JP2948454B2 - Method for stable production of unidirectional electrical steel sheets with excellent magnetic properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent magnetic properties and used as an iron core of a transformer or the like.

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet is mainly used as an iron core material for transformers and other electric equipment, and is required to have excellent magnetic properties such as excitation properties and iron loss properties. Numerical values representing the excitation characteristics include a normal magnetic field strength of 8
A magnetic flux density B _{8 at} 00 A / m is used. Further, as a numerical value representing the iron loss characteristic, an iron loss W _17/50 per kg when magnetized at a frequency of 50 Hz to 1.7 Tesla (T).
You are using The magnetic flux density is the largest controlling factor of the iron loss characteristics. Generally, the higher the magnetic flux density, the better the iron loss characteristics. In general, when the magnetic flux density is increased, the secondary recrystallized grains become large, and the iron loss characteristics may become poor. In contrast, by controlling the magnetic domain, the iron loss characteristics can be improved regardless of the particle size of the secondary recrystallized grains.

[0003] This unidirectional electrical steel sheet undergoes secondary recrystallization in the final finish annealing step to develop a so-called Goss structure having {110} on the steel sheet surface and a <001> axis in the rolling direction. Being manufactured. In order to obtain good magnetic properties, it is necessary that <001>, which is the axis of easy magnetization, be highly aligned in the rolling direction.

[0004] As a typical production technique of such a high magnetic flux density unidirectional magnetic steel sheet, Japanese Patent Publication No. 40-15644 is disclosed.
And JP-B-51-13469. In the former, MnS and AlN are used as main inhibitors, and in the latter, MnS, MnSe, Sb and the like are used. Therefore, it is indispensable in the current technology to appropriately control the size, morphology, and dispersion state of the precipitates functioning as these inhibitors. With regard to MnS, in the current process, MnS is used during slab heating before hot rolling.
Is once dissolved completely and then precipitated during hot rolling. A temperature of about 1400 ° C. is required to completely dissolve the required amount of MnS for secondary recrystallization.

[0005] This is 2 times lower than the slab heating temperature of ordinary steel.
Since the temperature is higher than 00 ° C., this high-temperature slab heat treatment has the following disadvantages. 1) A high-temperature slab heating furnace dedicated to directional magnetic steel is required. 2) The unit energy consumption of the heating furnace is high. 3) The amount of the molten scale increases, and the adverse effect on the operation is large as seen in so-called scraping.

In order to avoid such a problem, the heating temperature of the slab may be reduced to the level of ordinary steel.
This means at the same time that the amount of MnS effective as an inhibitor is reduced or not used at all, which necessarily leads to instability of secondary recrystallization. Therefore, in order to realize low-temperature slab heating, it is necessary to reinforce the inhibitor with a precipitate other than MnS in some form, and to sufficiently suppress normal grain growth during finish annealing.

As such inhibitors, nitrides, oxides, grain boundary precipitation elements and the like can be considered in addition to sulfides.
Known techniques include, for example, the following.
In Japanese Patent Publication No. 54-24687, As, Bi, Sn,
A method is disclosed in which a slab heating temperature is controlled to be in a range of 1050 to 1350 ° C. by containing a grain boundary segregation element such as Sb in steel. Japanese Patent Application Laid-Open No. 52-24116 discloses a method in which Zr, Ti, A method is disclosed in which a slab heating temperature is set in a range of 1100 to 1260 ° C. by containing a nitride-forming element such as B, Nb, Ta, V, Cr, and Mo. In Japanese Patent Application Laid-Open No. 57-158322, low-temperature slab heating is performed by lowering the Mn content and the Mn / S ratio to 2.5 or less, and further, the secondary recrystallization is stabilized by adding Cu. To disclose the technology.

