JP2001172718A - Method for producing nonoriented silicon steel sheet uniform in magnetic property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for stably producing a nonoriented silicon steel sheet excellent in magnetic properties in the longitudinal direction of a coil. SOLUTION: In this method for producing a nonoriented silicon steel sheet uniform in magnetic properties in which a hot rolling stage in which a slab containing at least one kind of, by mass, 0.1 to 4.0% SiO and 0.1 to 2.0% Mn in steel, and the balance substantial Fe is subjected to hot rough rolling to form into a sheet bar, and the same is moreover subjected to finish hot rolling to form into a hot rolled sheet is carried out, and a stage in which the hot rolled sheet subjected to the finish hot rolling is subjected to a cold rolling stage for one time and is next subjected to finish annealing or is subjected to cold rolling for two or more times including process annealing to control its sheet thickness into the final one or is furthermore subjected to skinpass rolling of 2 to <20% to control its sheet thickness into the final one is included, the hot rolling finishing temperature in the above finish hot rolling is controlled to 700 deg.C to the Ar3, and the varying range thereof is controlled to <=100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-oriented electrical steel sheet used as an iron core material for electrical equipment, in which magnetic properties are made uniform.

[0002]

2. Description of the Related Art In recent years, in the fields of electric machines, especially rotating machines and medium-sized and small-sized transformers in which non-oriented electrical steel sheets are used as iron core materials, worldwide electric power and energy savings, as well as chlorofluorocarbon gas regulations. Among the movements for global environmental conservation, such as the above, the movement for higher efficiency is rapidly spreading. Therefore, there is an increasing demand for non-oriented electrical steel sheets to have improved properties, that is, high magnetic flux density and low iron loss. For this reason, on the side of manufacturing non-oriented electrical steel sheets, the mission of stably producing non-oriented electrical steel sheets with such excellent characteristics is imposed, but as described below, with the current technology, Not enough.

Japanese Patent Laid-Open Publication No. Hei 8-92643 discloses a method of improving a skid mark, which is an example of a change in magnetic characteristics in the longitudinal direction of a non-oriented electrical steel sheet. The technology of unrolling and rolling is disclosed. Although this technique does have some effect on skid mark improvement, its effect is not sufficient.

Further, when rolling is performed for each continuous sheet bar, the rolling temperature and the rolling speed fluctuate in one sheet bar, so that magnetic fluctuation in the coil longitudinal direction is unavoidable, and the product yield is reduced. Although there was a drawback that it led to a decrease, it was an unknown issue how to set the control hot rolling conditions effectively. To solve this problem, Japanese Unexamined Patent Publication No.
176664 discloses that the peripheral speed of the roll of the final stand at the time of finish rolling affects magnetic properties, and proposes a technique for restricting the fluctuation of the peripheral speed to within a certain value.

[0005] However, as a result of a detailed investigation conducted by the inventors on variations in magnetic characteristics in the longitudinal direction of the coil, the peripheral speed of the final stand of the hot-rolled finish itself is considered to be a metallographic structure and precipitate even in metallurgical terms. It does not affect things,
It has been found that the dependence of the magnetic flux density on the peripheral speed in the published figures is only a local condition. That is, it was found that it was impossible to control the magnetic properties of the non-oriented electrical steel sheet at different hot rolling mills and different finish rolling temperatures only by the peripheral speed of the final stand.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, the present inventors have conducted intensive studies. As a result, the rolling conditions of the final stand at the time of finish rolling are controlled by precisely controlling the hot-rolling finishing temperature. The inventors have found that the magnetic properties in the longitudinal direction are remarkably stable, and have solved the above-mentioned problem. Furthermore, as a measure to facilitate this technology, the rolled sheet bar is taken up and held, and then unrolled and rolled, thereby inverting the head and tail of the sheet bar, making the rolling temperature uniform and Further, by joining the sheet bar to a preceding sheet bar and continuously rolling a plurality of sheet bars, it is possible to suppress a change in thermal history in a coil longitudinal direction called thermal rundown. Have been found, and the present invention has been completed.

The present invention provides a technique for stably producing a non-oriented electrical steel sheet having excellent magnetic properties in the longitudinal direction of a coil by overcoming the limitations of the prior art in a method for producing a non-oriented electrical steel sheet. Things.

