JPH0637694B2 - Silicon-containing steel plate with low iron loss - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) Since the energy crisis of several years ago, there has been an increasing tendency to seek electric devices with less power loss, and as core materials for them, iron loss is lower. Magnetic steel sheets are now required.

The present invention advantageously responds to the above-mentioned requirements, and relates to a silicon-containing steel sheet which is excellent not only in iron loss characteristics but also in coating adhesion.

(Prior Art) The iron loss of a silicon steel sheet consists of an eddy current loss and a hysteresis loss. There is a method of reducing the plate thickness as an effective means for reducing the iron loss of silicon steel sheets, and this method mainly contributes to the reduction of the iron loss and thus to the energy saving by mainly reducing the eddy current loss. However, the plate thickness is 11mi
When it becomes less than l, the ratio of hysteresis loss to total iron loss increases rapidly. Factors that influence the hysteresis loss include the orientation of crystal grains, the degree of impurities, the influence of the surface coating, and the roughness of the steel sheet surface.

As a method of reducing the hysteresis loss, especially as a method of reducing the hysteresis loss by improving the surface properties of the steel sheet, for example, in Japanese Patent Publication No. 52-24499, surface oxides of the grain-oriented silicon steel sheet after finish annealing are pickled. A method of chemically polishing or electrolytically polishing the surface to a mirror surface state after removing is proposed. In addition, Japanese Patent Publication No. 56-4150 discloses that
A technique is disclosed in which a non-metallic substance on the surface of a unidirectional silicon steel sheet is removed, and then the surface is chemically or electrolytically polished, and then a ceramic thin film is applied. Furthermore,
Japanese Patent Laid-Open No. 60-89589 discloses a technique of chemical polishing or electrolytic polishing after removing the surface oxide of the grain-oriented silicon steel sheet after secondary recrystallization performed by using an annealing separator containing alumina as a main component. Has been done. Further, Japanese Patent Laid-Open No. 60-39123 discloses a technique of directly controlling chemical polishing or electrolytic polishing without pickling after controlling the amount of oxide on the surface by using an annealing separator containing alumina as a main component. Is disclosed.

(Problems to be Solved by the Invention) However, none of these techniques has been industrially implemented today, although the iron loss reducing effect is very clear.

The reason is that it is used as a polishing liquid in the case of chemical polishing.
This is because HF + H ₂ O ₂ and H ₃ PO ₄ + H ₂ O ₂ are expensive and the cost is high. Similarly, in the case of electropolishing, all of the phosphoric acid-based baths, sulfuric acid-based baths, phosphoric acid-sulfuric acid-based baths and perchloric acid-based baths that are usually used as polishing liquids contain high-concentration acid as the main component and are added. This is because chromate, hydrofluoric acid, organic compounds, etc. are used as materials, resulting in high cost, and in processing a large amount of steel sheets, there are many unsolved problems such as homogeneity, productivity and early deterioration of liquid. .

Yet another major drawback that prevents industrialization is that the mirror-polished surface is less likely to have an insulating coat.

That is, the conventionally known phosphate coating and ceramic coating have poor adhesion due to their mirror surface and cannot withstand actual use.

The present invention advantageously solves the above-mentioned problems and prevents the movement of the magnetic domain wall which causes a magnetically smooth surface, that is, hysteresis loss, without applying a mirror finishing treatment by electrolytic polishing or chemical polishing. It is an object of the present invention to propose a silicon-containing steel sheet which forms a surface free from defects and has a surface state not only magnetically but also excellent in film adhesion.

(Means for Solving Problems) As a result of reexamination of the effects of various surfaces on iron loss, the inventors have obtained the following findings.

That is, the first one is that it is mainly the surface oxides that have a large effect on the hysteresis loss, and the surface irregularities do not necessarily have to be in a mirror state. Here, the mirror surface state is an optical concept and is not quantitatively defined, but usually the surface average roughness Ra
0.4 μm or less, preferably 0.1 μm or less.

FIG. 2 shows a conventional grain-oriented silicon steel sheet having oxides present on the surface, a grain-oriented silicon steel sheet subjected to a mirroring treatment thereafter, and a grain-oriented silicon steel sheet having a surface roughened by further pickling. The respective iron losses of No. 1 are shown in comparison, but as is clear from the figure, even if the mirror surface is lost by pickling, the iron loss is not so deteriorated.

Thus, in order to obtain a silicon steel sheet with low hysteresis loss, a so-called magnetically smooth surface is not necessarily required to be a mirror surface, and therefore electrolytic polishing and chemical polishing are indispensable conditions. Instead, the chemical treatment can be selected more freely.

