JPH07188938A - Separation agent for annealing for grain oriented electrical steel sheet - Google Patents

Abstract

PURPOSE:To improve B6 characteristics with which macrocrystal grains having a high scale of integration of (100)[101] bearings are obtainable without oblique annealing by adding and compounding a specific ratio of a Tl compd. to and with an MgO-based sepn. agent for annealing for a grain oriented electrical steel sheet. CONSTITUTION:The Tl compd. is added and compounded at 0.2 to 10 pts.wt. in terms of Tl per 100 pts.wt. MgO in the MgO-based sepn. agent for annealing into and with this sepn. agent for annealing. Such sepn. agent for annealing is used as the annealing agent for the grain oriented electrical steel sheet, by which the huge secondary recrystal grains extending in the transverse direction of the strip is obtd. even under ordinary finish annealing conditions and the grain oriented electrical steel sheet having the high scale of integration of (100)[101] and the excellent magnetic characteristics is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to provide an annealing separating agent which is effective in improving magnetic properties when used in finish annealing of grain-oriented electrical steel sheet.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are mainly used as iron cores for transformers and other electric equipment, and are required to have excellent magnetic characteristics such as excitation characteristics and iron loss characteristics. The improvement of the density is possible only with the advent of grain-oriented electrical steel sheet having a high magnetic flux density. In the production of this grain-oriented electrical steel sheet, an annealing separator is applied to a steel sheet cold-rolled to a final thickness and finish annealing is performed to form a forsterite-ceramic insulating coating (hereinafter simply referred to as forsterite coating) on the steel sheet surface. However, since the composition of the annealing separator greatly affects the properties of the coated film and the magnetic properties of the steel sheet,
Much research has been done and improvements are being made.

[0003]

2. Description of the Related Art Up to now, many proposals have been made as means for improving the excitation characteristic, that is, the B ₈ characteristic. For example, in Japanese Examined Patent Publication No. 58-50295 (manufacturing method of unidirectional silicon steel sheet with high magnetic flux density), in the boundary region between the primary recrystallization region and the secondary recrystallization region of the steel sheet, a secondary gradient is applied while a temperature gradient is applied. It is disclosed that a product with a high degree of (110) [001] orientation integration can be obtained by proceeding with recrystallization.

Further, in Japanese Patent Application Laid-Open No. 2-258923 (method for producing grain-oriented electrical steel sheet having extremely high magnetic flux density), during the finish annealing under a temperature gradient, the secondary recrystallization occurred at the initial stage. By subjecting the strip coil width direction end on the high temperature side to a process that suppresses the free growth of secondary recrystallized grains, the crystal grains are significantly elongated in the strip width direction, and the grain size width (line direction) is 50 mm. It is disclosed that a large crystal grain is suppressed to a certain degree, and a product having a high degree of (110) [001] orientation integration can be obtained.

As described above, in the method of realizing the crystal grains elongated in the width direction of the strip plate by the gradient annealing imparting the temperature gradient, the effect of improving the magnetic flux density is likely to vary from time to time. In many cases, finish annealing of the coil is performed by batch processing by winding the strip into a coil, and it is difficult to make the heat history uniform at the coil position (inner winding, middle winding, outer winding). It is difficult to control the secondary recrystallization behavior in the longitudinal direction. Further, the gradient annealing process is a batch process, and there is a problem that equipment cost and manufacturing cost increase.

[0006]

The present invention advantageously solves the above-mentioned problems, and obtains giant crystal grains with a high degree of (110) [001] orientation integration without gradient annealing and improves B ₈ characteristics. It is an object of the present invention to provide a completely new annealing separating agent.

[0007]

[Means for Solving the Problems] In the production of grain-oriented electrical steel sheets, an annealing separator has an effect of preventing fusion between coil layers during finish annealing and contributes to the improvement of magnetic properties during finish annealing. It plays an important role in controlling the behavior of the inhibitor components in the vicinity and suppressing the oxygen photons between the coil layers, and the effect of improving the electrical insulation by forming a forsterite coating on the steel sheet by this finish annealing. It has the effect of reducing iron loss by applying tension.

In order to further improve the properties of such an annealing separator, the inventors have conducted experiments by adding MgO 2 as a main component and various subcomponents to it, and as a result, have found that the addition of the Tl compound is in the right direction. The present invention has been achieved by newly finding that the secondary recrystallization behavior of a magnetic electrical steel sheet is significantly changed.

That is, the gist of the present invention is an MgO-based annealing separator, in which 0.2 to 10 parts by weight of a Tl compound in terms of Tl is added to 100 parts by weight of MgO in the annealing separator. Is an annealing separator for grain oriented electrical steel sheets.

