JPH0753884B2 - 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 produced 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.

As a method for producing such a high magnetic flux density unidirectional electrical steel sheet, a method characterized by a final strong reduction cold rolling of 80% or more (Japanese Patent Publication No. 40-15644, etc.) and a final weak reduction of 40 to 85%. A typical method is cold rolling (Japanese Patent Publication No. 51-13469). MnS and AlN in the former and Mn in the latter
S, MnSe, Sb etc. are used as main inhibitors,
It has been considered that the final cold rolling rate at which appropriate magnetic properties are obtained varies depending on the type of these inhibitors.

[Problems to be Solved by the Invention]

In the production of unidirectional electrical steel sheets, hot-rolled sheet annealing is usually performed after hot rolling for the purpose of homogenization of the structure, precipitation 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 casting-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 has been made on such a manufacturing process that consumes a large amount of energy, and there has been an increasing demand for simplification of the process. To answer such a request, for example, AlN
In the production method using as a main inhibitor, a method (Japanese Patent Publication No. 59-45730) in which the precipitation treatment of AlN in hot-rolled sheet annealing is replaced by high-temperature winding after hot rolling has been 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 normal method of winding in a coil shape of 5 to 20 tons, in the coil during the cooling process As a result, there is a difference in the thermal history depending on the location, the precipitation of AlN is inevitably non-uniform, and the final magnetic characteristics vary depending on the location in the coil, resulting in a decrease in yield.

Therefore, the present inventors revised the conventional rigid process design focusing on such inhibitors, returned to the elementary phenomenon of metal physics, and designed the process to enhance the magnetic properties of the product from a completely different viewpoint. , It was decided to try to simplify the hot-rolled sheet annealing. The following are two typical ideas regarding the relationship between the appropriate cold rolling rate and the inhibitor of the conventional grain-oriented electrical steel sheet.

(1) The higher the final cold rolling rate, the higher the driving force for the normal grain growth of the primary recrystallized grains. Therefore, the normal grain growth is suppressed, the secondary recrystallization is stabilized, and the degree of integration is high {110} <001> The idea that in order to generate secondary recrystallized grains, it is necessary to strengthen the inhibitor effect by the fine precipitation dispersed phase.

(2) The higher the degree of integration of the {110} <001> orientation or its corresponding orientation in the primary recrystallization texture in which the final cold rolling rate is dominant, the higher the degree of integration is {110} <001> secondary recrystallization. Thought that crystal grains are generated, it is the inhibitor strength (Zener factor) that determines the degree of secondary recrystallization orientation dispersion.

Such an idea is an idea of a process design focusing only on the secondary recrystallization phenomenon, and prior to the secondary recrystallization, strain accumulation in cold rolling, recovery by crystal rotation and subsequent annealing, recrystallization and grain Little attention is paid to elementary phenomena such as growth. The present inventors proceeded research based on the prediction that the properties of the steel sheet before cold rolling would influence such elementary phenomena, and carried out a process design to enhance the magnetic properties of the product from a completely different viewpoint from the conventional one. It was

[Means for Solving the Problems]

In the present invention, in order to achieve the object, a silicon steel slab consisting of ordinary components is hot-rolled, and then the silicon steel cold-rolled sheet obtained by the normal single cold-rolling step is subjected to an ordinary step to obtain one. In the method of manufacturing grain-oriented electrical steel, the recrystallization rate is 10
It is characterized in that cold rolling of a cold rolling ratio of 77 to 93% is performed on a steel sheet before cold rolling of less than 0%. In addition to this feature, the recrystallization rate (FR (%)) and cold rolling rate (CR
(%)), The cold rolling is performed so as to satisfy the following formula, whereby a grain-oriented electrical steel sheet having more excellent magnetic properties can be obtained.

0.05 × FR + 77 ≦ CR ≦ 0.05 × FR + 88 [Working] The unidirectional electrical steel sheet targeted by the present invention is obtained by continuously casting or ingoting molten steel obtained by the conventional steelmaking method, If necessary, the slab is sandwiched between slabs, then hot-rolled into hot-rolled sheets, then the hot-rolled sheets are annealed as required, then cold-rolled, decarburized annealed, and finally finished annealed. It is manufactured by sequentially performing.

