JP5098430B2 - Non-oriented electrical steel sheet excellent in punching workability and iron loss and manufacturing method - Google Patents

Description

  An object of the present invention is to provide a non-oriented electrical steel sheet that is used for an iron core of a motor or a transformer after being processed into a predetermined shape by punching or the like and has excellent magnetic properties and good punchability. To do.

  Non-oriented electrical steel sheets are used after being stamped by a customer in accordance with a predetermined iron core shape. At that time, there are many cases where machining strain remains around the punched fracture surface and the magnetic characteristics are deteriorated. As a countermeasure, it is common practice to apply high grade steel sheets with higher grades than required product characteristics by increasing the amount of Si or Al, or to remove strain by annealing after punching. . However, in either case, an increase in cost due to an increase in the amount of alloys required and an increase in processes is inevitable.

  In addition, punching is usually performed continuously, but as the number of punches is repeated, the end face of the tool wears. May occur.

  In view of the above, in order to obtain a punched product having good punchability and good magnetic properties, it is preferable that the steel sheet is more likely to break during punching, that is, punching with a lighter load and a shorter stroke. This characteristic is hereinafter referred to as good punchability.

  Various methods have been disclosed as methods for improving punchability, such as adjusting the steel sheet's composition and metal structure to adjust the hardness of the steel plate. Is disclosed.

  For example, as disclosed in (Patent Document 1), (Patent Document 2), etc., C in the steel is 0.1% to 1.0% in mass% higher than the electromagnetic steel sheet normally used, There is known a method in which coarse graphite is precipitated in steel, the shear resistance of the steel sheet is reduced by shear sliding of the coarse graphite, the plastic deformation region of the steel sheet is reduced, and the deterioration of magnetic properties after punching is suppressed.

  Further, as disclosed in (Patent Document 3), (Patent Document 4), etc., MnS in the steel is coarsened by adjusting the steel components and the temperature history of the heat treatment, and due to shear sliding of the coarse MnS. A method is known in which the lubrication effect is used to reduce the shear resistance of a steel sheet, reduce the plastic deformation region of the steel sheet, and suppress the deterioration of magnetic properties after punching.

  Furthermore, as disclosed in (Patent Document 5) and the like, by utilizing the fact that cracks easily propagate in the gaps of relatively dense inclusions, it is arranged so that cracks start and propagate in the interior of the steel sheet. There is known a method of providing inclusions arranged in a shape to promote cracking during punching, reduce the plastic deformation region of the steel sheet, and suppress deterioration of magnetic properties after punching.

Japanese Patent No. 1874281 Japanese Patent No. 1874282 Japanese Patent No. 1870070 Japanese Patent No. 3731625 JP 2000-160306 A

  In order to improve punchability, for example, by adjusting the hardness of the steel sheet while reducing the Al content and increasing the Si content while maintaining the specific resistance, or by adding Mn or P to increase the hardness of the steel sheet, According to the method of changing the components, there is a problem that the amount of alloy addition for obtaining predetermined punchability and magnetic characteristics increases, resulting in high cost.

  In addition, according to the method of reducing the crystal grain size of the steel sheet and promoting the propagation of cracks during punching and making it easy to break, the fine grain size increases the iron loss, resulting in inferior magnetic properties, or punching. The post-processing annealing must be sufficiently performed to grow the crystal grains, which complicates the process and increases the cost.

  On the other hand, according to the technique for improving the punchability by utilizing the inclusions inside the steel plate, the above problem can be avoided. However, according to the method disclosed above, the following problems may occur.

  When precipitation of coarse graphite by increasing the C content in steel and utilizing it, all of the C in the steel is not consumed for the formation of coarse graphite, free C remains in the steel, and the annealing stage of the steel sheet May react with impurity elements inevitably present in the steel to form, for example, low-temperature precipitates such as TiC. The low-temperature precipitates do not grow because their own precipitation temperature is low, and they are finely dispersed and precipitated in the steel, obstructing the growth of crystal grains in the annealing stage, and may deteriorate the magnetic properties.

