JP2019508574A - Non-oriented electrical steel sheet and method of manufacturing the same - Google Patents

Abstract

A non-oriented electrical steel sheet having improved magnetism by limiting the amount of alloying elements to be added so that precipitates grow large and facilitating grain growth and movement of magnetic domains during magnetization Providing the manufacturing method. A non-oriented electrical steel sheet according to an embodiment of the present invention is, by mass%, C: 0.005% or less (except 0%), Si: 1.0 to 4.0%, Al: 0 .15 to 1.5%, Mn: 0.1 to 1.0%, P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0 .001% to 0.006%, Ti: 0.005% or less (excluding 0%), O: 0.005% or less (excluding 0%) and the balance are Fe and unavoidable impurities thereof, the following numbers 1 is characterized in that the average size of oxides among the precipitates is larger than the average size of non-oxides. (In the formula 1, [Si], [Al] and [Mn] respectively indicate the content (mass%) of Si, Al and Mn).

Description

The present invention relates to a non-oriented electrical steel sheet and a method of manufacturing the same, and more specifically, the amount of alloying elements to be added is limited so that precipitates grow largely, and grain movement and movement of magnetic domains during magnetization are performed. The present invention relates to a non-oriented electrical steel sheet having improved magnetism by facilitating the method and a method of manufacturing the same.

Non-oriented electrical steel sheets are used as materials for iron cores in rotating devices such as motors and generators and in stationary devices such as small transformers, and play an important role in determining the energy efficiency of electrical devices. Therefore, recently, there is a demand for improving the efficiency of electrical devices in terms of energy saving, downsizing of electrical devices, etc., which leads to a demand for improving the characteristics of non-oriented electrical steel sheets. Typical characteristics of the magnetic steel sheet include iron loss and magnetic flux density, smaller iron loss and higher magnetic flux density are better, but iron loss is caused by adding electricity to the iron core to induce a magnetic field The lower the temperature, the less energy is dissipated by heat, and the higher the magnetic flux density, the larger the magnetic field can be induced at the same energy. Therefore, in order to save energy and meet the increase in demand for eco products, it is necessary to develop a manufacturing technology for non-oriented electrical steel sheet with low core loss and high magnetic flux density.

Among the magnetic properties of the non-oriented electrical steel sheet, as a typical method for improving the core loss, a method of greatly reducing the thickness and a method of adding an element having a large specific resistance such as Si or Al is there. However, in the case of thickness, it is determined according to the characteristics of the product to be used, and the thinner the thickness, the lower the productivity and the higher the cost. If the alloy element is added also in the method of adding Si, Al, Mn, etc. of alloy elements having large resistivity, which is a method of reducing iron loss due to the increase of electric resistivity of general materials, the core loss decreases, but the saturation flux Due to the reduction of the density, the reduction of the magnetic flux density also has an inevitable contradiction. In addition, if the amount of Si added is 4% or more, the workability is lowered and cold rolling becomes difficult, the productivity is lowered, and as more Al, Mn, etc. are added, the rollability is lowered, the hardness Increase and the processability also falls. Therefore, there is a need for a technique for adding these additive elements most appropriately to lower the cost and improve the magnetism.

On the other hand, in the steel, additive elements such as Fe, SI, Al, Mn, etc. are inevitably combined with C, S, N, O, Ti, etc. which are impurity elements to form fine precipitates. As a result, the growth of crystal grains is suppressed, the movement of the magnetic domain is hindered, and the magnetic properties are reduced. Such deposits in steel include carbides, nitrides, sulfides and oxides. These are shown alone or in combination. These fine compounds are classified into inclusions or precipitates depending on their size and formation cause, but since the inclusions have a size of 100 nm or more, they are found at 100 nm or less without significantly affecting grain growth. Precipitates are known to inhibit grain growth.
If these precipitates are fine, the number increases, and the size of the precipitates may be increased or two or more composite precipitates may be formed in order to suppress the movement of magnetic domains and grain growth. is important.

