JP3037878B2 - Non-oriented electrical steel sheet excellent in iron loss after strain relief annealing and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
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. To increase these energy efficiencies,
It is necessary to reduce iron loss of non-oriented electrical steel sheets. In recent years, it has become important to increase the efficiency of electrical devices for the purpose of energy saving, and there is a growing demand for non-oriented electrical steel sheets to reduce iron loss.

[0002]

2. Description of the Related Art As means for reducing the iron loss of a non-oriented electrical steel sheet, there are optimization of the crystal grain size and high Si. It is known that iron loss is minimized when the crystal grain size is 150 to 200 μm, and that iron loss is reduced by increasing Si. 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 subjected to strain relief annealing after being punched into a predetermined shape by a customer. In this case, a particularly excellent punching accuracy is required because the blank is punched into a complicated shape. However, if the Si content exceeds 1.0% or the crystal grain size of the product plate exceeds 40 μm, the punching accuracy is significantly deteriorated.

[0003] Conventionally, in order to satisfy such conflicting properties of iron loss and punching accuracy, the product sheet particle size must be reduced with a low Si composition.
The diameter was set to about 20 μm, and after the punching at the customer, the crystal grains were coarsened by strain relief annealing at 750 ° C. for 2 hours to reduce iron loss. However, in recent years, a reduction in the strain relief annealing temperature and a reduction in the strain relief annealing time (for example, at 725 ° C. for one hour) due to an improvement in productivity at the consumer have resulted in a non-directional electromagnetic wave having excellent crystal grain growth even at a low temperature. Steel plates have become necessary. However, there has been no non-oriented electrical steel sheet that can meet this demand. It is well known that the cause of inhibiting the grain growth is inclusions and precipitates finely dispersed in the base iron. As inclusions and precipitates in the non-oriented electrical steel sheet, various oxides (for example, SiO ₂ , MnO, Al
₂ O ₃ ) and various nitrides and sulfides (eg, AlN, Ti
N, ZrN, MnS, etc.). Hereinafter, these will be referred to.

[0004] If the Al oxide is added in an amount of 0.2% or more, the problem can be solved because agglomeration and flotation can be sufficiently performed at the molten steel stage.

Sulfide Si having a high γ → α transformation point: In non-oriented electrical steel sheets exceeding 1.0%, rare-earth components (REM: 15% of atomic numbers 57 to 71)
It is known that by adding an alloy or Ca containing an element and 17 elements including two elements of Sc and Y) and Ca, S can be fixed as a stable and coarse sulfide.
The techniques are described in JP-A-51-62115 (non-oriented silicon steel sheet with low iron loss), JP-A-52-2824 (cold rolled non-oriented silicon steel treated with rare earth metal and its production method), and JP-A-52-1824. No. 34675 (Method of manufacturing non-oriented silicon steel sheet with less ridging),
102550 (non-oriented silicon steel sheet with stable magnetic properties)
Nos. 57-192219 (manufacturing method of non-oriented silicon steel sheet with low iron loss) and 58-164724 (manufacturing method of non-oriented electrical steel sheet having excellent magnetic properties), etc. . Further, as a method of adding REM in steelmaking, Japanese Patent Application Laid-Open No. 59-43814 (a method of refining molten steel for ladle for producing non-oriented electrical steel sheets with low iron loss) involves adding REM together with desulfurization flux. However, Japanese Unexamined Patent Publication No. 59-74212 (method for ladle refining of molten steel for producing non-oriented electrical steel sheets with small iron loss) discloses a method of adding a non-reducible flux together with REM. On the other hand, a non-oriented electrical steel sheet having a low γ → α transformation point of Si: 1.0% or less becomes a single γ phase during slab heating, and therefore utilizes the fact that the solubility of MnS is smaller in the γ phase than in the α phase. Is contained in an amount of 0.1% or more to coarsen MnS. Regarding the addition of rare earth components in non-oriented electrical steel sheets of less than 1.0% Si, Japanese Patent Application Laid-Open No. Sho 60-145310 (method of producing molten steel for non-oriented electrical steel sheets with low iron loss) discloses the use of Al for deoxidation. Without using Si and RE
Japanese Patent Application Laid-Open No. Hei 3-2156 discloses a means for using Al together with M to make Al <10 ppm.
No. 27 (Method of manufacturing non-oriented electrical steel sheet) has Al <0.2%,
A method of performing direct rolling with REM / S = 3 to 8 is disclosed. However, the non-oriented electrical steel sheets obtained by these means had completely insufficient iron loss after low-temperature short-time strain relief annealing.

