JPH06306469A - Production of grain oriented silicon steel sheet excellent in magnetic property - Google Patents

Abstract

PURPOSE:To reduce an iron loss value and to improve magnetic flux density by using a tandem mill at the time of cold rolling of silicon-containing steel sheet with specific composition, specifying the draft at final cold rolling, and performing rolling on a nonlubricating system. CONSTITUTION:A hot rolled plate of silicon-containing steel, containing 0.02-0.1% C and 2.5-4.0% Si and also containing AIN- or MnS-type inhibitor component, is cold-rolled once or cold-rolled twice, while process-annealed between cold rolling stages, to final sheet thickness. At this cold rolling, a cold tandem mill is used and final cold rolling pass is done at 0.5-10% draft, and rolling is done on a nonlubricating system. After cold rolling, the resulting sheet is subjected to decarburizing annealing and to finish annealing, by which the grain oriented silicon steel sheet excellent in magnetic properties can be obtained. It is preferable to use, as work roll at final stand, a roll having 0.5-3mum surface roughness Ra and 100-400mm diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a unidirectional silicon steel sheet having a low iron loss value and a high magnetic flux density by a highly productive cold rolling method using a cold tandem rolling mill having a plurality of stands. The present invention relates to a manufacturing method to be obtained.

[0002]

2. Description of the Related Art Unidirectional silicon steel sheets are mainly used as iron cores for transformers and electric equipment, and are required to have excellent magnetization characteristics (high magnetic flux density) and low iron loss. In particular, a unidirectional silicon steel sheet having a high magnetic flux density is advantageous for downsizing and high performance of electrical equipment such as a transformer, and therefore, further improvement of the magnetic flux density is required as a product characteristic. In order to meet such a requirement, the orientation of the crystals should be extremely high after finishing annealing, that is, Goss orientation: {110} <00
It is necessary to highly integrate the crystal grains in the 1> orientation in the rolling direction.

Regarding cold rolling in the process of manufacturing a series of unidirectional silicon steel sheets, there are roughly two types of conventional rolling equipment. One is a multi-stage rolling mill that applies small-diameter work rolls, and a Zenzimer rolling mill is often used. The diameter of the work roll of this Zenzimer rolling mill is 70
It is about 130 mm. The other is a tandem rolling mill, which can produce a silicon steel sheet with high efficiency, as disclosed in JP-A-61-132205. In the tandem rolling mill, the rolling diameter is 300 to 600 mm, which is larger than that of the Zenzimer rolling mill because the rolling is performed at high speed.

By the way, in order to obtain good magnetic properties as described above, {1} is applied in the rolling direction of the unidirectional silicon steel sheet.
It is necessary to highly integrate the crystal grains of the 10} <001> orientation. Here, it is shown in JP-A-49-34417 that the roll diameter during cold rolling affects the orientation of the crystal grains and thus the magnetic properties of the unidirectional silicon steel sheet. Has a great effect on the magnetic properties of unidirectional silicon steel sheets, and the work roll diameter is 300 mm or less, especially 100
It is said that excellent magnetic properties can be obtained in the case of rolls with a small diameter of about mm.

[0005]

Rolling with a work roll having a relatively small diameter as disclosed in JP-A-49-34417 is performed by single-stand rolling using a multi-stage rolling mill such as a Zenzimer rolling mill. Therefore, the productivity is low, and there is a drawback that a plate surface defect called a heat streak is likely to occur between the roll and the plate when rolling at a high speed. Also,
When a unidirectional silicon steel sheet is rolled by a conventional tandem rolling mill as disclosed in Japanese Patent Laid-Open No. 61-132205, the work roll diameter is large, so that the above-mentioned Japanese Patent Laid-Open No. For the reason described in Japanese Patent Publication No. Sho 49-34417,
There is a drawback that a grain-oriented silicon steel sheet having excellent magnetic properties cannot be obtained. Furthermore, it is possible to incorporate a work roll of a relatively small diameter into the latter stage stand of the tandem rolling mill for rolling. There is a phenomenon called the neutral point that deviates from the roll bite, stable rolling at high speed rolling becomes difficult, there is a drawback that plate thickness fluctuation occurs and off gauge increases, so small diameter roll is applied to tandem rolling mill It was difficult to do.

