JPH062040A - Production of grain-oriented silicon steel sheet having extremely high magnetic flux density - Google Patents

Abstract

PURPOSE:To provide high magnetic flux density by subjecting a slab of silicon steel containing Al as inhibitor-forming component to annealing, after final cold rolling, in hydrogen having a specific dew point. CONSTITUTION:A slab of a silicon steel containing 0.2-4.5% Si and also containing Al as inhibitor component is hot-rolled and then cold-rolled once or cold-rolled two or more times while process-annealed between the cold rolling stages and formed to the final sheet thickness. Then annealing is done in an atmosphere containing >=at least 10% hydrogen and having <=15 deg. dew point at 750-1050 deg.C for 30sec-10min. Subsequently decarburizing annealing is done in the ordinary wet atmosphere. Successively a separation agent at annealing, composed essentially of MgO, is applied and final finish annealing is performed at about 1200 deg.C. It is preferable that the silicon steel slab has a composition containing 2.0-4.5% Si, 0.02-0.10% C, 0.010-0.065% Al, 0.0010-0.0150% N, 0.02-0.20% Mn, and 0.01-0.040%, independently or in total, of S or Se.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an extremely high magnetic flux density suitable for applications such as iron cores of transformers and other electrical equipment.
The present invention relates to a method for manufacturing a grain-oriented silicon steel sheet.

[0002]

2. Description of the Related Art Oriented steel sheets used for iron cores of transformers and other electric equipment are required to have low iron loss and high magnetic flux density. In order to improve the magnetic flux density, it is necessary to set the rolling reduction during cold rolling to 80% or more to generate secondary recrystallized grains with a small deviation from the Goss orientation. However, if the cold rolling rate is 80% or more, the secondary recrystallization is reduced because the Goss orientation and the number of crystal grains close to it, which should be the nucleus of the secondary recrystallization in the primary recrystallization structure after decarburization annealing, decrease. It will be difficult.

The problem was solved by the addition of Al
This is a technique using a material having N as an inhibitor. Al
N has a power of strongly suppressing primary recrystallized grain growth up to a higher temperature than MnS or MnSe. Therefore, even when the reduction ratio during cold rolling was set to 80% or more and the primary recrystallized grain size was reduced, the crystal grain growth was suppressed and secondary recrystallization could be caused. However, A
A great deal of effort has been made to improve and stabilize the magnetic flux density of grain-oriented silicon steel using 1N as an inhibitor.

[0004]

A problem of the technique using a material using AlN as an inhibitor is instability of secondary recrystallization due to high cold reduction. In order to improve the instability, it is necessary to improve the primary recrystallization structure. In order to obtain a good primary recrystallized structure, a technique of performing preliminary annealing before decarburization annealing is disclosed.
For example, Japanese Examined Patent Publication No. 40-16769 discloses a technique for generating primary recrystallized grains by holding a steel sheet after cold rolling in the range of 500 to 700 ° C. for at least 2 minutes or more. However, the main purpose of this technique is to cause secondary recrystallization in a relatively wide range of acid-soluble Al by primary recrystallization in the temperature range of 500 to 700 ° C., and it is extremely difficult to improve the value of magnetic flux density. Is insufficient.
Further, JP-A-59-70723 discloses a technique for increasing the (110) structure in the recrystallized structure and improving the magnetic properties by annealing the final cold rolled plate at a temperature lower than the recrystallization temperature. There is. By using this technique, the magnetic characteristics are improved, but the secondary recrystallization is difficult to improve the magnetic flux density when the plate thickness is thin. For example, in Example 3 of JP-A-59-70723. Is a plate thickness of 0.
The value of the magnetic flux density at 225 mm (B10) is 1.93T.
(It is estimated to be 1.92T in B8), and the improvement of the magnetic flux density is insufficient.

Therefore, an object of the present invention is to propose a method for stably producing a grain-oriented silicon steel sheet having an extremely high magnetic flux density, which cannot be achieved by the prior art.

[0006]

Means for Solving the Problems Now, as a result of careful investigation on the secondary recrystallization phenomenon, the inventors perform annealing in hydrogen having a dew point of 15 ° C. or lower after decarburization annealing after final cold rolling. Therefore, we have found that the intended purpose can be achieved advantageously. The present invention is based on the above findings.

