JP2004292829A - Non-oriented silicon steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-oriented silicon steel sheet which is composed of steel having minimal Al content and has excellent magnetic properties. <P>SOLUTION: The non-oriented silicon steel sheet has a composition which consists of, by mass, ≤0.004% C, 0.7 to 1.5% Si, 0.15 to 0.8% Mn, 0.06 to 0.2% P, ≤0.005% S, <0.0005% sol.Al, ≤0.003% N, ≤0.012% O, 0 to 0.03% Sn, 0 to 0.03% Sb and the balance Fe with impurities and in which the total content of Sn and Sb is made to 0.002 to 0.03%. Further, in the non-oriented electrical steel sheet, the ratio between the contents (mass%) of MnO and FeO in inclusions existing in the steel, MnO/FeO, is made to ≤2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５６】
この表の結果のうち、鋼成分が本発明で定める範囲内である試番１〜１２と、ｓｏｌ．Ａｌ量以外の鋼成分の量が本発明で定める範囲内である試番２１および試番２２について、ｓｏｌ．Ａｌ量と鉄損の関係を示すと図３のようになる。また、脱酸時の［Ａｌ添加量／Ｓｉ添加量］比と介在物中のＭｎＯ／ＦｅＯ比との関係を図４に示す。
【００５７】
これらからあきらかなように、本発明にて規定する化学組成を有する試番１から１２の鋼板の、歪み取り焼鈍後の鉄損Ｗ_{１５／５０}は、いずれも４．３Ｗ／ｋｇ未満で良好な値を示している。これらの中でも試番１〜１０は、Ｗ_{１５／５０}が４．０Ｗ／ｋｇを下回るすぐれた鉄損値が得られているが、その鋼板の介在物中のＭｎＯ／ＦｅＯ比はいずれも２以下である。そして、このような介在物組成を安定して実現させるためには、脱酸時に用いたＡｌとＳｉの添加量比が、０．４を以下とするのがよいことがわかる。
【００５８】
【発明の効果】
本発明は、Ａｌの含有量をできるだけ低くした鋼による、磁気特性にすぐれた無方向性電磁鋼板である。磁気特性のすぐれた電磁鋼板は、電気エネルギーを回転など他の形のエネルギーに変換するときの変換効率を高めるため、省エネルギーの観点から望ましいが、Ａｌの含有量を低くしたことは、さらにこの鋼板の加工屑などを溶解して再利用する際に、使用が容易でありリサイクル性にすぐれている。
【図面の簡単な説明】
【図１】Ｓｎ＋Ｓｂの添加の有無およびＰ量と、無方向性電磁鋼板の鉄損Ｗ_{１５／５０}の低下との関係を調べた例を示す図である。
【図２】Ｓｎ＋Ｓｂの添加量と無方向性電磁鋼板の磁束密度Ｂ_５０の変化との関係を調べた例を示す図である。
【図３】鋼中のｓｏｌ．Ａｌ量と、無方向性電磁鋼板の鉄損との関係を示す図である。
【図４】溶鋼の脱酸時に添加するＡｌおよびＳｉの添加量比と、鋼板の酸化物系介在物中のＭｎＯ／ＦｅＯの含有量比との関係を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a non-oriented electrical steel sheet. In particular, the present invention relates to a non-oriented electrical steel sheet which is applied to an iron core material of electric equipment such as a motor and a small transformer and is suitable for use after performing strain relief annealing after forming such as punching.
[0002]
[Prior art]
From the perspective of preventing global warming and saving energy, various types of electrical equipment are being made more efficient.Electromagnetic steel sheets, which are used as iron core materials in small motors and small transformers, have low cost, It is required to have excellent magnetic properties. Furthermore, from the viewpoint of effective use of resources and reduction of waste as a countermeasure against environmental pollution, it is necessary to respond to recycling of electrical equipment materials.
[0003]
Non-oriented electrical steel sheets are often used as core materials for small motors and small transformers. The improvement of the magnetic properties of the non-oriented electrical steel sheet mainly aims at reduction of iron loss and increase of magnetic flux density or improvement of magnetic permeability, and many measures have been studied and proposed.