[0006] In a low-Si non-oriented electrical steel sheet containing 1.0% or less of nitrided Si, addition of 0.2% or more of Al or B is performed to fix the nitride. There was almost no grain growth and the iron loss properties were not entirely satisfactory. As described above, the conventionally known means have been quite inadequate in reducing the grain growth and iron loss of the intended low-Si steel by low-temperature short-time strain relief annealing.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to propose a low-Si non-oriented electrical steel sheet capable of obtaining good iron loss by low-temperature and short-time strain relief annealing, and a method of manufacturing the same.

[0008]

In recent years, with the improvement of analysis accuracy, it has become possible to quantitatively analyze trace components of 10 ppm or less in the order of ppm. Therefore, the inventors have conducted various studies on the effect of trace components in steel on low-temperature short-time strain relief annealing. As a result, it was clarified that, in low Si steel, trace amounts of Ti and Zr of about 10 ppm deteriorate iron loss after low-temperature short-time strain relief annealing. In addition, the inventors have reported that 0.2-1.5% of Al, 15 ppm or less of Ti and 80% of Zr.
ppm or less and the coexistence of a trace amount of rare earth components significantly improve the crystal grain growth during strain relief annealing, and have excellent iron loss after low-temperature short-time strain relief annealing, which was not possible conventionally. It has been found that grain-oriented electrical steel sheets can be manufactured industrially.

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, REM: 2 wtppm or more, 80 wtppm or less, with the balance being Fe and unavoidable impurities. 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: containing 2 wtppm or more and 80 wtppm or less, and unavoidable mixing of Ti and Zr, respectively:
Non-oriented electrical steel sheet with excellent iron loss after strain relief annealing at low temperature and short time, characterized in that the content is controlled to 15 wtppm or less and Zr: 80 wtppm or less, with the balance being substantially Fe. 2
invention).

A non-oriented electrical steel sheet according to the second invention, wherein the iron loss (W _15/50 ) after strain relief annealing at 725 ° C. for 1 hour is less than 4.0 W / kg (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: contains 5 wtppm or more and 50 wtppm or less, and inevitably mixes Ti and Zr:
Non-oriented electrical steel sheet with excellent iron loss after strain relief annealing at low temperature and short time, characterized in that the content is suppressed to 10 wt ppm or less and Zr: 80 wt ppm or less, and the balance is substantially Fe. invention).

[0013] A non-oriented electrical steel sheet according to the fourth invention, wherein the iron loss (W _15/50 ) after strain relief annealing at 725 ° C. for 1 hour is less than 3.5 W / kg (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,
1.5 wt% or less and REM: containing 2 wtppm or more and 80 wtppm or less, the balance being steel consisting of Fe and unavoidable impurities, made into a slab after casting, and re-heated directly or after cooling, and then hot-rolled, It is excellent in iron loss after strain relief annealing characterized by performing cold rolling of one time or two or more times with intermediate annealing performed as it is, or performing hot rolled sheet annealing or self-annealing, and then performing finish annealing. A method for producing a non-oriented electrical steel sheet (a 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: containing 2 wtppm or more and 80 wtppm or less, and unavoidable mixing of Ti and Zr, respectively:
15 wtppm or less and Zr: suppressed to 80 wtppm or less, the balance is substantially slab after casting steel consisting essentially of Fe,
Directly or after reheating after cooling, hot rolling is performed, as it is, or hot rolled sheet annealing or self-annealing is performed, cold rolling is performed once or twice or more with intermediate annealing, and then finish annealing is performed. A method for producing a non-oriented electrical steel sheet having excellent iron loss after strain relief annealing in a short time at low temperature (seventh 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: contains 5 wtppm or more and 50 wtppm or less, and inevitably mixes Ti and Zr:
10 wtppm or less and Zr: suppressed to 80 wtppm or less, the remainder is made of steel substantially composed of Fe and turned into a slab after casting.
Directly or after reheating after cooling, hot rolling is performed, as it is, or hot rolled sheet annealing or self-annealing is performed, cold rolling is performed once or twice or more with intermediate annealing, and then finish annealing is performed. A method for producing a non-oriented electrical steel sheet having excellent iron loss after strain relief annealing in a short time at low temperature (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: contains 5 wtppm or more and 50 wtppm or less, and inevitably mixes Ti and Zr:
10 wtppm or less and Zr: suppressed to 80 wtppm or less, the remainder is made of steel substantially composed of Fe and turned into a slab after casting.
Directly or after reheating after cooling, hot-rolled, 800 ~
Short-time continuous hot-rolled sheet annealing with a soaking time of 40 seconds or less in the temperature range of 1100 ° C, cold rolling of one time or two or more times with intermediate annealing performed, and then finish annealing A method of producing a non-oriented electrical steel sheet having excellent iron loss after annealing at a low temperature for a short time in a short time (ninth invention).

