JP2000096145A - Manufacture of nonoriented silicon steel sheet with uniform magnetic property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably reduce the dispersion of magnetic properties in the coil- longitudinal direction of a nonoriented silicon steel sheet. SOLUTION: A slab, having a composition consisting of either or both of 0.1-4.0%, by weight, Si and 0.1-2.0% Mn and the balance Fe with inevitable impurities, is roughed into a sheet bar, and further, the sheet bar is subjected to finish hot rolling and formed into a hot rolled plate. At this time, finish hot rolling finishing temperature is regulated to 700 to 1,150 deg.C, and the maximum value of the parameter Z defined by equation at the final pass of finish hot rolling is regulated to <16.0 and also its range of fluctuation is regulated to <=2.0. The resultant hot rolled plate is cold rolled once and finish annealed or is cold rolled two or more times while process annealed between cold rolling stages. Subsequently, the resultant sheet is subjected or not subjected to skin pass rolling of 2 to <20%.

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 of electric equipment, with uniform magnetic properties.

[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, the side that manufactures non-oriented electrical steel sheets is tasked with stably producing non-oriented electrical steel sheets having such excellent characteristics. 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 sheet bar, the rolling temperature and the rolling speed fluctuate within one sheet bar, so that magnetic fluctuation in the coil longitudinal direction is unavoidable, and there is a problem that the product yield is lowered. However, how to set the control hot rolling conditions was effective was an unknown issue.

In order to solve this problem, Japanese Patent Laid-Open Publication No.
No. 6664 discloses that the peripheral speed of the roll of the final stand at the time of finish rolling affects the magnetic properties, and proposes a technique for limiting the fluctuation of the peripheral speed within a certain range. However, as a result of a detailed investigation by the inventors of the present invention on variations in magnetic properties in the longitudinal direction of the coil, the peripheral speed of the final stand of the hot-rolled finish itself affects the metallographic structure and precipitates in metallurgical terms. It was found that the dependence of the magnetic flux density on the peripheral speed in the published figure was 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.

In view of this point, the present inventors have conducted intensive studies, and as a result, by controlling the rolling conditions of the final stand at the time of finish rolling to conditions determined by a specific formula, the magnetic characteristics in the longitudinal direction of the coil can be improved. They have found that they are remarkably stable, and have solved the above-mentioned problem. Furthermore, as a measure to facilitate this technology, the rolled sheet bar is wound and held,
By unwinding and rolling this, the top and bottom of the sheet bar are reversed, and the rolling temperature is made uniform,
Further, by joining the sheet bar to the preceding sheet bar and continuously rolling a plurality of sheet bars,
The inventors have found that it is possible to more stably control the parameter Z defined by the equation (1) to produce a non-oriented electrical steel sheet having more uniform magnetic properties in the longitudinal direction of the coil, and have completed the invention. .

[0006]

SUMMARY OF THE INVENTION The present invention overcomes the limitations of the prior art in a non-oriented electrical steel sheet manufacturing method,
It is an object of the present invention to provide a technology for stably producing a non-oriented electrical steel sheet having excellent magnetic properties in a coil longitudinal direction.

[0007]

The gist of the present invention is as follows. (1) Rough rolling of a slab containing 0.1% ≦ Si ≦ 4.0% or 0.1% ≦ Mn ≦ 2.0% by weight and the balance being Fe and unavoidable impurities When the sheet bar is subjected to finish hot rolling to form a hot rolled sheet, the finish hot rolling end temperature is 700 ° C. or higher and 1150 ° C.
The maximum value of the parameter Z defined by the equation (1) in the final pass of the finish hot rolling is set to less than 16.0 and the variation range is set to 2.0 or less. Finish annealing after the cold rolling process, or
Alternatively, two or more cold rollings with intermediate annealing are performed, and then a skin pass rolling of 2% or more and less than 20% is performed or not performed. Manufacturing method of grain-oriented electrical steel sheet.

(Equation 2) (2) The production of a non-oriented electrical steel sheet having uniform magnetic properties according to the above (1), wherein the slab further contains 0.1% ≦ sol-Al ≦ 1.5% by weight. Method. (3) The variation of the parameter Z defined by the equation (1) in the final pass of the finish hot rolling is limited to 1.5 or less, and the magnetic characteristics according to the above (1) or (2) are uniform. Manufacturing method of non-oriented electrical steel sheet. (4) After winding and holding a sheet bar obtained by rough rolling for a certain period of time, the sheet bar is unwound, joined to a preceding sheet bar, and continuously subjected to finish hot rolling. The method for producing a non-oriented electrical steel sheet having uniform magnetic properties according to (1), (2) or (3).

