JPS60103121A - Production of grain oriented silicon steel sheet having high magnetic flux density and low iron loss - Google Patents

Abstract

PURPOSE:To obtain stably a titled steel sheet by shifting the integrated crystal nucleus parts which are the source for generating the secondary recrystal grains in the (110) <001> orientation formed near the surface of a hot rolled steel sheet toward the central part of the sheet thickness. CONSTITUTION:A silicic steel slab is subjected to hot rolling after rough rolling and continuous finish rolling and is made into a final sheet thickness by one or two passes of cold rolling, then a separating agent for annealing is coated thereon after decarburization and primary recrystallization annealing and the steel sheet is subjected to final annealing to obtain a grain oriented silicon steel sheet. The diameter of rolling rolls is made successively smaller from the upper stream side toward the down stream side in the stage of the above-described hot rolling of this method. For example, the diameter of the rolling roll of the 1st - 3rd stands is made D1 and the diameter of the 4th, 5th and 6th stands is made into the successively smaller values D2, D3, D4 than D1. The region (width) indicating the max. value of the intensity of the (110) face is thus expanded and the position indicating said max. value moves toward the center of the sheet thickness. The grain oriented silicon steel sheet having high magnetic flux density and low iron loss is obtd. although the reason is not fully elucidated.

Description

Detailed Description of the Invention (Summary of the Technology) The present invention relates to a method for producing grain-oriented silicon steel sheets with high magnetic flux density and low core loss, and particularly relates to a method for producing grain-oriented silicon steel sheets with high magnetic flux density and low core loss. We propose a method for advantageously manufacturing grain-oriented silicon steel sheets with extremely high magnetic flux density and low iron loss by moving the position where secondary recrystallized grains are generated closer to the center of the sheet thickness.

(Prior art) Unidirectional silicon steel sheets are mainly used as iron cores for transformers and other electrical equipment, and their properties include excellent magnetization properties, that is, magnetic flux density (B). (typically) is required to have high iron loss and low iron loss.

In general, the first effective method for improving the magnetic properties of unidirectional silicon steel sheets is to
00-1 > The axis is highly aligned in the rolling direction,
The second is to reduce as much as possible the impurities and precipitates remaining in the final product. By adopting these known methods, various improvements have recently been made in the production of unidirectional silicon steel sheets, and their magnetic properties have improved over the years, and today they have a high magnetic flux density with a Blo value of 1.8.9T or more. , the W17150 value is 1.05 W/9, so that a low iron loss can be obtained.

In this way, the performance of grain-oriented silicon steel sheets has improved, particularly in the field of iron core materials, as the energy crisis a few years ago led to the desire to further reduce power loss. There has been an increasing trend toward high-grade unidirectional silicon steel sheets with low iron loss.

(Motivation for the Invention) By the way, the present inventors have been conducting basic research on the development of secondary recrystallized grains in unidirectional silicon steel sheets.
In order to obtain grain-oriented silicon steel sheets that exhibit higher magnetic flux density and lower core loss values, conventional investigations and studies using X, li1 diffraction alone are insufficient, as only phenomenological considerations can be made. It turns out. Therefore, the inventors of the present invention have proposed the method described in Japanese Unexamined Patent Publication No. 55-83660 or Utility Model Application No. 55-88884.
We are proceeding with the development of a transmission thin cell device using a scanning electron image, as proposed in No. As a result of detailed investigation of crystal plates, initial secondary recrystallization plates, etc., we have obtained new findings as listed below.

(1) (110) (o O1) The locations where crystal nuclei, which are the sources of secondary recrystallized grains, accumulate are approximately all from the surface of the hot-rolled sheet. This occurs from a strain-free region in (110) (001) oriented elongated grains (secondary recrystallized grain generation source) that exist at depth.

