JPH083699A - Nonoriented silicon steel sheet excellent in iron loss after stress relief annealing and its production - Google Patents

Abstract

PURPOSE:To accelerate the growth of crystal grains at the time of short-time stress relief annealing at low temp. and to obtain superior iron loss characteristics by adding Al and trace amount of REM to a low Si silicon steel. CONSTITUTION:A silicon steel, having a composition consisting of, by weight ratio, <=0.01% C, <=1.0% Si, 0.1 to 1.5% Mn, 0.2X1.5% Al, 2 to 80ppm REM, and the balance Fe with inevitable impurities, is used. This steel is cast, and the resulting slab is subjected, directly or after cooling, to reheating and then to hot rolling. The resulting rolled plate is subjected, in the as-rolled state or after hot rolled plate annealing or self-annealing, to cold rolling once or two or more times and then to finish annealing. Further, it is preferable to control the amounts of Ti and Zr inevitably mixing into the composition, to 15ppm and <=80ppm, respectively. By this method, the nonoriented silicon steel sheet, having iron loss (W15/50)<4.0W/kg after stress relief annealing at 725 deg.C for 1hr, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to low Si having excellent magnetic properties.
A non-oriented electrical steel sheet and a method for manufacturing the same are proposed. Non-oriented electrical steel sheets are used for iron cores of rotating machines and transformers. In order to increase these energy efficiency,
It is necessary to reduce the iron loss of non-oriented electrical steel sheets. In recent years, it has become important to improve the efficiency of electric devices for the purpose of energy saving, and there is an increasing demand for low iron loss even in non-oriented electrical steel sheets.

[0002]

2. Description of the Related Art As means for reducing iron loss in non-oriented electrical steel sheets, there is optimization of crystal grain size and high Si content. It is known that the iron loss is minimized when the crystal grain size is 150 to 200 μm, and that the iron loss is reduced by increasing the Si content. On the other hand, punching accuracy is also an important characteristic required for non-oriented electrical steel sheets. The non-oriented electrical steel sheet is often punched into a predetermined shape by a consumer and then subjected to strain relief annealing. At that time, a particularly excellent punching accuracy is required because it is punched into a complicated shape, but if Si exceeds 1.0% or the crystal grain size of the product plate exceeds 40 μm, the punching accuracy is significantly deteriorated.

Conventionally, in order to satisfy such contradictory properties of iron loss and punching precision, the product sheet grain size is reduced with a low Si composition.
It was set to about 20 μm, and after punching by the customer, strain relief annealing was performed for 2 hours at 750 ° C. to coarsen the crystal grains and reduce iron loss. However, in recent years, due to the decrease in the stress relief annealing temperature and the reduction in the stress relief annealing time (for example, 725 ° C for 1 hour) due to the improvement in the productivity of consumers, a non-directional electromagnetic field that is excellent in grain growth even at low temperatures. Steel sheets are needed. However, there has been no non-oriented electrical steel sheet that can meet this demand. It is well known that the cause of grain growth inhibition is inclusions or precipitates finely dispersed in the base iron. Inclusions and precipitates in the non-oriented electrical steel sheet include various oxides (eg, SiO ₂ , MnO, Al
₂ O ₃ etc.) and various nitrides and sulfides (eg AlN, Ti
N, ZrN, MnS, etc.). These are mentioned below.

If the oxide Al is added in an amount of 0.2% or more, it is possible to sufficiently agglomerate and float in the molten steel stage, so that there is no problem.