The present inventors considered revising the conventional rigid process design focusing on the inhibitor and performing the process design from a completely different viewpoint. Specifically, it was decided to review the conventional method of selecting the cold rolling rate according to the type and amount of the inhibitor. The inventors of the present invention have extensively studied the relationship between the properties of the steel sheet before cold rolling and the cold rolling ratio (proper cold rolling ratio) that makes the magnetic properties of the product good from various viewpoints. It was confirmed that there is a very close relationship between the cold rolling rate and the appropriate cold rolling rate. Hereinafter, it demonstrates based on an experimental result.

FIG. 1 is a graph showing the relationship between the cold rolling rate and the magnetic flux density of the product when the recrystallization rate (average value of each point in the sheet thickness direction) of the steel sheet before cold rolling is 100% or less than 100%. Here C: 0.021 ~
0.100% by weight, Si: 3.2-3.5% by weight, acid-soluble Al: 0.010-
0.045% by weight, N: 0.0030 to 0.0100% by weight, S: 0.0030 to 0.0
A slab containing 300% by weight and Mn: 0.070 to 0.500% by weight and the balance Fe and unavoidable impurities was heated to 1150 to 1400 ° C to obtain a hot rolled sheet having a thickness of 1.6 to 4.0 mm. At this time, the hot rolling start temperature is 700 to 1350 ° C, the rolling reduction of each hot rolling pass is 10 to 80%, and the distribution is also performed under various conditions, and the time from the hot rolling to the start of water cooling is 0.1 to 100 seconds. And the winding temperature is 100.
It was set to ~ 800 ° C. Then, this hot-rolled sheet is processed at a temperature of 700 to 1200 ° C under the conditions of hot-rolled sheet annealing or without hot-rolled sheet annealing, and then final cold rolling with a final cold rolling rate of 70 to 98%.
A cold-rolled sheet having a thickness of 0.100 to 0.480 mm was subjected to decarburization annealing at a temperature of 830 to 1000 ° C., and subsequently, an annealing separator containing MgO as a main component was applied to perform final annealing.

As is clear from FIG. 1, when the pre-cold-rolled steel sheet having a recrystallization rate of less than 100% was cold-rolled at a cold rolling rate of 77 to 93%, B ₈
A high magnetic flux density of ≤1.88T is obtained. The present inventors also examined this new finding in more detail.

FIG. 2 shows the recrystallization of the pre-cold-rolled steel sheet under the condition that the re-crystallization rate of the pre-cold-rolled steel sheet with good magnetic flux density in FIG. 1 is less than 100% and the cold-rolled rate of 77-93%. It is a graph showing the effect of the cold rolling rate and the cold rolling rate on the magnetic flux density of the product.

As is clear from Fig. 2, when the recrystallization rate (FR (%)) and cold rolling rate (CR (%)) of the steel sheet before cold rolling are taken as FR and CR,
A high magnetic flux density of B ₈ ≧ 1.90T is obtained when the condition of 0.05 × FR + 77 ≦ CR ≦ 0.05 × FR + 88 is satisfied.

At this time, the recrystallization rate of the cold-rolled steel sheet was measured by a method of measuring crystal strain by image analysis of ECP (Electron channeling pattern) developed by the present inventors (Summary of Autumn Meeting of the Japan Institute of Metals (1988.11) P289 ), And E when cold-rolled by 1.5% on an annealed plate of a standard sample with almost random orientation.
The area ratio of grains showing a value higher than the sharpness of CP (area ratio of low strain grains) is called the recrystallization rate. Conventionally, the recrystallization rate of a hot rolled sheet of silicon steel or a steel sheet after hot rolled sheet annealing has been performed by visual judgment, but this method naturally has different values depending on the measurer and lacks objectivity. Was there. The main cause of this is that two recrystallizations of (1) nucleation-growth type recrystallization and (2) in-situ recrystallization are mixed in the recrystallization caused by hot rolling and annealing of hot rolled sheet. It was because of it. On the other hand, for example 70-90%
In the case of recrystallization after cold rolling of (1), the recrystallization of (1) is mainly
It is possible to accurately measure the recrystallization rate by visual judgment. The present inventors conducted a detailed investigation on the cold rolling recrystallization process of silicon steel in the case of 88% cold rolling of which the type (1) type recrystallization is predominant, by the above method, and ECP sharpness causes recrystallization. It was clarified that the ECP sharply increased and the ECP sharpness further increased (strain decreased) after the completion of recrystallization during annealing. And, when the ECP sharpness is higher than that when the standard sample is annealed to 1.5% cold rolled, the 88% cold rolled and annealed ECP sharpness measurement point is in a recrystallized state. It turns out that it can be judged. Therefore, this criterion is used to accurately measure the recrystallization rate of the hot-rolled sheet and the sheet after hot-rolled sheet annealing, which has been impossible in the past.