[0004]
The main means of reducing iron loss in steel is to increase the content of Si, Al or Mn, etc., in order to increase the specific resistance and generate eddy current, that is, to suppress eddy current loss. Although Si is the most effective in increasing the specific resistance, its content is limited because it significantly increases the hardness of steel, and the effect of Mn is smaller than that of Si and Al, so a large amount of Mn is necessary. become. Al has a specific resistance increasing effect close to that of Si, and does not have a hardness increase as much as Si. Therefore, iron loss can be reduced without increasing hardness.
[0005]
Means for increasing the magnetic flux density (usually B ₅₀ ) or improving the magnetic permeability include, for non-oriented electrical steel sheets, enlarging the crystal grains, non-metallic inclusions such as carbides, sulfides, oxides and nitrides or fine particles. Reduction of precipitates, increase of preferred orientations for magnetization parallel to the plate surface, and reduction of processing strain can be mentioned. These influence the movement of the domain wall at the time of magnetization, and not only affect each other but also relate to iron loss due to hysteresis loss.
[0006]
For example, the grain boundaries hinder the movement of the domain wall, so making the grains larger reduces the existing area of the grain boundaries in the same volume, making magnetization easier and improving magnetic properties in the form of an increase in magnetic flux density. I do. The fine precipitates not only hinder the movement of the domain wall as in the case of the grain boundaries, but also hinder the grain growth during annealing and reduce the crystal grains. In addition, when the domain wall movement is hindered, hysteresis loss increases, which also increases iron loss. Therefore, in order to improve the magnetic properties of the non-oriented electrical steel sheet, measures are taken to increase the specific resistance, reduce impurities and increase the crystal grains.
[0007]
Also, in order to further improve the magnetic flux density and reduce iron loss, after punching out a motor core, etc., the strain relief annealing is performed at 750 ° C. for 1 to 2 hours for the purpose of strain removal and further crystal grain growth. Is also widely practiced.
[0008]
However, when considering non-oriented electrical steel sheets used for iron cores, there is a possibility that customers will use an electric furnace to melt them when considering recycling, and reuse them. At that time, a material containing a large amount of Al is apt to damage the electrode, and a molten steel containing 0.1% by mass or more of Al causes nozzle clogging and the like during casting, which hinders the casting operation. Get up. Therefore, it is considered that a non-oriented electrical steel sheet having more excellent magnetic properties without using Al is desirable.
[0009]
Al increases the specific resistance of the steel as described above, but has an extremely high affinity for O (oxygen), and is usually used as a deoxidizing agent for molten steel and greatly affects the state of oxide-based inclusions in the steel. I do. In addition, a so-called sol. Al combines with N in steel to form AlN. When the amount of Al is about 0.005 to 0.1%, AlN is dispersed as fine precipitates, hinders the growth of crystal grains, and degrades magnetic characteristics. When it is contained, it is often limited to 0.1% or more, and when it is not contained, it is often limited to 0.005% or less.
[0010]
There have been several proposals regarding non-oriented electrical steel sheets in which the content of Al is reduced as much as possible. For example, in Patent Document 1, Si: 0.1 to 1.0%, Mn: 1.5% or less, sol. Al: 0.001 to 0.005%, and the ratio of the mass of MnO to the total mass of the three types of inclusions of SiO ₂ , MnO, and Al ₂ O ₃ in the steel is set to 15% or less, thereby removing distortion. There is disclosed an invention of a non-oriented electrical steel sheet in which crystal grains after annealing are increased and iron loss is small. Furthermore, in the invention disclosed in Patent Document 2, the ratio of the mass of MnO to the total mass of three types of inclusions of SiO ₂ , MnO, and Al ₂ O ₃ in steel is 15% or less with the same composition as described above. And the ratio of SiO ₂ is 75% or more.
[0011]
Patent Literature 3 discloses that a composition having a composition of Si: 0.05 to 0.55%, Mn: 0.1% or more and Mn-Si ≦ 0.5%, and Al: 0.004% or less. in grain-oriented electrical steel sheet, by mass% ratio MnO / SiO ₂ of SiO ₂ and MnO which is present in the steel is 0.3 or less, the invention is presented that can be reduced surface defects such as Hege or holes ing.