The aim of the present invention is to improve the magnetism by limiting the amount of alloying elements added to make the precipitates grow large and facilitating the grain growth and the movement of the magnetic domain during magnetization. A non-oriented electrical steel sheet and a method of manufacturing the same.

（但し、数１において、［Ｓｉ］、［Ａｌ］及び［Ｍｎ］は、それぞれＳｉ、Ａｌ及びＭｎの含有量（質量％）を示す。） The non-oriented electrical steel sheet according to the present invention is, by mass%, C: 0.005% or less (except 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1.5%, Mn: 0.1 to 1.0%, P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0.001% to 0.006% , Ti: 0.005% or less (excluding 0%), O: 0.005% or less (excluding 0%) and the balance consist of Fe and its unavoidable impurities, and satisfy the following formula 1; Among them, the average size of oxides is characterized by being larger than the average size of non oxides.

(However, in the formula 1, [Si], [Al] and [Mn] indicate the content (mass%) of Si, Al and Mn, respectively.)

Among the precipitates, the number of oxides is greater than that of non-oxides,
0.01 to 0.2% by mass of Sn and Sb alone or in combination, respectively, further
Among the precipitates, the number of precipitates containing FeO or FeO is 40% or more,
It is characterized in that the average grain size is 50 to 180 μm.

（但し、数１において、［Ｓｉ］、［Ａｌ］及び［Ｍｎ］は、それぞれＳｉ、Ａｌ及びＭｎの含有量（質量％）を示す。） The method for producing a non-oriented electrical steel sheet according to the present invention comprises, in mass%, C: 0.005% or less (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1. 5%, Mn: 0.1 to 1.0%, P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0.001% to 0 .006%, Ti: 0.005% or less (excluding 0%), O: 0.005% or less (excluding 0%) and the balance are Fe and incidental impurities thereof, and a slab satisfying the following formula 1 Heat-rolling and then hot-rolling to produce a hot-rolled sheet, winding-up and cooling the hot-rolled sheet, annealing and cooling the hot-rolled sheet, and cold-rolling the hot-rolled annealed sheet And at the temperature of 600 ° C. or higher in the step of cooling after rolling up the hot rolled sheet, including the steps of manufacturing the cold rolled sheet and finally annealing and cooling the cold rolled sheet. At the stage of maintaining for 0 minutes or more, cooling, hot-rolled sheet annealing and cooling, cooling at 600 ° C. or more for 5 seconds or more, and finally annealing and cooling the cold-rolled sheet at 600 ° C. or more for 5 seconds or more It is characterized by cooling.

(However, in the formula 1, [Si], [Al] and [Mn] indicate the content (mass%) of Si, Al and Mn, respectively.)

The slab further contains 0.01 to 0.2% by mass of Sn and Sb alone or in combination,
In the step of producing the hot-rolled sheet, the slab is heated at 1200 ° C. or less,
In the stage of cooling after winding the hot-rolled sheet, the winding temperature is 600 to 800 ° C.,
At the stage of annealing and cooling the hot-rolled sheet, the annealing temperature of the hot-rolled sheet is 850 to 1150 ° C.,
In the stage of cold rolling a hot rolled annealed sheet to produce a cold rolled sheet, cold rolling to a thickness of 0.1 to 0.7 mm,
In the stage of cold rolling a hot rolled annealed sheet to produce a cold rolled sheet, cold rolling includes primary cold rolling, intermediate annealing and secondary cold rolling,
At the stage of final annealing and cooling of the cold-rolled sheet, at the time of annealing, the crack temperature of the annealing is 850 to 1100 ° C.,
Among precipitates of manufactured electromagnetic steel sheet, the average size of oxide is larger than the average size of non-oxide,
Among the precipitates, the number of oxides is greater than that of non-oxides,
Among the precipitates, the number of precipitates containing FeO or FeO is 40% or more,
It is characterized in that the average grain size is 50 to 180 μm.

According to the present invention, the magnetism can be improved by making the precipitates grow large to facilitate the crystal grain growth and the movement of the magnetic domain during magnetization.

