JPH04228600A - Production of grain-oriented silicon steel sheet free from deterioration in characteristic due to stress relief annealing and reduced in iron loss - Google Patents

Abstract

PURPOSE:To prevent the occurrence of deterioration in characteristics even if subjected to stress relief annealing under high efficiency and to reduce iron loss by easily forming linear grooves in the surface of a cold rolled silicon steel sheet after cold rolling. CONSTITUTION:At the time of producing a grain-oriented silicon steel sheet, linear grooves are formed in the surface of this steel sheet by applying, after cold rolling, electrolytic etching to the surface of the steel sheet after decarburizing annealing or final finish annealing while pressing an electrode, having a pad infiltrated with electrolyte on the electrode surface, against this steel sheet surface via an insulating film provided with conductive markings having shape and spacing equal to those of the linear grooves to be introduced into this surface.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] Grain-oriented silicon steel sheets are mainly used as cores for transformers and other electrical equipment. The properties of grain-oriented silicon steel sheets are defined by magnetic flux density and iron loss, with high magnetic flux density (represented by magnetic flux density B8(T) at a magnetizing force of 800 A/m2) and iron loss (1 .7 T, 50 Hz (represented by W17/50) is required to be low. The present invention relates to a method for manufacturing grain-oriented silicon steel sheets with low iron loss, and in particular, the iron loss characteristics improved by magnetic domain refining by introducing linear grooves are prevented from disappearing even by strain relief annealing.

0002

[Prior Art] Conventionally, methods for reducing iron loss in grain-oriented silicon steel sheets include: (1) increasing Si content, (2) reducing product thickness, and (3) reducing secondary recrystallized grains. (4) reducing the impurity content, (5) aligning the crystal orientation of secondary recrystallized grains in the direction of the axis of easy magnetization. So-called magnetic domain refining technology, which reduces the 180° magnetic domain width that causes eddy current loss, has come to be utilized as an effective means. By the way, the magnetic domain refining technology is as follows:
Initially, a method of subdividing magnetic domains using local plastic strain was proposed, but this method loses its effect when the necessary strain relief annealing is applied to the iron core of a wound transformer. I end up. Therefore, a magnetic domain refining technique that does not use plastic strain is considered necessary, and several proposals have been made regarding such a technique.

[0003] Among the magnetic domain refining techniques in which the effect is not lost by strain relief annealing, the main ones are, for example, Japanese Patent Publication No. 2-80
27 and Japanese Patent Publication No. 2-8028, which utilizes the tension imparting effect of forsterite, and Japanese Patent Publication No. 2-5821, which involves forming foreign parts locally in forsterite. These include technologies that utilize elastic strain. However, although all of these techniques have certain effects, their effects are smaller than magnetic domain refining techniques that utilize plastic strain. Also disclosed is a technique that utilizes the demagnetizing field of a locally placed foreign object. For example, JP-A-60-89545 and JP-A-63
Japanese Patent Laid-Open No. 60-255927 discloses a technique for subdividing magnetic domains by placing foreign matter locally inside the surface layer of the steel and utilizing the demagnetizing field of the foreign matter. By making grooves locally inside the surface layer of the base metal and filling them with metal, we further developed the
No. 5 and Japanese Patent Publication No. 62-54873 disclose that the magnetic domains are subdivided by creating grooves in the surface layer of the base metal by pickling and filling the inside of the grooves with a phosphate coating on the upper layer. Each technology is disclosed. Furthermore, there is also a technique disclosed in Japanese Patent Laid-Open No. 197520/1983 as a technique for forming grooves on the plate surface before finish annealing. Although these techniques are equally effective, there are various drawbacks to the industrial implementation of groove formation.