That is, according to the present invention, Si is added in the range of 2.0-4.
A silicon steel slab containing 5% and further containing Al as an inhibitor-forming component is hot-rolled, then cold-rolled once or twice or more including an intermediate annealing to obtain a final plate thickness, and then decarburized-annealed. Then, in order to manufacture the grain-oriented silicon steel in a series of steps of applying an annealing separator having MgO as a main component on the surface of the steel sheet and then performing secondary recrystallization annealing and purification annealing, after the final cold rolling, 750 A magnetic flux density characterized by performing normal decarburizing annealing after annealing in an annealing atmosphere having a dew point of 15 ° C or less containing at least 10% or more hydrogen for 30 seconds to 10 minutes at a temperature of 1050 ° C. The method of manufacturing a grain-oriented silicon steel having a very high degree of grain size, and preferably the composition of the silicon steel slab is Si: 2.0 to
4.5%, C: 0.02 to 0.10%, Al: 0.01
0 to 0.065%, N: 0.0010 to 0.0150
%, Mn: 0.02 to 0.20%, and any one of S and Se alone or in a total amount of 0.01 to 0.040% is included. And more preferably the composition of the silicon steel slab is Si: 2.0 to 4.5%, C: 0.
02-0.10%, Al: 0.010-0.065%,
N: 0.0010 to 0.0150%, Mn: 0.02
0.20%, including any one of S and Se alone or in total 0.01 to 0.040%, and further Sb:
0.01 to 0.20%, Cu: 0.02 to 0.20%,
P: 0.01 to 0.30%, Mo: 0.01 to 0.05
%, Sn: 0.02-0.20%, Ge: 0.005-
This is a method for producing a grain-oriented silicon steel sheet having an extremely high magnetic flux density, which contains one or more selected from 0.30% and Ni: 0.02 to 0.20%.

[0008]

The following is a description of the experimental results on which the present invention is based. C: 0.069%, Si: 3.31%, M
n: 0.078%, Se: 0.024%, Sb: 0.0
26%, Al: 0.025% and N: 0.0089%
After heating the slab containing 1 to 1420 ° C. to form a hot-rolled plate having a thickness of 2.2 mm, hot-rolled plate is annealed at 1000 ° C. for 30 seconds, and then cold-rolled to an intermediate thickness of 1.5 mm. After that, after intermediate annealing at 1100 ° C. for 60 seconds, it was cold-rolled to a thickness of 0.22 mm. Then dew point-2
Annealing was performed at 900 ° C. for 5 minutes in a hydrogen atmosphere at 0 ° C.
As a comparison, an experiment was conducted under the conditions of annealing in a nitrogen atmosphere with a dew point of -20 ° C and conditions without annealing. Then 840
Decarburization annealing was performed in a wet hydrogen atmosphere with a dew point of 65 ° C. for 2 minutes. The texture of the surface after decarburization annealing was investigated by the X-ray inverse method. After that, an annealing separator containing 6% TiO ₂ added to MgO was applied. A sample of the cut plate was taken from those coils, and hydrogen was added at a temperature rising rate of 20 ° C / h from room temperature to 7% hydrogen.
Finish annealing is performed in an atmosphere of 5% nitrogen and 25%, and 850 ° C.
Samples were taken out every 15 ° C. to observe the crystal structure and investigate the change in the primary recrystallized grain size of the surface layer and the central layer. The body of the coil was also subjected to finish annealing under the same conditions and the final magnetic characteristics were investigated.

The texture of the surface of the decarburized annealed sheet thus obtained is shown in FIG. 1, the change in primary recrystallized grain size of the surface layer and the central layer in the final annealing is shown in FIG. 2, and the magnetic result of the product sheet is shown in FIG. . As is clear from FIG. 1, the texture does not change due to the annealing after the final cold rolling. As is clear from FIG. 2, when the annealing after the final cold rolling is performed in a hydrogen atmosphere, the primary As it is clear from FIG. 3 that the growth of recrystallized grains is promoted and the secondary recrystallization temperature is lowered by about 100 ° C., the coil under the condition of annealing in hydrogen after the final cold rolling and before decarburization annealing. Shows that the magnetic flux density is remarkably good.

As described above, according to the present invention, after the final cold rolling,
It was completed based on a completely new finding that the magnetic flux density is significantly improved by annealing in hydrogen before decarburization annealing. The reason why the magnetic flux density is improved by the present invention is not clear, but it is considered as follows.

