JPH0651897B2 - Semi-process electrical steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention is directed to a plate vertical direction by performing strain relief annealing accompanied with decarburization after processing into an iron core shape of a transformer or an electric motor or a magnetic shield material. In addition, the present invention relates to a semi-processed electromagnetic steel sheet which can be a material having a high magnetic flux density in which the <100> axis of the crystal lattice is integrated with high density.

<Prior Art> Generally, magnetic steel sheets containing Si at a high rate and suppressing impurity elements such as C as much as possible are used for iron core materials of electric motors, generators, transformers, etc. Requires a low iron loss value and a high magnetic flux density. In order to realize these required magnetic characteristics, the <100> axis of the body-centered cubic lattice, which is the axis direction of the easy magnetization, is set in the direction of the magnetic field used. It is considered effective to collect them.

Then, when the direction of the magnetic field used is limited to one direction, about 3% showing particularly good magnetic characteristics under such a usage pattern (hereinafter,% indicating the component ratio is weight%).
The grain-oriented electrical steel sheet containing Si is applied. this is,
As shown in Fig. 1 (a), in the grain-oriented electrical steel sheet {11
This is because the {0} plane is parallel to the plate surface and the <100> axis is integrated in the rolling direction, so that the magnetic properties are extremely excellent when used by applying a magnetic field in the rolling direction. However, on the other hand, this unidirectional electrical steel sheet is difficult to magnetize in a direction other than the rolling direction, and therefore, when it is used as a member in which a magnetic field acts in various directions within the plate surface, such as a rotating machine such as an electric motor or a generator. It wasn't a special effect.

Therefore, in the case where the magnetic field acts in an unspecified direction on the plate surface, a "non-oriented electrical steel sheet" having a texture as shown in Figs. 1 (b) to 1 (e) is used. used. However, even among these non-oriented electrical steel sheets, the fact that good magnetic properties are actually shown is that the {100} plane shown in FIGS. 1 (b) to 1 (d) is the plate surface. The parallel <100> axes are accumulated in the direction perpendicular to the plate surface. With such a texture, two out of three <100> axes which are orthogonal to each other are formed.
Up to two are parallel to the board surface. The desired degree of integration of the two <100> axes parallel to the plate surface differs depending on the application. For example, in the case of "EI type iron core" where magnetic fields are applied in two directions orthogonal to each other in the plate surface. Fig. 1 (b)
And {100} <001>, {1} as shown in FIG. 1 (c).
00} <011> orientation texture is preferred, and in the case where a magnetic field is applied in all directions within the plate surface, use the {100} in-plane non-directional texture shown in Fig. 1 (d). Alternatively, the {100} <001>, {100} <011> type textures shown in FIGS. 1 (b) and 1 (c) are punched at different angles in the plate plane, and these are stacked. It can be said that it is preferable to use them together.

By the way, such a non-oriented electrical steel sheet having a <100> axis in the direction perpendicular to the sheet surface has been conventionally manufactured by two methods, "a method using a solidification structure" and "a method by high temperature annealing" as shown below. There is.

Among them, the "method using a solidification structure" is "when solidifying steel, crystals having a <100> axis in the heat flow direction grow,
When solidified into a plate, the heat flow direction becomes perpendicular to the plate surface, which is the cooling surface, so the <100> axis is oriented in this direction. ”
And "the orientation of crystals during solidification of steel" are used, and specifically, there are two methods, "a method using a melt quenching method" and "a method using ingot columnar crystals".

"Melting by quenching" is a method of directly producing a thin plate with a thickness of about 0.05 to 0.5 mm by jetting the molten metal onto the surface of a cooling roll that rotates at a high speed, and using this method, silicon containing about 6% Si. When a thin strip is manufactured, a columnar grain structure having a long axis in a direction perpendicular to the plate surface or inclined by 20 to 30 ° with respect to the vertical direction is obtained.

On the other hand, in the "method using ingot columnar crystals", a columnar crystal ingot having a <100> fiber structure manufactured by a special casting method is rolled so that the {100} plane becomes a rolling plane, and this is rolled at 1000 ° C or higher. Annealed at temperature {100}
<001> A method for producing a silicon steel sheet having a texture.

On the other hand, the “method by high temperature annealing” is a method of growing crystal grains having a <100> axis in the direction perpendicular to the plate surface by high temperature annealing, and the following two methods are known.

