JPS5843466B2 - Annealing separator for unidirectional silicon steel sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an annealing separator for grain-oriented silicon steel sheets having high magnetic flux density and low core loss.

A unidirectional silicon steel sheet is a silicon steel sheet that is not easily magnetized and has a high degree of integration of the 001> orientation.In order to manufacture this silicon steel sheet with excellent <001> orientation, it is annealed in H2 gas at a high temperature of 1000 to 1300°C. are doing.

In order to prevent the steel plates from seizing together during this high-temperature annealing,
Before annealing, magnesium oxide is applied to the surface of the steel sheet as an annealing separator.

Recently, grain-oriented silicon steel sheets with a very high degree of integration of the <OO1> orientation have been manufactured by dispersing A7N in steel, and the annealing separator, which previously only served to prevent seizure, has become magnetic. It turns out that it plays an important role.

Generally, the quality of grain-oriented silicon steel sheets is evaluated by magnetic flux density and iron loss.

Here, the magnetic flux density B refers to the magnetic flux per unit cross-sectional area of a uniformly magnetized silicon steel plate, and the higher the magnetic flux density, the better the quality.

In addition, iron loss refers to the power consumed in the steel plate when the silicon steel plate is magnetized by AC magnetizing force, and this power consumption (
The smaller the iron loss), the better the quality.

The degree of integration in the <001> direction is approximately proportional to the magnetic flux density, and a silicon steel plate with a high degree of integration in the <ooi> direction can obtain a high magnetic flux density.

Crystals having this <001> orientation begin to grow from the surface of the steel sheet during high-temperature finish annealing during the process of manufacturing silicon steel sheets, and are greatly influenced by the chemical properties of the annealing separator applied to the surface of the steel sheet.

For this purpose, many methods have been proposed in the past to improve magnetism by adding various chemicals to the annealing separator.

The present invention uses a Li compound and a Na compound in non-hydrated magnesium oxide as an annealing separator, and further adds a B compound to the annealing separator.
It has been discovered that by adding a compound in combination, a grain-oriented silicon steel sheet with excellent magnetic flux density and iron loss can be produced.

The present invention uses crystalline non-hydrated magnesium oxide calcined at 1300° C. or higher, which is more economical than conventional magnesium oxide calcined at low temperatures.

In addition, less moisture is brought in during the formation of the film, which is advantageous in preventing oxidation of the steel sheet.

Further, the non-hydrated magnesium oxide used in the present invention can be applied better to steel plates when its particle size is 5 μm or less on a 70-layer plate.

In the past, methods have been proposed in which alkali metals are added to magnesium oxide, but these are all additives alone, and magnesium oxide is also easily hydrated.

However, even alkali metals do not have the same effect on the magnetic flux density and iron loss of grain-oriented silicon steel sheets;
It behaves completely differently.

That is, an annealing separator in which an L1 compound is added to non-hydrated magnesium oxide greatly improves magnetic flux density, but hardly improves iron loss.

On the other hand, an annealing separator in which Na or a compound is added to non-hydrated magnesium oxide does not improve magnetic flux density at all, but has a large effect on improving iron loss.

As mentioned above, the magnetic flux density is proportional to the degree of integration of the <001> orientation, but Li in the annealing separator diffuses to the steel surface, and this
It acts to increase the degree of integration in the ooi> direction.

On the other hand, Na has a large contribution to improving iron loss.

This is explained as follows.

Afterwards, the crystalline non-hydrated magnesium oxide applied to the surface of the steel sheet as an annealing separator forms a glass coating (mainly forsterite (Mg2Si04)) during high temperature annealing, but when Na or K is added, the crystalline non-hydrated magnesium oxide becomes crystalline. Non-hydrated magnesium oxide is strongly bonded to each other and provides a large tensile force to the base steel.

It is known that applying tensile force in the direction of the <001> orientation of a unidirectional silicon steel sheet greatly increases iron loss, and glass coatings with a small amount of Na or K added can reduce iron loss due to this tension effect. improve.

If the amounts of Na and K are less than 1100 pp, no improvement in iron loss can be expected.

However, if too much Na or K is added, the melting point of the glass coating will drop rapidly, and as a result, it will melt during high temperature annealing and no glass coating will be formed.

According to experimental results, the upper limit of addition of Na or K is 1000.
If the length exceeds 99 m, the formation of the glass coating will be greatly inhibited and the iron loss will deteriorate.

On the other hand, the L1 compound has almost no tension effect on the glass coating, so even though a high magnetic flux density can be obtained,
There is almost no improvement in iron loss.

Further, even if 110,000 pp of Li was added, the formation of the glass coating was not inhibited at all, and it is considered that Li hardly participates in the formation of the glass coating.

However, even with the addition of aluminum, the magnetic flux density did not improve any further.
Therefore, 10000-300ppm preferably 5000p
It may be less than pm.

However, if the amount of Li is less than 300 ppm, no improvement in magnetism is observed.

In addition to the above-mentioned components, a boron compound is further added to the annealing separator of the present invention.

The steel plate coated with the annealing separator was heated in an H2 atmosphere containing nitrogen.
The next step is heat treatment for recrystallization, but at this time steel sheets containing A7 may absorb nitrogen, resulting in a large amount of A7.
When N is formed, there is a tendency for fine grains to form without secondary recrystallization.

However, if a film is formed using an annealing separator containing a boron compound, the boron compound will have the effect of suppressing nitrogen absorption into the steel sheet, adjusting the amount of nitride to the optimum level, and stabilizing secondary recrystallization. .

That is, in order to improve and stabilize the properties of the film as described above and to improve magnetism, it is necessary to add 300 to 1500 ppm of a boron compound as boron in the present invention.