  Moreover, when forming and utilizing coarse MnS in steel, it is necessary to sufficiently increase S for coarsening of MnS. However, all S in steel is not consumed for formation of coarse MnS, and free S is steel. In this case, fine MnS precipitates in the annealing stage of the steel sheet, which may inhibit the growth of crystal grains in the annealing stage and deteriorate the magnetic properties.

  Also, when promoting cracks during punching by inclusions arranged in a row, it is normal to roll the inclusions in the rolling direction by rolling the steel sheet to break the inclusions into rows, Inclusions arranged in a row in the direction are not preferable because they not only inhibit the growth of crystal grains in the plate thickness direction of the steel plate, but also hinder magnetic domain wall movement in the plate thickness direction and lower the magnetic permeability and deteriorate the magnetic properties. Furthermore, if cracks propagate along the inclusions arranged in a line in the rolling direction during punching, the cracks that should originally penetrate in the plate thickness direction propagate in the rolling direction, and the dimensional accuracy after punching decreases. Problems arise.

  The present invention relates to a steel plate in which hard oxide inclusions such as alumina and silica (hereinafter referred to as inclusions) are adjusted in diameter and density within a predetermined range so as not to hinder crystal grain growth and domain wall movement. Dispersing them inside acts as a starting point for cracking during punching and improves punchability while minimizing the accumulation of processing strain on the base metal around the fracture surface to suppress the deterioration of the magnetic properties of the steel sheet. The object of the present invention is to provide a non-oriented electrical steel sheet capable of simplifying annealing after punching and improving magnetic properties.

The gist of the present invention is as follows.
(1) By mass%, C: 0.01% or less, Si: 0.1% to 7.0%, Al: 0.01% to 3.0%, Mn: 0.1% to 2. 0% or less, N: 0.005% or less, S: 0.005% or less, O: 0.005% or more and 0.02% or less, with the balance being iron and inevitable impurities, and a diameter of 2 μm or more A non-oriented electrical steel sheet excellent in punching workability and iron loss, characterized by containing 100 / mm ³ or more and 100000 / mm ³ or less of an oxide composed of one or more of alumina or silica having a size of 25 μm or less .
(2) Moreover, in mass%, R EM: characterized Rukoto that Yusuke containing 0.0005% or 0.05% or less, non-directional with excellent punching workability and core loss according to (1) Electrical steel sheet.

(3) By mass%, C: 0.01% or less, Si: 0.1% or more and 7.0% or less, Al: 0.01% or more and 3.0% or less, Mn: 0.1% or more. 0% or less, N: 0.005% or less, S: 0.005% or less, O: 0.005% or more and 0.02% or less, with the balance being iron or inevitable impurities, characterized Rukoto using cast slab oxide added was cast consisting of one or more of silica, method for producing a non-oriented electrical steel sheet excellent in punching processability and iron loss according to (1).
(4) said molten steel further contains, by mass%, R EM: characterized Rukoto that Yusuke containing 0.0005% or 0.05% or less, the punching workability and core loss according to (3) method for producing a superior non-oriented electrical steel plate.
(5) the oxide, characterized in that added to the mold casting, (3) or (4) The method of producing non-oriented electrical steel sheet excellent in punching processability and iron loss according to.

In addition , the above-mentioned “alumina, silica ” having a diameter of 2 μm to 25 μm may be referred to as an inclusion.
In addition, the diameter of the inclusion means a sphere equivalent diameter. Hereinafter, the sphere equivalent diameter of inclusions is simply abbreviated as diameter. The equivalent circle diameter means the diameter of a circle having the same area as the cross-sectional area of the inclusion.

  According to the present invention, it is possible to provide a non-oriented electrical steel sheet that has good punching dimensional accuracy, can extend the tool life, and has little deterioration in magnetic properties due to punching.

Hereinafter, the operation and mechanism of the present invention will be described in detail.
In order to clarify the influence of inclusions on the punchability, the present inventors have investigated and examined in detail the punched fracture surface of a steel plate having good punchability. As an example of the result, the fracture surface after punching of a steel plate with good punchability is shown in FIGS.

