JPS5849618B2 - Annealing method to improve magnetic properties of high silicon steel rapidly solidified ribbon - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an annealing method for improving the magnetic properties of a high-silicon steel quenched ribbon, which advantageously improves the magnetic properties of a high-silicon steel strip by adapting the annealing operation to this type of quenched ribbon. The purpose is to improve.

Recently, molten metal is spouted from a circular or slit-shaped nozzle onto a rotating body such as a roller that rotates at high speed, or a cooling body whose cooling surface is continuously updated and moved, such as a continuous running belt, and is rapidly solidified. , a technique has been developed to directly produce a ribbon with a thickness of 20 to 500 μm, and this ribbon is often called a quenched ribbon.

Ribbons containing Si in a proportion as high as 2-8%, preferably as high as 5-7%, can be manufactured with ease for the first time while being considerably less expensive to manufacture with this technology.

In other words, industrial production of high-silicon steel ribbon containing 5% or more of Si, which was virtually impossible to produce into ribbon using conventional rolling methods due to its brittleness, has become a reality. It was.

However, high-silicon steel quenched ribbon, in its original state,
Magnetic properties are generally poor because the strain is high, the crystal grain size is small, and the texture is not in a suitable state.

Therefore, when such a quenched ribbon is annealed as it is or after being further rolled, strain removal, recovery and recrystallization occur at about 600°C, and grain elongation begins at about 800°C or above. Although the magnetic properties are considerably improved by such annealing, the texture is generally the same as the texture formed during solidification.

On the other hand, when the annealing temperature for the quenched ribbon is increased to about 1000°C or higher, so-called tertiary recrystallization occurs, in which only crystal grains with (100) planes accumulated parallel to the sheet surface become abnormally (selected) or elongated. When tertiary recrystallization occurs, the texture becomes (10
0) (oKll) direction.

This is called a (100) in-plane non-directional structure. If the rapidly cooled ribbon is subjected to cold rolling two or more times, especially intermediate annealing, at an appropriate reduction rate, and then annealed at a temperature at which tertiary recrystallization occurs, the (100) (001) orientation is achieved. It has recently been disclosed that an integrated texture can be obtained.

This is especially called a bidirectional tissue.

When these textures are formed, the <100> axis, which is the axis of easy magnetization of iron (alloy), is aligned within the plane of the plate, resulting in even better magnetic properties.

Originally, such high-silicon steel ribbons were used as iron core materials for transformers, rotating machines, and generators, but in such applications, they were used in the (Zoo) [okl] direction as described above. It is clear that the higher the degree of accumulation in the (Zoo) (001) direction, the better the performance as an iron core material. Much depends on it.

In other words, the performance of the obtained ribbon is determined by the skill of this annealing.

The inventors conducted various experiments and found that the atmosphere during annealing has a great effect on the properties of the rapidly cooled thin film as follows.

That is, during annealing, in addition to exposing the iron surface of the ribbon to the atmosphere and preventing the formation of an oxidized layer, in particular, by including a trace amount of sulfur or its compound gas in the atmosphere, (100) (okA' ) or (100) [0
The inventors have completed the present invention by discovering that the degree of integration of the 01') orientations is further increased, and as a result, a high silicon steel ribbon having particularly excellent magnetic properties can be obtained.

The content of this invention will be explained in detail below according to the experimental progress.

By the way, silicon steel containing 2% or more of Si does not have γ transformation, so it is possible to enlarge the crystal grains by high-temperature annealing or to form a preferable texture by causing tertiary recrystallization. When it exceeds 8%, the saturation magnetic flux density becomes 1.
8T or less, which is not only unsuitable for iron cores such as transformers, but also extremely brittle, which is not preferable.

A set containing 5 to 7% Si is particularly preferable in terms of magnetic properties because the magnetostriction becomes extremely small.

Therefore, in this invention, Si 2~
The target is a silicon steel ribbon containing 8%.

Note that a small amount of Ni, Cu, Mo, W, Co, Cr, and/or AA can also be included as additional elements or unavoidably mixed elements other than Si.

The content of unavoidable impurities such as 0, N, and C must be limited depending on the intended grade of the ribbon.

According to the present invention, the molten steel having the above-mentioned structure is spouted from the container containing the molten steel onto the movable cooling surface of the movable cooling body through a suitably shaped nozzle attached to the container or separately provided, thereby rapidly solidifying the molten steel. The premise is to continuously produce quenched ribbons all at once.

In this invention, as the moving cooling body, conventionally known methods such as a single roll method, a twin roll method with unequal diameters, or a continuous belt method can be arbitrarily adopted, and furthermore, Of course, a method using the inner peripheral surface of the drum as disclosed in Japanese Patent Application No. 55-14799 (Japanese Unexamined Patent Publication No. 56-111506) can also be used.