If the B compound is less than 300 ppm, no improvement in magnetic flux density will be observed, whereas if it exceeds 1,500 ppm, the effect of suppressing secondary recrystallization will be too strong, and secondary recrystallization will not occur, resulting in poor magnetic flux density.

Furthermore, in the present invention, a titanium compound may be added as necessary.

This promotes crystallization of the film and contributes to imparting tension to the film, so when added, it may be added within a range of 1 to 10%.

The silicon steel sheet of the present invention is manufactured by a conventional method, and the steps such as casting, hot rolling, hot-rolled plate annealing and cold rolling, decarburization annealing, and final annealing may be performed under conventionally known conditions. Of course.

That is, continuous casting slabs or ordinary ingot-blooming slabs are used as starting materials, these slabs are hot-rolled, the hot-rolled sheets are annealed if necessary, and then cold-rolled.

The hot-rolled sheet contains 4.0% Si and 0.085% C, and further contains Mn, S, and Al such that A7N and MnS serve as secondary recrystallization promoting components.

Especially trace components such as N, Al 0.07 more, N 0.0
A material containing 10% is suitable for obtaining high magnetic flux density and low iron loss characteristics.

Other Ni as necessary. It may also contain a small amount of one or two of Cut sb, Se, etc.

Cold rolling may be performed in one stage under high pressure or in two stages including intermediate annealing.

Decarburization annealing An annealing separator, which is a feature of the present invention, is applied, and final finish annealing is performed.

Next, examples of the present invention will be shown.

Example I C0,04,Si 2.9. Mn O, 08, Po, 0
10°So, 025. AlO, 027, NO, 0080
After cold-rolling a hot-rolled silicon steel plate consisting of Fe in the balance to a thickness of 0.30 mm, H2 (7"5 = ) + N2 (2
5) Decarburization annealing was performed in an atmosphere.

After decarburization, 15g7tn of annealing separator with the following composition was applied to the steel plate.
``I applied it.

Composition of annealing separator After the steel plate coated with the annealing separator is dried at 250℃,
It was annealed in H2 gas at 1200°C to obtain a grain-oriented silicon steel plate.

Example 2 The same steel plate as in Example 1 was coated with an annealing separator having the following composition.
g/fn2 was applied.

This steel plate was dried at 250℃ and then heated to 1200℃ H2
Annealing was performed in gas to obtain a grain-oriented silicon steel plate.

Composition Example 3 of Annealing Separator An annealing separator having the following composition was applied to the same silicon steel plate as in Example 1 at a rate of 10 g/m''.

This steel plate was dried at 250°C and then heated to 1200°C.
Annealing was performed in 2 gases to obtain a grain-oriented silicon steel sheet.

Table 1 shows the relationship between the amounts of Li and Na added and magnetism, including the results of non-hydrated magnesium oxide calcined at 2100° C. produced by the method of the above examples.

From Table 1, the magnetic flux density B8 is extremely high at 1.94 to 1.95 T when Li addition is in the range of 300 to 5000 ppm.
It can be seen that when Na or K is added to this in an amount of 11,000 pp or less, the iron loss is improved.

If the Na content exceeds 11,000 pp, the iron loss will worsen.

When 11,000 pp of Na or Na is added alone, the magnetic flux density is low and the iron loss is slightly increased.

Example 4 An annealing separator having the following composition was applied to the same silicon steel plate as in Example 1 at a rate of 12 g/m''.

This steel plate was dried at 250℃ and then heated to 1200℃ H2
Annealing was performed in gas to obtain a grain-oriented silicon steel plate.

Example 5 An annealing separator having the following composition was applied to the same silicon steel plate as in Example 1 at a rate of 12 g/m''.

This steel plate was dried at 250℃ and then heated to 1200℃ H2
Annealing was performed in gas to obtain a grain-oriented silicon steel sheet.

Non-hydrated Magnesium Oxide Calcined at 1700'C Example 6 To the same silicon steel plate as in Example 1, 15 g of an annealing separator having the following composition was applied to the steel plate.

This steel plate was dried at 2500C, then heated to 1200C
Annealing was performed in 2 gases to obtain a grain-oriented silicon steel sheet.

Non-hydrated Magnesium Oxide Calcined at 1900'C Example 7 The same silicon steel plate as in Example 1 was coated with an annealing separator having the following composition at 13 g/m''.

This steel plate was dried at 2500C and then annealed in H2 gas at 1200C to obtain a grain-oriented silicon steel plate.

Examples of non-hydrated magnesium oxide calcined at 2100°C
8 To the same silicon steel plate as in Example 1, 15 g of an annealing separator having the following composition was applied to the steel plate in an amount of 7 m2.

This copper body was dried at 250'C and then heated to 1200'C.
Annealing was performed in 2 gases to obtain a grain-oriented silicon steel sheet.

Non-hydrated magnesium oxide calcined at 2100°C As explained in detail above, the annealing separator of the present invention significantly improves the magnetic flux density of the silicon steel sheet due to the action of Li contained therein, and Na'! or K to reduce iron loss.

Further, the action of B prevents nitrogen absorption in the silicon steel sheet, and these effects significantly improve the magnetic properties of the silicon steel sheet.

Furthermore, by adding B, the nitrogen compounds in the steel necessary for secondary recrystallization can be controlled within an optimal range, and a grain-oriented silicon steel sheet with excellent magnetism can be obtained.

Claims (1)

[Claims] 1 Li compound in non-hydrated magnesium oxide 300-50
00ppm (in terms of Li), B compound 300-5
000pm (in terms of B), and at least one Na compound or Ni compound at 100 to 11000p each.
A characterized by containing p (in terms of Na or)
A unidirectional silicon steel plate coral annealing separator that uses AN and MnS as secondary recrystallization promoting components.