JPS6039123A - Production of grain-oriented silicon steel sheet having low iron loss - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet having extremely low iron loss by subjecting the silicon steel sheet after cold rolling to decarburization annealing and final box annealing with the limited coating weight of oxygen then to direct polishing in an adequate range. CONSTITUTION:A silicon steel sheet after cold rolling to a desired final thickness is subjected to decarburization annealing and to final box annealing after an annealing separating agent consisting essentially of alumina is coated thereon to complete secondary recrystallization. The amt. of the alumina, etc. to be compounded in the above-mentioned annealing separating agent is adjusted to limit the amt. of the surface oxide to be formed in the stage of the final box annealing to <=0.3g/m<2> expressed in terms of the coating weight of oxygen per surface. The steel sheet after the annealing is removed of surface oxide and is then subjected directly to chemical polishing or electrolytic polishing without pickling in a shallow range of 2-10mum per surface then preferably to mirror finishing to the surface having 0.4mum smoothness expressed by Ra in center line average roughness, by which the grain-oriented silicon steel sheet having low iron loss is obtd.

Description

[Detailed Description of the Invention] Technical Field The technical content described in this specification regarding the method for producing grain-oriented silicon steel σi with low core loss is particularly focused on the method of preparing grain-oriented silicon steel σi, which has a low core loss. The present invention relates to the results of research and development on an attempt to advantageously achieve a mirror M1 finish, and occupies the field of technology involving the cracking of grain-oriented silicon steel sheets.

Background technology and the conventional grain-oriented silicon steel sheet is made by hot-rolling a silicon steel material containing 4.0% by weight of Si (hereinafter simply expressed as %), and then homogenizing and annealing it once. 1. Two or more times with intermediate annealing in between.
A cold-rolled steel plate with the final product thickness is obtained through the cold rolling process, and when decarburized and annealed, the surface of the steel plate mainly contains 510
After forming an oxide film consisting of 1.
(110)[0011
Forsterite (2M, 90.5102
) It was customary for the product to be made into a product through a series of manufacturing steps, including forming a high-quality base coat, sometimes using a phosphate-based treatment agent, and baking an insulating coating.

This kind of grain-oriented silicon steel sheet is commonly used as the iron core of transformers, etc., and has excellent magnetic properties such as FLR! High east density and low iron loss are required, especially as energy costs have increased in recent years... Iron loss has become more important and lower values have become required. There is. In other words, the iron loss of grain-oriented silicon steel sheets is a portion of the energy that is wasted as heat inside the iron core when used as the iron core of a transformer. This is the most important direction for improvement of silicon steel sheets.

Various techniques have been proposed as measures to improve the iron loss of grain-oriented silicon steel sheets manufactured by the process described above. The main technologies that have been proposed in recent years to reduce iron loss are: ■Increasing the amount of Sl in steel ■Decreasing product plate thickness ■Refining magnetic domains by laser irradiation, etc., and these have shown some results in improving iron loss. is obtained. However, the demand for the development of further low-iron materials is becoming stronger.

Prior art and its drawbacks In order to improve the iron loss of grain-oriented silicon steel sheets, in addition to the methods described in 1.1 above, for example, surface mirror polishing was proposed.
-24499, 9% Publication No. 56-4150.

In this method, after completing the secondary recrystallization by the final box annealing described above, surface oxides are removed by pickling, and the surface is smoothed and mirror-finished by chemical polishing or electrolytic polishing. This results in a fairly significant improvement in iron loss.

However, in the past, detailed studies have not been made on the conditions for pickling and subsequent chemical polishing or electrolytic polishing to make the surface mirror-finished. Therefore, if pickling is insufficient□, the iron loss improvement due to surface mirror polishing may be slight, and conversely, if sufficient pickling is performed, surface roughness will increase, so chemical polishing or electrolytic polishing The required mirror surface cannot be obtained unless the steel plate is polished to a depth of several tens of microns, resulting in a significant cost increase due to a decrease in the yield of steel sheets and an increase in the amount of chemical consumption. It was a turnaround.

Purpose of the Invention In addition to providing a series of surface property control means for the final box annealing that can omit the pickling process, it is also possible to determine the optimum polishing fill (depth) and its state (smoothness) in chemical polishing or electrolytic polishing. It is an object of the present invention to provide a method for producing a grain-oriented silicon steel sheet with extremely low iron loss without incurring any cost.

Structure of the Invention The above object is advantageously achieved by a procedure consisting of the following points.

