JPS62182223A - Production of low iron loss grain oriented electrical steel sheet - Google Patents

Abstract

PURPOSE:To produce a low iron loss grain oriented electrical steel sheet which is free from deterioration in magnetic characteristics even after a stress relief annealing treatment by periodically providing plural strain introducing zones partly superposed with plastic strain regions to a finish annealed sheet in the rolling direction thereof then subjecting the sheet to a heat treatment. CONSTITUTION:The plural strain introducing zones in proximity with the plastic strain regions so as to be partly superposed within the steel sheet are periodically provided in the rolling direction at 0.2-2.5mm width, 2-12mm intervals and the angle ranging right angle - 45 deg. with the rolling direction to the finish annealed sheet contg. about <=4% Si or after the sheet is subjected to a treatment to form a tension applying film thereon. The above-mentioned plastic strain introducing zones are adequately formed by the irradiation of a laser and are preferably constituted by plural times of the laser irradiation and by plural pieces of laser beams having 0.1-0.5mm width. The strength of the above-mentioned laser beam is adequately made U=1-100J/cm<2>. The steel sheet provided with the above-mentioned strain introducing zones is then subjected to the treatment such as stress relief annealing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a low core loss unidirectional electrical steel sheet whose magnetic properties do not deteriorate even after strain relief annealing, and a method for manufacturing the same.

[Conventional technology]

It is desired to reduce iron loss in grain-oriented electrical steel sheets from the viewpoint of energy saving. As a method of reducing iron loss, a method of subdividing magnetic domains by laser irradiation has already been disclosed in Japanese Patent Publication No. 58-26405. The reduction in core loss by this method is due to the strain introduced by the laser. Therefore, it can be used for laminated core transformers that do not require strain relief annealing, but cannot be used for wound core transformers that require strain relief annealing.

Further, Japanese Patent Publication No. 59-23822 discloses that the iron loss value is reduced even if strain relief annealing is performed after laser irradiation, but according to this method, the reduction rate of the iron loss value is improved by laser irradiation. This is about 50% of the improvement in iron loss value.

[Problem that the invention seeks to solve]

The present invention has the drawback that when stress relief annealing is performed on unidirectional electrical steel sheets, the elastic strain introduced into the steel sheet disappears, making it impossible to achieve low iron loss, and the effect of stress relief annealing does not disappear. The aim is to simultaneously solve the problem of not being able to obtain a low core loss value comparable to that of laser irradiated materials, and to provide a low core loss unidirectional electrical steel sheet whose magnetic properties do not deteriorate even after stress relief annealing. be.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a steel plate that has been subjected to finish annealing or a tension imparting film treatment, by periodically applying a plurality of strain introducing zones in close proximity in the rolling direction so that the plastic strain regions partially overlap within the steel plate. The present invention provides a method for producing a unidirectional electrical steel sheet with low core loss, which is characterized by subjecting the steel sheet to heat treatment after being subjected to heat treatment.

As a result of a detailed study of laser-irradiated materials, the present inventors noticed that plastic strain remained in the laser-irradiated materials even after heat treatment at a high temperature of 750°C or higher. We thought that if the strained region remained in a wider area than in conventional stress-relieving annealed material after laser irradiation, magnetic domain refinement could be achieved, so we irradiated the laser beam multiple times in close proximity by changing the irradiation area. This led to the conclusion that plastic strain is difficult to eliminate by annealing.

The present invention will be explained in detail below.

A slab containing 4% Si or less is heated and hot rolled to an intermediate thickness, the resulting hot rolled plate is pickled and heat treated at this stage if necessary, and then cold rolled twice with an intermediate rolling in between. Or, in the process of producing a normal grain-oriented electrical steel sheet, which consists of decarburizing the cold-rolled sheet obtained by performing one cold rolling to the final sheet thickness and then subjecting it to secondary recrystallization annealing. As shown in Fig. 1, a coating liquid for forming an insulating film such as a 1-non-acid-based tension imparting film is coated on a copper plate or a steel plate coated with a coating solution for forming an insulating film such as a 1-non-acid tension imparting film.
A belt-shaped laser irradiation area with a width of 0.2 to 2.5 mm, consisting of multiple irradiation marks, is introduced in the range of 45 degrees orthogonal to the rolling direction with an energy intensity of The area is alternately arranged with a band-shaped area having a width of 2 to 12 mm where laser irradiation is not performed.