[0004] Namely, Japanese Patent Application Laid-open No. 60-255926, Japanese Patent Application Publication No. 59-28525, and Japanese Patent Publication No. 62-54
Publication No. 873 is a method of forming grooves and filling them with foreign matter after finish annealing, so it is necessary to remove oxides generated during finish annealing before forming grooves in the base steel. Since these materials mostly consist of forsterite, they are very difficult to remove, and therefore they often add excessive strain to the base metal, causing deterioration of its magnetic properties. In this regard, the technique disclosed in JP-A-59-197520 forms the grooves before final annealing, and therefore has the advantage that such an oxide layer does not exist when the grooves are formed. However, the knife edge, laser beam, electrical discharge machining, and electron beam, which are exemplified as groove forming means, each have the following problems. That is, knife edge and electrical discharge machining have problems in processing speed, laser beams are inefficient on rolled surfaces, and electron beams require vacuum equipment, which poses problems in productivity.

[0005]

[Problems to be Solved by the Invention] The present invention advantageously solves the above-mentioned problems.By easily and simply forming grooves on the surface of the base steel, iron loss characteristics can be maintained even after strain relief annealing. The purpose of this study is to propose a new manufacturing method for raw steel sheets that will not deteriorate.

[0006]

[Means for Solving the Problems] In the method of the present invention, streaks or grooves are introduced into the surface of a steel sheet after cold rolling, decarburization annealing, or final finish annealing by a special electrolytic treatment. Normally, in order to form grooves by electrolytic etching, it is possible to mask the surface of the steel sheet except for the area where the grooves are to be formed, and then perform electrolytic etching, but such a method requires an additional masking process and its removal process. This not only significantly impairs productivity but also increases costs. This invention solves the problems of the prior art as described above by masking the electrodes with an insulator and using a liquid having an etching effect as the electrolyte.

[0007] In other words, the present invention involves cold rolling a silicon-containing hot-rolled steel sheet once or twice or more with intermediate annealing to obtain a product thickness, and then subjecting it to decarburization annealing and final finish annealing. When manufacturing grain-oriented silicon steel sheets, conductive markings are applied to the surface of the steel sheet after cold rolling, decarburization annealing, or final finish annealing at the same shape and spacing as the linear grooves to be introduced into the surface. By performing electrolytic etching while pressing an electrode equipped with a pad impregnated with an electrolytic solution on the electrode surface through an insulating film, striated grooves are formed on the surface of the steel sheet.There is no characteristic deterioration due to strain relief annealing. This is a method for manufacturing grain-oriented silicon steel sheets with low core loss.

[0008] This invention will be explained in detail below. Now, in this invention, after the hot-rolled sheet for grain-oriented silicon steel sheet is cold-rolled once or twice or more with intermediate annealing to achieve the final product thickness, or after decarburization annealing, or after final finish annealing. At some stage, linear flaws, or linear grooves, are introduced on the surface of the steel sheet. The width of such striated grooves is approximately 20 to 300 mm.
.mu.m, and the depth is preferably about 5 to 50 .mu.m, and is preferably introduced at intervals of 3 to 10 mm substantially perpendicular to the rolling direction.

For example, a roll electrode as shown in FIG. 1 is advantageously suitable for introduction here. In the figure, number 1 is an electrode, number 2 is a pad, and this pad 2 is impregnated with an electrolyte. 3 is an insulating film, preferably a stencil film or the like. A desired linear marking is provided on this insulating film 3, and only this marking portion is electrically conductive. Now, as shown in FIG. 2, the roll electrode is rotated while being pressed against the steel plate surface 4, and at this time, a voltage of usually about 3 to 20 V is applied from the power source 5, so that the steel plate surface is continuously etched in accordance with the markings. It is done in a specific manner.

[0010] Here, the current is intermittent energization, especially in FIG.
As shown in , the current conduction time (tc) and the current stop time (
It is advantageous to use a pulsed form with a ratio tc /ts of 10 or less. This is because, as shown in FIG. 4, when tc /ts is 10 or less, an appropriate groove depth can be obtained and the life of the insulating film is long;
When ts exceeds 10, the life of insulating films such as stencils will be significantly shortened due to the heat generated by the current.
This is also because the groove depth becomes shallower.

[0011] The current may be either alternating current or direct current, or may be a method in which direct current is first passed and then switched to alternating current, or vice versa. When a direct current is applied, oxygen is generated as the steel plate is anodized, and at the same time as the steel base is eluted, the oxide is also peeled off from the steel base by the oxygen, thereby introducing flaws into the base steel. On the other hand, when flowing alternating current, when the steel plate becomes an anode, it is the same as the case of direct current mentioned above, and even when the steel plate becomes a cathode, oxides are peeled off due to the generation of hydrogen gas, which causes scratches on the base steel. will be introduced.

