JPH10110218A - Production of grain oriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grain oriented silicon steel sheet excellent in magnetic properties and reduced in iron loss at a low cost by further incorporating Nb into steel having respectively specified C, Si, and Mn contents and specifying hot rolling, cooling velocity, and coiling temp., respectively. SOLUTION: Nb is further incorporated by 0.002-0.10wt.% into a silicon steel having a composition containing, by weight, 0.005-0.080% C, 2.0-5.0% Si, and 0.03-0.20% Mn. A slab of this silicon steel is heated to >=1100 deg.C, hot-rolled, cold-rolled while process-annealed between cold rolling stages, and then subjected to decarburizing annealing and final finish annealing. At this time, hot rolling finishing temp. is regulated to 850-1050 deg.C, and the resultant hot rolled plate is cooled while regulating the average cooling rate, from directly after the completion of hot rolling until after 5sec, to (20 to 55) deg.C/sec, followed by coiling at 450-650 deg.C. If <=0.050% sol.Al and <=0.020% N are incorporated to the silicon steel if necessary, magnetic properties can be improved. Further, it is desirable to control the value of (S+Se), contained in the slab, to <=0.010%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention proposes a method for manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties and reducing manufacturing costs for use in iron cores of transformers and other electric equipment.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets have the following magnetic properties:
High magnetic flux density and low iron loss are required. The former is represented by B8 (magnetic flux density at 800 A / m magnetizing force),
The latter is represented by W _17/50 (energy loss when magnetized to 1.7 T at a frequency of 50 Hz).

[0003] In order for a grain-oriented electrical steel sheet to have a high magnetic flux density and a low iron loss, the <001> orientation, which is the axis of easy magnetization of iron, must be highly integrated in the rolling direction of the steel sheet. During the manufacturing process of a grain-oriented electrical steel sheet, it is formed through a phenomenon called secondary recrystallization, in which crystal grains having a {110} <001> orientation called a Goss orientation are preferentially giganticly grown during final finish annealing. Such crystal orientation control techniques include, for example, Japanese Patent Publication No. Sho 33-4710 (a method for producing a silicon steel strip having directivity) and Japanese Patent Publication No. 40-15644 (production of a high magnetic flux density unidirectional silicon steel sheet). Method), the Al is contained in the material, and the final cold rolling reduction is 81-95%.
And the precipitation of AlN by annealing before final cold rolling, and Japanese Patent Publication No. 46-23820 (heat treatment of high magnetic flux density magnetic steel sheet), the cooling rate in this final annealing is 750. From 950 ℃ to 400 ℃
Each of the techniques for quenching in 200 seconds is disclosed.

[0004] Advances in manufacturing technology as described above have enabled industrial production of steel sheets with a B8 exceeding 1.92 T in recent years.
For example, with a steel plate having a thickness of _0.23 mm, products whose W17 / ₅₀ reaches 0.90 W / Kg are industrially produced. However, the following two problems have arisen in today's method of manufacturing a grain-oriented electrical steel sheet with a focus on increasing the magnetic flux density.

[0005] The first point is that the crystal grain size of the product is increased with the improvement of the magnetic flux density, and the magnetic domain width is increased, resulting in an increase in eddy current loss.

A second point is that a complicated process is required to achieve a high magnetic flux density, which increases the manufacturing cost of grain-oriented electrical steel sheets. In particular, high-temperature heating of the slab before hot rolling and high-temperature long-time annealing in the final finish annealing is a factor that increases the production cost of grain-oriented electrical steel sheet production, further hot-rolled sheet annealing, also intermediate annealing, If this can be omitted, manufacturing costs can be greatly reduced.

Heretofore, as a solution to the first problem,
Japanese Patent Publication No. 50-26493 (a method of cold rolling of high magnetic flux density unidirectional electrical steel sheet) discloses a technique of keeping the inter-pass temperature of the cold rolling at a predetermined temperature and aging, Even with this method, it is difficult to completely control the particle size of the secondary particles, and it is extremely complicated in actual operation.