Si having a high sulfide γ → α transformation point: In a non-oriented electrical steel sheet having a ratio of more than 1.0%, rare earth components (REM: atomic numbers 57 to 71 15
It is known that S can be fixed as a stable and coarse sulfide by adding an alloy or Ca containing 17 elements (general term of 17 elements including Sc, Y and 2 elements).
The technology is disclosed in JP-A-51-62115 (a non-oriented silicon steel sheet with low iron loss), JP-A-52-2824 (a cold-rolled non-oriented silicon steel treated with a rare earth metal and a manufacturing method thereof), and JP-A-55-55. No. 34675 (Manufacturing method of non-oriented silicon steel sheet with little ridging), 56-
No. 102550 (non-oriented silicon steel sheet with stable magnetic properties),
57-192219 (method for producing non-oriented silicon steel sheet with low iron loss) and 58-164724 (method for producing non-oriented electrical steel sheet with excellent magnetic properties), etc. . Further, as a method of adding REM in steelmaking, in JP-A-59-43814 (a ladle refining method for molten steel used for manufacturing non-oriented electrical steel sheets with low iron loss), REM is added together with desulfurization flux. However, JP-A-59-74212 (a ladle refining method for molten steel used for manufacturing non-oriented electrical steel sheets with low iron loss) discloses a method of adding a non-reducing flux together with REM. On the other hand, in a non-oriented electrical steel sheet with a low γ → α transformation point of Si: 1.0% or less, the γ single phase occurs when the slab is heated, so the fact that the solubility of MnS in the γ phase is smaller than that in the α phase is utilized. Of 0.1% or more can be added to coarsen MnS. Regarding the addition of a rare earth component in a non-oriented electrical steel sheet with Si: less than 1.0%, Japanese Patent Application Laid-Open No. 60-145310 (a method for producing molten steel for a non-oriented electrical steel sheet with low iron loss) uses Al for deoxidation Without using Si and RE
Means for making Al <10 ppm by using M together is disclosed in JP-A-3-2156.
No. 27 (method for producing non-oriented electrical steel sheet) has Al <0.2%,
A method of direct-feed rolling with REM / S = 3 to 8 is disclosed. However, in the non-oriented electrical steel sheet obtained by these means, the iron loss after low-temperature short-time stress relief annealing was completely insufficient.

[0006] In low Si non-oriented electrical steel sheets containing 1.0% or less of nitride Si, 0.2% or more of Al and B are added to fix the nitride. There was almost no grain growth, and the iron loss characteristics were not completely satisfactory. As described above, the conventionally known means has been completely inadequate in reduction of grain growth and iron loss in low-temperature short-time stress relief annealing of a target low-Si steel.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to propose a low Si non-oriented electrical steel sheet which can obtain a good iron loss by low temperature and short time strain relief annealing, and a method for producing the same.

[0008]

[Means for Solving the Problems] In recent years, it has become possible to quantitatively analyze even trace components of 10 ppm or less in the ppm order by improving the analysis accuracy. Therefore, the inventors conducted various studies on the effect of trace components in steel on low temperature short time stress relief annealing. As a result, it became clear that in low Si steel, trace amounts of Ti and Zr of about 10 ppm deteriorate iron loss after low temperature short time stress relief annealing. Furthermore, the inventors have found that Al is 0.2 to 1.5%, Ti is 15 ppm or less, and Zr is 80% or less.
By coexisting with a trace amount of rare earth component in addition to ppm or less, the crystal grain growth property during stress relief annealing is significantly improved, and iron loss after low temperature and short time stress relief annealing, which has been impossible in the past, is excellent. They have found that grain-oriented electrical steel sheets can be industrially manufactured.

That is, the gist of the present invention is as follows. C: 0.01 wt% or less, Si: 1.0 wt% or less, Mn: 0.1 wt%
Above, 1.5 wt% or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 2 wt ppm or more, 80 wt ppm or less, and the balance is Fe and inevitable impurities A non-oriented electrical steel sheet excellent in iron loss after annealing (first invention).

C: 0.01 wt% or less, Si: 1.0 wt% or less,
Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more,
1.5 wt% or less and REM: 2 wt ppm or more, 80 wt ppm or less, and Ti and Zr unavoidable contaminations are Ti:
Non-oriented electrical steel sheet with excellent iron loss after stress relief annealing at low temperature and short time characterized by suppressing to below 15 wt ppm and Zr: 80 wt ppm, and the balance is essentially Fe composition (No. Two
invention).

A non-oriented electrical steel sheet according to the second invention having a core loss (W _15/50 ) of less than 4.0 W / kg after strain relief annealing at 725 ° C. for 1 hour (third invention).

C: 0.01 wt% or less, Si: 1.0 wt% or less,
Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more,
1.5 wt% or less and REM: 5 wt ppm or more, 50 wt ppm or less, and Ti and Zr unavoidable contaminations are contained in Ti:
Non-oriented electrical steel sheet with excellent iron loss after stress relief annealing at low temperature in a short time characterized by suppressing to 10 wt ppm or less and Zr: 80 wt ppm or less, and the balance being substantially Fe composition (4th invention).

A non-oriented electrical steel sheet according to the fourth invention, which has an iron loss (W _15/50 ) of less than 3.5 W / kg after stress relief annealing at 725 ° C. for 1 hour (fifth invention).

