JPH086140B2 - Method for manufacturing low iron loss grain-oriented electrical steel sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a low iron loss grain oriented electrical steel sheet suitable for use as an iron core of a transformer or other electric equipment.

(Prior Art) A grain-oriented electrical steel sheet is mainly used as an iron core material of a transformer and is required to have good magnetic characteristics.
In particular, it is important that the energy loss when used as an iron core, that is, the iron loss is low.

Therefore, conventionally, in order to reduce iron loss, the crystal surrounding is highly aligned with the (110) [001] orientation, and the electrical resistance of the steel sheet is increased by increasing the Si content.
Various attempts have been made to reduce impurities and reduce the plate thickness. As a result, iron loss W _17/50 (magnetic flux density 1.7T, 50Hz) is 0.9W / k for steel plates with a thickness of 0.23mm or less.
Items below g have been manufactured.

However, metallurgical methods cannot be expected to further improve iron loss.

In recent years, various methods for artificially subdividing magnetic domains have been tried as means for achieving a significant reduction in iron loss. Among them, as a method which has been industrialized at present, there is a method of irradiating a laser on the surface of a steel sheet after finish annealing as proposed in Japanese Patent Publication No. 57-2252.

However, although this method is effective in reducing iron loss, it has the drawback of causing deterioration of iron loss due to stress relief annealing, and is not used for wound cores that require stress relief annealing.

On the other hand, as a technology capable of strain relief annealing, Japanese Patent Publication No. 62-5487
No. 3 gazette states that for steel sheets that have been finish annealed, the insulating coating is locally removed by laser or mechanical means, and then the coating removed portion is pickled, or the steel is directly scratched directly with a knife. The method of forming a linear groove locally by the method of, and then applying a phosphate-based tension-imparting coating treatment so as to fill the groove, and in JP-B-62-53579, finish annealing is performed. After forming a groove with a depth of more than 5 μm in the base steel part with a load of 90 to 220 kg / mm ^{2 on} the steel plate of 750 ℃
A method of heat treatment at the above temperature has been proposed.

All of these methods introduce linear grooves on the surface of the steel sheet that has been finish-annealed, but in the former method,
Since it is difficult to always remove the coating stably because of the difference in the coating thickness and the light absorption rate, a stable groove cannot be formed. There is a problem that the product ratio is lowered, while the latter method has a problem that it is difficult to adjust the load to obtain a groove having a constant depth. Further, when introducing a groove into a steel sheet that has been finish-annealed as in these methods, the coating is damaged by the introduction of the groove, so it is often necessary to reapply the insulating coating, and the space factor decreases and The disadvantage was that it resulted in an unnecessary increase in costs.

In this respect, the inventors previously proposed a method of introducing a linear groove into the final cold-rolled sheet as a method that does not cause the above-mentioned drawbacks. For example, a method of introducing a linear flaw by using a blade of a knife, a laser or the like disclosed in JP-A-59-197520, a photoetching disclosed in JP-A-63-42332, or an electrolytic etching using a stencil. Method.

(Problems to be Solved by the Invention) However, in the former case, the need for re-coating can be avoided, but it is necessary to remove the burrs generated around the groove, while in the latter case, photoetching can be used as a mask. It is difficult to keep the exposed state of the ultraviolet light through the phenomenon and the removed state of the exposed area when immersed in the solution uniform over the entire coil, and in electrolytic etching with a stencil, a uniform groove is always created due to the bleeding of the electrolytic solution. Where it was difficult to introduce, it left a problem.

This invention was developed as a result of intensive experiments and studies on a method for industrially stably obtaining a uniform groove over the entire length of the coil in order to solve the above problems. It was found that it is extremely effective to achieve the intended purpose by applying an etching resist by printing, baking, and then performing etching treatment, and then removing the resist.

 The present invention is based on the above findings.

That is, the present invention is a series in which a slab for grain-oriented electrical steel sheets is hot-rolled, and then cold-rolled once or twice or more with intermediate annealing to obtain a final plate thickness, and then decarburization annealing and then final finishing annealing. In the production of grain-oriented electrical steel sheet by the process of, after the final cold rolling, an etching resist is printed on the surface of the steel sheet to leave a continuous or non-continuous linear region in the direction intersecting the rolling direction as a non-coated region. The method for producing a low iron loss-oriented electrical steel sheet comprises: coating, baking, and then etching treatment to form continuous or discontinuous linear grooves on the surface of the steel sheet, and then removing the resist.

