JPH0696743B2 - Method for producing unidirectional silicon steel sheet having excellent magnetic properties - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a unidirectional silicon steel sheet having a low iron loss value and a high magnetic flux density, which is mainly used for iron cores of power transformers.

<Prior art> The magnetic properties required for unidirectional silicon steel sheet are low iron loss value and high magnetic flux density. Generally, the iron loss value is W17 / 50 (W / kg).
Therefore, the magnetic flux density is often evaluated by B ₁₀ (T).

Conventionally, the methods of reducing iron loss are to increase the Si content, reduce the product thickness, reduce the impurities in the product, and integrate the secondary recrystallized grains in the (110) [001] orientation, the so-called Goss orientation. Is known, or secondary recrystallized grains are made smaller.

Among the methods for improving magnetic iron loss, a method for reducing impurities in a product is disclosed in JP-A-61-177320 as follows. That is, a silicon steel strip of 2.5 to 4.5% Si composed of secondary recrystallized grains containing at least one of sulfide, selenide and nitride to be purified in steel,
When performing soaking at 1100-1250 ° C for 3 hours or more in an atmosphere mainly containing hydrogen gas, the temperature in the first half of the soaking cycle is
Keep the temperature 5 ° C or more higher than the latter temperature and hold it for a sufficient time to accelerate the solutionization of sulfide, selenide, or nitride precipitation dispersed phase in the steel. The diffused impurity elements in the converted steel are diffused to the surface of the steel sheet, and the reduction of the forsterite film formed on the steel sheet surface is not promoted within a temperature range sufficient to purify the steel sheet surface, and the creep deformation of the laminated steel sheet This is a method of improving the iron loss value and the film formation, which is maintained in a temperature range where it is not accelerated.

Further, in JP-A-60-138016, in producing a unidirectional silicon steel sheet, Mg was formed on the surface of the steel sheet after decarburizing primary recrystallization.
When applying the slurry of the annealing separator containing O as a main component,
In the stratified posture of the steel sheet to be subjected to secondary recrystallization annealing, the regions where the coating amount of the slurry is locally different are dispersedly formed within 40 mm of each other so that the coating amount difference is 10 to 50%. Ensure a ventilation gap between each other and then follow the usual method 2
A method of performing secondary recrystallization and purification annealing is disclosed.

<Problems to be Solved by the Invention> However, in the above-mentioned Japanese Patent Laid-Open No. 61-177320, it is necessary to control the heat cycle, gas atmosphere and dew point of complicated finish annealing, and the gas atmosphere is reduced. Impurities in the steel are trapped in the forsterite coating, and when strain relief annealing is performed after assembly of the actual equipment, the impurities in the forsterite coating precipitate in the steel due to this annealing, and the thinner the finished thickness, the better the characteristics of the actual equipment. Deteriorate. Therefore, this technique has the disadvantage that it can only be used for laminated cores that do not require strain relief annealing.

On the other hand, JP-A-60-138016 discloses a method in which the finisher annealing is advantageously guided by improving the air permeability based on the difference in coating amount, and the ringer roll is processed to continuously form the difference thickness portion. Since it is a slurry, it is difficult to control the thickness difference, and there are drawbacks such as severe wear of the ringer roll and high processing cost.

The present invention has been made in view of the above circumstances, and provides a manufacturing method for easily improving the magnetic characteristics of thin unidirectional silicon steel by easily promoting the exclusion of impurity elements in a normal manufacturing method. is there.

<Means for Solving the Problems> The present invention, in% by weight, C: 0.020 to 0.080%, Si: 2.5 to 4.0
%, Mn: 0.03 to 0.15%, S and / or Se in total of 0.008 to
0.100%, and optionally Sb: 0.008 to 0.100%, hot-rolled a silicon steel slab consisting of the balance Fe and unavoidable impurities, and then cold-rolled once or twice with intermediate annealing. The final cold rolling reduction is performed in the range of 40 to 80%, and after finishing to the final plate thickness, the decarburization annealing is applied with an annealing separator and the final finishing annealing is performed. In the method for producing a steel sheet, the method for producing a unidirectional silicon steel sheet having excellent magnetic properties, characterized in that the gas flow rate of the final finish annealing is 2 cc / min · kg or more,
Further, the present invention, in% by weight, C: 0.020 to 0.080%, Si: 2.5
~ 4.0%, Mn: 0.03-0.15%, acid-soluble AI: 0.010-0.070
%, N: 0.0035 to 0.0140%, and 0.008 to 0.100% in total of S and / or Se, and the balance Fe and unavoidable impurities are hot-rolled to anneal the hot-rolled sheet. After 80% or more cold rolling and finishing to the final thickness,
Regarding decarburizing annealing, in a method for producing a unidirectional silicon steel sheet comprising a series of steps of applying an annealing separator and performing final finishing annealing, the gas flow rate of the final finishing annealing is 2 cc / min · kg or more, And a method for producing a unidirectional silicon steel sheet having excellent magnetic properties.