The reason why the relationships shown in FIGS. 1 and 2 are established between the recrystallization rate of the steel sheet before cold rolling and the cold rolling rate and the magnetic flux density of the product is not necessarily clear, but the present inventors have I guess as follows.

FIG. 3 is a graph showing the relationship between the cold rolling rate and the magnetic flux density of the product when the hot rolled sheet is not annealed and when the hot rolled sheet is annealed. Further, FIG. 4 is an example of the texture (center of plate thickness) of the steel sheet before cold rolling (three-dimensional analysis result by the vector method). In this case, C: 0.053% by weight, Si: 3.28% by weight, Mn: 0.16% by weight, S:
After heating a 40 mm thick slab containing 0.007% by weight, acid-soluble Al: 0.027% by weight, N: 0.0076% by weight and the balance Fe and unavoidable impurities to 1150 ° C, the rolling start temperature was 1051%.
2 levels of ℃ and 778 ℃, 40 → 23 → 12 → 6 → 3.7 → 2.3
→ Winding simulation was conducted by hot rolling with a pass schedule of 1.8 (mm), water cooling after 1 second, water cooling to 550 ° C, holding at 550 ° C for 1 hour, and furnace cooling. At this time, the rolling finish temperatures were 925 ° C and 754 ° C, respectively. This hot-rolled sheet is then (a) without hot-rolled sheet annealing, (b) at 1120 ° C.
There was hot-rolled sheet annealing in which the material was held for 30 seconds and then held at 900 ° C for 30 seconds to be rapidly cooled. At this time, the recrystallization rate of the steel sheet before cold rolling was − (a): 55%, − (b): 100%,
-(A): 8%,-(b): 100%. Then, this cold rolled steel sheet is cold rolled at a cold rolling rate of 70 to 94% to obtain 0.100 to 0.54 m.
The final cold-rolled sheet having a thickness of m was subjected to decarburization annealing and final finishing annealing.

As is clear from FIG. 3, the lower the recrystallization rate of the steel sheet before cold rolling, the higher the magnetic flux density of the product becomes (the optimum cold rolling rate).
It turns out that is low. As is clear from FIG. 4, the lower the recrystallization rate of the pre-cold-rolled steel sheet, the more {100} <011> oriented grains of the pre-cold-rolled steel sheet.

In the research on crystal rotation in cold rolling of steel,
For example, the {110} <001> orientation before cold rolling is {11} after cold rolling.
Rotating in the 1} <112> direction, {111} <112 before cold rolling
＞ Orientation rotates to {211} <011> orientation after cold rolling,
The final stable orientation of cold rolling is {100} <011> or {211} <011
There are reports such as>. Crystal rotation in cold rolling is caused by the movement of dislocations in a specific slip plane and slip direction (slip system). Naturally, if the crystal orientation before cold rolling is different, the crystal orientation after cold rolling is different. Occurs. On the other hand, as is clear from FIG. 4, the lower the recrystallization rate of the steel sheet before cold rolling is, the more {100} <011> which is the final stable orientation of cold rolling. This indicates that the pre-cold-rolled steel sheet having a recrystallization rate of less than 100% has a texture as if the cold-rolled steel sheet having a recrystallization rate of 100% was subjected to cold rolling. Therefore, for example, in order to obtain a similar texture after cold rolling at a cold rolling rate of about 80%, it is necessary to lower the cold rolling rate as the recrystallization rate of the steel sheet before cold rolling is lower.

