JP2970436B2 - Manufacturing method of full process non-oriented electrical steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a non-oriented electrical steel sheet having a small magnetic property due to punching and having good magnetic properties 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, according to the method of use by users. The semi-process material is formed into a core shape by a punching process by a user, then subjected to strain relief annealing, laminated, and incorporated into an electric device. For this reason, magnetic steel sheets are often manufactured on the assumption that they are annealed before use. When annealing is performed, the distortion of the punched end face is removed, and the crystal grains become coarser. In general, even if the strain applied to a steel sheet is slight, the magnetic properties are greatly deteriorated, and the larger the crystal grains are, the better the magnetic properties are. Therefore, annealing after processing to the final shape can greatly improve the magnetic properties, but has the disadvantage of increasing the heat treatment cost and man-hours for the user.

On the other hand, a full process material is an electromagnetic steel sheet manufactured on the assumption that it is laminated as it is punched to form an iron core and is incorporated into an electric device. Although the user can omit the extra step of strain relief annealing, magnetic property deterioration due to punching strain cannot be avoided. Therefore, in order to cover the performance degradation due to the punching distortion, an expensive high-grade material showing excessively good magnetic properties may be used.

[0004] When the iron core shape is punched from a steel sheet, the processing strain of the steel sheet generated near the cut end face is estimated to be substantially constant along the cut end face, unless a special shape or tool setting is inadequate. . Then, with respect to the area of the punched iron core shape, the longer the cumulative length of the cut end face, the greater the amount of distortion with respect to the entire iron core.

[0005] For example, the magnetic properties of an electrical steel sheet are described in JIS-C-2550.
Is evaluated by an Epstein test using a strip-shaped test piece having a width of 30 mm and a length of 280 to 320 mm. However, the teeth of the stator core of a small-to-medium-sized motor may have a very narrow width of about 3 to 10 mm.

In the case of a narrow iron core shape, the ratio of the punched end face portion to the entire iron core is much larger than that of the Epstein test piece. For this reason, depending on the shape of the iron core, the magnetic properties expected from the Epstein test values may not be obtained in actual equipment.

[0007] The occurrence of distortion of the steel sheet at the punched end face, that is, the shear plane, is greatly affected by the tool shape and clearance of punches and dies used for punching, or the condition of care. On the other hand, it is considered that properties inherent to the steel sheet, such as moderate hardness and shear resistance, affect the amount of strain. However, the relationship between these properties and the magnetic properties 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 distortion at the punched end face without deteriorating the magnetic properties,
The grade of the full-process material to be applied can be reduced, and it is possible to replace the use of a semi-process material for unavoidable strain relief annealing in order to secure magnetic properties.

[0009]

SUMMARY OF THE INVENTION The present invention is to produce a full-process non-oriented electrical steel sheet in which the magnetic properties due to punching are small and the actual magnetic properties of the iron core are good without performing strain relief annealing. It seeks to provide a way.

[0010]

In order to reduce distortion due to plastic deformation near the punched end face, it is necessary to have a certain degree of hardness and further to reduce the shear resistance. It is conceivable to add distortion or increase inclusions. However, these methods greatly degrade the magnetic properties of the steel sheet itself.

As a method for quantifying the phenomenon that the magnetic characteristics are deteriorated due to the punching distortion, the present inventors have proposed JIS-C-25
The application of the measurement method with 50 Epstein test frames was considered.
The test piece used for the Epstein frame is usually 30 mm wide and 2 mm long.
It is 80mm. Therefore, 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 sampled from the steel sheet to be evaluated by punching.
In the case of the width, six sheets are arranged in 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 of the magnetic properties due to the punching strain. As compared to a 30 mm wide test piece, a 5 mm wide test piece has a large amount of punch distortion, and if the degree of magnetic property deterioration is small, it should be a material that hardly causes magnetic property deterioration due to punching.

As a result of measuring several steel sheets by using such an evaluation method, it has been found that a normal 30 mm wide test piece has almost the same level of magnetic properties but has a 5 mm width. It has been found that the degree of deterioration varies greatly depending on the type of the battery. Therefore, experiments and trial production were conducted on more steel sheets, measurement data were collected and analyzed. As a result, the amounts of Si, Mn and S as steel sheet components were controlled within a specific range, and finish annealing after cold rolling was performed at a high temperature. It has been found that non-oriented electrical steel sheets having good magnetic properties and less deterioration of magnetic properties due to punching can be obtained by continuous annealing.

The present invention has been completed based on such findings. The summary is as follows: (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 ~ 0.50%, the rest is a steel slab consisting essentially of Fe and unavoidable impurities, hot rolled, cold rolled and continuously annealed in the ferrite region above 800 ° C Method for producing full-process non-oriented electrical steel sheet having excellent magnetic properties. In this manufacturing method, (2) if the hot rolled sheet is annealed after hot rolling and before cold rolling, the magnetic properties can be improved. Further, in the above method (1) or (2), (3) the slab heating temperature before hot rolling is desirably set to 1050 to 1180 ° C., so that a more stable improvement in magnetic properties can be obtained.

