KR20110119101A - Non-oriented electrical steel sheets having excellent magnetic property and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A non-oriented electrical steel sheet with low iron loss and a manufacturing method thereof are provided to reduce energy loss when used for a motor core by optimizing the quantity of tin according to the aluminum content and controlling the amount of nitride and oxide to reduce iron loss. CONSTITUTION: A non-oriented electrical steel sheet with low iron loss comprises silicon of 4.0 weight% or less, manganese of 0.1~1.0 weight%, aluminum of 0.45~1.7 weight%, carbon of 0.005 weight% or less, phosphorus of 0.1 weight% or less, sulfur of 0.003 weight% or less, nitrogen of 0.003 weight% or less, titanium of 0.005 weight% or less, tin of less than 0.08 weight%, and iron and impurities of the remaining amount.

Description

Non-oriented electrical steel sheets having excellent magnetic property and method for manufacturing the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical steel sheet having excellent magnetic properties used as an iron core of an electric apparatus such as a motor and a transformer, and a method of manufacturing the same, and more particularly, to an electrical steel sheet having a low iron loss and a method of manufacturing the same.

As industrialization continues worldwide, demand for motors and transformers is increasing. In particular, demand for high efficiency, high value-added motors and transformers is gradually increasing as environmental pollution prevention and energy saving are required. Accordingly, efforts have been made to increase the efficiency of electrical steel sheets used as iron core materials for motors and transformers.

In order to increase the efficiency of electrical steel sheet, the increase of the magnetization value and the iron loss due to the excitation current has been reduced by increasing the Si alloy element, and recently, the iron loss by increasing the Al alloy element due to the limitation of Si input due to the inferior rolling property Has been reduced.

However, an increase in Al and a decrease in impurity elements such as S have been found to increase the surface reactivity, thereby producing Al-based nitrides and oxides under the surface layer during final annealing, thereby worsening iron loss. Therefore, in order to prevent the deterioration of iron loss caused by this, a study has been conducted such as adding a trace element, making a surface Al or Si enriched layer, or controlling the content of S.

For example, Japanese Patent Application Laid-Open Nos. 1998-183310 and 2001-140018 disclose techniques for suppressing subsurface nitride by forming a dense Al or Si thick layer of about 1 µm by improving the surface roughness by sufficiently pickling.

In addition, Japanese Patent 2006-241563 has an internal steam partial pressure ratio of 0.3 to 0.5 up to 650 degrees, but at a predetermined annealing crack temperature of 650 degrees, the steam hydrogen partial pressure ratio is adjusted to between 0.1 and 0.3 to provide SiO ₂ and 2-20 nm. A technique for improving iron loss by forming an MnO layer to prevent subsurface precipitates is disclosed.

In addition, Japanese Patent 1998-317111 and 2000-328207 disclose a technique for preventing surface subsurface nitriding by adding a trace element according to the content of S. When S is 10 ppm or less, Sb or Sn is added to form an Al oxide. We tried to improve the iron loss by preventing nitride.

However, in the case of the technique of forming an Al enriched layer on the surface layer, nitrogen absorption by the Al enriched layer proceeds, which is likely to infer the adhesion of the coating, and in order to make the enriched layer, Al must be increased. Workability problems due to degradation are likely to occur.

Further, by adjusting the hydrogen partial pressure of water vapor at the beginning when the technique of improving the core loss make the SiO ₂ layer, in the equipment operation, by setting the continuous gayeoldae the other partial region in which hydrogen is added, it is difficult.

In addition, in the case of a technique such as Japanese Laid-Open Patent Publication No. 1998-317111 which reduces the iron loss by inserting a trace element such as Sb or Sn when the S content is 10 ppm or less, and prevents subsurface nitriding, Sb and Sn are less than 10 ppm. Although the effect of reducing iron loss by the present invention is remarkably confirmed, according to the inventors' experiment, when the elements such as Sb and Sn are added to a material containing less than 10 ppm of S, a significant reduction of iron loss does not occur. However, it was confirmed that only the effects due to the addition of elements such as Sb and Sn are shown. The iron loss reduction effect is caused by the introduction of elements such as Sb and Sn, which concentrate on the steel plate surface and suppress the adsorption of nitrogen, rather than by reducing the S content. There was a problem that was derived under the assumption and could not be applied in the field.