In this way, in the present invention, the irradiation area is widened, and the irradiation area is changed within the area and the laser irradiation is performed multiple times in close proximity, so if the laser irradiation is continued, the iron loss value will be worse than before irradiation, but after annealing. Although the dislocations are organized, a plastic strain region remains due to the laser irradiation due to the superimposed strain, and this residual strain fragments the magnetic domain. Moreover, in the plastic strain region, no fine recrystallization is observed after stress relief annealing, and only plastic strain of the crystals is observed using the pseudo-Kottsel method.

Here, U is defined as follows. Figure 2(a).

(b) shows typical irradiation mark patterns when the steel plate surface is irradiated with a laser beam in continuous oscillation and pulse oscillation states, respectively, in the C direction. In the figure, F is the continuous wave laser irradiation area, and d is the inside of the irradiation trace. In the case of Fig. 2(a), the laser energy U (J/cm'') input per unit area of the steel plate is expressed as ■ 2, and in the case of Fig. 2(b), it is expressed as Pa is the laser oscillation power (W)
, V (cm/s) is the scanning speed of laser beam irradiation in the direction of the steel plate C, j! (cm) is the interval in the L direction of a line or dot sequence in the C direction, and a (cm) is the interval between pulse points in the C direction. n indicates the number of line rows or dot rows in the L direction.

What is important when introducing plastic strain using the above-mentioned laser is to change the irradiation area and introduce strain by scanning the strain introduction region twice or more with the laser. For example, when laser irradiation is performed over a width of 0.35 mm, a beam having a width of 0.11 scans the beam three times to form three adjacent plastic strain introduction zones. The advantage of doing this is that firstly, the bending of the plate due to beam irradiation is smaller than scanning once with a high-intensity beam, and secondly, compared to one-time laser irradiation, the difference in θ (2) By irradiating the region multiple times or with multiple laser beams, recovery of strain after stress-relieving annealing becomes significantly worse, which has a large effect on magnetic domain refining. The iron loss value after laser irradiation of the present invention is worse than before irradiation, probably because the tangle of dislocations is large due to the superposition of strain in the strain introduction region. However, when stress relief annealing is performed, excess dislocations are sorted out, so the iron loss value becomes significantly better than the value before laser irradiation, and an iron loss value almost equivalent to that of the same sample subjected to normal laser treatment is obtained. . Also, according to the present invention, Bsff1 may be because no fine crystal grains are observed in the strain introduction region.
The decrease in the amount of water is extremely small compared to other methods. Usually 800
When stress relief annealing is performed for 2 hours at ℃, the decrease in B value before and after treatment is less than 50 Gauss. Figure 3 shows the above phenomenon, in which a unidirectional electrical steel sheet with a tension coating applied to a 0.23 mm thick finish annealed plate is exposed to a laser beam diameter of 0.1 mmφ in a direction perpendicular to the rolling direction. Q
, Changes in iron loss value and B value after each heat treatment when 4 mm wide belt-shaped irradiated areas and 4 mm wide non-laser irradiated areas are arranged alternately are shown for samples before laser irradiation and for normal laser treatment It is a figure shown in comparison with the material. The laser irradiation intensity was U-10J/-.

As described above, according to the present invention, no decrease in magnetic permeability is observed, and the effect of low core loss is remarkable.

Next, Figure 4 shows U=10J using a pulse oscillation YAG laser.
Wl 7150 when a unidirectional electrical steel sheet with a thickness of 0.23 mm is subjected to stress-removal annealing at 800°C for 2 hours after scanning the beam 5 times with a beam diameter of Q and 1 mm mφ at an energy intensity of 0.23 mm. Laser irradiation angle (measured from the direction perpendicular to the rolling direction) to improve the iron loss value (based on before laser irradiation)
It is shown as a function of α), and it can be seen that the effect is effective up to an irradiation angle of 45°.

