JPS6257689B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) In order to advantageously achieve high magnetic flux and low core loss of unidirectional silicon steel sheets, during secondary recrystallization annealing, that is, decarburization and primary recrystallization annealing before final finish annealing, Focusing on the usefulness of the method of developing non-uniform secondary recrystallized grains with Goss orientation by applying micro-strain near the surface of the steel sheet and simultaneously applying non-uniform heat treatment, we
This paper proposes an advantageous manufacturing method for a unidirectional silicon steel sheet with low core loss. Unidirectional silicon steel sheets are used as core materials for transformers and other electrical equipment, and are required to have high magnetic flux density (represented by the _B10 value) and low iron loss (represented by the W17/50 value). be done. Since the two-stage cold rolling method was proposed by NPGoss to produce such unidirectional silicon steel sheets, numerous inventions and developments have been made since then.
Improvements have been made, and today unidirectional silicon steel sheets are produced that have a magnetic flux density _B10 value of 1.89T or more and a low iron loss W17/50 value of 1.05W/Kg or less. However, in the wake of the energy crisis, the production of unidirectional silicon steel sheets with lower iron loss has become an extremely urgent issue. Particularly recently, a system (Loss Evolution System) that provides bonuses for ultra-low iron loss unidirectional silicon steel sheets, mainly for beaten rice, has become popular. One way to reduce such iron loss is to increase the Si content in silicon steel. Reduce product board thickness. Increase the purity of steel plate. 2 of the fine grains without reducing the Goss orientation integration degree of the secondary recrystallized grains of the product.
Next recrystallization grains develop. etc. are being considered. In the first case, if the Si content is increased from the normal 3.0%, or if the thickness is reduced to 0.23, 0, or 20 mm, which is thinner than the normal product plate thickness of 0.35 or 0.30 mm, the secondary recrystallized structure will become non-uniform, and the Goss orientation will increase. A problem arises in which the value decreases. Furthermore, when the Si content is increased more than usual, hot embrittlement becomes noticeable, hot cracking occurs during slab heating or hot rolling, and the surface quality of the product deteriorates significantly. On the other hand, improvements in the purity or directionality of steel sheets have now reached the limit. For example, the Goss orientation of the secondary recrystallized grains of current products is concentrated within an average of 3° to 4° in the rolling direction, and it is extremely difficult from a metallurgical point of view to further reduce the grain size of such highly concentrated grains. It is said that (Prior technology) Under these circumstances, in order to develop and manufacture low core loss unidirectional silicon steel sheets, it was desired to fundamentally reconsider each process from material composition to coating treatment process. . For this reason, we melted a number of small steel ingots with different inhibitor components and started testing.
As a result, by adding a small amount of Mo, which was previously not used at all in unidirectional silicon steel (see Japanese Patent Publication No. 14737-1982 and Japanese Patent Publication No. 4613-1983), we increased the amount of Si, which had been a long-standing issue. Under these conditions, it is possible to improve the surface properties of the product (see Japanese Patent Publication No. 58-32215 and Japanese Patent Publication No. 58-33298), and develop fine secondary recrystallized grains that are advantageous for low iron loss. {Yukio Iguchi, Tsune Ito: Bulletin of the Japan Institute of Metals, 23 (1984), 276} In addition, silicon steel with a trace amount of Mo added has a thin base coat with excellent adhesion (Patent Application No. 100318/1982). It was discovered that it is possible to form a book (written in Japanese). Although these findings have greatly improved the magnetic properties and surface properties of products, they are still not in a satisfactory state. Separately, Japanese Patent Publication No. 57-2252 discloses that the surface of an Al-added unidirectional silicon steel sheet after finish annealing is irradiated with a laser beam at intervals of several mm approximately perpendicular to the rolling direction, resulting in a locally high dislocation density on the surface of the steel sheet. A method has been proposed in which the width of the magnetic domain is made finer by introducing regions to reduce iron loss. This manufacturing method aims to reduce iron loss by making the magnetic domain width finer, and is uniformly practical and has an excellent iron loss reduction effect.
