JPH07268567A - Grain oriented silicon steel sheet having extremely low iron loss - Google Patents

Abstract

PURPOSE:To produce a grain oriented silicon steel sheet having extremely low iron loss characteristic. CONSTITUTION:This steel sheet has a composition containing, by weight, <=0.005% C and 2.5-7.0% Si and also has a structure in which average crystalline grain size is regulated to 1-10mm and crystal orientation has an orientational deviation averaging <=8 deg. in a rolling direction with respect to the ideal orientation of (110)[001]. By this method, the grain oriented silicon steel sheet having extremely low iron loss can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has an S content of 2.5 to 7.0%.
In a steel sheet containing i and having a fine crystal grain size, (1
10) The high integration degree of the [001] orientation provides a unidirectional electrical steel sheet having an extremely low iron loss.

[0002]

2. Description of the Related Art Generally, the magnetic properties of a grain-oriented electrical steel sheet are evaluated by both the iron loss property and the excitation property. Increasing the excitation characteristics is effective for downsizing equipment that increases the design magnetic flux density. On the other hand, reducing the iron loss characteristics is effective in reducing the loss of heat energy when used as an electric device and saving the power consumption. further,
Aligning the <100> axes of the crystal grains of the product in the rolling direction can improve the magnetization characteristics and lower the iron loss characteristics.
In recent years, much research has been conducted especially in this respect, and unidirectional electrical steel sheets have been developed by various manufacturing techniques. As a result, the typical industrially produced grain-oriented electrical steel sheets are
It is manufactured by three representative technologies.

The first technique is a unidirectional electrical steel sheet which is disclosed in Japanese Patent Publication No. Sho 30-3651 and which has MnS functioning as an inhibitor and is produced by a double cold rolling process. Since this grain-oriented electrical steel sheet has a small secondary recrystallization grain size, the iron loss is relatively good, but there is a problem that a high magnetic flux density cannot be obtained. On the other hand, in order to obtain a high magnetic flux density, as a second technique, Japanese Patent Publication No. 40-1
Japanese Patent No. 5644 has been disclosed. This is AlN + MnS
Is used as an inhibitor, and the rolling rate in the final cold rolling step is a strong reduction that exceeds 80%.
By this method, a grain-oriented electrical steel sheet having a high degree of integration of the (110) [001] orientation of secondary recrystallized grains and a high magnetic flux density of B ₈ of 1.870 (T) or more can be obtained. Further, as a third technique, a production technique by a two-time cold rolling process has been developed, which is disclosed in Japanese Patent Publication No. 51-13469, in which MnS or MnSe + Sb functions as an inhibitor.

In general, iron loss is roughly classified into hysteresis loss and eddy current loss. Physical factors that influence the hysteresis loss include the purity of the material and internal strain in addition to the above-described crystal orientation. Further, physical factors that affect the eddy current loss include electric resistance (amount of components such as Si) of the steel sheet, sheet thickness, size of magnetic domain (grain size), and tension exerted on the steel sheet. Since eddy current loss accounts for 3/4 or more of total iron loss in ordinary grain-oriented electrical steel sheets, lowering eddy current loss than hysteresis loss is more effective in reducing total iron loss.

Therefore, in the manufacturing method according to the second technique, the degree of integration of the (110) [001] orientation of the secondary crystal grains is high, and B ₈ has a high magnetic flux density of 1.870 (T) or more. Even if the grain-oriented electrical steel sheet was obtained, the secondary recrystallized grain size was as large as 10 mm, so that the magnetic domain width that affected the eddy current loss was large. In order to improve this, a method of subjecting a steel sheet disclosed in JP-B-57-2252 to a laser treatment, a method of applying mechanical strain to a steel sheet disclosed in JP-B-58-2569, etc. ,
Various methods of subdividing magnetic domains have been disclosed. However, these methods require additional steps.

Therefore, in place of the technique requiring these additional steps, a unidirectional electrical steel sheet having a fine secondary recrystallized grain size to reduce the eddy current loss and have a lower iron loss than the conventional one Is disclosed. For example, in Japanese Patent Application Laid-Open No. 1-290716, a cold rolled steel sheet is subjected to a super rapid annealing treatment at a heating rate of 100 ° C./sec or more to a temperature of 675 ° C. or more, the strip is decarbonized, and finally hot annealed. A method for producing secondary growth, whereby the strip has secondary particles of reduced size and improved iron loss that persists without significant change after stress relief annealing. It is disclosed.