As a workaround for the second problem, Japanese Patent Publication No. Sho 61
-7447 (Method of manufacturing grain-oriented electrical steel sheet) states that
Japanese Patent Publication No. 4-71990 (Oriented electrical steel sheet and manufacturing method thereof) is a method that enables slab heating at a low temperature by performing finish annealing under a temperature gradient.
A method that enables finish annealing at a low temperature by limiting the contents of C and Si to a predetermined amount or less is disclosed in
Japanese Patent Application Laid-Open No. 59-45730 (Hot-rolling method for high magnetic flux density unidirectional silicon steel sheet) discloses a technology that enables the omission of hot-rolled sheet annealing by setting the winding temperature after hot rolling at a high temperature. ,
In Japanese Patent Publication No. 7-94689 (a method for manufacturing a grain-oriented electrical steel sheet having excellent magnetic properties), by appropriately controlling the cumulative rolling reduction and the hot rolling temperature in the final three passes of finish hot rolling, Disclosed are methods that enable omission of hot-rolled sheet annealing in a manufacturing process that does not include intermediate annealing. However, when the grain-oriented electrical steel sheet is manufactured by the above method, although the manufacturing cost can be reduced to some extent, there is a defect that a product having sufficient magnetic properties cannot be obtained yet.

[0009]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems by hot rolling a slab containing a predetermined amount of Nb under predetermined conditions. An object of the present invention is to propose a method for manufacturing a grain-oriented electrical steel sheet which enables a grain-oriented electrical steel sheet having fine secondary grains and low iron loss to be produced at low cost. In addition, an object of the invention described in claim 4 is to propose a method of manufacturing a grain-oriented electrical steel sheet having more excellent magnetic properties.

[0010] By adding Nb to silicon steel slabs, the magnetic properties of grain-oriented electrical steel sheets have been improved.
Alternatively, as a method of reducing the manufacturing cost, Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 52-24116 (Material for High Magnetic Flux Density Unidirectional Electrical Steel Sheet) and Japanese Patent Application Laid-Open No. 6-25747 (Method of Manufacturing Thin High Magnetic Flux Unidirectional Electrical Steel Sheet) However, none of these methods control the precipitation of the Nb compound in the hot rolling step, so that it is not considered that a product having sufficient magnetic properties can be stably obtained.

[0011]

Means for Solving the Problems As a result of research conducted to solve the above problems, the inventors have found that a slab containing Nb in steel is hot-rolled under strictly controlled temperature conditions. By doing so, it is possible to lower the slab heating temperature, shorten the finish annealing time, or omit the hot-rolled sheet annealing, and find that it is possible to reduce the iron loss by making the secondary grains finer. The present invention has been accomplished. That is, the gist of the present invention is as follows.

C: 0.005 to 0.080 wt%, Si: 2.0 to
Using a silicon steel slab containing 5.0 wt% and Mn: 0.03 to 0.20 wt% as a raw material, the slab is heated to a temperature of 1100 ° C. or more, then hot-rolled, and once or twice or more with intermediate annealing In the method for producing a grain-oriented electrical steel sheet that is subjected to decarburizing annealing and final finishing annealing after cold rolling of Nb: 0.002 to 0.10 wt% of Nb in the slab, and hot rolling end temperature of 850 And the average cooling rate of the hot-rolled sheet from immediately after the completion of hot rolling to after 5 seconds is 20 to 55
° C / sec and the coiling temperature of the hot rolled sheet is 45
0 to 650 ° C., a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties (first invention),
According to such a manufacturing method, a grain-oriented electrical steel sheet having excellent magnetic properties can be obtained even if the omission of hot-rolled sheet annealing is omitted or the time for long-time finish annealing is shortened, and the manufacturing cost can be significantly reduced.

[0013] In addition to the component composition of the silicon steel slab of the first invention, sol. Al: 0.050 wt% or less and N: 0.020 wt%
% Or less, which is a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties (second invention), whereby the magnetic properties can be further improved.

The value of S + Se contained in the slab is 0.01
0 wt% or less, and the heating temperature of the slab is 1100
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties according to the first or second invention (third invention), wherein the slab is in a low-temperature range. A product having excellent magnetic properties can be obtained even at the heating temperature, and the production cost can be significantly reduced.

