JPH05320766A - Production of grain-oriented silicon steel sheet capable of stably providing superior magnetic property - Google Patents

Abstract

PURPOSE:To usually obtain stable and superior magnetic properties by subjecting a silicon-containing steel containing B to decarburization of specific amount of decarburization in the course between the completion of hot rolling and the completion of final cold rolling. CONSTITUTION:The stock of a silicon-containing steel having a composition containing, by weight, 0.07-0.10% C and 0.0002-0.0050% B is hot-rolled. Cold rolling is done, while performing process annealing between cold rolling stages, and finished to <=0.23mm sheet thickness. The resulting sheet is subjected to decarburizing annealing, and, after the application of a separation agent at annealing to the surface of the sheet, final annealing is done, by which the grain-oriented silicon steel sheet is produced. At this time, decarburization of 0.01-0.06wt.% decarburization amount is done in the stage between the completion of hot rolling and the completion of final cold rolling. By this method, stable and superior characteristics can be obtained even by means of a single cold rolling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stably producing a unidirectional silicon steel sheet, that is, a unidirectional silicon steel sheet having a thickness of 0.23 mm or less and excellent magnetic properties. ..

[0002]

2. Description of the Related Art Unidirectional silicon steel sheets are mainly used as iron cores for transformers and other electric equipment, and are required to have excellent magnetic properties and iron loss properties as magnetic properties. The basic requirement for obtaining a material with excellent magnetic properties is that during the final annealing process (110)
This is to sufficiently develop the secondary recrystallized grains in the [001] orientation. For that purpose, (110) [0
The presence of an inhibitor that strongly suppresses the growth of crystal grains having an unfavorable crystal orientation other than the [01] orientation, and a suitable texture in which sharply aligned secondary recrystallized grains of the (110) [001] orientation are sufficiently developed. It is known that the formation of Generally MnS, MnSe, A as inhibitors
Fine precipitates such as lN are used. Further, regarding the formation of an appropriate texture, a method of appropriately combining the conditions of each step in the conventional hot rolling and cold rolling is adopted, and two cold rollings with intermediate annealing are performed, etc. The complicated process of is also adopted.

Due to such advances in the production technology of silicon steel sheets, magnets having excellent characteristics with a magnetic flux density represented by a B ₈ value of more than 1.91 T can be obtained, and miniaturization of transformers and the like can be obtained. And contributes to the reduction of the noise. As for the iron loss characteristics, the iron loss W _17/50 value is 0.90 W / Kg or less for a unidirectional silicon steel sheet having a thickness of 0.23 mm, that is, the magnetic flux density is 1.
Iron loss when magnetized at 7 T and frequency of 50 Hz is
Excellent materials of 0.90 W / kg or less have also been obtained.

Further, many attempts have been made to add B in order to improve the magnetic properties of silicon steel sheets. For example,
JP-B-58-43444, JP-A-51-106622
JP-A-52-39520 and JP-A-52-39520 show examples of a method of manufacturing a grain-oriented silicon steel sheet having a thickness of 0.29 mm or more, to which B is attached. However, in these methods, since the C is not controlled in the intermediate step, the plate thickness is further reduced, that is, stable and excellent magnetic properties can be obtained in the grain-oriented silicon steel sheet having a thickness of 0.23 mm or less. Left problems where it was impossible.

JP-A-54-6809 discloses a method for producing a grain-oriented silicon steel sheet from a thin cast body by cold rolling with intermediate annealing. However, since the amount of C at the time of hot rolling is small, it is difficult to obtain an appropriate texture and there is a problem that the characteristics become unstable. Further, JP-A-54-128425 discloses a method for improving the properties of the base coating,
It is difficult to manufacture a thin high-flux density unidirectional silicon steel sheet only by improving the properties of the base coating.

Further, JP-A-62-1213, 10 and 10
Nos. 214 and 130217 each disclose a method for manufacturing a unidirectional silicon steel sheet by a heating method using an induction heating furnace, but it is difficult to control induction heating and control of C in an intermediate step. Therefore, it is difficult to stably manufacture a product having excellent magnetic properties.