One is a method that has a main characteristic in the regulation of the annealing atmosphere, and is a method of using a thin silicon steel sheet having a thickness of 0.15 mm or less and performing annealing at a temperature of 1000 ° C. or more in a weakly oxidizing atmosphere. . According to this method, the existing crystal grains once grow to the size of the plate thickness, but thereafter the crystal grains having the <100> axis in the direction perpendicular to the plate surface preferentially grow with the surface energy as the driving force. It will be.

Another is to use silicon steel with a slight addition of Al, etc.
115 after rolling (cross rolling) in both 90 ° and 90 ° directions
This is a method of performing final annealing at a temperature of 0 ° C., which is a method of realizing crystal grains of {100} <001> orientation by secondary recrystallization.

However, in each of these methods, the following various problems have been pointed out, which has been a considerable obstacle to the stable manufacture of products with desired performance.

<Problems to be Solved by the Invention> That is, in the “melting quenching method” of “method using solidification structure”, the electrical steel sheet obtained has a <100> axial density of 3 to 6 times in the sheet surface vertical direction. Since the thickness is low and the plate thickness accuracy is low, the high space factor required for electromagnetic steel plates cannot be secured.

Further, in the "method using an ingot columnar crystal", when the <100> axis is densely integrated in the direction perpendicular to the plate surface, a very large crystal grain structure is formed, and the crystal grain is usually 10 to 100 times the plate thickness. Therefore, the eddy current loss is large in the AC magnetic field, and a sufficient low iron loss cannot be secured. Moreover, since it is necessary to adopt a special casting method, it is difficult to carry out on an industrial scale.

On the other hand, in the "method by high temperature annealing", the same problems as in the case of "method using ingot columnar crystals" in "method using solidified structure" are pointed out by any method. That is, even when annealing is performed in a weakly oxidizing atmosphere or when cross rolling is performed, it is attempted to increase the "integration degree of the <100> axis in the direction perpendicular to the plate surface" of the obtained electrical steel sheet. Then, the crystal grain structure became very large, and it was not possible to prevent deterioration of iron loss characteristics in an alternating magnetic field. In addition, the "method of annealing in a weakly oxidizing atmosphere" is 0.15mm thick
There is also a restriction that it can only be applied to the following extremely thin plates,
In any case, it was hard to say that it was an industrially satisfactory method.

Therefore, an object of the present invention is to eliminate the above-mentioned problems pointed out in conventional electromagnetic steel sheets, and to easily and stably provide an electromagnetic material product having a high magnetic flux density and good iron loss characteristics. To find a suitable means.

<Means for Solving the Problems> The inventors of the present invention conducted repeated research while repeating many experiments to achieve the above-mentioned object, and as a result, “the C content and the like in addition to the Si content are regulated within a specific range. A surface layer of "α single phase texture with high <100> axial density in the direction perpendicular to the plate surface" is formed on the formed silicon steel plate at the stage of the semi-processed electromagnetic steel plate not subjected to stress relief annealing, and The stress relief annealing performed after processing into the shape or the magnetic shield material should be performed under the condition that decarburization progresses, and inside the steel sheet other than the surface layer during the process of decarburization by the strain relief annealing that also serves as decarburization. When the γ → α transformation occurs in the sheet, the "100 degree" axis high-density magnetic steel sheet product with a low grain loss and high magnetic flux density in the direction perpendicular to the sheet surface over the entire sheet thickness has an exceptional size. We are not subject to the above restrictions, and we are fully satisfied industrially. That it has led to the knowledge that the simple and stable obtained "in scale.

The present invention has been made based on the above findings and the like, and includes "C: 0.02 to 1.0% and Si: 0.2 to 6.5%,
A steel sheet having a thickness of 0.05 to 5 mm, which also includes Mn: 5% or less if necessary, and C: becomes substantially an α-ferrite single phase at a temperature of 850 ° C. or less when decarburized to 0.01% or less, And, the average crystal grain size is 5 mm in the surface layer portion of 5 to 100 μm.
In the following, the point is that the semi-processed electromagnetic steel sheet is formed in a state in which a decarburized layer of C: 0.01% or less in which the <100> axis is densely accumulated in the sheet surface vertical direction ”.

<Operation> First, the production of the semi-processed electromagnetic steel sheet according to the present invention is performed from the following viewpoints.

That is, conventionally, it is customary to anneal an electromagnetic steel sheet in the temperature range of α-ferrite single phase. On the other hand, a cold rolled silicon steel sheet in which an appropriate amount of C is added to expand the temperature range of the austenite phase (γ phase) has, for example, a weak decarburization property in the “temperature range where the α single phase is obtained when decarburization is completed”. When annealed in an atmosphere, since C is sufficiently contained in this annealing, the annealing is performed in the [α + γ] two-phase region or the γ single-phase temperature region.