<Operation> The present invention will be specifically described below.

First, the background of the invention will be described.

C: 0.043% (all weight% thereafter), Si: 3.23%, Mn: 0.083
%, S: 0.023%, Se: 0.017%, Sb: 0.025% and a balance of substantially Fe made of a silicon steel slab made into a hot rolled sheet of 2.2 mm by an ordinary method, annealed at 950 ° C for 2 min, After washing, intermediate thickness 0.70m
It was cold rolled to m and then subjected to intermediate annealing at 975 ° C. for 2.5 min. Then, it was cold rolled to a thickness of 0.19 mm at a reduction rate of 73%, and after degreasing, 830
After decarburization annealing was performed in a wet hydrogen atmosphere at ℃ for 3 min, an annealing separator containing MgO as a main component was applied and then finish annealing was performed. This finish annealing was performed at room temperature in a dry N ₂ atmosphere at
After raising the temperature to 0 ℃ at a rate of 30 ℃ / Hr and maintaining it at 840 ℃ for 40Hr to terminate the secondary recrystallization, the temperature was set to 25 ℃ in a dry H ₂ atmosphere.
After raising the temperature at a rate of / Hr, the temperature was maintained at 1200 ° C for 10 hours and then the furnace was cooled. The gas flow rate during this finish annealing is 1 kg of steel plate weight.
The range was changed from 0.1 cc / min to 20 cc / min.

By the way, 840 ℃ from normal temperature to the end of secondary recrystallization
Fig. 1 shows the relationship between the gas flow rate when held at 40Hr at 40 ° C and the atmospheric dew point at 400 ° C during temperature increase. From this figure, when the gas flow rate from room temperature to the end of secondary recrystallization satisfies the range of 2 cc / min · kg or more, the atmospheric dew point at 400 ° C at the time of temperature rise is 0 ° C or less and low oxidative property. You can see that.

After finishing annealing, after removing the annealing separator, tension coating is applied, and after flattening annealing, the Epstein test piece (30 x 280 mm) is sheared and then dried in dry N _2.
Measurement of magnetic properties by strain relief annealing of Hr, analysis of S, Se, N components in the state with forsterite coating after MgO removal,
The secondary recrystallization rate was measured from the secondary recrystallization macrostructure of the product. Fig. 2 shows the magnetic characteristics, B ₁₀ (T), W17 / 50 (W / k
g) and the total content of S, Se and N and the secondary recrystallization rate are shown.

As is clear from the drawing, the gas flow rate of finish annealing is 2cc /
When the content of min / kg or more is satisfied, the secondary recrystallization is sufficiently developed and the secondary recrystallization rate is improved, and the S, Se and N components in the base iron and forsterite are significantly reduced. An excellent unidirectional silicon steel is obtained with an improved B ₁₀ value and a decreased iron loss W 17/50 value.

When the gas flow rate of finish annealing is less than 2 cc / min · kg, secondary recrystallization and purification of S, Se and N are significantly hindered and improvement of magnetic properties cannot be expected. Therefore, in the present invention, the gas flow rate during finish annealing is limited to 2 cc / min · kg or more. Also, the same effect is maintained even if the gas flow rate exceeds 20 cc / min · kg,
An economical usage method may be adopted in consideration of the cost of the used gas.

Next, the reason why the composition of the steel sheet is limited to the above range is as follows.

C: 0.020 to 0.080% If C is less than 0.020%, the texture after decarburization annealing is impaired, leading to deterioration of magnetic properties. On the other hand, if it exceeds 0.080%, it is difficult to decarburize by continuous annealing. Therefore, the C content is limited to the range of 0.020 to 0.080% because the magnetic properties of the final product are deteriorated.

Si: 2.5-4.0% When Si is less than 2.5%, it is difficult to obtain the iron loss value as low as expected in the present invention. Since industrial rolling becomes difficult, the Si content was limited to the range of 2.5 to 4.0%.

Mn: 0.03 to 0.15% Mn forms MnS and MnSe with S and Se, which will be described later, respectively, and acts as an inhibitor to suppress the growth of primary recrystallized grains in finish annealing and to suppress secondary recrystallization of the (110) [001] orientation. It is an element useful for sharply developing crystal grains, but if it is less than 0.03%, its addition effect is poor, while if it exceeds 0.15%, it is 2
Since secondary recrystallization will not occur, it was limited to the range of 0.03 to 0.15%.

S and / or Se: 0.008 to 0.100% S and Se are added in order to combine with Mn to form MnS and MnSe as described above, and at least one or two of S and Se. A total of 0.008% is required. However, if added in a too large amount, hot cracking occurs in the case of S, and since Se is an expensive element, it has the disadvantage of increasing the cost. The upper limit was 0.100%.