The present inventors presume that the lower the recrystallization rate of the steel sheet before cold rolling is, the more the {100} <011> is.
For example, the crystal rotation of the central layer in hot rolling is similar to that in cold rolling, and {100} <011> oriented grains tend to increase by rolling. On the other hand, the crystal orientation changes due to recrystallization during air cooling between passes and after hot rolling is completed, but the {100} <011> oriented grains are rarely generated during the recrystallization, and rather the reorientation of other orientations occurs. {100} <011> on the crystal grains
The direction grains are eroded and decrease. Therefore, even if the cumulative rolling reduction in hot rolling is the same, the number of {100} <011> oriented grains tends to be small in the case of hot rolling under conditions where recrystallization is likely to occur in hot rolling. In addition, {100} <0 even with recrystallization during hot-rolled sheet annealing.
11> orientation grains tend to be eroded by recrystallized grains in other orientations and decrease. Therefore, in the case of hot-rolled sheet annealing under conditions such as high temperature where recrystallization is likely to occur, {100} <011> oriented grains tend to decrease.

On the other hand, it has been conventionally known that the strain amount (dislocation density) after cold rolling has a dominant effect on the recrystallization phenomenon such as the nucleus generation frequency in cold rolling recrystallization. The lower the recrystallization rate of the steel sheet before cold rolling, the larger the strain amount, and the effect is inherited even after cold rolling, and the strain amount tends to be large. Therefore, in order to obtain the same strain amount in cold rolling at a cold rolling rate of about 80%, for example, it is necessary to lower the cold rolling rate as the recrystallization rate of the pre-cold rolling steel sheet is lower.

As described above, in order to make the crystal rotation in cold rolling and the cold rolling recrystallization phenomenon such that the magnetic flux density of the product becomes good, the lower the recrystallization rate of the steel sheet before cold rolling, the lower the cold rolling rate. It needs to be lowered.

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

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

Next, the reasons for limiting the above components will be described.

When C is less than 0.021%, secondary recrystallization becomes unstable,
Moreover, B ₈ > 1.80 (T) is not obtained easily even in the case of secondary recrystallization, and if it exceeds 0.100%, decarburization failure occurs, which is not preferable.

Further, 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, Sb, B, Cu, Bi, Nb, C
It is also possible to add r, 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 hot rolling process usually consists of heating a slab with a thickness of 100 to 400 mm, and then performing rough rolling and finish rolling each in multiple passes. The method of rough rolling is not particularly limited, and a general method is used. Finish rolling is usually performed by high speed continuous rolling with 4 to 10 passes. Normally, in the reduction distribution of finish rolling, the reduction ratio is high in the former stage and lower in the latter stage, and the shape is improved. Rolling speed is usually 100-300
It is 0 m / min, and the time between passes is 0.01 to 100 seconds. The reduction rate of finish rolling, reduction distribution, and cooling conditions after the final pass affect the recrystallization rate of the hot-rolled sheet, and the higher the reduction rate in the final stage, especially in the final pass, the higher the temperature of the steel sheet after hot rolling is finished. The longer the holding time, the higher the recrystallization rate of the hot rolled sheet. The coiling temperature after hot rolling is not particularly limited, but at 700 ° C or higher, variations in the precipitation state of precipitates such as AlN are caused in the coil due to the difference in thermal history in the coil during cooling. The surface decarburization varies, the metal structure varies, and the magnetic properties of the product vary, which is not preferable.

This hot rolled sheet is subsequently subjected to a treatment with or without annealing at a temperature of 700 to 1200 ° C., and then cold rolled.

A feature of the present invention is a cold rolling method for a pre-cold-rolled steel sheet (hot-rolled sheet or steel sheet after hot-rolled sheet annealing) having a recrystallization rate of less than 100%. Specifically, the cold rolling rate must be 77 to 93% for the pre-cold rolling steel sheet having a recrystallization rate of less than 100%. Also,
More preferably, the recrystallization rate (FR of the steel sheet before cold rolling is
(%)) And cold rolling rate (CR (%)), cold rolling must be performed so as to satisfy the following formula.

