JP3065853B2 - 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 80
A magnetic flux density B _{8 at} 0 A / m is used. As a numerical value representing the iron loss characteristic, the iron loss W _17/50 per kg when magnetized at a frequency of 50 Hz to 1.7 Tesla (T) is used. 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 grain-oriented electrical steel sheet is manufactured by causing 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. Have been. 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. This is more than 200 ℃ higher than the slab heating temperature of ordinary steel,
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.

[0005] In order to avoid such problems, the slab heating temperature may be lowered 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.

[0006] In addition to sulfides, nitrides, oxides, and intergranular precipitation elements can be considered as such inhibitors. Known techniques include, for example, the following. In Japanese Patent Publication No. 54-24687, As, Bi, Sn, S
Japanese Patent Application Laid-Open No. 52-24116 discloses a method in which a slab heating temperature is controlled to be in the range of 1050 to 1350 ° C. by containing a grain boundary segregation element such as b in steel. 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.

[0007] 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 low-temperature slab heating in the production of grain-oriented electrical steel sheets.

In Japanese Patent Application Laid-Open No. 59-56522, Mn is 0.08 to 0.45% and S is 0.007%.
A technique that enables low-temperature slab heating by the following has been disclosed. 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.

[0009]

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,
Excessive N content in the slab has room for reconsideration from the technical system. In other words, if there is essential Al in the slab and a certain amount of N or more, AlN is formed in the steps from slab heating to decarburizing annealing, which affects the grain growth of primary recrystallized grains during decarburizing annealing. Will give.

An object of the present invention is to reduce AlN in the above process and to examine a stable inhibitor instead of the AlN, and to stably produce a grain-oriented electrical steel sheet having excellent characteristics without magnetic fluctuations due to low-temperature slab heating. Is to provide a way.

[0011]

The gist of the present invention is as follows. That is, (1) C: 0.025 to 0.075% by weight%, S
i: 2.5 to 4.5%, acid-soluble Al: 0.010
0.060%, N: less than 0.0030%, S: 0.
1 to 0.05%, Mn: 0.02 to 0.8%, and the balance is 1 slab composed of Fe and unavoidable impurities.
280 was heated at a temperature below ° C., heat rolled, the final cold rolling at least a reduction ratio of 80% applied twice or more cold rolling sandwiching the including one or intermediate annealing, then decarburization annealing, final annealing In the method of producing a grain-oriented electrical steel sheet by subjecting the slab to Ti, Zr, and N contents (% by weight), the following formula is used to control the content of 0.5 × N (%) <0.292 × Ti (%) +0.154 x Zr
(%) <0.0050 This is a stable production method of a grain-oriented electrical steel sheet having excellent magnetic properties, characterized by subjecting the steel sheet to nitriding treatment after hot rolling and before the start of final finishing annealing. (2) Weight% At C: 0.025-0.075%, S
i: 2.5 to 4.5%, acid-soluble Al: 0.010
0.060%, N: less than 0.0030%, S: 0.
1 to 0.05%, Cu: 0.01 to 0.40%, and the balance is 1 slab composed of Fe and unavoidable impurities.
280 was heated at a temperature below ° C., heat rolled, the final cold rolling at least a reduction ratio of 80% applied twice or more cold rolling sandwiching the including one or intermediate annealing, then decarburization annealing, final annealing In the method of producing a grain-oriented electrical steel sheet by subjecting the slab to Ti, Zr, and N contents (% by weight), the following formula is used to control the content of 0.5 × N (%) <0.292 × Ti (%) +0.154 x Zr
(%) <0.0050 Stable production method of unidirectional electrical steel sheet with excellent magnetic properties, characterized by subjecting steel sheet to nitriding treatment after hot rolling and before the start of final finishing annealing. (3) C in weight% : 0.025 to 0.075%, S
i: 2.5 to 4.5%, acid-soluble Al: 0.010
0.060%, N: less than 0.0030%, S: 0.
01-0.05%, Cu: 0.01-0.40%, M
n: contains 0.02 to 0.8%, the balance being heated at a temperature below slab 1280 ° C. of Fe and unavoidable impurities, hot rolled, including a final cold rolling at least a reduction ratio of 80% Once
Or subjected to two or more cold rolling sandwiching the intermediate annealing, then decarburization annealing, the method by performing final annealing for manufacturing a grain-oriented electrical steel sheet, Ti slab, Zr, the content of N (wt% ) Is controlled by the following formula, and 0.5 × N (%) <0.292 × Ti (%) + 0.154 × Zr
(%) <0.0050 Stable manufacturing method of unidirectional electrical steel sheet with excellent magnetic properties, characterized by subjecting steel sheet to nitriding treatment after hot rolling and before the start of final annealing, and (4) Slab components And Sn: 0.01 to
0.15% is contained, the method for stable production of a grain-oriented electrical steel sheet having excellent magnetic properties as described in the preceding paragraphs, and (5) hot rolling at 850 to 1250 ° C. after hot rolling. (6) An average of primary recrystallized grains from the completion of decarburizing annealing to the start of final finishing annealing. A stable production method of a grain-oriented electrical steel sheet having excellent magnetic properties as described in the preceding items, wherein the grain size is 18 to 35 μm.

[0012]

The grain-oriented electrical steel sheet to which the present invention is directed is:
Molten steel obtained by a conventional steelmaking method is cast by a continuous casting method or an ingot-making method, and if necessary, a slab is sandwiched by a sizing process, and subsequently hot-rolled into a hot-rolled sheet, and then It is produced by performing one or more times of cold rolling including intermediate annealing as necessary, including final cold rolling with a rolling reduction of 80% or more, and then sequentially performing decarburizing annealing and final finish annealing.

The present inventors have studied in detail the causes of fluctuations in magnetism in the case of manufacturing a low-temperature slab heating material and measures for solving the problems. As a result, the present inventors have obtained a new finding that this phenomenon is caused by variation in precipitation of AlN based on a temperature difference in the slab during slab heating. Then, as a solution to the problem, lowering the amount of N, the amount of Ti, the amount of Zr,
The N amount is suppressed to a predetermined range defined by the relational expression of the three amounts, the S amount and the Cu amount are added in the predetermined amounts, the Mn amount is added in the predetermined amounts, and the final finish after the decarburizing annealing is completed. It was found that it is effective to control the average grain size of the primary recrystallized grains until the start of annealing, to add Sn, and to perform hot-rolled sheet annealing in a predetermined temperature range.

