JPH08138924A - Manufacturer of fully-processed non-directional electromagnetic steel plate - Google Patents

Abstract

PURPOSE: To provide a method of manufacturing a fully-processed non-directional electromagnetic steel plate which is hardly deteriorated in magnetic properties due to blanking and kept excellent in magnetic properties after it is formed into an iron core. CONSTITUTION: A steel slab composed of below 0.010% of C, 1.0 to 2.0% of Si, 0.25 to 1.00% of Mn, below 0.1% of P, 0.015 to 0.035% of S, 0.15 to 0.50% of Al, and residual % of substantially Fe and inevitable impurities is formed into a fully-processed non-directional electromagnetic steel plate by a method in which it is hot-rolled, then cold-rolled, and continuously annealed at a temperature of above 800 deg.C in a ferrite phase. Or, the hot-rolled steel plate may be annealed before it is cold-rolled, or the steel slab may be heated at temperatures of 1050 to 1180 deg.C. By this setup, a stress relief annealing process can be dispensed with when a non-directional electromagnetic steel plate is blanked out for use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a full-process non-oriented electrical steel sheet which has little deterioration in magnetic characteristics due to punching and has good magnetic characteristics after being formed into an iron core.

[0002]

2. Description of the Related Art Non-oriented electrical steel sheets can be classified into two types, full-process materials and semi-process materials, depending on how they are used by users. The semi-processed material is punched by a user to form an iron core, then subjected to strain relief annealing, laminated, and incorporated into an electric device. Therefore, electromagnetic steel sheets are often manufactured on the assumption that they are annealed before use. When annealed, the strain on the punched end face is removed, and the crystal grains become coarser. In general, even a small amount of processing strain applied to a steel sheet significantly deteriorates the magnetic characteristics, and the larger the crystal grains are, the better the magnetic characteristics. Therefore, although annealing after processing into the final shape can greatly improve the magnetic properties, there is a drawback in that the heat treatment cost and the number of steps for the user increase.

On the other hand, the full-process material is an electromagnetic steel sheet manufactured by assuming that it will be laminated as it is into a core to be an iron core and incorporated into electric equipment. The user can omit the extra step of strain relief annealing, but the magnetic characteristic deterioration due to punching strain cannot be avoided. Therefore, in order to cover the performance deterioration due to punching distortion, an expensive high-grade material that exhibits excessively good magnetic characteristics may be used.

When an iron core shape is punched out from a steel sheet, the processing strain of the steel sheet that occurs near the cutting edge surface is estimated to be substantially constant along the cutting edge surface, unless a peculiar shape or tool setting is inadequate. . Then, the larger the cumulative length of the cut end face with respect to the area of the punched iron core shape, the larger the amount of strain with respect to the entire iron core.

For example, the magnetic properties of electromagnetic steel sheets are JIS-C-2550.
It is evaluated by the Epstein test using a strip test piece with a width of 30 mm and a length of 280 to 320 mm as shown in. However, the teeth of the stator core of small and medium-sized motors may have a very narrow width of 3 to 10 mm.

In the case of an iron core having a narrow width, the ratio of the punched end face portion to the whole iron core is much larger than that of the Epstein test piece. Therefore, depending on the shape of the iron core, the magnetic characteristics expected by the Epstein test value may not be obtained by an actual device.

The occurrence of distortion of the steel plate at the punched end face, that is, the sheared surface, is greatly affected by the tool shape of the punch and die used for punching, the clearance, or the maintenance situation. On the other hand, it is considered that, as a steel sheet, proper hardness and characteristics peculiar to the steel sheet such as shear resistance influence the amount of strain generation. However, the relationship between those characteristics and the magnetic characteristics of the steel sheet base material is not always clear.

If it is possible to manufacture an electromagnetic steel sheet capable of reducing the occurrence of strain on the punched end face without deteriorating the magnetic properties,
It is possible to reduce the grade of the full process material to be applied, and in order to secure magnetic properties, it becomes unavoidable to replace it with the application in which strain relief annealing is performed using a semi-processed material.

[0009]

DISCLOSURE OF THE INVENTION The present invention produces a full-process non-oriented electrical steel sheet in which the deterioration of the magnetic properties due to punching is small and the actual magnetic properties of the iron core are good even without strain relief annealing. It is intended to provide a method.

[0010]

[Means for Solving the Problems] In order to reduce the strain due to plastic deformation near the punched end face, it is necessary to have a certain degree of hardness, and further it is necessary to reduce the shear resistance. It is possible to add strain and increase inclusions. However, these methods greatly deteriorate the magnetic properties of the steel sheet itself.