The terms first, second and third are used to describe various parts, components, regions, layers and / or sections, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Therefore, the first part, component, region, layer or section described below can be referred to as a second part, component, region, layer or section within the scope of the present invention.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms also include the plural unless the context clearly indicates otherwise. The term "comprising", as used in the specification, embodies a particular property, region, integer, step, action, element and / or component, and the other property, region, integer, step, action, element and / or component It does not exclude the existence or addition of
Where one part is said to be “above” the other part, this may be directly above or above the other part, or the other part may be interposed therebetween. In contrast to this, if one part is "above" another part, no other part is interposed therebetween.
Although not otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are further interpreted as having meanings that conform to the relevant technical literature and the content currently disclosed, and are interpreted as ideal or overly numerical meanings unless otherwise defined. I will not.
Also, unless otherwise stated,% means mass%, and 1 ppm is 0.0001 mass%.
Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention belongs can easily implement. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

（但し、数１において、［Ｓｉ］、［Ａｌ］及び［Ｍｎ］は、それぞれＳｉ、Ａｌ及びＭｎの含有量（質量％）を示す。） The non-oriented electrical steel sheet according to one embodiment of the present invention is, by mass%, C: 0.005% or less (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1 .5%, Mn: 0.1 to 1.0%, P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0.001% to 0.006%, Ti: not more than 0.005% (excluding 0%), O: not more than 0.005% (excluding 0%) and the balance are Fe and unavoidable impurities thereof, satisfying the following formula 1 Among the precipitates, the average size of the oxide is larger than the average size of the non-oxide.

(However, in the formula 1, [Si], [Al] and [Mn] indicate the content (mass%) of Si, Al and Mn, respectively.)

In one embodiment of the present invention, among the components of the non-oriented electrical steel sheet, the components such as Si, Al, Mn, etc. are precisely controlled, precipitates are formed as large as possible, and precipitates do not exist alone. Precipitates were intended to be largely precipitated by causing complex precipitation. Further, the magnetism is improved by forming the average size of the oxide among the precipitates larger than the average size of the non-oxide.
In one embodiment of the present invention, the element to be added is Si, Mn, Al, P or optionally Sn, Sb, and there is Fe as a base material. Other elements to be added include O, C, N, S, etc., which need to be managed low. There are nitrides and carbides that these elements N and C make with other elements, oxides that make Al, Mn, Si and Fe etc. with O, and sulfides that Mn and Cu make with S, etc. It occurs alone or in combination.

In one embodiment of the present invention, coarsening of the precipitates was attempted, and in particular, it was attempted to grow more easily by causing the precipitates to be complexly deposited not alone. Among them, since the oxide is a possible element without adding an additional element, coarsening was easier. It has been confirmed that this improves the magnetism of the magnetic steel sheet.
Among the precipitates, the oxide was 50% or more of the total number of precipitates, and among the oxides, FeO particularly occupied 40% or more. In particular, the influence of the oxide has a great effect on the complex precipitation of the precipitates. Although these oxides lowered O during steelmaking operations, it is judged that they remain as oxides in the steel or are precipitated after annealing. When the sulfides are re-heated and cooled after hot rolling, a considerable amount is deposited, and these appear as precipitation as CuS, MnS or their composite precipitates. However, the oxide has more complex precipitates of oxides such as FeO, Al ₂ O ₃ and SiO ₂ than sulfides, and the bond between the nitrides of the oxides and carbides is relatively small.

Among the precipitates generated in the present invention, oxides are present singly or in combination, and the average size is 15 nm to 70 nm, and the average number is confirmed to be 10,000 to 400,000 per 1 mm ² It was done. Further, among the precipitates, non-oxides were confirmed alone or in combination to have an average size of 10 nm to 50 nm, and an average number of 5,000 to 200,000 per 1 mm ² .
By thus forming the average size of the oxide among the precipitates larger than the average size of the non-oxide, the crystal grain growth can be facilitated, and specifically, the size of the average crystal grain It can be 50 to 180 μm. At this time, the grain size refers to the grain size measured by the intercept method generally used in the field of electrical steel sheet.

