JPH032380A - Separation agent at annealing - Google Patents

Abstract

PURPOSE:To obtain a separation agent at annealing free from film formation after final box annealing and capably of attaining a high level of magnetic properties of a grain-oriented silicon steel sheet by preparing the above agent by using, as principal component, a mixture composition in which respectively prescribed weight ratios of MgO powder and V compound are incorporated to Al2O3 powder. CONSTITUTION:The above separation agent at annealing is used for the final box annealing for a grain-oriented silicon steel sheet and is constituted by using, as principal component, a mixture composition prepared by incorporating 10-80 pts.wt. of MgO powder and 0.1-5 pts.wt. of V compound expressed in terms of V to 100 pts.wt. of Al2O3 powder. At this time, it is advantageous to regulate the average grain size of the above Al2O3 powder to <=1mum, and further, besides V oxide, V hydroxide, and V compound forming into oxide on heating, sulfide, etc., of V can be applied as the above V compound. By using this separation agent at annealing, the formation or remaining of oxide at the steel sheet surface can be effectively prevented, and a surface having attractive metallic luster can be obtained. Accordingly, the load at the time of succeeding surface smoothing treatment can be remarkably reduced, and further, the purification of S and Se can be satisfactorily attained and electric properties can be markedly improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to an annealing separator used in final box annealing of grain-oriented silicon steel sheets.

The grain-oriented silicon steel sheet contains Si: 4wt% or less (hereinafter simply referred to as %) and a small amount of 2 such as MnS, MnSe or AfN.
A silicon steel material containing a secondary recrystallization inhibitor is hot-rolled, subjected to annealing and one or two cold rolling processes to form a cold-rolled sheet with the final product thickness, and then subjected to a primary re-rolling process that also serves as decarburization. After crystal annealing to produce subscales mainly composed of 5i02, an annealing separator mainly composed of MgO is applied in the form of a water slurry, dried, and then wound into a coil before final production. Box annealing is performed to develop secondary recrystallized grains with 110) (001) orientation, and at the same time remove harmful impurities such as S and Se in the steel that have finished their role as recrystallization inhibitors, and at the same time remove the 2-5μm thick forsterite (MgzS+04) by reacting MgO
The product is typically manufactured through a series of manufacturing steps, including forming a film and sometimes baking an insulating coating with a topcoat of a phosphate-based treatment agent.

The grain-oriented silicon steel sheet obtained in this way is mainly used as the iron core of transformers and other electrical equipment, and has a high magnetic flux density (represented by the Bl value) and iron loss (Lt/ s (represented by the value) is required to be low. In particular, from the standpoint of energy conservation, reducing iron loss is becoming more important in order to avoid as much as possible the electricity that turns into heat inside the iron core and is wasted as energy.

As a measure to achieve a significant reduction in iron loss,
Publication No. 4499 states that after the final box annealing, surface products (oxides such as forsterite) are removed by pickling, and then chemical polishing or electrolytic polishing is performed to give a mirror-like finish, or the mirror-finished surface is coated with thin metal plating. Furthermore, Japanese Patent Publication No. 56-4150 discloses a method in which an oxide-based ceramic thin film is coated by a vapor deposition method after mirror finishing, and JP-A-61-201732 discloses a method in which an insulating film is applied and baked thereon.
The publication describes a method of forming an ultra-thin tension film of TiN or TiC by performing mirror finishing and then heat treatment in a gas atmosphere containing Ti, and JP-A-61-235514 further describes a method of forming an ultra-thin tensile film of TiN or TiC after mirror finishing.
Methods for forming N and Tic films by ion blating method and ion implantation method are disclosed.

The above-mentioned methods are intended to reduce hysteresis loss by making the surface of the steel as smooth as possible (mirroring state) to facilitate domain wall movement during the magnetization process, and to reduce hysteresis loss. There is no need for oxides such as coatings, and when they are removed by pickling, the surface of the base metal inevitably becomes rough, so unless deep polishing of more than 10 μm in thickness is performed using chemical polishing or electrolytic polishing, the necessary smooth surface cannot be obtained. As a result, the yield of steel sheets decreases and the consumption of chemicals increases, leading to a significant increase in costs and becoming a major hindrance to industrialization.

Therefore, if it is possible to sufficiently suppress the formation of oxides such as forsterite that are difficult to remove during final box annealing, and easily produce a smooth, metallic surface, then smoothing treatment will become possible on an industrial scale for the first time. Since the production of grain-oriented silicon steel sheets with excellent ultra-low core loss will become a reality, it is of great significance to develop an annealing separator that satisfies this requirement.