The inventors of the present invention firstly used JIS-C-25 as a method for quantifying a phenomenon in which magnetic characteristics are deteriorated by punching strain.
We considered the application of the measurement method with 50 Epstein test frames.
The test piece used for the Epstein frame is usually 30 mm wide and 2
It is 80 mm. Therefore, from the steel sheet to be evaluated, two types of test pieces, a test piece with a width of 30 mm and a test piece with the same length and a width of 5 mm, were punched out and
In the case of width, 6 pieces are arranged on a plane and assembled as a set into a 30 mm wide test piece. The magnetic properties were measured using these two types of test pieces, and the results were compared to evaluate the magnitude of the deterioration amount of the magnetic properties due to punching strain. The test piece with a width of 5 mm has a large amount of punching distortion introduced into the test piece with a width of 30 mm, and if the degree of deterioration in magnetic characteristics is small, it should be a material that does not easily deteriorate in magnetic characteristics due to punching.

As a result of conducting measurements on several steel sheets using such an evaluation method, when a normal test piece of 30 mm width has substantially the same level of magnetic characteristics, when it is set to 5 mm width, It was found that the degree of deterioration varied greatly depending on the type. Therefore, as a result of conducting experiments and trial production on a larger number of steel sheets, accumulating and analyzing the measurement data, the amounts of Si, Mn and S as the components of the steel sheets were controlled within a specific range, and the finish annealing after cold rolling was performed at a high temperature. It has been found that a non-oriented electrical steel sheet having good magnetic properties and having little deterioration in magnetic properties due to punching can be obtained by continuous annealing of No. 3).

The present invention has been completed based on these findings. The main points are (1) “C: 0.010% or less, Si: more than 1.0 to 2.0%, M
n: 0.25 to 1.00%, P: 0.1% or less, S: 0.015 to 0.03
5%, Al: 0.15 to 0.50%, the balance is steel slab consisting essentially of Fe and unavoidable impurities, hot-rolled, cold-rolled, and continuously annealed in the ferrite region of 800 ° C or higher. The method of manufacturing a full-process non-oriented electrical steel sheet with excellent magnetic properties ”. In this manufacturing method, if the hot rolled sheet is annealed after (2) hot rolling and before cold rolling, the magnetic properties can be improved. Further, in the production method of (1) or (2), (3) it is desirable that the slab heating temperature before hot rolling is set to 1050 to 1180 ° C., and a more stable improvement in magnetic characteristics can be obtained.

[0014]

The method of the present invention will be specifically described below, and the reason why the manufacturing conditions are limited as described above will be described together with the operation thereof.

A) Component of raw steel billet (1) C C content adversely affects iron loss, so the smaller the content, the better. The C remaining in the product forms a carbide, which acts as an obstacle to the domain wall movement and increases iron loss.

Therefore, the content needs to be 0.010% or less. 0.005% or less is desirable.

(2) Si Si is an element having a great influence on the magnetic properties, and as the content increases, the electrical resistance of the steel sheet increases and the eddy current loss decreases, resulting in a decrease in iron loss. In addition, it has the effect of increasing the hardness of the steel sheet. If it is 1.0% or less, it is difficult to secure a desired iron loss, and the deterioration of magnetic properties due to punching strain tends to be large if it is 1.0% or less. However, when the content exceeds 2.0%, the saturation magnetic flux density is greatly reduced, and it is not suitable for the iron cores for small and medium-sized motors, which are the main applications of the present invention. Therefore, the Si content exceeds 1.0
The range is 2.0%.

(3) Mn With respect to the magnetic steel sheet, the inclusion of Mn itself has only the effect of increasing the electric resistance.

However, MnS is formed by combining with S in steel, and the size and distribution of MnS precipitates change depending on the Mn content. The state of these precipitates significantly changes the metal structure and has an important influence on the magnetic properties.

Further, when a large amount of large MnS precipitates are formed, the deterioration of magnetic properties due to punching strain is reduced. This is considered to be because the presence of an appropriate amount of large MnS precipitates reduces the shear resistance, reduces the plastic deformation region, and reduces the deterioration of magnetic properties.

If the Mn content is less than 0.25%, the MnS precipitates do not coarsen and tend to be finely dispersed. In this case, not only the deterioration of magnetic properties due to punching strain cannot be reduced, but also the growth of crystal grains in continuous annealing after cold rolling is suppressed, and good magnetic properties cannot be obtained. However, 1%
Since the effect of Mn will be saturated even if added over M, M
The n content was set to 0.25 to 1.00%.