There is a drawback that the effect of introducing plastic strain is diminished by heat treatment such as strain relief annealing after punching, shearing, and winding of a steel plate, and baking treatment of a coating. Very recently, Japanese Patent Application Laid-Open No. 1983-100221 and
Publication No. 100222 discloses that, before final annealing of unidirectional silicon steel, a steel plate strip is locally annealed to create a large primary recrystallization region, resulting in non-uniform secondary recrystallization. Methods for developing grains have been proposed. Unlike the artificial grain boundary introduction method using a laser beam, this manufacturing method is revolutionary because the magnetic properties do not deteriorate due to strain relief annealing, but it stabilizes large local areas of primary recrystallization in the steel sheet. There are still quite a few problems left to create. (Problems to be Solved by the Invention) The inventors have been conducting more detailed research on exploratory experiments to improve iron loss by effectively utilizing metallurgical techniques. In other words, the inventors found that in order to obtain a grain-oriented silicon steel sheet that exhibits a higher magnetic flux density and lower iron loss value, conventional investigation and investigation using X-ray diffraction alone is insufficient as it can only provide phenomenological considerations. Therefore, the inventors of the present invention
-33660 and Utility Model Application Publication No. 55-383349, we are proceeding with the development of a transmission cell device using a scanning electron image, and by using this device, we can collect the heat collected from the mid-process of a unidirectional silicon steel plate. As a result of detailed investigation of rolled plates, intermediate annealed plates, decarburized/primary recrystallized plates, initial secondary recrystallized plates, etc., we obtained new findings as listed below. (1) The source of secondary recrystallization nuclei of secondary recrystallized grains with the (110) [001] orientation exists at a depth of about 1/10 from the surface of the hot-rolled sheet in the elongated grains with the (110) [001] orientation. This occurs from a small area where no distortion exists. Furthermore, when a small amount of Mo is added to silicon steel, the (110)
The frequency of secondary recrystallization nuclei in the [001] orientation is approximately three times higher than in conventional materials. (2) The generation of secondary recrystallization nuclei in the (110) [001] orientation occurs in the process of primary cold rolling → intermediate annealing → secondary cold rolling → decarburization and primary recrystallization annealing due to structure memory from hot rolling. Inherited, 30~50μ from the steel plate surface
occurs preferentially at a depth of m. (3) Secondary recrystallization nuclei after decarburization and primary recrystallization annealing are crystal grains in large aggregates formed by the coalescence of several (110) [001] oriented primary recrystallization grains, and the matrix It is 2 to 6 times the size of a grain. Also this (110)
It is a feature that aggregates of primary recrystallized grains with a large [001] orientation are preferentially produced in clusters within a specific region extending in the rolling direction. (4) At the beginning of secondary recrystallization annealing (110) [001]
An aggregate of highly oriented crystal grains preferentially grows as one large crystal grain. Based on the above knowledge, the inventors investigated how to generate good secondary recrystallized nuclei in the (110) [001] orientation and how the secondary recrystallized nuclei should be inherited in the intermediate process. , fundamental examinations were made on heating, hot rolling, cold rolling and annealing. (Means for solving the problem) As a result, decarburization before secondary recrystallization annealing. By applying micro-strain to the steel plate surface during primary recrystallization annealing and at the same time applying non-uniform heat treatment, non-uniform Goss orientation 2
The inventors discovered that it is possible to manufacture unidirectional silicon steel sheets with low core loss and magnetic flux density by developing secondary recrystallized grains, and this led to the completion of this invention. This invention provides a method for producing a unidirectional silicon steel sheet in which the hot rolled unidirectional silicon steel sheet is subjected to one or more cold rolling processes, primary recrystallization annealing that also serves as decarburization, and final finish annealing process. During the primary recrystallization annealing, a micro-strain is applied near the surface of the steel sheet, and at the same time, by temperature transfer from a high temperature roll that backs up the uneven rolls using a plurality of uneven rolls, a 0.1 to 5 mm width 1 is applied in a direction approximately perpendicular to the rolling direction. This is a method for producing a unidirectional silicon steel sheet with high magnetic flux density and low iron loss, which is characterized by generating non-uniform secondary recrystallized grains with a Goss orientation by applying non-uniform heat treatment at intervals of ~20 mm. The configuration of this invention is developed as follows. For example, C0.045%, Si3.40%, Se0.020%, Mn0.067
%, Sb0.025%, Mo0.025% was hot-rolled to a thickness of 2.2 mm, and then uniformly annealed at 900℃ for 3 minutes, followed by intermediate annealing at 950℃ for 3 minutes.