Sb: 0.008 to 0.100% If Sb exceeds 0.1%, cold workability is deteriorated and the magnetic properties are deteriorated. On the other hand, if less than 0.008%, the effect of addition is poor, so the range is 0.008 to 0.100%.

In addition, the content of As, Bi, Pb, Sn, Cn, Te, Mo, W alone or in a combined amount of about 0.010 to 0.20% as an inhibitor does not inhibit the effect of the present invention.

Any of these alone or in combination cannot function as an inhibitor if the content is less than 0.010%, while if they are contained in an amount exceeding 0.20%, they deviate from the role of the inhibitor and rather deteriorate the magnetic properties, or have a low cold rolling property. Since it significantly inhibits, the content of each of the above components is preferably in the range of 0.010 to 0.20% in both cases of single and complex.

Acid-soluble Al: 0.010-0.070% When using AlN for secondary recrystallization, 0.010% or more of acid-soluble Al is required to secure the necessary minimum amount of AlN, while acid-soluble Al exceeds 0.070%. Since the dispersion state of AlN in the hot rolled sheet becomes unsuitable and the secondary recrystallization becomes unstable, the content was made 0.070% or less.

N: 0.0035-0.0140% As described above, 0.0035% or more is required as N in order to secure the minimum amount of AlN required for secondary recrystallization, while if N is contained in excess of 0.0140%, AlN Since it is inappropriately dispersed, the content is set to 0.0140% or less.

Next, the manufacturing method according to the present invention will be specifically described in the order of steps.

The silicon steel material adjusted to the above preferable composition is usually used at 1250 ° C.
After heating to the above high temperature, the plate thickness 1.
Use a hot-rolled sheet of about 2 to 3.3 mm. Then, this hot-rolled sheet is annealed at a temperature of 850 to 1150 ° C for a short time if necessary, and this hot-rolled sheet using Mns or MnSe as an inhibitor is cold-rolled once or from 750 to 1100. The final strip thickness is finished by two cold rolling processes with intermediate annealing at about ℃. In such cold rolling, the final cold rolling reduction ratio is 40-80.
It is important to set it as%. If the reduction ratio in the final cold rolling is less than 40% or more than 80%, the degree of integration in the (110) [001] orientation is high enough to be sufficiently satisfied after decarburization annealing. This is because it is difficult to obtain a crystal structure, and the desired excellent magnetic properties cannot be obtained.

In the case of using AlN as an inhibitor, if the rolling reduction is less than 80%, it is suitable for the (111) [11] orientation of 1 after decarburization annealing.
Since a secondary recrystallization texture cannot be obtained and a sufficiently high magnetic flux density and a low iron loss value cannot be achieved, it was limited to 80% or more. Even if the reduction rate is increased in the range of more than 95%, the magnetism is not further improved, but on the other hand, the thickness of the hot rolled sheet becomes thicker and the rolling efficiency decreases. It is desirable to do.

Although the finish thickness is not particularly limited here, according to the results of various experiments conducted by the inventors, impurities existing in the steel or in the forsterite coating have a greater adverse effect on magnetism as the finish thickness decreases, and the present invention is It can be applied more advantageously by improving the magnetism of thin finish of 0.25 mm or less.

Next, the final cold-rolled sheet is decarburized and annealed in a temperature range of 750 to 900 ° C. in a wet hydrogen atmosphere to sufficiently decarburize the carbon content to 0.003% or less. After that, after applying an annealing separator such as MgO, final finish annealing is performed. The purpose of this final finish annealing was to add secondary recrystallized grains in the (110) [001] orientation to the steel sheet while at the same time adding them as inhibitors.
It is applied to purify and remove impurities such as S, Se and N, and is usually performed by box annealing. However, when using MnS or MnSe as an inhibitor, when high magnetic flux density and low iron loss value are obtained, It is desirable that the secondary recrystallized grains are sufficiently grown by holding them in a temperature range of about 920 ° C. for about 10 hours or more and then kept at a high temperature of 1050 ° C. or more for 5 hours or more to make them slow.
In the case of this finish annealing cycle, dry N ₂ gas (Ar gas may be used but cost will increase) until the secondary recrystallization is completed, but if the purification H ₂ gas described later is introduced early, S It is desirable to switch from N ₂ to H ₂ gas for the purpose of promoting de-S, de-Se, and de-N when secondary recrystallization is completed because de-Se occurs and the inhibitor function is impaired.

On the other hand, when the inhibitor is AlN, the direct-up finish annealing is usually used, but in that case also, even when the inhibitors are MnS and MnSe, normal straight-up is not performed at 820 to 920 ℃. For type of finish annealing,
After the secondary recrystallization is completed, it is preferable to switch from N ₂ to H ₂ and perform purification annealing.

As described above, in finish annealing, N ₂ gas is used until secondary recrystallization is completed, and H ₂ gas is selectively used in annealing. The reason for limiting the gas flow rate in these finish annealing to ₂ cc / min · kg or more is as follows. Is.

