JPH0325513B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, the axis of easy magnetization is <001 in the rolling direction of the steel plate.
＞ has a high magnetic flux density with well-aligned crystal grains,
The present invention relates to a method for manufacturing a unidirectional silicon steel plate with low iron loss. The characteristics required of unidirectional silicon steel sheets, which are mainly used as core materials for transformers, are that the magnetic flux density obtained at a constant magnetization force is high, and that the iron loss is low when a constant magnetic flux density is applied. That's low. As a representative value, the magnetizing force
It is expressed by the magnetic flux density (B ₁₀ , Tesla) at 1000 A/m and the iron loss (W _17/50 , W/Kg) at a magnetic flux density of 1.7 Tesla and a frequency of 50 Hz. Conventional unidirectional silicon steel sheets usually have 2.0 to 4.0%
After hot-rolling a material made by impregnating low-carbon steel containing Si with trace amounts of inhibitor component elements such as Mn, S, and Se, it is subjected to two or more times including intermediate annealing or once.
The cold rolled steel sheet was finished to a predetermined thickness by cold rolling twice, and the cold rolled steel sheet was subjected to primary recrystallization annealing which also serves as decarburization, and an annealing separator mainly composed of MgO was applied to the surface of this decarburized steel sheet. After that, the steel sheet is manufactured by performing secondary recrystallization and final annealing to remove impurities in the steel sheet. That is, by final annealing, secondary recrystallized grains are developed aligned in the {110}<001> orientation, impurities in the steel are removed, and good magnetic properties are obtained. Generally, methods for improving magnetic properties include improving various processes, such as the pass schedule during hot-cold rolling, the heat pattern during primary recrystallization annealing, and secondary recrystallization annealing.
Many proposals have been made, and each has yielded results. However, these methods based on process improvement are not necessarily effective for all unidirectional silicon steel materials that are produced with various contained components varying within a certain range, and in extreme cases, This may cause deterioration of magnetic properties. In other words, a certain degree of instability is unavoidable in methods based on process improvement. Eliminating this instability requires extremely strict control of material composition and process conditions, which is difficult to achieve from an economical or production efficiency standpoint. The present invention aims to overcome these drawbacks of conventional manufacturing methods and provide a method for manufacturing unidirectional silicon steel sheets with high magnetic flux density and low core loss without any operational problems. According to the present invention, the above object can be achieved by a simple method of fixing a predetermined amount of an alkaline earth metal compound to a steel plate before performing the above-described primary recrystallization annealing. The adhesion of the alkaline earth metal compound to the steel plate is achieved by electrolytic treatment of 1 to 15 coulomb/dm ² in an electrolytic bath containing 1.0 to 0.0001 mol/dm 2 of the alkaline earth metal compound converted to alkaline earth metal. is suitable. Next, a method for manufacturing a unidirectional silicon steel sheet with excellent magnetic properties according to the present invention will be explained in detail. In general, in the production of grain-oriented silicon steel sheets, precipitates such as MnS and MnSe, which suppress the normal grain growth of primary recrystallized grains, called inhibitors, or
Due to the action of grain boundary segregation elements such as Sb, the secondary recrystallized grains formed during final annealing are
001>A product with good magnetic properties is obtained by aligning the orientation with the rolling direction. As a result of investigation, the present inventors have found that the origin that can become the nucleus of this secondary recrystallization is unrecrystallized {110}<001> orientation existing at about 1/10 of the thickness from the surface layer of the hot rolled sheet. We have obtained the knowledge that it is a grain. In other words, secondary recrystallization occurs from the very surface layer of the steel sheet, and the more primary recrystallized grains in the {110}<001> orientation in the surface layer, the easier the generation of nuclei for secondary recrystallization, and the more
It is thought that the magnetic properties are improved because the next recrystallization progresses smoothly. In order to strengthen the {110}<001> orientation of the surface layer, it is necessary to
It is possible to either strengthen the orientation or to strengthen it during primary recrystallization annealing. In the former case, it is possible to lower the hot rolling finishing temperature, but if it is too low, surface defects will occur frequently, and there is a limit. Therefore, the present inventors determined that strengthening the {110}<001> orientation during primary recrystallization annealing while using the normal process is an easy and stable method, and therefore The experiment was repeated using this method. As a result, we found that the alkaline earth metal compound was fixed to the steel sheet surface by electrolytic treatment at 1 to 15 coulomb/dm ² in an electrolytic bath containing 1.0 to 0.0001 mol/dm 2 in terms of alkaline earth metal before primary recrystallization annealing. We were able to improve the magnetic properties using a simple method. As a result of examining the cause of this from the aspects of texture and decarburization, Transaction ISIJ,
Vol. 15 (1975), p. 324, it is known that graphite precipitation on the surface layer can be suppressed by applying a compound such as S before recrystallization annealing of low carbon steel, and that, conversely, graphite precipitation on the surface layer can be suppressed by applying compounds such as S before recrystallization annealing of low carbon steel. Since graphite precipitation is promoted by similar metal compounds, it is inferred that surface decarburization progressed rapidly in the materials related to the present invention due to the adhesion of alkaline earth metal compounds to the steel plate surface. Ru. Due to this rapid decarburization of the surface layer,
Primary recrystallized grains with {110}<001> orientation in the surface layer are more likely to occur than usual, and as a result, the {110}<001> orientation in the surface layer becomes stronger, which leads to improved magnetic properties. it is conceivable that. One example of the arrangement of the electrodes in the electrolytic (degreasing) tank in the above-mentioned electrolytic treatment method is as shown in Fig. 4, in which counter electrodes for electrolysis are located in parallel above and below the steel plate being passed.
