JPH08325678A - Nonoriented silicon steel sheet excellent in core loss after stress relieving annealing and its production - Google Patents

Abstract

PURPOSE: To attain low core loss and high magnetic flux density by forming the compsn. of a steel into the one contg. specified amounts of C, Si, Mn, Ti, Sb, Zr, Al and rare earth metals, and the balance iron with inevitable impurities. CONSTITUTION: The componental compsn. of a steel is formed of, by weight, <=0.001% C, 1.0 to 2.5% Si, 0.10 to 1.5% Mn, <=15ppm Ti, 0.002 to 0.5% Sb, <=80ppm Zr, 0.2 to 1.5% Al, 2 to 80ppm rare earth metals, and the balance iron with inevitable impurities. This steel is cast to form into a slab, which is, directly or after cooling, reheated, is thereafter subjected to hot rolling, is subjected to cold rolling for one time or >= two times including process annealing and is subsequently subjected to finish annealing. Thus, it can sufficiently meet the requirement of improving the characteristics of the quality of the nonoriented silicon steel sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention proposes a non-oriented electrical steel sheet which is excellent in magnetic properties and economical and a manufacturing method thereof.

Non-oriented electrical steel sheets are used for iron cores of electric equipment such as rotors and transformers. In recent years, the trend toward higher efficiency of these electric devices has increased, and for non-oriented electrical steel sheets used as their iron core materials, there is a strong demand for higher magnetic flux density and lower iron loss as well as improved economic efficiency. It has become to.

[0003]

2. Description of the Related Art As a means of reducing iron loss of non-oriented electrical steel sheets, there is a method of optimizing the crystal grain size and increasing the specific resistance. The crystal grain size is 150 to 200 μm and the core loss is the minimum. It is known that the increase in the specific resistance and the increase in the specific resistance can be achieved by increasing the Si and Al contents, and thus the iron loss is reduced.

However, when the Si and Al contents are increased, the saturation magnetic flux density decreases. -Punching performance is reduced. It is well known that there are problems such as the above.

Particularly, the punching property is an important characteristic required for a non-oriented electrical steel sheet, and it is usual for a customer to punch the product into a predetermined shape and then subject it to a strain relief annealing to obtain a complicated shape. Excellent punching accuracy is required for punching. This punching accuracy deteriorates due to an increase in hardness due to an increase in the amount of alloy components and an increase in crystal grain size. Practically, the Si content exceeds 1.0 wt% and the crystal grain size of the product plate is
If it exceeds 40 μm, the punching accuracy will be significantly deteriorated, causing a problem.

In order to satisfy such contradictory properties of iron loss and punching precision, conventionally, a product sheet crystal grain size of about 20 μm was used for a low Si composition, and after punching by a customer,
The grain is coarsened by applying strain relief annealing,
It was trying to reduce iron loss.

As described above, in recent years, there has been an increasing trend toward higher efficiency in rotating machines and the like, and even if punching performance is sacrificed to some extent,
There has been a strong demand for a material having a high magnetic flux density and an excellent crystal grain growth property during strain relief annealing that can finally obtain a very low iron loss. In order to meet this requirement, it is important to moderately increase the Si and Al contents and to further reduce the iron loss after the stress relief annealing (coarse grain size coarsening). Among them, increasing the strain relief annealing temperature is effective for coarsening the crystal grain size, but this is a cost problem, and the annealing temperature exceeding 750 ° C is not practically adopted.

Under these circumstances, a non-oriented electrical steel sheet capable of high-temperature magnetic flux density and finally low iron loss, and having excellent grain growth during strain relief annealing, which enables low-temperature short-time annealing. Until now, there has been no technology to manufacture.

By the way, it is well known that the cause of inhibiting crystal grain growth is inclusions or precipitates finely dispersed in matrix iron. Inclusions and precipitates dispersed in the non-oriented electrical steel sheet include various oxides (for example, SiO ₂ , Mn
O, Al ₂ O _3, etc.) and various nitrides and sulfides (eg, AlN, TiN, ZrN, MnS, etc.). Hereinafter, reference will be made to these oxides, nitrides and sulfides.

If the oxide Al is added in an amount of 0.2 wt% or more, it is sufficiently agglomerated in the molten steel stage,
Since it can be brought up, the problem is gone.