However, although it is possible to obtain secondary recrystallized grains which are small to some extent, in this manufacturing method, the proportion of fine secondary recrystallized grains in which the (110) [001] orientation deviates from the rolling direction is inevitable. It was found that a very good iron loss value could not be obtained due to the increase in the amount and the deterioration of the history loss. That is, there was a problem that the iron loss improvement rate of the treatment by the ultra-rapid annealing was as low as a few% as compared with the treatment by the conventional annealing. In addition, there is also a problem that the improvement rate of the iron loss value when a film such as forsterite or an insulating film is applied to the surface of the steel sheet later does not become so large.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a fine (1
10) A unidirectional electrical steel sheet having [001] secondary recrystallized orientation grains, which has a high degree of integration of (110) [001] orientation, thereby greatly improving the iron loss improvement rate. To do.

[0009]

In the present invention, as a result of repeated studies to solve the above problems, C: 0.005% by weight
Hereafter, Si: 2.5 to 7.0% is included, the average crystal grain size is 1 to 10 mm, and the crystal orientation is 8 ° in the rolling direction as an average value with respect to the ideal orientation of (110) [001]. It has been found that a grain-oriented electrical steel sheet having extremely low iron loss can be obtained by having the following misalignment.

The present invention will be described in detail below. First, the present inventors obtained the grain-oriented electrical steel sheet by the following two manufacturing methods. C: 0.080%, Si: 3.14%, M
n: 0.084%, P: 0.010%, S: 0.024
%, Sol.Al: 0.024%, N: 0.009%, a molten steel containing a component composition was cast, and after hot heating the slab, hot rolling was performed to obtain a hot rolled steel sheet of 2.0 mm. Next, it was annealed at 1100 ° C. for 5 minutes, further pickled, and then cold rolled to a thickness of 0.22 mm. About rolled steel plate, (a)
Is annealed at a heating rate of 20 ° C./s to 850 ° C.,
(B) is annealed at a heating rate of 300 ° C./s to 850 ° C., and (c) is heated at a heating rate of 300 ° C./s to 85 ° C.
Heat to 0 ° C, and within 0.1 seconds up to 750 ° C at 200 ° C
The cooling treatment was performed at a cooling rate of / s.

Next, in each of (a), (b) and (c),
After decarburization annealing in wet hydrogen and applying MgO powder, 12
High temperature annealing was performed at 00 ° C. for 10 hours in a hydrogen gas atmosphere. The average crystal grain size of the obtained product is (a) 15.1 mm,
(B) 2.3 mm and (c) 2.6 mm. As a result, fine secondary recrystallization is obtained in (b) and (c).
The crystal orientation of fine secondary recrystallized grains of each product was measured, and the crystal orientation was (110) in (a).
With respect to the ideal azimuth of [001], there is an average deviation of 6.4 ° in the rolling direction and 2.3 ° in the in-plane direction,
In (b), the crystal orientation has a deviation of 9.5 ° in the rolling direction and 2.7 ° in the in-plane direction on average from the ideal orientation of (110) [001]. ), The crystal orientation was misaligned by 6.3 ° in the rolling direction and 1.7 ° in the in-plane direction with respect to the ideal orientation of (110) [001].

The iron loss characteristics of the obtained product are (a) W _17/50
0.95 (W / kg), (b) W _17/50 0.88 (W / kg),
(C) It was _W17 / ₅₀ 0.79 (W / kg). From these facts, even if products with a sufficiently small crystal grain size were obtained in both (b) and (c), the (110) [001] orientation was deviated from the rolling direction, so that the iron loss of the comparative material (a) was reduced. The improvement rate is 7% for (b) and 17% for (c), indicating that the material of the present invention (c) has a higher improvement rate.

The reason why the deviation of the (110) [001] crystal orientation from the rolling direction is small and the improvement rate of iron loss is large is that the ratio of hysteresis loss to iron loss in fine secondary recrystallization is large. It is thought that it is necessary to aim at an improvement rate of iron loss by increasing the degree of integration of crystal orientations by the increase of the. The history loss ratio in the above embodiment is W
_17/50 (a) 20%, (b) 31%,
In (c), it was 25%.