[0010]

The present invention will be described in detail below. The essence of the present invention is to add 0.2 to 10 parts by weight of a Tl compound in terms of Tl to 100 parts by weight of MgO as an MgO-based annealing separator.

This Tl compound addition amount is limited to 0.1 in terms of Tl.
If it is less than 2 parts by weight, the effect of changing the secondary recrystallized grain morphology is poor.On the other hand, if it is added in an amount of more than 10 parts by weight, not only the secondary recrystallized grain morphology does not change so much, but it also forms on the steel sheet. It causes deterioration of the forsterite coating.

In the above, the MgO-based annealing separator is
In addition to preventing fusion of steel plates during finish annealing, it is also a raw material for forming a forsterite film during finish annealing. The addition of the Tl compound suppresses the decomposition of the inhibitor component and raises the secondary recrystallization start temperature. Near the temperature at which secondary recrystallization begins
At the time when nucleation and grain growth of (100) [001] secondary recrystallized grains proceed, the decomposition of the inhibitor is promoted by Tl (Tl compound), and coarse secondary grains are formed. As the Tl compound, Tl ₂ O, Tl ₂ O ₃ as an oxide, TlNO ₃ , as a metal salt,
Tl ₂ SO ₄ , Tl (NO ₃ ) ₃ 3H ₂ O and Tl ₂ CO ₃ are effective. Although Tl can be added to the separating agent as a simple substance, the metal Tl has a property of being easily oxidized and forms an oxide in the air, which is difficult to handle. Therefore, as a method of addition, the addition as a Tl compound is preferable in that uniform dispersion in the separating agent is easy.

Further, MgO, which is the main component of the annealing separator, may be a normal product such as CaO <0.7%, Cl ≤ 0.04%, SiO 2.
₂ <0.2%, SO ₃ <0.2%, R ₂ O ₃ <0.2% (R is Al ₂ O ₃ ,
Fe ₂ O ₃ etc.) and B <0.15% and other components or compounds thereof may be contained, and the average particle size is 0.4 to 2.0 μm and the citric activity CAA 40% = 60 to 90 seconds. And especially MgO
The chemical properties need not be specified.

Further, in order to improve the magnetic properties and the coating properties, it is also possible to compound and add other auxiliary components of the annealing separator, and the preferable ranges of these auxiliary components and the addition amount are as follows. is there. (The following addition amounts are shown in proportion to 100 parts by weight of MgO) TiO ₂ 0.5 to 10 parts by weight and SrSO ₄ , S
It is preferable to add 1 to 5 parts by weight of one or more Sr compounds such as r (OH) ₂ and SrCO ₃ . In addition to this, the total amount of calcium titanate and strontium titanate is 0.5-
You may add 20%.

Next, the annealing separator prepared in the above composition is
After applying it to a steel sheet in the form of a slurry, it is applied under normal finishing annealing conditions, for example, as finishing annealing at a temperature of 840 to 860 ° C for 10
Continuing the primary retention (secondary recrystallization annealing) for up to 20 hours
Purification annealing is carried out at a holding temperature of 1200 ° C for 5 to 10 hours.
As the atmosphere gas from room temperature to the end of the first retention, an inert gas or N ₂ gas is used, and H ₂ gas, H ₂ + N ₂ mixed gas, or both of them are used in a temperature range between the first retention temperature and the purification annealing temperature. You may use it separately. H during purification annealing retention
Annealing using ₂ gases is sufficient.

This finish annealing causes Tl to be adsorbed on the surface layer of the base steel of the steel sheet during annealing, which changes the distribution of the inhibitor component in the vicinity of the surface layer of the base steel. Recrystallized grain size width (line direction) is 30 to 10
Large crystal grains of about 0 mm are generated.

As described above, by using the annealing separator of the present invention, the finish annealing condition does not require the special heat treatment such as the gradient annealing as described above, and the giant annealing is performed in the sheet width direction under the normal annealing condition. It is possible to obtain various crystal grains.

Here, changes in secondary recrystallized grain morphology due to addition of a Tl compound to the annealing separator are shown in FIGS. 1, 2, 3 and 4 under the same normal finishing annealing conditions. Figure 1
Is a photograph of a secondary recrystallized metallographic structure using an annealing separator without Tl compound addition. Fig. 2 shows 3 parts by weight of Tl ₂ O ₃ (2.7 parts by weight in terms of Tl) and Fig. 3 shows Tl ₂ O. 6 parts by weight of ₃ (Tl conversion
5.4 parts by weight) and Fig. 4 show 9 parts by weight of Tl ₂ O ₃ (8 in terms of Tl.
FIG. 3 is an explanatory view showing secondary recrystallized grains when using an annealing separator added and compounded respectively.