[0012]
As described above, in order to improve the magnetic properties of the non-oriented electrical steel sheet in which the Al content is reduced as much as possible, it is considered important to control the amount of the oxide-based inclusions. However, in order to further improve the magnetic properties, the contents of Si and Mn must be changed, and in that case, it is not clear whether such control of the amount of oxides can be performed.
[0013]
[Patent Document 1]
JP-A-63-195217 [Patent Document 2]
Japanese Patent Publication No. 7-42555 [Patent Document 3]
JP-A-10-147849
[Problems to be solved by the invention]
An object of the present invention is to provide a non-oriented electrical steel sheet having excellent magnetic properties by using a steel having an Al content as low as possible and advantageous for recycling.
[0015]
[Means for Solving the Problems]
The present inventors have conducted various studies in order to improve the magnetic properties of a non-oriented electrical steel sheet in which the amount of Al is reduced as much as possible in consideration of recycling. In order to reduce iron loss, it is desirable to increase the specific resistance. However, since Al is not used, it is necessary to increase the amounts of Si and Mn or to use other elements.
[0016]
Therefore, various compositions were made based on ultra-low carbon steel and various compositions were vacuum-melted in a laboratory to produce an ingot, forged into a slab, then hot-rolled and cold-rolled to a thickness of 0.5 mm, and annealed. A non-oriented electrical steel sheet sample was prepared. After punching out and collecting test pieces from these magnetic steel sheets, the magnetic properties were measured by performing strain relief annealing at 750 ° C. for 2 hours, and the influence of various components on the magnetic properties was investigated.
[0017]
First, when the effect of increasing the amounts of Si and Mn was examined for the purpose of improving iron loss, the iron loss was not improved as expected from the increase in specific resistance, and the magnetic flux density was not good. The possible reason is that sol. This is the formation of Si-Mn nitride due to almost no Al. Generally, when Al is used as a deoxidizing agent, sol. Since Al remains in the steel and combines with N to form AlN, Si-Mn nitride does not appear. However, sol. When Al and the concentration of Si and Mn are high without Al, it is considered that Si-Mn nitrides are generated, and these are finely dispersed to reduce iron loss and decrease magnetic flux density.
[0018]
Thus, sol. The steel was assumed to be almost free of Al, and the possibility of improving the magnetic properties by adding other elements was examined. As a result, it has been found that by including a small amount of one or both of Sn and Sb together with P, an effect of reducing iron loss and improving magnetic flux density can be obtained.
[0019]
P, Sn and Sb are all elements that segregate at crystal grain boundaries. The inclusion of small amounts of these elements slightly increases the specific resistance, but has the effect of reducing the iron loss and increasing the magnetic flux density much more than expected. The reason for this effect is not clear, but as described above, sol. In order to contain Si and Mn as much as possible with Al being minimized, Si-Mn nitride is likely to be formed. On the other hand, by containing P, Sn and Sb in combination, Si -Mn nitride formation appears to be suppressed.
[0020]
It is presumed that the effect of suppressing the formation of fine precipitates promoted grain growth during annealing and improved magnetic properties. In particular, the strain relief annealing at the customer is an annealing at a lower temperature for a longer time than the finish annealing, and it is presumed that suppressing the formation of the Si-Mn nitride is more effective for improving the magnetic properties of the semi-process material. It is further believed that the inclusion of small amounts of these elements may increase the preferred orientation preferred for magnetic properties.
[0021]
Further, these magnetic steel sheets may be annealed at 750 ° C. for 2 hours after punching out a test piece in accordance with actual use conditions of a customer. This annealing is usually heated in a nitrogen atmosphere to prevent oxidation, but the nitrogen in the atmosphere is absorbed by the steel sheet to form nitrides, which may deteriorate magnetic properties. The presence of Sn or Sb also has the effect of suppressing this nitrogen absorption.