The present invention advantageously solves the above-mentioned problems, and it is possible to obtain a magnetic property superior to that obtained by using a conventional multi-stage rolling mill by using a cold tandem rolling mill having high productivity. It is an object of the present invention to propose a method of manufacturing a unidirectional silicon steel sheet that can be manufactured.

[0007]

Means for Solving the Problems The present invention, which achieves the above object, contains C: 0.02 to 0.1 wt%, Si: 2.5 to 4.0 wt%, and further contains an AlN-based or MnS-based inhibitor component. 1 time or intermediate annealing is sandwiched between hot rolled steel sheets 2
In the method for producing a unidirectional silicon steel sheet by a series of steps of performing decarburization annealing and then finishing annealing after performing cold rolling once to obtain the final plate thickness, the cold rolling uses a cold tandem rolling mill. The final cold rolling pass is reduced by 0.5% or more and 10%.
The method for producing a unidirectional silicon steel sheet having excellent magnetic properties, which is characterized by being performed below and without lubrication (first invention).

Further, the present invention provides C: 0.02 to 0.1 wt%,
Si: Contains 2.5 to 4.0 wt%, and also AlN or MnS
For hot-rolled silicon steel containing silicon containing inhibitor system 1
In the method for producing a unidirectional silicon steel sheet by a series of steps of performing decarburization annealing and then finishing annealing after performing cold rolling twice with intermediate or intermediate annealing to obtain a final plate thickness, the cold rolling is Using a cold tandem rolling mill, and using a roll having a surface roughness Ra of 0.5 μm or more and 3 μm or less and a diameter of 100 mm or more and 400 mm or less as a work roll of the final stand, the final cold rolling pass is rolled down. It is a method (second invention) for producing a unidirectional silicon steel sheet having excellent magnetic properties, which is characterized by being performed at 0.5% or more and 10% or less.

[0009]

The following chemical components and their ranges are advantageously suitable for the raw material components of the hot rolled sheet in the present invention. C: 0.02 to 0.1 wt% C not only effectively contributes to homogenization of the hot-rolled structure and the cold-rolled structure, but also in the recrystallized structure in the process of repeating cold rolling and annealing to obtain the final plate thickness. It is an effective component for increasing the degree of integration of the Goss azimuth component. However, if it is less than 0.02wt%, its effect is poor. The temperature for melting rises, causing a decrease in inhibitor grain growth suppressing effect due to insufficient solid solution, and decarburization annealing during primary recrystallization becomes difficult, so the range is set to 0.02 to 0.1 wt%. Si: 2.5 to 4.0 wt% Si is effective in increasing the electric resistance and reducing the iron loss, but if it is less than 2.5 wt%, a sufficient decrease in the iron loss cannot be expected, and during high temperature annealing. A part or all of the steel sheet undergoes γ-transformation, resulting in disordered crystal orientation. On the other hand, if it exceeds 4.0 wt%, cold rolling becomes extremely difficult and cracking occurs, so its content should be 2.5-4.0 wt%. Within that range.

The inhibitor may be either MnS type or AlN type, or a combination of both. For example, in the case of MnS type, Mn: 0.03 to 0.15 wt%, S: 0.008 to 0.035 wt%
It is a degree. Also, one or two selected from Se and Sb
Species: 0.008 to 0.08 wt% can also be contained together. In the case of AlN system, Al: 0.01-0.05wt%, N: 0.00
It is preferable to contain about 4 to 0.01 wt%.

The molten steel prepared in the above composition is subjected to continuous casting or ingot-slab rolling to form a slab, which is then hot-rolled. After the hot rolling, the hot rolled sheet is annealed as required, and after pickling, cold rolling is performed once or twice with an intermediate annealing.

