JPH04324A - Production of grain-oriented silicon steel sheet having large sheet thickness and excellent in magnetic property - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 B at a magnetic field strength of 800 A/m is usually used. In addition, the numerical value representing the iron loss characteristic is iron FjlW,,/5. are using.

Magnetic flux density is the most dominant factor in iron loss characteristics, and when fishing on a boat, the higher the magnetic flux density, the better the iron loss characteristics. In addition,
Generally, 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 type M! The steel plate undergoes secondary recrystallization in the final finish annealing process, and the steel plate surface has (1101, <0 in the rolling direction).
01> It is manufactured by developing a so-called Goss structure with an axis. In order to obtain good magnetic properties, it is necessary to highly align <001>, which is the axis of easy magnetization, in the rolling direction. The orientation of secondary recrystallized grains is MnS
, At 2 N, etc. as an inhibitor, and a final strong reduction rolling is performed, which significantly improves the iron loss characteristics.

[Problem to be solved by the invention]

By the way, in recent years, it has been used as iron core material for turbine generators, etc.
There has been a growing need to use grain-oriented electrical steel sheets in place of the currently used high-grade non-oriented electrical steel sheets. Regarding the above-mentioned uses, compared to other uses of non-oriented electromagnetic steel sheets, unidirectional magnetic properties are considered to be more important, so there has been an increasing need to use directional electromagnetic control plates.

On the other hand, the manufacturing process after hot rolling of grain-oriented electrical steel sheets consists of hot rolling annealing, cold rolling, charcoal annealing, and finishing annealing, which are the main processes after hot rolling of non-oriented electrical steel sheets. It is more complicated than cold rolling-annealing. Therefore, from the manufacturing cost, direction! Magnetic steel sheets are considerably more expensive than non-oriented electrical steel sheets. Furthermore, in the above-mentioned applications that mainly require a thickness of 0.5 m, for example, 0.08 w.
When a normal grain-oriented electrical steel slab containing approximately t% of C is used as a material, the time required to decarburize it to a C level (for example, 0.003 wt% or less) where magnetic aging does not occur in the decarburization annealing process. Since it takes too much, the manufacturing cost naturally increases.

In addition, in the production of oriented magnetic 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 AIN as the main inhibitor, as shown in Japanese Patent Publication No. 4,623,820, a method is used in which a precipitation treatment of AIN is performed during hot-rolled sheet annealing to control the inhibitor.

In recent years, the manufacturing process of grain-oriented electrical steel sheets, which consumes a large amount of energy, has been reviewed, and there has been a growing demand for simplification of the process and energy. In order to meet these demands, in a manufacturing method in which AIN is the main inhibitor, a method (Japanese Patent Publication No. 59-45730
Publication No.) was proposed. 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 5-20 ton coil, Differences in thermal history occur locally, which inevitably results in uneven precipitation of AIN.
The final magnetic properties vary depending on location within the coil, resulting in lower yields.

Therefore, the present inventors focused on the recrystallization phenomenon after the final bath 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 (occurrence of linear fine grains connected in the rolling direction) caused by coarse growth of slab crystal grains at temperatures of 960 to 1190°C 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 bath (Japanese Patent Publication No. 37172/1983). 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,
A method has been proposed in which MnS and MnSe are precipitated uniformly and finely by continuously hot rolling at a temperature of 10% or more with a reduction rate of 10% or more, followed by cooling at a cooling rate of 3°/sec or more, thereby improving the magnetic properties. (Unexamined Japanese Patent Publication No. 51-20
Publication No. 716). 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, Japanese Patent Publication No. 59-35415). In these methods as well, 1 without annealing the hot rolled sheet.
Production by the re-cold rolling method has not even been considered. In addition, when hot-rolling silicon steel slabs containing ultra-low carbon, we conduct 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 crystal grains characteristic of ultra-low carbon materials. A method has been proposed (Japanese Patent Publication No. 59-34212). 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 order to achieve such an objective, the present invention provides C:
For silicon steel slabs containing 0.010 to 0.060%, Si: 2.5 to 4.5%, and normal inhibitor components, with the remainder consisting of Fe and unavoidable impurities, the hot rolling end temperature was set to 750 to 1150. ℃, perform hot rolling with a cumulative reduction rate of 50% or more in the final three passes, followed by cold rolling with a reduction rate of 80% or more without hot-rolled sheet annealing, decarburization annealing,
0, 4 to 1.0 characterized by final annealing
The present invention provides a method for manufacturing a thick unidirectional electric plate having a thickness of m.