The final cold-rolled sheet with a thickness of 0.3 mm is obtained by cold rolling twice, and then decarburized and primary recrystallization annealed in a wet hydrogen atmosphere at 820°C. micro-strain is applied using a leveler method, and then non-uniform heat treatment {this heat treatment is carried out by temperature transfer (800 ~
850℃)}. After that, an annealing separator mainly composed of MgO is applied to the surface of the steel sheet, and then secondary reconsolidation annealing is performed at 850°C for 50 hours and purification annealing is performed at 1180°C for 5 hours in hydrogen to produce a product. To compare the magnetic properties, experiments were also conducted in which only a small strain was applied by a leveler during decarburization and primary recrystallization annealing, or where only nonuniform heat treatment was applied. Table 1 shows the magnetic properties of the products based on the results of these series of experiments.

[Table] As is clear from Table 1, the magnetic properties of B ₁₀ when microstrain is introduced using the leveler under condition (a) and non-uniform heat treatment is applied at the same time.
It can be seen that 1.92T, W17/50 is extremely good at 0.96W/Kg. Introducing minute strain using a leveler under conditions (b) or (c)
The magnetic properties of non-uniform heat treatment under the conditions of B ₁₀ are
1.91T, W17/50 is 1.00 to 1.01W/Kg, which is better than the comparison material (B ₁₀ is 1.90T, W17/50 is 1.05W/Kg), but the magnetic properties are lower than the condition (a). bad. (Function) The reason for the remarkable improvement in iron loss when micro-strain is introduced near the surface of the steel sheet and nonuniform heat treatment is applied at the same time is that iron loss is preferentially generated near the surface of the steel sheet during decarburization and primary recrystallization annealing. At the same time, by imparting micro-strain to the nuclei of secondary recrystallized grains with the (110) [001] orientation, the release of strain energy in the (110) [001] grains in the high-temperature region during non-uniform annealing is accelerated. )
[001] oriented crystal grains as a region that promotes coarsening and (110)
It is thought that by creating a coarsening retardation region of the [001] oriented crystal grains, the non-uniformity of the secondary recrystallized grains of the (110) [001] orientation was promoted, resulting in a product with extremely low iron loss. As is clear from the above description of the present invention in comparison with several prior art techniques, the structure of the present invention differs from the prior art in basic concept, and thus It can be seen that the property improvement effect obtained is also far superior. Next, the limiting conditions of the manufacturing process of this invention will be described. In this invention, conventionally known unidirectional silicon steel material components are used, for example, (1) C0.01~0.06%, Si2.0~4.0%, Mn0.01~0.2
%, Mo0.005~0.05%, Sb0.005~0.25%, composition containing S or Se 0.005~0.05%, and so on. (2) C0.01~0.08%, Si2.0~4.0%, Mn0 .01~0.2
%, Al0.01~0.05%, S0.005~0.05%, N0.001
Composition containing ~0.01%, (3) C0.01~0.06%, Si2.0~4.0%, Mn0.01~0.2
%, S or Se from 0.005 to 0.05, B0.0003 to
Composition containing 0.0040%, Cu0.1~1.0%, N0.001~0.01%, (4) C0.001~0.015%, Si2.0~4.0%, Mn0.005~
0.05%, S0.001~0.015%, Al0.01~0.05%,
Composition containing N0.001~0.01%, (5) C0.01~0.06%, Si2.0~4.0%, Mn0.01~0.2
%, Sb0.005~0.25%, S or Se 0.005~
Composition containing 0.05% or (6) C0.01~0.06%, Si2.0~4.0%, Mn0.01~0.2
%, S, or a composition containing 0.005 to 0.05% Se. These silicon steel material components are heated by a known method,
It is hot-rolled into a hot-rolled sheet with a thickness of usually about 2 to 4 mm. Next, the hot-rolled sheet is usually uniformly annealed at 800 to 1100°C and then cold rolled. Cold rolling is done either by a single cold rolling method in which the final plate thickness is reached in one rolling process, or by rolling twice with intermediate annealing at 850 to 1050°C, with an initial reduction rate of about 50% to 80%. Final reduction rate starts from 50%
Any two-time cold rolling method that produces a final plate thickness of about 85% and a final thickness of 0.2 mm to 0.35 mm may be used. Note that the normal finished plate thickness is often 0.3 mm. After the final cold rolling, the steel plate finished to the product thickness is
After surface degreasing, decarburization and primary recrystallization annealing are performed in wet hydrogen at a temperature range of 750 to 850°C. In this invention, it is essential to introduce a minute strain near the surface of the steel plate, and at the same time to perform non-uniform heat treatment on the steel plate. First of all, regarding the introduction of microstrain, rolling methods such as skin pass that produce a strain of several percent actually deteriorate the magnetic properties, so microstrain introduction methods are recommended, for example, by rolling with a roll diameter of 50 to 200 mm as shown from A to H in Figure 1.