After decarburization annealing, 100-
Although it is dried at 200 ° C, the water of crystallization in MgO is released at around 400 ° C when it is heated from room temperature by box annealing. At this point, the N ₂ gas flow rate is less than 2cc / min ・ kg. If,
The atmosphere in the box becomes remarkably oxidative and the dew point rises above 0 ° C, causing the surface of the steel sheet to remarkably oxidize.
The surface concentration of MnS and MnSe is promoted, and the inhibitory function is significantly reduced. Even after the subsequent H ₂ switching, the gas flow rate is 2cc / min ・ kg
Even if the slowdown is improved to some extent by increasing the above,
The secondary recrystallization rate deteriorates, and the magnetic properties do not reach the desired target values. Therefore, in order to keep the atmosphere in the box at a low oxidation rate until the completion of secondary recrystallization, the gas flow rate of 2cc / min.kg or more. is necessary. In the purification after switching from N ₂ to H ₂ gas, as described above, the gas flow rate is also 2 cc / min · kg or more and the atmospheric dew point is 0 ° C.
It is necessary to control the following. Because even 2
This is because even if the secondary recrystallization is sufficient, if the gas flow rate during purification is less than 2 cc / min · kg, magnetic degradation will occur due to insufficient purification.

By thus increasing the flow rates of N ₂ gas and H ₂ gas, sufficient secondary recrystallization and sufficient purification can be achieved, and the object of the present invention can be achieved. For the above reasons, the gas flow rate during finish annealing was limited to 2 cc / min · kg or more.

Further effects can be obtained even more by using a method of increasing the purity of N ₂ and H ₂ gas used for finish annealing and increasing the coil layer spacing.

Considering the cost aspect, it is effective to switch to N ₂ gas again when the furnace cooling is started after the completion of purification and to reduce the gas flow rate in that case.

In addition, although the finish thickness tends to be thin recently, for example, in the case of 0.35 mm thick finish and 0.14 mm finish, when MgO is applied with the same coil unit weight and the same amount of coating per unit area, naturally,
As mentioned earlier, the 0.14 mm finish contains 2.5 times more water of crystallization, so the thinner the finish, the more susceptible it is to impurities.Therefore, a proper treatment may be used to increase the gas flow rate for the thinner finish. The goals you have achieved are achieved.

After finishing annealing, apply insulation tension coating,
Although finished into a product by flattening annealing, usually when used in a laminated core, strain relief annealing is not required after shearing with a predetermined dimension, but in the case of a wound core material, the strain is evaluated by strain relief, so the inventors have After the finish annealing, the through-thickness analysis is performed with the forsterite attached to evaluate the degree of purification. Previously known documents such as Japanese Patent Laid-Open No. 61-177320 also have
Although it is evaluated by the S, N content, most of the S, Se, N components are trapped in forsterite, and flattening treatment at around 800 ° C or strain relief of about 3 Hr at 800 ° C after the winding core is performed. This is because the annealing easily diffuses and penetrates from the forsterite into the steel and significantly deteriorates the actual machine characteristics.

By such a treatment step, a unidirectional silicon steel sheet having excellent magnetic properties can be stably obtained.

<Example> Example 1 C: 0.048%, Si: 3.25%, Mn: 0.081%, S: 0.025%, Se: 0.024
%, Sb: 0.019% and the balance consisting essentially of Fe, 200 mm thick continuous cast slabs were heated to 1380 ° C for 1 hour and then 2.2 mm
Hot-rolled thickly, annealed at 930 ° C for 2 min, pickled, intermediate cold-rolled at 0.65 mm thickness, intermediate-annealed at 980 ° C for 1.5 min, finally cold-rolled at a reduction rate of 66%, and finished to 0.22 mm thickness .

Then, after degreasing, decarburization annealing was performed in wet hydrogen at 840 ° C. for 5 minutes, and then a separating agent mainly containing MgO was applied and then finish annealing was applied. After raising the temperature from room temperature at a heating rate of 30 ° C / h in dry N ₂ atmosphere and holding at 840 ° C for 40 hours to complete the secondary recrystallization, change to dry H ₂ atmosphere and change to 25 ° C / h. The temperature is raised to 1200 ℃ at a heating rate of 10 ℃, and the cooling rate is kept at 30 ℃ / h for 10 hours.
After reaching 0 ° C., a dry N ₂ atmosphere was established. In this finish annealing, the gas flow rate of the N ₂ atmosphere until the completion of secondary recrystallization was changed to 4 levels, and the gas flow rate of the H ₂ atmosphere in the purification annealing region was changed to 4 levels. The dew point (DP) of the N ₂ atmosphere was measured when the temperature was raised to 400 ° C.