(Prior Art) The use of AfzO3 powder as an annealing separating agent in order to prevent the formation of a forsterite film during final box annealing or to make it easily removable by pickling is described in, for example, US Pat. No. 3,785,882. In addition, in order to absorb impurities such as S and Se in steel that are harmful to magnetism to the surface and strengthen the purification of steel, serpentinite,
Japanese Patent Publication No. 58-44152 discloses a method using a hydrated silicate mineral powder such as talc, an Sr or Ba compound, and an annealing separator containing CaO or Ca(OH)z.
An annealing separator in which inert MgO is blended with ffi zos is disclosed in JP-A-59-96278.

We have examined these technologies in detail. Al2O3 alone has almost no ability to purify S, Se, etc., and is difficult to meet the recent strict requirements for improving magnetism.On the other hand, the method described in Japanese Patent Publication No. 58-44152 mentioned above has excellent purification performance, but During final box annealing, the surface of the part of the coiled steel sheet that is heated relatively rapidly has several μI11 to 1
Localized oxide seizures of about 0 μm are often observed and may not be completely removed by light pickling. The reason for this is that the separating agent contains hydrated salts, Ca(OH)z (CaO also immediately becomes Ca(OH)z in water slurry), 5r(
Because it contains components rich in 8.0 such as OH)z,
The dew point between the coil layers during final box annealing is increased, and the Si in the oxide layer (subscale) formed during decarburization annealing is increased.
It is thought that as a result of preventing the floating of O□, a large number of oxides remain near the surface.

The technique described in Japanese Unexamined Patent Publication No. 59-96278, which was previously proposed by the inventors, is A1 zo with the intention of improving the above points.
15 to 7% of inert MgO with a specific surface area of 0.5 to 10 m''/g fired at 1300°C or higher per 100 parts by weight of i.
With 0 parts by weight added, this MgO is virtually unhydrated, thus avoiding the problem of 820 carry-over from the separation agent. However, when this technology is applied to actual coils, depending on the condition of the coil and annealing conditions, S and Se in the steel may not be sufficiently purified, which tends to cause deterioration of magnetic properties, making it difficult to maintain a constant quality. Furthermore, the surface of the steel sheet is not sufficiently smoothed, which causes problems such as microscopic irregularities and penetration of oxides.

(Problems to be Solved by the Invention) The present invention makes it possible to easily obtain a smooth surface with metallic luster, which does not form a film after final box annealing, and has very little microscopic unevenness or penetration of oxides. The object of the present invention is to provide an annealing separator having a novel composition that has an excellent ability to purify impurities in steel that are harmful to magnetic properties, and also exhibits excellent magnetic properties.

(Means for Solving the Problems) In order to solve the above-mentioned difficulties of the conventional technology, the inventors have developed a technology that does not react with the steel plate to form a film, and has the ability to absorb and purify impurities such as S and Se in steel. is excellent,
As a result of various studies on separating agent components, which require not to roughen the surface of the steel sheet during annealing and to have the effect of improving magnetic properties, we found that AI! The inventors have discovered that an annealing separator whose main component is a mixed composition consisting of .

That is, the present invention provides an annealing separator for use in final box annealing of grain-oriented silicon steel sheets, which is A1. This is an annealing separator whose main component is a mixed composition containing 10 to 80 parts by weight of MgO powder and 0.1 to 5 parts by weight of a V compound, based on 100 parts by weight of t03 powder.

In practice, it is also advantageous for the average particle size of the A ffi gos powder to be 1 μm or less.

In this invention, the (2) compound includes not only the oxide, hydroxide, or a compound that becomes an oxide when heated, but also sulfides and the like.

For example, VzOs+VzOs ・n! IzO, V2O3
,VO2,VO,V(Oll)3゜NH4VO5,VS
, V2S:l, V2S5, etc.

The annealing separator according to the present invention is particularly suitable for decarburizing a grain-oriented silicon steel sheet rolled to the final thickness, then applying the annealing separator, and then performing final box annealing including secondary recrystallization annealing and purification annealing. After that, the surface of the steel plate is made smooth by polishing, and Ti, 5.
4 grade nitride and/or carbide or A! It is advantageously suited to a series of processes for forming ultra-thin tensile coatings made of oxides such as

In other words, by using the annealing separator according to the present invention, the generation or residue of oxides on the steel plate surface can be effectively prevented and a beautiful metallic shiny surface can be obtained, which greatly reduces the burden of subsequent smoothing treatment. At the same time, S and Se are sufficiently purified, and the magnetic properties are greatly improved.