In the first invention, cold rolling is performed by using a cold tandem rolling mill, in which the final cold rolling pass is rolled down.
It is important to perform it in the range of 0.5% to 10% and without lubrication. As described above, the influence of the work roll diameter on the magnetic properties of the unidirectional silicon steel sheet is known, but the inventors have found that the work roll having a relatively large roll diameter, such as the work roll used in the tandem rolling mill. In the case of using, cold rolling conditions are variously changed and cold rolling experiments are repeated,
As a result of investigating the iron loss and the magnetic flux density of the product, it was found that, by making the final stand unlubricated, magnetic properties superior to those in the past can be obtained. That is,
Fig. 1 shows the case where the work roll diameter of the final stand is changed and lubricated and rolled (circle) and non-lubricated (circle).
In particular, as shown in the graph of the result of the investigation on the influence on the magnetic properties, the magnetic properties after finish annealing are improved by rolling the final pass without lubrication. See also FIG.
Figure 2 shows the results of an examination of the effect on the magnetic properties when cold rolling is performed by changing the reduction ratio of the final pass using a rolling mill with a work roll diameter of 325 mm in the final stand. However, this reduction rate is a reduction rate under the condition of no lubrication. As is clear from FIG. 2, the reduction rate is 0.
The magnetic property is excellent in the range of 5 to 10%.

[0013] In the following, the final stand is non-lubricated and cold-rolled in a final pass rolling reduction range of 0.5 to 10%,
The reason why excellent magnetic characteristics are obtained will be described. First, the effect of non-lubricating rolling is that under the conditions, the coefficient of friction between the roll and the plate increases, the shear deformation amount increases in the surface layer of the plate, and Goss-oriented crystal grains are generated there, resulting in the degree of integration. Is estimated to improve. That is, in FIG. 3, cold rolling is performed by a tandem rolling mill with a work roll diameter of 325 mm, unlubricated rolling with a final pass reduction of 5%, and the texture of the surface layer of the decarburized steel sheet is measured. As shown in the results, it can be seen that the {110} strength is increased by making the last pass unlubricated. Further, it is considered that the {110} <001> oriented crystal grains were grown by the subsequent finish annealing and the magnetic characteristics were improved.

When the reduction ratio of the final pass is small, that is,
If it is less than 0.5%, the amount of shear deformation is not sufficient, so that the {110} texture after decarburization annealing does not sufficiently develop, and improvement in magnetic properties after finish annealing cannot be obtained. Further, when the rolling reduction is large, the accumulation of the Goss-oriented crystal grains becomes strong, but the shear deformation reaches the inside of the plate and the strength of the matrix (mainly the strength of {111}) becomes small, so that the Goss-oriented crystal grains are reduced. Does not grow sufficiently and the magnetic properties after finish annealing deteriorate. Therefore, the upper limit of the rolling reduction is 10%.

The roll diameter is not particularly limited, but is preferably 300 mm or more and 500 mm or less. this is,
Rolls smaller than about 300 mm may cause bearing seizure and heat streak at rolling speeds of over 1000 mpm, while rolls of more than about 500 mm increase the rolling load in non-lubricated rolling and lead to the target strip. This is because there is happiness that the thickness cannot be achieved.

Next, in the second invention, during cold rolling using a cold tandem rolling mill, the surface roughness Ra as a work roll of the final stand is 0.5 μm or more and 3 μm or less and the diameter is 100 mm.
It is essential that the final cold rolling pass be performed with a rolling reduction of 0.5% or more and 10% or less using a roll of 400 mm or more.
As a result of various cold rolling using a tandem rolling mill, the inventors can obtain magnetic properties superior to conventional ones even by performing a final pass rolling using a work roll having particularly high roughness. I found a thing. That is, FIG.
In addition, when the surface roughness of the work roll (diameter 325 mm) of the final stand was changed and the final pass rolling was performed at a reduction rate of 5%, the results of an investigation of the effect on the magnetic properties were shown in the graph. As the roughness increases, the magnetic properties after finish annealing improve. In addition, Fig. 5 investigates the influence on the magnetic properties when cold rolling is performed by changing the reduction ratio of the final pass by a rolling mill with a work roll diameter of the final stand of 325 mm and a surface roughness of 1.0 µm Ra. The results are further shown in Fig. 6 where the work roll surface roughness of the final stand is 1.0 μ.
The graphs show the results of investigations on the effect on magnetic properties when cold rolling was performed by changing the work roll diameter of a rolling mill of m Ra. As is clear from FIGS. 5 and 6, the rolling reduction is in the range of 0.5 to 10%, and the roll diameter is
The range of 100-400 mm has excellent magnetic properties.