As a result, the surface layer region is decarburized due to the annealing in the weakly decarburizing atmosphere, and only this portion becomes the α single phase. Then, the α crystal grains grow in the direction perpendicular to the plate surface as shown in FIG. 2 by holding under the condition of the weak decarburizing atmosphere such that the α single phase region does not reach the deep portion. Thus, the surface layer region of the silicon steel sheet has an α single phase texture in which the <100> axis is strongly integrated in the direction perpendicular to the sheet surface. Note that it is presumed that the grain growth at this time uses the surface energy as a driving force. And
At this stage, the α-grains on the surface of the silicon steel plate are 3 in the direction parallel to the plate surface.
It is a columnar particle having a size of about 0 to 300 μm.

The semi-processed electrical steel sheet produced in this way is processed into the core shape of transformers and electric motors and magnetic shield materials by punching at customers, for example, and then subjected to stress relief annealing in a decarburizing atmosphere for decarburization. , The surface α grains grow toward the internal [α + γ] 2 phase region or γ phase region,
Finally, as shown in FIG. 3, "a single phase columnar grain structure in which columnar grains extending inward from both surfaces collide at the center of the plate thickness" is obtained.

As described above, the semi-processed electromagnetic steel sheet according to the present invention,
When the γ → α transformation is generated in the decarburization process in the strain relief annealing, the {100} texture that had been previously grown in the surface layer is inherited to the inside by grain growth, and the entire plate can be easily and easily {10
0} texture. Moreover, the degree of integration of the <100> axis in the direction perpendicular to the plate surface is also improved in the course of grain growth.

Then, in the highly integrated {100} texture realized by such a treatment, if the diameter of the columnar crystals is several times or less the plate thickness, the eddy current loss is significantly reduced as compared with the conventional one. It was also found that the magnetic flux density was high.

By the way, in the present invention, the reason why the component composition, the plate thickness and the like of the semi-processed electromagnetic steel plate are numerically limited as described above is as follows.

A) Component composition of steel sheet C γ accompanying decarburization during stress relief annealing after processing at customers etc. →
In order to control the texture using α transformation, the C content of the semi-processed electrical steel sheet before the stress relief annealing is 0.02
% Or more, preferably 0.05% or more. But,
If the C content is too high, the decarburization time becomes long, which is not preferable for an industrial process. Therefore, the C content is
1.0% or less, preferably 0.5% or less, and preferably 0.3% or less.

The C content after the stress relief annealing is 0.01% or less, preferably 0.005% or less in order not to deteriorate the magnetic properties.
% Or less, preferably 0.003% or less.

In order to secure Si magnetic properties and mechanical properties, the Si content needs to be 0.2% or more, but preferably 1% or more is added. However, if Si is excessively contained, not only the embrittlement of the material becomes remarkable but also the magnetic flux density is lowered, so the upper limit of the Si content is set to 6.5%, but preferably 5% or less, More preferably, it should be suppressed to 4% or less.

Mn Mn not only has the effect of increasing the electrical resistance and reducing the eddy current loss, but also has the effect of expanding the γ phase temperature range and facilitating the texture control of the γ → α transformation utilization, so it is desirable to add it. If added, 0.5% or more, especially
It is desirable to contain 0.8% or more, and in any case, the maximum addition is the amount that substantially forms an α-ferrite single phase at 850 ° C. or lower after decarburization is completed. This is because when Mn is contained in a large amount, the temperature at which the α-ferrite single phase is substantially reduced after decarburization is completed, and the annealing temperature must be extremely lowered. However, if the Si content is high, a large amount of Mn can be contained, but if the Mn content exceeds 5%, the magnetic flux density will decrease, so the upper limit of the Mn content is 5%. I decided.

Note that "substantially becoming an α-ferrite single phase" means Mn
This means that a slight amount of second phase such as S or AlN may be present.

Then, as components other than C, Si and Mn which can be contained without impairing the effects of the present invention, the following can be mentioned. That is, Al: 3% or less, one or more of W, V, Cr, Co, Ni and Mo: 1
% Or less, Cu: 0.5% or less, Nb: 0.5% or less, N: 0.05% or less, S: 0.5% or less, one or more of Sb, Se and As: 0.05% or less, B: 0.005% or less and P: 0.5 %Less than.

B) Plate Thickness of Steel Plate In the present invention, it is not necessary to set an upper limit on the plate thickness in terms of crystallographic texture. However, if the plate is thick, it takes a long time to decarburize to the inside and the eddy current loss increases, so the upper limit was set to 5 mm, but preferably 1 mm or less, preferably 0.5 m.
It should be less than m. On the other hand, it was well accumulated {10
A plate thickness of at least 0.05 mm is required to form a 0} texture, but it is preferably 0.1 mm or more, and more preferably 0.15 mm or more.