The reasons for limiting the components of the non-oriented electrical steel sheet will be described below.
Si: 1.0 to 4.0 mass%
Silicon (Si) is a component that increases the specific resistance of steel and lowers the eddy current loss in the core loss, and thus is a main element to be added, and is an element that easily forms an oxide. If the Si content is too low, low core loss characteristics are difficult to obtain, and if Si is added excessively, cold rolling may be difficult. Therefore, it limits to 1.0 to 4.0 mass%.
Mn: 0.1 to 1.0% by mass
Manganese (Mn) has the effect of lowering core loss by increasing the specific resistance together with Si, Al, etc. Therefore, manganese (Mn) is added for the purpose of improving core loss by adding at least 0.1 mass% of Mn. Do. However, as the amount of addition of Mn increases, the saturation magnetic flux density decreases, so the magnetic flux density decreases, and, together with S, fine MnS precipitates are formed to suppress grain growth and domain wall motion. It has a disadvantage that it increases the hysteresis loss among the iron loss, and 1.0% by mass or less is added.

Al: 0.15 to 1.5% by mass
Aluminum (Al) is an element that is inevitably added for deoxidation of steel in the steel making process and is a main element that increases the specific resistance, so a large amount is added to lower core loss. The addition also plays a role of reducing the saturation magnetic flux density. In addition, if the amount of Al added is excessively small, fine AlN can be formed to suppress crystal grain growth and reduce magnetism. Moreover, since excessive addition of Al causes a decrease in magnetic flux density, the amount of addition is limited to 0.15 to 1.5% by mass.
P: 0.2% by mass or less Phosphorus (P) increases resistivity, lowers core loss, suppresses formation of a texture harmful to magnetism by segregating in a grain system, and has an advantageous texture The {100} is formed, but when it is added in excess, the rollability is reduced, so it is limited to 0.2% by mass or less.
C: 0.005% by mass or less Carbon (C), when added in a large amount, expands the austenite region, increases the phase transformation interval, suppresses grain growth of ferrite when annealing, and increases core loss In addition, it combines with Ti etc. to form carbides and lowers the magnetism, and after processing as an electrical product in the final product, increases iron loss due to magnetic aging during use, so it is less than 0.005 mass%. Restrict.

N: 0.005% by mass or less Nitrogen (N) is an element harmful to magnetism such as forming nitrides by strongly bonding to Al, Ti, etc. to suppress crystal grain growth, so the content should be small. Is preferable, and is limited to 0.005% by mass or less.
S: 0.001 to 0.006 mass%
Sulfur (S) is an element which forms sulfides such as MnS, CuS and (Cu, Mn) S which are harmful to magnetic properties, and therefore, it is preferable to add as low as possible. However, when the addition amount is too small, it is rather disadvantageous for texture formation and the magnetism is lowered. In addition, when added in excess, the increase in fine sulfides makes the magnetism inferior. Therefore, it limits to 0.001-0.006 mass%.
Ti: 0.005% by mass or less Titanium (Ti) forms fine carbides and nitrides to suppress crystal grain growth, and the addition of more carbides and carbides causes the texture to be inferior by increasing the amount of carbides and nitrides, Magnetism gets worse. Therefore, it limits to 0.005 mass% or less.

O: 0.005% by mass or less Oxygen (O) can be contained as low as possible to form various oxides to suppress grain growth. Therefore, it limits to 0.005 mass% or less.
Sn, Sb: 0.01 to 0.2% by mass
Tin (Sn) and antimony (Sb) are elements that segregate in the grain system, and are effective in suppressing the diffusion of nitrogen by the grain system and suppressing the {111} texture harmful to magnetism {100 } Adds in order to increase the texture and improve the magnetic properties, and when each of Sn and Sb is added singly or in combination, excessive addition of Sn and Sb suppresses crystal grain growth and lowers magnetism, and rolling properties deteriorate . Therefore, when Sn or Sb is contained, one or each of Sn and Sb is limited to 0.01 to 0.2% by mass.