[0022]
Next, the state of the nonmetallic inclusions dispersed in the steel of these prototype magnetic steel sheet samples was examined, and the MnO / FeO ratio (mass% ratio) in the oxide-based inclusions was small. It was found that the magnetic properties tended to be better. It is not clear why the magnetic properties are good if the MnO / FeO ratio is small, but as described above, sol. In a component system in which Al is reduced as much as possible, the low-melting-point oxide-based inclusions tend to be coarse, and such coarse oxide-based inclusions are crushed in a subsequent rolling step to be finely dispersed and finished. Since the grain growth during annealing or strain relief annealing is inhibited, the magnetic characteristics are improved by reducing the MnO / FeO ratio in the oxide-based inclusions and suppressing the formation of low-melting-point oxide-based inclusions. It is thought to be.
[0023]
It is presumed that the MnO / FeO ratio of the inclusions is substantially determined at the stage of smelting, deoxidizing, and further casting, such as steel. Thus, as a result of various investigations on the smelting conditions of the steel, it was found that the deoxidation method after decarburization of the molten steel by the vacuum treatment had a great effect.
[0024]
In the case of ultra-low carbon steel such as an electrical steel sheet, in order to reduce carbon as much as possible, a considerably large amount of oxygen is contained in the molten steel after decarburization. If solidified as it is, it becomes a steel ingot full of bubbles, so a deoxidizing agent is added to form an oxide, and oxygen is fixed or eliminated. When adding Si and Al as the deoxidizing agent, the MnO / FeO ratio of the inclusions could be reduced to a specific value or less by setting the additive amount ratio of Al / Si to a certain value or less.
[0025]
Based on the above findings, to obtain a non-oriented electrical steel sheet with better magnetic properties, the content range of each element in the steel, the state of non-metallic inclusions, or the manufacturing conditions for realizing these The limitations have been further clarified and the present invention has been completed. The gist of the present invention is as follows.
[0026]
(1) In mass%, C: 0.004% or less, Si: 0.7 to 1.5%, Mn: 0.15 to 0.8%, P: 0.06 to 0.2%, S : 0.005% or less, sol. Al: less than 0.0005%, N: 0.003% or less, O: 0.012% or less, Sn: 0 to 0.03% and Sb: 0 to 0.03%, provided that the total content of Sn and Sb A non-oriented electrical steel sheet having an amount of 0.002 to 0.03%, with the balance being Fe and impurities.
[0027]
(2) The non-oriented electrical steel sheet according to (1), wherein the ratio “MnO / FeO” of the content (% by mass) of MnO and FeO in the inclusions present in the steel is 2 or less.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the reason for limiting the chemical component or the composition of the inclusion will be described below. All content ratios are mass%.
[0029]
C: 0.004% or less C lowers the magnetic properties of steel, so the smaller the content, the better. If it is 0.004% or less, the effect can be almost ignored, but if it exceeds 0.004%, magnetic aging starts to occur, and if it further increases, the magnetic characteristics deteriorate remarkably. If possible, the content is desirably 0.003% or less.
[0030]
Si: 0.7 to 1.5%
Since Si increases the specific resistance of steel and reduces iron loss, it is contained in an amount of 0.7% or more to obtain a desired iron loss. However, an increase in the Si content increases the hardness and promotes wear of the punching die.
[0031]
Mn: 0.15 to 0.8%
Mn has the effect of increasing the specific resistance, and has the effect of making it harmless by combining with S that is mixed in as an impurity. If the amount is small, the generated MnS is finely dispersed, which inhibits crystal grain growth and deteriorates magnetic properties. However, sol. When the amount of Al is extremely small and the amount of Si is large as described above, when the amount of Mn is increased, the magnetic properties are significantly reduced. Therefore, it is limited to at most 0.8%. This is presumed to be due to an increase in grain growth inhibition during annealing due to an increase in Si-Mn nitride. Preferably it is 0.15 to 0.5%.
[0032]
P: 0.06-0.2%
In the steel sheet of the present invention, P has an important effect of reducing iron loss by the combined addition with Sn and / or Sb described later, and is positively utilized. In order to reduce the iron loss, it is necessary to contain 0.06% or more. However, if too much is contained, it becomes hard and brittle, and wear of the punching die becomes faster.