[0007]

SUMMARY OF THE INVENTION The present invention proposes a manufacturing method which can solve the above problems advantageously and can stably supply grain-oriented silicon steel sheets having a thickness of 0.23 mm or less and excellent magnetic properties. The purpose is to

[0008]

[Means for Solving the Problems] As a result of studying the cause of unstable magnetic properties in a thin unidirectional silicon steel sheet, as a result of the conventional composition, an inhibitor, MnS, which precipitates during hot rolling, It was found that MnSe and AlN did not sufficiently suppress the growth of secondary grains, so B was added for the purpose of strengthening the inhibitor, and in the steel to improve the hot rolling structure. It was found that a thin steel sheet having excellent magnetic properties can be stably manufactured by controlling C in an intermediate step to develop a texture suitable for secondary recrystallization.

That is, the present invention provides C: 0.07 to 0.10.
wt% (hereinafter simply referred to as%) and B: 0.0002 to 0.0050%
, Containing silicon steel material, after hot rolling, cold rolling including intermediate annealing to finish to a plate thickness of 0.23 mm or less, then subjected to decarburization annealing, an annealing separator on the steel plate surface. After applying, final annealing, in producing a unidirectional silicon steel sheet by a series of steps, in the step after the end of the hot rolling and before the end of the final cold rolling, in order to improve the hot rolling structure, A method for producing a unidirectional thin silicon steel sheet, which has a decarburization step of decarburizing C by 0.010 to 0.06% and stably obtains excellent magnetic properties.

[0010]

The starting material in the manufacturing method of the present invention is C:
A slab for a silicon-containing steel material, specifically, a grain-oriented silicon steel, containing 0.07 to 0.10% and. Here, the slab thickness is not particularly limited, but a thickness of 150 to 350 mm is generally suitable, and it can be obtained by continuous casting or slab rolling of a steel ingot.

Next, the reasons for limiting the composition of the above components will be described. C: 0.07 to 0.10% By controlling C to 0.07 to 0.10%, the α + γ region is allowed to pass during hot rolling to effectively improve the hot rolling texture. The upper temperature limit can be increased up to 1380 ° C. B: 0.0002 to 0.005% If B is less than 0.0002%, the effect of dispersing the precipitates is weak and the effect of suppressing the γ phase becomes small, while if it exceeds 0.005%, the precipitates become coarse and the magnetic properties deteriorate, so 0.0002 to 0.005%. %
The range is.

As the other components, any of the conventionally known component compositions are suitable, and the representative compositions are as follows. Si: 2.5-4.5% Si content is effective in increasing iron sheet resistivity and reducing iron loss.
If it exceeds 5%, the cold rolling property is impaired, while if it is less than 2.0%, the iron loss improving effect is weakened, and sufficient properties cannot be obtained due to the randomization of the crystal orientation due to α-γ transformation.

Mn, Al, S, Se, Sb, and Sn are all added as inhibitors to suppress the growth of primary recrystallized grains in the final annealing and to suppress the secondary recrystallized grains of (110) [001] orientation. It is a necessary ingredient for sharp development. Mn: 0.02 to 0.15% Mn is 0.02 to 0.15%. That is, if it is less than 0.02%, cracking occurs due to hot embrittlement, while if it exceeds 0.15%, MnS,
The solid solution temperature of MnSe increases, which is disadvantageous. Al: 0.005-0.1% Al does not function as an inhibitor below 0.005%, so 0.005% is the lower limit. On the other hand, if it exceeds 0.1%, the magnetic properties are mainly deteriorated, so 0.1% is made the upper limit. 0.005 to 0.10% in total of one or two of S and Se
contains. If the sum of any one or two of S and Se deviates from the above range, the secondary recrystallization becomes unstable and the desired excellent magnetic properties cannot be obtained, so the above range is limited. Sb: 0.005 to 0.2% If Sb is 0.005% or less, no effect is observed, and if it is 0.2% or more, magnetic properties deteriorate. Sn: 0.02 to 0.5% Sn is not effective at 0.02% or less, and magnetic properties are deteriorated at 0.5% or more. N: 0.003 to 0.01% N causes Al and B to act as inhibitors, so an amount of N that balances with these is required,
0.003% is required. On the other hand, if it exceeds 0.01%, the magnetization characteristics are deteriorated, so it is desirable to regulate the content to 0.01% or less.

As an inhibitor, in addition to this, A
Grain boundary segregation type components such as s, Pb, Bi, Cu and Mo are known, and the effect of the present invention is not impaired even if one or more of these components are added.