Minimum strain (rolling strain of 0.5
% or less) is sufficient, and any other known micro-strain introduction methods may be used. In addition to introducing such micro-strains, it is essential to perform non-uniform heat treatment on the steel plate in this invention, but in order to perform such heat treatment on the steel plate, for example, A roll with a diameter of about 50 to 200 mm as shown in the figure is used with unevenness on the surface almost perpendicular to the rolling direction, and these are transferred from the high temperature rolls I to L shown by the diagonal lines that back up the rolls. Ideally, the nonuniform heat treatment region should be 0.1 to 5 mm wide and 1 to 20 mm apart, which is effective in promoting nonuniform growth of secondary recrystallization nuclei. After such treatment, MgO is added to the surface of the steel sheet.
After applying an annealing separator mainly composed of, secondary recrystallization annealing is performed. This secondary recrystallization annealing is
This is done to sufficiently develop secondary recrystallized grains with the (110) [001] orientation, and is usually carried out by box annealing, which immediately raises the temperature to 1000℃ or higher and maintains it at that temperature. . For this secondary recrystallization annealing, it is more advantageous to perform holding annealing at a low temperature of 820°C to 900°C in order to develop secondary recrystallized grains that are highly aligned in the (110) [001] orientation. ~
Slow annealing with a heating rate of 15°C/h may also be used. Next, embodiments of this invention will be described. Example 1 C0.046%, Si3.38%, Mn0.062%, Se0.021%,
A slab with a composition of 0.035% Mo, 0.020% Sb, and the remainder substantially Fe was hot-rolled to form a hot-rolled sheet with a thickness of 2.6 mm. This hot-rolled sheet was uniformly annealed at 900°C for 3 minutes, then cold-rolled twice with an intermediate annealing of 3 minutes at 950°C to 0.3mm and 0.23mm.
A thick final cold-rolled sheet was obtained. After that, during decarburization and primary recrystallization annealing in wet hydrogen at 820°C, micro-strains are introduced using the method shown in Figure 1, and at the same time a non-uniform heat treatment is applied, after which annealing separation with MgO as the main component appears on the surface of the steel sheet. The agent was applied. after that,
Secondary recrystallization annealing at 850℃ for 50 hours and in hydrogen
Purification annealing was performed at 1180°C for 5 hours. The magnetic properties of the product at that time were as follows. 0.30mm thick product B ₁₀ : 1.92T, W17/50:
0.96W/Kg 0.23mm thick product B ₁₀ : 1.91T, W17/50:
0.76W/Kg Example 2 C0.05%, Si3.25%, Mn0.082%, S0.020%,
A slab with a composition of 0.025% Al, 0.08% Cu, and 0.02% Sn, with the remainder essentially Fe was hot-rolled to form a hot-rolled sheet with a thickness of 2.0 mm. Thereafter, it was homogenized annealed for 3 minutes at 1050°C and then rapidly cooled, followed by warm rolling at about 250°C to obtain a final cold-rolled sheet with a thickness of 0.23 mm. Then 850
During decarburization and primary recrystallization annealing in wet hydrogen at ℃, micro-strain is introduced using the method shown in Figure 1, and at the same time non-uniform heat treatment is applied, after which an annealing separator mainly composed of MgO is applied to the steel plate surface. did. Then from 850℃
After performing secondary recrystallization annealing by raising the temperature to 1050°C at a rate of 6°C/hr, purification annealing was performed at 1200°C for 10 hours in dry hydrogen. The magnetic properties of the product at that time were as follows. B ₁₀ : 1.93T, W17/50: 0.78W/Kg Example 3 C0.046%, Si3.26%, Mn0.049%, S0.028%,
A silicon steel slab containing 0.0029% B, 0.3% Cu, and 0.0049% N, with the remainder essentially Fe was heated at 1320°C for 4 hours and then hot rolled to form a rolled plate with a thickness of 1.8 mm. After that, homogenization annealing was performed at 1050℃ for 30 minutes, followed by strong cold rolling once to obtain a final cold rolled sheet with a thickness of 0.30mm, followed by decarburization and primary re-rolling in wet hydrogen at 800℃. After crystal annealing, micro-strain is introduced using the method shown in Figure 1, and at the same time, non-uniform heat treatment is applied.