[0018]

The operation of the present invention will be described below in detail. The present invention requires the above-described conditions, and the circumstances that led to the invention will be described.
The present inventors have found that the low Si
Regarding grain growth during low temperature strain relief annealing of non-oriented electrical steel sheet,
As a result of research and examination, it became clear that a small amount of Ti, Zr, REM, etc. had a significant effect on the 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 5 ppm Zr and 0.3% Al, plus REM: 2
Hot rolled with and without the addition of 0 ppm,
After cold rolling, finish annealing at 780 ° C for 30 seconds
Product plate. The grain size of these product plate crystals was 22-26 μm. Next, these product sheets were subjected to strain relief annealing at 725 ° C. for 1 hour, and then subjected to magnetic measurement to investigate the effect of Ti on iron loss after low-temperature short-time strain relief annealing. FIG.
Figure 8 shows the effect of Ti on iron loss after strain relief annealing at 725 ° C for 1 hour. As shown in FIG. 1, when the Ti content increases, the iron loss deteriorates, and especially when no rare earth component is added, the tendency is remarkable. Conversely, it has been clarified that extremely good iron loss can be obtained by adding a rare earth component and making Ti 15 ppm or less, particularly 10 ppm or less.

Zr With various Zr concentrations, Si: 0.5%, Mn: 0.55%, Ti:
Steel of 5 ppm, 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 grain size of these 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 subjected to magnetic measurement and measurement of the crystal grain size of the cross section. The effects on subsequent iron loss and grain growth were investigated. Figure 2 shows Zr
The effect on the iron loss (W _15/50 ) after strain relief annealing at 750 ° C. for 2 hours and at 725 ° C. for 1 hour is shown. As is clear from FIG. 2, good iron loss was obtained only at Zr: less than 5 ppm in the strain relief annealing at 725 ° C. for 1 hour. And, when Zr is 5 ppm or more, the iron loss deterioration of about 0.7 W / kg occurred by changing the condition of strain relief annealing from 750 ° C. for 2 hours to 725 ° C. for 1 hour.

FIG. 3 shows that Zr was 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: 5 ppm in the strain relief annealing at 725 ° C. for 1 hour.
It was confirmed that good grain growth was obtained only when the content was less than the above, and that 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 due to the strain relief annealing conditions is strongly influenced by the fine precipitates containing Zr, which is a grain growth inhibiting factor, in the low temperature strain relief annealing. Thus, when Zr is less than 5 ppm, it is clear that iron loss after low-temperature short-time strain relief annealing is good.
In factory scale smelting of steel containing Al> 0.2%, Zr is 5ppm
It is very difficult to make it less than. This is because, even if Zr in ferromagnetic iron added to molten steel is reduced, Zr in slag and refractories is reduced by Al, and the Zr concentration in steel is usually 5 ppm or more.

Therefore, the inventors investigated the effects of various added components on iron loss after annealing at low temperature and short time. Various Zr concentrations, Si: 0.5%, Mn: 0.55%, Ti: 5
ppm, Al: 0.3% steel, REM: 20ppm
Hot-rolled one containing REM and one without REM,
After cold rolling, it was subjected to finish annealing at 780 ° C. for 30 seconds to obtain a product sheet. The grain size of these product plates was 24-26 μm. Next, the product sheets were subjected to strain 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 strain relief annealing at 725 ° C. for 1 hour. As is clear from FIG. 4, good iron loss could be obtained up to 80 ppm Zr by adding the rare earth component. Thus, a very small amount (2-
(80 ppm) rare earth metal in steel, Zr
It was newly found that the adverse effect on iron loss after low-temperature short-time strain relief annealing can be eliminated.