[0008] Techniques have also been disclosed in which improvements are made from the metallographic side in combination with the reinforcement of these inhibitors. That is, in JP-A-57-89433, S,
By adding elements such as Se, Sb, Bi, Pb, Sn, and B, and combining the columnar crystal ratio of the slab and the secondary cold rolling reduction, a low-temperature slab heating of 1100 to 1250 ° C. is realized. Further, in JP-A-59-190324, an inhibitor is constituted mainly of Al, B and nitrogen in addition to S or Se, and this is subjected to pulse annealing at the time of primary recrystallization annealing after cold rolling to perform secondary recrystallization. The technology to stabilize is disclosed.

As described above, great efforts have been made so far to realize the low-temperature slab heating in the production of grain-oriented electrical steel sheets. Further, JP-A-59-5652
No. 2 discloses a technology that enables low-temperature slab heating by reducing Mn to 0.08 to 0.45% and S to 0.007% or less. By this method, the problem of occurrence of defective linear secondary recrystallization of a product due to coarsening of slab crystal grains during heating of a high-temperature slab was solved.

[0010]

The method using the low-temperature slab heating originally aims at reducing the manufacturing cost, but it cannot be industrialized unless it is a technique to obtain good magnetic properties stably as a matter of course. The present inventors, for industrialization of low-temperature slab heating, control of the average grain size of primary recrystallization before final finish annealing, and nitriding treatment of steel sheet after hot rolling and before the start of secondary recrystallization of final finish annealing. Has been built as a pillar. The nitride formed by this nitriding treatment is mainly AlN at the start of the secondary recrystallization. Al as an inhibitor that does not change easily at high temperatures
N is selected, and in that sense, it is an essential condition that Al is contained in the slab.

On the other hand, the fact that the slab contains N more than necessary has room for reconsideration in view of the present technical system.
In other words, if there is essential Al and a certain amount of N in the slab, in the process from slab heating to decarburizing annealing, Al
N is formed and affects the grain growth of primary recrystallized grains during decarburizing annealing. The purpose of the present invention is to examine a control method of AlN precipitation in the above process, and to perform low-temperature slab heating,
It is another object of the present invention to provide a method for producing a grain-oriented electrical steel sheet having excellent characteristics with no magnetic fluctuation even when the hot-rolled sheet annealing is omitted.

[0012]

The gist of the present invention is as follows. (1) By weight ratio, C: 0.075% or less, Si: 2.2
~ 4.5%, acid soluble Al: 0.010-0.060%,
N: 0.0130% or less, S + 0.405Se: 0.0
A slab containing 14% or less, Mn: 0.05 to 0.8%, and the balance being Fe and inevitable impurities is 1280 ° C.
Heating at a temperature less than or equal to, hot-rolling, and subsequently performing cold rolling under final high-pressure reduction of 80% or more without performing hot-rolled sheet annealing, and then performing decarburizing annealing and final finishing annealing to achieve unidirectionality In the method for producing an electromagnetic steel sheet, when the amount (weight ratio) of N as AlN in a hot-rolled sheet is defined as N as AlN, N-Na
sAlN ≦ 0.0030% and (N as AlN) / N
≧ 0.55, after completion decarburization annealing, an average particle size of the primary recrystallized grains to a final finish annealing started and 18～35Myuemu, de
A unidirectional electrical steel sheet having excellent magnetic properties, characterized in that the steel sheet is subjected to a nitriding treatment for absorbing 0.0010% by weight or more of nitrogen after the charcoal annealing and before the second recrystallization of the final finish annealing is started. Stable production method. (2) In the preceding paragraph, Sn:
A stable production method for a grain-oriented electrical steel sheet having excellent magnetic properties, characterized by containing 0.01 to 0.15%.

[0013]

The grain-oriented electrical steel sheet to which the present invention is directed is:
The molten steel obtained by the conventional steelmaking method is cast by the continuous casting method or the ingot-making method, and if necessary, the slab is sandwiched by the sizing process, and subsequently hot-rolled to form a hot-rolled sheet. It is manufactured by performing final cold rolling in which the rolling reduction becomes 80% or more without annealing the rolled sheet, and then sequentially performing decarburizing annealing and final finishing annealing.