[0008]

The gist of the present invention is as follows. (1) In steel, at least one of Si and Mn is mass%.
0.1% ≦ Si ≦ 4.0% 0.1% ≦ Mn ≦ 2.0
%, With the balance being Fe and unavoidable impurities, hot rolling is performed on the slab to form a sheet bar, and hot rolling is performed by finishing hot rolling. Then, the hot-rolled sheet that has been subjected to finish hot rolling is subjected to one cold rolling step and then to finish annealing, or to a final sheet thickness by two or more cold rolling steps including intermediate annealing, or Further, in the method for producing a non-oriented electrical steel sheet including a step of performing skin pass rolling of 2% or more and less than 20% to a final sheet thickness, the hot-rolling finishing temperature in the finishing hot rolling is made 700 ° C. or more and Ar 3 or less, A method for producing a non-oriented electrical steel sheet having uniform magnetic properties, wherein the variation range is 100 ° C. or less. (2) The magnetic properties as described in the above item (1), wherein the slab further contains, as an additional component, 0.1% ≦ sol.Al ≦ 2.5% by mass of acid-soluble Al. Manufacturing method of uniform non-oriented electrical steel sheet. (3) The method for producing a non-oriented electrical steel sheet having uniform magnetic properties according to the above (1) or (2), wherein the variation range of the hot rolling finish temperature during the finish rolling is within 50 ° C. . (4) After rolling the sheet bar, wind it up, hold it for a certain period of time, unwind it and join it to the preceding sheet bar,
The method for producing a non-oriented electrical steel sheet having uniform magnetic properties according to any one of the above (1) to (3), wherein hot rolling is performed continuously.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. First, the components will be described. Component content is mass%
It is. Si is added to increase the specific resistance of the steel sheet, reduce eddy current loss, and improve the iron loss value. If the Si content is less than 0.1%, sufficient resistivity cannot be obtained, so it is necessary to add 0.1% or more. On the other hand, if the Si content exceeds 4.0%, hot rolling becomes difficult, so that 4.0%.
% Or less.

Mn, like Al and Si, has the effect of increasing the specific resistance of a steel sheet and reducing eddy current loss. For this reason, the Mn content needs to be 0.1% or more. On the other hand, if the Mn content exceeds 2.0%, the deformation resistance during hot rolling increases and hot rolling becomes difficult, and the crystal structure after hot rolling tends to become finer, which deteriorates the magnetic properties of the product. The Mn content needs to be 2.0% or less. In the present invention, it is essential that at least one of the above Si and Mn is contained.

Although there is no problem even if Al in the steel is at the impurity level, Al has the effect of increasing the specific resistance of the steel sheet and reducing the eddy current loss similarly to Si. If desired, it is preferable to add 0.1% or more and 2.5% or less. If a large amount of Al is added, the magnetic flux density decreases and the cost increases, so the content is set to 2.5% or less.

In order to improve the mechanical properties, magnetic properties, and rust resistance of the product or for other purposes, P,
Even if one or more of B, Ni, Cr, Sb, Sn, and Cu are contained in steel, the effect of the present invention is not impaired.

Although C, N, S, B, and P are not specified in the claims of the present invention, in producing a non-oriented electrical steel sheet having good magnetic properties or workability, their contents are carefully controlled. It is necessary to do so, so the following is mentioned.
C is 0.0% to avoid magnetic aging and to prevent reduction of iron loss.
It is preferably at most 050%.

S and N partially re-dissolve during the slab heating in the hot rolling process, and form precipitates such as MnS and AlN during the hot rolling, which hinder the growth of recrystallized grains during finish annealing. When the product is magnetized, it exerts a so-called pinning effect of hindering the movement of the domain wall, which hinders a reduction in iron loss of the product. Therefore, S ≦ 0.0050%, N ≦ 0.0050%
Preferably

B forms AlN by forming BN during hot rolling.
Is added to prevent fine precipitation of N and render N harmless.
The B content needs to be balanced with the amount of N, and the content is preferably such that the ratio B% / N% of both satisfies the range of 0.5 to 1.5.

P is added in the range of up to 0.1% in order to improve the punchability of the product. P ≦
If it is 0.2%, there is no problem from the viewpoint of the magnetic properties of the product.

Next, the process conditions of the present invention will be described. A steel slab composed of the above components is produced by melting in a steelmaking furnace such as a converter and by continuous casting. The steel slab is heated by a known method. The slab is subjected to hot rolling including rough rolling and finish rolling to a predetermined thickness. The reasons for defining the finish rolling conditions of the present invention will be described below.