C: 0.01 wt% or less, Si: 1.0 wt% or less,
Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more,
Steel containing 1.5 wt% or less and REM: 2 wt ppm or more, 80 wt ppm or less, and the balance of Fe and inevitable impurities is formed into a slab after casting, and is directly or after cooling, reheated, and then hot rolled, Excellent in core loss after stress relief annealing characterized by performing finish annealing after performing one time or two or more times of cold rolling with an intermediate annealing as it is, or after performing hot-rolled sheet annealing or self-annealing. Manufacturing method of non-oriented electrical steel sheet (sixth invention).

C: 0.01 wt% or less, Si: 1.0 wt% or less,
Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more,
1.5 wt% or less and REM: 2 wt ppm or more, 80 wt ppm or less, and Ti and Zr unavoidable contaminations are Ti:
Suppressed to below 15 wt ppm and Zr: 80 wt ppm, the balance was made into a slab after casting of steel consisting essentially of Fe composition,
Directly or after cooling and then reheating, then hot rolling, as it is, or after hot-rolled sheet annealing or self-annealing, perform one or two or more cold rollings with intermediate annealing, and then perform finish annealing. A method for producing a non-oriented electrical steel sheet excellent in iron loss after stress relief annealing at low temperature in a short time (seventh invention), which is characterized by the above.

C: 0.01 wt% or less, Si: 1.0 wt% or less,
Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more,
1.5 wt% or less and REM: 5 wt ppm or more, 50 wt ppm or less, and Ti and Zr unavoidable contaminations are contained in Ti:
Suppressed to below 10 wt ppm and Zr: 80 wt ppm, and the balance was made into a slab after casting of steel consisting essentially of Fe composition,
Directly or after cooling and then reheating, then hot rolling, as it is, or after hot-rolled sheet annealing or self-annealing, perform one or two or more cold rollings with intermediate annealing, and then perform finish annealing. A method for producing a non-oriented electrical steel sheet which is excellent in iron loss after stress relief annealing at low temperature in a short time (eighth invention).

C: 0.01 wt% or less, Si: 1.0 wt% or less,
Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more,
1.5 wt% or less and REM: 5 wt ppm or more, 50 wt ppm or less, and Ti and Zr unavoidable contaminations are contained in Ti:
Suppressed to below 10 wt ppm and Zr: 80 wt ppm, and the balance was made into a slab after casting of steel consisting essentially of Fe composition,
Directly or after reheating after cooling, hot rolling, 800 ~
Characterized by performing short-time continuous hot-rolled sheet annealing in a temperature range of 1100 ° C for a soaking time of 40 seconds or less, performing cold rolling once or twice with intermediate annealing, and then performing finish annealing. A method for manufacturing a non-oriented electrical steel sheet excellent in iron loss after stress relief annealing at low temperature for a short time (ninth invention).

[0018]

The function of the present invention will be described in detail below. The present invention is subject to the above-mentioned conditions, but the background of the invention will be described.
The inventors of the present invention are more detailed than the conventional knowledge, and
Regarding grain growth during low temperature strain relief annealing of non-oriented electrical steel sheets,
As a result of research and study, it was revealed that a small amount of Ti, Zr, REM, etc. exerts a significant effect on grain growth during low temperature strain relief annealing. The details of the results are described below for each component. The following is a research on a laboratory scale.

Ti having various Ti concentrations, Si: 0.5%, Mn: 0.55%,
Steel containing Zr: 5ppm, Al: 0.3%, and REM: 2
Hot rolling the one with 0 ppm added and the one without addition,
After cold rolling, finish annealing at 780 ℃ for 30 seconds,
Product board. The grain size of these product plate crystals was 22 to 26 μm. Next, these product sheets were subjected to strain relief annealing at 725 ° C. for 1 hour and then magnetic measurements were performed to investigate the effect of Ti on iron loss after low temperature short time strain relief annealing. FIG.
Shows the effect of Ti on iron loss after stress relief annealing at 725 ° C for 1 hour. From FIG. 1, iron loss deteriorates as Ti increases, and this tendency is particularly remarkable when rare earth components are not added. On the contrary, it became clear that extremely good iron loss can be obtained by adding a rare earth component and setting Ti to 15 ppm or less, particularly 10 ppm or less.

