JPH0610306B2 - Manufacturing method of thin grain oriented silicon steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) A method for manufacturing a grain-oriented silicon steel sheet used as an iron core material of an electric device such as a transformer or a motor, particularly a thin grain-oriented silicon steel sheet excellent in iron loss. With regard to this specification, the results of development research focusing on the procedure and rolling behavior of the cold rolling stage will be described in this specification.

When a grain-oriented silicon steel sheet used as an iron core material is magnetized by an alternating current, energy consumption called iron loss occurs, which is dissipated wastefully as heat. Therefore, from the viewpoint of energy saving, the demand for iron core materials with low iron loss is increasing year by year.Recently, in Europe and the United States, when making transformers with low iron loss, the reduction in iron loss is converted into monetary value and the transformer price is calculated. The "iron loss evaluation system" to be accumulated is widespread. Since the iron loss evaluation value is increasing year by year, transformer manufacturers are increasingly demanding steel plates with lower iron loss.

By the way, the iron loss of the unidirectional silicon steel sheet mainly consists of eddy current loss and hysteresis loss. In recent high-grade unidirectional silicon steel sheets, the loss due to eddy current accounts for about 70% of the total, and reducing eddy current is most effective for reducing iron loss.

(Prior Art) It is effective to increase the electric resistance in a silicon steel sheet as one method of reducing the eddy current, and in the present manufacturing process, the Si content is increased to a range in which the silicon steel sheet can be processed. It is possible to increase the electrical resistance by increasing the electrical resistance or process the product sheet thickness to an extremely thin product (a steel plate treated in this way is called thin unidirectional silicon steel sheet) to increase the electrical resistance. Has been adopted by.

Recently Japanese Patent Publication No. 57-2252, Japanese Patent Publication No. 57-53419
As disclosed in each publication, the local micro-strain is introduced by laser irradiation on the surface of the steel sheet after finish annealing of the grain-oriented silicon steel sheet to subdivide the 180 ° axial width to reduce the low iron loss of the product. A method for achieving this has been proposed.

When the amount of Si in the silicon steel is increased among the iron loss improving methods described above, the problem of surface shape deterioration of the product or plate cracking during cold rolling causes a problem of 3.5% in the silicon steel in the actual manufacturing process. It is impossible to add a Si amount of not less than%.

Next, the laser beam irradiation method, which reduces iron loss by improving the magnetic domain structure, requires strain relief annealing when used, for example, in wound iron cores. Therefore, when this annealing treatment is performed, the plastic strain introduced by laser irradiation is applied. Is released and the magnetic domain width is widened, so that there is a drawback that the laser irradiation effect is lost.

The method of reducing the plate thickness of the product is considered to be the simplest and advantageous in terms of reducing iron loss. Conventional 0.35mm and 0.30mm
Many thick products were used, but from the viewpoint of energy saving, products with thin thicknesses of 0.23 mm and 0.20 mm are now being widely used. However, it is generally known that when the product plate thickness is reduced, secondary recrystallization becomes unstable, and it becomes very difficult to develop secondary recrystallized grains that are strongly integrated in the Goss orientation. It is important to solve this problem. In addition, the final cold rolling reduction ratio has an optimal reduction ratio that gives the best magnetism. Therefore, in order to secure the optimum reduction ratio and reduce the final strip thickness, the cold rolling single-rolling method is used. If the thickness is two or more, the intermediate plate thickness must be reduced.

However, there is a limit to the thickness of the hot rolled sheet,
Further, thinning of the intermediate process plate requires a long time in the subsequent processes, especially in continuous annealing, so that the cost increases remarkably.

Further, as described above, when the final plate thickness becomes thin, the secondary recrystallization becomes unstable at the time of final finish annealing, and particularly in the cold rolling once method using AlN as the inhibitor, the yield of products having good magnetic properties is increased. Noticeably worse.

For the above reasons, the product plate thickness that is currently stably manufactured in the manufacturing process is about 0.20 mm, and it is said that it is extremely difficult to manufacture thin unidirectional silicon steel plates with a plate thickness of 0.18 mm or less. ing.