Then, after heating the slab having the above-mentioned composition, it is hot-rolled into a hot-rolled sheet. Slab heating conditions,
The hot rolling conditions do not need to be particularly limited and may be a known method. For example, slabs are heated above 1350 ° C,
As hot rolling conditions, finish the rough rolling at 1200 ℃ or more,
After that, it is preferable to perform finish rolling.

Subsequently, the hot-rolled sheet is cold-rolled including intermediate annealing to a sheet thickness of 0.23 mm or less. here,
It is important to perform decarburization treatment during the process before the final cold rolling. This decarburization is performed by adjusting a known annealing atmosphere, and the decarburization amount is preferably 0.010% or more and 0.060% or less. Because the amount of decarburization is less than 0.010% or 0.060%
If it exceeds, the magnetic flux density may be insufficient and the iron loss may be relatively large, resulting in an insufficient magnetic property. Incidentally, the reduction ratio during the final cold rolling is preferably 60 to 90%.

The directional silicon steel cold-rolled sheet having a thickness of 0.23 mm or less, which has been finished as described above, is further subjected to decarburizing annealing, then an annealing separator is applied, and final annealing is performed. After that, an insulating coating is applied to obtain a product.

[0018]

EXAMPLES Example 1 C: 0.092%, Si: 3.17%, Mn: 0.074%, Se: 0.006
%, S: 0.0032%, Al: 0.019%, B: 0.0011%, N:
A 200 mm-thick unidirectional silicon steel slab containing 0.0069% was melted, the slab was heat-treated at 1380 ° C. for 1 hour, then hot-rolled and wound into a 2.0 mm-thick hot rolled coil. Then, after these 30 seconds coil at 1000 ° C. annealing, cold rolled to 0.75mm thick, further, when an intermediate annealing for 2 minutes at 950 ° C., a continuous annealing atmosphere in a known manner, the oxidation degree PH ₂ O / P
H _2: 0.003 adjusted to the range of 0.35 to decarburization amount [Delta] C, 0.007% respectively 0.013% and 0.055% and 0.070%, were finished to a thickness 0.23mm was rolled then final cold. Then, after decarburizing annealing in wet hydrogen at 800 ° C, a separating agent mainly composed of MgO is applied and a final annealing is performed at 1200 ° C for 10 hours, and further an insulating coating is applied. A product of unidirectional silicon steel sheet was obtained.

The results of measuring the magnetic properties of these products are shown in Table 1. When the decarburization amount ΔC is 0.007%, fine particles are generated due to the insufficient decarburization, and the decarburization amount ΔC
At 0.070%, decarburization becomes excessive and the crystal grains become coarse. That is, in the comparative example in which the decarburization amount ΔC is out of the range of 0.010 to 0.060%, the texture suitable for secondary recrystallization cannot be obtained, and the iron loss value is high and the variation is large. Also, the magnetic flux density becomes low. On the other hand, in the steel sheet obtained according to the present invention, a sufficiently low iron loss value and a high magnetic flux density were stably obtained.

[0020]

[Table 1]

Example 2 C: 0.114%, 0.092%, 0.073% and 0.058% of 4
Level: Si: 3.05%, Mn: 0.070%, Se: 0.025
%, S: 0.0028%, Al: 0.025%, B: 0.0020% and N: 0.0074%, a 200 mm thick unidirectional silicon steel slab is melted, and the slab is heat-treated at 1380 ° C. for 1 hour. Then, it was hot rolled and wound into a hot rolled coil having a thickness of 2.5 mm. Then, after these 30 seconds at 980 ° C. The coil annealing, and cold rolled to 0.80mm thick, further, when an intermediate annealing for 2 minutes at 950 ° C., a continuous annealing atmosphere in a known manner, the oxidation degree PH ₂ O
/ PH ₂ : Adjust 0.003 to 0.35 to decarburize ΔC 0.048%
After that, final cold rolling was performed to finish the plate thickness to 0.15 mm.
Then, after decarburizing annealing in wet hydrogen at 800 ℃, MgO
Was applied for final annealing at 1200 ° C. for 10 hours, and then an insulating coating was applied to obtain a unidirectional silicon steel sheet product according to the present invention. The results of measuring the magnetic properties of these products are shown in Table 2.