(4) P P increases the hardness of the steel sheet and increases the electrical resistance, so it is added if necessary. 0.02% when included to secure hardness
The above is desirable. However, the addition of more than 0.1% embrittles the steel sheet and may cause cracking during cold rolling or punching, so the content is made 0.1% or less.

(5) S S is usually a MnS precipitate, and magnetic properties deteriorate significantly when the amount increases, but deterioration of magnetic properties can be reduced by increasing the precipitate even with the same S content. . By forming an appropriate amount of this large precipitate, it is possible to reduce the deterioration of magnetic properties due to punching strain. This effect increases as the amount of S increases, but if the content is less than 0.015%, it is insufficient.
This is because the volume fraction of MnS in steel is too small.

However, if the amount of S exceeds 0.035%, the deterioration of the magnetic properties due to punching is small, but the magnetic properties of the steel sheet product deteriorate. Therefore, the S content is 0.015 to 0.035%
I decided.

(6) Al The addition of Al has the effect of increasing the electrical resistance and reducing the eddy current loss as in the case of Si, and consequently reducing the iron loss. On the other hand, it combines with N to form AlN, which hinders grain growth during continuous annealing after cold rolling and deteriorates iron loss.
However, AlN becomes coarse when 0.15% or more is contained,
The effects of grain growth inhibition and magnetic property deterioration are suppressed. However, even if Al exceeding 0.50% is added, further improvement in grain growth cannot be obtained, and the saturation magnetic flux density is greatly reduced.
Therefore, the Al content is 0.15 to 0.50%.

B) Manufacturing Conditions (7) Hot Rolling Conditions The slab to be subjected to hot rolling having the above composition is melted in a converter, an electric furnace or the like, and if necessary, a molten steel subjected to a treatment such as vacuum degassing. May be continuously cast or slab-rolled into ingots. Heating the slab gives the desired characteristics even under normal conditions, but it is 1050-1180 ° C.
A better iron loss value can be obtained by heating at a relatively low temperature. The low-temperature heating at 1180 ° C. or lower has an action of suppressing the generation of fine MnS precipitates, promotes grain growth, and improves the iron loss value. However, hot rolling becomes difficult at low temperature heating below 1050 ° C.

There are no particular restrictions on other hot rolling conditions, but a finishing temperature of 750 to 950 ° C.,
The winding temperature is 500-800 ℃.

(8) Cold rolling After hot rolling, cold rolling is performed to a predetermined product plate thickness. Cold rolling conditions are not particularly specified, but the rolling reduction is generally 60 to 90%.

(9) Continuous annealing After cold rolling, continuous annealing is performed for removing work strain, recrystallization and grain growth. When the S content is high, in order to obtain a good iron loss value, it is necessary to coarsen the crystal grain size by high temperature annealing, and the temperature is set to 800 ° C or higher. However, the magnetic properties deteriorate at a high temperature of about 1000 ° C. or higher at which austenite is generated. Therefore, the ferrite region is set to 800 ° C or higher.
After the annealing, it is common to apply a coating for insulation.

(10) Annealing of hot rolled sheet Annealed after hot rolling and before cold rolling (so-called hot rolled sheet annealing)
May be performed.

By carrying out this hot-rolled sheet annealing, recrystallization and grain growth of the hot-rolled sheet are promoted, and it is effective in obtaining good magnetic properties in the annealing after cold rolling. If the hot-rolled sheet is annealed by the continuous annealing method, it is soaked at 750 to 1000 ° C for 10 seconds to 5 minutes, and if it is performed by the box annealing method, it is 650 to 950 ° C for 30 minutes to 24 minutes.
It is desirable to make the temperature uniform.

[0032]

Example: After melting in a converter and adjusting the components by vacuum treatment,
A steel slab having the composition shown in Table 1 obtained by continuous casting was
2.3mm by hot rolling after heating the slab at the temperature shown in Table 1.
Finished thick. Next, the hot-rolled sheet is left as it is, or after the hot-rolled sheet is annealed under the soaking conditions shown in Table 1, cold-rolled to a thickness of 0.50 mm, and further subjected to continuous annealing under the soaking conditions shown in Table 1 for coating. The product was applied.

[0033]

[Table 1]

5 mm width or 30 mm from the product by punching
Width of 280 mm and two types of test pieces are collected, and in the case of 5 mm width, 6 pieces are assembled into a 30 mm width test piece.
A C-2550 Epstein frame test was performed to measure the magnetic properties of two types of test pieces having different punch widths. The magnetic measurement results are shown in Table 2. The magnetic properties are better as the iron loss is lower, and the magnetic flux density is higher as the magnetic properties are higher.

