JP3358138B2 - Method for producing semi-process non-oriented electrical steel sheet with excellent isotropic magnetic properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a non-oriented electrical steel sheet, and more particularly to a non-oriented electrical steel sheet having excellent isotropic magnetic properties used for a motor in the electric industry. is there.

[0002]

2. Description of the Related Art The magnetization of a motor core is applied in a random direction within the plane of a steel plate. Therefore, the magnetic properties are 3
It is required that the magnetic properties in various directions of 60 ° be uniform. In particular, stepping motors, motors for industrial robots, disk drive motors, and the like, which require uniformity of rotation torque at each angle and rotation stop position accuracy, require uniform and isotropic magnetic characteristics in the steel plate surface.

[0003] In general, as a process for manufacturing a non-oriented electrical steel sheet in the motor core field, a hot rolled sheet is subjected to one cold rolling and one time.
There are many so-called one-time cold-rolling methods in which a final product is produced by continuous annealing. However, when a lower iron loss is required, the single-pass cold rolling method is further subjected to skin pass rolling in the final step, and is subjected to magnetic annealing by a customer (typically, about 750 ° C. × 2 hr) to form a crystal. A step of increasing the particle size is employed. The present invention relates to this skin pass process method, and is a technical field that is also called a semi-process non-oriented electrical steel sheet because it is premised on annealing by a customer.

[0004] In this field, several techniques have conventionally been disclosed in order to improve iron loss and magnetic flux density. For example, Japanese Patent Application Laid-Open No. 53-109815 discloses a method in which molten steel is purified by Si deoxidation, and the permeability of steel sheets is improved by controlling the roughness of skin pass rolling. Specifically, the steelmaking is deoxidized with Si, and as skin pass rolling, a shot blast roll is used to apply
A first method for improving the magnetic permeability between the vertical and horizontal eyes in a step of providing a roughness of μ-in, rms or more. Further, the second method is to perform skin pass rolling with a smooth roll so that the surface roughness of the final product is 15 μ-in, rms or less, and drastically improve the magnetic permeability in the vertical direction.

In this method, the magnetic permeability of each of the vertical and horizontal eyes can be improved. However, in the first method, the product has a large surface roughness, so that the volume as a core becomes large at the time of lamination, and there is a problem of a so-called space factor in which the effective magnetic flux density as the core decreases. Also, the second
In the method (1), excellent magnetic properties were obtained for the vertical stitches, but there were defects that the magnetic properties in the direction of about 70 ° from the weft stitches and the rolling direction deteriorated.

In Japanese Patent Application Laid-Open No. 63-26313, in the second cold rolling, bright roll rolling is performed in the first half and dull roll rolling at a rolling reduction of 1 to 5% is performed in the second half, so that non-directional good magnetic characteristics are obtained. A method for producing a conductive electrical steel sheet has been proposed. Although magnetic properties can be expected by this method, there are problems of cost of changing rolls during skin pass rolling and deterioration of space factor of products.

Japanese Patent Application Laid-Open No. 53-31515 discloses a method of obtaining isotropic magnetic characteristics by annealing in the γ region. However, in this method, since internal strain due to transformation is introduced, a satisfactory iron loss could not be obtained even after the next annealing.

[0008]

SUMMARY OF THE INVENTION In view of the above, the present invention provides a technique for producing a non-oriented electrical steel sheet having both excellent isotropic magnetic properties and excellent space factor by skin pass rolling. Things.

[0009]

That is, the present invention provides (1)
By weight%, C ≦ 0.01%, Si ≦ 4%, Al ≦ 2%,
Mn ≦ 1.5%, P ≦ 0.3%, S ≦ 0.02%, N ≦
Molten steel containing 0.005% and the balance Fe and unavoidable components is continuously cast to form a slab, and after hot rolling,
In carrying out the steps of pickling, cold rolling under high pressure, annealing, and skin pass rolling at a rolling reduction of 2 to 15%, the roughness of the steel sheet after cold rolling is Ra: 0.7 to 3.0 μm, and the roughness after skin pass rolling. Is Ra: 0.6 μm or less, which is a method for producing a semi-processed non-oriented electrical steel sheet having excellent isotropic magnetic properties, wherein (2) hot-rolled sheet annealing is performed after hot-rolling. A method for producing a semi-process non-oriented electrical steel sheet having excellent isotropic magnetic properties according to the above (1).

