JPH0759753B2 - Insulation coating method for electrical steel sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to an insulating coating treatment method for an electromagnetic steel sheet, which can favorably maintain the properties of the insulating coating on the electromagnetic steel sheet.

<Prior Art and Its Problems> Generally, the properties required for an insulating coating of an electromagnetic steel sheet are excellent in electrical insulation, adhesiveness, punchability, weldability, corrosion resistance, heat resistance, and the like. The product ratio is high.

Conventionally, insulating coatings of various compositions have been developed and improved in order to satisfy these required characteristics.

By the way, the conventional method of insulating coating of electromagnetic steel sheet is to apply a treatment liquid (coating liquid) to form an insulating coating on both surfaces of a continuously flowing steel strip (hereinafter referred to as steel sheet), and then bake it in a baking furnace. , It is left to cool to room temperature and wound into a coil. In this method, the conveyance of the electromagnetic steel sheet in and after the baking furnace is carried out by a plurality of table rolls arranged inside and outside the baking furnace.

That is, as shown in FIG. 3, the magnetic steel sheet 1 is conveyed while the insulating coating 3 formed on the lower surface side (back surface side) thereof and the outer peripheral surface of the table roll 5 ′ are in contact with each other.

However, since the table roll 5'is a steel roll made of steel, when it comes into contact with the softer insulating coating 3,
The matching is not good, and the insulating coating 3 is scratched, which adversely affects the surface properties of the insulating coating 3.

When the insulating coating 3 is scratched in this way, the interlayer resistance value decreases, leak occurs during use, and the electrical insulation deteriorates.
Moreover, the corrosion resistance of the steel sheet is also deteriorated, which is not preferable.

On the other hand, since the insulating coating 4 formed on the upper surface side (front surface side) of the electromagnetic steel sheet does not come into contact with the table roll 5 ′ during transportation,
The above-mentioned scratches do not occur, and therefore, the insulating coating 4 on the front surface side and the insulating coating 3 on the back surface side of the electromagnetic steel sheet 1 differ in electrical insulation and corrosion resistance.

In order to eliminate such a difference between the front and back of the electromagnetic steel sheet, the thickness of the insulating coating 3 on the back side is currently increased to deal with it, but a fundamental solution to improve the properties of the insulating coating 3 is a fundamental solution. Not a means.

Therefore, it is conceivable to prevent the back surface of the insulating film from being scratched by using a roll having a peripheral surface made of an elastic material such as a rubber roll as the table roll 5 ', but the insulating film is baked at about 300 to 700 ° C. The temperature in the furnace is maintained for several tens to hundreds of tens of seconds, and the temperature of the steel plate is about 250 to 450 ° C, so the rubber melts when conveyed by a rubber roll, etc. Therefore, it is not possible to use a rubber roll etc. as a table roll. Can not.

In addition, a floater system in which the treatment liquid is applied to the steel sheet and then baked without contact in the baking furnace and conveyed,
This method is expensive in terms of equipment and is not economical.

<Purpose of the Invention> The object of the present invention is to solve the above-mentioned drawbacks of the prior art, prevent the insulating coating on the back surface side of the electromagnetic steel sheet from being scratched during conveyance by a table roll, and electrically insulate the front and back surfaces of the electromagnetic steel sheet. An object of the present invention is to provide a method for treating an insulating coating of an electromagnetic steel sheet, which can reduce the difference in corrosion resistance and corrosion resistance.

<Structure of the Invention> In order to achieve such an object, the inventors of the present invention have as a result of earnest research, and as a result, use a roll whose outer peripheral surface is made of an elastic body such as a rubber roll as a table roll for conveying electromagnetic steel sheets. Therefore, the inventors have found that the electrical steel sheet is rapidly cooled so as to lower the temperature of the electrical steel sheet after baking so that the present invention has been achieved.

That is, the present invention, in forming the insulating coating on the surface of the magnetic steel sheet, after coating and baking the treatment liquid on both sides of the magnetic steel sheet material, start the quenching after reaching the plate temperature 350 ° C. or less, then The present invention provides a method for insulating coating of an electromagnetic steel sheet, characterized in that the steel sheet is conveyed by a table roll having an outer peripheral surface made of an elastic body.

In the method of the present invention, the rapid cooling is preferably performed by water cooling.

The rapid cooling is preferably performed with a CrO ₃ solution of ₃ wt% or less.