In addition, in other fields of application, when the annealing separator of the present invention is used, almost no film or oxide is formed on the surface after final box annealing, so the obtained steel plate can be used as is or with chromate-based or chromium Wear of the punching tool is greatly reduced when punching is performed after applying a coating such as an acid salt + organic resin type or phosphate type, and further rolling is performed after the final box annealing. When producing ultra-thin grain-oriented silicon steel sheets suitable for uses such as transformers, there are advantages such as the ability to obtain products with excellent surface properties.

The experimental results that led to this invention will be explained below.

C: 0.044%, Si: 3.32%, Mn
: 0.06%, S; 0.004%, Se: 0
．． A hot rolled plate containing 0.020% and Sb: 0.02% was uniformly annealed at 900°C for 3 minutes, then cold rolled twice with an intermediate annealing at 950°C to obtain the final thickness. 0.
A cold-rolled sheet of 23 mm was then rolled at 82 mm in a wet hydrogen atmosphere.
Decarburization annealing was performed at 0°C for 2 minutes. A large number of specimens were cut from this steel plate, and MgO and v20. An annealing separator containing the following was applied to each box and subjected to final box annealing. The annealing conditions were a secondary recrystallization process at 850°C in N2 for 150 hours, followed by a purification process at 1180°C in I2 for 15 hours. ) and the amount of residual Se are shown in FIG.

From the same figure, v20. It can be seen that a small amount of addition shows a strong ability to promote purification, and that this effect increases with the addition of MgO, but as MgO increases, the oxygen basis weight also increases and the surface oxide amount increases.

Table 1 also shows the magnetic properties, base metal analysis values, and surface observation results by SEM of the specimens obtained in the same manner.

From the same table, v20. NO1 with added
It can be seen that in samples Nos. 2 to 6, Se is completely purified and the magnetic properties are improved. That is, B. Since the value improves, v20. It was also confirmed that this has the effect of increasing the degree of accumulation of Goss orientation in secondary recrystallization.

On the other hand, No. to which Ca5iOz was added as a purification accelerator,
7, although the purification of Se is complete, v20
Magnetic properties are inferior to that of additive No. 5. And both S
Comparing the surface observation results by EH, it was found that microscopic irregularities and pinhole-like defects were smooth with significantly less V and OS additives. Naori 20. Among the additives, Nα6, which had a relatively large amount of ■ at 5 parts by weight, had an increased V in the steel, slightly deteriorated its magnetism, and had slightly more dot-like deposits on the surface.

Furthermore, in the specimens of Nα2 (purification accelerator: VzOs) and Nα7 (purification accelerator: Ca5iO,) in the same table,
Strain relief annealing was performed at 800°C, followed by light pickling with 10% hydrochloric acid at room temperature for 15 seconds, followed by 85% H3P.
Regarding the iron loss after electrolytic polishing in a bath of O411 + Cr05250g at a current density of 70^/dm'', we measured the iron loss by pulling out specimens intermittently during electrolytic polishing, and compared the results with the polishing depth. This is shown in Figure 2. Also shown in the figure are the surface observation results during each measurement.

From the same figure, the specimen using the annealing separator containing VzOs as a purification accelerator achieves smoothing with a smaller amount of polishing than the specimen using the annealing separator containing Ca5iO. It can be seen that a significant reduction in iron loss can be easily achieved.

From the above experimental results, A l zoi MgOV2O
The annealing separator having the composition No. 5 has high purification ability, provides a smooth surface with less oxides, and improves magnetic properties, and is therefore suitable for obtaining materials that can be expected to have iron loss reduction effects through electrolytic polishing and chemical polishing. It can be seen that it is a good annealing separator.

(Function) Next, the role of each component in the annealing separator according to the present invention and the reason for limiting the mixing ratio thereof will be explained.

AfzOs is a main component that inhibits film formation, and is used as a powder with an average particle size of 10 μm or less, but it is particularly advantageous to suppress oxide formation and smooth the surface if fine particles of 1 μm or less are used. This is because the coating efficiency of the steel plate surface is high in the final box annealing (surface oxidation is suppressed, and
This is because the surface irregularities caused by the particles being pressed against the steel plate surface become smaller.