Hereinafter, these points will be described in detail.
The present inventors have focused on solid solution and precipitation of AlN during slab heating. At a temperature lower than 1280 ° C., which is a premise of the present invention, complete solid solution of AlN in the α phase is not guaranteed in the component range of Al, N, and Si of the present invention. On the other hand, there are various methods of slab heating, but after charging the slab into the furnace, moving the slab from the outlet while moving it with a pusher, or placing the slab on the skid, moving the skid to move the slab from the inlet to the outlet Etc. are generally performed. And the part of the slab that contacts the skid and the bottom of the furnace,
Often the temperature is lower. Therefore, it was considered that the difference in the amount of precipitated AlN and the amount of dissolved N caused by the temperature difference in the slab. In the process from hot rolling to decarburizing annealing, N dissolved in the slab during heating was mostly Al
Precipitates finely as N, and its degree is solute N during slab heating.
It was considered to be dependent on the amount. In fact, when an experiment was conducted at a factory, the average grain size of primary recrystallized grains after decarburization annealing was measured using an optical microscope and an image analyzer. It was found that the diameter fluctuated. And the degree of the variation is Al,
It varied with the amount of N.

Therefore, the present inventors have considered reducing the amount of fluctuating AlN. For that purpose, it is effective to reduce the amount of Al or N, but it is necessary to secure the amount of AlN as an inhibitor at the time of secondary recrystallization, and N can be introduced into a steel sheet by nitriding. In consideration of the fact that it is difficult to introduce Al into a steel sheet, reduction in the amount of N was studied. Considering that reducing the amount of N in the steelmaking stage is technically restrictive or leads to an increase in cost, it is expected that the affinity with N is strongly correlated with the amount of N that forms a solid solution with Al. Y (%) calculated from the atomic equivalents of the elements = 0.292 x Ti (%) + 0.
154 x Zr (%) (Ti (%): Ti content of slab, Zr (%): Zr content of slab, all are wt%)
And the relationship between Y (%) and the variation in magnetic properties was investigated based on the following two experiments.

The first experiment and the results were as follows. That is, C = 0.045% by weight, Si = 3.
20%, acid-soluble Al = 0.018 to 0.040%, N
= 0.0006-0.0098%, S = 0.015%,
Mn = 0.16%, Ti = 0.0007 to 0.0211
%, Zr = 0.0005 to 0.0414%, and a slab having a thickness of 250 mm was prepared, the balance being Fe and unavoidable impurities. Then, each slab was soaked for 60 minutes at two temperatures of 1100 ° C. and 1200 ° C. to be 2.3 mm thick by hot rolling of 11 passes, water cooled after about 3 seconds, cooled to 550 ° C., and then cooled to 550 ° C. For one hour. Without subjecting the hot-rolled sheet to annealing, the hot-rolled sheet was rolled under high pressure of about 88% to obtain a cold-rolled sheet having a final sheet thickness of 0.285 mm. This cold-rolled sheet was subjected to decarburizing annealing at 835 ° C. for 150 seconds, and then, at the time of annealing at 750 ° C. for 30 seconds, NH ₃ gas was mixed in the annealing atmosphere to allow the steel sheet to absorb nitrogen. The N amount after this nitriding treatment was 0.0187 to 0.0214% by weight. 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 B _{8 of the} product was measured, and the difference ΔB ₈ of B ₈ between two slabs with the same component under uniform heating conditions [B ₈ (T) at a slab heating temperature of 1100 ° C.]
- determine the B ₈ (T)] in the same temperature 1200 ° C., the iron loss
The results are shown in FIG. 1 together with the average value of W _17/50 (w / kg) . As is clear from FIG. 1, N (%) <0.0030, 0.
In the range of 5 × N (%) <Y (%) <0.0050, the difference ΔB in the magnetic flux density of the product caused by the difference in the slab heating temperature
₈ (T) is less than 0.02T, and W _17/50
(Average value) Good iron loss characteristics of <1.00 w / kg were exhibited.

The second experiment and the results were as follows. That is, C = 0.041% and Si = 3.
05%, acid-soluble Al = 0.019 to 0.045%, N
= 0.0004-0.0092%, S = 0.014%,
Cu = 0.18%, Ti = 0.0008-0.0204
%, Zr = 0.004 to 0.0409%, and a slab having a thickness of 250 mm was prepared, the balance being Fe and unavoidable impurities. Then, each slab was soaked for 60 minutes at two temperatures of 1100 ° C. and 1200 ° C. to be 2.3 mm thick by hot rolling of 11 passes, water cooled after about 3 seconds, cooled to 550 ° C., and then cooled to 550 ° C. For one hour. Without subjecting the hot-rolled sheet to annealing, the hot-rolled sheet was rolled under high pressure of about 88% to obtain a cold-rolled sheet having a final sheet thickness of 0.285 mm. This cold-rolled sheet was subjected to decarburizing annealing at 835 ° C. for 150 seconds, and then, during annealing at 750 ° C. for 30 seconds, NH3 gas was mixed into the annealing atmosphere to allow the steel sheet to absorb nitrogen. The N amount after this nitriding treatment was 0.0196 to 0.0209% by weight. 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 B _{8 of the} product was measured, and the difference ΔB ₈ of B ₈ between two slabs with the same component under uniform heating conditions [B ₈ (T) at a slab heating temperature of 1100 ° C.]
- determine the B ₈ (T)] in the same temperature 1200 ° C., the iron loss
The results are shown in FIG. 2 together with the average value of W _17/50 (w / kg) . As is clear from FIG. 2, in the case of the second experiment, similarly to the first experiment, N (%) <0.0030, 0.5 × N (%) <
In the range of Y (%) <0.0050, the difference ΔB ₈ (T) in the magnetic flux density of the product caused by the difference in the slab heating temperature is 0.02T.
And W _17/50 (average value) <1.00
Excellent iron loss characteristics of w / kg were exhibited. Mn, C
Even when u and S were added in combination, the same effects as those of the first and second experiments were obtained.