An annealing separator containing MgO as the main component was applied. After that, the temperature was raised from 820℃ to 1050℃ at 5℃/hr.
After recrystallization, purification annealing was performed in dry H ₂ at 1200° C. for 8 hours. The magnetic properties at that time were as follows. B ₁₀ = 1.92T, W17/50 = 0.97W/Kg Example 4 C0.009%, Si3.18%, Mn0.045%, S0.008%,
Contains Al0.028%, N0.0069%, the balance is essentially Fe
After heating the silicon steel slab at 1230℃ for 6 hours,
It was hot-rolled into a hot-rolled sheet with a thickness of 2.0 mm. Thereafter, it was uniformly annealed at 980°C for 3 minutes and then rapidly cooled, followed by warm rolling at about 300°C to obtain a final cold-rolled plate with a thickness of 0.30 mm.
Then, during decarburization and primary recrystallization annealing in wet hydrogen at 830°C, microstrain was introduced by the method shown in Figure 1, and at the same time non-uniform strain was introduced.
temperature gradient of 30℃/cm,
After secondary recrystallization by dropping at 10cm/hr, 1200
Purification annealing was carried out in dry H ₂ for 8 hours at °C. The magnetic properties of the product at that time were as follows. B ₁₀ = 1.96T, W17/50 = 0.99W/Kg Example 5 C0.043%, Si3.26%, Mn0.066%, Sb0.023%,
A silicon steel slab containing 0.020% Se and the remainder substantially Fe was heated at 1390℃ for 4 hours, then hot rolled to 2.4%
It was made into a hot-rolled sheet with a thickness of mm, and then cold-rolled twice with an intermediate annealing of 3 minutes at 950°C to a thickness of 0.27mm.
A thick final cold-rolled sheet was obtained. After that, after decarburization and primary recrystallization annealing in wet hydrogen at 820°C, microstrain was introduced by the method shown in Figure 1, and at the same time, after nonuniform heat treatment, MgO was mainly deposited on the surface of the steel sheet. The annealing separator as a component was applied as a slurry. after that
After secondary recrystallization annealing at 850℃ for 40 hours,
Purification annealing was carried out in dry H ₂ at 1180° C. for 6 hours.
The magnetic properties of the product at that time were as follows. B ₁₀ = 1.91T, W17/50 = 0.91W/Kg Example 6 A hot-rolled sheet containing 0.039% C, 3.21% Si, 0.062% Mn, 0.018% S, and the remainder substantially consisting of Fe ( 2.4mm
(thickness) was cold-rolled twice with intermediate annealing at 900°C for 3 minutes to obtain a final cold-rolled sheet with a thickness of 0.3 mm. After that, after decarburization and primary recrystallization annealing in wet hydrogen at 800°C, micro-strain was introduced by the method shown in Figure 1, and at the same time a non-uniform heat treatment was performed. The annealing portion. The agent was applied. Thereafter, secondary recrystallization annealing was performed at 850°C for 50 hours and purification annealing at 1200°C for 8 hours in hydrogen. The magnetic properties of the product at that time were as follows. B ₁₀ = 1.90T, W17/50 = 1.10W/Kg

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a method of performing nonuniform heat treatment at the same time as introducing minute strain.

Claims (1)

[Scope of Claims] 1. A method for producing a unidirectional silicon steel sheet in which the unidirectional hot rolled silicon steel sheet is subjected to one or more cold rolling processes, primary recrystallization annealing that also serves as decarburization, and final finishing annealing process, During decarburization and primary recrystallization annealing, a slight strain is applied near the surface of the steel sheet, and at the same time, the temperature transfer from the high-temperature rolls that back up the uneven rolls by multiple uneven rolls causes a distortion of 0.1 to 5 mm in a direction approximately perpendicular to the rolling direction. Width, 1
By applying non-uniform heat treatment at ~20mm intervals
A method for producing a unidirectional silicon steel sheet with high magnetic flux density and low iron loss, characterized by generating non-uniform secondary recrystallized grains with Goss orientation.