0.05 × FR + 77 ≦ CR ≦ 0.05 × FR + 88 (A) Next, the reasons for limiting the above conditions will be described.

For cold rolled steel sheet with recrystallization rate less than 100%, cold rolling rate is 77-9
The reason for setting it to 3% is that, as is clear from FIG. 1, a good magnetic flux density of B ₈ ≧ 1.88 (T) can be obtained in this range. Further, more preferably, it is necessary to satisfy the formula (A), as is clear from FIG. 2, a product having a better magnetic flux density of B ₈ ≧ 1.90 (T) in this range. Is obtained.

After cold rolling, the steel sheet is subjected to decarburization annealing, an annealing separator coating, and finish annealing in a usual manner to obtain a 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. Then, hot rolling was performed in 6 passes to obtain a hot rolled sheet having a thickness of 2.3 mm. At this time, the reduction distribution was set to 40 → 30 → 20 → 10 → 5 → 2.8 → 2.3 (mm). At this time, the hot rolling end temperature was 915 ° C. 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 was not annealed and treated under the condition of soaking at 900 ° C. for 3 minutes, and then the rolling reductions (a) 75%, (b) 85%, (c) 95
% Cold-rolled at 3 levels to make 0.115-0.575mm thick cold-rolled sheet,
Decarburization annealing was performed at 830 ° C for 150 seconds. The decarburized and annealed sheet thus obtained was coated with an annealing separator containing MgO as a main component, and N ₂ 2
The temperature is raised to 880 ° C at a rate of 10 ° C / hour in an atmosphere gas of 5% and H ₂ 75%, and then 10% in an atmosphere gas of N ₂ 75% and H ₂ 25%.
The final finishing annealing was performed by raising the temperature to 1200 ° C. at a rate of ° C./hour and then maintaining the temperature at 1200 ° C. for 20 hours in H ₂ 100% atmosphere gas.

Table 1 shows the process conditions, the recrystallization rate of the steel sheet before cold rolling, and the magnetic properties of the product.

-Example 2-C: 0.034 wt%, Si: 3.28 wt%, Mn: 0.14 wt%, S: 0.006
% By weight, acid-soluble Al: 0.027% by weight, N: 0.0079% 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 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 was set to 26 → 15 → 10 → 7 → 5 → 3 → 2.3 (mm). At this time, the hot rolling finish temperature was 892 ° C. After completion of hot rolling, the cooling conditions were the same as those in Example 1, followed by no annealing, treatment at 850 ° C. for 3 minutes, and subsequent process conditions until final annealing were the same as in Example 1. It was

Table 2 shows the process conditions, the recrystallization rate of the steel sheet before cold rolling, and the magnetic properties of the product.

-Example 3-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 is heated at a temperature of 1150 ° C. and then hot rolling is started at 800 ° C.,
Hot rolling was performed in 6 passes to obtain a hot rolled sheet having a thickness of 1.8 mm. At this time, the reduction distribution was set to 26 → 15 → 10 → 7 → 4 → 2.6 → 1.8 (mm). At this time, the hot rolling end temperature was 749 ° C. After the hot rolling, the cooling conditions were the same as in Example 1, and cold rolling was performed at 70% and 79% cold rolling rates without hot rolling sheet annealing, to obtain 0.38 to 0.54.
A cold rolled sheet having a thickness of mm was used. The process conditions up to the subsequent final finish annealing were the same as in Example 1.

Table 3 shows the process conditions, the recrystallization rate of the steel sheet before cold rolling, and the magnetic properties of the product.