[0014]

In the present invention, the reason why the steel composition and steel plate conditions are limited as described above will be described in detail. The reasons for limiting the steel composition are as follows. The upper limit of 0.005% for C is limited because if it exceeds this value, the magnetic properties of the product deteriorate. Si has a lower limit of 2.5% in order to improve iron loss, but if it is too much, it easily cracks when manufacturing a transformer and processing becomes difficult, so the upper limit is 7.0%.
And

In addition to the above unidirectional electrical steel sheet, there is an average deviation of 8 ° or less in the rolling direction from the ideal orientation of (110) [001], and the crystal grain size is 1
-10 mm is required. The upper limit of the crystal grain size is limited to 10 mm or less in order to reduce the eddy current loss of iron loss. The lower limit of 1 mm is limited because secondary recrystallization is difficult below this range. In these steel sheets having a small crystal grain size, the deviation of the orientation in the rolling direction is set to 8 ° or less in average in order to obtain good iron loss characteristics by imparting film tension. The upper limit of 8 ° is limited because the magnetic flux density is reduced beyond this and the effect of reducing the hysteresis loss of iron loss cannot be obtained.

Further, it is desirable that the deviation of the orientation in the in-plane direction is 1 to 5 ° on average. If the upper limit of 5 ° is more than this, the magnetic flux density is reduced and the effect of reducing the hysteresis loss of iron loss cannot be obtained. If the lower limit of 1 ° is less than this, the effect of iron loss reduction by imparting iron loss tension cannot be obtained. This is because. The average deviation of the direction perpendicular to the plate surface is preferably 5 ° or less. The plate thickness is preferably 0.15 to 0.55 mm. In addition, in order to further improve the iron loss of the obtained product, the unidirectional electrical steel sheet may be subjected to a coating such as forsterite, a coating tension imparted by an insulating coating, or a treatment for subdividing a magnetic domain. It is possible.

[0017]

EXAMPLE A molten steel containing the chemical composition shown in Table 1 was cast, and after heating the slab, hot rolling was performed to obtain a hot rolled steel sheet of 2.3 mm. Next, it was annealed at 1100 ° C. for 5 minutes, further pickled, and then cold rolled to a thickness of 0.27 mm and 0.22 mm. The rolled steel sheet was heated to 850 ° C. under various conditions by a direct current heating device having a set of heating electrodes in the absence of oxidation. The soaking time at 850 ° C. is 0.1 s.
(A) is a heating rate of 450 ° C./s, a cooling rate of 20 ° C./s,
(B) is a heating rate of 450 ° C / s and a cooling rate of 300 ° C / s
Is. In (c), an untreated material was used as a comparative material.

Next, decarburization annealing was performed in wet hydrogen, MgO powder was applied, and then high temperature annealing was performed at 1200 ° C. for 10 hours in a hydrogen gas atmosphere. Table 2 shows the plate thickness of the product obtained by the above method, the average value of the magnetic properties, the average secondary recrystallized grain size, and the ideal orientation of (110) [001] of the secondary recrystallization orientation from the rolling direction. The average value of the deviation is shown. Moreover, the iron loss improvement rate with respect to the comparative material (c) is also shown. INDUSTRIAL APPLICABILITY The unidirectional electrical steel sheet of the present invention has an average deviation of 8 ° or less in the rolling direction with respect to an ideal azimuth having a plate thickness of 0.15 to 0.35 mm and a crystal orientation of (110) [001]. Having a crystal grain size of 1 to
When it is 10 mm, a high iron loss improvement rate is obtained as compared with (c).

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

According to the present invention, a unidirectional electrical steel sheet having an extremely low iron loss can be obtained because the degree of integration of the (110) [001] orientation is higher in a steel sheet having a fine grain size than before. Since it can be provided, the industrial contribution is extremely large.

Claims (1)

[Claims] 1. C: 0.005% or less by weight, Si: 2.5 to 7.0% are included, the average crystal grain size is 1 to 10 mm, and the crystal orientation is (11
0) A unidirectional electrical steel sheet having an extremely low iron loss, which has an average deviation of 8 ° or less in the rolling direction with respect to the ideal orientation of [001].