There are three points of the present invention. One is to roughen the steel sheet after cold rolling under high pressure, then insert annealing,
To improve the texture of the steel sheet by reducing the roughness of the steel sheet by skin pass rolling. The second point is to improve the space factor at the time of lamination by making the surface of the final product smooth. The third point is that this method is industrially sufficient and stable production is possible.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reasons for limiting the present invention will be described below. C content is limited to 0.01% or less. If the C content exceeds this, the time required for decarburization in the decarburization annealing becomes longer, and the productivity decreases. If the C content of the product is not less than 0.005%, there is a problem of magnetic aging.
The amount of Si is set to 4% or less. Si is necessary in order to reduce iron loss, but if it is too much, there is a problem of embrittlement, which causes breakage in a threading line or trouble when punching into a motor core.
Since this limit is 4%, the lower limit of the amount of Si is set to 4%.

The Al content is 2% or less. Al is effective in reducing iron loss, but is limited to 2% or less due to the problem of addition cost. The Mn content is 1.5% or less. As a countermeasure against hot-rolling, MnS
In order to achieve the above, Mn is necessary, but if it is too much, there is a problem of addition cost.

The amount of P is limited to 0.3% or less. P is useful for reducing burrs and sagging when punching the motor core at the customer. However, if too large, P segregates in the central layer of the steel sheet and causes troubles such as cracks. The N amount is 0.005% or less. If the amount of N is large, blisters called blisters occur on the steel sheet surface,
Limit to 0.005% or less. The amount of S is set to 0.02% or less. Since S forms sulfides and deteriorates iron loss, it is better to reduce the amount of S to 0.02% or less.

As other components, known Cu, Cr, Sn, Ni, and B may be used to further improve the texture of the product. The content is Cu: 0.02-0.
2%, Sn: 0.01-0.35%, Cr: 0.04-
0.2%, Ni: 0.01-0.3%, B: 0.000
5-0.01% is preferred. There is no problem even if two or more of these compounds are added.

Molten steel containing these component compositions is formed into a slab by ordinary continuous casting. Hot rolling is performed by a conventional method to obtain a normal hot-rolled coil having a thickness of 1.0 to 3.0 mm. The hot rolled coil may or may not be annealed. If the annealing is performed, the magnetic flux density is particularly improved in each angular direction. However, annealing costs are required.

Next, after pickling, cold rolling is performed under high pressure. The surface roughness of the steel sheet after this cold rolling must be controlled. The surface roughness is 0.7 μm or more and 3.0 μm or less as a center line average roughness Ra. If the surface after cold rolling under high pressure becomes rough, the isotropic magnetic properties of the present invention can be obtained, but Ra <
At 0.7 μm, there is no large difference between the magnetic properties in the rolling direction and the other directions. Generally, a roll of dull roll for roughening the surface of a steel sheet is worn and smoothed with an increase in the number of rolling betons. Therefore, if the surface of the steel sheet is to be Ra> 3.0 μm, the number of times the roll must be dull by shot projection or the like increases in order to avoid the smooth roll, and this must be avoided in terms of cost. In addition, as a method for obtaining the steel plate roughness of the present invention, for example, in the case of tandem rolling, only the rolling at the final stand may be a dull roll, or all stands may be dull rolls. That is, the surface of the steel sheet before rolling is rough. Subsequent annealing is performed at normal 600-1000 ° for several seconds to
Perform a soak for several minutes. The atmosphere is conventional H ₂ and N
It is a _second mixing airflow, causing the decarburization blowing of H ₂ O as required.

Next, skin pass rolling is performed. The rolling reduction at this time is limited to 2 to 15%. If the content is out of the range of 2% or more and 5% or less, the crystal grain size does not become coarse after the magnetic annealing by the customer and iron loss is poor, so it is avoided. The skin pass rolling uses a smooth roll, and the surface roughness of the steel sheet after the skin pass needs to be 0.6 μm or less in Ra. Ra0.6
If it exceeds μm, the excellent space factor of the present invention cannot be obtained, and the magnetic properties of the motor core will be unsatisfactory. Magnetic annealing after skin pass at normal 700-800 ° C for 2h
The degree of heat equalization may be sufficient.

[0018]

Examples will be described in detail below with reference to examples. [Example-1] 0.002% C, 1.5% S by weight ratio
i, 0.5% Mn, 0.03% P, 0.2% Al, 0.
A continuously cast slab containing 001% S and 0.002% N was heated to 1150 ° C. to produce a hot-rolled sheet having a thickness of 2.5 mm. This was pickled, and strongly cold-rolled was rolled with rolls having various roll roughnesses to obtain a steel plate roughness shown in Table 1. The plate thickness was 0.535 mm. Next, after degreasing, the intermediate annealing was soaked in a 20% H ₂ + 80% N ₂ atmosphere at 800 ° C. for 30 seconds, and then cold rolled with a skin pass to 0.5 mm. At this time, the roughness of the skin pass roll was variously changed to obtain the steel plate roughness shown in Table 1.