After cold rolling to the desired final thickness, final box annealing is performed through decarburization annealing and application of an annealing separator to complete secondary recrystallization, and then surface oxides are removed and chemical polishing or electrolytic polishing is performed. In a method for manufacturing grain-oriented silicon steel sheets that includes a polishing step, the amount of surface oxide produced during final box annealing is determined by using an annealing separator containing alumina as the main component. Iron loss consists of the combination of limiting the oxygen basis weight to O-: 3E/m or less per cross section, and applying direct chemical polishing or electrolytic polishing to a range of 2 to 10 μm per side without pickling. Method for producing grain-oriented silicon steel sheet with low
1 invention).

After cold rolling to the desired final sheet J, final box annealing is performed through decarburization annealing and application of an annealing separator to complete secondary recrystallization, and then surface oxides are removed and Kagakuken I or 'A direction consisting of a step of applying electrolytic polishing.

In the manufacturing method of silicon steel sheets, an annealing separator containing aluminum as the main component is used to eliminate surface oxides generated during final box annealing by reducing the amount of oxygen per surface to 0. .81/m2 or less, direct chemical polishing or electrolytic polishing without pickling in the range of 2 to 10 μm per side, and applying a colloidal silica-phosphate treatment solution to the polished surface. Method 1 for producing a grain-oriented silicon steel sheet with low core loss (second invention), comprising: heat-treating at a temperature range of 500 to 750°C and applying a tension-applied insulating coating.

In addition, it is recommended as an embodiment that chemical polishing or electrolytic polishing in each invention has a surface smoothness of 0.4 μm or less in terms of center line average roughness Ra.

After decarburization annealing, final box annealing is carried out by e1.
Therefore, the amount of surface oxide produced during the final box annealing should be limited to 0.39/m2 or less, expressed as an oxygen ratio of 16 per side, by particularly using an annealing separator containing alumina as the main component. is the first requirement, followed by one-sided 2-1
Chemical ω■ polishing in the range of 0 μm.

The second requirement is to perform electrolytic polishing.

Previously, no consideration had been given to quantitatively evaluating the amount of this type of surface oxide, so pickling was always applied after the final box annealing, regardless of the amount produced, and therefore As mentioned above, the subsequent chemical polishing or electrolytic polishing for mirror polishing had to be carried out using a polishing method that was too deep to remove the surface roughness caused by pickling, which was uneconomical and inefficient.

Note that the method of using A12o8 powder as the main component of an annealing separator for the purpose of suppressing the formation of surface oxides during final box annealing has already been proposed in US Pat. No. 8,785,882. JP-A-58-2211 which uses high-purity AJ208 grains and its improvement
Publication No. 8 and JP-A-55-! - Serpentine in A12o8 as disclosed in Publication No. 89428.

Those containing Ca (OH) 2 and the like are also being talked about.

However, in these methods or in the method using a mixture of Al2O8 and MyO, the surface and amount of monooxide produced differs depending on the mixture, but a quantitative evaluation has not been performed to date. .

In this invention, the amount of generated oxide is expressed as oxygen basis weight, which is 0,8,! per one side of the steel plate. i'/
Conditions that can be suppressed to below m'' are used.

In this way, a mirror finish can be easily achieved on one side of a steel plate only by shallow chemical polishing or electrolytic polishing over a depth of 2 to 10 μm, without the need for a pickling process, which was conventionally considered indispensable for achieving a mirror finish. It is.

Chemical polishing or electrolytic polishing + iJ) The smoothness of the steel plate surface after polishing is expressed as center line average roughness (Ra) of 0.4 μm.
A grain-oriented silicon steel sheet with low core loss can be more effectively manufactured by following the procedure below.

In order to make these grain-oriented silicon steel sheets compatible with υ1 for actual use, a colloidal silica-phosphate treatment solution is applied to the above-mentioned polished surface, and heat treatment is performed in a temperature range of 500 to 750°C. It can be used to form tensioned insulating coatings.

Next, an explanation of an experimental example that led to the success of this invention is as follows.

Experimental example l G O, 045%, Si 8.82%, Mn O,
065%.

S O,004%, Se O,019% and Sb
A silicon steel sheet containing 21% O and the remainder substantially Fe was hot rolled to a thickness of 8u and heated at 950°C.
After 5 minutes of homogenization annealing, it was heated to 900°C for 8
Cold rolling is performed twice with an intermediate annealing of 1 minute in between.
The final plate thickness was 0.80 m.