(2) Secondary recrystallization nucleation in the (110) (o 01 ) orientation occurs due to struture memory from hot rolling.
1st cold rolling → intermediate annealing → 2nd cold rolling → decarburization/1st recrystallization power Z
Dull stingray JI! and occurs preferentially at a depth of 30-50μ from the surface.

(3) Secondary recrystallization nuclei after decarburization and primary recrystallization annealing are composed of several <11 (+) (o O1) oriented crystal grains that coalesce (5ub (<rain coalescence
) L/ large crystal grains made of matrix grains 2~
It is 6 times more.

(4) At the initial stage of secondary recrystallization annealing, (110)<0
Large crystal grains with 01> orientation grow preferentially.

Based on the above findings, the present inventors have determined that a good (1
10) When heating the slab for secondary recrystallization nucleation in the (001) orientation, as already proposed by the present inventors in Japanese Patent Application No. 57-154887, it is necessary to make the heating temperature uniform on the upper and lower surfaces of the slab. did. As a result, the generation rate of secondary recrystallized grain generation nuclei in the (110) (001) orientation that is formed near the surface during hot rolling can be uniformly and highly concentrated on both the upper and lower surfaces, and the magnetic properties are improved. It was done.

Therefore, the inventors conducted a detailed study on the hot rolling conditions and other aspects.

As a result, when manufacturing a series of unidirectional silicon steel sheets, (110) <001> is generated near the surface of the hot rolled steel sheet.
If the accumulation of crystal nuclei, which is the source of secondary recrystallized grains in orientation, is generated closer to the center of the plate thickness than in the past, fine secondary recrystallized grains can be developed, and B is 1. 91 T or higher, W, 775o: It was found that it exhibits excellent magnetic properties of 0.99 W/ic90.

Furthermore, the above knowledge can be achieved with high reliability by hot rolling in which the roll diameter is preferably gradually reduced from the upstream side to the downstream side during hot finish rolling. I also found out that.

(Objective of the Invention) An object of the present invention is to stably obtain a thick plate with a crystal nucleus accumulation portion that becomes a source of secondary recrystallized grains with (110) <001> orientation.

(Structure of the Invention) Preferred examples of the hot rolling conditions of the present invention that achieve the above object are as follows. The composition of the material is heavy ffi%, S
i 8.35%, 00.048%, seo, oxs%,
S't) 0.025%, No. 0.015%, the remainder being unavoidable impurities and 1re. After soaking and heating the silicon steel slab at 1820°C, rough rolling and continuous hot rolling were performed. A hot rolled sheet with a thickness of 2.7 as was used.

The continuous hot finish rolling is shown in (a) in Figure 1.

The finishing rolls (b) and (c) were used. In other words, the rolling conditions shown in (a) are conventional continuous rolling conditions, and the diameter of the rolling rolls from the A1 stand to the A6 stand (the work rolls indicated by diagonal lines in Fig. 1) are the same as D□. , The rolling conditions shown in (b) are &
The rolling roll diameter from the 1st stand to the A8 stand is Do, which is the same as in (a), but the rolling roll diameters D2 and Da*D4 from the A4 stand to the A6 stand are smaller than those of Do, and the rolling roll diameters from the A4 stand to the A6 stand are smaller than those of Do, and the rolling roll diameters from the A4 stand to the A6 stand are smaller than Do. The diameter of the rolls is gradually decreased, and the rolling conditions shown in (c) are such that the diameter of the rolling rolls is gradually decreased from the &1 stand to the 6 stand.

These hot-rolled sheets were uniformly annealed at 900°C for 8 minutes and then subjected to primary cold rolling at a rolling reduction of approximately 70%.
After performing intermediate annealing at ℃ for 3 minutes, secondary cold rolling was performed at a rolling reduction of about 65% to obtain a final cold rolled sheet with a rolling thickness of 0.8. After that, decarburization annealing that also serves as primary recrystallization in wet hydrogen at 820°C is applied, and then an annealing separator containing MgO as the main component is applied.
Next, secondary recrystallization annealing was performed at 850°C for 50 hours.
Purification annealing was performed at 1180°C for 5 hours in H2 gas.