The present inventors have studied in detail the causes of magnetic fluctuations and the solutions to the problem when a low-temperature slab heating material is manufactured by a single cold rolling method omitting hot-rolled sheet annealing. As a result, it has been found that the magnetic fluctuation can be drastically reduced by controlling the amount of AlN precipitation on the hot-rolled sheet.

First, the effects of the present invention will be described based on experimental results. FIG. 1 shows the relationship between the amount of AlN deposited on the hot-rolled sheet and the fluctuation of the magnetic flux density of the product. In this case, C: 0.
025-0.051%, Si: 2.6-3.1%, acid-soluble Al: 0.021-0.041%, N: 0.001
8-0.0095%, S: 0.005-0.007%,
A 250 mm thick slab containing Mn: 0.09 to 0.17%, the balance being Fe and unavoidable impurities was prepared.
Then, after holding at a temperature of 1000 to 1250 ° C. for about 90 minutes, rough hot rolling is performed in 7 passes to obtain a thickness of 40 mm, and then 6
Finish hot rolling was performed by a pass to obtain a 2.3 mm thick hot rolled sheet.

The hot-rolled sheet is subjected to strong rolling at a rolling reduction of about 85% without subjecting the hot-rolled sheet to annealing to obtain a final sheet thickness of 0.3.
35 mm cold rolled sheet, 810 ° C, 820 ° C, 83
Four conditions of decarburizing annealing at 150 ° C. and 150 ° C. for 150 seconds, and then annealing at 750 ° C. for 30 seconds, mixing NH ₃ gas into the annealing atmosphere to absorb nitrogen into the steel sheet I was sorry.

The amount of N after the nitriding treatment is 0.0198 to
0.0253% by weight, and the average particle size of primary recrystallized grains (average value of equivalent circle diameters) was 19 to 28 µm.
An annealing separator containing MgO as a main component was applied to the steel sheet after the nitriding treatment, and final finish annealing was performed. Thereafter, the magnetic flux density of the product was measured, and the difference ΔB ₈ between the highest value and the lowest value of B ₈ under the four conditions of decarburization annealing obtained for the hot-rolled sheet having the same components and the same hot-rolling conditions was determined. . In addition, in the hot-rolled sheet in this experiment, the amount of N present as AlN (weight ratio)
(N as AlN) is determined by chemical analysis, and N-N as Al
The amount of N, (N as AlN) / N was calculated for each sample.

As is apparent from FIG. 1, in the hot-rolled sheet, NN as AlN ≦ 0.0030% and (N as A
When 1N) /N≧0.55, ΔB ₈ becomes 0.02 T or less, and stable magnetic characteristics are obtained. The mechanism of the effect of controlling the amount of AlN precipitation in the hot-rolled sheet shown in FIG. 1 is not necessarily clear, but the present inventors presume as follows.

The present invention has been disclosed by the present inventors in Japanese Patent Laid-Open No. 2-182.
It belongs to a technical system disclosed in Japanese Patent Publication No. 866 which is based on making the crystal structure after decarburization annealing appropriate. on the other hand,
N dissolved in the slab at the time of completion of slab heating is fine nitride (mainly AlN) during hot rolling or during decarburizing annealing (especially during heating).
It is thought that it becomes. It is considered that the size and the amount of precipitation of this fine nitride fluctuate even with a slight temperature change during decarburization annealing.

However, the grain growth suppressing effect (Zener factor) of the precipitate is inversely proportional to the size of the precipitate.
It is proportional to its volume fraction. Therefore, even if the amount of solute N at the time of completion of slab heating is excessively reduced, the effect of suppressing grain growth of precipitates becomes too small, and as a result, the grain growth during decarburization annealing becomes too remarkable, and the control of the crystal structure Becomes difficult.

As described above, it is important to control the precipitation of AlN in the above process, but it is not easy to control the process conditions such as the components and hot rolling, and the annealing of the hot rolled sheet is omitted as in the present invention. In such a case, a new norm for controlling AlN precipitation is required. In this regard, we have performed extensive experiments,
As a result of the analysis, the knowledge shown in FIG. 1 was obtained.