  In a steel sheet with good punchability, cracks are generated starting from the inclusions shown in A of FIG. 1 and B of FIG. 2, and the crack propagates in the punching direction. It was issued. On the other hand, when a fracture surface of a steel sheet having poor punchability was investigated for comparison, the fracture surface was not affected by inclusions. That is, it was clear that a steel sheet with good punchability cracks starting from inclusions, propagates in the punching direction, and lightens the load during punching.

  Moreover, when the inclusions were polished from the surface of the steel plate to the center of the plate thickness and investigated for inclusions with an optical microscope, inclusions with various diameters were observed, but the inclusions that became crack initiation points on the fracture surface after punching were observed. It was found that the diameter was in the range of 2 μm to 25 μm, and inclusions outside this range did not act as crack initiation points.

  Next, the present inventors conducted the following experiment and intensively studied the relationship between the inclusions in the steel sheet and the magnetic properties and punchability of the steel sheet.

As shown in Table 1, steels with various changes were melted, oxides were added by the method shown in Example 1 described later, continuous casting, hot rolling, and cold rolling to a thickness of 0.5 mm. A final annealing was performed at 850 ° C. for 30 seconds, and an insulating film was applied to prepare a product plate.
Next, polishing was performed from the surface of the product plate to the center of the plate thickness, the diameter and number of inclusions were measured with an optical microscope, and the number density was calculated for inclusions having a diameter of 2 μm or more and 25 μm or less that acted as a crack starting point. The inclusion composition was analyzed by SEM-EDX. Further, the product plate was punched to a length of 25 cm with a clearance of 0.1 mm using a high-speed punching machine, and the magnetic characteristics were investigated by the JIS-C-2550 Epstein method.

The punchability was investigated and evaluated by the following method. First, it was punched into a circle with a clearance of 0.1 mm and a diameter of 12 mm with a high-speed punching machine. At that time, the punching load was measured with a load cell set in a punch. Further, the continuous punching, the sag height of the steel sheet after punching is measured, the wear state of the sagging punching number up to a height of 1% of the thickness (50 [mu] m), and 10 ⁵ times after successive punching tool investigated. The above results are shown in Table 1, Table 2 and FIG.

As shown in No. 1-1 to No. 1-6 in Table 2, when the composition of inclusions having a diameter in the product plate of 2 μm or more and 25 μm or less and the number density are within the range of the present invention, The iron loss (W15 / 50) value of the product plate was as low as 4.9 to 5.1 w / kg, and the magnetic properties were good. Moreover, the breaking load at the time of punching is as low as 6.45 to 6.5 kN, the number of continuous punching is as high as 1.8 × 10 ^{5 to} 2.2 × 10 ⁵ times, and tool wear after a predetermined number of continuous punching There was no problem, and the punchability was good. At this time, many cracks starting from inclusions as shown in FIGS. 1 and 2 were observed on the fractured surface after punching.

On the other hand, as shown in Nos. 1-7, 1-8, and 1-11 in Table 2, when the number density of inclusions having a diameter of 2 μm or more and 25 μm or less in the product plate is below the range of the present invention, punching is performed. The iron loss value of the processed product plate was as low as 4.9 to 5.0 w / kg, and the magnetic properties were good. However, the breaking load at the time of punching is as high as 6.75 to 6.80 kN, and when the number of times of punching is 0.7 × 10 ^{5 to} 0.8 × 10 ⁵ times, sagging of the end face occurs in the tool after punching. Therefore, the punchability was inferior.

As shown in No. 1-9 and No. 1-10 in Table 2, when the number density of inclusions having a diameter of 2 μm or more and 25 μm or less in the product plate exceeds the range of the present invention, The breaking load was as low as 6.4 kN, the number of continuous punching operations was as high as 2 × 10 ^{5 to} 2.5 × 10 ⁵ times, and there was no problem with tool wear after a predetermined number of continuous punching, and the punching performance was good. However, the iron loss value of the product plate after punching was as high as 5.9 to 6.3 w / kg, and the magnetic properties were poor.