The present inventors consider the mechanism of the phenomenon shown in FIGS. 1 and 2 as follows. In this experiment, the phenomenon caused by the temperature difference in the slab in the heating furnace was simulated by changing the slab heating temperature.
According to this, in the Al and N component ranges of the present invention, 128
In the case of a slab heating temperature condition of less than 0 ° C., a difference occurs in the amount of AlN dissolved and precipitated between a high temperature part and a low temperature part of the slab. That is, in the high temperature part of the slab at the time of slab heating, a large amount of solid solution N is present, and during the subsequent hot rolling and decarburizing annealing, this solid solution N is finely precipitated in the form of AlN. On the other hand, in the low temperature part of the slab at the time of slab heating, the amount of solid solution N is small, and the amount of AlN finely precipitated during the subsequent hot rolling and decarburizing annealing is small. Such spatial nonuniformity of AlN precipitation causes spatial nonuniformity in the growth of primary recrystallized grains during decarburizing annealing. That is, in the portion corresponding to the high temperature portion in the slab at the time of slab heating, fine AlN is large during decarburization annealing, so that the growth of primary recrystallized grains is suppressed. On the other hand, in a portion corresponding to a low-temperature portion in the slab at the time of slab heating, primary recrystallized grains are likely to grow because there is little fine AlN during decarburization annealing. Therefore, when decarburization annealing is completed,
In the coil, the locational unevenness of the primary recrystallized grain size occurs due to the temperature difference in the slab during slab heating. As disclosed by the present inventors in JP-A-2-182866,
The primary recrystallized grain size at the completion of the decarburization annealing has a very strong correlation with the magnetic flux density of the product. Therefore, the spatial non-uniformity of the primary recrystallized grain size causes the magnetic flux density in the product to be non-uniform. Therefore, if the variation in the amount of solute N in the slab during heating of the slab, which causes the variation in the magnetic flux density, falls within a predetermined range, the variation in the magnetic flux density of the product is considered to be reduced.

Therefore, in the present invention, TiN and ZrN are formed by adding necessary amounts of Ti and Zr,
The amount of dissolved N in the slab was reduced.
Since iN and ZrN remain in the final product and degrade iron loss characteristics, it is meaningless to add more than necessary.

Next, the reasons for limiting the constituent elements of the present invention will be described. First, the reasons for limiting the slab components and the slab heating temperature will be described in detail. C is 0.025% by weight
(Hereinafter simply abbreviated as%), the secondary recrystallization becomes unstable, and even when secondary recrystallization occurs, B ₈ > 1.80.
Since (T) is difficult to obtain, the content is set to 0.025% or more. on the other hand,
If C becomes too large, the decarburization annealing time becomes long and it is not economical, so the content was made 0.075% or less.

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. On the other hand, if it is less than 2.5%, the specific resistance of the material is too low, and a low iron loss required as a transformer core material cannot be obtained.
Desirably, it is at least 3.2%.

Al is AlN required 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.

As shown in FIG.
It is necessary to make it less than 0030%. This is effective for reducing fluctuations in magnetism caused by temperature deviation during slab heating. The lower limit of the amount of N is not particularly limited, but it is industrially difficult to reduce N to 0.0001% or less at the steel making stage.

Ti and Zr have a stronger affinity for N than Al and have the effect of forming TiN and ZrN and reducing the amount of dissolved N during slab heating. For this reason, there is an effect of reducing the non-uniformity of AlN precipitation caused by the slab temperature deviation during slab heating. However, TiN and ZrN remain in the product and deteriorate iron loss characteristics. Therefore, as shown in FIG. 1, there is an appropriate range according to the amount of N, and 0.5 × N (%) <
0.292 × Ti (%) + 0.154 × Zr (%) <
Must be 0.0050.

The range of S is defined as 0.01 to 0.05%. When the amount of N in the slab is reduced as in the present invention, an inhibitor other than AlN is used to control the growth of the primary recrystallized grains so that the average grain size falls within a predetermined range. There is a need. For this purpose, it is necessary to form a predetermined amount of Cu ₂ S or MnS. In this sense, the range of S must be between 0.01 and 0.05%.

One or both of Cu and Mn must be in the following range. Cu forms Cu ₂ S having a smaller size than MnS, and can be effectively used for controlling the growth of primary recrystallized grains. In order to form an appropriate amount of fine Cu ₂ S, Cu must be 0.01 to 0.40%. Mn forms MnS and can be used to control the growth of primary recrystallized grains. Therefore MnS
To form an appropriate amount of Mn: 0.02 to 0.8%
The addition is necessary to improve the magnetic properties.

Sn is known as a grain boundary segregation element and is an element that suppresses grain growth. On the other hand, Sn at the time of slab heating is considered to be completely solid-dissolved, and even in a slab at the time of heating having a temperature difference of several tens of degrees, which is normally considered, a solid solution is considered. Therefore, it is considered that Sn uniformly distributed in the slab at the time of heating, despite the temperature difference, has a uniform effect on the grain growth 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 N
The addition of Sn, in addition to the technique for limiting the amount of Ti, the amount of Ti, and the amount of Zr, and the control of the primary recrystallized grain size, which will be described later, are effective in further reducing the variation in the magnetic properties of the product. The appropriate range of Sn is set to 0.01 to 0.15%. 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, a small amount of Sb, Cr, Ni, B, Nb, etc., which are known as inhibitor constituent elements, may be contained. In particular, nitride constituent elements such as B and Nb may be positively added in order to reduce the positional difference in AlN caused by the temperature difference in the slab.

The slab heating temperature is limited to less than 1280 ° C. for the purpose of reducing the cost to the level of ordinary steel. Preferably it is 1200 ° C or lower. The heated slab is subsequently hot-rolled into a hot-rolled sheet. The hot rolling method is not particularly limited, but the hot rolling end temperature is set to 850 to 1050 ° C. and the cumulative rolling reduction of the last hot rolling pass is set to 40% or more. Is more preferable in reducing the variation in location and improving the magnetism.