When the electromagnetic steel sheet contains a relatively large amount of C in the steel, the quenching is preferably started at a sheet temperature of 250 ° C. or lower.

Hereinafter, the insulating coating method of the electrical steel sheet of the present invention will be described in detail.

FIG. 1 is an explanatory view schematically showing an insulating coating treatment line of an electromagnetic steel sheet according to the method of the present invention. As shown in the figure, a treatment liquid that is an insulating coating is uniformly applied to both surfaces of a continuously flowing electromagnetic steel plate (steel strip) material 2 by a treatment liquid application means 7 by, for example, a roll coater method, and then, For example, the baking is performed in a baking oven 8 such as a hot air oven.

The insulating coating in the method of the present invention is an organic coating, one or two coatings selected from phosphate-based and chromate-based coatings, and one or two phosphate-based or chromate-based coatings and organic coatings. It is possible to form a coating film in which a resin is mixed, and after baking, a treatment liquid for forming the above coating film may be applied.

The electromagnetic steel sheet 1 can be transported in the baking furnace 8 by the table roll 6 made of steel roll, or by a floater system in which it is transported without contact.

The electromagnetic steel sheet 1 exiting the baking furnace 8 is rapidly cooled by an arbitrary cooling means 9 after reaching a plate temperature of 350 ° C. or lower.

The temperature in the baking furnace 8 is usually about 300 to 700 ° C, and the plate temperature of the steel plate 1 in the furnace is about 250 to 450 ° C. If the plate temperature immediately after the electromagnetic steel plate 1 leaves the baking furnace 8 is 350 ° C. or lower,
Rapid cooling can be started immediately after baking, but if the plate temperature immediately after leaving the baking furnace 8 exceeds 350 ° C, it is allowed to cool until the plate temperature becomes 350 ° C or less, and then Start quenching.

The reason why the quenching start temperature is 350 ° C or lower is 350
This is because if the rapid cooling is started from a temperature exceeding ℃, thermal strain occurs in the magnetic steel sheet and the magnetic characteristics of the magnetic steel sheet deteriorate.

In the case of a normal electrical steel sheet, the quenching start temperature may be set to 350 ° C or less in consideration of the occurrence of the thermal strain, but when a special steel type is used for the electrical steel sheet, that is, a relatively large amount in the steel (for example, When a material containing C (0.0 wt% or more) is used, the quenching start temperature is preferably 250 ° C. or less in plate temperature. The reason is that when the rapid cooling is started from a temperature exceeding 250 ° C., C in the steel is solidified and carbide is precipitated due to aging to deteriorate the magnetic properties of the electrical steel sheet.

As such a rapid cooling method, it is efficient and preferable to use water cooling such as spraying water or immersing in water if it is cooled.

In addition, rapid cooling is preferably performed by spraying or dipping in a cooling liquid containing a CrO ₃ solution of ₃ wt% or less instead of the above water in order to improve the corrosion resistance. In this case, it is particularly effective when the electromagnetic steel plate in the baking furnace 8 is conveyed by the table roll 6 made of a steel roll. That is, even if the insulating coating 3 on the back surface has a flaw due to a poor matching with the table roll 6, the flaw will be left on the scratched portion.
This is because Cr ⁶⁺ enters and prevents deterioration of the corrosion resistance of the steel sheet.

Incidentally, the CrO ₃ concentration of the cooling liquid was less 3 wt% is, CrO ₃
If more than 3 wt%, a large amount of Cr ⁶⁺ adheres to the surface of the insulating coating, ^causing inconvenience in handling the steel sheet. Although the cooling rate in the rapid cooling is not particularly limited, it is preferably set to about 80 to 200 ° C / S from an economical point of view.

By the cooling means 9 as described above, the rapid cooling is started from a plate temperature of 350 ° C. or lower, and in some cases a plate temperature of 250 ° C. or lower, and the magnetic steel sheet 1 cooled to about room temperature is Multiple table rolls 5 arranged on the line
Is conveyed in the direction of the arrow in the figure, and is wound and held by the winding roll 10.

The outer peripheral surface of the table roll 5 that conveys the electromagnetic steel sheet 1 is formed of an elastic body 51.