The main causes of subsurface nitriding are described only for elements that suppress the formation of nitride layers, focusing only on the suppression of the formation of nitride layers, that is, elements such as Sb and Sn. It does not specify in detail how the atmospheric conditions and the like act on the formation of the nitride layer, there was a problem that can not expect a significant iron loss reduction effect.

JP 1998-183310 A 1998.07.14. JP 2001-140018 A 2001.05.22. JP 2006-241563 A 2006.09.14. JP 1998-317111 A 1998.12.02. JP 2000-328207 A 2000.11.28.

The present invention was devised to solve the above problems. In order to prevent magnetic deterioration due to subsurface nitriding and oxides occurring during the final annealing process, the dew point is controlled to be low, and the amount of Sn is added in an appropriate amount according to Al. It is an object to obtain this excellent non-oriented electrical steel sheet having a particularly low iron loss.

The present invention, in order to achieve the above object, by adding the Sn content of the non-oriented electrical steel sheet containing Al in conjunction with the Al content, and by controlling the dew point of the final annealing furnace, the surface layer nitride and oxide of the final product sheet It is characterized by suppressing the non-oriented electrical steel sheet with low iron loss.

Non-oriented electrical steel sheet having a low iron loss of the present invention, Si: 4.0% or less, Mn: 0.1 ~ 1.0%, Al: 0.45 ~ 1.7%, C: 0.005% or less, P: 0.1% or less, S: 0.003 % Or less, N: 0.003% or less, Ti: 0.005% or less, Sn: less than 0.08%, remainder Fe and other unavoidable impurities, but the content of Sn is in a range satisfying Equation 1 according to Al content Characterized in that made.

800> Sn (ppm)> 285 × Al (wt%)-125

In addition, the steel sheet, when observed by GDS (Glow discharge Spectroscopy) is characterized in that the maximum value of the sub-surface nitrogen fraction is 5% or less,

In addition, the steel sheet is characterized by a depth of less than 0.1㎛ the oxygen fraction of the surface layer 50% when observed by GDS.

The manufacturing method of the present invention, In the method for producing a non-oriented electrical steel sheet which is completed by a conventional process of reheating and hot rolling the slab, followed by hot rolling annealing, cold rolling, final annealing, the slab is made of the composition of the composition of claim 1, The final annealing is carried out in an atmosphere consisting of hydrogen and nitrogen, characterized in that the dew point is managed to be less than -10 degrees, the hot-rolled sheet annealing is characterized in that the surface layer is stripped from the pickling tank immediately after annealing do.

According to the present invention, it is possible to reduce energy loss during use as a motor core by optimizing Sn input amount according to Al content in high quality non-oriented electrical steel sheet and managing the dew point during final annealing to reduce the iron loss by controlling the amount of nitriding and oxides. .

In addition, it is possible to improve the quality of the non-oriented electrical steel sheet and reduce the manufacturing cost by preventing the deterioration of the magnetic and the increase of the alloying cost due to the addition of Sn more than necessary.

1 is a graph showing the correlation between Al content and Sn input amount to obtain the iron loss reduction effect of non-oriented electrical steel sheet,
2 is a graph showing the iron loss of the non-oriented electrical steel sheet according to the Al content and the input amount of Sn,
3 is a graph showing the iron loss of the non-oriented electrical steel sheet according to the Al content, the Sn input amount and the dew point at the final annealing is divided into less than 2.2 (W / Kg) and more than 2.2 (W / Kg).

Hereinafter, the present invention will be described in more detail.

In non-oriented electrical steel sheets containing Si, Al, and Mn, N is known as an impurity element that penetrates into the steel sheet during annealing to form nitride and inhibit grain growth to inhibit the development of texture.

The present inventors have studied the effects of various alloying elements on the magnetism to produce high quality non-oriented electrical steel sheets having excellent magnetic properties by suppressing the ingress of N in the steel, and the effect of the magnetic enhancement obtained by adding Sn is not constant. It was found to depend on the content of constituents in the cavity, especially on the content of Al.

With this in mind, the present inventors have repeatedly conducted experiments on various alloying components to determine the effect of Al content of the non-oriented electrical steel sheet on the effect of magnetic enhancement according to the amount of Sn input, and as a result, 0.45 to 1.7% of Al In the non-oriented electrical steel sheet composed of a component system containing, the effect of the improvement of magnetism by the addition of Sn is largely dependent on the Al content, and the addition of Sn to satisfy the specific conditional formula for the Al content can control the formation of nitride under the surface. The present invention was able to be completed for the first time, thereby stably securing excellent iron loss.