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.

[Function] The unidirectional electrical steel sheet targeted by the present invention is produced by casting molten steel obtained by a conventional steel manufacturing method using a continuous casting method or an ingot forming method, and inserting a blooming process as necessary. The slab is made into a slab, followed by hot rolling to make a hot rolled plate, and then cold rolled with a rolling reduction of 80% or more without annealing the hot rolled plate, decarburized 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: 0.036% by weight, Si: 3.20
Weight %, acid soluble At: 0.027 weight %, N:
0.0081% by weight, S: 0.007% by weight, M
n: 0.15% by weight, and the balance is Fe and unavoidable impurities.
Heated to 1400℃, hot-rolled into a hot-rolled sheet of 3 or 4 thickness in 6 passes, cooled with water after about 1 second, cooled to 550℃,
A winding simulation was performed in which the sheet was kept at 50°C for 1 hour and cooled in a furnace, and then a cold rolled sheet with a final thickness of 0.5 am was obtained by performing heavy reduction rolling of about 85% without performing hot rolled sheet annealing. ~
Decarburization annealing was performed at a temperature of 1000°C, followed by applying an annealing separator containing MgO as a main component, and final finish annealing was performed.

As is clear from Figure 1, the hot rolling finish temperature is 750 to 115.
A high magnetic flux density of B≧1.8 B T was obtained at 0° C. and when the cumulative reduction rate of the final three passes was 50% or more. The present inventors also investigated this new finding in more detail.

Figure 2 shows the rolling reduction in 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 in the final three passes of hot rolling was 50% or more. It is a graph showing the relationship between magnetic flux density and magnetic flux density.

As is clear from FIG. 2, a high magnetic flux density of 88≧1.907 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.

It has been conventionally believed that the matrix of (110) <001> secondary recrystallized grains is formed by shear deformation in the surface layer during hot rolling. In order to enrich after recrystallization, (110)<001 in hot rolled sheet
> It is considered effective to make the oriented grains coarse and have little strain. On the other hand, the roles of commonly performed hot-rolled sheet annealing are precipitation treatment of AIN, etc., formation of transformed phases during cooling,
The formation of solid solution C1, solid solution N, and fine carbonitrides during cooling may be considered, but in addition to these roles, reduction in strain due to recrystallization is also considered to be an important role of hot-rolled sheet annealing.

Therefore, the present inventors investigated the hot working recrystallization behavior in detail using a hot working simulator.

FIG. 3 is a graph showing recrystallization behavior after hot working. In this case, C: 0.040%, Si: 3.2 by weight
7%, Mn: 0.14%, S: 0.007%,
Acid soluble At: 0.027%, N: 0.007
A sample was cut out from a rough rolled material containing 6%.
After heating for 10 minutes at ℃, a one-pass reduction of 75% was applied at each temperature, and after holding at the processing temperature for a predetermined time, water quenching was performed. After that, E CP (Ele
ctron channeling pattern)
The recrystallization rate was measured using a method of measuring crystal strain by image analysis (Japan Institute of Metals Autumn Conference Abstracts (1988, November) P2S5). Here, the area ratio of grains (area ratio of low strain grains) that exhibits a value higher than the ECP sharpness when a standard sample annealed plate is cold rolled by 1.5% is called recrystallization ratio. This method is much more accurate than the conventional method of visually determining the metal structure and measuring the recrystallization rate. As can be seen from FIG. 3, it can be seen that recrystallization progresses fastest in the temperature range of 1000 to 1050''C.

In addition, samples of the same material were heated under the same conditions, rolled down at 1000°C with a rolling reduction rate of 10 to 90%, and
After being held at a temperature of 0° C. for 1 second, water quenching was performed.

Thereafter, recrystallized grains were determined in the same manner as above, and the grain size (circular equivalent diameter) and recrystallization rate (area ratio of low strain grains) of the recrystallized grains were measured using an image analyzer.

FIG. 4 shows the relationship between rolling reduction, grain size, and recrystallization rate. As can be seen from FIG. 4, the larger the rolling reduction, the higher the recrystallization rate and the smaller the recrystallized grain size.