(Problems to be solved by the invention) By eliminating the above-mentioned drawbacks, the sheet thickness of 0.18 mm or less and the magnetic property which has been remarkably difficult to manufacture by the cold rolling once method as well as the cold rolling twice or more method. It is an object of the present invention to provide an ingenuity in the process for realizing extremely stable production of a thin unidirectional silicon steel sheet having particularly excellent characteristics.

(Means for Solving the Problems) The present invention applies a hot-rolled sheet obtained by hot-rolling a silicon steel slab to one time or two or more times of cold rolling with intermediate annealing. After the final plate thickness, decarburization primary recrystallization annealing is performed, and then an annealing separator is applied to the surface of the steel sheet, followed by secondary recrystallization annealing and anneal annealing. In the manufacturing method, a thin grain-oriented silicon steel sheet is manufactured by performing CBS rolling for at least one pass during the final cold rolling to reduce the plate thickness to 0.18 mm or less.

The inventors have conducted CBS rolling (Contact-Bend-s
(Tretch rolling) was applied to the cold rolling process of grain-oriented silicon steel sheet.Unlike the conventionally known texture, the rolling texture was remarkably improved, the cold rolling reduction was increased, and therefore the product sheet thickness was reduced. Even if the thickness is reduced to 0.18 mm or less, good secondary recrystallized grains can be stably developed, and Goss
It has been found that the secondary recrystallized grains that are strongly integrated in the azimuth direction and the crystal grain size can be made fine.

For the starting material of the present invention, a conventionally known steelmaking method, for example, a converter, using a conventionally known unidirectional silicon steel material component,
Steel is made in an electric furnace, etc., and then made into a slab by the ingot-segmentation method, continuous casting method, etc.
After heating at a high temperature of 1450 ° C to dissociate the inhibitor and form a solid solution, a hot-rolled sheet having a thickness of 1.0 mm to 3.5 mm by hot rolling is used.

This hot-rolled sheet preferably has a composition containing Si of about 2.0 to 4.0%, because if the Si content is less than 2%, the iron loss is large, and if it exceeds 4.0%, the cold workability is poor. Because it deteriorates.

As for the other components, any of the grain-oriented silicon steel material components can be applied, but M is used as an inhibitor to develop the secondary recrystallization strongly integrated in the Goss orientation.
Optimally, one or more selected from nS, MnSe, AlN, Sb, BN, etc. are contained in the steel within a known range.

Next, this hot rolled sheet is cold-rolled once or twice or more to give a final sheet thickness of 0.18 mm or less. The plate thickness here is 0.18 mm
The reason for the following is that a product having a diameter of more than 0.18 mm can be manufactured by a conventional process, and the present invention aims to manufacture a thin grain-oriented silicon steel sheet having excellent iron loss characteristics.

In this case, it is necessary to perform at least one pass of CBS rolling during the primary cold rolling, preferably during the secondary cold rolling.

As shown in FIG. 1, the rolling by the CBS rolling is performed by disposing a floating roll 2 which is a work roll having a smaller diameter than the work rolls 1 and 3 having the same diameter, and winding a steel plate 4 to be rolled around the work roll 1. After passing between the work roll 1 and the floating roll 2 and then bending in the opposite direction along the floating roll 2 and passing between the floating roll 2 and the work roll 3 to wind around the work roll 3. Two
And between the floating roll 2 and the work roll 3 are subjected to tensile bending rolling.

The floating roll 2 is arranged so as to be displaced from the line connecting the central axes of the work rolls 1 and 3 in the direction opposite to the direction F of the force acting on the floating roll 2 by the tension applied to the steel plate 4. Further, the steel plate is provided with sufficient tension to pull the floating roll 2 toward the work rolls 1 and 3.

The diameter of the work rolls 1 and 3 is arbitrary as long as it is larger than that of the floating roll 2, but the diameter of the floating roll 2 is 10 to 40.
mm is preferred. This is because if the diameter is too small, the bending diameter of the steel sheet becomes small, which is likely to cause breakage, and if the diameter is too large, the effect due to bending decreases.