In the present invention, Si: 4.0% or less, Mn: 0.1 to 1.0%, Al: 0.45 to 1.7%, C: 0.005% or less, P: 0.1% or less, S: 0.003% or less, N: 0.003% or less, Ti: 0.005% or less, Sn: less than 0.08%, remainder Fe and other non-oriented electrical steel sheet containing other unavoidable impurities, the content of Sn is characterized in that the range of the following formula 1 according to the Al content do.

800> Sn (ppm)> 285 × Al (wt%)-125

First, look at the reasons for limiting the components of the present invention. The content is below% by weight.

[C: 0.005% or less]

C contains less than 0.005% by weight because it causes magnetic aging in the final product, which lowers the magnetic properties during use, and the lower the content of C, the better the magnetic properties. Do.

[Si: 4.0% or less]

Si is a component that decreases the eddy current loss during iron loss by increasing the specific resistance, and if it is added in excess of 4.0%, it is preferable to limit it to 4.0% or less because cold rolling is poor.

[P: 0.1% or less]

P is added to increase the resistivity, improve the texture, and improve the magnetism. If excessively added, cold rolling is deteriorated, so it is preferable to limit it to 0.1% or less.

[S: 0.003% or less]

S is preferably managed low because it forms fine precipitates MnS and CuS and suppresses grain growth to deteriorate magnetic properties, so the content is limited to 0.003% or less.

[Mn: 0.1-1.0%]

If Mn is present at less than 0.1%, fine MnS precipitates are formed to inhibit grain growth, thereby deteriorating magnetism. Therefore, when 0.1% or more exists, coarse MnS is formed and S component can be prevented from being precipitated by CuS which is a finer precipitate. However, when Mn increases, the magnetic content decreases, so it is added below 1.0%.

[Al: 0.45-1.7%]

Al is an effective component to lower the eddy current loss by increasing the specific resistance. In the case of less than 0.45%, AlN is microprecipitated to deteriorate the magnetism, and if it exceeds 1.7%, the workability is deteriorated, so it is preferable to limit it to 1.7% or less.

[N: 0.003% or less]

N is formed to contain fine and long AlN precipitate inside the base material to suppress grain growth, so it is contained less, it is preferable to limit to 0.003% or less in the present invention.

[Ti: 0.005% or less]

Ti suppresses grain growth by forming fine TiN and TiC precipitates, and when added in excess of 0.005%, Ti causes many fine precipitates to worsen the texture and deteriorate the magnetic properties.

[Sn: less than 0.08%]

Sn is a surface precipitation element, which concentrates on the surface of the steel sheet to suppress nitrogen adsorption and consequently serves to lower iron loss by not interfering with the growth of grains, and when the amount of Sn is excessively higher than 800 ppm, the grain growth is delayed. Rather, the magnetic deterioration is limited to less than 0.08%.

In addition to the above composition, the remainder consists of Fe and other inevitable impurities.

The slabs having the composition as described above are subjected to hot rolling, winding and hot rolled sheet annealing, followed by pickling and cold rolling, followed by final annealing. At this time, the hot-rolled sheet annealing is performed to improve the texture of the final annealing plate for the high-grade electrical steel sheet without phase transformation, and immediately after the annealing to remove the scale of the surface layer to ensure the surface quality.

After cold rolling, the rolling oil present on the surface is degreased and finally annealed. This process produces the final product, and because the surface quality is important, it is annealed in an atmosphere composed of hydrogen and nitrogen. Since hydrogen is included in the final annealing, Fe or Si-based oxides are mostly reduced, and some Al is oxidized or nitrided. In general, Al oxides are distributed in the surface layer, and Al nitrides are formed in angular agglomerates and in the surface layer and under the surface layer, both of which impede the movement of the magnetic domain, adversely affecting iron loss, and inferior coating adhesion. . In the case of Al oxide, the dew point is controlled to be low. In particular, when the dew point is managed at less than -10 degrees during final annealing, it is possible to reduce the partial pressure of oxygen so that almost no oxide is generated.