Now, the inventors found that 3i contains 6.4%, and the unavoidable impurities are C: 0.005%, Q: 0.002%, N: 0.
molten steel containing 0.004% and S: 0.006% with a width of 1
．． A nozzle having a rectangular slit with a length of 25 mm x 25 mm is sprayed downward near the biting part of twin rolls with a diameter of 500 mm rotating at 65 rpm to force rapid solidification, and the thickness is 130 mm.
A quenched thin ribbon with a diameter of μm was produced.

This quenched ribbon was pickled with a 10% aqueous sulfuric acid solution heated to 80°C, further skin-pass rolled to a thickness of 120 μm, and then degreased with a cleaning solution containing Na2S103 as the main component.

The surface of the quenched ribbon exhibited a silvery white metallic luster, and the surface roughness was 0.1 μm or less.

This rapidly cooled ribbon was placed so that its surface was exposed to the atmosphere, and the temperature was raised from room temperature to 1120° C. over 5 minutes, and annealing was performed for 20 minutes.

In one cycle of this annealing, the atmosphere in the furnace, that is, the atmosphere in the furnace, and the atmosphere gas set are set to be constant as follows, and the total pressure P total of the atmosphere in the annealing cycle for each quenched ribbon is (To
(expressed in rr units) and the partial pressure of gas contained in the sulfur or its compound, PΣS (expressed in TOrr units),
The influence of these factors on the magnetic properties of the ribbon after annealing was investigated.

That is, during the annealing period, iron sulfide is heated to a certain temperature in an annealing furnace to release a certain amount of sulfur alone or its compounds in gaseous form, and the gas of S compounds such as H2S is heated in a vacuum. However, if the furnace leaks at a certain rate, or if the pressure inside the furnace is close to that of a dog, a trace amount of H
H2 and Ar gas containing 2S and SO2 were circulated.

During the entire annealing period, some of the gas in the furnace is
It was measured with a mass spectrometer (manufactured by Nippon Vacuum Co., Ltd.).

The product of the peak value (or peak surface (capital) Pi) of a specific gas (type i) detected by this device and the known relative difficulty of ionization ωi of that specific gas, ptωi, is the gas type Therefore, the sum of the gas fractions of a simple substance or its compound (H20, SOX, etc.), PΣ8, can be expressed as:

Here, Σ5PsiWsi takes the sum of S or S compounds such as H2S, SO, SO2, and! 'piW
i is the sum of all gas fractions.

In this experiment, masses up to 300 were counted.

In each annealing, from the start to the end of heating,
Ptotal and PΣ5 were held approximately constant.

After annealing, the magnetic properties of the ribbon were measured.

Figure 1 shows the coercive force H when magnetized to Bm-1.2 to 1.3 T with direct current.

(moe), P. It was plotted against tota# and PΣ5.

It can be seen that when an appropriate amount of S atmosphere exists over a range from Ptotal O-7 Torr to atmospheric pressure, the Ho value is the lowest (in this example, marked ◎; 70 mOe or less).

If the S atmosphere is too strong, the Ho value becomes worse.

By the way, the first characteristic required for the magnetism of the high-silicon steel quenched ribbon, which is the subject of this invention, is low loss, which is H.

There is a good correlation with the Ho value, and the lower the Ho value, the lower the loss.

Today, H is a grain-oriented silicon steel sheet that is used for the iron core of transformers.

The value is approximately 70 mOe for the highest grade.

On the other hand, as shown in Figure 1, the Ho value is 100m
It is possible to obtain the highest performance of less than Oe, especially less than 70 mOe.

In other words, the present invention can be utilized to provide a transformer core material with lower core loss than conventional materials.

A ribbon having such excellent soft magnetic properties is achieved by allowing an appropriate amount of S or S compound gas to be present in the atmosphere during high-temperature annealing to cause tertiary recrystallization.

The S atmosphere having the effect shown in FIG. 1 is uniquely determined by the gaseous component EE and PΣ8 defined in this invention, regardless of the type of S or S compound, and its area is expressed by .

Therefore, in this invention, in high-temperature annealing that causes tertiary recrystallization, the in-furnace E P to tal and the organic gas fraction PΣ8 as shown in equation (1) are
The quenched ribbon was annealed in an atmosphere of

Generally, when a quenched ribbon is annealed at a high temperature, the surface becomes (ioo
) planes are abnormally elongated and this phenomenon is called tertiary recrystallization, but since the axis of easy magnetization of iron alloys is in the <l O O> direction, (100
) The so-called (100) in-plane non-directional structure accumulated in the {okl} orientation is preferable from the viewpoint of magnetism.

In this invention, it is thought that when S is made to exist in the atmosphere, especially during high-temperature annealing, the accumulation in the (100) (okA) direction becomes remarkable, and as a result, the Ho value becomes low.

By the way, high-temperature annealing that causes such tertiary recrystallization is disclosed in Japanese Patent Application No. 164693/1983 (Japanese Patent Application No. 87627/1983).
It is known that a simple vacuum atmosphere requires a temperature of 1050° C. or higher, as shown in Japanese Patent Publication No.