[0030] The hot-rolled sheet is then final cold rolling over reduction of 80% applied twice or more cold rolling sandwiching the including one or intermediate annealing. The reason why the rolling reduction of the final cold rolling is set to 80% or more is that, by setting the rolling reduction within the above range, sharp {110} <001> oriented grains and corresponding oriented grains ( This is because an appropriate amount of {111} <112> orientation grains) can be obtained, which is preferable in increasing the magnetic flux density.

After the hot rolling, it is more preferable to perform hot rolling annealing at 850 to 1250 ° C. in order to stabilize the magnetic properties at a high level. Heat treatment in this temperature range is caused by Al
N, Cu ₂ S, and MnS have an effect of reducing the spatial nonuniformity of the hot-rolled sheet.

The steel sheet after the final cold rolling is subjected to decarburizing annealing, application of an annealing separating agent, and final finishing annealing in a usual manner to be a final product. Here, it is more preferable to control the average grain size of the primary recrystallized grains from 18 to 35 μm after the completion of the decarburizing annealing until the start of the final finish annealing, in addition to the control of the amounts of N, Ti, and Zr. 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 a nitriding treatment before the secondary recrystallization of the final finish annealing after hot rolling is defined as follows:
This is because in the process based on low-temperature slab heating as in the present invention, the inhibitor strength required for secondary 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 in which nitrogen generated by the decomposition of nitrides in a temperature is absorbed in a steel sheet, a method in which the N ₂ partial pressure in the atmosphere of final finish annealing is increased, and the steel sheet is nitrided. The amount of nitriding is not particularly limited, but 1 ppm or more is required.

[0034]

Embodiments will be described below. Example 1 C: 0.042% by weight, Si: 3.00% by weight, Mn: 0.18% by weight, S: 0.016% by weight,
Acid-soluble Al: 0.024% by weight as a basic component, N content at two levels of 0.0083% by weight and 0.0012% by weight, and Ti content at 0.0002% by weight and 0.004% by weight.
Four 250 mm thick slabs were added at two levels of 1% by weight. The slab was a: 1180 ° C., b:
After soaking at two temperatures of 1110 ° C. for 60 minutes, hot rolling was started immediately, the thickness was increased to 40 mm by 5 passes, and then the hot rolled sheet was 2.3 mm thick by 6 passes. Next, after the hot rolling was completed, a winding simulation was performed in which air cooling was performed for 2 seconds, water cooling was performed to 550 ° C., the temperature was maintained at 550 ° C. for 1 hour, and the furnace was cooled.

The hot-rolled sheet was pickled to obtain a cold-rolled sheet having a rolling reduction of about 88% and a thickness of 0.285 mm, and was subjected to decarburizing annealing at 835 ° C. for 150 seconds. Thereafter, annealing was performed at 750 ° C. for 30 seconds, and NH ₃ gas was mixed in the annealing atmosphere to allow the steel sheet to absorb nitrogen. The N content of this steel sheet after nitriding was 0.0190 to 0.0217% by weight. Then
This steel sheet is coated with an annealing separator containing MgO as a main component,
The temperature was raised to 1200 ° C. at a rate of 15 ° C./hour in an atmosphere gas of 25% N _{2 and} 75% H ₂ , and then a final finish annealing was performed at 1200 ° C. for 20 hours in a 100% H ₂ atmosphere gas. . Table 1 shows the experimental conditions and the results of the magnetic characteristics.

[0036]

[Table 1]

Example 2 C: 0.048% by weight, S
i: 3.24% by weight, Mn: 0.14% by weight, S: 0.
015% by weight, N: 0.0010% by weight, acid soluble A
l: 0.024% by weight as a basic component, and
003% by weight, 0.0041% by weight and Zr of 0.0
004 wt% and 0.0054 wt% were added at two levels to prepare four types of 250 mm thick slabs consisting of the balance of Fe and inevitable impurities. The slab was heated at two levels of a: 1180 ° C. and b: 1110 ° C. for 60 hours.
Immediately after the heat was soaked, hot rolling was started immediately, the thickness was increased to 40 mm in 5 passes, and then the hot rolled sheet was 2.3 mm thick in 6 passes. Next, this hot-rolled sheet was treated under the conditions of Example 1 until final finish annealing. The N content after nitriding was 0.0195 to 0.0208% by weight. Table 2 shows the experimental conditions and the magnetic properties of the product.

[0038]

[Table 2]

Example 3 C: 0.045% by weight, S
i: 3.28% by weight, Mn: 0.21% by weight, S: 0.
018% by weight, acid-soluble Al: 0.025% by weight, N:
0.0018% by weight and 0.0045% by weight of Ti were added to prepare a 250 mm thick slab composed of the balance of Fe and unavoidable impurities. The slab was a: 1150 ° C., b:
After soaking for 60 minutes at two temperatures of 1080 ° C., hot rolling was started immediately, the thickness was increased to 40 mm in five passes, and the hot-rolled sheet was 2.3 mm thick in six passes.

Next, the hot-rolled sheet was pickled to obtain a cold-rolled sheet having a rolling reduction of about 88% and a thickness of 0.285 mm.
Decarburization annealing was performed at each of 40 ° C., 860 ° C., and 870 ° C. for 150 seconds. Thereafter, annealing was performed at 750 ° C. for 30 seconds, and NH ₃ gas was mixed into the annealing atmosphere to cause nitrogen absorption in the steel sheet. The N content of this steel sheet after nitriding was 0.0198 to 0.0237% by weight. Then, the average crystal grain size of the steel sheet was measured using an optical microscope and an image analyzer. Next, an annealing separator containing MgO as a main component was applied to the steel sheet, and N ₂ 50% and H ₂ 50%
The temperature was increased to 1200 ° C. at a rate of 20 ° C./hour in an atmosphere gas of 1,200 ° C. in a 100% H ₂ atmosphere gas.
For 20 hours. Table 3 shows the experimental conditions and the magnetic properties of the product.