The hot-rolled sheet is annealed at a temperature in the range of 850 to 1200 ° C. for 20 to 120 seconds after the hot rolling, and has excellent magnetic properties according to the first, second or third invention. This is a method for manufacturing a grain-oriented electrical steel sheet (fourth invention). According to this manufacturing method, a product having more excellent magnetic properties can be obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, requirements constituting the present invention will be described below based on experimental examples.

C: 0.040 wt% (hereinafter simply expressed as%), Si: 3.30%, Mn: 0.07%, Se: 0.015% and S
b: A molten steel containing 0.020%, with the balance being substantially composed of Fe and unavoidable impurities, and each molten steel obtained by adding Nb to the molten steel in a range of 0.20% or less and changing the content. Cast into.

After heating these ingots at 1400 ° C. for 60 minutes, they were hot-rolled into hot-rolled sheets each having a thickness of 2.2 mm. After pickling these hot-rolled sheets, they are cold-rolled to give cold-rolled sheets with a final thickness of 0.35 mm, decarburized at 870 ° C, and then annealed mainly with MgO. After the agent was applied, final finishing annealing was performed in each of the heat patterns shown in FIG. Here, FIG. 1 is a graph showing a heat pattern of the short-time final finish annealing.

Next, for the product sheet obtained by baking a tension coating on each of the steel sheets obtained in the above process, B ₈ (magnetizing force: magnetic flux density at 800 A / m) and W _17/50 (maximum magnetic flux density) were determined by the Epstein test method. : 1.7T, frequency:
Core loss at 50Hz) and average 2
The secondary particle size was measured. FIG. 2 is a graph showing the relationship between the Nb content, the iron loss W _17/50 , the magnetic flux density B ₈ and the average secondary particle size.

As apparent from FIG. 2, the Nb content is 0.00
In the range of 2 to 0.10%, the iron loss is reduced and the average secondary particle size is also reduced. Therefore, it can be said that the effect of reducing the iron loss by adding Nb is due to the refinement of the secondary particle size of the product sheet.

From this experiment, it was found that even in the manufacturing process in which the hot-rolled sheet annealing was omitted, there is a possibility that a product having good magnetic properties can be obtained by adding Nb. However, looking at FIG. 2, the variation in iron loss is quite large, and simply adding Nb cannot be expected to significantly improve the iron loss. Therefore, when investigating the cause of this variation in iron loss, may deteriorate the magnetic flux density B ₈ when containing occurs, this has revealed that degrade the iron loss.

[0022] Here, the deterioration of the B ₈ by Nb addition, precipitation state of Nb compound in hot rolling is believed to be due to be improper. Therefore, in order to stably obtain good magnetic properties when Nb is added, temperature conditions during hot rolling were examined.

FIG. 3 shows that the Nb content in the above experiment was 0.002 to 0.2.
About 10% of the range of samples, shows a graph of the relationship between hot rolling finishing temperature and the magnetic flux density B _8. From this figure, when the hot rolling finishing temperature is in the range of 850 to 1050 ° C., B ₈ is seen to be in the high level. Therefore, it has been clarified that the deterioration of the magnetic flux density can be prevented by appropriately controlling the hot rolling end temperature.

Subsequently, an experiment on cooling conditions after hot rolling was conducted. In manufacturing grain-oriented electrical steel sheets using a steel ingot containing 0.010% Nb, the hot rolling end temperature was set at 85.
0 to 1050 ° C, the average cooling rate from immediately after the completion of hot rolling to 5 seconds later is changed to 10 to 70 ° C / sec and the winding temperature of the hot-rolled sheet is changed to 450 to 650 ° C, respectively. Except for these conditions, a product plate was formed in the same process as in the above-mentioned experiment, and the iron loss W _17/50 was examined for each of the obtained product plates. FIG. 4 shows the results of these investigations. FIG. 4 is a graph showing the relationship between the average cooling rate and the winding temperature from immediately after hot rolling to 5 seconds later and the iron loss W _17/50 .