In addition, MgO is necessary for purifying S and Se, and Al 203
If the amount is less than 10 parts by weight per 100 parts by weight, the purification will be insufficient and the amount of the compound must be increased, which will increase the amount of the compound that penetrates into the steel and affect the magnetic properties and the surface. It is necessary to use 10 parts by weight or more since it causes deterioration of properties. On the other hand, if it exceeds 80 parts by weight, the formation of oxides and forsterite films on the surface cannot be ignored, and the object of the present invention cannot be achieved. Regarding the properties of the MgO used, it is desirable to use inert MgO produced by high-temperature firing and that is virtually not hydrated in the water slurry in order to prevent the formation of oxides or films on the surface of the steel sheet.

■As mentioned above, the compound is added as a purification accelerator for S and Se, and its function is currently unknown, but it is thought to exert some kind of catalytic action at the interface between the steel sheet and the annealing separator. .

Furthermore, (2) does not become a corrosion factor for steel sheets even at high temperatures, and purification is achieved without forming a film on the surface, so that a smooth surface can be achieved.

In addition, the magnetic properties are improved compared to the case of using conventional purification promoters such as Ca compounds because a smooth surface with fewer defects is obtained, and (1) also has the effect of increasing the concentration of Goss orientation in secondary recrystallization. This is thought to be for the purpose of demonstrating.

And ■ is 0.1 to A f zo3too parts by weight
If it is less than 5 parts by weight, purification will be insufficient and good magnetic properties will not be obtained, while if it exceeds 5 parts by weight, the amount of penetration into the steel will increase and the magnetic properties will tend to deteriorate. , surface deposits increase and surface quality deteriorates. Therefore, the amount of the V compound is limited to 0.1 to 5 parts by weight in terms of ■.

Here, the amount of subscale on the surface of the steel sheet after decarburization annealing to which the annealing separator of the present invention is applied is determined by: It is preferable to reduce the amount as much as possible without inhibiting decarburization.

In addition, in order to more completely perform secondary recrystallization during final box annealing and improve magnetic properties, S
, Se, Sb, V, etc., or their compounds can be added to the annealing agent of the present invention.

Furthermore, nitrides and/or carbides of Ti, Si, etc. obtained by applying this invention! When commercializing a steel plate coated with an ultra-thin tensile coating made of oxides such as It is of course possible to provide electrical insulation.

Examples of adding a compound (1) to an annealing separator for grain-oriented silicon steel sheets are described in, for example, JP-A-48-8611 and JP-B-Sho 49-3740.

However, all of these target steel sheets with oxide films, and do not mention Se purification, surface smoothing, and Goss orientation integration.

(Example) C: 0.041%, Si: 3.34%, Mn
: 0.07% 1MO: 0.012%, S:
0.003%, Se: 0.020% and Sb: 0
．． A hot rolled sheet containing 026% was homogenized at 900°C for 3 minutes.
After chemical annealing, a cold-rolled sheet with a final thickness of 0.23 mm was obtained by cold rolling twice with intermediate annealing at 950°C, and then wound into a coil to create a total of four coils.
Next, decarburization annealing was performed at 820° C. for 2 minutes in a wet hydrogen atmosphere, and each coil was coated with an annealing separator in the form of a water slurry having the proportions shown in Table 2 and dried. The coating amount after drying was 8 g/s+'' per side.

Table 2 A final box anneal was then applied which included a secondary recrystallization step of 860''C50 hours in N2 followed by a purification step of <1180''CIO hours in H2. After annealing, the annealing separator was removed by washing with water, and continuous flattening annealing (removal of winding curls in the coil) was performed for 1 minute at 820°C in N, +H, and then three locations each on the outer winding, middle winding, and inner winding of the coil. A sample was cut out from and lightly pickled in a 5% HCj2 bath at 40°C for 15 seconds, and then 250g of Cr03/41! The surface was smoothed by electrolytic polishing at 70° C. and 1100 A/dm in an electrolytic polishing bath containing additives.The degree of polishing was kept constant at 3μ ugliness per side.

Next, this smoothed steel plate was set on an ion brating surface and subjected to ion blating treatment for 3 minutes at an ionization voltage of 10 KV, and a Ti film with a thickness of 0.5 μm was applied.
A tension coating consisting of N was applied.

Table 3 summarizes the magnetic properties and other investigation results conducted on samples taken at each stage, ie, after planarization annealing, after electrolytic polishing, and after ion blating.