By annealing in hydrogen after the final cold rolling and before decarburizing and annealing, the texture of the decarburized and annealed sheet hardly changed, and the effect of this annealing changed to the primary recrystallization texture. Not what you are giving. After the final cold rolling, the effect of annealing in hydrogen before decarburizing annealing is that the growth of the crystal grains of the surface layer during finish annealing is greater than that of annealing performed in nitrogen or not annealed. Is promoted and the secondary recrystallization temperature is lowered.

The reason is that since the annealing in hydrogen after the final cold rolling is before decarburization annealing, the surface layer is not formed with an internal oxide layer mainly composed of SiO ₂ , and therefore the N of the surface layer is not formed. It is considered that this is because the decomposition of As a result, in the surface layer, since the amount of AlN in the initial stage of finish annealing is small, it is considered that secondary recrystallization nuclei are generated at a low temperature. Compared to the surface layer in the center part, Al in the initial stage of finish annealing
The amount of N is large, and the grain growth does not proceed, and the primary recrystallized grains are preserved. As a result, under the condition of annealing in hydrogen after the final cold rolling, the secondary recrystallization nuclei generated in the surface layer at low temperature erode the matrix in the center while the inhibitory force of the inhibitor is more leaning. Will grow up. As is clear from FIG. 2, when the annealing after the final cold rolling is performed in a hydrogen atmosphere, the primary recrystallization (grain size of about 10 μm) of the center layer immediately before the start of the secondary recrystallization is similar to that after the final cold rolling. It is smaller than the primary recrystallized grains (grain size of about 15 to 19 μm) of the central layer immediately before the start of secondary recrystallization under the conditions of annealing in a nitrogen atmosphere and the condition of not performing annealing, and at the time of starting secondary recrystallization. It can be said that the restraining power is maintained.
It can be said that the magnetic flux density is extremely high because the orientation of the secondary recrystallized grains grown from the surface layer is extremely close to the ideal Goss orientation in a state where the suppression force of the central layer is maintained, Probably, when the inhibitory power of the inhibitor is maintained as much as the ideal Goth orientation, it preferentially eats the matrix in the central portion and grows faster.

In order to stabilize secondary recrystallization and improve magnetic flux density, many techniques have been disclosed from the viewpoint of improving the primary recrystallization structure, particularly increasing the (110) structure that should be the secondary recrystallization nucleus. Has been done. For example, a method of performing an aging treatment during cold rolling or between passes of cold rolling, a method of decarburizing a part of the surface layer during intermediate annealing to suppress α → γ transformation, and a method of increasing the temperature rising rate of decarburizing annealing. and so on. The above-mentioned JP-A-59
The pre-annealing technique for cold-rolled sheets disclosed in Japanese Patent No. 70723 has the same effect. However, in these methods, the main effect is to simply increase (110) in the primary recrystallized structure and increase the probability that secondary recrystallized grains are generated.
Although secondary recrystallization was stable, it was essentially unavoidable that secondary recrystallized grains deviated from the Goss orientation occurred and the magnetic flux density decreased. The method of the present invention is completely different in the improvement effect of these primary recrystallization structures and the technical idea, and does not increase (110) in the primary recrystallization structure, but at the low temperature at the time of secondary recrystallization. By generating secondary recrystallization nuclei in the surface layer, only the grains extremely close to the ideal Goss orientation are selectively
This is an epoch-making technology that grows to the center and obtains an extremely high magnetic flux density.

Further, according to the technique of the present invention, it is not always necessary to increase the amount of (110) present in the primary recrystallization structure in order to improve the magnetic flux density. Therefore, the aging treatment in the cold rolling step described above is performed. Since it is not necessary to perform decarburization of the surface layer in the intermediate annealing or the like, the number of times of annealing is increased by one, but it can be said that it is an industrially extremely useful technique from the viewpoint of production when judged comprehensively.

The material targeted by the present invention is Si containing 2 to
It is a silicon steel slab containing 4.5% and further containing Al as an inhibitor-forming component. Here, the preferred component composition of the silicon steel slab is C: 0.02 to C in addition to the above Si.
0.10%, and Al: 0.010 to 0.065%,
N: 0.0010 to 0.0150%, Mn: 0.02
0.20%, at least one of S and Se alone or in a total of 0.010 to 0.040%, and optionally Sb: 0.01 to 0.20%, Cu:
0.02 to 0.20%, P: 0.01 to 0.30%, M
o: 0.01 to 0.05%, Sn: 0.02 to 0.20
%, Ge: 0.005 to 0.30%, Ni: 0.02
0.20%, including one or more selected from the group. The reason why each component is limited to the above range is as follows.

