JPH0935925A - Non-oriented electromagnetic steel excellent in punching and magnetic characteristics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase dimensional precision after punching non-oriented electromagnetic steel, prevent magnetic aging, and positively improve iron loss. SOLUTION: In the non-oriented electromagnetic steel, the following elements are contained by weight ratio: C: at most 0.01%, Si: at most 3.2%, Mn: at most 1.0%, S: at most 0.01%, Sol. Al: 0.01-2.0%, P: 0.005-0.1%, and Ti: more than or equal to 0.001% and less than 0.05%. The rest is composed of Fe and unavoidable impurities. Magnetic aging which is the trouble as the result of containing C and adding P when dimensional precision after punching is increased is effectively restrained by adding very small quantity of Ti. By adding Ti, the increase of iron loss which makes trouble is prevented and the iron loss is also positively improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-oriented electrical steel sheet having excellent punching properties, particularly dimensional accuracy after punching, and good magnetic properties, particularly iron loss.

[0002]

2. Description of the Related Art Since non-oriented electrical steel sheets are laminated and used for motors and transformers, their punchability is important. Generally, punchability is evaluated by the number of punches and the dimensional accuracy after punching. The number of times of punching is important because the burr after punching becomes higher as the number of times of punching increases, and if the allowable height is exceeded, the space factor after lamination is lowered and the performance of the motor or transformer is lowered. In order to improve the number of times of punching, a resin-containing surface coating as shown, for example, in JP-A-6-81162 and JP-B-6-104905 is effective.

On the other hand, the dimensional accuracy after punching largely depends on the mechanical properties of the steel sheet rather than on the surface coating, and is governed by YR represented by the yield point / tensile strength in a tensile test. Since a material having a large YR has excellent dimensional accuracy, it is necessary to increase the yield point to increase the YR. Here, if the crystal grains are made smaller by adding alloying elements or lowering the temperature of finish annealing in order to raise the yield point, magnetic characteristics, especially iron loss, increase. Therefore, normally, the yield point is increased by adjusting the amount of C or increasing the amount of P.

That is, C is effective in increasing the yield point, but on the other hand, it causes magnetic aging. In order to prevent magnetic aging, C <0.003% is desirable, but such extremely low carbonization prolongs the vacuum degassing treatment time during steelmaking, and causes problems in terms of productivity and cost. Therefore, C ≦
It is general to increase the yield point by 0.01% and P ≧ 0.01%.

[0005]

However, such a C-containing / P-added material cannot avoid some magnetic aging.
Regarding magnetic aging, it is disclosed in JP-A-56-51523 that addition of 0.05 to 0.2% of Ti is effective in preventing magnetic aging, but in order to improve the dimensional accuracy after punching. In the case where P is added to JP-A-56-51523
It has been found that the high level addition as shown in Japanese Patent Publication causes a significant increase in magnetic properties, particularly iron loss.

An object of the present invention is to provide a non-oriented electrical steel sheet having excellent dimensional accuracy after punching, large magnetic aging resistance, and good iron loss.

[0007]

As described above, addition of Ti is effective as a means for preventing magnetic aging of non-oriented electrical steel sheets. According to the investigation by the present inventor, addition of Ti is effective not only for preventing magnetic aging but also for improving dimensional accuracy after punching. However, when P is contained to improve the punching property, the inclusion of (Fe, Ti) P is generated, and the magnetic properties, especially the iron loss are remarkably increased.
Further, in the case of containing a relatively large amount of C from the viewpoint of economy, etc., inclusions such as Ti (CN) are generated to inhibit the crystal grain growth during finish annealing, so that the iron loss is further increased.

Therefore, the present inventor, when C and P are contained in a relatively large amount, specifically C ≦ 0.01%, P ≧
In the case of 0.01%, investigation and examination were conducted on a method of suppressing magnetic aging without increasing iron loss. As a result, T
When i is added in a small amount, specifically, less than 0.05%, not only an increase in iron loss is avoided but also the iron loss is positively improved, and even in such a small amount addition Nevertheless, we have found that magnetic aging is effectively suppressed.