An extremely large rolling reduction in one pass in CBS rolling is not preferable for improving the texture because the rolling pressure increases. Here, the rolling reduction per pass is preferably 50% or less.

Further, CBS rolling and constant velocity rolling may be combined without performing all-pass CBS rolling.

The highest pressure is possible when all-pass CBS rolling is performed,
With the single cold rolling method, which mainly uses AlN as an inhibitor, it is possible to achieve a total reduction of cold rolling of 90% or more, and it is possible to manufacture thin products with a finish thickness of up to about 0.15 mm. It is also possible to achieve a total reduction of 80% or more in the final cold rolling even with the double cold rolling method using MnSe as an inhibitor mainly. Can be made as thin as 0.10 mm.

The current one-time strong cold rolling method using AlN as an inhibitor is cold rolled by an intermediate annealing treatment by a cold rolling two-time method or a two-time method including a current intermediate annealing method using MnSe as an inhibitor. If it is newly applied as the three-time method, it is possible to make a thin grain oriented silicon steel sheet having a thickness of 0.10 mm or less.

By the cold rolling including the CBS rolling as described above, the cold-rolled sheet having the final thickness is subjected to primary recrystallization annealing in a dehydrocarburizing wet hydrogen atmosphere at 750 ° C. or higher. Next, an annealing separator mainly composed of MgO is applied to the surface of the steel sheet, and secondary recrystallization annealing is performed at 800 ° C for 50 hours and purification annealing is performed at 1200 ° C for 5 hours to obtain a product.

(Operation) The thin silicon steel sheet that has been CBS-rolled as described above is greatly characterized in that it undergoes shear deformation without receiving much compressive stress. The results are shown in FIG. 2 (a) and in FIG. 2 (b) comparing the textures of the conventional example. As is clear from the comparison of these (200) pole figures, the texture of cold-rolled sheet has a stable orientation in compression deformation {100} <okl>.
It is characteristic that the azimuth tissue becomes weak. Note that Fig. 2 (a) shows a work roll diameter of 200 mm and a floating roll diameter of 15 mm.
φ, the peripheral speed ratio is 1: 1.4
0.6mm thick steel plate finished to 0.15mm in 4 passes, 2 from the surface
It is a (200) pole figure on the ground surface of 0 μm, and the same figure (b) shows a 0.6 mm thick steel plate finished in 0.15 mm in 4 passes by constant velocity rolling using a 4-high rolling machine with a work roll diameter of 100 mmφ. FIG. 9 is a (200) pole figure of the surface of the rolled plate which was polished in the same manner as above.

After the CBS rolling according to the present invention, after the decarburizing primary recrystallization annealing, comparing with the result of the conventional rolling method shown in FIG.
The decrease of {100} <001> is remarkable, and the Goth direction is {110} <00
It can be seen that 1> is strongly accumulated. It should be noted that FIGS. 3 (a) and 3 (b) are cold rolling similar to those in FIGS. FIG. 3 is a (200) pole figure of a surface that has been annealed and polished by 20 μm from the surface in the plate thickness direction.

As can be seen from the above, the CBS-rolled sample had {100} <001> for both the rolling texture and the decarburized primary recrystallization texture.
The cube orientation component of is weakened.

This cube orientation component is considered to have the same effect as an inhibitor that normally suppresses grain growth, and the reduction of this orientation component means that a secondary reduction that is good even when rolled at a large reduction rate as compared with the ordinary rolling method. This is considered to be the reason why recrystallization can be developed.

In FIGS. 4 (a) and 4 (b), as in the case of FIG. 3 (a), the product rolled by the method of the present invention and also in FIG. 3 (b).
A photograph of a secondary recrystallized grain obtained by performing a macroetch after the secondary recrystallization annealing of the material rolled by the same conventional method as in the above case is shown. The material rolled by the method of the present invention is completely recrystallized in the secondary manner, but it is clear that the secondary recrystallization is incomplete in the comparative example.