As is apparent from FIG. 4, the average cooling rate from immediately after the completion of hot rolling to after 5 seconds is in the range of 20 to 55 ° C./sec, and the winding temperature of the hot rolled sheet is in the range of 450 to 650 ° C. By doing so, it is possible to stably produce a grain-oriented electrical steel sheet having excellent magnetic properties, and it is understood that these ranges are preferable ranges.

Further, an experiment was conducted to confirm the effect of improving the magnetic properties by adding Nb and controlling the hot rolling conditions. In steel
By changing the Nb content to 0.20% or less,
1000 ° C, average cooling rate of hot rolled sheet from end of hot rolling to 5 seconds after completion of 40 ° C / sec and winding temperature of hot rolled sheet at 550 ° C
With the exception of these conditions, grain-oriented electrical steel sheets were manufactured in the same steps as in the above-described experiment, and the magnetic properties of the obtained product sheets were investigated. Figure 5 shows the results of these surveys.
4 shows a graph of the relationship between Nb content and iron loss W _17/50 .

As is clear from FIG. 5, the variation in iron loss is smaller and the Nb content is 0.002 to 0.010% as compared to FIG.
It can be seen that a product with low iron loss can be obtained stably in the range of. Therefore, it was confirmed that a product having stable and good magnetic properties can be obtained by hot rolling a slab containing an appropriate amount of Nb under strictly controlled conditions.

After the above experiment, the grain size and texture of the decarburized annealed sheets with and without Nb were investigated. As a result, when the magnetic properties were improved by adding Nb, the grain size of the decarburized annealed sheet became finer, and
The intensity in the 1｝ <112> direction was increasing. In addition, despite the addition of Nb, those in which good magnetic properties could not be obtained because the hot rolling conditions were not appropriate, whereas coarse Nb compounds were precipitated in the hot-rolled sheet, In those having good magnetic properties, the Nb compound was uniformly and finely dispersed.

Through a series of these experiments, a method was established in which a grain-oriented electrical steel sheet having excellent magnetic properties could be produced at low cost by optimizing the Nb content and the temperature conditions in hot rolling.

As described above, according to the present invention, even when the steps are omitted, it is possible to manufacture a grain-oriented electrical steel sheet having good magnetic properties by appropriately adding Nb.

Nb in such steel forms precipitates such as NbC and NbN, thereby refining the recrystallized structure of the hot-rolled sheet and improving the crystal grain size distribution and texture of the decarburized annealed sheet. However, in the final finish annealing, it is considered to act as an inhibitor for suppressing normal grain growth. By such an action, it can be said that the addition of Nb to steel has enabled omission of hot-rolled sheet annealing and intermediate annealing, thereby enabling good magnetic properties to be obtained even when the finish annealing time is shortened.

Therefore, in order to improve the magnetic properties by adding Nb, it is important to uniformly and finely precipitate the Nb compound in the steel. For this purpose, it is important to optimize the hot rolling conditions.

The reason why a grain-oriented electrical steel sheet having excellent magnetic properties can be obtained by the hot rolling conditions specified in the present invention is presumed to be the fact that uniform and fine precipitation of the Nb compound was realized by the following mechanism.

That is, when the hot rolling end temperature is too low, Nb compounds (NbC, NbN, etc.) precipitate during rolling, and the distribution of the precipitates becomes uneven. Conversely, if the hot-rolling termination temperature is too high, it is considered that the temperature history in the cooling process after rolling becomes non-uniform, and the precipitation state becomes non-uniform.

Further, it is considered that the precipitate of the Nb compound is refined by rapidly cooling the hot-rolled sheet at an average cooling rate of 20 ° C./sec or more from immediately after the end of the hot rolling to after 5 seconds. . However, this average cooling rate is 55 ° C /
It is considered that if the time exceeds seconds, the solute Nb in the hot-rolled sheet becomes supersaturated, the precipitates decrease, and the absolute amount becomes insufficient, so that the magnetic properties deteriorate.

Further, the winding temperature of the hot rolled sheet is set at 450 to 650 ° C.
It is presumed that the reason why good magnetic properties can be obtained by setting the range as described above is that the distribution of the number of precipitated Nb compounds in the plate thickness direction becomes appropriate within this temperature range.