[0033]
S: 0.005% or less S forms fine precipitates and not only inhibits the growth of crystal grains, but also deteriorates magnetic properties. The fine precipitates due to S are mainly MnS, but it is presumed that the presence of MnS also serves as a nucleus for Si-Mn nitride formation and promotes the formation of this nitride. The range in which such adverse effects do not appear remarkably is limited to 0.005% or less, but is preferably 0.004% or less, and more preferably 0.003% or less.
[0034]
sol. Al: less than 0.0005% Al is used for the purpose of deoxidizing to obtain a defect-free steel ingot. Usually, as a result, sol. Al (acid-soluble Al) remains in the steel, but in the present invention, this sol. The amount of Al is made as small as possible and less than 0.0005%. This is sol. This is because, when the amount of Al increases, fine AlN precipitates are formed, which hinder the growth of crystal grains during annealing, and the crystal grains do not become sufficiently large to improve the magnetic properties.
[0035]
N: 0.003% or less The smaller the content of N, the better. N forms fine nitrides with Al or Si-Mn, thereby hindering the growth of crystal grains during annealing and hindering the improvement of magnetic properties, and the fine precipitates themselves also deteriorate magnetic properties. Therefore, the content is limited to 0.003% or less, and more preferably 0.002% or less.
[0036]
O: 0.012% or less O (oxygen) forms oxide-based inclusions and inhibits the growth of crystal grains to deteriorate magnetic properties. However, since the presence of oxygen is necessary for decarbonizing molten steel by vacuum treatment, it is inevitable that a certain amount of oxygen remains for extremely low carbon. The content is set to 0.012% or less as a range that does not have a significant adverse effect, but is preferably 0.008% or less.
[0037]
Sn: 0 to 0.03%, Sb: 0 to 0.03%, provided that Sn + Sb: 0.002 to 0.03%
One or two of Sn: 0.03% or less and Sb: 0.03% or less are contained in the total amount of Sn and Sb in the range of 0.002 to 0.03%. This is because the magnetic properties are improved by containing P together with 0.06 to 0.2% of P. It is considered that the reason for the improvement of the magnetic properties is that these elements suppress the formation of the Si-Mn nitride.
[0038]
The result of investigating the effect of the addition of P, Sn and Sb is shown below. Using a vacuum melting furnace, C: 0.002%, Si: 0.85%, Mn: 0.25%, S: 0.0025%, sol. Al: 0.0004% or less, N: 0.002%, O: 0.012% or less based on steel, P content 0.01 to 0.18%, Sn + Sb content 0.001 to 0.1% The ingot changed in the range described above was melted and forged into a 15 mm thick slab, then heated at 1100 ° C., hot rolled, finished to a 3 mm thickness, and ground to 2.3 mm. Then, it was cold-rolled to 0.5 mm. This steel sheet was subjected to finish annealing equivalent to continuous annealing at 750 ° C. for 30 seconds to obtain a non-oriented electrical steel sheet sample.
[0039]
A test piece having a width of 30 mm and a length of 100 mm was punched out of these steel sheets so that the length direction was parallel and perpendicular to the rolling direction, and used as magnetic property measurement test pieces. After annealing at 750 ° C. for 2 hours in a nitrogen atmosphere, The magnetic properties in the rolling direction and the direction perpendicular to the rolling direction were measured by a small single-plate magnetometer, and the average value was determined.
[0040]
FIG. 1 shows a change in iron loss _{W15 / 50} depending on the P content when Sn or Sb is not added (Sn + Sb: less than 0.002%) and when Sn + Sb is 0.015%. From this, iron loss is reduced by increasing the content of P, but when Sn and Sb are added, the iron loss is greatly reduced, especially when P is 0.06% or more, and the iron loss is less than 4 W / kg. You can see that.
[0041]
The case in FIG. 2 P is 0.03%, shows the results of examining the change in the magnetic flux density _{B 50} by the addition of Sn and Sb in the case of 0.10%, when it contains much P, Addition of Sn and Sb shows a remarkable improvement in magnetic flux density, and the effect is exhibited when the content of Sn + Sb is 0.002% or more. However, even if the content of Sn + Sb exceeds 0.03%, the effect is saturated and further improvement cannot be obtained.
[0042]
In addition, when Sn and Sb are re-dissolved in scrap and the like, the mixing of these elements may cause welding cracks and surface flaws, so the amount of Sn + Sb should not exceed 0.03%.