As shown above, the relationship between the number density of inclusions having a diameter of 2 μm or more and 25 μm or less in the steel sheet and the maximum load at the time of punching is as shown in FIG. 3, and the number density of inclusions is 100 / mm ^3. It has been found that the maximum load decreases and the punching can be performed with a smaller load, and the punchability is improved. Further, it was found that when the number density of inclusions exceeds 1000 / mm ³ , the maximum load is further reduced and the punch can be punched with a smaller load, and the punchability is further improved.

On the other hand, regarding the relationship between the number density of inclusions and magnetic properties, as shown in FIG. 3, when the number density of inclusions having a diameter of 2 μm or more and 25 μm or less in a steel sheet exceeds 100,000 / mm ³ , the magnetic properties are increased. It was clear that it deteriorated. This is considered to be due to the effect of pinching inhibition of crystal grain growth by inclusions and the effect of pinning inhibition of domain wall movement by inclusions.

  From the above, it has been found that there is an appropriate range for the number density of inclusions in order to maintain good magnetic properties while improving punchability.

Furthermore, the conditions that the inclusion of the present invention should have will be described in more detail.
Although a small number of inclusions having a relatively low melting point such as MnS were observed in the steel sheet described above, they were not present at the starting point of fracture, and the composition of the inclusions that became the starting point of cracking was alumina or silica. These oxides have a relatively high melting point, do not soften and deform during hot rolling or annealing, and do not stretch by rolling.

  The reason for this is that inclusions with a low melting point are relatively soft, so that when punching stress is applied to the steel sheet, slippage occurs on the surface of the inclusions, which does not become an effective crack starting point, but inclusions with a high melting point It is considered that the material softens and does not stretch during hot rolling or annealing, and the inclusions are relatively hard and do not deform during punching of the steel sheet, so that it is considered that the material effectively acts as a crack starting point. Hereinafter, the inclusion of alumina or silica is referred to as a hard oxide.

  Further, when the content of Mn and S in the steel is relatively large, sulfides such as MnS may be deposited around the hard inclusions and the hard inclusions may be covered. If the hard inclusions are covered with sulfide, slippage occurs on the surface of the hard inclusions, which is not preferable because it is not an effective crack starting point. Therefore, inclusions covered with sulfide are not included in the hard inclusions. In addition, when the content of Mn and S in the steel is relatively high, it is preferable to suppress sulfides such as MnS in order to make the hard inclusions function effectively as a fracture starting point during punching.

  As a method of suppressing sulfides in electromagnetic steel, sulfide inclusions such as Ca and REM are generated in steel by adding sulfide-forming elements such as Ca and REM, and S in steel is fixed. Techniques for reducing free S in steel have been conventionally known. Here, from the viewpoint of improving punchability, addition of REM is preferable for the reason described later. Note that REM is a generic name for a total of 17 elements including 15 elements from lanthanum having an atomic number of 57 to lutesium having an atomic number of 57 plus scandium having an atomic number of 21 and yttrium having an atomic number of 39.

  When a punch breaks with the appropriate hard inclusion mentioned above at the time of punching, the breakage occurs from the periphery of the hard inclusion and propagates to the steel plate. Accumulation of iron is reduced, and iron loss after punching is improved. In addition, since the steel sheet breaks sharply, sagging after punching is reduced, stacking accuracy is improved, and the frequency of tool adjustment is reduced, thereby improving productivity.

  On the other hand, when the punchability is changed by a relatively soft inclusion having lubricity based on the conventional knowledge, accumulation of strain due to slip inside the steel plate and sag after punching cannot be avoided, and the above effect Cannot be played effectively.

Furthermore, when Ca is added as a sulfide-forming element in order to suppress sulfides in the electrical steel, the CaS itself formed in the steel is stretched by rolling, and the stretched CaS exhibits magnetic properties and punchability. Since deterioration occurs, it is not preferable. On the other hand, when REM is added as a sulfide-forming element, REM oxide and REM oxysulfide are formed in the steel, but none of them are stretched by rolling. Therefore, it is preferable than that to suppress the generation of soft inclusions such as MnS.

  As shown above, when the inclusions in the product plate are hard inclusions and the diameter and number density are within the scope of the present invention, the magnetic properties of the product plate after punching are good, It was confirmed that the tool life was excellent and the tool life could be extended.