Next, the component composition of the silicon steel material used in the present invention will be described. The component composition of the present invention is as follows: C: 0.005 to 0.080%, Si: 2.0 to 5.0% and M
n: 0.03 to 0.20% for steel with basic components, Nb: 0.002 to
It is contained in the range of 0.10%. Hereinafter, the reason why the composition of the present invention is limited to the above range and the preferable composition of the composition will be described.

C: 0.005 to 0.080% C is a component useful for improving the hot-rolled structure by utilizing transformation, and the content is required to be at least 0.005%, but when it exceeds 0.080%, decarburization is performed. This is not preferable because of poor decarburization during annealing. Therefore its content is 0.005%
At least 0.080%.

Si: 2.0 to 5.0% Si is a main component for increasing electric resistance and reducing iron loss, and the content is required to be at least 2.0%.
%, The cold rolling becomes difficult, which is not preferable. Therefore, its content should be 2.0% or more and 5.0% or less.

Mn: 0.03 to 0.20% Mn not only effectively contributes to the improvement of hot workability of steel, but also forms precipitates such as MnS and MnSe when S or Se is mixed. Since it functions as an agent, its content needs to be in the range of 0.03% or more and 0.20% or less.

Nb: 0.002 to 0.10% Nb is an effective material that can obtain good magnetic properties even if the conventional manufacturing process is greatly simplified by appropriately controlling the cooling conditions in hot rolling. Component. Also,
Nb also has a function of reducing the eddy current loss by reducing the secondary recrystallized grain size. If the content is less than 0.002%, these effects are not sufficient. On the other hand, if the content exceeds 0.10%, the Nb compound precipitates coarsely and adversely affects magnetic properties. Therefore, its content should be not less than 0.002% and not more than 0.10%.

On the other hand, as in the case of a normal grain-oriented electrical steel sheet, it is also effective to include S, Se and Al, N, etc. in addition to the above-mentioned component composition as a suppressing force reinforcing component in order to obtain good magnetic properties. is there.

When the heating temperature of the slab is low, if the content of S and Se is large, non-uniform precipitation occurs, which causes deterioration of magnetic properties. For this reason,
In the present invention (third invention), when the heating temperature of the slab is lowered, the S + Se content is set to 0.010% or less.
Further, in the present invention, the addition of Nb complements the functions of S and Se as inhibitor-forming components.

Also, Al combines with N and precipitates as AlN, and as an inhibitor, has the effect of suppressing the growth of grains other than normal grains (grain in the Goss orientation), and has the function of increasing the action of the Nb compound. In order to exhibit this effect, it is preferable that Al is contained in a range of 0.050% or less as sol.Al, and N is contained in a range of 0.020% or less. However, sol.Al is 0.050%
If N exceeds 0.020%, the precipitated AlN becomes coarse and hinders the growth of secondary recrystallized grains, deteriorating the magnetic properties. Therefore, sol.Al is 0.050% or less and N is 0.020% or less. I do.

The object of the present invention can be achieved by the above-mentioned composition, but in addition to these, Sb, Bi, Mo, Cu, P, Sn and the like are added for reinforcing the suppressing force. Is also good.

Sb and Bi have the effect of segregating at the grain boundaries to increase the suppressing power, and Mo has the effect of sharpening the nuclei of the secondary grains to the Goss orientation. However, those effects are remarkable in the range of 0.001 to 0.20%.

Cu, like Mn, is a component that combines with S and Se to form precipitates and enhance the suppressing power, and its effect is preferably in the range of 0.01 to 0.30%.

P, like Sb, is a component that segregates at the grain boundaries to increase the suppressing power. If the content is less than 0.010%, the effect of addition is poor, while if it exceeds 0.030%, the magnetic properties and surface properties are unstable. So that the content is 0.010-0.030%
Range is good.

Sn is a component effective for reducing iron loss.
It is preferable to contain 008 to 0.025%.

In each of the above components, C, S, S
e, Al, N, etc. perform their respective functions,
Is mainly removed during decarburization annealing, S, Se, Al, N, etc. are removed in the annealing after the final annealing, so that only a trace amount of impurities remains in the base iron of the product.