[0043]
It is desirable that the content ratio of MnO / FeO in the inclusions is 2 or less. This is because by setting the ratio to 2 or less, the iron loss is greatly reduced. MnO and FeO in steel can be extracted and analyzed by the bromine-methanol method. In order to keep the MnO / FeO ratio at 2 or less, it is preferable to add Si and Al in the deoxidizing treatment of the molten steel, and to make the Al / Si ratio at that time 0.4 or less.
[0044]
The carbon content of the steel is reduced by a vacuum treatment method of molten steel such as an RH type degassing method. However, in the case of a target ultra-low carbon steel, the oxygen in the molten steel at the end of decarburization is considerably high. It is necessary to add an appropriate deoxidizing agent. In order to produce a sound slab, Si alone is incomplete and must use Al as a deoxidizing agent. However, when Al is left in a solid solution state, the magnetic properties of the steel sheet are deteriorated.
[0045]
Therefore, oxygen corresponding to the Al concentration is supplied to the molten steel, and Al is oxidized to reduce the sol. The Al content is controlled to less than 0.0005%. The Al concentration in the molten steel can be determined by a direct method of analyzing the molten steel or an indirect method of measuring the oxygen concentration with an oxygen sensor and calculating from the Al-O equilibrium. The amount of oxygen supplied to the molten steel may be an equivalent amount required for the reaction with Al, but it is more certain that sol. To reduce Al, it is preferable to further increase Al by 10 to 20% with respect to the equivalent amount. As a method for supplying oxygen, any method such as a method of adding a solid oxide lump or powder such as iron oxide or Mn oxide to molten steel, and a method of blowing or blowing oxygen gas to molten steel may be used.
[0046]
Si and Al as deoxidizing agents are added in the above ratio. At this time, both components may be added at the same time, but it is preferable to add Al after adding Si. Since Al relative to Si is force deoxidation is extremely large, it is added to Al above alumina inclusions and _FeO-MnO-Al 2 _{O 3} inclusions is generated, controls the MnO / FeO ratio 2 below Becomes difficult.
[0047]
On the other hand, when Al is added after Si is added, Al can be processed in a short time because Al has a greater deoxidizing power and a higher reaction rate. However, the ratio of the amount of Al added / the amount of Si to be added is set to 0.4 or less in any method.
[0048]
After the deoxidation treatment of the molten steel is performed by adding Si and Al in this way, a deficiency with respect to the target composition of Mn is added, and further, alloying elements of P, Sn and Sb are added to adjust the components. In addition, you may add these each component element before deoxidation.
[0049]
The molten steel whose composition is adjusted is used as a rolling slab by a continuous casting method or a steel ingot-bulking rolling method. The slab is subjected to hot rolling, cold rolling, annealing, surface coating, and the like according to a normal method for manufacturing a non-oriented electrical steel sheet to obtain a product.
[0050]
In the above manufacturing process, the slab heating temperature of the hot rolling is desirably 1000 to 1150 ° C. This is because by setting the temperature to 1150 ° C. or less, the magnetic characteristics of the obtained product are improved and the variation in the characteristics is reduced. However, at a heating temperature lower than 1000 ° C., the temperature of the portion of the slab hitting the skid is low. Too much, the deformation resistance may increase, and the thickness variation may increase. The finishing temperature of the hot rolling is preferably 830 to 930 ° C. This is because if the temperature is lower than 830 ° C. or exceeds 930 ° C., the iron loss and the magnetic flux density decrease, and sufficient magnetic properties cannot be obtained.
[0051]
In particular, when the magnetic properties are to be improved, it is preferable to perform hot rolled sheet annealing before cold rolling after hot rolling, but it is not necessary to perform annealing. The rolling reduction of the cold rolling is desirably 70 to 85%. This is because the thickness of non-oriented electrical steel sheet is mainly 0.5 mm, and at a rolling reduction of less than 70%, the thickness of the hot-rolled sheet is thin, the load on the hot rolling equipment increases, and the pickling efficiency decreases. This is because the magnetic properties deteriorate when the rolling reduction exceeds 85%.