REM (Rare Earth Metals) Various REM concentrations, Si: 0.5%, Mn: 0.55%,
A steel containing 7 ppm of Ti, 40 ppm of Zr, and 0.3% of Al was hot-rolled, cold-rolled, and then subjected to finish annealing at 780 ° C. for 30 seconds to obtain a product sheet. The grain size of these product plates is 23 ~ 26
μm. These sheets were subjected to strain relief annealing at 725 ° C. for 1 hour and then subjected to magnetic measurement to investigate the effect of REM on iron loss after low-temperature short-time strain relief annealing. FIG.
Figure 8 shows the effect of REM on iron loss after strain relief annealing at 725 ° C for 1 hour. As is clear from FIG.
Particularly good iron loss was obtained at 5 to 50 ppm.

As described above, the low Si non-oriented electrical steel sheet is
Is adjusted to 15 ppm or less, Al is set to 0.2 to 1.5%, and a rare earth component is added in a content range of 2 to 80 ppm, whereby the Zr concentration is reduced to 80%.
It has been found that good iron loss can be obtained after low-temperature short-time strain relief annealing down to ppm. Therefore, the present invention makes it possible to produce a low-Si non-oriented electrical steel sheet having excellent iron loss after low-temperature and short-time strain relief annealing on an industrial scale, which was impossible in the past.

Here, differences between the present invention and the above-mentioned prior art are listed below. JP-A-51-62
No. 115, No. 55-34675, No. 56-102550, No. 57-
In the Japanese Patent No. 192219, etc., a Si having a high γ → α transformation point (or no transformation): in a medium-high Si steel exceeding 1.0%,
This is a technique relating to the addition of rare earth components for lowering S and fixing S. However, according to the present invention, Si: γ of 1.0% or less →
A low Si steel having a low α transformation point is symmetrical, which can be understood as a technique different from the present invention. Further, it cannot be inferred from these conventional techniques that extremely good iron loss after low-temperature and short-time strain relief annealing can be obtained by the combined effect of setting the content of Ti to 15 ppm or less and the addition of a rare earth component.

JP-A-52-2824 discloses that Si is 0.5 to 4.0%.
No. 58-164724 discloses a technique of adding a rare earth component to 4% or less of Si steel. However, in any case, in the text and the examples, only the case where Si is more than 1.0% is taken up, and there is no description about the case where Si is less than 1.0%. Therefore, these are also techniques relating to the addition of rare earth components for lowering S and fixing S in middle and high Si steels having a high γ → α transformation point. In addition, 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 conventional techniques that extremely good iron loss after low-temperature and short-time strain relief annealing can be obtained by the combined effect of setting the content of Ti to 15 ppm or less and the addition of a rare earth component.

JP-A-59-43814 and JP-A-59-74212 relate to the REM desulfurization technology in steel making. In each of the texts and examples, only the case of 3% Si steel is taken up. : There is no description below 1.0%,
This is a technique for adding a rare earth component for lowering S and fixing S in Si steel. Japanese Patent Application Laid-Open No. 60-145310 aims to reduce O by using a combination of Si deoxidation and deoxidation by adding a rare earth component in a steel containing 0.1 to 1.0% of Si and Al <10 ppm. Therefore, it is a technique different from the present invention.

JP-A-3-215627 discloses Si: 0.1 to 1.4.
%, Al: a technique of adding a rare earth component to a non-oriented electrical steel sheet of less than 0.2%. On the other hand, the feature of the present invention is that due to the combined effect of Al content of 0.2 to 1.5% and Ti content of 15 ppm or less and addition of a rare earth component, extremely good grain growth during low-temperature and short-time strain relief annealing, And good iron loss can be obtained.
Nothing can be inferred from the publication No. 27, and the present invention is understood to be a more advanced technique.

Next, various conditions of the present invention will be described. First, the reasons for limiting the composition of the components will be described. C: 0.01 wt% or less C deteriorates magnetic properties due to precipitation of carbides.
Its content should be 0.01 wt% or less. Desirably 0.005 wt
% Is preferable.