[0022]

[Table 2]

As is clear from Table 2, the amount of C is 0.07-0.
In Comparative Examples not satisfying the range of 10%, no improvement in texture was observed, the iron loss value was high and the magnetic flux density was low. On the other hand, in the steel sheet obtained according to the present invention, a sufficiently low iron loss value and a high magnetic flux density were stably obtained.

Example 3 C: 0.074%, Si: 3.17%, Mn: 0.074%, Se: 0.010
%, S: 0.0050%, Al: 0.019% and N: 0.0069%, and further, the B content was changed to three levels of 0.0008%, 0.0046%, 0.0060%, and a 200 mm thick unidirectional silicon steel slab was prepared. After smelting, the slab was heat-treated at 1380 ° C. for 1 hour, then hot-rolled and wound into a hot-rolled coil having a thickness of 2.0 mm. Then
After these 30 seconds at 1000 ° C. the coil annealing, cold rolled to 0.75mm thick, further, when an intermediate annealing for 2 minutes at 950 ° C., a continuous annealing atmosphere in a known manner, oxidation degree PH ₂ O / P
H _2: 0.003 was adjusted to 0.35 by the decarburization amount ΔC 0.024% and finished to a thickness 0.23mm was rolled then final cold. Then, after decarburizing annealing in wet hydrogen at 800 ° C, a separating agent mainly composed of MgO is applied and a final annealing is performed at 1200 ° C for 10 hours, and further an insulating coating is applied. A product of unidirectional silicon steel sheet was obtained. The results of measuring the magnetic properties of these products are shown in Table 3.

[0025]

[Table 3]

As is clear from Table 3, the effect cannot be recognized with the amount of B outside the range of the present invention, but a steel plate satisfying the requirement of the present invention, B: 0.0002 to 0.0050%, is sufficient. A low iron loss value and a high magnetic flux density were obtained at the same time.

Example 4 C: 0.076%, Si: 3.27%, Mn: 0.082%, Se: 0.023
%, S: 0.0032%, Al: 0.025%, B: 0.0028%, N:
0.0082%, Sb 0.006 to 0.23% and Sn
200mm-thick unidirectional silicon steel slabs containing 0.02 to 0.61% by changing the content were melted, and the slabs were heated to 1380 ℃.
After heat treatment for 1 hour, it was hot rolled and wound into a hot rolled coil having a thickness of 2.0 mm. These coils are then placed at 1000 ° C for 30
Annealed for 2 seconds, cold rolled to 0.75 mm thickness, and then 950 ℃
Upon intermediate annealing for 2 minutes at a continuous annealing atmosphere in a known manner, oxidation degree PH ₂ O / PH _2: 0.003 and adjusted to a range of 0.35 to decarburization amount ΔC is 0.020 percent, between subsequent final cold Rolled to a plate thickness of 0.23 mm. Next, after decarburizing annealing in wet hydrogen at 800 ° C, a separating agent mainly composed of MgO is applied, final annealing is performed at 1200 ° C for 10 hours, and an insulating coating is further applied. A product of unidirectional thin silicon steel sheet was obtained. Table 4 shows the results of measuring the magnetic properties of these products.

[0028]

[Table 4]

As is apparent from Table 4, according to the present invention, excellent magnetic characteristics can be obtained even when Sb and Sn are added simultaneously. However, in Comparative Examples outside the scope of the present invention, the iron loss value was high and unstable, and the magnetic flux density was low.

[0030]

According to the present invention, in a unidirectional thin silicon steel sheet having a plate thickness of 0.23 mm or less, it is possible to always stably obtain excellent magnetic characteristics. Therefore, the step of performing the cold rolling twice, which sandwiches the intermediate annealing, which is conventionally required, is performed by one step.
It has become possible to obtain stable and excellent properties even by performing only one cold rolling.

Claims (1)

[Claims] 1. C: 0.07 to 0.10 wt% and B: 0.0002
~ 0.0050wt% containing silicon steel material, after hot rolling, cold rolling including intermediate annealing to finish to a thickness of 0.23mm or less, followed by decarburization annealing to the steel sheet surface After the annealing separator is applied, the final annealing is performed, and in producing a unidirectional silicon steel sheet by a series of steps, the decarburization amount in the step after the hot rolling is finished and before the final cold rolling is finished. A method for producing a unidirectional silicon steel sheet, which is capable of stably obtaining excellent magnetic properties, which is characterized by performing decarburization of 0.010 to 0.060 wt%.