The present invention has been made on the basis of such findings, and C: 0.01% or less by weight, Si: 3.2% or less by weight, M
n: 1.0% or less, S: 0.01% or less, Sol.Al: 0.01-
2.0%, P: 0.005-0.1%, Ti: 0.001% or more
The gist is a non-oriented electrical steel sheet that contains less than 0.05% and the balance is Fe and unavoidable impurities and is excellent in punchability and magnetic properties.

In order to improve the dimensional accuracy after punching, P is
0.01% or more is particularly desirable. Further, in order to secure punching property and economy, C is particularly preferably 0.003% or more. Ti is particularly preferably 0.005% or more from the viewpoint of improving punchability and iron loss.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The non-oriented electrical steel sheet of the present invention has the above composition. The reasons for limiting the component composition are as follows.

C is an element effective for improving the dimensional accuracy after punching, but if it is contained in an amount exceeding 0.01%, it becomes impossible to fix C by Ti and magnetic aging occurs, so 0.01% is added. Below. The lower limit of the amount of C is not particularly specified, but an extreme limit not only lowers the punchability but also causes a significant increase in steelmaking cost, so 0.003% or more is desirable.

Si is an essential element for improving the magnetic properties, but if it is contained in excess of 3.2%, troubles such as breakage will occur during cold rolling, so the content was made 3.2% or less. The lower limit of the amount of Si is not specified, but 0.1% or more is desirable for the purpose of improving the magnetic properties.

Mn is also an element effective in improving the magnetic properties, but if it is added in an amount exceeding 1.0%, cold rolling becomes difficult, so the content was made 1.0% or less. Although the lower limit of the Mn amount is not particularly specified, the steelmaking cost increases remarkably in order to extremely reduce it, so 0.1% or more is preferable.

Since S deteriorates the magnetic characteristics, S is made 0.01% or less. It is preferably 0.005% or less.

[0016] Sol.Al is an important element for improving the magnetic properties, but if it is less than 0.01%, fine AlN is formed to rather deteriorate the magnetic properties, and if it is added in excess of 2.0%. Cold rolling becomes difficult. Therefore, 0.01-2.0%, the lower limit is 0.1% or more, the upper limit is 1.0%
The following are particularly desirable:

P is an element necessary for improving the mechanical properties for improving the dimensional accuracy after punching. If it is less than 0.005%, it is not effective in improving the punching property and the cost of dephosphorization treatment increases, so 0.005% or more is preferable, and 0.01% or more is particularly desirable. However, if the content exceeds 0.1%, fracture occurs during cold rolling, so 0.1% was made the upper limit.

Ti is an element necessary for preventing magnetic aging which is a problem when C is contained and P is added. 0.001%
If it is less than the above range, C cannot be fixed as a solid solution so that the magnetic aging cannot be sufficiently suppressed. Further, improvement in dimensional accuracy and iron loss after punching cannot be expected. Therefore 0.
It is 001% or more, and particularly preferably 0.005% or more. However, if the content is 0.05% or more, inclusions harmful to the magnetic properties such as (Fe, Ti) P are generated, and conversely, a significant increase in iron loss is caused, so the content was made less than 0.05%.

The non-oriented electrical steel sheet of the present invention can be manufactured by the following process.

The slab having the above-mentioned composition is heated at a temperature of 1300 ° C. or lower and usually hot-rolled. A heating temperature exceeding 1300 ° C. causes MnS in the steel to be melted and causes deterioration of magnetic properties. It is preferably 1100 to 1250 ° C. After hot rolling, cold rolling is performed as it is, or cold rolling is performed after hot-rolled sheet annealing for improving magnetic properties. The annealing temperature in hot-rolled sheet annealing is 600 to 1100 ° C. 600
If the temperature is lower than 0 ° C, the effect of improving the magnetic properties is not obtained, and if the temperature exceeds 1100 ° C, problems such as breakage occur during cold rolling. Cold rolling can be repeated multiple times with an intermediate anneal at 600-1000 ° C interposed. Finish annealing after cold rolling is performed at 700 to 1100 ° C. by continuous annealing.