[0041]

[Table 3]

Example 4 C: 0.056% by weight, S
i: 3.34% by weight, Mn: 0.24% by weight, S: 0.3% by weight.
016% by weight, acid-soluble Al: 0.024% by weight, N:
0.0008% by weight, 0.0041% by weight of Zr as a basic component, and no addition of Sn (<0.01% by weight);
It is added at three levels of 0.05% by weight and 0.11% by weight.
A 0 mm thick slab was made. This slab is a: 117
0 ° C., b: After soaking for 60 minutes at two levels of temperature of 1100 ° C., immediately start hot rolling, and after making 5 passes to a thickness of 40 mm,
The hot-rolled sheet was 2.3 mm thick with 6 passes. Next, this hot-rolled sheet was treated under the conditions of Example 3 until final finish annealing. However, regarding the decarburizing annealing conditions, only 840 ° C. × 150 seconds (soaking) and 860 ° C. × 150 seconds (soaking) were performed.
The N content after nitriding was 0.0198 to 0.0226% by weight. Table 4 shows the experimental conditions and the magnetic properties of the product.

[0043]

[Table 4]

Example 5 C: 0.053% by weight, S
i: 3.44% by weight, Mn: 0.31% by weight, S: 0.
018% by weight, N: 0.0014% by weight, acid soluble A
l: 0.026% by weight as a basic component, acid-soluble Ti is added at two levels of 0.0006% by weight and 0.0037% by weight, and Sn is not added (a) (<0. (01% by weight) and (b) two levels of 0.06% by weight, and four types of slabs each having a thickness of 250 mm and comprising the balance of Fe and unavoidable impurities were prepared. This slab is a: 1
After soaking at two temperatures of 160 ° C. and b: 1090 ° C. for 60 minutes, hot rolling was started immediately, the thickness was increased to 40 mm in 5 passes, and then a 2.3 mm thick hot rolled plate was passed in 6 passes. Next, the hot-rolled sheet is kept at 1100 ° C. for 30 seconds and then kept at 900 ° C. for 30 seconds.
After holding for 2 seconds, the hot rolled sheet was quenched and then annealed.

Thereafter, at a rolling reduction of about 90%, 0.220 mm
The steel sheet was then cold-rolled, and then subjected to decarburizing annealing at 825 ° C. × 90 seconds (soaking). Thereafter, annealing was performed at 750 ° C. for 30 seconds, and NH ₃ gas was mixed into the annealing atmosphere to cause the steel sheet to absorb nitrogen. The N content of the steel sheet after nitriding is
0.0215 to 0.0223% by weight. Then
This steel sheet is coated with an annealing separator containing MgO as a main component,
The temperature was raised to 1200 ° C. at a rate of 10 ° C./hour in an atmosphere gas of 50% N _{2 and} 50% H ₂ , and then a final finish annealing was performed in which the atmosphere was maintained at 1200 ° C. for 20 hours in a 100% H ₂ atmosphere gas. . Table 5 shows the experimental conditions and the magnetic properties of the product.

[0046]

[Table 5]

Example 6 The hot-rolled 2.3 mm thick sheet described in Example 5 was cold-rolled to 1.8 mm, and then 1100
C. for 30 seconds, followed by annealing at 900.degree. C. for 30 seconds followed by rapid cooling. Thereafter, cold rolling was performed to 0.170 mm at a rolling reduction of about 91%, and then the steps from decarburizing annealing to final finish annealing were processed under the conditions described in Example 5. The N content of the steel sheet after nitriding is 0.0190 to 0.02.
43% by weight. Table 6 shows the experimental conditions and the magnetic properties of the products.
Shown in

[0048]

[Table 6]

Example 7 C: 0.040% by weight, S
i: 3.02% by weight, Cu: 0.08% by weight, S: 0.
012% by weight, acid-soluble Al: 0.025% by weight as a basic component, and N content of 0.0080% by weight, 0.001%
Four types of 250 mm thick slabs were prepared by adding two levels of 0% by weight and adding Ti at two levels of 0.0003% by weight and 0.0043% by weight. Such a slab is a:
After soaking at two temperatures of 1180 ° C. and b: 1110 ° C. for 60 minutes, hot rolling was started immediately, the thickness was reduced to 40 mm by 5 passes, and then a 2.3 mm thick hot rolled plate was passed by 6 passes. Next, after the hot rolling is completed, air-cooling is performed for 2 seconds and then water-cooled to 550 ° C.
, And the furnace was cooled for 1 hour, and a winding simulation was performed.

The hot-rolled sheet was pickled to obtain a 0.285-mm cold-rolled sheet at a rolling reduction of about 88%, and was subjected to decarburization annealing at 830 ° C. for 150 seconds. Thereafter, annealing was performed at 750 ° C. for 30 seconds, and NH ₃ gas was mixed in the annealing atmosphere to allow the steel sheet to absorb nitrogen. The N content of the steel sheet after nitriding was 0.0184 to 0.0204% by weight. Then
This steel sheet is coated with an annealing separator containing MgO as a main component,
The temperature was raised to 1200 ° C. at a rate of 15 ° C./hour in an atmosphere gas of 50% N _{2 and} 50% H ₂ , and then a final finish annealing was performed at 1200 ° C. for 20 hours in a 100% H ₂ atmosphere gas. . Table 7 shows the experimental conditions and the results of the magnetic properties.

[0051]

[Table 7]

Example 8 C: 0.045% by weight, Si: 3.28% by weight, Cu:
0.11% by weight, S: 0.014% by weight, N: 0.00
12% by weight, acid-soluble Al: 0.026% by weight as a basic component, 0.0004% by weight of Ti, 0.0039%
Wt%, Zr 0.0005 wt%, 0.0050
By weight of each of two levels, four types of 250 mm thick slabs each consisting of the balance of Fe and unavoidable impurities were prepared. Such a slab is a: 1180 ° C., b: 1110 ° C.
After the soaking at 60 ° C. for 60 minutes, hot rolling was started immediately, the thickness was reduced to 40 mm in 5 passes, and the hot rolled sheet was 2.3 mm thick in 6 passes. Next, this hot rolled sheet is subjected to final finish annealing.
Processing was performed under the conditions of Example 7 . N content after nitriding is 0.018
9 to 0.0206% by weight. Table 8 shows the experimental conditions and the magnetic properties of the product.