The stencil film does not necessarily need to be wound around the roll; the stencil may be wound around a separate coil and moved in synchronization with the advancement of the plate, as shown in FIG.

Furthermore, the electrodes do not necessarily have to be in the form of a roll; for example, they can be made into a flat plate as shown in FIG. 6, and the process can be applied to a strip-shaped plate by repeatedly moving the flat electrode back and forth. be able to.

[0014]

[Operation] In this invention, the electrolyte is an acidic solution,
All basic liquids are suitable, but as acidic liquids the alkali and alkaline earth metal salts or halides of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid are particularly preferred, while as basic liquids caustic soda, potassium potassium, etc. are particularly advantageous. These electrolytic solutions exert a chemical etching action simultaneously with electrolysis, increasing workability.

If the grooves are formed on the surface of the steel sheet after cold rolling, it is then subjected to decarburization annealing according to a conventional method, and then an annealing separator containing MgO as a main component is applied, and then the steel sheet is formed into a coil shape. Then, final annealing is performed in a hydrogen atmosphere at about 1200°C. If the grooves are formed after decarburization annealing, an annealing separator is then applied and final annealing is performed. Furthermore, if the grooves are formed after final annealing, a coating treatment of an insulating coating such as phosphate is then performed. The present invention can be applied to all conventionally known silicon steel materials, regardless of their composition.

[0016]

[Example] Example 1 C: 0.035%, Si: 3.2%, Mn:
0.08%, Se: 0.02%, sol. Al: 0
．． A silicon-containing hot-rolled sheet containing 0.02% and 0.006% N, with the remainder being essentially Fe, is cold-rolled in one step to produce a final cold-rolled sheet with a thickness of 0.23 mm. Finished. Then, on the surface of the steel plate, as shown in Figure 1 above, a width:
Electrolytic treatment was performed using a rolled electrode masked by a stencil film with conductive markings of 0.1 mm and groove spacing of 4 mm. The conveyance speed of the steel plate in this treatment was 10 m/min, sodium nitrate was used as the electrolyte, and the voltage was 10 V (tc:ts).
A pulse current (direct current) having a current application time of =10:3 was applied. Through this electrolytic treatment, grooves with a depth of 20 μm were formed. Then, after decarburization annealing, MgO was applied, finish annealing was performed at 1200°C, and a phosphate-based insulating coating was applied to produce a product.

[0017] The product thus obtained was heated to 800°C,
The result of measuring the iron loss characteristics after strain relief annealing for 3 hours was 0.75 W/kg at W17/50. For comparison, we also measured the iron loss characteristics after strain relief annealing of a material in which no grooves were formed, and found that the comparative material had 0.92 W/kg.

Example 2 C: 0.032%, Si: 0.033%, Mn: 0
．． 075%, S: 0.02% and Sb: 0.014
%, and the remainder is substantially Fe, is cold rolled in one step to a thickness of 0.23 m.
A final cold-rolled sheet of m. Next, on the surface of the steel plate, as shown in Figure 1 above, width: 0.1 mm, groove spacing: 4
Electrolytic treatment was performed using a rolled electrode masked by a stencil film with conductive markings of mm. The conveyance speed of the steel plate in this process is 20m/mi
Furthermore, sodium chloride was used as the electrolytic solution, and a direct current was continuously passed at a voltage of 10V. Through this electrolytic treatment, grooves with a depth of 15 μm were formed. Then, after decarburization annealing, MgO was applied, finish annealing was performed at 1200°C, and a phosphate-based insulating coating was applied to produce a product.

[0019] The thus obtained product was heated to 800°C,
The result of measuring the iron loss characteristics after strain relief annealing for 3 hours was 0.77 W/kg at W17/50. For comparison, we also measured the iron loss characteristics after strain relief annealing of a material in which no grooves were formed, and found that the comparative material had 0.92 W/kg.