After finish annealing, MgO was removed, tension coating was applied, and flattening annealing was performed. Epstein-sized specimens were sheared, strain relief annealed at 800 ° C for 3 hours, and magnetic properties were measured at a weight of 0.5 kg.
₁₀ (T) and W17 / 50 (W / kg) were measured. In addition, after the finish annealing, the Mg, O-free forsterite-coated S, Se, and N components were analyzed and the secondary recrystallization rate was measured from the macrostructure of the product sheet. The secondary recrystallization rate and magnetic properties are shown.

As is clear from the table, when the gas flow rates of both N ₂ and H ₂ gas satisfy the proper range of the present invention, sufficient secondary recrystallization and purification after finish annealing are promoted, resulting in high magnetic flux. Density and low iron loss values are obtained.

Example 2 C: 0.055%, Si: 3.20%, Mn: 0.088%, S: 0.025%, acid soluble
Al: 0.028%, N: 0.0091% and the balance essentially Fe 2
After heating the 20 mm thick continuous cast slab to 1400 ° C for 1 hour,
Hot rolled to a thickness of 1.8 mm, annealed at 1050 ° C for 1 min, then pickled 89
% Cold rolling reduction to 0.20 mm thickness, degreasing, decarburization annealing in wet hydrogen at 840 ° C. for 2 min, then applying an annealing separator containing MgO as a main component, and then finishing annealing. In dry N ₂
The secondary recrystallization is completed by heating up to 1000 ° C at a heating rate of 35 ° C / hr, switching to dry H ₂ and heating up to 1200 ° C at a heating rate of 25 ° C / h, then for 10 hours. After carrying out retention, purification annealing was carried out, cooling was carried out at a cooling rate of 40 ° C / hr, and when the temperature reached to 600 ° C, it was switched to dry N ₂ . The gas flow rate during this finish annealing was set to dry N ₂ until the completion of secondary recrystallization and dry gas during purification.
The H ₂ was changed to 4 levels. The dew point (DP) of N ₂ atmosphere is
The measurement was performed when the temperature was raised to 400 ° C.

After finish annealing, MgO is removed, tension coating is applied, flattening annealing is performed, and then Epstein size specimens are sheared, then strain relief annealing is performed at 800 ° C for 3 hours, and then 0.5 kg.
The magnetic properties B ₁₀ (T) and W17 / 50 (W / kg) were measured with the measured weight of. In addition, the S and N components with the forsterite coating from which MgO was removed after finish annealing and the secondary recrystallization rate were measured from the macrostructure of the product sheet, and Table 2 shows the total contents of the 2 components and 2 The secondary recrystallization rate and magnetic properties were shown.

As is clear from the table, those satisfying the proper range of the present invention obtained sufficient secondary recrystallization and purification, high magnetic flux density and low iron loss value.

Example 3 A continuous cast slab having a thickness of 180 mm and containing C: 0.049%, Si: 3.39%, Mn: 0.087%, Se: 0.027% and the balance being substantially Fe was 1
After heating at 360 ° C for 1 hour, hot rolling to 1.3mm thickness, annealing at 910 ° C for 2min, pickling, intermediate cold rolling to 0.40mm thickness, and final cold rolling at 65% reduction after intermediate annealing at 950 ° C for 2min. , Finished to 0.14mm thickness.
Then, after degreasing, decarburization annealing was performed in wet hydrogen at 820 ° C. for 3 min, then an annealing separator mainly composed of MgO was applied, and finish annealing was applied. 835 ° C in dry N ₂ at a heating rate of 33 ° C / hr
After holding for 45 hours at 50 ° C to complete the secondary recrystallization, switch to dry H ₂ gas and heat up at a heating rate of 30 ° C / hr to 10Hr at 1200 ° C.
After purification annealing by retention, it was cooled at a cooling rate of 35 ° C / hr and switched to dry N ₂ gas at 550 ° C on the way. The gas flow rate during this final annealing was set to N ₂ until the completion of secondary recrystallization and the purification annealing.
Each H ₂ was changed to 4 levels. The dew point (DP) of the N ₂ atmosphere was measured when the temperature was raised to 400 ° C.

Applying tension coating to remove MgO after finish annealing, after shearing the Epstein test piece size after flattening annealing, performed stress relief annealing at 3Hr at 800 ° C., and magnetic measurements with 0.5kg weight, B ₁₀ (T ), W17 / 50 (W / kg), and the Se and N components with the forsterite coating from which MgO was removed after finish annealing and the secondary recrystallization rate were measured. The results are shown in Table 3. .

As is clear from the table, under the conditions satisfying the proper range of the present invention, sufficient secondary recrystallization and purification were achieved and excellent magnetic properties were obtained.

Example 4 C: 0.055%, Si: 3.20%, Mn: 0.088%, S: 0.028%, Se: 0.018
%, Acid-soluble Al: 0.030%, N: 0.0095% and the balance is a 180 mm continuous cast slab consisting essentially of Fe at 1360 ° C.
After heating for 1 hour, hot rolled to 1.6 mm thickness, annealed at 1025 ° C for 1 min, pickled, finished to 0.17 mm thickness with 89% cold rolling reduction, decarburized and annealed in wet hydrogen at 825 ° C for 2 min. After that, after applying an annealing separator containing MgO as a main component, finish annealing was performed.