[0035]

[Table 2]

In Test Nos. 1 to 4, only the S content was variously changed, and all other components were almost the same. In the test number 1 in which the S content is out of the range of the present invention, the magnetic property value of the test piece of 30 mm width is good, but in the test piece of 5 mm width,
The iron loss W _15/50 and the magnetic flux density B ₃ are significantly deteriorated as compared with those of 30 mm width. In general, iron loss and magnetic flux density B _{3 in a} low magnetic field are easily affected by strain due to plastic deformation, and it is considered that Test No. 1 in which these magnetic properties are greatly deteriorated is greatly affected by punching strain. The magnetic flux density B of the high magnetic field
_It is said that ₅₀ is not easily affected by distortion, with a 30 mm width and 5
There is almost no difference from the mm width.

On the other hand, in the test number 4 in which the S content is out of the range of the present invention, the magnetic property deterioration amount of the 5 mm width test piece is not large compared to the 3 mm width test piece, but the magnetic property level of the 30 mm width test piece is high. Itself is inferior. On the other hand, in Test Nos. 2 and 3 within the scope of the present invention, the magnetic properties in the case of the width of 30 mm are good, and the deterioration amount is much smaller than that of Test No. 1 even when the width is 5 mm.

Test number 5 is test numbers 2 and 3 and S of the present invention.
Although it is almost the same except for the amount of i, the amount of Si deviates from the range of the present invention to a low level, the iron loss in the case of 30 mm width is poor, and the iron loss deterioration in the case of 5 mm width is also test numbers 2, 3 It is bigger than.

Test Nos. 6 to 11 have the same composition but different slab heating temperatures, hot-rolled sheet annealing and final continuous annealing conditions. Test numbers 6 to 8 are those in which hot-rolled sheet annealing was omitted at the same low temperature slab heating temperature, and in the case of test number 8 in which the final continuous annealing temperature was out of the range of the present invention, it was 5 mm.
Even if the deterioration in width is about the same, the magnetic property level in the width of 30 mm is inferior. Although the test number 9 is within the range of the present invention, the magnetic properties are slightly inferior to those of the test number 6 under the same conditions except that the slab heating temperature is high. This indicates that the lower the slab heating temperature, the better the magnetic characteristics.

Test No. 10 is obtained by adding hot-rolled sheet annealing to the manufacturing method of Test No. 9, and it is clear that the magnetic properties are improved. Although the test number 11 is performing hot-rolled sheet annealing, like the test number 8, the final continuous annealing temperature is out of the range of the present invention to be low, and the magnetic property in the width of 30 mm is poor.

Test No. 12 has almost the same composition as 13 and M
Only the n amount falls outside the scope of the present invention. In the case of this test number 12, the magnetic characteristic level in the case of the width of 30 mm is significantly inferior to that of 13 in the range of the present invention, and the difference of the magnetic characteristics becomes larger at the width of 5 mm.

Test No. 14 has the same composition as Test No. 13, but only the final continuous annealing falls outside the scope of the present invention. The deterioration of the magnetic properties of the 5 mm width with respect to the case of the 30 mm width is about the same as the test number 13, but the magnetic property level of the 30 mm width is significantly inferior.

Test Nos. 15 and 16 are within the scope of the present invention, and good magnetic properties are obtained. However, Test No. 16 having a lower slab heating temperature shows better results.

[0044]

As described above, according to the method of the present invention, there is little deterioration of the magnetic properties due to punching, and the magnetic properties of the iron core obtained without strain relief annealing are good, and there is no full process process. A grain-oriented electrical steel sheet can be manufactured.

[0045]

Claims (3)

[Claims] 1. By weight%, C: 0.010% or less, Si: 1.0
Super ~ 2.0%, Mn: 0.25 ~ 1.00%, P: 0.1% or less,
S: 0.015 to 0.035%, Al: 0.15 to 0.50%, the balance being a steel slab consisting essentially of Fe and unavoidable impurities, hot-rolled, then cold-rolled in a ferrite region of 800 ° C or higher. A method for producing a full-process non-oriented electrical steel sheet with excellent magnetic properties, characterized by continuous annealing. 2. The method for producing a full-process non-oriented electrical steel sheet according to claim 1, wherein the hot-rolled sheet is annealed after the hot rolling and before the cold rolling. . 3. The slab heating temperature before hot rolling is set to 1050 to 11
It is 80 degreeC, The manufacturing method of the full process non-oriented electrical steel sheet of Claim 1 or 2 characterized by the above-mentioned.