Example 3 C: 0.030%, Si: 0.032%, Mn: 0
．． 070%, S: 0.02% and Sb: 0.014
A silicon-containing hot-rolled sheet with a composition of % and the remainder being essentially Fe is cold-rolled in two steps to a thickness of 0.20 m.
A final cold-rolled sheet of m. Then, after decarburization annealing, as shown in Figure 1 above, width: 0.1 mm, groove spacing: 5 mm.
Electrolytic treatment was performed using a rolled electrode masked by a stencil film with conductive markings. The conveyance speed of the steel plate in this process is 18 m/min,
Further, sodium chloride was used as the electrolytic solution, and a DC current was passed intermittently for 2 seconds at a voltage of 10V. Through this electrolytic treatment, grooves with a depth of 15 μm were formed. Then, after cleaning, MgO was applied, finish annealing was performed at 1200°C, and a phosphate-based insulating coating was applied to produce a product.

[0021] The iron loss characteristic of the product thus obtained was 0.7.
It was 8W/kg. Also, for confirmation, 800℃,
When the iron loss characteristics were measured after 3 hours of strain relief annealing, no change was observed. For comparison, the iron loss characteristics of a material without grooves were measured and found to be 0.92 W/kg.

Example 4 C: 0.05%, Si: 3.2%, Mn: 0.08%
, S: 0.018%, sol. Al: 0.021%
and N: 0.009%, the remainder being substantially Fe.
A hot-rolled silicon-containing steel sheet having the composition was finished into a final cold-rolled sheet having a thickness of 0.23 mm by one-step cold rolling. Then, after decarburization annealing, using an electrode as shown in Figure 6 above,
Electrolytic treatment was performed using a stencil film marked with a width of 0.1 mm and a groove interval of 7 mm. The conveyance speed of the steel plate in this treatment was 18 m/min, and sodium chloride was used as the electrolyte. Furthermore, the voltage is 10V tc
A pulse current having a current application time of :ts = 10:3 was applied for 2 seconds. Through this electrolytic treatment, depth: 17 μm
grooves were formed. Then, after cleaning, MgO was applied, finish annealing was performed at 1200°C, and a phosphate-based insulating coating was applied to produce a product.

[0023] The iron loss characteristic of the product thus obtained was 0.7.
It was 7W/kg. Also, for confirmation, 800℃,
When the iron loss characteristics were measured after 3 hours of strain relief annealing, no change was observed. For comparison, the iron loss characteristics of a material without grooves were measured and found to be 0.91 W/kg.

Example 5 C: 0.040%, Si: 3.1%, Mn: 0.0
8%, Se: 0.02%, sol. Al: 0.018
% and N: 0.008%, the remainder being substantially F
The surface of a silicon steel plate after final finish annealing with a plate thickness of 0.23 mm having a composition of e, width: 0.05 mm, groove spacing: 4
Using a stencil film marked with mm, electrolytic treatment was performed using the electrode shown in FIG. 6 above. The conveyance speed of the steel plate in this process was 30 m/min, and an aqueous solution of sodium nitrate was used as the electrolyte, and the steel plate was used as an anode at 25 V.
A DC pulse current with a tc:ts ratio of 5:1 was applied for 2 seconds. Through this electrolytic treatment, grooves with a depth of 20 μm were formed. A phosphate-based insulating coating was then applied to the surface of the steel plate to produce a product. For comparison, the same insulation coating was applied to a steel plate that was not subjected to the above treatment.

[0025] The temperature of the thus obtained product at 800°C, 3
The measurement results of iron loss characteristics after strain relief annealing for hours are W
It was 0.75 W/kg at 17/50. Further, the iron loss characteristic of the comparative material was 0.92 W/kg.