However, it is needless to say that the distortion of the steel sheet surface during the process of magnetically smoothing the silicon steel sheet should be avoided as much as possible in order to deteriorate the iron loss.

Here, the mirroring phenomenon that characterizes the electrolytic polishing method will be described. In electrolytic polishing, the surface to be polished is the anode,
When an electric current is passed through a strong acid / strong alkaline electrolyte, the metal is eluted from the surface as ions by the electrolytic reaction, but a viscous film is formed between the metal surface and the electrolyte. Since this viscous film is thin on the convex portion of the surface, more current flows, so that the convex portion melts out more than the concave portion, and the metal surface is said to have a mirror surface without irregularities. Therefore, it can be said that chemical polishing or electrolytic polishing is a method of smoothing the metal surface without depending on the crystal grain size or orientation. In other words, the surface obtained by chemical polishing or electrolytic polishing is characterized by having high gloss by smoothing regardless of the underlying crystal.

Secondly, the second finding is that when silicon steel is electrolytically treated with a chloride aqueous solution, the surface properties are greatly different due to the difference in crystal grain orientation on the surface of the steel sheet.

Conventionally, electrolytic treatment with a chloride has not been carried out because it is poorly effective in terms of obtaining a mirror-polished surface, but the inventors have broadly explored the possibility of electrolytic treatment based on the above-mentioned first knowledge. Therefore, when conducting confirmation experiments on chlorides, the above-mentioned unique phenomenon was discovered.

FIG. 3 shows a microstructure photograph showing that the morphology of the crystal plane after electrolytic treatment differs depending on the difference in the plane orientation.

FIG. 3A shows the case where the {110} plane of the crystal grains is tilted by 5 ° with respect to the rolled surface, and exhibits a unique network surface morphology. This mesh-like grain is called a graining-like surface because it resembles a graining surface obtained by electrolytic etching formed by the concavities that appear like crystal grains being dispersed and adjacent to each other in the grain.

FIG. 3B shows the case of the same inclination of 11 ° and exhibits a scaly morphology. Furthermore, FIG. 3C shows a case where the tissue is in the form of wood-like texture when it is inclined by 25 °. As shown in FIGS. 3A to 3C, the surface having such a unique morphology is not a mirror surface even in the network structure A, and has a macroscopic appearance in the appearance of a pickled surface in which crystal grain boundaries appear.

More importantly, such a surface having a unique network structure can be obtained only when a silicon steel sheet having a {110} plane is electrolytically treated with a chloride aqueous solution as an electrolytic solution.
Moreover, the above-mentioned network structure is a magnetically smooth surface.

Figure 1 shows the results of examining the iron loss improvement margin of the material obtained by electrolytically treating the material mainly composed of {110} planes with NaCl. In addition, for comparison, the figure also shows the results of a survey on the iron loss improvement margin of grain-oriented silicon steel sheets that have been mirror-polished by electrolytic polishing with mixed acid (CrO ₃ 10%, H ₃ PO ₄ ).

As is clear from the figure, the improvement margin of iron loss is larger when the chloride bath is used.

In the above experiment, a NaCl electrolyte having a concentration of 20% was used, and electrolysis was performed under the condition of current density: 100 A / dm ² for 10 seconds.

Furthermore, a good effect of improving iron loss was observed when TiN was formed by ion plating.

The physical reason why the iron loss of the steel sheet according to the present invention shows a good value as compared with the product having a mirror surface by the conventional electrolytic polishing, chemical polishing, etc. has not yet been completely clarified, but first, the magnetic Geometrical smoothness is not required to be so high. Secondly, in the present invention, the grain boundaries form stepped or groove-shaped recesses, so that the magnetic domains are narrowed. It is considered that the reduction of the iron loss can be expected, and thirdly, the electrolytic polishing method causes deterioration due to the oxide film formed on the mirror surface, but it is presumed that this does not occur in the steel sheet of the present invention.

By the way, in a silicon steel sheet, an insulating coat is often used on the surface thereof, and in order to further improve the magnetic properties such as magnetostriction and iron loss, the insulating coat is provided with tension, or, Tension coat and insulation coat 2
Do heavy coating. However, not only is it difficult to apply these coatings to the surface obtained by mirror polishing, which is a conventional means for obtaining a magnetically smooth surface, but also the adhesion of the coat is poor.