The temperature was raised up to 1000 ° C in dry N ₂ at a heating rate of 37.5 ° C / Hr to complete the secondary recrystallization, and then switched to dry H ₂ 12
Heat up to 00 ℃ at a rate of 30 ℃ / hr, hold for 10 hours and anneal for purification, then cool at a rate of 40 ℃ / Hr and 600 ℃
When the temperature reached, the gas was switched to dry N ₂ gas. The gas flow rate during this finish annealing was changed to 4 levels of dry N ₂ until the completion of secondary recrystallization and dry H ₂ during purification. The dew point (DP) of the N ₂ atmosphere was measured when the temperature was raised to 400 ° C.

After finish annealing, MgO is removed to apply tension coating, flattening annealing, shearing to Epstein sample size, strain relief annealing at 800 ° C for 3 hours, magnetic measurement at 0.5 kg B ₁₀ (T), W17 / 50 (W / kg) was measured, and S, Se, with forsterite coating with MgO removed after finish annealing,
The N component was analyzed and the secondary recrystallization rate was measured, and Table 4 shows the total content of the three components, the secondary recrystallization rate, and the magnetic properties.

As is clear from the table, those satisfying the conditions of the present invention obtained sufficient secondary recrystallization and purification and excellent magnetic properties.

Example 5 A continuous cast slab having a thickness of 240 mm and containing C: 0.043%, Si: 3.15%, Mn: 0.087%, S: 0.024% and the balance being substantially Fe was 139.
After heating at 0 ° C for 1 hour, hot rolling to a thickness of 2.4 mm, pickling, intermediate cold rolling to 0.80 mm, intermediate annealing at 930 ° C for 2 minutes, cold rolling of 69% to 0.
Final cold rolling to a thickness of 25 mm, after degreasing, in wet hydrogen at 820 ° C for 3 min
After performing decarburization annealing in the meantime, an annealing separator mainly composed of MgO was applied, and then final annealing was performed. The temperature was raised in dry N ₂ at a rate of 35 ℃ / Hr and the secondary recrystallization was completed at 925 ℃.
Switch to dry H ₂ gas and raise the temperature at the same heating rate to 1200 ℃
Purification was completed by holding 10 Hr, cooling was performed at a rate of 35 ° C./hr, and switching to dry N ₂ gas was performed at 650 ° C. on the way. The gas flow rate during this finish annealing was changed to 4 levels for dry N ₂ until the completion of secondary recrystallization and dry H ₂ gas in the purification region. Note that
The dew point (DP) of the N ₂ atmosphere was measured when the temperature was raised to 400 ° C.

After finish annealing, remove MgO and apply tension coating,
After flattening annealing, after shearing to an Epstein-sized specimen, after strain relief annealing at 800 ° C for 3 hours, measure the magnetic properties B ₁₀ (T), W17 / 50 (W / kg) at a weight of 0.5 kg. With
With a forsterite film with MgO removed after finish annealing
The S and N components were analyzed and the secondary recrystallization rate was measured and shown in Table 5.

As is clear from the table, when the gas flow rates of N ₂ and H ₂ both satisfy the range of the present invention, secondary recrystallization and purification after finish annealing are sufficiently promoted, and high magnetic flux density and low The iron loss value is obtained.

Example 6 C: 0.050%, Si: 3.35%, Mn: 0.086% as an inhibitor
In addition to S: 0.025%, Se: 0.015%, Sb: 0.020%, Mo: 0.015%,
Bi: 0.017%, Te: 0.019% and balance Fe
After heating 20 mm continuous cast slabs to 1410 ℃ for 1 hour,
Hot rolled to a thickness of 2.2 mm, annealed at 960 ° C for 1.5 min, and then pickled to give 0.64
mm cold rolling, intermediate rolling at 950 ° C for 2 min, reduction rate 66
% Final cold-rolled to 0.22 mm thickness.

Then, after degreasing, decarburization annealing is performed in wet hydrogen at 840 ° C. for 3 minutes, and then a separating agent mainly containing MgO is applied and then finish annealing is applied. At this time, in a dry N ₂ atmosphere, from room temperature to 35
After raising the temperature at a heating rate of ℃ / h and holding at 845 ℃ for 35 hours to complete the secondary recrystallization, change to a dry H ₂ atmosphere and change to 30 ℃.
After heating up to 1200 ℃ at a heating rate of / h and holding for 10 hours, 35 ℃
After cooling with / h and reaching 500 ° C., the atmosphere was changed to dry N ₂ . In this finish annealing, the gas flow rate of the N ₂ atmosphere until the completion of secondary recrystallization was changed to 4 levels, and the gas flow rate of the H ₂ atmosphere in the purification annealing region was changed to 4 levels. The N ₂ atmosphere of dew point (D
P) was measured when the temperature was raised to 400 ° C.

