JPS60152628A - Manufacture of nonoriented silicon steel sheet with small iron loss - Google Patents

Abstract

PURPOSE:To reduce the iron loss by hot rolling a slab for a nonoriented silicon steel sheet contg. specified amounts of C, Si and Al and particles of inclusions restricted to a specified number and by carrying out cold rolling to the final thickness and two-stage annealing under specified conditions. CONSTITUTION:A slab for a nonoriented silicon steel sheet contg. <0.01wt% C, <4wt% Si, <1wt% Al and particles of inclusion of >=5mum size restricted to <=80 per 1mm.<3> steel is hot rolled and cold rolled to the final thickness by a conventional method. The cold rolled steel sheet is subjected to two-stage final annealing, that is, annealing at 750-850 deg.C soaking temp. for 1-4min and annealing at 900-1,000 deg.C soaking temp.

Description

[Detailed Description of the Invention] Technical Field Regarding the manufacturing method of non-oriented silicon steel sheets with low core loss, the technical content described in this specification is particularly focused on the addition of a device to the final annealing treatment during the manufacturing process of the steel sheets. This is related to improving overall iron loss.

Technical background Non-oriented silicon steel sheets are mainly used in motor stators and rotors, hydroelectric generator stators, and fluorescent lamp safety equipment, and are highly energy-saving.

From this point of view, in recent years there has been an increasing demand for further reducing the iron loss of non-oriented silicon steel sheets in order to further suppress the power loss of these devices.

One of the methods to completely improve the iron loss of non-oriented silicon steel is Si-? There is a method of increasing the specific resistance by increasing the amount of Al added, but this method has its limitations, as the cold rollability worsens as the amount of Al added increases, and the cost of the material also increases. . As another method, it is known to be effective to appropriately control the final annealing temperature to adjust the crystal grain size to an appropriate grain size.

Furthermore, O, N, S' (r) in steel is reduced, and oxides in steel are
It has been discovered that the method of reducing inclusions such as nitrides and sulfides is extremely effective in reducing iron loss, and recent advances in steelmaking technology have made it possible to reduce inclusions such as nitrides and sulfides. Thanks in part to the availability of these materials, materials with significantly lower iron loss have been manufactured.

Figures 1a and 1b show eight types, the compositions of which are shown in Table 1.

This is a non-oriented silicon steel sheet obtained by cold-rolling the steel to a thickness of 0.86mm according to a conventional method, and then annealing it according to a conventional thermal cycle with a constant soaking temperature as schematically shown in Fig. 2. The inclusion frequency in Table 1 is the number of inclusions per unit area when counting inclusions of 5 μm or more from a 600x microscopic field of view. This is a value calculated as N pieces 4□8, and means the number of inclusions per unit volume.

As is clear from FIG. 1, it can be seen that by reducing the inclusions in the steel and then setting the annealing temperature within an appropriate range, the iron loss can be significantly reduced. The appropriate annealing temperature for the steel types declared in the same figure is Steel l: 1000° C5 Steel ■ 975°
0 and steel ■, around 950°C, but this treatment temperature is a temperature suitable for adjusting the crystal grain size to the appropriate crystal grain size of 150 = 200 μm, and the higher the frequency of inclusions, the more
Since it tends to become fine particles, it is shifted to the high temperature side.

In addition, methods for improving the iron loss of silicon steel include improving the texture, for example, increasing the strength of the (110) plane and (200) plane, which contain many easy magnetization axes, and <222) There are methods such as suppressing the surface strength, and these methods include the one-time cold rolling method including hot-rolled plate annealing to achieve even greater effects.

Alternatively, various studies have been made regarding the cold rolling reduction rate and annealing temperature regarding a two-time cold rolling method in which a hot rolled sheet is pickled and then subjected to intermediate annealing. − History of the elucidation of the solution As described below, this invention has achieved a further reduction in iron loss by making it possible to improve the texture and adjust the grain size using a method completely different from conventional methods. be.

In other words, in order to improve the iron loss custom made of non-oriented silicon steel sheets, the inventors reexamined the manufacturing process of the steel sheets, and found that in the final annealing process, the formation of texture first progressed, and then We found that crystal grain growth occurs, and based on this knowledge, we conducted further research and found that the final annealing was divided into a front stage for proper texture adjustment and a rear stage for proper grain size adjustment. They discovered that by performing such two-stage annealing, it was possible to achieve a dramatic reduction in iron loss compared to the conventional method, and completed this invention.

Structure of the Invention The present invention is characterized in that 0: 0.010% by weight (hereinafter simply expressed as a ratio), Si: 4.0% or less, and Al: 1
．． A slab for non-oriented silicon steel which has a composition containing 0% or less and suppresses the frequency of inclusions in the steel with a size of 6 μm or more to 80 HI3 or less is hot rolled and then cooled according to a conventional method. In a method for producing a non-oriented silicon steel sheet, which consists of a series of steps in which a cold-rolled steel sheet has the final thickness by inter-rolling, and then final annealing is performed, the final annealing is performed in two stages, the first stage being Soak for 1-4 minutes at a soaking temperature range of 750-850"O, and at a temperature of 900-1000℃ for the second stage.
This is a method for producing a non-oriented silicon steel sheet with low iron loss, characterized by performing annealing treatment under conditions of a soaking temperature range of .