Next, the reason for limiting the preferable content of the component composition in the present invention will be described.
[C]: C is not only harmful to magnetic properties, but also magnetic aging due to precipitation of C becomes remarkable, so the upper limit was made 0.01 mass%. The lower limit includes 0% by mass.
[Si]: Si is an element that reduces iron loss. When less than the lower limit of 0.1% by mass, the iron loss is worsened. Further, when the upper limit of 7.0% by mass is exceeded, the punchability becomes extremely poor, so the upper limit was set to 7.0% by mass.

[Al]: Al is an element that reduces iron loss in the same manner as Si. If the lower limit is less than 0.01% by mass, the iron loss deteriorates, and if it exceeds the upper limit of 3.0% by mass, the cost increases remarkably. Further, from the viewpoint of generating alumina in the product plate, the lower limit of Al is preferably 0.015% by mass, more preferably 0.02% by mass.
[Mn]: Mn is added in an amount of 0.1% by mass or more in order to increase the hardness of the steel sheet and improve the punchability. The upper limit of 2.0% by mass is due to economic reasons.

[N]: N is a nitride such as AlN or TiN and deteriorates the iron loss. Therefore, the upper limit is set to 0.005% by mass. The lower limit includes 0% by mass.
[S]: S becomes a sulfide such as MnS, which deteriorates grain growth and iron loss. Moreover, although it may deposit covering a hard inclusion, in this case, in order to impair the effect of the hard inclusion as a rupture starting point of punching, the upper limit was made 0.005% by mass.
However, as described later, when REM is added, an oxysulfide is formed and S is fixed. Therefore, when REM is added, the upper limit of S may be 0.01% by mass. The lower limit includes 0% by mass.

[O]: O generates a hard inclusion as a starting point of punching breakage and functions effectively. O in the steel includes an oxide that forms an oxide and a dissolved one, but in the scope of the present invention, although a small amount of dissolved O exists, the oxide substantially constitutes an oxide, and 0.005 mass % Or more is necessary. However, if O is contained excessively, a large number of oxides are formed, and domain wall movement and crystal grain growth are inhibited by these oxides, so the content is made 0.02% by mass or less.

In the steel having the component composition described above, REM may be added as another form for exhibiting the effects of the present invention.
[REM]: REM forms oxysulfide to fix S, and suppresses the generation of a large number of relatively soft inclusions such as MnS. Although 0.0005 mass% or more is sufficient, the upper limit is set to 0.05 mass% for economic reasons.

  In addition to the elements described above, known elements can be added as long as the effects of the steel of the present application are not greatly affected. Below, a selective element is demonstrated. In addition, since the lower limit of these content should just be contained even if it is trace amount, it is all over 0 mass%.

[P]: P increases the strength of the material and improves punchability. However, if excessive, the cold rolling property is impaired, so 0.1% by mass or less is preferable.
[Cu]: Cu improves corrosion resistance and increases specific resistance to improve iron loss. However, if the amount is excessive, scabs or the like are generated on the surface of the product plate and the surface quality is impaired, so 0.5 mass% or less is preferable.
[Ca]: Ca is a desulfurization element, reacts with S in steel to form sulfide, and fixes S. However, unlike REM, when Ca is added excessively, CaS produced in the steel is stretched by rolling, which causes deterioration of magnetic properties and punchability. Therefore, 0.05 mass% or less is preferable.

Next, preferable manufacturing conditions in the present invention and the reasons for their definition will be described.
First, in the steelmaking stage, the steel is refined by conventional methods such as converters and secondary refining furnaces, molten steel in the desired composition range is melted, and then the molten steel is injected into the mold from the ladle through the nozzle and continuously cast. Or, ingot casting is performed to cast a slab or other slab.
In casting, an oxide as an oxygen source (hereinafter referred to as an oxygen source) is supplied to molten steel to form predetermined inclusions.
As an oxidation source, alumina and silica are most recommended because they are easily available. Moreover, when REM is contained in steel, a contained REM oxide or REM oxysulfide may be used.