（但し、数１において、［Ｓｉ］、［Ａｌ］及び［Ｍｎ］は、それぞれＳｉ、Ａｌ及びＭｎの含有量（質量％）を示す。） In particular, in one embodiment of the present invention, by adjusting Si, Mn, and Al among the additive elements to satisfy the following equation 1, it is made to have the condition that the Mn content is high and the Si content is high, A considerable amount of Al is also contained to suppress AlN and the like.

(However, in the formula 1, [Si], [Al] and [Mn] indicate the content (mass%) of Si, Al and Mn, respectively.)

In the method of manufacturing a non-oriented electrical steel sheet according to an embodiment of the present invention, C: 0.005% or less (excluding 0%), Si: 1.0 to 4.0%, Al: 0. 15 to 1.5%, Mn: 0.1 to 1.0%, P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0. 001% to 0.006%, Ti: 0.005% or less (excluding 0%), O: 0.005% or less (excluding 0%) and the balance are Fe and unavoidable impurities thereof, and the following number 1 After the slab is heated and then hot rolled to produce a hot rolled sheet, the step of winding the hot rolled sheet after cooling, the step of annealing and cooling the hot rolled sheet, the hot rolled annealed sheet Cold rolling to produce a cold rolled sheet, and finally annealing and cooling the cold rolled sheet, and in the step of cooling the hot rolled sheet after winding, C. for 30 minutes or more, cooling, hot-rolled sheet annealing and cooling, cooling at 600 ° C. or more for 5 seconds or more, and finally annealing and cooling a cold-rolled sheet at 600 ° C. or more Cool for 5 seconds or more.
After the hot-rolled sheet production, after the hot-rolled sheet annealing, when cooling after the cold-rolled sheet annealing, it was slowly cooled to allow time for the precipitates to grow to improve the magnetism.

The steps of each step will be described below.
First, the slab is heated and then hot rolled to produce a hot-rolled sheet. The reason for limiting the addition ratio of each composition is the same as the reason for limitation of the non-oriented electrical steel sheet described above. The composition of the slab in the process of hot rolling, hot rolled sheet annealing, cold rolling, final annealing, etc. described later does not substantially change, so the composition of the slab and the composition of the non-oriented electrical steel sheet are substantially the same. It is.
The slab may be introduced into a furnace and heated to 1200 ° C. or less. If the heating temperature is too high, precipitates such as AlN and MnS present in the slab are re-solidified and then finely precipitated during hot rolling, thereby suppressing grain growth and reducing magnetism. More specifically, it heats at 1050 ° C-1200 ° C.
The heated slab is hot-rolled to 1.4 mm to 3 mm to produce a hot-rolled sheet. The finish rolling in finish rolling in hot rolling is finished on the ferrite, and the final rolling reduction is performed at 20% or less for plate-like correction.

Next, the hot-rolled sheet is cooled after being wound up. The hot-rolled sheet is wound at a temperature of 600 ° C. to 800 ° C., and placed in air or in a separate furnace for cooling. The cooling temperature is maintained at 600 ° C. or more for at least 30 minutes or more. If the temperature is too low or the maintenance time is short, the growth of the precipitate is difficult and it is finely precipitated. More specifically, the temperature is maintained at a temperature of 600 to 800 ° C. for 30 minutes to 3 hours.
Next, the hot-rolled sheet is annealed and cooled. Annealing the hot-rolled sheet is to improve the magnetic properties, and the annealing temperature of the hot-rolled sheet is set to 850 to 1150 ° C. If the annealing temperature of the hot-rolled sheet is too low, grain growth may be insufficient. If the annealing temperature of the hot-rolled sheet is too high, crystal grains grow excessively and the surface defects of the sheet become excessive.
Cooling upon cooling after hot-rolled sheet annealing is maintained at 600 ° C. or more for 5 seconds or more without rapid cooling. If the temperature during cooling is too low or the maintenance time is short, coarsening of the precipitates is difficult and the plate may be bent. More specifically, the temperature at the time of cooling may be 600 to 800 ° C. and maintained for 5 to 30 seconds.
You may pickle after hot-rolled sheet annealing.