The hot rolling finish temperature, which is the condition of the present invention, is 750 to 1150.
As is clear from Figures 3 and 4, it is clear from Figures 3 and 4 that the cumulative rolling reduction rate of the final three passes should be 50% or more, and in addition, the rolling reduction rate of the final pass should be 20% or more. This is considered to be a requirement for facilitating recrystallization and making the recrystallized grain size fine after the final pass of finish hot rolling.

Therefore, in the case of the present invention, the grain size of the hot-rolled sheet is small, but the strain is small, and enriching the (110) <001> oriented grains after cold-rolling recrystallization is disadvantageous in terms of grain size. However, it is advantageous in terms of strain, and as a result, it is considered that it does not have a large effect on the (110) <001> oriented grains in the state after decarburization annealing.

On the other hand, the main orientation of the decarburization plate is (111) <112>.

(1001<025> is known as an orientation that affects grain growth of (110)<001> secondary recrystallized grains,
(111) <112> is common (100) <025>
It is considered that the smaller the (110)<001> secondary recrystallized grains, the easier the grain growth. In the present invention, in the recrystallization that follows after the final pass, recrystallization tends to progress and crystal grains also tend to become finer. When this hot-rolled sheet of the present invention is subsequently cold-rolled and recrystallized, many (111) <112> grains grow near the grain boundaries because the grain size before cold rolling is small, and (100) <025> is relatively reduced.

Therefore, in the present invention, since the recrystallization that continues after the final hot rolling pass brings the hot rolled sheet into a state of low strain and small grain size, the decarburized sheet (1101<00
1>(110)<00 without affecting the oriented grains
We succeeded in increasing (111) <112> oriented grains, which are advantageous for grain growth of 1> oriented grains, and decreasing (100) <025> oriented grains, which hinder the grain growth of (1101<001> oriented grains). It is thought that this makes it possible to obtain good magnetic properties even if hot-rolled sheet annealing is omitted.

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

The slab used in the present invention has a weight C: 0.010~
0.060%, Si: 2.5-4.5% and normal inhibitor components, with the remainder consisting of Fe and unavoidable impurities.

Next, the reason for limiting the above components will be described. C is 0.01
If it is less than 0%, secondary recrystallization will become unstable, and even if secondary recrystallization is performed, it will be difficult to obtain BIl≧1.80 (T), so it is set to 0.010% or more. Moreover, if it exceeds 0.060%, the plate thickness will be as thick as 0.4 to 1.0%, resulting in poor decarburization, which is not preferable. Furthermore, if Si exceeds 4.5%, cold rolling becomes difficult, which is undesirable, and if it is less than 2.5%, it becomes difficult to obtain good magnetic properties, which is undesirable. In addition, as an inhibitor constituent element, A
j, N, Mn, S, Se.

Sb, B, Cu, old, Nb, Cr, Sn,
Ti and the like 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 lower.

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

In other words, in order to obtain good magnetic properties, it is preferable that the hot rolling end temperature be 750 to 1150° C. and the cumulative reduction rate of the final three passes of finish hot rolling be 50% or more.

In addition, the rolling reduction ratio of the final bath for finish hot rolling was increased by 2.
It is more preferable to make it 0% or more in order to obtain good magnetic properties.

The hot rolling process usually consists of heating a slab with a thickness of 100 to 400 mm, and then rough rolling and finish rolling, both of which are performed in multiple baths. 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 ratio in finish rolling is such that the reduction rate is high in the earlier stage, and the reduction rate is lowered toward the later stage to obtain a good shape. The rolling speed is usually 100 to 3000+w/win, and the time between baths is 0.01 to 100 seconds. What is limited in the present invention is the hot rolling end temperature and the final 3
Only the cumulative rolling reduction rate of the passes and the rolling reduction rate of the final pass are included, and other conditions are not particularly limited.
If the inter-bus time of the final three passes is abnormally long, such as 1000 seconds or more, the strain will be released by recovery and recrystallization between the buses, making it difficult to obtain the effect of accumulated strain, which is not preferable. For reliability, it is difficult to expect that the strain applied in the first pass of hot rolling will remain until the final pass, so it is not particularly limited, and it is sufficient to focus only on the final three passes.

Next, the reason for limiting the above hot rolling conditions will be described.