Si: High sulfide γ → α transformation point: In a non-oriented electrical steel sheet of 1.0 wt% or more, rare earth components (REM: 15 elements up to atomic number 57 to 71 and 2 elements of Sc and Y) were added. It is known that S can be fixed as a stable and coarse sulfide by adding an alloy containing 17 elements (general term of 17 elements) or Ca, and the technique is disclosed in JP-A-51-62115 (in Japanese). Low non-oriented silicon steel sheet), No. 52-2824 (Cold rolled non-oriented silicon steel treated with rare earth metal and its manufacturing method), No. 55-34675 (Method for producing non-oriented silicon steel sheet with less ridging) , Ibid 56-10
No. 2550 (non-oriented silicon steel sheet with stable magnetic properties), 57
No. 192219 (method for producing non-oriented silicon steel sheet with low iron loss), No. 58-164724 (method for producing non-oriented electrical steel sheet having excellent magnetic properties), and the like.

Nitride Until now, in the non-oriented electrical steel sheet, it is necessary to fix the nitride to 0.
Although 2 wt% or more of Al or B is added, such a steel sheet has almost no crystal grain growth by strain relief annealing at a low temperature for a short time, and its iron loss characteristics are not completely satisfactory.

As described above, in the range of conventional knowledge, the crystal grain growth property at low temperature for a short time (for example, 725 ° C. for 1 hour) for strain relief annealing is insufficient, and the obtained iron loss is not sufficient at all. It was

[0014]

In view of the above-mentioned circumstances, the present invention is excellent in economic efficiency, and is excellent in grain growth during strain relief annealing. Therefore, low iron loss and high magnetic flux density are obtained after the strain relief annealing. It is an object of the present invention to propose a non-oriented electrical steel sheet and a manufacturing method thereof.

As described above, increasing the content of Si, Al or the like to reduce the iron loss generally lowers the magnetic flux density and the punchability, but in the present invention, the magnetic flux density and the punchability are reduced. It is intended to achieve a low iron loss without damaging the steel.

[0016]

[Means for Solving the Problems] In recent years, it has become possible to quantitatively analyze even minor components in the PPm order by improving the accuracy of analysis. Therefore, the inventors conducted various studies on the effects of trace components and Si and Al contents in steel on the magnetism after low-temperature and short-time strain relief annealing.
As a result, it was found that trace amounts of Ti and Zr of about 10 wtPPm significantly affect the iron loss after low-temperature and short-time strain relief annealing, and in addition, the Al amount contributes to the above influence in the high Si amount region. Got

Further, the inventors have remarkably improved the crystal grain growth property during strain relief annealing by controlling the Al amount in a high Si material to reduce Ti and Zr and coexisting with a trace amount of a rare earth component. The present invention has been accomplished by finding that a non-oriented electrical steel sheet having excellent iron loss after low-temperature and short-time strain relief annealing, which has been impossible in the past, can be industrially produced.

That is, the gist of the present invention is as follows. C: 0.01 wt% or less, Si: 1.0 wt% or more, 2.5 wt% or less, Mn: 0.10 wt% or more, 1.5 wt% or less, Ti: 15 wtPPm or less, Sb: 0.002 wt% or more, 0.5 wt% or less, Zr: 80wtPPm
Below, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 2
A non-oriented electrical steel sheet excellent in iron loss after strain relief annealing, characterized by containing wtPPm or more and 80wtPPm or less and the balance being a composition of iron and unavoidable impurities (first invention).

The steel having the chemical composition described in the first aspect of the invention is cast into a slab, which is hot-rolled directly or after cooling and then re-heating, followed by one or two or more cold-rolling steps with intermediate annealing. This is a method for producing a non-oriented electrical steel sheet having excellent iron loss after strain relief annealing, which is characterized by performing finish annealing after performing (second invention).

The steel having the composition as described in the first aspect of the invention is cast into a slab, which is either directly or after cooling, reheating, hot rolling, and hot-rolled sheet annealing in the temperature range of 800 to 1100 ° C. A method for producing a non-oriented electrical steel sheet having excellent core loss after strain relief annealing, which comprises performing cold annealing at least once or at least two times with intermediate annealing sandwiched, and then performing finish annealing (3rd invention).

[0021]

The operation of the present invention will be described below with reference to experimental examples. The inventors conducted experiments and studies on the crystal grain growth property of the non-oriented electrical steel sheet during low temperature strain relief annealing in more detail than the conventional knowledge. As a result, trace amount of Zr, Ti,
It was clarified that REM significantly affects the crystal grain growth during low temperature short time strain relief annealing, and that Al addition is effective for the crystal grain growth in the high Si content region.