Next, the manufacturing method of the present invention will be described. The material (slab) for a grain-oriented electrical steel sheet having the above-described component composition can be produced by any conventionally known method. Next, the material for an electromagnetic steel sheet is formed into a hot-rolled sheet by ordinary hot rolling and wound around a coil.

According to the present invention, in the hot rolling step,
The hot-rolling end temperature is in the range of 850 to 1050 ° C, the average cooling rate from immediately after hot-rolling to 5 seconds later is in the range of 20 to 55 ° C / sec, and the hot-rolled sheet winding temperature is 450 to 650 ° C. By setting the range, it is possible to largely omit the conventionally required steps.

If the temperature conditions from the end of hot rolling to the winding of the hot-rolled sheet deviate from the above-mentioned conditions, the Nb compound is not uniformly and finely precipitated in the hot-rolled sheet and magnetic properties are impaired. Therefore, when the material containing Nb of the present invention is used, it is overwhelmingly advantageous to perform hot rolling including winding under the above conditions, and the above conditions are essential. It is.

The main part of the structure of the present invention lies in that good secondary recrystallization is facilitated by adding Nb to the steel and controlling the temperature in the hot rolling step. Thereby, the heating temperature of the slab can be further reduced. As a technology for lowering the slab heating temperature,
The above-mentioned Japanese Patent Application Laid-Open No. 52-24116 discloses a method of including a predetermined amount of a nitride-forming component such as Nb. However, this method does not control the dispersion state of the precipitates, so that it cannot be said that sufficiently satisfactory magnetic characteristics can be obtained.

On the other hand, the present inventors have focused on Nb, and established a method for controlling the dispersed precipitation state of the Nb compound and improving the magnetic properties. However, by further controlling the amount of S + Se in the steel, It has been found that a product having good magnetic properties can be obtained even when the slab heating temperature is lowered, and this invention (third invention) has been achieved. That is, the amount of S + Se contained in the slab was set to 0.010% or less, and the slab heating temperature was set to 11%.
Even when the temperature is in the range of 00 to 1250 ° C., a grain-oriented electrical steel sheet having excellent magnetic properties can be obtained.

In the above, S and Se in steel are MnS
And precipitates as MnSe, affecting secondary recrystallization. However, when the slab heating temperature is low, solid solution of MnS and MnSe becomes incomplete, and segregation of S and Se occurs to deteriorate magnetic properties. On the other hand, reducing the content of S and Se avoids the occurrence of such segregation, and obtains good magnetic properties even when S and Se are reduced by adding Nb. Can be. This is presumably because the Nb compound precipitated uniformly and finely in the steel acts as an inhibitor, whereby favorable secondary recrystallization proceeds even when MnS and MnSe are reduced.

After hot rolling, cold rolling is performed once or two or more times with intermediate annealing, followed by ordinary decarburizing annealing and final finishing annealing, and, if necessary, by applying tension coating to the product sheet. I do.

By the above-described method, it is possible to produce a grain-oriented electrical steel sheet having excellent magnetic properties even when the hot-rolled sheet annealing step is omitted, but the dispersion state of precipitates in the steel can be made more uniform.
20 to 850 to 1200 ° C for fine control
By adding a hot-rolled sheet annealing step for a time range of 120 seconds (fourth invention), more excellent magnetic properties can be obtained. Further, regardless of the presence or absence of the above-mentioned hot-rolled sheet annealing, after the primary cold rolling in the rolling reduction range of 20 to 40%, 800 to 1200
Even better magnetic properties are obtained by subjecting the intermediate anneal to a temperature range of 30 ° C. for a time range of 30 to 240 seconds.