FIG.
0.23m when subjected to stress relief annealing for 2 hours at °C
This figure shows the relationship between the laser irradiation area, the non-laser irradiation area, and the achieved iron loss value for a m-thick one-way open unidirectional steel plate. In the shaded area Wl 7150≦0.8
This is the area where 2W/kg is obtained, the area with thin diagonal lines is the area where the effect is recognized, and the other areas are the areas where the same iron loss value as the original value is obtained. From this figure, the effective laser irradiation range, that is, a plurality of adjacent plasticity introduction zones, is 0.2 to 2.5 mm, and the most preferable range is 0.3 to 2 mm. It is effective if the area where laser irradiation is not performed is in the range of 2 to 12 mm, but if it becomes too narrow, B will decrease, which is not preferable. The most preferred range is 3-7 mm.

The width of one strain introducing band is O,l~Q,5 mm.

FIG. 6 shows the change in iron loss value after the introduction of strain when four people strain the laser beam with a width of 0.1 mm and change the beam center spacing in the direction perpendicular to the rolling direction.

It can be seen that by changing the center spacing, the iron loss value becomes worse than the original value. The effect of introducing strain is large when the beam center spacing is within 3 times the beam diameter, and is particularly noticeable when the spacing is within 2 times the beam diameter.

Of course, the present invention can be applied to a glass coating material that has been subjected to secondary recrystallization annealing, and the same effect can be obtained even if the coating is subjected to tension imparting coating treatment at a high temperature.

The type of laser device and the oscillation state of the laser used in carrying out the present invention are not limited at all, and for example, commercially available COx and C○.

Various laser devices such as YAG and Ar lasers can be used, and any of continuous, oscillation, and pulse oscillation is effective. The laser beam may be irradiated on only one side or on both sides.

In the present invention, heat treatment such as heat flattening and insulation film baking can be used as heat treatment after laser irradiation. Furthermore, under conditions where the insulating film does not peel off due to the irradiation conditions in YAG continuous wave mode or COz laser, there is no need to recoat the insulating film. In such cases, heat treatment is required to reduce iron loss after laser irradiation. Note that instead of laser irradiation, a tooth-shaped roll that satisfies the requirements of the present invention, for example, a roll with corrugated tooth tips, etc. may be used.

〔Example〕

Example 1 A unidirectional electrical steel sheet with a thickness of 0.23 mm after finish annealing and a tension coating was applied was subjected to 4 laser beams with a beam diameter of 0.1 mm in a direction perpendicular to the rolling direction using a pulsed YAG laser device. The beam was scanned twice to form a plurality of 0.5 mm wide plastic strain introduction irradiation areas, and the irradiation areas were periodically formed with 5 mm wide laser beam non-irradiation areas in between. Energy U per unit area of the steel plate at this time
Figure 7 shows the increase and decrease in iron loss value after stress relief annealing at 800°C for 2 hours after laser irradiation, with 0.1-100 J/cm'', based on the value before laser irradiation. As can be seen from this figure, when beam scanning is performed multiple times in the range of U-IJ/cm or more, the iron loss value after irradiation becomes bad (although it becomes better than the original value due to stress relief annealing). It can be seen that the iron loss value was on average 0.025 W better than the black circle in FIG. 7 in the case where the tension film was recoated to compensate for the peeled part after laser irradiation.

Example 2 After final annealing, a unidirectional 1i magnetic plate with a thickness of 0.23 mm was scanned five times with a laser beam having a beam diameter of 0.2 mm in a direction perpendicular to the rolling direction using a pulse oscillation YAG laser device. A plurality of plastic strain fuse zone irradiation regions each having a width of 1 mm were formed, and the irradiation regions were periodically formed with a laser beam non-irradiation region having a width of 7 mm interposed therebetween. Irradiation energy U
was IQJ/cm" before laser irradiation at this time,
Table 1 shows the iron loss values after irradiation and stress relief annealing at 800° C. for 2 hours. As shown in Table 1, it can be seen that the iron loss value after laser irradiation becomes an extremely good value after stress relief annealing.