The experimental results will be described in order below for each component. These experiments were conducted on a laboratory scale. The effect of Zr Zr on grain growth during low temperature short time strain relief annealing was investigated. Si with various Zr concentrations: 1.5 wt
%, Mn: 0.55wt%, Ti: 5wtPPm and Al: 0.5wt% steel hot-rolled, then cold-rolled, then 790
Finished annealing was performed at ℃ for 30 seconds to make each product plate. The crystal grain size of these product plates was in the range of 25 to 27 μm. Afterwards, apply these product plates to 750 ° C for 2 hours and 725
Strain relief annealing was carried out at ℃ for 1 hour, and iron loss (W15 / 50) and crystal grain size were investigated. The results of those investigations are shown in FIGS. 1 and 2.

FIG. 1 is a graph showing the effect of Zr concentration on the iron loss (W15 / 50) after strain relief annealing at 750 ° C. for 2 hours and 725 ° C. for 1 hour. 725 as is clear from FIG.
In the stress relief annealing at 1 ° C for 1 hour, good iron loss was obtained only when the Zr concentration was less than 5wtPPm. And the Zr concentration is 5wt
For PPm and above, strain relief annealing conditions are from 750 ° C for 2 hours
Approximately 0.7W / kg by reducing the temperature to 725 ° C for 1 hour
Deterioration of iron loss has occurred.

On the other hand, FIG. 2 shows 750 ° C. for 2 hours and 725 ° C.
-A graph showing the effect of Zr concentration on the crystal grain size after 1 hour of strain relief annealing. As is clear from FIG. 2, 72
In the strain relief annealing at 5 ° C for 1 hour, good grain growth was obtained only when the Zr concentration was less than 5 wtPPm. From these results, the cause of iron loss deterioration during low temperature short time annealing is the growth of grain size. I know that it is defective.

It is considered that the difference in the crystal grain growth property depending on the strain relief annealing conditions is strongly influenced by the fine precipitates containing Zr which is a grain growth inhibitor in the low temperature short time strain relief annealing.

As described above, when the Zr concentration was less than 5 wtPPm, it was revealed that the iron loss after the low temperature short-time strain relief annealing was good, but the steel containing Al of more than 0.2 wt% was found. It is extremely difficult to reduce the Zr concentration to less than 5 wtPPm in the smelting on a factory scale. The reason is that even if Zr in ferroalloy added to molten steel is reduced, Zr in slag and refractories is reduced.
The compound is reduced by Al and the Zr concentration in steel is 5wtPPm
That is all.

Therefore, the inventors investigated the effect of various additive components on the iron loss after strain relief annealing at low temperature for a short time. An example of the survey results is shown below.

Si having various Zr concentrations: 1.5 wt%, Mn:
Steel with 0.55wt%, Ti: 5wtPPm and Al: 0.5wt% with REM added at 20wtPPm and steel without additive were each hot-rolled and then cold-rolled, then 790 ℃ Finish annealing was performed for 30 seconds to obtain a product plate.
The crystal grain size of these product plates was in the range of 24-26 μm.

Thereafter, these product sheets were subjected to strain relief annealing at 725 ° C. for 1 hour, and then the iron loss (W / 15/50) was investigated.
The results of those investigations are shown in FIG. Fig. 3 shows the iron loss (W /
15 is a graph showing the influence of Zr concentration on 15/50). FIG.
As is clear from the above, even when strain relief annealing was carried out at a low temperature for a short time, good iron loss up to a Zr concentration of 80 wtPPm could be obtained by adding REM.

Thus, a very small amount (2-80 wtPPm) of RE
It was newly found that the inclusion of M can eliminate the adverse effect of Zr on iron loss after low temperature short time strain relief annealing.

Ti Si having various Ti concentrations: 1.5 wt%, Mn: 0.55 wt%, Z
REM for the composition of ingredients: r: 5wtPPm and Al: 0.5wt%
For steel with and without addition of 20 wtPPm
Each is hot-rolled, then cold-rolled, then 790 ° C
・ Finished annealing was performed for 30 seconds to make a product plate. The grain size of these product plates ranged from 23 to 27 μm.