In this invention, the resist thickness after coating and baking is
It is preferably 0.5 to 30 μm.

 The present invention will be specifically described below.

First, the experimental results that are the basis of the present invention will be described.

The grain-oriented electrical steel sheet is generally manufactured by the following steps. That is, a slab for grain-oriented electrical steel sheets is hot-rolled, and then hot-rolled sheet is annealed if necessary, and then cold rolled one or more times with intermediate annealing to obtain a final sheet thickness, and then decarburized. After annealing and final finish annealing, the product is usually top-coated.

Now, during the above manufacturing process, by gravure offset printing an etching resist ink mainly composed of an alkyd resin on the surface of the coil of the final cold-rolled sheet rolled to a sheet thickness of 0.20 mm, the non-coated portion is perpendicular to the rolling direction. Width in direction:
It was coated so as to remain linearly at 0.2 mm and a gap in the rolling direction: 4 mm, and then baked at 200 ° C. for 30 seconds. At this time, the gravure plate used was a roll processed to have a concave cell density of 150 cells / inch and a cell depth of 50 μm. The resist thickness after baking was 2 μm.

The steel plate coated with the etching resist in this manner is subjected to electrolytic etching or chemical etching to form a linear groove having a width of 0.2 mm and a depth of 20 μm, and then immersed in an organic solvent to remove the resist. . The electrolytic etching was carried out by treating with a current density of 10 A / dm ² for 20 seconds in a NaCl electrolytic solution, and the chemical etching was carried out by immersing in a HNO ₃ solution for 10 seconds.

After forming the groove, samples were taken from 20 positions in the longitudinal direction of the coil and 10 positions in the width direction, and the width and depth of the groove were measured by a roughness meter.

After such treatment, decarburization annealing and then final finish annealing were performed, and further, these finish annealed plates were overcoated to obtain products.

Epstein test pieces were cut out from 20 positions in the longitudinal direction of the product plate thus obtained, and after annealing for strain relief, magnetic properties were measured.

The results of the groove width and depth surveys obtained in Table 1 are also shown in Table 2.
Shows the results of investigation of magnetic properties.

Tables 1 and 2 also show, as comparative examples, the results of investigations on the case where the final cold-rolled sheet was subjected to photoetching, where electrolytic etching was performed using a stencil, and where no etching treatment was performed. Photoetching is performed by applying a synthetic dichromate colloid as a photoresist, irradiating it with an arc lamp, then immersing the steel plate in a developing solution to remove the exposed portion, and further using HNO ₃
The resist was removed by immersing it in the liquid for 10 seconds, then immersing it in alkali and then brushing. Further, in the method using a stencil, a stencil having holes formed only in a portion to be etched was covered on a steel plate, and a roller type cartridge containing an electrolytic solution and a cathode was rotated on the stencil. The treatment conditions at this time were a current density of 10 A / dm ² and a treatment time of 20 seconds.

As is clear from Tables 1 and 2, the steel sheet treated according to the present invention has grooves having extremely uniform width and depth as compared with the conventional method, and accordingly, the low iron loss is stable over the entire length of the coil. was gotten.

On the other hand, in the conventional method, the minimum value of the iron loss is almost the same as that according to the present invention, but the average value of the iron loss becomes large because the width and depth of the groove in the coil longitudinal direction vary widely. ing.

The space factor of the products obtained by this invention is 97.2%.
It was no better than the untreated one, which was 97.3%.

(Operation) The reason why the iron loss is reduced by the present invention has not been clarified yet, but it is considered that the local groove has a favorable effect in the finish annealing atmosphere and the magnetic domain refining effect in the product. It is highly probable that this was brought about.

In the present invention, the method of printing the resist is not particularly limited, and methods such as gravure offset printing, gravure printing without using an offset roll, lithographic offset printing and screen printing can be used. The gravure offset printing is most advantageously suited because continuous printing is easy, a stable printing surface is obtained with less wear of the roll, and the resist thickness is easily controlled.

Next, the thickness of the resist will be described. Since the inventors of the present invention use it as an etching resist, they obtained resists having different thicknesses under the expectation that a certain thickness would be required, and investigated the effect of the resists on the product characteristics.

