JPH075987B2 - Method for manufacturing non-oriented electrical steel sheet with excellent magnetic flux density in low magnetic field - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a non-oriented electrical steel sheet capable of obtaining a high magnetic flux density in a low magnetic field, and more particularly to an annealing method using a vertical continuous annealing furnace.

[Conventional technology and problems to be solved]

Magnetic steel sheets, especially non-oriented electrical steel sheets, which are relatively high grade, have a problem that their magnetic properties are likely to deteriorate due to the introduction of strain due to bending or tensioning during annealing. Especially in the vertical continuous annealing furnace, the internal tension is higher than that in the horizontal annealing furnace, and the strain is introduced into the plate by winding the plate around the furnace roll, so the magnetic characteristics, especially the low magnetic field characteristics, are easily deteriorated. . Therefore, it is difficult to manufacture high-grade electromagnetic steel sheets by the vertical continuous annealing furnace, and in reality, only low-grade electromagnetic steel sheets as shown in Japanese Patent Publication No. 62-49321 can be produced.

[Means for Solving the Problems]

The present invention has been made in view of such conventional problems,
In annealing in a vertical continuous annealing furnace, using an in-furnace roll having a specific roll diameter determined by the relationship between the specific crown amount and the plate thickness and plate temperature of the steel plate, to pass the steel plate under a predetermined tension. It was found that the non-oriented electrical steel sheet excellent in magnetic flux density in a low magnetic field can be obtained by preventing the introduction of strain when the sheet is wound around the roll, and thus completed the present invention.

That is, the present invention, when performing the final annealing in the vertical continuous annealing furnace, the steel plate tension at the time of passing through the furnace is 1.0 kg / mm ² or less, and in the temperature range of 400 to 900 ° C., the following conditions: 1200 ≦ D / t ≤ 2600 D / t ≥ 90 + 2.79T 0.5 ≤ ΔD ≤ 3.5 where D: Roll diameter in furnace (mm) t: Steel plate thickness (mm) T: Plate temperature of steel plate when passing through the roll (° C) ΔD: This is a method for producing a non-oriented electrical steel sheet having an excellent magnetic flux density in a low magnetic field, which is characterized by passing a steel sheet so as to satisfy a roll crown amount (mm).

Hereinafter, the details of the present invention will be described together with the reasons for limitation.

Conventionally, the in-furnace roll of a vertical continuous annealing furnace for cold-rolled steel sheets has been determined from the viewpoint of the roll diameter in consideration of bending of the plate and the amount of roll crown to ensure the threading property (centering property). . However, when an electromagnetic steel plate is passed through such a roll in the furnace, distortion is introduced into the plate, which causes deterioration of the magnetic flux density in a low magnetic field. Therefore, the present inventors have studied the diameter and crown of the roll in the furnace from the viewpoint of ensuring a high magnetic flux density in a low magnetic field, the results of various experiments,
Under a specific tension, by passing a steel plate using a furnace roll having a specific roll diameter determined by the relationship between a specific roll crown amount and the plate thickness and plate temperature of the steel plate, It was confirmed that the magnetic flux density could be effectively improved.

1 to 3 show the results. Of these, Fig. 1 shows the effect of the roll diameter D in the furnace / steel plate thickness t on the magnetic flux density (B ₃ ) in the low magnetic field of the product when the steel plate with a plate thickness of 0.3 to 0.8 mm (Si: 1 wt%) is 600 This is an examination of the case of passing a roll at ℃. In this case, when D / t is less than 1800, permanent deformation remains in the steel sheet and the magnetic flux density B ₃ deteriorates. Fig. 2 shows the results of such a test performed while changing the plate temperature during roll passing. In order to ensure good magnetic properties, the stress applied to the plate was determined by the yield at that plate temperature. It is necessary to keep the stress within a range that does not exceed it, and the lower limit of D / t for that purpose can be approximately expressed as a function of the plate temperature T (° C) of the steel plate during rolling, D / t = 90 + 2.79T. it can. Further, the plate temperature in the furnace is mainly 900 ℃ from the upper limit due to facility restrictions, and the plate temperature is less than 400 ℃ in the low temperature region strain residual is less of a problem, therefore the present invention should be targeted. The plate temperature during roll passing is 400 ° C to 900 ° C.
Therefore, in order to prevent distortion introduction, it is necessary to set D / t ≧ 90 + 2.79T and D / t: 1200 to 2600 based on the result of FIG.