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

Mn: 0.1 to 1.5 wt% Mn has a function of fixing S as coarse MnS, and therefore, 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 added Mn deteriorates the magnetic flux density, the upper limit of the content is preferably 1.5 wt%, and more preferably 1.
0 wt% is good. Therefore, its content is more than 0.1 wt%,
1.5 wt% or less, preferably 0.2 wt% or more, 1.0 wt%
wt% or less is preferred.

Al: 0.2% to 1.5% by weight When Al is less than 0.2% by weight, fine AlN is generated and the grain growth is deteriorated. Also, when 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 to 80 wt ppm REM is inevitable in steelmaking on an industrial scale by containing one or more of these components in a total range of 2 to 80 wt ppm. 5-80 wt included
It is possible to avoid adverse effects on grain growth during low-temperature short-time strain relief annealing of ppm Zr. If the content is less than 2 wt ppm, the above effect is insufficient, and the content is set to 2 wt ppm or more, preferably 5 wt ppm or more. On the other hand, excessive addition leads to an increase in inclusions formed by REM and inhibits grain growth by the REM-based inclusions themselves.Therefore, the content should be 80 wtppm or less, but preferably 50 wtppm or less. ppm or less is good.

Ti: 15 wt ppm or less Ti is a trace amount and significantly deteriorates the grain growth during low-temperature short-time strain relief annealing and iron loss. Therefore, the content of Ti is 15 wt ppm in order to obtain good iron loss. The following is assumed. 10 wt pp content
By setting the value to m or less, more favorable iron loss can be obtained. The effect is small even when Ti is used alone at 15 wt ppm or less, and the grain growth property during low-temperature short-time strain relief annealing is improved due to the combined effect of REM addition.

Zr: 80 wt ppm or less Zr is a very small amount and degrades iron loss after low-temperature and short-time strain relief annealing.
Achieving the following stably on an industrial scale leads to significant cost increases. Therefore, in the present invention, Zr is rendered harmless by adding REM in a range of Zr: 5 to 80 wt ppm which can be industrially stably achieved. Zr together with REM addition
To 80 wt ppm or less, the effect of reducing iron loss after low-temperature short-time strain relief annealing becomes remarkable.
wt ppm or less.

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

P: 0.2 wt% or less P can be added to improve the punching property. However, if the content exceeds 0.2 wt%, the cold rolling property is deteriorated, so the content is 0.2 wt%. It is desirable to make the following.

S: 0.01 wt% or less S forms MnS with Mn, hinders domain wall movement and grain growth, and degrades magnetic properties.
It is desirable that the content be 01 wt% or less.

N: 0.01 wt% or less N forms nitride, hinders domain wall movement and grain growth, and degrades magnetic properties.
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 hinders domain wall movement and grain growth and degrades magnetic properties.
It is desirable that the content be 50 wt ppm or less.

Next, preferable manufacturing conditions and reasons for limiting the manufacturing conditions in the present invention will be described. The composition is adjusted to the above composition by a conventional steelmaking method such as a converter and degassing, and cast into a slab by continuous casting or a casting-ingot method.
Subsequently, the slab is hot-rolled, and any of a method of hot-rolling after reheating the slab and a method of direct hot rolling after continuous casting without slab heating can be applied. When trying to obtain a particularly high magnetic flux density as a magnetic property,
It is effective to improve the texture by coarsening the crystal grains of the hot-rolled sheet by performing hot-rolled sheet annealing or self-annealing during winding after hot rolling. For 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 view of cost reduction and improvement in productivity. Until now, the hot rolled sheet annealing for a short time of soaking time of 30 seconds did not sufficiently increase the crystal grain size of the hot rolled sheet,
A high magnetic flux density could not be obtained. However, the present invention also has an effect that a high magnetic flux density can be obtained even by a short-time hot-rolled sheet annealing.

That is, the above effects will be described based on experimental examples. A slab having the composition shown in Table 1 was hot-rolled,
The magnetic flux density of the steel sheet subjected to hot-rolled sheet annealing at a temperature of 0 ° C. for various soaking times, cold rolling, finish annealing, and then subjected to strain relief annealing at 725 ° C. for 1 hour was examined.