Next, the hot-rolled annealed sheet is cold-rolled to produce a cold-rolled sheet. Cold rolling is final rolling to a thickness of 0.1 mm to 0.7 mm, and if necessary, primary cold rolling, intermediate annealing, secondary cold rolling, final rolling reduction in the range of 50 to 95% Make it
Next, the cold rolled sheet is finally annealed and cooled. The crack temperature of the cold rolled sheet annealing at the time of annealing in the step of annealing the cold rolled sheet is set to 850 to 1100 ° C. When the annealing temperature of the cold rolled sheet is below 850 ° C, the growth of crystal grains is insufficient, the {111} texture which is the texture harmful to magnetism increases, and the crystal grain grows excessively at 1100 ° C or more The crack temperature of the cold rolled sheet is set to 850 to 1100 ° C. because the magnetism is adversely affected.
Cooling when cooling after cold-rolled sheet annealing is maintained for 5 seconds or more at 600 ° C. or more without quenching. When the temperature for cooling is too low or the maintenance time is short, fine precipitates precipitate alone. More specifically, the cooling temperature is maintained at 600 to 800 ° C. for 5 to 30 seconds.
The annealed sheet is shipped to the customer after the insulation coating process. The insulating coating may be treated with an organic, inorganic and organic-inorganic composite coating, and may be treated with other insulating coatings. The customer company can use it as it is after processing the steel plate.

Hereinafter, the present invention will be described in more detail by way of examples. However, such examples are merely to illustrate the present invention, and the present invention is not limited thereto.
Example 1
Production of steel ingots as shown in Tables 1 and 2 below by vacuum melting to satisfy the number 1 of the invention steels A1 to A7 in which the amounts of% by mass of Si, Al and Mn satisfy the number 1 None of the comparison steels from A8 to A12 were melted.
The vacuum melting steels A1 to A7 are manufactured with contents of Si, Al and Mn in the range of the present invention, and each steel ingot is heated at 1120 ° C. and hot rolled to a thickness of 2.2 mm. The hot rolled steel sheet rolled up, gradually cooled in air as shown in Table 2 and then cooled, was annealed in a nitrogen atmosphere for 5 minutes, and at a temperature of 600 ° C. or more in an atmosphere in which nitrogen and oxygen were mixed It was slowly cooled and finally quenched with water. The annealed hot-rolled sheet was pickled and cold-rolled to a thickness of 0.35 mm, and the final annealing of the cold-rolled sheet was annealed for 2 minutes in a mixed atmosphere of 30% hydrogen and 70% nitrogen. The cooling zone was cooled in an atmosphere of 40% hydrogen and nitrogen. For the final annealed sheet, the size and number of oxides, sulfides, carbides, nitrides and their composite precipitates were investigated for each specimen, and the crystal grains and magnetism were measured, and the results are summarized in Table 3 below. .

As a method for analyzing the size, type and distribution of precipitates, a method of observing carbon replica extracted from a specimen by TEM and analyzing it by EDS was used. In TEM observation, types of precipitates were analyzed by EDS spectrum in randomly selected areas without bias.
Iron loss _{(W 15/50)} was measured in the rolling direction and the average loss in the rolling direction vertical when the magnetic flux density of 1.5Tesla is induced by 50Hz frequency (W / kg).
The magnetic flux density (B ₅₀ ) was measured by the magnitude (Tesla) of the magnetic flux density induced when a magnetic field of 5000 A / m was applied.