C) Crystal structure of semi-processed electromagnetic steel sheet (before stress relief annealing) 5-100 μm C: 0.01% or less decarburized layer exists in the steel sheet surface layer portion, and the crystal grains of the decarburized layer have an average diameter of 1 mm or less,
Moreover, it is necessary to have a crystal structure in which the <100> axis is highly integrated in the direction perpendicular to the plate surface. If this condition is not satisfied, the desired crystal structure can be realized in the product by subsequent strain relief decarburization annealing. Will be difficult. The degree of integration of the <100> axis is preferably 3 times or more, and more preferably 5 times, as compared with that without a crystal orientation orientation (random one) in order to secure sufficient magnetic properties after strain relief decarburization annealing. Above, if possible, it is better to be 10 to 15 times or more.

And, as mentioned above, such a special crystal structure of the steel sheet surface layer portion can be formed by the following method.

That is, the silicon steel plate cold-rolled to the final product thickness may be weakly decarburized and annealed in the temperature range where the α-ferrite single phase is obtained after the decarburization is completed.

The weak decarburizing annealing is performed in a vacuum of, for example, 10 ^-1 Torr or less, or in an atmosphere of one or more of H ₂ , He, Ne, Ar, Kr, Xe, Rn, N _{2 having} a dew point of 0 ° C. or less. At a temperature of 850 ° C. or higher to form an α single phase region at a depth of 5 to 100 μm from the surface on the surface layer of the steel sheet. The annealing time is preferably about 1 minute to 48 hours.

By the way, the strip for magnetic steel sheets according to the present invention does not particularly require the manufacturing conditions thereof, but the rolling reduction in cold rolling is 10% or more, preferably 30% or more, and preferably 50% or more. Is good. Normally, the steps of continuous casting-hot rolling-cold rolling are adopted, but after that, the weak decarburizing annealing step of forming the crystal structure before the stress relief annealing described above is adopted, and a semi-processed electromagnetic steel sheet is manufactured. To be done. At this time, annealing after hot rolling, or performing cold rolling a plurality of times and performing intermediate annealing during rolling does not hinder anything.

The cold-rolled sheet is made of, for example, 50 mm molten steel instead of continuous casting.
It goes without saying that a thin slab directly solidified to the following plate thickness or an ultrathin plate by a melt quenching method may be directly or hot rolled and then cold rolled.

The "cold rolling" referred to here means "rolling at 500 ° C or lower at which recrystallization does not occur".

By the way, the semi-processed electromagnetic steel sheet is used, for example, after being subjected to stress relief annealing after being processed into an iron core shape of a transformer or an electric motor or a magnetic shield material at a customer or the like.
The above-mentioned strain relief annealing in the semi-processed electromagnetic steel sheet according to the present invention is carried out in a form in which strong decarburization annealing is performed in a temperature range where a normal α-ferrite single phase is obtained after completion of decarburization. As a result, for the inside of the steel sheet that has not been decarburized before stress relief annealing, [α
+ Γ] Annealing is performed at a temperature of a two-phase region or a γ single-phase region, and as decarburization of this portion progresses by the decarburization annealing, a γ → α transformation occurs from the surface layer portion toward the inside, and finally <10 in the direction perpendicular to the plate surface through the entire plate thickness.
A substantially α single-phase columnar structure in which the 0> axis is strongly integrated is obtained.

The stress relief annealing atmosphere is a strong decarburizing atmosphere. For example, dew point: H ₂ at 0 ° C. or higher with an inert gas, CO, or CO.
Annealing is performed at a temperature of 650 to 900 ° C. in a gas containing ₂ to grow the α single phase region formed in the surface layer of the plate toward the inside of the plate. The annealing time is preferably about 5 minutes to 20 hours.

Note that this strain relief annealing step may be performed in a temperature range in which the α phase and cementite are mixed phases under the initial C content.

In addition, it is preferable to form an insulating film on the surface of the product manufactured from the semi-processed electromagnetic steel sheet according to the present invention by coating or the like, but this step is usually performed before being processed into an iron core or the like.

Next, the present invention will be described more specifically by way of examples.

<Examples> Vacuum ingots of 11 kinds of compositions (AK) shown in Table 1 were hot forged into a plate having a thickness of 30 mm, and each of the obtained plates was hot rolled to a thickness of 2.3 mm. After that, it was cold rolled to a thickness of 0.5 mm. Then, in vacuum, 870 ~ 1150 ℃,
Weak decarburization annealing was performed for 1 minute to 24 hours to obtain a semi-processed product.