In order to investigate the relationship between the hot rolling finish temperature and the magnetic properties in the present invention, the following experiment was conducted. A slab containing the components shown in Table 1 and having a balance of Fe and impurities and having a balance of 220 mm was cast by continuous casting, and the slab was rough-rolled into a sheet bar having a thickness of 50 mm.
These sheet bars are rolled under various conditions and 2.8 mm
Hot rolled sheet. This is pickled and cold-rolled to 0.5 m
m, and annealed by continuous annealing to cut out an Epstein sample. From the records of the rolling conditions of these samples, the relationship between the hot rolling finish temperature and the magnetic properties of the final pass of the finish hot rolling was examined. 1 and 2 show the relationship between the magnetic flux density, iron loss and hot-rolling finishing temperature.

[0019]

[Table 1]

From the results shown in FIGS. 1 and 2, it can be seen that the magnetic flux density and iron loss vary depending on the hot-rolling finishing temperature. The sharp decrease in magnetic flux density and the increase in iron loss at around 900 ° C. were observed because the finishing temperature was within the range in which the γ phase was present. This is because no rolled / recrystallized texture was obtained. By performing finish hot rolling so as to satisfy the hot rolling conditions of the present invention, it is possible to manufacture a non-oriented electrical steel sheet having uniform magnetic properties.

Here, the finishing temperature of the finishing hot rolling is 70
If the temperature is lower than 0 ° C., the hot deformation resistance sharply increases and rolling becomes difficult. If the temperature exceeds the Ar3 point, the crystal structure becomes finer as described above, which adversely affects magnetism.

In the present invention, in order to make the hot-rolling finishing temperature uniform during the finish rolling, the sheet bar after the rough rolling is once taken up, held for a certain period of time, subjected to a soaking treatment, and then unwound. It is extremely effective to join the preceding sheet bar and continuously roll a plurality of sheet bars. The winding and holding time of the sheet bar is preferably 30 seconds or more and 30 minutes or less. If it is less than 30 seconds, the effect of the soaking treatment cannot be obtained,
If the amount exceeds a certain value, the effect is saturated and productivity is reduced. This makes it possible to roll the intermediate sheet bar excluding the biting portion of rolling and the trailing edge of the final portion, satisfying the constituent requirements of the present invention.

The hot rolled sheet thus obtained is then
The product may be made by a single cold rolling and continuous annealing, or may be made into a final sheet thickness by two or more cold rollings including intermediate annealing, or may be further made by adding a skin pass rolling step. If the skin pass rolling ratio is less than 2%, the effect of improving iron loss cannot be obtained, and if it exceeds 20%, the iron loss is rather deteriorated.

[0024]

Next, an embodiment of the present invention will be described. [Example 1] Steel containing the components shown in Table 2 and the remainder consisting of Fe and unavoidable impurities was melted by a converter and made into a slab having a thickness of 220 mm by a continuous casting facility. The slab is heated to 1250 ° C. by a usual method, and 55 m
m sheet bar.

Further, the steel of the component 1 was 2.7 mm and the steel of the component 2 was 2.0 mm by a tandem finishing hot rolling mill of 7 stands.
Finished in thickness. At the time of finish rolling, the rolling speed, rolling temperature, and pass schedule were adjusted so that the hot-rolling finishing temperature became various temperatures.

After pickling the obtained hot-rolled sheet, it is finished to 0.50 mm by cold rolling, and the component 1 is 750 in a continuous annealing furnace.
The composition 2 was annealed at 950 ° C. for 30 seconds at 30 ° C. for 30 seconds, and the magnetic properties were measured. Tables 3 and 4 show the relationship between the hot rolling finish temperature and the results of the magnetic measurement.

From the results shown in Tables 3 and 4, when the variation range of the hot rolling finishing temperature is 100 ° C. or less, it is possible to reduce the variation in both the magnetic flux density and the iron loss. Further, when the range of the hot rolling finish temperature is 50 ° C. or less, the magnetic flux density,
It can be seen that it is possible to further reduce fluctuations in both iron loss. By performing the finish hot rolling so as to satisfy the hot rolling conditions defined in the present invention, it is possible to obtain a non-oriented electrical steel sheet having stable magnetic properties in the longitudinal direction.

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

Example 2 The hot-rolled steel sheet of the component 1 obtained in Example 1 was pickled, finished to 0.55 mm by cold rolling, and annealed at 780 ° C. for 20 seconds in a continuous annealing furnace. . This was further reduced to 0.50 mm by skin pass rolling and subjected to magnetic annealing at 750 ° C. for 2 hours, and then the magnetic properties were measured. Table 5 shows the relationship between the value of the hot rolling finishing temperature and the result of the magnetic measurement.