Zr Si: 0.5%, Mn: 0.55%, Ti: with various Zr concentrations.
Steel of 5 ppm and Al: 0.3% was hot-rolled, cold-rolled, and then finish-annealed at 780 ° C. for 30 seconds to obtain a product sheet.
The grain size of the product plates was 24-26 μm. Next, these product sheets were subjected to strain relief annealing at 750 ° C. for 2 hours and 725 ° C. for 1 hour, and then magnetic measurement and cross-sectional grain size measurement were carried out. The effects on subsequent iron loss and grain growth were investigated. Zr in Figure 2
The effect on iron loss (W _15/50 ) after strain relief annealing at 750 ° C for 2 hours and 725 ° C for 1 hour is shown. As is clear from FIG. 2, in the stress relief annealing at 725 ° C. for 1 hour, good iron loss was obtained only at Zr: less than 5 ppm. When Zr: 5 ppm or more, the strain relief annealing condition was reduced from 750 ° C. for 2 hours to 725 ° C. for 1 hour at a low temperature for a short time, resulting in iron loss deterioration of about 0.7 W / kg.

In FIG. 3, Zr is 750 ° C. for 2 hours and 725 ° C.
The effect on the crystal grain size after 1 hour of strain relief annealing is shown.
From Fig. 3, Zr: 5ppm in strain relief annealing at 725 ° C for 1 hour
It was confirmed that good grain growth was obtained only when the amount was less than the range, and the cause of iron loss deterioration during low temperature short time annealing was poor grain growth.

It is considered that the difference in grain growth property depending on the strain relief annealing condition is strongly influenced by the fine precipitates containing Zr which is a grain growth inhibitor in the low temperature strain relief annealing. Thus, it was revealed that if Zr is less than 5 ppm, the iron loss after low-temperature short-time stress relief annealing is good, but
For factory-scale melting of steel containing Al> 0.2%, Zr is 5ppm.
It is very difficult to be less than. This is because even if Zr in the ferroalloy added to the molten steel is reduced, Zr in the slag and refractory is reduced by Al, and the Zr concentration in the steel is usually 5 ppm or more.

Therefore, the inventors investigated the effect of various additive components on iron loss after low temperature short time stress relief annealing. With various Zr concentrations, Si: 0.5%, Mn: 0.55%, Ti: 5
ppm, Al: 0.3% steel, REM: 20 ppm
Hot-rolled one containing REM and one without REM,
After cold rolling, finish annealing was carried out at 780 ° C for 30 seconds to obtain a product sheet. The grain size of the product plates was 24-26 μm. Next, the product sheets were subjected to stress relief annealing at 725 ° C. for 1 hour and magnetic measurements were performed.

FIG. 4 shows the effect of Zr concentration on iron loss after stress relief annealing at 725 ° C. for 1 hour. As is clear from FIG. 4, by adding the rare earth component, good iron loss could be obtained up to Zr: 80 ppm. In this way, very small amount (2-
(80ppm) Rare earth metal in steel
It was newly found that the adverse effect on iron loss after low temperature short time stress relief annealing can be eliminated.

REM (rare earth metal) Having various REM concentrations, Si: 0.5%, Mn: 0.55%,
Steel containing Ti: 7 ppm, Zr: 40 ppm, and Al: 0.3% was hot-rolled, cold-rolled, and then subjected to finish annealing at 780 ° C. for 30 seconds to obtain a product sheet. The crystal grain size of those product plates is 23 to 26.
It was μm. These product sheets were subjected to stress relief annealing at 725 ° C. for 1 hour and then magnetic measurements were performed to investigate the effect of REM on iron loss after low temperature short time stress relief annealing. Figure 5
Shows the effect of REM on iron loss after stress relief annealing at 725 ° C for 1 hour. As is clear from Fig. 5, REM is 2-80ppm
Especially, a very good iron loss was obtained at 5 to 50 ppm.

As described above, the low Si non-oriented electrical steel sheet is
Content of 15 ppm or less, Al content of 0.2 to 1.5%, and addition of rare earth component in the content range of 2 to 80 ppm
It was found that good iron loss can be obtained after low temperature short time stress relief annealing up to ppm. Therefore, the present invention enables industrial-scale production of a low-Si non-oriented electrical steel sheet having excellent iron loss after low-temperature short-time strain relief annealing, which has been impossible in the past.

Here, 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-
In the 192219 publication, etc., Si having a high γ → α transformation point (or no transformation): Middle-high Si steel exceeding 1.0%,
This is a technology related to the addition of rare earth components for lowering S and fixing S. However, according to the present invention, Si: 1.0% or less γ →
It can be understood that this is a technology different from the present invention because the low Si steel having a low α transformation point is symmetrical. Further, it cannot be inferred from these conventionally known techniques that a remarkably excellent iron loss after low-temperature short-time stress relief annealing can be obtained by the combined effect of setting Ti to 15 ppm or less and addition of a rare earth component.