In the past, since no emergency was performed after baking the electromagnetic steel sheet, the electromagnetic steel sheet 1 had to be conveyed by a table roll 5'of a steel roll as shown in FIG. When the insulating coating 3 was in contact with the insulating coating 3, the insulating coating 3 was scratched due to the poor matching. However, in the present invention, since the electromagnetic steel sheet 1 has already been cooled to about room temperature during transportation, for example, as shown in FIG. 2, the table roll 5 made of an elastic material coated roll can be used to transport the electromagnetic steel sheet 1, Since the insulating coating 3 can be prevented from being scratched by the buffering action of the elastic body 51 at the contact portion with the steel sheet 1, there is almost no reduction in the electrical insulation of the insulating coating 3 on the back surface side and in the corrosion resistance of the steel sheet.

Therefore, there is almost no difference in properties between the insulating coating 4 on the front surface side and the insulating coating 3 on the back surface of the electromagnetic steel sheet 1, and the electromagnetic steel sheet 1
There is almost no difference in electrical insulation and corrosion resistance between the front and back.

The outer peripheral surface of the table roll 5 that is in contact with the back side insulating coating 3 of the electromagnetic steel plate 1 may be made of an elastic body, and the steel roll core shown in FIG. 2 is coated with the elastic body 51. The elastic body-covered roll may be a roll such as a rubber roll in which the entire roll is made of an elastic body.

The elastic body 51 of the table roll 5 may be any material, and examples thereof include synthetic rubber, natural rubber, non-woven fabric, and various plastics.

<Example> (Example 1) Under the following conditions, after applying a treatment liquid to be an insulating coating on both sides of a magnetic steel sheet material and winding the same, the quenching start temperature is variously changed and the magnetic steel sheet is immersed in water. And then quickly cooled.

(1) Material used Electrical steel sheet JIS S 08 Material in charge (Si: 3.1wt%, C: 0.005wt
%), 0.5 mm thick electromagnetic steel sheet JIS S 60 materials (Si: 0.1 wt%, C: 0.039 wt)
%), Thickness 0.5 mm (2) Composition of treatment liquid (coating liquid) Magnesium monobasic phosphate Mg (H ₂ PO ₄ ) ₂ 30% PO in aqueous solution
₄ 100 parts by weight of CrO ₃ 20 parts by weight of chromic anhydride, 20 parts by weight of aluminum nitrate Al (NO ₃ ) ₃ (3) Coating and baking conditions The above treatment solution with a specific gravity of 1.06 is applied to the above electromagnetic steel sheet at a pitch of 0.5 mm. It was applied with a rubber roll of and heated at 450 ° C for 150 seconds (plate temperature 400 ° C). The amount of adhesion of the obtained insulating coating on one side was in the range of 1.5 to 2.0 g / m ^{2 in} dry weight.

Magnetic properties of each electromagnetic steel sheet thus obtained,
The corrosion resistance and electrical insulation were investigated. The result is the fourth
Shown in Figures, 5 and 6.

Fig. 4 is a graph showing the measurement results of the magnetic properties (iron loss W _15/50 ) of electromagnetic steel sheets.
The mark indicates the measured value after aging treatment (200 ° C × 100Hr, in air), and the mark × indicates strain relief annealing (750 ° C × 2Hr, in nitrogen).

FIG. 5 is a graph showing the measurement results of the corrosion resistance (corrosion rate%) of electromagnetic steel sheets. The corrosion resistance was measured by examining the rusting rate after 7 hours of the salt spray test according to JIS Z 2371.

Fig. 6 shows the electrical insulation of electromagnetic steel sheets (interlayer resistance value Ω · cm ² /
It is a graph which shows the measurement result of (sheet). This measurement of electromagnetic insulation was performed according to JIS C-2250 second method. In addition,
In the graphs of FIGS. 4 to 6 above, the solid line shows the JIS S08 equivalent material, and the broken line shows the JIS S 60 equivalent material used.

[Results] (1) As is clear from the graph of FIG. 4 in which the measured values of iron loss (W _15/50 ) are plotted, the S 08 equivalent material is the material that is left in the sheared state when the rapid cooling start temperature (plate When the temperature is 400 ℃, the iron loss is 2.64 W / kg, and when the quenching start temperature (plate temperature) is 350 ℃ or less, the iron loss is 2.60 W / kg to 2.59 W / kg, and the former has poor magnetic properties.

Also, in the case of S 60 equivalent material, the same tendency as the S 08 equivalent material was observed in the measurement of the raw material after shearing and the material after aging treatment, and the material was rapidly cooled from a temperature of 350 ° C or less, particularly 250 ° C or less. The magnetic properties of those that started are good.

