JPS6311407B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a high magnetic flux density unidirectional electrical steel sheet with excellent magnetic properties. Unidirectional electrical steel sheets are soft magnetic materials that are mainly used as core materials for transformers and other electrical equipment, and must have good magnetic properties in terms of excitation properties and iron loss properties. In order to obtain good magnetic properties, it is important that the <001> axis, which is the axis of easy magnetization, is highly aligned in the rolling direction. In addition, plate thickness, crystal grain size, specific resistance, surface coating, etc. have a large effect on magnetic properties. The directionality has been greatly improved by a method characterized by final cold rolling under heavy reduction using AlN and MnS as inhibitors, and now products with magnetic flux density of about 96% of the theoretical value are manufactured. It's here.
Along with this, iron loss has improved significantly. On the other hand, reflecting the rise in energy prices in recent years, transformer manufacturers are increasingly turning to low core loss materials as materials for energy-saving transformers. Amorphous amorphous and 6.5% Si steel are being developed as low iron loss materials, but many problems still remain to be solved before they can be used as commercial materials for transformers. (Prior Art) In order to meet the current demand for low core loss materials, the present inventors have conducted various studies on reducing core loss in unidirectional electrical steel sheets. Based on the results of this research, the present inventors have previously proposed a high magnetic flux density unidirectional steel with excellent iron loss, characterized by the composite addition of Sn and Cu to silicon steel, as shown in Japanese Patent Application Laid-Open No. 58-23414. We proposed a manufacturing method for electrical steel sheets. This method has made it possible to manufacture products with significantly better core loss than before. However, the demand from transformer manufacturers for materials with lower core loss shows no signs of stopping, and in order to meet these demands, the present inventors have continued to conduct research into methods for more stably manufacturing materials with lower core loss. Ta. (Objective of the invention) (Structure and operation of the invention) As a result, C: 0.02 to 0.12%, Si: 2.7 to 4.0%,
Mn: 0.03-0.02%, at least one of S and Se:
0.01~0.05%, acid soluble Al: 0.01~0.05%, N:
0.004~0.012%, Sn: 0.03~0.5%, Cu: 0.02~
A silicon steel slab containing 0.4%, Ti: 0.0020% or more and less than 0.0100, with the balance consisting of iron and unavoidable impurities is hot rolled, annealed and quenched before final cold rolling, and then final cold rolled. and decarburization annealing.
By applying an annealing separator and performing high-temperature finish annealing, it is possible to stably produce unidirectional electrical steel sheets with good secondary recrystallization, small grain size, extremely low iron loss, and extremely high magnetic flux density. I found it. The details of the present invention will be explained below. First, I will explain based on experimental data. C: 0.070%, Si: 3.25%, Mn: 0.074%, S:
0.024%, acid soluble Al: 0.027%, N: 0.0083%,
For molten steel containing Sn: 0.10%, Cu: 0.08%, the Ti content is varied from 0.0005 to 0.0200%,
A slab with the balance consisting of iron and unavoidable impurities was produced, heated at a high temperature of 1350°C, and hot rolled to obtain a hot rolled sheet with a thickness of 2.3 m/m. The hot rolled sheet was annealed at 1100° C. for 2 minutes, rapidly cooled after annealing, and then cold rolled to 0.30 m/m. Subsequently, decarburization annealing was performed at 850°C for 3 minutes in a moist hydrogen atmosphere, an annealing separator mainly composed of MgO was applied, and the temperature was raised to 1200°C at a rate of 20°C/hr in a hydrogen atmosphere containing nitrogen. Thereafter, purification annealing was performed for 20 hours in a hydrogen atmosphere. Figure 1 shows the magnetic flux density (B ₁₀ ) and B shows the iron loss (W _17/50 ) of the magnetic properties of the product. Figure 1A,
As shown in B, the magnetic properties changed depending on the Ti content, and in the range of 0.0020% or more and less than 0.0100%, the magnetic flux density _B10 was high and the iron loss was extremely low. Ti
When the content was lower than 0.0020%, the magnetic flux density _B10 decreased and the iron loss became poor. Also, Ti content is 0.0100%
Above this, the magnetic flux density B ₁₀ decreased and the iron loss became poor. Particularly when it exceeded 0.0140%, the magnetic flux density B ₁₀ decreased significantly and the iron loss also became extremely poor. After measuring the magnetic properties, the sample was pickled, the surface coating was removed, and the macrostructure of the product was observed. The results are shown in FIG. 1C and D. Figure 1C shows the area ratio of the good secondary recrystallization area (hereinafter referred to as the secondary recrystallization rate).