After the finish annealing, the surface of the steel sheet is subjected to surface coating for the purpose of increasing the number of punches. The coating material is resin alone or a mixture of resin and inorganic binder. As the resin, vinyl acetate resin, epoxy resin, acrylic resin, polyethylene, polypropylene or the like can be used, and as the inorganic binder, one or more of chromate, borate, colloidal silica, layered mica compound and the like are used. be able to. The coating film thickness is 0.1-5 μm. If it is less than 0.1 μm, the effect of improving the punching property is small, and if it exceeds 5 μm, the adhesion of the coating is deteriorated, and the space factor is deteriorated when the electromagnetic steel sheets are laminated, so that the performance of the final product such as a transformer is deteriorated. As a coating method, a commonly used coating method such as a roll coater method, a curtain flow method, a dip method may be used.

[0022]

EXAMPLES Examples of the present invention will be shown below, and the effects of the present invention will be clarified by comparison with comparative examples.

A slab (227 mm thick x 1000 mm wide) having the composition shown in Nos. 1 to 8 in Table 1 was heated to 1150 ° C. and hot-rolled normally to finish a hot-rolled coil having a thickness of 2.3 m. . After each pickling each hot rolled coil normally,
The electrical steel sheet was finished by the process shown in. For the surface coating, a mixture of acrylic resin emulsion, magnesium chromate and boric acid was applied to the surface of the steel sheet by a roll coater method.

The iron loss of the manufactured electromagnetic steel sheet of each composition is 25
cm Epstein tester and 200 ℃
After aging treatment for × 100 hr, the iron loss was measured again,
I examined the magnetic aging. Also, the outer diameter 1 made of SKD-11
A ring tool having an inner diameter of 80 mm and an inner diameter of 80 mm is used, and kerosene is used as a punching oil. A ring plate is punched from a magnetic steel sheet by a 25 ton press, and an outer diameter L in the rolling direction and an outer diameter C in a direction perpendicular to the rolling direction are obtained. Was measured. The punching speed was 200 trokes / minute, and the clearance was 6%. The measurement results are shown in Table 3. Further, the amounts of S and Ti of Nos. 1 to 6 and the scope of the present invention are shown in FIG.

Nos. 1 to 4, which are examples of the present invention, are 0.003 to 0.
Since it contains 08% C and 0.01 to 0.07% P,
Good dimensional accuracy (roundness) after punching. Also, 0.
Since it contains Ti of 004 to 0.036%, magnetic aging is effectively suppressed, and iron loss is also good. However, No. 1
Since the Ti content is relatively small, the dimensional accuracy and core loss characteristics after punching are slightly inferior.

On the other hand, No. 5 does not contain Ti, so
Magnetic aging is remarkable, and dimensional accuracy and iron loss after punching are also poor. Since No. 6 contains Ti in an excessive amount, the magnetic aging is suppressed, but the iron loss is significantly increased, and the dimensional accuracy after punching is slightly inferior. Nos. 7 and 8 lack P, so the dimensional accuracy (roundness) after punching is poor.

[0027]

[Table 1] Note) Underline is outside the scope of the present invention

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

As described above, the non-oriented electrical steel sheet of the present invention effectively suppresses magnetic aging, which is a problem when the dimensional accuracy after punching is improved by adding C and P, by a small amount of Ti. In addition to suppressing the increase of iron loss, which is a problem with the addition of Ti, and positively improving it, the punching property and the magnetic properties are remarkably excellent.

[Brief description of drawings]

FIG. 1 is a chart showing the effect of the ranges of P and Ti of the present invention and the respective amounts on the characteristics of steel sheet.

Claims (1)

[Claims] 1. A weight ratio of C: 0.01% or less and Si: 3.2.
% Or less, Mn: 1.0% or less, S: 0.01% or less, Sol.A
l: 0.01 to 2.0%, P: 0.005 to 0.1%, Ti: 0.
A non-oriented electrical steel sheet containing 001% or more and less than 0.05% and the balance being Fe and unavoidable impurities and having excellent punchability and magnetic properties.