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. First, the components will be described. 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 is difficult. Therefore, it is necessary to make it 4.0% or less.
Mn has the effect of increasing the specific resistance of a steel sheet and reducing eddy current loss, similarly to Al and Si. 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, the above S
It is essential that at least one of i and Mn be contained.

There is no problem even if Al in the steel is at the impurity level, but 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 1.5% or less. When a large amount of Al is added, the magnetic flux density is reduced and the cost is increased.

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, their contents are carefully controlled in producing a non-oriented electrical steel sheet having good magnetic properties or workability. Since it is necessary, the following is mentioned. C
Is 0.00 to avoid magnetic aging and prevent iron loss
It is preferably 50% or less. 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 final annealing or magnetize the product. When this is performed, a so-called pinning effect that hinders the movement of the domain wall is exerted, which hinders a reduction in iron loss of the product. Therefore, S ≦ 0.0050
%, N ≦ 0.0050%. B forms BN during hot rolling and hinders fine precipitation of AlN,
It is added to render N harmless. The B content needs to be balanced with the amount of N, and the content is a ratio B% of both.
/ N% preferably satisfies the range of 0.5 to 1.5. P is added in a range of up to 0.1% in order to improve the punchability of the product. P ≦ 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. The steel slab composed of the above components is produced by continuous casting and produced by melting in a converter. The steel slab is heated by a known method. Thickness.

The reasons for defining the hot rolling conditions for the finish of the present invention are described below. In order to investigate the relationship between hot rolling conditions and magnetic properties in the present invention, the following two types of experiments were performed.
A slab cast to a thickness of 220 mm by continuous casting was rough-rolled into a sheet bar having a thickness of 50 mm. These sheet bars were rolled under various conditions to obtain 2.8 mm hot-rolled sheets. This was pickled, finished to a thickness of 0.5 mm by cold rolling, annealed by continuous annealing, and an Ebstein sample was cut out. From the record of the rolling conditions of these samples, the relationship between the parameter Z (defined by the above-mentioned formula (1)) of the final pass of the finish hot rolling and the magnetic properties was examined. In the present invention, the finishing temperature is used for the calculation as the rolling temperature of the final pass.
1 and 2 show the relationship between the magnetic flux density, iron loss, and the parameter Z. From the results shown in FIGS. 1 and 2, it can be seen that the magnetic flux density and the iron loss vary depending on the value of the parameter Z. As described above, by performing finish hot rolling so as to satisfy the conditions of the present invention, it is possible to manufacture a non-oriented electrical steel sheet having uniform magnetic properties.

[0014]

[Table 1]

Here, the finishing temperature of the finishing hot rolling is 700 ° C.
If it is less than 700 ° C., the hot deformation resistance rapidly increases and rolling becomes difficult. On the other hand, if the temperature exceeds 1150 ° C., the rigidity of the hot-rolled sheet becomes insufficient, and winding of the coil becomes extremely unstable. There is no particular upper or lower limit for the value of the parameter Z. The value of the parameter Z increases when the rolling temperature is lowered or the strain rate is increased, but when the rolling temperature is too low, the rolling reaction force during hot rolling becomes too large, so the lower limit value is naturally determined by the performance of the hot rolling machine. This is because the upper limit of the strain rate is naturally determined by the capacity of the hot rolling mill from the limit of the rolling rate. The same applies to the lower limit of the parameter Z.

Here, in order to obtain the value of the Z parameter Z, it is necessary to obtain the distortion speed. There are various methods as the method, but in the present invention, the strain rate is determined according to the following equation (2).

[0017]

(Equation 3)

In the present invention, in order to make the value of the parameter Z during rolling more uniform, the sheet bar obtained by rough rolling is wound up and held for a certain period of time, then the sheet bar is unwound, and then the unwound sheet It is extremely effective that the bars are joined and continuously subjected to finish hot rolling. The holding time of the wound 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 time is longer than 30 minutes, the effect is saturated and productivity is lowered. This makes it possible to roll the intermediate sheet bar except for the biting of rolling and the trailing edge of the last part, satisfying the constituent requirements of the present invention. The hot-rolled sheet obtained in this way is then made into a product by one cold rolling and continuous annealing, or made into a final sheet thickness by two or more cold rollings including intermediate annealing, or further subjected to skin pass. A product may be obtained by adding a 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 0%, iron loss worsens, so it is 2% or more and 20%
The following is assumed.