In this respect, the surface of the steel sheet according to the present invention not only has convex portions at the boundaries of the mesh-like grains, but also the crystal grain boundaries form steps or groove-shaped concave portions, so that the adhesion of the coating film is extremely good.

Table 1 below shows the phosphate tension of grain-oriented silicon steel sheets obtained by electrolytic polishing in a (H ₃ PO ₄ + CrO ₃ ) solution and grain-oriented silicon steel sheets obtained by electrolytic treatment in NaCl. The results of examining the adhesion of the coated and ion-plated TiN coatings (thicknesses are both 0.30 mm) are shown. The adhesion is 20 mm for each steel plate.
Those that were wrapped around a φ cylinder and had no film peeling had good adhesion, while those with even a slight film peeling had poor adhesion.

As shown in the table, the adhesion of the coating in this invention was very excellent.

(Operation) The silicon steel plate that is the material of this invention is
0) It is necessary that the crystal grains with the plane inclination within 10 ° occupy 80 vol% or more of the whole. This is because, when the inclination of the (110) plane with respect to the plate surface exceeds 10 °, the electrolytically treated surface in the chloride bath becomes a mesh-like structure, a scale-like structure, or a skin-like structure, and loses magnetic smoothness.

Further, if the ratio of the crystal grains in the preferred orientation is less than 80 vol%, iron loss is increased by electrolytic treatment because there are many magnetically non-smooth surfaces. Such a steel sheet can be obtained by finish annealing an ordinary grain-oriented silicon steel material, but in that case it is not necessary to use MgO as a separating agent, rather it is difficult to form an oxide coating layer such as Al ₂ O _3. Those are preferable. In particular, it is preferable to use an alkali metal, chloride or the like mixed with Al ₂ O ₃ to prevent the formation of oxides.

The surface of this invention steel sheet has a grain boundary of 0.4 μm at R _max.
In addition to forming a step-like or groove-like concave portion of m or more, the surface of the crystal grain on the surface must present a surface adjacent to the depression through the boundary of the convex portion, that is, a graining-like surface. .

What is more, the adhesion of the coating applied to the surface of the invention steel sheet is increased by the grain boundary of the convex portion and the grain boundary of the concave portion, and the magnetic domain width becomes fine due to the step-shaped or groove-shaped grain boundary. This is because the loss is improved.

Here, the magnetically smooth graining-like surface can be easily obtained by electrolytic treatment with a water-soluble chloride electrolytic solution.

The water-soluble chlorides mentioned here mean chlorides of NaCl, HCl, NH ₄ Cl and various metals. All of these have a magnetic smoothing effect on a silicon steel plate having a {110} plane, but from the viewpoint of preventing the precipitation of metal on the cathode, chlorides of alkali metals or alkaline earth metals or NH ₄ Cl, HCl and AlCl ₃ are suitable.

Further, the reason why the depth of the concave portion of the crystal grain boundary is limited to 0.4 μm or more in R _max is that if the depth is less than 0.4 μm, the effect of improving iron loss characteristics and coating adhesion is poor.

Although the magnetic properties can be effectively improved by performing such a series of treatments, the present invention further improves the magnetic properties by forming a tension-imparting ultrathin film on the graining-like surface. Can be achieved. The thin coating may be a conventionally known phosphate coating containing colloidal silica, or may be formed by dry or wet plating.

That is, Ti, Nb, Si, V, Cr, Al, Mn, B, Ni, Co, M are deposited by vapor deposition or plating such as CVD or PVD (ion plating or ion implantation).
An ultra-thin film mainly consisting of at least one selected from nitrides and / or carbides of o, Zr, Ta, Hf, W and oxides of Al, Si, Mn, Mg, Zn, Ti is toughened on the steel sheet surface. To cover.

In addition to the above listed materials,
Any material having a low coefficient of thermal expansion and firmly adhering to the steel sheet may be used.

Further, if necessary, a tension-imparting low thermal expansion topcoat insulating coating can be formed by a conventional method.

(Example) Example 1 C: 0.03%, Si: 3.3%, Mn: 0.06%, Se: 0.02%, Sb: 0.0
0.23 mm of cold-rolled silicon steel hot-rolled sheet containing 2%
After thickening, decarburization annealing was performed. A part of the obtained annealed plate was left as the comparative material A, and the rest was applied with an annealing separator containing Al ₂ O ₃ as a main component (containing 0.1% of NaCl), wound on a coil, and then subjected to finish annealing. Comparative Material B was obtained. Part of it is a comparative material C that was polished to a mirror surface with emery and buffing.
Also, a part of the mixture was made into a comparative material C'by mirror-polishing it with a mixed solution of chromic acid and phosphoric acid (1: 9) to make it a comparative material C '. Material D was used.