After that, these product sheets were subjected to strain relief annealing at 725 ° C. for 1 hour, and then the iron loss (W / 15/50) was investigated.
The results of those investigations are shown in FIG. Fig. 4 shows the iron loss (W / W) after strain relief annealing at 725 ° C for 1 hour with and without REM addition.
15 is a graph showing the effect of Ti concentration on 15/50). FIG.
As is clear from the above, the iron loss deteriorates as the Ti concentration increases, and this tendency becomes remarkable especially when REM is not added, but when REM is added and the Ti concentration is 15 wtPPm or less,
It can be seen that good iron loss can be obtained by setting the content to 10 wtPPm or less.

REM Si having various REM concentrations: 1.5 wt%, Mn: 0.55 wt%,
Steel containing Ti: 8 wtPPm, Zr: 42 wtPPm and Al: 0.5 wt% was hot-rolled, then cold-rolled, and then finish-annealed at 790 ° C for 30 seconds to obtain a product sheet. The grain size of these product plates was 24-47 μm.

After that, these product sheets were subjected to strain relief annealing at 725 ° C. for 1 hour and then the iron loss (W15 / 50) was investigated. The results are shown in FIG. Fig. 5 is a graph showing the effect of REM concentration on iron loss (W15 / 50) after strain relief annealing at 725 ° C for 1 hour. As is clear from FIG. 5, it is clear that remarkably good iron loss can be obtained when the REM concentration is 2 to 80 wtPPm, particularly 5 to 50 wtPPm.

Sb Si: 1.5 wt%, Mn: 0.55 wt%, Ti: 5 wtPPm, Zr: 15 wt
PPm, Al: 0.5 wt% and REM: 20 wtPPm of the composition with Sb added at a concentration of 0.05 wt% and the additive-free steel were hot-rolled and cold-rolled, respectively, and then
Finished annealing was performed at 790 ° C for 30 seconds to obtain a product plate.

The crystal grain size of these product plates was measured, and the magnetic flux density (B ₅₀ ) and iron loss (W 15/50) were measured. As a result, the crystal grain size was in the range of 25 to 27 μm, and the magnetic flux density and iron loss were the values shown in Table 1.

[0037]

[Table 1] As is clear from Table 1, the magnetic flux density (B ₅₀ ) is improved by adding Sb.

As described above, in the non-oriented electrical steel sheet containing 1.5% Si-0.5% Al, REM is contained in the range of 2 to 80 wtPPm and the Ti content is set to 15 wtPPm or less, so that the Zr content is It was revealed that up to 80 wtPPm, good iron loss can be obtained after low temperature and short time strain relief annealing.
Therefore, the present invention enables industrial-scale production of a non-oriented electrical steel sheet having excellent iron loss after low-temperature short-time strain relief annealing, which has been impossible in the past.

The differences between the present invention and the above-mentioned prior art will be listed below. JP-A-51-62
115, 55-34675, 56-102550 and 57-
Japanese Patent No. 192219 discloses that Si having a high γ → α transformation point (or no transformation): 1.0% by weight or more of low-S
It is a technology related to the addition of rare-earth components for liquefying and fixing S. However, it is suggested from these conventionally known techniques that, by setting Ti to 15 wtPPm or less and the combined effect of adding a rare earth component, a remarkably good iron loss can be obtained in low-temperature short-time strain relief annealing. Absent.

JP-A-52-2824 discloses that Si: 0.5-4.0%
Steel, No. 58-164724, is a technique for adding rare earth elements in Si steel of 4% or less, which is a technology for reducing S and fixing S in medium and high Si steels having a high γ → α transformation point. is there. However, since the purpose of adding the rare earth component in the present invention is to render Zr harmless, it is understood that this is a technique different from the present invention. Furthermore, Ti is 15wtPPm
There is no suggestion from these prior arts that a remarkably good iron loss can be obtained after low temperature and short time strain relief annealing due to the combined effect of the following and addition of a rare earth component.

Japanese Unexamined Patent Publication No. 3-215627 discloses Si: 0.1 to 1.4.
%, Al: This is a technology for adding rare earth components in non-oriented electrical steel sheets of less than 0.2%. On the other hand, the feature of the present invention is that Al is 0.2 to 1.5 wt% and Ti is 15 wtPPm or less, and due to the combined effect of the addition of a rare earth component, remarkably good grain growth during low temperature short time strain relief annealing, In addition, good iron loss can be obtained, and the effect thereof is described in the above-mentioned JP-A No.
It is not suggested at all from the publication of -215627, and it can be said that the present invention is a further advanced technology.