The resist thickness was changed by variously changing the concave mesh cell depth of the gravure roll plate cylinder and the pressing thickness of the rubber transfer roll in gravure offset printing, and by using screen printing. Test material is plate thickness
It was a 0.20 mm final cold-rolled sheet, and linear grooves were introduced by electrolytic etching after resist application. The pattern at the time of printing and the processing conditions of electrolytic etching were the same as those in the above experiment.

FIG. 1 shows the relationship between the iron loss W _17/50 after the final finish annealing and the resist thickness.

As is clear from the figure, in the range of the resist thickness of 0.5 μm or more and 30 μm or less, the iron loss is remarkably reduced as compared with the case of no treatment, but the resist thickness is less than 0.5 μm or less than 30 μm. As the thickness increases, the reduction in iron loss decreases.

To elucidate the cause of this, the steel plate after etching was carefully observed. When the resist thickness was less than 0.5 μm, the resist itself was affected by etching, and the thickness of 30 μm
It has been found that when the thickness is thicker, the linear non-coated portion is covered with the resist in many portions, and it is difficult to form a groove having a desired depth in any of the portions.

Therefore, in order to sufficiently reduce the iron loss, the thickness of the resist to be printed is preferably 0.5 μm or more and 30 μm or less.

Particularly in gravure offset printing, the mesh cell depth of the gravure roll is preferably at least 10 μm or more.

Next, as an ink used as an etching resist, an ink containing an alkyd-based, epoxy-based, or polyethylene-based resin as a main component is suitable. Also, after applying the resist ink, it is necessary to perform baking to cure the resin, but such baking is sufficient at a temperature at which the solvent, water, etc. contained in the ink evaporates, and it is usually 100
A temperature of about ℃ or more is sufficient.

Next, the etching performed after printing will be described. The etching may be electrolytic etching or chemical etching. For electrolytic etching, NaCl solution or KC
It is preferably carried out in an electrolytic bath such as an aqueous solution at a current density of 1 to 100 A / dm ² . This is because if the current density is too low, a sufficient etching effect cannot be obtained, while if it is too high, the resist may be damaged during etching.

For chemical etching _{FeCl 3, HNO 3, H 2} SO 4, H 3 PO 4 Hitoshiya mixtures thereof is preferably used.

In order to obtain an industrially stable effect, electrolytic etching in which the current density is easily controlled is more suitable than chemical etching in which the resist is easily damaged.

The method for removing the resist after etching is not particularly limited, but an alkali, an organic solvent, or the like is suitable.

The shape of the groove thus introduced may be a continuous line or a discontinuous dotted line, but a continuous line is preferable. The width of the linear groove is 5 to 300 μm, and the depth is 100 μm or less, preferably 5 to 50 μm. The direction of the linear groove is best in the direction perpendicular to the rolling direction.
If the range is within °, almost the same effect can be obtained. Further, it is preferable that the distance between the linear grooves is in the range of 3 to 30 mm.

It should be noted that the groove can be formed only on one side of the steel plate,
It goes without saying that it has an effect when applied to both sides.

In the present invention, the composition of the grain-oriented electrical steel sheet of interest is not particularly limited, and any conventionally known composition is suitable. The typical composition is, for example,
It is a composition containing C: 0.01 to 0.08% and Si: 2.0 to 4.0%, and a small amount of one or more of MnSe, MnS, AlN, BN and the like as an inhibitor. In addition to the above, inhibitors containing Sb, Sn, Cu, Bi, etc. are also included in the present invention.

The slab adjusted to the above-mentioned preferable component composition is hot-rolled, then hot-rolled sheet is annealed if necessary, and then cold rolled once or twice with intermediate annealing to obtain a final product sheet thickness. Then, decarburization annealing is performed, and etching is performed by using the final cold-rolled sheet as a raw material by the method described above.

After etching, the resist is removed, decarburization annealing is performed, an annealing separator is applied, and then final finishing annealing is performed. After such finish annealing, the annealing separating agent is removed, and a topcoat coating is applied as necessary to obtain a product. The effect of the present invention is exhibited regardless of the presence or absence of the topcoat.

The steel sheet produced as described above stably exhibits an extremely low iron loss value, and since the value is retained even after the strain relief annealing, it can be stably used as a material for a wound core.
Needless to say, it may be used for a laminated core that generally does not require strain relief annealing.

(Example) Example 1 C: 0.062%, Si: 3.3%, Mn: 0.076%, Se: 0.024%, Al: 0.02
A 0.20 mm final plate was obtained by hot rolling a slab of silicon steel containing 5% and N: 0.008%, the balance being substantially Fe, and annealing at 1050 ° C for 2 min and then cold rolling. Rolled to thickness.