[0014]

The method of the present invention will be specifically described below, and the reason for limiting the manufacturing conditions as described above will be described together with the operation.

A) Components of raw steel slab (1) C The content of C adversely affects iron loss, so the smaller the better, the better. C remaining in the product forms carbides, which become obstacles for domain wall movement and increase iron loss.

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

(2) Si Si is an element that has a great influence on magnetic properties. As the content increases, the electrical resistance of the steel sheet increases, the eddy current loss decreases, and as a result, the iron loss decreases. 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 distortion 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 is not suitable for a core for a small and medium-sized motor, which is a main application of the present invention. Therefore, the Si content is more than 1.0
The range is 2.0%.

(3) Mn The content of Mn in the magnetic steel sheet only has an effect of increasing the electric resistance.

However, it combines with S in steel to form MnS, and the size and distribution of MnS precipitates change depending on the Mn content. The state of the precipitate greatly changes the metal structure and has an important effect on the magnetic properties.

Further, when an appropriate amount of large MnS precipitates is formed, deterioration of magnetic properties due to punching distortion is reduced. This is probably because the presence of an appropriate amount of the large MnS precipitate reduces the shear resistance, reduces the plastic deformation region, and reduces the deterioration of the magnetic properties.

If the Mn content is less than 0.25%, the MnS precipitate does not become coarse and tends to be finely dispersed. In this case, not only deterioration of magnetic properties due to punching strain cannot be reduced, but also crystal grain growth in continuous annealing after cold rolling is suppressed, and good magnetic properties cannot be obtained. However, 1%
, The effect of Mn saturates, so that M
The n content was determined to be 0.25 to 1.00%.

(4) PP increases the hardness of the steel sheet and increases the electric resistance, and is added as necessary. 0.02% when included to ensure hardness
The above is desirable. However, the addition exceeding 0.1% embrittles the steel sheet and may cause cracking during cold rolling or punching, so the content is set to 0.1% or less.

(5) S S is usually a MnS precipitate, and when its amount is increased, the magnetic properties are significantly deteriorated. However, even if the S content is the same, the precipitates are made large, so that the magnetic properties can be reduced. . By forming an appropriate amount of this large precipitate, deterioration of magnetic properties due to punching distortion can be reduced. This effect increases as the amount of S increases, but the content of less than 0.015% is insufficient.
This is because the volume fraction of MnS in the steel is too small.

However, when the S content exceeds 0.035%, the magnetic properties of the steel sheet product are deteriorated, although the magnetic properties are not deteriorated by punching. Therefore, the S content is reduced from 0.015 to 0.035%
It was decided.

(6) Al Addition of Al has the effect of increasing the electrical resistance and reducing the eddy current loss similarly to 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, if the content is 0.15% or more, AlN coarsens,
The effect of inhibiting grain growth and deteriorating magnetic properties is suppressed. However, even if Al is added in excess of 0.50%, no further improvement in grain growth can be obtained, and the saturation magnetic flux density is greatly reduced.
Therefore, the Al content is set to 0.15 to 0.50%.

B) Manufacturing Conditions (7) Hot Rolling Conditions The slab to be subjected to hot rolling of the above composition is melted in a converter, an electric furnace or the like and, if necessary, subjected to a treatment such as vacuum degassing. May be either continuously cast or slab rolled into an ingot. Heating of the slab can achieve the desired characteristics under normal conditions, but 1050-1180 ° C
By heating at a relatively low temperature, a better iron loss value can be obtained. Low-temperature heating at 1180 ° C. or lower has an effect of suppressing the generation of fine MnS precipitates, promotes grain growth, and improves the iron loss value. However, low-temperature heating of less than 1050 ° C. makes hot rolling difficult.

There are no particular restrictions on other hot rolling conditions, but it is preferable that the finishing temperature be 750 to 950 ° C.
The winding temperature is 500 to 800 ° C.

(8) Cold rolling After hot rolling, cold rolling is performed to a predetermined product thickness. The 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 to remove work strain, recrystallize, and grow grains. When the S content is large, in order to obtain a good iron loss value, it is necessary to coarsen the crystal grain size by high-temperature annealing. However, at a high temperature of about 1000 ° C. or more at which austenite is generated, the magnetic properties deteriorate. Therefore, the ferrite region is set to 800 ° C. or higher.
In addition, it is common to apply a coating for insulation after annealing.

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

By performing the hot-rolled sheet annealing, recrystallization and grain growth of the hot-rolled sheet are promoted, and it is effective to obtain good magnetic properties by annealing after cold rolling. When performing hot-rolled sheet annealing by the continuous annealing method, soak at 750 to 1000 ° C for 10 seconds to 5 minutes, and when performing the box annealing method, at 650 to 950 ° C for 30 minutes to 24 hours.
It is desirable to have a soaking time.