Example 6 C: 0.040%, Si: 0.032%, Mn: 0
．． 080%, Se: 0.02% and Sb: 0.01
Plate thickness containing 6% Fe and the remainder being substantially Fe:
The surface of the final annealed silicon steel plate of 0.23 mm was electrolytically treated using a roll electrode shown in FIG. 1 above using a stencil film marked with a width of 0.03 mm and a groove interval of 4 mm. The conveyance speed of the steel plate in this process is 4
0 m/min, a mixture of hydrochloric acid and sodium chloride was used as the electrolyte, and tc:ts was 10:3 at 10V.
An alternating current of was applied for 1 second. Through this electrolytic treatment, grooves with a depth of 20 μm were formed. A phosphate-based insulating coating was then applied to the surface of the steel plate to produce a product. For comparison, the same insulation coating was applied to a steel plate that was not subjected to the above treatment.

[0027] The product thus obtained was heated to 800°C, 3
The measurement results of iron loss characteristics after strain relief annealing for hours are W
It was 0.73 W/kg at 17/50. Further, the iron loss characteristic of the comparative material was 0.89 W/kg.

Example 7 C: 0.032%, Si: 0.033%, Mn: 0
．． 075%, S: 0.018% and Sb: 0.0
A stencil film marked with a width of 0.1 mm and a groove interval of 5 mm on the surface of a silicon steel plate after final annealing with a thickness of 0.20 mm. Electrolytic treatment was carried out using the electrode shown in FIG. 5 above. The conveyance speed of the steel plate in this process is
m/min, and a mixed solution of hydrochloric acid and potassium iodide was used as the electrolyte, and a 20 V direct current was passed for 1 second using a steel plate as an anode, and then a 10 V alternating current was passed for 2 seconds. Through this electrolytic treatment, grooves with a depth of 35 μm were formed. A phosphate-based insulating coating was then applied to the surface of the steel plate to produce a product. For comparison, the same insulation coating was applied to a steel plate that was not subjected to the above treatment.

[0029] The product thus obtained was heated to 800°C, 3
The measurement results of iron loss characteristics after strain relief annealing for hours are W
It was 0.70 W/kg at 17/50. Further, the iron loss characteristic of the comparative material was 0.83 W/kg.

[0030]

Thus, according to the present invention, linear grooves can be easily and conveniently formed on the surface of a silicon steel sheet after cold rolling, decarburization annealing, or final finish annealing, and as a result, distortion It is possible to stably obtain a low iron loss grain-oriented silicon steel sheet whose properties do not deteriorate even after pre-annealing.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a roll electrode suitable for use in implementing the present invention.

FIG. 2 is an explanatory diagram of a groove forming procedure using a roll electrode.

FIG. 3 is a waveform diagram showing an example of power supplied to an electrode.

[Figure 4] Current conduction time (tc) and current stop time (ts
) is a graph showing the relationship between the ratio tc/ts, the groove depth, and the life of the insulating film.

FIG. 5 is an explanatory diagram of a groove forming procedure using a combination of a stencil film coil and a roll electrode.

FIG. 6 is an explanatory diagram of a groove forming procedure using a flat electrode. 1... Electrode 2... Pad 3... Insulating film 4... Steel plate surface 5... Power supply

Claims (4)

[Claims] [Claim 1] A silicon-containing hot-rolled steel sheet is cold-rolled once or twice or more with intermediate annealing to obtain the product thickness, and then subjected to decarburization annealing and final finish annealing to improve the directionality. When manufacturing silicon steel sheets, an insulating film is applied to the surface of the steel sheet after cold rolling, decarburization annealing, or final finish annealing, with conductive markings in the same shape and spacing as the linear grooves to be introduced into the surface. This method is characterized by forming striated grooves on the surface of the steel sheet by performing electrolytic etching while pressing an electrode equipped with a pad impregnated with electrolyte onto the electrode surface. A method for producing iron loss grain-oriented silicon steel sheets. 2. The method of manufacturing a grain-oriented silicon steel sheet with low iron loss according to claim 1, comprising using a rolled electrode as the electrode and continuously processing the steel sheet. 3. A method for manufacturing a grain-oriented silicon steel sheet with low iron loss according to claim 1, comprising using a flat plate electrode as the electrode and continuously processing the steel sheet by repeatedly reciprocating the electrode. 4. The method for producing a grain-oriented silicon steel sheet with low iron loss according to claim 1, wherein the current applied to the electrode during electrolytic etching is a pulsed current having a current flow time/current stop time ratio of 10 or less.