TW201502285A - Isotropic electromagnetic steel sheet - Google Patents

Abstract

This invention discloses an isotropic electromagnetic steel sheet which contains: C below 0.01 mass%, Si above 1.0 mass% and below 3.5 mass%, Al above 0.1 mass% and below 3.0 mass%, Mn above 0.1 mass% and below 2.05 mass%, P below 0.1 mass%, S below 0.005 mass%, Ti above 0.001 mass% and below 0.01 mass%, N below 0.005 mass%, and Y above 0.05 mass% and below 0.2 mass%. The balance part is iron and inevitable impurities.

Description

Non-directional electromagnetic steel sheet Technical field

The present invention relates to a high-grade non-oriented electrical steel sheet for use in high-frequency applications such as an iron core of a motor, which is capable of reducing energy loss and promoting efficiency of an electric machine to help save energy, particularly A non-oriented electrical steel sheet excellent in iron loss after force annealing.

Background technique

In recent years, from the viewpoint of preventing global warming, energy conservation is being pursued, and in the fields of motors for heating and cooling appliances or main motors for electric vehicles, efforts are being made to further reduce power consumption. These motors are often used for high rotation. Therefore, the non-oriented electrical steel sheet (hereinafter referred to as "steel sheet"), which is a motor material, is required to improve iron in the field of 400 Hz to 800 Hz, which is higher than the commercial frequency of 50 Hz to 60 Hz. damage.

In the method of improving the iron loss in the high-frequency region of the non-oriented electrical steel sheet, for example, as described in Patent Document 1, the electric resistance is increased by increasing the content of Si or Al. Further, recently, in order to reduce costs, there is a case where an alloy raw material of Si or Al having a high Ti content is used as a cheap alloy raw material.

As the content of Si or Al increases, Ti which inevitably has high affinity with these elements is inevitably contained in the alloy raw material, so it is inevitable in the steel sheet. Mix in Ti. When Ti in the steel sheet is 0.001% by mass or more, a large amount of fine Ti inclusions having a diameter of about several tens of nanometers such as TiN, TiS, or TiC are formed in the steel sheet. The fine Ti inclusions in the steel sheet hinder the growth of the crystal grains during annealing of the steel sheet, and deteriorate the magnetic properties.

Therefore, it is necessary to minimize the Ti inclusions in the steel sheet. One of the methods is to use an alloy raw material having a low Ti content of an impurity. However, when this method is used, there is a problem that the cost of the alloy raw material rises. Further, reducing N, S, and C in the steel sheet is also one of methods for reducing Ti inclusions, and the current technique can sufficiently reduce S or C by vacuum degassing treatment or the like. However, in order to reduce the S or C in the steel sheet, it takes a long time to process, which leads to a decrease in productivity. Further, in order to prevent the N from being mixed into the molten steel, it is also conceivable to strengthen the sealed refining container, but the reinforced sealing causes an increase in cost, and even if such treatment is performed, the problem of N being mixed into the molten steel cannot be avoided.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2007-16278

Patent Document 2: Japanese Patent Laid-Open Publication No. 2005-336503

Patent Document 3: Japanese Patent Publication No. Sho 54-36966

Patent Document 4: Japanese Patent Laid-Open No. 2006-219692

Summary of invention

The invention can be manufactured at low cost and excellent productivity by the manufacturing steps of the usual method, and aims to provide a crystal grain during annealing. A non-oriented electrical steel sheet excellent in growth and high-frequency iron loss.

The gist of the present invention for solving the above problems is as follows.

(1) A non-oriented electrical steel sheet comprising: C: 0.01% by mass or less, Si: 1.0% by mass or more and 3.5% by mass or less, Al: 0.1% by mass or more and 3.0% by mass or less, and Mn: 0.1% by mass or more and 2.0% by mass; Hereinafter, P: 0.1% by mass or less, S: 0.005% by mass or less, Ti: 0.001% by mass or more and 0.01% by mass or less, N: 0.005% by mass or less, and Y: more than 0.05% by mass and 0.2% by mass or less, and the remainder is Iron and inevitable impurities.