Table 1 Example 3 A unidirectional electrical steel sheet with a thickness of 0.20 mm after finish annealing and the application of a tension coating was heated with a laser beam with a beam diameter of 0.15 mmφ in a direction perpendicular to the rolling direction using a COz laser device. The beam was scanned twice to form a plastic strain introduction irradiation area with a width of 0.6 mm, and the irradiation area was periodically formed with a laser beam non-irradiation area of 5 mm width in between. The irradiation energy U was 15 J/cm''. Table 2 shows the iron loss values before laser irradiation, after irradiation, and after stress relief annealing at 800°C for 2 hours. As shown in Table 2, it can be seen that the steel of the present invention has a significantly low iron loss value.

Table 2 [Effects] The steel plates obtained by the method of the present invention exhibit extremely good iron loss values. Therefore, according to the present invention, it is possible to obtain an electrical steel sheet with low iron loss by applying it to a continuous line.

According to the present invention, even if stress-relieving annealing is performed, an iron loss value equivalent to that obtained by ordinary laser irradiation can be obtained, so the obtained electrical steel sheet can be used not only as a wound core transformer but also as a stacked core transformer. It can be used and its industrial effects are extremely large.

[Brief explanation of drawings]

Figure 1 is a diagram showing the laser irradiation area in the present invention. Figure 2 (a) and (b) are schematic diagrams of the irradiation pattern in the present invention. Figure 3 is a diagram showing the laser treated material before, after, and after each heat treatment. Figure 4 is a diagram showing the improvement in iron loss value and the laser irradiation angle measured from the direction perpendicular to the plate rolling direction, Figure 5 is the laser irradiation area Figure 6 is a diagram showing the relationship between the core loss value reached during the laser beam and the laser non-irradiation area. FIG. 7 is a diagram showing the laser irradiation energy and the improvement and deterioration of the iron loss value after stress relief annealing after laser irradiation.

Claims (1)

[Scope of Claims] 1. A plurality of strain introduction zones are formed in the rolling direction of the finished annealed plate or the steel plate that has been treated with a tension coating on the finished annealed plate, so that the plastic strain regions are partially overlapped within the steel plate. After periodically applying
A method for producing a low iron loss unidirectional electrical steel sheet, which is characterized by subjecting it to heat treatment. 2. The method for manufacturing a steel plate according to claim 1, wherein the width of the plurality of plastic strain introduction zones is 0.2 to 2.5 mm. 3. The method for manufacturing a steel plate according to claim 1, wherein the width of the plastic strain introduction zone is 0.1 to 0.5 mm. 4. The method for manufacturing a steel plate according to claim 1, wherein the width of adjacent plastic strain introduction zones is within twice the width of the said introduction zone. 5. The gap between the plurality of plastic strain introducing zones is 2 in the rolling direction.
The method for manufacturing a steel plate according to claim 1, wherein the thickness is in the range of 12 mm. 6. The method for manufacturing a steel plate according to claim 1, wherein the plurality of plastic strain introducing zones are within a range of 45° from a direction perpendicular to the rolling direction. 7. The method for manufacturing a steel plate according to claim 1, wherein the plastic strain introduction zone is formed by laser irradiation. 8. The method of manufacturing a steel plate according to claim 1, wherein the plastic strain introduction zone is formed by scanning the laser beam a plurality of times. 9. The method of manufacturing a steel plate according to claim 1, wherein the plastic strain introduction zone is formed by scanning with a plurality of laser beams. 10. Set the energy intensity of the laser beam to U=1~10
0J/cm^2 The method for manufacturing a steel plate according to claim 1. 11. The method for producing a steel sheet according to claim 1, wherein a plurality of adjacent strain introduction bands are periodically applied in the rolling direction and then a tension imparting coating treatment is performed.