[0059]

【Example】

Example 1 C: 0.040%, Si: 3.30%, Mn: 0.07%, Se: 0.015%
And Sb: a slab containing 0.020% and the balance substantially consisting of Fe and unavoidable impurities, and each slab having a composition in which Nb is added to the above-mentioned component composition in a range of 0.03% or less. After heating at a temperature of 1400 ° C. for 60 minutes, hot rolling was performed under the following conditions to obtain a hot-rolled sheet having a sheet thickness of 2.2 mm.・ Hot rolling end temperature: 700 ° C, 1000 ° C ・ Average cooling rate of hot rolled sheet from immediately after hot rolling to 5 seconds later: 10 ° C / sec, 30 ° C / sec ・ Hot rolling sheet winding temperature: 500 ℃, 700 ℃

Each hot-rolled sheet thus obtained was pickled, cold-rolled at a rolling reduction of 85% to give a cold-rolled sheet having a final thickness of 0.35 mm, and then decarburized and annealed at a temperature of 840 ° C. And then Mg
After applying an annealing separator containing O 2 as a main component, each was subjected to final finish annealing according to the heat pattern shown in FIG. Tensile coatings were baked on each steel sheet obtained by the above steps to produce product sheets, and the magnetic properties of each product sheet were investigated. Table 1 summarizes the results of the investigation of the magnetic properties of each product plate.

[0061]

[Table 1]

As is clear from Table 1, the Nb content was 0.00
2 to 0.10%, hot rolling end temperature in the range of 850 to 1050 ° C, average cooling rate from immediately after hot rolling to 5 seconds later in the range of 20 to 55 ° C / sec, and winding of hot rolled sheet Temperature 45
All of the applicable examples of the present invention in the range of 0 to 650 ° C. show good magnetic properties despite omitting the hot-rolled sheet annealing and shortening the finish annealing.

Example 2 C: 0.035%, Si: 3.20%, Mn: 0.07%, Sb: 0.020%
Each slab containing various amounts of Nb, S, and Se, and the balance substantially consisting of Fe and unavoidable impurities.
After heating at a temperature of 1150 ° C. for 60 minutes, hot rolling was performed to obtain a hot-rolled sheet having a sheet thickness of 2.2 mm.

At this time, the hot-rolled sheet end temperature: 1000 ° C., the average cooling rate of the hot-rolled sheet (from immediately after the end of rolling to after 5 seconds):
50 ° C./sec, hot-rolled sheet winding temperature: 550 ° C. These hot rolled sheets are subjected to hot rolled sheet annealing at 1000 ° C for 1 minute, and after pickling,
After cold rolling at a rolling reduction of 85% to obtain a cold-rolled sheet having a final thickness of 0.35 mm, decarburizing annealing was performed at a temperature of 870 ° C. Thereafter, an annealing separating agent containing MgO as a main component was applied, and then a final finish annealing was performed according to the heat pattern shown in FIG. 1 described above.
Table 2 summarizes the results of the investigation of the magnetic properties of each product plate obtained in this manner.

[0065]

[Table 2]

As is clear from Table 2, even when the slab heating temperature was set to 1150 ° C. lower than the conventional one, good magnetic characteristics were obtained by applying the present invention. By setting the amount to 0.010% or less (third invention), the magnetic properties are further improved.

Example 3 C: 0.07%, Si: 3.30%, Mn: 0.07%, sol. Al: 0.025
%, N: 0.008%, Se: 0.020%, and Sb: 0.025%, with the balance being a slab substantially composed of Fe and unavoidable impurities, and Nb in the above composition within a range of 0.20% or less. Is heated at a temperature of 1400 ° C. for 60 minutes, and then hot-rolling termination temperature:
Hot rolling under the conditions of 1000 ° C, average cooling rate of hot rolled sheet (from immediately after rolling to 5 seconds later): 40 ° C / sec, and hot rolling sheet winding temperature: 600 ° C. A 2.2 mm hot rolled sheet was used.

These hot-rolled sheets were divided into two parts at the center, and one of them was subjected to hot-rolled sheet annealing at a temperature of 1000 ° C. for 1 minute, and then the other was pickled in the same state, and the reduction rate was reduced. : 30
% Primary cold rolling, and then an intermediate annealing at a temperature of 1100 ° C. for 1 minute. Thereafter, it is subjected to pickling and second cold rolling to form a cold-rolled sheet having a final sheet thickness of 0.23 mm. After decarburizing annealing at a temperature of 870 ° C., an annealing separator containing MgO as a main component is applied. 1 was subjected to final finish annealing according to the heat pattern shown in FIG. Table 3 summarizes the results of the investigation of the magnetic properties of each product sheet obtained in this manner.