Si is an element necessary for increasing the electrical resistance of the product and reducing the eddy current loss, but if it is less than 2.0%, the crystal orientation is impaired by α-γ transformation during final finish annealing. On the other hand, if it exceeds 4.5%, there arises a problem in cold rolling property, so it is limited to 2.0 to 4.5%. C is 0.0
If it is less than 2%, a good primary recrystallization structure cannot be obtained. On the other hand, if it exceeds 0.010%, decarburization becomes poor and the magnetic properties deteriorate, so the content is made 0.02 to 0.10%.

Al and N function as inhibitors, but in order to obtain a good magnetic flux density, Al:
0.010 to 0.065%, N: 0.0010 to 0.0
150% is required. When the amount exceeds this, AlN coarsens and loses its restraining power.
This is because the amount of 1N is insufficient and the desired inhibitory effect cannot be expected.

Mn, S and Se function as inhibitors, but if Mn is less than 0.02% or S and / or Se is less than 0.010%, the inhibitor function is insufficient, while Mn is Over 0.20%,
If S or / and Se exceeds 0.040%, the temperature required for slab heating is too high to be practical.
02 to 0.20%, S or / and Se is 0.010
~ 0.040%.

Further, in order to improve the magnetic flux density, Sb, C
It is possible to add u and P. However, S
When b exceeds 0.20%, the decarburizing property deteriorates, while 0.
If less than 01%, the effect of Sb addition is weak, so 0.01-
0.20% is desirable. If the Cu content exceeds 0.20%, the pickling property deteriorates. On the other hand, if the Cu content is less than 0.01%, the effect of adding Cu is weak, so 0.01 to 0.20% is desirable. If P exceeds 0.30%, the brittleness deteriorates, and if it is less than 0.01%, the effect of P addition is poor, so 0.01 to 0.30% is set.

Further, 0.05% Mo can be added to complete the surface properties, but if it exceeds 0.05%, the decarburizing property is deteriorated, while if it is less than 0.01%, the effect of addition is poor, so addition is carried out. In this case, 0.01 to 0.05% is preferable. Further, Sn, Ge, and Ni can be added to improve the iron loss. If Sn exceeds 0.30%, it becomes brittle, and if it is less than 0.01%, the effect of addition is poor.
1 to 0.30% is preferable. When Ge exceeds 0.30%, a good primary recrystallized structure cannot be obtained, while 0.005%
If it is less than 0.005%, the effect is poor, so 0.005 to 0.30% is desirable. If Ni exceeds 0.20%, the hot strength decreases, and if it is less than 0.01%, the effect is poor.
0.20% is desirable.

Next, the manufacturing method according to the present invention will be specifically described. In the production of grain-oriented silicon steel, which is the object of the present invention, molten steel obtained by a conventional steelmaking method is cast by a continuous casting method or an ingot casting method, and hot rolling plate annealing is performed as necessary. After that, cold rolling is performed once or twice or more with intermediate annealing to obtain the final plate thickness.

In the present invention, it is important to anneal after the final cold rolling. Here, the annealing temperature is 750 to 1
It is 30 seconds to 10 minutes at 050 ° C. If the annealing temperature is less than 750 ° C, the effect of improving the magnetic flux density is poor,
On the contrary, when the temperature exceeds 1050 ° C, the magnetic flux density decreases.
It is set to 0 to 1050 ° C. If the annealing time is less than 30 seconds, the effect of improving the magnetic flux density is poor, and if it exceeds 10 minutes, the magnetic flux density decreases, so the annealing time is set to 30 seconds to 10 minutes. It is essential that the annealing atmosphere contains at least 10% hydrogen at a dew point of 15 ° C. or less. This is because when the dew point is 15 ° C. or higher, an oxide film is formed on the surface, the effect of decomposing AlN in the surface layer is insufficient, and decarburization in the decarburization annealing that is the next step is hindered and the magnetic flux density is reduced. If hydrogen is less than 10%, the effect of decomposing AlN in the surface layer of the plate is insufficient, and the effect of improving the magnetic flux density is not obtained. The annealing method may be performed in an independent step after the final cold rolling, but it is advantageous in terms of production efficiency if performed in the first half of the decarburization annealing step.