[0053]

[Table 8]

Example 9 C: 0.047% by weight, S
i: 3.29% by weight, Cu: 0.11% by weight, S: 0.
015% by weight, acid-soluble Al: 0.024% by weight, N:
0.0015% by weight and 0.0041% by weight of Ti were added to prepare a 250 mm thick slab composed of the balance of Fe and unavoidable impurities. The slab was a: 1150 ° C., b:
After soaking for 60 minutes at two temperatures of 1080 ° C., hot rolling was started immediately, the thickness was increased to 40 mm in five passes, and the hot-rolled sheet was 2.3 mm thick in six passes.

Next, the hot-rolled sheet was pickled to obtain a cold-rolled sheet having a rolling reduction of about 88% and a thickness of 0.285 mm.
Decarburization annealing was performed at each of 40 ° C., 860 ° C., and 870 ° C. for 150 seconds. Thereafter, annealing was performed at 750 ° C. for 30 seconds, and NH ₃ gas was mixed into the annealing atmosphere to cause nitrogen absorption in the steel sheet. The N content of this steel sheet after nitriding was 0.0194 to 0.0240% by weight. Then, the average crystal grain size of the steel sheet was measured using an optical microscope and an image analyzer. Next, an annealing separator containing MgO as a main component was applied to the steel sheet, and N ₂ 50% and H ₂ 50%
The temperature was increased to 1200 ° C. at a rate of 15 ° C./hour in an atmosphere gas of 1,200 ° C. in a 100% H ₂ atmosphere gas.
For 20 hours. Table 9 shows the experimental conditions and the magnetic properties of the product.

[0056]

[Table 9]

Example 10 C: 0.054% by weight, Si: 3.30% by weight, Cu:
0.20% by weight, S: 0.013% by weight, acid soluble A
l: 0.025% by weight, N: 0.0009% by weight, Z
r: 0.0036% by weight as a basic component, no addition of Sn (<0.01% by weight), 0.06% by weight,
Three types of slabs each containing 0.1% by weight of 0.12% by weight were added to form a 250 mm-thick slab consisting of a balance of Fe and unavoidable impurities. Such a slab is a: 1180 ° C., b: 1110 ° C.
After the soaking at 60 ° C. for 60 minutes, hot rolling was started immediately, the thickness was reduced to 40 mm in 5 passes, and the hot rolled sheet was 2.3 mm thick in 6 passes. Then the real to the final finish annealing the hot-rolled sheet
Processing was performed under the conditions of Example 9 . However, regarding the decarburization annealing conditions, 840 ° C. × 150 seconds (soaking), 860 ° C. × 1
Only 50 seconds (soaking). The N content after nitriding is 0.01
90 to 0.0221% by weight. Table 10 shows the experimental conditions and the magnetic properties of the product.

[0058]

[Table 10]

Example 11 C: 0.052% by weight, S
i: 3.41% by weight, Cu: 0.26% by weight, S: 0.
016% by weight, N: 0.0013% by weight, acid soluble A
l: 0.026% by weight as a basic component, acid-soluble Ti is added at two levels of 0.0008% by weight and 0.0035% by weight, and Sn is not added (a) (<0. 01% by weight) and (b) two levels of 0.07% by weight, and four types of slabs each having a thickness of 250 mm and comprising the balance of Fe and unavoidable impurities were prepared. This slab is a: 1
After soaking at two temperatures of 160 ° C. and b: 1090 ° C. for 60 minutes, hot rolling was started immediately, the thickness was increased to 40 mm in 5 passes, and then a 2.3 mm thick hot rolled plate was passed in 6 passes. Next, the hot rolled sheet is kept at 1120 ° C. for 30 seconds,
After holding for 2 seconds, the hot rolled sheet was quenched and then annealed.

Thereafter, at a rolling reduction of about 90%, 0.220 mm
The steel sheet was then cold-rolled, and then subjected to decarburizing annealing at 830 ° C. × 90 seconds (soaking). Thereafter, annealing was performed at 750 ° C. for 30 seconds, and NH ₃ gas was mixed into the annealing atmosphere to cause the steel sheet to absorb nitrogen. The N content of the steel sheet after nitriding is
It was 0.0219 to 0.0228% by weight. Then
This steel sheet is coated with an annealing separator containing MgO as a main component,
The temperature was raised to 1200 ° C. at a rate of 10 ° C./hour in an atmosphere gas of 50% N _{2 and} 50% H ₂ , and then a final finish annealing was performed in which the atmosphere was maintained at 1200 ° C. for 20 hours in a 100% H ₂ atmosphere gas. . Table 11 shows the experimental conditions and the magnetic properties of the product.

[0061]

[Table 11]

Example 12 The 2.3 mm-thick hot-rolled sheet described in Example 11 was cold-rolled to 1.8 mm, then kept at 1130 ° C. for 30 seconds, and then kept at 900 ° C. for 30 seconds. After that, it was subjected to annealing for rapid cooling. Thereafter, cold rolling was performed at a rolling reduction of about 91% to 0.170 mm, and then the steps from decarburizing annealing to final finishing annealing were processed under the conditions described in Example 11 . The N content of the steel sheet after nitriding was 0.0190 to 0.0220% by weight. Table 12 shows the experimental conditions and the magnetic properties of the product.

[0063]

[Table 12]

Example 13 C: 0.040% by weight, S
i: 3.04% by weight, Cu: 0.12% by weight, Mn:
0.21% by weight, S: 0.014% by weight, acid soluble A
l: 0.025% by weight as a basic component and N content of 0.0
081% by weight and 0.0013% by weight.
Four types of slabs having a thickness of 250 mm were prepared by adding two amounts of i of 0.0003% by weight and 0.0038% by weight. Such a slab is a: 1180 ° C., b: 1110 ° C.
After the soaking at 60 ° C. for 60 minutes, hot rolling was started immediately, the thickness was reduced to 40 mm in 5 passes, and the hot rolled sheet was 2.3 mm thick in 6 passes. Next, after the end of hot rolling, after air cooling for 55 seconds,
Winding simulation was performed in which the mixture was cooled with water to 0 ° C., held at 550 ° C. for 1 hour, and then cooled in a furnace.