The magnetic properties of the product at that time are shown in FIGS. 2 and 8, and the change in (110) plane strength (X-ray inverse strength) in the thickness direction of the hot rolled sheet is shown in FIG.

Spear ＾ R o J arrogance 'I+ C a shi n 舊オ
Δζ Yuru' mouth n\ Y inside - Iruhi J/I-7
As is clear, under the continuous finish rolling conditions of the conventional method of equal diameter roll rolling (A), Bo. is 1.90 T.

W17/60 is about 9 to 1.04 W/, whereas the present invention example (B) of the upstream side equal diameter downstream side different diameter roll according to the present invention and the present invention example (0
) So, Bo. is 1.916 to 1.918 T,,W
It is noteworthy that 17150 has an extremely improved magnetic flux density and iron loss of 0.98 to 0.97 W/9. Further, in a comparison of conditions (B) and (3), which are examples of the hot rolling conditions of the present invention, the conditions of example (0), which gradually reduce the diameter, have slightly better characteristics.

As is clear from the graph of the (110) plane strength change in the thickness direction of the hot-rolled sheet (not shown in Figure 4), in the conventional method (A) using rolls of equal diameter, from the surface of the hot-rolled sheet in the thickness direction About issue. The strength of the (110) plane reaches its maximum at a depth of about 100 mL, and rapidly weakens at deeper positions. On the other hand, inventive examples (B) and (
0), the area showing the maximum value of the (110) surface strength (
Width) is larger than the conventional example (A), and (110)
It is noteworthy that the position of the secondary recrystallization nucleus generation source in the (001) orientation, that is, the position showing the maximum value of the (110) plane strength, has moved toward the center of the plate thickness. (B)l of the method of the present invention
C) In G, the position of maximum (110) plane strength is
The depth of the hot-rolled sheet toward the center of its thickness is approximately cloudy to stormy, and at this position, it exhibits excellent magnetic properties as shown in FIGS. 2 and 3.

Although the reason for the improvement in properties by moving the position of the secondary recrystallization nucleus generation source in the (110)(001) direction toward the center of the plate thickness has not been completely elucidated,
As is clear from the comparison shown in Figures 2 and 8, the frequency of occurrence of secondary recrystallized nuclei in the (110) (001) orientation increases and the position of the secondary recrystallization nuclei moves in the thickness direction. It is true that this phenomenon occurs due to differences in deformation behavior during hot rolling. Therefore, if the diameter of the rolling rolls is gradually decreased toward the downstream side, the indentation effect will occur and the phenomenon described above will occur. It gives birth to

As explained above, fine grain (110) (OO1,)
...The hot rolling conditions for developing secondary recrystallized grains that are strongly concentrated in the orientation are as follows: the presence of many (110)(001) oriented crystal grains near the surface of the hot rolled sheet, as is already known. In addition to making the (lto)(
The generation position of crystal grains with the Ool) orientation is shifted from near the surface toward the center of the plate thickness, and by creating such a situation, the orientation of the crystal grains is originally a stable cold rolling orientation.
100) <o], 1> orientation crystal grains can be reduced as much as possible. It is believed that as a result of satisfying these conditions, the present invention is able to manufacture unidirectional silicon steel sheets with high magnetic flux density and low iron loss.

In response to this, several attempts have been proposed to change the texture during hot rolling, and the representative one proposed in Japanese Patent Publication No. 58-5970 generates an asymmetric flow in the vertical direction. There is a method of rolling at different circumferential speeds. However, although this known variable circumferential speed rolling method is effective in changing the texture by introducing an asymmetrical plastic flow on the upper and lower surfaces in the thickness direction, it is difficult to change the texture (110) as in the present invention. It is impossible to bring the generation position of crystal grains with the 001) orientation closer to the center of the plate thickness.