The work roll of the final stand has a surface roughness Ra of 0.5 μm or more and 3 μm or less and a diameter of 100.
The reason why excellent magnetic properties can be obtained by cold rolling the final cold rolling pass with a rolling reduction of 0.5% or more and 10% or less using a roll of mm to 400 mm will be described.
First, the effect of increasing the surface roughness of the work roll is that the coefficient of friction between the roll and the plate increases under that condition, and the amount of shear deformation increases in the surface layer of the plate, resulting in the formation of Goss-oriented crystal grains. Therefore, it is estimated that the degree of integration will improve. That is, in FIG. 7, cold rolling is performed with a tandem rolling mill with a work roll diameter of 325 mm at a rolling reduction of 5% in the final pass, and the measurement results of the texture of the surface layer of the decarburized steel sheet are shown. As shown, conventional (WR roughness 0.
It can be seen that the {110} intensity is larger than 1 μm Ra). Furthermore, by the subsequent finish annealing, {11
It is considered that the 0} <001> oriented crystal grains grew and the magnetic characteristics were improved. If the surface roughness is less than 0.5 μm Ra, the friction coefficient cannot be increased, the amount of shear deformation in the surface layer is small, and it is inconvenient if the Goss orientation cannot be sufficiently accumulated. Since the coefficient becomes too large and the load becomes large and it cannot be rolled down, the range is 0.5 to 3 μm Ra.

Similarly to the above, when the rolling reduction in the final pass is small, that is, when it is smaller than 0.5%, the amount of shear deformation is not sufficient, so that the {110} texture after decarburization annealing is sufficiently developed. No improvement in magnetic properties after finish annealing can be obtained. Further, when the rolling reduction is large, the accumulation of Goss-oriented crystal grains also becomes strong, but the shear deformation extends to the inside of the plate,
Since the strength of the matrix (mainly the strength of {111}) decreases, not only the Goss-oriented crystal grains do not grow sufficiently but the magnetic properties after finish annealing deteriorate, but the rolling load increases and Rolling may not be possible due to limitations. Therefore, the upper limit of the rolling reduction is 10%.

In the range of the rolling reduction and the roughness of WR, the roll deformation of the roll of the final stand is smaller than 100 mm, the amount of shear deformation is not sufficient.
10} Texture does not develop sufficiently, magnetic properties cannot be improved after finish annealing, and if it exceeds 400 mm, shear strain increases and Goss-oriented crystal grains develop, but the matrix strength decreases. It is considered that the magnetic properties do not improve.

The diameter of rolls other than the final stand is not particularly limited, but is preferably 300 mm or more and 500 mm or less. This is for rolls smaller than 300 mm
At rolling speeds over 1000 mpm, bearing seizure and heat streak may occur, while 500 mm
This is because if it exceeds a certain level, the rolling load increases in unlubricated rolling, and it may be difficult to achieve the target sheet thickness.

[0021]

【Example】

Example 1 FIG. 8 schematically shows an example of a cold tandem rolling mill suitable for carrying out the first invention. In FIG. 8, an example of four stands is shown. In the figure, numeral 1 is a silicon steel plate, which is sequentially rolled by the work roll 2 from the preceding stand to a predetermined thickness. At this time, in the former three stands, the rolling oil supply nozzle 3
Lubricating oil is supplied from. Lubricating oil is a low-concentration rolling oil whose main component is natural oil or fat. An oil removing roll 4 is provided between the third stand and the final stand so that the rolling oil on the surface of the steel sheet can be removed. Then, in the final stand, the hot water is sprayed from the nozzles 5, while the hot water is pressed down to the final plate thickness and wound on the reel 6.