(2) The non-oriented electrical steel sheet according to (1), further comprising an element selected from the group consisting of one or more of the following groups: selected from the group consisting of Cu: 0.5% by mass or less, and Cr : the first group of one or two of the groups of 20% by mass or less, and the second group of one or two selected from the group consisting of Sn and Sb and totaling 0.3% by mass or less The third group in which Ni is 1.0% by mass or less, and the fourth group in which Ca is 0.01% by mass or less.

Non-directional electromagnetic steel sheet produced by the invention is used in steel plate Since the fine Ti inclusions are small, the crystal grain growth property during annealing is good, and the iron loss in the high frequency region is excellent. In addition, it can be manufactured at low cost and excellent productivity, and can improve motor characteristics and help save energy.

The relationship between the Y content in the steel sheet shown in Fig. 1 and the Ti inclusion content and crystal grain size of the product sample after the relaxation of the relaxation force is shown.

Form for implementing the invention

When an appropriate amount of Y is added to the non-oriented electromagnetic steel, generation of Ti inclusions such as TiN, TiS, and TiC in the steel sheet is suppressed, and the number density of the Ti inclusions is remarkably reduced. As a result of the investigation, it is known that the growth of the crystal grains of the steel is suppressed, and the crystal grain growth property can be greatly improved. In addition, the Y system is an element of atomic number 39 and one of rare earth elements.

Hereinafter, the effect of adding Y will be described in detail.

Laboratory experiments using vacuum melting were performed in the following order. First, the melting includes C: 0.0019 mass% to 0.0032 mass%, Si: 2.7 mass% to 3.1 mass%, Al: 0.2 mass% to 0.46 mass%, Mn: 0.3 mass% to 0.5 mass%, and P: 0.03. Mass%~0.05% by mass, S: 0.0022% by mass to 0.0035 mass%, Ti: 0.002% by mass to 0.005 mass%, and N: 0.0018% by mass to 0.0033% by mass, and Y: 0% by mass to 0.25 mass% A variety of molten steels that vary in composition. Further, after the ingot was solidified, an experiment of hot rolling, hot rolling, annealing, cold rolling, finishing annealing, and relaxation annealing was sequentially performed as a laboratory test to produce a product sample having a thickness of 0.35 mm. Next, investigation of inclusions and crystal grains was carried out by the following method.

First, the investigation method of inclusions will be explained. Initially from the surface This is ground to an appropriate thickness and the sample surface is mirrored. Thereafter, after performing the etching described later, the inclusions were investigated using a field emission type scanning electron microscope and an energy dispersive spectroscopic analyzer. In this investigation, the composition of the inclusions was analyzed for inclusions having a diameter of 10 nm to 500 nm, and the number of inclusions in the unit observation area was calculated. Further, the number density of inclusions per unit volume of the sample is converted into a sample by the DeHoff formula shown in ASTM E127: Annual Book of ASTM Standards Vol. 03.03, (1995). Further, the above method is an example, and a replica or a film may be prepared from a sample, and then investigated, or a transmission electron microscope may be used.

For the etching method, for example, Takizawa et al. (黒泽文夫, Taguchi) Yong, Matsumoto Ryotaro: The method described in the Japanese Society of Metals, 43 (1979), p. 1068). By this method, the sample is electrolytically etched in a water-insoluble solvent, and only the steel is melted in the case of residual inclusions, and the inclusions are extracted. Further, when the crystal grain size was measured, the cross section of the sample was mirror-polished, and the crystal granules were visualized by etching with a oxidizing agent to measure the average crystal grain size.

Figure 1 shows the Y content of the product sample under the above experiment. Relationship with the amount of Ti inclusions and crystal grain size. Further, in Fig. 1, the relationship between the Y content and the amount of Ti inclusions is indicated by a broken line, and the relationship between the Y content and the crystal grain size is indicated by a solid line. Here, the types of Ti inclusions observed are TiN, TiS, and TiC. The Ti inclusions are formed at different temperatures, and TiN is formed at 1000 ° C or higher, TiS is formed at 900 ° C or higher, and less than 1000 ° C, and TiC is formed at 700 ° C or higher and 800 ° C or lower. These Ti inclusions usually have a crystal grain boundary or a difference row as a precipitation position, and a large amount of fine particles of about several tens of nanometers are formed. Inclusions hinder the growth of crystal grains of steel.