The above-mentioned annealing conditions, the thickness of the decarburized layer of C ≦ 0.01% or less in the surface layer, the crystal grain size, and the decarburized layer <10
Table 2 collectively shows the {200} plane reflection intensities of X-rays corresponding to the 0> axis density.

Next, from the obtained semi-processed electrical steel sheet, an outer diameter of 45 mm,
After punching out a ring-shaped specimen having an inner diameter of 33 mm, as stress relief annealing "dew containing H ₂ 20%: + 40 ℃ of 850 ° C. in Ar stream, strong decarburization annealing of 5 minutes to 5 hours" was subjected to . The amount of C after this strain relief annealing is It became 0.003% or less for all the samples.

Then, from the surface of each sample that has undergone strain relief annealing,
X-ray diffraction measurement was performed at the "5 position", and the {200} plane reflection intensity of the X-ray corresponding to the <100> axis density in the direction perpendicular to the plate surface was calculated as a multiple of the non-oriented one and the crystal grain size was also calculated. It was

The results of these measurements are also shown in Table 2.

The following can be confirmed from the results shown in Table 2. That is, a steel sheet obtained from an ingot having a composition B having a C content of less than 0.02%, which is lower than the definition in the present invention, is not a product according to the present invention in which only a surface layer portion has a decarburized layer in a semi-process product stage. However, in such a material, the degree of <100> axis integration in the direction perpendicular to the plate surface over the entire thickness after strain relief annealing is extremely low.

Further, the steel sheet obtained from the ingot having the composition J having a Si content much higher than 6.5% has an extremely low saturation magnetic flux density even after stress relief annealing, and even if a good texture is formed, B _{10 in the} rolling direction is
The value of is not so high.

Further, the steel sheet obtained from the ingot having the composition K having a Mn content greatly exceeding 5% does not become the α single phase even if decarburized at the temperature of the weak decarburization annealing performed after cold rolling. The above-mentioned product cannot be obtained and good magnetic properties cannot be obtained because the <100> axial density does not increase even after strain relief annealing.

On the other hand, in the semi-processed products according to the present invention obtained from the ingots having the compositions A and C to I, the "columnar structure of the α phase grown in the direction perpendicular to the plate surface" is realized after the strain relief annealing. Moreover, it can be confirmed that the <100> axis is strongly integrated in the direction perpendicular to the plate surface over the entire plate thickness and exhibits excellent magnetic characteristics.

<Summary of Effects> As described above, according to the present invention, an electromagnetic material product having a high magnetic flux density and a low iron loss, in which the <100> axis of the crystal lattice is densely integrated in the direction perpendicular to the plate surface, is provided. It is possible to obtain a semi-processed electrical steel sheet that can be easily and stably realized.
It has an extremely useful effect on the industry.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating the crystal arrangement of an electromagnetic steel sheet, and includes FIGS. 1 (a), 1 (b), 1 (c), 1 (d) and 1 ( e) shows different examples. FIG. 2 is a photograph showing an example of the metallographic structure of the cross section of the semi-processed electromagnetic steel sheet according to the present invention. FIG. 3 is a metallographic photograph showing the cross-sectional structure of the semi-processed electromagnetic steel sheet according to the present invention after strain relief decarburization annealing.

Claims (2)

[Claims] 1. C: 0.02 to 1.0% by weight and Si: 0.2 to 6.5% by weight, and 8 when decarburized to C: 0.01% by weight or less.
A steel sheet having a thickness of 0.05 to 5 mm, which is a substantially α-ferrite single phase at a temperature of 50 ° C. or lower, and having a surface layer portion of 5 to 1
A semi-processed electrical steel sheet characterized by a decarburized layer of C: 0.01 wt% or less, in which 00 μm has an average crystal grain size of 1 mm or less and the <100> axis is densely accumulated in the direction perpendicular to the plate surface. 2. C: 0.02 to 1.0% by weight, Si: 0.2 to 6.5% by weight and Mn: 5% by weight or less, and when decarburized to C: 0.01% by weight or less, it is substantially at a temperature of 850 ° C. or less. A steel plate with a thickness of 0.05 to 5 mm, which is an α-ferrite single phase,
5-100 μm of the surface layer has an average crystal grain size of 1 mm or less, and the <100> axis is densely integrated in the direction perpendicular to the plate surface C:
A semi-processed electrical steel sheet characterized by having a decarburized layer of 0.01% by weight or less.