Subsequent to the above annealing, decarburization annealing in a normal wet atmosphere is performed, an annealing separating agent containing MgO as a main component is applied, and then final finishing annealing is performed at a temperature of about 1200 ° C. A coating is applied to give a product.

[0024]

【Example】

(Example 1) C: 0.069%, Si: 3.25%, A
1: 0.024%, N: 0.0085%, Mn: 0.0
75%, Se: 0.020% and Sb: 0.026%
A silicon steel slab containing
After heating at 420 ℃ for 30 minutes, hot-roll it to 2.2 mm
After making a thick hot-rolled sheet, annealed at 1000 ° C for 30 seconds, cold-rolled to 1.5 mm, and then at 1100 ° C for 6 seconds.
It was annealed for 0 seconds and then cold rolled to 0.23 mm. Then, after annealing under the conditions shown in Table 1, decarburization annealing was performed at 840 ° C. for 120 seconds, MgO was applied, and then 1
Finish annealing was performed at 200 ° C. for 5 hours.

The results of examining the magnetic properties of the products thus obtained are also shown in Table 1.

[0026]

[Table 1]

Example 2 A silicon steel slab having the composition shown in Table 2 was heated at 1430 ° C. for 20 minutes and then hot-rolled into a hot-rolled sheet having a thickness of 2.3 mm, and then 10
Annealing is performed at 00 ° C for 60 seconds, and then cold rolling is performed to a thickness of 1.5 mm, and then intermediate annealing is performed at 1100 ° C for 2 minutes.
Cold rolled to 0.23 mm. Then, it was annealed at 900 ° C. for 3 minutes in an atmosphere of dew point -20 ° C., hydrogen 50% and nitrogen 50%. Thereafter, decarburization annealing was performed at 840 ° C. for 2 minutes, MgO was applied, and then final annealing was performed at 1200 ° C. for 5 hours.

The results of examining the magnetic properties of the products thus obtained are also shown in Table 2.

[0029]

[Table 2]

[0030]

As described above, according to the present invention, after the final cold rolling, annealing is performed in an atmosphere containing at least 10% of hydrogen to decompose AlN in the surface layer, lower the secondary recrystallization temperature, and reduce the ideal Goss orientation. By promoting selective growth, an extremely high magnetic flux density can be obtained.

[Brief description of drawings]

FIG. 1 shows the measurement results of the texture of the decarburized annealed plate surface.

FIG. 2 shows the primary recrystallized grain size of the surface layer and the central portion during finish annealing.

FIG. 3 shows the relationship between the annealing conditions after the final cold rolling and the magnetic properties of the product.

Claims (3)

[Claims] 1. Containing 0.2 to 4.5% of Si, and further comprising A
After hot-rolling a silicon steel slab containing 1 as an inhibitor-forming component, it is cold-rolled once or twice or more including intermediate annealing to obtain a final plate thickness, and then decarburized-annealed, and then the steel plate surface In producing a grain-oriented silicon steel in a series of steps of applying an annealing separator containing MgO as a main component, and then performing secondary recrystallization annealing and purification annealing, after the final cold rolling, a temperature of 750 to 1050 ° C. 30 seconds ~
Dew point 15 containing at least 10% hydrogen for 10 minutes
A method for producing a grain-oriented silicon steel sheet having an extremely high magnetic flux density, which comprises performing an ordinary decarburization annealing after performing an annealing in an annealing atmosphere at ℃ or less. 2. The composition of the silicon steel slab according to claim 1,
Si: 2.0-4.5%, C: 0.02-0.10%,
Al: 0.010 to 0.065%, N: 0.0010
0.0150%, Mn: 0.02 to 0.20%, any one of S and Se alone or in total 0.01 to.
A method for producing a grain-oriented silicon steel sheet having an extremely high magnetic flux density, which comprises 0.040%. 3. The composition of the silicon steel slab according to claim 1 is S
i: 2.0 to 4.5%, C: 0.02 to 0.10%, A
1: 0.010 to 0.065%, N: 0.0010
0.0150%, Mn: 0.02 to 0.20%, any one of S and Se alone or in total 0.01 to.
0.040%, and Sb: 0.01 to 0.20
%, Cu: 0.02 to 0.20%, P: 0.01 to 0.
30%, Mo: 0.01 to 0.05%, Sn: 0.02
-0.20%, Ge: 0.005-0.30%, Ni:
A method for producing a grain-oriented silicon steel sheet having an extremely high magnetic flux density, which comprises one or more selected from 0.02 to 0.20%.