Hereinafter, based on the experimental results that led to this invention, 1. Kiko's invention will be specifically explained.

Now, the eight types of cold-rolled sheets 1 and II whose component compositions are shown in Table 1 above.
For and ■, two-stage annealing was performed in the thermal cycle shown in FIG. 8 to produce a non-oriented silicon steel plate.

In the same figure, the second processing condition is 950°C for X minutes because the grain size after annealing is in the optimum range.
This is because, in order to obtain a thickness of 0 to 200 μm, it is necessary to adjust the soaking time appropriately between about 0.5 seconds and about 10 minutes depending on the steel type. The annealing atmosphere was H,:
75%.

A non-oxidizing atmosphere with N2: 25% was used.

The results of examining the iron loss characteristics of each steel plate thus obtained are shown in FIGS. 4a and 4b, respectively, in terms of the relationship between the pre-soaking temperature and the iron loss value.

For comparison, the figure also shows the best iron loss value obtained in the heat cycle according to the method shown in Figure 2 above.

As is clear from Fig. 4, vI41 has a high inclusion frequency.
Although the effect of two-stage annealing was hardly seen in steels with few inclusions, two-stage annealing in which the previous stage was lowered to 750 to 850"0 resulted in extremely superior low-iron steels. Waste material is obtained.

Next, Fig. 5 a, b and Fig. 6 a, b, c show (200) pole figures showing part of the texture of Steel I and Steel I, respectively.

In Fig. 5 (a), Steel I is subjected to two-stage annealing at 850°0 + 950°C, and Fig. 5 (b) is the case in which trapezoidal annealing is performed at 1000''C. a) is steel ■
Two-stage annealing at 850'O + 950℃, and the width of the same drawing)
is a two-stage annealing at 900℃+950℃, and the same figure (o) is 2.

This is a case where trapezoidal annealing of 50"O was performed.

As shown in FIG. 5, in the case of steel (2) with a high frequency of inclusions in the steel, the (222) plane strength is strong overall, and the effect of two-stage annealing is not clearly evident. The reason for this is
Inclusions cause increase in (222) surface strength (111)
This is thought to be because it becomes a place for grain nucleation.

On the other hand, in steel (2) with few inclusions in the steel, as shown in FIG. 6, the strength of the (200) plane and the (110) plane is high, and the strength of the (222) plane is low. And Kayo 1. .

This tendency is particularly observed in the two-stage annealing according to the present invention (Fig. 6a).
) is significant in cases where

Next, in this invention, the reason why the basic components of the material are limited to the above range will be described.

0 brings about aging deterioration, so it is preferable to have a small number of 1,000, but decarburization is possible in the middle of the process, so 0.0 has good decarburization efficiency.
Up to 0.010% is acceptable.

Si is effective in increasing specific resistance, reducing eddy current loss, and improving iron loss, but if added in excess, cold rollability deteriorates, so Si should be added in a range of 4.0% or less.

limited to.

AI not only contributes effectively to deoxidizing steel and reducing i of AJN-based precipitates, but also, like Si, is a useful component in improving specific resistance 'lrM and overall iron loss. If added in excess, cold rollability deteriorates, so the amount was limited to 1.0% or less.

Next, regarding the frequency of inclusions in the steel, if there are more than 80 inclusions with a size of 5 μm or more in the steel, the effect of the two-stage annealing of the present invention will not appear as described above. Therefore, for particles larger than 5 μm, the frequency of forward movement is 80
The number of pieces was 4□8 or less. However, as is clear from the measurement method, inclusions in this invention naturally include precipitates such as sulfides and A/IN.

In order to reduce such inclusions, steel 1, medium N
What is necessary is to reduce the amount of leaves, S amount, and O amount. Incidentally, the allowable amounts of each of the above components necessary to keep the inclusion frequency within the appropriate range according to the present invention are N≦0.0025%, S
50.0015% and O≦0.0020%.

Now, in this invention, molten steel is processed by continuous casting method or l ingot making method.
A slab is formed by the blooming method and then hot-rolled in a normal process, but by adjusting the ingredients as described above, the frequency of inclusions in the steel is reduced to 80 with a size of 5 μm or more.4. It is regulated to be 8 or less.

In the cold rolling process, the thickness of the product is obtained by one cold rolling, the thickness of the product is obtained by cold rolling twice with intermediate annealing, or the hot rolled sheet is annealed and then
After cold rolling, the product may have a thickness of 1.

Then, according to the present invention, a two-stage final annealing is performed.

The two-stage annealing according to the present invention consists of a thermal cycle consisting of a two-stage soaking section, a front stage and a rear stage, as shown in FIG. Become,
As mentioned above, the first low-temperature annealing section is for improving the texture, and the second high-temperature annealing section is for adjusting the grain size.