Then, at 820°C for 8 minutes in a humid hydrogen atmosphere...
Decarburization annealing is performed in the air, and the surface of this steel plate is AA! 2
A final glaze annealing was carried out at 1180°C and 10hrH2 by coating various annealing separators consisting of 08 and mainly high-temperature fired M and O.

After this annealing, the surface surface was washed with water to remove residual annealing material and abrasion, and then chemical polishing was performed in HF + H2O2 so that the polishing amount per side was 8 μm and 7 μm, respectively. Iron loss by law (W□?150)
was measured.

The iron loss difference before this chemical polishing treatment is 4 (ΔW□7150
) The mixing conditions of the separating agent on □, Table 1r
■Table 1 shows the shadow of the oxygen basis weight of oxides.

The amount of oxide formed below 71 (ν) expressed in terms of oxygen basis weight is 71 (ν).Improvement of iron loss after chemical polishing by using Akatsuki Minute 1 Dangerous Agent Black 8, 4 and 5. It is clear that there has been a significant increase.

° Figure 1 shows the influence of center line average roughness (Ra) on the iron loss improvement amount when chemical polishing is performed with a target of 7 μm on the samples under the conditions of 8, 4, and 5 in Table 1. The results are shown using the sheet iron loss measurement method (SST).

The smoothness of the surface after chemical polishing is defined as the center line average roughness (Ra)
It can be seen that reducing the thickness to 0.4 μm or less contributes more advantageously to improving iron loss.

Experimental Example 2 The final glaze firing 1 under the conditions of Mu5 used in the experiment in Experimental Example 1...The sample after annealing was chemically polished at various stages in HF + H20□, and the effect on iron loss was investigated in detail. I looked into it.

Figure 2 shows the measured iron loss (W□7150) and the thickness-corrected iron loss (W
□7/. ) shows the results of investigating the effect of the amount of chemical polishing on the same sample. As is clear from FIG. 2, the measured iron loss (W17150) is greatly improved by a small amount of chemical polishing, and even by polishing exceeding 10 μm, the apparent improvement is further improved.

On the other hand, for plate thickness correction iron tfl (W,,*15o) IL, it is 10,,.

There is almost no improvement even if the polishing exceeds μm □
I know what will happen.

In addition, excessive polishing exceeding 103 m will only reduce the yield of the steel material and increase the cost due to chemical costs for Kagakuken 1% F, but it will not actually improve iron loss (thickness correction iron loss) and is meaningless. became clear from this experiment.

On the other hand, according to Fig. 2, it can be seen that the amount of polishing l# less than 2 ttm results in only a slight improvement in iron loss, and based on these experimental facts, in this invention, the amount of grinding l# is less than 2 ttm. 10μ
m.

Although the results of the above-mentioned experiments are based on experiments with chemical polishing in HF + H2O2, electrolytic polishing, for example 0
rb8+ H3P0. Comparable results were also obtained by electrolytic polishing.

The reason why iron loss is significantly improved only within a certain polishing depth range when the outermost layer of a steel plate is polished and smoothed is estimated as follows.

Namely, N in the purification process of final glaze annealing.

S, 5efJ'' - Since it cannot be completely removed from the steel, it forms nitrides, MnS, MnSe, and MnS-MnSe solid solutions especially in the outermost layer of the steel sheet after final glaze annealing. It precipitates and remains.

These precipitates are said to significantly increase iron loss, especially hysteresis loss, so polishing away the surface layer where these precipitates exist is effective in improving iron loss. It can be estimated that

It has been known for a long time that surface smoothing and mirror polishing themselves greatly contribute to the improvement of iron 411.

Using a grain-oriented silica plate with a smooth surface obtained by this invention, a colloidal silica/phosphate coating treatment solution is further applied, and baking is performed at a temperature range of 500 to 750°C. Furthermore, a more desirable product can be obtained by forming a tension-applying top insulating coating on the surface of the rice (second invention).

For the treatment of colloidal silica-phosphate tension coating qp7-, Japanese Patent Publication No. 1986-.

Colloidal silica-magnesium phosphate coating treatment liquids disclosed in Patent Publications No. 5211, No. 7 and JP-A-52-25296 are suitable for this invention.