The experimental results show that the steel sheet contains more than 0.05% by mass. In the case of Y, the number density of Ti inclusions in the product sample is remarkably reduced, and it is understood that the growth of crystal grains of steel is greatly improved.

Here, when Y is added, hundreds of diameters are observed in the steel sheet. The Y inclusion of nm Y oxide and Y oxysulfide, but the amount of Y present as such Y inclusion does not exceed 0.01% by mass. Therefore, when the addition is more than 0.01% by mass, it is presumed that Y is solid-solved in the steel sheet. When the Y content in the steel sheet is more than 0.01% by mass, it is presumed that the number density of Ti inclusions monotonously decreases as the amount of solid solution Y increases. Further, it is understood that when the Y content in the steel sheet is more than 0.05% by mass, the number density of Ti inclusions in the steel sheet is remarkably small. Further, although the mechanism for suppressing Ti inclusions by Y is not clear, it can be considered that when solid solution Y is formed in the steel sheet, the activity of Ti in the steel sheet is lowered, and the formation of Ti inclusions is suppressed. In addition, this effect is unique to Y, and such an effect was not confirmed among other rare earth elements.

Through the above experiments, it was found to significantly reduce Ti inclusions, steel The desired range of the Y content in the sheet is more than 0.05% by mass. On the other hand, when the Y content in the product sample is more than 0.2% by mass, the segregation of Y at the crystal grain boundary becomes remarkable, the crystal grain boundary is embrittled, and a cast flaw is generated on the surface of the product sample.

Therefore, by containing more than 0.05% by mass of Y in the steel sheet, charging The Ti precipitate is suppressed in a layer, and the Y content in the steel sheet is 0.2% by mass or less, and the grain boundary segregation of Y is suppressed, and the non-oriented electrical steel sheet having good crystal growth property, good magnetic properties, and good surface quality is produced. It is important.

The effect of Y described above can suppress Ti inclusions in the steel sheet In other words, it helps to suppress TiN, TiS, etc. during hot-rolled sheet annealing or cold-rolled sheet finish annealing, and helps to suppress TiC during relaxation annealing.

Next, the reason for limiting the components of the present invention will be described.

[C]

C not only forms TiC in the steel sheet to deteriorate magnetic properties, but also exhibits significant magnetic attenuation by precipitation C. Therefore, the upper limit of the C content is made 0.01% by mass. The lower limit of the C content is preferably as small as possible, and is not particularly limited, and may be contained in an amount of 0% by mass.

[Si]

The Si system reduces the element of iron loss. If the Si content is less than 1.0% by mass of the lower limit, the iron loss cannot be sufficiently reduced. Further, from the viewpoint of further reducing the iron loss, the lower limit of the Si content is preferably 1.5% by mass, more preferably 2.0% by mass. Further, when the Si content is more than 3.5% by mass of the upper limit, the workability is remarkably poor, so the upper limit is made 3.5% by mass. Further, a preferable value of the upper limit of the Si content is 3.3% by mass, more preferably 3.1% by mass, and more preferably 3.0% by mass, which is more excellent in workability in cold rolling.

[Al]

Al and Si are elements that reduce iron loss. If the A1 content is less than 0.1% by mass of the lower limit, the iron loss cannot be sufficiently reduced. Further, when the Al content is more than 3.0% by mass of the upper limit, the cost is remarkably increased. From the viewpoint of iron loss, the lower limit of the Al content is preferably 0.2% by mass, more preferably 0.3% by mass, and still more preferably 0.4% by mass. Further, from the viewpoint of cost, the upper limit of the Al content is preferably 2.5% by mass, more preferably 2.0% by mass, still more preferably 1.8% by mass.