Figure D shows the average grain size for a sample with a secondary recrystallization rate of 100%. As shown in Figure 1 C, Ti content is 0.0010% or more
In the range less than 0.0100%, the secondary recrystallization rate is
When it was 100% and lower than 0.0010%, the secondary recrystallization rate decreased slightly. Further, when the Ti content was 0.0100% or more, the secondary recrystallization rate decreased, and when it exceeded 0.0140%, it decreased significantly. Ti content less than 0.0010% and
The deterioration of magnetic properties at 0.0100% or more is considered to be due to poor secondary recrystallization. Next, as shown in Figure 1D, the secondary recrystallization rate is 100
% Ti content in the range of 0.0010% or more and less than 0.0100%, the higher the Ti content, the smaller the crystal grain size. In particular, when Ti is 0.0020% or more, the crystal grain size is small and the iron loss is low. Ti content 0.0010%
Even if it is less than 0.0020%, the secondary recrystallization rate is 100% as described above, but the iron loss is not so low. Generally, as the magnetic flux density B ₁₀ increases, hysteresis loss decreases, and as the grain size decreases, eddy current loss tends to decrease.
As described above, the change in iron loss in the range of less than 0.0100% can be explained by the change in magnetic flux density B ₁₀ in FIG. 1A and the change in crystal grain size in FIG. 1D. FIG. 2 shows the product macrostructures of samples A, B, C, D, and E shown in FIG. 1C. Linear fine grains can be seen in A. In case B, the secondary recrystallization is complete, but the crystal grain size is large. In case 3, the secondary recrystallization is complete and the grain size is small. In D, the occurrence of mixed grains and fine grains is observed, and in E, the occurrence of mixed grains and fine grains is severe. In the production of unidirectional electrical steel sheets using AlN as the main inhibitor, the
Although the mechanism by which Ti content affects the secondary recrystallization, grain size, and magnetic properties of products is not fully understood, Ti is an element that has a strong affinity with N, C, O, etc., and their precipitation may occur. AlN, MnS,
It is thought that as a composite precipitate such as MnSe, it has a subtle influence on the inhibition effect. Figure 3 shows C=0.070%, Si=3.25%, Mn=0.074
%, S = 0.024%, acid soluble Al = 0.027%, N =
Ti added to 0.0083%, Sn=0.10%, Cu=0.08% steel
Contain 0.0012%, 0.0030%, 0.0049%, respectively,
The texture of a decarburized annealed plate for a material in which the remainder consists of iron and unavoidable impurities is shown. The surface strength of this texture was measured at a point 40μ below the plate surface. It can be seen that the (110) surface strength increases as the Ti content increases. If we consider the phenomenon shown in Figure 1, we can think of it as follows. When the Ti content is less than 0.0010%
The inhibition effect support by the Ti compound was insufficient, and secondary recrystallization failure occurred. Ti content 0.0010
In the range of % or more and less than 0.0100%, the higher the Ti content, the more appropriate the inhibition effect and the stronger the (110) plane strength of the decarburized annealed plate, especially when the Ti content is 0.0020%.
Above, the product directionality is high in the range of less than 0.0100,
The grain size was small and iron loss was good. It also has excellent magnetic flux density. When the Ti content exceeds 0.0100%, it is thought that N, which should originally become AlN, is consumed by Ti too much, and AlN, which serves as the main inhibitor, is insufficient, resulting in the generation of mixed particle diameters. By the way, Ti is used in the production of unidirectional electrical steel sheets.
Several proposals have been made so far to add . For example, in Japanese Patent Publication No. 46-26621, silicon steel
Unidirectional electrical steel sheets are produced by adding 0.01 to 0.2% Ti and using TiN as an inhibitor.