(2) As shown in FIG. 5 and FIG. 6, the corrosion resistance and electrical insulation of the electromagnetic steel sheet were not different between when the quenching start temperature was within the range of the present invention and outside.

(Example 2) The following treatment liquid A was applied to a magnetic steel sheet of JIS S 08 equivalent material having a plate thickness of 0.5 mm and a plate width of 980 mm with a rubber roll having a pitch of 0.5 mm and the temperature was 400 ° C.
It was baked for 60 seconds in a hot air oven (plate temperature 290 ° C). Immediately after that, water spray was sprayed on the steel plate at the exit side of the hot stove to perform rapid cooling. The electromagnetic steel sheets cooled to room temperature were transported about 40 m by a table roll (total of 15 rolls) made of urethane rubber rolls arranged side by side on the line and wound on a winding roll.

Incidentally, adhesion of the insulating film formed on the electrical steel sheet surface by dry weight 0.8 g / m ^2, the back surface side was 0.9 g / m ^2.

Regarding the characteristics shown in Table 1, the difference between the front and back of the electromagnetic steel sheet obtained above was examined. In terms of electrical insulation (interlayer resistance value), there was almost no difference in the corrosion resistance between the front and back of the electrical steel sheet.

<Treatment liquid A> 30% magnesium dichromate solution 130 parts by weight Ethylene glycol 10 parts by weight Acrylic emulsion resin (solid content 50%) 20 parts by weight Boric acid 10 parts by weight (Comparative Example 1) Plate thickness 0.5 mm, plate width 980 mm Apply the above treatment liquid A to a JIS S 08 equivalent electromagnetic steel plate with a 0.5 mm pitch rubber roll and apply 400 ° C.
It was baked for 60 seconds in a hot air oven (plate temperature 290 ° C). Then, about 40 m was conveyed by a table roll (15 in total) by steel rolls arranged in parallel on the line and wound on a winding roll.

Incidentally, adhesion of the insulating film formed on the electrical steel sheet surface by dry weight 0.9 g / m _2, the back surface side was 1.2 g / m ^2.

Regarding the characteristics shown in Table 1, the difference between the front and back of the electromagnetic steel sheet obtained above was examined. The insulating film on the back surface is considerably scratched, and as a result, the interlayer resistance value is as low as about half that on the back surface side, and the corrosion resistance on the back surface side is also extremely poor.

(Example 3) The following treatment liquid B was applied to a magnetic steel sheet of JIS S 60 equivalent material having a sheet thickness of 0.5 mm and a sheet width of 1250 mm by a 3-roll coater and baked in a hot air oven at 450 ° C for 50 seconds (sheet temperature 320. C). Then, the plate was allowed to cool to a temperature of 250 ° C., then the steel plate was immersed in a water tank and rapidly cooled.

Thereafter, the electromagnetic plate was conveyed by the same table roll as in Example 2 and wound on the winding roll.

The surface side 6.28 g / m ² coating weight of the insulation film formed on the electromagnetic steel sheet by dry weight, the back side was 6.30 g / m ^2.

Regarding the characteristics shown in Table 1, the difference between the front and back of the electromagnetic steel sheet obtained above was examined. Electrical insulation (interlayer resistance value) Almost no difference in corrosion resistance between the front and back of the electromagnetic steel sheet.

<Treatment liquid B> Water-soluble epoxy ester / melamine-based resin (mixing ratio 70:30) (nonvolatile content 50%) (Comparative example 2) A magnetic steel sheet equivalent to JIS S 60 with a thickness of 0.5 mm and a width of 1250 mm is prepared as described above. The treatment liquid B was applied with a 3-roll coater and baked in a hot air oven at 450 ° C for 50 seconds (plate temperature 320 ° C). Thereafter, the electromagnetic steel sheet was transported by the same table roll as in Comparative Example 1 and wound on the winding roll.

The surface side 6.6 g / m ² coating weight of the insulation film formed on the electromagnetic steel sheet by dry weight, the back surface side was 6.4 g / m ^2.

Regarding the characteristics shown in Table 1, the difference between the front and back of the electromagnetic steel sheet obtained above was examined. The interlayer resistance value is slightly inferior on the back surface side as compared with the front surface side, but the corrosion resistance on the back surface side is considerably worse than that on the front surface side.