The reason why the hot rolling end temperature was set at 750-1150°C and the cumulative reduction ratio of the final three baths was set to 50% or more is that, as is clear from Figure 1, a good magnetic flux density of B8 ≥ 1.88 (T) is achieved in this range. This is because a product with B6 can be obtained. The upper limit of the cumulative reduction rate of the final three passes is not particularly limited, but industrially it is difficult to apply a cumulative 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. Although the upper limit of the rolling reduction rate in the final pass is not particularly limited, it is industrially difficult to apply a rolling reduction of 90% or more.

After the final bath of hot rolling, it is usually air cooled for about 0.1 to 100 seconds, then water cooled and wound up at a temperature of 300 to 700'C.
It is 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 in the above range, sharp (110) <OOi> oriented grains and corresponding oriented grains ((111) <112> orientation grains, etc.), which is preferable for increasing magnetic flux density.

The thickness of the cold-rolled sheet was defined as 0.4 to 1.0 ym because
It is for the purpose of the present invention to obtain thick unidirectional electrical vLiil plates. Moreover, if it exceeds 1.0 ym, decarburization annealing takes too much time, which is not preferable.

After cold rolling, the steel plate is decarburized and annealed in the usual way, coated with an annealing separator,
Finish annealing is applied to the final 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 in finish annealing or the like is required. An example of an inhibitor strengthening method is A! A method is known in which the nitrogen partial pressure of the final annealing atmosphere gas is set to be high for steel containing .

〔Example〕

Examples will be described below.

Example 1 - C: 0.034% by weight, Si: 3.21% by weight, Mn
20.16% by weight, S: 0.007% by weight, acid soluble! : 0.026% by weight, N: 0.0078% by weight, and the remainder consists of Fe and inevitable impurities.
■ After heating a thick slab at a temperature of 1150″C, 10
Hot rolling was started at 50° C. and hot rolled in 6 passes to obtain a 3.4 m hot rolled sheet. At this time, the pressure distribution is ■60 → 28 → 13 → 6
．． 5 → 5.0 → 3.8 → 3.4 (m), ■60 → 40 →
26 → 14 → 7.3 → 4.1 → 3.4 (m), ■60 →
40 → 26 → 14 → 7.3 → 4.4 → 3.4 (M) 3
It was made a condition. After hot rolling, a winding simulation was performed in which the material was air cooled for 1 second, then water cooled to 550° C., held at 550° C. for 1 hour, and then cooled in a furnace. This hot-rolled sheet was pickled to obtain a cold-rolled sheet with a rolling reduction of 85% and a thickness of 0.5 mm, and was subjected to decarburization annealing at 830° C. for 250 seconds. Mg was applied to the obtained decarburized annealed plate.
Apply an annealing separator mainly composed of O, N225%, N
1200 at a rate of 15°C/hour in 275% atmospheric gas
Final annealing was carried out by raising the temperature to "C" and then holding it at 1200C for 20 hours in a 100% Hz atmosphere gas.

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

Example 2 - C: 0.035% by weight, Si: 3.28% by weight, Mn
=0.16% by weight, S: 0.007% by weight, acid soluble! : 0.027% by weight, N: 0.0080% by weight, and the balance consists of Fe and inevitable impurities.
A thick slab was heated at a temperature of 1150°C and then hot-rolled in 6 passes to form a 3-4 m hot-rolled plate. At this time, the pressure distribution is 4o → 21 → 14 → 10-7.0-4.0 → 3.4
(m), hot rolling start temperature is 01000℃, ■900℃
There were four conditions: 'C1, 800°C, 1 and 700°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: 0.048% by weight, Si: 3.30% by weight, Mn
20.15% by weight, S: 0.006% by weight, acid-soluble Af: 0.031% by weight, N: 0.0080% by weight, and the balance consists of Fe and inevitable impurities.
A slab with a thickness of 0 m was heated at a temperature of 1250° C. and then hot-rolled in 6 passes to obtain a hot-rolled sheet with a thickness of 3.0 mm. At this time, the reduction distribution is 70 → 45 → 30-15-7.5 → 4.5 → 3.0
(m), and the hot rolling start temperature is ■1250℃1■1100℃
Three conditions were used: 1°C and 1000°C. After the hot rolling was completed, cooling was performed under the same conditions as in Example 1. This hot-rolled sheet was pickled to obtain a cold-rolled sheet with a rolling reduction of 83% and a thickness of 0.5 wm.
Decarburization annealing was performed by holding at 850° C. for 0 seconds and then holding at 850° C. for 20 seconds. The resulting decarburized annealed plate was coated with an annealing separator mainly composed of MgO, heated to 880°C at a rate of 10°C/hour in an atmospheric gas of 225% N2 and 75% Hz, and then heated to 880°C at a rate of 10°C/hour. % atmosphere gas at a rate of 15°C/hour to 1200°C, and then H! 100%
Final annealing was performed at 1200° C. for 20 hours in an atmospheric gas.