Japanese Unexamined Patent Publication No. 52-2824 discloses that Si: 0.5 to 4.0%
Steel, JP-A-58-164724 is a technique for adding a rare earth component in Si steel of 4% or less. However, in any case, in the text and examples, only the case where Si: 1.0% is exceeded, and there is no description about the case where Si: 1.0% or less. Therefore, these are also the techniques related to the addition of rare earth components for lowering S and fixing S in medium-high Si steels having a high γ → α transformation point. Further, since the purpose of adding the rare earth component in the present invention is to render Zr harmless, it is understood that the above technique is different from the present invention. Further, it cannot be inferred from these conventionally known techniques that a remarkably excellent iron loss after low-temperature short-time stress relief annealing can be obtained by the combined effect of setting Ti to 15 ppm or less and addition of a rare earth component.

Japanese Unexamined Patent Publication Nos. 59-43814 and 59-74212 relate to REM desulfurization technology in steelmaking, but in both the text and examples, only the case of 3% Si steel is taken up. : No description below 1.0%, high
It is a technology related to the addition of rare earth components for lowering S and fixing S in Si steel. Further, JP-A-60-145310 aims to reduce O by simultaneously using Si deoxidation and deoxidation by adding a rare earth component in a steel having Si: 0.1 to 1.0% and Al <10 ppm. Therefore, the technology is different from the present invention.

Japanese Patent Laid-Open No. 3-215627 discloses Si: 0.1 to 1.4.
%, Al: 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%, Ti is 15 ppm or less, and due to the combined effect of the rare earth component addition, the grain growth property during the extremely low temperature short time stress relief annealing, In addition, good iron loss can be obtained, and the effect thereof is described in the above-mentioned JP-A-3-2156
Nothing can be inferred from the publication No. 27, and the present invention is understood to be a further advanced technology.

Next, various conditions of the present invention will be described. First, the reasons for limiting the component composition will be described. C: 0.01 wt% or less Since C deteriorates the magnetic properties due to the precipitation of carbides,
Its content is 0.01 wt% or less. Desirably 0.005 wt
It is preferably less than%.

Si: 1.0 wt% or less Addition of Si increases hardness and deteriorates punching accuracy. Therefore, its content is set to 1.0 wt% or less, but Si is a useful component for reducing iron loss by increasing the specific resistance, so it is desirable to contain 0.1 wt% or more.

Mn: 0.1-1.5 wt% Mn has a function of fixing S as coarse MnS, and therefore, it is contained in an amount of 0.1 wt% or more, preferably 0.2 wt% or more. On the other hand, since an increase in the amount of Mn added deteriorates the magnetic flux density, the upper limit of its content is set to 1.5 wt%, but preferably 1.
0 wt% is good. Therefore, its content is 0.1 wt% or more,
1.5 wt% or less, preferably 0.2 wt% or more, 1.0
Wt% or less is preferable.

Al: 0.2% to 1.5 wt% When Al is less than 0.2 wt%, fine AlN is produced and the grain growth property is deteriorated. Further, if the content exceeds 1.5 wt%, the magnetic flux density is deteriorated. Therefore, its content is 0.2 wt.
% Or more and 1.5 wt% or less.

REM: 2-80 wt ppm REM is unavoidable in steel making on an industrial scale by containing one or more of these components in a total amount of 2-80 wt ppm. 5 to 80 wt included
It is possible to avoid the adverse effect of ppm Zr on grain growth during low temperature short time stress relief annealing. If the content is less than 2 wtppm, the above effect is insufficient, and the content is set to 2 wtppm or more, but preferably 5 wtppm or more. On the other hand, excessive addition causes an increase in inclusions formed by REM, and there is a problem of inhibition of grain growth by the REM inclusions themselves.Therefore, the content should be 80 wt ppm or less, but preferably 50 wt ppm. ppm or less is good.

Ti: 15 wt ppm or less Ti is a very small amount and significantly deteriorates grain growth property and iron loss at the time of low temperature short time stress relief annealing. Therefore, the content is 15 wt ppm in order to obtain good iron loss. Below. Content of 10 wt pp
By setting m or less, it is possible to obtain a better iron loss. The above effect is small even if Ti alone is 15 wt ppm or less, and due to the combined effect of REM addition, grain growth during low temperature short time stress relief annealing is improved.