As shown in Tables 1 to 3, A1 to A7 satisfy the composition range and the number 1 of the magnetic steel sheet, and the size of the oxide among the precipitates is larger than the size of the non-oxide. It can be confirmed that crystal grains also grow well, and iron loss and magnetic flux density are also excellent. On the other hand, A8 to A12 do not satisfy the composition range and the number 1 of the magnetic steel sheet, and it can be confirmed that the size of the oxide among the precipitates is smaller in part than the size of the non-oxide. Therefore, it can be confirmed that iron loss and magnetic flux density are inferior.

Example 2
The steel ingots as shown in Tables 4 and 5 below were manufactured by vacuum melting, and the invention steels A13 to A15 in which the amounts of% by mass of Si, Al and Mn satisfy the formula 1 were melted.
Each steel ingot was heated at 1120 ° C., hot rolled to a thickness of 2.2 mm, wound, gradually cooled and wound in the air as shown in Table 5, and cooled; It was annealed for a minute in a nitrogen atmosphere, gradually cooled at a temperature of at least 600 ° C. in a mixed atmosphere of nitrogen and oxygen, and finally quenched with water. The annealed hot-rolled sheet was pickled and cold-rolled to a thickness of 0.35 mm, and the final annealing of the cold-rolled sheet was annealed for 2 minutes in a mixed atmosphere of 30% hydrogen and 70% nitrogen. The cooling zone was cooled in an atmosphere of 40% hydrogen and nitrogen. For the final annealed sheet, the size and the number of oxides, sulfides, carbides, nitrides and their composite precipitates were investigated for each specimen, and the crystal grains and magnetism were measured, and the results are summarized in Table 6 below. .

As shown in Tables 4 to 6, as compared with the comparative steels, the invention steels allow sufficient cooling time after winding, and allow sufficient time at 600 ° C. or more after annealing hot-rolled sheets and cold-rolled sheets. It is possible to confirm that formation of oxides including FeO oxide is performed well, crystal grains grow well, and magnetism is excellent.
On the other hand, in Comparative Steel 6, the annealing temperature of the hot-rolled sheet was low, the maintenance time at 600 ° C. or higher was short when cooling, and the size of oxides among the precipitates was small and the number was also small. Since the comparative steel 7 also had a short cooling time after hot-rolled sheet annealing, the size of the oxide among the precipitates was relatively small compared to the non-oxide, and the number was small. The proportion of FeO oxide was also low at 40% or less. The comparative steel 8 is cooled by water cooling after winding and cooled rapidly, and the cooling time at 600 ° C. or higher after hot-rolled sheet annealing is short, and the time after cold-rolled sheet annealing is also short. Insufficient formation of oxides including FeO, relatively high core loss, and low magnetic flux density. Comparative steel 9 also satisfies the components but has a low coiling temperature and a short annealing time at the time of cooling after hot-rolled sheet annealing, so the size of FeO and other oxides alone or composite precipitates is small and the number is also small Since the amount is smaller than that of non-oxide, it can be confirmed that the size of the crystal grain is small and the magnetism is low. In Comparative Steel 10, the cooling is quenched into water after winding, and the cooling time after annealing of the hot-rolled sheet and the cold-rolled sheet is shortened with the comparative steel 11, and as a result, the FeO ratio in the precipitate is low and oxide Since the formation is small, it can be confirmed that the crystal grains are small and the magnetism is insufficient.

The present invention is not limited to the embodiments, but can be manufactured in various forms different from one another, and those having ordinary knowledge in the technical field to which the present invention belongs can understand the technical idea and essential features of the present invention. It will be appreciated that it may be implemented in other specific forms without changing the Therefore, it should be understood that the above embodiments are illustrative in all aspects and not limiting.

Claims (17)

C: not more than 0.005% (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1.5%, Mn: 0.1 to 1.0% by mass , P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0.001% to 0.006%, Ti: 0.005% or less (0 %, O: not more than 0.005% (excluding 0%) and the balance consist of Fe and its unavoidable impurities,
The following number 1 is satisfied,
A non-oriented electrical steel sheet characterized in that the average size of oxides among the precipitates is larger than the average size of non-oxides.