All of FIGS. 1 to 4 have a sample size of 400 (plate width direction) × 100 (line direction) mm, and the vertical direction of the drawing is the plate width direction. Also, the addition amount is
It is the ratio to 100 parts by weight of MgO.

As is clear from these figures, in FIGS. 2, 3 and 4 in which the Tl compound was added to the annealing separator, the secondary recrystallized grains were coarser than those in FIG.
It is shown that the compound significantly affects the coarsening of the secondary recrystallized grains.

[0021]

【Example】

Example 1 C: 0.08 mass%, Si: 3.30 mass%, Mn: 0.065 mass%
%, Se: 0.018 mass%, Al: 0.027 mass% and N: 0.00
A slab containing 82 mass% was hot-rolled, then cold-rolled to a cold-rolled sheet having a final sheet thickness of 0.27 mm, and subjected to decarburization annealing. of
An MgO-based annealing separator is applied to the above steel sheet in a slurry form, and then finish annealing is performed at a temperature of 850 ° C for 15 hours in a first holding annealing (secondary recrystallization annealing) process, followed by a 1200 ° C purification annealing product. And

[0022]

[Table 1]

The magnetic flux density (B ₈ characteristic) and _iron loss value (W _{17/5 0} ) of each of the products thus obtained were measured. The results of these measurements are also shown in Table 1 above.

In Table 1, Samples Nos. 1 to 9 are MgO-based annealing separators to which an appropriate amount of Tl compound was added (the addition amount is adjusted in terms of Tl) as a conforming example of the present invention. NO.10 but is a comparative example of Tl compound without additives, adaptations sample NO compared to the comparative example sample NO.10. 1 to 9 is B ₈
The characteristics are improved and the iron loss value is also reduced.

Example 2 C: 0.07 mass%, Si: 3.25 mass%, Mn: 0.07 mass%,
Se: 0.017 mass%, Al: 0.023 mass% and N: 0.0085ma
A slab containing ss% is hot-rolled, and then cold-rolled, and subjected to decarburization annealing on a cold-rolled sheet having a final sheet thickness of 0.22 mm,
Tl compounds shown in Table 2 and various MgO with different addition amounts
The main component of the annealing separator was applied in the form of a slurry to the above steel sheet, and then the final annealing was carried out at 850 ° C. for 15 hours of primary holding annealing, followed by purification annealing at 1200 ° C. to obtain a product.

[0026]

[Table 2]

The magnetic flux density (B ₈ characteristic) and the _iron loss value (W _{17/5 0} ) of each of the products thus obtained were measured. The results of these measurements are also shown in Table 2 above.

In Table 2, sample Nos. 1 to 9 are those using an MgO-based annealing separator to which an appropriate amount of a Tl compound was added (the addition amount is adjusted in terms of Tl) as a conforming example of the present invention. NO.10 is a reference example excessively added Tl compounds, reference example sample NO.10 than the adaptations sample NO. 1 to 9 is B ₈ characteristics are deteriorated. In addition, sample NO.10 had an unfavorable grain size because excessive addition of Tl compound caused excessive nucleation of (100) [001] -oriented grains and accelerated decomposition of the inhibitor that proceeded in parallel during grain growth. This is because the grains grow up to.

[0029]

EFFECT OF THE INVENTION The present invention is one in which an appropriate amount of Tl compound is contained in an MgO-based annealing separator for grain-oriented electrical steel sheets. Even under the annealing conditions, huge secondary recrystallized grains extending in the width direction of the strip plate can be obtained (110) [001] It becomes possible to obtain a grain-oriented electrical steel sheet having a high degree of integration and excellent magnetic properties.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing secondary recrystallized grains when an annealing separator without Tl compound addition is used.

FIG. 2 is an explanatory diagram showing secondary recrystallized grains when an annealing separator containing 3 parts by weight of Tl ₂ O ₃ is used.

FIG. 3 is an explanatory diagram showing secondary recrystallized grains when an annealing separator containing 6 parts by weight of Tl ₂ O ₃ is used.

FIG. 4 is an explanatory diagram showing secondary recrystallized grains when an annealing separator containing 9 parts by weight of Tl ₂ O ₃ is used.

Claims (1)

[Claims] 1. An MgO-based annealing separator, wherein the Tl compound is calculated as Tl based on 100 parts by weight of MgO in the annealing separator.
An annealing separator for grain-oriented electrical steel sheets, which contains 0.2 to 10 parts by weight.