[0046]

[Table 1] Table 1 also shows these hot rolled sheet annealing conditions and investigation results.

As apparent from Table 1, REM: 5 to 50 wt.
In the case of a component composition that satisfies ppm, Ti: 10 wt ppm or less and Zr: 80 wt ppm or less, the grain growth of the hot rolled sheet is remarkably excellent, so that 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 performed for 40 seconds or less. As a result, a product excellent in both magnetic flux density and iron loss at low cost can be obtained. In the above,
If the hot-rolled sheet annealing temperature is less than 800 ° C, the effect of hot-rolled sheet grain growth by the hot-rolled sheet annealing is small, and if it exceeds 1100 ° C, it is economically disadvantageous. It is good to be a range.

Thereafter, cold rolling is performed. The product is formed by one of a method of making the product thickness by one cold rolling and finish annealing, or a method of performing the cold rolling two or more times with intermediate annealing to make the product thickness and finish annealing.
For the finish annealing, any of the conventional methods can be applied. However, if the crystal grain size of the product is large, the punching accuracy is significantly impaired. Therefore, the annealing conditions (temperature: temperature: less than 40 μm, preferably in the range of 10 to 30 μm) And time). Further, an insulating coating may be formed on the surface of the steel sheet by a known method.

[0049]

EXAMPLES Example 1 Two components were melted in a converter, degassed, formed into a slab by continuous casting, and the slab was reheated and then subjected to hot rolling to obtain hot rolled sheets. . Next, after the hot rolled sheet was annealed and untreated, it was pickled and then cold rolled into a cold rolled sheet having a thickness of 0.5 mm, and then subjected to finish annealing at 800 ° C. for 15 seconds to remove the insulating coating. Each product was formed. The grain size of all of these products was less than 35 μm. After shearing, each product was subjected to strain relief annealing at 725 ° C. for 1 hour in a nitrogen atmosphere, and then subjected to magnetic measurement by a 25 cm Epstein method.

Table 2 summarizes the analytical component composition of the product sheet, the annealing conditions of the hot-rolled sheet, and the results of the magnetic measurements after the strain relief annealing.

[Table 2]

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

Example 2 Ingots were melted into various component compositions in a converter, degassed, formed into a slab by continuous casting, 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 are performed to obtain a sheet thickness of 0.5m.
m, and then subjected to finish annealing at 800 ° C. for 15 seconds to form an insulating coating, thereby obtaining respective products. The grain size of all of these products was less than 35 μm. Thereafter, each product was sheared, subjected to strain relief annealing at 725 ° C. for 1 hour in a nitrogen atmosphere, and subjected to magnetic measurement by a 25 cm Epstein method.

Table 3 summarizes the composition of the analytical components of the product plate and the results of the magnetic measurements.

[Table 3]

As is clear from Table 3, the iron loss of the invention example is lower than that of the comparative example, and the iron loss of the invention examples of samples Nos. 1 to 4 is particularly good. Is particularly good. Sample Nos. 1 to 3 also show excellent values of magnetic flux density. Sample No. 13 contained 1.25 wt% of Si, and although the iron loss was good, there was a problem in the punching property and poor punching accuracy occurred.

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 sheet annealing was not performed.

The crystal grain size of each of the product sheets was 35 μm or less. Table 4 summarizes the composition of the analytical components and the results of the magnetic measurement of the product plate.

[Table 4]

As is apparent from Table 4, even when the hot-rolled sheet annealing is not performed, the same tendency as in Example 2 is shown, such as the iron loss of the invention example is lower than that of the comparative example.

Example 4 Five components were melted in a converter, degassed, formed into a slab by continuous casting, and directly hot-rolled without cooling to obtain hot-rolled sheets. After that, 950 ℃ ・ 30
After performing a short-time hot-rolled sheet annealing for 2 seconds, after pickling, a cold plate having a thickness of 0.5 mm is formed by cold rolling, and a finish annealing is performed at 780 ° C. for 15 seconds to form an insulating film. Each was a product. The grain size of all of these products was in the range of 15-25 μm. After that, each product is sheared and then placed in a nitrogen atmosphere for 72 hours.
Strain relief annealing was performed at 5 ° C. for 1 hour, and magnetic measurement was performed by a 25 cm Epstein method.