[Mn]

Mn can increase the hardness of the steel plate. To improve the punching property, Mn0.1 can be added. More than % by mass. Further, from the viewpoint of economy, the upper limit of the Mn content is set to 2.0% by mass.

[P]

P can increase the strength of the material, and contains P in order to improve the workability. However, when P is excessively contained, the workability of cold rolling is lowered, so the P content is made 0.1% by mass or less. Further, since P is inevitably mixed in the production process of the steel sheet, the lower limit of the P content is not provided, and usually, it is preferably not less than 0.0001% by mass from the viewpoint of steelmaking cost.

[Y]

Y acts on Ti in the steel sheet in a solid solution state to suppress the formation of Ti inclusions. This effect can be obtained when the Y content is more than 0.05% by mass. Further, the more the Y content, the more clear the effect is, and it is preferably 0.055 mass% or more, more preferably 0.06 mass% or more. However, when the Y content is excessive, Y in the steel sheet is segregated at the crystal grain boundary, and the crystal grain boundary is embrittled, and the quality of the product is deteriorated due to the occurrence of casting defects. Therefore, there is an upper limit to the Y content, and if it is 0.2% by mass or less, segregation of Y in the crystal grain boundary can be suppressed. The upper limit of the Y content is preferably 0.15% by mass or less, more preferably 0.12% by mass or less.

[S]

S will become a sulfide such as TiS or MnS, which will deteriorate the crystal grain growth property and deteriorate the iron loss. In order to prevent the upper limit of the S content from being 0.005 mass%, the upper limit is preferably 0.003 mass%. The lower limit of the S content is preferably as small as possible, and is not particularly limited, and may be contained in an amount of 0% by mass.

[N]

N will become a nitride such as TiN to deteriorate the iron loss, so the allowable N content The upper limit is set to 0.005 mass%. Further, the upper limit of the N content is preferably 0.003 mass%, more preferably 0.0025 mass%, still more preferably 0.002 mass%. Further, from the viewpoint of suppressing nitride, N is preferably as small as possible. Therefore, the lower limit of the N content is not particularly limited, but the industrial limit is large to be unrestricted to 0% by mass. Therefore, it is preferable to set the lower limit of the N content to more than 0% by mass. Further, in the range in which the denitrification can be carried out in the industrial production process, the lower limit of the N content is preferably 0.001% by mass. Further, when the denitrification is performed extremely, it is preferable to reduce the N content to 0.0005 mass% to further suppress the nitride.

[Ti]

Ti forms fine inclusions such as TiN, TiS, and TiC, which deteriorates crystal grain growth and deteriorates iron loss. Although the Ti inclusions can be suppressed by the present invention, the upper limit of the Ti content which can be tolerated is 0.01% by mass. Moreover, for the above reasons, the upper limit is preferably 0.005 mass%. On the other hand, when the Ti content is less than 0.001% by mass, the Ti precipitates become too small, and the effect of inhibiting the growth of the crystal grains is not substantially problematic. On the other hand, an alloy raw material having a Ti content of less than 0.001% by mass is expensive, so the cost is increased. Therefore, the lower limit required for suppressing Ti inclusions of the present invention can be inevitably mixed as an impurity to 0.001% by mass. Further, in particular, when a cheap alloy raw material is used, it is contained in the alloy raw material in an amount of 0.002% by mass or more of Ti. In this case, it is particularly effective in the present technology.

Elements other than those described above, as long as they are not The ground effect effect may also contain other elements as the scope of the present invention. Hereinafter, the selection element will be described. Further, the lower limit of the content is preferably contained in a small amount, and is therefore more than 0% by mass.

[Cu]

Cu improves corrosion resistance and increases specific resistance to improve iron loss. However, when the Cu content is excessive, the surface quality is deteriorated by casting ruthenium or the like on the surface of the product sheet, so the Cu content is preferably 0.5% by mass or less.

[Cr]

Cr improves corrosion resistance and increases specific resistance to improve iron loss. However, when Cr is excessively added, since the cost is high, it is preferable to set the upper limit of the Cr content to 20% by mass.