As shown in FIG. 2, using the aforementioned quenched ribbon, PΣ5=I O-5 Torr and PΣ5= I O- at P total = I O- 2 Torr, respectively.
Annealing was performed at various temperatures and times under two types of vacuum atmospheres of 7 Torr, and the Ho values were compared.
Under normal vacuum (PΣ, = I O-9 Torr),
H below 100mOe for the first time at a temperature above 1050℃
.

In contrast, when the S atmosphere is introduced into the vacuum as described above, PΣ,=I O −'To
When set to rr, H reaches 100 mOe or less even during annealing at 1000°C.

value is obtained. Generally, in such high-temperature annealing, as the annealing temperature increases, control in industrial production becomes difficult and manufacturing costs rise, which is a serious disadvantage.

Therefore, by introducing the S atmosphere name in this invention, lower temperature and lower H.

It is extremely useful industrially to be able to produce a thin ribbon of.

In this invention, the temperature of high-temperature annealing for causing tertiary recrystallization is defined as a minimum of iooo'c.

Note that the time required for annealing can be shortened by increasing the annealing temperature.

The selection of these temperatures and times is left to engineering and cost.

It should be noted that it is generally difficult to set the annealing temperature to 1300'C or higher on an industrial production scale in actual operation today, and is contrary to the aim of the present invention.

By employing the annealing method described above, a silicon steel road strip with extremely excellent magnetic properties can be manufactured.

Any method may be used for this annealing as long as the specified conditions are met, and in particular, annealing at 1000℃~
A continuous furnace can be used in the temperature range around 1100°C.

On the other hand, at a relatively high temperature, a thin ribbon can be wound into a coil and annealed in a Box type furnace.

It is also good to take a method in which the ribbon coil is continuously passed through a high temperature section in the furnace.

Ribbons annealed using any of these known annealing methods typically have an average of 0. It has a grain size of 5 mm or more, and the texture is highly concentrated in the (100) [okl] direction.

In particular, in a ribbon that has been cold-rolled twice and intermediately heated before high-temperature annealing, a texture accumulated in the (ioo)[001) direction is obtained, so it is more desirable to apply this invention to the practice. .

The quenched ribbon that has undergone the above-mentioned high-temperature annealing already exhibits excellent magnetic properties in its original state.

However, if the coil is wound into a coil and annealed, there may be a coil set (winding curl), so it is recommended to apply tension when unwinding or to remove the coil set by passing it through a leveler. desirable.

Furthermore, since the material of this invention is used for the core of transformers and rotating machines, it is wound or laminated in layers, so it is necessary to provide electrical insulation between the layers of the quenched ribbon. Any conventionally known method can be used for this purpose.

That is, after the final high-temperature annealing, a coating liquid mainly containing phosphoric acid (salt) is applied, and continuous annealing is performed at a temperature of about 800° C. to add an insulating coating to the surface of the ribbon.

In particular, if strain relief annealing is not performed after punching and laminating for use in iron cores of rotating machines, etc., a coating made of organic resin C may be added.

By using the above-described steps, the present invention can advantageously improve the magnetic properties of a rapidly solidified high-silicon steel ribbon.

Examples are given below.

Example 1 Each set of molten steel shown in Table 1 was
It was ejected from nozzles arranged in a row at L intervals (4 holes), and was quenched and solidified using a twin roll method to produce a quenched ribbon with a thickness of 150 μm.

Its surface has an average roughness of 0.08 μm, and FeO and St
An oxidized layer of 02 (approximately 500 people) was observed.

After lightly polishing these ribbons with emery paper, they were annealed at 1080° C. for 300 minutes under the two types of atmospheres listed in Table 1.

A sulfur-based gas or a H2S gas was introduced into the annealing atmosphere.

The Ho values of the obtained high silicon steel ribbons were as shown in Table 1.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the suitability of annealing atmosphere according to the present invention, and FIG. 2 is a graph showing suitability of annealing temperature and time.

Claims (1)

[Scope of Claims] 1. A quenched ribbon obtained by quenching and solidifying a molten high-silicon steel spouted onto a cooling body whose cooling surface is continuously renewed, and a gas of sulfur or its compound as shown in the following formula. conditions are satisfied, and the total pressure P total is I O-
Annealing method for improving the magnetic properties of a rapidly solidified high silicon steel ribbon consisting of annealing in an atmosphere of 7 Torr or higher 4 12 4 1
951 o'n total-->logPΣs≧
9 1o'i'P total-a5 In the formula PΣS represents the sum of the gaseous fractions of sulfur and its compounds in Torr. 2. The method according to claim 1, wherein the annealing temperature range is 1000-1300°C. 3. The method according to claim 1 or 2, wherein the quenched ribbon to be annealed has been subjected to rolling history two or more times including short rolling or intermediate annealing.