Five such rolled coils were prepared and subjected to the following treatments.

(1) After applying resist by gravure offset printing,
Electrolytic etching.

(2) After applying resist by gravure offset printing,
Chemical etching.

(3) Photo etching.

(4) Electrolytic etching using a polyurethane stencil.

(5) No treatment.

Gravure offset printing is 175 mesh, 40μ
An ink containing an epoxy resin as a main component was resisted using a gravure roll having m mesh cells. The resist thickness after baking was 3 μm. The electrolytic etching was carried out in a KCl electrolytic solution at a current density of 8 A / dm ² for 30 seconds. The chemical etching was carried out by immersing it in a FeCl ₃ solution for 20 seconds. Photoetching was performed using Fe dichromate synthetic colloid as a photoresist and Fe
An etching process is performed by spraying a Cl ₃ solution for 20 seconds, and an electrolytic etching process using a stencil is performed.
A polyurethane stencil was put on a steel plate, and a roller type cartridge containing a NaCl electrolyte and a cathode was rotated on the stencil, and treated so that the current density was 8 A / dm ² and the treatment time was 30 seconds.

The etching region by the above treatment was a linear region having a width of about 0.2 mm and a gap of 3.5 mm in the direction perpendicular to the rolling direction. The depth of the groove obtained by etching was in the range of 20 ± 2 μm over the entire length of the coil in (1) and (2), but (3) and (4) were (1) and (2), respectively. Even though the treatment conditions were the same, the depth of the groove was 0.35 μm and varied.

The coil treated as described above, together with the untreated coil (5), were subjected to decarburization annealing and then final finish annealing.

Table 3 shows the results of measuring the magnetic properties at 20 points in the longitudinal direction of each product coil, together with the average value and its variation.

As is clear from the table, the steel sheet treated according to the present invention showed a stable low iron loss value as compared with the conventional method.

Example 2 C: 0.045%, Si: 3.2%, Mn: 0.070%, Se: 0.020% and S
b: containing 0.025%, the balance being substantially Fe composition, hot-rolled silicon steel slab, then cold-rolled twice with 1000 ℃, 1min intermediate annealing, 0.20mm final Rolled to plate thickness.

Five such rolled coils were prepared and subjected to the following treatments.

(6) After resist coating by gravure offset printing,
Electrolytic etching.

(7) After resist application by gravure offset printing,
Chemical etching.

(8) Scribing with a knife blade.

(9) Introducing grooves with leather light.

(10) No treatment.

The processes of (6) and (7) are (1) and (7) of the first embodiment, respectively.
The same treatment as in (2) was performed, and in both (8) and (9), a groove having a width of 0.2 mm and a depth of 20 μm was introduced.

These coils, including the untreated one (10), were decarburized and annealed, and after final finish annealing, magnetic properties and space factor were measured.

 The results thus obtained are shown in Table 4.

As shown in the table, according to the present invention, a significant improvement in iron loss is achieved without lowering the space factor.

(Effects of the Invention) Thus, according to the present invention, it is possible to obtain a grain-oriented electrical steel sheet having a low iron loss value that is industrially cheaper and more stable than conventional ones, and moreover, such a steel sheet has an iron loss due to strain relief annealing. Since there is no deterioration, both laminated cores and wound cores can be used, which greatly contributes to the efficiency improvement of the transformer.

[Brief description of drawings]

Figure 1 shows the etching resist thickness and iron loss W of the product.
It is a graph which shows the relationship with _17/50 (W / kg).

Claims (2)

[Claims] 1. A slab for grain-oriented electrical steel sheets is hot-rolled, then cold-rolled once or two or more times with intermediate annealing to obtain a final thickness, followed by decarburization annealing and then final finishing annealing. In the production of grain-oriented electrical steel sheet by the process of, after the final cold rolling, an etching resist is printed on the surface of the steel sheet to leave a continuous or non-continuous linear region in the direction intersecting the rolling direction as a non-coated region. A method for producing a low iron loss-oriented electrical steel sheet, which comprises applying, baking, and then performing an etching treatment to form continuous or discontinuous linear grooves on the surface of the steel sheet, and then removing the resist. 2. The method for producing a low iron loss grain-oriented electrical steel sheet according to claim 1, wherein the resist thickness after coating and baking is 0.5 to 30 μm.