As seen in the characteristics after flattening annealing, both coils obtained using the annealing separator according to the present invention have very little residual oxide (expressed in terms of oxygen basis weight) over the entire length and have a uniform metallic luster. It was completely purified and had good magnetic properties. In other words, a grain-oriented silicon steel sheet with excellent punching workability and magnetic properties can be obtained by carrying out the above treatment or by further applying an optional insulating coating.

In particular, the coil Nα2, which uses fine particles of A j2 zo* with a particle size of 0°4μI, has a lower oxygen basis weight and good magnetic properties, and after electrolytic polishing, the amount of polishing is 3μ per side.
0.17 m, which is significantly less than the conventional model.
A large reduction in iron loss of ~0.20 W/kg was achieved, and when TiN ion blating was applied, the M
1ff/S. The value reaches 0.714/kg or less.

On the other hand, the coil suspension 3 without adding a wire forming accelerator is S in the base steel.
The magnetic properties were low due to the large residual amounts of Se and Se, and the oxygen basis weight was also high. Also, serpentine and Sr are used as purification accelerators.
Although the coil Nα4 containing (OH) z and Ca (Oll) 2 was completely purified, it was not possible to obtain a smooth surface by electrolytic polishing to a depth of 3 μm due to the large amount of surface oxide, and therefore it was not possible to obtain a uniform surface by ion blating. Since no film was formed, the improvement in magnetic properties was insufficient.

C: 0.063%, Si: 3.35%, Mn
: 0.078%, S: 0.018%, Se
: 0.0020%, sol, 8ffi : 0
．． A hot rolled sheet containing 0.026% and N: 0.0072% was uniformly annealed at 1100''C for 3 minutes and then rapidly cooled, and then cold rolled once to form a cold rolled sheet with a thickness of 0.23++on. After that, by winding it into a coil, a total of 3
Two coils were created. Then, in a wet hydrogen atmosphere, 840
Decarburization annealing was performed for 2 minutes at °C, and each coil was
An annealing separator having the blending ratio shown below was applied in the form of a water slurry and dried. The amount of coating after drying is 9 per side.
g/m”.

Table 4 Next, final box annealing was performed in which the temperature was raised to 1180''C at a rate of 20°C/h in 112C and held for 10 hours.

After annealing, the coil was unwound and the annealing decomposer was washed away with water, and then the same treatment as in Example 1 was performed to obtain a coil.

The same evaluation as in Example 1 was performed on the product.

Table 5 shows the survey results for the samples at each stage.

From the same table, the two coils obtained using the annealing separator according to the present invention both exhibited uniform metallic luster with very little residual oxide (expressed in oxygen basis weight) over the entire length,
It was completely purified and had good magnetic properties.

On the other hand, serpentine and Sr(OH) as purification accelerators!
Although the coil Nα3 doped with Ca(Oll)2 was completely purified, there were many surface oxides, and the magnetic properties were relatively poor, and the surface could not be smoothed and a uniform film could not be formed by ion blating. Therefore, the improvement in magnetic properties was insufficient.

(Effects of the Invention) By using the annealing separator of the present invention, it is possible to obtain a clean and smooth surface with no film formation after final box annealing, that is, with less oxides, and it also has an excellent ability to purify impurities in steel. Therefore, the magnetic properties of the grain-oriented silicon steel sheet after the final box annealing can reach a high level, and the grain-oriented silicon steel sheet with ultra-low core loss can be provided by post-processing.

Furthermore, since there are few surface oxides, it is possible to easily manufacture grain-oriented silicon steel sheets for punching.

[Brief explanation of drawings]

Figure 1 shows the annealing separator v20. and a graph showing the relationship between the amount of MgO added and the analysis value of Se in steel, and the appearance of the steel plate surface. Figure 2 shows the polishing depth by electrolytic polishing and the iron loss -1.7. 2 is a graph showing the relationship between the two and the appearance at each polishing stage for a case using the present invention and a conventional example. V and (Tawo size toriro! (11 @ giant) Figure 2

Claims (2)

[Claims] 1. An annealing separator used for final box annealing of grain-oriented silicon steel sheets, based on 100 parts by weight of Al_2O_3 powder,
An annealing separator whose main component is a mixed composition containing 10 to 80 parts by weight of MgO powder and 0.1 to 5 parts by weight of a V compound in terms of V. 2. The annealing separator according to claim 1, wherein the Al_2O_3 powder has an average particle size of 1 μm or less.