Zr: 80 wt ppm or less Zr deteriorates the iron loss after the stress relief annealing at a low temperature for a short time in a very small amount, so it is desirable to reduce it as much as possible, but it is 5 wt ppm.
Stable achievement of the following on an industrial scale is extremely costly. Therefore, in the present invention, Zr is made harmless by adding REM within the range of Zr: 5 to 80 wt ppm which can be achieved industrially stably. Zr together with REM addition
Content of 80 wt ppm or less, the effect of reducing iron loss after low-temperature short-time strain relief annealing becomes remarkable, so its content is 80%.
It should be below wt ppm.

In the present invention, the components other than those described above are not particularly limited, but preferred ranges will be described below.

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

S: 0.01 wt% or less S forms MnS together with Mn, obstructs domain wall movement and grain growth, and deteriorates magnetic properties.
It is desirable to set it to 01 wt% or less.

N: 0.01 wt% or less N forms a nitride, hinders domain wall movement and grain growth, and deteriorates magnetic properties, so its content is 0.01 wt%.
It is desirable to make the following.

O: 50 wt ppm or less When O is contained in an amount of 50 wt ppm or more, it interferes with domain wall movement and grain growth and deteriorates magnetic characteristics.
It is desirable to set it to 50 wt ppm or less.

Next, suitable manufacturing conditions and reasons for limiting the manufacturing conditions in the present invention will be described. The composition is adjusted to the above-mentioned composition by a conventional steelmaking method such as a converter or degassing, and cast by a continuous casting or a casting-ingot making method to obtain a slab.
Subsequently, the slab is hot-rolled, but either a method of reheating the slab and then hot-rolling it, or a method of directly hot-rolling after continuous casting without heating the slab can be applied. As a magnetic property, when trying to obtain a particularly high magnetic flux density,
It is effective to anneal the hot-rolled sheet or perform self-annealing at the time of winding after hot rolling to coarsen the crystal grains of the hot-rolled sheet and improve the texture. 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.

In recent years, hot-rolled sheet annealing has been continuous and shortened in terms of cost reduction and productivity improvement. So far, in hot-rolled sheet annealing for a short soaking time of 30 seconds, the crystal grain size of the hot-rolled sheet is not sufficiently coarsened,
It was not possible to obtain a high magnetic flux density. However, the present invention also has an effect that a high magnetic flux density can be obtained even by annealing the hot rolled sheet for a short time.

That is, the above effects will be described based on experimental examples. The slabs with the composition shown in Table 1 were hot-rolled to 95
The magnetic flux densities of the steel sheets were annealed at a temperature of 0 ° C. for various soaking times, cold rolled, finish annealed, and then subjected to strain relief annealing at 725 ° C. for 1 hour.

[0046]

[Table 1] Table 1 also shows the annealing conditions for hot-rolled sheets and the results of the investigation.

As is clear from Table 1, REM: 5 to 50 wt
With a composition that satisfies ppm, Ti: 10 wt ppm or less and Zr: 80 wt ppm or less, the grain growth property of the hot-rolled sheet is remarkably excellent. Therefore, conventionally, it took 5 minutes to obtain a good magnetic flux density. It has a remarkable effect that the hot-rolled sheet annealing can be done for 40 seconds or less. As a result, a product having excellent magnetic flux density and iron loss can be obtained at low cost. In the above,
If the hot-rolled sheet annealing temperature is less than 800 ° C, the effect of hot-rolled sheet crystal grain growth due to hot-rolled sheet annealing is small, and if it exceeds 1100 ° C, it is economically disadvantageous. It should be a range.

After that, cold rolling is performed. A product is obtained by either one of a method in which the product thickness is obtained by one cold rolling and finish annealing, or a method in which the product thickness is obtained by performing cold rolling two or more times with intermediate annealing between them and finish annealing.
Any of the usual methods can be applied to finish annealing, but punching accuracy is significantly impaired if the crystal grain size of the product is large.Therefore, annealing conditions (temperature range of 40 μm or less, preferably 10 to 30 μm) should be used. And time). Further, an insulating coating may be formed on the surface of the steel sheet by a known method.

[0049]

【Example】

Example 1 Two types of component compositions were melted in a converter, degassed, and continuously cast into slabs. The slabs were reheated and hot-rolled to obtain hot-rolled sheets. Next, hot-rolled sheet annealed and non-annealed, after pickling, cold-rolled into a cold-rolled sheet with a thickness of 0.5 mm, and finish annealing at 800 ° C for 15 seconds to remove the insulation coating. Each was covered and made into a product. The crystal grain sizes of those products were all 35 μm or less. After that, each product was sheared, subjected to stress relief annealing at 725 ° C. for 1 hour in a nitrogen atmosphere, and then magnetically measured by the 25 cm Epstein method.