The hot rolled sheet was pickled to form a 0.285 mm cold rolled sheet at a reduction of about 88%, and was subjected to decarburizing annealing at 830 ° C. for 150 seconds. Thereafter, annealing was performed at 750 ° C. for 30 seconds, and NH ₃ gas was mixed in the annealing atmosphere to allow the steel sheet to absorb nitrogen. The N content of this steel sheet after nitriding was 0.0192 to 0.0209% by weight. Then
This steel sheet is coated with an annealing separator containing MgO as a main component,
The temperature was raised to 1200 ° C. at a rate of 20 ° C./hour in an atmosphere gas of 25% N _{2 and} 75% H ₂ , and then a final finish annealing was performed at 1200 ° C. for 20 hours in a 100% H ₂ atmosphere gas. . Table 13 shows the experimental conditions and the results of the magnetic characteristics.

[0066]

[Table 13]

Example 14 C: 0.045% by weight, Si: 3.21% by weight, Cu:
0.13% by weight, Mn: 0.10% by weight, S: 0.01
2% by weight, N: 0.0011% by weight, acid-soluble Al:
0.026% by weight as a basic component and 0.000% by weight of Ti
4% by weight, 0.0038% by weight, 0.000% of Zr
Four types of slabs each containing 3% by weight and 0.0052% by weight were added at each of two levels, and four types of 250 mm thick slabs comprising the balance of Fe and unavoidable impurities were prepared. This slab is a: 1
After being soaked at two temperatures of 190 ° C. and b: 1120 ° C. for 60 minutes, hot rolling was started immediately, the thickness was reduced to 40 mm by 5 passes, and the hot rolled sheet was 2.3 mm thick by 6 passes. Next, this hot-rolled sheet was treated under the conditions of Example 13 until final finish annealing. N content after nitriding is 0.0198 to 0.0209% by weight
Met. Table 14 shows the experimental conditions and the magnetic properties of the product.

[0068]

[Table 14]

Example 15 C: 0.040% by weight, S
i: 3.20% by weight, Cu: 0.13% by weight, Mn:
0.20% by weight, S: 0.017% by weight, acid soluble A
l: 0.026% by weight, N: 0.0013% by weight, T
i: 0.0040% by weight was added, and a 250 mm thick slab containing the balance of Fe and inevitable impurities was prepared. After the slab was soaked at two levels of temperature of a: 1150 ° C. and b: 1070 ° C. for 60 minutes, hot rolling was started immediately, the thickness was increased to 40 mm in 5 passes, and then increased to 2.3 mm in 6 passes. It was a rolled sheet.

Then, the hot-rolled sheet was pickled to obtain a cold-rolled sheet having a rolling reduction of about 88% and a thickness of 0.285 mm.
Decarburization annealing was performed at each of 40 ° C., 860 ° C., and 870 ° C. for 150 seconds. Thereafter, annealing was performed at 750 ° C. for 30 seconds, and NH ₃ gas was mixed into the annealing atmosphere to cause nitrogen absorption in the steel sheet. The N content of this steel sheet after nitriding was 0.0197 to 0.0206% by weight. Then, the average crystal grain size of the steel sheet was measured using an optical microscope and an image analyzer. Next, an annealing separator containing MgO as a main component was applied to the steel sheet, and N ₂ 25% and H ₂ 75%
The temperature was increased to 1200 ° C. at a rate of 20 ° C./hour in an atmosphere gas of 1,200 ° C. in a 100% H ₂ atmosphere gas.
For 20 hours. Table 15 shows the experimental conditions and the magnetic properties of the product.

[0071]

[Table 15]

Example 16 C: 0.053% by weight, Si: 3.32% by weight, Cu:
0.09% by weight, S: 0.017% by weight, acid soluble A
l: 0.024% by weight, N: 0.0008% by weight, Z
r: 0.0041% by weight as a basic component, no Mn added (<0.01% by weight), 0.08% by weight,
Three types were added at three levels of 0.18% by weight to prepare three types of slabs having a thickness of 250 mm and consisting of a balance of Fe and unavoidable impurities. Such a slab is a: 1170 ° C., b: 1100 ° C.
After the soaking at 60 ° C. for 60 minutes, hot rolling was started immediately, the thickness was reduced to 40 mm in 5 passes, and the hot rolled sheet was 2.3 mm thick in 6 passes. Then the real to the final finish annealing the hot-rolled sheet
Processing was performed under the conditions of Example 15 . However, regarding the decarburizing annealing conditions, 840 ° C. × 150 seconds (soaking), 860 ° C. ×
Only 150 seconds (soaking). The N content after nitriding is 0.0
189 to 0.0208% by weight. Table 16 shows the experimental conditions and the magnetic properties of the product.

[0073]

[Table 16]

Example 17 C: 0.050% by weight, S
i: 3.47% by weight, Cu: 0.23% by weight, Mn:
0.35% by weight, S: 0.019% by weight, N: 0.00
10% by weight, acid-soluble Al: 0.025% by weight as a basic component, and 0.0005% by weight of acid-soluble Ti, 0.1% by weight.
0035% by weight, and Sn was added (a) without addition (<0.01% by weight),
(B) Four types of slabs each having a thickness of 0.06% by weight and having a thickness of 250 mm and consisting of a balance of Fe and unavoidable impurities were prepared. The slab was subjected to a: 1160 ° C., b: 1090
After soaking at 60 ° C. for two minutes at two levels of temperature, hot rolling was started immediately, the thickness was reduced to 40 mm in five passes, and the hot rolled sheet was 2.3 mm thick in six passes. Next, the hot-rolled sheet was kept at 1090 ° C. for 30 seconds, then kept at 920 ° C. for 30 seconds, and then rapidly cooled to perform hot-rolled sheet annealing.