As is clear from the above explanation of the present invention in comparison with the prior art, the rolling roll diameter of the continuous finishing mill shown in C as a preferred embodiment is gradually reduced to (110)<00.
The continuous hot rolling method in which the source of secondary recrystallization nuclei in the 1> orientation is shifted to the center of the plate thickness is fundamentally different from previous known techniques, and the effects achieved by it are is also far superior.

Next, the specific details of the manufacturing process in the present invention will be described below based on a preferred example in which the rolling roll diameter is changed between the upstream side and the downstream side.

The starting material used in the method of the present invention is a steel made by a known steelmaking method such as a converter furnace and then made into a slab by ingot making or continuous casting. A method according to the method is preferably used.

The released material, like the conventional well-known silicon steel sheet, has Si 2.0-4.0%, for example.
, MO0,005P-0,05%, sb o, o O5
~0.25%, S or 880.005~0.05%
A composition containing ■si 2.0 to 4.0%, IO,
01-0.05%, SO, 005-0.05%, N
Composition containing O,001 to 0.01%, or ■Si
2.0~4゜0%, SO, 005~0.05%, B
O,0008~0.0040%, NO,001~o,
Compositions such as those containing 1% o are preferably employed.

Next, the silicon steel slab obtained by continuous casting or ingot-blooming method is heated to 1250°C in order to dissociate and dissolve MnS or MnSe contained in the material
It is necessary to perform high temperature heating of ~14oo'C. This high-temperature heating is applied to the (
In order to obtain crystal grains with a strong 110) (001) orientation, it is necessary to perform soaking heating.

After heating, the slab is subjected to rough rolling and hot finish rolling.
It is said to be a hot-rolled sheet with a thickness of ~3 mm. In the present invention, the relationship with product characteristics (iron loss) is shown under the condition that the finishing roll diameter during hot finishing rolling is gradually decreased in the rolling direction. As can be seen from this figure, the best characteristics are obtained when the ratio of the upstream and downstream roll diameters is 1.1 to 5 times, preferably 1.2 to 4.5 times. You can see what you can get. Regarding the combination of rolling roll diameters of such a continuous finishing mill, it is advantageous to gradually reduce the diameters of the product in the rolling direction as shown in the condition shown in Fig. 1-(c). As shown in Figure-(B), the diameter of the first half roll from A1 to A8 or the diameter of the roll from A1 to A2 should be the same, and then the diameter of the second half reel from A4 to A6 or from A8 to BLACK 6 should be the same. Even if it is made smaller, it is possible to improve the magnetic properties of the product. In addition, there is no particular restriction on the difference in roll diameter between the large and small rolls, but it is better to avoid sudden changes as they tend to cause operational problems. Furthermore, in order to solve problems such as the increase in load applied by reducing the roll diameter on the downstream side (second half) of the continuous finishing mill, and how to control the crown or shape, different rolling mills are used (4Hi-mill and 5.Hi-mill). -Mill combination or 4Hi-mil (!:
Any conventionally known technique such as the combination of 6Hi-mil and branecrimil may be used, and there are no restrictions on the combination of these techniques.

The hot-rolled sheet hot-rolled by this method has a temperature of 8oO℃~1】
One-time cold rolling method in which the final plate thickness is obtained by one cold rolling after uniform annealing at 00°C, or usually from 850°C to 1050°C.
In the two-step method of intermediate annealing at °C and further cold rolling, the initial rolling reduction is about 50% to 80%, and the final downstream ratio is 5.
It can be carried out by a two-time cold rolling method in which the final sheet thickness is approximately 0.2 to 85% and 3115 g thick. Normally, the finished board 1'X is often approximately 0.8 mm thick.

After finishing the final cold rolling and finishing the chain plate to the product thickness, the surface is degreased and then heated in wet hydrogen at a temperature range of 780°C to 850°C.
Decarburization annealing, which also serves as next recrystallization annealing, is performed for about 3 to 15 minutes.