In addition, a magnetic material was prepared by immersing it in a 75% NaCl solution (comparative material E) and immersing it in electrolytic solution at 100 A / dm ² for 10 seconds using stainless steel as an anion (compliance example). Was measured.

The surface morphology was also observed. The same electrolytic treatment was applied to the comparative material A.

The results are shown below.

Comparative material A Hc increased by 5% before and after electrolytic treatment, and magnetic smoothing was not achieved.

Most of the surface morphology (90% or more) was a wood-like texture.

Iron loss of the steel sheet after the comparative material B finish annealing in W _17/50 0.95W /
It was kg. Examination of 30 secondary grains {110} plane 10
Within ° was 100%.

Comparative material C The iron loss of the mirror-finished material due to emery and buff is
Was 1.32W / kg in W _17/50.

Comparative material C'The iron loss of the mirror-finished material by electrolytic polishing is W ₁₇ /
It was 0.86 W / kg at ₅₀ .

Comparison material D iron loss W _17/50 was 1.01W / kg.

Comparison material E iron loss W _17/50 was 0.97W / kg.

Adaptations iron loss W _17/50 is 0.80 W / kg, also tissue had become reticulated structure (graining like surface).

Next, when TiN was vapor-deposited to a thickness of 1 μm by ion plating for the comparative materials B, C, C ′, D and the conforming example, the following results were obtained.

Regarding the adhesion of the coating, in the bending test of 20 mmφ, the conforming examples and the comparative materials B and D were good, but the comparative materials C and C ′ were peeled off.

Example 2 C: 0.03%, Si: 3.2%, Mn: 0.08%, S: 0.02% and Al:
A hot-rolled silicon-containing steel sheet containing 0.02% was cold-rolled to 0.30 mm, decarburized and annealed, and then MgO 2 was applied as an annealing separator, followed by finish annealing. Iron loss after the finish annealing was 1.02W / kg in W _17/50. When the orientation of 30 crystal grains was examined by X-ray, the deviation from the {110} plane of all 30 grains was 10 ° or less. After removing the surface forsterite of the steel sheet by pickling, the material was used as an anode in 50% NH ₄ Cl solution at 50 A / dm ² , 2000 coulomb / dm ²
Was subjected to conditions in the electrolytic process, the surface of the obtained steel sheet exhibited a beautiful graining like surface, also iron loss W _17/50
= 0.83 W / kg.

Iron loss Furthermore Si ₃ N ₄ and was Kotengu (thickness 1 [mu] m) by ion grating was reduced to _{W 17/50 = 0.71W / kg} .

The adhesion of the coating was good.

(Effects of the Invention) Thus, according to the present invention, a silicon steel sheet having excellent iron loss characteristics can be stably obtained at low cost.

[Brief description of drawings]

Fig. 1 is a graph comparing iron loss improvement margins when the surface of grain-oriented silicon steel sheets is electrolytically treated in a phosphoric acid bath or a chloride bath and then TiN coating is applied. The figure is a graph showing a comparison of iron loss values when the surface of the grain-oriented silicon steel sheet is subjected to a mirror-finishing treatment and when it is subsequently subjected to a pickling treatment, and FIGS. 3A, 3B, 3C are respectively 3 is a microstructure photograph showing a difference in surface texture due to a difference in crystal orientation when electrolytic treatment is performed in a chloride bath.

Front Page Continuation (72) Inventor Naruko Sueda 1 Kawasaki-cho, Chiba City, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. Within

Claims (2)

[Claims] 1. A silicon-containing steel sheet having a crystal structure in which a crystal grain having an inclination of a {110} plane with respect to a plate plane within 10 ° occupies 80 vol% or more, and the surface of the crystal grain on the surface of the base metal is grained And the grain boundaries have the maximum height R _max .
Silicon-containing steel sheet with low iron loss formed by forming steps or grooves of 0.4 μm or more. 2. A silicon-containing steel sheet having a crystal structure in which a crystal grain having an inclination of {110} plane with respect to a plate plane within 10 ° occupies 80 vol% or more, and the surface of the crystal grain on the surface of the base metal is grained. And the grain boundaries have the maximum height R _max .
A silicon steel sheet having a low iron loss, in which a step or groove of 0.4 μm or more is formed, and a tension-imparting insulating coating is further provided on the surface of the base iron.