[0032]

[Example] After melting in a converter and adjusting the components by vacuum processing,
A steel slab having the composition shown in Table 1 obtained by continuous casting was
After heating the slab at the temperature shown in Table 1, hot-rolling 2.3mm
Finished thick. Next, the hot-rolled sheet is left as it is or after being subjected to hot-rolled sheet annealing 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, To give the product.

[0033]

[Table 1]

From the product, 5mm width or 30mm by punching
Two types of test specimens with a width of 280mm are collected. In the case of 5mm width, six specimens are assembled into a 30mm width test specimen.
The magnetic properties of two types of test pieces having different punching widths were measured by a test using an Epstein frame of C-2550. Table 2 shows the results of the magnetic measurement. In addition, as the magnetic properties, the lower the iron loss, the better, and the higher the magnetic flux density, the better.

[0035]

[Table 2]

Test Nos. 1 to 4 differed only in the amount of S, and all other components were almost the same. In Test No. 1 in which the amount of S deviated from the range of the present invention, the magnetic property value of the test piece having a width of 30 mm was good.
The iron loss W _15/50 and the magnetic flux density B ₃ are significantly deteriorated as compared with those having a width of 30 mm. Typically iron loss and low magnetic field flux density B ₃ of susceptible to distortion due to plastic deformation, greater Test No. 1 of degradation of these magnetic characteristics are considered to have significantly affected the punching distortion. The magnetic flux density B of the high magnetic field
₅₀ is said to be less susceptible to distortion, with a 30mm width and 5
There is almost no difference with mm width.

On the other hand, in Test No. 4 in which the S content deviated from the range of the present invention, the deterioration of the magnetic properties of the 5 mm width test piece was not large compared to the 3 mm width test piece, but the level of the magnetic properties of the 30 mm width test piece was small. In itself is inferior. On the other hand, Test Nos. 2 and 3 in the range of the present invention have good magnetic properties when the width is 30 mm, and the deterioration amount is much smaller than Test No. 1 even when the width is 5 mm.

Test number 5 is the same as test numbers 2 and 3 of the present invention and S
Except for the amount of i, the amounts were almost the same, but the amount of Si was slightly lower than the range of the present invention, and the iron loss was poor when the width was 30 mm. It is larger than.

Test Nos. 6 to 11 are the same compositions but with different slab heating temperatures, hot rolled sheet annealing and final continuous annealing conditions. Test Nos. 6 to 8 were those in which hot-rolled sheet annealing was omitted at the same low-temperature slab heating temperature. In the case of Test No. 8 in which the final continuous annealing temperature was lower than the range of the present invention, 5 mm
Despite the same degree of degradation when the width is set, the magnetic characteristic level at a width of 30 mm is inferior. Test No. 9 is within the scope of the present invention, but the magnetic properties are slightly inferior to Test No. 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 properties.

Test No. 10 is obtained by adding hot-rolled sheet annealing to the production method of Test No. 9, and the improvement in magnetic properties is apparent. In Test No. 11, the hot-rolled sheet was annealed, but as in Test No. 8, the final continuous annealing temperature was out of the range of the present invention, and the magnetic properties at a width of 30 mm were poor.

Test No. 12 has almost the same components as 13 and M
Only the n amount falls outside the range of the present invention. In the case of Test No. 12, the magnetic characteristic level in the case of a 30 mm width was significantly inferior to that of 13 in the range of the present invention, and the difference in magnetic characteristics was further increased in the case of a 5 mm width.

Test No. 14 has the same composition as Test No. 13, and only the final continuous annealing deviates from the range of the present invention. The deterioration of the magnetic characteristics of the 5 mm width with respect to the case of the 30 mm width is almost the same as that of the test number 13, but the magnetic characteristic level of the 30 mm width is significantly inferior.

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

[0044]

As described above, according to the method of the present invention, the deterioration of the magnetic characteristics due to the punching is small, and the magnetic characteristics of the iron core obtained without performing the strain relief annealing are excellent. A grain-oriented electrical steel sheet can be manufactured.

[0045]

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01F 1/16 C21D 8/12 C22C 38/00 303 C22C 38/06

Claims (3)

(57) [Claims] (1) In weight%, C: 0.010% or less, Si: 1.0
Ultra-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 remainder being a steel slab consisting essentially of Fe and unavoidable impurities, hot rolled, then cold rolled, and in a ferrite region above 800 ° C A method for producing a full-process non-oriented electrical steel sheet having 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 hot rolling and before cold rolling. . 3. The slab heating temperature before hot rolling is 1050-11
The method for producing a full-process non-oriented electrical steel sheet according to claim 1 or 2, wherein the temperature is 80 ° C.