After that, a reduction ratio of about 90% and 0.220 mm
The steel sheet was then cold-rolled, and then subjected to decarburizing annealing at 835 ° C. × 90 seconds (soaking). Thereafter, annealing was performed at 750 ° C. for 30 seconds, and NH ₃ gas was mixed into the annealing atmosphere to cause the steel sheet to absorb nitrogen. The N content of the steel sheet after nitriding is
0.0204 to 0.0219% by weight. Then
This steel sheet is coated with an annealing separator containing MgO as a main component,
The temperature was raised to 1200 ° C. at a rate of 15 ° C./hour in an atmosphere gas of 50% N _{2 and} 50% H ₂ , and then a final finish annealing was performed at 1200 ° C. for 20 hours in a 100% H ₂ atmosphere gas. . Table 17 shows the experimental conditions and the magnetic properties of the product.

[0076]

[Table 17]

Example 18 The hot-rolled 2.3 mm thick sheet described in Example 17 was cold-rolled to 1.8 mm, then kept at 1090 ° C. for 30 seconds, and then kept at 910 ° C. for 30 seconds. After that, it was subjected to annealing for rapid cooling. Thereafter, cold rolling was performed at a rolling reduction of about 91% to 0.170 mm, and then the steps from decarburizing annealing to final finishing annealing were processed under the conditions described in Example 17 . The N content of the steel sheet after nitriding was 0.0195 to 0.0219% by weight. Table 18 shows the experimental conditions and the magnetic properties of the product.

[0078]

[Table 18]

[0079]

As described above, according to the present invention, the amount of N, the amount of Ti, the amount of Zr, the amount of S, the amount of Mn, and the amount of Cu are controlled. Control the average grain size of the primary recrystallized grains between
By adding n, and further performing hot-rolled sheet annealing at a predetermined temperature, it is possible to obtain good magnetic properties stably without spatial variation due to temperature deviation of the slab during slab heating. The industrial effect is extremely large.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 In the present invention, Mn and S are added in predetermined amounts,
N amount without adding Cu (that is, in the case of the first experiment), Y (%) = 0.292 × Ti (%) + 0.154
5 is a graph showing a relationship between × Zr (%), a magnetic property difference caused by a slab heating temperature difference, and an iron loss property.

FIG. 2 is a graph showing the addition of Cu and S in a predetermined amount according to the present invention;
N amount without adding Mn (that is, in the case of the second experiment), Y (%) = 0.292 × Ti (%) + 0.154
5 is a graph showing a relationship between × Zr (%), a magnetic property difference caused by a slab heating temperature difference, and an iron loss property.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C21D 8/12 C23C 8/26 H01F 1/16 C22C 38/00 303 C22C 38/14

Claims (6)

(57) [Claims] 1. C: 0.025 to 0.075% by weight, Si: 2.5 to 4.5%, acid-soluble Al: 0.010 to 0.060%, N: less than 0.0030% by weight% , S: 0.01 to 0.05%, Mn: 0.02 to 0.8%, the remainder being Fe and unavoidable impurities, the slab is heated at a temperature lower than 1280 ° C, hot rolled, Reduction rate 8
Sandwich including one or intermediate annealing at least 0% of the final cold rolling
In a method of producing a grain-oriented electrical steel sheet by performing cold rolling two or more times, and then performing decarburizing annealing and final finishing annealing,
The content (% by weight) of Ti, Zr, and N in the slab is controlled according to the following equation: 0.5 × N (%) <0.292 × Ti (%) + 0.154 × Zr
(%) <0.0050 A stable production method of a grain-oriented electrical steel sheet having excellent magnetic properties, wherein the steel sheet is subjected to a nitriding treatment after hot rolling and before the start of final finish annealing. 2. C: 0.025 to 0.075% by weight, Si: 2.5 to 4.5%, acid-soluble Al: 0.010 to 0.060%, N: less than 0.0030% by weight% , S: 0.01 to 0.05%, Cu: 0.01 to 0.40%, the balance being Fe and unavoidable impurities, the slab is heated at a temperature of less than 1280 ° C., hot rolled, Reduction rate 8
Sandwich including one or intermediate annealing at least 0% of the final cold rolling
In a method of producing a grain-oriented electrical steel sheet by performing cold rolling two or more times, and then performing decarburizing annealing and final finishing annealing,
The content (% by weight) of Ti, Zr, and N in the slab is controlled according to the following equation: 0.5 × N (%) <0.292 × Ti (%) + 0.154 × Zr
(%) <0.0050 A stable production method of a grain-oriented electrical steel sheet having excellent magnetic properties, wherein the steel sheet is subjected to a nitriding treatment after hot rolling and before the start of final finish annealing. 3. In% by weight, C: 0.025 to 0.075%, Si: 2.5 to 4.5%, acid-soluble Al: 0.010 to 0.060%, N: less than 0.0030% , S: 0.01 to 0.05%, Cu: 0.01 to 0.40%, Mn: 0.02 to 0.8%, the balance being 1280 ° C. Heated at a temperature of less than, hot rolled and reduced at a rate of 8
Sandwich including one or intermediate annealing at least 0% of the final cold rolling
In a method of producing a grain-oriented electrical steel sheet by performing cold rolling two or more times, and then performing decarburizing annealing and final finishing annealing,
The content (% by weight) of Ti, Zr, and N in the slab is controlled according to the following equation: 0.5 × N (%) <0.292 × Ti (%) + 0.154 × Zr
(%) <0.0050 A stable production method of a grain-oriented electrical steel sheet having excellent magnetic properties, wherein the steel sheet is subjected to a nitriding treatment after hot rolling and before the start of final finish annealing. 4. The slab component further comprises Sn: 0.
4. The method for stably producing a grain-oriented electrical steel sheet having excellent magnetic properties according to claim 1, wherein the content is in the range of 0.1 to 0.15%. 5. The method for stably producing a grain-oriented electrical steel sheet having excellent magnetic properties according to claim 1, wherein the hot-rolled sheet is annealed at 850 to 1250 ° C. after the hot rolling. 6. The magnet according to claim 1, wherein the average grain size of the primary recrystallized grains after completion of the decarburization annealing until the start of the final finishing annealing is 18 to 35 μm. A stable production method for unidirectional electrical steel sheets with excellent properties.