Ta.

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

Example 4 C: 0.019% by weight, Si: 3. lQ weight%, Mn
: 0.16% by weight, S: 0.007% by weight, acid soluble A! : 0.031% by weight, N: 0.0078% by weight, and the remainder consists of Fe and inevitable impurities.
After heating a slab of 0 cabinet thickness at a temperature of 1150℃, 10
Start hot rolling at 50°C and hot roll in 5 passes to 3.8 mm.
It was made into a hot rolled sheet.

At this time, the reduction distribution was set to the following three conditions.

■40 → 16 → 7.4 → 5.8 → 4.3 → 3.8 (m+
)■40→30→22.7→13.6→6.8→3.8
(mm)■40→30→23→14→7.6→3.8(
mm) Cooling after hot rolling was performed under the same conditions as in Example 1.

This hot-rolled sheet was pickled to obtain a cold-rolled sheet of 0.5M with a rolling reduction of about 87%, 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 product.

-Example 5- C: 0.033% by weight, Si: 3.20% by weight, Mn
=0.14% by weight, S: 0.007% by weight, acid soluble! 40 containing 20.027% by weight, N: 0.0079% by weight, and the balance consisting of Fe and inevitable impurities.
After heating a mm thick slab at a temperature of 1150°C, 10
Hot rolling was started at 50° C. and hot rolled in 6 passes to obtain a hot rolled sheet of 3.4 mm.

At this time, the pressure distribution is ■40 → 15 → 7.3 → 5.1 → 4.
4→3.8-=3.4 (m), ■40-25-15
→ Two conditions were set: 10 → 8 → 5.7 → 3.4 (Kaku). The cooling conditions after hot rolling and the process conditions up to the subsequent decarburization annealing were the same as in Example 1. Next, this decarburized plate was subjected to heat treatment at 750° C. for 30 seconds, and at this time, Nlh gas was mixed with the atmospheric gas to cause nitrogen absorption in the steel plate.

After that, an annealing separator mainly composed of MgO is applied,
Final annealing was carried out by increasing the temperature to 1200° C. at a rate of 10° C./hour in an atmospheric gas containing 275% N and 8225%, and then holding the temperature at 1200° C. for 20 hours in an atmospheric gas containing 100% Hz.

Table 5 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 rate of the final bath of hot rolling. Since a thick unidirectional electrical steel sheet having good magnetic properties can be produced by a single cold rolling process without any 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 of the final three passes of hot rolling on the magnetic flux density of the product. FIG. 3 is a graph showing the effect on density; FIG. 3 is a graph showing hot working recrystallization behavior; FIG. 4 is a graph showing the effect of rolling reduction on recrystallization rate and recrystallized grain size. . 20 4θ 6θ θO Integer Final pass rolling reduction rate (%) Figure 1 O1lθθ≦Bl(T) e + t19o≦B11(r)<1. ri e・;
δ# (T) < 180 θ 2θ 40〃6θ 〃 ν Cumulative reduction drop of 3 passes of Funobe (l' time after completion of phantom machining (δec)

Claims (2)

[Claims] (1) C: 0.010-0.060%, Si: 2 by weight
．． Hot-rolling a silicon steel slab containing 5 to 4.5% and normal inhibitor components, with the remainder consisting of Fe and unavoidable impurities, followed by cold rolling at a rolling reduction of 80% or more without hot-rolled plate annealing, In a method of producing thick unidirectional electrical steel sheets with a thickness of 0.4 to 1.0 mm by performing decarburization annealing and final finish annealing, the hot rolling end temperature is 750 to 1150 ° C., and the cumulative reduction rate of the final three passes is 50% or more, a method for producing a thick unidirectional electrical steel sheet with excellent magnetic properties. (2) The method for manufacturing a thick 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.