Table 5 summarizes the analytical component composition and magnetic measurement results of the slab.

[Table 5]

As is clear from Table 5, Sample No. 1, which conforms to the fourth, fifth, eighth and ninth inventions, did not suffer from short time hot rolled sheet annealing for 40 seconds or less. , 4 and 5 are excellent in iron loss as well as good magnetic flux density.

[0061]

The present invention relates to a low-Si non-oriented electrical steel sheet having a Si content of 1.0 wt% or less, and particularly to the RE composition,
Add M or mix into its component composition
According to the present invention, Ti and Zr are suppressed.
Not only good punching properties but also good iron loss can be obtained by low-temperature and short-time strain relief annealing, and good magnetic flux density can be obtained even in short-time hot-rolled sheet annealing. With the increase in the efficiency of these types, it is possible to sufficiently meet the demand for higher quality and lower cost for non-oriented electrical steel sheets used as the iron core material, and the industrial effect is extremely large.

[Brief description of the 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 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 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 strain relief annealing at 725 ° C. for 1 hour.

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

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-51-62115 (JP, A) JP-A-59-83723 (JP, A) JP-A-62-222021 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C22C 38/00 303 C21D 8/12 H01F 1/16

Claims (9)

(57) [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 wtppm
A non-oriented electrical steel sheet having excellent iron loss after strain relief annealing, characterized by containing 80 wt ppm or less, with 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 wtppm
Above, 80 wt ppm or less, and inevitable contamination of Ti and Zr, respectively: Ti: 15 wt ppm or less and Zr: 80 wt pp
A non-oriented electrical steel sheet which is excellent in iron loss after low-temperature and short-time strain relief annealing, wherein the iron loss is suppressed to not more than m and the balance substantially becomes Fe composition. 3. The method according to claim 2, wherein the strain is at 725 ° C. for one hour.
Iron loss after annealing (W _15/50) Is less than 4.0W / kg
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 wtppm
Above, containing 50 wtppm or less, and unavoidable mixing of Ti and Zr respectively: Ti: 10 wtppm or less and Zr: 80 wtppm
A non-oriented electrical steel sheet having excellent iron loss after low-temperature and short-time strain relief annealing, characterized in that the composition is substantially as follows: 5. The strain according to claim 4, wherein the strain is at 725 ° C. for one hour.
Iron loss after annealing (W _15/50) Is less than 3.5W / kg
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 wtppm
Above, 80 wt ppm or less, the balance being steel consisting of Fe and unavoidable impurities, made into a slab after casting, directly or after cooling and reheating and then hot rolling, as it is, or as hot rolled sheet annealing or self-rolling. A method for producing a non-oriented electrical steel sheet excellent in iron loss after strain relief annealing, wherein the steel sheet is annealed, cold-rolled once or twice or more with intermediate annealing, and then subjected to 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 wtppm
Above, 80 wtppm or less, and Ti and Zr unavoidable contamination: Ti: 15 wtppm or less and Zr: 80 wtppm
Suppressed below, the remainder is a slab after casting the steel substantially consisting of the composition of Fe, hot rolled directly or after reheating after cooling, 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 strain relief annealing at a low temperature for a short time, after performing cold rolling once or two or more times with intermediate 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, containing 50 wtppm or less, and unavoidable mixing of Ti and Zr respectively: Ti: 10 wtppm or less and Zr: 80 wtppm
Suppressed below, the remainder is a slab after casting the steel substantially consisting of the composition of Fe, hot rolled directly or after reheating after cooling, 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 strain relief annealing at a low temperature for a short time, after performing cold rolling once or two or more times with intermediate 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, containing 50 wtppm or less, and unavoidable mixing of Ti and Zr respectively: Ti: 10 wtppm or less and Zr: 80 wtppm
The balance is controlled as follows, the remainder is made of steel substantially composed of Fe and cast into a slab, directly or cooled and then re-heated and then hot-rolled, soaking at a temperature in the range of 800 to 1100 ° C for 40 seconds or less. Characterized by applying a short-time continuous hot-rolled sheet annealing, performing cold rolling once or twice or more with intermediate annealing, and then subjecting to finish annealing, wherein iron loss after low-temperature and short-time strain relief annealing is performed. Method for manufacturing non-oriented electrical steel sheets with excellent performance.