FIG. 3 shows the influence of the crown amount ΔD of the in-furnace roll on the magnetic flux density (B ₃ ) in a low magnetic field and the stripability (the amount of meandering) of the steel sheet. According to this, when ΔD is large, the centering property at the time of passing the plate is improved, but the strain difference in the width direction is increased, and when the residual stress in the width center part is increased and becomes remarkable, the state becomes a middle stretched state. , Magnetic flux density B ₃
Is significantly deteriorated. In order to improve the magnetic flux density B ₃ without excessively impairing the stripability of the steel sheet, the crown amount ΔD is set to 0.5.
Must be in the range of ~ 3.5 mm. Further, in order to obtain a higher magnetic flux density B ₃ is divided sheet passing property to some extent loss of the steel sheet, 0.5 to 3.0 mm crown amount, and more preferably 0.5 to 2.
A range of 5 mm is preferable.

The crown shape to be applied to the sheet passing roll is not particularly limited, and may be any shape such as a flat shape and a sine curve shape as shown in FIG.

Further, when the steel plate tension during passing through the annealing furnace exceeds 1.0 kg / mm ² , even if the furnace roll diameter and the crown are regulated as described above, high magnetic flux density in a low magnetic field is still caused by the introduction of strain. Therefore, in the present invention, the steel plate is passed through the steel sheet with a tension of 1.0 kg / mm ² or less.

Needless to say, the present invention can be applied to any zone of heating, soaking, and cooling. The steel sheet targeted by the present invention is a steel sheet having an Si content of about 4.0 wt% or less.

〔Example〕

In a vertical continuous annealing furnace in which the in-furnace roll to be passed at a plate temperature of 600 ° C has the roll diameter and crown amount shown in Table 1, Si: 0.8 wt% cold-rolled steel plate (0.5 mm ^t × 960 mm ^w ) Was continuously annealed under the conditions of an annealing temperature of 800 ° C and a tension of 0.5 kg / mm ^{2 in} the furnace, and the in-furnace threadability and the magnetic properties of the obtained steel sheet were investigated. The results are also shown in Table 1.

[Effects of the Invention] According to the present invention described above, in the vertical continuous annealing furnace,
By passing the steel plate under a predetermined tension by using an in-furnace roll having a certain range of in-furnace roll diameter and crown, the strain is appropriately prevented from being introduced when the plate is wound around the roll, and it is high in a low magnetic field. A non-oriented electrical steel sheet having a magnetic flux density can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the effect of D / t on the magnetic flux density B ₃ . FIG. 2 shows the range in which the magnetic flux density B ₃ is good with respect to D / t and the steel plate temperature. FIG. 3 shows the influence of the crown amount ΔD on the magnetic flux density B ₃ and the sheet passing property.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takaaki Hata, 1-2, Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Haruo Hayashi, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Date Inside the Steel Pipe Co., Ltd. (72) Inventor Junichi Inagaki 1-2 1-2 Marunouchi, Chiyoda-ku, Tokyo Inside the Nippon Steel Pipe Co., Ltd. (56) Reference JP-A-61-119620 (JP, A)

Claims (1)

[Claims] 1. When performing final annealing in a vertical type continuous annealing furnace, the steel plate tension is set to 1.0 kg / mm ² or less when passing through the furnace and the following conditions are satisfied in the temperature range of 400 to 900 ° C. A method for producing a non-oriented electrical steel sheet having an excellent magnetic flux density in a low magnetic field, which is characterized in that the steel sheet is passed through. 1200 ≤ D / t ≤ 2600 D / t ≥ 90 + 2.79T 0.5 ≤ ΔD ≤ 3.5 However, D: Roll diameter in furnace (mm) t: Steel plate thickness (mm) T: Plate temperature of the steel plate when passing through the roll (℃ ) ΔD: Roll crown amount (mm)