[0019]

Next, an embodiment of the present invention will be described. Example 1 The components shown in Table 2 were combined, steel consisting of the balance 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 was heated to 1250 ° C. by a usual method, and rough-rolled into a 55 mm sheet bar. Further, the steel of component 1 is 2.7 mm and the steel of component 2 is 3.0 mm by a tandem finishing hot rolling mill with 6 stands.
Finished in thickness. At the time of finish rolling, the rolling speed, rolling temperature, and pass schedule were adjusted so that the value of the parameter Z, which is an index of the hot rolling condition, takes various values in the final pass. After pickling the obtained hot rolled sheet, 0.50
mm, component 1 in a continuous annealing furnace at 800 ° C for 30 seconds,
Component 2 was annealed at 950 ° C. for 30 seconds and its magnetic properties were measured.

Tables 3 and 4 show the relationship between the value of the parameter Z in the final pass, which is an index of the hot rolling conditions, and the results of the magnetic measurement. From the results shown in Tables 3 and 4, when the variation range of the parameter Z is 2.0 or less, it is possible to reduce the variation in both the magnetic flux density and the iron loss. Further, it can be seen that when the variation range of the parameter Z is 1.5 or less, it is possible to further reduce the variation in both the magnetic flux density and the iron loss.

Here, it can also be seen that when the value of the parameter Z exceeds 16.0, the magnetic properties are significantly 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.

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[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 is further reduced to 0.50 mm by skin pass rolling,
After magnetic annealing at 750 ° C. for 2 hours, the magnetic properties were measured. Table 5 shows the relationship between the value of the parameter Z in the final pass, which is an index of the hot rolling conditions, and the result of the magnetic measurement. From the results shown in Table 5, when the variation range of the parameter Z is 2.0 or less, it is possible to reduce the variation in both the magnetic flux density and the iron loss. Further, it can be seen that when the variation range of the parameter Z is 1.5 or less, it is possible to further reduce the variation in both the magnetic flux density and the iron loss. here,
It can also be seen that when the value of the parameter Z exceeds 16.0, the magnetic properties are significantly reduced.

As described above, by performing the finishing hot rolling so as to satisfy the hot rolling conditions defined in the present invention, a non-oriented electrical steel sheet having stable longitudinal magnetic properties can be obtained even in a semi-process non-oriented electrical steel sheet. It is possible.

[0027]

[Table 5]

[0028]

As described above, according to the present invention, it is possible to manufacture a non-oriented electrical steel sheet having uniform magnetic properties.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a magnetic flux density and a Z parameter Z.

FIG. 2 is a diagram showing a relationship between iron loss and a Z parameter Z.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4K033 AA01 FA03 FA04 HA01 HA03 HA06 JA07 5E041 AA03 AA11 AA19 CA04 HB05 HB07 HB11 NN01 NN17 NN18

Claims (4)

[Claims] 1. A slab containing, by weight%, one or both of 0.1% ≦ Si ≦ 4.0% and 0.1% ≦ Mn ≦ 2.0%, with the balance being Fe and unavoidable impurities. When subjected to rough rolling to form a sheet bar, and further subjected to finish hot rolling to form a hot rolled sheet, the finish hot rolling end temperature is 700 ° C. or higher and 1150 ° C.
The maximum value of the parameter Z defined by the equation (1) in the final pass of the finish hot rolling is set to less than 16.0 and the variation range is set to 2.0 or less. Finish annealing after the cold rolling process, or
Alternatively, two or more cold rollings with intermediate annealing are performed, and then a skin pass rolling of 2% or more and less than 20% is performed or not performed. Manufacturing method of grain-oriented electrical steel sheet. (Equation 1) 2. The non-oriented electrical steel sheet according to claim 1, wherein the slab further contains 0.1% ≦ sol-Al ≦ 1.5% by weight. Production method. 3. The method according to claim 1, wherein the variation range of the parameter Z defined by the equation (1) in the final pass of the finish hot rolling is within 1.5. Manufacturing method of grain-oriented electrical steel sheet. 4. After winding the sheet bar obtained by the rough rolling and holding it for a certain period of time, unwind the sheet bar,
4. The method for producing a non-oriented electrical steel sheet having uniform magnetic properties according to claim 1, wherein the sheet is joined to a preceding sheet bar and continuously subjected to finish hot rolling.