That is, by controlling the amount of N as AlN and the ratio to the amount of N in the hot-rolled sheet, good magnetic properties can be stably obtained even if the hot-rolled sheet annealing is omitted in low-temperature slab heating. This result indicates that there is a precipitation state of AlN that facilitates the control of the crystal structure during the decarburizing annealing, and is considered to suggest that it can be checked in the state of the hot-rolled sheet.

Next, the reasons for limiting the constituent elements of the present invention will be described. First, the reasons for limiting the components of the slab and the slab heating temperature will be described in detail. If C is excessively large, the decarburizing annealing time becomes long and it is not economical. A particularly preferable range in terms of magnetic properties is 0.020 to 0.070%. If the content of Si exceeds 4.5%, cracking at the time of cold rolling becomes remarkable, so the content is set to 4.5% or less. If it is less than 2.2%, the specific resistance of the material is too low, and a low iron loss required as a transformer core material cannot be obtained.

Al is AlN necessary for stabilizing secondary recrystallization.
Alternatively, to secure (Al, Si) N, acid-soluble A
l must be 0.010% or more. Acid soluble Al
Exceeds 0.060%, the AlN of the hot-rolled sheet becomes inappropriate and secondary recrystallization becomes unstable. When N exceeds 0.0130%, blisters on the surface of the steel plate called blisters are generated.
30% or less.

Even if MnS and MnSe are present in the steel, it is possible to improve the magnetic properties by properly selecting the conditions of the manufacturing process. However, when S or Se is high, a secondary recrystallization defective portion called linear fine grain tends to occur. To prevent the occurrence of the secondary recrystallization defective portion, (S + 0.405Se) ≦ 0.014 Should be%. If S or Se exceeds the upper limit, the probability of occurrence of a secondary recrystallization defective portion increases, no matter how the manufacturing conditions are changed, which is not preferable. In addition, the time required for purification in the final finish annealing is too long, which is not preferable. From such a viewpoint, it is meaningless to increase S or Se unnecessarily.

The lower limit of Mn is 0.05%. 0.0
If it is less than 5%, the shape (flatness) of the hot rolled sheet obtained by hot rolling, that is, the side edge portion of the strip becomes corrugated, which causes a problem of lowering the product yield. On the other hand, if the Mn content exceeds 0.8%, the magnetic flux density of the product is lowered, which is not preferable. Therefore, the upper limit of the Mn content is set to 0.8%.

Sn is known as a grain boundary segregation element and is an element that suppresses grain growth. On the other hand, it is considered that Sn is completely dissolved in the slab when heated, and is uniformly dissolved in the slab during heating having a temperature difference of several tens degrees Celsius which is normally considered. Therefore, it is considered that Sn which is uniformly distributed in the slab at the time of heating despite the temperature difference also acts uniformly in terms of the grain growth suppressing effect at the time of decarburizing annealing. For this reason, it is considered that Sn has the effect of diluting the spatial nonuniformity of the grain growth during the decarburizing annealing caused by the spatial nonuniformity of the AlN. Therefore, the addition of Sn is effective in further reducing the variation in the magnetic properties of the product. The proper range of Sn is 0.01 to 0.1.
5%. Below this lower limit, the effect of suppressing grain growth is undesirably too small. On the other hand, if the upper limit is exceeded, nitriding of the steel sheet becomes difficult, which causes secondary recrystallization failure, which is not preferable.

In addition, trace amounts of Sb, Cu, Cr, Ni, B, Ti, Nb, etc., which are known as inhibitor constituent elements, may be contained. In particular, B, Ti,
The nitride constituent elements such as Nb are dissolved N in the steel during slab heating.
It may be added positively to reduce the amount. In the case where there is an element having a higher affinity for N than Al, when N-N as AlN, (N as A
In calculating the value of (1N) / N, subtracting the N amount of the nitride formed for the contained B, Ti, and Nb from the total N amount is effective in improving the accuracy of the effect in the present invention. preferable. The slab heating temperature was limited to less than 1280 ° C. for the purpose of reducing costs to the same level as ordinary steel. Preferably it is 1200 ° C or lower.