A large amount of Ti is added. In the case of the production method related to the present invention, the Ti content is
If it exceeds 0.0100%, as can be easily estimated from FIG. 1, secondary recrystallization will occur and the magnetic properties will be significantly deteriorated. In JP-A No. 52-24116, C: 0.085
% or less, Si: 2.0~4.0%, acid soluble Al: 0.010~
Contains 0.065%, and further contains Zr, Ti, B, Nb, Ta, V,
Contains one or more nitride-forming elements such as Cr, Mo, etc., and the content is Zr, Ti, B
It has been suggested that the content be 0.0005 to 0.05%. However, it is extremely difficult to obtain a product with stable magnetic properties over a wide range of Ti: 0.0005 to 0.05% in Si 2.7% or more, which is the target range of the present invention, and as shown in the present invention, Sn, By controlling Ti to 0.0020 or more and less than 0.0100% in addition to the combined addition of Cu, it is possible to stably produce products with complete secondary recrystallization, high directionality, small grain size, and extremely good iron loss. It became possible to manufacture it. In JP-A-55-14858, C: 0.06% or less, Si: 2.0 to 4.0%, Mn: 0.02 to 0.15%, Se, S
Any one or two of: 0.008 to 0.080% of at least one of Nb and Ti in the material,
0.002 to 0.0012% for Nb, and 0.002% for Ti.
It is proposed to contain 0.005 to 0.018%. As shown in the specification, this is an acid-soluble
A technology based on materials with Al: 0.003% or less, acid-soluble Al: 0.01-0.05%, N: 0.004-0.012%
The present invention is different from the present invention, which relates to the production of high magnetic flux density unidirectional electrical steel sheets using AlN as the main inhibitor. Next, the reasons for determining the components and other manufacturing conditions in the present invention will be described below. When C is less than 0.02%, secondary recrystallization becomes poor, and when it exceeds 0.12%, it is unfavorable from the viewpoint of decarburization and magnetic properties. If Si is less than 2.7%, the low core loss that is the aim of the present invention cannot be obtained, and if it exceeds 4%, cold rollability will be significantly degraded. From the point of view of iron loss, the preferred range of Si is 3.0 to 4.0.
%. Mn and S or Se are elements necessary to form MnS or MnSe. The appropriate amount of Mn to obtain a suitable inhibitor effect is 0.03-0.20%, preferably 0.05-0.15%. If S or Se is less than 0.01%, a sufficient inhibitor effect cannot be obtained, and if it exceeds 0.05%, purification becomes difficult, which is not preferable. Moreover, at least one type of S and Se is contained. Acid soluble Al and N as main inhibitors
These are important elements for forming AlN, and each must be controlled within an appropriate range in order to sufficiently exhibit secondary recrystallization through appropriate inhibition effects and obtain excellent magnetic properties. Acid soluble Al is 0.01
If it is less than 0.05%, the orientation of the product will be poor, and if it exceeds 0.05%, secondary recrystallization will become unstable, so a particularly preferable range is 0.020 to 0.040%. If N is less than 0.004%, secondary recrystallization becomes unstable, and if it exceeds 0.012%, blistering occurs, so 0.005 to 0.009% is a particularly preferable range. Sn is useful for stabilizing secondary recrystallization and refining the crystal grain size of the product. If it is less than 0.03%, the effect is weak, and if it exceeds 0.5%, cold rollability is poor. 0.05~0.20%
is a particularly preferred range. Cu helps produce a good glass film in Sn-added materials, and if it is less than 0.02%, its effect is poor, and if it exceeds 0.4%, pickling properties and decarburization properties deteriorate.
A particularly preferred range is 0.05-0.20%. Regarding Ti, as described in detail in Figure 1 earlier, the magnetic flux density B ₁₀ lower than 0.0020% decreases,
The crystal grain size of the product increases and iron loss deteriorates.
If it exceeds 0.0100%, secondary recrystallization will not be performed sufficiently, resulting in poor magnetic flux density B ₁₀ and iron loss. In addition to the above components, Sb, Cr, Ni, Mo, V,
Even if one or more elements such as B, which are known to have inhibitory effects, are included, the effects of the present invention will not be inhibited. A silicon steel slab containing the above components with the remainder consisting of iron and unavoidable impurities is hot rolled, and before final cold rolling, a so-called AlN precipitation treatment is performed by annealing and rapid cooling. As for this annealing, the present inventors previously filed an application for JP-A-57-
A method of heating in two temperature ranges as shown in Japanese Patent No. 198214 is also applicable. After that, it is finally cold rolled to a thickness of 0.10 to 0.35 mm. A preferable rolling reduction ratio in the final cold rolling is 80% or more. The cold-rolled sheet thus obtained is then decarburized and annealed in a decarburizing atmosphere such as wet hydrogen or a wet hydrogen atmosphere containing nitrogen. After decarburization annealing, an annealing separator mainly composed of MgO is applied to the surface of the steel sheet, dried, and final annealed at a high temperature. Next, an example will be described. Example 1 C: 0.072%, Si: 3.36%, Mn: 0.075%, S:
0.023%, acid soluble Al: 0.028%, N: 0.0084%,
Ti (a) is added to molten steel containing Sn: 0.10% and Cu: 0.08%.