  When these oxygen sources are added to the molten steel, the oxygen source is once decomposed in the molten steel to release oxygen to the molten steel, and the oxygen reacts with the molten steel to form oxides. Is done. At this time, if an oxygen source is supplied to the molten steel before the ladle, the oxygen source floats and separates in the molten steel and the yield deteriorates, and the nozzle is blocked by the oxygen source and the molten steel supply to the mold is hindered. In some cases, it is not preferable. Therefore, casting may be performed by supplying the oxygen source after the molten steel is discharged from the nozzle into the mold and mixing the molten steel and the oxygen source.

There are various methods for supplying an oxygen source to molten steel. For example, when alumina is used as the oxygen source, a wire in which a predetermined alumina is packed in a thin iron pipe is used, and the wire is supplied to the nozzle discharge flow. The oxygen source may be mixed with the molten steel. By this method, in order to adjust the composition, size and number density of the hard oxide in the product plate within the range of the present invention, alumina (Al ₂ O ₃ ) and iron oxide (Fe ₂ O ₃ ) in mass ratio. It is good to use the wire which packed the powder mix | blended and mixed in the range of 3: 1 to 1: 3 to the thin-walled iron pipe. As this powder, it is preferable to use powder particles having a diameter of 1 mm or less without sintering because of good dispersibility in molten steel.

  The reason for mixing alumina and iron oxide is to improve the wettability of the oxygen source and the molten steel, suppress the generation of oxygen source clusters in the molten steel, reduce the oxygen source loss due to cluster levitation, and increase the oxygen yield. This is for improving dispersibility. Here, the oxygen yield means the ratio of the amount of oxygen in the steel increased by supplying the oxygen source to the amount of oxygen contained in the supplied oxygen source. Considering that the oxygen yield by wire supply is 20 to 40%, oxygen is supplied into the molten steel by the supplied oxygen source, and the composition, size and number density of the hard oxide in the steel are within the range of the present invention. Thus, it supplies with the wire supply speed according to the discharge flow rate of molten steel. Thereby, it becomes possible to produce | generate the hard inclusion which comprised the scope of the present invention in steel.

  After this, the slab is hot-rolled, hot-rolled sheet annealed as necessary, finished to product thickness by one or more cold rollings sandwiching intermediate or intermediate annealing, then finish-annealed and coated with insulating film To do. By the method described above, the inclusions in the product plate can be controlled within the scope of the present invention.

As shown in Table 1, steels with various changes were dissolved, and alumina (Al ₂ O ₃ ) and iron oxide (Fe ₂ O ₃ ) were mixed at a mass ratio of 1: 1. The product powder is coated on a wire and supplied into the mold at a supply rate of 3 to 4 kg / min, continuously cast with a molten steel discharge flow rate of 3 tons / min, hot-rolled, and a thickness of 0.5 mm. The plate was cold-rolled and subjected to finish annealing at 850 ° C. for 30 seconds, and an insulating film containing an organic component and an inorganic component applied to a normal non-oriented electrical steel sheet was applied to prepare a product plate.

Next, the number density of the inclusions having a product plate diameter of 2 μm or more and 25 μm or less was examined by an optical microscope, and the inclusion composition was analyzed by SEM-EDX. Further, the product plate was punched to a length of 25 cm with a clearance of 0.1 mm using a high-speed punching machine, and the magnetic characteristics were investigated by the Epstein method shown in JIS-C-2550. Further, a punching process was performed with a high-speed punching machine into a circle having a clearance of 0.1 mm and a diameter of 12 mm, and the punching load was measured. Further, the continuous punching, the sag height of the steel sheet after punching is measured, the wear state of the sagging punching number up to a height of 1% of the thickness (50 [mu] m), and 10 ⁵ times after successive punching tool investigated. Moreover, the punching fracture surface was investigated by SEM-EDX, and the inclusion composition was analyzed. A water-soluble lubricating oil was used for punching.