It is known that the addition of Sb improves the texture (improves the magnetic flux density).
The contribution to the optimization of the texture has not been confirmed so far, and it is a new finding that the effect of Sb addition appeared in this component system.

Next, with respect to the component composition of the present invention, the reasons for limitation and the preferable ranges will be described. C: 0.01 wt% or less C deteriorates the magnetic properties due to the precipitation of carbides, so the C content of the product is 0.01 wt% or less.

Si: 1.0 to 2.5 wt% Si is a useful component for reducing iron loss by increasing the specific resistance. The higher the content, the more effective the iron loss is, but on the other hand, it increases the hardness and deteriorates the punching accuracy. If the content is less than 1.0 wt%, the decrease in iron loss is insufficient, and if it exceeds 2.5 wt%, the punchability deteriorates. Therefore, its content is 1.0 wt% or more, 2.5 wt%
Below.

Mn: 0.10 to 1.5 wt% Mn has an advantageous function for fixing iron loss by fixing S as coarse MnS. Therefore, the content is set to 0.10 wt% or more, preferably 0.5 wt%. The above is good. On the other hand, an increase in the Mn content deteriorates the magnetic flux density, so the upper limit of the Mn content is 1.5 wt%, but preferably 1.0 wt%.

Ti: 15 wtPPm or less Ti has a very small amount of 15 wtPPm or less in order to obtain good iron loss because it deteriorates the grain growth property during low-temperature short-time stress relief annealing and remarkably deteriorates iron loss. However, in order to obtain a better iron loss, it is desirable to set it to 10 wtPPm or less.

The effect is small even if Ti alone is 15 wtPPm or less, and by adding REM at the same time, the grain growth property during low temperature short time strain relief annealing becomes good.

Sb: 0.002 to 0.5 wt% Sb is a grain boundary segregation component and is known as a component that contributes to (110) orientation increase and (111) orientation reduction as a texture for obtaining a high magnetic flux density. . In the component system of the present invention, in order to significantly improve the magnetic flux density, the content is 0.002 wt.
If it is less than%, the effect is poor, and if it exceeds 0.5 wt%, the effect is saturated. Therefore, its content is 0.002 wt%
It should be above 0.5wt%.

The effect of adding Sb is manifested by controlling the contents of Ti, Zr and REM.
The reason is not clear, but Sb that contributes to texture formation
However, it is considered that the latent effect becomes remarkable by suppressing the action of the factor that inhibits the grain growth.

Zr: 80 wtPPm or less Zr deteriorates the iron loss after low temperature and short time strain relief annealing in a very small amount, so it is desirable to reduce it as much as possible.
Achieving industrial stability below wtPPm will lead to significant cost increase. Therefore, in the present invention, Zr is rendered harmless by adding REM within the range of Zr: 5 to 80 wtPPm, which can be achieved industrially stably. Therefore, the effect of reducing iron loss becomes remarkable by adding Zr to 80 wtPPm or less together with the addition of REM, so the content should be 80 wtPPm or less.

Al: 0.2 to 1.5 wt% Al, like Si, is a component that increases the specific resistance of steel and contributes to lower iron loss. Therefore, the larger the content, the greater the contribution to the reduction of iron loss, but if it exceeds 1.5 wt%, the magnetic flux density and the punchability are deteriorated. In addition, the content is 0.2 wt%
When the amount is less than the above, the AlN generated becomes fine, the growth property of the crystal grains is deteriorated, and the iron loss cannot be improved. Therefore, its content should be 0.2 wt% or more and 1.5 wt% or less.

REM: 2 to 80 wtPPm REM is a Zr compound which is unavoidably mixed in steelmaking on an industrial scale by containing one or more of these components in a total amount of 2 to 80 wtPPm. It is possible to avoid adverse effects on the crystal grain growth during low temperature short time strain relief annealing. In the above, the content of REM is 2wt
The effect is exhibited at PPm or more, but preferably 5 wtPP
It is better to contain m or more. On the other hand, excessive addition causes RE
Since the inclusions formed by M increase and the problem of the inhibition of the crystal grain growth by the REM inclusions themselves becomes a problem, the content is set to 80 wtPPm or less, preferably 50 wtPPm or less.

The present invention is not particularly limited to the components other than those mentioned above, but the preferred ranges are as follows.

P: 0.2 wt% or less P can be added in order to improve the punching property, but if the content exceeds 0.2 wt%, the cold rolling property deteriorates, so the content is P.
It is desirable to set it to 0.2 wt% or less.