After finish annealing, MgO is removed, tension coating is applied, flattening annealing is performed, and then Epstein size specimens are sheared, then strain relief annealing is performed at 800 ° C. for 3 hours, and 0.5 kg weight is applied to magnetic properties B ₁₀ (T), W17. / 50 (W / kg) was measured. In addition, after the finish annealing, with the forsterite film with MgO removed
The S, Se and N components were analyzed and the secondary recrystallization rate was measured. Table 6 shows the total content of the three components, the secondary recrystallization rate and magnetic properties.

As is clear from the table, in the case where the gas flow rates of both N ₂ and N ₂ gas satisfy the range of the present invention, a high magnetic flux density and a low iron loss value are obtained.

Example 7 C: 0.053%, Si: 3.25%, Mn: 0.089% and S: 0.022% as an inhibitor, Se: 0.018%, acid-soluble Al: 0.023%, N: 0.0
In addition to 099%, Sn: 0.077%, Cu: 0.083% are included, and the balance is substantially
220mm thick continuous cast slabs made of Fe were all heated to 1425 ℃.
After time heating, hot rolled to 2.0mm thickness, annealed to 1030 ℃ for 1.5min, pickled and finished at 0.20mm thickness with 90% cold rolling reduction, and after degreasing in wet hydrogen at 845 ℃ for 2.5min. After decarburizing and annealing, the annealing separator containing MgO as a main component was applied, and then the final annealing was performed. Complete the secondary recrystallization by heating up to 1025 ℃ in dry N ₂ at a heating rate of 40 ℃ / h, and switch to dry H ₂ to 1200 ℃.
Was heated at a rate of 20 ° C / h, held for 10 hours, cooled at a rate of 45 ° C / h, and switched to dry N ₂ when it reached a temperature of 550 ° C. The gas flow rate during this finish annealing was changed to 4 levels for dry N ₂ until the completion of secondary recrystallization and dry H ₂ during purification. The dew point of the N ₂ atmosphere was measured when the temperature was raised to 400 ° C.

After finish annealing, MgO is removed, tension coating is applied, and flattening is performed to shear the specimen of Epstein size, and then strain relief annealing is performed at 800 ° C for 3 hours, and then magnetic measurement is performed at a weight of 0.5 kg B ₁₀ ( T) and W17 / 50 (W / kg) were measured. In addition, after the finish annealing, the S, Se and N components with the forsterite coating from which MgO was removed were analyzed and the secondary recrystallization rate was measured. Table 7 shows the total content of the three components, the secondary recrystallization rate and the magnetic properties. showed that.

As is clear from the table, those satisfying the proper range of the present invention had excellent magnetic characteristics.

Example 8 C: 0.049%, Si: 3.31%, Mn: 0.085% and S: 0.025%, Se: 0.023% as an inhibitor, and the balance is essentially Fe.
After continuously casting 220mm thick continuous cast slabs at 1420 ℃ for 1 hour
Hot rolled to a thickness of 3.0 mm, annealed at 950 ° C for 2 minutes, then pickled to 0.90
Cold rolled to an intermediate thickness of mm and rolled at 950 ° C for 2 min after intermediate annealing.
The final cold rolling was performed at 7% to a thickness of 0.30 mm.

Then, after degreasing, decarburization annealing was performed in wet hydrogen at 835 ° C for 3 minutes, and then a separating agent mainly composed of MgO was applied,
Apply finish annealing. At this time, from room temperature in a dry N ₂ atmosphere
Heat at a heating rate of 35 ℃ / h and hold at 840 ℃ for 40 hours.
After completing the next recrystallization, change to a dry H ₂ atmosphere.
After raising the temperature to 1200 ℃ at a heating rate of ℃ / h and holding for 10 hours,
After cooling at ℃ / h and reaching 500 ℃, it was switched to a dry N ₂ atmosphere. In this finishing annealing, the gas flow rate of the N ₂ atmosphere until the completion of secondary recrystallization was set to 4 levels, and H ₂ in the purification annealing region was changed.
The gas flow rate of the atmosphere was changed to 4 levels. The dew point of the N ₂ atmosphere was measured when the temperature was raised to 400 ° C.

After finish annealing, MgO is removed, tension coating is applied, flattening annealing is performed, and then Epstein size specimens are sheared, and strain relief annealing is performed at 800 ° C for 3 hours, and magnetic measurement is performed with a weight of 0.5 kg B ₁₀ (T ) And W17 / 50 (W / kg) were measured. In addition, after the finish annealing, analysis of S, Se, N components with forsterite coating with MgO removed and from the macrostructure of the product sheet
The results of the measurement of the next recrystallization rate are shown in Table 8.

As is clear from the table, under the conditions satisfying the proper range of the present invention, sufficient secondary recrystallization and purification after finish annealing are promoted, and high magnetic flux density and low iron loss value are obtained. .