However, if the dew point falls below a certain temperature during final annealing, the possibility of nitride formation due to relative absorption is increased. In particular, if the dew point is low during final annealing, the Al content is relatively high, and the S content is low, the surface reactivity is good, so that nitrogen penetrates under the surface layer and deteriorates the magnetic properties. Therefore, when the surface precipitation element is added, such as Sn, the surface reactivity may be lowered, and thus, the magnetic property may be improved by preventing further nitriding.

When Al is less than 0.45% in the steel, absorption is hardly generated. However, the higher Al is, the higher the effectiveness of the magnetic enhancement effect by lowering the surface reactivity becomes. By increasing the amount of Sn in accordance with the content can be secured excellent magnetic. However, when the amount of Sn is too high, such as 800ppm or more, the magnetism deteriorates due to the delay of grain growth.

800> Sn (ppm)> 285 × Al (wt%)-125

As a method for analyzing the surface layer of the steel sheet in a short time, there is a method of analyzing the content of elements depending on the depth through surface evaporation such as glow discharge spectroscopy (GDS). When the surface layer of the non-oriented electrical steel sheet was observed by GDS, the maximum nitrogen content of the surface layer was 5% or less when manufactured according to the above conditions. In the case of oxygen, the maximum value is mostly observed at 100% on the surface, and then tends to decrease rapidly with depth. Therefore, it is meaningful how rapidly it decreases with depth rather than the maximum value of oxygen content. When Sn is appropriately added according to Al content according to [Equation 1], the magnetic content is excellent, and the time when the oxygen content is 50% is less than 0.1 μm, more preferably 0.08 μm or less.

Hereinafter, the present invention will be described in more detail with reference to Examples.

By weight, C: 0.0030%, P: 0.012%, S: 0.0003 ~ 0.0036%, N: 0.0013%, Mn: 0.17%, Ti: 0.0015% and the remaining Fe and other unavoidable impurities and Al, Si as shown in Table 1 Re-heated the slab composed of Sn, 1130 ℃ and then hot rolled to 2.3mm to prepare a hot rolled steel sheet. At this time, Al + Si value was maintained within the range of 4.1 ~ 4.3 (wt%) to eliminate the iron loss caused by the difference in resistivity. The hot rolled steel sheet was wound at 650 ° C., cooled in air, hot rolled annealed at 1040 ° C. for 2 minutes, and cold rolled to 0.35 mm after pickling, changing the dew point to -42 to -2 degrees. After the final annealing in an atmosphere of 20% hydrogen and 80% nitrogen for 10 seconds at 1040 ℃, the magnetic and surface analysis of the steel sheet. Magnetic measurements of the steel sheets were averaged by measuring in the rolling direction and the right angle direction using a 60 × 60 mm ² size plate measuring instrument, and the surface of the steel sheets was analyzed by measuring the fraction of nitrogen and oxygen according to the depth from the surface layer using GDS.

Table 1 shows the results of iron loss and surface analysis of steel sheets according to dew point and steelmaking composition during final annealing.