This steel sheet was sheared to a width of 30 mm and a length of 60 mm. The longitudinal direction at this time is 0 °, 22.5 ° with the rolling direction.
75 °, 45 °, 67.5 °, 90 °
After performing soaking at 0 ° C. for 2 hours in an N ₂ atmosphere, the magnetic properties of the samples in the respective angular directions were measured. Table 1 shows the maximum and minimum values of the magnetic properties and the difference between the two. The space factor was measured based on JIS C 2550 (1987) by preparing 16 sheets each of Epstein samples.

[0020]

[Table 1]

Experiment No. Since (4)-(9) are within the scope of the present invention, isotropic magnetic properties are obtained and a high space factor is secured. Experiment No. In (1)-(3), the isotropic magnetic properties cannot be obtained since the steel plate roughness after the deep cold rolling, that is, before the skin pass rolling, is too small and out of the range of the present invention. Experiment No. (10)-(12) do not fall within the scope of the present invention because the steel plate roughness after skin pass is too large and the space factor deteriorates. The direction with the best magnetic properties was the rolling direction (0 °), and the worst direction was 45 ° or 67.5 ° with the rolling direction.

Example 2 0.005% C by weight ratio
0.3% Si, 0.2% Mn, 0.10% P, 0.00
A continuous cast slab containing 5% Al, 0.001% S, and 0.002% N was heated to 1100 ° C to a thickness of 2.5 mm.
Was manufactured. A part of these was subjected to hot rolled sheet annealing at 800 ° C. for 1 minute, then pickled, and subjected to strong cold rolling with a dull roll to obtain a constant steel sheet roughness of Ra 1.1 μm. It was adjusted to the following skin pass roll reduction ratio shown. Next, after degreasing, intermediate annealing is performed at 40% H ₂ + 60%.
After soaking at 700 ° C. for 30 seconds in an N ₂ atmosphere, 0.5 mm
Cold rolled skin pass until. At this time, the roughness of the skin pass roll was variously changed to obtain the steel plate roughness shown in Table 1.

This steel sheet was sheared to a width of 30 mm and a length of 60 mm. The longitudinal direction at this time is 0 °, 22.5 ° with the rolling direction.
°, 45 °, 67.5 °, 90 ° in 5 types 750
After soaking in a N ₂ atmosphere at a temperature of 2 ° C. for 2 hours, the magnetic properties of the samples in the respective angular directions were measured. Table 1 shows the maximum and minimum values of the magnetic characteristics and the difference between the two.

[0024]

[Table 2]

The skin pass rolling reduction of the example of the present invention is 2 to 15%.
Experiment No. (2)-(4) show excellent iron loss, but other test Nos. (1), (5),
Regarding (6), iron loss has deteriorated. Also, in Experiment No. in which hot rolled sheet annealing was performed. In (7)-(10), the magnetic flux density is particularly improved as compared with the case where the hot rolled sheet is not annealed, but the iron loss is not satisfied unless the skin pass rolling reduction is within the range of the present invention. The direction with the best magnetic properties was the rolling direction (0 °), and the worst direction was 45 ° or 67.5 ° with the rolling direction.

[0026]

As described above, by controlling the roughness in the cold rolling of the strong cold rolling and the skin pass rolling, a semi-process non-directional electromagnetic having an isotropic magnetic property and an excellent space factor at the same time. A steel plate was obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-56-13485 (JP, A) JP-A-60-131917 (JP, A) JP-A-1-139721 (JP, A) JP-A-2- 118020 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C21D 8/12 C22C 38/00 303 C22C 38/06 H01F 1/16

Claims (2)

(57) [Claims] 1. wt%, C ≦ 0.01%, Si ≦ 4%, Al ≦ 2%, Mn ≦ 1.5%, P ≦ 0.3%, S ≦ 0.02%, N ≦ 0 0.0005%, the molten steel containing the balance Fe and unavoidable components is continuously cast into a slab, hot rolled, then pickled, cold rolled under high pressure, annealed, and subjected to skin pass rolling at a rolling reduction of 2-15%. In carrying out the process, the isotropic magnetic properties are characterized in that the steel sheet after cold rolling has a roughness of Ra: 0.7-3.0 μm and the steel sheet after skin pass rolling has a roughness of Ra: 0.6 μm or less. Manufacturing method of semi-process non-oriented electrical steel sheet with excellent quality. 2. The method for producing a semi-process non-oriented electrical steel sheet having excellent isotropic magnetic properties according to claim 1, wherein hot-rolled sheet annealing is performed after hot-rolling.