[Sn] and [Sb]: Sn and Sb segregation elements hinder magnetic evil The assembly of the (111) plane improves the magnetic properties. These elements may be used alone or in combination of two or more types to exhibit the aforementioned effects. However, when the total of Sn and Sb is more than 0.3% by mass, the workability of the cold rolling is deteriorated. Therefore, the upper limit of the total of Sn and Sb is preferably 0.3% by mass.

[Ni]

Ni can develop a favorable magnetic organization and improve iron loss. However, since the excessive addition of Ni increases the cost, it is preferable to set the upper limit of the Ni content to 1.0% by mass.

[Ca]

The Ca-based desulfurization element fixes S in the steel sheet to prevent or inhibit the formation of sulfide inclusions such as TiS or MnS. However, when the Ca content is more than 0.01% by mass, problems such as dissolution of the refractory material are not preferable, so the upper limit of the Ca content is preferably 0.01% by mass.

In addition, inevitable impurities, for example, contain the following elements In the case of the prime, there is no problem as long as it is within the range shown below.

[Zr]

Even if Zr is in a small amount, it will hinder the growth of crystal grains and deteriorate the iron loss after the relaxation of the relaxation force. When the amount is as small as possible, the Zr content is usually 0.01% by mass or less, and when the Zr content is within this range, no harmful effect is caused, and there is no problem.

[V]

V will form nitrides or carbides, hindering the movement of the magnetic walls or the growth of crystal grains. When the amount is as small as possible, the V content is usually 0.01% by mass or less, and when the V content is within this range, no harmful effect is caused, and there is no problem.

[Nb]

Nb will form nitrides or carbides that hinder magnetic wall movement or crystal grain growth. When the amount is as small as possible, the Nb content is usually 0.01% by mass or less, and when the Nb content is within this range, no harmful effect is caused, and there is no problem.

[Mg]

The Mg-based desulfurization element reacts with S in the steel sheet to form a sulfide, and fixes S. When the content is increased, the desulfurization effect can be enhanced. However, when the Mg content is more than 0.05% by mass, excessive Mg sulfide will hinder the growth of crystal grains. Usually, the Mg content is 0.05% by mass or less, and when the Mg content is in this range, no harmful effect is caused, and there is no problem.

[O]

An oxide will be formed by O in the steel sheet. However, in the present invention, 0.1% by mass or more of Al is sufficiently deoxidized, so the O content in the steel sheet is 0.005% by mass or less. When the content of O is in this range, there is no problem that harmful effects such as movement of the magnetic wall of the oxide or inhibition of growth of crystal grains are caused.

[B]

The B-series grain boundary segregation elements can form nitrides. By this nitride, the grain boundary is prevented from moving and the iron loss is deteriorated. When the amount is as small as possible, the B content is usually 0.005% by mass or less, and when the B content is within this range, no harmful effect is caused, and there is no problem.

Next, the manufacturer of the non-oriented electrical steel sheet of the present invention will be described. law. In the steel making stage, it is refined by a usual method such as a converter or a secondary refining furnace, and is melted in the range of the composition. Thereafter, a flat steel embryo such as a slab is cast by continuous casting or ingot casting. Thereafter, the obtained flat steel blank is hot rolled, and the hot rolled sheet is subjected to hot rolling and annealing in the range of 1100 ° C to 1300 ° C as needed. Next, the thickness of the product is completed by one cold rolling or two or more cold rolling of an intermediate annealing at 850 ° C to 1000 ° C. Then, annealing is completed in the range of 800 ° C to 1100 ° C, and an insulating film is applied to obtain a product. Further, depending on the case, the relaxation annealing is performed in the range of 700 ° C to 800 ° C.

As described above, according to the present invention, it is possible to suppress the number density of Ti inclusions in the steel sheet to be 0.3 × 10 ¹⁰ /mm ³ or less, and preferably 0.2 × 10 ¹⁰ /mm ³ or less, without changing the manufacturing steps. More preferably, it is 0.1 × 10 ¹⁰ / mm ³ or less. Thereby, a non-oriented electrical steel sheet having good crystal grain growth property can be produced.