sample
number 1) dew point
(° C) Steelmaking component 2) under the surface
Nitrogen fraction
Maximum value (%) 3) oxygen 50%
Penetration depth
(μm) Iron loss
(W15 / 50, W / Kg)
division Al (wt%) Si (wt%) Sn (ppm) S (ppm) One -41 0.45 3.70 10 7 5 0.051 2.15 Invention 1 2 -40 0.46 3.65 120 8 4 0.047 2.16 Invention 2 3 -40 0.81 3.41 0 7 10.5 0.051 2.35 Comparative Material 1 4 -40 0.82 3.42 55 6 9 0.062 2.32 Comparative Material 2 5 -41 0.80 3.38 90 5 7.5 0.058 2.30 Comparative Material 3 6 -42 0.83 3.40 120 6 4 0.053 2.19 Invention 3 7 -40 0.82 3.40 200 7 2.5 0.049 2.12 Invention 4 8 -40 1.21 3.03 150 8 7 0.051 2.35 Comparative Material 4 9 -40 1.09 3.08 210 7 3.5 0.047 2.13 Invention 5 10 -40 1.23 3.01 304 4 3 0.049 2.10 Invention 6 11 -40 1.45 2.66 150 5 6.5 0.051 2.31 Comparative Material 5 12 -40 1.55 2.71 320 7 3 0.051 2.16 Invention Material7 13 -40 1.54 2.70 800 5 3 0.051 2.31 Comparative Material 6 14 -40 1.50 2.65 1000 3 3.5 0.050 2.32 Comparative Material7 15 -25 0.46 3.65 120 5 3.5 0.069 2.10 Invention Material 8 16 -26 0.80 3.38 90 7 7 0.070 2.31 Comparative Material 8 17 -22 0.82 3.40 200 6 2 0.073 2.13 Invention Material 9 18 -23 1.21 3.03 150 8 6.5 0.069 2.34 Comparative Material 9 19 -18 1.09 3.08 210 6 4 0.071 2.19 Invention 10 20 -23 1.45 2.66 150 7 6 0.072 2.33 Comparative Material 10 21 -21 1.55 2.71 320 5 2.5 0.069 2.21 Invention Material 11 22 -10 0.45 3.70 0 6 4 0.120 2.31 Comparative Material 11 23 -8 0.46 3.65 120 4 2.5 0.170 2.35 Comparative Material 12 24 -4 0.81 3.41 0 6 4.5 0.160 2.33 Comparative Material 13 25 -5 0.80 3.38 90 6 4 0.180 2.31 Comparative Material14 26 -5 0.83 3.40 120 5 3.5 0.170 2.31 Comparative Material 15 27 -5 0.82 3.40 200 7 2.5 0.180 2.32 Comparative Material 16 28 -6 1.21 3.03 150 8 4.5 0.210 2.35 Comparative Material17 29 -5 1.09 3.08 210 5 3 0.180 2.32 Comparative Material 18 30 -2 1.23 3.01 304 8 2.5 0.170 2.31 Comparative Material 19 31 -8 1.45 2.66 150 4 4 0.170 2.33 Comparative Material 20 32 -6 1.60 2.70 250 6 4.5 0.200 2.41 Comparative Material21 33 -5 1.55 2.71 320 5 3 0.170 2.40 Comparative Material 22 34 -5 1.50 2.65 400 6 3.5 0.170 2.41 Comparative Material 23 35 -40 0.82 3.39 196 9 2.1 0.043 2.12 Invention Material12 36 -41 0.79 3.40 180 15 2.3 0.045 2.13 Invention Material 13 37 -41 0.81 3.42 189 25 2.2 0.046 2.09 Invention 14 38 -42 0.80 3.39 210 28 2.1 0.043 2.15 Invention 15 39 -41 0.82 3.43 190 35 2.5 0.042 2.35 Comparative Material 24 40 -40 1.21 2.96 250 8 2.5 0.042 2.10 Invention 16 41 -40 1.22 3.01 245 11 2.4 0.044 1.98 Invention 17 42 -40 1.18 3.10 220 15 2.4 0.045 2.03 Invention 18 43 -40 1.23 3.02 230 26 2.3 0.043 2.00 Invention Material 19 44 -40 1.22 3.03 250 33 2.3 0.044 2.31 Comparative Material 25 45 -40 1.15 3.00 0 9 9.8 0.045 2.28 Comparative Material 26 46 -40 1.22 3.02 0 15 11.2 0.043 2.31 Comparative material 27 47 -40 1.21 2.95 0 30 10.1 0.044 2.32 Comparative Material 28 48 -22 0.82 3.30 130 9 2.3 0.074 2.11 Invention 20 49 -22 0.81 3.31 150 15 2.4 0.072 2.10 Inventive Materials21 50 -22 0.83 3.35 140 26 2.3 0.074 2.12 Invention Material22 51 -22 0.82 3.30 0 9 9 0.071 2.28 Comparative Material 29 52 -21 0.81 3.31 0 15 8.5 0.069 2.29 Comparative Material 30 53 -19 0.83 3.35 0 26 9 0.074 2.30 Comparative Material 31 54 -15 1.11 3.08 250 13 4.1 0.076 1.96 Invention 23 55 -16 1.12 3.08 240 25 3.8 0.075 2.15 Invention 24 56 -14 1.20 3.08 260 36 3.9 0.074 2.32 Comparative Material32

1) Final annealing furnace dew point measured by chilled mirror type dew point meter

2) Maximum nitrogen in the depth distribution graph of nitrogen as measured by GDS

3) Depth at which the fraction of oxygen reaches 50% as measured by GDS

Comparative materials 11 to 23 have a dew point of more than -10 degrees at the time of final annealing, but the amount of nitride under the surface layer decreases, but the iron loss is deteriorated due to the oxide penetrating deeply from the surface of the steel sheet, which can be seen in FIG. 3.