In the second invention, baking of such a tension coating is limited to a temperature range of 500 to 750°C. The reason for limiting this temperature range is that a tension-applied coating cannot be formed at temperatures lower than 500'C, and conversely, at temperatures higher than 750'C, even if sufficient tension is generated, the adhesion of the coating is poor. This is because it is not good.

Examples of this invention will be described below.

Example GO O, 043%, Si 8.05%, Mn 0.
060%.

s o, ooa%, Se O, 018% and Sb
A silicon material having a composition of 24% O,024% and the remainder being Fe was hot rolled to a thickness of 8 mm, and then cold rolled twice with an intermediate annealing in between. After decarburizing the O, aO dragon plate and annealing it in a wet hydrogen atmosphere, it was coated with an annealing separator consisting of 8 parts by weight of A1080 and 9020 parts by weight of M, and then annealed at 1180''C for 10 minutes. Hr HB
The final glaze annealing was carried out inside.

The annealing separating agent remaining on the loose surface was removed by washing with water.

In this state, the total amount of surface oxide, expressed as an oxygen cap, was 0.1 g/m per side.

Then, HPO-P O-Cr0a polishing at 50°C 8
4 25 Electrolysis and dissolution 1il) F calendar were applied in the liquid.

Table 2 shows the influence of surface roughness on the nationally determined insulating properties of the same sample at each polishing stage.

Table 2 (Note) *: Sheet thickness calculated from weight reduction As shown in Table 2, the first invention makes it possible to manufacture grain-oriented silicon steel sheets with extremely low iron loss by simply polishing the outermost layer of the steel sheet. can.

Next, the tension-applied coating treatment solution shown below was applied to the surface of the sample shown in the example in Table 2 to a film thickness of 8 μm on one side after baking, and after drying in the air at 400°C for 2 minutes, Baked in N2 for 1 minute at °C.

The iron loss after baking of the coating treatment solution composition was the same as the iron loss after electrolytic polishing, and the adhesion of the coating was also good.

Effects of the Invention According to the present invention, by applying an annealing separator containing alumina as a main component to the steel sheet surface after decarburization annealing and prior to final glaze annealing, the surface generated during final glaze annealing is reduced. The oxidation of oxides is 0.8 C per oxygen basis per side.
1/m2 or less, and thus can be directly subjected to chemical fine polishing or electrolytic polishing without the need to go through the pickling process that is indispensable for conventional mirror finishing. 2 to 10 μm, which is much smaller than when there is roughness, and is effective in improving iron loss.
A mirror finish can be easily achieved with the sharpening beak.

Further, in the second invention, the adhesion of the tension coating is further advantageously improved.

[Brief explanation of the drawing]

Figure 1 is a chart showing the relationship between the center line average roughness of the surface of a grain-oriented silicon steel plate chemically polished with a polishing amount of 7 μm and the measured iron loss improving wax. It is a chart showing the correlation between iron 1° loss and plate thickness corrected iron loss. 0,f O,2θ3 (1,!i (15θ6 inside C-fold 1,000-yen super Rα) (μ division) Fig. 2

Claims (1)

[Claims] 1. After cold rolling to the desired final plate thickness, decarburization annealing and final box annealing via application of an annealing separator are performed to complete secondary recrystallization, and then surface oxidation is performed. The amount of surface oxide produced during final box annealing using an alumina-based annealing separator in a method for producing grain-oriented silicon steel sheets comprising the steps of removing materials and applying chemical polishing or electrolytic polishing. The oxygen basis weight per side is 0.8I! /@2 or less, direct chemical polishing or electrolytic polishing without pickling in the range of 2 to 10 μm per 1° side. Production method. λ Chemical polishing or electrolytic polishing increases center line average roughness (Ra')
Surface smoothness of 0.4 μm or less. The method □ according to claim 1, which is & After cold rolling to the desired final plate thickness, a final glaze annealing is performed through decarburization annealing and application of an annealing separator to complete secondary recrystallization, and then surface oxides are removed and chemical In a method for producing a grain-oriented silicon steel sheet comprising a step of polishing or electrolytic polishing, the amount of surface oxide generated during final box annealing is determined using an annealing separator mainly containing alumina. The amount of oxygen per side must be limited to 0.8,!7/m” or less, and direct chemical polishing or '11 solution (
Apply tJf polishing in the range of 2-10 μm per side,
and applying a colloidal silica monochloride-based treatment solution to the surface and heat-treating it at a temperature range of 500 to 750°C to apply a tension-applied insulating coating. Made of grain-oriented silicon steel plate
? Method.