[0052]
【Example】
Molten steel refined in a converter is decarburized using an RH-type vacuum degasser, and after adding Mn, P, Sn and Sb, Al and Si are simultaneously added at a different ratio to deoxidize. Then, it was continuously cast into a slab. Table 1 shows the composition of the prototype steel and the addition ratios of Al and Si used during deoxidation.
[0053]
Using these slabs, hot rolling was performed at a heating temperature of 1100 ° C, and finishing was performed at 860 to 880 ° C to obtain a steel sheet having a thickness of 2.3 mm. After pickling, it was cold-rolled to a thickness of 0.5 mm, annealed at 810 ° C. in a continuous processing line, and coated with a 0.2 μm-thick insulating film on the surface.
[0054]
Test pieces having a width of 30 mm and a length of 280 mm were punched out of these steel sheets, annealed in a nitrogen atmosphere at 750 ° C. for 2 hours, and then magnetic properties were measured based on JIS-C-2550. Further, inclusions were extracted from these steel sheet samples by the bromine-methanol method, and the amounts of MnO and FeO in the inclusions were analyzed to determine the MnO / FeO ratio. Table 1 also shows the measurement results of the magnetic characteristics and the MnO / FeO ratio.
[0055]
[Table 1]

[0056]
Of the results in this table, sample numbers 1 to 12 in which the steel component is within the range defined by the present invention, sol. Sample No. 21 and Sample No. 22 in which the amounts of the steel components other than the amount of Al are within the range specified in the present invention, are described in sol. FIG. 3 shows the relationship between the Al content and the iron loss. FIG. 4 shows the relationship between the [Al addition amount / Si addition amount] ratio during deoxidation and the MnO / FeO ratio in inclusions.
[0057]
As is apparent from the above, the iron loss W _15/50 after strain relief annealing of each of the steel sheets of Nos. 1 to 12 having the chemical composition specified in the present invention is less than 4.3 W / kg, which is favorable. Indicates the value. Among them, Test Nos. 1 to 10 have excellent iron loss values in which W _15/50 is less than 4.0 W / kg, but the MnO / FeO ratio in the inclusions of the steel sheet is 2 or less. It is. Then, in order to stably realize such an inclusion composition, it is found that the ratio of the added amount of Al and Si used at the time of deoxidation should be 0.4 or less.
[0058]
【The invention's effect】
The present invention is a non-oriented electrical steel sheet having excellent magnetic properties, which is made of a steel having an Al content as low as possible. Electromagnetic steel sheets with excellent magnetic properties are desirable from the viewpoint of energy saving in order to increase the conversion efficiency when converting electric energy into energy of other forms such as rotation.However, lowering the Al content further reduces this steel sheet. It is easy to use and excellent in recyclability when dissolving and recycling processing wastes.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example in which the relationship between the presence or absence of Sn + Sb and the amount of P and the decrease in iron loss _{W15 / 50} of a non-oriented electrical steel sheet is examined.
2 is a diagram showing an example of examining the relationship between the change in the magnetic flux density B ₅₀ of the addition amount and the non-oriented electrical steel sheet Sn + Sb.
FIG. 3 shows sol. It is a figure which shows the relationship between the amount of Al and the iron loss of a non-oriented electrical steel sheet.
FIG. 4 is a diagram showing the relationship between the addition ratio of Al and Si added during deoxidation of molten steel and the content ratio of MnO / FeO in oxide inclusions of a steel sheet.

Claims (2)

In mass%, C: 0.004% or less, Si: 0.7 to 1.5%, Mn: 0.15 to 0.8%, P: 0.06 to 0.2%, S: 0. 005% or less, sol. Al: less than 0.0005%, N: 0.003% or less, O: 0.012% or less, Sn: 0 to 0.03%, and Sb: 0 to 0.03%, provided that the total content of Sn and Sb A non-oriented electrical steel sheet having an amount of 0.002 to 0.03%, with the balance being Fe and impurities. 2. The non-oriented electrical steel sheet according to claim 1, wherein the ratio “MnO / FeO” of the content (% by mass) of MnO and FeO in the inclusions present in the steel is 2 or less.

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