If the first counter electrode is an anode, the next counter electrode is a cathode, and electrolysis may be performed by alternately replacing the anode and cathode of the steel plate, but it is not necessarily limited to this method. In FIG. 4, 1 is a steel plate, 2 is an electrolytic cell, 3 is a power source, 4 is an anode, and 5 is a cathode. The purpose of the above-mentioned electrolytic treatment method is to fix an alkaline earth metal compound to the surface of a steel sheet. In the case of electrolytic treatment, alkaline earth metal compounds are electrodeposited on the steel sheet surface depending on the electrification state due to ionization of the compounds in the electrolyte, and it is thought that the adhesion is stronger than that in the coating drying method or dipping method. . Therefore, peeling or scraping due to contact between the steel plate and a roll in a subsequent process is less likely, but it is necessary to manage the amount of electricity applied to the steel plate. The present inventors investigated the amount of fixed alkaline earth metal compounds that have the effect of improving magnetic properties, and found that in the electrolytic treatment method, the electrolytic bath has a concentration of 0.0001 to 1.0 mol/concentration in terms of alkaline earth metal. It was discovered that the magnetic properties could be improved by controlling the amount of electricity during electrolysis to 1 to 15 coulomb/dm ² . The temperature of the electrolyte does not need to be particularly limited as long as it satisfies the conditions for the concentration of the alkaline earth metal compound, but when electrolytic degreasing is performed at the same time as fixation of the compound, in order to increase the degreasing effect, it is necessary to A liquid temperature of ~100℃ is desirable. Next, the reasons for limiting the concentration of the alkaline earth metal compound aqueous solution, the amount of electrolyzed electricity, etc. in the present invention will be explained using experimental examples conducted by the present inventors. Figures 1 and 2 are diagrams showing the relationship between concentration converted to alkaline earth metal ions and magnetic properties, with MgCl ₂ and Sr(NO ₃ ) ₂ selected as representative examples of alkaline earth metal compounds, respectively. . The composition and process of the sample material are the same as in Example 3, which will be described later. Whether simply immersed or electrolytically treated,
Effects are seen at 0.0001 mol/or more.
A concentration of about 0.05 mol/about has the greatest effect, and even if the concentration is increased beyond that, there is little change.
If it exceeds 1.0 mol/mol, it is not preferable because it inhibits the formation of a forsterite film. Based on the above results, the concentration was limited to a range of 0.0001 to 1.0 mol/. FIG. 3 is a diagram showing changes in magnetic properties when the amount of electricity is changed during electrolytic degreasing. The liquid temperature was 80°C, and the alkaline earth metal equivalent concentration of the alkaline earth metal compound was 0.05 mol/. The composition and process of the sample material are the same as in Example 3, which will be described later. Compared to electroless treatment, magnetic properties are improved by electrolytic treatment with an amount of electricity of 1 coulomb/dm ² or more. The reason why the upper limit of the amount of electricity for electrolysis was set at 15 coulomb/dm ² is that it requires a longer electrolyzer, a lower threading speed, and a larger capacity power source for electrolysis, which is unfavorable from the viewpoint of production efficiency and economy. It is. Therefore,
The amount of electrolytic electricity was limited to 1 to 15 coulomb/ ^dm2 .
Electrolytic treatment is essentially the same as immersion in an aqueous solution, so it is effective even when the amount of electricity is low. However, if degreasing is also desired, it is obvious that too low an amount of electricity is not preferable. Next, the reason for limiting the composition of the steel material used in the present invention will be explained. If C is less than 0.02%, a coarse band structure will remain in the center of the sheet thickness during hot rolling, and secondary recrystallization will be incomplete; if it is more than 0.06%, decarburization will take a long time, resulting in poor decarburization. 0.02 as it is unfavorable in terms of inviting magnetic properties.
A range of ~0.06% is good. If Si is less than 2.0%, the electrical resistance of the material will be low and the iron loss value based on eddy current loss will be large.