(Embodiment 4) The following treatment liquid C was applied to a magnetic steel sheet of JIS S 60 equivalent material having a sheet thickness of 0.5 mm and a sheet width of 1250 mm with a rubber roll having a pitch of 0.5 mm to give 400
It was baked for 50 seconds in a hot air oven at ℃ (plate temperature 250 ℃). Immediately after that, the steel plate was immersed in a bath of an aqueous solution of 1% by weight of CrO ₃ on the outlet side of the hot-blast stove to make an emergency. Thereafter, the electromagnetic steel sheet was conveyed by the same table roll as in Example 2 and wound on the winding roll.

The surface side 6.28 g / m ² coating weight of the insulation film formed on the electromagnetic steel sheet by dry weight, the back surface side was 6.3 g / m ^2.

Regarding the characteristics shown in Table 1, the difference between the front and back of the electromagnetic steel sheet obtained above was examined. Regarding electrical insulation (interlayer resistance value) and corrosion resistance, there was almost no difference between the front and back of the electromagnetic steel sheet. In addition, there was almost no adhesion of Cr ^{6+ on} the surface of the insulating coating, and there was no problem in handling the steel sheet.

<Treatment liquid C> 30% calcium dichromate 130 parts by weight Ethylene glycol 20 parts by weight <Effects of the Invention> According to the insulating coating treatment method for an electromagnetic steel sheet of the present invention, after the treatment liquid is applied to both sides of the electromagnetic steel sheet material and baked, the sudden start temperature is rapidly cooled at a sheet temperature of 350 ° C or less, and then the By transporting the steel sheet with a table roll whose outer peripheral surface is made of an elastic material, it is possible to prevent the back surface of the electromagnetic steel sheet, that is, the side in contact with the table roll, from being scratched, and to prevent the electric insulation (interlayer Since it is possible to prevent a decrease in the resistance value and a decrease in the corrosion resistance of the steel sheet, it is possible to reduce the difference between the electrical insulation and the corrosion resistance between the front and back of the electromagnetic steel sheet.

In particular, if a CrO ₃ solution of ₃ wt% or less is used as the cooling liquid for quenching, even if scratches are formed on the insulating film on the back side before quenching, Cr ⁶⁺ will enter the scratches and reduce the corrosion resistance of the steel sheet. Can be prevented.

Further, in the method of the present invention, the magnetic properties of the electromagnetic steel sheet are impaired by setting the quenching start temperature to 350 ° C. or less, and particularly in the case of an electromagnetic steel sheet having a relatively large C content, setting the quenching start temperature to 250 ° C. or less. The above effect can be exerted without any.

Further, in the conventional method, a constant line length was required for cooling after baking, but in the method of the present invention, the line length can be shortened by rapid cooling, which is advantageous in terms of equipment cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically showing a line of an insulating coating treatment method for an electromagnetic steel sheet according to the present invention. FIG. 2 is a partial perspective view showing a state of the electromagnetic steel sheet during transportation according to the method of the present invention. FIG. 3 is a partial perspective view showing a state of a conventional method of transporting an electromagnetic steel sheet. FIG. 4 is a graph showing the relationship between the quenching start temperature and iron loss in the example. FIG. 5 is a graph showing the relationship between the quenching start temperature and the rusting rate in the examples. FIG. 6 is a graph showing the relationship between the quenching start temperature and the interlayer resistance value in the example. Explanation of symbols 1 ... Electromagnetic steel sheet, 2 ... Electromagnetic steel sheet material, 3 ... Insulating coating (front side), 4 ... Insulating coating (back side), 5 ... Table roll, 51 ... Elastic body, 5 ' , 6 ... Table roll (steel roll), 7 ... Treatment liquid applying means, 8 ... Baking furnace, 9 ... Cooling means, 10 ... Winding roll

Claims (4)

[Claims] 1. When forming an insulating coating on the surface of an electromagnetic steel sheet, a treatment liquid is applied to both surfaces of an electromagnetic steel sheet material and baked, and then quenching is started after the sheet temperature reaches 350 ° C. or lower, and then the A method for insulating coating of electromagnetic steel sheet, comprising transporting the steel sheet by a table roll having an outer peripheral surface made of an elastic body. 2. The method for insulating coating of electromagnetic steel sheet according to claim 1, wherein the rapid cooling is performed by water cooling. 3. The method for insulating coating of electromagnetic steel sheet according to claim 1, wherein the quenching is performed with a CrO ₃ solution of ₃ wt% or less. 4. The method for insulating coating of an electromagnetic steel sheet according to claim 1, wherein the quenching is started at a plate temperature of 250 ° C. or lower.