From the results shown in Table 5, when the fluctuation range of the hot-rolling finishing temperature is 100 ° C. or less, it is possible to reduce fluctuations in both magnetic flux density and iron loss. Further, it can be seen that when the variation range of the hot-rolling finishing temperature is 50 ° C. or less, it is possible to further reduce the variation in both the magnetic flux density and the iron loss. By performing the finish hot rolling so as to satisfy the hot rolling conditions defined in the present invention, it is possible to obtain a non-oriented electrical steel sheet having a stable longitudinal magnetic property even in a semi-process non-oriented electrical steel sheet. It is possible.

[0033]

[Table 5]

Example 3 A steel containing the components shown in Table 6 and the balance of Fe and unavoidable impurities was melted by a converter,
A slab having a thickness of 200 mm was formed by a continuous casting facility. This slab was heated to 1250 ° C. by a usual method and rough-rolled to form a 30 mm sheet bar. The rough-rolled sheet bar was connected to the preceding sheet bar, and finishing hot rolling of five sheet bars was continuously performed. Finish rolling was finished to 2.7 mm by a 7-stand tandem finishing hot rolling machine. As a comparative example, a single sheet bar was similarly subjected to finish hot rolling. After pickling the obtained hot rolled sheet, 0.50
mm, and annealed at 750 ° C. for 30 seconds in a continuous annealing furnace to measure magnetic properties.

At the time of sampling, in the present invention, the strip obtained from the intermediate sheet bar after the finish hot rolling has been subjected to finish rolling (TOP).
, The middle (MIDDLE), and the end (BOTTOM). On the other hand, in the comparative example, when the coil was a sheet bar, the coil was the most advanced (TOP) and the middle (MIDDL).
E), a sample was taken from the position corresponding to the last end (BOTTOM). Table 7 shows the relationship between the sampling position, the hot rolling finish temperature, and the results of the magnetic measurement.

From the results shown in Table 7, the sheet bar is connected to the preceding sheet bar and the finish hot rolling is performed continuously, thereby suppressing the fluctuation of the hot rolling finish temperature, and the magnetic flux density,
Variations in both iron loss can be reduced. By performing the finish hot rolling so as to satisfy the hot rolling conditions defined in the present invention, it is possible to obtain a non-oriented electrical steel sheet having stable magnetic properties in the longitudinal direction.

[0037]

[Table 6]

[0038]

[Table 7]

[0039]

As described above, according to the present invention, a non-oriented electrical steel sheet having uniform magnetic properties can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a magnetic flux density and a hot rolling finishing temperature.

FIG. 2 is a diagram showing a relationship between iron loss and hot rolling finishing temperature.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenichi Murakami 1-1 Hiba-cho, Tobata-ku, Kitakyushu Nippon Steel Inside Yawata Works (72) Inventor Takeaki Wakisaka 20-1 Shintomi, Futtsu-shi New Japan 4K033 AA01 FA03 FA04 HA01 HA03 RA03 5E041 AA11 AA19 CA02 CA04 HB00 HB05 HB07 HB11 NN01 NN17 NN18

Claims (4)

[Claims] 1. The steel contains at least one of Si and Mn in mass% in the range of 0.1% ≦ Si ≦ 4.0% 0.1% ≦ Mn ≦ 2.0%, and the balance Is subjected to rough hot rolling to form a sheet bar, and further subjected to finish hot rolling to form a hot rolled sheet. The hot rolled sheet subjected to finish hot rolling is subjected to one cold rolling step. , Followed by finish annealing, cold rolling two or more times with intermediate annealing to obtain a final thickness, or skin pass rolling of 2% to less than 20% to obtain a final thickness. In the method for producing a non-oriented electrical steel sheet, the hot rolling finishing temperature in the finishing hot rolling is set to 700 ° C or higher and an Ar3 point or lower,
A method for producing a non-oriented electrical steel sheet having uniform magnetic properties, wherein the variation range is 100 ° C. or less. 2. The magnetic characteristic according to claim 1, wherein the slab further contains, as an additional component, acid-soluble Al in a mass% of 0.1% ≦ sol.Al ≦ 2.5%. Method for producing non-oriented electrical steel sheet with uniformity. 3. The method for producing a non-oriented electrical steel sheet having uniform magnetic properties according to claim 1 or 2, wherein a variation range of a hot rolling finishing temperature during the finish rolling is within 50 ° C. 4. The sheet bar according to claim 1, wherein the sheet bar is rolled, rolled up, held for a predetermined time, unwound, joined to a preceding sheet bar, and subjected to continuous hot rolling.
4. The method for producing a non-oriented electrical steel sheet having uniform magnetic properties according to any one of items 3 to 3.