If it is more than 4.0%, plate cracking is likely to occur during cold rolling, so a range of 2.0 to 4.0% is preferable. Both S and Se combine with Mn to form MnS and MnSe, and are added to act as inhibitors. If S is less than 0.008% and Se is less than 0.003%, the amount of MnS and MnSe produced will be reduced. The growth suppression effect of primary recrystallized grains is weak, and both are 0.1%.
If S is exceeded, the rolling workability will be significantly deteriorated.
It is preferable to keep Se in the range of 0.008 to 0.1%, and Se in the range of 0.003 to 0.1%. Next, the present invention will be specifically explained using examples. Example 1 A steel ingot containing 0.040% C, 2.95% Si, 0.062% Mn, and 0.018% S was hot rolled, homogenized annealed and
0.3mm after two times of cold rolling including intermediate annealing.
Mg(NO 3 ) 2 , Mg(NO ₃ ) ₂ ,
CaCl ₂ , Sr(NO ₃ ) ₂ , and BaCl ₂ are attached to the surface, and then through decarburization annealing and MgO separating agent coating process,
Table 1 shows the magnetic properties of unidirectional silicon steel sheets obtained by heating from 820°C to 1000°C at a heating rate of 3°C/hr and then performing purification annealing in a hydrogen atmosphere at 1180°C for 5 hours. . Example 2 A steel ingot containing 0.041% C, 3.05% Si, 0.066% Mn, and 0.017% Se was hot rolled, homogenized annealed and
0.3mm after two times of cold rolling including intermediate annealing.
MgCl ₂ , Ca
(NO ₃ ) ₂ , Sr(OH) ₂ , and Ba(NO ₃ ) ₂ are fixed on the surface, followed by decarburization annealing, MgO separating agent application process, and secondary recrystallization at 850°C for 50 hours. Table 2 shows the magnetic properties of the unidirectional silicon steel sheets obtained by annealing and then purification annealing for 5 hours in a hydrogen atmosphere at 1180°C. Example 3 C0.045%, Si3.35%, Mn0.064%, Se0.018%,
A steel ingot containing Sb0.025 was hot rolled, homogenized annealed, and cold rolled twice including one intermediate annealing to a final thickness of 0.3 mm, and then decarburized and primary recrystallized in wet hydrogen. Before annealing, under the conditions shown in Table 3,
MgCl ₂ , Ca(OH) ₂ , Sr(NO ₃ ) ₂ , and Ba(OH) ₂ are fixed on the surface, followed by decarburization annealing, MgO separating agent application process, and secondary heating at 850°C for 50 hours. Table 3 shows the magnetic properties of unidirectional silicon steel sheets obtained by recrystallization annealing and then purification annealing for 5 hours in a hydrogen atmosphere at 1180°C. As is clear from the results of the above examples, when electrolytically treated, due to the adhesion of alkaline earth metal compounds to the steel sheet surface, the magnetic flux density is approximately 0.01 T and the iron loss is approximately 0.03 to 0.05 W/Kg. improvement can be seen. As described above, by fixing alkaline earth metal compounds to the steel sheet surface, it is possible to improve the magnetic properties extremely easily, and there are no operational difficulties or instability, which is advantageous in terms of economic efficiency and stability. The contribution of the present invention is significant from both aspects of performance.

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【table】 [Brief explanation of drawings]

Figures 1 and 2 are graphs showing the relationship between the concentration of the alkaline earth metal compound added and magnetic properties, Figure 3 is a graph showing the relationship between the amount of electricity during electrolytic treatment and magnetic properties, and Figure 4 is a graph showing the relationship between the amount of electricity and magnetic properties during electrolysis treatment. 1 is a diagram showing one example of arrangement of electrodes of an electrolytic cell; FIG. Explanation of symbols, 1... Steel plate, 2... Electrolytic cell, 3...
...power supply, 4...anode, 5...cathode.

Claims (1)

[Claims] 1 Low carbon steel containing C0.02~0.06%, Si2.0~4.0% S0.008~0.1% and or Se0.003~0.1%
a step of hot rolling a unidirectional silicon steel material containing Decarburization of rolled steel plate 1
In the method for manufacturing a unidirectional silicon steel sheet, the method includes a step of performing secondary recrystallization annealing, and a step of final annealing after applying an annealing separator to the surface of the decarburized steel sheet, before performing the primary recrystallization annealing. 1.0 to 0.0001 mol/Mg in terms of alkaline earth metals,
A method for producing a unidirectional silicon steel sheet with excellent magnetic properties, characterized by subjecting the steel sheet to an electrolytic treatment of 1 to 15 coulomb/dm ² in an electrolytic bath containing a compound of alkaline earth metals such as Ca, Sr, and Ba. .