 20 seconds. The process conditions up to the subsequent final finish annealing were the same as in Example 1.

Table 6 shows the hot rolling conditions, hot rolling finish temperature, and magnetic properties of the products.

-Example 7- C: 0.045 wt%, Si: 3.20 wt%, Mn: 0.65 wt%, S: 0.023
%, Cu: 0.08% by weight, Sb: 0.018% by weight, balance F
26 mm thick slab consisting of e and inevitable impurities at 1300 ℃
After heating at the temperature of 1, the hot rolling was started at 1050 ° C. and the hot rolling was performed in 6 passes to obtain a hot rolled sheet of 2.3 mm. The reduction distribution at this time is 40 → 1
5 → 7 → 3.5 → 3 → 2.6 → 2.3 (mm), 40 → 30 → 20 → 12 →
Two conditions of 8 → 4 → 2.3 (mm) were set. After the hot rolling, the process conditions from cooling to cold rolling were the same as in Example 1. Next, hold this cold-rolled sheet at 830 ° C for 120 seconds and continue
Decarburization annealing was carried out at 0 ° C for 20 seconds. The process conditions up to the subsequent final finish annealing were the same as in Example 1.

Table 7 shows the hot rolling conditions, hot rolling finish temperature, and magnetic properties of the products.

[Effects of the Invention] As described above, in the present invention, by controlling the hot rolling end temperature, the cumulative rolling reduction of the final three hot rolling passes, and more preferably, the rolling reduction of the final hot rolling pass, Good magnetic properties can be obtained by the one-time cold rolling method without performing sheet annealing, so that its industrial effect is extremely large.

[Brief description of drawings]

Fig. 1 is a graph showing the effect of the hot rolling end temperature and the cumulative rolling reduction of the final 3 passes of hot rolling on the magnetic flux density of the product, and Fig. 2 is the rolling reduction of the final pass of hot rolling. Fig. 3 is a graph showing the influence on the density, Fig. 3 is a micrograph showing an example of a metallographic structure of a hot rolled sheet under different hot rolling conditions, and Fig. 4 is a decarburized sheet under different hot rolling conditions. It is an example of a collective organization.

Claims (2)

[Claims] 1. A silicon steel slab containing C: 0.021 to 0.100% by weight, Si: 2.5 to 4.5% by weight, and a usual inhibitor component, and the balance consisting of Fe and inevitable impurities is hot-rolled and hot-rolled sheet annealed. In the method of producing a unidirectional electrical steel sheet by continuously performing cold rolling with a rolling reduction of 80% or more, decarburizing annealing, and final finishing annealing without performing, the hot rolling end temperature is set to 750 to 1150 ° C,
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the cumulative rolling reduction in the final three passes is 40% or more. 2. The method for producing a grain-oriented electrical steel sheet having excellent magnetic properties according to claim 1, wherein the rolling reduction in the final pass of finish hot rolling is 20% or more.