The content was changed to 0.0006%, (b) 0.0050%, and (c) 0.0155% to form three types of slabs with the remainder consisting of iron and unavoidable impurities, and the slabs were heated to 1350°C to a thickness of 2.3 m. /m hot rolled sheet. This hot-rolled sheet was annealed at 1130° C. for 2 minutes, rapidly cooled after annealing, and then cold-rolled to a thickness of 0.30 m/m. This cold-rolled sheet was decarburized annealed at 850°C for 3 minutes in a wet hydrogen atmosphere, coated with an annealing separator, heated to 1200°C at a rate of 25°C/hr in a hydrogen atmosphere containing nitrogen, and then heated to 1200°C in a hydrogen atmosphere containing nitrogen. Purification annealing was carried out at 1200°C for 20 hours. Table 1 shows the magnetic properties and secondary recrystallization status of the product.

[Table] Example 2 C: 0.080%, Si: 3.35%, Mn: 0.076%, S:
0.024%, acid soluble Al: 0.027%, N: 0.0083%,
Ti (d) is added to molten steel containing Sn: 0.13% and Cu: 0.09%.
0.0006%, (e) 0.0015%, (f) 0.0042%, (g) 0.0125%
1350°C.
The slab was heated to produce a hot-rolled sheet with a thickness of 2.0 m/m. Before final cold rolling, it was annealed at 1120°C for 2 minutes, rapidly cooled after annealing, and then cold rolled to a thickness of 0.20 m/m. The thus obtained cold-rolled sheet was decarburized and annealed at 840°C for 3 minutes in a humid hydrogen atmosphere, coated with an annealing separator, and then annealed at 20°C/hr in a nitrogen-containing hydrogen atmosphere.
The temperature was raised to 1200℃ and then heated at 1200℃ for 20 minutes in a hydrogen atmosphere.
A time purification annealing was performed. Table 2 shows the magnetic properties and secondary recrystallization status of the product.

[Table] Example 3 C: 0.070%, Si: 3.25%, Mn: 0.075%, Se:
0.025%, acid soluble Al: 0.028%, N: 0.0085%,
Ti (h) is added to molten steel containing Sn: 0.12% and Cu: 0.08%.
The content was changed to three levels: 0.0010%, (i) 0.0067%, and (j) 0.0142%, and three types of slabs were prepared, with the remainder consisting of iron and unavoidable impurities, and hot rolled and rolled according to the method described in Example 1. Process processing was performed. Table 3 shows the magnetic properties and secondary recrystallization status of the product.

[Table] As detailed above, according to the method of the present invention, an excellent unidirectional electrical steel sheet with high magnetic flux density and low core loss can be produced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the results of an experiment related to the present invention;
FIG. 2 is a metallurgical microscope photograph showing the macrostructure of a product in an experiment related to the present invention, and FIG. 3 is a diagram showing the influence of Ti content on the texture of a decarburized annealed plate.

Claims (1)

[Claims] 1 C: 0.02-0.12%, Si: 2.7-4.0%, Mn:
0.03~0.20%, at least one of S and Se: 0.01~
0.05%, acid soluble Al: 0.01~0.05%, N: 0.004~
0.012%, Sn: 0.03~0.5%, Cu: 0.02~0.4%,
Hot-rolling a silicon steel slab containing Ti: 0.0020% or more and less than 0.0100%, with the balance consisting of iron and unavoidable impurities, annealing and rapid cooling treatment before final cold rolling, followed by final cold rolling, A method for producing a high magnetic flux density unidirectional electrical steel sheet with excellent magnetic properties, which comprises performing decarburization annealing, applying an annealing separator, and performing high-temperature finish annealing.