Example 9 C: 0.054%, Si: 3.26%, Mn: 0.090%, Se: 0.028% as an inhibitor, acid-soluble Al: 0.030%, N: 0.0105, and the balance is a Fe continuous cast slab having a thickness of 220 mm. For both 1
After heating at 425 ℃ for 1 hour, hot rolled to 3.0mm thickness, annealed at 1050 ℃ for 1min, pickled and finished at 88.5% cold rolling reduction to 0.35mm thickness, and after degreasing at 840 ℃ in wet hydrogen. After decarburization annealing for 3 minutes, an annealing separator containing MgO as a main component was applied, and then final annealing was performed. After the secondary recrystallization is completed by raising the temperature from room temperature to 1000 ° C in dry N ₂ at a rate of 35 ° C / h, switch to dry H ₂ and raise the temperature to 1200 ° C at a rate of 25 ° C / h, After holding for 10 hours, it was cooled at a rate of 50 ° C / h, and when it reached a temperature of 550 ° C, it was switched to dry N ₂ . The gas flow rate during this final annealing was set to dry N ₂ until the completion of secondary recrystallization and dry H ₂ during purification.
For each of the four levels. The dew point (DP) of the N ₂ atmosphere was measured when the temperature was raised to 400 ° C.

After finish annealing, MgO is removed, tension coating is applied, and flattening is performed to shear the specimen of Epstein size, and then strain relief annealing is performed at 800 ° C for 3 hours, and then magnetic measurement is performed at a weight of 0.5 kg B ₁₀ ( T) and W17 / 50 (W / kg) were measured. In addition, after the finish annealing, MgO was removed and the Se and N components with the forsterite coating were analyzed and the macrostructure of the product sheet
The secondary recrystallization rate was measured, and Table 9 shows the total content of the three components, the secondary recrystallization rate, and the magnetic properties.

As is clear from the table, those satisfying the proper range of the present invention had excellent magnetic characteristics.

<Effect of the Invention> Thus, according to the present invention, a thin unidirectional silicon steel sheet having a sufficiently high magnetic flux density and a low iron loss value can be easily and stably obtained.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the gas flow rate and the atmospheric dew point in the finish annealing, and FIG. 2 is the gas flow rate in the finish annealing when the forsterite coating after removal of the finish annealing MgO was applied.
A graph showing the effect on the total content of S, Se, N components, the secondary recrystallization rate of the product sheet, and the magnetic properties after stress relief annealing {B ₁₀ (T), W17 / 50 (W / kg)} is there.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 60-67625 (JP, A) JP 61-119650 (JP, A) JP 62-31050 (JP, B2)

Claims (3)

[Claims] 1. C: 0.020-0.080%, Si: 2.5-
4.0%, Mn: 0.03 to 0.15%, further containing S and / or Se in a total of 0.008 to 0.100%, hot-rolling a silicon steel slab consisting of balance Fe and unavoidable impurities, followed by one or intermediate annealing Two cold rolling, the final cold rolling reduction
In the manufacturing method of the unidirectional silicon steel sheet comprising a series of steps of applying 40 to 80% in range, finishing the final plate thickness, followed by decarburization annealing, applying an annealing separating agent and performing final finishing annealing, A method for producing a unidirectional silicon steel sheet with excellent magnetic properties, characterized in that the gas flow rate of final finish annealing is 2 cc / min · kg or more. 2. In% by weight, C: 0.020 to 0.080%, Si: 2.5 to
4.0%, Mn: 0.03 to 0.15%, Sb: 0.008 to 0.100%, and S
And / or Se in a total amount of 0.008 to 0.100% and the balance of Fe and unavoidable impurities are hot-rolled into a silicon steel slab, followed by one or two cold-rolling steps with intermediate annealing and final cold rolling. A unidirectional silicon steel sheet consisting of a series of steps in which the reduction ratio of 40 to 80% is applied to finish the final plate thickness, decarburization annealing, then an annealing separator is applied, and final finishing annealing is performed. In the method, the gas flow rate of the final annealing is
A method for producing a unidirectional silicon steel sheet with excellent magnetic properties, which is characterized by 2 cc / min · kg or more. 3. In weight%, C: 0.020 to 0.080%, Si: 2.5 to
4.0%, Mn: 0.03-0.15%, acid-soluble Al: 0.010-0.070%,
N: 0.0035 to 0.0140%, and S and / or Se in total of 0.
Hot rolling a silicon steel slab containing 008 to 0.100% and the balance Fe and unavoidable impurities, and annealing the hot rolled sheet
% Or more cold rolling to finish the final plate thickness, followed by decarburization annealing, then applying an annealing separating agent, and finally finishing annealing. A method for producing a unidirectional silicon steel sheet with excellent magnetic properties, characterized in that the gas flow rate for finish annealing is 2 cc / min · kg or more.