Table 2 shows the analytical component composition of the product sheet, the conditions for hot-rolled sheet annealing, and the magnetic measurement results after stress relief annealing.

[Table 2]

As is clear from Table 2, sample Nos. 1 and 2 (first and sixth invention examples) show better iron loss than the comparative examples of sample Nos. 3 and 4.

Example 2 Various components were melted in a converter, degassed, continuously cast into slabs, and directly hot-rolled without cooling to obtain hot-rolled sheets. Next, after hot-rolled sheet annealing at 950 ° C for 2 minutes, pickling and cold rolling sheet thickness: 0.5m
After making a cold-rolled sheet of m, finish annealing was performed at 800 ° C for 15 seconds, and an insulating coating was formed to obtain each product. The crystal grain sizes of those products were all 35 μm or less. After that, each product was sheared, subjected to stress relief annealing at 725 ° C. for 1 hour in a nitrogen atmosphere, and magnetically measured by the 25 cm Epstein method.

Table 3 shows the analytical composition and magnetic measurement results of the product plate.

[Table 3]

As is apparent from Table 3, the iron loss of the invention examples is lower than that of the comparative example, and particularly the iron loss of the invention examples of sample Nos. 1 to 4 is good, and among them, the iron loss of sample No. 1 is good. Is exceptionally good. Further, sample Nos. 1 to 3 also show excellent magnetic flux densities. Sample No. 13 contained 1.25 wt% of Si, and although the iron loss was good, there was a problem with the punchability and poor punching accuracy.

Example 3 Production of a product plate, and subsequent treatment and investigation of the product plate were performed in the same manner as in Example 2 except that the hot-rolled plate annealing was not performed.

The crystal grain sizes of the product plates were all 35 μm or less. Table 4 shows the analysis composition and magnetic measurement results of the product plate.

[Table 4]

As is clear from Table 4, even when the hot-rolled sheet is not annealed, the iron loss of the invention example is lower than that of the comparative example and the same tendency as that of the example 2 is shown.

Example 4 Five component compositions were melted in a converter, degassed, and then continuously cast into slabs, which were directly hot-rolled without cooling to obtain hot-rolled sheets. After that, 950 ℃ · 30
After hot-rolled sheet annealing for a short time of 2 seconds, after pickling, cold rolling to make a cold plate with a thickness of 0.5 mm, finish annealing at 780 ° C for 15 seconds, and form an insulating film. Each product. The grain sizes of those products were all in the range of 15 to 25 μm. After that, each product is sheared and then 72
Strain relief annealing was performed at 5 ° C. for 1 hour, and magnetic measurement was performed by the 25 cm Epstein method.

Table 5 shows the analysis component composition of the slab and the magnetic measurement results.

[Table 5]

As is clear from Table 5, the sample No. 1 conforming to the inventions of the fourth, fifth, eighth and ninth inventions, despite the short time hot-rolled sheet annealing of 40 seconds or less, the sample Nos. 2, 3 , 4 and 5 are excellent in iron loss, and good magnetic flux density is obtained.

[0061]

EFFECTS OF THE INVENTION The present invention is particularly applicable to the RE composition of the low Si non-oriented electrical steel sheet with Si: 1.0 wt% or less.
Add M or mix it further into its composition
It suppresses Ti and Zr, and according to the present invention,
Not only good punching property but also good iron loss can be obtained by strain relief annealing at low temperature for a short time, and good magnetic flux density can be obtained even in short-time hot rolled sheet annealing. With the increase in efficiency of the class, the non-oriented electrical steel sheet used as the iron core material can sufficiently meet the demand for higher quality and lower cost, and its industrial effect is very large.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of Ti on iron loss after strain relief annealing at 725 ° C. for 1 hour.

FIG. 2 is a graph showing the effect of Zr on iron loss after stress relief annealing at 750 ° C. for 2 hours and 725 ° C. for 1 hour.

FIG. 3 is a graph showing the effect of Zr on the crystal grain size after strain relief annealing at 750 ° C. for 2 hours and 725 ° C. for 1 hour.

FIG. 4 is a graph showing the effect of Zr on iron loss after stress relief annealing at 725 ° C. for 1 hour.