The heated slab is subsequently hot-rolled into a hot-rolled sheet. The hot rolling process generally comprises a rough hot rolling and a finishing hot rolling, which are performed in a plurality of passes after heating a slab having a thickness of 100 to 400 mm. Although there is no particular limitation on the method of rough hot rolling, in order to promote AlN precipitation,
It is preferable to take measures such as actively cooling the water. The time from rough hot rolling to finish hot rolling is not particularly limited, but it is preferable to start finishing hot rolling over 1 second or more in terms of accelerating the precipitation of AlN.

The subsequent finishing hot rolling is usually performed by high-speed continuous rolling of 4 to 10 passes. Normally, the reduction distribution of the finish hot rolling is such that the former has a higher reduction ratio and the lower the reduction ratio is, the better the shape is. Rolling speed is usually 100-300
0m / min and the time between passes is 0.01-10
0 seconds.

Although the present invention does not limit the conditions of the hot-rolling process, the starting temperature and the ending temperature of the hot-rolling process are adjusted in order to realize an appropriate range of AlN precipitation on the hot-rolled sheet described later. Or to adjust the rolling distribution should be aggressive. Temperature range where AlN is likely to precipitate (800-95)
At or near 0 ° C.), aggressively increasing the rolling reduction to cause work-induced precipitation is also an effective means for controlling the amount of AlN precipitation.

After the final pass of hot rolling, the steel sheet is usually 0.1 to 1
After air cooling for about 00 seconds, it is water cooled, wound up at a temperature of 300 to 700 ° C., and gradually cooled. The cooling process is not particularly limited, but a method of performing air cooling or the like for at least one second after hot rolling and maintaining the steel sheet in the AlN precipitation temperature range for as long as possible is used for controlling the amount of AlN precipitation. Is preferred.

The amount of N as AlN in the steel sheet after the hot rolling is as follows: N−N as AlN ≦ 0.0030% and (N as
AlN) /N≧0.55. This is because, as shown in FIG. 1, by controlling the precipitation of AlN in this range, good magnetic characteristics can be stably obtained.

This hot rolled sheet is then subjected to final cold rolling at a rolling reduction of 80% or more without performing hot rolled sheet annealing. The reason why the rolling reduction of the final cold rolling is set to 80% or more is that the sharpening {110} <0 in the decarburized plate is achieved by setting the rolling reduction within the above range.
This is because an appropriate amount of <01> orientation grains and corresponding orientation grains (e.g., {111} <112> orientation grains) easily susceptible to silkworm can be obtained, which is preferable in increasing the magnetic flux density. The steel sheet after such cold rolling is subjected to decarburizing annealing, application of an annealing separating agent, and final finish annealing by a usual method, and becomes a final product. Here, it is necessary to control the average grain size of the primary recrystallized grains from 18 to 35 μm after the completion of the decarburization annealing until the start of the final finish annealing. The reason is that a good magnetic flux density is easily obtained in the range of the average particle diameter, and the change of the magnetic flux density with respect to the fluctuation of the particle diameter is small.

The reason that the steel sheet is subjected to the nitriding treatment after the decarburizing annealing and before the start of the secondary recrystallization of the final finish annealing is that the process premised on the low-temperature slab heating as in the present invention is performed by This is because the inhibitor strength required for recrystallization tends to be insufficient. The method of nitriding is not particularly limited, but may be a method of nitriding by mixing NH ₃ gas in the annealing atmosphere after decarburizing annealing, a method using plasma, adding a nitride to the annealing separator, and increasing the final finish annealing. Any method may be used, such as a method of absorbing nitrogen formed by separating nitrides in a temperature into a steel sheet, or a method of nitriding a steel sheet by increasing the N ₂ partial pressure in an atmosphere of final finish annealing. The amount of nitriding is required to be 10 ppm or more in order to stably develop secondary recrystallization.