(Example) Example 1 C: 0.045 wt%, Si: 3.35 wt%, Mn: 0.068 wt%, S
2.2m containing e: 0.020wt% and Sb: 0.025wt%
A hot rolled sheet with a thickness of m is divided into two equal parts, and the primary cold rolling method is 0.6
Finished to 0 mm and the other to 1.00 mm, and then 1000 ℃ in a continuous annealing furnace.
Intermediate annealing was performed for 3 minutes.

Then, the steel plate finished to 1.00 mm was finished to 0.35 mm by secondary cold rolling, and again subjected to intermediate annealing at 950 ° C. for 3 minutes in a continuous annealing furnace.

Here, the aforementioned 0.60 mm steel plate and 0.35 mm steel plate were divided into two equal parts and divided into samples (A), (B), (C) and (D) in order.

Next, the samples (A) and (C) were rolled using a reverse mill having a work roll diameter of 100 mm, while the (B) and (D) were rolled by a CBS rolling method with a work roll diameter of 100 mm and a floating roll diameter of 20 mm. Where (A) and (B) are 0.15 mm (C),
(D) was finished to 0.10 mm.

Then, decarburization annealing was performed at 840 ° C for 5 minutes in a wet hydrogen atmosphere, MgO was applied to the steel sheet surface, annealed at 850 ° C for 50 hours, and then box annealed at 1200 ° C for 5 hours in a hydrogen stream. . The magnetic properties of the product plate thus obtained are shown in Table 1.

Example 2 C: 0.055 wt%, Si: 3.20 wt%, Al: 0.025 wt%,
A 1.8 mm thick hot-rolled sheet containing N: 0.0065 wt% and S: 0.025 wt% was annealed at 1100 ° C. for 2 minutes, and then the material was divided into two equal parts, which were described in Example 1 above. Roll under the same conditions and finish to 0.15mm thickness after applying MgO
After annealing at 850 ° C for 50 hours, box annealing was performed at 1200 ° C for 5 hours in a hydrogen stream. Table 2 shows the magnetic properties of the product plate thus obtained.

Example 3 C: 0.055 wt%, Si: 3.20 wt%, Al: 0.025 wt%,
3.0 mm containing N: 0.0065 wt% and S: 0.025 wt%
After annealed a hot-rolled sheet at 1100 ° C for 2 minutes, it is first cold-rolled to a sheet thickness of 0.700 mm, then at 1050 ° C.
The material was subjected to intermediate annealing for 1 minute, and the material was divided into two equal parts and rolled under the two conditions described in Example 1 to obtain 0.10 each.
After finishing to a thickness of 0 mm, MgO was applied, followed by annealing at 850 ° C. for 50 hours and then box annealing at 1200 ° C. for 5 hours in a hydrogen stream. Table 3 shows the magnetic properties of the product plate thus obtained.

(Effect of the Invention) According to the present invention, even if the reduction ratio of the final cold rolling is large and the final plate thickness is thin, the crystal orientation is not disturbed,
The magnetic properties, especially iron loss, can be greatly improved.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a CBS rolling procedure according to the present invention, and FIG. 2 is a (200) positive electrode diagram on a surface polished by 20 μm from the surface of a steel sheet rolled by the present invention and a conventional method, and FIG. Fig. 4 is a (200) positive electrode dot diagram of the surface of the steel sheet rolled by the method of the present invention and the conventional method, which was subjected to primary recrystallization annealing and polished by 20 µm from the surface. Fig. 4 shows the steel sheet after final annealing is macro-etched. Is a photograph of the metal structure shown by.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yo Ito 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Division

Claims (1)

[Claims] 1. A hot-rolled sheet obtained by hot-rolling a silicon steel slab is cold-rolled once or twice or more with intermediate annealing to obtain a final sheet thickness, and then removed. In the method for producing a grain-oriented silicon steel sheet, which comprises a series of steps of performing primary recrystallization annealing of carbon, then applying an annealing separator on the surface of the steel sheet, and then performing secondary recrystallization annealing and purification annealing, the final cold A method of manufacturing a thin grain-oriented silicon steel sheet, characterized in that at least one pass is subjected to CBS rolling during rolling to reduce the sheet thickness to 0.18 mm or less.