-Example 4-C: 0.079 wt%, Si: 3.25 wt%, Mn: 0.080 wt%, S: 0.026
% By weight, acid-soluble Al: 0.028% by weight, N: 0.0082% by weight, Sn:
A slab containing 0.11% by weight and Cu: 0.06% by weight and consisting of balance Fe and unavoidable impurities and having a thickness of 40 mm was heated at a temperature of 1300 ° C., then hot rolling was started at 1100 ° C., and hot rolling was performed in 6 passes. 2.3m
It was a hot rolled sheet with a thickness of m. The reduction distribution at this time is 40 → 30 → 20 → 10
→ 6 → 3.6 → 2.3 (mm). At this time, the hot rolling end temperature is
It was 975 ° C. After hot rolling, air-cool for 2 seconds and then 70 ℃ /
Water-cooling to 550 ° C. was performed at a cooling rate of 2 seconds, the temperature was kept at 550 ° C. for 1 hour, and then a furnace cooling simulation was performed. 0.14 to 0.37 of this hot rolled sheet was treated with cold rolling rate (a) 84% and (b) 94% under the condition that the hot rolled sheet was not annealed and kept at 800 ° C for 3 minutes.
A cold rolled sheet having a thickness of mm was used. 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 4 shows the process conditions, the recrystallization rate of the steel sheet before cold rolling, and the magnetic properties of the product.

-Example 5-C: 0.043 wt%, Si: 3.20 wt%, Mn: 0.066 wt%, S: 0.024
%, 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 1000 ° C., hot rolling was started at 1000 ° C., and hot rolling was performed in 6 passes to obtain a 1.6 mm thick hot rolled sheet. At this time, the reduction distribution is 40
→ 15 → 7 → 5 → 3.5 → 2.1 → 1.6 (mm). At this time,
The hot rolling end temperature was 921 ° C. After the hot rolling was completed, cooling was performed under the same conditions as in Example 1. Then, the hot rolled sheet was not annealed, treated at 850 ° C. for 3 minutes, and cold rolled at a cold rolling rate (a) of 75% and (b) 80% to obtain a cold rolled sheet of 0.4 to 0.32 mm thickness. . Next, this cold rolled sheet was subjected to decarburization annealing at 830 ° C for 120 seconds and then at 910 ° C for 20 seconds. The process conditions up to the subsequent final finish annealing were the same as in Example 1.

Table 5 shows the process conditions, the recrystallization rate of the steel sheet before cold rolling, and the magnetic properties of the product.

(Effect of the invention) As described above, in the present invention, the recrystallization rate is 100
%, The cold rolling rate is 77 to 93% with respect to the steel sheet before cold rolling, and more preferably, the hot rolling sheet annealing is simplified by selecting the cold rolling rate according to the recrystallization rate of the steel sheet before cold rolling. Since it is possible to obtain good magnetic properties, its industrial effect is extremely large.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the cold rolling rate and the magnetic flux density of the product when the recrystallization rate of the cold rolling steel sheet is 100% or less than 100%, and FIG. FIG. 3 is a graph showing the influence of the crystallinity and the cold rolling rate on the magnetic flux density of the product. FIG. 3 is a graph showing the relationship between the cold rolling rate and the magnetic flux density of the product with and without annealing of the hot rolled sheet. 4 is an example of the texture of the pre-cold rolled steel sheet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Satoru Arai Satoshi Arai 1-1-1 Edamitsu, Yawatahigashi-ku, Kitakyushu, Fukuoka Prefecture (3) Technical Research Laboratories, Nippon Steel Co., Ltd. (56) References JP-B-59-41488 ( JP, B2) JP-B-50-37009 (JP, B2)

Claims (2)

[Claims] 1. C: 0.021 to 0.100% by weight, Si: 2.5 to 4.5% by weight
In addition, a silicon steel slab containing a usual inhibitor component and the balance Fe and unavoidable impurities is hot-rolled, followed by decarburization annealing and final finishing annealing on a silicon steel cold-rolled sheet obtained by a normal single cold rolling process. In the method for producing a grain-oriented electrical steel sheet by applying the above method, the steel sheet before cold rolling having a recrystallization rate of less than 100% is subjected to cold rolling at a cold rolling rate of 77 to 93%, which is excellent in magnetic properties. Method for producing unidirectional electrical steel sheet. 2. When the recrystallization rate (FR (%)) and cold rolling rate (CR (%)) of a steel sheet before cold rolling are defined, cold rolling is performed so as to satisfy the following formula. The method for producing a grain-oriented electrical steel sheet having excellent magnetic properties according to claim 1. 0.05 x FR + 77 ≤ CR ≤ 0.05 x FR + 88