[0036]

【Example】

Example 1 By weight%, Si: 3.01%, C: 0.028%, acid-soluble Al: 0.034%, N: 0.0065%, Mn:
A 250 mm thick slab containing 0.12% and S: 0.007% is held for 1 hour under each of (1) 1250 ° C. and (2) 1100 ° C., and then rough-heated to 40 mm thick in 7 passes. Then, finish hot rolling was performed in 6 passes to obtain a 2.3 mm thick hot rolled sheet. At this time, during (A) rough hot rolling, forced water cooling is performed, and the finish hot rolling start temperature is set to 90-
The hot rolling method of lowering by 100 ° C., (B) by water cooling lighter than A, the finishing hot rolling starting temperature is 30
Two types of hot rolling were performed as a hot rolling method in which the temperature was lowered by ~ 50 ° C.

The hot rolled sheet was pickled and cold rolled at a rolling reduction of about 85% to obtain a 0.335 mm thick cold rolled sheet. After a while
Four types of decarburizing annealing (25% N ₂ +) maintained at 810 ° C., 820 ° C., 830 ° C., and 840 ° C. for 150 seconds.
75% H ₂ , dew point 62 ° C) and then 750 ° C
For 30 seconds, and NH ₃ gas was mixed into the annealing atmosphere to allow the steel sheet to absorb nitrogen. The N content of the steel sheet after nitriding was 0.0185 to 0.0245%, and the average grain size of the primary recrystallized grains of the steel sheet was 20 to 28 μm.
Next, an annealing separator containing MgO as a main component was applied to the steel sheet, and final finish annealing was performed by a known method. N of hot rolled sheet
As AlN is analyzed, and N-N as AlN and (N as
(AlN) / N was calculated. Table 1 shows the experimental conditions and the results of the magnetic characteristics.

[0038]

[Table 1]

EXAMPLE 2 Si: 3.15%, C: 0.035%, acid-soluble Al: 0.032%, N: 0.0060%, Mn:
A 250 mm thick slab containing 0.13% and S: 0.007% was kept at 1150 ° C. for 1 hour, and then 4 passes in 7 passes.
The sheet was roughly hot-rolled to a thickness of 0 mm and then hot-rolled in 6 passes to give a 2.3 mm-thick hot-rolled sheet. At this time, (A) a hot rolling method in which forced water cooling is performed after the rough hot rolling to lower the finish hot rolling start temperature by 70 to 80 ° C. from the slab heating temperature, (B) A
(C) Air-cooling is performed for 30 seconds after rough hot rolling, and the finishing hot rolling start temperature is set to the slab heating temperature. Thus, three types of hot rolling were performed by a hot rolling method in which the temperature was lowered by 65 to 75 ° C.

The hot rolled sheet was pickled and cold rolled at a rolling reduction of about 88% to obtain a cold rolled sheet having a thickness of 0.285 mm. After a while
Four types of decarburizing annealing (25% N ₂ +) maintained at 810 ° C., 820 ° C., 830 ° C., and 840 ° C. for 150 seconds.
75% H ₂ , dew point 62 ° C) and then 750 ° C
For 30 seconds, and NH ₃ gas was mixed into the annealing atmosphere to allow the steel sheet to absorb nitrogen. The N content of the steel sheet after nitriding was 0.0190 to 0.0231%, and the average particle size of the primary recrystallized grains of the steel sheet was 21 to 27 μm.
Next, an annealing separator containing MgO as a main component was applied to the steel sheet, and final finish annealing was performed by a known method. N of hot rolled sheet
As AlN is analyzed, and N-N as AlN and (N as
(AlN) / N was calculated. Table 2 shows the experimental conditions and the results of the magnetic properties.