The rolling conditions will be described in detail below, and the effect of the present invention will be clarified by a comparative example with the conventional method. (Rolling method of the present invention) Rolling mill: tandem rolling mill consisting of four stands shown in FIG. 8, work roll diameter 325 mm Rolling material: grain-oriented silicon steel, cold tandem rolling mill entrance side plate thickness 0.7 mm, exit side plate thickness 0.23 mm Rolling speed: 1200m / min at 4th stand Final pass rolling reduction: 5%

(Conventional rolling method) Rolling mill: Single-stand 20-stage Sendzimer rolling mill, 4-pass lubrication rolling, work roll diameter 100 mm Rolled material: grain-oriented silicon steel plate, side plate thickness of rolling mill 0.7 mm,
Plate thickness after 4 passes 0.23mm Rolling speed: 300 m / min in each pass

The rolling method of the present invention and the conventional rolling method have substantially the same components before cold rolling, hot rolling conditions, primary recrystallization annealing and finish annealing conditions after cold rolling, and C :
0.03wt%, Si: 3.41wt%, Mn: 0.07wt%, S: 0.02wt%
%, Al: 0.029 wt%, N: 0.008 wt%, Se: 0.02 wt% molten steel by continuous casting into a slab with a thickness of 200 mm, and then this slab is heated for 1 hour at 1350 ° C A hot rolled sheet with a plate thickness of 2.5 mm is obtained by rolling, subjected to hot rolling sheet annealing at 1000 ° C for 5 minutes, pickling, and then subjected to cold rolling. After cold rolling, 850 ° C, 3 After decarburization annealing for 1 minute and applying the annealing separating agent containing MgO as the main component,
Finished annealing was performed at 00 ° C for 20 hours.

The results of examining the magnetic properties of the thus-obtained unidirectional silicon steel sheet are shown in FIG. From FIG. 9, it can be seen that according to the present invention, the magnetic characteristics are remarkably improved as compared with the conventional manufacturing method.

Embodiment 2 FIG. 10 schematically shows an example of a cold tandem rolling mill suitable for carrying out the second invention. 10 has almost the same structure as that of FIG. 8, except that the lubricating oil is supplied from the rolling oil supply nozzle 3 also in the final stand, and the surface roughness of the work roll of this final stand is in the range of 0.5 μm Ra to 3 μm Ra. The difference is that the roll 7 is used. The details of the rolling conditions will be described below, and the effect of the present invention will be clarified by a comparative example with the conventional method.

(Rolling Method of the Present Invention) Rolling Mill: Tandem rolling mill consisting of four stands shown in FIG. 10, work roll diameter 325 mm, work roll surface roughness 1.0
μm Ra rolled material: grain-oriented silicon steel sheet, cold tandem rolling mill side plate thickness 0.7 mm, output side plate thickness 0.23 mm Rolling speed: 1200 m / min at 4th stand Final pass reduction: 5%

(Conventional rolling method) Rolling mill: 20-stage Zenzimer rolling mill with single stand, 4-pass lubrication rolling, work roll diameter 100 mm Rolled material: grain-oriented silicon steel sheet, side thickness of rolling mill 0.7 mm,
Plate thickness after 4 passes 0.23mm Rolling speed: 300 m / min in each pass

As a comparative example, a cold roll was also prepared in which the work roll roughness of the final stand was the same as that of the first to third stands (0.1 μm Ra). Further, in the rolling method of the present invention and the conventional rolling method, the components before cold rolling, hot rolling conditions, primary recrystallization annealing and finish annealing conditions after cold rolling are almost the same, and C: 0.03 wt. %, Si: 3.4 wt% of molten steel is continuously cast into a slab with a thickness of 200 mm.
Then, this slab is heated at 1350 ° C. for 1 hour and then hot rolled to obtain a hot rolled sheet having a thickness of 2.5 mm, which is subjected to hot rolling annealing at 1000 ° C. for 5 minutes, pickling, and cold rolling. After cold rolling, perform decarburization annealing at 850 ° C for 3 minutes in a wet hydrogen atmosphere, apply an annealing separator containing MgO as the main component, and then
Finished annealing was performed at 00 ° C for 20 hours.

FIG. 11 shows the results of examining the magnetic characteristics of the thus-obtained unidirectional silicon steel sheet. From FIG. 11, it is understood that according to the present invention, the magnetic characteristics are remarkably improved as compared with the conventional manufacturing method.