FIG. 5 is a graph showing the effect of REM on iron loss after stress relief annealing at 725 ° C. for 1 hour.

Claims (9)

[Claims] 1. C: 0.01 wt% or less, Si: 1.0 wt% or less, Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 2 wt ppm
As described above, a non-oriented electrical steel sheet excellent in core loss after stress relief annealing, characterized by containing 80 wt ppm or less and the balance being Fe and inevitable impurities. 2. C: 0.01 wt% or less, Si: 1.0 wt% or less, Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 2 wt ppm
Above, 80 wt ppm or less, and Ti and Zr unavoidable mixture of Ti: 15 wt ppm or less and Zr: 80 wt pp, respectively.
A non-oriented electrical steel sheet excellent in core loss after stress relief annealing at low temperature and in a short time, characterized in that the composition is suppressed to m or less and the balance is substantially Fe composition. 3. The strain of claim 2 at 725 ° C. for 1 hour.
Iron loss after annealing (W _15/50) Is less than 4.0 W / kg
Magnetic electrical steel sheet. 4. C: 0.01 wt% or less, Si: 1.0 wt% or less, Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 5 wt ppm
Above, 50 wt ppm or less and Ti and Zr unavoidable mixture of Ti: 10 wt ppm or less and Zr: 80 wt ppm, respectively
A non-oriented electrical steel sheet excellent in iron loss after stress relief annealing at low temperature and in a short time, characterized in that the balance is suppressed to the following, and the balance is substantially Fe composition. 5. The strain of claim 4 at 725 ° C. for 1 hour
Iron loss after annealing (W _15/50) Is less than 3.5 W / kg
Magnetic electrical steel sheet. 6. C: 0.01 wt% or less, Si: 1.0 wt% or less, Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 2 wt ppm
Above, 80 wt ppm or less, and the balance is steel having a composition of Fe and inevitable impurities, which is made into a slab after casting, and is directly or after cooling and reheating, and then hot rolling, as it is, or after annealing or hot rolling. A method for producing a non-oriented electrical steel sheet excellent in core loss after stress relief annealing, which comprises performing annealing once and performing cold rolling once or twice or more with intervening intermediate annealing, and then performing finish annealing. 7. C: 0.01 wt% or less, Si: 1.0 wt% or less, Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 2 wt ppm
Above, 80 wt ppm or less, and Ti and Zr unavoidable mixture of Ti: 15 wt ppm or less and Zr: 80 wt ppm, respectively
Suppressed below, the rest is made into a slab after casting steel consisting essentially of Fe, and then directly or after cooling and hot rerolling, hot rolling, as it is, or subjected to hot-rolled sheet annealing or self-annealing, A method for producing a non-oriented electrical steel sheet excellent in iron loss after stress relief annealing at low temperature in a short time, which comprises performing cold annealing once or twice or more with intervening intermediate annealing and then performing finish annealing. 8. C: 0.01 wt% or less, Si: 1.0 wt% or less, Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 5 wt ppm
Above, 50 wt ppm or less and Ti and Zr unavoidable mixture of Ti: 10 wt ppm or less and Zr: 80 wt ppm, respectively
Suppressed below, the rest is made into a slab after casting steel consisting essentially of Fe, and then directly or after cooling and hot rerolling, hot rolling, as it is, or subjected to hot-rolled sheet annealing or self-annealing, A method for producing a non-oriented electrical steel sheet excellent in iron loss after stress relief annealing at low temperature in a short time, which comprises performing cold annealing once or twice or more with intervening intermediate annealing and then performing finish annealing. 9. C: 0.01 wt% or less, Si: 1.0 wt% or less, Mn: 0.1 wt% or more, 1.5 wt% or less, Al: 0.2 wt% or more, 1.5 wt% or less and REM: 5 wt ppm
Above, 50 wt ppm or less and Ti and Zr unavoidable mixture of Ti: 10 wt ppm or less and Zr: 80 wt ppm, respectively
Suppress the temperature below and make the rest a steel consisting essentially of Fe to form a slab after casting, and either directly or after cooling and reheating, hot rolling, soaking time in the temperature range of 800-1100 ° C for 40 seconds or less. Iron loss after stress relief annealing at low temperature in a short time characterized by carrying out finish annealing after performing short-time continuous hot-rolled sheet annealing and performing cold rolling once or twice with intermediate annealing sandwiched A method for producing a non-oriented electrical steel sheet with excellent heat resistance.