(However, in the formula 1, [Si], [Al] and [Mn] indicate the content (mass%) of Si, Al and Mn, respectively.) The non-oriented electrical steel sheet according to claim 1, wherein among the precipitates, the number of oxides is larger than the number of non-oxides. The non-oriented electrical steel sheet according to claim 1, further comprising 0.01 to 0.2 mass% of Sn and Sb alone or in combination. The non-oriented electrical steel sheet according to claim 1, wherein the number of precipitates containing FeO or FeO is 40% or more. The grain size of an average grain size is 50-180 micrometers, The non-oriented electrical steel sheet of Claim 1 characterized by the above-mentioned. C: not more than 0.005% (excluding 0%), Si: 1.0 to 4.0%, Al: 0.15 to 1.5%, Mn: 0.1 to 1.0% by mass , P: 0.2% or less (excluding 0%), N: 0.005% or less (excluding 0%), S: 0.001% to 0.006%, Ti: 0.005% or less (0 %, O: not more than 0.005% (except 0%) and the balance are Fe and unavoidable impurities thereof, and after hot-rolling the hot-rolled sheet after heating the slab satisfying the following equation (1) Manufacturing stage,
Cooling the hot rolled sheet after winding;
Annealing and cooling the hot-rolled sheet;
Cold rolling the hot rolled annealed sheet to produce a cold rolled sheet;
Final annealing and cooling the cold rolled sheet;
In the step of cooling after winding the hot-rolled sheet, cooling is performed by maintaining for 30 minutes or more at 600 ° C. or more,
In the step of annealing and cooling the hot-rolled sheet, cooling is performed at 600 ° C. or more for 5 seconds or more,
In the step of final annealing and cooling the cold-rolled sheet, the method for manufacturing a non-oriented electrical steel sheet, comprising cooling at 600 ° C. or more for 5 seconds or more.

(However, in the formula 1, [Si], [Al] and [Mn] indicate the content (mass%) of Si, Al and Mn, respectively.) The method for producing a non-oriented electrical steel sheet according to claim 6, wherein the slab further contains 0.01 to 0.2 mass% of Sn and Sb alone or in combination. The method for producing a non-oriented electrical steel sheet according to claim 6, wherein the slab is heated at 1200 ° C or lower in the step of producing the hot-rolled sheet. The method for manufacturing a non-oriented electrical steel sheet according to claim 6, wherein the coiling temperature is 600 to 800 ° C in the step of cooling after winding the hot-rolled sheet. The method for manufacturing a non-oriented electrical steel sheet according to claim 6, wherein the annealing temperature of the hot-rolled sheet is 850 to 1150 ° C in the stage of annealing and cooling the hot-rolled sheet. The non-directional electromagnetic wave according to claim 6, wherein the cold rolled sheet is cold rolled to a thickness of 0.1 to 0.7 mm in the step of cold rolling the hot rolled annealed sheet to produce a cold rolled sheet. Method of manufacturing steel plate. In the step of cold rolling the hot rolled annealed sheet to produce a cold rolled sheet, the cold rolling includes primary cold rolling, intermediate annealing and secondary cold rolling. The manufacturing method of the non-oriented electrical steel sheet as described in-. The manufacturing method of the non-oriented electrical steel sheet according to claim 6, wherein, at the stage of final annealing and cooling the cold-rolled sheet, a crack temperature of the annealing is 850 to 1100 ° C. The method for producing a non-oriented electrical steel sheet according to claim 6, wherein the average size of the oxide among the precipitates of the manufactured electrical steel sheet is larger than the average size of the non-oxide. The method for producing a non-oriented electrical steel sheet according to claim 14, wherein among the precipitates, the number of oxides is larger than that of non-oxides. The method of manufacturing a non-oriented electrical steel sheet according to claim 14, wherein the number of precipitates containing FeO or FeO among the precipitates is 40% or more. The grain size of an average crystal grain is 50-180 micrometers, The manufacturing method of the non-oriented electrical steel sheet of Claim 14 characterized by the above-mentioned.