In the final annealing, if the dew point is lower than -10 degrees, the iron loss is changed according to the alloy composition. When the Al content is relatively small, such as Inventive Materials 1,2 and 0.45%, the nitrogen value under the surface is lowered and the iron loss is improved. This is because a small amount of Al reduces the probability of forming AlN, which occupies most of the nitride in the steel.

When the Al content is increased, the maximum nitrogen value in the surface layer changes according to the amounts of Al and Sn. As Al increases and the Sn decreases, the nitrogen value in the surface layer increases. When the Al value is 0.8% and the Sn value is 120ppm or more, Al is 1.2% or more, 200ppm or more, Al 1.5% is more than 250ppm magnetism was good. As the amount of Al increases, the amount of the appropriate Sn increases because the absorption is better as the amount of Al increases.

As a result of custom calculation of the experimental results on the basis of these points, as shown in FIG. 1, it was confirmed that the magnetic properties were excellent when the Sn input amount was larger than 285 × Al (wt%)-125. In the case of the excellent magnetic material, the maximum subsurface nitrogen was 5% or less, and the oxygen penetration depth was found to be less than 0.1 μm.

Figure 2 is a graph showing the iron loss of the non-oriented electrical steel sheet according to the Al content and the input amount of Sn. As shown in FIG. 2, in the range of the present invention in which the Sn input amount (ppm) is greater than 285 × Al (wt%)-125, the iron loss was as low as 2.1 (W / Kg), but the Sn input amount (ppm) was 285. It was found that the iron loss increased to 2.3 (W / Kg) or more when less than xAl (wt%)-125 and outside the scope of the present invention.

As in Comparative Materials 6 and 7, Sn tends to deteriorate in the case of more than 800 ppm, which is thought to be because Sn impairs grain growth.

In Comparative Materials Nos. 25-32, under the condition that dew point was less than -10 degrees and easily absorbed, when Sn was not added, the maximum value of subsurface nitrogen was high regardless of the S content. It was. However, in the Inventive Materials Nos. 12-24, the magnetic properties were excellent in the case where the amount of Sn was higher than 285 × Al (wt%)-125 regardless of the content of S in the range of 30 ppm or less.

From these results, the effect of S on the absorption of the non-oriented electrical steel sheet containing 0.45% or more of Al is not great, but S is managed to 30ppm or less so that the magnetism does not deteriorate due to the fine precipitates produced during restocking. It can be seen that it is sufficient, and by adding Sn in an appropriate amount determined according to the Al content, formation of surface nitride is suppressed, and thus it is possible to manufacture non-oriented electrical steel sheet having extremely excellent iron loss characteristics.

Claims (5)

Si: 4.0% or less, Mn: 0.1 to 1.0%, Al: 0.45 to 1.7%, C: 0.005% or less, P: 0.1% or less, S: 0.003% or less, N: 0.003% or less, Ti: 0.005 Less than 0.08% Sn, less than 0.08%, remainder Fe and other unavoidably mixed impurities, but the content of Sn is low iron loss non-oriented electrical steel sheet, characterized in that it is made to satisfy the following formula 1 .
800> Sn (ppm)> 285 × Al (wt%)-125 The method of claim 1,
The steel sheet is low iron loss non-oriented electrical steel sheet, characterized in that the maximum value of the nitrogen fraction under the surface layer is 5% or less when observed by GDS. The method according to claim 1 or 2,
The steel sheet has a low iron loss non-oriented electrical steel sheet, characterized in that the depth of the surface layer oxygen fraction 50% when observed by GDS is less than 0.1㎛. In the method for producing a non-oriented electrical steel sheet which is completed by the usual process of reheating and hot rolling the slab, hot rolling annealing, cold rolling, final annealing,
The slab is made of the composition of the components of claim 1, The final annealing is carried out in an atmosphere consisting of hydrogen and nitrogen, the method of producing a low iron loss non-oriented electrical steel sheet, characterized in that the dew point is managed to be less than -10 degrees. The method of claim 4, wherein
The hot rolled sheet annealing is a method of producing a low iron loss non-oriented electrical steel sheet, characterized in that the surface of the scale in the pickling bath immediately after annealing.

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