The final annealing is performed to sufficiently develop secondary recrystallized grains with the (110)(001) orientation, and is usually carried out by immediately raising the temperature to 1000''C or higher by box annealing and maintaining it at that temperature. This final annealing is usually performed by applying an annealing separator mainly composed of MgO and box annealing, but in the present invention, a secondary recrystallized structure highly aligned in the (110) (001) orientation is developed. In order, 82
It is more advantageous to carry out holding annealing at a low temperature of 0''C to 900°C, and alternatively, heat removal annealing at a temperature increase rate of 0.5 to 15°O/h may also be used.

(Example) Example 1 The component composition is heavy ffi%, OO, 048%, Si 8
．． 85%, Se 0.018%, MO0,015
%, silicon steel slab containing 0.0251% Sb.
After heating at 350"C, a hot rolled plate with a fin thickness of 2.7 was obtained by continuous hot rolling through rough rolling and finishing rolling.The conditions for the continuous hot rolling were as shown in (c) in Figure 1. The same method as the arrangement conditions, namely A1 roll diameter: 800 mm
) to //l1tO (D, ,: 472 mm φ) by successively decreasing the rolling roll diameter (reducing the radius by 10% for each previous roll). These hot rolled sheets are 90
After uniform annealing at 0°C for 3 minutes, the reduction rate was approximately 70.
%, and intermediate annealing at 950°C for 3 minutes, followed by double-law rolling at a reduction rate of approximately 65% to obtain a final cold-rolled sheet with a thickness of 0.8 mm. After that, 820
After decarburization annealing in wet hydrogen at ℃, an annealing separator mainly composed of MgO was applied, secondary recrystallization annealing was performed at 850℃ for 50 hours, and then at 1180℃ for 6 hours in H2 gas. Purification annealing was performed. The magnetic properties of the product at that time were as follows.

B: 1.91T, W1?15o: 0.99W/kg
0 Example 2 Component composition is heavy weight %, OO, 046%, Si 3.1
3%, At ff, 025%, In 0.072%
, NO,0068%
After heating at 400°C, a hot rolled sheet having a thickness of 2.0 mm was obtained by continuous hot rolling through rough rolling and finish rolling. This continuous hot finishing and rolling conditions are the same as the roll arrangement conditions shown in (c) of Figure 1, that is, from 711L1 (roll diameter of AI is D: 850mm) to A6 (Da' 279mm).
), the diameter of the rolling rolls was successively reduced (reducing the radius by 20% for each previous roll).

These hot-rolled sheets were uniformly annealed at 1050°C for 8 minutes and then rapidly cooled. Thereafter, strong cold rolling including warm rolling at 250° C. was performed to obtain a final cold rolled sheet having a thickness of 0.0 m or 0.0 m. After that, decarburization annealing was performed in wet hydrogen at 850°C,
After applying an annealing separator mainly composed of MgO, 850
After secondary recrystallization by raising the temperature from °C to 1050 °C at a rate of 5 °C/h, purification annealing was performed in hydrogen at 1200 °C for 8 hours. The magnetic properties of the product at that time were as follows.

BIO:1.94 T I Wl? 150:O-97
W/kg Example 8 Component composition is in weight%, OO, 042%, si, a,
a.

%, SeO,020%, MO0,018%,
13 silicon steel slabs containing 80% SbO
After heating at 60°C, a hot rolled sheet of 2.7+nJ was obtained by continuous hot rolling through rough rolling and finishing rolling. The conditions for continuous hot finish rolling are similar to the roll arrangement conditions shown in Figure 1 (B), namely, the roll diameter for A1.2 is 800 smφ, and the roll diameter for J63.4 is 500 mmφ. φ,
The roll diameters of Nos. 5 and 6 were hot rolled with a roll diameter of 400 mm. These hot-rolled sheets were uniformly annealed at 950°C for 3 minutes, and then subjected to primary cold rolling at a rolling reduction of about 70%.
After intermediate annealing at 950°C for 8 minutes, the reduction rate is approximately 6.
5% two-law rolling? A final cold-rolled sheet with a thickness of 0.8 fl was obtained. After that, decarburization annealing was performed in wet hydrogen at 820°C, and an annealing separator mainly composed of MgO was applied.
Secondary recrystallization annealing was performed at 50°C for 50 hours, and 118
Purification annealing was performed in hydrogen at 0°C for 5 hours. The magnetic properties at that time were as follows.