Example

Embodiments will be described below in accordance with the effects of the present invention. Further, the conditions of the experiments and the like are examples for confirming the applicability and effects of the present invention, and the present invention is not limited by the examples.

First, it is prepared to contain C: 0.0015 mass%, Si: 2.9% by mass, Mn: 0.5 mass%, P: 0.09 mass%, S: 0.002 mass%, and Al: 0.43 mass%, and N: 0.0022 mass%, and containing various elements as shown in Table 1, and the remainder is a steel composed of iron and unavoidable impurities. Further, the steel of the components is refined by a converter and a vacuum degassing device and injected into a bucket, and the molten steel is supplied to the casting mold through a funnel through a funnel to be continuously cast to obtain a flat steel blank. Further, when Y is contained, metal Y is added to the vacuum degassing tank. Thereafter, the flat steel slab is hot rolled, and the obtained hot rolled slab is annealed at 1150 ° C by hot rolling, and cold rolled to a thickness of 0.35 mm. Further, after completion annealing at 950 ° C for 30 seconds, an insulating film was applied as a product, and then subjected to relaxation annealing at 750 ° C for 2 hours.

The precipitates and crystal grain size of the product sheets were investigated by the above method, and the iron loss of the product sheets was cut into 25 cm lengths and examined by the Epstein method shown in JIS-C-2550. The results of the survey are shown in Table 1 in the same manner.

As shown in Table 1, in No. 6 to No. 21 of the present invention, the number of Ti inclusions (number density) such as TiN, TiS, and TiC in the product sheet was 0.3 × 10 ¹⁰ /mm ³ or less. In addition, the crystal grain size of the samples was 100 μm or more, and the crystal grain growth property was good, and the iron loss value was good with respect to the comparative examples other than No. 22.

On the other hand, Comparative Examples No. 1 to No. 5 are lower than the Y content and greater than In the case of the lower limit of the range of 0.05% by mass or less and 0.2% by mass or less, the comparative example No. 23 is larger than the upper limit of the range of 0.001% by mass or more and 0.01% by mass or less of the Ti content. Further, in Comparative Examples No. 24 and 25, a rare earth element other than Y was used instead of Y. In these comparative examples, a large amount of Ti inclusions such as TiN, TiS, and TiC were generated in the product sheet, and crystal grain growth and iron loss values were inferior to those of the present invention. Further, in Comparative Example No. 22, which is larger than the upper limit of the range of the Y content of more than 0.05% by mass and 0.2% by mass or less, segregation of Y was observed in the crystal grain boundary of the product sheet, and cast iron was formed on the surface of the product sheet, and the surface quality was poor.

Industrial availability

As described above, by sufficiently controlling the precipitation of TiN, TiS, and TiC contained in the non-oriented electrical steel sheet, good magnetic properties can be obtained, and the user's demand can be satisfied and contribute to energy saving.

Claims (2)

A non-oriented electrical steel sheet comprising: C: 0.01% by mass or less, Si: 1.0% by mass or more and 3.5% by mass or less, Al: 0.1% by mass or more and 3.0% by mass or less, and Mn: 0.1% by mass or more and 2.0% by mass % or less, P: 0.1% by mass or less, S: 0.005% by mass or less, Ti: 0.001% by mass or more and 0.01% by mass or less, N: 0.005% by mass or less, and Y: more than 0.05% by mass, 0.2% by mass or less, and the remainder Iron and inevitable impurities. The non-oriented electrical steel sheet according to claim 1, further comprising an element selected from the group consisting of one or more of the following groups: selected from the group consisting of Cu: 0.5% by mass or less, and Cr: 20% by mass. The first group of one or two of the following groups, and the second group selected from the group consisting of one of Sn and Sb and having a total of 0.3% by mass or less, and Ni : a third group of 1.0% by mass or less and a fourth group of Ca: 0.01% by mass or less.