S: 0.01 wt% or less S forms MnS together with Mn, which becomes an obstacle to domain wall movement and crystal grain growth and deteriorates magnetic properties. Therefore, the upper limit of its content is preferably 0.01 wt%.

N: 0.01 wt% or less N forms a nitride, which interferes with domain wall movement and crystal grain growth and deteriorates magnetic properties. Therefore, the upper limit of its content is preferably 0.01 wt%.

O: 50 wtPPm or Less If O is contained in an amount of 50 wtPPm or more, it becomes an obstacle to domain wall movement and crystal grain growth and deteriorates magnetic properties. Therefore, its content is preferably 50 wtPPm or less.

Next, the reasons for limiting the manufacturing conditions of the present invention and suitable manufacturing conditions will be described.

The steel is melted by a conventional steel-making method such as a converter and degassing, and is made into a slab by continuous casting or a casting-ingot-making method.

Thereafter, the slab is hot-rolled, and either a method of reheating the slab and then hot-rolling it, or a method of directly hot-rolling the slab without reheating it can be applied.

In order to obtain a particularly high magnetic flux density as the magnetic property, the crystal grains of the hot-rolled sheet are coarsened by hot-rolled sheet annealing or self-annealing during winding after hot rolling. It is effective to improve the organization. As the hot-rolled sheet annealing, either box annealing (for example, 850 ° C. for 1 hour) or continuous annealing (for example, 950 ° C. for 2 minutes) can be applied.

Here, an experimental example in which the hot-rolled sheet annealing conditions are changed will be described. A slab having the composition shown in Table 2 was hot-rolled, annealed at a temperature of 950 ° C for various soaking times, cold-rolled, and then finish-annealed.
The magnetic flux density was investigated for the steel sheet that had been subjected to strain relief annealing at 725 ° C for 1 hour.

[0063]

[Table 2] Table 2 also shows these hot rolled sheet annealing conditions and investigation results.

As is clear from Table 2, in the component system of the present invention (Sample No. 1), since the crystal grain growth property during strain relief annealing is remarkably excellent, a good close packing density is conventionally obtained. It can be seen that the hot-rolled sheet annealing that required 5 minutes for 40 seconds or less can be achieved. As a result, magnetic flux density at low cost,
A product with excellent iron loss can be obtained.

In the above, when the hot-rolled sheet annealing temperature is less than 800 ° C., the effect of coarsening the hot-rolled sheet crystal grains is small,
Since it is economically disadvantageous to exceed ℃, the temperature is 800
It is preferable that the temperature is not less than 0 ° C and not more than 1100 ° C (third invention).

Then, after cold rolling, finish annealing is performed to obtain a product plate. At that time, it is carried out by one of a method of performing final annealing by one cold rolling to obtain a product sheet thickness and a method of performing final annealing by performing cold rolling two or more times with intermediate annealing interposed therebetween to obtain a product sheet thickness.

Any of the usual methods can be applied to the finish annealing, but if the crystal grain size of the product plate is too large, the punching precision is remarkably impaired. Therefore, the crystal grain size of less than 40 μm, preferably 10 to 30 μm. Annealing conditions (temperature and time)
Should be selected. Further, there is no problem even if an insulating coating is formed on the surface of the steel sheet by a known method.

[0068]

【Example】

Example 1 A slab was prepared by melting in a converter in various component compositions, degassing, and continuous casting to form slabs, which were directly hot-rolled without cooling to form hot-rolled sheets. Then, after hot-rolled sheet annealing at 920 ° C for 2 minutes, it is pickled and cold-rolled to give a sheet thickness of 0.5 m.
A cold-rolled sheet of m was prepared, and after finishing annealing at 800 ° C for 15 seconds, an insulating coating was applied to each of the product sheets. At that time, the crystal grain size of each product plate was 35 μm or less. After that, each product plate was sheared and then subjected to strain relief annealing at 725 ° C for 1 hour in a nitrogen atmosphere.
The magnetic properties were investigated by cm Epstein method. Table 3 shows the analysis results of the analysis components of each product plate and the magnetic properties after the strain relief annealing.

[0069]

[Table 3] As is clear from Table 3, the conforming examples (Samples No. 1 and 2) conforming to the present invention have good punching accuracy and are superior in magnetic flux density and iron loss to the comparative examples.