B. : 1,92T,"x715o: 0-9
7W/9 (Effect of the invention) As explained above, the present invention provides (110)<OO1>
Continuous hot finish rolling moves the accumulation and position of crystal nuclei, which are the source of oriented secondary recrystallized grains, to the center of the plate thickness, developing secondary recrystallization of fine grains, resulting in 81.90'I 'that's all,
W F150'' It is possible to advantageously produce a unidirectional silicon dynamic plate with extremely high magnetic flux density of 0 or less and low iron loss.

[Brief explanation of the drawing]

FIG. 1 is a route map showing the roll arrangement of a continuous hot finishing mill according to the conventional method (a), the method of the present invention (b), and (c);
The figure is a graph showing a comparison of magnetic flux density between the conventional method and the present invention method. Figure 3 is a graph showing a comparison of iron loss between the conventional method and the present invention method. Figure 4 is a graph showing the comparison between the conventional method and the present invention method. Figure 5 is a graph showing changes in iron loss characteristics when the finishing roll diameter ratio is changed. Figure 2 Figure 3 Figure 4 ○ Rushing water (A) ・Kida Ming test (B)

Claims (1)

[Claims] L A silicon-containing steel slab is rough rolled, continuously finished rolled, then hot rolled, cold rolled once or twice to achieve the final thickness, and then decarburized and primary recrystallized. In a series of methods for producing grain-oriented silicon steel sheets in which an annealing separator is applied after annealing and final annealing is performed, the (110)<001> orientation is preferentially generated near the surface of the hot-rolled steel sheet in the hot finish rolling step. A method for producing a grain-oriented silicon steel sheet with high magnetic flux density and low core loss, characterized in that an accumulation part of crystal nuclei, which is a source of secondary recrystallized grains, is generated near the center of the sheet thickness. The method according to claim 1, wherein the position of the crystal nucleus accumulation portion is such that the position exhibiting the maximum value of the (110) plane strength is at a distance of ξ from the steel plate surface toward the center of the plate thickness. - & A silicon-containing steel slab is rough rolled, continuous finish rolled, hot rolled, cold rolled once or twice to obtain a final thickness of ゛C, and then decarburized and primary recrystallized annealed. In a series of methods for producing grain-oriented silicon steel sheets in which an annealing separator is applied and final annealing is performed, the diameter of the rolling roll of the continuous finishing mill is changed to the diameter of the rolling roll located on the upstream side during the hot finishing rolling described above. (110)<OO1
＞ The accumulation area of crystal nuclei that becomes the source of secondary recrystallized grains in the orientation is
A method for producing a grain-oriented silicon steel sheet with high magnetic flux density and low core loss, characterized in that the magnetic flux is generated near the center of the sheet thickness. 4. The method according to claim 3, wherein the rolling rolls are arranged so that their diameters decrease sequentially from the upstream side to the downstream side. B. Claim 3, characterized in that the above-mentioned rolling rolls are arranged so that a plurality of rolls located on the upstream side have the same diameter, and a plurality of rolling rolls located on the downstream side successively have a smaller diameter.
Method described. The method according to 4 or 5, wherein the ratio of the diameters of the rolling rolls located on the upstream side and the downstream side is within the range of 1.1 to 5 times. 5. The method according to claim 4, wherein the diameter is successively reduced in sets of two or more rolls in the arrangement of the rolls.