  The above results are shown in Table 2 and FIGS. Hard inclusions having a diameter of 2 μm or more and 25 μm or less were observed at the crack starting point of the punched fracture surface, and other inclusions were not observed. Moreover, as shown in Table 2 and FIG. 3, the product plate in which the chemical components and inclusions are within the scope of the present invention gave good results with respect to the iron loss value and punchability. On the other hand, a product plate having chemical components and inclusions outside the scope of the present invention was inferior in iron loss value and punchability.

An oxide having an average particle size of 0.8 mm, in which steels whose components were adjusted as shown in Table 3 were dissolved and alumina (Al ₂ O ₃ ) and iron oxide (Fe ₂ O ₃ ) were mixed at a mass ratio of 1: 1. The powder is coated on the wire and supplied into the mold at a supply rate of 3 to 4 kg / min, continuously cast at a molten steel discharge flow rate of 3 tons / min, hot-rolled, and cold-rolled to a thickness of 0.5 mm. Then, finish annealing was performed at 850 ° C. for 30 seconds, and an insulating film containing an organic component and an inorganic component applied to a normal non-oriented electrical steel sheet was applied to prepare a product plate.

Next, the number density of the inclusions having a product plate diameter of 2 μm or more and 25 μm or less was examined by an optical microscope, and the inclusion composition was analyzed by SEM-EDX. Further, the product plate was punched to a length of 25 cm with a clearance of 0.1 mm using a high-speed punching machine, and the magnetic characteristics were investigated by the Epstein method shown in JIS-C-2550. Further, a punching process was performed with a high-speed punching machine into a circle having a clearance of 0.1 mm and a diameter of 12 mm, and the punching load was measured. Further, the continuous punching, the sag height of the steel sheet after punching is measured, the wear state of the sagging punching number up to a height of 1% of the thickness (50 [mu] m), and 10 ⁵ times after successive punching tool investigated. Moreover, the punching fracture surface was investigated by SEM-EDX, and the inclusion composition was analyzed. A water-soluble lubricating oil was used for punching.

  The results are shown in Table 4. Hard inclusions having a diameter of 2 μm or more and 25 μm or less were observed at the crack starting point of the punched fracture surface, and other inclusions were not observed. Further, as shown in No. 2-1 to No. 2-3 of Table 4, when the composition and number density of inclusions in the product plate are within the scope of the present invention, the iron loss of the product plate after punching is performed. The value was relatively low, the magnetic properties were good, the breaking load at the time of punching was relatively low, the tool wear after a predetermined number of continuous punching was no problem, and the punchability was good.

On the other hand, No. 2-4 has the same grade of steel as No. 2-1, but the number density of inclusions in the product plate exceeds the range of the present invention, and the iron loss value is compared. The magnetic properties were poor. In addition, No. 2-5 is equivalent to No. 2-2 in steel components, but the number density of inclusions in the product plate is below the range of the present invention, and the number of punches is 0.00. The sagging of the end face occurred in the tool after punching at 7 × 10 ⁵ times, the tool had to be adjusted, and the punchability was inferior. In addition, No.2-6 and No.2-7 have the same grade of steel as No.2-3, but No.2-6 has the number density of inclusions in the product plate. It is below the scope of the invention, and the punching number is 0.6 × 10 ⁵ times, and the end face of the tool after punching occurs, the tool needs to be adjusted, the punchability is inferior, and No. 2-7 The number density of inclusions in the product plate exceeded the range of the present invention, the iron loss value was relatively high, and the magnetic properties were poor.
As shown above, a product plate with chemical components and inclusions within the scope of the present invention has a better iron loss value and punchability than a product plate with chemical components and inclusions outside the scope of the present invention. It was.

As shown in Table 5, steels with various changes were dissolved, and alumina (Al ₂ O ₃ ) and iron oxide (Fe ₂ O ₃ ) were mixed at a mass ratio of 1: 1. The product powder is coated on a wire and supplied into the mold at a supply rate of 3 to 4 kg / min, continuously cast with a molten steel discharge flow rate of 3 tons / min, hot rolled, and cold to a thickness of 0.5 mm. The product plate was produced by rolling and finishing annealing at 850 ° C. for 30 seconds, and applying an insulating film containing an organic component and an inorganic component applied to a normal non-oriented electrical steel sheet.