[0031]

Industrial Applicability The method for producing a unidirectional silicon steel sheet according to the present invention uses a tandem rolling mill for cold rolling, and performs non-lubricating rolling or surface rolling so that shear deformation of the sheet surface becomes large during final pass rolling. By rolling with a work roll having a high degree of roughness, it has become possible to obtain a unidirectional silicon steel sheet having excellent magnetic properties with high efficiency.

[Brief description of drawings]

FIG. 1 is a graph showing the influence on the magnetic properties of lubricated rolling and non-lubricated rolling performed by changing the work roll diameter of the final stand.

FIG. 2 is a graph showing the influence of the rolling reduction of the final pass on the magnetic properties of the product.

FIG. 3 is a diagram showing strength improvement of a texture of a steel sheet surface layer by non-lubricating rolling.

FIG. 4 is a graph showing the influence of cold rolling performed by changing the surface roughness of the work roll of the final stand on the magnetic properties.

FIG. 5 is a graph showing the influence of the rolling reduction of the final pass on the magnetic properties of the product.

FIG. 6 is a graph showing the influence of work roll diameter on the magnetic properties of products.

FIG. 7 is a diagram showing an improvement in the strength of the texture of the steel sheet surface layer by rolling using a roll having a large surface roughness.

FIG. 8 is a schematic view of an example of a cold tandem rolling mill suitable for carrying out the first invention.

FIG. 9 is a diagram showing a comparison of magnetic characteristics of unidirectional silicon steel sheets obtained by the rolling method of the first invention and the conventional rolling method.

FIG. 10 is a schematic view of an example of a cold tandem rolling mill suitable for carrying out the second invention.

FIG. 11 is a diagram showing a comparison of magnetic properties of unidirectional silicon steel sheets obtained by the rolling method of the second invention and the conventional rolling method.

[Explanation of symbols]

 1 Silicon-containing steel plate 2 Work roll 3 Rolling oil supply nozzle 4 Oil cutting roll 5 Nozzle 6 Reel 7 roll

Front page continued (72) Inventor Isao Akagi 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Prefecture (No house number) Inside the Mizushima Steel Works, Kawasaki Steel Co., Ltd. None) Kawasaki Steel Co., Ltd. Mizushima Steel Works (72) Inventor Masao Akita 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. (72) Inventor Masahisa Kitahama Kawasaki, Chuo-ku, Chiba City, Chiba Prefecture Town No. 1 Kawasaki Steel Co., Ltd. Technical Research Headquarters (72) Inventor Hiroki Tomita 1-chome, Mizushima Kawasaki-dori, Mizushima Kurashiki City, Okayama Prefecture (No house number) Kawasaki Steel Co., Ltd. Mizushima Steel Works

Claims (2)

[Claims] 1. A hot rolled sheet of silicon steel containing C: 0.02 to 0.1 wt%, Si: 2.5 to 4.0 wt% and further containing an AlN-based or MnS-based inhibitor component is sandwiched once or by intermediate annealing. In the method for manufacturing a unidirectional silicon steel sheet by a series of steps of performing decarburization annealing and then finish annealing after performing cold rolling twice to obtain the final plate thickness, the cold rolling is performed by a cold tandem rolling mill. A method for producing a unidirectional silicon steel sheet with excellent magnetic properties, which comprises performing a final cold rolling pass with a rolling reduction of 0.5% or more and 10% or less and without lubrication. 2. A hot rolled sheet of silicon steel containing C: 0.02 to 0.1 wt%, Si: 2.5 to 4.0 wt% and further containing an AlN-based or MnS-based inhibitor component is sandwiched once or by intermediate annealing. In the method for manufacturing a unidirectional silicon steel sheet by a series of steps of performing decarburization annealing and then finish annealing after performing cold rolling twice to obtain the final plate thickness, the cold rolling is performed by a cold tandem rolling mill. Using a roll having a surface roughness Ra of 0.5 μm or more and 3 μm or less and a diameter of 100 mm or more and 400 mm or less as the work roll of the final stand, the final cold rolling pass is reduced by 0.5% or more and 10% or less.
A method for producing a unidirectional silicon steel sheet having excellent magnetic properties, which is characterized by: