JP2636604B2 - Soft magnetic steel excellent in direct current magnetization characteristics and coating adhesion, and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft magnetic steel material excellent in direct current magnetization characteristics and paint adhesion and a method for producing the same. In particular, the direct current characteristics are excellent in coercive force and magnetic flux density and impart corrosion resistance by coating. It is an object of the present invention to provide a soft magnetic steel material excellent in paint adhesion, which is important for the production of such a material, and a method for producing the same.

[0002]

2. Description of the Related Art A soft magnetic steel material constituting a magnetic circuit has a so-called AC characteristic when an operating magnetic field is a DC magnetic field, or when an AC magnetic field has a time-dependent change in the intensity of the operating magnetic field that is relatively slow below a commercial frequency. The iron loss property, which is one of the evaluation items, is not important.Rather, it is one of the evaluation items of the DC magnetization characteristics of soft magnetic steel to reduce the residual magnetism of magnetic circuit components and to ensure the linearity of operation. It is desired that the coercive force is small. Further, in order to function efficiently as a magnetic circuit component, it is desired to have a high magnetic flux density value.

In order to solve these relationships, Japanese Patent Laid-Open No. 3-75
314, JP-A-3-75315, JP-A-2-4918-4923, JP-A-2-
8323-8326, JP-A-3-134140, JP-A-3-94046, JP-A-Hei.
3-82715, JP-B-63-45443, JP-A-3-87313, JP-B-3-3-
4606, JP-A-3-20447 and JP-A-2-213421 are disclosed. In other words, all of these techniques aim at improving the DC magnetization characteristics of pure iron-based soft magnetic steel, and have a good magnetic flux density value reflecting the high saturation magnetization inherent to iron. However, among these known techniques, examples relating to coercive force are described in JP-A-2-8324, JP-B-63-45443, and JP-A-3-3443.
20447, considering JP-A-2-213421, JP-A-3-20447
Only JP-A-2-213421 shows excellent characteristics of 0.4 Oe (32 A / m) or less, but all others are 0.65 Oe.
(50 A / m) or more, which is not sufficiently satisfactory.

[0004] Further, since all of these techniques are iron-based materials, it is expected that the corrosion resistance of the material itself is not always sufficient. Also, none of these technologies discloses a technology for ensuring corrosion resistance. Therefore, when applying a magnetic circuit component using these techniques to an application requiring corrosion resistance, surface treatment such as plating and painting is indispensable. However, on the other hand, in order to solve the corrosion resistance, a large amount of Cr is contained, and as a technology for imparting the same corrosion resistance as stainless steel, Japanese Patent Laid-Open Nos.
115546, JP-A-3-72028, JP-A-2-310345, JP-A-2-25
Although 9047 and the like have been announced, these techniques require that a large amount of expensive Cr be added in a large amount of 5 to 8% or more in order to impart corrosion resistance.
As shown by 2-259047, the value decreases with the addition of Cr, and in this technology, the lower limit of the magnetic flux density value is set to 11000G.

[0005] Techniques for improving the corrosion resistance by applying a coating on the surface of a steel material are widely and generally used. However, in order to exhibit sufficient corrosion resistance, it is necessary to ensure sufficient adhesion between the coating surface and the coating film. No. However, if the coating is performed without any pretreatment on the steel surface, sufficient coating adhesion is not necessarily obtained, so that the coating film peels off from the edges and defects, resulting in sufficient corrosion resistance. Can't expect.
Therefore, in order to improve the coating adhesion, the surface of the steel material is subjected to a chemical conversion treatment such as a zinc phosphate treatment and a chromate treatment as a pretreatment of the coating, and then the coating is performed.More preferably, a primer having a good adhesion is applied. It is common practice to perform a two-coat coating, which is performed once more.

Japanese Patent Application Laid-Open No. 1-283343 is known as a technique for forming an oxide film on the surface of a steel material. The purpose of these techniques is to improve the iron loss value, which is an AC characteristic, and to generate the steel during conventional annealing. The purpose is not to form an internal oxide layer, but to improve corrosion resistance and paint adhesion.

[0007]

As described above, the prior art relating to this kind of material for magnetic circuit components is constituted as described above, so that the iron-based material has a sufficient magnetic flux density value. There are disadvantages that the coercive force is not sufficiently reduced, and that a surface treatment such as plating or painting has to be performed if necessary, and a technique for ensuring the corrosion resistance of the material has not been started yet, which increases the cost of the magnetic circuit components as necessary.

[0008] In the prior art as described above,
In stainless steel material with greatly improved corrosion resistance, painting,
Although surface treatment such as plating is unnecessary, there is a disadvantage that a large amount of expensive Cr must be added, and the magnetic flux density value must be low. In addition, when coating with an iron-based material that has a sufficiently good magnetic flux density and coercive force to ensure sufficient corrosion resistance, it is necessary to ensure coating adhesion. processing)
It is necessary to perform the final coating of the second coat after the coating, preferably the coating of the primer, and the cost must be increased.

[0009]

According to the present invention, as a result of repeated studies on solving the above-mentioned problems in the prior art, it has been found that Al is added to iron having an upper limit of impurity content in a certain amount or more. Obtaining excellent coercive force by securing the growth of ferrite crystals and forming an Al ₂ O ₃ particle coating layer on the surface to obtain corrosion resistance, and also ensuring the soft magnetism and adding the above Al content addition upper limit The upper limit and the impurity content of other alloying elements are also specified so as not to impair the high magnetic flux density inherent in iron, and are as follows.

(1) By weight%, C: 0.0005-0.0070%, TN: 0.0005-0.0100%, Si: 0.005-0.50%, Mn: 0.01-0. .25%, P: 0.2000% or less, S: 0.0100% or less, sol. Al: 0.5-3.5%, TO: 0.0100% or less, with the balance being Fe and inevitable impurities A steel plate having a thickness of 0.1 to 6 mm or a steel material processed into a required shape, comprising at least 10% of ferrite crystal grains having a grain size of at least 0.3 mm or more; and particle size on the surface
DC magnetization characteristics characterized by being densely covered with Al ₂ O ₃ particles of 0.1 to ₅ μm, and exhibiting a coercive force of 0.4 Oe or less and a magnetic flux density at a magnetomotive force of 25 Oe of 15000 G or more without distortion. Soft magnetic steel with excellent paint adhesion.

(2) By weight%, C: 0.0005-0.0070%, TN: 0.0005-
0.0100%, Si: 0.005 to 0.50%, Mn: 0.01 to 0.2
5%, P: 0.2000% or less, S: 0.0100%
Below, sol.Al: 0.5-3.5%, TO: 0.0100%
A steel sheet having the following composition and the balance consisting of Fe and unavoidable impurities having a thickness of 0.1 to 6 mm or a steel product processed into a required shape from this is finally subjected to an oxygen partial pressure of 10 ⁻⁶ to 10 ^−. Heat treatment at a temperature of 850 to 1300 ° C in an atmosphere of ² atm.
Excellent direct current magnetization characteristics and paint adhesion, characterized in that ferrite crystal grains of 3 mm or more are formed at 10% or more, and a dense Al ₂ O ₃ particle coating layer with a particle size of 0.1 to ₅ μm is formed on the surface. Method of manufacturing soft magnetic steel.

[0012]

The components according to the present invention as described above will first be described as follows. sol.Al: 0.5-3.5%. Al is a key additive element of the present invention, and not only has the effect of fixing solid solution N and the effect of agglomerating AlN particles, but also raises the transformation temperature, thereby enlarging the ferrite region, thereby regulating the oxygen partial pressure. Annealing in an atmosphere that reduces the coercive force due to coarsening of ferrite crystal grains and at the same time, a predetermined amount or more in order to generate an Al ₂ O ₃ particle coating layer on the surface preferentially over Fe oxide Requires addition.
That is, the lower limit of the amount of added Al is 0.4 as shown in FIG.
In order to obtain Oe stably, it is necessary to add 0.5% or more. In addition, in order to form an Al ₂ O ₃ particle film sufficient for obtaining coating adhesion, the content needs to be 0.5% or more, preferably 0.8% or more. The upper limit of the amount of Al added is Al ₂ O ₃
From the viewpoint of sufficiently forming a particle film, the larger the amount, the better. However, the addition of a large amount causes a decrease in the magnetic flux density value as shown in FIG. Therefore, it was set to 3.5%.

Si: 0.005 to 0.50%. Si has a function of expanding the ferrite region similarly to Al, but it is not necessary to intentionally add the ferrite region because the purpose of the present invention is to add Al by means of the present invention. Further, the addition exceeding 0.5% not only causes an increase in cost but also lowers the magnetic flux density value. However, intentionally reducing the content also causes an increase in cost, so 0.005.
It is contained in the range of 0.5% to appropriately achieve the objects of the present invention such as good magnetic flux density and low cost.

Mn: 0.01 to 0.25%. Since Mn is an element that deteriorates the DC magnetization characteristics, it is desirable to reduce it. Further, when MnS is generated, it is considered that the workability or the mechanical properties of the steel material are impaired. Therefore S
However, in order to prevent hot brittleness, 0.25% is added with an upper limit of 0.25% within a range not less than 10 times the S content. When the S content is less than 0.001%, the Mn content is reduced in order to avoid a high cost for Mn reduction.
The lower limit of the content is 0.01%.

P: 0.2000% or less, S: 0.0100% or less, TO: 0.0100% or less P, S, and O are treated as impurity elements in the present invention, and in order to secure excellent DC magnetization characteristics. In addition, it is necessary to reduce the cost together with other unavoidable impurity elements so as not to increase the cost so as not to impair the basic properties as a steel material including the soundness, reliability and workability as a material. However, as for P, it is preferable to set the upper limit to about 0.01 which does not require punching workability,
When the punching property of the steel sheet is regarded as important, 0.2% may be added to the upper limit.

C: 0.0005-0.0070%, TN: 0.0005-0.0100% C and N are also treated as impurity elements in the present invention, but act as compared with other impurity elements. Since the effects are remarkable and the mechanism is also involved in the stem root of the present invention, their contents need to be defined in detail. In other words, both C and N must be reduced as much as possible in order to secure excellent DC magnetization characteristics without increasing costs. In other words, the lower limit of the content that does not cause an extremely high cost is set to 0.0005% for both C and N in consideration of the steelmaking technology.
If the content of C exceeds 0.007%, the effect of expanding the ferrite region by adding Al is extremely reduced, and the coercive force is deteriorated.
On the other hand, if the N content exceeds 0.010%, the number of AlN particles increases, which hinders the growth of ferrite crystals and cannot improve the coercive force. The effects of both C and N are as shown in FIGS. 2 and 3, respectively.

The alloy according to the present invention may contain about 0.001% to 0.02% of a nitride-forming alloy element such as Ti or B only when the reduction of N cannot be sufficiently reduced. Also,
The upper limit of the C content can be reduced to 0.007% or more by limiting the atmosphere to a decarburizing atmosphere by including hydrogen in the annealing atmosphere.

With regard to the microstructure, the steel of the present invention has a ferrite single phase structure, and the ferrite crystal grain size is averaged.
Although it is 0.2 mm or more, good coercive force is exhibited when the steel of the present invention contains 10% or more of crystal grains having a particle size of at least 0.3 mm or more.

Regarding production, in the present invention, the annealing is carried out with the atmosphere limited by the oxygen partial pressure, thereby not only suppressing the production of iron oxide particles, but not only providing excellent DC magnetizing properties but also being effective for corrosion resistance. Also, a film layer made of fine Al ₂ O ₃ particles is formed. Depending on the method of application, simply applying Al ₂ O ₃ particles whose particle size is externally adjusted is not only easy to detach, but also difficult to impart sufficient corrosion resistance, and costs associated with application work before that High cannot be ignored. In the present invention, the above-mentioned corrosion-resistant Al ₂ O ₃ film can be simultaneously generated by annealing for securing soft magnetism, and the Al ₂ O ₃ particles generated here are solid-solved in the steel material. Is generated by diffusion in the steel material during annealing and a part of the material is oxidized on the surface of the steel material. Therefore, the adhesion to the steel material is extremely high, and the particle size of the particles forming the coating layer is 0.1 μm. ~ 5μm,
Therefore, the coating layer is extremely dense and exhibits good corrosion resistance. Here, if the oxygen partial pressure of the atmosphere at the time of annealing is not at least 10 ^-6 atm or more, the formed film layer is not sufficient to exhibit corrosion resistance, and at 10 ^-2 atm or more, the formation of Al ₂ O ₃ particles At the same time, iron oxide particles are also generated, which hinders ensuring corrosion resistance.

Specifically, the oxygen partial pressure is controlled by using a wet hydrogen gas in which oxygen is mixed into an inert gas such as pure Ar or the like.
Alternatively, it can be easily implemented by setting the pressure to be higher than 10 ⁻³ torr in a vacuum atmosphere. Annealing temperature depends on DC magnetization characteristics,
The temperature must be 850 ° C. or higher from both viewpoints of formation of the Al ₂ O ₃ particle film layer, but when corrosion resistance is particularly required, it is preferable to carry out at 950 ° C. In addition, 1
Annealing at 300 ° C. or more is not preferred because deformation of the steel of the present invention or a part manufactured by processing the steel of the present invention and high costs associated with high-temperature annealing can be considered.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the following examples. The present inventors smelt each steel having the composition shown in Table 1 below to form a steel ingot, and then hot-roll it. 5mm thick
Alternatively, a 2 mm steel plate was manufactured.

[0022]

[Table 1]

Further, these steel plates are cold-rolled to obtain steel plates having a thickness of 1 mm or less, and ring-shaped test pieces having an outer diameter of 45 mm and an inner diameter of 33 mm are collected from these steel sheets by machining or punching. After annealing under the conditions shown in Table 2 (1) and (2), the DC magnetization characteristics were evaluated. Regarding paint adhesion, in the case of hot-rolled steel sheets, after removing the surface by machining, in the case of cold-rolled steel sheets, all are cut to 70 mm × 150 mm, and the same annealing is performed, and a bar coater is used on the steel material bare surface After coating, the center part was cross-cut with a cutter knife to create an artificial defect in the coating and a 48-hour salt spray test was carried out. The evaluation was made with a value of 1/2 of the total peeling width when peeled.

[0024]

[Table 2]

That is, for Nos. 1 to 9, the annealing conditions for the steels A to I in Table 1 were set within the range specified in the present invention, and mainly for So
l. Examples of the present invention and comparative examples in which changes in DC magnetization characteristics and paint adhesion were examined by changing the Al content. FIG. 1 shows a comparative example in which a comparative example of No. 22 material is added thereto. A coercive force of 0.4 Oe is obtained when the content of Sol. Al is at least 0.5%, but when the content of Sol. Al is more than 3.5%, the magnetic flux density (hereinafter referred to as B25) at a magnetomotive force of ₂₅ Oe is obtained. 1
It becomes less than 5000G. On the other hand, from the viewpoint of paint adhesion
As shown in the No. 1 material, 0.30% Al addition is not enough.
The sufficient paint adhesion is obtained by containing 0.73% like o.2 material. Note that the Al ₂ O ₃ particle film tends to be formed thicker and thicker as the added amount of Al increases.

Nos. 10, 18, and 19 are examples of the present invention in which the content of Sol. Al is about 1% and the content of Si is changed. Although accompanied suggests that decline of B ₂₅ value increased Si content, coating adhesion is confirmed good DC magnetization properties.

No. 11 to No. 13 are Examples of the present invention and Comparative Examples in which the C content was changed based on No. 4 and
14 to 17 are examples of the present invention and comparative examples in which the N content was changed. No. 13 material and No. 17 material whose C and N contents deviate from the specified range of the present invention show good coating adhesion but deteriorated coercive force.

The No. 20 material is an example of the present invention in which the Mn content is 0.16%, but is excellent in both DC magnetization characteristics and coating adhesion, and is 10 times or less of the S content. In that case, the same result is observed even when the content exceeds 0.20%.

No. 35-37 materials have a P content of 0.074.
This is an example of the present invention in which it was confirmed that there was no deterioration in both the coating adhesion and the DC magnetization characteristics even when the content was increased from 0.2% to 0.2%.

Nos. 21 to 22 are examples in which a composite addition of Al and Si was studied. That is No. 21 material in the range of the present invention, while the above B ₂₅ value 15000 G is ensured, in No. 22 material departing from the scope of the present invention is less than 15000 G ₂₅ value B. However, in both cases, sufficient Al addition was achieved and the coating adhesion was good.

No. 23 is a comparative example showing the results of a study on industrial pure iron, which has been widely used as a soft magnetic material for a DC magnetic field. Although B ₂₅ value is the invention examples and equal to or higher than the coercive force, less significant to the invention samples in coating adhesion.

Nos. 24 to 28 are examples in which the annealing temperature was examined using a steel plate having a steel number D and a plate thickness of 2 mm. That is, as shown in No. 24 material, the annealing temperature was 800 ° C.
Is insufficient in coercive force and the atmosphere is 10 ^-3 torr
At 800 ° C., a sufficient Al ₂ O ₃ particle film could not be formed because of the above vacuum, and the coating adhesion was insufficient.
In the inventive examples of Nos. 25 to 28, the coercive force and the coating adhesion were good by setting the annealing temperature to 850 ° C. or higher regardless of the same steel sheet and the same annealing atmosphere.
Nos. 29 to 34 are also examples of the present invention in which the sheet thickness and the annealing temperature of steel No. D are changed within the range of the present invention, and both the coercive force and the paint adhesion are good.

Of the above Examples Nos. 1 to 37, all Examples except Nos. 23 and 24 contain at least 10% or more ferrite crystal grains having a grain size of 0.3 mm or more. Was. Nos. 1, 2, 13, and 17 contain ferrite crystal grains with a grain size of 0.3 mm or more, but form sub-grains (subcrystals) finer than 0.3 mm or have an average grain size. Was less than 0.2 mm.

Materials Nos. 38 to 47 are examples in which the coating adhesion of an Al ₂ O ₃ particle film produced in an annealing atmosphere in which the oxygen partial pressure was changed was evaluated. In an atmosphere with an oxygen partial pressure of 0.8 ppm, it is difficult to form an Al ₂ O ₃ particle film sufficient to obtain sufficient coating adhesion, whereas in an atmosphere with an oxygen partial pressure of more than 5.2 ppm, good coating adhesion is obtained. A satisfactory Al ₂ O ₃ particle film is produced.

[0035]

According to the present invention as described above, 0.5 to 3.5% of Al is added, the content of other alloying elements is specified, and further, the structure morphology and surface texture, or By defining the manufacturing conditions for obtaining such a texture and surface texture, it is possible to achieve a good balance between excellent DC magnetization characteristics and coating adhesion at low cost, and to provide products that are useful in applying to magnetic circuit components. At the very least, it has a great industrial effect.

[Brief description of the drawings]

FIG. 1 shows coercive force and magnetomotive force 25 according to the amount of Sol.Al added.
Is a graph showing changes in magnetic flux density (B ₂₅₎ in oe.

FIG. 2 is a graph showing a change in coercive force with an increase in C content.

FIG. 3 is a graph showing a change in coercive force with an increase in N content.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tetsuya Sanbe 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Masayoshi Nakagawa 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Inside the Company (72) Inventor Kazuhiro Kane 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-2-179856 (JP, A)

Claims (2)

(57) [Claims] 1. In weight%, C: 0.0005 to 0.0070%, TN: 0.0005 to 0.0100%, Si: 0.005 to 0.50%, Mn: 0.01 to 0.000%. 25%, P: 0.2000% or less, S: 0.0100% or less, sol. Al: 0.5-3.5%, TO: 0.0100% or less, with the balance being Fe and unavoidable impurities A steel product having a composition of 0.1 to 6 mm in thickness or a steel product processed into a required shape from the above, wherein at least 10% of ferrite grains having a grain size of at least 0.3 mm or more are contained. wherein, and the surface is covered in a state where Al ₂ O ₃ particles having a particle diameter 0.1~5μm is in close contact with the coercive force 0.4Oe less in the absence of distortion, the magnetic flux density in the magnetomotive force 25Oe is more 15000G Soft magnetic steel excellent in direct current magnetization characteristics and paint adhesion characterized by: 2. In% by weight, C: 0.0005 to 0.0070%, TN: 0.0005 to 0.0100%, Si: 0.005 to 0.50%, Mn: 0.01 to 0.000%. 25%, P: 0.2000% or less, S: 0.0100% or less, sol. Al: 0.5-3.5%, TO: 0.0100% or less, with the balance being Fe and unavoidable impurities A steel product having a composition of 0.1 to 6 mm in thickness or a steel product processed into a required shape from the above is heated in an atmosphere having an oxygen partial pressure of 10 ^-6 to 10 ^-2 atm at a temperature of 850 to 1300 ° C. Heat treated with 0.3mm
It has excellent direct current magnetization characteristics and excellent coating adhesion, characterized in that the above ferrite crystal grains are formed at 10% or more and a dense Al ₂ O ₃ particle coating layer having a particle size of 0.1 to ₅ μm is formed on the surface. Manufacturing method of soft magnetic steel.