[0041]

[Table 2]

Example 3 By weight%, 2.85% of Si, 0.031% of C, 0.035% of acid-soluble Al, 0.0058% of N, Mn:
0.11%, S: 0.006%,
(1) Sn <0.005%, (2) Sn: 0.06%,
(3) After holding three types of slabs of 250 mm thickness containing Sn: 0.11% at 1050 ° C. for 1 hour, rough hot rolling to 30 mm thickness by 7 passes, and then finish hot rolling by 6 passes. And a hot rolled sheet having a thickness of 2.8 mm was obtained. At this time, (A) a hot rolling method in which forced water cooling is performed between each pass of the rough hot rolling to lower the finishing hot rolling starting temperature by 80 to 90 ° C. from the slab heating temperature, and (B) water cooling of A is not performed. Then, two types of hot rolling were performed: a hot rolling method in which the finishing hot rolling start temperature was lowered by 30 to 50 ° C. from the slab heating temperature.

The hot rolled sheet was pickled and cold rolled at a rolling reduction of about 84% to obtain a 0.46 mm thick cold rolled sheet. After a while, 8
Four types of decarburization annealing (25% N ₂ +7) maintained at each of 10 ° C., 820 ° C., 830 ° C., and 840 ° C. for 250 seconds.
5% H _2, dew point 62 ° C.) alms, thereafter, subjected to annealing for holding 30 seconds at 750 ° C., was allowed to absorb nitrogen steel is mixed NH ₃ gas into the annealing atmosphere. The N content of the steel sheet after nitriding was 0.0220 to 0.0242%, and the average grain size of the primary recrystallized grains of the steel sheet was 21 to 28 μm. Next, an annealing separator containing MgO as a main component was applied to the steel sheet, and final finish annealing was performed by a known method. N a of hot rolled sheet
s AlN was analyzed and N-N as AlN and (N as A
1N) / N was calculated. Table 3 shows the experimental conditions and the results of the magnetic characteristics.

[0044]

[Table 3]

[0045]

In the present invention, by controlling the amount of precipitation of AlN in the hot-rolled sheet, by controlling the average particle size of the primary recrystallization grains, de
After the charcoal annealing , the steel sheet is subjected to nitriding treatment before the start of the secondary recrystallization of the final finish annealing, and furthermore, by adding Sn, it is still good even if the low-temperature slab heating and the hot-rolled sheet annealing are omitted. Since such magnetic characteristics can be stably obtained, the industrial effect is great.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of AlN deposited on a hot-rolled sheet and the variation in magnetic flux density of a product.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Koji Yamazaki, 1-1, Tobata-cho, Tobata-ku, Kitakyushu-shi Nippon Steel Corporation Yawata Works (56) References JP-A-59-190324 (JP, A) JP-A-59-56522 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21D 8/12 C22C 38/00 303 C22C 38/06 H01F 1/16

Claims (2)

(57) [Claims] 1. C: 0.075% or less by weight, Si: 2.2 to 4.5%, acid-soluble Al: 0.010 to 0.060%, N: 0.0130% or less, S + 0. 405Se: 0.014% or less, Mn: 0.05 to 0.8%, balance of slab consisting of Fe and unavoidable impurities is 128
Heating is performed at a temperature of less than 0 ° C., hot rolling is performed, followed by final high-pressure cold rolling at a rolling reduction of 80% or more without performing hot-rolled sheet annealing, followed by decarburizing annealing and final finishing annealing. In the method for manufacturing a grain-oriented electrical steel sheet, the method for producing Al
When the amount of N as N (weight ratio) is N as AlN, N−N as AlN ≦ 0.0030%, and (N as AlN) /N≧0.55. The average particle size of the primary recrystallized grains until the start of annealing is 18 to 35 μm, and after decarburizing annealing ,
0.010% of the steel sheet before the start of the secondary recrystallization in the final finish annealing
A stable production method for a grain-oriented electrical steel sheet having excellent magnetic properties, characterized by performing a nitriding treatment for absorbing 010% by weight or more of nitrogen. 2. The slab component further contains Sn: 0.0
2. The method for stably producing a grain-oriented electrical steel sheet having excellent magnetic properties according to claim 1, wherein the content is 1 to 0.15%.