In such two-stage annealing, the soaking temperature in the first stage is
At temperatures above 0°, the texture deteriorates and the iron loss deteriorates significantly, while at temperatures below -1,750°, recrystallization hardly progresses in the front stage, and recrystallization develops only in the rear stage. Since the result is the same as that of conventional trapezoidal annealing, the effect of improving the texture is poor and no significant improvement in iron loss can be expected. Therefore, the pre-stage soaking temperature is 750
~850°0. In addition, if the annealing time is less than 1 minute, the proper texture improvement effect will not be noticeable, so the soaking time should be longer than 1 minute. However, even if the soaking time is kept for more than 4 minutes, the texture improvement effect will reach saturation. Therefore, it was set to within 4 minutes.

In addition, regarding the subsequent high-temperature annealing, if the soaking temperature is lower than 900°C, crystal grains of sufficient size will not be obtained.
If it exceeds 00"0, the grain growth rate of the crystal grains increases and it becomes difficult to adjust the crystal grains to an appropriate size. Therefore, the soaking temperature in the latter stage was limited to a range of 900 to 1000°C. The annealing time may be appropriately adjusted according to the appropriate crystal grain size, and is usually preferably about 0.6 seconds to 10 minutes.

Example Examples of the present invention will be described below.

Example 1 O: 0.0 (134 sections, Si: 8.22 sections, AJ
: 0.620%S: 0.0006%, N:
After heating a steel slab having a composition containing 0.0017% and 0:0.0009%, it was hot rolled to a thickness of 2.0 mm, pickled, and then cold rolled to a 90.7011.
It was then subjected to an intermediate annealing at 950°0 for 8 minutes, and then subjected to a second cold rolling to a final thickness of 0.85 mm.

This cold-rolled sheet was subjected to two-stage annealing in an atmosphere with ■265%, residual N, and fog point θ"0, with a thermal cycle of 850°C x 2 minutes in the first stage and 950°C x 1 minute in the latter stage, resulting in a non-directional manufactured silicon steel sheets.

The magnetic customization of the obtained steel plate was made into a 25 crrL nib style.
.

Table 2 shows the results of the investigation using the analysis method.

For comparison, the above cold-rolled sheet was heated at 950°C according to the conventional method.
A silicon steel sheet obtained by final annealing in a trapezoidal thermal cycle of ×2 minutes was also examined for magnetic properties (t-) in the same manner, and the results are also listed in Table 2.

Table 2 As is clear from the results in the table, the non-oriented silicon steel sheets obtained according to the method of the present invention are much better in iron loss characteristics and magnetic flux density than conventional materials.

Example 2 0: 0.008%, Si: 3.25%, A
l: 0-598%, 1sS: 0.005%,
A steel slab having a composition containing 0.0022% N and 0.0012% O was heated and hot-rolled to a thickness of 2.0mm, and this hot-rolled steel strip was subjected to a standard of 95m0Xa. The sample was pickled and then cold-rolled to obtain a cold-rolled plate having a thickness of 0.85JIl11. To this cold-rolled plate, -...H265
840 in the atmosphere with a residual Ng and a dew point of 40'Q.
A non-oriented silicon steel sheet was manufactured by performing two-stage annealing, which consisted of a thermal cycle of 2 minutes at OXI and 7 minutes at OXI in the second stage.

Table 8 shows the results of measuring the magnetic customization of the obtained steel plate using the 25CIn Epstein method.

Table 8 As is clear from the results shown in the table, the magnetic properties of the materials obtained according to the method of this invention are much improved compared to the conventional materials.

Effects of the Invention Thus, according to the present invention, the magnetic properties, particularly the iron loss properties, of a non-oriented silicon steel sheet can be significantly improved compared to the conventional method, which is advantageous. .

[Brief explanation of the drawing]

Figures 1a and 1b show the final annealing soaking temperature and iron loss value W1515o, respectively, according to the conventional thermal cycle. To. Graph showing the relationship between Figures a and b show the pre-soaking temperature and iron loss characteristics of products obtained by two-stage annealing according to the present invention, respectively.
, W10150 in comparison with the characteristic values of conventional materials, Fig. 5 a, b and Fig. 6 a, b, c are graphs of (200 ) is a pole figure. -(~system) 菖謬- 8, ri, miA (-4 thing)' しょう(a Figure 2, Figure 3, Figure 4)

Claims (1)

[Claims] Inclusions in steel having a composition containing L O: 0.010% by weight or less, Si: 4.0% by weight or less, and AI: 1.0% by weight or less, and having a size of 5 μm or more A slab for non-oriented silicon steel with a frequency suppressed to 8Q gA/A- or less was hot rolled, and then cold rolled according to a conventional method to obtain a cold rolled steel plate of the final thickness. In a method for manufacturing a non-oriented silicon steel sheet, which includes a series of steps of successively performing final annealing, the final annealing is performed in two stages, and the above-mentioned final annealing is performed in two stages. The stage is annealed at a soaking temperature range of 750-850°C for 1-4 minutes, and the latter stage is annealed at a soaking temperature range of 900-1000°C. Method for manufacturing grain-oriented silicon steel sheet.