Next, the number density of the inclusions having a product plate diameter of 2 μm or more and 25 μm or less was examined by an optical microscope, and the inclusion composition was analyzed by SEM-EDX. Further, the product plate was punched to a length of 25 cm with a clearance of 0.1 mm using a high-speed punching machine, and the magnetic characteristics were investigated by the Epstein method shown in JIS-C-2550. Further, a punching process was performed with a high-speed punching machine into a circle having a clearance of 0.1 mm and a diameter of 12 mm, and the punching load was measured. Further, the continuous punching, the sag height of the steel sheet after punching is measured, the wear state of the sagging punching number up to a height of 1% of the thickness (50 [mu] m), and 10 ⁵ times after successive punching tool investigated. Moreover, the punching fracture surface was investigated by SEM-EDX, and the inclusion composition was analyzed. A water-soluble lubricating oil was used for punching.

  The results are shown in Table 6. Hard inclusions having a diameter of 2 μm or more and 25 μm or less were observed at the crack starting point of the punched fracture surface, and other inclusions were not observed. In addition, No. 3-1 to which REM is added has the inclusion size and number density within the range of the present invention, and the produced inclusion is a single granular alumina, which has good iron loss value and punchability. Results were obtained. On the other hand, No. 3-2 in which the REM content deviated from the lower limit value was an alumina in which the size and number density of inclusions were within the range of the present invention, but the generated inclusions were covered with MnS. Yes, the iron loss value was good, but the punching property was inferior. In No. 3-3 to which Ca was added, the size and number density of inclusions were within the scope of the present invention, but the produced inclusion was stretched CaS, and the punchability was good. However, the result that an iron loss value is inferior was obtained.

  As described above, by properly controlling the hard inclusions contained in the non-oriented electrical steel sheet according to the present invention, the punchability is good, the tool life can be extended, and the magnetic properties are deteriorated by punching. It is possible to provide a non-oriented electrical steel sheet with few and excellent quality.

It is a figure which shows the SEM image of the torn surface which punched the product board with favorable punching property. It is a figure which shows the SEM image of the location which fractured | ruptured from the inclusion of the torn surface which punched the product board with favorable punching property. It is a figure which shows the correlation with the number density of the hard inclusion in a product board, the iron loss value of a product board, and the breaking load at the time of punching.

Explanation of symbols

A Locations of inclusions that become the starting point of fracture during punching B Inclusions that become the starting point of fracture during punching

Claims (5)

In mass%, C: 0.01% or less, Si: 0.1% or more and 7.0% or less, Al: 0.01% or more and 3.0% or less, Mn: 0.1% or more and 2.0% or less N: 0.005% or less, S: 0.005% or less, O: 0.005% or more and 0.02% or less, with the balance being iron and inevitable impurities, and a diameter of 2 μm or more and 25 μm or less A non-oriented electrical steel sheet excellent in punching workability and iron loss, characterized in that it contains 100 / mm ³ or more and 100000 / mm ³ or less of an oxide of alumina or silica. Moreover, in mass%, R EM: characterized Rukoto that Yusuke containing 0.0005% or 0.05% or less, non-oriented electrical steel sheet excellent in punching processability and iron loss according to claim 1 . In mass%, C: 0.01% or less, Si: 0.1% or more and 7.0% or less, Al: 0.01% or more and 3.0% or less, Mn: 0.1% or more and 2.0% or less N: 0.005% or less, S: 0.005% or less, O: 0.005% or more and 0.02% or less, and the balance of the molten steel consisting of iron and unavoidable impurities is 1 of alumina or silica. characterized Rukoto using slab was added oxide of the seed or the casting method for producing a non-oriented electrical steel sheet excellent in punching processability and iron loss according to claim 1. Said molten steel further contains, by mass%, R EM: characterized Rukoto that Yusuke containing 0.0005% or 0.05% or less, excellent punching workability and core loss according to claim 3 No method for producing oriented electrical steel plate. It said oxide is added to the mold, wherein the casting method for producing a non-oriented electrical steel sheet excellent in punching processability and iron loss according to claim 3 or 4.