Example 2 Various components were melted in a converter, degassed and continuously cast into slabs, which were directly hot-rolled without cooling to obtain hot-rolled sheets. Then, after pickling, cold rolling was performed to obtain a cold rolled sheet having a sheet thickness of 0.5 mm, then finish annealing was performed at 800 ° C. for 15 seconds, and an insulating coating was applied to each to obtain a product sheet. At that time, the crystal grain size of each product plate is 35 μm
It was below. After that, each product plate was sheared and then subjected to strain relief annealing at 725 ° C. for 1 hour in a nitrogen atmosphere, and the magnetic properties of the obtained annealed plates were investigated by the 25 cm Epstein method. Table 4 shows the analysis results of the analytical components, punching accuracy, and magnetic properties after strain relief annealing of each product plate.

[0071]

[Table 4] As is apparent from Table 4, the conforming examples (Samples No. 1 and 2) conforming to the present invention have good punching accuracy and are superior in magnetic flux density and iron loss to the comparative examples.

[0072]

EFFECTS OF THE INVENTION The present invention improves grain growth by adding REM and controlling Ti and Zr as impurities, and improves texture by adding Sb to reduce iron loss after strain relief annealing. And high magnetic flux density Si:
A non-oriented electrical steel sheet of 1.0 wt% or more. According to the present invention, good iron loss with high magnetic flux density can be obtained by strain relief annealing at low temperature for a short time without impeding punching workability. With the trend toward higher efficiency of electrical equipment, it is possible to fully meet the demands for improving the quality characteristics of the non-oriented electrical steel sheet used as the iron core material, and because it is also economically advantageous, its industrial effect Is extremely large.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of Zr concentration on iron loss (W15 / 50) after strain relief annealing at 750 ° C. for 2 hours and 725 ° C. for 1 hour.

FIG. 2 is a graph showing the effect of Zr concentration on the crystal grain size after strain relief annealing at 750 ° C. for 2 hours and 725 ° C. for 1 hour.

FIG. 3 is a graph showing the effect of Zr concentration on iron loss (W15 / 50) after strain relief annealing at 725 ° C. for 1 hour with and without REM addition.

FIG. 4 is a graph showing the effect of Ti concentration on iron loss (W15 / 50) after strain relief annealing at 725 ° C. for 1 hour with and without REM addition.

[Fig. 5] Iron loss (W15 / W) after strain relief annealing at 725 ° C for 1 hour
FIG. 50 is a graph showing the effect of REM concentration on 50).

Claims (3)

[Claims] 1. C: 0.01 wt% or less, Si: 1.0 wt% or more, 2.5 wt% or less, Mn: 0.10 wt% or more, 1.5 wt% or less, Ti: 15 wtPPm or less, Sb: 0.002 wt% or more, 0.5 wt % Or less, Zr: 80 wtPPm or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 2 wtPPm
As described above, a non-oriented electrical steel sheet excellent in iron loss after strain relief annealing, characterized by containing 80 wtPPm or less and the balance being composition of iron and unavoidable impurities. 2. C: 0.01 wt% or less, Si: 1.0 wt% or more, 2.5 wt% or less, Mn: 0.10 wt% or more, 1.5 wt% or less, Ti: 15 wtPPm or less, Sb: 0.002 wt% or more, 0.5 wt% % Or less, Zr: 80 wtPPm or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 2 wtPPm
As a result, a steel containing 80wtPPm or less and the balance of iron and unavoidable impurities is cast into a slab, which is directly or after cooling and reheating, and then hot rolling, once or twice with intermediate annealing. A method for producing a non-oriented electrical steel sheet excellent in iron loss after strain relief annealing, which comprises performing finish annealing after performing the above cold rolling. 3. C: 0.01 wt% or less, Si: 1.0 wt% or more, 2.5 wt% or less, Mn: 0.10 wt% or more, 1.5 wt% or less, Ti: 15 wtPPm or less, Sb: 0.002 wt% or more, 0.5 wt. % Or less, Zr: 80 wtPPm or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 2 wtPPm
Above, 80wtPPm or less is contained, and the balance is steel with iron and unavoidable impurities composition cast into a slab, directly or after cooling and reheating, then hot rolling, 800-1100 ℃
Non-oriented with excellent iron loss after strain relief annealing, characterized in that after hot-rolled sheet annealing in the temperature range of 1, the cold rolling is performed once or twice or more with intermediate annealing, and then finish annealing is performed. For manufacturing high-performance electrical steel sheet.