[0069]

[Table 3]

As is evident from Table 3, the Nb content was 0.002 to 0.2.
All of the conforming examples of the present invention contained in the range of 10% show good magnetic properties, and show that the addition of hot-rolled sheet annealing further reduces iron loss.

[0071]

According to the first to fourth aspects of the present invention, in producing a grain-oriented electrical steel sheet, Nb is contained in a limited material component composition, a rolling end temperature in hot rolling, and a rolling end temperature. The present invention specifies the cooling rate after completion of the process, the hot rolled sheet winding temperature, and the like. According to the first or second aspect of the present invention, the hot rolled sheet annealing can be omitted or the finish annealing can be shortened. Thus, a grain-oriented electrical steel sheet having excellent economic properties and excellent magnetic properties, such as good magnetic properties, can be manufactured.

Further, according to the third aspect of the invention, by limiting the S + Se content, good magnetic properties can be obtained even when the slab heating temperature is lowered, and the cost can be greatly reduced. In addition, the invention according to claim 4 makes it possible to manufacture a grain-oriented electrical steel sheet having more excellent magnetic properties by adding hot-rolled sheet annealing with a specified temperature and time.

[Brief description of the drawings]

FIG. 1 is a graph showing a heat pattern of final finishing annealing for one hour.

FIG. 2 is a graph showing the relationship between the Nb content and iron loss W _17/50 , magnetic flux density B ₈ and average secondary particle size.

3 is a graph of the relationship between hot rolling finishing temperature and the magnetic flux density B _8.

4 is a graph of the relationship between the average cooling rate and coiling temperature and the iron loss W _{1 7/50} from immediately after completion of hot rolling until after 5 seconds.

FIG. 5 is a graph showing the relationship between Nb content and iron loss W _17/50 .

Claims (4)

[Claims] C: 0.005 to 0.080 wt%, Si: 2.0 to 5.
Using a silicon steel slab containing 0 wt% and Mn: 0.03 to 0.20 wt% as a raw material, the slab is heated to a temperature of 1100 ° C. or higher, then hot-rolled, and subjected to one or intermediate annealing 2
In a method for producing a grain-oriented electrical steel sheet which is subjected to decarburizing annealing and final finishing annealing after cold rolling at least once, Nb: 0.002 to 0.10 wt% is contained in the slab, hot rolling end temperature In the range of 850 to 1050 ° C., and the average cooling rate of the hot-rolled sheet from immediately after the completion of hot rolling to after 5 seconds is 20
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the temperature is in the range of ~ 55 ° C / sec and the winding temperature of the hot-rolled sheet is in the range of 450-650 ° C. 2. C: 0.005 to 0.080 wt%, Si: 2.0 to 5.
Using a silicon steel slab containing 0 wt%, Mn: 0.03 to 0.20 wt%, sol. Al: 0.050 wt% or less and N: 0.020 wt% or less, heating the slab to a temperature of 1100 ° C or more. A hot rolling, a cold rolling of one time or two or more times of intermediate annealing, followed by a decarburizing annealing and a final finishing annealing, wherein the slab has Nb: 0.002 The hot-rolling end temperature is in the range of 850 to 1050 ° C., and the average cooling rate of the hot-rolled sheet immediately after the end of the hot rolling to 5 seconds later is 20%.
A method for producing a grain-oriented electrical steel sheet having excellent magnetic properties, characterized in that the temperature is in the range of ~ 55 ° C / sec and the winding temperature of the hot-rolled sheet is in the range of 450-650 ° C. 3. The value of S + Se contained in the slab is 0.010
wt% or less, and the heating temperature of the slab is 1100 ° C
The method for producing a grain-oriented electrical steel sheet having excellent magnetic properties according to claim 1 or 2, wherein the temperature is in the range of 1 to 1250 ° C. 4. After hot rolling, in a temperature range of 850 to 1200 ° C.
4. The method for producing a grain-oriented electrical steel sheet having excellent magnetic properties according to claim 1, wherein the hot-rolled sheet is annealed for 20 to 120 seconds.